Deposition of Tungsten Nitride Thin Films from ( t BuN) 2 W(NH t Bu) 2
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DEPOSITION OF TUNGSTEN NITRIDE TIIN FILMS FROM (tBuN) 2 W(N1tlu) 2 Hsin-Tien Chiu and Shiow-Huey Chuang Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan, 30050, R. 0. C.
ABSTRACT The possibility of growing tungsten nitride thin films from (tBuN) 2 W(NHtBu) 2, a single-source molecular precursor with two nitrogen to tungsten double bonds, by low pressure chemical vapor deposition (LPCVD) was investigated. Deposition of thin films on silicon and glass substrates was carried out at temperatures 500 - 650 oC in a cold-wall
reactor while the precursor was vaporized at 60 - 100 oC. Elemental composition of the thin films, studied by wavelength dispersive spectroscopy (WDS), is best described as WNx (x = 0.8 - 1.8). Elemental distribution within the films, studied by Auger depth profiling, is uniform. X-ray diffraction (XRD) studies show that the films have a cubic structure with a lattice parameter a = 4.14 - 4.18 A. A stoichiometric WN thin film has a
lattice parameter a equal to 4.154 A. Volatile products, trapped at -196oC, were analyzed by nuclear magnetic resonance (NMR) and gas chromatography-mass
spectrometry (GC-MS). Isobutylene, acetonitrile, hydrogen cyanide and ammonia were detected in the condensable mixtures.
INTRODUCTION
There are many transition metal nitrides possessing interesting mechanical and electrical properties [1]. Many of them are potentially useful interconnect materials for diffusion barriers and gates in vary large scale integrated circuits (VLSI) [2]. Growing the thin films of these materials by conventional chemical vapor deposition (CVD) usually requires high temperatures ( > 1000 OC) when metal halides and ammonia / hydrogen or nitrogen / hydrogen mixtures are employed as the precursors. Thus, their usefulness is severely limited. On the other hand, there are many interests in the deposition of mixedelement thin films from single-source precursors, molecules having all of the desirable elements. Usually, metallo-organic compounds are employed here as the precursors to grow thin films at temperatures much lower than the ones recorded previously. For example, metal carbides and oxides, such as TiC, WC, SiO 2 , and TiO 2 , have been deposited successfully into thin films by this route using Ti(CH 2 tBu) 4 , (tBuCH 2 )3 W-CtBu, Si(OEt) 4 , and Ti(OiPr) 4 , respectively [3 - 6]. Previously, our laboratory has shown that an ethylimido tantalum complex, (Et 2 N) 3 Ta=NEt, can be used to deposit polyMat. Res. Soc. Symp. Proc. Vol. 250. @1992 Materials Research Society
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crystalline cubic TaN thin films at relatively low temperatures 500 - 650 °C, with minor carbon incorporation [7]. In order to test whether it is a general route to metal nitrides by using metal imido complexes as the precursors, we performed the following metallo-organic
tBuN
NHtBu W
chemical vapor deposition (MOCVD)experiments employing another metal-imido complex, (tBuN) 2 W(NHtBu) 2, 1, as the precursor.
tBuN
NHtBu
Our observations are reported below.
EXPERIMENTAL (tBuN) 2W(NHtB
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