Abstract: A wafer position and clamp sensor. A circuit monitors capacitance between two electrodes within a wafer support. With no wafer on the support, the capacitance falls in one range, with the wafer in place but not clamped, the capacitance falls in a second range and with the wafer held in place by an electrostatic attraction the capacitance falls in a third range. The sensed capacitance is converted to a frequency and then a D.C. voltage level that can easily be sensed and used to confirm wafer placement and then wafer clamping. After the wafer has been treated, the wafer is removed and a next subsequent wafer treated. A clamping voltage applied to clamp the wafer to its support is reversed at a controlled frequency to release the wafer. The voltage reversal disrupts the electrostatic attraction between the wafer and its support.

Abstract: A wafer position and clamp sensor. A circuit monitors capacitance between two electrodes within a wafer support. With no wafer on the support, the capacitance falls in one range, with the wafer in place but not clamped, the capacitance falls in a second range and with the wafer held in place by an electrostatic attraction the capacitance falls in a third range. The sensed capacitance is converted to a frequency and then a DC voltage level that can easily be sensed and used to confirm wafer placement and then confirm wafer clamping.