Papers by Author: Makoto Yamaguchi

Abstract: Raman spectroscopic study is carried on the Vickers indented area on the surface of a single crystal silicon carbide (4H- and 6H-SiC) as a nondestructive structure probe to investigate a residual stress and crystal structure. LO phonon frequency shifts and the broad and weak bands around LO phonon band were observed. The residual strain field around the indentation is discussed.

Abstract: We carried out cross-sectional transmission electron microscopy (TEM) investigation of femtosecond laser-induced ripples formed on 4H-SiC single crystal surface. Here, we paid attention to the crystal structures underlying the coarse and fine ripples and the three-dimensional distribution of amorphous phase. Conventional and high-resolution TEM analyses made clear that a continuous amorphous layer approximately of 50 nm thick exist at the topmost region of both coarse and fine ripples. The result strongly suggests that the fundamental surface deformation process is common for coarse and fine ripples, even though the factors which determine their periods are different.

Abstract: In this paper, the surface and subsurface of silicon wafers ground by different wheels have been studied. In the conventional grinding with diamond wheels, it is shown from the top that the subsurface of wafer consists of amorphous Si, followed by a thin damaged layer, strained crystal with a large compressive residue stress, and then the bulk material in single crystal. In a severe condition which causes grinding burn, part of amorphous Si is re-crystallized to form a poly-crystal Si, and part of amorphous Si possibly reacts with oxygen to form SiO2. This phenomenon becomes more pronounced in the backgrinding process with a fine grit diamond wheel when the conditions are improperly selected. In order to obtain a defect-free crystal Si structure in grinding, authors have proposed a new chemo-mechanical grinding (CMG) process which enables to remove Si from wafer but with no structure transformation induced to its surface.