Papers by Author: Akira Sakai

Abstract: Using X-ray microdiffraction (XRMD) and transmission electron microscopy (TEM) techniques, we have investigated the microscopic structure of Si(011)/Si(001) direct silicon bonding (DSB) substrates. XRMD was performed to measure the local lattice spacing and tilting in the samples before and after oxide out-diffusion annealing. Diffraction analyses for (022) lattice planes with two orthogonal in-plane directions of X-ray incidence revealed anisotropic domain textures in the Si(011) layer. Such anisotropy was also confirmed by TEM in the morphology at the Si(011)/Si(001) bonded interface. The anisotropic crystallinity is discussed on the basis of interfacial defect structures which are proper to the DSB substrate.

Abstract: The use of Si(011)/Si(001) direct silicon bonding (DSB) substrates is a key element of future complementary metal-oxide-semiconductor device technology. In the conventional bonding process, it is necessary to remove interfacial SiO2 to achieve direct atomic bonding. In this study, using X-ray microdiffraction and transmission electron microscopy, we investigate the structural changes caused by oxide out-diffusion annealing (ODA). It is revealed that crystallinity of the bonded Si(011) layer is degraded after low temperature ODA and gradually recovered with an increase in the ODA temperature and annealing time, which is well correlated with the interfacial SiO₂/Si morphology. Characteristic domain textures depending on the ODA temperature are also detected.

Abstract: We have investigated the growth and crystalline structures of Ge1-xSnx buffer and tensile-strained Ge layers for future use in CMOS technology. We have demonstrated that strain relaxed Ge1-xSnx layers with an Sn content of 12.3% and 9.2% can be grown on Ge and Si substrates, respectively. We achieved a tensile-strain value of 0.71 % in Ge layers on a Ge0.932Sn0.068 buffer layer. We have also investigated the effects of Sn incorporation into Ge on the electrical properties of Ge1-xSnx heteroepitaxial layers.

Abstract: We have developed new microdiffraction system at the SPring-8. This system uses a focused beam produced using a phase zone plate combined with a narrow slit, which makes a small focused beam that has a small angular divergence. Furthermore, we can use the two-dimensional x-ray CCD detector, which enable us to measure local reciprocal space maps at many points in a sample, that is, the distribution of strain fields and lattice tilts can be revealed in high-angular- and high-spatial-resolution.