Dispatching In An Integrated Circuit Wafer Fabrication Line

Wafer Fabrication has been described as the most complicated manufacturing environment existing today. This paper describes a method used to dispatch lots in one of AT&T's Wafer Fabrication Clean Rooms. The objective is to minimize idle time on important facilities in the clean room. For each lot in the clean room, the method indicates the slack time the lot can incur before it is needed at the next important facility group in its route. The slack time is the amount of time the lot can be delayed in queue with the implication that a lot with a smaller slack time needs to be processed more urgently than a lot with a larger slack time.