Polishing pad

Abstract

To provide a polishing pad that can improve sagging of an end part, without changing a physical property / bubble structure of a polishing layer.SOLUTION: A polishing pad comprises a polishing layer having a polishing surface for polishing an object to be polished and a cushion layer arranged at the opposite side of the polishing surface of the polishing layer. With respect to a ratio (tanδ) of storage elastic modulus E' and loss elastic modulus E'' in the whole of the polishing pad which are obtained by dynamic viscoelastic test by frequency dispersion (25°C) in a bending mode, a ratio of a maximum value (tanδmax100-1000) of tanδ measured at 100-1000 rad / s to a maximum value (tanδmax1-10) of tanδ measured at 1-10 rad / s is 0.75-1.30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polishing pad. More particularly, the present invention relates to a polishing pad that can be suitably used for polishing optical materials, semiconductor wafers, semiconductor devices, hard disk substrates, and the like. [Background technology]

[0002] Chemical mechanical polishing (CMP) is a commonly used polishing method for planarizing the surfaces of optical materials, semiconductor wafers, semiconductor devices, and hard disk substrates.

[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 the 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 the polishing, and a cushion 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 grains. As the chemical components and abrasive grains 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, polishing pads 3 have been used with a polishing layer 4 made of foamed polyurethane. However, the polishing layer 4 conforms to the shape of the edge of the workpiece 8 during polishing, resulting in overpolishing, known as "edge sagging" (8a in Figure 2), in which the edge of the workpiece 8 is polished more than the center, as shown in Figure 2. Figure 3, which shows a workpiece polished using conventional technology, plots the polishing rate (RR) on the vertical axis and the distance along a line passing through the center of the workpiece 8 on the horizontal axis ("0" on the horizontal axis represents the center of the workpiece), revealing that the polishing rate at both ends is higher than in other areas, resulting in edge sagging. This edge sagging can be problematic in semiconductor polishing (especially in oxide film polishing processes) when the polishing rate at the outermost edge (periphery) of the workpiece is 1.5 times or more higher than that of the rest of the workpiece.

[0005] To address this over-polishing phenomenon known as edge sagging, Patent Document 1 discloses a polishing pad that prevents edge sagging while suppressing the occurrence of polishing scratches by using a specific structure of air bubbles in the foam, thereby keeping the hardness of the polishing layer within a certain range.

[0006] Patent Document 2 discloses a polishing pad that does not have the problem of edge sagging by setting the hardness and tear strength of the polishing layer within a predetermined range. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-714 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-190313 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the polishing pads described in Patent Documents 1 and 2 above require specific physical properties and cell structures in the polishing layer, and even if edge sagging can be improved, other polishing performance may be inferior.

[0009] The present invention has been made in consideration of the above problems, and aims to provide a polishing pad that can improve edge sagging without significantly changing the physical properties and cellular structure of the polishing layer. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that edge sagging can be suppressed by setting tan δ, which is the ratio of the storage modulus E′ to the loss modulus E″ of the entire polishing pad, within a specific range. 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 cushioning layer disposed on the opposite side of the polishing surface of the polishing layer; The ratio (tanδ) of the storage modulus E' to the loss modulus E'' of the entire polishing pad obtained by dynamic viscoelasticity testing using frequency dispersion (25°C) in bending mode was measured at 1 to 10 rad / s. max1-10 ) for the maximum value of tanδ measured at 100 to 1000 rad / s (tanδ max100-1000 ) ratio is 0.75 to 1.30. [2] The maximum value of tanδ measured at 1 to 10 rad / s (tanδ max1-10 ) for the maximum value of tanδ measured at 100 to 1000 rad / s (tanδ max100-1000 ) is 0.85 to 1.15. [3] The ratio of the maximum value to the minimum value of tanδ measured at 0.1 to 10,000 rad / s (maximum value (tanδ max0.1-10000 ) / minimum value (tanδ min0.1-10000 )) is 1 to 1.3. [4] The difference between the maximum and minimum values ​​of tanδ measured at 0.1 to 10,000 rad / s (maximum value (tanδ max0.1-10000 ) / minimum value (tanδ min0.1-10000 )) is 0 to 0.1. [Effects of the Invention]

[0011] According to the polishing pad of the present invention, edge sagging can be suppressed by setting tan δ, which is the ratio of the storage modulus E' to the loss modulus E'' of the entire polishing pad, within a specific range without changing the physical properties or cell structure of the polishing layer. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a polishing apparatus 1. As shown in FIG. [Figure 2] FIG. 2 is a side view of the workpiece 8 with its end sagging. [Figure 3] FIG. 3 shows the profile of the polishing rate of the entire workpiece 8 polished by the conventional technique (the polishing pad of Comparative Example 1) along a straight line passing through the center of the workpiece 8 (the profile when the 50th workpiece was polished). [Figure 4] FIG. 4(a) is a perspective view and FIG. 4(b) is a cross-sectional view of a polishing pad 3 of the present invention. [Figure 5] 5 shows the state in which the object to be polished (8) is placed in a retainer ring 16A and polished on a polishing pad. The arrows in the figure indicate the direction of rotation of the object to be polished 8 and the polishing pad 3. [Figure 6] FIG. 6 shows a schematic diagram of the dynamic viscoelasticity test performed on the entire polishing pad 3. [Figure 7] FIG. 7 is a graph of tan δ when dynamic viscoelasticity was measured in bending mode for the entire polishing pad of Example 1. [Figure 8] FIG. 8 shows the profile of the polishing rate of the entire workpiece 8 along a straight line passing through the center of the workpiece 8 polished by the polishing pad of Example 1 (the profile when the 50th workpiece was polished). [Figure 9] FIG. 9 is a graph of tan δ when dynamic viscoelasticity was measured in bending mode for the entire polishing pad of Example 2. [Figure 10]FIG. 10 shows the profile of the polishing rate of the entire workpiece 8 along a straight line passing through the center of the workpiece 8 polished by the polishing pad of Example 2 (the profile when the 50th workpiece was polished). [Figure 11] FIG. 11 is a graph of tan δ when dynamic viscoelasticity was measured in bending mode for only the polishing layer B of the polishing pads of Examples 1 and 2. [Figure 12] FIG. 12 is a graph of tan δ when dynamic viscoelasticity was measured in bending mode for the entire polishing pad of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the embodiments of the invention will be described, but the present invention is not limited to the embodiments of the invention.

