Micro structure of N-implanted Ti thin films prepared by ion beam sputtering deposition

Ti thin films with and without nitrogen implantation was prepared by cold-sputtering for advanced processing of nano-structured materials. Ti films were grown on (001) Si substrates by ion-beam sputter deposition. Ti target of 99.9% purity was sputtered at room temperature by Ar⁺ with the beam energy of 1keV and the pressure of 5×10^-2 Pa. Target and substrate were well-cooled in order to reduce the grain growth by increase of temperature. N⁺ implantation was carried out for 150 nm thick Ti films with the ion-energy of 100keV and the dose of 0.6∼5 × 10 ¹⁷ ion/cm². Cross-sectional TEM observation for as-deposited Ti film revealed that columnar grains in the order of 10 nm grew with the direction perpendicular to the Si substrate. Diffraction pattern from Ti film showed the Debye-ring consistent to fee structure, not the conventional hcp structure. After N⁺ implantation, strong [111] texture with the direction parallel to [001]Si was confirmed from diffraction pattern. Formation of nitride was confirmed by annealing the higher-dose samples. Tetragonal structure of Ti₂N was detected among the tranceformed titanium phase with hcp structure. Formation of nitrides was discussed from the depth profile of nitrogen and chemical shift of Ti 2p spectrum through XPS analysis.