US Patent 9059257 Self-aligned vias formed using sacrificial metal caps

A method including forming a sacrificial metal cap on a metal line formed in a first dielectric layer; forming a second dielectric layer on the first dielectric layer; removing the sacrificial metal cap selective to the second dielectric layer and metal line to form a cap opening; forming a dielectric cap in the cap opening and on the metal line; forming an interconnect dielectric layer over the dielectric cap and the second dielectric layer; forming an interconnect opening in the interconnect dielectric layer; removing a portion of the dielectric cap exposed by the interconnect opening selective to the interconnect dielectric layer, the second dielectric layer, and the metal line; and forming an interconnect structure in the interconnect opening, the interconnect structure comprising a contact line above a via, the via having an upper via portion with angled sidewalls and a lower via portion with substantially vertical sidewalls.