Process for fabricating a semiconductor device having an improved metal interconnect structure

A process for fabricating a semiconductor device comprising the steps of:

• providing a semiconductor substrate;
• depositing a layer of aluminum-copper alloy on the semiconductor substrate and etching the layer to form a metal interconnect layer;
• forming a copper layer to overlie the metal interconnect layer;
• forming a refractory metal overlying the copper layer;
• and
• diffusing copper from the copper layer into the metal interconnect layer to form a copper-diffused region.

A process for forming a semiconductor device comprising the steps of:

• forming a first metal body selected from the group consisting of aluminum-copper, and aluminum-copper-silicon having grain boundaries therein;
• forming a second metal body;
• forming a copper layer intermediate to the first and second metal bodies;
• and
• passing an electric current through the first and second metal bodies,
• wherein the electric current induces copper from the copper layer to migrate into the first metal body to form a copper region in the first metal body, and
• wherein the copper region is in intimate contact with the copper layer.

A process for fabricating a semiconductor device comprising the steps of:

• providing a semiconductor substrate having an insulating layer thereon,
• wherein the insulating layer has an opening, and
• wherein a refractory metal plug fills the opening;
• forming a copper layer overlying the metal plug;
• forming an aluminum metal interconnect overlying the insulating layer and the copper layer,
• wherein the aluminum is alloyed with at least copper;
• and
• diffusing copper from the copper layer into the metal interconnect to form a copper-diffused region therein.

A process for fabricating a semiconductor device comprising the steps of:

• providing a semiconductor substrate having an insulating layer thereon,
• wherein the insulating layer has an opening, and
• wherein a refractory metal plug fills the opening;
• forming a copper layer overlying the metal plug;
• depositing an alloy of aluminum and copper,
• wherein the alloy has a copper concentration of less than 1 weight percent;
• etching the alloy of aluminum and copper to form a metal interconnect overlying the insulating layer and the copper layer;
• and
• diffusing copper from the copper layer into the metal interconnect to form a copper-diffused region therein.