Electrical Characteristics of Crystalline Gd 2 O 3 Film on Si (111): Impacts of Growth Temperature and Post Deposition A

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Electrical characteristics of crystalline Gd2O3 film on Si (111): impacts of growth temperature and post deposition annealing G. Niu 1, B. Vilquin 1, N. Baboux 2, G. Saint-Girons 1, C. Plossu 2, G. Hollinger 1 1 INL-UMR5270/ECL, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, Ecully Cedex, 69134, France 2 INL, INSA de Lyon, Lyon Cedex, 69432, France. ABSTRACT This work reports on the epitaxial growth of crystalline high-k oxide Gd2O3 on Si (111) by Molecular Beam Epitaxy (MBE) for CMOS gate application. Epitaxial Gd2O3 films of different thicknesses have been deposited on Si (111) between 650°C~750°C. Electrical characterizations reveal that the sample grown at the optimal temperature (700°C) presents an equivalent oxide thickness (EOT) of 0.73nm with a leakage current density of 3.6×10-2 A/cm2 at |Vg-VFB|=1V. Different Post deposition Annealing (PDA) treatments have been performed for the samples grown under optimal condition. The Gd2O3 films exhibit good stability and the PDA processes can effectively reduce the defect density in the oxide layer, which results in higher performances of the Gd2O3/Si (111) capacitor. INTRODUCTION The continuous scaling of the gate dielectric thickness requires high-k metal oxide as an alternative to SiO2 for future CMOS (Complementary Metal Oxide Semiconductor) technology. Recently, the epitaxy of crystalline oxides on silicon attracted intensive researches: the epitaxial nature of these oxides allows circumventing the recrystallization issue encountered with amorphous oxides, which leads to a tremendous augmentation of the leakage current. In addition, using epitaxial growth techniques allows subtly monitoring the oxide stoichiometry. Gadolinium oxide (Gd2O3), which belongs to the family of rare-earth (RE) metal oxides (lanthanide oxides) possesses a cubic bixbyite Mn2O3 (II) structure in which the unit cell includes eight unit cells of an incomplete fluorite structure. It is identified as one of the most promising candidates due to its[1] i) high dielectric constant of 20, ii) high bandgap of 5.3eV, iii) thermodynamical stability on silicon even at high temperature, and iv) very small lattice mismatch(only -0.46%) with Si (one Gd2O3 unit cell on two Si unit cells). Gottlob et al. reported for the first time a fully functional n-MOSFET with a TiN/Gd2O3/Si (001) system [2]. However, Gd2O3 exhibits bidomain structure on Si (001), which could significantly increase the leakage current [3]. At the same time, due to the highly perfect crystallinity of Gd2O3 on Si(111) and its potential application as template to integrate semiconductor (Si and Ge) [4,5] or ferroelectric/multiferroic materials with hexagonal structure (such as YMnO3) [6] , Gd2O3/Si(111) system attracts wide research interests. Several good electrical results of this system have been reported [7,8]. Nevertheless, the reliability and stability of the Gd2O3 dielectric still remains acute and requires further investigations.

In the present work, we demonstrate a good quality epitaxial single domain growth