Patent ID: 7186297

Claim:
A wafer holding apparatus having a flat base material; drive means with a pressing element, the element being attached to a root section of the base material that has a substantially U-shaped portion and being actuated back and forth in a longitudinal direction of the base material, the longitudinal direction being an opening direction of the U-shaped portion of the base material; optical detection means for detecting advancing/receding action of the pressing element; fixing elements fixed at extremities of the base material; and supporting elements provided on the base material and between the pressing element and the fixing elements, an outer edge of a wafer being gripped and fixed with the pressing element and the fixing elements while the wafer is placed on the supporting elements, wherein, when the optical detection means has detected that the pressing element has advanced to and stopped at a predetermined position, the wafer is determined to be properly gripped; and wherein, when the optical detection means has detected that the pressing element has advanced in excess of the predetermined position, the wafer is determined not to be present on the wafer holding apparatus.