Polishing pad and polishing method

Abstract

The objective of the present invention is to provide a polishing pad that enables an improvement in the roll-up shape without significantly changing the physical properties and cell structure of a polishing layer.　This polishing pad comprises a polishing layer having a polishing surface for polishing an object to be polished, and a base material layer disposed on the opposite side of the polishing layer to the polishing surface, wherein the base material layer has a compressive deformation amount of 20 μm or less in a MAG compression test, a storage elastic modulus of 3.5-20 MPa in a dynamic viscoelasticity measurement in compression mode, and a base material layer thickness that is 40% or more and less than 65% of the thickness of the polishing layer.

Description

Polishing pad and polishing method

[0001] The present invention relates to a polishing pad. In particular, the present invention relates to a polishing pad that can be suitably used for polishing optical materials, semiconductor wafers, semiconductor devices, hard disk substrates, etc. In particular, the present invention is suitably used for polishing devices in which an oxide layer, a metal layer, etc. is formed on a semiconductor wafer.

[0002] Typically, polishing of semiconductor wafers and the like is performed using the so-called CMP technique, in which a slurry (abrasive liquid) is supplied between a polishing pad and the wafer while they are slid relative to each other under pressure, thereby planarizing the wafer surface through a combined chemical and mechanical polishing action.

[0003] The CMP method will be described with reference to FIG. 1 . As shown in FIG. 1 , a polishing apparatus 1 for performing the CMP method is equipped with a polishing pad 3. The polishing pad 3 contacts a workpiece 8 held by a holding platen 16 and a retainer ring (not shown in FIG. 1 ) that prevents the workpiece 8 from shifting. The polishing pad 3 includes a polishing layer 4, which is the layer that performs polishing, and a substrate layer 6 that supports the polishing layer 4. The polishing pad 3 is rotated while pressed against the workpiece 8, polishing the workpiece 8. During this process, a slurry 9 is supplied between the polishing pad 3 and the workpiece 8. The slurry 9 is a mixture (dispersion liquid) of water, various chemical components, and hard, fine abrasive particles. As the chemical components and abrasive particles flow, the relative movement with the workpiece 8 increases the polishing effect. The slurry 9 is supplied to and discharged from the polishing surface via grooves or holes.

[0004] Conventionally, the polishing pad 3 uses a polishing layer 4 made of polyurethane foam, but this can cause profile abnormalities in the workpiece 8, particularly in the edge portion, which is the periphery of the workpiece 8. Edge profile abnormalities are known to occur in oxide film polishing, including over-polishing, known as "edge sagging," in which the edge portion of the workpiece is polished more than the center, and a polishing defect called "rebound," in which unevenness occurs in the periphery slightly inside the edge portion. Furthermore, when polishing a workpiece having a metal film such as a Cu film (damascene structure), a polishing defect occurs in which the edge portion of the workpiece is not polished as much as the center portion, resulting in a "spring shape."

[0005] Patent Document 1 discloses a polishing pad that prevents "edge sagging" while suppressing the occurrence of polishing scratches by controlling the hardness of the polishing layer within a certain range by specifying the structure of the cells in the foam. Also, Patent Document 2 discloses a polishing pad that does not have the problem of "edge sagging" by controlling the hardness and tear strength of the polishing layer within a predetermined range.

[0006] JP 2012-714 A JP 2016-190313 A

[0007] However, the polishing pads described in Patent Documents 1 and 2 require specific physical properties and bubble structures of the polishing layer, and even if the "edge sagging" is improved, other polishing performance may be inferior. Furthermore, although the "edge sagging" is improved, there is no mention of improving the "bounce shape," which is another edge profile abnormality.

[0008] The present invention has been made in consideration of the above problems, and aims to provide a polishing pad that enables improvement of the wave shape without significantly changing the physical properties and cell structure of the polishing layer.

[0009] In light of the above-mentioned problems, the present inventors conducted extensive research and discovered that the "bounce shape" can be improved by using a specific substrate layer, thereby arriving at the present invention. Specifically, the present invention encompasses the following: [1] A polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, and a substrate layer disposed on the opposite side of the polishing layer from the polishing surface, wherein the substrate layer exhibits a compressive deformation of 20 μm or less in a MAG compression test, a storage modulus of 3.5 MPa or more and 20 MPa or less in a compression-mode dynamic viscoelasticity measurement, and a thickness of the substrate layer relative to the thickness of the polishing layer of 40% or more and less than 65%. [2] The polishing pad according to claim 1, wherein the ratio of the storage modulus of the polishing layer to the storage modulus of the substrate layer (polishing layer / substrate layer) is 5 or more and 30 or less. [3] The polishing pad according to [1], wherein the substrate layer is made of polyurethane foam or a polyurethane material having hollow microspheres dispersed therein. [4] The polishing pad according to [1], which is a polishing pad for metal polishing. [5] A polishing method for polishing an object having a metal surface, comprising the steps of: preparing an object having a metal surface; and bringing the polishing surface of the polishing pad according to claim 1 into contact with the metal surface to polish the metal surface.

[0010] The polishing pad of the present invention uses a highly resilient material for the base layer, which has a compressive deformation of 20 μm or less in a MAG compression test and a storage modulus of 3.5 MPa to 20 MPa in a compression mode dynamic viscoelasticity measurement, thereby suppressing edge profile abnormalities (especially the shape of a metal film).In addition, it can suppress the intrusion of slurry into the base layer, suppress peeling between the polishing layer and the base layer, and suppress changes in compression behavior over time due to the voids inside the base being replaced by water.

