Macroparticle interaction with a substrate in cathodic vacuum arc deposition

Abstract

The presence of macroparticles (MP) in the vacuum arc cathodic jet is the critical problem of cathodic vacuum arc deposition technology. The MP distribution on the substrate depends on MP generation, MP transport to the substrate, and the MP—substrate interaction. In the present work different aspects of the interaction of the MP with a substrate are studied theoretically. The MP temperature evolution during transport to the substrate was studied and it was found that the MP is liquid in the case of low melting point cathode materials. It was found that the MP temperature does not depend on the initial MP temperature in the near cathode region. Possible MP acceleration in the substrate direction resulting from ion friction was calculated by solving the equation of motion for the MP taking into account the plasma density and the velocity distribution obtained in previous analyses of the 2-D plasma expansion. The voltage drop in the substrate sheath as a function of the background pressure was calculated assuming charge exchange between ions and gas atoms. It was found that the voltage drop in this sheath increases with increasing background pressure p g by factor of 2 for p g ∼ 1 Pa. The MP motion in this sheath was calculated taking into account MP charging and reflection from the substrate. The probability of reflection decreases with MP size, velocity, angle of the MP velocity vector with respect to the substrate, and increases with the background pressure.