Hi folks:

I am told that if a silicon wafer has a high oxygen content, the oxygen can
form a precipitate during a high-temperature process (1000C - 1100C). And if
that wafer is etched in KOH subsequently, the etchant tends to attack the
(111) sidewalls resulting in larger cavity sizes than expected and rough
(111) sidewalls. I have observed this on 2 of my wafers recently.

I spoke with a couple of wafers vendors regarding oxygen content of wafers
and was told that typical silicon wafers for MEMS applications have a oxygen
content in the 10 - 30 ppma range.

Can anyone recommend a spec for Oxygen content so that it does not form a
precipitate and cause subsequent KOH etching issues?

Thanks a lot,

Shivalik
Cambridge MA