Wiring structure and method for fabricating the same
A wiring structure has a silicon layer, a backing layer provided on the silicon layer, the backing layer comprising a copper alloy containing a nickel, and a copper layer provided on the backing layer, and a diffusion barrier layer having an electrical conductivity, the diffusion barrier layer being provided at a region including an interface between the silicon layer and the backing layer, in which a nickel in the diffusion barrier layer is enriched compared with the backing layer.
1. A wiring structure, comprising:
a silicon layer;
a backing layer provided on the silicon layer, the backing layer comprising a copper alloy containing a nickel;
a copper layer provided on the backing layer; and
a diffusion barrier layer having an electrical conductivity, the diffusion barrier layer being provided at a region including an interface between the silicon layer and the backing layer,
wherein a nickel in the diffusion barrier layer is enriched compared with the backing layer.
2. The wiring structure according to claim 1 , wherein the diffusion barrier layer comprises a silicon composing the silicon layer, a copper composing the backing layer, and the nickel moved to the interface when the silicon layer and the backing layer are heated.
3. The wiring structure according to claim 2 , wherein the diffusion barrier layer is in ohmic contact with the silicon layer.
4. The wiring structure according to claim 3 , wherein the backing layer provided on the silicon layer has a nickel concentration enough to form the diffusion barrier layer showing a diffusion barrier property.
5. The wiring structure according to claim 4 , wherein the copper layer comprises an oxygen free copper with a purity of 3N or more.
6. The wiring structure according to claim 1 , wherein the copper alloy comprises the nickel of 5 at % or more, a balance of a copper and inevitable impurities.
7. A method for fabricating a wiring structure, comprising:
forming a backing layer comprising a copper alloy containing a nickel on a silicon layer in an oxygen free atmosphere;
forming a copper layer on the backing layer; and
carrying out a heat treatment on the silicon layer and the backing layer to enrich the nickel at an interface between the silicon layer and the backing layer, thereby forming a diffusion barrier layer having an electrical conductivity, wherein a nickel in the diffusion barrier layer is enriched compared with the backing layer.
8. The method for fabricating a wiring structure according to claim 7 , wherein the copper alloy comprises the nickel of 5 at % or more, a balance of a copper and inevitable impurities.
9. The method for fabricating a wiring structure according to claim 8 , wherein the heat treatment is carried out on the silicon layer and the backing layer at a temperature from 200° C. to 300° C. in vacuum.