I am using a 1 micron thick PMMA as a mask for RIE. It worked for
fabricating 1 micron holes and I am trying to get define smaller features
in the resist through Electron Beam lithography. My problem is with the
stability of PMMA (9%). After a few days of spinning the PMMA resist my
surfaces of my samples have become foggy and I have put them in acetone
for sometime thinking that the fogginess is because of the degradation of the
resist. But that didn't work.

Can anyone please let me know why that is due to.

Thanks
Sreemanth