[0011] FIG. 1 is a perspective view of a polishing apparatus 1. FIG. 2 is a perspective view of a polishing pad 3 of the present invention. FIG. 3 is a cross-sectional view of a polished object 8 in a serrated state. FIG. 4 is a film thickness profile of a polishing pad of the prior art, showing a method for measuring the film thickness difference. FIG. 5 is a change in the thickness profile of a Cu film using a conventional polishing pad. FIG. 6 shows the thickness profile of the Cu film at the edge of a polished object 8 using the polishing pads 3 of Examples 1 to 4 and Comparative Examples 1 and 2.

[0012] Hereinafter, the embodiments of the invention will be described, but the present invention is not limited to the embodiments of the invention.

[0013] <<Polishing Pad>> The structure of the polishing pad 3 will be described with reference to FIG. 2. As shown in FIG. 2, the polishing pad 3 includes a polishing layer 4 and a substrate layer 6. The shape of the polishing pad 3 is preferably disc-shaped, but is not particularly limited thereto. The size (diameter) can also be determined appropriately depending on the size of the polishing apparatus 1 equipped with the polishing pad 3, and can be, for example, approximately 10 cm to 2 m in diameter. Preferably, as shown in FIG. 2, the polishing pad 3 of the present invention has the polishing layer 4 bonded to the substrate layer 6 via an adhesive layer 7. The polishing pad 3 is attached to the polishing platen 10 of the polishing apparatus 1 by double-sided tape or the like disposed on the substrate layer 6. As shown in FIG. 1, the polishing pad 3 is rotated by the polishing apparatus 1 while pressing against the workpiece 8, thereby polishing the workpiece 8.

[0014] Here, we will explain the rippled shape, which is an abnormality in the edge profile. The rippled shape is a polishing defect in which the edge portion of the workpiece 8 is not polished as much as the center portion. Figure 3 is a cross-sectional view of the workpiece 8, showing that the disk-shaped workpiece 8 has an edge portion (edge) 8a that is not polished as much as the center portion. This is the rippled shape. Note that Figure 3 exaggerates the rippled shape for ease of understanding. In this specification, the strength of the rippled shape is expressed by measuring the film thickness of the thin film when the workpiece 8 has a thin film such as Cu. Figure 4 shows the film thickness difference caused by the rippled shape, and is a profile of the workpiece 8 exhibiting a typical rippled shape when using a conventional polishing pad. As shown in Figure 4, the film thickness difference is the distance from the thickest film thickness at the edge of the workpiece 8 to the thinnest film thickness. If the workpiece 8 does not have a thin film, the overall thickness profile of the workpiece 8 can be measured and evaluated by determining the difference between the thickest and thinnest film thicknesses at the edge, as in Figure 4. In this specification, for convenience, the shape of the ripple is evaluated using the film thickness difference in the polished object 8 having a Cu thin film.

[0015] FIG. 5 shows Cu film thickness profiles (FIGS. 5-1, 5-3, and 5-5) for a polished object 8 having a Cu coating polished with a conventional polishing pad, where the vertical axis represents the thickness of the Cu film and the horizontal axis represents the distance along a line passing through the center of the polished object 8 (the center of the polished object 8 is set to 0, and the portion 140-150 mm from the center is shown), and polishing rate profiles (FIGS. 5-2 and 5-4) for a polished object 8 having a Cu coating polished with a conventional polishing pad, where the vertical axis represents the thickness of the Cu film and the horizontal axis represents the distance along a line passing through the center of the polished object 8 (the center of the polished object 8 is set to 0, and the portion 140-150 mm from the center is shown). As can be seen from the Cu film thickness profile before polishing in FIG. 5-1, the Cu film originally has a slightly jutting shape, with the film thickness at the edge portions increasing rapidly. That is, the film thickness at the edge portions is approximately 1500 angstroms thicker than the other portions (hereinafter, the difference between the film thickness at the edge portions and the other portions will be referred to as the film thickness difference). Figure 5 (2) (top right) shows the polishing rate profile during the first polishing pass, showing that the polishing rate at the edge portion is approximately 1200 Å faster than that at the other portions. Figure 5 (3) (middle left) shows the thickness profile of the Cu film after the first polishing pass, showing that the difference in film thickness has decreased to approximately 1000 Å. Figure 5 (4) (middle left) shows the polishing rate profile after the second polishing pass, showing that the polishing rate at the edge portion is 300 Å faster than that slightly inside the edge portion (147 mm), but is about the same as that at the portion closer to the center (below 142 mm). Figure 5 (bottom) shows the thickness profile of the Cu film after the second polishing pass, showing that the difference in film thickness remains at 1000 Å, and the 1000 Å ridge shape still remains. That is, even when polishing is performed multiple times with conventional polishing pads, no improvement is seen in the film thickness difference of the resulting polished object 8, and the film thickness difference is not desirable. Note that, with regard to the "rippled shape," when the film thickness difference between the outermost edge (peripheral portion) of the polished object 8 and other portions of the polished object 8 exceeds 350 angstroms, this can be problematic in semiconductor polishing (particularly in the process of polishing metal films), and therefore in this specification, a rippled shape when the film thickness difference exceeds 350 angstroms is considered to be a rippled shape that should be improved.

