Fundamental characteristics of electrostatic wafer chuck with insulating sealant

The electrostatic wafer chuck is the most preferable handling method in advanced semiconductor manufacture. Even in a vacuum environment, it enables not only the ability to retain a wafer flat, but also to enhance heat transfer through the whole surface area because of firm contact. We have investigated the fundamental characteristics of an electrostatic chuck consisting of a pair of comb-type electrodes and a thin polymer film as a dielectric layer. In order to prevent breakdown between electrodes, the air gap between electrodes was filled with sealing material. The electrostatic force acting on the 4-inch silicon wafer is measured. Several types of insulating sealants and dielectric films were examined. The attractive force increased with the square of the applied voltage in the region of lower applied voltage and gradually saturated at higher voltage. The maximum force obtained in our experiments was approximately 30 N. These experimental results proved the high potentiality in actual use of the electrostatic chuck for silicon wafer handling. However, a few problems have to be overcome. Although the higher electrostatic force can be gained with the thinner dielectric layer, the thin polymer film is easily deformed and torn by tension when the object starts moving.