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目前,N_2、Ar、H_2这些体积气体中的杂质(也包括水分)已能被控制在1ppb以下。但是,为了进一步提高半导体工艺的质量,迫切希望能提高特殊气体的纯度,尤其需要降低其中的残留水分。现有的特殊气体水分浓度计测装置主要有电容式,压电晶体振荡器式等。然而,由于特殊气体的反应性,腐蚀性、反应生成物的堆积等问题,测定装置的时效变化较为显著,为此,传感器必须经常清洗并作短期再校正等。特别是在传感器吸附了水分时,特殊气体出现溶入现象,那就根本不可能进行精密的,再现性好的测定。日本东北大学大见忠弘最近研究成功了一种新的测定方法:他发现,当含有一定量水分的气体在完全脱离了吸附水的管道内流动时,固体表面的水分量与气相水分量到达平衡吸附状态,气体中的水分便吸附在管内表面,籍此现象,即可用来测定特殊气体中的水分量。亦即,一边给配管供给水分浓度为50ppt的超高纯度氩气,一边将不锈钢管子加热到400～450℃,使吸附在内表面的水分完全除去,接着再供给特殊气体,直至管内表面到达平衡吸附状态为止,因吸附的全是特殊气体中的水分,故只需一边供给超高纯度氩气,一边使吸附水分脱离,就可用气压离子质谱计(APIMS)测定这种脱附水分的总量,然后求出它与在管道内流动的特殊气体的总量之比,即可测出特殊气体中的?
Currently, N_2, Ar, H_2 gas volume of these impurities (including water) can be controlled at 1ppb or less. However, in order to further improve the quality of the semiconductor process, there is an urgent need to increase the purity of the special gas, in particular, to reduce the residual moisture therein. The existing special gas moisture concentration measuring devices are mainly capacitive, piezoelectric crystal oscillator type. However, because of the reactivity of special gases, corrosiveness, and the accumulation of reaction products, the aging of the measuring device changes significantly. For this reason, the sensor must be frequently cleaned for short-term re-calibration. In particular, when the sensor absorbs moisture and the special gas dissolves, it is impossible to perform a precise and reproducible measurement at all. In recent research, Daihatsu Tadashi, Northeastern University, Japan, succeeded in a new measurement method. He found that when a gas containing a certain amount of water flows in a pipe completely free from adsorbed water, the amount of water on the surface of the solid reaches a balance with the amount of gas-phase water Adsorption state, the gas in the water will be adsorbed on the tube surface, take this phenomenon, which can be used to determine the amount of water in a special gas. That is, the stainless steel tube was heated to 400 to 450 ° C while supplying ultra-high purity argon gas having a water concentration of 50 ppt to the pipe to completely remove the water adsorbed on the inner surface, and then the special gas was supplied again until the inner surface of the pipe reached equilibrium In the adsorption state, since all the adsorbed water is the water in the special gas, the total amount of desorbed water can be measured by a gas pressure ion mass spectrometer (APIMS) just by supplying the ultra-high purity argon gas while desorbing the adsorbed water , And then find it with the total amount of special gas flowing in the pipeline ratio, you can measure the special gas?