On Fri, Aug 15, 2008 at 1:39 PM, madhav rao  wrote:
>       I am experiencing a problem in patterning on silicon-di-oxide wafers; I
am using SHIPLEY 1818 resist to get a thickness of 2.5 micron; 6 seconds of
exposure time. After developing for 60 seconds, I observe, the resist layer
peels off; leaving no patterns on the wafer. Also I had soft-baked the resist at
95 C for 2 minutes in hot-plate.
> This seems strange to me, as a month ago, I had successfully transferred the
patterns on to silicon-di-oxide wafers.
> I am using mylar film masks.
> Please let me know, if any one had experienced similar problems before; and if
so, could you let me know suggestions to solve ?
> Madhav Rao,
> Graduate student,
> University of Alabama.

Madhav,
  1. exposure time without the context of the uv light intensity is
meaningless. You might want to borrow a uv light meter and see how
much the lamp has dimmed in the intervening months. Nevertheless S1818
is a positive resist and only the areas exposed to UV should be
developing away.

  2. you mentioned you performed this procedure several months ago:
Assuming nothing has changed, may I suggest a pre-spin bake of your
substrate on a 120 C hot plate or oven to improve resist adhesion. Let
the substrate cool before you spin, but in a dry place (nitrogen?) If
your substrates are subject to humid air (summer in alabama) it may be
reducing adhesion. You might also try an adhesion promoter.

Regards,
Jon Fox

Dr. Jon R. Fox
email: [email protected]
website: http://www.drfox.com
facebook: http://www.facebook.com/profile.php?id=536676463
linkedin: http://www.linkedin.com/in/drjonfox