Mahoney Edward J D, Mushtaq Sohail, Ashfold Michael N R, Mankelevich Yuri A
School of Chemistry , University of Bristol , Bristol BS8 1TS , U.K.
Centre for Doctoral Training in Diamond Science and Technology , University of Warwick , Gibbet Hill Road , Coventry CV4 7AL , U.K.
J Phys Chem A. 2019 Apr 4;123(13):2544-2558. doi: 10.1021/acs.jpca.8b12294. Epub 2019 Mar 26.
Microwave (MW) activated H/Ar (and H/Kr) plasmas operating under powers and pressures relevant to diamond chemical vapor deposition have been investigated experimentally and by 2-D modeling. The experiments return spatially and wavelength resolved optical emission spectra of electronically excited H molecules and H and Ar(/Kr) atoms for a range of H/noble gas mixing ratios. The self-consistent 2-D( r, z) modeling of different H/Ar gas mixtures includes calculations of the MW electromagnetic fields, the plasma chemistry and electron kinetics, heat and species transfer and gas-surface interactions. Comparison with the trends revealed by the spatially resolved optical emission measurements and their variations with changes in process conditions help guide identification and refinement of the dominant plasma (and plasma emission) generation mechanisms and the more important Ar-H, Ar-H, and H-H coupling reactions. Noble gas addition is shown to encourage radial expansion of the plasma, and thus to improve the uniformity of the H atom concentration and the gas temperature just above the substrate. Noble gas addition in the current experiments is also found to enhance (unwanted) sputtering of the copper base plate of the reactor; the experimentally observed increase in gas phase Cu* emission is shown to correlate with the near substrate ArH (and KrH) ion concentrations returned by the modeling, rather than with the relatively more abundant H (and HO) ions.
已通过实验和二维建模研究了在与金刚石化学气相沉积相关的功率和压力下运行的微波（MW）激活H/Ar（以及H/Kr）等离子体。实验给出了一系列H/稀有气体混合比下电子激发的H分子以及H和Ar（/Kr）原子的空间分辨和波长分辨光发射光谱。不同H/Ar气体混合物的自洽二维（r，z）建模包括微波电磁场、等离子体化学和电子动力学、热量和物种传输以及气体-表面相互作用的计算。与空间分辨光发射测量揭示的趋势及其随工艺条件变化的比较，有助于指导识别和完善主要的等离子体（和等离子体发射）产生机制以及更重要的Ar-H、Ar-H和H-H耦合反应。结果表明，添加稀有气体会促进等离子体的径向扩展，从而提高衬底上方H原子浓度和气体温度的均匀性。在当前实验中还发现，添加稀有气体会增强（不需要的）反应器铜基板的溅射；实验观察到的气相Cu*发射增加与建模返回的近衬底ArH（和KrH）离子浓度相关，而不是与相对更丰富的H（和HO）离子相关。
