Spatial structures of rf ring-shaped magnetized sputtering plasmas with two facing cylindrical ZnO/Al2O3 targets

Abstract

Spatial structures of the ion flux to the substrate are measured in an rf ring-shaped magnetized sputtering plasma with two facing cylindrical ZnO/Al2O3 targets at various argon gas pressures of 0.13, 0.67, and 0.93 Pa. Spatial distributions of the Hall parameter and Larmor radius of electrons and ions are also discussed by using simulated values of the magnetic flux density. The magnitude of the ion flux for 0.13 and 0.67 Pa is of the order of 1020 m−2 s−1, while for 0.93 Pa it is of the order of 1021 m−2 s−1 at a fixed rf power of 20 W. The radial profile of the ion flux has a peak at the position of the ring-shaped groove near an rf electrode and then becomes uniform further away from the electrode at all gas pressures. It is found that the axial profile of the deviation from a uniform profile estimated from the radial profile of the ion flux has two decay characteristics (1st decay length of 13.9–17.5 mm and 2nd decay length of 52.6–66.7 mm) and their decay lengths decrease with increasing the gas pressure.