Mike, and others-
While the success of single unsupported substrate  may have some success
  - depending on what you were trying to accomplish- but  I would find
this method a poor method to create a defined square or rectangular chip
from the wafer. Edge 'fracturing' is hardly a decent method as it will
follow the cleavage lines but may not fit the ones that you have laid
out on your mask , if patterned , unless you are very exact, precise and
LUCKY--
for this thickness- secure the wafer and you should not have the
problems with dicing that is suggested here- as has been mentioned -
tensioned tape on ring or wax would be your best options- but with the
thickness of the wafer, I would suggest that you reduce the pressure of
both the saw spray nozzles as well as any High Pressure clean if other
than perpendicular to the wafer surface as it could create a peeling
affect and wash your work down the drain...
Good luck.
Ken

Michael Barger wrote:
> Dr. Broitman,
>
> I don't know if you have been helped, yet, but I used a fairly crude method
> on thicker silicon wafers. I used an Exacto knife blade that had a curved
> tip. I placed the wafer on a very flat surface. I then placed the knife
> blade next to the edge of the wafer, aligned with the (100) cleavage plane.
> I then rocked the blade onto the edge of the wafer. A crack would start at
> the edge and progress across the wafer, producing a very clean break. This
> process did not work every time, but seemed to improve with practice.
>
> I did not have any success with scribing or dicing. Scribing generated a
> multitude of defects that caused cracks to radiate in all directions. Dicing
> tore the wafer creating a lot of damage.
>
> I hope this helps.
>
> Regards,
>
> Mike Barger
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Mario Robles
> Sent: Thursday, April 17, 2003 3:51 PM
> To: 'General MEMS discussion'
> Subject: RE: [mems-talk] cleaving of ultra-thin Si wafers
>
>
> Hello,
>
> It sounds like you have tried a "scribe and break" process. This is when
> you use a diamond tip to scribe the top surface of the silicon then
> apply pressure on the backside to break the cleave mark. It could be
> that the wafer is too stressed and not able to break properly.
>
> How is the wafer thinned to the 30µm thickness? The thinning process is
> critical to reduce the stress of the wafer. I would guess it was ground
> then lapped or polished.
>
> You can also use a dicing saw to cut he wafer to final substrate or die
> size. This uses a diamond blade to cut through the wafer, which is
> mounted on an adhesive tape or could be waxed onto another silicon wafer
> for better support.  You can choose the blades specification to achieve
> the best cut quality.
>
> If you like I can supply you with the names of companies that perform
> dicing, grinding and scribing services.  They could perform some test
> cuts to show you the results. Or if you are looking to cut your wafers
> in house I can also point you in the right direction. You can then
> decide what your best option is.
>
> Thank you,
>
> Mario Robles
>
> Tanaka Systems, Inc.
> 2577 Leghorn Street
> Mountain View, CA 94043
>
> 650-966-8001 ofc
> 650-966-1881 fax
> www.dicingblades.com
>
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Esteban Broitman
> Sent: Tuesday, April 15, 2003 8:57 AM
> To: [email protected]
> Subject: [mems-talk] cleaving of ultra-thin Si wafers
>
> Does anybody know how to "cleave" ultra thin Si wafers?
> I need to cut, from ultra-thin (30 microns) Si wafers, substrates of ~
> 10 x 20 mm. I tried to use different kind of diamonds, but I always have
> the same problem: the substrate is not more "flexible", if I try to bent
> it, it cracks in many parts. I suspect that I am generating defects
> during the cutting of the substrates that propagate during the bending.
> Any suggestion?.
> Thanks for the reply to my e-mail: [email protected]
> E. Broitman
> ----------------------------------
> Dr. Esteban Broitman
> Senior Research Associate
> Department of Chemical Engineering
> Carnegie Mellon University
> Pittsburgh,  PA 15213
> Phone: (412) 268-9537
> FAX: (412) 268-7139
> ----------------------------------
>
>
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>
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