Method for preparing superfine line based on oxidization and chemically mechanical polishing process

The invention provides a method for preparing a superfine line based on oxidization and a chemically mechanical polishing process, belonging to the technical field of extra-large scale integrated circuit manufacturing. The method of the invention comprises the following steps: preparing a chemically mechanical polishing stopping layer; depositing a silicon nitride film; depositing a polysilicon film on the silicon nitride film; processing the polysilicon film into a strip shape; growing silicon oxide on the top surface and two side surfaces of the strip-shaped polysilicon, wherein a substratematerial is not oxidized because of the protection of the silicon nitride; depositing another layer of polysilicon, and chemically mechanical polishing the polysilicon based on the stopping layer; sequentially etching the polysilicon, the silicon nitride and the substrate material by a dry method under the protection of the silicon oxide; and then corroding to remove a silicon oxide hard mask to prepare a fine line of the substrate material. The shape of the superfine line prepared by the invention can be close to a rectangle, and the distribution conditions of the substrate materials at the right and left sides of the line are the same.