Enhancement of oxygen precipitation in Czochralski silicon wafers by high-temperature anneals

The effect of the prior conventional furnace anneal at 1250 deg. C with different cooling rates on oxygen precipitation in Czochralski silicon during the subsequent low-high two-step heat treatment was investigated. In comparison with oxygen precipitation in the as-received sample, that in the samples with the prior 1250 deg. C anneal with fast or slow cooling rate was significantly enhanced. It is believed that the prior 1250 deg. C anneal with fast cooling rate introduced a considerable amount of vacancies, thus enhancing oxygen precipitation in the subsequent anneal; while, that with slow cooling rate substantially removed the silicon interstitials generated during the formation of grow-in oxygen precipitates, thus eliminating the retard effect on oxygen precipitation in the subsequent anneal