Evaluation of PECVD deposited boron nitride as copper diffusion barrier on porous low-k materials

Ultra low dielectric constant (k) material is needed as the inter-metal dielectrics to reduce RC delay when device dimension is scaled to sub-100nm. Porous dielectric films have been considered as good candidates for the application as inter-metal dielectrics due to their ultra low-k properties. Identifying proper dielectric copper diffusion barrier on the porous low-k films is critical for the low-k/Cu damascene fabrication process. In this study, we have evaluated the compatibility of plasma-deposited amorphous Boron Nitride film as a dielectrics copper diffusion barrier on a MSQ-based porous low-k LKD5109 film (from JSR). Both microwave plasma enhanced CVD (2.45 GHz) and radio-frequency plasma enhanced CVD (13.56 MHz) were applied for the BN deposition in order to evaluate the compatibility of the two plasma processes with the porous film. Growth parameters were optimized to minimize the boron diffusion and carbon depletion in the porous low-k films, which were found to have deleterious effects on the dielectric properties of the low-k films. FTIR and micro-Raman were employed for analyzing the changes in chemical structure of the low-k films after BN growth. Capacitance-voltage measurement was used to characterize the dielectric constants of BN film on Si and the BN-deposited porous low-k film. SIMS characterization was carried out to evaluate the performance of the BN film against copper diffusion.