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.