Low-temperature plasma-enhanced atomic layer deposition growth of WN_xC_y from a novel precursor for barrier applications in nanoscale devices

A low-temperature plasma-enhanced atomic layer deposition (PEALD) process has been developed for the growth of ultrathin WN_xC_y films, using a halide-free W precursor. A 32-nm-thick PEALD WN_xC_y film deposited using this process at 250 °C possesses a composition of W₇₂C₂₀N₅, resistivity of ∼250 μΩ·cm, a root-mean-square (rms) surface roughness of 0.23 nm, and a thickness conformality of more than 80% on trench structures with a width of 120 nm and an aspect ratio of 11. The WN_xC_y films exhibited excellent thermal stability, whereby resistivity, thickness, surface roughness, and crystal structure were stable after 30 min anneals in 700 Torr, forming gas ambient at temperatures up to 700 °C. Copper diffusion barrier performance measurements show that a 9 nm thick WN_xC_y film could prevent copper diffusion after a 30 min anneal at 700 °C, while a 2-nm-thick film could prevent copper diffusion after a 30 min anneal at 500 °C.