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https://doi.org/10.1007/s11664-020-08392-4 Ó 2020 The Author(s)

Ion-Implanted Epitaxially Grown Gd2O3 on Silicon with Improved Electrical Properties A. JOSEPH

,1,2,4 G. LILIENKAMP,3 T.F. WIETLER,1 and H.J. OSTEN1

1.—Institute of Electronic Materials and Devices, Leibniz Universitat Hannover, Schneiderberg 32, 30167 Hannover, Germany. 2.—Hannover School for Nanotechnology, Leibniz Universitat Hannover, Schneiderberg 39, 30167 Hannover, Germany. 3.—Clausthal University of Technology (TU Clausthal), Adolph-Roemer-Straße 2A, 38678 ClausthalZellerfeld, Germany. 4.—e-mail: [email protected]

The effects of nitrogen incorporation by high-dose ion implantation in epitaxial gadolinium oxide (Gd2O3) films on Si (111) followed by annealing have been investigated. The nitrogen content in the oxide layer was changed by altering the implantation dose. The presence of nitrogen incorporation on the Gd2O3 layer was studied using Auger electron spectroscopy. Nitrogen incorporation is believed to occur by filling the oxygen vacancies or by removing hydroxyl group ions in Gd2O3. A maximum concentration of 11% was obtained for nitrogen in the interface between the silicon dioxide and Gd2O3 layer and the implanted areas of the Gd2O3 oxide layer after sputter depth profiling. The nitrogen distribution in the layer was found to be non-uniform. Nitrogen incorporation sharply reduced the leakage current and effectively suppressed the hysteresis. Leakage current was two orders lower compared with the pure Gd2O3. Key words: Ion implantation, nitrogen concentration, epitaxial growth, oxynitrides, leakage current

INTRODUCTION Due to high direct tunnelling current,1 silicon dioxide thinner than 1.5 nm cannot be used for the gate dielectric of complementary metal oxide semiconductor (CMOS) devices.2 High-dielectric-constant (high-k) oxides offer an alternative to silicon dioxide (SiO2) in very-large-scale integrated (VLSI) devices. The basic concept of using high-dielectricconstant materials is increasing the film thickness to reduce the tunnelling leakage current and improve reliability, while scaling the capacitance equivalent oxide thickness (CET) below the direct tunnelling limit of SiO2.3 Rare earth oxides (REOs) have received much attention due to their many advantages, including high dielectric constant,4–6 sufficiently high breakdown strength, extremely low leakage current, and well-behaved interface

(Received March 22, 2020; accepted August 1, 2020)

properties. REOs7,8 such as La2O3,9 and Gd2O3,10 have been studied in detail. Also, the epitaxial growth of crystalline Gd2O3 on silicon in the cubic bixbyite structure has been widely investigated.11 This material has a large band gap of about 6 eV and nearly symmetrical band offsets, as well as a low lattice mismatch of about 0.4% to Si.12 Layers grown by an optimized process can display a sufficiently high- k value to achieve equivalent oxide thickness (EOT) values below 1 nm, combined with ultra-low leakage current densities, excellent reliability, and high electrical breakdown