At this point, it is preferable that the wiring pattern portions 510 formed on the glass electrode substrate 500 are not of a metal such as aluminum or silver, but of a transparent electrode substance such as ITO. In this way, foreign objects adhering to the ITO surface can also be detected. [0251] (6) Dry Etching of Boron Doped Layer 422 [0252] For the etching of the boron doped layer 422, dry et