I spin coat Sylgard 184(1:10)  onto a Cr/Au coated wafer (PDMS thickness
between 3 to 20 micron). E-beam deposit Cu and pattern the Cu (100 to 200
nm). I use the Cu as a etch mask to pattern the PDMS in RIE (CF4:O2). Any
residual PDMS left on the surface is cleaned by a mixture of
tetrabutylammoniumflouride and N-methylpyrrolidione.

When I measure the resistance of the PDMS it was in the range of 200 kohms
(30 micron PDMS). The expected resistance of PDMS in this thickness range
should be around gigaohms.

One possibility could be holes. I have tried spinning twice but still I
could not overcome the issue. Penetration of the deposited Cu could be a
reason but I do not expect it to penetrate more than a micron.

Any suggestion will be great.

Thank you!