Petri net modeling and performance analysis of cluster tools with chamber revisiting

Timed Petri nets are convenient models of cluster tools as they represent the flow of wafers through the chambers of the tool as well as consecutive actions performed by the robotic transporter. Since the durations of all activities are also represented in such model, performance characteristics can be derived for steady-state as well as for transient behaviors. Steady-state performance of tools with chamber revisiting is investigated in this paper. A general description of cluster tools is proposed for systematic derivation of schedules, and a Petri net model is automatically derived from this description. The performance of the modeled system is derived by using place invariants, without exhaustive reachability analysis.