New Tungsten(VI) Guanidinato Complexes:  Synthesis, Characterization, and Application in Metal−Organic Chemical Vapor Deposition of Tungsten Nitride Thin Films

Abstract

Two new tungsten complexes, [W(NtBu) 2 (NMe 2 ){(iPrN) 2 CNMe 2 }] (2) and [W(NtBu) 2 (H){(iPrN) 2 CNMe 2 }] (3), as precursors for metal-organic chemical vapor deposition (MOCVD) of tungsten nitride thin films were synthesized from the starting compound [W(NtBu) 2 (Cl){(iPrN) 2 CNMe 2 }] (1) by substitution of the chloro ligand by a dimethylamido and a hydrido group, respectively. Compounds 1-3 were characterized by 1 H NMR, 13 C NMR, EI-MS, IR, and elemental analysis including single-crystal X-ray diffraction studies on 1 and 3. The thermal properties of the compounds were studied by thermogravimetric and differential thermal analysis. Precursors 2 and 3 were compared for the growth of tungsten nitride thin films by MOCVD. The obtained films were characterized by X-ray diffraction and scanning electron microscopy and by depth-profiling the composition with secondary neutron mass spectroscopy. Films grown without ammonia had surprisingly low nitrogen levels, indicating that 2 and 3 are not suited as single-source precursors for pure WN x phases. When ammonia was used as a co reactant gas, the carbon content in the films decreased significantly and crystalline β-W 2 N was obtained. Interestingly, films grown in the presence of ammonia by amido compound 2 yielded lower carbon contents than films obtained from hydrido compound 3. Supporting Information Available: X-ray crystallographic data in CIF format for the structures of compounds 1 and 3 and schemetic of the MOCVD reactor and table with film composition (PDF). This material is available free of charge via the Internet at http://pubs.acs.org. CM061999D

MOCVD of tungsten nitride thin films: Comparison of precursor performance and film characteristics

“…Films deposited during WN_2 and WN_4, which consist of WN material, show resistivity values between $500 and 1100 mV cm. These values are comparable to the lowest values reported for WN thin films grown by MOCVD [20,24,25]. The resistivity increased at higher deposition temperature which could be attributed to increased crystallinity and grain size that possibly increases electron scattering along grain boundaries.…”

“…Amido–imido complexes of tungsten such as [W(N t Bu) 2 (NH t Bu) 2 ] and [Cl 4 (RCN)W(NR′)] (R = CH 3 , Ph; R′ = i Pr, C 3 H 5 , Ph) have been used as MOCVD precursors under single source precursor (SSP) conditions or in combination with NH 3 as reactive gas for the deposition of WN thin films. Earlier, we demonstrated that all nitrogen coordinated amidinato‐based tungsten complexes [W(N t Bu) 2 {( i PrN) 2 CMe} 2 ] and guanidinato‐based tungsten compounds like [W(N t Bu) 2 (NMe 2 ){( i PrN) 2 CNMe 2 }] and [W(N t Bu) 2 (H){( i PrN) 2 CNMe 2 }] can serve as potential precursor for the deposition of WN thin films in a home built CVD reactor .…”

“…Metal organic complexes containing metal nitrogen bonds have been proven useful as precursors for the metal organic chemical vapour deposition (MOCVD) of transition metal nitrides. Many refractory transition metal nitrides [25].…”

Novel Precursors for the MOCVD of Molybdenum Nitride

“…To avoid incorporation of halide or carbon atoms inside the films a new class of all nitrogen coordinated, mixed imido-amido-complexes of molybdenum, like [Mo(N t Bu) 2 (NEt 2 ) 2 ] (9) and [Mo(N t Bu) 2 (NMe 2 ) 2 ] (10), were developed and tested as precursors for the MOCVD of Mo x N y . In the past we have shown, that it is possible to design volatile, all nitrogen coordinated tungsten-complexes by introducing chelating guanidinato-ligands which have been successfully used as precursors for the MOCVD of tungsten nitride thin films (11,12,13).…”

Tungsten imido complexes as precursors to tungsten carbonitride thin films

“…WF 6 ) a number of precursors have been developed. 11, 12 The compounds a Department of Chemistry, Materials Chemistry Centre, University College London, 20 2 ], 16 and [W(N t Bu) 2 R{h 2 -( i PrN) 2 CNMe 2 }] (R = NMe 2 , H), 17 have been employed in either CVD or ALD processes, often in the presence of ammonia, affording films of tungsten nitride or tungsten carbonitride. The tungsten imido compounds, [W(=NR)Cl 4 (R¢CN)] (R = i Pr, Ph, C 3 H 5 ; R¢ = Me, Ph) were used in an (AA)CVD process with hydrogen in the carrier gas stream.…”