Hi Forum.

If you are depositing the resist manually while the wafer is spinning one would
expect to see a lot of streaking.  This is due to the relatively high viscosity
of the material and it not spreading well as the angular velocity of the wafer
is pretty high.

Try this, dispense the material into a puddle in the middle of the wafer without
spinning.  Then ramp the wafer up to the 3000 RPM.  With a 7 μm film, you will
undoubtedly see a little streaking (especially using a manual spinner), but this
should give you a better coating.

Good luck!

Best Regards,

Dustin Warren, PE

EV Group
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Application Engineer - Direct: +1 (480) 305 2447, Main: +1 (480) 305 2400 Fax:
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E-Mail: D.Warren@EVGroup.com, Web: www.EVGroup.com

-----Original Message-----
From: Shah, Forum N [mailto:forum@exchange.uta.edu]
Sent: Tuesday, July 21, 2009 2:19 PM
To: General MEMS discussion
Subject: [mems-talk] SPR 220-7

Hi everyone,

I am using SPR 220-7 photoresist and am looking at 7 micron thickness. I am
spinning at 3500 rpm for 30 seconds and also tried 3k rpm for 30 seconds.

I see a lot of streaks on the wafer and not getting a uniform coating. I did
take a look at Stanford nanofab website (www.snf.edu) but the problem is that I
have manual spinners and their manual procedure is also not working fine for me.

If anyone has worked with it before, your suggestions would be invaluable.

Thanks in advance.
Forum