Oxygen Incorporation in Reactive-Sputter-Deposited TiN Films: Influence of the Metal to O₂ Gas Flux Ratio

Abstract

  The incorporation of oxygen impurities under ambient environment conditions during reactive sputter deposition of titanium nitride (TiN) films has been studied. TiN films, prepared by DC sputtering of a Ti metal target in 100% N₂ at 1 Pa in an ultra-high vacuum (UHV) sputtering apparatus, were essentially free from oxygen. When oxygen was intentionally introduced into the vacuum chamber, an impurity level of a few atomic percent was obtained at a partial pressure of 3×10⁻⁴ Pa, but the percentage increased rapidly to 10-20 at.% when the partial pressure was 1×10⁻³ Pa or above. It is shown that the increase in the oxygen incorporation is not well explained by the oxygen impingement rate calculated from the partial pressure. We demonstrate that the impurity concentration is related to the ratio of the number of oxygen atoms introduced into the chamber to the number of Ti atoms sputtered from the target. This suggests that oxygen gettering by Ti atoms deposited on the chamber wall significantly reduces the oxygen pressure during deposition and that oxygen incorporation in the film is governed primarily by the total amount of sputtered metal.