Zn deposition in the Metalica

Jim McVittie mcvittie at cis.Stanford.EDU
Wed Apr 14 10:38:51 PDT 2004


I think it is would be a big mistake to open up the Metalica up to general
Zn use. I have a number of reasons for saying this.

1. Zn is a problem material in vacuums. One has to be very careful in
using it in a vacuum dep system. If not controlled, it will go everywhere
in the system and every deposition will be Zn doped. It will move around
if a surface goes above 100C.  There is no way Zn will be contained to
removable parts if the tool is opened up for general Zn.
2. Although the Matelica is a "dirty" system, Zn contamination is a
problem for some users. Users do use this tool for contacting Si and Ge
devices. The fact that they are using the Metalica means these are not
critical devices.

3. Rafael and Mike are working with low percentages of Zn (< 5%) in Au and
thin layers ( 300A). So the amount of Zn being sputtered is very small (
range of 15A thickness at sample).

4. Rafael spent the weekend machining replacement parts for all surfaces 
onto which the Zn is deposited. The exception is the wafer turret/plate 
where Al foil will be used as a barrier.

5. On removing all the surfaces with Zn on them, I feel a very careful 
user can keep the small amounts of Zn in control.

6. I have a lot of faith in Rafael and Mike following a special procedure. 
I do not have faith in our general users' ability to follow the same 

7. For Stanford students, who have demonstrated excellent experimental
ability, I willing to go the extra mile to find solutions for their
processing problems.


On Wed, 14 Apr 2004, Mary Tang wrote:

> JIM!!!!  AAACK!!!
> We've been abiding by your guideline, stated last summer for Innotec, and by
> inference, for metalica, that anything with a vapor pressure higher than that
> of In would not be allowed in these systems.  We have had several requests for
> zinc since then, and have deferred people to Berkeley or Ginzton.  Including
> Rafael and Mike...
> Truly, I'm glad they went to you to work this out....  but PLEASE keep us
> (SpecMat and Jeannie) informed.  It's only courteous, and it helps that our
> organization should be presenting a consistent front.  Please, Jim, this
> happens more often than we'd like (Ge in the 4108, most recently, for example)
> and when are not in communication, it makes things difficult for the
> maintenance, labmembers, and process folk who are not in the same loop.  It
> ends up in a lot of misunderstanding and a lot of yelling that does not have
> to happen.  It seems to me that SpecMat ought to be the forum in which these
> things are decided, or at least, the info is disseminated, and from there it
> should be each of our responsibilities to inform the correct people.  Since
> emails to SpecMat are archived, we have a record of what was decided and
> when.  And it seems that in light of recent events in which the manner in
> which we execute on policy was called into question, that we should try to be
> more diligent in documenting such decisions.
> So, that's my rant.  Jim, there is no doubt that you are the expert and final
> word on issues of contamination (among many others), but all I ask is that
> people involved be informed...  Please?
> Back to the request:  does this mean that Zn may be run by others who abide by
> these guidelines?  (Providing their own parts and limiting to thin
> depositions?)  If so, would an OK and training by Jeannie/maintenance (who
> would vet the user to be sure the requestor was competent on the system) be
> sufficient to allow other users to do this?  Or is this a one-time OK?  Since
> this involves hardware changes, should we also inform Dick/Jim Haydon?  (I
> admit that I don't know how involved these hardware changes are.)
> Mary
> Jim McVittie wrote:
> > Hi Jeanie,
> >
> > Sorry, for not bring you on board. I have worked out an arrangement with
> > Rafael and Mike on they can run Zn in the Metalica without impacting other
> > users. Here is what we agreed to:
> >
> > 1. Make their own target clamp for sputter gun.
> >
> > 2. Make their own anode for sputter gun.
> >
> > 3. Use their own sputter "chimmy".
> >
> > 4. Cover bottom of wafer tray with Al foil.
> >
> > 5. Cut hole in Al foil and mount samples to the foil above the hole.
> >
> > 6. Limit deposition < 500A.
> >
> > 7. Only use gun A.
> >
> > 8. Replace re-install all the system std part after their run is complete.
> >
> > By using this method they should be able to do thin Au-Zn (5 %)
> > depositions without leaving any Zn in the system after their runs.
> >
> >         Thanks, Jim
> >
> > On Tue, 13 Apr 2004, Jeannie Perez wrote:
> >
> > >
> > > Hi Jim,
> > > I've not been notified that Zn has been approved by the SpecMat
> > > committee to be use in the Metalica or Innotec. Is this a one time deal?
> > > Is this an OK for both system? Could you give me some details. melting
> > > point below In.
> > > --
> > > Jeannie Perez
> > > Stanford Nanofabrication Facility
> > > CIS Room 146, Mail Code 4070
> > > Stanford, CA  94305
> > > (650) 723-7997
> > > jperez at snf.stanford.edu
> > >
> > >
> >
> > --
> > --------------------------------------------------------------
> > Jim McVittie, Ph.D.                     Senior Research Scientist
> > Allen Center for Integrated Systems     Electrical Engineering
> > Stanford University                     jmcvittie at stanford.edu
> > Rm. 336, 330 Serra Mall                 Fax: (650) 723-4659
> > Stanford, CA 94305-4075                 Tel: (650) 725-3640
> --
> Mary X. Tang, Ph.D.
> Stanford Nanofabrication Facility
> CIS Room 136, Mail Code 4070
> Stanford, CA  94305
> (650)723-9980
> mtang at stanford.edu
> http://snf.stanford.edu

Jim McVittie, Ph.D.    			Senior Research Scientist 
Allen Center for Integrated Systems     Electrical Engineering
Stanford University             	jmcvittie at stanford.edu
Rm. 336, 330 Serra Mall			Fax: (650) 723-4659
Stanford, CA 94305-4075			Tel: (650) 725-3640

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