Method to fabricate self-aligned dual damascene structures

Abstract

A method to form dual damascene structures is described. A first silicon oxynitride layer is deposited overlying a provided substrate. A silicate glass layer is deposited overlying the first silicon oxynitride. A second silicon oxynitride layer is deposited overlying the silicate glass. Photoresist is deposited overlying the second silicon oxynitride and is etched to define areas of planned lower trenches. The second silicon oxynitride layer is etched to expose the top surface of the silicate glass layer. The remaining photoresist layer is etched away. An hydrogen silsesquioxane layer is deposited overlying the second silicon oxynitride and the silicate glass. An oxide layer is deposited overlying the hydrogen silsesquioxane. Photoresist is deposited overlying the oxide and is etched to define areas of planned upper trenches. The oxide layer and the hydrogen silsesquioxane layer are etched by reactive ion etching by a recipe comprising C,F,, CO, Ar, and N,gases to form the upper trenches. The second silicon oxynitride acts as an etch stop. The silicate glass is etched by reactive ion etching by a recipe comprising C,F,, CO, and Ar gases to form the lower trenches. The first silicon oxynitride acts as an etch stop. A metal layer is deposited filling the trenches. The metal layer is etched back to the top surface of the oxide.