Freon Use Contaminated PQuest

shabbir.bashar shabbir.bashar at
Wed Jan 24 17:51:57 PST 2007

Hi Everyone,
I just wanted to bring to your attention the policy regarding usage of
the ECR etcher, PQuest.
As I understand it, the first three weeks of a given month are allocated
to non-Freon use - i.e. no polymers, only semiconductors like Gallium
Arsenide or Indium Phosphide.
Earlier this month (first week of January) I used the Pquest using my
standard recipe and was pleased to get the desired etch rate and results
I wanted with my Indium Phosphide wafer.  A week later (Second week of
January), Pradeep used the same recipe on parts of the same wafer that I
had used (i.e. identical pieces in all respect as the two pieces dry
etched at a week's interval came from the same original wafer and had a
hard oxide mask).  His results were drastically different to mine -
considerably slower and left a lot of debris on the wafer.  We have
since then put our work on hold.
Pradeep and I have since discussed this issue at length with Rafael
Aldaz from Prof. Jim Harris's group.  It is Rafael's opinion that
someone must have used the a Freon based etch recipe sometime between my
use and Pradeep's use i.e. late first week of January to early second
week of January.  The Freon eats up the Chlorine in my recipe and as a
result slows down the etch rate;  in addition it also produces the
unwanted debris around the etched areas.  In order to decontiminate the
etch chamber, it has to be opened to atmosphere and hand wiped with IPA
and the chlorine based recipe run for a day or so to pre-condition it.
Only after that can there be any confidence of reproducing chlorine
based etch results.
There is currently no log book for the PQuest.
I believe the PQuest is scheduled for routine chamber-clean around this
time of the month.  I would like to use the tool in the early part of
next week (first week of February) if at all possible.
Would someone please look into these issues and let me if this sounds
Kind regards,
Shabbir A. Bashar, PhD
nLight Photonics Corp.
5408 NE 88th Street, Bldg. E
Vancouver, WA 98665
Cell: +1 510 386 7304
Office: +1 360 713 5145
Fax: +1 360 546 1960
E-mail: Shabbir.Bashar at
Web: <> 
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