[0014] <<Polishing pads>> The structure of the polishing pad 3 will be described with reference to Fig. 4. As shown in Fig. 4, the polishing pad 3 includes a polishing layer 4 and a cushion layer 6. The shape of the polishing pad 3 is preferably disc-shaped, but is not particularly limited thereto, and 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, about 10 cm to 2 m in diameter. In the polishing pad 3 of the present invention, the polishing layer 4 is preferably bonded to the cushion layer 6 via an adhesive layer 7, as shown in FIG. The polishing pad 3 is attached to the polishing platen 10 of the polishing apparatus 1 by double-sided tape or the like arranged on the cushion layer 6. The polishing pad 3 is rotated by the polishing apparatus 1 while pressing against the object 8 to be polished, and polishes the object 8 to be polished.

[0015] <Polishing layer> (composition) The polishing pad 3 includes a polishing layer 4 that is a layer for polishing an object to be polished 8. The material constituting the polishing layer 4 can be suitably selected from polyurethane resin, polyurea resin, and polyurethane-polyurea resin, and more preferably polyurethane resin. The size (diameter) of the polishing layer 4 is the same as that of the polishing pad 3, and can be about 10 cm to 2 mm in diameter, and the thickness of the polishing layer 4 can usually be about 1 to 5 mm. The polishing layer 4 is rotated together with the polishing table 10 of the polishing device 1, and while a slurry 9 is poured onto it, the chemical components and abrasive grains contained in the slurry 9 are moved relative to the object 8 to be polished, thereby polishing the object 8 to be polished. The polishing layer 4 has hollow microspheres 4A (foam) dispersed therein.

[0016] (grooving) It is preferable to provide grooves on the surface of the polishing layer 4 of the present invention that faces the polished object 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, or both slurry discharge grooves and slurry retention grooves. Examples of the slurry discharge grooves include lattice grooves and radial grooves, while examples of the slurry retention grooves include concentric grooves and perforations (through holes), and these can also be combined. In low-pressure polishing, the platen is rotated at high speed to reduce the pressing force on the workpiece 8 and ensure a high polishing rate. This can lead to the so-called hydroplaning phenomenon, in which a layer of slurry 9 exists between the polishing surface and the polishing surface, hindering the polishing process. Grooving 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 can be U-shaped, V-shaped, or semicircular. The groove pitch, width, and depth are not particularly limited. To improve the flatness of the polishing pad 3, a surface grinding process such as buffing may be performed on the polishing surface side or the side opposite the polishing surface.

[0017] (Shore D hardness) The Shore D hardness of the polishing layer 4 of the present invention is not particularly limited, but is, for example, 20 to 100, preferably 30 to 80, and more preferably 40 to 70. If the Shore D hardness is low, it becomes difficult to flatten fine irregularities by low-pressure polishing. In addition, it may affect edge sagging. If the Shore D hardness is too high, the polishing layer 4 may be strongly rubbed against the polished object 8, causing scratches on the polished surface of the polished object 8.

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

[0019] In the polishing pad 3 of the present invention, hollow microspheres 4A are used to encapsulate air bubbles within the polyurethane resin molding. Hollow microspheres refer to microspheres with voids. The shapes of the hollow microspheres 4A include spherical, elliptical, and shapes similar to these. Examples include pre-expanded microspheres and those obtained by thermally expanding unexpanded thermally expandable microspheres. The physical properties of the abrasive layer 4, such as the Shore D hardness, can be adjusted to a desired range by adjusting the composition of the abrasive layer 4, the number and size of the hollow microspheres 4A, and the like.

[0020] <Cushion layer> (composition) The polishing pad 3 of the present invention has a cushion layer 6. The cushion layer 6 desirably allows the polishing layer 4 to contact the workpiece 8 more uniformly. Materials for the cushion layer 6 include resins; impregnated materials in which the resins are impregnated into a base material; flexible materials such as synthetic resins and rubbers; and sponge materials using the resins. Examples of the resins include resins such as polyurethane, polyethylene, polybutadiene, and silicone, and rubbers such as natural rubber, nitrile rubber, and polyurethane rubber.

