Interface stability and microstructure of ultrathin Mo/MoN diffusion barrier in Cu interconnects

Abstract An ultrathin Mo (7 nm)/MoN (3 nm) bilayer film covered by Cu film was deposited on the Si substrate using reactive magnetron sputtering in N2/Ar ambient. The film stacks of Cu/Mo (7 nm)/MoN (3 nm)/Si were then annealed in a vacuum chamber at 500–800°C for 1 h. X-ray diffraction, scanning electron microscopy, cross-sectional transmission electron microscopy and energy dispersive X-ray spectroscopy line scans were employed to investigate the microstructure evolution and the diffusion behaviour of the film stacks. The results show that the Mo (7 nm)/MoN (3 nm) bilayer film as a diffusion barrier has sufficient interface stability, which can prevent Cu atom diffusion at elevated temperatures up to 700°C. The relationship between the interface stability and the microstructure of the bilayer barrier is characterised in detail.