Keith,
   What sort of reactor are you using? If you can use an inductively coupled
reactor at say 30-40mTorr you might be able to improve the anisotropy. Or if you
have a DRIE with ICP and a pulsed DC source (such as used for clean oxide stops)
you might be able to use this feature to mitigate charging effects. Another
trick you might try is to use a metal masking layer, e.g. alumini. We've
observed differences in isotropy for small features as a function of masking
material.

-Mike Martin
 U. of Louisville
>>> [email protected] 09/08/05 12:11 PM >>>
Hello everyone,

I've been using O2 plasma (60 mTorr, 30 sccm, 150 W) and have seen an etch
rate of about 120 nm/min and a selectivity to resist of about 1:1. A problem
that I've been seeing is that there is considerable isotropy to the etch.
For instance, a 700 nm diameter hole in 2 um resist that I try to transfer
into 1.6 um of parylene becomes a ~3 um hole in the parylene after 15
minutes of etch. Has anyone seen a similar effect, and if so, found a way to
improve the anisotropy of the etch?