Polishing pad, polishing apparatus, method for manufacturing polishing pad, and method for manufacturing polished object

Abstract

To provide a polishing pad capable of achieving both a high polishing rate and high processing quality.SOLUTION: There is provided a polishing pad comprising a resin containing bubbles, in which a surface layer including a surface serving as a polishing surface of the resin is a hard resin having a hardness higher than that of other regions of the resin, and when a value of a circle-equivalent diameter with respect to bubbles in the polishing surface is defined as a bubble diameter of a surface, and a value of a circle-equivalent diameter with respect to bubbles in a surface opposite to the polishing surface is defined as a bubble diameter of a back surface, a difference between the bubble diameter of the surface and the bubble diameter of the back surface is within 15%.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present technology relates to a polishing pad for finishing the surface of an object to be polished to a flat surface, a polishing apparatus, a method for manufacturing a polishing pad, and a method for manufacturing an object to be polished. [Background technology]

[0002] Conventionally, polishing using a polishing pad has been performed for materials (workpieces) such as optical materials such as optical lenses and reflective mirrors, substrates for hard disks, silicon wafers, and glass substrates for liquid crystal displays, which require high-precision flatness. In such polishing, the polishing pad is attached to a base, and during processing, the workpiece is brought into contact with the polishing pad and moved relative to it, while a polishing liquid containing abrasive particles is supplied between the workpiece and the polishing pad.

[0003] The polishing pads widely used have properties such as hardness and Young's modulus that vary along the thickness direction. This is because high processing quality can be achieved by providing a hard layer with appropriate rigidity on the polishing surface to improve flatness, and an underlying soft layer with sufficient elasticity to accommodate the warpage of the wafer.

[0004] For example, in Patent Technology 1, a hard layer is formed by reducing the bubble diameter in the surface layer, including the polished surface, and increasing the apparent hardness. The soft layer below that is formed by increasing the bubble diameter and decreasing the apparent hardness. This achieves high processing quality. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-220550 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when using a polishing pad in which a hard layer is formed by reducing the diameter of conventional bubbles in the surface layer, the problem of a reduced polishing rate occurs. Bubbles are spherical depressions formed in the polishing pad, and their role is to retain and supply polishing slurry to the processing surface. Reducing the size of the bubbles reduces the ability to retain the slurry and impairs the ability to supply it to the processing surface, resulting in a reduced polishing rate. Therefore, the present disclosure aims to provide a polishing pad that can achieve a high polishing rate and high processing quality. [Means for solving the problem]

[0007] In order to solve the above problems, the present disclosure provides: A polishing pad having a resin containing bubbles, a surface layer of the resin including a surface to be polished is made of a hard resin having a higher hardness than other regions of the resin, This polishing pad is characterized in that, when the value of the circle-equivalent diameter of the bubbles on the polishing surface is defined as the bubble diameter on the surface, and the value of the circle-equivalent diameter of the bubbles on the surface opposite the polishing surface is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is within 15%. The present disclosure also provides a polishing pad comprising: a fixing portion to which the polishing pad is fixed; a holding portion for holding the object to be polished; The polishing apparatus is provided with: The present disclosure also provides: a preparation step of preparing a resin containing bubbles; a curing step of performing a curing treatment on a surface layer including one surface of the resin to provide a cured resin layer having a higher resin hardness than other regions of the resin; Including, This is a method for manufacturing a polishing pad, characterized in that when the circle-equivalent diameter of the bubbles on the surface that has been hardened is defined as the bubble diameter on the surface, and the circle-equivalent diameter of the bubbles on the surface opposite to the surface that has been hardened is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is within 15%. The present disclosure also provides: A method for producing an object to be polished, characterized in that the object to be polished is polished with the above polishing pad. [Effects of the Invention]

