Hello,

Over the years, I have observed (and this is purely anecdotal) that
different silicon starting material etches differently in, say, KOH or
TMAH of fixed temperature and concentration.  I have also observed that
the yield strength of silicon membranes, created using KOH or TMAH
etching, depends upon the starting material.

My conjecture on this observation centers on oxygen precipitates:  that
higher O2 concentration in the silicon leads to faster etch rate of
higher-order planes, and also to lower yield strength.

Microelectronic silicon technology benefited from decades of fundamental
materials work by NIST, and by individual researchers, to establish the
relationship between dopants and other silicon defects, and electronic
properties of Si.  MEMS has not benefited from the same intensity of
research, it seems to me, in terms of coupling dopant and defect
concentrations to mechanical properties of Si.

If anyone has experience or references on this topic to share with the
community, I'm sure they would be much appreciated, by me and by others.

Albert K. Henning, PhD

Director of MEMS Technology
NanoInk, Inc.
215 E. Hacienda Avenue
Campbell, CA  95008
408-379-9069  ext 101
ahenning@nanoink.net