A new compound priority control strategy in semiconductor wafer fabrication

Control problems in semiconductor manufacturing include lot release and scheduling, while they were investigated separately. A new compound priority control strategy, CPC, is discussed, which takes both the lot release strategy and the scheduling strategy into account. According to the compound priorities of jobs that compete for processing, the CPC strategy can determine which lot(s) is/are processed when the machine is available, and determine when the new lot(s) is/are released into the wafer fab. The CPC strategy can even halt the non-bottleneck machines to prevent overstock of WIP before the bottleneck machines. Simulation results indicate that the CPC strategy has higher performance in reducing the cycle time and its standard deviation, and decreasing the WIP inventory.