Pad flattening ratio, coefficient of friction and removal rate analysis during silicon dioxide chemical mechanical planarization

Pad flattening ratio (PFR) was investigated as a non-destructive pad surface analysis method on the IC1000 K-groove pad during silicon dioxide chemical mechanical planarization. The PFR defines as the ratio of the bright area to the total image area. A series of marathon polishing runs were performed under ex-situ diamond disc pad conditioning, ex-situ high-pressure micro jet (HPMJ) pad conditioning and no pad conditioning methods where PFR analysis was performed to estimate the amount of pad surface flattening or glazing under these conditions. With no conditioning, PFR increased rapidly to 40% indicating severe glazing. With ex-situ diamond disc pad conditioning, PFR remained relatively constant below 12%, suggesting a rough and stable pad surface for polishing, while with ex-situ HPMJ conditioning it increased gradually and stabilized at the value of about 23%. Real-time analysis of friction force and silicon dioxide removal rate showed a clear correlation among the PFR, the coefficient of friction and the removal rate during the silicon dioxide chemical mechanical planarization.