Apparatus and method for monitoring the relative relationship between the wafer and the chuck

An apparatus and a method for monitoring the relative relationship between the wafer and the chuck, especially for monitoring whether the wafer is sticky on the chuck if the wafer is un-clamped. The lift pins may be extended outside the chuck to separate the wafer and the chuck if the wafer is un-clamped. By detecting the capacitance between the un-clamped wafer and the chuck, especially by comparing the detected capacitance with the capacitance if the wafer is clamped by the chuck, whether the wafer is sticky on the chuck, even whether the wafer is properly supported by the lift pins, may be detected. Accordingly, an early alarm may be sent out if the wafer sticky is happened or improperly picked away. Besides, by controlling a switch electrically connected to the grounding pin(s) contacting the wafer, the charges appeared on the wafer may be eliminated.