Nitrogen evolution is a by product of the photoactive compunds in most
photoresists as they age.  Your resist may simply be degrading/decomposing
from age.  Also, particles of debris will be accompanied by bubbles in the
coating.
*********************************************************
Mac McReynolds
Sr. R&D Process Engineer
Caliper Technologies
email:  [email protected]
www.calipertech.com

> ----------
> From:         Winston Chan
> Reply To:     Winston Chan;[email protected]
> Sent:         Monday, October 19, 1998 6:27 AM
> To:   [email protected]
> Subject:      Re: lithography problems
>
> 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
>
>