Chemical-mechanical polishing of copper with oxide and polymer interlevel dielectrics

Chemical-mechanical polishing (CMP) of copper with oxide interlevel dielectrics has been demonstrated as a viable patterning approach for copper interconnect structures. This paper summarizes our understanding of the mechanisms involved in copper CMP and presents our results with both oxide interlevel dielectrics (ILDs) and low dielectric constant polymer ILDs. Our two-step model of copper CMP consists of mechanical abrasion of the copper surface followed by removal of the abraded material from the vicinity of the surface and has been developed after extensive electrochemical and CMP experiments with alternative slurries. Although the softer and less process tolerant polymers result in Damascene patterning difficulties compared with oxide ILDs, our results with both benzocyclobutene and parylene indicate that manufacturable processes for on-chip interconnect structures can be established with additional fundamental understanding and further development.