[0008] The polishing pad of the present disclosure has a hard surface layer, which allows for high flatness of the processed surface of the object to be polished, and the lower layer can be made flexible, allowing for high conformability to the workpiece shape, and also has an appropriate bubble diameter, which allows for a high polishing rate. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a polishing apparatus according to the present disclosure. [Figure 2] FIG. 2(a) is a schematic perspective view of a polishing pad of the present disclosure, and FIG. 2(b) is a cross-sectional view taken along line AA in FIG. 2(a). DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment The first embodiment is directed to a polishing pad. The polishing pad of the present disclosure comprises: A polishing pad having a resin containing bubbles, a surface layer of the resin including a surface to be polished is made of a hard resin having a higher hardness than other regions of the resin, When the value of the circle equivalent diameter of the bubbles on the polished surface is defined as the bubble diameter on the front surface, and the value of the circle equivalent diameter of the bubbles on the surface opposite to the polished surface is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the front surface and the bubble diameter on the back surface is within 15%. The explanation is given below. [Polishing equipment] The polishing apparatus of the present disclosure includes a polishing pad of the present disclosure, a fixing portion to which the polishing pad is fixed, and a holding portion to hold an object to be polished. Fig. 1 is a schematic diagram of the polishing apparatus of the present disclosure. The polishing apparatus 1 is a wet polishing processing device, and includes a polishing pad 10, a base 5 (fixing portion to which the polishing pad is fixed) that fixes and holds the polishing pad 10, a supply portion 2 that supplies a polishing slurry S such as water or a chemical solution to the polishing surface of the polishing pad 10, and a carrier holder 4 (holding portion that holds an object to be polished).

[0011] 1, a workpiece 3 to be processed is held in contact with the polishing surface of a polishing pad 10 by a carrier holder 4 (a holder that holds the workpiece) applying force from above the workpiece 3, and the workpiece 3 is polished in this state. Examples of the workpiece 3 (workpiece to be polished) include semiconductor substrates, optical lenses, optical materials such as reflective mirrors, hard disk substrates, silicon wafers, and glass substrates for liquid crystal displays. In this specification, the workpiece 3 that has been polished is defined as an article.

[0012] [Polishing pad] The polishing pad of the present disclosure is a polishing pad having a resin containing bubbles. Figure 2 is a schematic diagram of the polishing pad of the present disclosure. Figure 2(a) is a perspective view, and Figure 2(b) is an AA cross-sectional view when cut from the z-axis direction so as to pass through the line AA in Figure 2(a). In Fig. 2, the plane horizontal to the polishing surface 6S is the xy plane, and the axis perpendicular to the xy plane is the z axis. The dashed line AA in Fig. 2(a) is parallel to the x axis and perpendicular to the y axis.

[0013] The polishing pad 10 has a surface layer 6 and a lower layer 7 arranged in the negative z direction from the polishing surface 6S. The surface layer 6 has a polishing surface 6S. The polishing surface 6S is the part of the polishing pad 10 that comes into contact with the workpiece 3.

[0014] Both the surface layer 6 and the lower layer 7 contain bubbles 11. The bubbles 11 function to retain and supply the slurry S to the polishing surface 6S. In the present disclosure, the polishing surface 6S of the polishing pad is referred to as the surface, and the surface opposite the polishing surface 6S is referred to as the back surface. In the polishing pad of the present disclosure, when the circle-equivalent diameter of the bubbles on the polishing surface 6S is defined as the bubble diameter on the surface, and the circle-equivalent diameter of the bubbles on the surface opposite the polishing surface 6S is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is within 15%. The difference between the bubble diameter on the surface and the bubble diameter on the back surface is preferably 5% to 13%, and more preferably 5.1% to 12.8%. Here, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is the absolute value of the difference between the bubble diameter on the surface and the bubble diameter on the back surface divided by the bubble diameter on the back surface. Specifically, the circle-equivalent diameter refers to the diameter of a circle equivalent to a projected area. By doing so, the polishing pad of the present disclosure can achieve a high polishing rate.

[0015] In the polishing pad of the present disclosure, when the ratio of the area of ​​bubbles on the polishing surface to the area of ​​the polishing surface is defined as the bubble area ratio on the front surface, and the ratio of the area of ​​bubbles on the surface opposite to the polishing surface to the area of ​​the surface opposite to the polishing surface is defined as the bubble area ratio on the back surface, the difference between the bubble area ratio on the front surface and the bubble area ratio on the back surface is preferably within 10% (-10% or more and +10% or less).By doing so, the polishing pad of the present disclosure can achieve a higher polishing rate.

[0016] For the same reason, the polishing pad of the present disclosure preferably has an average bubble diameter on the surface of 100 μm or more and 500 μm or less, more preferably 150 μm or more and 300 μm or less. The bubble area ratio on the surface is not particularly limited, but is, for example, in the range of 40% or more and 80% or less. To obtain a higher polishing rate, the difference in average bubble density between the front and back surfaces is preferably within ±10%.

