Determining the Effects of Slurry Surfactant, Abrasive Size, and Abrasive Content on the Tribology and Kinetics of Copper CMP

Abstract

The effects of slurry surfactant, abrasive size, abrasive content, wafer pressure, and sliding velocity on frictional 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 ͑COF͒. 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 rate. 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 frictional 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-slip͒ was the rate-determining step.

Editors' Choice—Efficiency of a CMP Pad at Removing Protective Material from Copper during CMP

“…Nevertheless, the separation between the embedded abrasives remained much larger than the size of the abrasives; only 1.90% of area was occupied by the abrasive particles held under an asperity contacting the copper when 5 wt% abrasives was used, as indicated in Table II. The conclusion that deflected asperities completely or partly contacted the copper is consistent with the work of DeNardis et al 10 and Li et al, 36 who deduced a contact mode during copper CMP from the slopes of experimentally obtained Stribeck curves. The contact mode during copper CMP was "partial lubrication", in which abrasive particles and slurry separate the pad asperities and the copper in part or "boundary lubrication", where the asperities, abrasives and copper are in direct contact.…”

The influence of abrasive particle size in copper chemical mechanical planarization

“…In Li's study [8], slurries containing a larger abrasive increase the removal rate. It's easy to understand why the removal rate is lower in the slurry solution without abrasive particles.…”

Colloid aspects of chemical–mechanical planarization

“…16. There is a significant amount of additional literature where effects of slurry flow and pad/particle/wafer surface interactions have also been analyzed [87][88][89][90][91][92][93][94][95].…”