Scheduling Analysis of Cluster Tools with Buffer/Process Modules

Modeling and scheduling of cluster tools are critical to improving the productivity and to enhancing the design of wafer processing flows and equipment for semiconductor manufacturing. In this paper, we extend the decomposition methods in the work of Dwande et al. (2005) for multi-cluster tools with buffer/process modules (BPMs). The computation of the lower-bound cycle time (fundamental period) is presented. Optimality conditions and robot schedules that realize such lower-bound values are then provided using "pull" and "swap" strategies for single-blade and double-blade robots, respectively. The impact of BPMs on throughput and robot schedules is studied. It is found that such an impact depends on the BPM processing time and the cycle times of the decomposed clusters on both sides of BPMs. A chemical vapor deposition (CVD) tool is used as an example of multi-cluster tools to illustrate the proposed method, analysis, and algorithms. The numerical and experimental results demonstrate the effectiveness and efficiency of the algorithms.