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<reference>
Monday Morning, November 6, 2023
Atomic Scale Processing Mini-Symposium
Room A107-109 - Session AP+PS+TF-MoM
Thermal Atomic Layer Etching and Deposition
Moderator: Jean-Francois de Marneffe, IMEC, Belgium
8:20am AP+PS+TF-MoM-1 Atomic Layer Etching of Aluminum and
Aluminum Oxide for Optical Applications, John Hennessy, R. Rodríguez, A.
Jewell, Jet Propulsion Laboratory
INVITED
Thermal atomic layer etching can be utilized for the surface preparation of
aluminum in order to improve its optical performance at ultraviolet
wavelengths. In this work we report on the use of trimethyaluminum and
anhydrous hydrogen flyoride to remove the native oxide of aluminum prior
to encapsulation with fluoride dielectric materials. This ALE/ALD process is
used for the fabrication of reflective coatings and bandpass filters operating
at wavelengths shorter than 200 nm. The etch rate of aluminum oxide is
observed to be dependent on chamber conditioning with a significant
enhancement in etch rate observed when the cyclic etching is performed in
the presence of alkali halide materials. This enhancement can reduce the
temperature threshold where etching dominates the reaction cycle over
deposition.
The reduction of the overall processing temperature can enhance the
compatibility of the full coating process with some temperature-sensitive
substrates, and limit the amount of etch damage experienced by aluminum
surfaces. Etching into the aluminum surface is generally observed to result
in non-conformal etching which greatly increases the surface roughness of
films and degrades the optical performance of resulting structures.
Reducing the etch temperature can mitigate this effect by increasing the
selectivity of the native oxide removal over the underlying metal.
Optimization of these processes may provide insight into achieving
conformal ALE of aluminum surfaces. The extension of these atomic layer
processing methods towards the fabrication of meter-class mirror coatings
is also discussed in the context of future large UV space observatories for
NASA
astrophysics
applications.
9:00am AP+PS+TF-MoM-3 Thermal Etching of First Row Transition Metal
Oxides using Acetylacetone and O3: Pathway for Atomic Layer Etching,
Jonathan Partridge1, S. George, University of Colorado at Boulder
Etching metal oxides with halogen-free methods is important during
processing to avoid corrosion.Acetylacetone (Hacac) is an organic
hydrocarbon.Hacac can supply acac ligands that can form volatile metal
complexes with most transition metals.Consequently, Hacac can
spontaneously etch metal oxides to form M(acac)x and H2O.One difficulty is
that Hacac can also decompose on the metal oxide surface and block the
spontaneous etching.However, this surface poisoning also leads to a selflimiting reaction. The O3 exposure can then remove the carbonaceous
decomposition species and produce a pathway for atomic layer etching.
Thermal etching of first row metal oxides was demonstrated using Hacac
and O3 at pressures of 2.5 Torr at 250 °C.A quadrupole mass spectrometer
(QMS) reactor with molecular beam expansion and line-of-sight to the
ionizer was employed to detect etch species with high sensitivity.Metal
oxide nanopowders were used to maximize the surface area and signal
intensity of the etch products. The reactant sequence used five sequential
Hacac exposures, one O3 exposure, and one final Hacac exposure to check
for etch product enhancement after O3 exposure.Etching was monitored by
the production of M(acac)x etch products.
M(acac)x etch products were observed for Sc2O3, V2O5 and VO2, Cr2O3,
Mn2O3 and MnO, Fe2O3 and Fe3O4, Co3O4 and CoO, CuO and Cu2O, and ZnO.
No etching was observed for TiO2, MnO2, and NiO. The metal oxides that
etched either displayed (1) spontaneous etching by Hacac with no selflimiting behavior or (2) etching that limited itself versus Hacac exposure.The
metal oxides that were spontaneously etched by Hacac were Mn2O3 and
MnO, Co3O4 and CoO, and ZnO.The metal oxides that displayed self-limiting
behavior were Sc2O3, V2O5 and VO2, Cr2O3, Fe2O3 and Fe3O4, and CuO and
Cu2O.ALE processes for these metal oxides that displayed self-limiting
reactions are possible using Hacac and O3.
A comparison between the M(acac)x etch products and the metal oxide also
provided information about oxidation state changes during etching.The x in
M(acac)x is both the number of acac ligands and the oxidation state of the
M metal center.Sc2O3, Cr2O3, MnO, Fe2O3, CoO, CuO, and ZnO all formed
M(acac)x etch products with the same oxidation state as the metal oxide.In

1 TFD James Harper Award Finalist

Monday Morning, November 6, 2023

contrast, the other metal oxides all displayed evidence for reduction during
etching.This reduction may occur by oxygen loss during the combustion of
Hacac.
9:20am AP+PS+TF-MoM-4 Selectivity between Silicon-Based Materials for
Thermal Atomic Layer Etching and Spontaneous Etching, Marcel Junige, S.
George, University of Colorado at Boulder
Sub-10-nm technology nodes must overcome the limits of
photolithography. This requires selectivity between various Si-based
materials for thermal atomic layer etching (ALE) and spontaneous etching.
This work examined selectivity between silicon dioxide (SiO2) and silicon
nitride (SiNx) for thermal ALE using trimethylaluminum (TMA) and hydrogen
fluoride (HF), as well as for spontaneous etching using HF alone, at 275℃.
Distinct etch rates between SiO2 and SiNx achieved inherent selectivity.
Experiments were conducted in a hot-wall, viscous-flow vacuum reactor
with good control over the pressure during static reactant dosing to ensure
reproducibility. In situ spectroscopic ellipsometry (iSE) was utilized to study
etch-per-cycle (EPC), synergy, and selectivity characteristics. Sodium
bifluoride (NaHF2) was tested as an alternative HF source. NaHF2 is a solid
salt with negligible HF vapor pressure at room temperature, making NaHF2
safer to handle than HF-pyridine. NaHF2 delivered HF pressures up to 15
Torr when heated to 150℃ without releasing sodium. During thermal ALE
of alumina (Al2O3), NaHF2 exhibited diffusion-limited fluorination and EPC
characteristics comparable with HF-pyridine.
For thermal ALE of SiO2 alternating TMA and HF, the EPC and synergy were
–0.2 Å and 88%, indicating minor spontaneous etching by HF alone. This
moderate synergy for SiO2 thermal ALE improved to 95% by ensuring waterfree conditions during fluorination. On the other hand, the EPC for SiN x
thermal ALE was –1.1 Å. The EPC for SiNx was expected to be much lower
than for SiO2 because no oxygen reactant was employed to oxidize SiNx.
However, iSE experiments revealed that repeated exposures of HF alone
spontaneously etched SiNx. Anhydrous HF vapor might form F− species at
the surface that have been attributed to dominate SiNx etching.
Spontaneous etching using static exposures of 45 s at 3 Torr HF alone
obtained a high selectivity of ~50:1 for SiNx removal over SiO2 retention.
For thermal ALE alternating TMA and HF in co-dose with ammonia (NH3),
the selectivity inverted to ~9,000:1 for SiO2 over SiNx. HF+NH3 co-dosing led
to rapid spontaneous etching of SiO2. NH3, similar to water, might facilitate
the dissociation of HF into H+ and F−, where the increased F− concentration
immediately produces HF2− species. HF2− species have been attributed to
dominate SiO2 etching.
In conclusion, this work demonstrated conditions for inherently selective
gas-phase etching of either SiO2 or SiNx.
9:40am AP+PS+TF-MoM-5 Thermal Atomic Layer Etching of SnO2 by
Fluorination and Ligand-Exchange Using HF and Al(CH3)3, C. Li, University
of Colorado Boulder, China; J. Partridge, Steven George, University of
Colorado Boulder
Thermal atomic layer etching (ALE) can be achieved with sequential, selflimiting surface reactions. One mechanism for thermal ALE is based on
fluorination and ligand-exchange reactions. For metal oxide ALE,
fluorination converts the metal oxide to a metal fluoride. The ligandexchange reaction then removes the metal fluoride by forming volatile
products. Previous studies have successfully applied this thermal ALE
strategy for Al2O3, HfO2, and ZrO2 ALE. However, no previous investigations
have explored the thermal ALE of SnO2 films.
This study demonstrated the thermal ALE of SnO2 thin films using
sequential, self-limiting thermal reactions with hydrogen fluoride (HF) and
trimethylaluminum (Al(CH3)3, TMA) as the reactants. The initial SnO2 films
were grown by atomic layer deposition (ALD) using tetrakis(dimethylamino)
tin and H2O2. The thermal SnO2 ALE process was then studied using various
techniques including quartz crystal microbalance (QCM), spectroscopic
ellipsometry (SE), and quadrupole mass spectrometry (QMS).
In situ QCM experiments monitored SnO2 ALE at temperatures from 250 to
300 ℃. The SnO2 etching was linear versus the number of HF and TMA
reaction cycles. The QCM studies also showed that the sequential HF and
TMA reactions were self-limiting versus reactant exposures. The SnO2
etching rates increased at higher temperatures. The QCM analysis
measured mass change per cycle (MCPC) values that varied from −44.32
ng/(cm2 cycle) at 250 °C to −123.5 ng/(cm2 cycle) at 300 °C. These MCPCs
correspond to SnO2 etch rates from 0.64 Å/cycle at 250 °C to 1.78 Å/cycle at
300 °C.
SE measurements confirmed the linear removal of SnO2 and the etching
rates. QMS analysis also revealed the volatile etching products during the
1
8:20 AM

Monday Morning, November 6, 2023
sequential HF and TMA exposures on SnO2 at 300 ℃. These QMS
investigations observed Sn(CH3)3+, indicating Sn(CH3)4 as the etch product
during TMA exposures. AlxFy(CH3)z dimer and trimer species were identified
as the ligand-exchange products. QMS analysis during multiple sequential
TMA doses before HF/TMA cycling also revealed that fluorination was
necessary for Sn(CH3)4 etch product evolution. This observation indicated
that TMA does not convert SnO2 to Al2O3. The results indicate that thermal
SnO2 ALE using sequential HF and TMA exposures occurs by fluorination
and ligand-exchange reactions.

temperatures. ATR-FTIR studies corroborated the salt formation at lower
temperatures and the salt decomposition at higher temperatures.
To demonstrate that HF exposures could achieve high SiNx etch rates
without salt formation, experiments were conducted at T≥140oC with
higher HF pressures. A four-fold increase in HF pressure to 2.0 Torr led to a
~five-fold increase in SiF4 signal intensity measured by QMS. At these higher
temperatures T≥140oC, SiNx etching can proceed with no inhibition from
the salt.
11:20am AP+PS+TF-MoM-10 Crystal Phase Transformations During
Thermal Atomic Layer Etching of Hafnium–Zirconium Oxide (HZO) Using
Hydrogen Fluoride and Dimethylaluminum Chloride, Aziz Abdulagatov, J.
Partridge, University of Colorado at Boulder; M. Surman, ASM
Microchemistry Ltd., Finland; S. George, University of Colorado at Boulder
Thermal atomic layer etching (ALE) of Hf0.5Zr0.5O2 (HZO) was previously
demonstrated using hydrogen fluoride (HF) and dimethylaluminum chloride
(DMAC) [1]. This current work focused on crystallographic transformations
of HZO during ALE. Grazing incidence x-ray diffraction (GIXRD) analysis of
initial 10 nm thick HZO film on 20 nm thick TiN on Si revealed orthorhombic
(o-phase), tetragonal (t-phase), and monoclinic phases (m-phase). Ex situ
spectroscopic ellipsometry and X-ray reflectivity (XRR) measurements
showed that sequential exposures of HF and DMAC at 250 oC resulted in a
linear decrease in film thickness with an HZO etch rate of ~0.45 Å/cycle.

10:40am AP+PS+TF-MoM-8 Reactivity and Volatility as Key Metrics for
Classifying the Substrate Selectivity of Ligands in Atomic Level Processing,
Hadi Abroshan, Schrödinger, Inc.; S. Lim, Schrödinger, Inc., Republic of
Korea; A. Chandrasekaran, Schrödinger, Inc.; S. Elliott, Schrödinger, Inc.,
Germany; H. Kwak, M. Halls, Schrödinger, Inc.
One of the main challenges in the area-selective deposition or etch for
semiconductor processing is finding a single reagent that undergoes
different chemistry on different substrates. The reagent may be an
organometallic complex containing a particular ligand or may be the
protonated version of that ligand. In this work we propose that examining
just two properties of the organometallic complex across a series of metal
cations is sufficient to give an indication of the area-selectivity that can be
achieved with reagents based on the particular ligand chemistry.

GIXRD studies observed that the peaks associated with the o- and t-phases
decreased faster in intensity than the m-phase peaks. As the number of ALE
cycles increased, only the m-phase remained before the majority of the
HZO film was removed by etching. Interestingly, as o- and t-phases were
removed, the grain size of the m-phase crystallites increased in size
according to the Scherrer equation. XRR investigations also monitored a
decrease in the film density with ALE. In addition, atomic force microscopy
(AFM) measurements observed that the density decrease was
accompanied by an increase in film roughness.

The first property is reactivity towards the hydrolysis reaction, which gives
information about oxide formation versus surface passivation or etching,
and the second property is volatility of the organometallic reagent or etch
by-product. Figure 1a shows the four limiting cases of the combination of
these two properties. Using quantum chemical and machine learning
methods to predict the properties, such reactivity-volatility maps can be
plotted quickly for a wide range of ligands and metal-containing substrates.
We validate our results on the chloro ligand (Figure 1b), thd, RCp and NR2
against area-selective experiments, including those using HCl as etchant [1],
ruthenocene and ferrocene [2] as metal sources and β-diketonates as
inhibitors [3]. While approximate, this approach provides a starting point
for designing and understanding atomic-level processes that are areaselective with respect to a wide variety of substrates.
[1]

M.F.J.

Vos

et

al.,

Chem.

Mater.

