In Situ Monitoring for Wet Rinse Process Using Electrochemical Impedance Spectroscopy on Sensing Wafers

In recent years, the interest in reducing environmental impact has been increasing. This trend is evident in the semiconductor manufacturing, where the development of a tool that can simultaneously offer environmental friendliness and high performance is becoming more in demand. The semiconductor cleaning process, which uses a significant amount of liquids, is one area where reduction efforts are particularly needed. To reduce the consumption of liquids, it is crucial to understand the current process. This paper focuses on in situ measurement of the wet rinse process on a wafer, especially the transition from ammonia (NH 4 OH) solutions to ultrapure water (UPW). Several kinds of sensing wafers with sensors on a Si substrate were made to monitor the impedance of liquids flowing on the wafer in situ using electrochemical impedance spectroscopy (EIS). By evaluating four different types of sensor electrode configurations, the importance of surface area and the outermost layer of the sensor were revealed. An impedance measurement during rinse process was demonstrated in a single wafer cleaning tool.