Photoresist distorts some during hardbake if you bake at a higher temp than
your post exposure bake. If you want no minimize your distortion, bake at
same temp as your PEB. If you're not doing a PEB, put one in your flow.

Robert
-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Rupesh Sawant
Sent: Tuesday, March 14, 2006 11:01 AM
To: General MEMS discussion
Subject: [mems-talk] Post bake for AZ P4620 photoresist

In my experiments, I tried a post bake procedure for a 20 u thick AZ
P4620 photoresist spun on a glass slide. i observed that the features
were destroyed after the post bake. the post bake was done for 5 min
at 120 deg. C. According to the literature, post bake is an optional
step for thick photoresist layer and the features may distort due to
"Reflow" if the hard bake is done. Can someone tell me a clear  reason
for this distortion for thick photoresist.