Advanced Direct-Polishing Process Development of Non-Porous Ultralow-k Dielectric Fluorocarbon with Plasma Treatment on Cu Interconnects

A direct-polishing process was applied to the ultralow-k dielectric without a dielectric protective layer to reduce the effective dielectric constant in damascene interconnects. The direct-polishing process on organic non-porous ultralow-k dielectric, fluorocarbon (k = 2.2), was demonstrated and an optimum direct-polishing process condition was investigated. Mechanically enhanced chemical reaction on the fluorocarbon degraded the electrical properties by changing the structure of the fluorocarbon. Higher down-pressure, one of the most important factors in mechanical effects, resulted in both higher leakage current and a variance of the structure of th fluorocarbon. A surface nitrogen plasma treatment of fluorocarbon before polishing to form an effective protective layer was applied to avoid the degradation of electrical characteristics during the direct-polish, and this result revealed that the surface nitrogen plasma treatment of fluorocarbon is a practical technique for a direct-polishing process in advanced Cu interconnects.