Selected Publications - 2005:

1) Atomic-scale properties of high-k dielectrics: ab initio study for Pr-based materials

J. Dąbrowski, A. Fleszar*, G. Lippert, G. Lupina, A. Mane, H.-J. Müssig, T. Schroeder, R. Sorge, H. Thieme, Ch. Wenger and P. Zaumseil

IHP-Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany

* Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

accepted for publication in Advances of Solid State Physics 2005 (2005).

We discuss the atomic and electronic structures and energetics of native point defects and of impurities (Si, Ti, B, moisture) in Pr₂O₃ and, to some extent, also in PrO_x and in Pr₂Si₂O₇, as obtained from ab initio total energy calculations. We introduce the concept of Silicon-related Nitrogen-Coordinated Oxygen (SiNCO) which we then use to explain the origin of fixed charge in classical SiO₂ films thermally grown on Si substrates and in high-k dielectrics deposited on Si substrates.

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2) Charge traps in high-k dielectrics: ab initio study of defects in Pr-based materials

J. Dąbrowski, A. Fleszar*, G. Lippert, G. Lupina, A. Mane and Ch. Wenger

IHP-Microelectronics, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany

* Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

accepted for publication by Springer Verlag “Topics in Applied Physics” (July 2005)

In the nearest future, a dielectric with a dielectric constant k several times higher than that of SiO₂ will be needed for the fabrication of CMOS (Complementary Metal-Oxide-Semiconductor) devices. Numerous metal oxides and silicates are investigated as candidates and various deposition and annealing techniques are being developed. They try to utilize the effects attributed to alloying, incorporation of nitrogen, gettering of oxygen, etc. At the same time, the basic knowledge on the microscopic properties of these materials is poor, particularly for rare-earth oxides.

We present our fundamental understanding of point defects in Pr-based dielectrics (PrO_1.5, PrO₂, PrO_x, and PrSiO_3.5) in the context of their influence on the electrical properties of the Metal Oxide Semiconductor (MOS) stack. From this point of view, there are three major issues associated with the presence of point defects: fixed charges, Trap Assisted Tunneling (TAT) centers, and electrically active interface states. The paper focuses on the first of these issues, as seen from the perspective of ab initio total energy calculations for atomic and electronic structures of point defects. We discuss the dependence of point defect formation on the chemical potential of oxygen and the role of impurities such as moisture, silicon, and boron. In particular, we derive a model of Si-related fixed charge and argue that this model is valid also for typical high-k dielectrics and also for thermal SiO₂/Si films.

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