Low dielectric constant 3MS α-SiC:H as Cu diffusion barrier layer in Cu dual damascene process

The primary candidate for the barrier/etch stop layer in damascene process is silicon nitride. However, silicon nitride has a high dielectric constant. To reduce the effective dielectric constant in the copper damascene structure, silicon carbide, which is prepared by plasma enhanced chemical vapor deposition (PECVD) using 3 methyl silane source (Z3MS), is studied for the dielectric copper diffusion barrier. The dielectric constant of PECVD alpha -SiC:H is varied from 4.0 to 7.0 and the fourier transform infrared (FTIR) spectra peak intensity ratio of Si-CH3 bond to Si-C is also examined. The reduction in dielectric constant of alpha -SiC:H using 3MS gas seems to be related to the decreased density upon incorporation of Si-CH3 groups. The value of capacitance with alpha -SiC is 8-10% lower than that with PECVD SiN. The leak-age current with alpha -SiC:H barrier is lower by 1 order of magnitude than that with PECVD SiN barrier.