Epitaxial Growth of TiN Films on (100) Silicon Substrates by Laser Physical Vapor Deposition
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EPITAXIAL GROWTH OF TiN FILMS ON (100) SILICON SUBSTRATES BY LASER PHYSICAL VAPOR DEPOSITION P.TIWARI, T. ZHELEVA, AND J. NARAYAN
Department of Materials Science and Engineering North Carolina State University, Raleigh, NC 27695-7916. ABSTRACT
We have synthesized epitaxial TiN films having low resistivity on (100) silicon substrates using pulsed laser deposition method. The TiN films were characterized using X-ray diffraction, Rutherford back-scattering, four-point-probe ac resistivity, high resolution transmission electron microscopy techniques and epitaxial relationship was found to be TiN // Si. TiN films showed 10-20% channeling yield. In the plane, four unit cells of TiN match with three unit cells of silicon with less than 4.0% misfit. This domain matching epitaxy provides a new mechanism of epitaxial growth in systems with large lattice misfits. Room-temperature resistivity of these films was found to be about 15 P.Q-cm. Implications of low-resistivity epitaxial TiN in silicon device fabrication are discussed. INTRODUCTION
Titanium nitride films and coatings having polycrystalline microstructure have found applications ranging from corrosion and erosion resistance coatings to diffusion barriers in advanced integrated circuit devices to wavelength-selective films [1-3]. In previous studies, these polycrystalline films were deposited by a variety of techniques: chemical vapor deposition, ion plating, activated reactive evaporation, dc, rf, and magnetron sputtering [4,5]. The polycrystalline films tend to grow columnar with grain boundaries normal to the substrate. In the columnar structure, faster diffusion along the grain boundaries makes these films susceptible to environmental degradation and reduces their effectiveness as a diffusion barrier. The above problems in polycrystalline films can be solved by producing equiaxed microstructure, where grain boundaries are randomized and direct fast diffusion paths between the interface and the free surface are eliminated. Recently, polycrystalline TiN films with equiaxed-grain microstructure were produced by laser physical vapor deposition (LPVD) in the temperature range 400-5000 C on silicon substrates [6,7] compared to higher temperatures ( in excess of 900*C ) needed for chemical vapor deposition methods [4]. Subsequently, we reported the formation of single crystal TiN films by LPVD on lattice-matched substrates such as (100) MgO in the temperature range 450 to 750'C [7]. Earlier work by Johansson et. al. [81 reported growth of single crystal TiN films on (111) MgO in the temperature range 600-800*C using a reactive magnetron sputtering technique. In LPVD, the epitaxial films were obtained at a temperature as low as 450*C. The higher energy of laser evaporated species (_ 5-8 eV per particle) compared to thermal evaporation ( - 0.1 eV per particle ) is envisaged to enhance the surface mobility and provide recrystallization at lower temperature.Recently, we reported synthesis of epitaxial TiN on (100)Si using laser physical vapor deposition technique [9]. In t
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