[0017] In the polishing pad of the present disclosure, the surface layer 6, which includes the surface that becomes the polishing surface of the resin, is made of a hard resin 8 that is harder than the other regions of the resin (resin 9). The surface layer 6 contains the hard resin 8, and the lower layer 7 contains the resin 9. The hard resin 8 and resin 9 are integrally molded resin bodies, and are made from the same raw materials. After being molded integrally with the resin 9, the hard resin 8 is further crosslinked to make it harder than the resin 9. The crosslinking method will be described later.

[0018] To achieve both the flatness of the workpiece surface and the ability to conform to the warp of the workpiece, the hardness of the hard resin 8 in the polishing pad of the present disclosure is preferably at least 1.2 times, and more preferably at least 2 times and no more than 10 times, the hardness of the other region (resin 9). For the same reasons, the hardness of the hard resin 8 in the polishing pad of the present disclosure is preferably at least 20 MPa and no more than 100 MPa, more preferably at least 25 MPa and no more than 60 MPa, and even more preferably at least 26 MPa and no more than 58 MPa. The hardness refers to the nanoindenter hardness described below. Similarly, to ensure the ability to conform to the warp of the workpiece, the thickness of the hard resin (thickness of the surface layer 6 in the negative z direction) is preferably at least 0.1 μm and no more than 100 μm, and more preferably at least 5 μm and no more than 50 μm.

[0019] The polishing pad 10 is a resin molded body, in other words, the polishing surface 6S, the surface layer 6, and the lower layer 7 are molded integrally without the use of adhesive. The raw material of the resin material (resin containing bubbles) that is the cured product that constitutes the resin molded body is not particularly limited, and examples that can be used include polyurethane, polyethylene, polypropylene, polystyrene, polyester, nylon, polyvinyl chloride, polyvinylidene chloride, polybutene, polyacetal, polyphenylene oxide, polyvinyl alcohol, polymethyl methacrylate, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyamideimide, polycarbonate, polyarylate, liquid crystal polymer, aromatic polysulfone resin, biodegradable polyester resin, polyamide resin, polyimide resin, fluororesin, ethylene-propylene resin, ethylene-ethyl acrylate resin, epoxy resin, acrylic resin, norbornene resin, styrene copolymer (e.g., vinyl polyisoprene-styrene copolymer, butadiene-styrene copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, etc.), natural rubber, synthetic rubber, and thermoplastic elastomer.

[0020] These exemplified resin materials may be used alone or may be mixed or copolymerized. From the viewpoint of excellent wear resistance and ease of manufacturing, in the polishing pad of the present disclosure, the resin having bubbles is preferably mainly composed of polyurethane, and the hard resin preferably contains polyurethane having allophanate bonds. In the present disclosure, the main component of a resin molded body refers to the component with the heaviest mass of the resin material contained when the resin molded body is composed of multiple resin materials. The proportion of polyurethane in the resin molded body is 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

[0021] As described above, the polishing pad 10 of the present disclosure has a resin portion of the surface layer 6 that is harder than the resin portion of the lower layer 7, thereby achieving both the ability to improve the flatness of the workpiece (object to be polished) polished using the polishing pad 10 and the ability to adapt to warpage, thereby achieving high processing quality. The polishing pad of the present disclosure can achieve a high polishing rate by defining the circle-equivalent diameter of the bubbles on the polishing surface as the bubble diameter on the surface and the circle-equivalent diameter of the bubbles on the surface opposite the polishing surface as the bubble diameter on the back surface, with the difference between the bubble diameter on the surface and the bubble diameter on the back surface being within 15%. Therefore, the polishing pad of the present disclosure can achieve a high polishing rate while obtaining high processing quality compared to conventional polishing pads.

[0022] <Second embodiment> The second embodiment relates to a method for manufacturing a polishing pad. The method for manufacturing a polishing pad of the present disclosure includes: a preparation step of preparing a resin containing bubbles; a curing process in which a surface layer including one surface of the resin is subjected to a curing treatment to provide a cured resin having a higher hardness than other regions of the resin; Including, The difference between the bubble diameters on the front surface and the back surface is 15% or less, where the circle-equivalent diameter of the bubbles on the surface that has been hardened is defined as the bubble diameter on the front surface, and the circle-equivalent diameter of the bubbles on the surface opposite to the surface that has been hardened is defined as the bubble diameter on the back surface.

