Wafer clamp detection based on analysis of vibration or acoustic properties

摘要

A workpiece clamp state detection system and method for detecting a clamp state of a clamping device is provided. A clamping device having a clamping surface selectively clamps the workpiece against the clamping surface. The clamping device may be an electrostatic chuck or a mechanical clamp for selectively holding a semiconductor wafer. A vibration generating mechanism is further provided for selectively vibrating the one or more clamping devices and the workpiece. In addition, a vibration detection mechanism for detecting vibration of the one or more clamping devices and the workpiece is further provided. For the detection of the clamped state, a change in acoustic characteristics (such as a shift in natural resonance frequency or an acoustic impedance) for determining the condition under which the workpiece is clamped is used. A controller is further provided for determining a clamping condition associated with clamping the workpiece relative to the clamping surface. The clamping condition is related to the detected vibration of the one or more clamping devices and the workpiece.