Daniel,
140nm of LPCVD nitride is enough for few mm thick Si etch in KOH. You
shouldn't have any problem.
shay

-----Original Message-----
From: Daniel Park
Subject: [mems-talk] KOH Wet Etching of Si wafers

I am trying to etch the center area (2.5 inch diameter) of the backside of
500 um thick Si wafers (4inch diameter) using KOH wet etching process. I am
considering to use 300 nm LPCVD nitride to protect the edge area of the Si
backside. I am just wondering whether 300 nm thick nitride will be enough to
etch the center area of 500 um thick Si wafers.