Survey of research in modeling conveyor-based automated material handling systems in wafer fabs

Automated material handling systems (AMHS) play a central role in modern wafer fabrication facilities (fabs). Typically, AMHS used in wafer fabs are based on discrete vehicle-based overhead systems such as overhead hoisted vehicles. Conveyor-based continuous flow transport (CFT) implementations are starting to gain support with the expectations that CFT systems will be capable of handling high-volume manufacturing transport requirements. This paper discusses literature related to models of conveyor systems in semiconductor fabs. A comprehensive overview of simulation-based models is provided. We also identify and discuss specific research problems and needs in the design and control of closed-loop conveyors. It is concluded that new analytical and simulation models of conveyor systems need to be developed to understand the behavior of such systems and bridge the gap between theoretical research and industry problems.