Self-aligned via and plug patterning with photobuckets for back end of line (BEOL) interconnects
Self-aligned via and plug patterning with photobuckets for back end of line (BEOL) interconnects is described. In an example, an interconnect structure for an integrated circuit includes a first layer of the interconnect structure disposed above a substrate, the first layer having a first grating of alternating metal lines and dielectric lines in a first direction. The dielectric lines have an uppermost surface higher than an uppermost surface of the metal lines. The integrated circuit also includes a second layer of the interconnect structure disposed above the first layer of the interconnect structure. The second layer includes a second grating of alternating metal lines and dielectric lines in a second direction, perpendicular to the first direction. The dielectric lines have a lowermost surface lower than a lowermost surface of the metal lines of the second grating. The dielectric lines of the second grating overlap and contact, but are distinct from, the dielectric lines of the first grating. The integrated circuit also includes 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 is composed of a cross-linked photolyzable material.
1. A method of fabricating an interconnect structure for an integrated circuit, the method comprising:
providing a metallization structure comprising an alternating metal line and a dielectric line of first grating having a direction, wherein the alternating dielectric lines have an uppermost surface higher than an uppermost surface of the alternating metal lines;
forming an inter layer dielectric (ILD) layer above the first grating, the ILD layer having a second grating in a direction perpendicular to the direction of the first grating, the second grating exposing a plurality of via locations above the alternating metal lines;
forming a plurality of photobuckets in the plurality of via locations;
removing fewer than all of the plurality of photobuckets to form one or more via openings; and
forming metal lines above, and vias in a same plane as, remaining ones of the plurality of photobuckets.
2. The method of claim 1 , wherein forming the plurality of photobuckets comprises forming a layer of photolyzable material.
3. The method of claim 1 , wherein the dielectric line of the first grating comprise a first dielectric material, and the ILD layer comprises a second dielectric material different from the first dielectric material.
4. The method of claim 1 , wherein the dielectric line of the first grating and the ILD layer comprise a same dielectric material.
5. The method of claim 1 , wherein removing fewer than all of the plurality of photobuckets comprises using an extreme ultra-violet (EUV) lithographic process.
6. The method of claim 1 , wherein forming the ILD layer comprises:
forming an unpatterned layer of an ILD layer material;
forming a hardmask layer above the ILD layer, the hardmask layer having a pattern of the second grating; and
etching the unpatterned layer of the ILD layer material to provide the pattern of the second grating for the ILD layer.
7. 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 alternating dielectric lines have an uppermost surface higher than an uppermost surface of the alternating metal lines; and
a second layer of the interconnect structure disposed above the first layer of the interconnect structure, the second layer of the interconnect structure comprising a second grating of alternating metal lines and dielectric lines in a second direction, perpendicular to the first direction; and
a region of dielectric material disposed between the alternating metal lines of the first grating and the alternating metal lines of the second grating, the region of dielectric material comprising a cross-linked photolyzable material.
8. The interconnect structure of claim 7 , further comprising:
a conductive via disposed between and coupling a metal line of the first grating to a metal line of the second grating, the conductive via in the same plane as the region of dielectric material.
9. The interconnect structure of claim 8 , wherein the conductive via has a center directly aligned with a center of the metal line of the first grating and with a center of the metal line of the second grating.
10. The interconnect structure of claim 7 , wherein the dielectric lines of the first grating comprise a first dielectric material, and the dielectric lines of the second grating comprise a second dielectric material different from the first dielectric material, and wherein the first and second dielectric materials are different from the cross-linked photolyzable material.
11. The interconnect structure of claim 7 , wherein the dielectric lines of the first grating and the dielectric lines of the second grating comprise a same dielectric material different from the cross-linked photolyzable material.