Hi Patrick,
You can use sputtering system to etch very fine features. what you
have to do is place the gold coated substrate in the target place. you
can use any photoresist as mask. etching rate is pretty slow.
as long as u can very good pattern transfer onto  the photoresist you
should be able to get very fine feature.
I hope this is useful.
Good Luck.
regards
Ramesh
Syracuse University