A time window rolling- and GA-based method for the ynamic dispatching problem in photolithography area

The operation requirements and constraints in the photolithography area considered include lot-priority, machine load balance for critical layers, machine bounded by critical layers, heterogeneous processing capability, reticle pilot run, and dummy wafer test. Under these considerations, this paper presents a time window rolling- and GA-based scheduling system to assign and schedule arrived and on-the-way wafer lots to the photolithography machines. Time window is defined when the scheduler is triggered by extending a time period to round in wafer lots on the way within this window. The scheduled jobs are then executed accordingly until the next scheduling event is triggered; and thus the widow rolls. The presented model proposed four minimization sub-goals to enhance the machine utilization and throughput while reducing cycle time and nonproductive time. To verify the proposed methods, a prototype system namely “Photolithography Area Simulation System,” was developed. In addition, four performance indices are proposed for evaluating the scheduling methods. Numerical tests were conducted using historical operation data from a Taiwanese DRAM manufacturing factory. Results showed that the proposed method outperformed the manual one and a simple FCFS scheduling method.