QUANTITATIVE-ANALYSIS OF TRACE HYDROGEN IN HIGHLY PURIFIED NITROGEN GAS-USING RAPID REACTIONS IN ATMOSPHERIC-PRESSURE IONIZATION MASS-SPECTROMETER

Quantitative analysis of trace hydrogen in highly purified nitrogen ga s for the semiconductor fabrication process was investigated using an atmospheric pressure ionization mass spectrometer (APIMS). A previous method wherein the sample gas is directly introduced into the APIMS is not capable of providing high-sensitivity measurements for hydrogen i n nitrogen gas. By mixing 20% argon gas with the sample gas, the sensi tivity was increased to ten times that of the previous method. This is due to the occurrence of a previously unreported rapid reaction throu gh which the quantity of hydrogen ions is increased: (N2Ar)+ +H2-->N2H + +H + Ar. The detection limit in this method and the rate constant fo r this reaction were estimated to be 40 ppt and 1.4 X 10(-10) molecule -1 cm3 s-1, respectively.