Hi Sandhya,
There are a number of possibilities.

1. Make sure your wafer is VERY clean before spin-coating. I usually do a
piranha clean followed by DI water rinse, and dehydration bake, HMDS
treatment, then spin-coat.

2. Make sure your PR is clean. I pour some PR from the stock bottle into a
small CLEAN beaker about an hour before I spin-coat, and pour it from the
beaker onto the wafer just before spin. If you're one of the people who
uses a dropper bottle to apply PR, make sure it's clean before you put any
PR in it, and never blow bubbles in the PR with the dropper. It sounds
like your PR is dirty, from your description.

Jesse Fowler
  UCLA/MAE Dept., 420 Westwood Plaza, Room 37-129, ENGR IV
  Los Angeles, CA 90095-1597 | (310)825-3977
"Observations of nature, no matter how seemingly arcane, are like
peeling off one more layer from the great onion of knowledge"
    -- Don Petit, ISS science officer

On Tue, 27 May 2003, sandhya sandhya wrote:

> Hai all,
> I am Sandhya,a research student In Boise State University. I have a question
regarding photolithography, I am getting striations and small bubbles in the
resist after spinning and i am using SPR 220.7 resist. Can someone please kindly
say me what might be causing it and what should i do for eliminating them.
> Sincerely
> Research student
> Sandhya Reddy
>
>
>
>
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