31,

3878

Powder diffraction (PXRD) studies were also conducted to investigate the
phase transformation of crystalline ZrO2 powder at 250 oC. ZrO2 powder
was used as a model system since the chemical properties of HfO 2 and ZrO2
are very similar. PXRD analysis of as-received ZrO2 powder showed
crystallographic planes of mostly m-phase with some cubic (c-phase) and tphase. As expected, the etching of ZrO2 powder resulted in a mass loss.
PXRD also observed the loss of c- and t-phases and an increase in grain size
of m-phase crystallites. The results for the HZO films and ZrO2 powder are
similar. There are crystal phase transformations that occur with loss of oand t-phases and growth of m-phase during thermal ALE.

(2019).

[2] H. Nadhom et al., J. Phys. Chem. Lett. 12, 4130 (2021).
[3]

A.

Mameli

et

al.,

ACS

Nano

11,

9303

(2017).

[1] J. A. Murdzek and S. M. George, J. Vac. Sci. Technol. A 38, 022608 (2020)
11:40am AP+PS+TF-MoM-11 Novel Conversion Half-Cycle for Thermal ALD
of High-Density Hfo2 and Its Use in HfO2/Al2O3 Nanolaminate Dielectric
Barriers, Dane Lindblad, Forge Nano
Hafnium dioxide, HfO2, is an attractive material for use as a dielectric
barrier in high-power SiC and GaN electronics, both MOSFET and HEMT,
due to its high dielectric constant and thermal stability. Current techniques
for depositing HfO2 by thermal atomic layer deposition (ALD) tend to
produce low density and performing films. While plasma enhanced ALD
(PEALD) is employed to improve the performance, the high field and fast
switching requirements of the device can make the barriers insufficient. In
addition, not all applications can accommodate plasma. As such, a novel
conversion process, referred to as the “CRISP” process, for the deposition
of HfO2 via thermal ALD has been explored. Utilizing the tool’s unique
ability to introduce a small amount of non-metal catalyst during the
conversion half-cycle, the CRISP process employs surface catalysis to
increase growth per cycle, improve stoichiometry, increase density, and
modify crystal morphology compared to HfO2 films grown with
conventional conversion methods, O3, as shown in Figure 1 and Table 1
below. A comparison of the HfO2 films grown using the CRISP process and
the conventional O3 process, both deposited at 250°C, will be presented.
Furthermore, due to the layer-by-layer growth of ALD, this deposition
technique lends itself well to the fabrication of nanolaminate materials.
Specifically, HfO2/Al2O3 laminate stacks can be precisely manufactured to
alter the bulk material properties and curate device performance, allowing
one to choose improvements in leakage current or dielectric breakdown in
the nanolaminate film. An initial investigation into the performance of
various HfO2/Al2O3 laminate stacks is presented, and this work, coupled
with higher quality HfO2 films, gives insight into the use of these materials
for the next generation of high-power electronic devices.

11:00am AP+PS+TF-MoM-9 Etching of Silicon Nitride Using Vapor-Phase
HF Exposures at Various Temperatures: Role of Ammonium
Hexafluorosilicate Salt, Vahid Ghodsi, S. George, University of Colorado
Boulder
The etching of silicon nitride (SiNx) was explored using vapor-phase HF
exposures at various temperatures. The investigations were performed
using in situ quadrupole mass spectrometry (QMS) and ex situ attenuated
total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to
detect the volatile and non-volatile etch products, respectively. These QMS
and ATR-FTIR studies provide valuable understanding of the SiNx atomic
layer etching (ALE) process employing hydrofluorocarbon plasma to form
(NH4)2SiF6 salt at low temperatures and then thermal annealing at higher
temperatures to desorb the salt [N. Miyoshi et al., Jpn. J. Appl. Phys. 56,
06HB01 (2017)].
At low temperatures, T≤60oC, QMS detected the evolution of SiF4 from HF
exposure at 0.5 Torr on SiNx. SiF4 formed concurrently with the formation of
a (NH4)2SiF6 salt layer on the SiNx surface according to: Si3N4 + 16HF(g) —>
2(NH4)2SiF6 + SiF4(g). To verify the presence of the salt, the temperature
could be ramped up to 200oC in the absence of HF exposure. During this
temperature ramp, QMS detected SiF4 at higher temperatures T≥80oC
corresponding to the thermal decomposition of the (NH4)2SiF6 salt
according to: (NH4)2SiF6 —> 2NH3(g) + 2HF(g) + SiF4(g).
When the HF exposure was performed at higher temperatures T≥120oC,
SiF4 was again observed as an etch product. However, no secondary rise of
SiF4 was detected by QMS during the temperature ramp to 200oC in the
absence of HF exposure. This behavior indicated that the (NH4)2SiF6 salt did
not form on the surface at temperatures T≥120oC. The spontaneous etching
of SiNx with no salt on the SiNx surface is possible at these higher
Monday Morning, November 6, 2023

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Monday Morning, November 6, 2023
Biomaterial Interfaces Division
Room B117-119 - Session BI1+PS-MoM

the material-bacteria interactions beyond “kill or repel” towards signaling
and control.

Microbes and Fouling at Surfaces

9:40am BI1+PS-MoM-5 Using Flow-Cells to Culture Microbial Biofilms for
Improved Secondary Ion Mass Spectral Imaging, Yuchen Zhang, Oak Ridge
National Laboratory, USA; X. Yu, Oak Ridge National Laboratory
Bacterial biofilms are a main player in organic processing in the
environment. Therefore, characterization and understanding of the biofilm
interactions with groundwater and soil components is important in
deepening our knowledge in the biosphere and rhizosphere. We present
two approaches to prepare the bacterial biofilms suitable for time-of-flight
secondary ion mass spectrometry (ToF-SIMS). Shewanella MR-1 was used
as the model bacteria biofilm due to their known traits in subsurface,
surface, and soil microbiology. A mixture of silica, alumina, and iron oxide
was used as the model soil system. In the static culture, the bacteria were
inoculated in a multi-well cell culture dish at their log phase. Then minerals
were added to the culturing well. The mixture of the bacteria biofilms and
minerals were scratched off carefully and deposited onto the clean silicon
(Si) wafers before ToF-SIMS analysis. Second, we used a microfluidic cell to
culture biofilms. We made a modification of the system for analysis at the
liquid vacuum interface (SALVI) microfluidics for biofilm attachment in the
growth and detection chamber. The mineral components were mixed to the
growth media at a ratio of 1:1 by volume as nutrients to support the
biofilm’s growth. During static culturing, a series of Si wafers were used to
capture the temporal progression of the biofilms and the soil components
over days. In dynamic cultures, effluents were collected onto clean Si
substrates. The time intervals were chosen based on the growth curve of
the strain. Distinctive fatty acids peaks of Shewanella biofilms, such as
myristic acid (m/z− 227, C14H27O2−), palmitic acid (m/z− 255, C16H31O2−), and
arachidic acid (m/z− 311, C20H39O2−), and the biomarker riboflavin peak
(m/z− 241, C12H9N4O2−) are observed in the dynamic results. In contrast, the
static results do not provide as much information. This finding indicates
that static culture is not optimal for studying biofilms using ToF-SIMS. Our
results demonstrate that sample preparation is quite critical in
microanalysis of bacteria biofilms, specifically in surface analysis like ToFSIMS. The microfluidic growth chamber is more flexible in microbial culture
and media tuning, both are important in simulating a variety of conditions
to understand microbes and soil interactions at the microscale. Additionally,
characteristic signals of biofilms are not buried under the mineral
components in the dynamic setup, which is imperative in understanding the
role of biofilms in soil aggregation and bioremediation occurring at the
microbial interface.

Moderators: Kenan Fears, U.S. Naval Research Laboratory, Sally M.
McArthur, Deakin University, Australia
8:20am BI1+PS-MoM-1 Amphiphilic Coatings for Marine Low-Fouling
Applications, Axel Rosenhahn, Ruhr University Bochum, Germany INVITED
Manmade materials in contact with ocean water become rapidly colonized
by living matter like bacteria, diatoms, barnacles, or mussels. Increased fuel
consumption, failure of devices, and substantial maintenance costs are
among the penalties associated with marine biofouling. As the historical
paradigm to combat fouling by biocide releasing coatings is increasingly
challenged by legal restrictions, environmentally benign low-fouling
materials for marine applications are intensively explored [1]. While several
hydrophilic and hydrophobic materials show promising properties, their
combination into amphiphilic coatings unites the best of the two worlds [2].
As hydrophilic compound, zwitterionic materials with different molecular
architectures were developed and their structure-function relationship
against different fouling organisms have been studied [3]. Amphiphilic
coatings based on zwitterionic polymers have been designed and their antipolyelectrolyte properties have been characterized by several methods
including AFM and SPR. Their antifouling properties against a range of
marine fouling species and in short term field exposures have been
assessed and the results will be discussed under consideration of the
interaction of the organic coatings with inorganic particulate matter in the
ocean [4,5,6]. Based on the obtained data, design criteria for optimized
zwitterionic building blocks for fouling-release technologies will be
discussed.
[1] M. Callow, J. Callow, Nature Communications 2011, 2, 244
[2] S. Krishnan, C. Weiman, C. Ober, J. Materials Chemistry 2008, 18, 3405
[3] A. Laschewsky, A. Rosenhahn, Langmuir 2018, 35, 1056
[4] F. Koschitzki, R. Wanka, L. Sobota, J. Koc, H. Gardner, K.Z. Hunsucker,
G.W. Swain, A. Rosenhahn, ACS Applied Materials & Interfaces 2020, 12(30),
134148
[5] J. Koc, E. Schönemann, R. Wanka, N. Aldred, A.S. Clare, H. Gardner, G.W.
Swain, K. Hunsucker, A. Laschewsky, A. Rosenhahn, Biofouling 2020, 36(6),
646
[6] L. Schardt, A.M. Guajardo, J. Koc, J.L. Clarke, J.A. Finlay, A.S. Clare, H.
Gardner, G.W. Swain, K. Hunsucker, A. Laschewsky, A. Rosenhahn
Macromolecular Rapid Communications 2021, 43(12), 2100589

10:00am BI1+PS-MoM-6 Role of Microbial Biofilms in the Settlement of
Macrofoulers on Antifouling Marine Coatings, Sara Tuck, M. Kardish, US
Naval Research Laboratory; B. Orihuela, Duke University; G. Vora, US Naval
Research Laboratory; D. Rittschof, K. Franz, Duke University; K. Fears, US
Naval Research Laboratory
Accumulation of biofouling on submerged surfaces is a foundational
problem for maritime transport and human health. Biofouling build-up
increases the drag coefficient, fuel consumption, exhaust emissions, and
operational costs. Traditionally, biofouling is inhibited by the application of
antifouling coatings, the most popular of which, contain copper. Copperbased antifouling coatings can contain up to ~75% CuO, by weight, in
attempt to release sufficient levels of copper to deter the settlement of
fouling organisms. Despite these high loadings, the efficacy of these
antifouling coatings has been declining with the emergence and spread of
copper tolerant species. Microbial communities resistant to copper have
been found to form mature biofilms on these coatings, which could be
altering the interfacial properties to create more favorable conditions for
the settlement of a broader biofouling community. To gain an
understanding of the mechanisms responsible for the loss in antifouling
performance, coated and uncoated polyvinyl chloride panels were
submerged at estuarine and marine field test sites and microbial
communities were harvested. Collected biofouling communities were
cultured and individual species were collected and identified. Copper
tolerance was assessed by re-exposing cells to copper-containing coatings
and traditional antimicrobial assays to determine susceptibility to an array
of biocides. Finally, resistant biofilms were formed on marine coatings to
assess the effect of their presence on the settlement of acorn barnacle
larvae.

9:00am BI1+PS-MoM-3 Bio-Informed Interface Design and Synthesis to
Manipulate Microbial Behavior, Rong Yang, Cornell University
INVITED
Biofilm is often considered detrimental, which needs to be minimized as it
can cause infections and fouling in healthcare, food and water
manufacturing, and underwater civil and military activities. Nevertheless,
we also believe such naturally occurring biofilm can be desirable, upon
appropriate programming via precise control over the surface they inhabit,
as building blocks for self-actuated and self-repairing “living” coatings. To
gain insight into the biointerface, research in the past two decades has
unraveled the fundamental thermodynamics and hydrodynamics that have
guided the design of numerous antifouling/antimicrobial surfaces.
However, the biological effects of insoluble materials remain elusive.
Recent advances in vacuum-based synthesis have enabled well-defined
material properties at length scales relevant to microbes' biochemical and
biophysical activities, enabling a bio-informed materials design approach.
Motivated by the unmet needs for antifouling materials and living
materials, our recent research has advanced our current understanding of
the biointerface in three critical ways: (i) leveraging dynamic surface chain
reorientation to achieve antifouling at the air-liquid-solid interface, the
importance of which has been overlooked in past research; (ii) recognizing
bacteria to be complex microorganisms with dynamic structure and
metabolism and sophisticated chemical communication systems and
leveraging the recent breakthroughs in microbiology to guide the design of
bio-active polymer coatings; (iii) enabling living materials by performing
polymerization directly on living organisms, which overcomes the limited
tunability of the native microbial extracellular scaffolds and preserves the
function and viability of coated organisms by avoiding harmful synthesis
conditions. We seek to underscore the importance of understanding
detailed microbe-material interactions and provide an outlook on extending
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Monday Morning, November 6, 2023
compared to radical flux formed by plasma reaction in vapor phase.
Furthermore, we confirmed that the phosphorous-containing gas acts as an
effective catalyst in the HF reaction. The phosphorous-containing gas
stabilizes the HF or etchant physisorption on the SiO2 film, which provides
an etch rate enhancement at cryogenic temperature. In this conference, we
will present a detailed surface reaction model.

