Single-Source Precursors to Titanium Nitride Thin Films
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SINGLE-SOURCE PRECURSORS TO TITANIUM NITRIDE THIN FILMS CHARLES H. WINTER,* T. SUREN LEWKEBANDARA,* PHILIP H. SHERIDAN,* AND JAMES W. PROSCIA** *Department of Chemistry, Wayne State University, Detroit, MI 48202 **Ford Motor Company, Glass Division, Dearborn, MI 48120.
ABSTRACT The syntheses of the first single-source precursors to gold-colored titanium nitride films are reported. The precursors have the empirical formula [TiCl 2 (NHR) 2 (NH 2 R) 0 -2] and [TiCI4 (NH 3 ) 2] and are obtained upon treatment of titanium tetrachloride with alkylamines or ammonia in nonpolar organic solvents. Both precursors sublime without decomposition between 80-120 'C and 0.01-0.1 mmHg. Deposition of titanium nitride films on glass and silicon substrates was achieved using either precursor at substrate temperatures of 475-600 'C. The films were characterized by x-ray diffraction, resistivity measurements, and X-ray photoelectron spectroscopy. In particular, low levels of carbon and chlorine contaminants were observed in the films.
Introduction Titanium nitride possesses a number of useful properties including extreme hardness, 1 high chemical resistance, and good electrical conductivity. Moreover, the optical properties 2 of titanium nitride are similar to those of gold, which has led to extensive use of titanium nitride films as decorative gold coatings. Prominent application of titanium nitride coatings 4 3 include wear resistant coatings for tools, solar control coatings for glass, conductive 6 5 coatings in microelectronic devices, and barrier materials in microelectronics. A variety of Chemical Vapor Deposition (CVD) processes have been developed for the preparation of titanium nitride coatings. For example, the CVD reaction of titanium tetrachloride, nitrogen, and hydrogen at temperature at or above 1000 'C yields titanium nitride films (eq 1),7 however, the high temperatures place severe restrictions on the substrates that can be coated. Gordon and Kurtz have reported that the CVD reaction of titanium tetrachloride and ammonia provides titanium nitride films at temperatures as low as 550 'C (eq 2).8 Gordon and Hoffman have described the low temperature (200-450 'C) deposition of titanium nitride films utilizing the gas phase reaction of tetrakis(dialkylamido)titanium(IV) complexes and ammonia (eq 3).9 Recently, Proscia has disclosed that the CVD reaction of titanium tetrachloride with alkylamines afford high quality titanium nitride films at >475 'C (eq 4).10 Finally, titanium nitride films can be prepared 1t (e.g., ion beam deposition, reactive using a variety of physical deposition techniques sputtering, etc.), but the density, step coverage, and growth rates of films produced by CVD processes is generally better that of films produced by physical depositions. 2TiCI4
+
N2
6TiCI4
+
8NH3
Ti(NR 2 )4
+
+
4H 2 -
excess NH 3
-
6TiN -
2TiN + TiN
+
24HC1 +
8HCI
(1) N2
(2)
organic products
(3)
+
Mat. Res. Soc. Symp. Proc. Vol. 282. Q1993 Materials Research Society
294
TiCI4
+
excess NR3
-
TiN
+
organ
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