hi all,

i'm interested in etching gratings that are about 1 um deep with about 300nm
feature sizes in a quartz substrate. i prefer a dry etch because i want my
sidewalls to be as vertical as possible (and since my etch depth exceeds my
horizontal feature sizes, a wet etch will undercut significantly). i'm
finding it challenging to do this with photoresist/PMMA--to get those fine
feature sizes, i'm forced to use resist that is not more than a micron, but
to get those depths i think i need resist that is at least 3 um deep. i've
heard of cases of people using chrome as a mask for etching quartz. can
anyone confirm the effectiveness of this or suggest any other materials? i
need a thin, durable etch mask.

i've actually tried using 50nm of chrome as a mask during a CF4/O2 plasma
etch. I didn't expect the gases to attack the chrome at all, but I found
that the chrome didn't hold up during the etch.

thanks for any info!

Patrick Lu
Department of Electrical Engineering
Stanford University
http://www.stanford.edu/~patlu