I tried this. You should do some silane chemistry on the SiO2 surface to promote
parylene adhesion (see e.g.
http://engineering.tufts.edu/microfab/index_files/docs/Parylene.pdf).
Even then, it doesn't work too well, the parylene tended to delaminate during
long etch cycles.

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On
Behalf Of Konstantin Glukh
Sent: Tuesday, October 07, 2008 4:30 PM
To: General MEMS discussion
Subject: [mems-talk] Parylene mask for KOH etch

Can anyone comment on using Parylene as a mask for KOH etch, either by
itself or in addition to SiO2 hardmask? Is there any way to ensure
good adhesion to Si and SiO2 and minimize undercut rate?