A control method to reduce the standard deviation of flow time in wafer fabrication

This paper proposes a control method for reducing flow time variability in a wafer fabrication facility with multiple wafer types. We employ stochasti c petri nets to model and analyze the machine module, and define operation due dates using a novel utilization index metric. An operation due date (OP NDD) rule for lot dispatch is proposed and evaluated against other tot disp atch policies.