Polishing pad comprising particles with a solid core and polymeric shell

#The invention pertains to a polishing pad that can be used for the polishing of a substrate, as well as a method of using the polishing pad to polish a substrate.

#A semiconductor wafer typically includes a substrate, such as a silicon or gallium arsenide wafer, on which a plurality of integrated circuits have been formed. Integrated circuits are chemically and physically integrated into a substrate by patterning regions in the substrate and layers on the substrate. The layers are generally formed of materials having either a conductive, insulating, or semiconducting nature. It is crucial that the surface onto which the layers are placed is as flat as possible. If a wafer is not flat and smooth, various problems can occur that may result in an inoperable device. Specifically, a smooth topography is desirable because it is difficult to lithographically image and pattern layers applied to rough surfaces. For example, in fabricating integrated circuits, it is necessary to form conductive lines or similar structures above a previously formed structure. However, prior surface formation often leaves the top surface topography of a wafer highly irregular and containing bumps, areas of unequal elevation, troughs, trenches, and other types of surface irregularities. The semiconductor industry continues to concentrate on achieving a surface of even topography by decreasing the number and size of surface imperfections through improved polishing techniques.

#Although several surface polishing techniques exist to ensure wafer surface planarity, processes employing chemical-mechanical polishing (also referred to as planarization) techniques have achieved widespread usage during the various stages of integrated circuit fabrication to improve yield, performance, and reliability. A chemical-mechanical polishing (CMP) process typically involves the circular motion of a substrate to be polished (such as a wafer) under a controlled downward pressure relative to a polishing pad that is saturated with a polishing composition (also referred to as a polishing slurry) under controlled conditions.

#FIG. 1 is a cross-sectional view of a composite particle useful in the invention.

#FIG. 2 is a partial cross-sectional view of a polishing pad of the invention.

#FIGS. 3A and 3B are partial cross-sectional views of polishing pads of the invention with an interstitial substance near the polishing surface (FIG. 3A) or at the polishing surface (FIG. 3B) of the polishing pad.

#The invention provides a polishing pad comprising composite particles. The composite particles comprise a solid core encapsulated by a polymeric shell material, wherein the solid core comprises a material that differs from the polymeric shell material. The invention also provides a method for polishing a substrate using such a polishing pad.

#As shown in FIG. 1, the composite particles 100 are comprised of a solid core 102 and a polymeric shell 104. The solid core 102 comprises a material that differs from the material of the polymeric shell 104. The solid core 102 can be of any suitable material that is solid under the conditions of use. The solid core desirably is selected from the group consisting of ceramic materials, metals, metal oxides, and polymers. The metal oxide desirably is selected from the group consisting of alumina, silica, titania, ceria, zirconia, germania, magnesia, co-formed products thereof, and combinations thereof. The solid core also can be one or more inorganic matters selected from the group consisting of oxides, carbides, nitrides, diamond, mixtures thereof, and combinations thereof. The solid core can be, but need not be, a single entity. Thus, the solid core can be in two or more discrete parts. For example, the core can comprise solid particles, such as, an agglomeration of particles, e.g., metal oxide particles.

#The polymeric shell 104 can be of any suitable polymeric material, such as an ionomer or a polyurethane or any other polymer or derivative thereof. The polymeric shell material desirably shows a high wear resistance similar to that of polyurethane, such as nylon 6/10, nylon 11, or polyethylene. In addition, the polymeric shell can contain any suitable substances in addition to one or more polymers. Such substances can be the same or different than the solid core material as described herein. In particular, a liquid suspension comprising solid abrasive components or merely solid abrasive components can be placed within the polymeric shell (i.e., within the matrix of the polymeric shell) of all or some, e.g., one or more layers, of the composite particles of the polishing pad. Such a liquid suspension can be a polar (e.g., water) or nonpolar (e.g., alcohols) suspension. The abrasive components desirably are one or more inorganic matters selected from the group consisting of oxides (especially metal oxides), carbides, nitrides, diamond, mixtures thereof, and combinations thereof. The abrasive components are released when the polymeric shell of the particle is at least partially removed, e.g., by breaking, deconstructing, degrading, or wearing of the composite particles. The presence of abrasive components within the polymeric shell can reduce the wear rate of the polymer shell (i.e., the speed at which the polymer shell is eroded). The number of layers of such composite particles, therefore, can determine the practical life of the polishing pad during use in polishing substrates.