On Wed, 21 Feb 2001, Karen Smith wrote:

> I am putting together a project at present but the 2
> principal partners process wafers on 6" and 4" wafers
> respectively. Fortunately, the 6" processing is complete
> before the 4" processing is required and so one way forward
> might be to reduce the 6" wafers to 4" wafers between
> processing at the respective partners.
>
> * Is anyone aware of companies offering this wafer size
>   reduction as a commercial service?
>
> * Alternatively, is could anyone providfe advice on suitable
>   techniques that may be applicable?
>
> The technique used and edge profile obtained will obviously be
> critical in determining yield to preventing crack propagation,
> etc.).

Karen,

We traditionally use laser cutting (in our case using a Nd-YAG laser, spot
size 50 um) to reduce wafer diameter (from 6" to 3", or even from 8"
to 3"), both on non-processed and processed wafers. We didn't experience
too much crack propagation / increased fragility problems with this
technique (the wafers are used for fabrication of pressure and flow
sensors, resonators, accelerometers). Of course, in some cases you'll need
a lapping/polishing step as well to adapt the wafer thickness to your
equipment. I'm sure there are companies around who can offer or are offering
these services...



Dirk De Bruyker

K.U.Leuven, Dept. Esat-Micas

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