Thermal Chemistry of Cu(I)-Iminopyrrolidinate and Cu(I)-Guanidinate Atomic Layer Deposition (ALD) Precursors on Ni(110) Single-Crystal Surfaces

Abstract

The thermal chemistry of tetrakis[Cu(I)-N-sec-butyl-iminopyrrolidinate] and bis[Cu(I)-N,N-dimethyl-N′,N″-di-iso-propyl-guanidinate], promising precursor for atomic layer deposition (ALD) applications, was investigated on a Ni(110) single-crystal under ultrahigh vacuum (UHV) conditions by using X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD). Both precursors, which exist as tetramers and dimers in the solid phase, respectively, undergo dissociative adsorption at temperatures below 200 K to produce adsorbed monomers on the surface. A β-hydride elimination step is then operative near 300 K that leads to the release of some of the ligands in dehydrogenated form. The remaining adsorbates obtained from either precursor undergo similar further decomposition between 350 K and 600 K as the Cu atoms are reduced from a Cu(I) oxidation state to metallic Cu(0). Hydrocarbons resulting from the elimination of the terminal moieties include ethene and acetonitrile from the Cu(I)-iminopyrrolidinate and propene from the Cu(I)-guanidinate, which are ejected at ∼420–490 K, and HCN in both cases at ∼570–580 K. These results shows several similarities with the surface chemistry previously reported for bis[Cu(I)-N,N′-di-sec-butyl-acetamidinate], and they suggest a common behavior in the surface reactions of these families of Cu(I)-amidinate, Cu(I)-iminopyrrolidinate, and Cu(I)-guanidinate ALD precursors.