Idle vehicle circulation policies in a semiconductor FAB

Abstract

Idle vehicle handling is addressed for the path-based automated material handling system (AMHS) in a semiconductor fabrication line. Since a typical semiconductor fabrication line has a single path in each bay and no sidetracks to park idle vehicles, a vehicle should be dispatched to somewhere if necessary even without a new assignment to prevent blocking of other vehicles. We investigate the continuous-move policy, the move-when-necessary policy and their variants. Our simulations show that the idle vehicle circulation policy significantly affects the AMHS productivity, so the policy should be carefully designed for the AMHS instance.