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?

Thanks.
Keith L. Aubin, Ph.D.
Cornell University
School of Applied and Engineering Physics
212 Clark Hall, Ithaca, NY 14853
607-255-6286


Your undercut sounds somehow extreme, but generally sounds like you have
plasma etching (like in a barrel asher) vs reactive ion etch action (as
in an RIE).

You need proper electrode geometry and be in the proper pressure/flow
regime to direct ions to achieve anisotropic RIE action.

If you don't have an RIE, you are pretty much up against needing all new
hardware. After that, pressure, power and gas recipes are chamber
dependent, but generally RIE is running at lower pressure than a barrel
asher to increase mean free path.

Linas.