Simulating the Transport and Scheduling of Priority Lots in Semiconductor Factories

As high technology product market becomes more dynamic and competitive, chip manufacturers need to bring products to customers in short periods of time. As a result, semiconductor fabrication plants regularly contain lots with priority status. These lots have several unique characteristics compared to other production lots, both in terms of lot transport and scheduling on tools. These lots consume tool capacity that may impact the factory output rate. Priority lots also have specific policies for transport. The impact of these priority lots on other lots in the fab is not easily quantified, as many factors are involved. Dynamic factory and AMHS simulation models are capable of capturing the variability of a factory, and the interactions of critical constraints that prevent predictable manufacturing. This paper presents a breakthrough modeling approach to study the behaviors of priority lots, and to quantify their impact to manufacturing.