AVS 57th International Symposium & Exhibition
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP1
MORTON S. TRAUM AWARD FINALIST: Uptake of Copper Acetamidinate ALD Precursor on Metal Surfaces and the Effect of Coadsorption of Hydrogen

Tuesday, October 19, 2010, 6:00 pm, Room Southwest Exhibit Hall

Session: Surface Science Poster Session
Presenter: Q. Ma, University of California, Riverside
Authors: Q. Ma, University of California, Riverside
F. Zaera, University of California, Riverside
Correspondent: Click to Email
Acetamidinate precursors have shown great promise for atomic layer deposition (ALD) applications, but potentially deposit impurities that may degrade the quality of the films and hinder their practical applications. To help solve this problem, the uptake and thermal activation of bis[(N,N'-di-sec-butylacetamidinate)Cu] and N,N'-di-sec-butylacetamidine on metals were characterized under ultrahigh vacuum (UHV) conditions by using a combination of X-ray photoelectron spectroscopy (XPS), low-energy ion scattering (LEIS), and temperature programmed desorption (TPD).

In initial studies on a Ni(110) single crystal, a temperature window between approximately 350 and 450 K was identified for the ALD of the Cu acetamidinate on Ni surface: lower temperatures are insufficient for activation of the dissociative adsorption, and higher temperatures lead to continuous decomposition beyond Cu monolayer saturation. Approximately three dosing cycles are required to reach full Cu monolayer saturation, the equivalent of a film growth rate of ~0.75 Å/cycle in ALD. Preadsorption of hydrogen on the surface does not modify any of this behavior because of its rapid desorption at temperatures below 350 K once the gas-phase H2 is removed.

The surface chemistry of the Cu precursor is complex, leading to the desorption of not only hydrogen but also butene and N-sec-butylacetamidine (H2N-C(CH3)=N-CH(CH3)(CH2CH3)), it seems that the amidine ligands decompose via beta-hydride elimination from one of their terminal sec-butyl moieties. Copper precursors leading to relatively stable organic surface intermediates are required in ALD because their clean removal can only happen in the second half-cycle of processes that rely on hydrogenation reactions. The ligand of the copper acetamidinate precursors further decomposed on Ni (110) surfaces. The free hydrogenated amidine ligand is less reactive and no N-sec-butylacetamidine is produced by its thermal activation, but the remaining chemistry is seen with similar temperature transitions.