Hi Yuanfang,

We have done the same with Ta/Au layers and had no adhesion/
delamination problems (they could even be used as etch masks)
both with TMAH and KOH.
Both also do not chemically attack SiN, but mask overhang
sometimes breaks off mechanically. Sufficient circulation of
the bath provided, this will not affect your etch result.
Be sure to use a double-layer SiN (or SiN/SiC) to reduce pin-
holes.

Greetings,
        Frank Berauer
        Senior R&D Engineer
        Hewlett-Packard Singapore


-----Original Message-----
From: Gao, Yuanfang (UMC-Student) [mailto:ygfff@mizzou.edu]
Sent: Wednesday, April 10, 2002 6:10 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Etching through a silicon wafer


Dear all,

I plan to use anisotropic wet etching to etch through holes in a
<100>silicon
wafer, using LPCVD silicon nitride as mask layer,
also there is a exposed Ti/Au layer(Ti act as a adhesion layer)
on top of silicon nitride.
My concern is:

1. Will Ti/Au layer resist the long time KOH etching?
2. If KOH doesn't work, will other etchants like TMAH do?
3. Will KOH etching damage the silicon nitride membrane?

Thank you very much!

Yuanfang Gao

University of Missouri
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