WIP evolution of a semiconductor factory after a bottleneck workcenter breakdown

In semiconductor fabrication facilities, an increase in work in progress (WIP) can be observed even weeks after the failure of the bottleneck workcenter. We develop a simple fab model that facilitates the study of this phenomenon. The simplified factory consists of a detailed model of the bottleneck workcenter and a delay unit that represents the rest of the factory. After passing the delay unit, the lots are fed back to the bottleneck to model the cyclic flow of lots of real wafer fabs. We study the behavior of this model for numerous scenarios, and it turns out that by means of the model, the WIP increase phenomenon can successfully be reproduced. In addition, we provide first results on how to avoid the unwanted increase in inventory