Breaking wafers? We saw it also today

Ben Jian ben.jian at arrayedfiberoptics.com
Wed Sep 15 14:30:37 PDT 2004


Hi Mary,

Today Wei was doing wafer docing and we saw the same phenomenon, for the
first time ever. We were trying to dice the top-most part of a four inch
wafer. The blade came down on our wafer and the blade was broken.
Luckily, our wafer is OK.

We suspect that this problem might have something to do with two other
things. First, maybe a sensor is defective (we did see some warning
message like "sensor bad" when the problem occurred but did not write it
down carefully, sorry). Second, the fact that the machine does not go to
the true center of the wafer stage when you hit "Align" but to the
bottom part of the wafer chuck. Maybe one of these two is the source of
the problem?

Regards.

Ben Jian

-----Original Message-----
From: Mary Tang [mailto:mtang at snf.stanford.edu] 
Sent: Tuesday, September 07, 2004 3:06 PM
To: Myers, Alan M
Cc: wafersaw at snf.stanford.edu; rcrane; Paul Rissman; jhaydon
Subject: Re: Breaking wafers?


Thanks,

I'd absolutely no idea about this.  I'd been told (by Len, the saw
expert) that setting the diameter larger was helpful for the occasional
problem in which the saw didn't cut all the way across, but maybe this
is related to starting in the middle...  This is easy to do in
principle, but does mean we wouldn't be able to take advantage of a slow
entry speed (though perhaps small insurance against breaking wafers...)

I'll try it out and see if I can likewise induce/cure the problem.

And unless I hear otherwise, I'll plan on adding Alan's method to the
operating procedures and training...

Mary

"Myers, Alan M" wrote:

> Mary,
>         I used to have this problem every time I use the saw.  I 
> learned the secret is to set the wafer diameter 200 mm whenever I get 
> near the top of the wafer.  It may take a little longer, but at least 
> the blades and the wafers remain intact.
>
> Alan
>
> -----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

--
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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