Plasma Science and Technology Division
Room A106 - Session PS+TF-MoM
Plasma Processing for Advanced Emerging Memory
Technologies
Moderators: Harutyun Melikyan, Micron Technology, Jeffrey Shearer, TEL
8:20am PS+TF-MoM-1 IBE Patterning and Characterization of High Density
STT-MRAM at Pitch 50nm and MTJ CD 20nm, Romuald Blanc, L. Souriau, K.
Wostyn, S. Couet, F. Lazzarino, IMEC, Belgium
Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) is a
promising non-volatile memory technology that offers high-density storage,
low power consumption, and fast read/write operations. One potential
application of STT-MRAM is as a last level cache (LLC) in computer systems,
since it can offer higher performance, lower power consumption, and
higher scaling potential than traditional SRAM. However, the patterning of
STT-MRAM with Ion Beam Etching (IBE) at CD 20nm and pitch 50nm
presents several challenges such as high aspect ratio, damaged magnetictunneling junction (MTJ) and sidewall shorts[1,2]. IBE relies on physical ion
sputtering which does not allow high selectivity to the hard mask, therefore
the choice of the hard mask stack is crucial to avoid excessively high aspect
ratio[3]. In this study, we use a hybrid hard mask composed of high-density
diamond-like carbon (DLC) to increase etch selectivity and TiN which
becomes
the
STT-RAM
top
electrode.

Applying this innovative process to HAR etching enables a higher etch rate,
higher selectivity, and higher aspect ratio etching capability. This novel
process will enable the manufacturing of next-generation 3D NAND flash
memory
devices.
[1] K. Ishikawa, et al., Jpn. J. Appl. Phys. Vol. 57, No. 6S2, 06JA01, (2018).
[2] T. Ohiwa, et al., Jpn. J. Appl. Phys. Vol. 31, p.405, (1992).
[3]

R.

Dussart,

et

al.,

J.

Phys.

D:

47123001,

(2014).

9:00am PS+TF-MoM-3 Plasma Etching Processes Challenges in Emerging
Non-Volatile Memories, C. Boixaderas, T. Magis, C. Socquet, A. Roman, B.
Martin, CEA-LETI, France; B. Fontaine, P. Gouraud, STMicroelectronics,
France;
J. Dubois,
STMicrolectronics,
France;
N.
Posseme,
STMicroelectronics, France; L. Grenouillet, C. Jahan, G. Navarro, G.
Bourgeois, M. Cyrille, Thierry Chevolleau, CEA-LETI, France
INVITED
Since the appearance of flash memory in 1980s, the non-volatile memory
(NVM) market is in constant evolution. Nowadays the random access
memory (RAM) market is divided into two categories: standalone memories
and embedded memories that are integrated into the core CMOS.Since the
2010s, new non-volatile embedded memories are emerging to achieve
specific performances in terms of storage, speed, endurance and retention.
Such advanced memories are based on resistive (RRAM), material phase
change (PCRAM), magnetic (MRAM) and ferroelectric (FeRAM) properties.
An overview of the main advanced memory technologies will be presented
(operation principles, materials and investigated multilayers stacks).

In this talk, we present the magnetic and electrical results obtained for STTMRAM at pitch 50nm using multiple process conditions of IBE main etch,
sidewall clean and post-oxidation. We demonstrate that the etch
parameters have a significant impact on device yield, with the best
condition leading to a wafer-level yield of 95% functional devices with
Tunnel Magnetoresistance (TMR) higher than 100%. On the best devices,
we measure a TMR of 170% which corresponds to the TMR value before
MTJ patterning. Finally, we report a switching current of 20µA with low
dependence on pulse width from 5 to 20ns which is consistent with a MTJ
CD of 20nm.
References:

We will address the patterning challenges that we are facing for the
integration of the advanced non-volatile memories. We will mainly focus on
the etching and stripping development in terms of scaling down, profile
control and plasma induced damages on features sidewalls. The etch
process optimization to control the profile and potential technological
solutions to minimize plasma damages will be also presented and discussed
in terms of plasma surface-interaction.

[1] Lei Wan et al, Fabrication and Individual Addressing of STT-MRAM Bit
Array With 50 nm Full Pitch, IEEE TRANSACTIONS ON MAGNETICS, VOL. 58,
NO. 5, MAY 2022
[2] Murat Pak et al, Orthogonal Array Pillar Process Development for High
Density 4F2 Memory Cells at 40nm Pitch and Beyond, SPIE Advanced
Lithography 2022, Paper 12051-45
[3] Kuniaki Sugiura et al, Ion Beam Etching Technology for High-Density Spin
Transfer Torque Magnetic Random Access Memory, Japanese Journal of
Applied Physics 48 (2009) 08HD02
8:40am PS+TF-MoM-2 Cryogenic Etching by Physisorption of Neutrals for
High-Aspect-Ratio Contact, Masahiko Yokoi, R. Suda, K. Tanaka, M.
Tomura, K. Matsushima, Y. Ohya, M. Honda, Y. Kihara, Tokyo Electron
Miyagi Limited, Japan
The most crucial challenge in High-Aspect-Ratio (HAR) dielectric etching is
supplying both ions and etchants [1] at the same rate to the etch front. If a
large amount of etchant supplied to bottom of the feature is consumed by
sufficient ion bombardment, higher aspect ratio etching with superior
etching rate can be achieved. Conventional HAR processes which rely on
the formation of radicals utilize fluorocarbon and hydrofluorocarbon gases
combined with high-applied bias power. However, the stable chemisorption
of radicals on feature sidewalls decreases the radical flux at the etch front,
which results in a lack of radical supply and a drastic etch rate attenuation
in the high aspect region. A technological breakthrough has long been
required to solve this problem.

9:40am PS+TF-MoM-5 Principle and Application of Etching Lag Mitigation
in High Aspect Ratio Contact Process, Kyoungsoo Chung, H. Kim, S. Park, J.
Min, K. Yoon, B. Kuh, Samsung Electronics, Republic of Korea
High Aspect Ratio Contact (HARC) etching is associated with various
defects, such as random bending, global tilting, hole distortion, and vertical
CD reduction. Depth loading, in particular, is significant and is intricately
linked to all these issues. The implementation of a cryogenic process with
specific gases has been verified to increase the initial etch rate by nearly
threefold compared to the high-temperature process. Furthermore, this
procedure has also amplified the patterned aspect ratio where etching lag
is observable, in addition to increasing the etch rate. We engage in a
comprehensive review and investigation of the mechanisms contributing to
the improvement of etching lag. Firstly, it is essential to attain a substantial
physisorption amount of neutrals, including radicals, while concurrently
delivering highly directional ion energy to activate the surface. Additionally,
the transport of neutrals within the hole is crucial for the etchant to be
effectively adsorbed up to the etch front. We argue that elements such as a
cryogenic environment, low-molecular-weight etchants, compounds that
facilitate surface reactions, and a distribution of highly energetic ions are
vital for overcoming depth loading. Ultimately, we propose advanced
strategies for next-generation HARC etching, based on the lag reduction
mechanisms.

In this work, we focus on neutral physisorption at cryogenic temperatures.
There have been several reports on plasma etching in the cryogenic
temperature regime [2, 3], but the mechanism has not yet been well
understood nor implemented for HAR dielectric etching. We have evaluated
a novel etchant in cryogenic temperature and discovered a synergy
between hydrogen fluoride (HF) as the etchant and HAR etching process.
The dielectric etch rate strongly correlates with the physisorption of the HF,
enhanced in the cryogenic temperature regime. The direct injection of HF
as the process gas yields higher partial pressure and increased flux

10:00am PS+TF-MoM-6 Etching Selectivities of SiO2 and SiN Against a-C
Films Using CF4/H2 with a Pseudo-Wet Plasma Etching Mechanism, Yusuke
Imai, S. Hsiao, M. Sekine, T. Tsutsumi, K. Ishikawa, Nagoya University, Japan;
M. Iwata, M. Tamura, Tokyo Electron Ltd., Japan; Y. Iijima, tokyo Electron,
Japan; T. Gohira, K. Matsushima, Y. Ohya, Tokyo Electron Ltd., Japan; M.
Hori, Nagoya University, Japan
With the advancement of cloud computing and AI technology, there is a
growing demand for high-speed processing of large amounts of data and

Monday Morning, November 6, 2023

4

8:20 AM

Monday Morning, November 6, 2023
2T. Panagopoulos, T. Lill, J. Vac. Sci. Technol. A 41, 033006 (2023)

high-capacity storage. To manufacture 3D NAND, it is necessary to etch the
layer structure where SiO2 and SiN layers are alternately stacked, utilizing
the amorphous C layer as a mask. A continuous increase of interest using
cryogenic etching for high aspect ratio structure can be observed. Recently,
etch selectivities among SiO2, SiN and poly-Si with CHF3/Ar and an ultrahigh speed etch process at cryogenic temperature for 3D NAND have also
been reported.[1,2] However, the cryogenic etching on variation of
selectivities among SiN and SiO2 over a-C have not been discussed yet. In
this study, the etching selectivity among SiO2, SiN and a-C was investigated
by varying the hydrogen content (20 to 60 %) in CF4/H2 plasma at substrate
temperature (Ts) of -60 and 20 °C. A capacitively coupled plasma reactor
was used in the experiments, The total flow rate of gas mixture of CF4 and
H2 was set at 150 sccm and the pressure during process was fixed at 4 Pa.
As shown in the supplementary file, at Ts = 20 °C, the both ER of SiO2 and
SiN films decreased with increasing the hydrogen content, which is
consistent with previous studies. Contrarily, for Ts = -60 °C the ER of SiO2
reached its maximum at around 30-40% hydrogen additives, while the ER
value of SiN decreased by nearly half compared to that at 20 °C. As a
consequence, the etching selectivity of SiO2/SiN at 20 °C was found to be
less than 1 for all hydrogen contents, indicating that SiN was preferentially
etched. For Ts = -60 °C it exhibited values greater than unity with the same
process. This demonstrates that surface reactions and etching mechanism
were changed when substrate was cooled. On the other hand, for a-C films
increasing the hydrogen content in the CF4/H2 plasma results in a transition
from etching to deposition. The transition point was found to be H2 additive
of around 50% at 20 °C and around 30% at -60 °C, indicating a wider
process window with infinite etching selectivities of SiO2/SiN over a-C mask
at low Ts. The etching characteristics at low temperature is correlated to the
surface reactions between the films and neutral HF, based on the results of
HF molecular density during plasma discharge using FTIR. A pseudo-wet
etching mechanism was proposed to explain the obtained results. The bias
power was also varied to investigate the etching behavior further at
cryogenic
temperature.

11:20am PS+TF-MoM-10 High Selectivity Etching via Pulsed Selective
Deposition, André Amend, M. Yakushiji, K. Kuwahara, Hitachi High-Tech,
Japan
Semiconductor device structures are shrinking and increasing in verticality,
thus requiring novel plasma dry-etching processes to manufacture high
Aspect-Ratio (AR) profiles on nanometer scales. Fabrication of such devices
requires hard masks (HM) with high etching resistance that have small
Critical Dimension (CD) and large height, corresponding to the needs of the
device dimensions. As a result, creating the HMs themselves becomes more
expensive and requires costly multi-layer processes to deal with the
relatively low etching resistance of the C-rich photomask, which transfers
the device pattern via photolithography. HM fabrication could be
significantly simplified by an etching process that selectively etches hard
materials, such as SiO2, even under soft C-rich masks.
Here, a Phase Mask Reconstruction Process (P-MRP) is introduced, that
drastically increases the SiO2 etching selectivity and is compatible with
small CD structures. P-MRP allows control of the C-based mask shape while
etching SiO2 via a time-modulated bias voltage, that tunes separate
selective mask deposition and sample etching phases with a frequency up
to above 1000 Hz. While a high voltage is applied to the sample, highenergy ions promote etching, whereas deposition occurs during the low
voltage phase. Preferential deposition on the mask is achieved via chemical
selectivity and radical shading due to the mask AR.
By precise control of the time-modulated sample bias voltage to adjust
etching and deposition phases, the etching selectivity, as well as the mask
shape and stability, can be controlled, which is critical to processing small
patterns. To achieve high selectivity, the net etching rate on top of the mask
can be decreased by reducing average ion energy, while controlling the
mask side-deposition rate via the maximum ion energy and duration of the
deposition phase. Since P-MRP rapidly alternates mask etching and mask
passivation (during the deposition phases) low pattern roughness is
achieved as well. For Line/Space and Hole patterns with CD 16-26 nm,
etching selectivity as high as 10 was demonstrated while etching a depth of
up to 200 nm of SiO2, with AR of up to about 10.

[1] R. Dussart et.al., J. Appl. Phys. 133, 113306 (2023).
[2] Y. Kihara etal., VLSI symposium T3-2 (2023)

This result indicates that P-MRP could be used to simplify and accelerate
HM fabrication. Furthermore, since deposition selectivity is also achieved
through AR shading, it can be adopted to process materials other than Cmasks and SiO2 etching targets, as well.

