Compact Sensor for Environmental Monitoring

This report describes a simple means of detecting trace amounts of gaseous substances in the atmosphere. In the fabrication processes for semiconductor LSIs, production defects occur if gas phase contaminants in the atmosphere stick to the wafer being processed. To overcome this problem, I have developed and am currently applying a contamination sensor that uses a quartz crystal microbalance (QCM) to detect such contamination. The detection system using this sensor has high sensitivity and is well suited to tracking the time-varying concentration of an atmospheric contaminant. Investigating the behavior of contaminants in a semiconductor LSI fabrication plant makes it possible to identify contamination sources and eliminate them. Therefore, this sensor system should be effective in lowering production costs and improving product quality. Moreover, the sensor is compact, so it can be easily installed, for example, at various locations around a plant and in the wafer container. Besides being compact, the QCM controller is easy to use and offers outstanding portability: it simply needs to be plugged into the universal serial bus (USB) port of a device such as a notebook computer. As a result of these features, it is likely that this sensor will not only be used in semiconductor fabrication plants but also be applied to other kinds of environmental measurement.