Hi Group, I know it sounds like a trivial question, but I am recently having great difficulty in removing AZ5214 photoresist that has undergone image reversal. Even after no further processing beyond PR developing, I cannot easily strip the resist in Acetone. Boiling acetone seems to have little effect on the resist. This is a standard procedure which I have not until recently had any problems with. See process below. There is not prblem when I do the positive-image process. Should I try lower postbake temp or lower flood exposure? Why do you think I cannot remove the resist in acetone?? Thanks! Process is as follows: Spin AZ5214E PR at 5000 RPM / 30 sec. prebake at 110deg. C / 30 sec. expose 8 sec. in KS - MJB-3 (I don't know the intensity offhand) Postbake at 125deg. C / 60 sec. Flood expose 330 mJ/cm^2 Develop 45 - 50 sec. in AZ327 MIF.