[0021] The cushion layer 6 may be a foam having a cellular structure. As the cellular structure, in addition to a nonwoven fabric or the like having voids formed therein, a suede-like material having teardrop-shaped bubbles formed by a wet film-forming method, or a sponge-like material having fine bubbles formed therein may be preferably used.

[0022] <Adhesive layer> The adhesive layer 7 is a layer for adhering the cushion layer 6 and the polishing layer 4, and is usually made of a double-sided tape or an adhesive. Any double-sided tape or adhesive known in the art (e.g., an adhesive sheet) can be used. The polishing pad 3 and the cushion layer 6 are bonded together by an 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 is used, and the thickness can be set to 0.1 mm.

[0023] <tanδ> When the entire polishing pad 3 of the present invention is subjected to a dynamic viscoelasticity test by frequency dispersion (25°C) in a bending mode, the maximum value of tanδ (tanδ) in the range of 1 to 10 rad / s is 1 to 10 rad / s, which is the ratio of the storage modulus E' to the loss modulus E''. max1-10 ) for the maximum value of tanδ at 100 to 1000 rad / s (tanδ max100-1000 ) is 0.75 to 1.30. Preferably, the ratio of the maximum value to the minimum value of tan δ in the range of 0.1 to 10,000 rad / s (maximum value (tan δ max0.1-10000 ) / minimum value (tanδ min0.1-10000 )) is 1 to 1.3. Preferably, the difference between the maximum and minimum values ​​of tan δ in the range of 0.1 to 10,000 rad / s (maximum value (tan δ max0.1-10000 )-minimum value (tanδ min0.1-10000 )) is 0 to 0.1.

[0024] Tan δ is the ratio (E'' / E') of E'' (loss modulus) to E' (storage modulus). Noting that the value of tan δ affects the dishing phenomenon, we investigated the relationship between edge sagging and tan δ and found that edge sagging can be suppressed if tan δ obtained in a bending mode test of the entire polishing pad 3 is within the above range. That is, the ratio of the maximum value of tan δ at frequencies of 100 to 1000 rad / s to the maximum value of tan δ at frequencies of 1 to 10 rad / s is 0.80 to 1.25, which means that there is no large difference in tan δ even over a wide range of frequencies. The consideration of frequency will be explained using FIG. 5. FIG. 5 is a diagram showing the state of polishing as viewed from above. The arrow indicates the direction of rotation. The object to be polished 8 is placed inside the retaining ring 16A (or holding platen 16) and placed on the polishing layer 4 of the polishing pad 3. In this example, the polishing layer 4 rotates counterclockwise as shown by the arrow. The object to be polished placed inside the retaining ring 16A rotates clockwise to perform polishing. The conventional approach to polishing frequency is to calculate the angular frequency from the contact time calculated from the diameter and speed of the object to be polished and the object to be polished, and the typical frequency in polishing is approximately 1 to 10 rad / s. This is calculated based on a model in which the polishing pad 3 deforms at a constant speed from the time it starts to contact the object to be polished 8 until it passes by, and then is released at a constant speed after the object to be polished 8 has passed, and the deformation returns to its original state. However, when arriving at the present invention, it was found that the workpiece 8 is actually held by the retainer ring 16A. Therefore, as the polishing layer 4 rotates, a certain portion of the polishing layer 4 first comes into contact with the retainer ring 16A, then comes into contact with the workpiece 8, then comes into contact with the retainer ring 16A, and finally is released. Taking this situation into account, the frequency is estimated to be about 100 to 1000 rad / s. Considering these factors, it is preferable that the frequency does not vary not only between 1 and 10 rad / s but also over a wide frequency range of 100 to 1000 rad / s. In other words, it is preferable that the ratio of the maximum value of tan δ at 1 to 10 rad / s to the maximum value at 100 to 1000 rad / s fluctuates little. In fact, it was found that edge sagging is small with a polishing pad 3 in which the ratio of the maximum value of tan δ at 100 to 1000 rad / s to the maximum value of tan δ at frequencies of 1 to 10 rad / s is 0.75 to 1.30.

[0025] When calculating the frequency of 100 to 1000 rad / s, near the reference symbol E (near the edge) in FIG. 5, the rotation direction of the polishing pad and the rotation direction of the workpiece are essentially opposite, so the relative velocity is the difference between the respective velocities. On the other hand, near the reference symbol C (near the center), the rotation direction of the polishing pad and the rotation direction of the workpiece are essentially the same, so the relative velocity is the sum of the respective velocities. Note that near the reference symbol M (near the middle), the angular velocity of the workpiece is 0, so the relative velocity is the same as the rotation speed of the polishing pad. It goes without saying that these were used when calculating the frequency of 100 to 1000 rad / s.

[0026] (Dynamic viscoelasticity test) Tan δ is measured on the entire polishing pad in a bending mode using dynamic viscoelasticity testing (DMA). Dynamic viscoelasticity testing (DMA) is a method for measuring the mechanical properties of a sample by applying time-varying (oscillating) strain or stress to the sample and measuring the resulting stress or strain. Figure 6 shows a schematic diagram of the dynamic viscoelasticity test performed on the entire polishing pad 3 of the present invention. As shown in Figure 6, the polishing surface of the polishing layer 4 is positioned on the upper side, and the surface of the cushioning layer 6 is positioned on the lower side, and the pad is clamped between jig 12. Stress is measured when a small amplitude sinusoidal strain is applied. That is, in the present invention, the dynamic viscoelasticity test is performed on the entire polishing pad 3, but "entire" does not mean measuring only the polishing layer 4 of the polishing pad, nor does it mean measuring only the cushioning layer 6. This means that the measurement is performed on a polishing pad in which the polishing layer 4 and cushioning layer 6 are bonded together by an adhesive layer. Note that the adhesive layer is not shown in Figure 6.

