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X-ray photoelectron spectroscopy (XPS) studies of initial stages of copper deposition from bis(hexafluoroacetylacetonato) copper(II) (Cu(hfac)2) on Si(111)-7×7 at room temperature. Part C

C. IONESCU1,* , M. A. IONESCU1, I. CIUCA1

Affiliation

  1. Faculty of Science and Materials Engineering, Politehnica University of Bucharest, Romania

Abstract

Organometallic chemical vapour depostion (OMCVD) of copper compounds is the preferred method for metallization of semiconductors over physical vapour deposition. The advantages of CVD are selectivity and ambient conditions for deposition (low vacuum and room temperature). UPS and XPS spectra of Cu deposited from Cu(hfac)2 via chemical vapour deposition onto Si(111)-7x7 were studied for apparent exposures of 0.02, 0.04, 0.06, 0.08, 0.1 L at room temperature. Cu(hfac)2 adsorption on Si(111)-7x7 at RT follows a ligand dissociative pathway with ligand fragmentation. At low exposures (i.e. 0.04 L) the precursor adsorbs onto Si surface in the reduced form, probably as Cu(I). This is supported by the absence of the shake-up features in the Cu XPS spectrum. Also Cu(II) was accounted for 5% of the total amount of Cu. The driving force for the reduction (Cu(II) → Cu(I)) is the Si(111) surface in its 7x7 reconstructed form. The process takes place at electron states on adatoms in Takayanagi’s model. The reaction products at the end of deposition at the surface are: ligands (L), fragmented ligands (Lf), Cu(I)(hfac) (Cu-L), and copper (Cu). The fact that the Cu(II) intensity is constant over all depositions while the Cu(I) intensity continues to grow from one depostion to the other suggests that Cu(I) is associated with ligands or fragments of ligands. Cluster growth terminates via ligand saturation. This is our explanation to the “magic “ number Cu cluster described by Horton et al. (6)..

Keywords

Chemical vapour deposition, Copper, Low index single crystal Si surfaces, Ultraviolet photoelectron Spectroscopy, X-ray photoelectron spectroscopy, Takayanagi’s model.

Citation

C. IONESCU, M. A. IONESCU, I. CIUCA, X-ray photoelectron spectroscopy (XPS) studies of initial stages of copper deposition from bis(hexafluoroacetylacetonato) copper(II) (Cu(hfac)2) on Si(111)-7×7 at room temperature. Part C, Optoelectronics and Advanced Materials - Rapid Communications, 5, 11, November 2011, pp.1146-1153 (2011).

Submitted at: Aug. 25, 2011

Accepted at: Nov. 23, 2011