Ok Guys,

Here's a tough one??

I've been given a set of instructions, ' How to produce 100umx100um SiN
membranes' and Si wafers (300um thick) coated with a layer of SiN 50nm
thick. So off I went to the lab to produce these windows and guess what?
After one whole week in the lab, the end result was a badly etched wafer
with no windows. So where did I go wrong? and why's my supervisor angry with
me?? After a whole month in the lab I seem to have sourced the problem, but
require your expert advice. The instructions specifically state I should wet
etch using NaOH @ a temp of 112C, but this recipe seems to etch away the SiN
hard mask and the Si etch distribution is uneven across the wafer. I believe
this may possibly be a typing error as NaOH  is the recipe given to etch SiN
and the correct recipe should be KOH as reported in many publications. So my
question is, is it possible to etch Si using NaOH without etching away the
SiN hard mask? If so please can you provide a recipe.

Thanking you in advance,
Asif

a.aziz@physics.gla.ac.uk

Asif Aziz
Department of Physics and Astronomy
Kelvin Building
University of Glasgow
University Avenue
Glasgow
G12 8QQ

Tel. no. +44 141 339 8855 extn 0896