[0027] The measurement of tan δ for the entire polishing pad 3 will be described below. Tan δ is the ratio (E'' / E') of E'' (loss modulus) to E' (storage modulus), and these values ​​are affected not only by the polishing layer 4 but also by the cushion layer 6. Conventionally, in the art, tan δ has only been measured for the material of the polishing layer. However, in reality, it has been found that the material of the cushion layer, as well as the polishing layer, significantly affects the tan δ, and the amount of edge sagging varies depending on the cushion layer. Measurement results for tan δ of the entire polishing pad in Examples 1 and 2 (described below) are shown in Figures 7 and 9, and measurement results for tan δ of the polishing layer B alone used in Examples 1 and 2 are shown in Figure 11. As is clear from Figures 7, 9, and 11, the behavior of tan δ in frequency dispersion can vary significantly between the polishing layer alone and the entire polishing pad in which the polishing layer and cushion layer are integrated. Therefore, in the present invention, tan δ is measured for the entire polishing pad, including not only the polishing layer but also the cushion layer.

[0028] Generally, dynamic viscoelasticity tests are performed in either bending mode or tension-compression mode, but in the present invention, bending mode measurements are used. In actual polishing, the polished object 8 is pressed perpendicularly against each layer of the polishing pad 3. Therefore, it was found that measurements should be performed in a measurement mode (bending mode) in the same direction as the pressing direction.

[0029] The ratio of the maximum value of tan δ at a vibration frequency of 1 to 10 rad / s to the maximum value of tan δ at a vibration frequency of 100 to 1000 rad / s is 0.80 to 1.25, which means that there is no significant difference in the storage modulus E' and loss modulus E'' between the range of 1 to 10 rad / s and the range of 100 to 1000 rad / s. Such a polishing pad can suppress edge sagging.

[0030] Furthermore, a polishing pad in which the maximum / minimum value of tan δ between 0.1 and 10,000 rad / s is 1 to 1.3 means that tan δ does not fluctuate significantly over a wide frequency range, and a polishing pad in which the difference between the maximum and minimum values ​​of tan δ between 0.1 and 10,000 rad / s (maximum value - minimum value) is 0 to 0.1 also means that tan δ does not fluctuate significantly over a wide frequency range.

[0031] The value of tan δ can be adjusted, for example, by changing the materials of the polishing layer 4 and the cushion layer 6, or by changing the size, number, or density of the bubbles contained in the polishing layer 4 and the cushion layer 6.

[0032] <<Polishing pad manufacturing method>> A method for producing the polishing pad 3 of the present invention will be described.

[0033] <Abrasive layer material> The material of the polishing layer 4 is not particularly limited, but for example, polyurethane resin, polyurea resin, and polyurethane polyurea resin are preferable as the main component, and polyurethane resin is more preferable. Specific examples of the main component material include a material obtained by reacting a urethane bond-containing polyisocyanate compound with a curing agent.

[0034] Hereinafter, a method for producing the material of the polishing layer 4 will be described using an example in which a urethane bond-containing isocyanate compound, a polyol compound, and a curing agent are used.

[0035] 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.

[0036] The material preparation process, the mixing process, and the molding process will be explained below.

[0037] <Material preparation process> 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.

[0038] Each component will be described below.

[0039] (Urethane bond-containing polyisocyanate compound) The urethane bond-containing polyisocyanate compound (urethane 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.

[0040] 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 a method and conditions known in the art for producing polyurethane resins. For example, the urethane bond-containing polyisocyanate compound may be added to a polyol compound heated to 40°C under stirring in a nitrogen atmosphere. After 30 minutes, the mixture may be heated to 80°C and then reacted at 80°C for 60 minutes. The urethane bond-containing polyisocyanate preferably has an NCO equivalent of about 300 to 600. Therefore, when the urethane bond-containing polyisocyanate is a commercially available product, it is preferable that the NCO equivalent falls within the above range, and when it is produced by synthesis, it is preferable to adjust the NCO equivalent within the above range by using the following raw materials in appropriate proportions.

[0041] (Polyisocyanate compounds) 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- 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.

[0042] The polyisocyanate compound preferably contains 2,4-TDI and / or 2,6-TDI.

[0043] (Polyol compounds as raw materials for prepolymers) 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 synthesizing the urethane bond-containing polyisocyanate compound as a prepolymer include diol compounds, triol compounds, etc., such as ethylene glycol, diethylene glycol (DEG), and butylene glycol; and polyether polyol compounds, such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG). Among these, DEG and PTMG are preferred. The number average molecular weight (Mn) of PTMG is not particularly limited and can be, for example, 500 to 2000. Here, the number average molecular weight can be measured by gel permeation chromatography (GPC). When measuring the number average molecular weight of a polyol compound from a polyurethane resin, each component can be decomposed by a conventional method such as amine decomposition, and then the number average molecular weight can be estimated by GPC. The above polyol compounds may be used alone or in combination of two or more polyol compounds.

