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[en] The quality of MOS devices is a strong function of gate oxide and its interface with the substrate. In this work we have presented a detail of atomic layer deposition of ultrathin HfO2, oxide on silicon wafer and its characterization. HfO2 has been deposited from tetrakis (ethyl methyl amino) hafnium (TEMAH) and water (H2O) by atomic layer deposition (ALD) on 200mm silicon wafers. There is gradual surface behavior is shown by half saturation reactions. Very good uniformity was obtained with almost 100% step coverage. Film thickness increased linearly with increase in number of deposition cycles. Deposition rate of about 1 Å/cycle was obtained. Presence of carbon and hydrogen content in the deposited film was determined by EDX, CV and GV measurements have been done to establish the quality of the deposited samples. The results show that H2O and TEMAH based ALD HfO2 deposition is promising for various nano-electronic applications. (author)
[en] The energy of preference of ion Li+ to octahedral position in the rock salt structure, E = -10 kcal/g-ion, was estimated from heats of formation of LiFeO2, LiAlO2 and Li2TiO3. The heats of formation of the LiVO2, LiCrOL2, LiCoO2, and LiMnO2 compounds were calculated from the corresponding oxides (-13--m14 kcal/mole)
[en] The key features of the inverse problem of X-ray reflectometry (i.e., the reconstruction of the depth profile of the dielectric constant using an experimental angular dependence of reflectivity) are discussed and essential factors leading to the ambiguity of its solution are analyzed. A simple approach to studying the internal structure of HfO2 films, which is based on the application of a physically reasonable model, is considered. The principles for constructing a film model and the criteria for choosing a minimal number of fitting parameters are discussed. It is shown that the ambiguity of the solution to the inverse problem is retained even for the simplest single-film models. Approaches allowing one to pick out the most realistic solution from several variants are discussed.
[en] To remove iron and titanium from hafnium, the process of precipitating ammonium sulfohafnates (ASH) from sulfuric solutions of hafnium is studied. Ammonium chloride is used as an ASH precipitator. To precipitate ASH and produce the conditioned product as far as the iron and titanium impurities are concerned the following optimal procedure is selected: 275-300 g/l HfO2 concentration (1.3-1.4 mol/l); molar ratio SO3:HfO2=2.3-2.5; molar ratio NH4Cl:HfO2=3.0-4.0. Under optimum condition isolated is the salt of the following composition: 47.39 HfO2, 31.5SO3; 14.0 (NH4)2SO4, 0.0076Fe2O3, 0.018TiO2, 8.08H20, 47.98SO4
[en] The effect of nitrogen doping by the NH3 plasma treatment approach on the resistive switching properties of a HfO2-based resistive random access memory (RRAM) device is investigated. Test results demonstrate that significantly improved performances are achieved in the HfO2-based RRAM device by nitrogen doping, including low operating voltages, improved uniformity of switching parameters, satisfactory endurance and long retention characteristics. Doping by nitrogen is proposed to suppress the stochastic formation of conducting filaments in the HfO2 matrix and thus improve the performances of the Pt/Ti/HfO2/Pt device. (paper)