Modularized simulation for lot delivery time forecast in automatic material handling systems of 300 mm semiconductor manufacturing

Abstract

The more accurate the forecast is to lot delivery time, the more effective it is in fab scheduling. In fab operations, scheduling is the major impact factor of tools capacity allocation, tools utilization control and bottleneck management. However, there is no effective method to estimate delivery time in 300 mm automatic material handling systems (AMHS) operation. Computer simulations are authentic, but they are either too complex to model fab operations as well as the whole AMHS, or too time-consuming to simulate with a full-scaled fab model. This paper proposes an analytic methodology to estimate the loop-to-loop delivery time for differentiated lots in a 300 mm AMHS environment. Combining simulation and statistics techniques, we develop a modularized simulation method (MSM) for delivery time forecast of priority lots. Numerical experiments based on data from a local 300 mm manufacturing fab are conducted. Simulation demonstrates that the MSM has credible results in estimating lot delivery times. The time differences between MSM and simulation for both priority lots and regular lots are 0.2 s and 0.1 s, respectively. Using the MSM method to forecast AMHS delivery time is a great contribution for streamlining shop floor operations, such as scheduling and dispatching, for eliminating time delays in the 300 mm automatic environment.