A method includes transferring a wafer to a position over a wafer chuck; lifting a lifting pin through the wafer chuck to a first position to support the wafer; holding the wafer on the lifting pin using a negative pressure source in gaseous communication with an inner gas passage of the lifting pin; introducing a gas to a region between the wafer and the wafer chuck through an outer gas passage of the lifting pin, wherein in a top view of the lifting pin, the inner gas passage has a circular profile, while the outer gas passage has a ring-shape profile; and lowering the lifting to dispose the wafer over the wafer chuck.