This disclosure describes a low particle concentration formulation for
slurry which is particularly useful in continuous CMP polishing of copper
layers during semiconductor wafer manufacture. The slurry is
characterized by particle concentrations generally less than 2 wt %, and
advantageously less than 1 wt %. In particular embodiments, where the
particle concentration is in a range of 50 to 450 PPM, an 8-fold increase
in polishing rate over reactive liquid slurries has been realized.
Slurries thus formulated also achieve a reduction in defectivity and in
the variations in planarity from wafer to wafer during manufacture, by
improving the stability of polishing quality. The slurry formulations
permit substantial cost savings over traditional 2-component, reactive
liquid and fixed/bonded abrasive slurries. In addition the formulations
provides an advantageous way during CMP to easily change the selectivity
or rate of removal of one film material vs. another. Yet another use is
to provide slurry "pulsing" as a means to activate bonded abrasive or
fixed abrasive slurry technology.