Hello Richard,

In order to strip all of the nitride, you will have to over-etch somewhat. This
will etch the underlying silicon to some degree. However, you can limit this by
carefully choosing your etch chemistry. [CH3 + N2] can provide you with a
selectivity of up to 16:1 for nitride over silicon. See the following reference:

Li, French, and Wolffenbuttel
Selective Reactive Ion Etching of Silicon Nitride over Silicon Using CHF3 with
N2
Addition
Journal of Vacuum Science and Technology B
Vol. 13, No. 5
September/October, 1995

Best wishes for all your work,

Craig McGray
6211 Sudikoff Laboratory
Dartmouth College
Hanover, NH 03755



> Date: Mon, 22 Apr 2002 16:45:06 +0100
> From: "Haigh, Richard" 
> Subject: [mems-talk] REMOVAL OF NITRIDE
>
> Dear All
>
> I've had some SOI wafers coated with Si3N4 and patterned on one face.
> Unfortunately, the wrong face has been patterned. I don't want to
> dispose of the wafers because of their cost. I've been told that I can
> have the nitride striped off both faces (with RIE), then re-applied and
> patterned on the correct face. What I need to know, does the stripping
> damage the silicon in anyway?
>
> Regards
>
> Richard Haigh