PURPOSE: An electrostatic chuck system for securely holding a wafer on a surface of the electrostatic chuck is disclosed. CONSTITUTION: The electric chuck system (302) for holding a wafer (108) comprises a wafer bias sensor (400) coupled to a first portion of the electrostatic chuck for sensing an alternating current signal at the first portion. The sensor outputs, responsive to the alternating current signal, a direct current voltage level representative of a direct current bias level of the wafer and is coupled to a variable power supply (412) which provides a first potential level to the first portion of the electrostatic chuck. The first potential level is modified, responsive to the direct current voltage level, to substantially maintain a first predefined potential difference between the first portion of the electrostatic chuck and a first region of the wafer overlaying the first portion irrespective of a magnitude of the direct current bias of the wafer.
