concept regarding piezoresistivity

[kishanb]

Hi all
I have a doubt as the piezoresistivity does not change in (111) plane and is minimum in all directions why do we still use (100) wafer what are the advantages using (100) orientation and how do i reduce piezoresistivity in (100) ?

Thanks and Regards
Kishan.B

 

[dick_freebird]

It kind of "is what it is". But I've seen people do things like
lay out critical bandgap resistors at 45 degrees for exactly
this reason (automotive guys in plastic packaging, the strain
would jack the reference voltage after trimming).

100 may be preferred because it gives better mobility for
MOS. Other axes were used for things like V-groove dielectric
isolation, back before wafer bonding existed, etc. The
resistor always gets picked last at the care-about dance.

 

[erikl]

(100) also is said to be the best orientation to prevent channelling - the undesirable traveling of longer distances of the implanted ions. Still, the ion implant ray usually will be inclined a few degrees against the vertical to further hinder the channeling.