Operational modeling and simulation of an inter-bay AMHS in semiconductor wafer fabrication

This paper studies the operational logic in an inter-bay automated material handling system (AMHS) in semiconductor wafer fabrication. This system consists of stockers located in a two-floor layout. Automated moving devices transfer lots between stockers within the same floor (intra-floor lot transfer) or between different floors (inter-floor lot transfer). Intra-floor lot-transferring transports use a two-rail one-directional system, whereas inter-floor lot-transferring transports use lifters. The decision problem consists of selecting rails and lifters that minimize average lot-delivery time. Several operation rules to deliver lots from source stocker to destination stocker are proposed and their performance is evaluated by discrete event simulation.