A Hybrid Vehicle Dispatching Approach for Unified Automated Material Handling System in 300mm Semiconductor Wafer Fabrication System

The automation of unified automated material handling system (UAMHS) in 300mm semiconductor wafer fabrication system (SWFS) is complex due to complicated product mixes, numerous and dynamic transportation demands, transportation deadlock, and vehicle blockages. Vehicle dispatching has become one of crucial means to improve the overall operating efficiency of UAMHS. Currently, many vehicle dispatching studies have been devoted to the optimization of the performance indexes of UAMHS. However, more important performance indexes related to SWFS, such as cycle time, throughput, and due date satisfaction, were seldom considered. To bridge this gap, a fuzzy logical and Hungarian algorithm-based (FLHA) vehicle dispatching approach is proposed to obtain better comprehensive performance of UAMHS and SWFS simultaneously. In the proposed approach, candidate wafer lots' transport priority is identified and sorted by fuzzy logic method firstly. Then the wafer lots with higher priority are selected as candidate lots, and it is assigned to the idle transport vehicles based on Hungarian method. After the optimized assigning solution is found, a greedy vehicle transport policy is design to execute it, which can reduce temporary transportation deadlock and vehicles' waste movement effectively. With experimental data from an UAMHS of 300 mm SWFS and running simulation experiments, the results demonstrated that the proposed approach is feasible and effective. Further comparisons with other traditional vehicle dispatching approaches show that the proposed approach has better comprehensive performance in terms of cycle time, throughput, due date satisfaction, delivery time, transport time, and OHT vehicle utilization.