EFFECT OF POINT-DEFECT REACTIONS ON BEHAVIOR OF BORON AND OXYGEN IN DEGENERATELY DOPED CZOCHRALSKI SILICON

The behavior of boron and oxygen in degenerately doped Czochralski silicon has been studied after an extended annealing at temperatures ranging between 750 and 900-degrees-C in nitrogen ambient. The results from secondary ion mass analysis show an accumulation of boron atoms near the silicon surface while oxygen outdiffusion appears to be significantly retarded. Based upon the defect morphology examined using high resolution electron microscopy, it is concluded that degenerate silicon is saturated with interstitial defect species during an extended annealing. From the point defect reaction and dynamic clustering models, an accumulation of boron near the silicon surface is hypothesized to be due to boron outdiffusion which may be driven by the difference in chemical potential of boron saturation between the bulk and surface regions. A retardation of oxygen diffusion, on the other hand, may be caused by a strong pairing reaction between boron and oxygen atoms.