Highly sensitive trace moisture ball SAW sensor using SiOx film SiOx SAW

In highly pure semiconductoer-related gases, it is neccesary to measure trace moisture less than (frost point -76 ). A chilled mirror hygrometer and capasitive hygrometer are used for this purpose, but they are not sensitive nor fast enough [1]. A surface acoustic wave (SAW) sensor using metal-organic framework film achieved to measure (frost point -85 ), but the sensitivity and response time are still not sufficient. On the other hand, a ball SAW sensor [3], developed by our group, achieved the measurement of in 15 s using a delay time response [4]. However, the response mechanism was not clear and the repeatability in production was nor established. In this study, we aim to develop highly reproducible fabrication technique of sensitive and fast ball SAW trace moisture sensor.