Volume 40, Issue 6 (November 2012)
Precision Tool Condition Monitoring for Grinding Wheel in IC Manufacturing of Silicon Wafer
In integrated circuit (IC) manufacturing industries, wafer grinding is an important step because it improves wafer flatness and thickness. The diamond-grinding wheel used for grinding the wafers is expensive. Inevitably, the diamond-grinding wheel wears gradually during the grinding process, and the wafer surface is contaminated by grinding chips. Consequently, the fraction of defectives gradually becomes significant. In this situation, cost reduction is important for silicon wafer suppliers in the global market. Therefore, it is essential to monitor the grinding wheel in order to reduce the manufacturing cost and minimize the fraction of defectives. In this paper, we consider the grinding-wheel replacement problem in IC factories with the aim of determining the optimal replacement time for the grinding wheels. In order to maintain high wafer process quality and minimize the production cost, we propose a tool condition monitoring procedure for assessing the true capability at each time period of the grinding process and then find the optimal time for tool replacement. The procedure can be used practically for the silicon wafer manufacturing industry.