If you need to align with very good accuracy to the actual crystal
planes, the article below will help you. We have found flats in
commercial wafers to be up to 1.5 deg off the crystal direction,
which causes size and location inaccuracies of etched cavities and
"steps" on etched <111> slopes.
We used the method in the paper, which requires an additional KOH/
TMAH etch step and visual inspection by microscope, to successfully
align to less than 0.1deg accuracy and have no more such problems.

M. Vangbo, Y. Baecklund, "Precise Mask Alignment to the Crystallographic
Orientation of Silicon Wafers using Wet Anisotropic Etching", J. Micromech.
Microeng. 6 (1996) 279 - 284

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


-----Original Message-----
From: Brian Semak [mailto:[email protected]]
Sent: 21 January 2002 23:06
To: [email protected]
Subject: [mems-talk] Allignment marks for proper orientaion of KOH mask


Hello everyone

Can anyone help me with some allignment marks. I am looking for allignment
marks, which ensures proper orientation of a KOH mask in the 100 plane of a
wafer. The masks I am looking for, should be etched into the wafer, thus be
used for alignment of the mask for subsequent KOH etching. If anyone here as
some ideas and suggestions, I would be very gratefull.

Med venlig hilsen/Kind regards

Brian S. Semak, M.Sc.
R&D Silicon Processing

Hymite Aps
DTU, Bygn. 325, 1st floor
2800 Lyngby

Telephone(Direct): + 45 4525 9147
Fax:                     + 45 4525 9156
E-mail: [email protected]
www.hymite.com
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