Effect Of Vacancy On Nucleation For Oxygen Precipitation In Czochralski Silicon

Rapid thermal processing(RTP)has been extensively employed in the fabrication of integrated circuits.In recent decade,MEMC company in America,a worldwide leading silicon wafer supplier,has presented a so-called "magic denuded zone"(MDZ^?)technology based on RTP,the basic idea behind which is to enable the oxygen precipitation in CZ silicon wafer to be controlled by an RTP-created vacancy profile with the vacancy concentration increasing from the surface to bulk of wafer,thus forming a denuded zone above the region of high density bulk micro-defects(BMDs).The fundamental issue associated with this novel technology is how the vacancy affects oxygen precipitation in Czochralski(CZ)silicon.In this thesis,the nucleation of oxygen precipitates in CZ silicon subjected to the ramping anneal in different low temperature ranges following the RTP at elevated temperature has been investigated in order to reveal the temperature range in which the vacancy exerts significant effect on the nucleation of oxygen precipitates.In the following,the primary results achieved in this thesis are described.The oxygen precipitation behaviors in conventional and nitrogen-doped Czochralski (NCZ)silicon subjected to the RTP at 1250℃for 50s followed by the ramping anneal in the different temperature intervals in the range of 600-1000℃and isothermal annealing at 1000℃have been investigated.It was shown that the RTP-induced vacancies enhanced the nucleation of oxygen precipitates most significantly during the ramping anneal in 700-800℃for conventional CZ silicon,while,the most significant vacancy-enhancement of nucleation of oxygen precipitates occurs during the ramping anneal in 800-900℃.Moreover,it was found that nitrogen was superior to vacancy for enhancement of oxygen precipitates nucleation at temperatures higher than 800℃.Furthermore,the internal gettering processes appropriate for CZ and NCZ silicon wafers based on the RTP and ramping anneal in the low temperature range were proposed.The oxygen precipitation behaviors in heavily boron-doped and heavily arsenic-doped CZ silicon subjected to the RTP at 1250℃for 50s followed by the ramping anneal in the different temperature intervals in the range of 600-1000℃and isothermal annealing at 1000℃have been investigated.Regarding the heavily boron-doped CZ silicon,the RTP-induced vacancies enhance the nucleation of oxygen precipitates in the temperature range of 800-900℃because they facilitate the formation of B-O complexes that act as the heterogeneous nucleation centers, while,at low temperatures,the vacancies do not exhibit enhancement role in the formation of oxygen precipitate nuclei.In the case of heavily arsenic-doped CZ silicon,the RTP-induced neutral vacancies significantly enhance the nucleation of oxygen precipitates in the temperature range of 600-800℃,which is likely due to that the neutral vacancies promote the arsenic-charged vacancy-oxygen complexes to grow up to be oxygen precipitate nulei;whereas, the RTP-induced neutral vacancies do not facilitate the nucleation of oxygen precipitates at high temperatures.