[Fwd: Re: Breaking wafers?]

afflannery at comcast.net afflannery at comcast.net
Wed Sep 8 15:24:24 PDT 2004


Hi,

Just for the record, we've diced about 5 wafers in the last 6 weeks setting the diameter between 105 and 110. We've not had a problem with breaking. 
I think the reason the blade sets down in the middle of the wafer is that it thinks that it is the top. If you look at the pattern of dicing when this happen, the edges of the incomplete cuts form a circle. I think it gets confused as to its Y location relative to the wafer when you do your alignment on a dicing lane at the edge, not in the center. I may make my first cut at the edge, but I always align to a dicing lane in the center.
Just my $0.02, and that's about all it is worth.

Tony


-------------- Original message -------------- 

> Hi everyone! 
> 
> Thanks for your inputs! I think Karl has provided the historical 
> perspective, and explains why a larger diameter is useful. So, I'll 
> change the operating procedure to reflect these inputs (with the 
> recommendation to run at 150 mm, whatever the substrate size, 
> recognizing that this negates the entry speed feature). By the way, 
> this morning I tried using 200 mm as suggested by some, but it seems 
> that the stage sometimes gets stuck because it's hit a limit switch - so 
> based on this, I think 150 mm might be better (please let me know if 
> your experience suggests otherwise!) 
> 
> Thanks again -- 
> 
> Mary 
> 
> 
> -------- Original Message -------- 
> Subject: Re: Breaking wafers? 
> Date: Tue, 7 Sep 2004 17:38:15 -0700 (PDT) 
> From: Karl Brandt 
> To: Mary Tang 
> 
> 
> Believe it or not, this was a problem from the first day we got the tool 
> from K&S. After repeated attempts by K&S to resolve it, they finally 
> threw 
> up their hands and said they simply had no idea what was wrong or how to 
> fix it. The accepted workaround has been to set the wafer diameter to 
> some 
> large diameter. 
> 
> -Karl 
> 
> ********************************************************************* 
> Karl Brandt 
> http://people.ucsc.edu/~kbrandt/ 
> 
> 
> On Tue, 7 Sep 2004, Mary Tang wrote: 
> 
> > 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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