Hi, all, The structure of our device composed of silicon/Patterned PMMA(~200 nm)/ALD Al2O3 (~40 nm). I have tried to dip the device in acetone to do lift-off but the Al2O3 layer on the entire substrate surface does not lift-off. It seems that either acetone can not penetrate the Al2O3 layer or the PMMA layer is hardened. The deposition temperature for ALD Al2O3 is ~ 150 C which should not be high enough to harden PMMA. Does anyone have any suggestions on the lift-off process? Thanks a lot. Best regards, Jun