Process for forming trenches and vias in layers of low dielectric constant carbon-doped silicon oxide dielectric material of an integrated circuit structure

Abstract

A low k carbon-doped silicon oxide dielectric material dual damascene structure is formed by improvements to a process wherein a first photoresist mask is used to form via openings through a first layer of low k carbon-doped silicon oxide dielectric material, followed by removal of the first photoresist mask; and wherein a second photoresist mask is subsequently used to form trenches in a second layer of low k carbon-doped silicon oxide dielectric material corresponding to a desired pattern of metal interconnects for an integrated circuit structure, followed by removal of the second photoresist mask. The improved process of the invention comprises: forming a first hard mask layer over an upper layer of low k carbon-doped silicon oxide dielectric material previously formed over an etch stop layer formed over a lower layer of low k carbon-doped silicon oxide dielectric material on an integrated circuit structure; forming a first photoresist mask having a pattern of via openings therein over the first hard mask layer; etching the first hard mask layer through the first photoresist mask to form a first hard mask having the pattern of vias openings replicated therein without etching the layers of low k carbon-doped silicon oxide dielectric material beneath the first hard mask; then removing the first photoresist mask; forming a second hard mask layer over the first hard mask; forming a second photoresist mask having a pattern of trench openings therein over the second hard mask layer; etching the second hard mask layer through the second photoresist resist mask to form a second hard mask having the pattern of trench openings replicated therein without etching the layers of low k carbon-doped silicon oxide dielectric material beneath the first and second hard masks; then removing the second photoresist mask; then using the first and second hard masks to respectively form the via openings in the lower layer of low k carbon-doped silicon oxide dielectric material and trench openings in the upper layer of low k carbon-doped silicon oxide dielectric material; whereby a pattern of via openings and a pattern of trench openings can be formed in layers of low k carbon-doped silicon oxide dielectric material without damage to the low k carbon-doped silicon oxide dielectric material during removal of the photoresist masks used respectively in the formation of the pattern of via openings and the pattern of trench openings.