Hi,

As your mask material is oxide you should definitely use TMAH.
Especially if you need to etch through 500 microns. Using TMAH you do
not need more than 0.5 micron oxide, but with KOH you'd need almost 1.5
micron (I guess, never tried...).

Try 20-25 wt% TMAH in DI water at 80-90 degC. Make sure the etch volume
is large enough (at least one litre for a 4 inch wafer), and that your
agitation is good. It is also very important to make sure the native
oxide is removed in an HF dip prior to etching.

Good luck

Knut

Knut Lian
Process Engineer
Wafer Fab Technology
SensoNor asa
PO Box 196, N-3192 Horten
Norway
http:\\www.sensonor.com
Tel: +47 33 03 50 68
Fax: +47 33 03 51 05

-----Original Message-----
From: aslam muhammad [mailto:[email protected]]
Sent: 11. april 2002 10:48
To: [email protected]
Subject: [mems-talk] Wet Etching

Hi Friends

              I want to use TMAH and KOH as etchant to
etch bulk silicon ( 500 micron).  which one is more
suitable.  my etch mask is SiO2.  what is the recipe
of a good etching rate KOH and TMAH please.

Thankx


M. Aslam
Yahoo! Tax Center - online filing with TurboTax
http://taxes.yahoo.com/
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