Method for preparing ultra-narrow groove

The invention provides a method for preparing an ultra-narrow groove, which belongs to the technical field of ultra-large scale integrated circuit preparation. The method comprises the following steps of: preparing a chemical mechanical polishing stop layer on a substrate; then depositing a silicon nitride layer, and depositing a polycrystalline silicon layer on the silicon nitride layer; processing the polycrystalline silicon into a narrow groove; and transferring the narrow groove defined on the polycrystalline silicon to a substrate material so as to realize the preparation of the ultra-narrow groove on the substrate material. The sectional shape of the polycrystalline silicon ultra-narrow groove prepared by the method is approximate ideal rectangle so that the shape of the ultra-narrow groove prepared on the substrate material is approximate rectangle; and the width of the ultra-narrow groove prepared by the method can be precisely controlled at 10 nanometers. Moreover, the materials on left and right sides of the ultra-narrow groove prepared by adopting the process have consistent distribution conditions, so the method can prepare the ultra-narrow groove of the substrate material with the same depth on the left and right sides.