Reaction mechanism of cobalt with silicon dioxide

Abstract

The reaction mechanism of thin cobalt ͑Co͒ films with silicon dioxide ͑SiO 2 ͒ substrate under rapid thermal annealing conditions has been investigated. Reaction of thin cobalt film ͑12.5 nm͒ with a SiO 2 substrate is observed in an inert ambient ͑N 2 ͒ and in vacuum ͑ϳ10 Ϫ8 Torr͒. The reaction is manifested by the formation of craterlike depressions on the SiO 2 substrate and by the presence of a Co 2 SiO 4 reaction product determined by transmission electron microscopy diffraction patterns. Much less damage is observed with no reaction product observed if the samples are annealed in a forming gas ambient ͑90% N 2 /10% H 2 ͒, the cobalt film is much thicker ͑150 nm͒, or the cobalt film is in situ cleaned ͑e.g., 5 min in 400°C, forming gas ambient͒ prior to annealing in either inert or vacuum ambient. It is proposed that the presence of oxygen is required in order to initiate the reaction between cobalt and SiO 2 . The source of the oxygen contaminant, in our studies, is the oxygen on the surface of the cobalt film. The proposed reaction is 2 CoϩSiO 2 ϩ2͗0͘→Co 2 SiO 4 where ͗0͘ represents oxygen contaminant at the surface.

Hard magnetism in structurally engineered silica nanocomposite

“…In earlier studies of thin film growth, Co 2 SiO 4 was produced by reacting metallic cobalt with an SiO 2 substrate under fast thermal annealing. 33,34 Excess oxygen is known to play roles in initiating the reaction by making cobalt oxide before being transformed to cobalt orthosilicate. 33 Generally, diffusion of Co 2+ is slower than the diffusion of Fe 3+ into tetrahedral SiO 4 units.…”

Study on NiO/Fe interface with X-ray photoelectron spectroscopy

“…However, free oxygen atoms can be adsorbed at the surface of NiO substrates during NiO substrate annealing in an oxygen atmosphere. According to the mechanism of interface reactions reported by Nguyen et al [18], free oxygen atoms adsorbed at the surface may accelerate the reactions between Fe and NiO.…”

Investigation of a Self-Aligned Cobalt Silicide Process for Ohmic Contacts to Silicon Carbide

“…While direct reaction of cobalt with SiO 2 at 800 C is thermodynamically unfavorable, 33 cobalt can react with SiO 2 at 800 C in the presence of oxygen contamination. 34 To avoid this possibility, the FSA temperature should be kept under 700 C. 10 In the absence of reaction, the cobalt could conceivably diffuse through the SiO 2 through defects or pinholes (depending on the quality of SiO 2 ) and react with the underlying 4H-SiC. Of more concern is the commonly observed silicon-diffusion causing bridgingfault, wherein silicon atoms, which are the dominant diffusers in forming CoSi, diffuse from the silicon source (in this case 4H-SiC) through the CoSi and reacts with the cobalt lying on the SiO 2 between contacts.…”