CHF3 plasma has a tendency to deposit a Teflon-like fluorocarbon film.
Exposure to an oxygen plasma following etch should remove it.

Roger Shile

-----Original Message-----

Hello,

I have a process with PECVD silicon nitride layer on Al metal pads.

 I would like to pattern the PECVD nitride layer to reveal part of the
metal pads and connect to them electrically by evaporation of another Al
layer on top.

The patterning of the PECVD nitride is done by RIE with a chemistry of
CHF3. This etching method is known to leave a residual polymeric layer
that might act as a buffer between the two Al layers resulting in a bad
electrical contact or no contact at all.

Could anyone explain this phenomenon?

What is the nature of the residual layer and how can it be avoided?

Thank you,

Golda