PURPOSE: To detect an error of the operation of a turning means by a method wherein the volume to be turned which is preset at the turning means for positioning a semiconductor wafer is compared with the actually turned volume of the turning means.
CONSTITUTION: When a semiconductor wafer 2 is sucked and held by an alignment table, a CPU detects the starting edge and the end edge of an orientation flat OF by using a pulse motor 24 and a photoelectric device PHSW 1. The CPU calculates the turned volume corresponding to an angle θ which is formed by the starting edge and the end edge of this OF in relation to the center of the semiconductor wafer 2. If the turned volume is within a reference value, the volume, to be turned, of one-half of this turned volume is set at the motor 24 and the motor is turned so as to position the OF. Said volume, to be turned, which is set at the motor 24 is compared with the actually turned volume. If there is a discrepancy, the motor 24 has been driven abnormally; as a result, an error is displayed.
NODA KAZUHIRO
KANEHARA MATSURO
ISHIHARA AKIRA
