Did you thoroughly dehydrate the wafer prior to spinning? I would recommend
at least 250degC for 30mins on a hotplate. Otherwise your piranha may be
contaminated (it also needs to be freshly made which is why I prefer to use
just conc. H2SO4).


On Tue, Mar 31, 2009 at 08:54,  wrote:

> hi all
>      i am spin coating SU8 2050 on piranha cleaned silicon wafer but
>    during prebake it is shrinking and coming into the center of the
>    wafer. What could be the possible cause ?
> --
> Kamlesh Pawar
> M.Tech (Biomedical Engg)
> Mob :+919870062960
> IIT-Bombay