The effect of structured electrodes on heating and plasma uniformity in capacitive discharges

Summary form only given. The effect of structured (non-planar) electrode topologies, e.g. rectangular, rounded, and triangular trenches, on the electron heating dynamics and ion density profile in capacitive radio frequency plasmas is investigated experimentally and by an analytical model [1]. 2D Phase Resolved Optical Emission Spectroscopy is utilized to study the dynamics of energetic electrons inside and outside these structures. In the presence of structured electrodes non-planar RF sheaths form, that affect the electron heating dynamics. We observe a local increase of energetic electrons above the structures caused by a combination of cross-firing of electron beams generated by sheath expansion heating and a temporal confinement of energetic electrons between the sheaths within the structure. The confinement within the trench is limited to the phase of sheath expansion. Also the ionization and, as a consequence the plasma density, are modified by these effects. This is characterized by radially resolved Langmuir probe measurements and described by a diffusion model. The control of the radial plasma density profile is demonstrated. Via customized electrode topologies high plasma uniformity at specific pressures and heights above the electrode is achieved.