[0016] <Polishing Layer> (Configuration) The polishing pad 3 includes a polishing layer 4, which is a layer for polishing the workpiece 8. Polyurethane resin, polyurea resin, and polyurethane-polyurea resin are preferably used as materials for the polishing layer 4, and polyurethane resin is more preferably used. The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3, and can be approximately 10 cm to 2 m in diameter, and the thickness of the polishing layer 4 can usually be approximately 1 to 5 mm. The polishing layer 4 is rotated together with the polishing platen 10 of the polishing device 1, and while a slurry 9 is flowed onto the polishing layer 4, the chemical components and abrasive grains contained in the slurry 9 are moved relative to the workpiece 8, thereby polishing the workpiece 8.

[0017] (Grooving, Embossing) Grooving or embossing is preferably performed on the surface of the polishing layer 4 of the present invention facing the workpiece 8. The grooves are not particularly limited and may be either slurry discharge grooves that communicate with the periphery of the polishing layer 4 or slurry retention grooves that do not communicate with the periphery of the polishing layer 4. Alternatively, both slurry discharge grooves and slurry retention grooves may be present. Examples of slurry discharge grooves include lattice-shaped grooves and radial grooves, while examples of slurry retention grooves include concentric grooves and perforations (through holes), and these may be combined. In low-pressure polishing, the platen is rotated at high speed to reduce the pressing force against the workpiece 8 and ensure a high polishing rate. This can lead to the so-called hydroplaning phenomenon, in which the slurry 9 exists in a layer between the polishing surface and the processing surface, hindering the polishing process. Grooving or embossing the polishing surface can suppress this phenomenon. It also facilitates the discharge of polishing debris and the movement of the polishing liquid. The cross-sectional shape may be U-shaped, V-shaped, or semicircular. There are no particular limitations on the pitch, width, and depth of the grooves. In addition, in order to improve the flatness of the polishing pad 3, a surface grinding treatment such as buffing may be performed on the polishing surface side or the side opposite to the polishing surface of the polishing pad 3.

[0018] The polishing layer 4 is formed by slicing a foam obtained by pouring a mixture of a urethane prepolymer obtained by reacting an isocyanate group-containing compound with a polyol compound, hollow microspheres, and a curing agent (chain extender) into a mold and hardening the mixture. In other words, the polishing layer 4 is dry-molded.

[0019] The voids formed inside the polishing layer 4 have a substantially circular cross section due to the hollow microspheres added to the dispersion liquid during dry molding. That is, in the polishing layer 4, multiple hollow microspheres are formed so as to overlap in the thickness direction, and can be formed substantially evenly in two directions intersecting the thickness direction. Because the polishing layer 4 is formed from slices of foam, some or all of the hollow microspheres may be open on the polishing surface. The average diameter of the openings formed on the polishing surface is adjusted to a range of 10 to 100 μm.

[0020] (Shore D Hardness) The Shore D hardness of the polishing layer 4 of the present invention is not particularly limited, but is preferably 40 to 70. If the Shore D hardness is less than 40 degrees, it becomes difficult to flatten fine irregularities by low-pressure polishing. If it exceeds 70 degrees, abrasive particles may be strongly rubbed against the polished object 8, possibly causing scratches on the polished surface of the polished object 8. The lower limit of the Shore D hardness of the polishing layer 4 is preferably 40 or more, 42 or more, and 45 or more, in that order, and the upper limit is preferably 70 or less, 65 or less, and 60 or less, in that order.

[0021] (Poisson's Ratio) The Poisson's ratio of the polishing layer 4 is not particularly limited. The Poisson's ratio of the polishing layer 4 is, for example, 0.20 to 0.50, and preferably 0.30 to 0.40. If the Poisson's ratio of the polishing layer 4 is less than 0.20, it may not exhibit sufficient elasticity and the polishing rate may decrease. In addition, the upper limit of the Poisson's ratio is 0.5, and materials with a Poisson's ratio close to 0.5 are special materials such as rubber materials, which are highly water-repellent and may cause problems such as being unable to retain polishing slurry.

[0022] The abrasive layer 4 preferably contains hollow microspheres.

[0023] <Substrate Layer> (Configuration) The polishing pad 3 of the present invention has a substrate layer 6. Although the substrate layer is sometimes referred to as a cushion layer in the art, it will be referred to as a substrate layer in this specification. The substrate layer 6 enables the polishing layer 4 to contact the workpiece 8 more uniformly.

[0024] The substrate layer 6 used in the present invention is preferably composed of polyurethane foam or a polyurethane material in which hollow microspheres are dispersed. Polyurethane foam is a uniform plastic foam obtained by mixing a polyisocyanate having an NCO (isocyanate) group and a polyol having an OH (hydroxy) group together with a catalyst, a blowing agent, a foam stabilizer, etc., and simultaneously carrying out a foaming reaction and a resinification reaction. Examples of such a foam include flexible polyurethane foam and rigid polyurethane foam. Flexible polyurethane foam is a foam with interconnected cells that is soft and has good resilience, and generally has an expansion ratio of 60 to 100 times and an apparent density of 16 to 100 kg / m. ３ Rigid polyurethane foam is a lightweight plastic foam, and is a collection of small air bubbles, each of which is an independent cell. Rigid polyurethane foam is preferred because it has a small amount of compression deformation, high resilience, and excellent bounce shape improvement performance.

[0025] The polyurethane material with dispersed hollow microspheres is a foam obtained by casting and curing a mixture of an isocyanate group-containing compound containing hollow microspheres and a curing agent (chain extender), as described for the polishing layer 4. Hollow microspheres refer to microspheres having voids inside. The shapes of hollow microspheres include spherical, elliptical, and shapes similar to these. Examples include pre-expanded microspheres and those in which unexpanded heat-expandable microspheres are added during the raw material mixing stage and then heat-expanded. The physical properties of the substrate layer 6, such as its A hardness, can be adjusted to a desired range by adjusting the composition of the substrate layer 6 and the number and size of the hollow microspheres.

