Is it possible that the PMMA pattern was undercut in the fine areas?

Dan

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of luhaorice
Sent: Monday, August 17, 2009 4:30 PM
To: General MEMS discussion
Subject: [mems-talk] Gold peel off with PMMA mask

Dear all,

we created patterns on SiO2 with Cr and Au(etching process).  Then, PMMA

was spin coated on the chip followed by EBeam lithography to create a
few windows on PMMA.  We etched part of SiO2 in diluted HF(5:50ml) for
5mins.  After removing PMMA in acetone, we found all fine gold
structures peeled off even under areas protected by PMMA.

Could I have some suggestions to solve it please?

Thanks,
Hao