Homogeneous copper-tin alloy plating for enhancement of electro-migration resistance in interconnects

A method for plating a homogenous copper-tin alloy onto a semiconductor substrate, comprising:

• providing a plating solution to an electrochemical plating cell, the plating solution comprising:
• an acid comprising at least one of sulfuric acid and phosphoric acid.;
• a copper ion source at a concentration of between about 0.4M and about 0.9M;
• a tin ion source, the tin ion source including at least one of SnSO4 and SnCl2, the tin ion source being at a concentration of between about 0.1M and 0.4M;
• and
• at least one organic plating additive;
• exposing a deposition surface of the substrate having a seed layer formed thereon to the plating solution;
• supplying an electrical deposition bias to the seed layer, wherein the deposition bias generates a current density of between about 5 mA/cm2 and about 60 mA/cm2 across the surface of the seed layer;
• and
• simultaneously plating tin ions and copper ions on the substrate surface to form a homogenous copper-tin alloy.

A method for plating a substantially homogenous copper tin alloy layer on a conductive seed layer formed onto a semiconductor substrate, comprising:

• providing a plating solution having both copper ions and tin ions therein;
• exposing the conductive seed layer to the plating solution;
• and
• applying a plating bias to the conductive seed layer to plate the substantially homogenous copper tin alloy layer onto the conductive seed layer, wherein the plating solution includes between about 0.2M and about 0.5M of copper ion concentration and between about 0.4M and about 0.8M of tin ion concentration, and wherein the plating bias includes a current density of between about 5 mA/cm2 and about 60 mA/cm2.