Differential hardmasks for modulation of electrobucket sensitivity

An interconnect structure for an integrated circuit, the interconnect structure comprising:

• a first layer of the interconnect structure disposed above a substrate, the first layer comprising a first grating of alternating metal lines and dielectric lines in a first direction, wherein the dielectric lines have an uppermost surface higher than an uppermost surface of the metal lines;
• and
• a second layer of the interconnect structure disposed above the first layer of the interconnect structure, the second layer comprising a second grating of alternating metal lines and dielectric lines in a second direction, perpendicular to the first direction, wherein the dielectric lines have a lowermost surface lower than a lowermost surface of the metal lines of the second grating, wherein the dielectric lines of the second grating overlap and contact, but are distinct from, the dielectric lines of the first grating;
• and
• a region of dielectric material disposed between the metal lines of the first grating and the metal lines of the second grating, and in a same plane as upper portions of the dielectric lines of the first grating and lower portions of the dielectric lines of the second grating, the region of dielectric material comprising a cross-linked photolyzable material disposed on a distinct underlying hardmask portion.

A method of fabricating an interconnect structure for an integrated circuit, the method comprising:

• forming a mask above an ILD material layer, the mask having a plurality of spaced apart features each with a central portion and a pair of sidewall spacers;
• forming, using the mask, a first plurality of trenches partially into the ILD material layer;
• forming first hardmask portions and a first plurality of electrobuckets in the first plurality of trenches;
• forming a second mask from the mask by removing the central portion of each feature of the mask;
• forming, using the second mask, a second plurality of trenches partially into the ILD material layer;
• forming second hardmask portions and a second plurality of electrobuckets in the second plurality of trenches, wherein the second plurality of electrobuckets has less sensitivity to e-beam or extreme ultra-violet (EUV) radiation than the first plurality of electrobuckets;
• exposing, developing and removing fewer than all of the first plurality of electrobuckets by using a lithographic exposure;
• forming via locations where the fewer than all of the first electrobuckets were removed;
• and
• forming metal vias in the via locations and metal lines above the metal vias.