Plasma diagnostics in a triode ion plating system

Abstract

Langmuir probes combined with an energy resolved mass analyzer make satisfying contributions to the characterization of plasmas. The probes provide spatially resolved information on the well known plasma parameters, while the mass analyzer gives information on the energy distribution functions for ions/neutrals originating from some point in the plasma volume. These diagnostic tools have been used to investigate the glow discharge of the triode ion plating system of Balzers (BAI 640), a physical vapor deposition installation for the production of hard coatings. Two identical, planar Langmuir probes, positioned in the main argon plasma body, and an energy-resolved mass analyzer (Balzers PPM 421), directed to the crucible, were used to investigate the influence of the four most important process parameters, i.e., (1) the low voltage (LV) are current, (2) the high voltage (HV) electron gun current, (3) the total pressure, and (4) the substrate voltage on the plasma parameters and on the energy spectra of ions and neutrals, during the evaporation of titanium without reactive gases. The substrate bias had no significant influence on the plasma parameters and on the energy spectra, but is very important for the microstructure of the thin film. The HV electron gun, used to melt the titanium, changed the plasma parameters only at high current values, but the energy spectra of the Ti ions changed drastically. The LV are current and the total pressure are the process parameters that do affect both the probe characteristics and the energy spectra of ions and neutrals. (C) 1998 American Vacuum Society. [S0734-2101(98)05305-6].