Electrostatic chuck with a thin ceramic insulation layer for wafer holding

An electrostatic chuck is one of the useful device holding a thin object flat on a bed by electrostatic force. The authors have investigated the fundamental characteristics of an electrostatic chuck consisted of a pair of comb type electrodes and a thin insulation layer between the electrodes and an object. When a thin polymer film is used as an insulation, the holding force for a wafer was large enough in practical use, while the large residual force remains after removing the DC applied voltage. Thus, it was concluded that AC applied voltage will be more preferable than DC, though the electrostatic force for DC applied voltage is somewhat greater than that for AC voltage. Since the electrostatic chuck is generally used in high temperature atmosphere, for example plasma etching, in the semiconductor industry, the insulating layer must be heat resistant. By using a thin ceramic plate, which was made specially for this purpose, the fundamental characteristics of the electrostatic chuck has been investigated. The greater holding force was obtained with a ceramic plate than that with a polymer film. Furthermore, almost no residual force was observed even for the DC applied voltage. The experimental results are reported both in air and in vacuum condition.