基于化学发光法的高纯气体中ppb量级NO_(x)浓度测量

Measurement of NO_(x) concentration at ppb level in high-purity gases based on chemiluminescence method

高纯气体在半导体器件制作及燃料电池等行业应用广泛,但其杂质气体直接对加工精度及效果产生显著影响,因此对关键痕量杂质气体进行浓度诊断尤为必要.本文基于化学发光光谱理论和氮氧化物催化转化机理,设计了一套痕量NO/NO_(x)同步高精度测量系统,通过标定实验可知,该测量系统具有高线性度(R^(2)=0.99967)、高灵敏度、低检测下限(约25 ppt,1 ppt=10^(–12))、易操作性等优势;同时,综合考虑不同背景气体对荧光、磷光的淬灭效应,建立不同高纯气体中NO_(x)测量方法,并利用该探测系统对实验室常用4种高纯气体(Ar,O_(2),CO_(2),N_(2))中ppb量级的氮氧化物进行测量,结果表示CO_(2)中的NO含量最高,约为9 ppb(1 ppb=10^(–9)),其他高纯气体中的NO含量较低,仅有0—4 ppb,4种高纯气体的NO_(2)含量均较低(<6 ppb);最后结合气体制备及提纯方式对高纯气体中杂质NO_(x)含量进行评价及分析,旨在为燃料电池、半导体器件制备等尖端科技领域提供可靠的杂质气体成分诊断方法和数据基础.

High-purity gases are widely used in semiconductor device manufacturing and fuel cell industries.However,the impurities have a significant influence on the processing accuracy directly.Thus,it is particularly necessary to carry out the concentration diagnosis of key trace impurity gases.In this work,an integrated system for the simultaneous detection of trace NO/NO_(x) is designed based on the chemiluminescence spectrum theory and the catalytic conversion mechanism of nitrogen oxides.The test experiments reveal that the measurement system has the advantages of high linearity(R^(2)=0.99967),high sensitivity,low detection limit(~25 ppt),and easy operation.Subsequently,the measurement method for NO_(x) with different high-purity gases are established considering the quenching effects of different background gases on fluorescence and phosphorescent.The detection system is then used to measure the ppb-level NO_(x) impurities in four commonly used high-purity gases(Ar,O_(2),CO_(2),N_(2))in the laboratory.The results show that the NO impurity in CO_(2) gas is the highest,approximately 9 ppb,but relatively low,0–4 ppb,in the other high-purity gases.The NO_(2) impurities in all four high-purity gases are very low(<6 ppb).Finally,the NO_(x) impurity content values in high-purity gases are evaluated and analyzed based on the gas preparation and purification approach.The aim of the work is to provide a reliable diagnostic approach and data basis of the impurity composition for the fuel cell,semiconductor and other cutting-edge technological fields.