¹⁸O study of the oxidation of reactively sputtered Ti_1−xAl_xN barrier

Abstract

The preparation of high-permittivity perovskite materials requires high-temperature (550–750 °C) oxidizing environments, providing stringent limitations on the choice of electrode materials. To minimize interdiffusion and oxidation reactions, an electrically conductive diffusion barrier such as Ti1−xAlxN is needed below the electrode material (Pt, IrO2, RuO2…). Ti1−xAlxN films were deposited by multitarget reactive sputtering in a mixture of Ar and N2. The stability of these films has been investigated under typical conditions for crystallization of perovskite dielectrics. Sample composition was characterized using Rutherford backscattering spectroscopy and nuclear reaction analysis. In particular, the concentration depth profiles of both 18O and 27Al were measured before and after RTA treatments via the narrow resonances of 18O(p,α)15N at 151 keV (FWHM = 100 eV) and 27Al(p,γ)28Si at 992 keV (FWHM = 100 eV). The different 18O excitation curves show that the oxidation resistance increases with Al incorporation. The Al excitation curves indicate a uniform Al content for as-deposited TixAl1−xN and reveal Al diffusion to the surface during the oxidation process which indicates the formation of an Al-rich oxide layer at the TixAl1−xN surface, leaving a layer depleted in Al below it.

Protective Transition Metal Nitride Coatings

“…Due to the extremely limited kinetics (condensation from the vapor phase can be assigned with cooling rates up to 10 13 K s À1 (104)) apparent in PVD deposition techniques it is possible to synthesize a supersaturated solid solution of Ti 1Àx Al x N (10,11,(105)(106)(107)(108)(109), although c-TiN and w-AlN exhibit essentially no solubility for each other; see the schematic quasibinary phase diagram in Figure 7(a) (110). Ti 1Àx Al x N can be regarded as a model system in materials science of thin films, as it was shown that hardness, oxidation resistance, and thus thermal stability increases with the Al content, x, within the cubic regime (24,79,80,103,111,(114)(115)(116)(117)(118)(119). In the region where E f exhibits almost similar values for cubic and wurtzite structures, a dual phase regime is preferred, followed by a single-phase wurtzite regime for higher Al contents (79,81,98,111,112).…”

Effects of deposition and post-annealing conditions on electrical properties and thermal stability of TiAlN films by ion beam sputter deposition

“…It is reported that the thickness of the oxide layer grown on the film surface decreases with increasing Al content in the films. The fine aluminum oxide on the surface of films prevented films from further oxidation [7]. The SIMS oxygen depth profile and the GAXRD patterns in Fig.…”