IN-LINE MOISTURE MONITORING IN SEMICONDUCTOR PROCESS GASES BY A REACTIVE-METAL-COATED QUARTZ-CRYSTAL MICROBALANCE

A new in-line sensor for trace moisture monitoring has been developed based on a piezoelectric quartz crystal microbalance (QCM) coated with a reactive metal thin film. The properties of the metal coating and Q CM allow the sensor to have fast response and fast recovery to moistur e in the process gas stream. The propel ties of the metal-coated QCM a lso allow the sensor to be compact so it cart be in-line in the gas di stribution system and readily integrated into the process tools. This paper presents the principle of moisture detection using this technolo gy. The experimental results of accuracy, limit of detection (< 1 ppb) , and en or analysis of this sensor in parallel with atmospheric press ure ionization mass spectrometry (APIMS) are presented. The experiment al setup and procedures are described. The effect of an upstream gas p urifier on its rate of response was also studied and the results are p resented and discussed The applications of this technology in semicond uctor processing are briefly mentioned.