In case of double guard ring for PMOS which should come first whether N+ first or P+

[Akshaya katkar]

In case of double guard ring for PMOS which should come first whether N+ first and then P+ or reverse...... please explain

 

[ripoo82]

The N+ first, it sits in the same well and doubles as bulk contact. You always need the bulk, so why not make a ring of it. Then the P+ to pick up substrate noise. You can then add another N+/NW ring around that. This will force the passing noise deeper into the substrate (more resistive), before it gets up again, and is picked up by the P+ ring.

 

[Akshaya katkar]

Thanks you