Atmospheric pressure chemical vapor deposition of TiN from tetrakis(dimethylamido)titanium and ammonia
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Atmospheric pressure chemical vapor deposition of TiN from tetrakis(dimethylamido)titanium and ammonia Joshua N. Musher and Roy G. Gordon Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138 (Received 15 December 1994; accepted 28 October 1995)
Near stoichiometric titanium nitride (TiN) was deposited from tetrakis(dimethylamido)titanium (TDMAT) and ammonia using atmospheric pressure chemical vapor deposition. Experiments were conducted in a belt furnace; static experiments provided kinetic data and continuous operation uniformly coated 150-mm substrates. Growth rate, stoichiometry, and resistivity are examined as functions of deposition temperature (190–420 ±C), ammonia flow relative to TDMAT (0–30), and total gas-flow rate (residence time 0.3 –0.6 s). Films were characterized by sheet resistance measurements, Rutherford Backscattering Spectrometry, and X-Ray Photoelectron Spectrometry. Films deposited without ammonia were substoichiometric (NyTi , 0.6 –0.75), contained high levels of carbon (CyTi 0.25–0.40) and oxygen (OyTi 0.6 –0.9), and grew slowly. Small amounts of ammonia (NH3yTDMAT > 1) brought impurity levels down to CyTi , 0.1 and OyTi 0.3 –0.5. Ammonia increased ˚ thick the growth rates by a factor of 4–12 at temperatures below 400 ±C. Films 500 A ± had resistivities as low as 1600 mV-cm when deposited at 280 C and 1500 mV-cm when deposited at 370 ±C. Scanning electron micrographs indicate a smooth surface and poor step coverage for films deposited with high ammonia concentrations.
I. INTRODUCTION
Nitrides are technologically important materials because of their hardness, stability at high temperatures, chemical inertness, and electrical and optical properties. Transition metal nitrides comprise an important subclass, with applications in wear-resistant, electronic, and optical coatings. Titanium nitride, in particular, is used for tool coating, solar-control films, and microelectronic applications. Optically similar to gold, it is harder than alumina and thermally stable to 3000 ±C. TiN is chemically stable with respect to most etching solutions, has a low resistivity, and provides an excellent diffusion barrier against metals. These properties make TiN useful in integrated circuit manufacturing, in which TiN is used as a glue layer for tungsten deposition, and as a diffusion barrier between silicon and metals. Early chemical vapor deposition (CVD) techniques coated tools by the reaction of TiCl4 1 N2 1 H2 at temperatures above 1000 ±C. Many substrates cannot be subjected to such high temperatures. Kurtz and Gordon1 demonstrated that the deposition temperature could be lowered by introducing preheated ammonia into the gas stream. Reaction (1) allows some less thermally sensitive substrates to be coated, such as glass or unmetallized silicon wafers. ± –°700 6TiCl 1 8NH °°500 °°° °°! 6TiN 1 24HCl 1 N 4
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(1) J. Mater. Res., Vol. 11, No. 4, Apr 1996
http://journals.cambridge.org
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