Mechanical Removal in CMP of Copper Using Alumina Abrasives

Results from experiments on the removal of copper using chemical mechanical polishing (CMP) by alumina abrasives suspended in deionized water are reported. The experiments were carried out in a benchtop polishing tool using IC1000 perforated pads and SUBA 500 pads. The removal rate was measured over a good range of values of the relative velocity and pressure, and for different values of the abrasive concentration in the slurry. The results support the use of Preston's equation over a limited range of values of the relative velocity and pressure in the case of the IC-1000 pad; however, at larger velocities and pressures, the linear behavior implied in Preston's equation is not observed. At low abrasive concentration, the removal rate increases with increasing concentration, but beyond about 2.5 wt % abrasives, there is little further increase in removal rate. In the case of the SUBA 500 pad, Preston's equation is inadequate for describing the dependence on pressure. It is found that the removal rate is indeed linear with increasing velocity at low to moderate pressures, but is proportional to the square root of pressure and the abrasive concentration.