Method to provide consistent electrostatic clamping through real time control of electrostatic charge deposition in an electrostatic chuck

A system for controlling electrostatic clamping pressure, the system comprising:

• an electrostatic clamp configured to selectively electrostatically clamp a workpiece to a clamping surface associated therewith, wherein the electrostatic clamp comprises one or more electrodes;
• a power supply configured to selectively supply a clamping voltage at a clamping frequency to the one or more electrodes, therein selectively electrostatically clamping the workpiece to the clamping surface;
• a data acquisition system configured to measure a current associated with the clamping voltage and clamping frequency, therein defining a measured current;
• and
• a controller configured to integrate the measured current over time, therein defining a determined charge value associated with a clamping force between the workpiece to the electrostatic clamp, and wherein the controller is further configured to selectively vary one or more of the clamping voltage and clamping frequency based on the determined charge value, therein controlling the clamping force between the workpiece and electrostatic clamp.

A method for maintaining an electrostatic clamping force, the method comprising:

• applying a clamping voltage at a clamping frequency to one or more electrodes of an electrostatic clamp, therein electrostatically attracting a workpiece to a clamping surface of the electrostatic clamp;
• measuring a current associated with the clamping voltage and clamping frequency applied to the one or more electrodes, therein defining a measured current;
• integrating the measured current over time, therein defining a charge value associated with a clamping force between the workpiece and electrostatic clamp;
• and
• controlling one or more of the clamping voltage and clamping frequency based on the charge value, wherein the charge value is maintained within a predetermined range.