Ion flux characteristics in arc vapor deposition of TiN

Abstract

In this paper the ionization and energy characteristics of the particle flux impinging TiN films during arc vapor ion deposition are described. Langmuir probe measurements of voltage and current were made using a planar shielded substrate as the probe. Plasma species were observed using emission spectrometry. Substrate mass gain was measured as a function of voltage and nitrogen pressure. Ion current to the substrate was eliminated by applying a negative voltage to a fine wire screen located in front of the substrate and, at the same time, applying a positive voltage to the substrate. The ionized fraction of the titanium vapor at the substrate was determined by comparing the deposition rate obtained while excluding ions with the deposition rate obtained under normal conditions when ions were part of the depositing flux. The Langmuir probe measurements were used to estimate the plasma parameters and the average ion energy at the substrate. The results are as follows: (1) in the absence of a nitrogen gas discharge, the density of nitrogen ions is small; (2) most of the titanium vapor is ionized; (3) the average charge carried by titanium ions to the substrate during TiN deposition is (1.6 ± 0.3) e; (4) the average energy of titanium ions at the substrate is approximately 1.6 e(10 + | V s|) eV, where V s is the negative substrate bias.