[0026] When the base layer 6 used in the present invention is made of a polyurethane material in which hollow microspheres are dispersed, the base layer 6 has closed cells rather than open cells, which prevents the intrusion of slurry and the like into the base layer 6, thereby preventing peeling between the polishing layer 4 and the base layer 6 and preventing changes in compression behavior over time due to the voids inside the base layer 6 being replaced by water.

[0027] (Amount of Compression Deformation) The amount of compression deformation of the base material layer 6 in a compression test using MAG is 20 μm or less. The amount of compression deformation is determined by subtracting the thickness of the base material layer at a predetermined number of compressions after repeated compression / recovery from the thickness of the base material layer before the test. The predetermined number of compressions is preferably 10 to 200 times, and more preferably 20 to 100 times. If the amount of compression deformation exceeds 20 μm, there is a risk that sufficient edge profile improvement performance will not be exhibited. The amount of compression deformation is preferably 18 μm or less, and more preferably 16 μm or less. The compression test using MAG is a continuous compression / recovery test performed using a MAG (Micro Autograph, MST-1, manufactured by Shimadzu Corporation).

[0028] (Storage Modulus) The base layer 6 has a storage modulus of 3.5 MPa or more and 20 (20.0) MPa or less in a compression mode dynamic viscoelasticity test (DMA). If the storage modulus is less than 3.5 MPa, there is a risk that the performance of improving the ripple shape will not be sufficient, and if the storage modulus exceeds 20 MPa, there is a risk that other polishing performance will be adversely affected, such as an increase in scratches on the polished object 8. The lower limit of the storage modulus is preferably 4.0 MPa, more preferably 4.5 MPa. The upper limit is preferably 15.0 MPa, more preferably 12.5 MPa. The dynamic viscoelasticity test (DMA) is a method of measuring the mechanical properties of a sample by applying a strain or stress that changes (oscillates) over time to the sample and measuring the resulting stress or strain.

[0029] (Ratio of storage modulus between polishing layer and base layer) The ratio of the storage modulus (MPa) of the polishing layer 4 to the storage modulus (MPa) of the base layer 6 (polishing layer / base layer) is 5 or more and 30 or less. If the ratio of the storage modulus of the polishing layer 4 to the storage modulus of the base layer 6 (polishing layer / base layer) is less than 5, the base layer may not exhibit sufficient cushioning performance, and if the ratio of the storage modulus of the polishing layer 4 to the storage modulus of the base layer 6 (polishing layer / base layer) is greater than 30, the base layer may not exhibit sufficient spring shape improvement performance. The lower limit of the ratio of the storage modulus of the polishing layer 4 to the storage modulus of the base layer 6 (polishing layer / base layer) is preferably 7.5, more preferably 10. The upper limit is preferably 25, more preferably 20.

[0030] (Ratio of thickness of base layer to thickness of polishing layer) The ratio of the thickness (mm) of the base layer 6 to the thickness (mm) of the polishing layer 4 is 40% or more and less than 65%. If the ratio of the thickness of the base layer 6 to the thickness of the polishing layer 4 is less than 40%, the base layer may not exhibit sufficient cushioning performance, and if the ratio of the thickness of the base layer 6 to the thickness of the polishing layer 4 is 65% or more, the base layer may not exhibit sufficient performance to improve the shape of the burrs. The lower limit of the ratio of the thickness of the base layer 6 to the thickness of the polishing layer 4 is preferably 45%, more preferably 50%. The upper limit is preferably 65%, more preferably 62.5%.

[0031] (Shore A Hardness) The Shore A hardness of the base layer 6 is not particularly limited, but is preferably, for example, 50 to 80. If the Shore A hardness is less than 50, there is a risk that the base layer will not exhibit sufficient edge profile improvement performance, and if it exceeds 80, there is a risk that the base layer will not exhibit the certain degree of cushioning property required.

[0032] (Density) The density of the base layer 6 is not particularly limited. For example, it may be 0.10 to 0.80 g / cm ３ In addition, when air bubbles are contained, the density here does not refer to the density of the material itself, but to the density of the base material layer 6 in a state in which air bubbles are contained.

[0033] <Adhesive Layer> The adhesive layer 7 is a layer for adhering the base layer 6 and the polishing layer 4, and is typically composed of a double-sided tape or adhesive. Any double-sided tape or adhesive known in the art (e.g., an adhesive sheet) can be used. The polishing layer 4 and the base layer 6 are bonded together by the adhesive layer 7. The adhesive layer 7 can be formed of at least one adhesive selected from, for example, acrylic, epoxy, and urethane adhesives. For example, an acrylic adhesive can be used, and the thickness can be set to 0.1 mm.

[0034] <<Method of Manufacturing Polishing Pad>> A method of manufacturing the polishing pad 3 of the present invention will be described.

[0035] <Material of Polishing Layer> The material of the polishing layer 4 is not particularly limited, but for example, polyurethane resin, polyurea resin, and polyurethane polyurea resin are preferred as the main component, and polyurethane resin is more preferred. Specific examples of the main component material include a material obtained by reacting a urethane bond-containing polyisocyanate compound with a curing agent.

[0036] The method for producing the material of the polishing layer 4 will be described below using an example in which a urethane bond-containing isocyanate compound, a polyol compound, and a curing agent are used.

