Effective overhead hoist transport dispatching based on the Hungarian algorithm for a large semiconductor FAB

Abstract

This paper considers the vehicle dispatching problem in large-scale overhead hoist transport (OHT) systems of semiconductor fabrication lines. We propose a Hungarian algorithm based OHT reassignment approach named HABOR. HABOR attempts to take advantage of simultaneous vehicle reassignment based on up-to-date system status using the formulation of the assignment problem. The effectiveness of HABOR is demonstrated using a sample OHT system of a semiconductor fabrication line with more than 130 vehicles, where the flow path of the line allows direct delivery so that an inter-bay wafer movement can be accomplished by a single vehicle without an intermediate storage step at a stocker. HABOR compares favorably with the shortest travel distance first rule and with the reassignment-based rule recently proposed by the authors.

Keywords:

• reassignment
• dispatching rule
• overhead hoist transport
• assignment problem
• automated guided vehicle

Acknowledgements

We thank the anonymous referees for useful comments and suggestions for improving the paper. This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF-2007-331--D00548).