Oxygen Precipitation Behaviors In Heavily Antimony-doped Czochralski Silicon

Heavily antimony(Sb) -doped Czochralksi silicon(CZ-Si) wafers have long been employed as the substrates for the epitaxial silicon wafers.The internal getteing (IG) capability of silicon epitaxial wafers is substantially dependent on oxygen precipitation(OP) in the substrate wafers.Consequently,it is worthwhile to investigate OP in the heavily Sb-doped Cz-Si.It has been well known that OP is suppressed in the heavily Sb-doped CZ-Si.Nevertheless,the knowledge of OP for the heavily Sb-doped CZ-Si is far much less than that for the lightly doped counterpart.In this thesis,the OP behaviors the heavily Sb-doped CZ silicon subjected to different anneals have been investigated by means of second ion mass spectroscopy(SIMS),scanning infrared microscopy(SIRM) as well as the preferential etching in combination with optical microscopy(OM).The primary results are described in the following.The OP behaviors in the lightly P-doped and heavily Sb-doped CZ-Si wafers of different oxygen concentrations([O]s) subjected to the two-step annealing successively at low and high temperatures have comparatively investigated.Low temperature annealing effect on OP in heavily Sb-doped CZ-Si was clarified.It is found that:(1) the oxygen precipitate nucleation for a short period of time at low temperatures in the heavily Sb-doped CZ-Si is notably suppressed,(2) the oxygen precipitate nucleation for a long period of time at 650℃is nearly not suppressed while that at 450℃or 750℃is still significantly suppressed in the heavily Sb-doped CZ-Si of high initial[O],(3) the oxygen precipitate nucleation in the heavily Sb-doped CZ-Si of low initial[O]is always suppressed irrespective of the annealing time at low temperatures.It is supposed that quite a number of Sb-V-O complexes can be formed at 650℃,which act as the heterogeneous centers for the oxygen precipitate nucleation.While,the Sb-V-O complexes are too few at 450℃and they are unstable at 750℃.In this context,the oxygen precipitation nucleation is still suppressed.For the heavily Sb-doped CZ-Si of low initial[O],the supersaturation of oxygen is too small to enable oxygen precipitate nucleation.The formation process of grown-in oxygen precipitates in the heavily Sb-doped CZ-Si on oxygen precipitate nucleation has been investigated.It is indicated that the grown-in oxygen precipitates are most likely formed between 800～650℃during the cooling process of post-crystal-growth.Moreover,their sizes are between the critical sizes for OP at 600℃and that at 700℃.The influence of rapid thermal processing(RTP) on OP in heavily Sb-doped CZ-Si wafers has been investigated.It is revealed that RTP enhances oxygen precipitation at 450-1000℃.Such an enhancement effect at 450-800℃is due to the increased concentration of Sb-V-O complexes that act as the heterogeneous nucleation centers,while that at 1000℃is ascribed to the formation of VO₂ complexes that are precusors of oxygen precipitates.