Seigô Kishino

Thermally Induced Microdefects in Czochralski-Grown Silicon: Nucleation and Growth Behavior

The current understanding of thermally induced microdefects in Czochralski-grown silicon crystals is briefly reviewed and our investigations of the defects are described. The microdefects originate in oxygen precipitation occurring during thermal treatments after crystal growth. Both homogeneous and heterogeneous nucleation models have been proposed for the oxygen precipitation. The homogeneous nucleation model is contradicted because a low density of microdefects are induced in recent high-quality crystals even at high oxygen concentrations. A heterogeneous nucleation model is proposed, based on detailed investigations of the thermal behaviors of microdefects. It is demonstrated that the oxygen precipitation is governed by nucleation sites (carbon atoms) and the thermal history of wafers after crystal growth besides the oxygen concentration of the wafer.

Theoretical Considerations on Bragg-case Diffraction of X-rays at a Small Glancing Angle

X-ray diffraction phenomenon, for which the glancing angle of the incident beam is so small that the effect of specular reflection can not be neglected, is studied theoretically. Two wave fields, one of which is usually neglected, are considered as the solution of the dispersion equation, and the boundary conditions of the waves are considered for the gradient of amplitude normal to the surface besides the amplitude. Numerical calculations are made for (220) reflection of CuKα1 from a germanium single crystal. The diffracted beam is stronger in intensity and broader in half-value width than that where specular reflection is not considered.

A study on thermally induced microdefects in czochralski-grown silicon crystals: Dependence on annealing temperature and starting materials.

Thermally induced microdefects in Czochralski-grown (CZ) silicon crystals have been investigated by both TEM and IR absorption techniques. Dependence of the defect behavior on both the annealing temperature and the starting materials was studied. It was found that the defect nature varies with the temperature, and that the defect density increases exponentially with the decrease of the annealing temperature. The increase in density also has a strong correlation with the initial carbon concentration in the wafer. It is concluded that the oxygen precipitates are heterogeneously formed at sites which have certain correlation with carbon atoms.

Anomalous Enhancement of Transmitted Intensity in Asymmetric Diffraction of X-Rays from a Single Crystal

A theoretical and experimental study has been made on the anomalous transmission of X-rays in the Laue-case diffraction of nearly perfect crystals with a special reference to the asymmetric diffraction. For the theoretical analysis the dispersion equation has been solved to an approximation higher than that usually used, because the usual two-wave approximation is rather poor in the extremely asymmetric case of diffraction. The theoretical analysis shows that the intensity of the anomalously transmitted wave increases with the asymmetry of diffraction and reaches 42% of the incident intensity when \(\mu{\cdot}\textbf{\itshape t}{\fallingdotseq}10\). These facts have been confirmed experimentally with the use of the parallel setting of the double-crystal arrangement, in which (220) diffraction of Si is used with CrK α1 .

X‐ray topographic study of dark‐spot defects in GaAs‐Ga1−xAlxAs double‐heterostructure wafers

Dark‐spot defects (DSD) in a GaAs‐Ga1−xAlxAs double‐heterostructure (DH) wafer are studied by x‐ray topography. Such DSD’s are one of the primary sources of the dark‐line defects (DLD) that cause rapid degradation of GaAs‐Ga1−xAlxAs DH lasers. By using x‐ray topography almost all DSD’s observed by photoluminescence topography are correlated with dislocations in a GaAs substrate. In addition, it is observed that some dislocations in the substrate are not sources of DSD’s when the dislocation axes are nearly parallel to the surface of the substrate.

A high-speed X-ray topography camera for use with synchrotron radiation at the photon factory

Abstract A detailed description of the high-speed X-ray topography camera designed for the vertical wiggler beam line at the Photon Factory is presented. The camera has been successfully operated with a white beam from a normal dipole magnet beam line since June 1982. The flexibility of the camera is sufficiently large to meet various user requirements. Some of its characteristic features are as follows: it has two TV detector arms providing a view coverage of 50° upwards and 30° downwards from the horizontal plane. The goniometer can support a load of 30 kg, to mount specimen environmental conditioners such as magnets and cryostats, while it can rotate with a precision of 2″ of arc over a full circle. The entire camera is placed on a special movable carriage to enable a simple and rapid interchange between a white beam outlet and a monochromatic one. Some 20 different samples and more than 20 people were involved both in commissioning the instrument and in the preliminary experiments, using about 900 h of machine time.

Suppression of oxidation‐stacking‐fault generation by preannealing in N2 atmosphere

Suppression of oxidation‐stacking‐fault (OSF) generation is studied by x‐ray section topography, etching technique, and transmission electron microscopy (TEM). Microdefects (MD’s) are generated in bulk Si during N2 atmosphere annealing at about 1000–1100 °C, and their generation is confined to the inner part of the Si wafer. These MD’s grow rapidly during subsequent oxidation. The grown MD’s contribute to stacking faults (SF’s) in the inner part of bulk Si. On the contrary, surface OSF’s are not introduced by the subsequent oxidation because no MD’s are generated in the surface layer by the preannealing. The suppression effect of OSF generation by N2 atmosphere preannealing is demonstrated using several samples.

Lattice mismatch and crystal system in epitaxial garnet films

Abstract The inclination and spacing of the net planes were separately measured with high accuracy by the X-ray double crystal method for garnet films epitaxially grown on (111) gadolinium gallium garnet substrates. The apparent symmetry of the epitaxial garnet films was shown to the rhombohedral. The difference in lattice spacing between the film and the substrate was maximum in the case of the (111) net plane parallel to the growth surface. These facts are probably due to an elastic deformation induced by the lattice mismatch.

Growth and propagation mechanism of 〈110〉‐oriented dark‐line defects in GaAs‐Ga1−xAlxAs double heterostructure crystals

Application of external stress on a double heterostructure (DH) crystal is used to induce 〈110〉‐oriented dark‐line defects (DLD). The stress is applied by using a four‐point mechanical bending apparatus. Resulting DLD formation is found to depend on stress direction and DH crystal orientation. This asymmetric DLD introduction can be explained by the difference in glide motion between α and β dislocations. It is shown that a threshold stress exists for the DLD formation. This threshold stress and the growth velocity of the DLD’s strongly depend on optical pump intensity. Extension of the DLD’s into the ternary passive layers is observed by x‐ray topography and phase‐contrast microscopy. This observation suggests that stresses caused by local heating at the site of a defect play an important role in inducing 〈110〉 DLD’s. These experimental results lead to the conclusion that dislocation glide processes are responsible for 〈110〉‐DLD propagation.

Heavy Metal Gettering by an Intrinsic Gettering Technique Using Microdefects in Czochralski-Grown Silicon Wafers

The ability of an intrinsic gettering (IG) using microdefects in Czochralski silicon wafers is verified on copper diffused wafers with the help of a neutron activation analysis (NAA). The IG technique used here is an improved double preannealing technique. It is ascertained that the copper concentration is enhanced in the bulk region where a high density of microdefects were induced. Moreover, the concentration in the denuded zone near the surface is proved to be below the detection limit of the NAA technique.