Dual metal interconnects for improved gap-fill, reliability, and reduced capacitance

A method comprising:

• providing a substrate having formed thereon a dielectric layer, a trench and an opening to expose an underlying metal surface;
• depositing a refractory interconnect in the opening directly adjacent to the underlying metal surface, wherein the refractory interconnect is deposited by bottom-up electroless plating on the underlying metal surface;
• depositing a trench interconnect comprising a seed layer and a conductor in the trench, wherein the seed layer acts as a nucleation surface for the conductor, and;
• planarizing the trench interconnect and the dielectric layer.

A microelectronic device comprising:

• a substrate having formed thereon a low-k dielectric and an opening having an opening width substantially equal to or larger than 50 nanometers (nm) formed in the low-k dielectric;
• an underlying metal directly adjacent to the opening;
• a refractory interconnect in the opening, wherein the refractory interconnect is directly adjacent to the underlying metal and a wall of the opening and the refractory interconnect substantially fills the opening;
• a barrier layer on the refractory interconnect;
• and
• a trench interconnect on the barrier layer.