| 摘要 |
<p>PROBLEM TO BE SOLVED: To simplify the structure and make easy alignment and correctly detect a substrate such as a wafer by detecting a change in electrostatic capacity by an electrostatic capacity-method sensor, and thereby detecting whether a substrate exists on a substrate carrying plate. SOLUTION: Whether wafers 5 exist on wafer carrying plates is detected by a change in the electrostatic capacity detected by electrostatic capacity- method sensors 32a, 32b, 32c, 32d, and 32e. The change in electrostatic capacity which determines whether the wafers 5 exist or not is determined mainly by the overlapping length of the end of the electrostatic capacity-method sensors 32 and the wafer 5. Since the change in electrostatic capacity is not effected very much by the attitudes, etc., of the electrostatic capacity-method sensors 32 themselves and a change in electrostatic capacity caused by a variation in alignment is sufficiently small compared with the change caused by the existence or non-existence of the wafers 5, the alignment of the ends of the electrostatic capacity-method sensors 32 is further facilitated in comparison with the alignment of optical axes in an optical sensor.</p> |
