Growth And Characterization Of The Gd₂O₃ High-k Gate Dielectric Films

This dissertation mainly introduces the growth and structure characterizations of high k dielectric Gd₂O₃ films, and next introduces the transformation about the infrared and far infrared station of National Synchrotron Radiation Laboratory (NSRL).1. With the development of integrated circuit, the device dimensions in complementary metal–oxide–semiconductor (CMOS) technology is reduced rapidaly. As a result, the thickness of the gate dielectric must reduce with the decrease of the gate length. A major challenge that needs to be overcome is the thickness of the conventional silicon dioxide insulator. Tunneling-induced leakage currents and dielectric breakdown will lead to unacceptable device performance for oxide thickness below¹.5nm, so the thin silicon dioxide gate-insulated layer must ultimately be replaced by a high-dielectric constant (high-k) material.As the candidates of conventional SiO2, there are some strict requirements to fulfill, including high dielectric constant, moderate band gap, reasonable band alignment to Si, low oxygen diffusivity, thermodynamic stability in contact with silicon at temperature exceeding 800℃, and high-quality interface with silicon with low interfacial state density. In recent years, Many candidate materials especially the IIIA, IIIB, and IVB metal oxides (Y₂O₃, Al₂O₃, TiO2, ZrO2, HfO2, Lu₂O₃ et al.) and their silicate, aluminate have been widely investigated. Recently, Gd₂O₃ has attracted people's attention because of its dielectric constant (k ¹6), closest lattice matches to silicon, and thermal stability in contact with Si at 1000 K.In this paper, we introduce the research background , requirements of high k matericals and the advantages, basic properties and experimental equipments of Gd₂O₃ films, For example, Gd₂O₃ films have been grown by means of different deposited methods such as metal-organic chemical vapor deposition (MOCVD), Magnetron Sputtering, molecular-beam epitaxy (MBE), atomic layer deposition (ALD) and pulsed laser deposition (PLD) etc. Then mainly introduces the growth, research methods and structure characters of Gd₂O₃ thin film. Gd₂O₃ thin film was grown on Si (100) substrate by PLD method. The structure, interfacial component, band offset and dielectric constant are characterized by combining X-ray diffraction (XRD), X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and fourier transform infrared spectroscopy (FTIR). It was found that the different substrate temperatures and oxygen concentration strongly influenced the crystal structure of the samples. The XRR spectra and XPS spectra revealed the presence of gadolinium silicate interfacial layer, presumably Gd and Si Complex Oxides. The valence band offset was obtained by measuring the VBM between the Gd₂O₃ and Si substrate, which result was -2.28±0.1eV. And from Fourier transform infrared (FTIR) transmission spectra of Gd₂O₃ thin film, we can know that the dielectric constant of Gd₂O₃ thin film with different Crystallization is different but only a little difference.2. The second part mainly introduces the the basic features and latest progress of synchrotron radiation infrared, and discusses the transformation, properties test about the infrared and far infrared station of NSRL. The results shows that the transformation about the station meet the design requirements. Besides, because the brightness of synchrotron radiation infrared has obvious advantages, so the application of infrared spectra obtained expanded, especially the study of the microscopy and imaging. Now the infrared and far infrared station of NSRL can be used in many fields, such as, life science, condensed matter physics and material science, chemistry and geology and so on.