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 differe nt 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 rele ase wafers into the wafer fab, while it is necessary to determine sequ ences of processing waiting lots in front of workstations for lot sche duling. New dispatching rules are developed for lot release control an d scheduling considering special features of the wafer fabrication pro cess. Simulation experiments are carried out to test the dispatching r ules, Results show that lot release control and lot scheduling at phot olithography 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 mul timachine scheduling.