射频容性耦合等离子体放电特性的光谱诊断

摘要

利用流体模型模拟和发射光谱实验诊断相结合的方法,研究了中等气压、中等功率下射频容性耦合等离子体的放电特性.理论上,采用基于流体模型的COMSOL软件仿真,建立一维等离子体放电模型,以Ar气为工作气体,研究了不同气压以及不同射频输入功率下等离子体电子温度和电子密度的分布规律.实验上,依据仿真模型设计制作了相同尺寸的密闭玻璃腔体和平板电极,采用13.56 M Hz射频放电技术电离腔体内的工作气体Ar气,测量了不同气压、不同射频输入功率时放电等离子体的发射光谱.通过分析和选择适当的Ar Ⅰ和Ar Ⅱ的特征谱线,分别利用玻尔兹曼斜率法以及沙哈-玻尔兹曼方程计算了等离子体的电子温度与电子密度,并结合模拟仿真结果对光谱诊断结果进行了修正.结果表明:当气体压强为300~400 Pa、输入功率为600~800 W时,等离子体近似服从玻尔兹曼分布,此时利用光谱法得到的等离子体参数与仿真结果相符合.仿真模拟与光谱实验诊断相结合的方法可初步诊断出中等气压下等离子体的放电参数,增加了玻尔兹曼斜率法和沙哈-玻尔兹曼方程在等离子体放电中的使用范围,扩大了光谱法在低电子密度容性耦合等离子体参数诊断的应用场合,为中等气压容性耦合等离子体在工业与军事上的应用研究提供了重要物理状态的分析手段.%A method of combiningthe fluid model simulation and the emission spectrum was used to study the discharge charac-teristics of Radio-frequency(RF)capacitive coupled plasma in medium pressure and medium power.In theory,one-dimensional discharged plasma model is taken using COMSOL software based on the fluid model.The distributions of electron temperature and electron density of plasma were studied under different air pressures and different radio-frequency powers with the Ar gas as the working gas.In experiment,a glass sealed cavity and a pair of plate electrodeswere designed and fabricated with the same si-zes of the simulation model.Using 13.56 M Hz radio frequency discharge technology to ionize the working gas of Ar gas in the cavity.The emission spectra of discharge plasma at different pressures and different RF input powers were measured.Through the analysis and selection of suitable spectral lines of ArⅠ and ArⅡ,the electron temperature and electron density of the plasma were calculated by the Boltzmann method and the Shah-Boltzmann equation,respectively.And then these results of spectral di-agnosis were modified by combining with simulation results.The results show that when the gas pressure is 300~400 Pa and the radio-frequency power is 600~800 W,the plasma satisfy the Boltzmann distribution approximately.The plasma parameters ob-tained by the spectroscopic method are in agreement with the simulation results.The discharge parameters of the plasma under the medium pressure can be diagnosed by the method of combing the fluid model simulation and the emission spectrum,which provides a reference for the following study about the plasma properties.The method combining the fluid model simulation and the experimental spectrum diagnosis can be used to diagnose the plasma discharge parameters at medium pressure and medium power,which increases the range of use in plasma discharge in the Boltzmann slope method and the Saha-Boltzmann equation, and expands the application of spectroscopy in low electron density capacitive coupled plasma diagnostics.Also it provides an im-portant physical state analysis for the study of medium pressure capacitive coupled plasma in industrial and military applications.