Combined Spatially Resolved Optical Emission Imaging and Modeling Studies of Microwave-Activated H2/Ar and H2/Kr Plasmas Operating at Powers and Pressures Relevant for Diamond Chemical Vapor Deposition

Microwave (MW) activated H2/Ar (and H2/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 H2 molecules and H and Ar(/Kr) atoms for a range of H2/noble gas mixing ratios. The self-consistent 2-D(r, z) modeling of different H2/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–H2, and H–H2 coupling reactions. Noble gas addition is shown to encourage radial expansion of the plasma, and thus to improv...