Narrow resonance profiling study of the oxidation of reactively sputtered Ti 1− xAl xN thin films

Abstract

The bottom electrode structure used with ferroelectric (FE) and high dielectric constant (HDC) materials requires a material to promote FE or HDC cristallisation (Pt or IrO 2) and a material with diffusion barrier properties; this last material being between Pt (or IrO 2) film and Si substrate. TiN, TiAlN and TaSiN have been proposed for diffusion applications. Ti 1− x Al x N films have drawn much attention as alternatives to TiN diffusion barriers. In this paper we have investigated the effect of Al content on the oxidation resistance of Ti 1− x Al x N films prepared by radio frequency reactive sputtering in a mixed Ar+N 2 discharge. The concentration depth profiles of both 18O and 27Al were measured before and after the rapid thermal annealing of samples at 750°C for 30 s in 18O 2, 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). It was found that Al incorporation in the films reduces oxide growth. The Al excitation curves indicate a uniform Al content for as deposited Ti 1− x Al x N, and reveal Al diffusion to the surface during oxidation, which indicates the formation of an Al rich oxide layer at the Ti 1− x Al x N surface. The results suggest that Ti 1− x Al x N films with x>0.39 are promising candidates as electrically conductive diffusion barrier layers.