Theoretical Analysis of Oxygen Diffusion in monoclinic HfO 2
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E5.4.1
Theoretical Analysis of Oxygen Diffusion in monoclinic HfO2 Minoru Ikeda, Georg Kresse1, Toshihide Nabatame and Akira Toriumi2,3 MIRAI, Association of Super-Advanced Electronics Technologies (ASET), AIST Tsukuba West 7, 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan 1 Institut für Materialphysik, Univeisität Wien, Sensengasse 8/12, A-1090 Wien, Austria 2 MIRAI, Advanced Semiconductor Research Center (ASRC), National Institute of Advanced Industrial Science and Technologies (AIST), AIST Tsukuba West 7, 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan 3 Department of Materials Science School of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo. 113-8656, Japan ABSTRACT In this report, we present the detailed analysis of the interstitial oxygen (O2+, O0, O2-) diffusion in monoclinic HfO2 (hafnia) using the first principles calculations. The interstitial oxygen atom kicks out the oxygen atom at the 3-fold-site and occupies the 3-fold-site. And then the newly kicked-out interstitial oxygen atom jumps to the nearest neighbor site and couples again with the atoms at the crystal sites. This kick-out- mechanism is valid for all charge states of the interstitial oxygen in monoclinic HfO2. In hafnia, the interstitial oxygen atom can take 3 charge states (+2, 0, -2) depending on the chemical potential (Ef), whereas the oxygen-vacancy in hafnia can get +2 or 0 charge state being dependent on Ef. In the lower range of Ef, O2+ and O0 might contribute. In the middle range of Ef, the O2- does not contribute to the diffusion process in hafnia because of the pair annihilation process between O2- and oxygen vacancy (V2+) defect pair. We can simulate such a pair annihilation process in hafnia. In the higher range, O2- might contribute the diffusion process. INTRODUCTION Recently, HfO2 (hafnia) grown on Si substrates is widely studied as a potential candidate for replacing silicon dioxide as the gate dielectrics in scaled Complementary Metal Oxide Semiconductor (CMOS) being the basic transistor in modern electronic devices. At the interface between Si and hafnia, the interfacial layer has been formed. And this layer thickness increases by the post thermal annealing after the deposition process [1]. This fact indicates that atomic oxygen diffuses through hafnia. Foster et al. reported the interstitial oxygen diffusion in hafnia using the ultra-soft pseudopotential method [2]. They concluded that the O2- diffuses in the bulk HfO2. In this report, we present the detailed analysis of the interstitial oxygen (O2+ O0, O2-) diffusion in hafnia using the first principles method with all electrons method. And we report the whole view of the diffusion process of oxygen with different charge states in hafnia.
E5.4.2
METHODOLOGIES Throughout this work, we used the Projector Augmented Plane Wave method (PAW) with the local spin density functional theory corrected by the generalized gradient approximation [3-5]. As for the brillouin zone integration, one k-point sampling was employed. We used 250 eV for the cut off energy. In
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