Hello Dave,
Sometime ago i wanted to thin down a (100) silicon wafer. I have used 20%
KOH at room temperature. Etch rate is slow (i'm not sure but it should be
about 3um/hour, i don't remeber the exact value). I obtained a very good
uniform etch. I hope this will work also for your highly doped wafers.

Best regards,
Andrea
________________________________

Da: Dave Goldstein [mailto:d.goldstein.2007@gmail.com]
Inviato: giovedì 20 dicembre 2007 4.22
A: mazzolari@fe.infn.it; General MEMS discussion
Oggetto: Re: [mems-talk] How to uniformly etch ~0.05 - 0.3um off a 3" Si
wafer?


Thanks Edward and Andrea for the reply!
I need to remove the top ~ 0.1 um of Si with diffusion 'cause I am
suspecting my top surface is rich with defects due to the saturating
concentration of dopants right at the surface.

About surface roughness: I think you don't get rougher than 0.1um when you
are etching 0.1um off. And my requirement for surface roughness is very
lenient. 0.1um will do. But uniformity is the problem.