Microstructure modification in copper interconnect structure
View Patent ↗Cobalt is added to a copper seed layer, a copper plating layer, or a copper capping layer in order to modify the microstructure of copper lines and vias. The cobalt can be in the form of a copper-cobalt alloy or as a very thin cobalt layer. The grain boundaries configured in bamboo microstructure in the inventive metal interconnect structure shut down copper grain boundary diffusion. The composition of the metal interconnect structure after grain growth contains from about 1 ppm to about 10% of cobalt in atomic concentration. Grain boundaries extend from a top surface of a copper-cobalt alloy line to a bottom surface of the copper-cobalt alloy line, and are separated from any other grain boundary by a distance greater than a width of the copper-cobalt alloy line.
1. A metal interconnect structure comprising:
a dielectric material layer containing a recessed line pattern;
a metallic barrier layer abutting said dielectric material layer at sidewalls of said recessed line pattern and overlying an entirety of said dielectric material layer;
a copper-containing seed layer abutting said metallic barrier layer and overlying an entirety of said dielectric material layer; and
a copper-containing layer comprising electroplated copper and abutting said copper-containing seed layer, wherein at least one of said copper-containing seed layer and said copper-containing layer comprises a copper-cobalt alloy containing a cobalt concentration from about 1 ppm to about 10 atomic percent.
2. The metal interconnect structure of claim 1 , wherein said copper-containing layer comprises O, N, C, Cl , and S, a sum of concentrations of which is from about 1 ppm to about 200 ppm.
3. The metal interconnect structure of claim 1 , wherein said copper-cobalt alloy contains a cobalt concentration from about 10 ppm to about 2 atomic percent.
4. The metal interconnect structure of claim 1 , wherein said copper-containing seed layer comprises a copper-cobalt alloy containing a cobalt concentration from about 1 ppm to about 10 atomic percent and has a thickness from about 5 nm to about 60 nm.
5. The metal interconnect structure of claim 1 , wherein said copper-containing layer comprises a copper-cobalt alloy containing a cobalt concentration from about 1 ppm to about 10 atomic percent and has a thickness from about 50 nm to about 800 nm above a portion of said dielectric material layer located outside said recessed line pattern.
6. A metal interconnect structure comprising:
a dielectric material layer containing a recessed line pattern;
a metallic barrier layer abutting said dielectric material layer at sidewalls of said recessed line pattern and overlying an entirety of said dielectric material layer;
a copper-containing seed layer abutting said metallic barrier layer and overlying an entirety of said dielectric material layer;
a copper-containing layer comprising electroplated copper and abutting said copper-containing seed layer; and
a copper-cobalt alloy cap layer containing a cobalt concentration from about 1 ppm to about 50 atomic percent and abutting said copper-containing layer.
7. The metal interconnect structure of claim 6 , wherein said copper-containing layer comprises O, N, C, Cl , and S, a sum of concentrations of which is from about 1 ppm to about 200 ppm.
8. The metal interconnect structure of claim 6 , wherein said copper-cobalt alloy contains a cobalt concentration from about 10 ppm to about 40 atomic percent.
9. A metal interconnect structure comprising:
a dielectric material layer containing a recessed line pattern;
a metallic barrier layer abutting said dielectric material layer and embedded in said recessed line pattern; and
a copper-cobalt alloy line abutting a copper alloy seed layer and embedded in said metal barrer layer and having an atomic concentration of cobalt from about 1 ppm to about 10 atomic percent, wherein an average grain size measured at a bottom of said copper-cobalt alloy line exceeds a width of said copper-cobalt alloy line.
10. The metal interconnect structure of claim 9 , wherein said copper-cobalt alloy line comprises O, N, C, Cl , and S, a sum of concentrations of which is from about 1 ppm to about 200 ppm.
11. The metal interconnect structure of claim 9 , wherein said atomic concentration of cobalt is from about 10 ppm to about 10 atomic percent.
12. The metal interconnect structure of claim 9 , wherein a top surface of said copper-cobalt alloy line is substantially coplanar with a top surface of said dielectric material layer.
13. The metal interconnect structure of claim 12 , wherein said copper-cobalt alloy line has a bamboo microstructure, wherein each grain boundary extends from said top surface of said copper-cobalt alloy line to a bottom surface of said copper-cobalt alloy line, and is separated from any other grain boundary by a distance greater than a width of said copper-cobalt alloy line.
14. The metal interconnect structure of claim 9 , further comprising a copper-cobalt alloy via of integral construction with said copper-cobalt alloy line and free of any grain boundary perpendicular to a substrate.
15. The metal interconnect structure of claim 14 , wherein said metallic barrier layer is of unitary construction and abuts and encloses said copper-cobalt alloy via.