removing PR after argon dry etching

Hi labmembers,

I am running into a wall with my new process. We are using 1.6 um of 3612 resist as an etch mask for dry etching in the MRC etcher. Our dry etch recipe is argon sputtering/etching for 10 minutes at 100 W. This causes hardening/texturing of the resist, which looks like craters in the SEM after the dry etch.

The problem is that I have not been able to remove this PR after this hardening occurs. I have tried 10 minutes O2 plasma in drytek 1, followed by acetone sonication for 10 minutes, followed by another O2 descum, but the resist still remains. The samples have Al metal on them, so that I can not use piranha. They are also gold contaminated. I imagine this is a problem people have encountered before, so any advice, especially specific recipes would be greatly appreciated.

Thanks,
Neil Dasgupta