Surface Chemistry of Copper(I) Acetamidinates in Connection with Atomic Layer Deposition (ALD) Processes

• Published in: Chemistry of materials Vol. 23; no. 14; pp. 3325 - 3334
• Main Authors: Ma, Qiang, Guo, Hansheng, Gordon, Roy G, Zaera, Francisco
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26.07.2011
• Subjects: atomic layer deposition; surface chemistry; copper films; X-ray photoelectron spectroscopy; amidinate complex
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm200432t

The thermal chemistry of copper(I)-N,N′-di-sec-butylacetamidinate on Ni(110) single-crystal and cobalt polycrystalline surfaces was characterized under ultrahigh vacuum (UHV) conditions by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). A complex network of reactions were identified, starting with the dissociative adsorption of the precursor, from its dimeric form in its free state to a monomer once bonded to the nickel surface. The dissociation of a C–N bond in the acetamidinate ligand at ∼200 K leads to the formation of adsorbed 2-butene and N-sec-butylacetamidinate. Some of the latter intermediates hydrogenate around 300 K to release N-sec-butylacetamidine into the gas phase, while the remaining adsorbed species dissociate further around 400 K, as the copper atoms become reduced to a metallic state, possibly to form acetonitrile and a sec-butylamido surface species that reacts further at 485 K to release 2-butene. By 800 K, only copper and a small amount of carbon can be seen on the surface by XPS. The implications of this chemistry to the growth of metal films by atomic layer deposition (ALD) are discussed.