Dr. Marcus,

   I read, with interest,  your comments on the MEMS news group on silicon tip
formation and tip defects. This is an area that I am very interested
in. I am developing a silicon cantilever/tip for atomic force
microscopy. The tip is formed using a KOH etch to form a high aspect
ratio tip (typically 15 um tall) in an epi layer. I find that the yield of tips
is
lower than I would like. The most common faults are the formation of
wedge shaped tips (often microns wide) or smaller 200 nm wide
wedges. I rarely see the large wedge shaped in CZ silicon, but often
in the epi layer tips.  I have also seen tips where the one edge of
the tip is at different angle than the other sides. This is observed
in CZ silicon, but the amount varies depending on the batch of
silicon the wafers are from.
   I am interested in any comments you might have on these problems
and if possible I would like a preprint of your paper on atomically
sharp Si tips.


   Ken Westra
  Staff Scientist- MEMS
  Alberta Microelectronic Centre
  westra@amc.ab.ca