10:40am PS+TF-MoM-8 Enhancing Etching Processes at Lower Wafer
Temperatures: New Insights into Chemical and Physical Mechanisms,
Thorsten Lill, Clarycon Nanotechnology Research, Inc.
INVITED
Lower temperatures hold significant importance for etching advanced
memory devices. In this presentation, we provide a comprehensive
overview of the chemical and physical processes involved in etching at
lower wafer temperatures. Traditionally, plasma etching techniques heavily
rely on the generation of radicals that readily chemisorb onto the surface.
However, at low temperatures, molecules tend to adsorb through
physisorption, lacking the necessary energy to overcome the energy barrier
required for a chemical reaction. However, the concentration of neutrals in
typical plasma used for semiconductor manufacturing is notably higher (by
one to two orders of magnitude) than that of radicals. At lower
temperatures, the physisorption of neutrals becomes significant, increasing
their concentration on the surface and contributing to the etching process
once chemically activated by energy from the plasma 1.
Etching of high aspect ratio structures utilizes ions and neutral reactive
species that must effectively traverse through high aspect ratio features to
reach the etch front. We present computational results on neutral transport
within such features, exploring the influence of aspect ratio, profile shape,
and surface processes including adsorption, desorption, and diffusion of
neutral species. Our findings indicate a substantial increase in the steadystate transmission probability with the introduction of surface diffusion 2.
While spontaneous and collision-induced desorption of adsorbed neutrals
alone do not alter the steady-state transmission probability, they do impact
the time required to reach it. However, in the presence of surface diffusion,
spontaneous desorption enhances the transmission probability, whereas
desorption resulting from collisions with co-flowing nonreactive gas
reduces it. These results unveil the potential for enhancing neutral
transport at low surface temperatures, facilitated by physisorption and
surface diffusion mechanisms.
By shedding light on the intricate interplay between chemical and physical
phenomena during etching processes at lower temperatures, this
presentation provides insights into the optimization of etching techniques
for advanced memory devices.
1T. Lill, I. L. Berry, M. Shen, J. Hoang, A. Fischer, T. Panagopoulos, J. P. Chang,

and V. Vahedi, J. Vac. Sci. Technol. A 41, 023005 (2023).
Monday Morning, November 6, 2023

5

8:20 AM

Monday Afternoon, November 6, 2023
Finally, using a SiO2-patterned Ru structure, a highly anisotropic etch profile
was obtained:the nitrogen plasma exposure forms RuN on the exposed
surface and sidewalls. Hydrogen plasma with an applied bias anisotropically
reduces RuN. Then, an oxygen plasma selectively etches Ru while leaving
RuN on the sidewall intact. By creating the anisotropy in the previous steps,
a gentler O2 plasma exposure can be used, which results in anetch rate of 4
nm per cycle and a selectivity of Ru vs. SiO2/Si3N4 of 15, compared to
conventional O2 + Cl2 RIE plasma etching in literature that reports etch rates
in excess of 40 nm per minutes and selectivities around 6.

Atomic Scale Processing Mini-Symposium
Room A107-109 - Session AP+PS-MoA
Plasma Enhanced Atomic Layer Etching
Moderators: Robert Bruce, IBM Research, T. J. Watson Research Center,
Scott Walton, Naval Research Laboratory
1:40pm AP+PS-MoA-1 Chemical Contrast by Nitridation for Improving
Atomic Layer Etching Selectivity in Interconnect and EUV Absorber
Applications, Taylor G. Smith1, University of California, Los Angeles; J. de
Marneffe, V. Philipsen, IMEC, Belgium; J. Chang, University of California, Los
Angeles
As extreme ultraviolet lithography (EUVL) dominates the fabrication of
future integrated circuits, advanced EUV photomask absorber materials
such as Ni and Ni-Al alloys are needed. As Ru emerges as the capping layer
for EUV absorber and a potential supplementary material for backend
interconnects, the fact that Ru etches rapidly in oxygen requires a different
approach (e.g., nitridation) to create the needed chemical contrast for
atomic layer etching. In this work, we present a plasma-thermal atomic
layer etching (ALE) approach to etch Ni that relies on nitriding the metal
surface using nitrogen plasma, then removing the surface metal nitride
with formic acid (FA) vapor. Previous work relied on oxygen plasma as the
modification step to form a surface NiO 1. However, oxygen plasma is
known to etch Ru, the standard capping material in EUVL masks. Here we
explore a nitrogen plasma-based ALE process to increase the selectivity of
the Ni etch to the Ru capping layer. An additional motivation for exploring
nitridation-based ALE is that metal nitrides, unlike metal oxides, do not
form spontaneously in air, making it possible to ascertain that all surface
metal nitride formation must be a result of the plasma processing.

2:20pm AP+PS-MoA-3 Mechanisms and Benefits of Cryogenic Processes in
Silicon Based Material Atomic Layer Etching, Remi Dussart, R. Ettouri, J.
Nos, G. Antoun, P. Lefaucheux, T. Tillocher, GREMI CNRS/Université
d'Orléans, France
INVITED
Since its introduction in 1988, plasma cryogenic processing has been
applied to deep etching of silicon for microelectronics and MEMS devices.
High aspect ratio structures can be obtained at very low temperature
(typically -100°C) of the substrate in SF6/O2 plasma. The mechanism is
based on a passivation SiOxFy layer, which forms at low temperature only.
The formation of this passivation layer has been characterized by in-situ
diagnostics such as ellipsometry, mass spectrometry and XPS. SiF 4
molecules which correspond to the main by products of silicon etching by
fluorine can also participate in the passivation layer formation and reinforce
it. The composition of the SiOxFy layer formed in SiF4/O2 plasma strongly
depends on temperature. In particular, the fluorine content significantly
increases below a temperature threshold between -60°C and -100°C.
However, this threshold is reached at higher temperature if we process a
Si3N4 surface instead of a Si surface.
We can take advantage from these interesting properties at cryogenic
temperature to develop new cryo-ALE processes. In this presentation, two
different types of cryo-ALE will be introduced. The first one is based on the
physisorption of C4F8 molecules without plasma followed by an argon
plasma step to etch SiO2 at the atomic scale. The second one consists in
alternating SiF4/O2 plasma interacting with a cooled substrate with argon
plasma. During the SiF4/O2 plasma, the passivation layer composition can
be tuned depending on temperature and substrate material surface. In
particular, we will show that a very good etch selectivity between Si3N4 and
Si can be obtained at a temperature of -65°C for which a very low etch rate
is obtained for Si while Si3N4 surface is etched at a higher rate. This property
can be explained by the chemical analysis of the two surfaces at low
temperature. Finally, some experiments of cryoetching in CHF3/Ar plasma
will be presented showing some interesting trends at low temperature on
different
silicon
based
materials.

The composition of the metal nitride layer is measured by X-ray
photoelectron spectroscopy (XPS) and is controlled by varying the plasma
power, pressure, and exposure time. Ni films nitridized in a 500 W, 35 mTorr
nitrogen plasma for 5 min have a surface composition of Ni2.8N, close to the
stoichiometric Ni3N composition. XPS also confirmed the removal of the
surface NixN after exposure to FA vapor at 80°C as manifested by the
disappearance of the metal nitride N 1s peak at 397.6 eV. The thickness of
the Ni films as a function of ALE cycles is measured by scanning electron
microscopy (SEM) and spectroscopic ellipsometry (SE), with the etch rate
measured by SE being 0.49 ± 0.20 nm/cycle. We also determine the
selectivity of the plasma nitridation ALE process to common hardmasks and
to Ru. Finally, we extend this plasma nitridation ALE chemistry to Ni-Al
alloys, determining both the etch rate and the stoichiometry changes in the
film as a function of ALE cycles.
1. X. Sang and J. P. Chang, J. Vac. Sci. Technol. A 38 (4), 042603 (2020).

3:00pm AP+PS-MoA-5 Damage Formation Analyses of Steady PlasmaEnhanced Atomic Layer Etching for Silicon Nitride with Molecular
Dynamics Simulations, Jomar U. Tercero2, Osaka University, Japan; A.
Hirata, Sony Semiconductor Solutions Corporation, Japan; M. Isobe, K.
Karahashi, Osaka University, Japan; M. Fukasawa, Sony Semiconductor
Solutions Corporation, Japan; S. Hamaguchi, Osaka University, Japan
Molecular dynamics (MD) simulations were performed to study the etching
mechanisms and surface damage formations during the plasma-enhanced
atomic layer etching (PEALE) of silicon nitride (SiN). PEALE is a thin-layer
etching technique to achieve a uniform and precisely etched material
surface. The typical ALE process consists of alternating self-limiting
adsorption and desorption steps. In the adsorption step, the material is
exposed to reactive species, which modifies the surface layer. In contrast, in
the desorption step, the modified surface is bombarded with low-energy
inert ions, resulting in the removal of the modified layer. A recent report on
SiN PEALE processes with hydrofluorocarbon (HFC) radical adsorption and
Ar ion impacts has shown that C tends to accumulate on the surface, which
causes an etch stop [1]. Our simulations of an ideal PE-ALE system with
CH2F radical adsorption and Ar ion bombardment have revealed that the
remaining C atoms from the initial ALE cycle can trigger the C accumulation.
The surface damage was also observed due to the ion bombardment. Due
to the formation of a C layer, high-density Si-C bonds were found to remain
on the surface after several ALE cycles, causing further accumulation of C
atoms. Therefore, we introduced a short O2 plasma irradiation process after
the desorption step to help remove the problematic C atoms [2]. Our
simulations agree with the experimental observations that the additional
O2 plasma irradiation step can prevent the etching from stopping. The Si-C
bonds were minimized since O atoms reacted with the C atoms, forming CO

2:00pm AP+PS-MoA-2 Anisotropic and Selective Atomic Layer Etching of
Ruthenium, Owen Watkins, University of California at Los Angeles; H.
Simka, Samsung; J. Chang, University of California at Los Angeles
Ruthenium has been proposed as a replacement for copper in sub-10 nm
interconnects, where it has a lower resistivity and does not need as thick of
a diffusion or adhesion layer. Ruthenium is known to be etched aggressively
in an oxygen plasma by the formation of RuO4. A reactive ion etching
process using plasma with both O2 and Cl2 is a direct, high etch rate
method, but there is a need to achieve better control and selectivity in
order for Ru to be a viable interconnect material. In this work, a
thermodynamic approach was first taken to determine viable chemistries. It
confirmed that Ru and RuO2 react with atomic O spontaneously to form
RuO4, and with atomic N to form a metastable RuN layer.RuN reacts with
atomic O, but the reaction is less favorable, and can be reduced by H and H2
into metallic Ru. The thermodynamic assessment led to a novel three-step
process to control the etching of ruthenium where a nitrogen plasma forms
RuN on the surface of the ruthenium thin film, a hydrogen plasma reduces
some of the RuN, creating a surface layer of Ru, then an oxygen plasma
etches this topmost layer of Ru but is unable to etch into the
RuN.Experimental validation was first realized by exposing blanket Ru film
to the sequential process. Compared to a baseline of continuous O2 plasma
with equal conditions and total exposure time as the O2 plasma step, the
three-step process shows an increase in RMS surface roughness of 0.05
nm/cycle and a post-etching resistivity of 30 μΩ-cm, whereas continuous O2
plasma shows an increase of 0.2 nm/30s of exposure and a post-etching
resistivity of 280 μΩ-cm.

1 PSTD Coburn & Winters Student Award Finalist

Monday Afternoon, November 6, 2023

2 PSTD Coburn & Winters Student Award Finalist

6

1:40 PM

Monday Afternoon, November 6, 2023
and CO2 species. Regardless, Ar ions with sufficient incident energy are still
needed for the etching to proceed, which can cause damage to the etched
surface. To understand the effect of the energetic ions in the desorption
step, we also performed SiN PEALE with heavier inert gas ions such as Kr. It
has been observed that, while Kr ions have shallow penetration depths
than Ar ions and therefore cause less surface damage, Ar ions remove C
atoms from the surface more efficiently than Kr ions.
References
[1] A. Hirata, M. Fukasawa, K. Kugimiya, K. Nagaoka, K. Karahashi, S.
Hamaguchi, and H. Iwamoto, JVST A, 38, 062601 (2020).
[2] A. Hirata, M. Fukasawa, J.U. Tercero, K. Kugimiya, Y. Hagimoto, K.
Karahashi, S. Hamaguchi, and H. Iwamoto, JJAP (2022).
3:20pm AP+PS-MoA-6 Orientation Dependent Etching of Silicon: A
Computational Chemistry Study, Yuri Barsukov, O. Dwivedi, S. Jubin, J.
Vella, I. Kaganovich, Princeton University Plasma Physics Lab
Orientation dependent etching of silicon is a phenomenon, when etch rate
of silicon surface depends on the surface orientation. It was experimentally
established that Si(111) surface is slower etched than Si(100) and Si(110). In
this case the etch profile becomes anisotropic (without plasma and ions)
and the surface is textured with micro- and nano-scale pits. In other words,
anisotropy of the etching determines surface roughness. Plasma-less
atmospheric dry etching is one of the applications of this processing in
technology of black silicon production for photovoltaic solar cell
manufacturing, where F2 gas makes silicon surface rougher. On the other
hand, rough surface is unwanted during manufacturing of integrated
circuits, because it leads to degradation of device characteristics. Thus,
basic understanding of this phenomenon is needed to better control
surface structure during the etching.
We performed modeling of Si(100), Si(110) and Si(111) etching by F2
molecule combined with DFT (density functional theory), TST (transition
state theory) and MD (molecular dynamics) approaches like it was done in
[1,2]. The combination of DFT and TST enables us to calculate probabilities
of gas-surface reactions and perform kinetic modeling of the etching, while
under MD approach evolution of the surface at different temperatures at ns
time-scale is considered.
We assumed that F2 dissociative chemisorption leading to Si-Si bond
breaking is rate-determining step of whole etching process and reproduce
the experimental measurements that the barrier of F2 dissociation on
Si(111) is significantly higher than on Si(100) and Si(110). We established
that the value of the barrier is determined by the charge distribution on the
surface, and the charge distribution in turn is determined by the number of
F atoms incorporated into the surfaces.
Our modeling was validated and well reproduced experimental data such as
values of activation barrier and etch rate as a function of temperature.
Based on our mechanism of the etching we will perform similar modeling
aimed to design new etchants for Si etching to better control roughness and
surface texturing.
References:
1.
2.

S Jubin et al, Frontiers in Physics 10, (2022) DOI:
10.3389/fphy.2022.908694.
Y Barsukov et al, Nanotechnology 32, 475604 (2021) DOI:
10.1088/1361-6528/ac1c20.

