A New Stage-Wise Control Release Policy for Semiconductor Wafer Fabrication Systems

This article presents a new closed-loop release policy: Stage-Wise Control (SWC) that maintains the overall shop floor's workload distributed into stages at a specified level by controlling the release of new jobs along the production line A simulation model is developed for the well-known Mini Fab and a real-life fab to examine the potential advantage of SWC over traditional release policies in terms of the average cycle time, the standard deviation of cycle time, WIP level, the average number of tardy jobs, and throughput. The simulation results indicate that the SWC efficiently generates high-quality schedules for the average cycle time and the standard deviation of cycle time for a prescribed throughput level. Further, several simulation experiments are carried out in this study to understand the relative performance of SWC in comparison with the existing release policies with different dispatching rules, with different system variability levels caused by machine failure, and with different segmentation method. The performance of SWC is satisfactory in most of the considered scenarios compared to the tested release policies.