Effect Of Rapid Thermal Processing On Oxygen Precipitation Behavior In Large Diameter Czochralski Silicon

In recent years, rapid thermal processing (RTP) has been employed in the manufacturing and research of Czochralski (CZ) silicon wafer. MEMC Electronic Materials, Inc., a worldwide famous silicon wafer manufacturer, has developed a so-called 'Magic Denuded Zone (MDZ)' process based on RTP. The main idea underlying the MDZ process 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 MDZ process initiates a fundamental problem that how the vacancy affects the oxygen precipitation in CZ silicon, which has been addressed in this thesis. Thorough a series of investigation, the following conclusions have been derived.As for the standard two-step anneal of 800℃/4h +1000℃/16h used in the MDZ process, the RTP-introduced vacancies are involved in the formation of oxygen precipitate nuclei during the low temperature anneal and, therefore, enhancing the oxygen precipitation during the subsequent high temperature anneal; the amounts of precipitated oxygen in the samples were positively in proportional to the RTP temperature.During the single-step high temperature (1050℃) anneal, the RTP-induced vacancies significantly enhance the early stage oxygen precipitation in terms of precipitation rate, but do not increase the amount of precipitated oxygen in the CZ silicon wafer subjected to prolonged anneal. It was found that after lengthy anneal at 1050℃ the silicon wafer with prior RTP treatment had relatively lower density of BMDs than the one without prior RTP treatment, the reason for which is that the prior RTP treatment had dissolved a part of grown-in oxygen precipitates that are the nuclei of oxygen precipitation occurring at 1050℃.Through investigating the effects of RTP-induced vacancies on the oxygen precipitation in CZ silicon wafers subjected to lengthy anneals at 650℃,750℃,850℃and 950℃, it is revealed that the vacancies significantly foster the nucleation of oxygen precipitation occurring at the above-mentioned temperatures.Moreover, it has been found that the RTP at high temperatures has superior capability to dissolve the oxygen precipitates existing in the CZ silicon wafer, implying that the dissolution of oxygen precipitates is primarily determined by the anneal temperature, not like the case of oxygen precipitation that is dependent on both anneal temperature and time.