Due-date based scheduling and control policies in a multiproduct semiconductor wafer fabrication facility

This paper focuses on lot release control and scheduling problems in a semiconductor wafer fab producing multiple products that have different due dates and different process flows. For lot release control, it is necessary to determine the type of a wafer lot and the time to release wafers into the wafer fab, while it is necessary to determine sequences of processing waiting lots in front of workstations for lot scheduling. New dispatching rules are developed for lot release control and scheduling considering special features of the wafer fabrication process. Simulation experiments are carried out to test the dispatching rules. Results show that lot release control and lot scheduling at photolithography workstations are more important than scheduling at other workstations. Also, it is shown that new dispatching rules work better in terms of tardiness of orders than existing rules such as the EDD (earliest due date) rule and other well-known dispatching rules for multimachine scheduling.