Apparatus and method for actively controlling surface potential of an electrostatic chuck

摘要

An apparatus and method for actively controlling surface potential of an electrostatic chuck. The apparatus and method utilize a sensor and a control circuit. The sensor comprises an antenna on the chuck surface coupled to a field effect transistor (FET). The sensor produces a signal indicative of an electrical characteristic such as surface potential of the electrostatic chuck. The sensor signal provides feedback to the control circuit. The control circuit compares the sensor signal to a predetermined setpoint corresponding to a desired value of the surface potential. The control circuit provides a control signal to a power supply coupled to one or more chuck electrodes. The control signal causes the power supply to change the electrode voltage such that the resulting change in surface potential tends to null the difference between the sensor signal and the set point thus ensuring a constant chucking force.