Multi-ant colony-based sequencing method for semiconductor wafer fabrication facilities with multi-bottleneck

Abstract

In this paper, a multi-ant colony optimisation method is proposed to make a sequence plan for a semiconductor wafer fabrication facility (fab) with multi-bottleneck. Its main idea is to find a scheduling solution for each bottleneck of the fab with an ant colony optimisation (ACO) algorithm first, then synchronise these solutions to reunify a sequence plan for these bottlenecks satisfying job sequence constraints, and finally obtain the scheduling plans of non-bottlenecks of the fab subject to that of bottlenecks and job sequence constraints. The sequence plan of the whole fab is translated into the pheromones to guide ant colonies to make their next search processes. There are two kinds of ACO algorithms in the multi-ant colony optimisation method. One (ACO-1) is for common machines and the other (ACO-2) is for batch processing machines. The mini-fab model and a simplified model from a real wafer fab are used to verify and validate the proposed method. The simulation results show that the multi-ant colony optimisation method improves the total weighted tardiness of jobs and the utilities of the bottlenecks with better performances.