Hot lot management: minimizing cycle time in batch processes

In semiconductor manufacturing, hot lots are often introduced into the system out of marketing and business considerations for extra flexibility regarding delivery lead times. The objective of this paper is to study the scheduling policies to minimize the cycle time of hot lots in batch processes. We present three scheduling policies based on look ahead batching (LAB) and study their effect on the performance of cycle time of hot lots and other priority lots in the system. In LAB, the scheduling decisions are based on the arrival epochs of incoming lots, which are easily predictable in a computer integrated manufacturing environment. The steady state simulation results show that exploiting the knowledge of future arrivals leads to 10% reduction in the cycle time of hot lots without affecting their standard deviation and also without affecting the cycle time performance of other priority lots in batch processes at lower values of utilization level.