Production Rate Based Dynamic Dispatching Rule Selection in a Wafer FAB

Abstract

Abstract-This paper proposes a state-dependent dispatching rule to achieve on-time delivery as well as minimum of mean cycle time in a wafer FAB. Dispatching rule should be selected dynamically according to current system state and operation objective, since condition in a wafer fab is dynamically changed. In this paper, we use 'pegging' to identify a current state of a wafer FAB. Pegging is defined as the process of assigning wafer lots to orders, and it is very essential to meet customers' demands in terms of quality, quantity, and due dates in a wafer FAB. As a result, pegging decides target move for each step, it is necessary to select WIP lot to be processed next. The proposed state-dependent dispatching rule consists of two stages. At the first stage, WIP lots are classified into two groups which has priority, and classical dispatching rule is applied to select a WIP lot at the second stage. The target move and actual move are computed by the combination of pegging and simulation. We developed a simulation model by using MIMAC6, and conducted simulation with SEEPLAN®.