Paper PS-WeM5
On the Role of CF in Fluorocarbon Plasmas: Gas-Phase Reactions and Surface Interactions

Wednesday, October 20, 2010, 9:20 am, Room Aztec

A complete understanding of the nature of fluorocarbon (FC) plasma systems necessarily includes a description of CF_x species behavior, including CF, CF₂, and CF₃. Our current research focuses primarily on understanding the gas-phase properties and reactions and gas-surface interactions of CF molecules produced from sparsely polymerizing CF₄ and C₂F₆ plasmas. An enriched understanding of these systems can elucidate the mechanisms contributing to film growth and may pave the way for enhanced plasma deposition and etching applications. To this end, we have employed laser induced fluorescence spectroscopy (LIF) and optical emission spectroscopy (OES) to probe the gas-phase behavior of CF, including calculations of rotational and vibrational temperatures. From these analyses, we determine that CF rotational states equilibrate with the plasma gas temperature at around 300 K. In addition, time-resolved actinometry has been employed to investigate gas-phase kinetics of the CF molecule as well as other CF_x species in a range of FC systems. We have also extended the LIF studies to our unique imaging of radicals interacting with surfaces (IRIS) technique which probes the gas-surface interface during plasma processing. CF species exhibit a surface gain in density, with surface scattering coefficients greater than unity for Si and ZrO₂ substrates, indicating production of the molecule at film-passivated surfaces. For comparison, IRIS results for CF₂ in the same plasmas will also be discussed. Surface analyses by high-resolution x-ray photoelectron spectroscopy (XPS) and variable angle spectroscopic ellipsometry along with the gas-phase data have culminated in a proposed mechanism for gas-surface interactions of these molecules during plasma processing of Si and ZrO₂ whereby the contributions of both CF and CF₂ molecules to film formation is summarily developed.