Patent ID: 9036326
Filing Date: 2015-05-19
Classification: H01L

Abstract:
1. An electrostatic clamp for selectively maintaining a position of a workpiece, the electrostatic clamp comprising: a clamping plate having a clamping surface associated with the workpiece, wherein the clamping plate has a central region and an annulus region defined therein, and wherein the annulus region is generally disposed about a periphery of the central region; a plurality of gas supply orifices defined in the central region of the clamping plate, wherein the plurality of gas supply orifices are in fluid communication with a pressurized gas supply, and wherein the pressurized gas supply is configured to provide a cushion of gas between the clamping surface and the workpiece in the central region of the clamping plate via the plurality of gas supply orifices; one or more gas return orifices defined in one or more of the central region and annulus region of the clamping plate, wherein the one or more gas return orifices are in fluid communication with a vacuum source, therein generally defining an exhaust path for the cushion of gas; a seal disposed in the annulus region of the clamping plate, wherein the seal is configured to generally prevent a leakage of the cushion of gas from the central region to an environment external to the annulus region, and wherein the seal comprises one or more concentric differential pumping grooves defined in the clamping surface in the annulus region, wherein each of the one or more concentric differential pumping grooves are in fluid communication with one or more respective vacuum sources; and one or more electrodes associated with at least the central region, wherein the one or more electrodes are electrically connected to a first voltage potential.