Method for maximizing air gap in back end of the line interconnect through via landing modification

A method of forming an interconnect to an electrical device comprising:

• forming at least one aft gap between adjacent metal lines in a plurality of metal lines by depositing a non-conformal material stack atop the plurality of metal lines, wherein forming the plurality of metal lines comprises forming a plurality of line trenches in a low-k dielectric layer, forming a liner material in the line trenches, forming said plurality of metal lines on the liner material in the plurality of line trenches and selectively forming a metal cap layer on an upper surface of the plurality of metal lines, wherein the non-conformal material stack includes an air gap forming dielectric and a hard mask dielectric layer, wherein said forming said aft gap further comprises damaging the low-k dielectric material, removing a damaged portion of the low-k dielectric material to open a space between said adjacent metal lines in said plurality of metal lines, forming a conformal dielectric layer on sidewalls and upper surfaces of said plurality of metal lines, forming said air gap forming dielectric, wherein said aft gap forming dielectric is non-conformally deposited and encloses said air gap within said space between said adjacent lines by pinching off an opening to said space, said air gap forming dielectric being composed of a low-k dielectric, and forming said hard mask dielectric layer, wherein said hard mask dielectric layer comprises a bilayer of a nitride containing dielectric present on the low-k dielectric and a metal nitride present atop the nitride containing dielectric;
• forming a sacrificial dielectric layer atop the non-conformal material stack, wherein an opening is present in the sacrificial dielectric layer exposing an apex of the non-conformal material stack substantially aligned to a metal line of the plurality of metal lines;
• removing an exposed portion of an apex portion of the hard mask dielectric layer selectively to the air gap forming dielectric;
• forming a trench through the air gap forming dielectric using a remaining portion of the hard mask dielectric layer as an etch mask to expose the metal line without opening said at least one air gap;
• and
• forming a contact to the metal line in said trench.