particle count update

Dan Grupp grupp at snow.stanford.edu
Tue May 8 13:59:17 PDT 2001


Lest we forget the "N" in "SNF": BIG particles are just an indicator.
Their visibility is an indicator that there are MANY SMALL PARTICLES on
the wafer. Many can mean THOUSANDS. Yup, it's a problem...

On Tue, 8 May 2001, Sharleen Beckwith wrote:

> 
> Early this afternoon I put 10 spankin' new wafers through program 25 (etch
> time = 60 sec/wf.) None of the wafers had any particles on them prior to
> going through the lam.
> 
> After the lam etch, the best wafer had no particles, the second best wafer
> had one particle, the worst wafer had 6 particles. The rest of the wafers
> had between 2 and 4 particles each. There was no pattern, as far as
> placement in the cassette is concerned; or looking at it from a time
> perspective, it didn't matter if the wafers went through the etch first
> or last; the best and worst wafers were randomly found in the cassette.
> 
> 

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Dr. Daniel Grupp, Visiting Scholar
Center for Integrated Systems
Stanford University
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