[0023] Next, a method for producing the hard resin 8 of the surface layer 6 of the polishing pad 10 will be described. The method for producing the polishing pad 10 of the present disclosure is not particularly limited, but a preferred embodiment will be described. In the production method of the present disclosure, the hard resin 8 is produced by irradiating a resin containing bubbles with, for example, ionizing radiation to promote crosslinking of the resin in the surface layer of the polishing pad.

[0024] The polyurethane resin that forms the cellular resin contains uncrosslinked urethane bonds with a linear main chain. During the curing process, for example, by irradiation with ionizing radiation, the molecular chains of the uncrosslinked urethane resin are cut, and when re-crosslinking occurs, allophanate bonds with a branched structure are formed. These allophanate bonds enable the formation of a hard resin. Each step will be described in detail below. Of the steps, the description of those already described in the first embodiment will be omitted.

[0025] (preparation process) The manufacturing method of the polishing pad of the present disclosure includes a preparation step of preparing a resin containing bubbles. First, the resin containing bubbles is prepared. As described above, the resin containing bubbles is, for example, polyurethane. The resin containing bubbles may be procured from an external source or may be prepared by chemical synthesis. The resin containing bubbles is then cut into a desired shape and adhered to a base. The resin containing bubbles used here preferably has a hardness of 10 MPa or more and 40 MPa or less, and a bubble area ratio of 40% or more and 80% or less. The method for adhering the resin containing bubbles to the base is not particularly limited, but may be, for example, adhesion using double-sided tape (manufactured by Nitto Denko: No. 5000NS).

[0026] (Heating process) The method for manufacturing a polishing pad according to the present disclosure preferably further includes a heating step of heating the resin before the curing step, and preferably involves heating the resin at a temperature of 100°C or higher and 180°C or lower for at least one hour in the heating step. The heating method may be, for example, heating in an oven, but is not limited to this as long as heating is possible. Heating reduces the amount of moisture contained in the resin, including bubbles. This is because high moisture content may inhibit urethane molecular chain scission and re-crosslinking reactions when irradiated with ionizing radiation in the curing step. After heating, the resin is preferably removed from the oven and allowed to cool to room temperature. In this case, it is preferable to allow the resin to cool in a humidity-controlled desiccator.

[0027] (hardening process) The method for manufacturing a polishing pad according to the present disclosure includes a curing step in which a surface layer including one surface of a resin is cured to provide a cured resin having a higher hardness than other regions of the resin. The curing method in the curing step is preferably a method using ionizing radiation, but may also be, for example, a method using a chemical agent, and is not limited to these methods as long as the curing step can be achieved. In this disclosure, the method using ionizing radiation will be described.

[0028] When irradiating a resin containing bubbles with ionizing radiation, examples of the ionizing radiation include gamma rays, electron beams, X-rays, neutron beams, and high-energy ions. Among these, electron beams are preferred from the viewpoint of the versatility of the device. In this example, electron beams are used for irradiation.

[0029] At this time, the depth at which the hard resin layer is formed can be controlled by changing the dose and irradiation time. In the polishing pad manufacturing method of the present disclosure, it is preferable that allophanate bonds are formed on the one surface of the resin in the curing step. For this purpose, the irradiation dose of ionizing radiation is preferably selected appropriately within the range of 1 to 1000 kGy, particularly 50 to 200 kGy, so that the amount required for the uncrosslinked urethane resin to form allophanate bonds is selected appropriately. The irradiation time is preferably 10 minutes or more, and similarly, the time required for the uncrosslinked urethane resin to form allophanate bonds is selected appropriately.

[0030] Furthermore, when irradiating with ionizing radiation, the resin containing bubbles may be heated. Furthermore, it is preferable that the ionizing radiation be irradiated in a low-oxygen atmosphere, particularly in an atmosphere substantially free of oxygen. A specific atmosphere preferably has an oxygen concentration of 1000 ppm or less. If the oxygen concentration is 1000 ppm or less, the irradiating may be performed under vacuum or in an inert gas atmosphere such as nitrogen or argon. From the viewpoint of cost, a nitrogen atmosphere is preferable. By providing a hard resin in this way, the polishing pad manufactured by the polishing pad manufacturing method of the present disclosure can achieve high processing quality.

