Hi
I have Si/SiO2 sample exfoliated with black phosphorous flakes and then spin coated with PMMA for ebeam lithography . After e-beam lithography of PMMA, it was developed in MIBK and IPA, and then Cr and Al thermally evaporated for metallization. Next, the sample is soaked in acetone overnight at room temperature for liftoff. What I observed is that the liftoff is still not clean. How can I obtain a clean liftoff in this case?
Any possible solutions to this question greatly appreciated.
Thanks
I've had good results with AZ 300T and 400T photoresist strippers. You will need to heat the solutions to ~80 C in a fumehooded environment, but it will take off any resulting ebeam resist in 10-20 minutes.
Remover PG (N-methyl-2-pyrrolidone, NMP) is also another common option that I've had good experience with for removing PMMA. Heating it also facilitates quicker lift-off (60-70 C should be fine).
Thickness of resist and the film are very important. I mostly use 300 nm thick PMMA for 50 nm thick film and completed the lift-off in half an hour or max one hour. Heating acetone is also a good option but not safe.
In an out way, you can try bilayer resist PMMA/MMA then you will have an undercut which will provide way to acetone to remove resist smoothly.
Muhammad Shahbaz Anwar Hello I immersed my sample(Al on SiO2) in acetone for 4,12,24hours ， but the Al is still adhere to the substrate. Why ? Do you have some suggestions? Since I have strutures on my substrate, I don;t want to use supersound wave.
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