A Dopant Cluster in a Highly Antimony Doped Silicon Crystal

A dopant cluster consisting of two antimony atoms facing each other in a six-member ring was found in the silicon crystals of a dopant concentration of 5×1020 cm-3, slightly above the critical value for generating electrically deactivated clusters. This cluster was detected with a 50-pm-resolution aberration corrected scanning transmission electron microscope. A large angle convergent beam, 30 mrad in semi-angle, yields section images with an improved depth of field of about 2 nm. The dopant clusters were discriminated from isolated antimony atoms by statistical analysis of image intensity. These clusters can cause electrical deactivation at critical dopant concentration.