Band offsets of a ruthenium gate on ultrathin high-κoxide films on silicon

Abstract

grown on silicon͒ and their shifts upon sequential metallization with ruthenium have been measured using synchrotronradiation-excited x-ray, ultraviolet, and inverse photoemissions. From these techniques, the offsets between the valence-band and conduction-band edges of the oxides, and the ruthenium metal gate Fermi edge have been directly measured. In addition the core levels of the oxides and the ruthenium have been characterized. Upon deposition, Ru remains metallic and no chemical alteration of the underlying oxide gates, or interfacial SiO 2 in the case of the high-thin films, can be detected. However a clear shift of the band edges is measured for all samples due to the creation of an interface dipole at the ruthenium-oxide interface. Using the energy gap, the electron affinity of the oxides, and the ruthenium work function that have been directly measured on these samples, the experimental band offsets are compared to those predicted by the induced gap states model.

(Invited) Electron Spectroscopic Measurements of Band Alignment in Metal/Oxide/Semiconductor Stacks

“…For a number of oxides, S and the position of the CNL have been calculated theoretically (3,5). Using these calculated parameters along with experimental measurements of φ M , χ O and the oxide gap, we have shown in a recent work that for the case of Ru metallization of high-κ oxide films, that the CBO predicted by the MIGS model is in excellent agreement with those obtained experimentally (12).…”

“…Although the mechanism of Al oxidation is still unclear, this behavior as been observed during Al deposition on a HfO 2 /Ge stacks with the concomitant reduction of an interfacial GeO x (17). Not central to our discussion, but worthy of note is that Si 2p core levels shifts are observed at the oxide/semiconductor interface,, indicating that the energy alignment of the entire stack reorganizes upon metal deposition (12,18). For a better description of these processes, higher photon energy XPS could enable tracking chemical and energy alignment modifications of buried layers across the entire stacks.…”

An interface dipole predictive model for high-k dielectric/semiconductor heterostructures using the concept of the dipole neutrality point

“…As such, the CNL used will be rescaled accordingly using the theoretical CNL (i.e., CNL th ) via the relation, CNL ¼ CNL th (E g,meas /E g,th ). 20 This is valid because the position of the CNL is directly affected by the relative position in energy of the occupied and unoccupied states, as dictated by the band gap.…”

Structure and morphology of Ru films grown by atomic layer deposition from 1-ethyl-1’-methyl-ruthenocene

“…Moreover, studies on atomic layer deposition of Ru from advanced precursors such as (methylcyclopentadienyl)(pyrrolyl)ruthenium on SrTiO 3 [15] have revealed that the growth of Ru on such materials is poorly controlled unless plasma-assisted cleaning of underlying oxide film is applied despite the possible structural damage of the oxide surface. Nevertheless, noble metal electrodes (Ru, RuO 2 ) are of significant importance [16,17] despite the related increase in processing costs. Notable amount of studies on Ru so far have been devoted to the issues related to the nucleation of ruthenium thin films as well as to the parametrization of growth processdependence of the growth rate and roughness on growth temperature, pressure and time [2,[18][19][20][21].…”