A deadlock recovery strategy for unified automated material handling systems in 300 mm wafer fabrications

• A novel recovery strategy for deadlock caused by limited buffers in unified automated material handling systems was proposed in this paper.
• A formal model is presented and sufficient conditions of deadlock are defined.
• A novel recovery strategy using spare stockers as temporary buffers is put forward.
• An effective heuristic algorithm for parallel deadlock resolving is presented.
• Simulation results indicate that the proposed strategy is effective and feasible for real-time operation and large scale cases of UAMHS in semiconductor fabrication system.

A key issue emerging from the unified automated material handling systems (UAMHSs) in 300 mm wafer fabrications is the system deadlock. This paper addresses the deadlock recovery strategy of unified automated material handling systems (UAMHSs) with limited buffers. A formal model for UAMHSs deadlock detection is proposed. Sufficient conditions for system deadlocks based on actual UAMHS characteristics are defined along with a novel deadlock recovery strategy. Moreover, an effective heuristic algorithm is proposed for parallel resolving UAMHS deadlocks. The performances are evaluated in simulation by monitoring indexes reflecting efficiency of the material handling system. Results of the simulation experiments show that the novel deadlock recovery strategy is superior to the benchmark strategy in reducing deadlock time and improving tools’ utilization. Furthermore, the proposed algorithm features real-time operation and large scale cases, and is suitable for practical applications.