Building a Digital Twin of the Photolithography Area of A Real-World Wafer FAB To Validate Improved Production Control

Since the photolithography area is generally the bottleneck of a wafer fab, effective scheduling in this area can increase the performance of the complete fab significantly. However, the potential benefit of proposed solution methods is often validated in a static and deterministic scheduling setting, while the manufacturing environment is dynamic and stochastic. In this paper, we build a discrete-event simulation model based on real-world data of the photolithography area, which can be used to accurately determine the performance of new scheduling solutions. A case study at a global semiconductor manufacturer is presented. The simulation model, a so-called digital twin, captures the vast majority of the stochastic behavior such as the arrival of jobs, processing times, setup times and machine downs. In addition, a dispatching heuristic is developed to replicate the current practice of production control. Both the simulation model and the dispatching heuristic are validated and shown to be accurate.