Diffusion of silicon in titanium dioxide thin films with different degree of crystallinity: Efficiency of TiO2 and TiN barrier layers

Abstract

Two kinds of reactively sputtered titanium dioxide films with columnar and fine-grained structures were investigated as diffusion barriers, preventing the silicon diffusion. The only differences in the deposition conditions were the oxygen percentage concentration (OC) in the discharge, kept for 10% and 30% of the total working pressure. The resulting films were found to have different thicknesses being 800 and 240 nm for 10% and 30% OC, respectively. The films were studied by X-Ray diffraction spectrometry (XRD) and their composition by Rutherford Backscattering Spectrometry (RBS). In order to describe the diffusion processes, the two batches were annealed up to temperature of 800 °C. The diffusivity from 300° to 800 °C is D(m2/s)=2.43.10−18exp[−(15kJ/mol)/(RT)] andD(m2/s)=2.36.10−18exp[−(18.4kJ/mol)/(RT)] for (10% OC) and TiO2 (30% OC), respectively. The physical meaning of the derived diffusion parameters are discussed in view of the crystalline peculiarities of the obtained films. Arrhenius plots show clearly that higher activation energy is characteristics for films with better-packed crystallites. These results are compared with known diffusion barrier layer such as TiN.