Composition and formation mechanism of zirconium oxynitride films produced by reactive direct current magnetron sputtering

Abstract

Direct current magnetron sputtered zirconium oxynitride films show an improvement in both deposition rate and physical properties compared to zirconium oxide. Here we seek to understand these beneficial effects and report on the film composition and crystallographic structure. Based on a thermochemical description together with a modeling of formation kinetics we propose a film formation mechanism, which explains many of the observations. Rutherford backscattering spectroscopy (RBS) shows early nitrogen incorporation at 64% N 2 flow in disagreement with the predictions of thermochemistry. The stoichiometry is only successfully simulated with the use of an expanded Berg-Larsson model with a low replacement coefficient of about 0.1 of nitrogen by oxygen after metal-nitrogen bond formation. The deviation from complete replacement as predicted by thermodynamics illustrates the importance of kinetics in film formation. The model further successfully predicts the variation of the mass deposition rate. The X-ray diffraction analyses suggest that, within the crystalline phase, nitrogen atoms occupy oxygen sites, resulting in an unchanged zirconium oxide structure.

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

“…8). Band gap narrowing by nitrogen incorporation has been previously observed in different transition metal oxynitrides [9,10,12,15,16,38].…”

“…The introduction of nitrogen into the oxide lattice or oxygen into the nitride lattice resulted in modifications of the film properties. For example, the substitution of oxygen by nitrogen in the TiO 2 [9], ZrO 2 [10] or Ta 2 O 5 [11] lattice increased the index of refraction. This is because the metal-nitrogen bonds tend to be less polar than the corresponding metal-oxygen bonds, which leads to a higher polarizability for the metal nitrides [12] and a decrease of the optical band gap.…”

Evolution of target condition in reactive HiPIMS as a function of duty cycle: An opportunity for refractive index grading

“…However, the tungsten oxynitride films exhibit modifications in their optical properties (refractive index and optical band gap) with respect to the degree of nitrogen inclusion. The substitution of nitrogen into the metal oxide matrix increases the refractive index, as observed in general for metal oxides [57][58][59] including tungsten oxide. 60 However, the optical bandgap decreases because of the shifts in the absorption edges at long and short wavelengths due to the mixing of nitrogen 2 p states with oxygen 2 p states.…”

Multi-technique characterization of tantalum oxynitride films prepared by reactive direct current magnetron sputtering

“…However, the partial pressure where the formation of metal -nitrogen bonds are starting to form as well as the non-linear increase of the nitrogen content point to the role of kinetics, which enables metal -nitrogen bonds, once formed, to survive since newly impinging metal and nitrogen atoms on the surface will help bury metastable structures before the more stable metal -oxygen bonds can be formed. We have explicitly modeled this behavior for the formation of ZrO x N y [22].…”