[Fwd: RE: Breaking wafers?]

Mary Tang mtang at snf.stanford.edu
Wed Sep 8 15:36:23 PDT 2004


Hi again --

And Don Arnold agrees with Tony.  And Jim Kruger mentioned that his
recently diced wafer likewise had concentric undiced areas...  So, this
will be another change to the operating procedures...  Hey, I like this
practice of deciding on operating procedures by consensus...

Mary

-------- Original Message --------
Subject: RE: Breaking wafers?
Date: Tue, 7 Sep 2004 15:04:36 -0700
From: "Don W. Arnold" <dwarnold at eksigent.com>
To: "Mary Tang" <mtang at snf.stanford.edu>

Mary,

I used to have this problem.  I t has been some time since I used the
KS, but I believe that it has to do with where you do the alignment. I
got the impression that the machine was assuming that the line on which
you were doing your alignment was the center (and thus the widest part)
of the wafer. In this mode, for example, if you were aligning at the
near edge of the wafer, the machine would assume that your wafer was
getting narrower as the cutting line was moving away from you. In fact
the wafer was getting wider. 

When I encountered the problem, I noticed that others had been setting
the machine to 200 mm diameters, but I think, in retrospect, this was
going the long way around to solve the problem. As I recall, I found
that if I aligned in the center of the wafers, things were OK. You would
be able to quickly confirm this on a dummy wafer to see if, perhaps,
things changed as a result of the rebuild.

Hope this helps.

Don

Don Wesley Arnold
Eksigent Technologies, LLC
2021 Las Positas Court, Suite 161
Livermore, CA 94550
925-960-8869 x302 - Phone
925-960-8867 - FAX
dwarnold at eksigent.com


-----Original Message-----
From: Mary Tang [mailto:mtang at snf.stanford.edu]
Sent: Tuesday, September 07, 2004 2:37 PM
To: wafersaw at snf.stanford.edu
Cc: rcrane; Paul Rissman; jhaydon
Subject: Breaking wafers?


Hi everyone --

"rosti" dropped by my office to say that he was thinking about using the
wafersaw, but was concerned about a problem he had experienced a couple
of times in which the saw BROKE his wafer.  He says that instead of
starting on the edge, in these instances, the saw blade dropped onto the
middle of the wafer and thus broke his wafers.  The last instance that
he observed was some time back last October or so.

Now I'm worried!  Usually, when a wafer is ready for dicing, you've
expended a lot of time and energy into it -- you simply can't afford to
have it smashed.  I'm also really concerned because I've been training
on the wafersaw for a couple of years now, but have not observed this
problem nor had I heard about it from anyone (and here I thought I knew
all the machine's quirks).  I had heard that it used to be a problem,
but not seen since the system was basically rebuilt a few years ago.
Now, I'm hearing otherwise...

Has anyone else had this problem?  If so, could you let me know
approximately when it happened and how often (if you were "lucky", like
rosti, and got hit more than once?)  And maybe even the circumstances
when it occurred (if you remember).  Your feedback will help us decide
what to do (if the darned thing is breaking wafers intermittently, we
may need to take it off-line...)

And, most importantly, if you observe this or any other problem, please,
please, please report it on Coral!  (I'm going back several years, and
don't happen to see anything about the machine breaking wafers...)

Thanks,

Mary


--
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



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