A method involving plasma cleaning of deposit residues in process chamber using duo-step wafer-less auto clean method is detailed. As a result, upon resumption of power generation by the electric power generator 10, entire electric energy generated can be effectively utilized, so that the restart of a time-keeping operation by the timing means 20 is speeded up, and the operation thereafter is stabilized. Thus the wafer scanning device improves responsiveness with respect to the scanning speed control, enhances the uniformity of the scanning speed, has the motor or the like arranged properly and achieves the tilt of a wafer in a most preferable manner. Upon notification of an event, the user application also is provided with specific information classifying the nature and details of the event. The thickness of the third insulating layer where the first wiring layer is located is equal to the total thickness of the first insulating layer and the second insulating layer where the second wiring layer is located. Other embodiments are described and claimed.