Dear all:

I have questions about the TMAH and KOH etching.
I use a layer of LPCVD nitride with 1500A thick.
After 3 hours KOH etching (30% w.t., 80C), the nitride layer is etched
seriously.
Similarly, the nitride layer cannot survive in TMAH (8% w.t., 90C) for more than
5 hours.
Is there any method or material that can be used as the etching mask in TMAH and
KOH for at least 11 hours?
Please give me some advice.
I really appreciate it.

Regards,

Y.C. Lin

Dept. of Power Mechanical Engineering,  National Tsing Hua University, Taiwan.