Here are a couple of references on crystallographic etching and compensation
of convex corners on silicon:

Mayer et. al, J. Electrochem. Soc. Vol 137, No. 12 (Dec '90) p. 3947

Offrens et. al. Sensors and Materials, 3,3 ('92) p. 127

Zubel, Sensors and Actuators A 94 (2001) p. 76

The convex corners of a mask tend to be undercut by fast etching planes.  I am
puzzled by the disagreement in the literature as to which planes etch fastest.
The first two references above indicate that in KOH etching of Si, the the
highest etch rate always occurs normal to the <411> plane.  Data given by the
third reference indicates that the highest etch rate occurs normal to the
<311> plane.

The ACES etch simulator gives the <311> plane the highest KOH etch rate and
doesn't even allow specifying an etch rate for the <411> plane.

The ratio of etch rates on different planes is a function of the etchant
composition (e.g. KOH vs. EDP), the concentration (e.g. 20% KOH vs. 40% KOH)
and the temperature.

I would be grateful is someone could explain the reason for the apparent
contradiction in the literature as to which is the fasting etching plane when
Si is etched with KOH.

Knowledge of which planes are dominating the undercut of convex corners is
necessary to properly design corner compensation and other masks for processes
which utilize this undercut.

Roger Shile


>>> michelefinardi@yahoo.it 04/22/02 01:48AM >>>
Hallo,
I'm about to start working on convex corner
compensation. Could you please indicate me some
references or share your personal knowledge?
Thank you very much.

Michele Finardi

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