Determining the effects of slurry surfactant, abrasive size, and abrasive content on the tribology and kinetics of copper CMP

The effects of slurry surfactant, abrasive size, abrasive content, wafer pressure, and sliding velocity on factional and kinetics attributes of copper chemical mechanical planarization were studied. While abrasive content did not affect the tribological mechanism of the process, abrasive size was shown to be a significant factor. Surfactant-containing formulations were also shown to dramatically reduce coefficient of friction (COF). At low pressures and velocities, the removal rate was independent of surfactant content, abrasive diameter, and abrasive concentration, while at high pressures and velocities, surfactant-containing slurries caused an increase in removal rale. Slurries containing a larger abrasive increased removal rate. No correlation was observed between the removal rate and COF. Instead the removal rate was shown to loosely correlate with the variance of the factional force, thus suggesting that the rapid formation and extinction of the copper oxide layer as captured by the variance of frictional forces (i.e., stick-slip) was the rate-determining step.