A wafer transfer system for use in a wet cleaning equipment frequently
checks the state of alignment of wafers while the wafers are transferred
between a plurality of baths. The system includes at least one transfer
robot a sensor and a controller. The plurality of baths are disposed
adjacent one another in one line. The transfer robot has a robot chuck
that can hold a plurality of the wafers and is driven to transfer the
wafers into and from each of the baths. The sensor is oriented to face
the direction in which the wafers are held by the chuck at a sensing area
outside of the baths. The sensor is thus operable to detect the state of
alignment of flat zones of the wafers. The controller receives a
detection signal from the sensor and controls respective components of
the equipment, such as the transfer robot, if an alignment error is
determined to exist.