4:20pm AP+PS-MoA-9 Process Drift of SiO2 Atomic Layer Etching in HFC
and FC/Ar Chemistries by Optical Spectroscopy and Surface Chemistry
Analysis, Antoine Ronco1, F. Boulard, N. Posseme, Univ. Grenoble Alpes,
CEA, Leti, France
Manufacturing new semiconductor devices requires atomic scale control of
etching processes in order to decrease their dimensions. Atomic Layer
Etching (ALE) allows such thin control of the processes [1][2]. One of the
challenges is tuning the durations of the deposition and activation steps to
obtain a process with a stable amount of material etched per cycle. If not
tuned correctly the fluorocarbon (FC) film can accumulate on the sample’s
surface causing a drift in the amount of material etched per cycle (EPC)[3].
In this paper, we investigate the use of Optical Emission Spectroscopy (OES)
to monitor the drift of a quasi-ALE process. Then, we study the impact of
the gas chemistry on the appearance of the drift. Finally, we optimize
contact hole etching and especially the landing on the etch stop layer.
1 PSTD Coburn & Winters Student Award Finalist

Monday Afternoon, November 6, 2023

The samples studied consist of 100 nm SiO2 on Si blanket wafers. The
experiments are carried out in a 300 mm capacitively coupled plasma
reactor. The wafers are etched using C4F8, C4F6, or CH3F/Ar based chemistry
in a two steps approach, namely deposition and activation. The reactor is
cleaned using an O2 plasma before and after etching each wafer.
We observe a decrease in EPC of a quasi-ALE process when increasing the
number of cycles. The examination of the evolution of the intensities of OES
spectra through deposition and activation steps reveals that the line at 251
nm, which could correspond to CF/CF2 radicals, is an indicator of the drift of
the process [4]. The decreasing intensity observed during the activation
step suggests the accumulation of a carbon film on the sample’s surface.
This is confirmed through XPS analysis showing an increase in carbon
content on the sample’s surface when increasing the number of cycles. The
correlation between XPS analysis, OES observation, and EPC evolution with
the number of cycle shows that the EPC drift can be monitored in real time
using OES.
We use this method to study the impact of gas chemistry on the drift of our
etching process for SiO2 and SiN etching. The effect of the FC gas used on
the selectivity and uniformity of our process is also reported.
Finally, the impact of gas chemistry and number of cycles on pattern
etching is characterized using a Scanning Electron Microscope (SEM).
Particular interest is paid to the conformality of the FC film deposited on
patterns and etching at the bottom of the contact.
[1] K. J. Kanarik et al., JVSTA 33, no 2, 020802, 2015
[2] G. S. Oehrlein, et al., ECS J. Solid State Sci. Technol. 4, no 6, N5041–
N5053, 2015
[3] C. M. Huard, et al., JVSTA 36, no 6, 06B101, 2018
[4] R. W. B. Pearse, et al., The identification of molecular spectra, 4th ed.
London: Chapman & Hall, 1976.
4:40pm AP+PS-MoA-10 Atomic Layer Etching of Superconducting Titanium
Nitride Thin Films Using Molecular Oxygen and H2/SF6 Plasma, Azmain
Hossain, A. Minnich, California Institute of Technology
Microwave loss in superconducting titanium nitride (TiN) films is attributed
to two-level systems in various interfaces arising in part from oxidation and
microfabrication-induced damage. Atomic layer etching (ALE) is an
emerging subtractive fabrication method which is capable of etching with
Angstrom-scale etch depth control and potentially less damage. However,
while ALE processes for TiN have been reported, they either employ HF
vapor, incurring practical complications; or the etch rate lacks the desired
control. Further, the superconducting characteristics of the etched films
have not been characterized. Here, we report an isotropic plasma-thermal
TiN ALE process consisting of sequential exposures to molecular oxygen and
an SF6/H2 plasma. For certain ratios of SF6:H2 flow rates, we observe
selective etching of TiO2 over TiN, enabling self-limiting etching within a
cycle. Etch rates were measured to vary from 1.1 Å/cycle at 150 °C to 3.2
Å/cycle at 350 °C using ex-situ ellipsometry. We demonstrate that the
superconducting critical temperature of the etched film does not decrease
beyond that expected from the decrease in film thickness, highlighting the
low-damage nature of the process. The ALE-treated films were also studied
using XPS and AFM. These findings have relevance for applications of TiN in
microwave kinetic inductance detectors and superconducting qubits.
(arXiv:2307.02821)
5:00pm AP+PS-MoA-11 Quasi-Atomic Layer Etching of X-Cut MgO-Doped
Lithium Niobate Using Sequential Exposures of H2 and SF6 Plasma, Ivy
Chen, J. Solgaard, R. Sekine, A. Hossain, A. Ardizzi, D. Catherall, A. Marandi,
California Institute of Technology; F. Greer, Jet Propulsion Laboratory
(NASA/JPL), California Institute of Technology; A. Minnich, California
Institute of Technology
Lithium niobate (LiNbO3, LN) is an emerging platform for integrated
photonics. Recent demonstrations of record on-chip quantum states, >100
GHz electro-optic modulators with CMOS compatible voltages, and multioctave frequency combs with ~100 fJ pump pulse energies highlight the
potential of this platform to enable novel on-chip photonic functionalities.
However, thin-film lithium niobate (TFLN) devices suffer from large
scattering losses resulting from the surface roughness left by Ar+ milling,
the standard technique used for nanophotonic LN waveguide fabrication,
negatively impacting device performance. Atomic layer etching (ALE) can
potentially mitigate scattering losses due to its ability to smooth surfaces to
sub-nanometer length scales, but no ALE process has been reported for
TFLN. Here, we report an anisotropic quasi-ALE process for X-cut MgOdoped LN using sequential exposures of H2 and SF6 plasma. We observe
etch rates up to 2.1 nm/cycle with a synergy of ~97% and characterize the
7
1:40 PM

Monday Afternoon, November 6, 2023
etched surfaces using X-ray photoelectron spectroscopy, secondary ion
mass spectrometry, and atomic force microscopy. This process has the
potential to serve as a post-processing step to smooth patterned TFLN
surfaces which may both increase the performance of existing TFLN devices
and enable novel devices not attainable in other integrated photonic
platforms.

Plasma Science and Technology Division
Room A106 - Session PS+SE-MoA
Plasma Sources, Diagnostics, Sensors and Control
Moderators: Michael Gordon, University of California at Santa Barbara,
Yohei Ishii, Hitachi High Technologies America Inc.
1:40pm PS+SE-MoA-1 On the Influence of the Target Material on the
Discharge Properties of the High Power Impulse Magnetron Sputtering
Discharge, Jon Tomas Gudmundsson, K. Barynova, University of Iceland; M.
Rudolph, Leibniz Institute of Surface Engineering (IOM), Germany; J. Fischer,
Linköping University, Sweden; S. Suresh Babu, University of Iceland; M.
Raadu, N. Brenning, KTH Royal Institute of Technology, Sweden; D. Lundin,
Linköping University, Sweden
High power impulse magnetron sputtering (HiPIMS) operation results in
increased ionization of the sputtered species and lower deposition rate
than the dc magnetron sputtering discharge, when operated at the same
average power. We have applied the ionization region model (IRM) [1] to
model HiPIMS discharges in argon with a number of different targets [2,3],
to study various processes, such as working gas rarefaction and refill
processes, the electron heating mechanisms, ionization probability and
back-attraction of the sputtered species, and recycling mechanisms. The
HiPIMS discharge can contain a large fraction of ionized sputtered material
and often a significant fraction, of the ions involved in the sputter process
are ions of the target material. This also implies that a large fraction of the
ions of the sputtered species can be attracted back to the target and are
not deposited on the substrate to form a film or coating. Self-sputtering and
the self-sputter yield are therefore expected to play a significant role in
HiPIMS operation, and have a decisive impact on the film deposition rate,
at least for metal targets. We explore the relationship between the selfsputter yield and deposition rate as well as the ionization and back
attraction probabilities. The back-attraction probability appears to decrease
with increased self-sputter yield. The various contributions to working gas
rarefaction including electron impact ionization, kick-out by the sputtered
species, and diffusion, are evaluated and compared for the different target
materials, over a range of discharge current densities. For all cases the
working gas rarefaction is found to be significant, and to be caused by
several processes, and that their relative importance varies between
different target materials. In the case of a graphite target, electron impact
ionization is the dominating contributor to the working gas rarefaction, with
55 - 64 % contribution, while the kick-out, or sputter wind, has negligible
influence, whereas in the case of tungsten target, the kick-out dominates,
with 39 - 48 % contribution. The relative role of kick-out by the sputtered
species increases and the relative role of electron impact ionization
decreases
with
increased
mass
of
the
target
atoms.
[1] Huo et al., Journal of Physics D: Applied Physics 50, 354003 (2017)
[2] Gudmundsson et al., Surface and Coatings Technology 442, 128189
(2022).
[3] Babu et al., Plasma Sources Science and Technology 31, 065009 (2022)

2:00pm PS+SE-MoA-2 Numerical Analysis of Curling Probe Designing for
an Effective Electron Density Measurement in Plasma, Daisuke Ogawa, S.
Kato, H. Sugai, K. Nakamura, Chubu University, Japan
Electrons make a main contribution to generating reactive species in a lowtemperature plasma. Optical emission is often utilized to monitor plasma,
but it should be noted that the ultimate origin of the emission is due to
collisions with the electrons in the plasma. This means that electron
monitoring could be the primary information of the plasma. A curling probe
is one of the probes that enable an electron density measurement in the
plasma. The probe measures the density derived from a shift of the
fundamental resonant frequency that the probe holds. Therefore, the
probe measures the density even in an environment where the plasma
makes a dielectric film deposition. The probe utilizes a slot antenna to make
Monday Afternoon, November 6, 2023
8

the electromagnetic resonance, which is equipped on the top surface of the
probe. This antenna structure gives an advantage in directional electron
density measurement. This directionality is useful, particularly when the
probe desires to be embedded into a wall and/or an electrode. Recently, we
have also developed a technique with the curling probe that enables one to
make in-situ measurements of electron density in plasma and the film
thickness deposited on the probe surface. The technique requires two
different-sized curling probes, so we named it the double curling probe
method. This technique is potentially powerful in a plasma-processing
reactor with electron density monitoring. However, we noticed that the
technique requires further improvement in their measurement resolution;
the frequency shift is not always noticeable, especially when the deposited
film thickness is small. The frequency resolution depends on the quality
factor of an inverted peak in the reflectance spectrum. According to the
circuit theory, the factor depends on antenna configuration, such as the
antenna's resistance, inductance and capacitance. These parameters
depend on the antenna design, so we have researched how curling probe
design affects the factor with an electromagnetic wave simulator, CST
microwave studio. Our recent result showed that the factor depends on the
antenna material, the antenna length, and the antenna thickness. In
particular, the long antenna helps stabilize the factor even when increasing
electron density in plasma. In this presentation, we will show our recent
analysis to suggest what antenna design a curling probe ought to have to
improve electron density measurement with a curling probe.
2:20pm PS+SE-MoA-3 Annular Beam Confocal Laser-Induced Fluorescence
Diagnostic for Measurements of Ion Velocity Distribution Function in
Industrial Plasmas, Ivan Romadanov, Y. Raitses, Princeton Plasma Physics
Laboratory
Laser-Induced Fluorescence (LIF) is a powerful diagnostic tool for analyzing
ion velocity distribution functions (VDFs) in plasma [1]. However, the
requirement for two-sided access to plasma for beam injection and
fluorescence collection in conventional LIF configuration is not always
practical. Confocal LIF configurations, which are widely used in various
fields such as biology and medicine, have been developed for several
plasma diagnostic applications [2]. The primary advantage of confocal LIF
configurations is the coincidence of the laser beam injection and
fluorescence collection branches, enabling measurements in systems with
limited optical access or complex geometries. This study introduces a novel
variation of confocal LIF - Annular Beam Confocal Laser-Induced
Fluorescence (ABC-LIF) configuration [3]. The proposed LIF configuration
utilizes a structured Laguerre-Gaussian laser beam with an annular intensity
profile, generated by diffractive axicons. This approach facilitates LIF signal
collection along the main optical axis within the ring region while
controlling spatial resolution through laser beam parameters, such as
annulus thickness and beam diameter. Consequently, all enclosed
fluorescence light is collected, maximizing the signal-to-noise ratio (SNR).
This method achieves a spatial resolution of approximately 5 mm at a 300
mm focal distance, with the potential for 1 mm resolution, comparable to
conventional LIF. The ABC-LIF configuration benefits from a small depth of
field (DOF), typically achieved by Gaussian beams of large diameter, while
the Laguerre-Gaussian beam allows for maintaining spatial separation
between fluorescence and laser lights at comparable DOF values.
Additionally, the configuration circumvents issues with beam back
reflection. The ABC-LIF configuration was experimentally verified in
industrial DC plasma source measurements of argon ion VDFs. Comparisons
between confocal and conventional LIF revealed good agreement in
determining plasma parameters, such as ion temperature, flow velocities,
and ion density profiles. Applicable to various plasma processing
equipment and sources, including hollow cathodes, microplasmas, and
electric propulsion, the ABC-LIF configuration presents a promising
diagnostic tool for industrial plasmas.
References
[1] Bachet G et al 1998 Phys. Rev. Lett. 80 3260
[2] Thompson D et al 2017 Rev. Sci. Instrum. 88 103506
[3] I. Romadanov, Y. Raitses, arXiv preprint arXiv:2303.12580. (2023)
Funding Acknowledgement: This work was performed under the U.S.
Department of Energy through contract DE-AC02-09CH11466.
2:40pm PS+SE-MoA-4 Control of Electron Energy Distribution Function in
Electron Beam Generated ExB Plasma, Nirbhav Chopra, Y. Raitses,
Princeton Plasma Physics Laboratory
Electron beam (e-beam) generated plasmas are promising for low pressure,
low damage threshold material processing applications requiring efficient
1:40 PM

Monday Afternoon, November 6, 2023
generation of ions and radical species [1,2]. The production of reactive
species generated by electron impact is controlled by the electron energy
distribution function (EEDF). In this work, we investigate the EEDF and
plasma parameters of a partially magnetized plasma generated by e-beam
in low pressure (0.1-10 mTorr) argon and nitrogen. The e-beam (energy <
100 eV) is extracted from a negatively biased thermionic filament and
injected into a cylindrical vacuum chamber with applied axial magnetic
field. The EEDF is measured using electrostatic probes. Results show the
presence of e-beam electrons with energies comparable with the applied
cathode voltage and a group of warm electrons (10-30 eV). Mechanisms of
the formation of this intermediate group of electrons will be discussed. In
addition, we will present and discuss the effect of the addition of nitrogen
gas to the argon plasma on the EEDF.

