Plasma stream homogeneity in metal plasma immersion ion implantation and deposition

The homogeneity of metal plasma immersion ion implantation and deposition (MePIIID) was investigated for flat substrates and the materials systems Al, AlN, Ti, TiN, TiO₂, and ZnO. A shield was installed in the line-of-sight between the cathode and substrates (diameter 60 and 100 mm) to reduce macroparticle counts. An influence of pulse voltage, cathode material, and backfill on the lateral homogeneity was observed so the plasma stream emanating from the arc as well as the plasma sheath evolving around the substrates contributed to the radial homogeneity in MePIIID. The major factor was the ratio of the sheath width to the sample diameter, with additional influences from the ion velocity and mean free path. For small, conformal sheaths, a normal ion incidence was observed for the substrate, whereas larger, spherical sheaths resulted in oblique ion trajectories near the edge, with an increased sputter yield and lower dose.