Dry etching of small features

[Morgan Douglas Mager]

I was wondering if anyone has experience etching small features in thin 
layers and could share with me what tools/recipes seemed to work? I will 
be definine 100nm wide features with ebeam lithography, then metallizing, 
then dry etching. The active layer is 20nm thick Si (I'm interested in 
both amorphous and poly) and the stop layer is oxide. Selectivity isn't 
much of an issue, as I'll be stripping the oxide anyway, but I do care 
about undercutting of the Si feature layer. Any thoughts or advice? Thanks.

-Morgan