Study of point defect clusters in high purity single crystals of silicon grown by Czochralski and float-zone methods by diffuse X-ray scattering technique

Abstract

Results of study of point defect clusters in high purity ( ∼ 10 kΩ · cm ) dislocation-free Czochralski (Cz) and float-zone (FZ) grown crystals (∼ 50 mm diameter, 11 mm thick, p-type) are reported. A multicrystal X-ray diffractometer set in (+, −, −, +) geometry and employing a well-collimated Mo K α 1 beam was used. High resolution X-ray diffractometry, absolute integrated intensity measurements and diffuse X-ray scattering (DXS) measurements were carried out. The specimens gave sharp diffraction curves and the integrated intensities were found to be close to the theoretical value for an ideally perfect silicon crystal. DXS measurements were made around 111 reciprocal lattice point (RLP) along four directions of K ∗ : [111], [1̄1̄1̄], [01̄1] and [011̄]. K ∗ is the vector which connects the elemental reciprocal volume under investigation with the nearest RLP. From the analysis of the DXS intensity versus K ∗ plots, it was found that the source of DXS is interstitial defect clusters in Cz-grown crystals and vacancy defect clusters in FZ-grown crystals. By using a phenomenological model, the values of cluster size R cl, cluster volume A cl and number of defects per cluster N cl, respectively, were found to be: 0.8 μm, 2.02 × 10 −16 cm 3, 1.26 × 10 6 for Cz specimen and 0.6 μm, 1.32 × 10 −16 cm 3, 8.3 × 10 5 for the FZ specimen.