Method of forming air gaps for reducing interconnect capacitance

Abstract

A method for manufacturing integrated circuits increases the aspect ratio of the electrical conductor members connected to the circuits by increasing the effective height of the conductors, either by forming a thicker layer of conductor material prior to patterning the conductor members, or by adding a capping dielectric layer to the conductor material prior to patterning, or by overetching the dielectric material underlying the conductor members. The structure is then covered by a dielectric layer having poor step coverage, resulting in a number of voids and open spaces in the dielectric layer to thereby reduce the dielectric constant between the patterned conductors. A plasma etchback of the dielectric layer is employed to open and shape additional voids and open spaces in the dielectric layer. This is followed by the deposition of a second layer of dielectric material to seal the structure, including any open spaces in the first layer of dielectric material.