You will be provided with a reference and some statements. Please determine whether each statement is 'supported', 'unsupported', or 'unknown' with respect to the reference. Please note:
First, assess whether the reference contains any valid content. If the reference contains no valid information, such as a 'page not found' message, then all statements should be considered 'unknown'.
If the reference is valid, for a given statement: if the facts or data it contains can be found entirely or partially within the reference, it is considered 'supported' (data accepts rounding); if all facts and data in the statement cannot be found in the reference, it is considered 'unsupported'.

You should return the result in a JSON list format, where each item in the list contains the statement's index and the judgment result, for example:
[
    {
        "idx": 1,
        "result": "supported"
    },
    {
        "idx": 2,
        "result": "unsupported"
    }
]

Below are the reference and statements:
<reference>
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</reference>

<statements>
1. Lithium niobate (LiNbO3, LN) is chemically inert, mechanically resilient, and electrostatically complex, which makes dry pattern transfer exceptionally challenging
2. Plasma-based reactive ion etching (RIE) and inductively coupled plasma reactive ion etching (ICP-RIE) inevitably introduce physical lattice damage, stoichiometric deviations, and chemical redeposition
3. High Ar+ physical sputtering fractions must be retained to dislodge LiF, which increases sub-surface lattice damage.
4. This promotes vertical ion trajectories, suppresses lateral ion collisions into the waveguide sidewalls, and prevents bottom micro-trenching.
5. Continuous helium backside cooling is required to maintain substrate temperatures below 15°C-20°C throughout long plasma exposures.
6. Without efficient heat extraction, thermal accumulation hardens electron-beam resists, causes mask reticulation, degrades line-edge definition, and promotes the thermal diffusion of lattice defects deeper into the crystal core.
7. Chamber pressure is kept between 1.5 mTorr and 2.5 mTorr to ensure directional, anisotropic ion bombardment, while active helium backside cooling maintains the substrate below 20°C to avoid resist degradation and defect diffusion.
</statements>

Begin the assessment now. Output only the JSON list, without any conversational text or explanations.