Geoff:

You might consider placement of an inline trap, possibly a cold trap with
cooling lines, in your foreline between the etch chamber and the pump.  This
will prevent most of the polymeric etch residues that you are seeing from
reaching the pump.  Periodic cleaning or replacement of the trap, depending on
the solution, will be needed to maintain your pumping speed.  Traps are
available at most vacuum parts suppliers along with the expertise to help select
an appropriate trap.

Robert

-----Original Message-----
From: mems-talk-bounces+rditizio=tegal.com@memsnet.org [mailto:mems-talk-
bounces+rditizio=tegal.com@memsnet.org] On Behalf Of g4lee@uwaterloo.ca
Sent: Thursday, December 01, 2011 8:10 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] CHF3 Damaging Pump

Hello all,

We are using a pure CHF3 process to etch oxide for our process and our
roughing pumps are being damaged as a result. Small white flakes can
be found in the filter, which is also dyed red (from an initial beige
colour). Does anyone have any experience with this problem, and are
there any methods to over come it?

Regards,

-Geoff