Preparation And Characterization Of Silicon Carbonitride Dielectric Barrier Layers In Integrated Circuit Copper Interconnect

The interconnect resistance-capacitance (RC) delay is a dominant factor in determining the performance of ultra large-scale integrated circuits as critical dimension below 130 nm. Although many low-k materials have been used as interlayer dielectrics (ILD), high dielectric constant (k =7-8) of silicon nitride (Si₃N₄) film is still the primary candidate for the Cu cap barrier and etch stop layer (ESL) required in the Cu damascene process. Thus, this increases the effective k value of stack dielectric films, and limits the reduction of the RC delay in ultra large-scale integration. As a result, amorphous silicon nitricarbide (SiCN) have received much attention for applications as Cu dielectric diffusion barrier and ESL in Cu damascene process.On the basis of a comparative study of the diffusion barriers on their fabrication methods and characteristics, SiCN thin films and Cu/SiCN thin films were deposited on n-type Si(111) substrates by magnetron reactive sputtering. Then rapid thermal annealing (RTA) was performed on the samples. The sheet resistance, surface morphology, crystalline structures, chemical composition and chemical bonding status of the films were characterized by four-point probe (FPP) sheet resistance measurement, atomic force microscopy (AFM), scanning electron microscope (SEM), X-ray diffraction method (XRD), energy disperse spectroscopy (EDS), and fourier transform infrared spectroscopy(FTIR), respectively.The results revealed the formation of complex networks among the three elements, Si, C and N, and the existence of different chemical bonds in the SiCN films such as Si-C, Si-N, C-N, C=N and C-Si-N. Further more, there are C and Si clusters in the samples. The as-deposited SiCN thin-films were amorphous structure with smooth and compact surfaces, and their crystallization temperature is about 1200℃, which shows their good thermal stability. The sheet resistance measurement and C-V measurement results shows that the dielectric constant of the as-deposited SiCN thin-films is 4.22.The SiCN thin-films play a good performance as Cu dielectric diffusion barriers and they can prevent the diffusion reaction between Cu and Si interface after 5min RTA processing below 600℃. The Cu/SiCN thin films have a good thermal stability and the adhension of Cu with SiCN is strong, and no Cu film falling is observed. The failure of the barriers is mainly attributed to Cu diffusion and reactions among multilayered films. Cu atoms diffuse through the flauts of the amorphous structure of SiCN layers directly, and react with Si and N of SiCN barriers untill the barriers fail, and finally react with Si substrates to form the Cu₃Si phase.