Optimal scheduling analysis of treelike hybrid multi-cluster tools

A hybrid multi-cluster tool is composed of both dual and single-arm robotic tools. Since their behavior is different, it is very challenging to coordinate their activities in such a tool and to schedule it optimally. This work aims at finding such a schedule for a treelike hybrid multi-cluster tool whose bottleneck tool is assumed to be process-bound. Resource-oriented Petri nets are extended to model the system. With the model, this work shows the conditions under which there is a one-wafer cyclic schedule such that the least cycle time can be obtained. An efficient algorithm is proposed then to test the existence of such a schedule and find it if existing. Example is given to illustrate the derived approaches.