AVS2003 Session DI-TuP: Poster Session
Tuesday, November 4, 2003 5:30 PM in Room Hall A-C
Tuesday Afternoon
Time Period TuP Sessions | Topic DI Sessions | Time Periods | Topics | AVS2003 Schedule
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DI-TuP-1 Investigation of Initial Growth Stage of HfO2 Films on Si (100) Grown by Atomic-layer Deposition using In-situ Medium Energy Ion Scattering
H.S. Chang, H. Hwang (Kwangju Institute of Science and Technology (KJIST), South Korea); M.-H. Cho, Y.J. Cho, K.J. Kim, D.W. Moon (Korean Research Institute of Standards and Science (KRISS), South Korea) The initial growth stage of HfO2 films on p-type Si(100) grown by atomic-layer deposition (ALD) was investigated using in-situ medium energy ion scattering (MEIS). The interaction between adsorbed HfCl4 molecules and Si substrate was examined in relation to the film thickness, substrate temperatures, and surface states of the Si substrates. Interfacial reaction between Hf and Si at the initial growth stage was occurred and significantly depended on the surface state of the Si. The hafnium silicate with an amorphous structure was grown on the oxidized Si substrate at an initial growth stage. In particular, the interfacial layer thickness and the stoichiometry of the layer were depended on the surface state of Si substrate. As thickness of the film increased, the silicate formation was gradually changed into HfO2 state. The physical analysis of the films with XPS and TEM also supported the interfacial reactions. Based on the interfacial interaction at the initial growth stage, we suggested the model for the interaction between Hf and Si at the initial growth stage in relation to the atomic size, bonding characteristics, and formation energy. This study will be helpful to understand the interfacial reactions at the initial growth stage and to control the reactions for the application of high-k dielectrics. |
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DI-TuP-2 Effects of Annealing Temperature on the Characteristics of HfO2/HfSixOy High-k Gate Oxides
H.-D. Kim, Y. Roh, D. Jung, N.-E. Lee (Sungkyunkwan University, Korea) Several candidates for the future high-k gate oxides have been extensively studied by many research groups to overcome the problems such as large leakage current caused by the direct tunneling through extremely thin SiO2. Recently, we reported that simple oxidation of sputtered Hf films on Si produces HfO2/HfSixOy high-k oxides with excellent properties. We argued that the effective k of HfO2/HfSixOy film may be controlled by changing the thickness ratio between HfO2 and HfSixOy. In this work, we further investigated the characteristics of HfO2/HfSixOy high-k gate oxides to clarify the roles of annealing process. The 1.5 nm Hf film was directly deposited on Si substrate by sputtering at plasma power of 50 W for 4 min. Oxidation was performed at 500 °C for 60 min, followed by annealing at 500-900 °C in furnace under N2 ambient. Pd gate metal was thermally evaporated on the HfO2 film. Using the physical and electrical measurement techniques, we confirmed that the oxidation of the thin Hf films on Si results in the HfO2/HfSixOy stack layer with the excellent electrical properties; negligible hysteresis, excellent EOT value (1.2 nm) and low leakage current (~2 X 10-3 A/cm2 at 1.5 V after compensating Vfb). Furthermore, we found that the level of leakage current decreases as annealing temperature increases. However, over 500 °C, annealing deteriorates the EOT value; e.g., 1.2 and 1.7 nm EOT values were obtained from 500 and 900 °C samples, respectively. We speculate that both thickness increase of HfO2/HfSixOy films and the formation of additional SiO2 layer between HfSixOy and Si cause these phenomena. We therefore suggest that annealing temperature must be carefully controlled to maintain the excellent characteristics of HfO2/HfSixOy high-k gate oxides. |
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DI-TuP-3 Thermal Stability of Al- and Zr- doped HfO2 Thin Films by DC Magnetron Sputtering
Y.E. Hong, Y.S. Kim, D.H. Ko, D.W. Lee (Yonsei University, South Korea); J.-H. Ku (Samsung Electronics, South Korea) Currently, high-k materials are under consideration as replacements for SiO2 because physically thick film with high dielectric constant is possible solution for reducing leakage current. Among some metal oxides such as Al2O3, ZrO2, and HfO2, particularly HfO2 exhibits excellent material properties such as high permittivity of up to 30, energy gap of 5.6eV and thermal stability in contact with silicon. However, after post-deposition annealing above 400°C, as-deposited amorphous HfO2 crystallizes which may induce grain boundary leakage current. In addition, annealing in an oxygen rich ambient leads to fast diffusion of oxygen through the HfO2, resulting in the growth of uncontrollable interfacial layer between HfO2 and silicon substrate. In this study, we investigated comparatively the thermal stability properties of HfO2 based films with Al- and Zr-doping. HfO2 was prepared by sputtering Hf target in a mixture of oxygen and argon at room temperature. Al- and Zr-doping