[0037] Examples of methods for producing the polishing layer 4 using a urethane bond-containing polyisocyanate compound and a curing agent include a material preparation step of preparing at least a urethane bond-containing polyisocyanate compound, an additive, and a curing agent; a mixing step of mixing at least the urethane bond-containing polyisocyanate compound, the additive, and the curing agent to obtain a mixture for molding a molded body; and a curing step of molding the mixture for molding a polishing layer 4.

[0038] The material preparation process, the mixing process, and the molding process will be explained below.

[0039] <Material Preparation Step> To manufacture the polishing layer 4 of the present invention, a urethane bond-containing polyisocyanate compound and a curing agent are prepared as raw materials for a polyurethane resin molded body (cured resin). Here, the urethane bond-containing polyisocyanate is a urethane prepolymer for forming a polyurethane resin molded body. When the polishing layer 4 is to be a polyurea resin molded body or a polyurethane-polyurea resin molded body, a prepolymer appropriate for the purpose is used.

[0040] Each component will be described below.

[0041] (Urethane bond-containing polyisocyanate compound) The urethane bond-containing polyisocyanate compound (urethane prepolymer or simply prepolymer) is a compound obtained by reacting the following polyisocyanate compound with a polyol compound under commonly used conditions, and contains a urethane bond and an isocyanate group in the molecule. Furthermore, the urethane bond-containing polyisocyanate compound may contain other components within the range that does not impair the effects of the present invention.

[0042] The urethane bond-containing polyisocyanate compound may be a commercially available product, or may be synthesized by reacting a polyisocyanate compound with a polyol compound. There are no particular limitations on the reaction, and the addition polymerization reaction may be carried out using methods and conditions known in the production of polyurethane resins. For example, the urethane bond-containing polyisocyanate may be produced by adding a polyisocyanate compound heated to 50°C to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, then raising the temperature to 80°C after 30 minutes and continuing the reaction at 80°C for 60 minutes. The urethane bond-containing polyisocyanate preferably has an NCO equivalent of approximately 300 to 600. Therefore, when the urethane bond-containing polyisocyanate is commercially available, it is preferable that the NCO equivalent falls within the above range. When producing the urethane bond-containing polyisocyanate by synthesis, it is preferable to adjust the NCO equivalent within the above range by using the following raw materials in appropriate proportions.

[0043] (Polyisocyanate Compound) In this specification, the term "polyisocyanate compound" refers to a compound having two or more isocyanate groups in the molecule. The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule. For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 4,4 ... Examples of the polyisocyanate compound include diphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethylidine diisothiocyanate, etc. These polyisocyanate compounds may be used alone, or multiple polyisocyanate compounds may be used in combination.

[0044] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI.

[0045] (Polyol Compound as Raw Material for Prepolymer) In this specification, the term "polyol compound" refers to a compound having two or more hydroxyl groups (OH) in the molecule. Examples of polyol compounds used in the synthesis of a urethane bond-containing polyisocyanate compound as a prepolymer include diol compounds, triol compounds, etc., such as ethylene glycol, diethylene glycol (DEG), and butylene glycol; polyether polyol compounds, such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG); polyester diols, and combinations thereof. Among these, it is preferable to use a combination of polypropylene glycol, polyester diol, and diethylene glycol. The polyester diol can be obtained, for example, by reacting a dicarboxylic acid compound with a diol compound. Examples of the dicarboxylic acid compound include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, and dodecanedioic acid; unsaturated bond-containing dicarboxylic acids such as maleic anhydride, maleic acid, and fumaric acid; alicyclic polycarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as orthophthalic acid, terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, diphenic acid, and anhydrides thereof; and the like, which may be used alone or in combination. Examples of diol compounds used in the synthesis of polyester diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol, and these can be used alone or in combination.Among the above, polyester diols of adipic acid and 1,4-butanediol and polyester diols of adipic acid and diethylene glycol are preferred. The number average molecular weight (Mn) of the polyol compound is not particularly limited and can be, for example, 500 to 2500. Here, the number average molecular weight can be measured by gel permeation chromatography (GPC). Note that when measuring the number average molecular weight of the polyol compound from the polyurethane resin, it can also be estimated by GPC after decomposing each component by a conventional method such as amine decomposition. The above polyol compounds may be used alone, or multiple polyol compounds may be used in combination.

[0046] (Additives) As described above, additives such as an oxidizing agent can be added to the material of the polishing layer 4 as needed.

[0047] (Curing Agent) In the method for producing the polishing layer 4 of the present invention, a curing agent (also called a chain extender) is mixed with the urethane bond-containing polyisocyanate compound, etc. in the mixing step. By adding the curing agent, in the subsequent molding step, the main chain terminal of the urethane bond-containing polyisocyanate compound bonds with the curing agent to form a polymer chain, which then hardens.Examples of the curing agent include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 4-methyl-2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis[3-(isopropylamino)-4- polyvalent amine compounds such as 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-diamino-4-hydroxyphenyl)propane, 2,6-diamino-4-methylphenol, trimethylethylenebis-4-aminobenzoate, and polytetramethyleneoxide-di-p-aminobenzoate; ethylene glycol, propane, Pyrene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3- Examples of polyhydric alcohol compounds include methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, trimethylolpropane, trimethylolethane, trimethylolmethane, poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol.Furthermore, the polyvalent amine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, etc. As the polyvalent amine compound, a diamine compound is preferred, and it is more preferred to use, for example, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA).

