| 摘要 |
PURPOSE:To obtain a shallow impurity diffusion length of 1 mum or less in a highly precise manner by a method wherein a plurality of silicon wafers are reciprocated in longitudinal direction inside the diffusion tube having a fixed non-uniformity temperature distribution in longitudinal direction. CONSTITUTION:The silicon wafer 11 placed on a boat 13 is put on the first temperature region, and they are moved forward toward the inner part of the tube 1 to be used for diffusion at a fixed speed using a rod 13. Then, when the wafers pass the second temperature region and they reach the end point, they are moved in the opposite direction. Impurities are diffused when the silicon wafers 11 pass the second temperature region. The reciprocating movement of the wafers is repeated until the desired diffusion length is obtained. As impurities are diffused little by little, the diffusion can be performed in a highly precise manner even when the diffusion length is shallow. Also, as the first temperature is about 800 deg.C, the diffusion speed of impurities is very low, and the second temperature is the diffusion temperature. Preciseness is unnecessary in the first temperature, and the second temperature only is to be controlled in the extent of + or -1 deg.C or thereabout.
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