Hi guys,

I want to etch a slit (1-2um width at the top side, 200um long) through
a Si-wafer with 1um thermal oxide on top. I was thinking of a backside
etch selectively stopping at the SiO2, thus creating a membrane a little
bit larger than the final slit (I guess, control of the etch rates is
very challenging). Then, an additional dry etch of the 1-2um slit
through the oxide by RIE.

Do you know about a good process flow and/or do have any references?
Anything about a highly selective etchant, which mask (hard or soft) to
use, how to protect the front side etc.

Best wishes
Daniel