chang830
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I have a question on resistor and PVT simulation.
In my cmos process, there are five reistor types, nwell, P+,N+, poly1, poly2. And the spice model also gives three corners, i.e., fast resistor, slow resistor and typical resistor. So I can select these three resistor corners combined with other PVT corners to search the wcs cases. But I have a puzzle on it. For these five resistor types, they were done with different implantation on different time. So they should be considered as independent and can deviate in different direction. So if my block use different resistors, one is fast res and another is slow, which may induce the worst case. Then why the spice model(in fact, all the cmos process I used before) just provide fast, typical and slow for all five types resistors? It assume they vary in the same direction?
Thanks
In my cmos process, there are five reistor types, nwell, P+,N+, poly1, poly2. And the spice model also gives three corners, i.e., fast resistor, slow resistor and typical resistor. So I can select these three resistor corners combined with other PVT corners to search the wcs cases. But I have a puzzle on it. For these five resistor types, they were done with different implantation on different time. So they should be considered as independent and can deviate in different direction. So if my block use different resistors, one is fast res and another is slow, which may induce the worst case. Then why the spice model(in fact, all the cmos process I used before) just provide fast, typical and slow for all five types resistors? It assume they vary in the same direction?
Thanks