Any shape of mask opening will eventually etch to a pyramidal pit
bounded by 111 planes.  The orientation of this pit is fixed.  The size
is determined by the extent of the mask opening in the 110 directions.
A square opening with side length d aligned to the 100 direction will
result in a pyramidal pit with a base dimension d*sqrt2.  (a square
circumscribed on the original square at 45 degrees).

Roger Shile



From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Xing Sheng
Sent: Wednesday, February 29, 2012 3:20 PM
To: mems-talk
Subject: [mems-talk] silicon KOH etch



Hi,



I have a question about 100 silicon wafer KOH anisotropic etch.



I opened a square window on 100 silicon using SiN as protection.
Normally the window should be aligned along 110 direction, so that we
can get inverted pyramid structure, and the plane angle is 55 degree.
However, I opened the window along 100 direction. It seems similar
pyramid is obtained. This is weird. What is the plane direction I got,
and what is the side wall angle at this time?



Thanks!



------------------

Best regards,

Xing Sheng

2012-02-29

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