A numerical study of oxygen precipitation in CZ-silicon: LO-HI and CMOS-type thermal cycles

Control of oxygen precipitation is important for increasing the yield in ULSI-processing. In the present work, computer modeling is used to investigate the formation of oxygen precipitates during double-step (LO-HI) and multi-step CMOS-type thermal anneals. The calculations agree well with a large number of experimental results. The proposed model is used to investigate the influence of processing parameters such as initial oxygen content, annealing temperature and time, and the thermal history of wafers on the amount of precipitation observed. The model is also used to determine 2-step and 3-step substitutional anneals showing precipitation behavior similar to that of a multi-step CMOS-type anneal. It is concluded that application of the computer model offers the potential of reducing both time and costs for the development of shorter substitutional thermal processes, which are necessary for routine testing of the precipitation behavior of wafers used in multi-step device processing.<
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