Could the bubbles be from water mixed in the photoresist?  If you store
photoresist in the refrigerator, you have to let it warm up to room
temperature before opening the bottle.  Water from the atmosphere will
condense on the photoresist if you open the bottle too soon.  I have
never seen (air) bubbles in spun on photoresist.  If it isn't from water
droplets, the problem may be in how you dispense the photoresist onto
the wafer for spin coating or from spin coating at too low a speed.

I use acetone to wash away photoresist, and follow it with methanol
before the acetone has evaporated away.  Then I blow dry the methanol
with dry nitrogen.

Winston

Radhakrishna Vatedka wrote:
>
> Hi all,
>
>    I am new to lithography technique. I am facing few practical problems.
> I will be grateful if some one helps me in this regard.
>
>    1. I face problem of bubbles on the photoresist. If i remove bubbles
> with difficulty, still i find discontinuity in resist film of microns after
> spin coating.
>    2. how to store photoresist? in refrigerator?
>    3. Which is the best solvent for photoresist (to wash away after etching)?
>   Is it universal one? I used acetone.
>   The photoresist i am using is a positive one HPR204.
>
> with regards
> Radhakrishna.V
>                   _________________________________________
>
>                                Radhakrishna.V
>                                Research Student
>
>                   Dept. of Instrumentation   |   Room No: R47
>                   IISc, Bangalore-560 012    |   IISc Hostel
>                   Ph: 309 2349               |   Ph: 309 2539
>                   ___________________________________________
>
>

--
Winston Chan                            | phone: (319) 353-2398
Dept. of Electrical Engineering         | fax: (319) 353-1115
University of Iowa                      | email: [email protected]
Iowa City, IA 52242