[0044] (additives) As described above, additives such as an oxidizing agent can be added to the material of the polishing layer 4 as needed.

[0045] (hardening 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 a urethane bond-containing polyisocyanate compound in the mixing step. By adding the curing agent, the main chain terminal of the urethane bond-containing polyisocyanate compound bonds with the curing agent to form a polymer chain and harden in the subsequent molding step. 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- polyamine compounds such as 2,2-bis[3-(1-methylpropylamino)-4-hydroxyphenyl]propane, 2,2-bis[3-(1-methylpentylamino)-4-hydroxyphenyl]propane, 2,2-bis(3,5-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).

[0046] The polishing layer 4 can be formed by using a material to form hollow microspheres 4A, which have an outer shell and a hollow interior. The hollow microspheres 4A may be made of commercially available materials or may be synthesized by conventional methods. The material for the outer shell of the hollow microspheres 4A 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 constituting these resins (e.g., acrylonitrile-vinylidene chloride copolymer). 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 4A is not particularly limited, but may be, for example, a hydrocarbon, specifically, isobutane.

[0047] The shape of the hollow microspheres 4A is not particularly limited and may be, for example, spherical or nearly spherical. The average particle size of the hollow microspheres 4A 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 (for example, Mastersizer 2000, manufactured by Spectris Co., Ltd.).

[0048] The material for the hollow microspheres 4A 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.

[0049] In addition to the above components, conventional blowing agents may be used in combination with the hollow microspheres 4A within the range that does not impair the effects of the present invention, and a gas that is non-reactive with the above components may be blown into the hollow microspheres 4A during the mixing step described below. Examples of the blowing agent include water and blowing agents whose main component is a hydrocarbon having 5 or 6 carbon atoms. Examples of the hydrocarbon include linear hydrocarbons such as n-pentane and n-hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane.

[0050] <Mixing process> In the mixing step, the urethane bond-containing polyisocyanate compound (urethane prepolymer) obtained in the preparation step, additives, and curing agent are fed into a mixer and stirred and mixed. The mixing step is carried out in a state where the components are heated to a temperature that ensures the fluidity of each component.

[0051] <Forming process> In the molding process, the mixture for molding prepared in the mixing process 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 form a cured polyurethane resin (polyurethane resin molded product). At this time, the urethane prepolymer and curing agent react to form a polyurethane resin, which hardens the mixture. If the viscosity of the urethane prepolymer is too high, its fluidity will be poor, making it difficult to achieve uniform mixing. Increasing the temperature to lower the viscosity shortens the pot life, resulting in uneven mixing and uneven size of the hollow microspheres 4A formed in the resulting foam. Conversely, if the viscosity is too low, air bubbles will move within the mixture, making it difficult to form uniformly dispersed hollow microspheres 4A in the resulting foam. For this reason, it is preferable to set the viscosity of the prepolymer at a temperature of 50 to 80°C within the range of 500 to 4000 mPa·s. This can be achieved, for example, by changing the molecular weight (degree of polymerization) of the prepolymer. The prepolymer is heated to approximately 50 to 80°C to become flowable.

[0052] 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.

[0053] After obtaining the molded body, it is sliced ​​into sheets to form multiple 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, for example, in the range of 1.3 to 2.5 mm. For a foam molded in a 50 mm thick mold, for example, approximately 10 mm of the upper and lower layers of the foam are not used due to scratches, etc., and 10 to 25 polishing layers 4 are formed from approximately 30 mm of the center. A foam with hollow microspheres 4A formed approximately uniformly inside is obtained in the hardening and molding step.

[0054] The polishing surface of the resulting polishing layer 4 is grooved as needed. Grooves with any pitch, width, and depth can be formed by cutting the polishing surface with a required cutter. Examples of the slurry-retaining grooves include circular grooves formed in a concentric pattern, and examples of the slurry-discharging grooves include linear grooves formed in a lattice pattern or linear grooves formed radially from the center of the polishing layer.

[0055] 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.

[0056] <Method of manufacturing cushion layer 6> As described above, the material of the cushion layer 6 can be an impregnated material in which resin fibers (nonwoven fabric, flexible film, etc.) such as polyethylene or polyester are impregnated with a resin solution such as urethane; a suede material using a resin material such as urethane; and a sponge material using a material such as urethane, among which, the manufacturing method of an impregnated woven or nonwoven fabric using polyurethane resin and a suede material using a resin material such as urethane will be described. The cushion layer 6 can be manufactured according to the manufacturing method described below, but commercially available products can also be used.

[0057] <For impregnated materials and suede materials> In the process of forming the cushion layer 6, the cushion layer 6 is formed by a wet film formation process. That is, the cushion layer 6 is formed through the following steps: a preparation step of preparing a resin solution in which a polyurethane resin is substantially uniformly dissolved in an organic solvent; a coagulation / regeneration step of spreading the resin solution prepared in the preparation step into a sheet shape and removing the organic solvent from the resin solution in an aqueous coagulation liquid to coagulate and regenerate a polyurethane body; and a washing / drying step of washing and drying the polyurethane body coagulated and regenerated in the coagulation / regeneration step to form the cushion layer 6. The steps will be described in order below.

