Determination of intrinsic stresses in textured and epitaxial TiN thin films deposited by dual ion beam sputtering

Abstract

TiN thin films with thickness ranging from 50 to 300 nm were deposited by a dual ion beam sputtering technique, which consisted in sputtering a pure Ti target with primary Ar ions, while an (Ar+N 2) gas mixture was used as a secondary assistance beam during deposition. Two different substrates were used: Si wafers covered with native oxide for which TiN films exhibited a fibre-texture, and MgO (001) single crystals for which a cube-on-cube epitaxial growth was observed. The intrinsic stresses in the TiN films were measured by X-ray diffraction using the sin 2 ψ method after subtracting the thermal stress contribution at room temperature. The influence of the substrate, energy of primary and secondary ion beam on the strain/stress state of the films have been systematically studied. The stress results are discussed and analysed using a stress model that includes a hydrostatic and biaxial component. For the fibre-textured TiN films deposited on Si wafers at room temperature, large hydrostatic stresses, ranging from 5 to 6 GPa are obtained. For the epitaxial TiN films grown on MgO at 500 °C, the intrinsic hydrostatic stress decreases to 1.7 GPa. We show that this stress analysis satisfactorily accounts for the results obtained in TiN films with mixed (002)+(111) texture.