Titanium Oxynitride Thin Film Deposition by Pulsed Laser Ablation of Titanium Targets in Nitrogen
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TITANIUM OXYNITRIDE THIN FILM DEPOSITION BY PULSED LASER ABLATION OF TITANIUM TARGETS IN NITROGEN V. CRACIUN*, D. CRACIUN*, S. AMIRHAGHI*, M. VICKERS**, S. TARLING**, P. BARNES** AND I. W. BOYD*
*Electronic and Electrical Engineering, University College London, London WClE 7JE, UK **Department of Crystallography, Birbek College, London WClE 7HX, UK
ABSTRACT Reactive pulsed laser deposition of titanium targets in a nitrogen atmosphere has been used to deposit thin titanium oxynitride films on Si substrates. The gold coloured layers exhibited a smooth, featureless surface and good chemical resistance in HF-HNO 3 mixtures. The films had a high oxygen content which was responsible for relatively high electrical resistivity, measured to be 200-600 gft.cm. This new method can easily be applied to the growth of other important nitrides such as ZrN, WN, HfN or the deposition of multilayer structures such as TiN/Ti on a variety of substrates. INTRODUCTION
Thin films of TiN have been studied extensively in recent years because of their numerous applications as hard, protective, corrosion resistant coatings or as diffusion barrier layers to a variety of mobile species [1-8]. Many different methods have been employed for the deposition of thin TiN films, including laser-based techniques. The simplest and most successful approach to obtain thin films of TiN by laser processing has been by direct synthesis, where a thin Ti film is submitted to pulsed laser irradiation in a nitrogen containing atmosphere [9-11]. Nuclear reaction analysis, transmission electron microscopy and Rutherford backscattering spectroscopy (RBS) have shown that stoichiometric TiN films with thicknesses up to 1 gim and less than 1% oxygen could be obtained by this method. Unfortunately, their surface morphology is far from being smooth. Because of the multiple subsequent melting-solidifying cycles imposed, the TiN films exhibited many cracks. The corrosion resistance of such a TiN film was found to be almost identical with that of a reference untreated Ti sample [12], implying that these films were not suitable for diffusion barriers or protective coatings. Recently, a great deal of work concerning the deposition of high quality thin film materials has been performed using the Pulsed Laser Deposition (PLD) technique. This technique has also been applied for the deposition of TiN by ablating TiN targets in a vacuum or in nitrogen [ 1316]. These investigations have shown that even though thin TiOxNy or TiN films could be deposited at room temperature, there were two significant drawbacks. Firstly, the oxygen content of the films was fairly high, the target pellets themselves being the source of some of this oxygen contamination. Secondly, the morphology of the films was greatly dependent on the precise fabrication procedure followed when preparing the pellet. Amongst the more conventional film-forming methods, sputtering of Ti in a nitrogen atmosphere for the deposition of high quality TiN films has been successfully demonstrated using RF sputtering [17, 1
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