Kishan-

The wrinkles in your SiN "windows" are due to stresses in the nitride film.
Your KOH process will have very little (if any) effect on the stresses
(intrinsic, thermal, lattice mismatch, etc).  You should focus on the nitride
deposition process for reducing stress, and the resulting wrinkles in the
film.

-Jon Engel
MASS Group, UIUC


>----- Forwarded Message -----
>From: General MEMS discussion 
>To: mems-talk 
>Subject: [mems-talk] KOH Etching
>
>Has anyone had significant experience etching nitride windows on silicon
using
>a KOH etch? I am trying to create very thin (4200 Angstroms) Silicon Nitride
>windows, but my yield goes below 50%. My KOH bath is composed of KOH pellets
>and water at 80 degrees C. Are there any ways to reduce wrinkles in windows?
I
>currently dip my wafers in cool DI water for 10 minutes and then dry them in
a
>120 degree oven with my pits opening upward (i.e. window surface downward).
>
>Any help would be great. Thanks.
>
>-- Kishan Gupta
>UC Berkeley