Fundamental study of an electrostatic chuck for silicon wafer handling

Mechanical holding systems of a wafer might cause serious problems in the semiconductor industry. Electrostatic wafer handling might be one of the possible solutions for such problems. We have investigated an attractive force on a silicon wafer by using an electrostatic chuck which consists of interdigitated electrodes and a dielectric thin film. Electrostatic attractive force increases as the applied voltage increases, and with a thinner dielectric layer. With the narrower width and spacing of interdigitated electrodes, the stronger electrostatic force is obtained. When 1-mm width and spacing interdigitated electrodes and 50-mum-thick polymer film are used, the strongest force obtained was about 17 N in the vertical direction at 3.5 kV, for a 4-in silicon wafer. When dc high voltage is used, some residual force remains, even after the applied voltage is removed. This was overcome by using variable-frequency ac high voltage.