Breaking wafers? We saw it also today
eap at gloworm.Stanford.EDU
Wed Sep 15 15:20:39 PDT 2004
It goes to the last place aligned, so if you re-align at the center,
it will start going to the center.
On Wed, 15 Sep 2004, Ben Jian wrote:
> 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?
> 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?
> 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...
> "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
> mtang at stanford.edu
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