Patent ID: 8029224

Claim:
A substrate transfer apparatus that is mounted in a substrate processing apparatus to accommodate a plurality of substrates, the substrate transfer apparatus comprising: a holder for holding the plurality of substrates in a shelf form; substrate transport means that removes a substrate from the holder, the transport means including a substantially horizontal retention arm which retains the substrate and is positioned to freely advance and retract along an advance/retraction axis, and a transport base which is connected to the retention arm and supports the retention arm; an optical sensor that is used to define a horizontal optical axis, which crosses a circumferential side surface of the retention arm when the optical sensor ascends or descends relative to the transport base; elevator means that is coupled to the transport base to lift or lower the transport base relative to the optical sensor; height detection means that is connected to the elevator means to detect the height of the transport base relative to the optical axis; and a control section having judgment means that is connected to the optical sensor and the height detection means to judge, in accordance with a light-reception/no-light-reception detection result fed from the optical sensor, which is obtained when the transport base ascends or descends relative to the optical sensor while no substrate is held by the retention arm, and the height of the transport base, whether the posture of the retention arm relative to the horizontal plane is a predefined posture or not; wherein, when the judgment means judges that the posture of the retention arm relative to the horizontal plane is not the predefined posture, the control section exercises to stop the substrate transport means before a next substrate is removed from the holder.