Dear All,

I am trying to make SU8-50  square wells (height- 40um) to be used as masters
for PDMS moulds. The square dimensions vary from 1mm x 1mm to 2.5 mm
x 2.5 mm. When I finally develop these wells after exposure and post bake, I
find that almost all of them have undeveloped SU8 remaining along the a
single ( or sometimes two adjacent ) edge which is same for all the wells
and gets repeated also. I had developed it for the recommended time i.e. 6
min for 40 um height well but even after developing for longer time it still
stays their. Is it because of over exposure? if so then why is it that only
a particular edge (of all the wells) has the residual SU8 due overexposure
whereas the other edges, particularly the opposite one is absolutely fine?
kindly help.

I would also like to ask whether the UV exposure dose for SU8 on SiO2 is
less than that of SU8 on Si and adhesion of SU8 is better over Sio2 or Si?
I shall be highly obliged if anyone can kindly help me.

Thanks in advance.

Debashis Maji