The characteristics of the plasma surrounding the substrates in a planar magnetron sputtering system with a graphite target have been investigated by electrostatic probe measurements. The behaviour of the ion density ni and the electron temperature T,, determining the ion flux that can be extracted b y the substrate, with the variation of the basic system parameters, has been studied.

The ion and deposition fluxes to the substrate during sputtering of a vanadium target in neon, argon, krypton, and xenon discharges were measured as a function of the discharge power and gas pressure. The measurements of the deposition fluxes were also compared with calculations obtained using an analytical model for transport of the sputtered species through the gas discharge. The calculation takes into account both the ballistic and thermal components of the deposition flux. Overall, a good agreement between the calculated and the experimentally measured values was obtained. The results show that, at a constant discharge current, the vanadium flux at the substrate position is a strong function of both pressure and the type of inert gas used. The ion flux, on the other hand, remains relatively constant as the gas and pressure are changed. This implies that the ion-to-neutral arrival rate ratio was dominated by changes in the neutral deposition flux and it was found to increase with pressure, remain relatively constant with power at low pressures, and decrease with power at high pressures. By increasing the field strength of the outer pole in the magnetron source (unbalanced magnetron source of type II), the ion flux impinging the substrate was strongly increased for all pressures, while the vanadium deposition flux remained the same as in the ‘‘balanced’’ magnetron configuration.

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