[0058] (preparation process) In the preparation step, a polyurethane resin and, if necessary, additives are dissolved in an organic solvent to prepare a resin solution. The resin solution is prepared by dissolving the polyurethane resin and additives substantially uniformly in a water-miscible organic solvent capable of dissolving the polyurethane resin, removing aggregates by filtration, and then degassing under vacuum. Examples of organic solvents that can be used include N,N-dimethylformamide (hereinafter abbreviated as DMF) and dimethylacetamide (hereinafter abbreviated as DMAc). For example, DMF is used as the organic solvent. The polyurethane resin can be selected from polyester-based, polyether-based, polycarbonate-based, and other resins.

[0059] Optional additives include pigments such as carbon black, hydrophilic surfactants that promote foaming, and hydrophobic surfactants that stabilize the solidification and regeneration of the polyurethane resin. The size and quantity (number) of teardrop-shaped bubbles 6A formed within the cushion layer 6 can be controlled by changing the type and amount of additive. The tan δ of the polishing pad 3 is affected by the physical properties of the cushion layer 6, so it can be adjusted by appropriately selecting the material, organic solvent, the mixing ratio of the resin and organic solvent, the size and quantity of the teardrop-shaped bubbles 6A, and the thickness of the cushion layer 6. For example, the polyurethane resin and DMF are mixed in the range of 45 to 62 parts and 8 to 32 parts per 100 parts of resin solution, respectively.

[0060] (Coagulation regeneration process) In the coagulation and regeneration process, the resin solution prepared in the preparation process is continuously applied (spread into a sheet) to the film-forming substrate, which is then immersed in an aqueous coagulation liquid to coagulate and regenerate the polyurethane resin into a sheet. The resin solution prepared in the preparation process is applied uniformly to the strip-shaped film-forming substrate at room temperature using a coating machine such as a knife coater. The coating thickness (coating amount) of the resin solution is adjusted by adjusting the clearance between the coater and the film-forming substrate. In this example, the coating amount is adjusted so that the thickness of the cushion layer 6 is in the range of 0.5 to 2.0 mm. Flexible films, nonwoven fabrics, woven fabrics, etc. can be used as the film-forming substrate. When using nonwoven fabrics or woven fabrics, pretreatment (sealing) is performed by immersing them in water or a DMF aqueous solution (a mixture of DMF and water) to prevent the resin solution from penetrating into the film-forming substrate during application. When using flexible films such as PET as the film-forming substrate, pretreatment is not required because they are not permeable to liquids.

[0061] The film-forming substrate coated with the resin solution is immersed in an aqueous coagulation solution whose main component is water, a poor solvent for polyurethane resin. In the aqueous coagulation solution, micropores constituting a skin layer are first formed on the surface of the applied resin solution, approximately several micrometers thick. Subsequently, as the DMF in the resin solution is replaced with the aqueous coagulation solution, a polyurethane body is solidified and regenerated in a sheet form on one side of the film-forming substrate. As the DMF is removed from the resin solution and replaced with the aqueous coagulation solution, numerous teardrop-shaped bubbles 6A are formed in the polyurethane body, forming a three-dimensional network of teardrop-shaped bubbles 6A. Because the PET film of the film-forming substrate prevents water from penetrating, desolvation occurs on the surface side (skin layer side) of the resin solution, resulting in the formation of teardrop-shaped bubbles 6A with larger pore diameters on the film-forming substrate side than on the surface side. In other words, numerous bubbles 6 with rounded, approximately triangular cross sections are formed approximately evenly distributed within the polyurethane body along the thickness direction of the polyurethane body.

[0062] (Washing and drying process) In the washing and drying process, the strip-shaped (long) polyurethane body that has been coagulated and regenerated in the coagulation and regeneration process is washed and then dried to form the cushion layer 6. That is, the polyurethane body is washed in a washing liquid such as water to remove any DMF remaining in the polyurethane body. After washing, the polyurethane body is dried in a cylinder dryer. The cylinder dryer is equipped with a cylinder with an internal heat source. The polyurethane body passes along the circumferential surface of the cylinder and dries, forming the cushion layer 6.

[0063] <Joining process> In the bonding step, the formed polishing layer 4 and cushion 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 P and the surface of the cushion layer 6 (the surface on which the skin layer is formed) are pressed together via the applied adhesive, and the polishing layer 4 and cushion layer 6 are bonded together with the adhesive layer 7. Then, after cutting into a desired shape such as a circle, an inspection is performed to check for the absence of dirt or foreign matter, etc., and the polishing pad 3 is completed. [Example]

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0065] In each example and comparative example, unless otherwise specified, "parts" means "parts by mass."

[0066] 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)]".

[0067] (Regarding polishing layer A) A mixed solution was obtained by adding 2.6 parts of unexpanded hollow microspheres, each of which had an acrylonitrile-vinylidene chloride copolymer shell and contained isobutane gas, to 100 parts of an isocyanate-terminated urethane prepolymer with an NCO equivalent of 460, prepared by reacting 2,4-tolylene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG), and diethylene glycol (DEG). The resulting mixed solution was then placed in a first liquid tank and kept warm. Next, 25.5 parts of MOCA and 8.5 parts of polypropylene glycol (PPG) were added separately from the first liquid and mixed, and the mixture was kept warm in a 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 and hydroxyl groups 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, then the mold was clamped and heated for 30 minutes for primary curing. The primarily cured molded product was demolded and then subjected to secondary curing in an oven at 130°C for 2 hours to obtain a urethane molded product. The obtained urethane molded product was allowed to cool to 25°C, heated again in an oven at 120°C for 5 hours, and then sliced ​​to a thickness of 1.3 mm to obtain abrasive layer A.

