Optimizing multi-station scheduling in consideration of equipment flexibility and loading balance in semiconductor wafer fabrication

This research studies multi-station scheduling with flexible capacity and loading balance. In semiconductor manufacturing industry, QTime restriction is one of important factors, severely affecting throughput since waiting time of wafer exceeding remaining QTime leads to wafer scrap. A flexible capacity to produce multiple processes provides additional capacity for each job, and reduces job waiting time. However, operators have to allocate capacity manually while several decisions would be considered. Therefore, with the consideration of flexible capacity and QTime restrictions, resource allocation is extremely difficult. We model this problem by applying mixed integer programming. The objective is to minimize wafer scrap as well as cycle time. In numerical study, we apply our model to real production line, and the results show that the proposed strategy provides significant improvements in semiconductor wafer fabrication.