Photo-enhanced electrochemical mechanical polishing for Cu damascene

A new CMP technology using TiO2 photocatalyst was developed for Cu damascene wiring. The slurry consists of only 3wt% TiO2 particle and no chemicals are added except for pH adjustment. It was found that drastic enhancement of Cu removal rate was observed in the case of UV light illumination to the pad surface compared to the case with no light illumination. Cu CMP rate of 900nm/min was achieved at 500W mercury lamp illumination. Furthermore, the slurry showed excellent planarity. These advantages are attributable to the photo-enhanced electrochemical mechanical polishing by TiO2 particle. The band gap of the TiO2 is 3.2eV and the irradiation by the mercury lamp produced hole-electron pairs. The hole oxidized Cu directly and CuOx is formed at Cu surface. Then, the oxide is removed by TiO2 abrasion. This chemical-free polishing can achieve Cu/WN damascene wiring successfully. The photo-enhanced electrochemical mechanical polishing would be advantageous in terms of productivity, planarity, corrosion and environmental impact.