| 摘要 |
PROBLEM TO BE SOLVED: To achieve selective diffusion to one side of a substrate at a specified high concentration even in an open pipe system by heat-treating the substrate under a mixed gas atmosphere of argon and nitrogen which contains nitrogen within an specified percentage to argon by volume, after heat-treating under an oxidation atmosphere. SOLUTION: A substrate is heat-treated under an oxidation atmosphere. At that time, a part of aluminum on the surface of the substrate becomes aluminum oxide and enters oxide film being formed, a portion of which is diffused as impurity. Subsequently, the atmosphere is changed to a mixed gas of argon and nitrogen which contains 1 part argon and 1-3 parts nitrogen by volume. A specified high concentration is obtained by properly selecting mixing percentage of the gas. If nitrogen is less than 1 part with respect to 1 part argon by volume, then a nitride film can not inhibit out diffusion of aluminum; and if nitrogen is greater than 3 part with respect to 1 part argon by volume, then it is difficult to remove the nitride film in the following process.
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