Real-time control of multiproduct bulk-service semiconductor manufacturing processes

This work demonstrates how knowledge of future arrivals can be used to improve control of multiproduct bulk-service semiconductor manufacturing processes. The objective of the research reported is to reduce the average time that lots spend waiting to be processed. A review of the current literature reveals that several researchers have dealt with the control of bulk-service queuing systems; however, only one paper has addressed the use of knowledge of future arrivals and it only considered the single-product case. This research reexamines the single-product-single-tube case and then explores the multiple-products-single tube case. For both cases, a control strategy is devised and evaluated through the use of systems simulation. The steady-state performance of each control strategy is then compared to the steady-state performance of the theoretically optimal control strategy not considering the timing of any future arrivals (i.e., a minimum batch size strategy). The experimental results indicate that the control strategies developed in this work perform well under a wide variety of conditions