Flexible job-shop scheduling with extended route flexibility for semiconductor manufacturing

Scheduling decisions have an important impact on the overall performance of a semiconductor manufacturing facility (fab). To account for machines that consist of several interdependent components, we generalize the flexible job-shop scheduling problem. We introduce the concept of route graphs to describe resource dependencies. Beside specifying feasible routes, route graphs can, for example, prescribe two different operations in the route of a job to use the very same resource. To solve the problem, we introduce an adapted disjunctive graph representation and propose a heuristic method that iteratively inserts jobs to construct an initial solution. This solution is then improved using a simulated annealing meta-heuristic. Several numerical experiments are performed. First, improved results for a real-world instance justify the increased complexity of our model. Second, a comparison to results of dedicated methods for the flexible job-shop scheduling problem shows that our approach obtains good results.