[0048] (Hollow Microspheres) The polishing layer 4 may contain hollow microspheres having an outer shell and a hollow interior, if necessary. As mentioned above, commercially available hollow microspheres can be used as the material for the hollow microspheres. Alternatively, those obtained by conventional synthesis may be used. The material for the outer shell of the hollow microspheres is not particularly limited, but examples thereof include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride, and organic silicone resins, as well as copolymers of two or more of the monomers constituting these resins. In addition, commercially available hollow microspheres include, but are not limited to, the Expancel series (trade name, manufactured by Akzo Nobel) and Matsumoto Microsphere (trade name, manufactured by Matsumoto Yushi Co., Ltd.). The gas contained in the hollow microspheres is not particularly limited, but examples thereof include hydrocarbons, specifically isobutane.

[0049] <Mixing Step> In the mixing step, the urethane bond-containing polyisocyanate compound (urethane prepolymer) obtained in the preparation step, hollow microspheres, additives, and curing agent are fed into a mixer and stirred and mixed. The mixing step is carried out under a heated condition at a temperature that ensures the fluidity of each of the above components.

[0050] <Molding Step> In the molded body molding step, the mixture for molding the molded body prepared in the mixing step is poured into a rod-shaped mold preheated to 30 to 100°C for primary curing, and then heated at about 100 to 150°C for about 10 minutes to 5 hours for secondary curing to mold a cured polyurethane resin (polyurethane resin molded body). At this time, the urethane prepolymer and the curing agent react to form a polyurethane resin, which hardens the mixture.

[0051] In the molding process, the mixture is reacted in a mold as needed to form a foam. At this time, the prepolymer is crosslinked and hardened by the reaction between the prepolymer and the curing agent.

[0052] After obtaining the molded body, it is sliced ​​into sheets to form a plurality of polishing layers 4. A general slicing machine can be used for slicing. During slicing, the lower layer of the polishing layer 4 is held, and the polishing layer 4 is sliced ​​to a predetermined thickness starting from the upper layer. The slice thickness is set to a range of 1.3 to 2.5 mm, for example.

[0053] The polishing surface of the resulting polishing layer 4 is provided with grooves as required.

[0054] After that, a double-sided tape is attached to the surface of the polishing layer 4 opposite to the polishing surface of the polishing layer 4. There are no particular restrictions on the double-sided tape, and any double-sided tape known in the art can be selected and used.

[0055] <Method for manufacturing substrate layer 6> As described above, polyurethane foam or a polyurethane material with hollow microspheres dispersed therein is used as the material for substrate layer 6. The polyurethane foam may be commercially available, or a polyurethane foam may be manufactured and used in the same manner as described in the method for manufacturing polishing layer 4. The polyurethane material with hollow microspheres dispersed therein may be commercially available, or, when hollow microspheres are used, a polyurethane material with hollow microspheres dispersed therein may be manufactured and used in the same manner as described in the method for manufacturing polishing layer 4.

[0056] The hollow microspheres that may be used for the base layer 6 are hollow microspheres that have an outer shell and a hollow interior. Commercially available hollow microspheres may be used as the material for the hollow microspheres, or microspheres obtained by conventional synthesis may be used. The material for the outer shell of the hollow microspheres is not particularly limited, but examples include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, poly(meth)acrylonitrile, polyvinylidene chloride, polyvinyl chloride and organic silicone resins, and copolymers of two or more of the monomers that constitute these resins (e.g., acrylonitrile-vinylidene chloride copolymer). Commercially available hollow microspheres include, but are not limited to, the Expancel series (trade names, manufactured by Akzo Nobel) and Matsumoto Microsphere (trade name, manufactured by Matsumoto Yushi Co., Ltd.). The gas contained in the hollow microspheres is not particularly limited, but examples thereof include hydrocarbons, specifically isobutane.

[0057] The shape of the hollow microspheres is not particularly limited and may be, for example, spherical or nearly spherical. The average particle size of the hollow microspheres is not particularly limited, but is preferably 5 to 200 μm, more preferably 5 to 80 μm, even more preferably 5 to 50 μm, and particularly preferably 5 to 35 μm. The average particle size can be measured using a laser diffraction particle size analyzer (e.g., Mastersizer 2000, manufactured by Spectris Co., Ltd.).

[0058] The material for the hollow microspheres is added in an amount of preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 4 parts by mass, per 100 parts by mass of the urethane prepolymer.

[0059] In addition to the above components, a conventionally used blowing agent may be used in combination with the hollow microspheres, and a gas that is non-reactive with the above components may be blown into the mixing step described below, provided that the effects of the present invention are not impaired. The foam (bubbles) and hollow microspheres of the base layer 6 have closed cells, which is advantageous in that there is no risk of peeling due to the slurry permeating the base layer 6.

[0060] <Bonding Step> In the bonding step, the formed polishing layer 4 and base layer 6 are bonded together (bonded) with an adhesive layer 7. For example, an acrylic adhesive is used for the adhesive layer 7, and the adhesive layer 7 is formed to a thickness of 0.1 mm. That is, the acrylic adhesive is applied to a substantially uniform thickness on the surface of the polishing layer 4 opposite the polishing surface. The surface of the polishing layer 4 opposite the polishing surface and the surface of the base layer 6 are pressed together via the applied adhesive, bonding the polishing layer 4 and base layer 6 with the adhesive layer 7. The polishing pad 3 is then cut into a desired shape, such as a circle, and inspected to ensure that there is no dirt or foreign matter attached, thereby completing the polishing pad 3.

