Pepsi Challenge

Kai-Mei Camilla Fu kaimeifu at
Fri Jun 20 18:24:28 PDT 2003

It sounds like we really should have a meeting where people can talk face
to face.  This e-mails don't seem to be solving the issue and are making
people angry.

Perhaps we can together come up with a set of guidelines for general use
of the p-quest with penalties for not following the guidelines (using
logbook, clearing new processes with some authority as well as testing
machine after processes).

I propose next week, unless many people are out of town.  If this is the
case, the week after.

There are many users of different schedules.  So I am not sure how to
arrange this.  Unless Jim McVittie has a problem with this, could users
just e-mail me if they can make either of the two days (not just their

Tuesday June 25th 10:00 a.m.
Tuesday July 1st at 10:00 a.m.

If these days turn out to be horrible for everyone, I can try again.
Otherwise, if they are good for most of the interested people and a few
people cannot attend, these people can voice their opinions through
someone else.

Let me know-


On Fri, 20 Jun 2003, Randy True wrote:

> Mark-
> There are simple ways not to exclude people from the discussion, use the
> log book, the pquest at snf email list, and coral. I'm asking for the 2nd
> time to please document the details of these experiments you refer to.
> As an example, look at the summary from last July, it's in the pquest
> email archive. Here, I will copy it to the end of this email. I do not
> know if you are aware of this, but almost identical problems to those
> you are reporting were encountered last July by Vijit Sabnis. Initially,
> my process was blamed and Jim McVittie forbid me to run it. I think that
> the resolution of the issue was that the use of copper tape to attach
> pieces was the culprit, not my process
> Since August of 2002 up until the recent problems, no one has reported
> (in any public format) problems with their etches that they suspected
> were due to interactions with other processes. Basically it has been
> smooth sailing. In the last month, usage of the pquest has quadrupled,
> including several new processes. I'm not blaming these new processes for
> the problems, but given the number of different materials being etched
> and the lack of monitoring and characterization, it's not a suprise that
> standard processes have gone south (my process included!).
> The only GaAs user I have talked to, Gigi, said that he has only had one
> abnormal etch, and in this case he changed some of his experimental
> parameters. With regard to ruining one of your valuable samples, you
> should certainly be running test samples beforehand, and if these turned
> out fine but your "real" chip didn't, I don't think it's logical to
> blame chamber conditions. Looking at the log book, I only saw one entry
> under your name (along with sbanks) on 6/12. How many times have you
> used the pquest in the last month? Why aren't you logging your runs?
> When did you first start using the pquest and have you established a
> reproducible baseline etch process?
> When you mentioned PMMA, were you refering to my polyimide etch process,
> ot perhaps another process that uses PMMA as an etch mask? About my
> process: I etch polyimide (PI) not PMMA, though I do not think there
> would be a difference since PI and PMMA are very similar polymers. I use
> Al as a hard mask and the gases in the etch are Ar and O2. My wafers are
> "clean" at the point that they go into the pquest, they are coming from
> the P5000 metal chamber. I have been doing this same etch for over a
> year, running consistently (at least several times a month and sometimes
> several times a year) and concurrently with many GaAs users (gigi,
> ethrush, kaimeifu) and some non-GaAs users (cmfalukner).  It is not
> impossible that my process (perhaps in an interaction effect with
> another) is now causing problems, but I think it is quite obvious that
> above information shows that it's unlikely. Is using the machine
> frequently for 6 months with GaAs users enough of a demonstration for
> you that I am not "ruining the machine for everyone else". It's not
> unfair to ask me to demonstrate this (though it does take the guilty
> until proven innocent approach), but no one has asked, they've just
> accused. So I invite you to take the Pepsi Challenge: you run your
> season process, etch a test GaAs chip, etch another test GaAs chip,
> measure the etch rates and confirm that everything is normal. Then I
> will run my process on the Si dummy wafer (my season step), then etch a
> PI wafer, then you repeat your part and we see if the results compare
> with those from the first round. Sound good? I reserved the Pquest next
> Thurs, starting at 7am. Does that day work for you? If not perhaps, we
> could have someone else from your group run the GaAs chips. It may be
> easier to arrange things by phone, my cell phone number is 415-269-2974
> . Let's do this, it will go along way toward settling this issue, at
> least with my PI etch process.
> --Randy
>  From the Pquest archive July 02:
> Here is a summary of the etches done since the etcher came back up last
> Thurs:
>  > PQuest Etches
>  >
>  > Date & Time     User    Recipe                  Material
> Brown?  Temp    Bias
>    Etch Rate
>  > 7/25 4pm        true    Ar=40,O2=20             Dummy Si
> No      0 C
>  >                         Ar=40,O2=20             Polyimide
> No      0 C     150
> V   Normal, >5000A/min
>  > 7/25 9pm        sabnis  O2                      Carrier
> NA      85 C
>  >                         Ar=15,BCL3=10,CL2=3     Carrier
> Brown   85 C
>  >                         Ar=15,BCL3=10,CL2=3     InP
> Brown   85 C
>       10% of Normal, 250A/min
>  > 7/26 3pm        gigi    O2                      Dummy Si
> NA      5 C
>  >                         Ar=15,BCL3=10,CL2=2     Dummy Si
> No      5 C
>  >                         Ar=15,BCL3=10,CL2=2     GaAs
> No      5 C
>       Normal, 1000A/min
>  > 7/27 2pm        sabnis  O2                      Carrier
> No      25 C
>  >                         Ar=15,BCL3=10,CL2=3     Carrier
> No      25 C
>  >                         Ar=15,BCL3=10,CL2=3     InP
> No      25 C
>       Normal, 330A/min
>  >                         Ar=15,BCL3=10,CL2=3     InP
> No      25 C
>       Normal, 260A/min
>  >                         Ar=15,BCL3=10,CL2=3     Carrier
> No      85 C
>  >                         Ar=15,BCL3=10,CL2=3     InP
> Brown   85 C    50
> V    10% of Normal, 260A/min
>  >                         Ar=15,BCL3=10,CL2=3     InP
> Brown   85 C    50
> V    10% of Normal, 290A/min
>  >                         Ar=15,BCL3=20,CL2=6     InP
> Brown   85 C    55
> V    10% of Normal, 265A/min
>  >
> Mark Wistey wrote:
> >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
> >
> >
> >

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