Tap cell & Power switch
A domain uses header switches to disconnect its virtual VDD from the always-on VDD. Its standard-cell PMOS sources connect to virtual VDD, and its n-well is intended to remain biased from always-on VDD.
The selected tap cell has its n-well contact internally connected to its VDD rail. During implementation, that rail is connected to both the domain’s virtual-VDD rail and the always-on supply.
What is the primary problem?