The coefficient of thermal expansion (CTE) mismatch between the SiO2 and the
polyimide is significant (~40x), the SiO2 is too thick to deform elastically so
when perform your cure step the SiO2 cracks.  The spalling possibly indicates
poor adhesion between the SiO2 and polyimide but may simply be a secondary
function of differential expansion.

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Aamer Mahmood
Sent: Tuesday, August 31, 2004 7:50 AM
To: [email protected]
Subject: Spam:[mems-talk] Deposition of thick SiO2 layer


Hello all,
I have deposited ~ 2-3um of SiO2 on a polyimide (PI2610). Subsequent
process steps require curing @ ~ 265 C. I notice big cracks in the Oxide
and also large chunks of it just peel off.
Before resorting to sputtering, I have also tried spin-on-glass but faced
similar problems.
Any suggestions on the cause and/or remedy would be greatly appreciated.
Thanks.

Aamer Mahmood
Grad Res Assist
Microsensors lab
UT Arlington

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