Interconnect structures including self aligned vias
Back end of line metallization structures and methods for fabricating self-aligned vias. The structures generally include a first interconnect structure disposed above a substrate. The first interconnect structure includes a metal line formed in a first interlayer dielectric. A second interconnect structure overlies the first interconnect structure. The second interconnect structure includes a second cap layer on the first interlayer dielectric, a second interlayer dielectric thereon, and at least one self-aligned via in the second interlayer dielectric conductively coupled to at least a portion of the metal line of the first interconnect structure, wherein any misalignment of the at least one self-aligned via results in the at least one self-aligned via landing on both the metal line of the first interconnect structure and the second cap layer. The second cap layer is an insulating material.
1. A method for forming a self-aligned via in a second interconnect structure overlying a first interconnect structure, wherein the first interconnect structure includes a metal line formed in a first interlayer dielectric, the method comprising:
selectively depositing a first cap layer on only exposed surfaces of the metal line formed in the first interlayer dielectric;
blanket depositing a second cap layer onto the first interconnect structure;
planarizing the second cap layer to the first cap layer, wherein the first cap layer is coplanar to the second cap layer;
selectively removing the first cap layer to form a recess exposing the metal line; and
depositing and patterning a second interlayer dielectric to form a self-aligned via opening to at least a portion of the metal line, wherein a misalignment of the self-aligned via opening results in the at least one self-aligned via opening landing on both the metal line of the first interconnect structure and the second cap layer, wherein a portion of the second interlayer dielectric is immediately over the metal line, the portion of the second interlayer dielectric having a bottom surface below a top surface of the second cap layer such that a sidewall face of the second cap layer and a sidewall face of the portion of the second interlayer dielectric are directly opposite one another with the at least one self-aligned via opening in between.
2. The method of claim 1 , wherein the first and/or second interlayer dielectric is an ultra-low k dielectric having a dielectric constant (k) of less than about 3.0 to about 1.5.
3. The method of claim 1 , wherein the second cap layer comprises a silicon nitride, a silicon dioxide, a silicon carbide, or an aluminum nitride.
4. The method of claim 1 , wherein the second cap layer comprises SiN, SiC, or SiC (N,H).
5. The method of claim 1 , wherein the first cap layer comprises ruthenium, cobalt, tungsten, alloys thereof, or combinations thereof.
6. The method of claim 1 further comprising conformally depositing a third cap layer prior to depositing the second interlayer dielectric, wherein the third cap layer comprises an insulating material and is at a fraction of a thickness of the first cap layer.
7. The method of claim 1 further comprising selectively depositing a third cap layer prior to depositing the second interlayer dielectric onto only the metal line, wherein the third cap layer comprises a metal material and is at a fractional thickness of the first cap layer, wherein the self-aligned via opening lands on the third cap layer and on the second cap layer upon the misalignment such that the third cap layer is on an uppermost surface of the metal line in the first interconnect in its entirety.