A Time Window Rolling- and GA-Based Method for the Dynamic Dispatching Problem in Photolithography Area
Date Issued
2008
Date
2008
Author(s)
Kuo, Chun-Nan
Abstract
The operation management of photolithography area is the most important yet difficult task in semiconductor manufacturing. Due to numerous constraints and operation goals imposed, manual decision and action are adopted in scheduling and dispatching the jobs for the machines in this area. The operation requirements and constraints considered in this paper include lot-priority, machine load balance for critical layers, machine bounded by critical layers, heterogeneous processing capability, reticle pilot run, dummy wafer test, etc. Under these considerations, this paper presents a time window rolling- and GA-based scheduling system to assign and schedule both the 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 the wafer lots on the way to the photo area 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, weighted cycle time, extra time, makespan, and critical layer loading unbalanced value, to conduct the scheduling results to enhancing the machine utilization and throughput while reducing cycle time and nonproductive time. To verify the proposed GA model, a prototype system namely “Photolithography Area Simulation System,” was developed implementing the proposed scheduling method and a simulation platform for the photolithography area. In addition, four performance indices are proposed, tool utilization, throughput, cycle time, and extra operation time, for evaluating the scheduling methods. Numerical tests were conducted using historical operation data from a Taiwanese DRAM manufacturing factory. Production activities are simulated by the historical data and executed by the scheduling results from the proposed model. Results showed that the proposed method outperformed the manual one and a simple FCFS scheduling method. In particular, the performance improvement reached a peak subject to a time window width specification.
Subjects
Photolithography Area
Scheduling and dispatching
Time Window Rolling
Genetic Algorithm
Type
thesis
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