Multi-Factor OHT Scheduling Method of AMHS for Semiconductor Fabrications

A multi-factor scheduling method was proposed to improve the comprehensive performance of semiconductor fabrication systems. Firstly, five key factors, which include the distance between wafer lots and vehicles, lots' waiting time, lots' priority, bottleneck stations and OHT (overhead hoist transporter) utilization, were analyzed in three aspects of stations, wafer lots and AMHSs. A multi-factor scheduling mathematical model was set up with an objective function of the minimizing cost. On the basis of the five-factor, a bipartite graph method was introduced to build an algorithm for solving the scheduling model. Finally, experiments were designed and analyzed to evaluate the proposed method. Results indicate the proposed method is valid and feasible.