4:20pm PS+SE-MoA-9 Mass Spectral Characterization and Control of
Plasma Etch Processes, L. Shoer, P. Heil, S. Pursel, Intel Corporation; N.
Salovich, Edwards Vacuum; David Shykind, Intel Corporation
As semiconductor critical dimensions have reached the single-digit
nanometer scale, reproducible control of etch processes has become
critically dependent on consistent wafer-to-wafer processing. Nanometer
feature sizes and atomically thin layers have led to a regime where
traditional bulk plasma characterization techniques no longer give insight
into the chemical processes occurring on the wafer. Furthermore, the
number of moles of reactants on the walls of an etch chamber are greater
than or equal to the quantity of reactants intended to be etched on a wafer
itself. Uncontrolled, this situation complicates etch processes, introducing
hysteretic behavior even assuming an ideal input stream of identical wafers,
and exacerbates actual wafer-to-wafer variation effects. We show how
high-speed (subsecond time resolution), non-invasive mass spectrometry of
plasma cleaning, seasoning and actual etch steps themselves leads to
improved performance and enhanced mechanistic understanding of plasma
etch processes.

[1] Zhao F et al C G 2021 Carbon 177 244–51
[2] Walton S G et al 2015 ECS J. Solid State Sci. Technol. 4 N5033–40
3:00pm PS+SE-MoA-5 Expanding the Capabilities of Microwave Hairpin
Resonator Probes, Steven Shannon, North Carolina State University
INVITED
Microwave hairpin resonator probes are a common diagnostic for
measuring electron density in plasmas. They are particularly effective in low
temperature plasmas, RF driven plasmas, reactive (particularly depositing)
plasma chemistries, and other plasma environments that can challenge the
effective use of comparable probe diagnostics such as Langmuir probes or
emissive probes. Efforts to increase the utility of these probes through both
innovative probe design (such as biasing and curling probe design) and
combination of the hairpin probe with other diagnostic techniques (such as
laser photodetachment studies in electronegative discharges) have
increased the utility of hairpin probes in the field of experimental plasma
science. This work presents efforts to expand on the measurement
capabilities of these probes in two ways. First, the analysis of resonance
data is expanded to account for plasma contributions to the Q-factor of the
loaded resonance circuit. From this, additional plasma parameters such as
electron neutral collision frequency can be estimated. Second, the time
resolution of these probes are expanded to provide insight into the time
modulation of plasma discharges including pulsed RF discharges, and can
be extended to time resolved measurements within the period of an RF
driven system, complimenting the growing area of phase resolved plasma
characterization. The methods for expanding the capabilities of these
probes are presented in this talk as well as examples of where this
extension of probe capability has provided insight into basic plasma
phenomena including moderate pressure operation of RF discharges,
sheath heating, probe perturbation effects on density measurement,
electronegative plasma instabilities, and the role of plasma edge uniformity
on power coupling in inductively coupled plasma reactors. This work has
been supported by the National Science Foundation, U.S. Department of
Energy, Samsung Electronics, Applied Materials Inc. MKS Instruments and
the state of North Carolina.

4:40pm PS+SE-MoA-10 Development of a Catalytic Probe for the
Detection of Fluorine Radicals with Applications to Semiconductor
Manufacturing, Nicholas Connolly, J. Mettler, R. Garza, R. Sankaran, D.
Ruzic, University of Illinois Urbana-Champaign
Plasma processing is an essential part of integrated circuit manufacturing,
with plasma etching, plasma strip, and chamber cleaning being three
critical steps. All of these steps rely on radicals, highly reactive neutral
species created in the plasma, to drive the desired etching reactions.
Because of the importance of radical species in etching reactions and rates,
quantification of the densities of these species is important for
understanding plasma etching dynamics. Additionally, spatial resolution of
radical densities allows specific knowledge of etch dynamics at a substrate
or a chamber component of interest.
One technique that has been developed to detect and quantify radical
species is a catalytic probe, which consists of two thermocouples each
coated with a different metal. The different metals catalyze the
recombination of radical species at different rates, leading to a temperature
difference between the thermocouples. This temperature difference is
proportional to the density of radical species, and so a radical density can
be determined. The catalytic probe technique provides in-situ, spatially
resolved radical densities. This has advantages over techniques which
gather a line-averaged signal, such as optical emission spectroscopy (OES),
and measurement methods that require ex-situ analysis, such as coupon
etch rates.
Previous studies have applied catalytic probes to the detection of hydrogen
(H), oxygen (O), and nitrogen (N) radicals.1 To our knowledge, a catalytic
probe for fluorine (F) has yet to be reported. Here, we present a
thermocouple-based catalytic probe to determine spatially resolved
fluorine radical densities in SF6/Ar plasmas. The catalytic activity of zinc,
copper, and gold is reported. The radical densities determined from the
radical probes are compared to those determined via actinometry and
coupon etch rates. These methods also provide verification of the
recombination coefficient of the probe material and thereby confirm the
quantitative
results
of
the
radical
probe.

4:00pm PS+SE-MoA-8 Time-Resolved Electron Energy Distribution in a
Multi-Frequency Capacitively Coupled Plasma Reactor, C. Kelly, Md.
Amzad Hossain, D. Kapelyan, D. Ruzic, University of Illinois at UrbanaChampaign
This work uses a time-resolved Langmuir probe to measure the electron
energy distribution function (EEDF) in a capacitively-coupled parallel-plate
(CCP) plasma reactor. The EEDF completely determines the plasma
chemistry in a low-temperature plasma, and that is why it is so important
to obtain. By seeing how the EEDF changes throughout an RF cycle, both as
a function of time and position, one then knows the extent by which
altering the RF waveform can affect the energy of the electrons. Often
industry mixes RF frequencies to alter the plasma -- particularly the ion
energy distribution at the substrate. Here we add a second frequency in a
systematic manner and examine the changes in the instantaneous EEDF. We
also examine the turn on and turn off times of the RF generator itself.

[1] D. Qerimi, I. Shchelkanov, G. Panici, A. Jain, J. Wagner, and D.N. Ruzic. J.
Vac. Sci. Technol. A 39, 023003 (2021).
5:00pm PS+SE-MoA-11 Multi-Diagnostic Investigation of Etching Plasma
Species in an Industry-Grade Inductively-Coupled Plasma Etcher, Jeremy
Mettler1, N. Connolly, S. Dubowsky, D. Ruzic, University of Illinois at UrbanaChampaign
Plasma etching kinetics and reaction mechanisms often involve complex
interactions between radical, neutral, and charged species. Optimization of
etch rate and selectivity for a given process can be tedious without a
detailed mechanistic understanding of the etching mechanisms, which in
turn can be difficult to determine without accurate measurements of all
relevant plasma species. Many diagnostics exist which are able to measure
some of these species, but each has their own tradeoffs, and none are able
to measure all species under all conditions.

Specialized circuits were designed for this work to ensure high frequency
fidelity so digitization at 1.5 GHz is possible and accurate. A set of
experiments were conducted to show how only altering circuit parameters
affect the results, and steps were taken to eliminate those effects. Spatial
variations of the resulting EEDFs were investigated, especially near the edge
of the CCP reactor, to see which aspects change the most with radius.

In this work we discuss the development of a suite of plasma diagnostics for
measuring the environment in an etching system, including neutral,
charged, and radical species. To accurately measure each component of the

1 PSTD Coburn & Winters Student Award Finalist

Monday Afternoon, November 6, 2023

9

1:40 PM

Monday Afternoon, November 6, 2023
etch process, results from appearance energy mass spectroscopy, optical
emission spectroscopy, fluorine radical probe analysis, and Langmuir probe
analysis are combined, with overlap in the sensing capabilities of each
diagnostic used for cross-validation. The use of multiple independent
diagnostics with different spatial resolutions and species sensitivities
provides flexibility and increased confidence in quantitative results. This
work will present a comparison of results obtained by the individual
diagnostics across several CF4 based etching conditions in an industry-grade
inductively-coupled plasma etching tool. Further comparison will be made
between experimental etching results and 0-D plasma modeling of the
etching system.

Monday Afternoon, November 6, 2023

10

1:40 PM

Tuesday Morning, November 7, 2023
precursor blocking by SMIs involves two components: the chemical removal
of reactive surface sites and the physical blocking of the surface, also
referred to as chemical passivation and steric shielding respectively [1].
However, it is difficult to differentiate between these two factors as they
occur simultaneously. In this work we attempt to unravel the steric
shielding and the chemical passivation contributions by the SMI
acetylacetone (Hacac) with the use of reflection adsorption infra-red
spectroscopy (RAIRS) on dehydroxylated Al2O3 surfaces obtained through
annealing.

Atomic Scale Processing Mini-Symposium
Room A107-109 - Session AP+EM+PS+TF-TuM
Area Selective Processing and Patterning
Moderators: Eric A. Joseph, IBM Research Division, T.J. Watson Research
Center, Adrie Mackus, Eindhoven University, Netherlands
8:00am AP+EM+PS+TF-TuM-1 Area-Selective Deposition in Nanoscale
Patterns, Annelies Delabie, Imec Belgium, and KU Leuven Belgium; J. Clerix,
IMEC Belgium; K. Van Dongen, IMEC, Belgium; J. Sinha, IMEC Belgium; L.
Nyns, IMEC, Belgium; R. Nye, LAM Research; G. Parsons, North Carolina
State University; J. Swerts, IMEC Belgium
INVITED
Manufacturing nano-electronic devices becomes more and more complex
as the device dimensions reach the nanoscale and a wide range of new
materials is being implemented to achieve high device performance.
Additional complexity comes from the use of three dimensional (3D)
structures to reduce the active footprint. Area-Selective Deposition (ASD)
provides a promising avenue to assist and/or even simplify device
manufacturing processes. ASD is a technique to deposit material only on a
pre-defined area of a patterned surface (the growth area), while no
deposition is intended on other areas of the same surface (the non-growth
area). As such, ASD can be used to replicate patterns on 3D substrates and
to (partly) fill narrow trenches or holes from the bottom up. ASD can be
achieved by tuning the adsorption and diffusion kinetics in atomic layer
deposition (ALD) and chemical vapor deposition (CVD) processes. Insight in
the chemical and physical processes is essential to enable rational design of
new ASD processes for nano-electronic device manufacturing for advanced
technology nodes.

When comparing Hacac adsorption on an as-prepared and an annealed
Al2O3 surface using RAIRS, a lower amount of Hacac adsorbates was
observed on the annealed surface. Furthermore, a higher fraction of the
Hacac adsorbates was present in the more strongly bonded chelate
configuration. This difference in the distribution of the binding
configurations demonstrates that the density of surface sites affects the
SMI adsorption behavior. We expect that this different adsorption behavior
is caused by a lower amount of steric hindrance between the SMIs on the
annealed Al2O3 surface. Furthermore, the increase in the amount of
adsorbates in the chelate configuration will result in a higher contribution
of chemical passivation on the dehydroxylated surface, since only the
adsorbates in the chelate configuration chemically passivate the surface [2].
From this we can conclude that the removal of surface sites can be used to
obtain a better understanding of the two precursor blocking mechanisms.
This better understanding will create opportunities for the development of
new area-selective ALD strategies involving the removal of reactive surface
sites before the functionalization with SMIs to improve selectivity.
[1] Merkx, et al., Chem. Mater. 32, 3335–3345 (2020).
[2] Mameli et al., ACS Nano 11, 9303–9311 (2017).
9:40am AP+EM+PS+TF-TuM-6 Topographically-Selective Deposition Using
Amorphous Carbon as Inhibition Layer, Thijs Janssen, M. Merkx, W.
Kessels, A. Mackus, Eindhoven University of Technology, The Netherlands
To accommodate the increasing complexity of device architectures in
nanoelectronics, new nanoscale processing techniques are required.
Selective deposition techniques have been developed in recent years to
enable bottom-up and self-aligned processing12. While traditional areaselective deposition distinguishes between areas depending on their
chemical character, topographically-selective deposition (TSD) distinguishes
between areas based on their orientation within a 3D structure2,3. Such TSD
approaches offer new fabrication opportunities, for example when the
growth and non-growth areas possess similar material properties, or when
too many different materials are present within the device structure.
Previously reported TSD methods have been demonstrated only for specific
materials.

This presentation will discuss the growth mechanisms during ASD on
substrates that contain nanoscale patterns, where the geometry of the
nanopatterns can affect the growth behavior, selectivity and uniformity. An
aminosilane small molecule inhibitor can enable ASD on a wide range of
materials with SiO2 as the non-growth surface [1]. The selectivity of TiO2
ALD relies mainly on adsorption. Selectivity loss during TiO2ALD occurs via a
nucleation site generation mechanism: small TiO2 nanoparticles are
continuously generated during ALD by slow, unintentional adsorption on
the passivated non-growth surface area [2]. ASD super cycles consisting of
inhibitor adsorption, TiO2 ALD and etch effectively improve the selectivity,
but may compromise the height uniformity in nanoscale patterns. The
selectivity of Ru and Ge2Sb2Te5 ALD relies on a complex interplay of
adsorption, diffusion and aggregation. We reveal a pattern-dependent
selectivity for Ru ALD, which is explained by aggregation of Ru adspecies at
the pattern edges [3]. We conclude that the selectivity and uniformity of
ALD processes can change when pattern dimensions reach the nanoscale.

In our work, we develop a versatile TSD strategy that is potentially suitable
for a broad range of materials. Our approach utilizes a pulsed Ar/CH4
plasma to selectively apply an amorphous carbon (aC) inhibition layer on
horizontally-oriented surfaces by relying on the directional ions from the
plasma. The vapor-phase selective deposition of aC is integrated together
with existing ALD processes and plasma treatments into a TSD supercycle
recipe.

