Kazufumi Sakai

A three-dimensional study of dislocation lines in an in-doped GaAs crystal by layer-by-layer tomography

Abstract A three-dimensional observation of dislocation lines in an indium-doped GaAs is performed using IR light scattering tomography. The shapes of the dislocation lines are compared with those observed by X-ray topography and wide IR beam imaging, and some misunderstandings of previous observations are clearly revealed by the layer-by-layer tomography.

A study on defects in a ZnSxSe1−x crystal by Raman scattering tomography

Raman spectra of ZnSxSe1−x mixed crystals were measured as a function of x (x<0.1) where the Raman peak of the ZnS-like mode was clearly observed near 300 cm-1. Raman scattering tomography was applied for these crystals to analyze two- and three-dimensional homogeneity. Fluctuation of the ZnS composition parallel to the growth plane (110) was found. The microscopic uniformity of the ZnS composition was analyzed using tomographic images and the composition of ZnS was found to have a tendency to swarm.

A Proposal for Measurement of Implanted Ion Dose in Semiconductor Wafers by IR Light Scattering Technique

It was confirmed here that the IR light scattering caused by ion-implanted regions of GaAs wafers was inversely proportional to the 4th power of the IR wavelength. The scattering power was increased with an increase in implanted ion dose when the acceleration voltage of the ions was kept constant, and the scattering was also increased with an increase in the voltage. From this evidence, tracks of the high energy ion particles, where atomic arrangement is locally disordered from the regular positions of atoms by collisions with the ions, act as Rayleigh scatterers, while the deformed volume of ion tracks is dependent upon the energy and species of implanted ions. Therefore, a new ion dose indicator will be designed using this principle for an in situ dose measurement of an implanter under operation.

Fourier-transformed light-scattering tomography for determination of scatterer shapes

The diffraction patterns due to light scattering from precipitates in Si crystals annealed at for 6 - 18 h or at for 8 - 64 h following pre-annealing at for 4 h were observed at a de-focus position using light-scattering tomography (LST) apparatus. The patterns clearly differed from one another and every image at a focus position was a small point. The diffraction patterns obtained at a position deviating by from the focus position were transformed into an image by Fourier analysis in terms of Fresnel diffraction using tentative phase data. The process is similar to the process of X-ray structural analysis. A good similarity between the images observed here and images from transmission electron microscopy (TEM) was obtained.

Study on the Light Scattering Mechanism at Precipitates on Dislocation Lines in an Indium Doped GaAs Crystal

The light intensities scattered from the precipitates on dislocations in an In-doped GaAs crystal were measured as a function of the temperature with three different frequencies of lasers. The scattered intensity showed a few peaks from 30 K to 260 K depending upon the wave length of the incident beams. The temperature dependence of resonance frequencies was obtained by Ogawas resonance scattering model (R.S.M.) and compared with the experimental result.

Detection Limit for Defect Density by Light Scattering Tomography

We obtained simulation images by light scattering tomography at various bulk-microdefect densities, and studied the effect of parameters on the detection limit in light scattering tomography measurements. We found that the detection limit is mainly attributable to the numerical aperture of the objective lens, incident beam width and threshold level, and for standard light scattering tomography equipment, the detection limit is about 1011 cm-3.

Measurement of stress distribution inside crystals by multi-channel Raman scattering tomography

We have developed the method of obtaining distribution of the stress in the crystal by using a multi channel Raman scattering apparatus. It is difficult to obtain the presence of the stress from the amount of the Raman shift because it is small though the Raman-spectrum shifts by the stress. We have shown that the Raman intensity ratio on both sides (± a few cm−1) of the center wave number of the Raman spectrum was sensitive in the peak wave number shift. We developed an apparatus which measured the intensity distribution on both sides of the peak at the same time, and obtained intensity ratio distribution. The stress distribution in the neighborhood of a dislocation wall in the ZnSe crystal was obtained as an example of applying this method.

A three-body calculation for collision-induced dissociation

Abstract A formulation of the distorted-wave Born approximation for the dissociative reaction A + BC → A + B + C is obtained using the T-matrix representation. The computational procedures for obtaining the cross section are presented. Numerical values of the Ar + H 2 → Ar + H + H reaction are calculated with the analytic potential surface BC 3 (6,8) when the total energies of the system are 0.3, 0.5, 1.0 and 1.2 eV. Present results are compared with those of a Monte Carlo trajectory study and the available-energy hard-sphere model. The cross sections of the reaction for the initial diatomic state ν = 4 and ν = 6 j = 0 are much smaller than those obtained from quasi-classical trajectory (ACT) calculations, but those for the initial state ν = 10 and ν = 14 j = 0 are close to the cross sections calculated from QCT. We also calculated the rate constants for the initial state ν = 4 j = 0 at six different temperatures. The rate constant of the present calculation at temperature T = 4500 K is about a half of that obtained from QCT.

Origin of light scattering variations of a latent flaw through light scattering measurement with applied stress effect

The stress-induced light scattering method (SILSM) was proposed for inspecting surface to detect polishing induced latent flaws. In this study, in order to clarify the mechanism of the light scattering intensity variation of latent flaws using SILSM, we have investigated stress effect of light scattering intensities using polarized light system and calculated the reflectance and the retardation using Jones matrix. As the results, we evaluated the change in the birefringence around a tip of a latent flaw between before and after stress were applied.

Change in shape of oxygen precipitate grown by thermal annealing

The shape of the oxygen precipitate in Si wafers generated by thermal annealing takes various forms depending on thermal annealing time and temperature. In this experiment, we observed, in detail, the shape of the oxygen precipitate in a Cz-Si sample after two-step annealing at different thermal annealing times by transmission electron microscopy (TEM). We found that the precipitate shape changed from octahedral to polyhedral to octahedral. Moreover, a lot of punch-out dislocations were generated with this change. This shape change was considered from the viewpoint of thermodynamics.