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Role of Frictional Force on the Polishing Rate of Cu Chemical Mechanical Polishing

In the chemical mechanical polishing (CMP) of low-dielectric-constant (low-k) materials and Cu for ultralarge-scale integrated circuits, one of the major issues is the adhesion failure of the film caused by frictional force. An in situ quantitative measurement technique for frictional force during CMP has been developed. We have examined frictional force with respect to process parameters and slurries. A low frictional force and a high polishing rate (PR), which are desirable for a low-k/Cu CMP process, have been achieved simultaneously by optimizing slurry flow rate. The groove structures of the polishing pad did not affect frictional force at a low relative velocity. Frictional force and polishing rate increased with increasing glycine and H2O2 concentration in the slurry, and saturated at concentrations above 0.3 M and 3 vol%, respectively. A modified Preston's equation describing polishing rate as a function of frictional force instead of polishing pressure was proposed.