Detection of Trace Water Vapor Using SiO_x-Coated Ball SAW Sensor

Abstract

In manufacturing process of semiconductor, blue light emitting diode (LED), and lithium ion battery, detection and monitoring of trace water vapor (<1 µmol/mol) are significantly important techniques. We have been researching about detection of trace water vapor with high speed and sensitivity by using ball surface acoustic wave (SAW) sensor.
In this paper, we tried to detect trace water vapor by coating silicon oxide (SiO_x) on ball SAW sensor using sol–gel method. It was confirmed that SiO_x-coated ball SAW sensor could detect water vapor in a wide range from −95 to 0°C in frost point (0.035–6.0 × 10³ µmol/mol in concentration) and its response time to frost point change from −70 to −60°C was one half of that of a chilled-mirror hygrometer.