The effect of sputtering bias on the composition and microstructure ZrSiN diffusion barrier films

Zr-Si-N diffusion barriers were sputtered by RF reactive magnetron sputtering with different bias voltages. The Cu films were subsequently sputtered onto the Zr-Si-N films without breaking vacuum. Energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscope, Auger electron spectroscopy, and four-point probe method were employed to characterize the microstructure and properties of the Zr-Si-N films. The results reveal that as the bias voltage increases the Zr/Si ratio and the surface roughness increase, but the resistivity of the film decreases. High sputtering bias is in favor of the growth of ZrN grains in the Zr-Si-N film. With the decrease of sputtering bias the microstructure of Zr-Si-N film changes from the composite that consists of nano-grain ZrN and amorphous SiN_x to the composite that consists of amorphous ZrN and SiN_x phases.