A simulation study on lot release control, mask scheduling, and batch scheduling in semiconductor wafer fabrication facilities

This paper focuses on production scheduling in semiconductor wafer fabrication. Included in this study are decision problems of lot release control (to determine the time and quantity of wafers to release into the wafer fab), mask scheduling (to determine the time to change masks in photolithographic expose workstations), and batch scheduling (to determine the number of lots to be produced simultaneously in a batch and the processing sequence of batches in front of batch processing workstations such as cleaning and oxidation workstations). Unlike previous research, in which these three problems are dealt with separately the three problems are considered simultaneously using simulation, and new rules for the three problems are suggested in this study. Moreover, the setup time (mask change time) and the processing time were considered separately in the photolithographic expose workstations. Simulation results snow that the new rules give better performance than existing rules with respect to throughput rate, flow time, and work-in-process inventory.