Qualification for Germanium bench cleans

Jim McVittie mcvittie at cis.Stanford.EDU
Thu Mar 13 12:17:43 PDT 2008


The test should be guided by what are the likely contamination problems
for the particular tool or material. For a cleaning bench the likely
problem is that someone put a metal wafer one or all the tanks. I am sure
TXRF should be fine. But for the diff clean benches, I do not remember
ever seeing a problem with them if we cleaned the hot pots and rinse tanks
with HCl any time there was a question about a bench.  I can say this
because we did a number of TXRF tests where we uses a diff cleaned wafer
as the ref and we never saw problems with our ref wafers. I assume the HCl
cleaning method will work for the Ge cleaning tanks. As for looking as
post cleaning contaminants on Ge, I would refer you to Jungyup Kim's
thesis. He did a lot of Ge cleaning and measurements. As to what is a good
TXRF result, our old criteria was that all the metal levels should below
mid 10E10 atoms/cm2. I would think we should keep this criteria for Si
wafers coming out of a Diff clean. For other places in the lab, we may
want to relax this pass level because we now have to deal with a number 
of new materials and processes.  


On Tue, 11 Mar 2008, Mary Tang wrote:

> Hi all --
> The germanium group wants to qualify wbgen2 for their cleans.  What kind 
> of qual should they do?  TXRF is standard.  So, what kind of TXRF 
> testing should be done?  And what kind of levels are considered "wbdiff 
> clean"?  Should CV's be done?
> I ask, because what is done here is very likely going to be what will be 
> recommended for the spin-etch station.
> Mary

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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