Chemical mechanical planarization of copper/polyimide damascene structure with glycerol-based slurr

This thesis describes the results of an investigation of the Chemical Mechanical Planarization (CMP) of copper and polyimide films with glycerol-based (high viscosity) slurry. A physical planarization model of the polyimide CMP carried out with high viscosity slurry has been developed, with the removal mechanism was primarily being mechanical abrasion. The high viscosity slurry minimizes the impact between the abrasive and polyimide film, thus reducing scratching and damage. However, the scratch density is also strongly dependent on the pad, with soft pads leading to less scratching. The use of BTAH in forming a passivating film on copper surface during CMP was proven to be effective. The effect of glycerol on the passivation of copper was found to be insignificant.;The addition of glycerol in the slurry results in a unique CMP removal rate behavior for both copper and polyimide. The removal rate increases with increasing glycerol concentration and reaches a maximum value at 30 vol% glycerol due to particle aggregation and decreases at higher glycerol concentrations due to reduction in the frictional forces between the abrasive particles and the film surface.;The possibility of implementing the unique removal rate behavior on the planarization of copper/polyimide damascene structure was also investigated. Dual-step polish process was designed by utilizing the high removal rate with the slurry containing 30 vol% of glycerol, followed by the slurry containing 50 vol% glycerol for over-polish step process. The high viscosity slurry was to protect the soft polymer film as the metal film is abraded away. It was also found that high viscosity slurry induces lower dishing and erosion on the pattern structure.