In Situ Surface Diagnostics during Plasma-Material Interactions

\textit{In-situ} diagnostics methods for plasma-surface interactions will be reviewed, with a focus on recombination of Cl on alumina, silica and ytttria coated surfaces during exposure to chlorine-containing inductively-coupled plasmas. Both gas-phase (optical emission and rare gas actinometry, optical absorption, and mass spectrometry) and surface diagnostics (Auger electron spectroscopy, sputter depth profiling) methods will be covered. The influence of Cl, F O and Si-containing adsorbates will be discussed. Cl loss coefficients, $\gamma_{\mathrm{Cl}}$, have been measured for a variety of plasma and surface conditions. Cl$_{\mathrm{2}}$ (i.e. recombination) and other products such as ClO and SiCl$_{\mathrm{2}}$ can be produced. Cl recombination is enhanced 1) by the presence of F, due to its electron-withdrawing effect on metal atoms, and 2) by excess oxygen that cannot coordinate to a second metal atom. Recombination appears to occur mainly by a Langmuir Hinshelwood mechanism, with perhaps added contribution by an Eley-Rideal process. $\gamma_{\mathrm{Cl}}$ is as high as 0.30 after exposure to F, and as low as 0.03 to \textless 0.001 on a SiCl$_{\mathrm{x}}$F$_{\mathrm{y}}$ surface during Si etching in a Cl$_{\mathrm{2}}$/O$_{\mathrm{2}}$ plasma.