AVS 50th International Symposium
    High-k Gate Dielectrics and Devices Topical Conference Monday Sessions
       Session DI-MoM

Paper DI-MoM9
Separate and Independent Control of Interfacial Band Alignments and Dielectric Constants in Transition Metal-rare Earth Ternary Oxides

Monday, November 3, 2003, 11:00 am, Room 317

Session: Electronic Properties of High-k Dielectrics and their Interfaces
Presenter: D.G. Schlom, Pennsylvania State University
Authors: D.G. Schlom, Pennsylvania State University
J.L. Freeouf, Oregon Graduate Institute
G. Lucovsky, North Carolina State University
Correspondent: Click to Email
The electronic structure of transition metal, Tm, and trivalent rare earth, Re, binary (TmO@sub x@ and Re@sub 2@O@sub 3@) and ternary mixed oxides (TmRe@sub x@O@sub y@) are qualitatively different from those of silicon oxide, silicon nitride, and silicon oxynitride alloys. The lowest conduction band states are associated with localized anti-bonding d*-states of the Tm/Re atoms, rather than extended Si 3s*-states, and/or O/N 2p*-states. Based on quantitative agreement between the Zr silicate anti-bonding state electronic structure obtained from Zr M@sub 2,3@ and O K@sub 1@ XAS spectra, and ab initio calculations on small clusters, the ordering and overlap of anti-bonding Zr 4d*- and 5s*-states, and Si 3s*-states in the O K@sub 1@ spectra is the same as the features of the conduction band electronic structure that determine band-offset energies at Si-Zr silicate alloy interfaces. These relationships have been extended to Re ternary oxide compounds, including LaAlO@sub 3@ and GdScO@sub 3@, through direct comparisons between O K@sub 1@ XAS spectra and band edge optical absorption constants obtained from analysis of SE measurements extending to 9 eV. As a result of near-neighbor interactions between Tm and Re d-states induced by bonding to a common O atom, ternary oxide minimum band gaps, and conduction band offset energies are increased in oxide phases containing Tm and Re species. This identifies new and technologically important opportunities for band gap engineering at the atomic scale. Relative energy shifts of coupled Re and Tm d*-states are important for the ultimate scaling of CMOS devices since they increase the effective band gaps/offset energies for ternary oxides containing highly polarizable Sc, Ti, Nb, and Ta atoms above what had previously been proposed as a fundamental limitation inferred from the band gaps and/or band offset energies of their respective binary oxides.