Study of the influence of oxygen on structural perfection of silicon single crystals by high-resolution X-ray diffraction and infrared absorption measurements

摘要

High-resolution X-ray diffractometry, absolute integrated intensity (rho) measurements, diffuse X-ray scattering (DXS) and infrared (IR) absorption techniques were used to investigate the influence of oxygen on the structural perfection of high purity (resistivity of the order of 4 k Omega cm) float zone (FZ) grown (111) silicon single crystals. A multicrystal diffractometer set in (+, -, -, +) geometry, with Mo K alpha(1) radiation, was employed. From the infrared measurements, the oxygen concentration in the sample was determined to be 1.3 x 10(17) atoms cm(-3). High-resolution X-ray diffraction curves of the as-grown crystal had half-widths of similar to 11 arcsec; the rho value was 3.5 x 10(-5) rad. To incorporate oxygen in a controlled manner into the specimens, they were annealed under dry oxygen ambient for 8 h in the temperature range 573-1373 K tin eight steps). Up to 723 K there was no appreciable change in oxygen content or in the: degree of perfection. Annealing at temperatures (A(T)) > 873 K resulted in considerable increases in the oxygen content, as well as significant improvements in the degree of perfection. For example, as the level of oxygen increased from 1.3 x 10(17) to 3.6 x 10(17) atoms cm(-3) for A(T) = 873 K, the values of half-widths and rho decreased to similar to 7 arcsec and 2.4 x 10(-5) rad, respectively. However, annealing above 1273 K produced deterioration in lattice perfection. DXS measurements showed remarkable changes in the nature of point defects and their clusters with change in A(T). Up to A(T) = 973 K, the defects were predominantly vacancy clusters. However, with A(T) in the range 1073-1273 K, the predominent defects were isolated interstitials. Further increase in A(T) led to interstitial cluster formation, which deteriorated the lattice perfection. This study clearly demonstrates that oxygen concentration in the range similar to 3 x 10(17) to 13 x 10(17) atoms cm(-3) leads to significant improvement in structural perfection of silicon single crystals. [References: 26]