Why dummy transistor requires diffusion instead we can put o

[amitabh262002]

dummy transistor

Why dummy transistor requires diffusion instead we can put only poly ??

 

[stuck_adc]

dummy transister

dummy transistors help us in two ways-
1) to fix density errors:-
if we have both poly and diffusion min. density error than best way to fix is thrugh dummy transistors, best area utilization.

2) to provide matching to core transistors mainly in analog circuits.

if your requirement doesn't require any of the conditions you can use only poly.

Note:-
we need uniformly distributed layers over the complete area...............this is to prevent sagging of any layer at the time of fabrication.

hope this answers your question.