request for a pquest user meeting very soon

Mark Wistey wistey at snowmass.Stanford.EDU
Thu Jun 19 18:54:28 PDT 2003

Randy -

Although it's true that several of us have been discussing our
respective problems with the PQuest, it's certainly not been our
intention to keep you--or any other user--out of the discussion.  What
happened was that several of us GaAs folks were having problems with
etch rates, junk being deposited, etc., but each just assumed it was
something we were doing wrong.  That has changed over the past
2 weeks, as we've started swapping notes with each other.  So the
circle of discussion has been gradually expanding, until it finally
reached Jim McVittie and, now, you and all the other PQuest users.

It boils down to this: Most of the GaAs users are having severe and
unrepeatable problems with the PQuest.  I'm not talking about a few
percent change in etch rates.  I'm talking about wafers that come out
so contaminated that they're grey.  Some of these wafers (in my case
in particular) are irreplaceable on the short term.  With all due
respect, writing comments in the log book doesn't solve our problem.
Conventional wisdom has been that a long O2 descum, followed by a long
seasoning, returns the PQuest to "clean" condition.  If you want to
take a look at my ash-colored wafer, you will see that this is not
true.  (90min O2 descum, 1+ hour seasoning.)

Anecdotal evidence suggests that the worst of the problems arise after
someone etches PMMA in the PQuest.  We are trying to be as accommodating
as possible to you and other users, and as far as I know, no existing
processes have been banned yet.  Jim McVittie will be doing tests to
try to reproduce the problems we're seeing, so we can make informed
decisions from there.

The PlasmaQuest was purchased by III-V people for clean III-V etching,
and at the moment, it's not serving that purpose.  I don't believe
it's unfair to ask you to demonstrate that your own process--however
long it may have taken you to develop--is not ruining the machine for
everyone else.  I can assure you, we've invested considerably (!) more
"time and money" developing growth and fabrication processes which are
worthless while the PQuest is in such a sorry state.

More in another email.  The most-affected III-V people are madly
preparing for a conference, so email will have to serve as the
"meeting" for the time being.

 - Mark

More information about the pquest mailing list