is achieved by co-sputtering using Al and Zr target. And the compositions of the doped films were controlled by target power. After the formation of the films, annealing at 500~900°C for 5min by furnace in N2 ambient was followed. The compositions and the chemical states of the oxide films were confirmed by RBS and XPS. The crystallization temperature of the HfO2 film which has 10% Al was 900°C. However, most of the Zr-doped HfO2 films were crystallized from as deposited condition. As an annealing temperature increases, HRTEM analyses of the all doped films show the increased interfacial layer thickness, and the interfacial layer of the Zr-doped HfO2 films is thicker than the Al-doped. The increased CET and leakage current values through CV/IV measurements and dielectric constant difference between Al- and Hf-doped HfO2 films will be presented and discussed. |
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DI-TuP-5 NH3 Nitridation Effect on HfO2-Al2O3 Films in the MOS Capacitor
C. Lee, J. Choi, M. Cho, C.S. Hwang, H.J. Kim (Seoul National University, Korea) High-k gate dielectrics, such as HfO2 and Al2O3, have been investigated as an alternative to SiO2 for low power device due to high dielectric constant, thermodynamic compatibility of the interface with Si substrate, and a relatively large band gap. We investigated the nitrogen diffusion behavior and electrical characteristics, especially flat band voltage (Vfb) shift and Vfb hysteresis by NH3 nitridation of the MOS capacitors. The nitrided MOS capacitors include the various high-k gate dielectric stacks such as Pt gate/HfO2/p-type Si, Pt gate/HfO2-Al2O3/p-type Si, and Pt gate/capping Al2O3-HfO2-Al2O3/p-type Si. HfO2 and Al2O3 films were deposited on p-type epitaxial Si (100) wafers with a resistivity of 1 Ωcm by atomic layer deposition (ALD) technique using HfCl4, Al(CH3)3 and H2O at 300°C after RCA SC1 and HF cleaning. Post deposition annealing (PDA) of the samples was performed with rapid thermal annealing (RTA) at 700°C, 800°C, and 900°C in NH3 for 30 seconds. Post-metallization annealing (PMA) of Pt-top electrodes was performed at 400°C for 30 min. under a 5% H2 + 95% N2 atmosphere. Vfb shifted negatively with increasing nitridation temperature, but it moved positively with increasing Al2O3 thickness. HfO2-Al2O3 film showed excellent Vfb shift and hysteresis characteristics when it was post-metallization annealed in NH3 at 800°C for 30 seconds. NH3 nitridation effect on Pt gate/HfO2-Al2O3/p-type Si MOS capacitors with increasing PDA temperature was analyzed by electrical evaluation, Auger Electron Spectroscopy (AES), atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). |
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DI-TuP-6 Structural and Electrical Characterization of Aluminum Oxynitride Thin Films Obtained by RF-Sputtering
J.J. Araiza (UAZ, Mexico); M.A. Aguilar (CICATA-IPN, Mexico); C. Falcony, M. Jergel (CINVESTAV-IPN, Mexico) The structural and electrical characteristics of aluminum oxynitride thin films deposited on silicon substrates by rf-sputtering are reported. The properties of the films were studied as a function of the deposition parameters, such as substrate temperature, RF sputtering power and the relative amount of argon and nitrogen gases introduced to the chamber. The films were characterized by atomic force microscopy, transmission and scanning electron microscopy, X ray diffraction, Infrared and Uv-vis spectroscopy and ellipsometry. Metal-Oxide-Semiconductors structures were also fabricated with the films deposited. Films with characteristics close to aluminum oxide and aluminum nitride were obtained, depending on the deposition parameters. It was found that the films can withstand electric fields up to 4.5 MV/cm, without observing destructive breakdown, with dielectric constants up to 8.7. In addition, the as deposited films present a surface roughness lower than 1.6 nm, refractive indexes from 1.5 to 2.0 and deposition rates up to 7.0 nm/min. |
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DI-TuP-7 Plasma and Thermal Etching of High-k Materials for ALD Chamber Cleaning
B. Ji, D. Wu, R.M. Pearlstein, S.A. Motika, E.J. Karwacki, M.J. Plishka (Air Products and Chemicals, Inc.) High dielectric constant (high-k) materials such as Al2O3, HfO2, and ZrO2 are deposited onto semiconductor wafer surfaces by atomic layer deposition (ALD) in integrated circuits manufacturing. High-k ALD reactors must undergo periodic chamber cleaning to remove deposition residues from the internal surfaces of the reactor in order to maintain production yield. Due to their high chemical inertness and extremely low volatility, etching and cleaning high-k deposition residues has been technically challenging. By combining thermochemical calculations and experimental screening, we have identified BCl3 as the most effective reagent for removing high-k materials from ALD chambers. We will report both plasma and thermal etching of Al2O3, HfO2, and ZrO2 using BCl3. We will discuss the chemical mechanism of BCl3-metal oxide reaction, and the influence of various process parameters on high-k materials etch rate. |