[0061] <About the object to be polished> The object to be polished 8 that can be used with the polishing pad 3 described in this specification is not particularly limited, but it is likely to be effective if the object to be polished 8 is one that is easily affected by the rippled shape. An example of an object to be polished 8 that is likely to be affected by the rippled shape is an object to be polished 8 that has a metal film on its surface, and the polishing pad 3 described in this specification can be used to polish such a metal film. The object to be polished 8 is a wafer with a SiO2 film on the surface that is easily etched. ２ The metal of the metal film is not particularly limited, but is preferably a metal with high conductivity such as gold, silver, or copper.

[0062] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0063] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass".

[0064] The NCO equivalent is a numerical value showing the molecular weight of the prepolymer (PP) per NCO group, which is calculated by the formula "(mass (parts) of the polyisocyanate compound + mass (parts) of the polyol compound) / [(number of functional groups per molecule of the polyisocyanate compound × mass (parts) of the polyisocyanate compound / molecular weight of the polyisocyanate compound) - (number of functional groups per molecule of the polyol compound × mass (parts) of the polyol compound / molecular weight of the polyol compound)]".

[0065] (Regarding the Polishing Layer) The same polishing layer A was used in all of the Examples and Comparative Examples. The polishing layer A was produced as follows. A mixture of 50 parts of an isocyanate-terminated urethane prepolymer having an NCO equivalent of 560, obtained by reacting 2,4-tolylene diisocyanate (TDI), polypropylene glycol (PPG) having a number average molecular weight of 1000, and diethylene glycol (DEG), and 50 parts of an isocyanate-terminated urethane prepolymer having an NCO equivalent of 600, obtained by reacting 2,4-tolylene diisocyanate (TDI), a polyester diol of adipic acid and 1,4-butanediol having a number average molecular weight of 2000, and diethylene glycol (DEG), was mixed with 3.5 parts of unexpanded hollow microspheres having a shell portion made of an acrylonitrile-vinylidene chloride copolymer and containing isobutane gas, to obtain a mixed solution. The resulting mixed solution was charged into a first liquid tank and kept warm. Next, 20.3 parts of MOCA were added as a curing agent to the second liquid tank separately from the first liquid, and the mixture was kept warm in the second liquid tank. The liquids from the first and second liquid tanks were each injected into a mixer equipped with two injection ports so that the R value, which represents the equivalent ratio of amino groups and hydroxyl groups present in the curing agent to the terminal isocyanate groups in the prepolymer, was 0.90. The two injected liquids were mixed and stirred while being injected into a preheated mold of a molding machine, and then the mold was clamped and heated at 80°C for 30 minutes to perform primary curing. The primary cured molded product was demolded and then subjected to secondary curing in an oven at 120°C for 4 hours to obtain a urethane molded product. The obtained urethane molded product was allowed to cool to 25°C, then heated again in an oven at 120°C for 5 hours, and then sliced ​​to the specified thickness to obtain abrasive layer A. Thicknesses of 1.3 mm, 1.6 mm, and 2.0 mm were prepared.

[0066] (Regarding the substrate layer) Substrates A to F were prepared to be used as the substrate layer. Substrate A: A commercially available sponge-like urethane foam ("Sekisui Sponge 2504KMS" manufactured by Sekisui Chemical Co., Ltd., A hardness 60, density 0.55 g / cm ３ , and adjusted to thicknesses of 0.8 mm and 1.3 mm). Substrate B: Balloon-expanded rigid urethane (prepared in the same manner as for the polishing layer, except that 4.0 parts of the same hollow microspheres (unexpanded hollow microspheres) used for the polishing layer were added and mixed to 100 parts of an isocyanate-terminated urethane prepolymer having an NCO equivalent of 460, which was obtained by reacting 2,4-tolylene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 650, and diethylene glycol (DEG), and 41.8 parts of a 1:1 mixture of MOCA and PTMG having a number average molecular weight of 1,000 were added as a curing agent). Hardness A: 80, density: 0.75 g / cm ３ , thickness 1.0 mm) Substrate C: commercially available sponge-like urethane foam ("Sekisui Sponge 2504GMS" manufactured by Sekisui Chemical Co., Ltd., A hardness 71, density 0.65 g / cm ３ , thickness 1.0 mm) Substrate D: commercially available sponge-like urethane foam ("Sekisui Sponge 2504MP4" manufactured by Sekisui Chemical Co., Ltd., A hardness 72.5, density 0.52 g / cm ３ , thickness 1.0 mm) Substrate E: Sponge-like low-resilience urethane ("Volara VSC" manufactured by Sekisui Chemical Co., Ltd., A hardness 65, density 0.19 g / cm ３ , thickness 0.8 mm) Base material F: sponge-like low-resilience urethane ("Volara S" manufactured by Sekisui Chemical Co., Ltd., A hardness 46, density 0.19 g / cm ３ , thickness 0.8 mm)

[0067] (Measurement of compressive deformation amount) For substrates A to F, a continuous compression / recovery test was carried out using a MAG (Micro Autograph, MST-1, manufactured by Shimadzu Corporation) to measure the compressive deformation amount. The compressive deformation amount was calculated by subtracting the thickness of the substrate layer before the test from the thickness of the substrate layer after the 100th compression. The results are shown in Table 1. The MAG measurement conditions were as follows: Load: 50 g / cm at recovery ２, 300 g / cm when compressed ２ Indenter: diameter 20 mm; Sample: diameter 40 mm; Compression speed: 0.3 mm / min; Number of cycles: 100 times

