| 摘要 |
PURPOSE:To obtain a high-quality N/N<+>/N epitaxial wafer having an impurity layer of a high concentration and whose epitaxial layer is not deteriorated in quality by high-temperature heat treatment, by providing a high-concentration N type epitaxial layer on a CZ N type semiconductor substrate, providing a low-concentration N type epitaxial layer thereon, and then heat treating these layers. CONSTITUTION:A CZ N type semiconductor substrate 1 having a resistivity of 1-several 10OMEGAcm is provided thereon with an As or Sb doped N<+> type epitaxial layer 2 having an impurity concentration of 10<17>cm<-3> or more. Subsequently, an N<-> type epitaxial layer 3 having an impurity concentration of 10<16>cm<-3> or less is formed thereon. The substrate is subjected to heat treatment at 700 deg.C for 16 hours or at 1,000 deg.C for six hours to produce defects 4. The conditions of the heat treatment are not fixed but determined, depending upon history such as an interstitial oxygen concentration of the substrate 1 or a picking-up condition of the substrate 1. Heat treatment of the semiconductor device at 1,200 deg.C for six hours will not produce such defects 4 as observed near the surface of the N<-> epitaxial layer 3 after the high-temperature heat treatment is produced. Accordingly, the N<-> epitaxial layer 3 is maintained as a defect-free region having little variation in resistivity. |
