The impact of Ge codoping on grown-in O precipitates in Ga-doped Czochralski-silicon

The intensity of the infrared absorption band at 1107 cm^-1, related to interstitial oxygen (O_i) concentration, decreased as the Ge concentration increased in Ga and Ge codoped CZSi crystals. In contrast, the number of precipitates observed on the etched surfaces of CZSi wafers increased as the Ge concentration increased. From an energy dispersive X-ray (EDX) analysis, O was observed to be one of the major components of the precipitates. Moreover, Ge was found as one of the components in the precipitate observed on the heavily Ge (>1×10¹⁸ cm^-3) codoped CZSi wafers. These results suggest that the grown-in O precipitates increase as the O_i concentration decreases when the Ge concentration increases in the Si crystal. The Ge-vacancy (V) complex in the Si lattice probably acted as a heterogeneous nucleation center and may enhanced the grown-in O precipitates thereby reducing the dissolved O_i concentration in the Si lattice.