Restoration and pore sealing of low-k films by UV-assisted processes

Porous low-k dielectrics are susceptible to damages by steps such as etch, ash, and CMP in the BEOL process flow. Such damages degrade the structural and electrical properties of low-k materials. To uphold the value of integrating low-k dielectrics, restoration processes are needed to repair such damages. In this work, UV-assisted silylation is used to repair damages and restore properties of porous low-k dielectrics. The repair process is able to restore carbon content, as indicated by the increase in water contact angle (WCA), and restore the electrical properties, as shown by the decrease in dielectric constant (k) and increase in break-down electrical field based on blanket-film data. On structured wafers, the post-etch repair process effects a 4-6% reduction in RC when compared to without repair. The same UV-assisted platform may be used to effect pore sealing to prevent metals used in BEOL metallization from penetrating into porous low-k materials. On structured wafers, the pore-sealing process is able to reduce Mn penetration into porous low-k when ALD MnN is used as the copper barrier.