Study On The Flow Pattern Defects (FPDs) In The CZ Silicon Crystals

In this paper, the flow pattern defects (FPDs) were revealed by Secco etchant and their shape, distribution on wafer and tip structure were studied in details by optical microscope and atomic force microscope (AFM). The relationship between etching time and the tip structure of FPDs was also discussed. Furthermore, by studying the effect of rapid thermal annealing (RTA) on the density of FPDs in Ar, the annihilation mechanism of FPDs was discussed in this paper.The void trait of FPDs was discovered for the first time. The study results obtained by AFM suggest that the flow pattern defects were revealed as having wedge shape and there were small octahedron voids surrounded by {111} which were the same as COPs and LSTDs planes were observed at the tips of flow pattern defects. Moreover, the octahedron voids would change to shallow orbicular pits and vanished at last if the etching time was prolonged. Our results were contrasted to the result that the FPDs are interstitial type defects concluded by Takeno et al and support the views that the FPDs are vacancy-type defects.In addition, the effect of rapid thermal annealing (RTA) on the FPDs density and the annihilation mechanism of FPDs were also studied in this paper. The RTA results suggest FPD was very stable under 1100 C but above 1100 C, the FPD density was decreased deeply by the RTA processing, and the longer the annealing time was, the lower the FPD density was. The annihilation of the octahedron voids at the tips of FPDs was divided two processes: (1) The oxide on the void was removed by the out-diffusion of Oi in the shallow region , especially the Oi aroud the void and by the entry of the interstitial Si atomics .(2) The void without oxide shrinked by emitting vacances and the migration of silicon atoms from edge to the bottom of void.