Amorphous Ta x Mn y O z Layer as a Diffusion Barrier for Advanced Copper Interconnects

An amorphous Ta Mn O 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 Ta Mn O 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 Ta Mn O layer, and a tape peeling test showed that the Ta Mn O 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 Ta Mn O barrier. Also, the J-E and C-V measurements of the fabricated metal-oxide-semiconductor sample showed that the Ta Mn O barrier significantly improved the electrical stability of the Cu interconnect. Our results indicate that the 1.0-nm-thick Ta Mn O 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 Ta Mn O 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 Ta Mn O barrier is a promising Cu diffusion barrier for advanced interconnect technology.