Amorphous TaMnO Layer as a Diffusion Barrier for Advanced Copper Interconnects.

An amorphous TaMnO layer with 1.0 nm thickness was studied as an alternative Cu diffusion barrier for advanced interconnect. The thermal and electrical stabilities of the 1.0-nm-thick TaMnO barrier were evaluated by transmission electron microscopy (TEM) and current density-electric field (J-E) and capacitance-voltage (C-V) measurements after annealing at 400 °C for 10 h. X-ray photoelectron spectroscopy revealed the chemical characteristics of the TaMnO layer, and a tape peeling test showed that the TaMnO barrier between the Cu and SiO layers provided better adhesion compared to the sample without the barrier. TEM observation and line profiling measurements in energy-dispersive X-ray spectroscopy after thermal annealing revealed that Cu diffusion was prevented by the TaMnO barrier. Also, the J-E and C-V measurements of the fabricated metal-oxide-semiconductor sample showed that the TaMnO barrier significantly improved the electrical stability of the Cu interconnect. Our results indicate that the 1.0-nm-thick TaMnO barrier efficiently prevented Cu diffusion into the SiO layer and enhanced the thermal and electrical stability of the Cu interconnect. The improved performance of the TaMnO barrier can be attributed to the microstructural stability achieved by forming ternary Ta-Mn-O film with controlled Ta/Mn atomic ratio. The chemical composition can affect the atomic configuration and density of the Ta-Mn-O film, which are closely related to the diffusion behavior. Therefore, the 1.0-nm-thick amorphous TaMnO barrier is a promising Cu diffusion barrier for advanced interconnect technology.