Dispatching in semiconductor fabs with machine-dedication features

Abstract

This research develops dispatching algorithms for a fab with machine-dedication characteristics. Machine-dedication, a new feature in a modern fab, has not been addressed in previous studies of dispatching. Three performance indices, including hit rate, mean cycle time, and throughput are of concern in dispatching. This research develops an algorithm, called LB-SA, based on a proposed simplification model of the process route. The line balance (LB) component aims to smooth the flow rate of the process route; and the starvation avoidance (SA) component aims to ensure that the bottleneck machine is not "starving" and has enough work-in-progress (WIP) to process all the time. Thirty dispatching algorithms, including the LB-SA algorithm, are compared by simulation. The LB-SA algorithm outperforms the other 29 algorithms both in terms of hit rate and mean cycle time, and is only slightly less than the best benchmark in throughput. Of the 29 other algorithms, one algorithm, called CR-SA, also performs very well. These two algorithms are both recommended for fabs with machine-dedication feature.