Regensburg 2010 – wissenschaftliches Programm
DS 24.4: Vortrag
Mittwoch, 24. März 2010, 12:00–12:15, H8
Band structure and electrical properties of MBE grown HfO2 - based alkaline earth perovskites — •Dudek Peter1, Łupina Grzegorz1, Kozłowski Grzegorz1, Dabrowski Jarek1, Lippert Gunther1, Müssig Hans-Joachim1, Schmeißer Dieter2, and Schroeder Thomas1 — 1IHP-Microelectronics, Im Technologiepark 25, D-15236 Frankfurt (Oder) — 2BTU Cottbus, Konrad-Wachsmann-Allee 17, D-03046 Cottbus, Germany
Ultra thin dielectric films (<20 nm) deposited on TiN electrodes are interesting for MIM capacitor application. High capacitance density and dielectric permittivity must be accompanied by extremely low leakage currents (10−8 A/cm2) at bias 0.5 V. To achieve such low leakage currents, high band gap and proper band alignment is required. Occupied electronic states can be probed with standard laboratory photoemission methods. Probing of unoccupied states is more challenging. Synchrotron based PES in combination with XAS forms a powerful method to study the band alignment. ASAM end station located at the U 49/2 PGM 2 beamline of BESSY II (Berlin) offers excellent conditions for performing such measurements. We investigated HfO2 - based alkaline earth perovskite - BaHfO3 with subsequent admixture of TiO2, resulting in formation of BaHf0.5Ti0.5O3 compound. The analysis of data indicates that band gap for HfO2 is similar to BaHfO3 and amounts 5.8 eV; for BaHf0.5Ti0.5O3 it decreases to 3.8 eV. We conclude that the addition of TiO2 to BaHfO3 increases significantly the dielectric permittivity but also impacts the band gap alignment. The conduction band offset shrinks, influencing the leakage current behavior.
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