[0031] (others) In the method for manufacturing a polishing pad of the present disclosure, when the circle-equivalent diameter of the bubbles on the surface subjected to the hardening treatment is defined as the bubble diameter on the front surface, and the circle-equivalent diameter of the bubbles on the surface opposite the hardening treatment is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the front surface and the bubble diameter on the back surface is within 15%. The difference between the bubble diameter on the front surface and the bubble diameter on the back surface is preferably 5% to 13%, and more preferably 5.1% to 12.8%. Here, the difference between the bubble diameter on the front surface and the bubble diameter on the back surface refers to the absolute value of the difference between the bubble diameter on the front surface and the bubble diameter on the back surface divided by the bubble diameter on the back surface. Specifically, the circle-equivalent diameter refers to the diameter of a circle equivalent to the projected area. By doing so, a polishing pad manufactured by the method for manufacturing a polishing pad of the present disclosure can achieve a high polishing rate. Therefore, a polishing pad manufactured by the method for manufacturing a polishing pad of the present disclosure can achieve a high polishing rate while obtaining higher processing quality compared to conventional polishing pads.

[0032] <Third embodiment> The third embodiment relates to a method for manufacturing an object to be polished. The method for manufacturing an object to be polished according to the present disclosure is characterized in that the object to be polished is polished with the polishing pad described above. Polishing an object to be polished with a polishing pad is as described above (for example, in the explanation of [Polishing Apparatus]), and the polishing method using a polishing apparatus is a well-known technique, so detailed explanation will be omitted. [Example]

[0033] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples. Prior to the description of the production examples, the evaluation methods for the examples and comparative examples will be described.

[0034] <Resin hardness> The hardness of the hard resin and the hardness of the resin in the lower layer were measured as follows. A nanoindenter (Agilent Technologies: G-200) was used as the measuring device, and the polishing pad was cut into pieces approximately 3 cm square and set on the measurement table. The resin part of the polishing pad was selected as the measurement area, and measurements were taken, with the average value of the values ​​from 10 locations being taken as the hardness. The hardness of the lower layer of the polishing pad was measured by cutting the pad in the thickness direction and measuring from the cross section, or by cutting the pad parallel to the thickness direction and measuring. The thickness of the hard resin is determined by cutting the pad in the thickness direction, measuring the hardness of the cut surface at multiple points in the thickness direction, and determining the change in hardness.

[0035] <Bubble area ratio> The bubble area ratio was evaluated as follows. A color 3D laser microscope (Keyence: VK-9700) was used as the measuring device, and the surface (top surface) of the polishing pad was measured at 10 points using a 10x objective lens. The measured images were binarized using image processing software (ImageJ: National Institutes of Health, USA) to separate the resin part and the bubble part of the polishing pad. To remove noise, bubbles were recognized as those with an area of ​​200 μm 2 The above was used. The bubble area ratio was calculated by adding up the areas of the bubble parts and dividing by the area of ​​the entire image. The bubble area ratio was also calculated in the same way for the surface opposite to the polishing pad surface (back surface).

[0036] <Average bubble diameter> The bubble area ratio was evaluated as follows. A color 3D laser microscope (Keyence: VK-9700) was used as the measuring device, and the surface (top surface) of the polishing pad was measured at 10 points using a 10x objective lens. The measured images were binarized using image processing software (ImageJ: National Institutes of Health, USA) to separate the resin part and the bubble part of the polishing pad. To remove noise, bubbles were recognized as those with an area of ​​200 μm 2The above was the case. The bubbles were approximated as circles, and the bubble diameters were calculated from the areas. The average value of the bubble diameters was taken as the average bubble diameter. The average bubble diameter was also calculated in the same way for the surface opposite to the surface of the polishing pad (back surface). The difference in average bubble diameters listed in Table 1 is the difference between the bubble diameter on the front surface and the bubble diameter on the back surface, and is the absolute value of the difference between the bubble diameters on the front surface and the back surface divided by the bubble diameter on the back surface.

