| 摘要 |
PURPOSE:To sufficiently reduce the concentration of impurities in a wafer with minimum change of conventional processes, by thermally oxidizing the surface of a silicon wafer obtained by slicing an ingot before polishing the wafer. CONSTITUTION:A silicon wafer is heat-treated at an elevated temperature under oxidizing atmosphere, whereby an oxide layer (SiO2 layer) is formed on the surface of the silicon wafer. Mechanical distortion occurs on the interface between this oxide layer and the silicon crystals, and this distortion getters impurities such as heavy metals. Subsequently, the oxide layer is removed, for example by treating with fluohydric acid (HF), whereby undesirable impurities gathered on the interface of the wafer can be removed. In such a manner, the concentration of undesirable impurities such as copper, iron, nickel, chromium, sodium or the like can be reduced, in the stage of a wafer, by one tenth or more, so that a miller wafer with high purity can be obtained. |
