Regensburg 2013 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 15: High- and low-k-dielektrics (joint session with DS)

DF 15.2: Vortrag

Mittwoch, 13. März 2013, 09:50–10:10, H11

Mixed Sr/Ba oxides as high-k dielectric material on Si(100) — •Shariful Islam¹, Karl Hofmann², and Herbert Pfnür¹ — ¹Institut für Festkörperphysik, Leibniz Universität Hannover — ²Inst. f. Bauelemente der Mikroelektronik, Leibniz Universität Hannover

Mixed Sr/Ba oxide layers can be grown perfectly lattice matched as crystalline and epitaxial layers on Si(100). At a mixing Sr/Ba ratio of 30:70, a band gap of 4.3eV was found. Here we demonstrate that band alignment is possible both for p- and n-type Si with a band offset of >1eV. Dielectric constants of 27± 1 were determined for layer thickness between 4 and 16 nm, corresponding to capacitance equivalent thickness (CET) between 0.5 and 2.6 nm. The capacitance-voltage curves in MOS diodes fabricated by covering the oxide layers with 100 nm of Au show small hysteresis (< 1 mV) indicating a small density of rechargeable traps in the oxide films. Trap densities at the Si/oxide interface were determined by the conductance method to be close to 4× 10¹⁰ eV⁻¹cm⁻². These properties are coupled with low leakage currents (< 4 mA/cm² at 5 nm thickness). These electrically excellent properties contrast with its limited thermal stability. At temperatures above 450^∘C the oxides are transformed into a well defined and again crystalline (Ba_0.8Sr_0.2)₂SiO₄, which turns out to be stable up to desorption above 750^∘C, forming a band gap of 6 eV. First electrical measurements on this material will be discussed, too.