Cobalt(I) Olefin Complexes: Precursors for Metal–Organic Chemical Vapor Deposition of High Purity Cobalt Metal Thin Films

Abstract

We report the synthesis and characterization of a family of organometallic cobalt(I) metal precursors based around cyclopentadienyl and diene ligands. The molecular structures of the complexes cyclopentadienyl-cobalt(I) diolefin complexes are described, as determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis and thermal stability studies of the complexes highlighted the isoprene, dimethyl butadiene, and cyclohexadiene derivatives [(C5H5)Co(η(4)-CH2CHC(Me)CH2)] (1), [(C5H5)Co(η(4)-CH2C(Me)C(Me)CH2)] (2), and [(C5H5)Co(η(4)-C6H8)] (4) as possible cobalt metal organic chemical vapor deposition (MOCVD) precursors. Atmospheric pressure MOCVD was employed using precursor 1, to synthesize thin films of metallic cobalt on silicon substrates under an atmosphere (760 torr) of hydrogen (H2). Analysis of the thin films deposited at substrate temperatures of 325, 350, 375, and 400 °C, respectively, by scanning electron microscopy and atomic force microscopy reveal temperature-dependent growth features. Films grown at these temperatures are continuous, pinhole-free, and can be seen to be composed of hexagonal particles clearly visible in the electron micrograph. Powder X-ray diffraction and X-ray photoelectron spectroscopy all show the films to be highly crystalline, high-purity metallic cobalt. Raman spectroscopy was unable to detect the presence of cobalt silicides at the substrate/thin film interface.

Editors' Choice—Review—Cobalt Thin Films: Trends in Processing Technologies and Emerging Applications

“…32 r Co precursor based on cyclopentadienyl and diene ligands [(C 5 H 5 )Co(η 4 -CH 2 CHC(Me)CH 2 )] with H 2 as co-reactant at a substrate temperature of 400 • C (Co oxidation state: 1; key parameter: substrate temperature). 16 Co-W alloy thin films were also deposited by MOCVD from the coreaction of dicobalt octacarbonyl (Co-001) and tungsten hexacarbonyl [W(CO) 6 ] as Co and W sources, respectively. The resulting alloys were then tested as a diffusion barrier in IC Cu metallization, 34 and the addition of W was shown to improve the barrier properties of the resulting CoW films against Cu diffusion.…”

Low Temperature, Selective Atomic Layer Deposition of Cobalt Metal Films Using Bis(1,4-di-tert-butyl-1,3-diazadienyl)cobalt and Alkylamine Precursors

“…Cobalt metal films have applications as magnetic materials, , intermediate layers in the fabrication of CoSi 2 contacts, and caps and liners of copper metal structures in microelectronics devices to minimize electromigration. − Cobalt metal may even replace copper metal as the conductors in future devices . Cobalt metal films have been traditionally grown by physical vapor deposition (PVD) − and chemical vapor deposition (CVD) from a range of molecular precursors. − Decreasing dimensions to <10 nm in microelectronics devices will require cobalt metal film growth by atomic layer deposition (ALD) to provide conformal, controlled thickness layers. − The self-limiting growth mechanism in ALD inherently leads to conformal films with subnanometer thickness control. , Plasma-enhanced ALD of cobalt metal films has been demonstrated with a variety of cobalt precursors and ammonia or hydrogen reactant gases. − While plasma-based ALD methods provide high quality cobalt metal films, the reactive plasmas can damage substrates and may give poor conformal coverage of narrow and deep features because the reducing species recombine on the feature walls before they are able to promote film growth . The thermal ALD of cobalt metal is difficult because of the negative electrochemical potential of the cobalt­(II) ion (Co­(II) ↔ Co(0), E ° = −0.28 V) and the limited range of coreagents that can reduce precursors in positive oxidation states to cobalt metal at moderate temperatures .…”

Review of Cobalt Oxide (CoO) thin films prepared by various techniques

“…It was observed that Co films used in sensor application, data storage, CNT (carbon nano-tube), reflective films, for optical devices and also used for coating purpose such as antibacterial coating, decorative coating, protective coating and also for coating in optical devices [10][11][12][13][14][15] both energy production and energy storage have equal importance and cobalt oxide proves a very promising candidate for sensor such as gas sensor and magnetic sensor. Cobalt oxide is anodic colored material which is subpart of electro-chromic materials [16].…”