Patent ID: 6967156

Claim:
A method of forming an aligned dual damascene opening, comprising the sequential steps of: providing a structure having a metal structure formed thereover; forming a layer stack over the metal structure; the layer stack comprising, in ascending order: a bottom etch stop layer; a lower dielectric material layer; a middle etch stop layer; a middle dielectric material layer; and an upper dielectric layer; wherein: the lower and middle dielectric layers are comprised of the same material; or the bottom etch stop layer, the middle etch stop layer and the upper dielectric layer are comprised of the same material; patterning the upper dielectric layer to form an opening exposing a portion of the underlying middle dielectric material layer; the opening having a width; forming a patterned mask layer over the patterned upper dielectric layer leaving exposed opposing portions of the patterned upper dielectric layer; patterning the middle dielectric material layer to form an opening therein using the patterned mask layer and the exposed portions of the upper dielectric layer as masks; the middle dielectric material layer opening exposing a portion of the middle etch stop layer; removing the middle etch stop layer at its exposed portion to form a patterned middle etch stop layer having an opening exposing a portion of the lower dielectric material layer; simultaneously patterning: the patterned middle dielectric material layer using the patterned upper dielectric layer as a mask to form an inchoate upper trench opening; and the lower dielectric material layer using the patterned mask layer and the patterned middle etch stop layer as masks to form an inchoate lower via opening aligned with the inchoate upper trench opening; the inchoate lower via opening exposing a portion of the underlying bottom etch stop layer; removing the patterned mask layer; and removing the patterned upper dielectric material layer, the exposed portions of the patterned middle etch stop layer and the exposed portion of the bottom etch stop layer to convert: the inchoate upper trench opening into a final upper trench opening; and the inchoate lower via opening into a final lower via opening; to form the aligned dual damascene opening.