An in-situ technique for the estimation of surface coefficients based on characteristics in the ion energy distribution of capacitively coupled plasmas

Secondary electron emission (SEE) is known to have a significant influence on plasma properties such as electron temperature and plasma density due to the injection of high-energy electrons into the plasma, which are generated when the emitted electrons are accelerated in the sheath potential. As the plasma properties and emitted electrons also have an impact on the sheath width and spatiotemporal potential distribution, the ion energy distribution function (IEDF) at the electrodes show signatures that depend indirectly on the emission coefficients. Here, the influence of SEE on the bimodal peak structure, which is formed by ions that traverse the sheath without collisions is analyzed in detail. In particular, (i) its position corresponding to the acceleration through the mean sheath potential and (ii) the peak separation in the bimodal structure corresponding to the sheath potential variation during an rf cycle, depend differently on the effective ion induced SEE yield (γ_eff) and the effective elastic electron reflection probability (r_eff). We present a technique that combines energy-resolved mass spectrometric measurements and 1d3v particle-in-cell/Monte Carlo collision simulations to determine both parameters simultaneously and independently in a symmetric rf capacitively coupled plasma in argon. The method is applied to stainless steel and aluminum oxide surfaces resulting in a good agreement with literature values. This technique allows for a straightforward estimation of SEE coefficients for all materials that can be deposited on the plasma electrodes.