| 摘要 |
PURPOSE:To improve the accuracy of the size of a polycrystalline silicon wiring, by making effective oxygen concentration approximately constant before and after the exposing of a silicon oxide film beneath a polycrystalline silicon film, which is to become a stopper, and performing reactive ion etching of the polycrystalline silicon film, in which high concentration phosphorus is diffused, with chlorine based gas. CONSTITUTION:On a semiconductor substrate 1, a silicon oxide film 2 is formed. A polycrystalline silicon film 3, in which high concentration phosphorus is diffused, is formed thereon. A patterned resist is formed on the film 3. The polycrystalline silicon film is etched to the middle of the depth with ions or radical 6 using chlorine based gas including a specified amount of oxygen. A chlorine based carbide 5 is attached and grown on the side surface of the polycrystalline silicon film. Then the ratio of the chlorine in the chlorine based gas including the specified amount of oxygen is changed. In some case, the oxygen gas is made to be zero. The remaining polycrystalline silicon film and the lower silicon oxide film are continuously etched. Thus the polycrystalline silicon wiring without local side etching is formed without removing the chlorine based carbide 5.
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