Hello everyone!
I need to etch Si to the depth of 1mm approximately, not affecting the surface of the sample (which is atomically flat and must be kept as it is, so we can't anneal the sample). I would prefer a high-concentrated KOH solution (45% wt) close to the boiling point.
I have already tried electron beam deposited Cr, Ni, Ti, Au (with Cr and Ti as adhesion layers) and SiO2 (Cr adhesion layer), but none of them worked at 30% wt KOH 100°C. Au on Cr had shown the best result but peels off after half an hour; Au on Ti didn't stay 20% wt KOH at 80°C.
Can anyone please suggest masking layers (preferably with solutions concentrations and temperatures in which they can be applied) for the purpose I have?
Thank you in advance!
You may want to try alternatives of metals - polymeric coatings instead. But their removal/stripping may be critical to maintain the surface integrity in your case.
Ref: Article A spin-on photosensitive polymeric etch protection mask for ...
In metals, however, Mo & Ni are fairly resistant to KOH. Also, if you want to try using tetramethyl ammonium hydroxide (TMAH) instead of KOH, you may get more flexibility with metal coatings.
Alternatively, LPCVD grown SiN on SiO2 buffer can act as a good mask for KOH etch.
Ref: https://iopscience.iop.org/article/10.1149/1.1838668/meta
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