Cycle Planning for Concurrent Processing in a Dual-Armed Cluster Tool

In semiconductor manufacturing, a cluster tool, which consists of several processing modules (PMs) and a single wafer handling robot, often processes multiple wafer types concurrently to maximize its throughput. In this case, each PM is usually dedicated to a specific wafer type to meet quality requirements. When processing multiple wafer types, cyclic scheduling is widely used to maintain the resulting schedule simple and traceable. In cyclic scheduling of multiple wafer types, a cycle plan which determines the number of wafers of each type produced in a cycle plays a critical role in maximizing the tool's throughput. Determining a cycle plan is very challenging because the workload balance and robot task timings between different wafer types should be considered simultaneously. In this paper, we propose an efficient algorithm for cycle planning while assuming that each wafer type is produced based on the well-known swap sequence. We also present an algorithm to determine the input sequence of wafer types for a given cycle plan. Finally, the performance of the proposed algorithms is verified by numerical experiments.