Multicluster tools scheduling: an integrated event graph and network model approach

Steady-state throughput and scheduling of a multicluster tool become complex as the number of modules and clusters grows. We propose a new methodology integrating event graph and network models to study the scheduling and throughput of multicluster tools. A symbolic decision-move-done graph modeling is developed to simplify discrete-event dynamics for the multicluster tool. This event graph is further used for searching feasible action sequences of the cluster tool. By representing sequences with networks, an extended critical path method is applied to calculate the corresponding cycle time. Grouping methods that are based on network are also introduced to reduce the searching complexity. Compared with optimization-based scheduling approaches, the proposed methodology can directly capture the cyclic characteristic of cluster tool schedules and be applied to analyze the impact of process and wafer flow variations on cycle time and robot schedules. We have successfully applied this new methodology to dozens of cluster tools at Intel Corporation. A chemical-mechanical planarization polisher is employed as an example to illustrate and validate the proposed methodology.