I do not know enough about your problem, but it sounds very like a problem we
had at the beginning of time circa 1960 spinning 1", then 2" wafers with photo
resist. Because there were more than 1 solvent with more than 1 vapor pressure
the solvents tended to dry at different times in the spin cycle. As soon as
this happened the remaining solvent resist liquid flowed around the dry solvent
area creating comet tails and or streaks. One very large manufacturer
experimented with an artificial atmosphere that was a vapor mix of the 3
solvents that we used at that time to try to inhibit preferential drying. The
ultimate solution was a 1 solvent resist system. Not sure how this helps you.
How thick are you trying to put down the sol-gel. Possible thought, do not spin
coat try spray coat or roller coat. Lots of luck Bill Moffat
-----Original Message-----
From: X. Yuan [mailto:[email protected]]
Sent: Saturday, January 25, 2003 1:11 PM
To: [email protected]
Subject: [mems-talk] titania sol-gel spin-coating issue
Hi, I am doing TiO2 sol-gel spin-coating process.
The sol that I got from the precursor Ti(OC3H7)4
looks clear and I use ethanol as the solvent.
However, after spinning on the spin station usually
used in the cleanroom, I found there are very thin
streaks emanating from the center of the wafer and
they are very uniformly distributed on the entire
surface of the wafer. I changed the solvent to IPA
assuming it evaporates slower than ethanol. The
situation doesn't change.
I am wondering if it is because of the spinning
process or still due to some problems with the sol.
Thanks very much for any suggestions!
Yuan
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