Petri Net-Based Deadlock Avoidance for Single-arm Cluster Tools with Concurrently Processing Two-type Wafers

A modern fabrication tends to arrange different wafer types with similar recipes in a lot in order to increase the utilization of cluster tools, meet the demand of customization, and improve the flexibility of the system. Nevertheless, the wafer flow patterns of the different wafer types may be different such that cluster tools are deadlock-prone. This work aims at solving the deadlock problem of single-arm cluster tools with concurrently processing two wafer types. In order to solve it, the deadlock analysis of the system is conducted. Then, a general Petri net (PN) model is developed for the system. Furthermore, a novel method called the PN-based earliest starting strategy is proposed for the system such that the system can operate without deadlock. Moreover, such a method can be used for real-time scheduling. Therefore, it is significant for semiconductor manufacturing.