Method for fabricating dual-via pattern damascene structure

A method for fabricating a dual-via pattern damascene structure, comprising the following steps:

• S1:
• providing a substrate, and growing a dielectric film layer on the substrate;
• S2:
• forming a spin-on carbon layer, a silicon-containing anti-reflection layer, and a photoresist layer sequentially from bottom to top on the dielectric film layer, and performing a first via pattern lithography process to form a first via photoresist pattern in the photoresist layer;
• S3:
• sequentially performing etching on the silicon-containing anti-reflection layer and the spin-on carbon layer at via locations of the first via pattern by using the photoresist layer as a mask, stopping on the dielectric film layer;
• S4:
• removing the photoresist layer, and then coating a directed self-assembly material on a wafer, wherein
• the directed self-assembly material is a polymer formed by connecting a polystyrene homopolymer and a poly methyl methacrylate homopolymer through a covalent bond;
• and
• etch selectivity ratios of the poly methyl methacrylate homopolymer and the polystyrene homopolymer are between 3:1 and 10:1;
• S5:
• performing baking on the directed self-assembly material to cause microphase separation of a polystyrene layer and a poly methyl methacrylate layer, wherein the polystyrene layer is formed on surfaces of the silicon-containing anti-reflection layer and the spin-on carbon layer, and encapsulates the poly methyl methacrylate layer within a central region of the via locations of the first via pattern;
• S6:
• performing etching-back on the directed self-assembly material after microphase separation, exposing an upper surface of the poly methyl methacrylate layer encapsulated by the polystyrene layer;
• S7:
• performing etching on the directed self-assembly material to cause the poly methyl methacrylate layer to be completely removed by using the different etch rate of the poly methyl methacrylate homopolymer and the polystyrene homopolymer, exposing the dielectric film layer located beneath the poly methyl methacrylate layer, while simultaneously retaining a portion of the polystyrene layer on sidewalls of the spin-on carbon layer, wherein a second via is formed within the retained portion of the polystyrene layer;
• and
• S8:
• performing etching on the dielectric film layer by using the second via to expose the substrate beneath the dielectric film layer at the location of the second via, removing the retained portion of the polystyrene layer at the via locations of the first via pattern and thinning the dielectric film layer beneath the retained portion of the polystyrene layer, thereby forming the dual-via pattern damascene structure.