Regensburg 2010 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 12: High-k and Low-k Dielectrics II (Joint Session DS/DF)

DF 12.4: Talk

Wednesday, March 24, 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 BaHf_0.5Ti_0.5O₃ compound. The analysis of data indicates that band gap for HfO₂ is similar to BaHfO₃ and amounts 5.8 eV; for BaHf_0.5Ti_0.5O₃ 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.