Tungsten nitride thin films prepared by MOCVD

Hsin-Tien Chiu, Shiow Huey Chuang

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Abstract

Polycrystalline tungsten nitride thin films were grown by low pressure metallo-organic chemical vapor deposition (MOCVD) using (tBuN)2W(NHtBu)2as the single-source precursor. Deposition of uniform thin films on glass and silicon substrates was carried out at temperatures 723–923 K in a cold-wall reactor, while the precursor was vaporized at 333–363 K. The growth rates were 2–10 nm/min depending on the condition employed. Bulk elemental composition of the thin films, studied by wavelength dispersive spectroscopy (WDS), is best described as WNx (x = 0.7-1.8). The N/W ratio decreased with increasing temperature of deposition. X-ray diffraction (XRD) studies showed that the films have cubic structures with the lattice parameter a — 0.414-0.418 nm. The lattice parameter decreased with decreasing N/W ratio. Stoichiometric WN thin films showed an average lattice parameter a of 0.4154 nm. X-ray photoelectron spectroscopy (XPS) showed that binding energies of the W4/7/2, W4/5/2, and Niselectrons were 33.0, 35.0, and 397.3 eV, respectively. Elemental distribution within the films, studied by secondary ion mass spectroscopy (SIMS) and Auger spectroscopy depth profilings, was uniform. The SIMS depth profiling also indicated that C and O concentrations were low in the film. Volatile products trapped at 77 K were analyzed by gas chromatography—mass spectroscopy (GC-MS) and nuclear magnetic resonance (NMR). Isobutylene, acetonitrile, hydrogen cyanide, and ammonia were detected in the condensable mixtures. Possible reaction pathways were proposed to speculate the origin of these molecules.

Original languageEnglish
Pages (from-to)1353-1360
Number of pages8
JournalJournal of Materials Research
Volume8
Issue number6
DOIs
StatePublished - 1 Jan 1993

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