Patent ID: 8118640

Claim:
A wafer transferring apparatus comprising: a wafer holding mechanism for holding a wafer on a lower end surface thereof; and a wafer transferring mechanism for transferring a wafer to and from the wafer holding mechanism; wherein the wafer transferring mechanism includes a wafer rest for placing the wafer thereon, and is arranged to allow the wafer released from the lower end surface of the wafer holding mechanism to be seated on the wafer rest, and wherein the wafer transferring mechanism includes at least three sensor mechanisms for detecting when the wafer is properly seated on the wafer rest, each of the sensor mechanisms comprising a light-emitting device for emitting light and a light-detecting device for detecting the light emitted from the light-emitting device, and each of the light-emitting devices being installed at one of an outside and an inside of an outer periphery of the wafer seated on the wafer rest and each of the light-detecting devices being installed at another of the outside and the inside of the outer periphery of the wafer seated on the wafer rest such that the light emitted from each of the light-emitting devices is blocked by the outer periphery of the wafer when the wafer is properly seated on the wafer rest.