[1] K. Van Dongen et al, J. Vac. Sci. Technol. A 2023, 41, 032404.
[2] R. A. Nye et al, Appl. Phys. Lett. 2022, 121, 082102.
[3] J.-W. J. Clerix et al, Appl. Surf. Sci. 2023,626, 157222.
8:40am AP+EM+PS+TF-TuM-3 N-Heterocyclic Carbenes as Small Molecule
Inhibitors in AS-ALD, Cathleen Crudden, Queen's University, Canada
INVITED
A unique carbon-based SMI, called an N-heterocyclic carbene (NHC), has
been developed as a small molecule inhibitor using carbon as the
heteroatom. NHCs have been used in organometallic and catalysis
chemistry for decades, where they are renowned for their ability to form
strong bonds to metal surfaces. We have developed a suite of organic SMIs
with high volatility and thermal stability enabling deposition in an ALD tool.
We demonstrated strong binding of the SMI to Ru, Co, Mo and Cu and
selectivity for binding to metal surfaces in the presence of insulators. These
results are informed by surface science studies including microscopy and
spectroscopy.

The highly inert surface of aC lacks suitable absorption sites for ALD
precursors and co-reactants, making it an effective inhibition layer. It was
found that only the horizontally-oriented surfaces are covered by the aC
layer, thus subsequent ALD of target materials proceeds exclusively on
vertically-oriented surfaces.
Successful ALD inhibition on the aC surface is established for several
different target materials such as TiO2 using TDMAT and H2O, Nb2O5 using
TBTDEN and H2O, and NiOx using Ni(BuAMD)2 and H2O. In particular 90%
selectivity was maintained for 35 cycles TiO2 deposition (1.09 ± 0.01 nm
selective growth), 70 cycles Nb2O5 deposition (4.38 ± 0.02 nm) and 40
cycles of NiOx deposition (1.28 ± 0.01 nm). It is demonstrated for NiOx that
the supercycle can be repeated, which effectively resets the nucleation
delay, such that a thicker film (nominally ~5 nm after 4 supercycles) can be
deposited selectively.

9:20am AP+EM+PS+TF-TuM-5 Unraveling Precursor Blocking Mechanisms
in Area-Selective Atomic Layer Deposition Using Small Molecule
Inhibitors, Olaf Bolkenbaas, M. Merkx, Eindhoven University of Technology,
Netherlands; P. Yu, eindhoven University of Technology, Netherlands; T.
Sandoval, Universidad Tecnica Federico Santa Maria, Chile; E. Kessels, A.
Mackus, Eindhoven University of Technology, Netherlands
Area-selective atomic layer deposition (ALD) has garnered significant
attention as a potential technique for enabling the further miniaturization
of semiconductor devices. One method for achieving area-selective ALD is
through the use of small molecule inhibitors (SMIs) that selectively block
deposition on certain materials. Previous research has indicated that
Tuesday Morning, November 7, 2023

1.

2.

11

Mackus, A. J. M., Merkx, M. J. M. & Kessels, W. M. M. From the
Bottom-Up: Toward Area-Selective Atomic Layer Deposition with
High Selectivity. Chem. Mater.31, 2–12 (2019).
Parsons, G. N. & Clark, R. D. Area-Selective Deposition:
Fundamentals, Applications, and Future Outlook. Chem.
Mater.32, 4920–4953 (2020).
8:00 AM

Tuesday Morning, November 7, 2023
3.

Chaker, A. et al. Topographically selective deposition. Appl. Phys.
Lett.114, (2019).

particular, a remote NF3 plasma has been studied as a means for forming a
co-inhibitor. Dosing before or after TMSDMA treatment has been
investigated. The deposition of the small molecules were carried out on 10
Å SiO2/Si(100) substrates. Water contact angle measurements were taken
to determine relative surface passivation of each sample. Angle-resolved Xray photoelectron spectroscopy and attenuated total reflection/Fourier
transform infrared spectroscopy were performed in order to characterize
the chemical state of each surface. Our results indicate that exposure of the
substrate to the NF3 plasma after passivation with TMSDMA, results in
damage to the passivating layer. However, exposure of the surface to the
NF3 plasma before TMSDMA exposure maintains the passivation of the
SiO2 surface. In addition, temperature programmed desorption (TPD)
measurements are being conducted to assess the relative coverage of the
inhibiting film on each sample and its thermal stability.

11:00am AP+EM+PS+TF-TuM-10 A ReaxFF Study for Hacac Interaction on
Al2O3 Surface in Area-Selective ALD, Naoya Uene, Tohoku University,
Japan; I. Tezsevin, W. Kessels, A. Mackus, Eindhoven University of
Technology, Netherlands; A. van Duin, Pennsylvania State University; T.
Tokumasu, Tohoku University, Japan
An area-selective ALD process of SiO2 was developed comprising
acetylacetone inhibitor (Hacac), bis(diethylamino)silane precursor (BDEAS),
and O2 plasma reactant pulses. Hacac inhibitors lead to delayed SiO2 growth
on the Al2O3 surface for about 15 ALD cycles, after which the selectivity is
lost. Two chemisorption configurations of Hacac inhibitors on Al2O3 surfaces
have been reported: monodentate and chelate configurations. (Merkx et al.
2020) Density functional theory (DFT) calculations have shown that the
monodentate configuration is relatively reactive with incoming BDEAS,
causing the loss of selectivity due to precursor-inhibitor reactions.
Therefore, exploration of the relative densities of the chelate/monodentate
configurations on the surface is crucial for the understanding of the
selectivity loss mechanism. We aim to understand the reaction mechanisms
of Hacac inhibitor adsorption on Al2O3 surfaces at the atomic scale.

11:40am AP+EM+PS+TF-TuM-12 A Study of Elucidation and Improvement
of TiO2 Selectivity by First-Principles Based Thermodynamic Simulation,
Yukio Kaneda, Sony Semiconductor Solutions Corporation, Japan; E.
Marques, S. Armini, A. Delabie, M. van Setten, G. Pourtois, IMEC, Belgium
INVITED
Area-selective deposition (ASD) enables the deposition of materials in a
targeted area, typically a pre-patterned surface, while preventing the
growth on adjacent surfaces.[1] The technique is appealing for both
academia and industry as it offers a vehicle to simplify material
developments in nanoelectronics. Consequently, numerous efforts have
been dedicated to investigate the factors driving the selectivity mechanisms
and to identify optimal process deposition conditions, including surface
treatments,
that
enable
highly
selective
processes.

Up to now, the investigation of the adsorption of inhibitor molecules has
been studied via DFT calculations. Thereactive force-field molecular
dynamics (ReaxFF MD), which can simulate chemical reactions and physical
dynamics at the atomic scale, has been used for gas-surface systems. (van
Duin et al. 2001) We performed ReaxFF MD simulations to consider the
chemical reactions of Hacac inhibitor molecules with dislocation effects on
the surface. An initial force field has been developed for the Hacac
interaction on Al2O3 surface based on the two existing force fields:
Li/Si/Al/O force field for Al2O3 structure and protein force field for
carbohydrate interactions. (Kim et al. 2016; Monti et al. 2013) The initial
force field is trained for Hacac geometry, and their reaction on an OHterminated Al2O3 surface is also modeled.

The “selectivity” dimension results from the identification of the right
combination of precursors (including co-agents), surface treatments, and
reactor operating conditions. This is typically a complex and laborious
process that requires many systematic and tightly controlled experiments.
As a result, the development of highly selective ASD processes is often a
slow and challenging task where any form of guidance provided by
modeling
insights
can
be
precious.

We performed ReaxFF MD simulations using the developed force field. The
simulation consists of three steps. First, the Al2O3 surface is pre-thermally
relaxed. Then, the Hacac inhibitor is supplied on the relaxed surface,
followed by post-thermal relaxation of the Hacac-adsorbed surface. We first
confirmed the temperature stability of the Al2O3 surface with different
temperatures. Our force field can control the temperature of the Al2O3
surface ranging from 300 K to 1500 K. Next, sequential adsorption of 20
Hacac inhibitor molecules was simulated on the temperature-controlled
Al2O3 surface, as shown in the supplemental document. The findings from
our ReaxFF simulations provide in-depth insights into the mechanisms of
Hacac adsorption and saturation on the surface. These insights will be used
for the investigation of precursor blocking and blocking selectivity loss in
our future work.

In this context, we studied, by combining thermodynamic considerations
and first principle simulations, the reactivities of complex surface chemical
reaction networks and the factors impacting on selectivity. In this talk, we
will discuss the case of the ASD of TiO2 on SiO2 substrates terminated with
either “reactive” (-OH) or “passivated” alkyl-silyl groups. First, we will first
briefly discuss the validation of our approach by comparing our model
prediction with experimental measurements for the case of the ALD of TiO2
using the precursors TiCl4 and Ti(OMe)4 and then report the insights gained
for the identification of optimum Ti precursor and inhibitor for the ASD of
TiO2. We will then extend the discussion to the case of the ASD supercycles
of TiO2, where the interaction of some Ti precursors (or of their ligands)
leads to the degradation of the surface “passivation” and then requires
restoring the surface by injecting of alkyl-silyl functional groups. We will
review the strategies that worked with their drawbacks.

11:20am AP+EM+PS+TF-TuM-11 Enhancement of TMSDMA Passivation on
SiO2 by Surface Fluorination, Anthony Valenti, SUNY College of Nanoscale
Science and Engineering; C. Vallée, SUNY College of Nanoscale Science and
Engineering, France; C. Ventrice, SUNY College of Nanoscale Science and
Engineering; K. Tapily, K. Yu, S. Consiglio, C. Wajda, R. Clark, G. Leusink, TEL
Technology Center, America, LLC, USA
With the ever-shrinking scale of semiconductor devices, area-selective
atomic layer deposition (AS-ALD), a bottom-up and self-aligned patterning
process with atomic-scale control has been in development in order to
meet the demands of industry. This technique is typically conducted by
promoting growth on specific surface termination types, while inhibiting
growth on the other surface types of the substrate via selective
chemisorption of molecules that are inert to the deposition process. With
its affinity for chemisorbing to hydroxylated oxide surfaces, specifically
SiO2, but not on Si or non-oxidized metal surfaces, N(trimethylsilyl)dimethylamine (TMSDMA) has been of recent interest for its
use as a small molecule inhibitor (SMI) for area selective deposition (ASD).
Upon interaction with a surface hydroxyl group, the TMSDMA molecule
dissociates, resulting in a trimethylsilyl group bonded to the chemisorbed
oxygen atom of the hydroxyl group. Although TMSDMA-passivated SiO2
typically remains inert over several ALD cycles, nucleation of the growth
precursor can eventually occur. This may be due to hydroxyl groups on the
surface that did not interact with TMSDMA molecules and/or nonhydroxylated sites that were not passivated by trimethylsilyl groups. For
instance, surface siloxane bridges do not dissociate TMSDMA and can act as
nucleation sites for the ALD growth precursor. In order to enhance the
passivation of SiO2 surfaces, the use of co-passivants has been explored. In
Tuesday Morning, November 7, 2023

[1] Gregory N. Parsons and Robert D. Clark, Chem. Mater. 2020, 32, 12,
4920–4953
[2] Job Soethoudt, et al.,The Journal of Physical Chemistry C2020124 (13),
7163-7173
[3] Janne-Petteri Niemelä et al.,Semicond. Sci. Technol.2017 9 (32), 093005

Biomaterial Interfaces Division
Room B117-119 - Session BI+AS+PS-TuM
Biomolecules and Biophysics at Interfaces
Moderators: Christopher So, Naval Research Laboratory, Markus Valtiner,
Vienna University of Technology, Austria
8:00am BI+AS+PS-TuM-1 Probing Protein Structure on Nanoplastic Surface
by Sum Frequency Scattering, Akriti Mishra, T. Weidner, Aarhus University,
Denmark
The safe use of nanoparticle protein conjugates in biomedical applications
like disease diagnosis, drug delivery, biosensing, etc. depends on the
efficacy and stability of these conjugates in body fluids. To date, several
analytical techniques like UV-Vis, dynamic light scattering, Fourier
transform infrared spectroscopy, circular dichroism, nuclear magnetic
12

