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Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 10: Semiconductor Substrates: Epitaxy and Growth

O 10.3: Talk

Monday, February 25, 2008, 13:45–14:00, MA 042

Combined electrical and chemical characterization of BaO thin films on Si(001) — •Dirk Müeller-Sajak1, Alexandr Cosceev2, Herbert Pfnür1, and Karl R. Hofmann21Leibniz-Universität Hannover, Inst. f. Festkörperphysik — 2Leibniz-Universität Hannover, Bauelemente der Mikro- und Nanoelektronik

In context with the search for alternative gate oxides on SiO2 in CMOS technology, we have grown high-k BaO films at a thickness between 5 and 20 nm on clean Si(001) using molecular beam epitaxy of Ba metal in ambient oxygen pressure. Interface states and color centers were characterized by XPS and EELS while varying temperature and oxygen partial pressure during growth. For the electrical measurements, Si(001) has been pre-structured by optical lithography and BaO was only generated on small squares using a tungsten mask. After preparation, the films were capped with 250nm of Au and electrically characterized ex situ.
From capacity-voltage measurements on known areas of BaO windows, a dielectric constant of 30 was calculated. This means that for a 5nm BaO film corresponds to an equivalent oxide thickness (EOT) of 0.65 nm of SiO2. These measurements also show very low hysteresis (<5mV), and flatband voltages are close to that of the workfunction difference between Si and Au (+0.65eV). These results are encouraging in terms of the concentrations of fixed and mobile oxide charges both in the bulk and at the interface. The influence of different defects at the interface and within the BaO films will be discussed.

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