PROBLEM TO BE SOLVED: To provide an ion beam fine machining method for forming a fine circuit pattern used for a quantum device on an Si substrate surface without forming any mask for dry etching.
SOLUTION: On the surface of an Si wafer substrate 1, an Al layer 2 and an Si amorphous layer 3 are formed, and then a metal ion 6 is implanted onto the surface of the Si amorphous layer 3 through a mask 5. After that, the mask 5 is removed for implanting a metal ion 9. A surface natural oxide film is selectively substituted for SiO27 or is generated under the presence of a surface natural oxide film 4 that is formed on the surface of the Si amorphous layer 3 or oxygen molecule radiation, and further ions are implanted. As a result, after AlxOy8 is produced on the surface of the Al layer 2, dry etching is made in one atom layer unit by bromide, and the surface natural oxide film other than a portion that is substituted for SiO2 and AlxOy8, the Si amorphous layer, the Al layer, and one portion of the Si wafer substrate are removed.