Daily stepper scheduling rule in the semiconductor manufacturing for MTO products

The make-to-order (MTO)-type semiconductor manufacturing line may suffer from the complexity of the operational management since the wafer lump corresponding to the specific order can be flown in various patterns, experiencing reentrancy, and complicated product mix. Different from the make-to-stock (MTS)-type memory products, the efficient scheduling policy is not much studied to achieve the demand, meeting related performance measure such as the order fill rate, inventory and shortage, and the cycle time. Because of the computational tediousness, the optimized mathematical programming approach for scheduling is not practical, but the scheduling rule, flexible and fast in computation, is preferred. In this study, the new scheduling priority index, accumulated urgency index (AUI), is developed for the MTO manufacturing line. The urgency index (UI) and balance index (BI) appeared in a literature are compared with AUI to evaluate the performances. It is shown through the computational experiment that AUI outperforms UI and BI in most MTOrelated measures and MTS-related ones such as throughput, utilization as well, which are also critical measures even in the MTO manufacturing lines. The experiment is also validated by the ANOVA and Duncan test.