Chemical mechanical planarization pad having polishing layer with multi-lobed embedded features
View Patent ↗A polishing pad for chemical mechanical polishing comprises a polishing layer that comprises a polymer matrix that is the reaction product of an isocyanate terminated prepolymer with a curative, wherein the polymer matrix has hard segments and soft segments wherein multi-lobed polymeric elements formed from pre-expanded polymeric microspheres are present in the polymer matrix. The polishing pad can be made by preparing a pre-blend of the isocyanate terminated prepolymer and the pre-expanded fluid filled polymeric microspheres in a stirred tank; pumping a portion of the pre-blend from a bottom of the stirred tank through a conduit and recycling to a top region of the stirred tank, mixing a portion of the pre-blend with the curative to form a mixture, casting the mixture in a mold, curing the mixture in the mold.
1. A polishing pad for chemical mechanical polishing comprising:
a polishing layer that comprises a polymer matrix that is the reaction product of an isocyanate terminated prepolymer with a curative, wherein the polymer matrix has hard segments and soft segments wherein multi-lobed polymeric elements formed from pre-expanded polymeric microspheres are present in the polymer matrix and wherein the multi-lobed polymeric elements are deflated residues of the pre-expanded polymeric microspheres and wherein the polishing layer further comprises pores formed by a portion of the pre-expanded polymeric microspheres that retain a shape that is substantially spherical or ellipsoid and 0.1 to 20 percent of the pre-expanded polymeric microspheres form the multi-lobed polymeric elements.
2. The polishing pad of claim 1 wherein the multi-lobed polymeric elements comprise three or more lobes.
3. The polishing pad of claim 1 wherein at least a portion of the deflated residues of the pre-expanded polymeric microspheres comprise a residual irregular void space.
4. The polishing pad of claim 1 wherein at least a portion of the lobes of the multi-lobed polymeric elements comprise plate-like protrusions that project from a central region.
5. The polishing pad of claim 1 wherein the pre-expand led polymeric microspheres specific gravity of 0.06 to 0.096.
6. The polishing pad of claim 1 wherein the pre-expanded polymeric microspheres comprise a polymeric shell having a chlorine content less than 0.1 wt % based on total weight of the polymeric shell around a fluid filled core, where the fluid comprises a gas.
7. The polishing pad of claim 1 wherein the deflated residues of the pre-expanded polymeric microspheres do not include holes or tears when examined under scanning electron microscope at 50× magnification.
8. A method of making the polishing pad of claim 1 comprising
preparing a pre-blend of the isocyanate terminated prepolymer and the pre-expanded fluid filled polymeric microspheres in a stirred tank,
pumping a portion of the pre-blend from a bottom of the stirred tank through a conduit and recycling to a top region of the stirred tank,
mixing a portion of the pre-blend with the curative to form a mixture,
casting the mixture in a mold, and
curing the mixture in the mold.
9. A method of polishing comprising providing a substrate comprising a metal, a metal oxide, or both, and polishing the substrate using the polishing pad of claim 1 .