Cycle time distributions of semiconductor workstations using aggregate modeling

Recently an aggregate modeling method has been developed to predict cycle time distributions as a function of throughput for manufacturing workstations with dispatching. The aggregate model is a single-server representation of the workstation with a workload-dependent process time distribution, and a workload-dependent overtaking distribution. The process time and overtaking distribution can be determined from arrival and departure events measured from the workstation at the factory floor. In this paper, we validate the proposed method in the context of semiconductor manufacturing. In particular we consider a lithography workstation. First, we present a simulation case that demonstrates the accuracy of the aggregate model to predict cycle time distributions. Second, we apply the aggregate modeling method to a case from semiconductor industry, and illustrate how the method performs using arrival and departure data obtained from the manufacturing execution system.