Interconnects with hybrid metal conductors
A back end of line interconnect structure and methods for forming the interconnect structure including a fully aligned via design generally includes wide lines formed of copper and narrow lines formed of an alternative metal. The fully aligned vias are fabricated using a metal recess approach and the hybrid metal conductors can be fabricated using a selective deposition approach.
1. A process for forming a fully aligned via to an underlying metallization level comprising:
forming an underlying metallization level by patterning a first interlayer dielectric layer to form one or more narrow trenches and one or more wide trenches, wherein the wide trenches have a width dimension that is two times to ten times a width dimension for the narrow trenches;
conformally depositing a barrier layer onto the patterned interlayer dielectric;
conformally depositing a first metal layer comprising a metal other than copper onto the patterned dielectric to completely fill the narrow trenches to form narrow metal lines and form an overburden thereon and partially fill the wide trenches;
selectively removing a portion of the first metal layer to form a recess in the narrow metal lines relative to the first interlayer dielectric and completely remove the first metal from the wide trenches;
conformally depositing a second metal layer comprising a metal other than copper onto the patterned dielectric;
depositing a copper metal and forming an overburden thereon to completely fill the recess in the narrow metal lines and completely fill the wide trenches;
removing a portion of the copper metal to completely remove the copper metal from the recess above the narrow metal lines and form a recess in the copper metal in the wide trenches to form wide metal lines;
selectively removing exposed surfaces of the barrier layer and the second metal layer from the recesses above the narrow and wide metal lines;
conformally depositing a dielectric cap layer;
depositing a second interlayer dielectric layer on the dielectric cap layer;
forming a fully aligned via opening in the second interlayer dielectric to at least one of the narrow metal lines in the underlying metallization level; and
filling the fully aligned via opening with a metal conductor to form a fully aligned via in electrical communication with the narrow metal line.
2. The process of claim 1 further comprising selectively depositing a metal cap layer onto a top surface of the copper metal prior to conformally depositing the dielectric cap layer, wherein the metal cap layer comprises a metal other than copper.
3. The process of claim 1 , wherein the barrier layer comprises titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, ruthenium nitride, cobalt, cobalt nitride, or combinations thereof.
4. The process of claim 1 , wherein the first and second metal layers comprise aluminum, ruthenium, cobalt, rhodium, iridium, nickel, combinations thereof, or alloys thereof.
5. The process of claim 1 , wherein selectively removing exposed surfaces of the barrier layer comprises exposing the exposed surfaces to an etchant composition comprising a compound selected from group consisting of -azole, -triazole, and combinations thereof; a compound containing one or more peroxy groups; one or more alkaline metal hydroxides; and water.
6. The process of claim 1 , wherein selectively removing the portion of the first metal layer comprises exposing the first metal layer to a chemical composition comprising an oxidizer, wherein the chemical composition is buffered to include a pH greater than about 7.
7. The process of claim 1 , wherein the conformal dielectric cap layer comprises SiCN, SiC, or aluminum oxide.
8. The process of claim 1 , wherein the first and second metal layers comprise different metals.