I've never tried it, but I've heard that Au can serve as an excellent
mask for KOH.  A key point I imagine would be to have a thin, low
stress Cr adhesion layer to minimize undercutting.

Gabriel Matus

>From: "D. Zhou" 
>Subject: [mems-talk] Any metal as KOH masking layer?
>
>I am just wondering if any metal can act as the masking layer( strong
>enough in KOH and easy to be removed) for deep KOH etching (say,~600 um
>deep) at 80 degrees. (It may take about 10 hours to finish the etching
>process). I tried NiCr (50 nm) but it could not sustain after 2 hours.