Semiconductor device contact structure having stacked nickel, copper, and tin layers

A semiconductor device :fabrication method comprising:

• forming a barrier layer upon a dielectric layer, the barrier layer being a TiW layer;
• forming an electrically conductive plating layer upon the barrier layer, the plating layer being composed of Cu;
• forming a multilayered contact upon the plating layer by plating a Nickel layer upon the plating layer. plating a Copper layer upon the Nickel layer, and plating a Tin layer upon the Copper layer;
• and
• heat treating the multilayered contact to reflow the Tin layer with the Copper layer to form a Copper-Tin layer,
• wherein the heat treating fully converts the Copper layer into the Copper-Tin layer such that the Copper-Tin layer is directly upon the Nickel layer;
• the heat treating partially converts the Tin layer into the Copper-Tin layer such that a remaining portion of the Tin layer is retained upon the Copper-Tin layer;
• the TiW layer is 0.125 microns to 0.205 microns thick;
• the plating layer is 0.1 microns to 0.6 microns thick;
• the Nickel layer is 2 microns thick;
• the Copper-Tin layer is 2 microns thick;
• and
• the remaining portion of the Tin layer is 0.5 microns thick.

A semiconductor device fabrication method comprising:

• forming a barrier layer upon a dielectric layer. the barrier layer being a TiW layer;
• forming an electrically conductive plating layer upon the barrier layer, the plating layer being composed of Cu;
• forming a multilayered contact upon the plating layer by plating a Nickel layer upon the plating layer. plating a Copper layer upon the Nickel layer, and plating a Tin layer upon the Copper layer;
• and
• heat treating the multilayered contact to reflow the Tin layer with the Copper layer to form a Copper-Tin layer,
• wherein the heat treating fully converts the Copper layer into the Copper-Tin layer such that the Copper-Tin layer is directly upon the Nickel layer;
• the heat treating partially converts the Tin layer into the Copper-Tin layer such that a remaining portion of the Tin layer is retained upon the Copper-Tin laver;
• and
• the Copper-Tin layer is a Cu6Sn3 layer.