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This method for formulating silicon chemical mechanical polishing slurries entails the use of bimodal particle size distributions to provide faster stock removal rates.
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Polishing Slurries with Varied Particle Size
This method for formulating silicon chemical mechanical polishing slurries
entails the use of bimodal particle size distributions to provide faster stock
Slurries used for chemical mechanical polishing of silicon wafers are
generally comprised of colloidal dispersions of silicon dioxide in water, at pH
values greater than 9. The solids content is normally in the range 8-15 weight
percent SiO(2). Instead of using a conventional bell shaped particle size
distribution, the particle size distribution of the colloidal silica used should be
bimodal in nature. The physical distribution of the SiO(2) particles in our
recommended formulation would consist of several distinct sizes, for instance, 10
weight percent blend of 60 and 30 or 90 and 30 millimicron sized SiO(2)
particles. These mixtures will result in greater stock removal rates than a slurry
mixture comprised of say, only 10 weight percent of 60 and 90 millimicron sized
The basic mechanism of stock removal in chemical mechanical polishing is
different when compared to mechanical polishing. In chemical mechanical
polishing, accelerated removal rates occur using bimodal particle size
distributions. Reaction product is more readily formed between the slurry and the
workpiece surface with the smaller particles because they have more surface
area than the larger particles. The larger particles are more efficient for the
removal of the...