Flexible job-shop scheduling problem with separable sequence-dependent setup

Abstract

This thesis focuses on a flexible job-shop scheduling problem with separable sequence-dependent setup time in semiconductor manufacturing. In this problem, all the jobs require five serial operations which can be performed by one of three identical multi-purpose machines. Each machine needs a setup time between different types of operations. Scheduling problems at the photolithography process in semiconductor wafer fabrication facilities are typical examples for this problem. For the problem with the objectives of minimizing mean flow time and mean tardiness, we develop a priority rule-based scheduling method and a two-stage scheduling method considering job release times and due dates. In these methods, the operations are assigned to machines and then the sequence of operations is determined on each machine. To evaluate performance of the suggested scheduling method, we perform computational experiments with randomly generated data sets reflecting real situations relatively well. Results of the computational experiments shows that the proposed methods perform better than existing methods developed in other researches and a method used in a real semiconductor manufacturing system.