[mems-talk] Photolithography - Resist peeling

[madhav rao]

Hi,
       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 ? 

Thanks

Regards,
Madhav Rao,
Graduate student,
University of Alabama.