A highly reliable interface of self-aligned barrier CuSiN thin layer between the Cu film and the nano-porous SiC:H (p-SiC:H) capping barrier (k=3.3) has been developed in the present work.With the introduction of self-aligned barrier (SAB) CuSiN between a Cu film and a p-SiC:H capping barrier,the interfacial thermal stability and the adhesion of the Cu/p-SiC:H film are considerably enhanced.A significant improvement of adhesion strength and thermal stability of Cu/p-SiC:H/SiOC:H film stack has been achieved by optimizing the pre-clean step before cap-layer deposition and by forming the CuSiN-like phase.This cap layer on the surface of the Cu can provide a more cohesive interface and effectively suppress Cu atom migration as well.
Cu thin films with different thicknesses were deposited by magnetron sputtering at various oblique angle θ of incidence between the deposition flux and the substrate surface normal.Cross-section microstructure and surface morphology of the films were investigated by scanning electron microscope(SEM)and atomic force microscope(AFM),respectively.Then the scaling behaviors of film surface roughening were analyzed in terms of dynamic scaling theory.With the increasing of the deposition angle θ,the angleφbetween grain growth direction and substrate surface normal increased gradually.With increasing θ in the range of<50°,the roughness exponent α increased from 0.76 to 0.82 and the growth exponent β decreased from 0.42 to 0.35.However,when θ increased to 70°,α and β changed to 0.72 to 0.61,respectively.The evolution of the scaling exponents effectively revealed the fact that the film surface roughening arises from the competition between surface diffusion and shadowing effect.
The main purpose of the present micro-structural analysis by transmission electron microscopy(TEM)and X-ray diffraction(XRD)was to investigate whether amorphous Zr-Ge-N films are a potential candidate as a diffusion barrier for Cu wiring used in Si devices.The Zr-Ge-N films were prepared by a radio frequency(RF)reactive magnetron sputter-deposition technique using N2 and Ar mixed gas,and the film structure was found to be sensitive to the gas flow ratio of N2 vs.Ar during sputtering.Polycrystalline Zr-Ge-N films were obtained when the N2/(Ar+N2)ratio was smaller than 0.2 and amorphous-like Zr-Ge-N films were obtained when the ratio was larger than 0.3.Diffusion barrier test was performed by annealing the Cu/Zr-Ge-N/Si film stack under Ar atmosphere.The deposited Zr-Ge-N(C)films remained amorphous even after high temperature annealing.The Cu diffusion profile in the film was assessed by the Auger electron spectroscopy(AES).The results indicate that Cu diffusion was minimal in amorphous Zr-Ge-N(C)films even at high annealing temperatures of 800℃.
