Effects of ion flux density and energy on the composition of TiNx thin films prepared by magnetron sputtering with an anode layer ion source

Abstract

Titanium nitride films deposited by conventional magnetron sputtering are prone to contamination, especially residual gas species, and the composition and properties can be affected. In this work, an anode layer ion source (ALIS) is used in magnetron sputtering to deposit TiN films and the effects of the average energy Ei and ion flux density Ji on the chemical composition of the deposited films are determined. By coupling and varying the magnetron discharge current It, the ALIS can be used to control Ei to as low as 80 eV and Ji as high as 3.5 × 1016 ions cm−2 s−1. To discern the roles of Ei and Ji, the films are deposited under three different conditions of magnetron discharge It. A reduction of 95% in the oxygen concentration and an increase of 30% in the nitrogen concentration are observed by increasing Ji. X-ray photoelectron spectroscopy reveals decreased peak broadening, shifts to higher binding energies, and increase initial slope of the Ti 2p peak with larger Ji. The N 1s peak shows decreased broadening while the O 1s peak indicates less oxide-related compounds. Raman scattering reveals reduced intensity ratios of the Ti to N vibration phonon peaks (ITi/IN) indicating enhanced nitrogen-related optical phonon peaks and that the film resistivity decreases as the oxygen concentration decreases. Our experiments disclose compositional changes especially reduced oxygen incorporation with ALIS assistance during magnetron sputtering. The hybrid technique which can be scaled up readily to meet industrial demand enables control of the film composition without resorting to other parameters like high temperature, biasing, and ultrahigh vacuum that may adversely affect other film properties and add manufacturing costs.