[0068] (Regarding polishing layer B) Polishing layer B was prepared in the same manner as polishing layer A, except that the first liquid mixture used in polishing layer A was a mixture of 100 parts of an isocyanate-terminated urethane prepolymer with an NCO equivalent of 455 and 2.7 parts of unexpanded hollow microspheres, and the second liquid used in polishing layer A was only 25.8 parts of MOCA.

[0069] (Regarding polishing layer C) Polishing layer C was obtained by the same method as that for polishing layer A, except that 2 parts of 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI) was further mixed with the first liquid used for polishing layer A, the amount of unexpanded hollow microspheres added was 2.85 parts, and the second liquid used for polishing layer A was only 28 parts of MOCA.

[0070] (Regarding polishing layer D as a polishing layer) The polishing layer D was made by Nitta Haas under the trade name "IC1000".

[0071] (Regarding cushion layers (I) to (V)) Polyester MDI (diphenylmethane diisocyanate) polyurethane resin was used as the polyurethane resin for the cushion layer (I). A polyurethane resin solution was prepared by mixing 100 parts of a 30% polyurethane resin solution with 25 parts of DMF solvent, 40 parts of a DMF dispersion containing 20% ​​carbon black as a pigment, and 2 parts of a hydrophobic surfactant as a film-forming stabilizer. The resulting resin solution was applied to a PET substrate (0.188 mm thick) at a thickness of 0.7 mm, and the organic solvent was removed from the resin solution in an aqueous coagulation solution to produce the cushion layer (I), including the PET substrate. A commercially available polyurethane sheet having fine bubbles ("Sekisui Sponge 2504KMS" manufactured by Sekisui Chemical Co., Ltd.) was used as the cushion layer (II). A commercially available polyurethane sheet having fine bubbles ("PORON HH-48C" manufactured by Inoac Corporation) was used as the cushion layer (III). Nonwoven fabric made of polyester fiber (density: 0.216 g / cm 3 The nonwoven fabric was immersed in a urethane resin solution (manufactured by DIC Corporation, product name "C1367"). After immersion, the resin solution was squeezed out using a mangle roller capable of applying pressure between a pair of rollers, allowing the nonwoven fabric to be substantially uniformly impregnated with the resin solution. The nonwoven fabric was then immersed in a coagulation liquid of water at room temperature to coagulate and regenerate the impregnated resin, yielding a resin-impregnated nonwoven fabric. The resin-impregnated nonwoven fabric was then removed from the coagulation liquid and further immersed in a washing liquid of water to remove N,N-dimethylformamide (DMF) from the resin, followed by drying. After drying, the surface skin layer was removed by buffing to produce a cushion layer (IV). The resin adhesion rate of the cushion layer (IV) was 55%, and the thickness was 1.00 mm. Nitta Haas "SUBA400" was used as the cushion layer (V).

[0072] Examples and Comparative Examples The polishing layers A to D and cushion layers (I) to (V) were joined with 0.1 mm thick double-sided tape (a PET substrate with adhesive layers made of acrylic resin on both sides), and double-sided tape was attached to the opposite side of the cushion layer and adhesive layer to produce the polishing pads of the Examples and Comparative Examples. The polishing layers and cushion layers of each Example and Comparative Example are as shown in Table 1.

[0073] [Table 1]

[0074] (Dynamic viscoelasticity measurement) Dynamic viscoelasticity measurements were performed on the polishing pads (polishing layer and cushion layer bonded with double-sided tape) of Examples and Comparative Examples under the following conditions. A dry polishing pad was stored in a thermo-hygrostat at a temperature of 23°C (±2°C) and a relative humidity of 50% (±5%) for 40 hours, and dynamic viscoelasticity measurements were performed in bending mode under normal atmospheric conditions (dry conditions). The measurement conditions for bending mode are shown below.

[0075] Measurement conditions Measurement device: RSA3 (TA Instruments) Sample: 5cm long x 0.5cm wide x 0.125cm thick Test mode: Bending mode Frequency: 0.001 to 100000 (10 -3 ~10 5 )rad / s Measurement temperature: 5℃, 25℃, 45℃ Distortion range: 0.10% As described above, measurements were taken using frequency dispersion at temperatures of 5°C, 25°C, and 45°C, and measurement graphs were synthesized using the temperature-frequency conversion rule to calculate tan δ from 0.01 rad / s to 10,000 rad / s. The measurement results for each example and comparative example are shown in Table 2. Overall results are shown in Figures 7, 9, and 12 for Example 1, Example 2, and Comparative Example 1, respectively, and for reference, the results for using polishing layer B alone are shown in Figure 11.

[0076] [Table 2]

[0077] (Polishing test results) Polishing was carried out using the polishing pads of the Examples and Comparative Examples under the polishing conditions below. During polishing, the removal rate (RR) was measured at 121 points around the diameter. The removal rate profile for the entire workpiece to be polished in Comparative Example 1 is shown in Figure 3, and the removal rate profiles for the entire workpieces to be polished in Examples 1 and 2 are shown in Figures 8 and 10, respectively. In addition, measurements were made at 2.5 mm intervals inside a radius of 140 mm, and at 1 mm intervals outside.