8:00 AM

Tuesday Morning, November 7, 2023
resonance, etc. have been used to study the interaction of proteins on
nanoparticle surface. Since most of the techniques can not differentiate
between the surface bound and the free proteins in solution, it becomes
impossible to gather any information about the interfacial proteins. The
confirmation of a protein after adsorption on nanoparticle surface can be
drastically different from that in solution, which may hamper or amend the
activity and function of proteins. Surface sensitive sum frequency scattering
(SFS) stands out best in this case since it selectively probes the vibrational
modes of the adsorbed analytes on any interface. Sum frequency
generation from flat interfaces has been successfully shown to provide rich
information about the structure, order, and composition of molecules at
the interface. Recently, our group has shown that SFS can effectively probe
the structure and orientation of model peptides at nanoscopic oil particle
surfaces.1 We will here discuss how also complex human corona proteins
can be probed on particle surfaces. We focus on alpha synuclein (aS)
interactions with nanoparticles relevant for medical applications and
environmental nanoplastics. aS is a 14 kDa intrinsically disordered protein
known to form amyloids called Lewy bodies, which can propagate across
the neurons to induce Parkinson’s disease (PD). Using SFS we follow how aS
binds and folds on polymer nanoparticle surfaces. SFS spectra in the amide
I region strongly suggest that aS folds into beta sheet and fibrillated
structures at the nanointerfaces This is in contrast with flat surfaces, where
monomers and helical folds dominate based on reflection SFG
experiments.2 We believe, aS binding to the nanoparticles leads to close
packing of aS monomers, which leads to the formation of beta sheet and
fibrillar type structures.
Fig 1. Schematic of the SFS experiments to follow the binding of aS to
polymer nanoparticles particles and the corresponding SFS spectrum
References:
1.) Thaddeus W. Golbeck, Kris Strunge, Adam S. Chatterly, and Tobias
Weidner* J. Phys. Chem. Lett. 2022, 13, 10858-62.
2.) Kris Strunge, Tucker Burgin, Thaddeus W. Golbek, Steven J. Roeters, Jim
Pfaendtner and Tobias Weidner* Umbrella-like helical structure of alphasynuclein at the air-water interface observed with experimental and
theoretical sum frequency generation spectroscopy, in preprint.
8:20am BI+AS+PS-TuM-2 The Structure of Alpha-Synuclein at Lipid
Interfaces Determined by Experimental and Theoretical Sum Frequency
Generation Spectroscopy, K. Strunge, K. Pedersen, T. Golbek, M. Brgenhøj,
D. Otzen, B. Schiøtt, Tobias Weidner, Aarhus University, Denmark
The aberrant folding of α-synuclein (αS) into amyloid aggregates is
associated with Parkinson’s disease. It has been shown that the refolding
into oliogomers and harmful fibrils can be catalyzed by lipid-membrane
surfaces. Despite the importance of lipid interactions, the 3D-structure of
lipid-membrane bound αS, and thereby, the mechanism of the catalysis
process, is still not known at the molecular level. Here, we report interfacespecific sum-frequency generation (SFG) experiments revealing how
monomeric αS binds, folds and orients at anionic lipid membranes. Since
SFG is inherently surface specific and unbond proteins are not detected, the
experiments can be performed at high αS concentrations, far beyond
previous structural studies. To interpret the experimental SFG data and
develop a high fidelity structural model of the aS binding motif, we
developed an analysis method in which out-of-equilibrium moleculardynamics (MD) simulations are linked to excitonic amide-I SFG spectra
calculations. 10s of thousands of theoretical spectra calculated for frames
of extensive MD simulations are evaluated pooled for their experimental
fitness to determine the structure of aS binding at low, physiological and
pathological aS concentrations. We find that at low and physiological αS
concentrations, the protein binds in a flat geometry, while at elevated,
pathological concentrations, a transition to an upright αS binding pose
occurs. This upright conformation promotes lateral interactions and likely
explains how protein concentrations can catalyze the formation of αS
amyloids.
8:40am BI+AS+PS-TuM-3 Lubricant Viscosity Affects the Antifouling
Activity of PFPE Based SLIPS Coatings, Onur Özcan, J. Karthäuser, R.
Kopecz, A. Gelhar, A. Rosenhahn, Ruhr-Universitat Bochum, Germany
Settlement of organisms on submerged surfaces can enhance the spread of
life-threatening infections.[1] Therefore it is desired to identify methods for
the prevention of biofilm formation. The omniphobic properties of slippery
liquid infused porous surfaces (SLIPS) have been shown to provide
outstanding protection against biofouling, icing, corrosion and to be
repellent against complex liquids like blood.[2] In this study, we examine
the fouling behavior of E. coli, P. fluorescence, and B. subtilis on seven
different superhydrophobic perfluoropolyether (PFPE) urethane
Tuesday Morning, November 7, 2023
13

methacrylate-based SLIPS with varying lubricant viscosities. The polymers
were fabricated following our previously published grafting-through
protocolby which superhydrophobic micro-structured porous PFPE matrices
could be obtained by adding cychlohexanol as pore forming agent to the
monomer mixture.[3,4] The coatings were incubated in an excess of seven
different lubricants of varying viscosities to obtain SLIPS. In dynamic
attachment assays we were able to show the antifouling capabilities of
these SLIPS with organism reductions of up to 90% compared to the dry,
smooth, and hydrophobic butyl methacrylate references. Our results
further revealed critical species-specific settlement on the coatings that
depended on the viscosity of the incorporated liquid, highlighting the
relevance of the choice of the lubricant in the design of low-fouling SLIPS.
[1] M.V. Horton, J. E. Nett, Curr. Clin. Microbiol. Rep. 2020, 7, 51-56. [2] T.-S.
Wong, S. H. Kang, S. K. Y. Tang, E. J. Smythe, B. D. Hatton, A. Grinthal, J.
Aizenberg, Nature 2011, 477, 443-447. [3] F. Koschitzki, R. Wanka, L.
Sobota, J. Koc, H. Gardner, K. Z. Hunsucker, G. W. Swain, A. Rosenhahn, ACS
Appl. Mater. Interfaces. 2020, 12, 34148-34160. [4] N. Keller, J. Bruchmann,
T. Sollich, C. Richter, R. Thelen, F. Kotz, T. Schwartz, D. Helmer, B. E. Rapp,
ACS Appl. Mater. Interfaces, 2019, 11, 4480-4487.
9:00am BI+AS+PS-TuM-4 Orientation of the Dysferlin C2A Domain is
Responsive to the Composition of Lipid Membranes, A. Carpenter, Oregon
State University; S. Roeters, T. Weidner, Aarhus University, Denmark; Joe
Baio, Oregon State University
Dysferlin is a 230 kD protein that plays a critical function in the active
resealing of micron-sized injuries to the muscle sarcolemma by recruiting
vesicles to patch the injured site via vesicle fusion. Muscular dystrophy is
observed in humans when mutations disrupt this repair process or dysferlin
is absent. While lipid binding by dysferlin’s C2A domain (dysC2A) is
considered fundamental to the membrane resealing process, the molecular
mechanism of this interaction is not fully understood. By applying nonlinear
surface-specific vibrational spectroscopy, we have successfully
demonstrated that dysferlin’s N-terminal C2A domain (dysC2A) alters its
binding orientation in response to a membrane’s lipid composition. These
experiments reveal that dysC2A utilizes a generic electrostatic binding
interaction to bind to most anionic lipid surfaces, inserting its calcium
binding loops into the lipid surface while orienting its β-sheets 30–40° from
surface normal. However, at lipid surfaces, where PI(4,5)P2 is present,
dysC2A tilts its β-sheets more than 60° from surface normal to expose a
polybasic face, while it binds to the PI(4,5)P2 surface. Both lipid binding
mechanisms are shown to occur alongside dysC2A-induced lipid clustering.
These different binding mechanisms suggest that dysC2A could provide a
molecular cue to the larger dysferlin protein as to signal whether it is bound
to the sarcolemma or another lipid surface.
9:20am BI+AS+PS-TuM-5 Probing the Interfacial Action of Thermomyces
Lanuginosus Lipase at Lipid Surfaces with Vibrational Sum Frequency
Spectroscopy – from Monolayers to Emulsions, Khezar Saeed, K. Strunge,
T. Golbek, T. Weidner, Aarhus University, Denmark
Lipases are a diverse class of biologically important enzymes with a key role
in the digestion of dietary fats. The general ability to catalyse triacyl
glyceride hydrolysis also enables their application to a wide variety of
systems outside of the digestive tract, including transesterification,
enantioselective synthesis and as an additive to laundry detergents. Key to
their efficacy is the phenomenon of interfacial activation. For lipases this
almost universally involves the “opening” of a lid domain upon interaction
with a lipid surface, revealing a hydrophobic region containing the active
site. The lipase derived from the Thermomyces lanuginosus fungus (TLL) is
used extensively on an industrial scale as an additive to laundry detergents.
As such significant effort has been expended to genetically engineer
improvements to the lipase function, with particular attention paid to this
lid region. Gaining a deeper understanding of the interfacial activation
mechanisms of such lipases could inform the design of improved enzymes
in the future.
The inherent surface sensitivity of vibrational sum frequency generation
(VSFG) spectroscopy can provide the required molecular level information
to further our understanding of the interfacial activation of TLL. VSFG
spectroscopy relies on the selection rules associated with frequency mixing
of high power visible and infrared laser beams, resulting in a vibrational
spectrum of solely the interfacial region. Three key results are presented
here:
(i)The TLL-catalysed reaction at the air/triglyceride/water interface can be
monitored by reflection VSFG spectroscopy, showing loss of ester carbonyl
modes and appearance of carboxylate stretching modes of the fatty acid
products.
8:00 AM

Tuesday Morning, November 7, 2023
(ii)Comparison of experimental and predicted VSFG spectra of the amide I
band are used to interpret structural changes in the lid domain of TLL upon
interaction with a hydrophobic surface.
(iii)Specially formulated emulsions allow further analysis using our new
angle-resolved sum frequency scattering spectrometer, showing the first
example of reaction dynamics at a particle surface probed by vibrational
sum frequency scattering spectroscopy.
This work highlights the utility of VSFG spectroscopy for studying interfacial
reactions. Not only does it offer a label-free method of following surface
reactions, but it also provides structural and orientational information on
interfacial species when combined with appropriate simulations.
Furthermore, the results from the sum frequency scattering spectrometer
open the door to studying a whole new class of chemical systems at particle
surfaces with as yet unseen levels of molecular detail for such systems.
11:00am BI+AS+PS-TuM-10 An in Situ Look at Interfacial Controls on
Nucleation, Self-Assembly, and Crystal Growth in Biomolecular and
Biomimetic Systems, Jim De Yoreo, Pacific Northwest National Laboratory
INVITED
From harvesting solar energy to capturing CO2 to purifying water, living
organisms have solved some of the most vexing challenges now faced by
humanity. They have done so by creating a vast library of proteins and
other macromolecules that can assemble into complex architectures and
direct the mineralization of inorganic components to produce materials
characterized by a hierarchy of structure. While the high information
content contained within the intricate sequences of the proteins is crucial
for accomplishing these tasks, self-assembly and mineralization are
nonetheless constrained to proceed according to the physical laws that
govern all such processes, even in synthetic systems. An understanding of
the mechanisms by which biological systems successfully manipulate those
laws to create hierarchical materials would usher in an era of materials
design to address our most pressing technological challenges. In this talk, I
will present the results of recent research using in situ atomic force
microscopy and in situ transmission electron microscopy to directly observe
interfacial structure, protein self-assembly, and nanocrystal formation in
biomolecular and biomimetic systems, including protein-directed
nucleation of calcium carbonate and calcium phosphate and mineraldirected nucleation of two-dimensional protein assemblies. The results
elucidate the mechanisms by which the interface between biomolecules
and materials directs nucleation, self-assembly and crystal growth, leading
to unique materials and morphologies. The results reveal the importance of
surface charge, facet-specific binding, solvent organization near interfaces,
and, more generally, the balance of protein-substrate-solvent interactions
in determining how ordered materials emerge in these systems.
11:40am BI+AS+PS-TuM-12 the Surface Chemistry of Gecko Toe Pads,
Mette Heidemann Rasmussen, K. Holler, Department of Chemistry, Aarhus
University, Denmark; J. Baio, School of Chemical, Biological and
Environmental Engineering, Oregon State University; C. Jaye, D. Fischer,
National Institute of Standards and Technology, Gaithersburg; S. Gorb,
Functional Morphology and Biomechanics, Zoological Institute, Kiel
University, Germany; T. Weidner, Department of Chemistry, Aarhus
University, Denmark
Geckos can climb nearly all surface and are able to cling to walls and
ceilings using their toe pads. The gecko adhesion mechanism has been
debated over the past years. Current models include van der Walls,
hydrophobic and acid-base interactions. Even though the adhesion
mechanism of the spatulas has been studied in detail, the surface chemistry
involved in the gecko adhesion mechanism is unclear. What is the structure
of the supporting proteins within the spatula at the very tips of the setae
within the gecko toe pad? What is the role of lipids in the adhesion
process? Understanding the surface chemistry of the adhesion of the gecko
toe pads gives insight into this highly specialized biological interface, and
give clues for materials scientists aiming at mimicking the gecko adhesion
mechanisms. Using near edge X-ray absorption fine structure (NEXAFS)
imaging and spectroscopy we have studied the structure and order of the
molecules at the outermost surface layer of gecko toe pads. We show that
the keratin molecules within the spatulas are highly organized and adopt a
flat, strand-like geometry, which may support the stability and adaptability
of gecko setae (1). We will also discuss evidence showing that a nanometerthin ordered lipid layer is covering the beta proteins (2).
1.

Structure of Keratins in Adhesive Gecko Setae Determined by
Near-Edge X-ray Absorption Fine Structure Spectromicroscopy. J
Phys Chem Lett. 2022 Mar 10;13(9):2193–6.
Tuesday Morning, November 7, 2023
14

1.

Evidence that gecko setae are coated with an ordered
nanometre-thin lipid film. Biology Letters. 18(7):20220093.

12:00pm BI+AS+PS-TuM-13 All-Atom Simulations of Peptide Aggregation:
Understanding and Predicting Biopolymeric Morphologies, A. Kwansa, A.
Cannon, North Carolina State University; Yaroslava Yingling, 911 Partners
Way, Engineering Building I, Campus Box 7907
The self-assembly and aggregation of partly or completely disordered
peptides have emerged as crucial areas of research with broad implications
in therapeutics, supramolecular assembly, and functional biomaterials.
Understanding the intricate processes underlying the self-assembly and
aggregation of these proteins is essential for harnessing their functional
properties and expanding their applications. Simulations can be used to
isolate the importance of the interplay between aggregate morphology and
secondary structure formation. However, most of the simulation’s studies
investigate either single peptide in solution or several short peptide
analogues. We used large-scale all-atom MD simulations to investigate the
structure of hydrated peptide aggregates in detail. Two example systems
were investigated, reflectin and elastin-like peptides (ELP). Reflectin
proteins, found in cephalopods, play a pivotal role in dynamic coloration for
camouflage and communication. On the other hand, ELP proteins possess
unique thermoresponsive properties, making them attractive for drug
delivery systems, tissue engineering, and biomaterial design. We found
significant differences between the structure of a single polypeptide in
water and the structure of peptide within the aggregate. Overall, the
aggregation process is driven by the formation of peptide–peptide
interactions whereas the average hydration of peptides remains almost the
same between dissolved and aggregated states. Even though the
aggregation is driven by hydrophobic interactions, aggregate has no
hydrophobic core and contains many water molecules. Overall, our findings
provide an insight into the sequence-dependent structure of aggregates
and molecular behavior of individual peptides during aggregation.

Plasma Science and Technology Division
Room A106 - Session PS-TuM
Plasma Processing for Advanced Logic Device Fabrications
Moderators: John Arnold, IBM Research Division, Albany, NY, Tetsuya
Tatsumi, Sony Semiconductor Solutions Corporation
8:00am PS-TuM-1 Chemical Role of a Small Amount of Cl­­2 in O2/C

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<statements>
1. Sequential, self-terminating gas-surface reactions using trimethylaluminum (Al(CH3)3) and water vapor directly terminate surface dangling bonds and fill exposed lattice sites.
</statements>

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