I'm a little surprised this ended up being resist. Photolithography usually involves quite a lot of looking at SEM imagery of test patterns. (These usually go

I'm a little surprised this ended up being resist. Photolithography usually involves quite a lot of looking at SEM imagery of test patterns. (These usually go in the scribe lines.) The problem must have been pretty subtle for it not to get flagged. Maybe (since they mention unexpected polymerization) it left an unexpected residue after cleans? Post-photo clean usually starts with ashing in an oxygen plasma, so it would have to be some pretty serious gunk to survive that and the subsequent wet clean.