| 摘要 |
PURPOSE:To prevent the generation of a thermal strain, to keep the temperature of a semiconductor wafer in a high temperature region constant at all times and to obtain a junction in uniform depth and uniform resistivity extending over the whole surface of the wafer by preheating the wafer so that its temperature is elevated slowly in the low temperature region of the same oven, transferring its to the high temperature region and diffusing an impurity while heating it at a high temperature. CONSTITUTION:A heater 5A is controlled so that the temperature of the low temperature region 5 is kept at an initial temperature (such as 600 deg.C) at its maximum where the wafer is not thermally strained. The semiconductor wafers (W) are loaded on a boat (B), and charged into the low temperature region 5 from an oven inlet. Temperature distribution is stabilized, and the temperature of the low temperature region 5 is elevated step by step or in a rampy manner up to a first temperature (such as 1,000 deg.C) higher than the initial temperature by the heater 5A. The boat (B) is moved to the high temperature region 4, and the impurity is diffused according to a predetermined manner. Both the high temperature region 4 and the low temperature region 5 are kept at fixed temperature during the diffusion. Diffusion is completed, the boat (B) is moved into the low temperature region 5, the region 5 is cooled slowly, and the temperature of the region 5 is dropped step by step or the rampy manner up to the initial temperature by the heater 5A. |