[0068] (Measurement of Storage Modulus of Substrate) A dynamic viscoelasticity test was carried out on substrates A to F using an RSA-G2 manufactured by TA Instruments to measure the storage modulus. The results are shown in Table 1. The measurement conditions for the storage modulus test were as follows: Frequency: 1 Hz Sample: 10 mm length x 10 mm width x 0.1 cm thickness Test mode: Compression Measurement temperature: 40°C Strain range: 0.10% Initial load: 100 g (Measurement of Storage Modulus of Polishing Layer) A dynamic viscoelasticity test was carried out on polishing layer A using an RSA-G2 manufactured by TA Instruments under the following measurement conditions to measure the storage modulus, which was 98.2 MPa. Frequency: 1.6 Hz Sample: 50 mm length x 5 mm width x 0.16 cm thickness Test mode: Tension Measurement temperature: 40°C Strain range: 0.10% Initial load: 148 g

[0069] (Measurement of Shore A Hardness) The Shore A hardness of the substrate was determined in accordance with Japanese Industrial Standards (JIS K 7311) from the penetration depth of an indenter pressed against the surface of a test piece via a spring.

[0070]

[0071] (Examples and Comparative Examples) The polishing layer A obtained above and the substrates A to F as the base layer were joined with 0.1 mm thick double-sided tape (a PET substrate with adhesive layers made of acrylic resin on both sides), and the double-sided tape was attached to the side opposite the adhesive layer of the base layer to produce the polishing pads of the examples and comparative examples.

[0072] (Polishing Test) Polishing was performed using the polishing pads of each Example and Comparative Example under the following polishing conditions. The thickness of the Cu film was measured at 121 points on the diameter during polishing. Figure 6 shows the thickness profiles of the Cu film at the edge of the workpiece polished using the polishing pads of each Example and Comparative Example. The vertical axis represents the thickness of the Cu film, and the horizontal axis represents the distance from the center of the line (diameter) passing through the center of the workpiece (the center of the workpiece is set to 0, and the part 140 to 150 mm from the center). For ease of comparison, the profiles of each Example and Comparative Example are conveniently displayed side by side. Compared to the Comparative Examples, the polishing pads of the Examples have a small film thickness difference of less than 350 angstroms, and the Cu film is straight even when approaching the edge, demonstrating a stable thickness.

[0073] (Polishing conditions) Polishing machine: F-REX300X (manufactured by Ebara Corporation) Disk: 34R (manufactured by KINIK) Retainer ring: Retainer ring GXKD (manufactured by Ebara Corporation) Rotation speed: (platen) 90 rpm, (polishing head) 81 rpm Polishing pressure: 1.6 psi Polishing agent temperature: 20°C Polishing agent discharge rate: 200 ml / min Polishing agent: Cu slurry Workpiece: Silicon wafer with Cu film (disc-shaped, 300 mm diameter) Polishing time: 60 seconds Pad break: 32N 20 minutes Conditioning: Ex-situ 32N2 scan

[0074] The film thickness difference obtained in the examples and comparative examples was determined by obtaining an edge profile after the polishing test, and measuring the distance from the most raised part of the edge to the most polished part, as shown in FIG. 4, as the "film thickness difference."

[0075]

[0076] From Tables 1, 2 and Figure 6, it can be seen that the polishing pads of Examples 1 to 4, which use substrates with a large storage modulus and a small amount of compressive deformation, have smaller film thickness differences, are straight even near the edges, and have stable Cu film thicknesses than the polishing pads of Comparative Examples 1 and 2, which use substrates with a storage modulus of less than 3.5 MPa and a large amount of compressive deformation.

[0077] Next, a polishing pad was prepared by combining layers of different thicknesses, using substrate A (thicknesses 0.8 mm and 1.3 mm) for the substrate layer and polishing layer A (thicknesses 1.3 mm, 1.6 mm, and 2.0 mm) for the polishing layer, and a polishing test was performed. The combinations are as follows. The results are shown in Table 3.

[0078]

[0079] Table 3 shows that when the thickness of the base layer relative to the thickness of the polishing layer is 40% or more but less than 65%, the film thickness difference is small, the Cu film is straight even when approaching the end, and the thickness is stable.

[0080] The present invention provides a polishing pad that can improve the profile abnormality of the edge portion, that is, the ridge shape, and therefore contributes to the manufacture and sale of polishing pads and has industrial applicability.

[0081] REFERENCE SIGNS LIST 1 Polishing device 3 Polishing pad 4 Polishing layer 6 Base material layer 7 Adhesive layer 8 Object to be polished 8a Spike shape 9 Slurry 10 Polishing surface plate 11 Base 16 Holding surface plate

Claims

1. A polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, and a base layer arranged on the opposite side of the polishing surface of the polishing layer, wherein the base layer has a compressive deformation of 20 μm or less in a compression test using MAG, a storage modulus of 3.5 MPa or more and 20 MPa or less in dynamic viscoelasticity measurement in a compression mode, and the thickness of the base layer relative to the thickness of the polishing layer is 40% or more and less than 65%.

2. The polishing pad according to claim 1, wherein the ratio of the storage elastic modulus of the polishing layer to the storage elastic modulus of the base layer (polishing layer / base layer) is 5 or more and 30 or less.

3. The polishing pad of claim 1, wherein the substrate layer is made of polyurethane foam or a polyurethane material having hollow microspheres dispersed therein.

4. The polishing pad according to claim 1, which is a polishing pad for metal polishing.

5. A polishing method for polishing an object having a metal surface, comprising the steps of: preparing an object having a metal surface; and bringing the polishing surface of the polishing pad according to claim 1 into contact with said metal surface to polish said metal surface.

Images