The streaks are normal in AZ4620.  You can try AZ 9000 series.

Hanqing Li

At 01:47 PM 1/15/02 -0800, you wrote:
>I have a requirement for a thick (~6+ um) positive resist layer. I've been
>trying to use AZ4620 at 4000 rpm for this purpose, but it always gives me
>an uneven, streaky coating, with the streaks running in the  radial
>direction on the wafer. I have tried ramping the spin rate to avoid this,
>but the streaks remain. If anybody has had a similar experience, and could
>help me out, it would be great. Alternately, I'd appreciate any
>suggestions for another resist that could give me a thick coat, and could
>be exposed on an i-line stepper.
>Thanks
>Alok Paranjpye
>
>Graduate Student
>University of California,
>Santa Barbara
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