Monday, 1 October 2018: 09:20
Universal 7 (Expo Center)
D. R. Islamov (Novosibirsk State University, Rzhanov Institute of Semiconductor Physics SB RAS), V. A. Gritsenko (Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk State University), V. N. Kruchinin (Rzhanov Institute of Semiconductor Physics SB RAS), and M. S. Lebedev (Nikolaev Institute of Inorganic Chemistry SB RAS)
Hafnia-based high-κ dielectrics are widely used in modern MOS devices, perspective RRAM and FRAM cells, dopand of ceramics in teeth prosthetic. The electronic properties of HfO2, such as leakage currents and luminescence, are defined by traps and defects. The presence of traps increases the conductance of dielectric. Electron or hole localization on traps shifts the voltage threshold and leads to device degradation. In active layers of RRAM, traps act as precursors of a filament during the HRS/LRS switch. The trap density ≲1022 cm-3 is a huge for degeneration of devices, but is very low for detecting within chemical analytical techniques. Previously, it was reported that comparison measured J-V dependencies with multiphonon transport models allows extracting the density of oxygen vacancies (VO), which acts as traps, in the HfO2. In the study, we try to get correlations between the trap density and optical properties of hafnia films.Variation of the trap density in HfO2 was supported by different conditions of film synthesis using ALD technique and different precursors: TEMAH+H2O and Hf(thd)4+O2. The series of samples was annealed in N2-flow for 1 hour at different temperatures. Annealing was performed directly in the reaction chamber at Tann = 440, 550 and 700 °C for TEMAH+H2O samples and Tann = 550 and 700 °C for samples deposited from Hf(thd)4+O2 precursor system. Dispersion dependencies of refractive index were measured by spectral and laser ellipsometry. It was found that the refractive index grows as films are depleted by oxygen. The results offer a new in situ technique for quality evaluation of synthesized HfO2 films, namely evaluation of oxygen vacancy density.
The work was supported by the Russian Science Foundation, grant #16-19-00002.