[0078] (polishing conditions) Polishing machine used: F-REX300 (manufactured by Ebara Corporation) Polishing agent temperature: 20℃ Polishing platen rotation speed: 70 rpm Polishing head rotation speed: 71 rpm Grinding pressure: 3.5psi Polishing slurry: manufactured by Cabot Microelectronics Corporation, product name: SS25 Polishing slurry flow rate: 200 ml / min Polishing time: 60 seconds Polished object: Silicon wafer with TEOS (Tetra Ethyl Ortho Silicate)

[0079] The polishing results for each polishing pad of the Examples and Comparative Examples are shown in Table 3. The "edge rate" of the polishing results was calculated by dividing the polishing rate at the edge of the workpiece (149 mm from the center) by the average polishing rate at 100 to 140 mm from the center.

[0080] [Table 3]

[0081] As shown in Figures 3, 12 and Tables 2 and 3, the ratio (tanδmax100-1000 / tanδ max1-10 In the polishing pad of Comparative Example 1, where the ratio (tan δ) was as large as 1.364, the rate at the very edge was as large as 1.58, and sagging at the edge was confirmed. Also, in Comparative Example 2, where a different polishing layer and cushion layer were used, the ratio (tan δ max100-1000 / tanδ max1-10 ) was large at 1.366, and drooping at the edges was also observed. On the other hand, as shown in Figures 7 and 8 and Tables 2 and 3, the ratio (tanδ max100-1000 / tanδ max1-10 In the polishing pad of Example 1, where the ratio (tan δ) was as small as 1.18, the rate at the very edge was 1.18, which was 1.5 or less, and edge sagging was suppressed. max100-1000 / tanδ max1-10 ) was as small as 1.29, and edge sagging could be suppressed as in Example 1. Note that tan δ for the polishing layer B used in Examples 1 and 2 alone is shown in FIG. 11, but the behavior of tan δ was significantly different from that in FIGS. 7 and 9, which were measured for the entire polishing pad. Furthermore, in Examples 3 to 6, in which the polishing layer and cushion layer were variously changed, the ratio (tan δ max100-1000 / tanδ max1-10 ) within a predetermined range, the polishing rate of the outermost edge was 1.5 or less, edge sagging could be suppressed, and a good edge profile could be obtained. [Industrial Applicability]

[0082] The present invention provides a polishing pad that can improve edge sagging, and therefore contributes to the manufacture and sale of polishing pads, and has industrial applicability.

[0083] 1 Polishing equipment 3 polishing pads 4 Polishing layer 4A Hollow microspheres 6 Cushion layer 7 Adhesive layer 8 Object to be polished 8a End droop 9. Slurry 10 Polishing plate 11 Foundation 12 Jig 16 Holding plate

Claims

1. The polishing pad comprises a polishing layer having a polishing surface for polishing an object to be polished, and a cushion layer disposed on the opposite side of the polishing surface of the polishing layer, The ratio (tan δ) of the storage modulus E' to the loss modulus E'' of the entire polishing pad obtained by a dynamic viscoelasticity test using frequency dispersion (25°C) in a bending mode under the following measurement conditions and the following analysis method is the maximum value of tan δ (tan δ) measured at 1 to 10 rad / s. ｍａｘ１－１０ ) the maximum value of tan δ measured at 100 to 1000 rad / s (tan δ ｍａｘ１００－１０００ ) is 0.75 to 1.30: (Measurement conditions) Measurement atmosphere: Normal air atmosphere (dry state) Measurement device: RSA3 (manufactured by TA Instruments) ・Sample structure: Polishing layer and cushioning layer bonded with double-sided tape Double-sided tape used in the sample: 0.1 mm double-sided tape (PET base material with adhesive layers made of acrylic resin on both sides) Sample used: A dry polishing pad that was kept in a constant temperature and humidity chamber at a temperature of 23°C (±2°C) and a relative humidity of 50% (±5%) for 40 hours was used. ・Sample size: length 5cm x width 0.5cm x thickness 0.125cm - Test mode: Bending mode Distortion range: 0.10% ・Measurement temperature: 5℃, 25℃, 45℃ Frequency: 0.001 to 100,000 rad / s (Analysis method) The measurement results at each temperature obtained under the above measurement conditions were synthesized into a frequency range of 0.01 rad / s to 10,000 rad / s using the temperature-frequency conversion rule with 25°C as the reference.

2. The maximum value of tan δ measured at 1 to 10 rad / s (tan δ ｍａｘ１－１０ ) the maximum value of tan δ measured at 100 to 1000 rad / s (tan δ ｍａｘ１００－１０００ 2. The polishing pad of claim 1, wherein the ratio of

3. The ratio of the maximum value to the minimum value of tan δ measured at 0.1 to 10,000 rad / s (maximum value (tan δ ｍａｘ０．１－１００００ ) / minimum value (tan δ ｍｉｎ０．１－１００００ 3. The polishing pad according to claim 1, wherein )) is 1 to 1.

3.

4. The difference between the maximum and minimum values ​​of tan δ measured at 0.1 to 10,000 rad / s (maximum value (tan δ ｍａｘ０．１－１００００ ) / minimum value (tan δ ｍｉｎ０．１－１００００ 4. The polishing pad according to claim 1, wherein the value of )) is 0 to 0.1.

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