Ultrasonic time-of-flight method for on-line quantitation of semiconductor gases

An ultrasonic method is described for online determination of on-demand generated arsine in process streams. For online monitoring of dangerously toxic gases, the ultrasonic method has proven to be superior to other techniques. Accurate, noninvasive, real-time determinations of arsine in hydrogen have been accomplished. Highly precise experimental calibrations are in excellent agreement with theoretical predictions based on an appropriate acoustic model. The acoustic time-of-flight method was also found to be insensitive to pressure and volumetric gas flows. For these reasons, it is a versatile and practical tool for monitoring a broad range of binary gas flow streams of reagents used for device fabrication