Electrostatic wafer clamp

Abstract

Apparatus for electrostatic clamping of a semiconductor wafer in a vacuum processing chamber wherein an ion beam is applied to the wafer. In a first embodiment, the apparatus includes an electrically conductive platen, a resilient, thermally-conductive dielectric layer affixed to the platen and one or more conductive wires positioned on the clamping surface. A clamping voltage is applied between the wires and the platen to firmly clamp the wafer against the clamping surface and depress the wires into the resilient dielectric layer. In a second embodiment, a three-phase wafer clamping apparatus includes a platen divided into three electrically isolated sections. One phase of a three-phase clamping voltage is connected to each of the platen sections. In the three-phase configuration, the wafer charging current is very small, and the clamping force is essentially constant. In a third embodiment, a six phase wafer clamping apparatus includes a platen having six symmetrically located electrodes. Voltages with six different phases are applied to the electrodes, with the voltages applied to electrodes on opposite sides of the platen being one-half cycle out of phase. The applied voltages are preferably bipolar square waves.

Dependencies are inferred from the claim text.