[0037] <Polishing rate> The polishing rate was evaluated as follows. The glass material used for the glass substrate to be polished was S-FSL5 (manufactured by Ohara Inc.), measuring Φ50 and 10 mm thick. The slurry used for polishing was a mixture of cerium oxide (HL40 manufactured by Mitsui Mining & Smelting Co., Ltd.) and water, adjusted to a cerium oxide content of 1 wt%. A polishing pad was fixed to a base plate with double-sided tape, and polishing was performed for 30 minutes while applying the slurry at a rotation speed of 500 rpm. The mass of the glass substrate was measured before and after polishing, and the polishing rate was calculated from the difference in mass. The polishing rate value was evaluated according to the following criteria, and a rating of A or B was considered to have sufficient polishing ability and a high polishing rate. A: Polishing rate is 1.3 μm / min or more B: Polishing rate is 0.5 μm / min or more and less than 1.3 μm / min C: Polishing rate is less than 0.5 μm / min

[0038] <Processing quality> The processing quality was evaluated as follows: Lenses were polished using the following polishing pads, and the flatness of the lens surface was evaluated using an interferometer (Verifire, manufactured by ZYGO Corp.). The flatness values ​​were evaluated according to the following criteria, and a rating of A or B was deemed to guarantee sufficient processing quality. A: Flatness less than 10nm B: Flatness is 10nm or more and less than 30nm C: Flatness is 30nm or more

[0039] Example 1 For the resin containing bubbles, a cerium oxide-containing urethane pad (KSP66A, 0.5 mm thick, manufactured by Kokonoe Electric Co., Ltd.) was used. This resin containing bubbles was fixed to a plate with double-sided tape and heated in an oven at 100°C for 1 hour. The resin containing bubbles was then removed from the oven and allowed to cool to room temperature.

[0040] Next, the resin containing bubbles was irradiated with electron beams to promote crosslinking of the surface of the resin containing bubbles. The resin containing bubbles was irradiated with electron beams at a dose of 100 kGy for 20 minutes to obtain polishing pad 1 having a hard resin on the surface layer.

[0041] Example 2 For the resin containing bubbles, a cerium oxide-containing urethane pad (KSP66A, 0.5 mm thick, manufactured by Kokonoe Electric Co., Ltd.) was used. This resin containing bubbles was fixed to a plate with double-sided tape and heated in an oven at 100°C for 1 hour. The resin containing bubbles was then removed from the oven and allowed to cool to room temperature.

[0042] Next, the resin containing bubbles was irradiated with electron beams to promote crosslinking of the surface of the resin containing bubbles. The resin containing bubbles was irradiated with electron beams at a dose of 100 kGy for 10 minutes to obtain a polishing pad 2 having a hard resin on the surface layer.

[0043] Example 3 A non-filler urethane pad (KSP90, 0.5 mm thick, manufactured by Kokonoe Electric Co., Ltd.) was used for the resin containing bubbles. This resin containing bubbles was fixed to a plate with double-sided tape and heated in an oven at 100°C for 1 hour. The resin containing bubbles was then removed from the oven and allowed to cool to room temperature.

[0044] Next, the resin containing bubbles was irradiated with electron beams to promote crosslinking of the surface of the resin containing bubbles. The resin containing bubbles was irradiated with electron beams at a dose of 150 kGy for 10 minutes to obtain a polishing pad 3 having a hard resin on the surface layer.

[0045] Example 4 A non-filler urethane pad (FXA9H, 0.8 mm thick, manufactured by Fujibo Ehime Co., Ltd.) was used for the resin containing bubbles. This resin containing bubbles was fixed to a plate with double-sided tape and heated in an oven at 100°C for 1 hour. The resin containing bubbles was then removed from the oven and allowed to cool to room temperature.

[0046] Next, to promote crosslinking of the surface of the resin containing bubbles, the resin containing bubbles was irradiated with an electron beam at a dose of 150 kGy for 10 minutes to obtain a polishing pad 4 having a hard resin on the surface.

[0047] Example 5 For the resin containing bubbles, a cerium oxide-containing urethane pad (KSP66A, 0.5 mm thick, manufactured by Kokonoe Electric Co., Ltd.) was used. This resin containing bubbles was fixed to a plate with double-sided tape and heated in an oven at 100°C for 1 hour. The resin containing bubbles was then removed from the oven and allowed to cool to room temperature.

[0048] Next, the resin containing bubbles was irradiated with electron beams to promote crosslinking of the surface of the resin containing bubbles. The resin containing bubbles was irradiated with electron beams at a dose of 50 kGy for 3 minutes to obtain polishing pad 5 having a hard resin on the surface layer.

