Monitoring for parts-per-billion trace gas impurity contamination in semiconductor fab process gases

Summary form only given. A major innovation in trace gas impurity contamination monitoring has led to the development of a complete analyzer system, the MTO-1000, for continuous detection of ultra low trace gas impurities in semiconductor process gases. The analyzer is based on infrared laser absorption spectroscopy. It provides 500 part\´s per trillion (PPT) sensitivity for moisture, and PPB or sub-PPB for other trace gas impurities. Moisture is a major contaminant that originates from the atmosphere and causes severe damage to UHP piping and semiconductor wafers. The principle of operation of the MTO-1000 is cavity ring-down spectroscopy (CRDS), which was jointly developed by MEECO and Princeton University. The availability of an inexpensive diode laser that can be operated in various parts of the infrared spectrum is part of the new trace gas analyzer. Conventional infrared limitations to measuring low PPB concentrations are amplitude noise of light sources and the detector. There are no such limitations with CRDS since it measures the time it takes for the signal to "ring down" or decrease in amplitude.