Method and apparatus for determining wafer warpage for optimized electrostatic chuck clamping voltage

摘要

Method and apparatus are provided for determining a warpage of a wafer (14) for providing a minimum clamping voltage to an electrostatic chuck (ESC) when the wafer is subsequently processed thereon. The apparatus includes an electrostatic chuck (12, 120) and a control arrangement (16, 18, 20). The electrostatic chuck includes a clamping surface (13, 130) for clamping a wafer thereto by a clamping force that is dependent on a clamping voltage applied to the electrostatic chuck. The control arrangement is used to detect an inherent warpage in the wafer prior to a processing of that wafer, and determine a minimum clamping voltage from the measured warpage that is to be applied to the electrostatic chuck during a subsequent processing of the wafer. The minimum clamping voltage has a value for each wafer that securely clamps the wafer to the clamping surface and avoids excessive warpage and backside abrasion of the wafer. The control arrangement includes a suitable wafer warpage measuring tool (20, 50, 52, 54) such as, for example, a capacitance warpage measuring tool (50, 52, 54) or a optical warpage measuring tool (20) that measures the inherent warpage of a wafer, and an electrostatic chuck software control (18). The electrostatic chuck software control uses the measured warpages to determine and store data of a minimum clamping voltages and an associated wafer identification for each wafer for use in subsequently processing each wafer.