| 摘要 |
An object of the present invention is to accurately detect presence or absence of a substrate or a misalignment thereof with a reduced number of sensors, when a plurality of substrates held in multi-stage processing is transferred. An optical sensor (21) includes a light transmitting part (23) configured to irradiate light, and a light receiving part (25) configured to receive the light irradiated from the light transmitting part (23). The light transmitting part (23) and the light receiving part (25) are arranged such that the optical axis (27) of the light irradiated from the light transmitting part (23) toward the light receiving part (25) intersects with an upper surface or a lower surface (substantially horizontal position) of a wafer (W) supported by a support part (13) in multi-stage processing, at predetermined angle except for a right angle. When the support part (13) of the transfer arm (11a) moves in the direction indicated by the white arrow, the light from the light transmitting part (23) can be irradiated in sequence starting from the wafer (W) held in the lowermost stage to the wafer (W) held in the uppermost stage, and proximal to the left and right ends of the wafer (W) in a normal transferred condition. |
