Queueing network analysis for an IC foundry

A hybrid decomposed queueing network model is developed based on actual operating data from one particular foundry fabrication (fab) for rapid analysis of several performance measures. The queueing model includes analyzer and predictor modules. The system analyzer module provides the analysis of arrival pattern and service pattern for each tool group. The system predictor module provides the forecast of important performance measures, such as products cycle time, lots remaining cycle time, tool utilization, queueing length, tool moves, stage moves. In addition, a modularized system, QFAB, is designed to implement the model proposed. A systematic analysis of arrival pattern and service pattern for tool groups is proposed. An approach to compute the effective tool number for tool groups is also addressed. Based on the analysis, the supervisors can gain more insights and choose the proper queueing models. Comparing the obtained results to the actual fab data, the accuracy of prediction of cycle time is satisfactory.