SpecMat logsheet Sept. 12, 2006

Jim McVittie mcvittie at cis.Stanford.EDU
Mon Sep 11 16:44:13 PDT 2006


Here my views on ouyr equipment and ZnS. 

Litho -- We traditionally have not restricted materials in the litho area 
as long as they are safe and do not affect the performance of the 
particlar tool. 

Furnaces -- The allowed materials for the clean ox tubes are pretty clear.  
For the "dirty" ox tube (Tylan #4), the materials are resticted to those
which do not melt or move around by vapor transport at high temperatures .  
I suspect all Zn compounds have too high of a vapor pressure for a general
purpose furnace like Tylan #4. For the FGA and LTO tubes where the
temperature is limited to < 500C, we are less restictive in terms of
allowed material because of the lower temperatures. I do not know enough
about the vapor pressures of ZnS to say it would not cause problems.  
Without clear proof, it should kept out.

Etchers -- All the semiclean etchers are clearly out for ZnS. The GaAs
users have requested that Zn be kept out of PQuest. This request should
also go for Drytek4 since this was obtain to do SiO2 and nitride etching
on III-V materials. Drytek1 should be restricted to gold and standard
materials. This leaves the MRC. I have always viewed the MRC at a dirty
etcher where everythings goes. So far, I do not see the Zn compounds as a
problem. The Zn vapor pressure is not a significant problem for the
temperature and pressure where the MRC runs.

Metal dep -- We already allow Zn in the Metallica with restrictions.  
Evaporating onto ZnS wafers should not be a problem as long as the samples
are not being heated. The SCT and Gryphon are restricted to semiclean


On Mon, 11 Sep 2006, Mary Tang wrote:

> Hi everyone --
> I had understood that Jim arranged for Mike/Rafael (Zn/Au?) and Zheng 
> (ZnCdS/ZnCdSe) have their own metalica inserts/spare parts, in order to 
> minimize possible cross-contamination.  They were also trained to 
> install and replace these parts...  Whatever is decided, we should be 
> consistent in administering the policy.  If we OK ZnS, we should be 
> consistent with previous practice, unless we decide that it is no longer 
> a good method for controlling contamination. 
> I take it, then, that materials containing Zn were never approved for 
> processing in tylan4?  And I'd like to double-check with everyone else 
> -- is our policy on tylans3 and 4 still to have everything SpecMat 
> approved on a case-by-case basis (or am I behind the times)?
> Mary
> Jim McVittie wrote:
> >Ed,
> >
> >Regarding Zn, I believe pure Zn has been sputtered in Metallica a few
> >years back by Michael Wiemer and Rafael Aldaz. I think Simon Wong's
> >students have sputter etched ZnCdS in the MRC. As for Tylan #4, I believe
> >Simon's ZnCdS students are using a furnace over in Paul McIntyre's area.
> >Simon's students sometimes report processing details at the NVM mtgs,
> >which I attend.
> >
> >	Jim 
> >
> >On Mon, 11 Sep 2006, Ed Myers wrote:
> >
> >  
> >
> >>SpecMat Members,
> >>
> >>The agenda for this week is very light.  It should be a quick meeting.
> >>
> >>I believe we have some pretty good agreement on most of the 
> >>items.  The one I'm worried about is processing of ZnS.  Both of 
> >>these elements are fall below the indium vapor pressure cut off.  We 
> >>have approved ZnCdS deposition in the metallica, but with 
> >>restrictions.  I have not logged any allowed Zn alloy processing in 
> >>any other pieces of equipment.  We did have a complaint from a user 
> >>who detected large quantities of Zn after processing in Tylan 4.
> >>
> >>Ed
> >>    
> >>
> >
> >  
> >

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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