In order to augment the oxygen content in a CZ silicon wafer doped with heavy antimony, we suggest a double-typed heat shield (DTHS) instead of the conventional single-typed heat shield (STHS), which plays an important part mounted above the Si-melt-free surface to protect thermal energy loss during the crystal growth. The DTHS system turns out to produce a higher temperature zone under the ingot compared to the melt-free surface while the STHS has quite the reverse effect. This different phenomenon comes from the competition between thermal buoyancy force around the crucible wall and centrifugal force from the SR, which has been confirmed by a two-dimensional flow simulation. The overall Si-melt-flow pattern from crucible wall to ingot bottom enhances the oxygen segregation into the crystal. Many manufactured wafers show that the oxygen content in heavy antimony doped (HAD) CZ-Si crystal with DTHS is higher than that with STHS. (C) 2011 Elsevier B.V. All rights reserved.