Inhomogeneous Distributuon of Dislocations in Phosphorus-Diffused Silicon

Abstract

CZ-silicon wafers subjected to phosphorus diffusion to a relatively deep diffusion depth (X j=8 µm, C s=1020 cm-3) using a POCl3 source are examined both by X-ray topography and by transmission electron microscopy. The diffusion corresponds to that for the formation of the emitter of the usual silicon power transistors. Diffusion-induced dislocations are inhomogeneously distributed, forming dislocation clusters about 50 µm wide at a depth of 4–6 µm. In the cluster, the maximum dislocation density is as high as 109 cm-2 at a depth of 4 µm and some dislocations reach the diffusion depth. Between the clusters, there are dislocation networks of relatively low density. The deep penetration of dislocations is attributed to the formation of the clusters.