Diffusion barrier for semiconductor device and method

A device comprising:

• a first conductive feature over a substrate;
• an etch stop layer extending along an upper surface of the first conductive feature distal from the substrate;
• a first insulating layer over the first conductive feature and the etch stop layer;
• and
• a via on the first conductive feature and within the first insulating layer, wherein the via comprises:
• a conductive material;
• and
• a barrier layer between the conductive material and the first insulating layer, wherein the barrier layer and the conductive material comprise different materials, wherein the barrier layer comprises a layer of a second transition metal interposed between a first layer of a nitride of a first transition metal and a second layer of the nitride of the first transition metal, wherein the first transition metal is tantalum, and the second transition metal is ruthenium, wherein each of the layer of the second transition metal, the first layer of the nitride of the first transition metal, and the second layer of the nitride of the first transition metal is a single layer of a respective material, wherein the first layer of the nitride of the first transition metal directly contacts and extends along sidewalls of the first insulating layer and sidewalls of the etch stop layer, wherein the second layer of the nitride of the first transition metal directly contacts and extends along sidewalls of the conductive material, wherein the layer of the second transition metal directly contacts the first layer of the nitride of the first transition metal and the second layer of the nitride of the first transition metal, wherein the barrier layer directly contacts and extends along an upper portion of the sidewalls of the etch stop layer, wherein the conductive material directly contacts and extends along a lower portion of the sidewalls of the etch stop layer, wherein the conductive material directly contacts a bottom surface of the barrier layer facing the substrate.

A device comprising:

• a first conductive feature in a first dielectric layer;
• an etch stop layer over the first conductive feature;
• a second dielectric layer over the etch stop layer;
• and
• a second conductive feature in the second dielectric layer, the second conductive feature comprising:
• a barrier layer comprising:
• a first layer of a metal nitride, wherein the first layer of the metal nitride directly contacts and extends along sidewalls of the second dielectric layer and sidewalls of the etch stop layer;
• a layer of a transition metal directly on the first layer of the metal nitride, wherein the transition metal is a different metal than a metal of the metal nitride;
• and
• a second layer of the metal nitride directly on the layer of the transition metal, wherein the layer of the transition metal is a single layer of ruthenium, the first layer of the metal nitride is a single layer of tantalum nitride, and the second layer of the metal nitride is another single layer of tantalum nitride;
• and
• a conductive filling material over the barrier layer, wherein the second layer of the metal nitride directly contacts and extends along sidewalls of the conductive filling material, wherein the conductive filling material extends through the etch stop layer and physically contacts a top surface of the first conductive feature, wherein the top surface of the first conductive feature is free of the metal nitride and the transition metal, wherein the barrier layer directly contacts and extends along an upper portion of the sidewalls of the etch stop layer, wherein the conductive filling material directly contacts and extends along a lower portion of the sidewalls of the etch stop layer, and directly contacts a bottom of the barrier layer facing the first conductive feature.