Hello to all, when i fabricate my device, i met one problem about KOH
etching.I deposited around 3500-4000A low stress LPCVD nitrid as KOH
etching through mask.I opened one window and then KOH etching.After five
to six hours, even 3500-4000A LPCVD nitrid was mostly stripped off.I do
not know the exact reason for this.i used 49% wt KOH 80deg c etching.I
know at this condition, nitrid etching rate is nearly zero.how come like
this? After that, i thought it over.it maybe the following reason. Even
i chose Low stress LPCVD nitrid, but the deposited time is still too
long,it is about 20 hours and the deposit temprature is high.so at the
last, the accumulted stress in nitrid is still high.when KOH etching, H2
bubble comes out.When bubble broken, suface tension will strip off high
stress nitrid. I amnot sure about this.some one has my similar
experiences.please confirm this for me. Thanks shifeng Li

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