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 (700 °C anneal+1000 °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 700 °C, but no enhancement effects during the second step anneal at 1000 °C.