Automated material handling system (AMHS) rail methodology

A semiconductor wafer transport system rail management system comprising:

• an overhead transport (“OHT”) system of an associated automated material handling system (“AMHS”) comprising a plurality of fixed rails and at least one wafer carrier vehicle configured to travel along the plurality of fixed rails;
• a controller comprising a processor in communication with memory, the controller in electronic communication with the overhead transport system;
• a turntable having a set of parallel fixed rails positioned thereon, the turntable located on a portion of the OHT and providing a rotatable intersection of a first OHT fixed rail section aligned with a first run-through direction with the turntable at a first position and a second OHT fixed rail section aligned with a first run-through direction with the turntable at a second position;
• wherein the memory further stores instructions that are executed by the processor causing the processor to:
• receive a request to rotate the turntable from the first run-through direction to the second run-through direction,
• prior to rotating the turntable, purge the first OHT fixed rail section of one or more first wafer carrier vehicles moving on the first OHT fixed rail section to allow the one or more first wafer carrier vehicles to complete travel across the turntable;
• prior to rotating the turntable, and after purging the first OHT fixed rail section, detect and stop subsequent first wafer carriers traveling on the first OHT fixed rail section by activating at least one first stopper sensor positioned on the first OHT fixed rail section, the first stopper sensor located proximate to the turntable and the first wafer carrier vehicle stopping prior to transiting the turntable;
• prior to rotating the turntable, detect and stop a second wafer carrier vehicle moving on the second fixed rail section by activating at least one second stopper sensor positioned on the second OHT fixed rail section, the second stopper sensor located proximate to the turntable and the second wafer carrier vehicle stopping prior to transiting the turntable;
• rotate the turntable from the first run-through direction to the second run-through direction while receiving an alignment signal from at least one alignment sensor pair positioned on the turntable and positioned proximate to the turntable on the second OHT fixed rail section, the alignment signal representative of a relative alignment of the turntable with respect to the second OHT fixed rail section;
• and
• in response to a completed rotation of the turntable from the first run-through direction to the second run-through direction indicated by the alignment signal, deactivating the oner or more second stopper sensors and instructing the stopped second wafer carrier vehicle to continue movement along the second OHT fixed rail section to transit the turntable along the second run-through direction.

A computer implemented method for wafer carrier vehicle rail traffic management on an automated material handling system (“AMHS”) comprising an overhead transportation (“OHT”) system, the method comprising:

• receiving a request to rotate a turntable on the OHT of the AMHS from a first run-through direction to a second run-through direction, the turntable having a set of parallel fixed rails positioned thereon, the turntable located on a portion of the OHT, the turntable providing a rotatable intersection of a first OHT fixed rail section aligned with the first run-through direction with the turntable at a first position and a second OHT fixed rail section aligned with the first run-through direction with the turntable at a second position;
• prior to rotating the turntable, the controller purging the first OHT fixed rail section of one or more first wafer carrier vehicles moving on the first OHT fixed rail section to allow the one or more first wafer carrier vehicles to complete travel across the turntable;
• prior to rotating the turntable and after purging the first OHT fixed rail section, the controller detecting and stopping subsequent first wafer carriers traveling on the first OHT fixed rail section by activating at least one first stopper sensor positioned on the first OHT fixed rail section, the first stopper sensor located proximate to the turntable and the first wafer carrier vehicle stopping prior to transiting the turntable;
• prior to rotating the turntable, detecting and stopping a second wafer carrier vehicle moving on the second OHT fixed rail section by activating at least one second stopper sensor positioned on the second OHT fixed rail section, the second stopper sensor located proximate to the turntable and the second wafer carrier vehicle stopping prior to transiting the turntable;
• rotating the turntable from the first run-through direction to the second run-through direction while receiving an alignment signal from at least one alignment sensor pair positioned on the turntable and positioned proximate to the turntable on the second OHT fixed rail section, the alignment signal representative of a relative alignment of the turntable with respect to the second OHT fixed rail section;
• receiving a switch complete signal from the turntable confirming rotation from the first run-through direction to the second run-through direction in accordance with an output of the at least one alignment sensor pair;
• and
• in response to a completed rotation of the turntable from the first run-through direction to the second run-through direction, i deactivating the oner or more second stopper sensors and instructing the stopped second wafer carrier vehicle to continue movement along the second OHT fixed rail section to transit the turntable along the second run-through direction.