Hi Shweta
first of all, HF either as it is or in form of a BOE
does not etch silicon practically at all. If you want
to etch silicon by HF based solution, you have to add
an oxidant, such as nitric acid. And nitrid acid is a
PR stripper so quite obviously it will remove your PR
very well. You can use as a mask either good silicon
oxide (such as thermal) or LPCVD silicon niitride.
Dry etching is far mor comfortable, either SF6 plasma
or XeF2 vapor will do the job very well. in case you
are interested to try out the XeF2 vapors, you can
just send us your wafer (wafers) or samples and we
will do it for you free of charge.
In both cases, SF6 or XeF2 you can use PR as a masking
material for the depth of 4 um. For the lnger etching,
XeF2 might be better as it does not attack PR at all.
Pavel

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Pavel Neuzil
CTO SiMEMS Pte Ltd

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