A system for decharging a wafer or substrate disposed on an electrostatic chuck, includes a capacitance detector for measuring a capacitance between the electrostatic chuck and the wafer or substrate, and a decharging voltage calculator for calculating a decharging voltage based at least in part on the capacitance measured by the capacitance detector. The decharging voltage calculated by the decharging voltage calculator of the system is applied to the electrostatic chuck after dechucking to substantially neutralize electrostatic charges on the wafer or substrate.