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Recent Progress in X-ray Topography for Silicon Materials

The present paper reviews recent synchrotron x-ray topographic studies on minute fluctuations of impurity- and point-defect concentration in CZ and FZ silicon crystals, and studies on microdefects such as oxygen precipitates and dislocation clusters in CZ silicon crystals. Plane wave x-ray topography enables us to determine the degree of strain with a sensitivity of 108 and to clarify the relationship between oxygen-concentration fluctuation and lattice-spacing variation. Ultra-plane wave x-ray topography and Lang topography using high-order reflection of high-energy x-rays give some information about microdefects, but the identification of defect images is not easy. The possibility of topographic observation of nearly strain-free microdefects such as octahedral voids in as-grown CZ crystals is briefly discussed.