Yoshimitsu Sugita

Measurements on Local Variations in Spacing and Orientation of the Lattice Plane of Silicon Single Crystals by X-Ray Double-Crystal Topography

A method of measuring the local variations in the spacing and the orientation of a lattice plane in a single crystal is reported. The angular positions of diffraction peak at each point of the specimen are measured at four incident azimuths making 90° to each other by a double-crystal spectrometer. This method is applied to two specimens of silicon single crystals doped with arsenic and containing oxygen respectively. The growth striations observed in the two specimens are for the most part due to the variation in lattice spacing. The intensity contrast extended in the long range is due to misorientation.

Shrinkage and annihilation of stacking faults in silicon

Shrinkage and annihilation of oxidation‐induced stacking faults in silicon have been investigated by means of combined methods of successive annealing in nitrogen atmosphere and etching technique. The shrinkage rates were measured and the activation energies for shrinkage were determined to be 4.1 and 4.9 eV for (111) and (100) surfaces, respectively. Experimental results are interpreted in terms of climbing of a Frank loop, indicating that the shrinkage process is governed by a mechanism in connection with the self‐diffusion of silicon. A novel gettering technique is proposed.

Measurement and Analysis of the Static Debye-Waller Factor of Cz-Silicon with Small Oxygen Precipitates

The static Debye-Waller factor and its dependence on the crystal perfection have been obtained through the detailed analysis of the intensity distribution in X-ray diffraction topograph for heat-treated Cz-silicon crystals. The size and density of oxygen precipitates have been determined using the experimental and calculated static Debye-Waller factors and the results of the infrared absorption experiments.

Erratum: Misfit Dislocations in the Bicrystal System of Silicon–Boron-Doped Silicon

Arrangement of atoms at the interface of a bicrystal system with small lattice parameter differences has been investigated through the observation of the creation of misfit or interfacial dislocations. Specimens were prepared by epitaxial deposition of pure-silicon films onto boron-doped silicon substrates. The conditions required to create misfit dislocations were investigated as a function of the film thickness for both cases of thin and thick substrates. The well-defined critical film thickness was found, and smaller values were found for the thick substrate specimens. Results are interpreted in terms of the van der Merwe theory. Effect of heat treatment upon the misfit dislocation distribution was examined. It was observed that dislocations reacted to form networks in a complicated manner. The dislocation climb rate was negligibly small compared to the diffusion length of boron impurity.

Formation of a Stacking Fault-Free Region in Thermally Oxidized Silicon

A stacking fault-free region was found to be formed beneath a Si–SiO2 interface when a silicon crystal was oxidized to generate stacking faults and subsequently annealed in nitrogen atmosphere. This region extends further with prolonged annealing, irrespective of the size and density of the stacking faults already introduced in the crystal. Experimentally it is found that the growth of a stacking fault-free region during annealing follows the equation, d=const. tnexp (-Q/kT) where n and Q are 0.63±0.06 and 4.5±0.6 eV, respectively. The stacking fault nuclei were confirmed to be dissolved after annealing of oxidized crystals.

Distribution and Character of Misfit Dislocations in Homoepitaxial Silicon Crystals

Misfit dislocations generated by the lattice mismatch between the epitaxially grown film and the (111) silicon substrate have been studied mainly through transmission electron microscopy to reveal their distribution, character and interaction. The dislocations were found only in the thin layer of a few microns near the interface. Their maximum density was located at depth near the maximum concentration gradient in the boron distribution caused by interdiffusion from the substrate to the film. The dislocations extended from one edge of the crystal to the other in the samples with the film thickness close to the critical value required to generate misfit dislocations. With increasing film thickness they reacted each other to form networks, curved and inclined ones. The structure of dislocation networks resulting from the interaction between intersecting dislocations was examined.

Measurement of the Static Debye-Waller Factor of Silicon Crystals by the Pendellösung Fringe Method

The static Debye-Waiter factor of Czochralski-grown silicon crystals heat-treated at a high temperature has been measured by X-ray section topography. The static Debye-Waiter factor was determined through the variations in the Pendellosung fringes in a topograph. The measured static Debye-Waiter factor was proportional to the square of the scattering vector used, as expected from the theory. From an analysis of the experimental results the average size of the micro-defects formed by the heat treatment could be estimated.

X-Ray Observations of Defect Structures in Silicon Crystals

The structure of defects in silicon crystals, which causes X-ray double images, was studied in detail by the X-ray diffraction topography and the etching technique. Generation of these defects was found to be closely related to growing conditions of the crystal, particularly to the condition of hydrogen gas flow used as an ambient. A pair of parallel etch pit arrays was observed on an etched surface and was confirmed to have one-to-one correspondence to the double image. When a specimen was annealed in the range from 700°C to 1000°C, the double image showed fine structures, which could be only observed by using softer radiation, CuKα1. Two types of dislocation loops were generated from the defect corresponding to the double image when a specimen was annealed at 1200°C. The origin and the mechanism of formation of the defect was discussed.

Grown-in Microdefects in a Slowly Grown Czochralski Silicon Crystal Observed by Synchrotron Radiation Topography

Grown-in microdefects of a slowly grown Czochralski (CZ) silicon crystal were studied by short wavelength synchrotron radiation topography and successfully visualized. It was shown that the microdefects had spherical strain fields, by comparing the defect images in the two topographs taken with the Bragg reflections perpendicular and parallel to the growth direction. The radial distributions of the microdefect size and density were measured from the defect images in the topographs. The misfit volume of the microdefects was approximately 1 ×10-12 cm3 at the central axis region of the crystal ingot, and decreased monotonically toward the peripheral region of the crystal. The density of the microdefects was approximately 300/cm3 at the center of the crystal, increased toward the periphery and then decreased rapidly to almost zero in the very peripheral region approximately 7 mm from the surface of the crystal ingot. These radial distributions are discussed in connection with the self-interstitial atoms of silicon crystals.

Misfit dislocations in (110), (112), and (113) homoepitaxial silicon crystals

Misfit dislocations generated in (110), (112), and (113) silicon p‐on‐p+ epitaxial wafers are investigated through x‐ray topography. Dislocations observed are of mixed type and arranged along the intersection of the four {111} planes with the specimen surface. The dislocations are formed by slip to relieve the interfacial shear resulting from the misfit.