Spectroscopic analysis of microwave generated plasmas

Microwave generated plasmas present a simple and versatile tool for numerous plasma-technological applications. Detailed analysis of the plasma properties and of their temporal and spatial distributions is an important prerequisite for optimizing the process technology and the quality of the application as well. Examples among many others are the homogeneity, the permeability and the mechanical and electrical properties of deposited thin layers on numerous surfaces. Spectroscopy is offered to be a diagnostic method that does not disturb or change the plasma. From diagnosing absolute spectral line and continuum intensities or simply line intensity ratios many of the important plasma parameters as kind of species, species densities, electron density, temperatures of neutrals, ions and electrons can be explored. Among these the species ground state density as an important quantity can quantitatively be determined by "passive" emission and absorption spectroscopy of spectral lines with self absorption. This was first developed for the silicon ground state density in a plasma target interaction experiment by the spectral analysis of the silicon multiplet 3p^{2 3}P-3p4s ³P⁰ in the ultraviolet spectral range at 251.611 nm. Because of the importance of carbon in plasma technological processes and their applications and in the boundary layers of magnetic fusion devices this method was also applied for the carbon ground state determination by analyzing the multiplet 2s²2p²-2s² 2p(²P⁰)3s of carbon in the spectral range of 165.7 nm in the near VUV. The investigations of plasmas generated and heated by electron cyclotron resonance (ECR) with microwaves of a frequency of 2.45 GHz at a power of 800 W resulted in ground state densities of about 10¹⁸ m^-3 of carbon. Several further spectroscopic results for the different analyses of temperatures and densities in micro- - wave generated plasmas and torches will be presented.