Hi all, I'm trying to pattern Bragg gratings through e-beam lithography on a = SiO2 layer deposited by cvd on silicon. I am using 950PMMA resist from = Microchem. The minimum feature of the grating is 115nm, the pattern = needs to be written by ebeam, developed and etched afterwards. I would = be grateful if you could give me any suggestions for the PMMA thickness. = As a rule of thumb I knew that thinner PMMA (let's say 100nm) is good = for higher resolution features, although this could be a problem for the = subsequent etching step (as the PMMA might be burned away completely = during the process). What do you think? Thank you, R.