Self-aligned barrier formed with an alloy having at least two dopant elements for minimized resistance of interconnect

A method for fabricating an interconnect structure formed within an interconnect opening surrounded by dielectric material, the method comprising the steps of:

• A. filling the interconnect opening with a conductive fill material comprised of copper doped with a first dopant element and a second dopant element that is different from the first dopant element;
• wherein the first dopant element includes at least one of Mg (magnesium), Ca (calcium), Cr (chromium), and Zr (Zirconium);
• and wherein the second dopant element includes at least one of Ti (titanium), Co (cobalt), Ni (nickel), and Ta (tantalum);
• and wherein the dielectric material is comprised of a first dielectric reactant element and a second dielectric reactant element;
• B. forming a diffusion barrier material from a reaction of the first dopant element of the conductive fill material and the first dielectric reactant element,
• wherein the first dopant element of the conductive fill material diffuses out of the conductive fill material to the surrounding dielectric material at walls of the interconnect opening during a thermal anneal process;
• and
• C. forming a boundary material from a reaction of the second dopant element of the conductive fill material and the second dielectric reactant element,
• wherein the second dopant element of the conductive fill material diffuses out of the conductive fill material to the surrounding dielectric material at the walls of the interconnect opening during the thermal anneal process;
• and wherein the diffusion barrier material and the boundary material form a self-aligned skin layer on the walls of the interconnect opening between the conductive fill material and the dielectric material;
• and wherein the self-aligned skin layer prevents diffusion of the conductive fill material into the dielectric material;
• and wherein formation of the boundary material prevents diffusion of the second dielectric reactant element into the conductive fill material;
• and wherein the thermal anneal process is performed at a temperature in a range of from about 100° Celsius to about 500° Celsius for a time period in a range of from about 30 seconds to about 2 hours.
• and wherein the first dielectric reactant element is one of oxygen, nitrogen, or carbon such that the diffusion barrier material is one of a metal oxide, a metal nitride, or a metal carbide;
• and wherein the second dielectric reactant element is silicon such that the boundary material is a metal silicide;
• and wherein a portion of the first dopant element remains within the conductive fill material after the thermal anneal process;
• and wherein a portion of the second dopant element remains within the conductive fill material after the thermal anneal process;
• and wherein the interconnect opening is one of a metal line, a via hole, or a dual damascene opening.