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 method of forming a metal interconnect structure comprising:
providing a dielectric material layer containing a recessed line pattern;
forming a metallic barrier layer directly on said dielectric material layer at sidewalls of said recessed line pattern;
forming a copper-containing seed layer directly on said metallic barrier layer;
electroplating a copper-containing layer directly on 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; and
increasing grain size and decreasing resistance within said copper-containing seed layer and said copper-containing layer, wherein said copper-containing seed layer and said copper-containing layer form a bamboo microstructure within said recessed line pattern, and wherein each grain boundary within said bamboo microstructure extends to a bottom surface of said copper-containing layer.
2. The method of claim 1 , further comprising annealing said copper-containing seed layer and said copper-containing layer at a temperature from about 20° C. to about 400° C. for a time period from about 1 second to about 1 week, wherein grain size increases during said annealing within said copper-containing layer.
3. The method of claim 1 , further comprising planarizing said copper-containing layer, wherein a remaining portion of said copper-containing seed layer and said copper-containing layer constitutes a copper-cobalt alloy line, wherein an average grain size measured at a bottom of said copper-cobalt alloy line exceeds a width of said copper-cobalt alloy line.
4. The method of claim 3 , wherein said copper-cobalt alloy line has said 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 said width of said copper-cobalt alloy line.
5. The method 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 wherein said copper-containing seed layer is formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), electrodeposition, or electroless deposition.
6. A method of forming a metal interconnect structure comprising:
providing a dielectric material layer containing a recessed line pattern;
forming a metallic barrier layer directly on said dielectric material layer at sidewalls of said recessed line pattern;
forming a copper-containing seed layer directly on said metallic barrier layer;
electroplating a copper-containing layer directly on said copper-containing seed layer;
forming a copper-cobalt alloy cap layer containing a cobalt concentration from about 1 ppm to about 50 atomic percent directly on said copper-containing layer; and
increasing grain size and decreasing resistance within said copper-containing seed layer and said copper-containing layer, wherein said copper-containing seed layer and said copper-containing layer form a bamboo microstructure within said recessed line pattern, and wherein each grain boundary within said bamboo microstructure extends to a bottom surface of said copper-containing layer.
7. The method of claim 6 , further comprising planarizing said copper-containing layer, wherein a remaining portion of said copper-containing seed layer and said copper-containing layer constitutes a copper-cobalt alloy line, wherein an average grain size measured at a bottom of said copper-cobalt alloy line exceeds a width of said copper-cobalt alloy line.
8. The method of claim 7 , wherein said copper-cobalt alloy line has said 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 said width of said copper-cobalt alloy line.
9. A method of forming a metal interconnect structure comprising:
providing a dielectric material layer containing a recessed line pattern;
forming a metallic barrier layer directly on said dielectric material layer at sidewalls of said recessed line pattern;
forming a copper-containing seed layer directly on said metallic barrier layer;
electroplating a copper-containing layer directly on 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; and
planarizing said copper-containing layer, wherein a remaining portion of said copper-containing seed layer and said copper-containing layer constitutes a copper-cobalt alloy line, 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 method of claim 9 , further comprising annealing said copper-containing seed layer and said copper-containing layer at a temperature from about 20° C. to about 400° C. for a time period from about 1 second to about 1 week, wherein grain size increases during said annealing within said copper-containing layer.
11. The method of claim 9 , 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 said width of said copper-cobalt alloy line.
12. The method of claim 9 , 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 wherein said copper-containing seed layer is formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), electrodeposition, or electroless deposition.