Depending on how heavily doped the resistors are and how you're making the
measurements, it could be that the resistance variations you observe are due
more to contact resistance than variation in the doping.

Unless it's degenerately doped, you can't be certain that you'll make good
contact to your polysilicon. In general, you'll want to pick a metal for
contact pads that will yield an ohmic contact. Another trick is to dope
twice: once to form your resistors, and again to form heavily doped contact
pads.

Another factor could be the probes you're using. If they're not sharp, you
may not be able to guarantee that you'll break through the native oxide on
top of the pads. Or worse, you'll make intermittent contact and get
confusing results.

Good luck,

Bill Eaton, Ph.D.
Materials & Analysis Manager
NP Photonics
5706 Corsa Avenue, Suite 100
Westlake Village, CA  91362



> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of krishna
> Sent: Thursday, March 13, 2003 10:02 AM
> To: General MEMS discussion
> Subject: [mems-talk] Piezoresistors
>
>
>
> Dear Members,
>
> we have fabricated Polysilicon Piezoresistors on Si(100) surface.The
> polysilicon was doped with spin on dopant(phosphourous
> dopant) and drive
> in and oxidation was done at same time at 1050C. The poly
> resistors are
> barely 5 microns distance apart.when i measured the resistance value
> the value of the resistance differed alot more than 300%
> change among the adjacent resistors..
>
> Can any one suggest me why this happened?
>
> Thanks
>
> kris
>
>
>
>
>
>
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