Dear Golda,

CHF3 chemistry is known to generate polymers. You can try CF4/CHF3
chemistry with Ar  instead. Fluorine etch species do not etch Al pads, so
you have very selectivity.

good luck
bhat s

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From: "Fradkin Evgenia - Golda" 
Sent: Thursday, September 01, 2011 5:42 PM
To: "General MEMS discussion" 
Subject: [mems-talk] Electrical contact to metal afer nitride removal with
RIE

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