Papers by Author: Naoki Fukata

Abstract: In this work we report the enhancement of the 3C-SiC band edge luminescence induced by the SiO2 shell in SiC/SiO2 core/shell nanowires (NWs) system. We demonstrate that the shell enhances the SiC near band edge luminescence and we argue the formation of a type-I quantum well between the SiC core and the SiO2 shell, with the consequent injection of carriers from the larger band-gap shell to the narrower band-gap core.

Abstract: We report a dynamic and microscopic investigation of electrical stress induced defects in metal-oxide-semiconductor (MOS) devices with high-k gate dielectric by using electron-beam induced current (EBIC) technique. The correlation between time-dependent dielectric breakdown (TDDB) characteristics and EBIC imaging of breakdown sites are found. A systematic study was performed on pre-existing and electrical stress induced defects. Stress-induced defects are related to the formation of electron trapping defects. The origin of pre-existing defects is also discussed in terms of oxygen vacancy model with comparing different gate electrodes.

Abstract: The effect of phonon confinement and impurity doping in silicon nanowires (SiNWs) synthesized by laser ablation were investigated. The diameter of SiNWs was controlled by the synthesis parameters during laser ablation and the subsequent thermal oxidation. Thermal oxidation increases the thickness of the SiNWs’ surface oxide layer, resulting in a decrease in their crystalline Si core diameter. This effect causes a downshift and asymmetric broadening of the Si optical phonon peak due to phonon confinement. Boron doping was also performed during the growth of SiNWs. Local vibrational modes of boron (B) in silicon nanowires (SiNWs) synthesized by laser ablation were observed at about 618 and 640 cm–1 by Raman scattering measurements. Fano broadening due to coupling between discrete optical phonons and the continuum of interband hole excitations was also observed in the Si optical phonon peak. These results prove that B atoms were doped in the SiNWs.

Abstract: We have succeeded in imaging the leakage sites of hafnium silicate gate dielectrics of metal-oxide-semiconductor field-effect transistors (MOSFETs) by using electron-beam-induced current (EBIC) method. Leakage sites of p-channel MOSFETs were identified as bright spots under appropriate reverse bias condition when the electron beam energy is high enough to generate carriers in the silicon substrate. Most of the leakage sites were observed in the peripheries of shallow trench isolation. These results suggest that some process induced defects are the cause of leakage in these MOSFETs. Our observation demonstrates the advantage of EBIC characterization for failure analysis of high-k MOSFETs.