Dear Giancarlo,

  Thanks a lot for your response.
  Can you please give me some more details about protek? How dose it work (like
wax?) and where I can get it?

  Do you think wax is unable to resist KOH for long KOH etching? I need to have
a long KOH etch for a 500 um Si bulk to remain a 10 um thinkness silicon
membrance with 1mm by 1mm square.

  Best regards
  Lawrence

CANAVESE GIANCARLO  說：
  Dear Chin-Jen Chiang
I think that protek is better than black wax for koh wet
etching protection.

Giancarlo Canavese