Polishing pad and method for manufacturing the polishing pad

Abstract

A polishing pad is disclosed which is less likely to cause scratches, and has an excellent planarization performance and polishing stability. In one aspect, the invention provides a polishing pad comprising an ultrafine fiber-entangled body formed of ultrafine fibers having an average fineness of 0.01 to 0.8 dtex, and a polymeric elastomer. The polymeric elastomer has a glass transition temperature of −10° C. or below, storage moduli at 23° C. and 50° C. of 90 to 900 MPa, and a water absorption ratio, when saturated with water at 50° C., of 0.2 to 5 mass %.

Description

TECHNICAL FIELD[0001]The present invention relates to a polishing pad, and more particularly to a polishing pad for polishing various devices, substrates and other products on which planarization or mirror polishing are carried out, examples of which include semiconductor substrates, semiconductor devices, compound semiconductor devices, compound semiconductor substrates, compound semiconductor products, LED substrates, LED products, bare silicon wafers, silicon wafers, hard disk substrates, glass substrates, glass products, metal substrates, metal products, plastic substrates, plastic products, ceramic substrates and ceramic products, and to a method for manufacturing the polishing pad.BACKGROUND ART[0002]In recent years, with the increasing levels of integration and multilayer interconnection in integrated circuits, there has existed a need for high-precision flatness on the semiconductor wafers where the integrated circuits are formed.[0003]One known process for polishing semicon...

AI Technical Summary

Benefits of technology

[0071]The polyurethane resin may additionally include, within ranges that do not compromise the advantageous effects of the invention: penetrating agents, foam inhibitors, lubricants, water repellents, oil repellents, thickeners, bulking agents, curing accelerators, antioxidants, ultraviolet absorbers, mold inhibitors, blowing agents, water-soluble polymeric compounds such as polyvinyl alcohol and carboxymethyl cellulose, dyes, pigments, and inorganic fine particles.

[0072]Preferably, the polymeric elastomer is present inside ultrafine fiber bundles of from 5 to 70 ultrafine fibers having an average fineness of 0.01 to 0.8 dtex which make up the ultrafine fiber-entangled body. The ultrafine fibers converge as bundles under the effect of the polymeric elastomer present inside the ultrafine fiber bundles. Owing to the convergence of the ultrafine fibers, a part or all of the interior of the fiber bundle converges as a bundle, in addition to which the bundle of ultrafine fibers is restrained. The convergence of the ultrafine fibers as a bundle, together with the restraint of the fiber bundle, increases the stiffness of the polishing pad, which is advantageous from the standpoint of enhancing the planarizing performance, the polishing uniformity and the stability over time.

[0073]A volumetric ratio of a portion excluding voids in the polishing pad (also referred to below as the filling ratio of the polishing pad) is preferably in a range of from 40 to 95 wt %. That is, the presence of the voids such that the void volume is in a range of from 5 to 60% is preferable both for a suitable stiffness of the polishing pad and for slurry retention by the polishing pad.

[0074]In this case, the void volume in the polymeric elastomer-impregnated polishing pad of 50% or more is desirable because slurry retention, suitable stiffness and moreover cushionability are concurrently achieved, which is excellent for polishing bare silicon wafers. An upper limit in this case of 70% or less is desirable because this results in a good polishing rate and flatness in rough polishing such as bare silicon wafer polishing.

[0075]From the standpoint of enhancing slurry retention, it is more desirable for some of the voids to form continuous pores which afford communication with the interior of the polishing pad.

[0076]Moreover, the polymeric elastomer is preferably an aqueous polyurethane because of the good wettability to abrasive slurry, and the aqueous polyurethane preferably has an average particle size of 0.01 to 0.2 μm. At an average particle size of at least 0.01 μm, the water resistance is good, resulting in an excellent stability over time during polishing. An average particle size of 0.2 μm or less enhances the fiber bundle restraining strength, confers good planarizing properties, and increases the pad life during polishing, providing good stability over time. To adjust the above particle size, it is preferable, for example, that the polymeric elastomer includes at least one type of hydrophilic group selected from the group consisting of carboxylic groups, sulfonic acid groups and polyalkylene glycol groups having 3 or fewer carbons.

Problems solved by technology

Because such polishing pads have a relatively high stiffness, convex parts on the substrate being polished tend to incur selective loading during polishing, resulting in a relative high polishing rate.

However, when clumped abrasive grains are present on the polishing surface, because such clumped abrasive grains also selectively incur loading, scratches are readily formed on the surface being polished.

In particular, as described in Non-Patent Document 1, when a substrate having copper wiring that is scratched easily or a material with a low dielectric constant and with weak interfacial adhesion is polished, there is a particular tendency for scratches and interfacial separation to occur.

Moreover, in a cast-foam-molding, because it is difficult to uniformly foam a polymeric elastomer, variability tends to arise in the flatness of the substrate being polished and in the polishing rate during the polishing operation.

Moreover, in a polishing pad having closed cells, the voids that originate from the closed cells become clogged with abrasive particles and abrasion debris.

However, the polishing characteristics of nonwoven fabric-type polishing pads have a tendency to change readily over time, making such pads difficult to use for a precise planarization treatment.

Also, because the polishing pad is too flexible and deforms so as to follow the surface shape of the substrate being polished, it is difficult to obtain a high planarization performance (the ability to render the substrate being polished flat).

In addition, the fibers have a fineness of 2 to 10 dtex and are thus large, making it difficult to avoid local stress concentration.

However, because the polishing pads like those described in Patent Documents 15 to 18 make use of a nonwoven fabric obtained by needlepunching ultrafine staple fibers having a low fineness, such pads have a low apparent density and a high void volume.

Because these polishing pads deform so as to follow the surface shape, a sufficiently high planarization performance cannot be achieved.

Also, none of these documents provide details concerning the polymeric elastomer used in such nonwoven fabric-type polishing pads.