Connecting transport AMHS in a wafer fab

Automated material handling system (AMHS) plays a significant role in wafer fabrication. In this paper, a new concept of an automated material handling system in a 300mm wafer fabrication, called the connecting transport AMHS, is proposed. It can accomplish the wafer moving tasks by using different types of vehicles between bays and, within each bay, by a single system with interconnected lines. In the connecting transport system, the time that is spent waiting for an empty vehicle is eliminated effectively, and the WIP level can be reduced. Four different vehicle types are found and their operational issues are also discussed. Furthermore, three different combinations of vehicles are found and the AMHS for a 300 mm wafer fab can be one of the above three methods, or any mixture of these methods. A simple mathematical model is used to determine the minimum number of vehicles for the different connecting transports.