I wish to use deep-UV lithography to pattern my sample with 1 micron wide and 1 micron spaced inter digitated contacts (100 nm thickness Ni/Au as the metal stack). Since deep- UV (193 nm) lithography has a higher throughput compared to e-beam litho, I wanted to go ahead with this procedure.

The process I have been using is spin coating of bilayer PMMA (450 A2 + 950A2) at 4000 rpm for 45 seconds , baking each of the resists at 180C for 2 mins. Then I am exposing using 193 nm deep UV source for 15 minutes followed by development for 3 min 30 s.

Features look good after development and I see contrast as well but unfortunately, post-deposition when I keep the sample for lift-off in acetone, metal peels off from everywhere. It's not an issue with stiction as metal didn't peel off from other similar samples co-loaded for deposition with these samples patterned using deep-UV lithography. I have also tried PR ashing in low power oxygen plasma post development but that didn't help either.

I would extremely appreciate if some one could help and guide me in this regard.