patterning silicon nitride

[Ben Jian]

Hi,

I am trying to pattern 1700 A of LPCVD nitride on a silicon wafer. The features are 450 micron size. The nitride etch process should not etch silicon surface at all. Does anyone have a process for it?

I am thinking about using hot phosphoric acid to etch nitride without etching silicon at all. But what should be the etch mask during phosphoric etch?

Thanks for your help.

Ben

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