Characteristics of titanium nitride films grown by pulsed laser deposition
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Characteristics of titanium nitride films grown by pulsed laser deposition R. Chowdhury, R. D. Vispute, K. Jagannadham, and J. Narayan Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7916 (Received 10 October 1994; accepted 9 February 1996)
Laser physical vapor deposition (LPVD) has been used to grow titanium nitride films on hydrogen-terminated silicon(100) substrates at deposition temperatures ranging from room temperature to 600 ±C. A pulsed KrF excimer laser (l 248 nm, t 25 ns) was used with the deposition chamber maintained at a base pressure of 1027 Torr prior to deposition. Different properties of the films were investigated by x-ray diffraction, Auger electron spectroscopy, Raman spectroscopy, optical, scanning, and high resolution transmission electron microscopy, and measurement of electrical resistivity. When the substrate temperature was low (at and below 500 ±C), oxygen atoms from the residual gases were incorporated in the films. The microstructures and resistivities of TiN films were found to be strongly dependent on the temperature of the silicon substrates. The TiN films deposited at 600 ±C were oxygen-free, as observed from Auger analysis, and the room temperature resistivity was found to be 14–15 mV-cm. Raman spectroscopy of the films showed that the nitrogen-related optical phonon peak increased with deposition temperature in comparison with the titanium-related acoustic peak. Transmission electron microscopy and x-ray diffraction analyses showed that the films were polycrystalline at ˚ depending on the temperature low temperature with grain size ranging from 300 –600 A, of the substrate. At 600 ±C, the films were found to be single crystals with occasional presence of dislocation loops. The spacing of Moir´e fringes in TiNySi samples deposited at 600 ±C established the nearly periodic elastic strain field extending into the TiN and Si at the interface. Although there exists a large misfit between TiN and Si (24.6%), the epitaxial growth of TiN films on Si(100) substrates was explained by means of domain-matched epitaxy with a 4-to-3 match in unit cells for TiNySi structure, giving rise to a residual lattice misfit of only 4%.
I. INTRODUCTION
Thin films of titanium nitride are important in many applications, such as for hard and wear resistant coatings in machine tool industry, for reflective coatings, and as passive diffusion barriers in silicon device fabrication. Titanium nitride in the polycrystalline form on silicon substrates has been deposited using a variety of physical and chemical vapor deposition techniques. The resistivity of TiN in polycrystalline form is of the order of 50 mV-cm and higher, a value too high for contact metallurgy of microelectronic devices. Furthermore, polycrystalline TiN formed by CVD contains columnar grains along which fast diffusion of dopants and impurities can occur, leading to nonuniform junctions and impurity contamination. We envisaged the f
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