Synthesis and characterization of group 6 and cobalt metal complexes containing nitrogen-rich donor ligands for metal nitride nanoparticles and thin films

Metalorganic and organometallic group 6 source compounds for the growth of MNx and MNxCy thin films for application as diffusion barriers in integrated circuits by Atomic Layer Deposition (ALD) are limited to a few compounds. In addition, group 6 metal nitride nanoparticles and their use as diffusion barriers have not been explored. Accordingly, the work described entailed the synthesis and characterization of group 6 source compounds for metal nitride thin films and nanoparticles bearing nitrogen-rich ligands such as pyrazolato, triazolato, tetrazolato, and amidinato. All new complexes were characterized by spectroscopic and analytical techniques and by X-ray crystal structure determinations. Thin films of WNxC y were grown from the volatile and thermally stable W(NtBu)2(tBu 2pz)2 molecular precursor and ammonia by the ALD technique at 400-450 °C. Thermolysis of the nonvolatile M(NtBu)2(Ph 2pz)2 (M = Mo, W) molecular precursors at 800 °C afforded insoluble 2-3 nm M2N (M = 234 Mo, W) nanoparticles that were embedded in an amorphous carbon-oxygen matrix, as determined by analytical and spectroscopic techniques. Thermolysis of the same precursors at 425 °C afforded amorphous 2-3 nm nanoparticles, as determined by XRD. The nanoparticles prepared at 425 °C were not embedded in a matrix, and were soluble in tetrahydrofuran. This work provides the first description of tungsten nitride nanoparticles, as well as the first description of soluble group 4-6 nanoparticles. W 2N thin films were grown by the ALD technique from W2(NMe 2)6 and ammonia at 180-210 °C. Surface saturative growth was achieved at 180 °C with W2(NMe2)6 pulse lengths of ≥ 2.0 s. AIN thin films were used as protective overlayers, since the as deposited films were air and moisture sensitive. Several mixed ligand complexes of chromium(III) complexes bearing amidinato and pyrazolato, triazolato, or tetrazolato were synthesized and fully characterized. Most of these new complexes are volatile, sublime without decomposition at moderate temperatures, show no evidence for thermal decomposition below 300 °C, and are thus promising potential precursors for ALD growth.{09}In addition, this study provides the first example of an eta2-1,2,4-triazolato ligand coordinated to a transition metal ion with a partially filled d shell. Dimeric and monomeric chromium(II) pyrazolato complexes were also prepared and fully characterized. The dimeric complex Cr2(tBu2pz) 4 contains the longest known chromium-chromium bond distance. Finally, a series of tetramethylcyclobutadienecobalt(I){09}complexes containing{09}pyrazolato and tetrazolato with various coordination modes were prepared and characterized. These complexes are not volatile and decompose under sublimation conditions.