Masanobu Ogino

Suppression effect upon oxygen precipitation in silicon by carbon for a two‐step thermal anneal

The suppression effect on oxygen precipitation by carbon was observed under a certain heat treatment condition. The amount of precipitate oxygen in a high carbon silicon crystal is less than that in a low carbon silicon crystal, when silicon crystals are heat treated by the two‐step thermal anneal (700u2009°C anneal+1000u2009°C anneal), whose first step annealing time is long. This is caused by the generation of too many precipitate nuclei during the first step thermal anneal. Growth rate for small precipitates is retarded. Carbon has the enhancement effect on oxygen precipitation during the first step anneal at 700u2009°C, but no enhancement effects during the second step anneal at 1000u2009°C.

Embryo formation during crystal growth

Abstract Oxygen precipitation in CZ silicon crystal depends on the existence of an ambryo. During crystal growth embryos are assumed to form at carbon atoms. We simulated the embryo formation based upon a thermally-activated heterogeneous nucleation model. Results for the case of an isothermal pre-anneal agree with experiment for homogenized wafers with various carbon content. Results for the cooling process during crystal growth indicate that the thermal history during tailing and slow cooling determine embryo formation in a large part of a silicon crystal with a larger diameter and reduced carbon content.