hi,
When testing our silicon, I supprisly found that in the same die, some transistors seemed in SF corner while others in FS corner. I am confused with it. I tested others dies from the same wafer, they all have the same phenomena.
I wonder is it possible for a single die, the same type MOS transistors is in the different corners?
Fisrt thing you can do,
is ask the fab to mapping those WAT key for
Vth and IDsat (40~50 shots/wafer) measurement.
See if variation match with your conclusion.