White spots or streaks are a precipitate of SU-8 caused by an incomplete
develop process.  Gareth brings up many good points about the develop
process.  You should try longer expose, longer PEB, longer develop or,
unfortunately, combinations of these factors to solve the problem.

Good luck,

- Garrett

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-----Original Message-----
From: Gareth Jenkins [mailto:[email protected]]
Sent: Tuesday, July 08, 2008 5:59 AM
To: [email protected]; General MEMS discussion
Subject: Re: [mems-talk] SU-8 2035 white spots

Development times can vary a lot depending on temperature and
agitation etc. If you have sufficient exposure dose and PEB it is
pretty much impossible to overdevelop SU-8. If you see white streaks
after the IPA wash, put it back in the developer for a few more
minutes. If you still see streaks you can repeat this as many times as
you like (replacing with fresh developer along the way).
If this doesn't work, then it is most likely partially exposed SU-8
somewhere (perhaps due to poor mask contact or incorrect exposure
dose).