This may be tied to a problem I had with streaks decades ago.  It was
because the resist had 3 different solvents in and they dried at
different rates.  When the resist manufacturer moved to a single solvent
the problem went away.  I know this may not help your situation but you
may want to talk to the resist manufacturer.  Bill Moffat

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Shah, Forum N
Sent: Wednesday, July 22, 2009 5:29 PM
To: Brad Cantos; General MEMS discussion
Subject: Re: [mems-talk] SPR 220-7

Brad,

The problem still persists even with a two step spinning. I do use the
same recipe that you suggested. Streaks are radial in appearance as you
mentioned. If two step recipe has worked for you, can you suggest what
ramp rate should i be looking at? the recipe that i followed was:

Step 1: Spin at 500 rpm with ramp rate of 100 rpm/s (lowest) for 10 sec.
Step 2: Spin at 3000rpm /3500 rpm at ramp rate of 100 rpm/s for 30 sec.

What soft bake do you prefer for this kind of recipe?  Does it help get
rid of streaks? If you have any other suggestions do let me know.

Thanks in advance. I appreciate your help.
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