Processing defects arising during processing of a semiconductor wafer prior to back-grinding are reduced with systems and methods of sensor placement. One or more holes are bored into a chuck table for receiving semiconductor wafers, or a support table next to the chuck table. One or more sensors are disposed in the holes for monitoring parameters during a pre-back-grinding (PBG) process. A control box converts a set of signals received from the sensors. A computer-implemented process control tool receives the converted set of signals from the control box and determines whether the PBG process will continue.