Dielectric barrier characteristics of Si-rich silicon nitride films deposited by plasma enhanced atomic layer deposition

This work proposes a new method toward improving dielectric barrier characteristics through low dielectric permittivity (k) amorphous silicon nitride films (SiN_x) deposited by plasma enhanced atomic layer deposition (PEALD). The dielectric constants of the atomic layer deposition (ALD) SiN_x films were in the range of 4.25–4.71 and were relatively lower than that of SiN_x deposited by plasma enhanced chemical vapor deposition (PECVD). The dielectric constants of the PEALD SiN_x films were nearly identical to the values for PECVD silicon carbon nitride films (SiCN). Although the ALD SiN_x films were low-k, they exhibited similar levels of film stress as PECVD SiN_x, and the density of ALD SiN_x film was higher than that of PECVD SiCN films. The ability to suppress copper (Cu) diffusion through 10-nm thick SiN_x dielectric barriers in silicon dioxide/barrier/Cu/tantalum nitride structures on Si substrates was evaluated via Auger electron spectroscopy analysis. Although PEALD SiN_x films possessed low dielectric constants (<5), their barrier property to Cu diffusion was nearly equivalent to that of PECVD SiN_x. The PECVD SiCN films also exhibited low dielectric constants but showed weak barrier property. Therefore, the low-k ALD SiN_x reported herein could be used as a thin film thickness dielectric barrier layer in future advanced technologies.