[0049] (Comparative Example 1) A cerium oxide-containing urethane pad (KSP66A, 0.5 mm thick, manufactured by Kokonoe Electric Co., Ltd.) was used for the resin containing bubbles. This resin containing bubbles was fixed to a base plate with double-sided tape and heated in an oven at 100°C for 1 hour. The resin containing bubbles was then removed from the oven and allowed to cool to room temperature, yielding polishing pad 6. In Comparative Example 1, no electron beam irradiation was performed.

[0050] (Comparative Example 2) A cerium oxide-containing urethane pad (KSP66A, 0.5 mm thick, manufactured by Kokonoe Electric Co., Ltd.) was used for the bubbly resin. Bubbles with a diameter of approximately 450 μm were formed on the surface of this bubbly resin by laser irradiation. The bubbly resin was fixed to a plate with double-sided tape and heated in an oven at 100°C for 1 hour. The bubbly resin was then removed from the oven and allowed to cool to room temperature.

[0051] Next, the resin containing bubbles was irradiated with electron beams to promote crosslinking of the surface of the resin containing bubbles. The resin containing bubbles was irradiated with electron beams at a dose of 50 kGy for 3 minutes to obtain polishing pad 7 having a hard resin on the surface.

[0052] The evaluation results of the polishing pads of Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Table 1. In the Comparative Examples, both processing quality and polishing rate could not be achieved. On the other hand, in the Examples, since the surface layer contains a hard resin and the difference in average bubble diameter is small, it was found that both processing quality and polishing rate could be achieved.

[0053] [Table 1]

[0054] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A polishing pad having a resin containing bubbles, a surface layer of the resin including a surface to be polished is made of a hard resin having a higher hardness than other regions of the resin, A polishing pad characterized in that, when the value of the circle-equivalent diameter of the bubbles on the polishing surface is defined as the bubble diameter on the surface, and the value of the circle-equivalent diameter of the bubbles on the surface opposite to the polishing surface is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is within 15%. (Configuration 2) 2. The polishing pad according to claim 1, wherein the difference between the bubble diameter on the front surface and the bubble diameter on the back surface is 5% or more and 13% or less. (Configuration 3) 3. The polishing pad according to claim 1, wherein the hardness of the hard resin is at least 1.2 times the hardness of the other region. (Configuration 4) 3. The polishing pad according to claim 1, wherein the hardness of the hard resin is at least 2 times and at most 10 times the hardness of the other region. (Configuration 5) 5. The polishing pad according to any one of configurations 1 to 4, wherein the thickness of the hard resin is 0.1 μm or more and 100 μm or less. (Configuration 6) 6. The polishing pad according to any one of configurations 1 to 5, wherein the average bubble diameter on the surface is 100 μm or more and 500 μm or less. (Configuration 7) The polishing pad according to any one of configurations 1 to 6, wherein the ratio of the area of ​​bubbles on the polishing surface to the area of ​​the polishing surface is defined as the bubble area ratio on the front surface, and the ratio of the area of ​​bubbles on the surface opposite to the polishing surface to the area of ​​the surface opposite to the polishing surface is defined as the bubble area ratio on the back surface, and the difference between the bubble area ratio on the front surface and the bubble area ratio on the back surface is 10% or less. (Configuration 8) 8. The polishing pad according to any one of configurations 1 to 7, wherein the hard resin has a hardness of 25 MPa or more and 60 MPa or less. (Configuration 9) the resin having bubbles is mainly composed of polyurethane, 9. The polishing pad according to any one of configurations 1 to 8, wherein the hard resin comprises a polyurethane having an allophanate bond. (Configuration 10) A polishing pad according to any one of configurations 1 to 9, a fixing portion to which the polishing pad is fixed; a holding portion for holding the object to be polished; A polishing apparatus comprising: (Method 1) a preparation step of preparing a resin containing bubbles; a curing process in which a surface layer including one surface of the resin is subjected to a curing treatment to provide a cured resin having a higher hardness than other regions of the resin; Including, A method for manufacturing a polishing pad, characterized in that, when the circle-equivalent diameter of bubbles on the surface that has been hardened is defined as the bubble diameter on the surface, and the circle-equivalent diameter of bubbles on the surface opposite to the surface that has been hardened is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is within 15%. (Method 2) The method further includes a heating step of heating the resin before the curing step, The method for producing a polishing pad according to method 1, wherein in the heating step, the resin is heated at 100°C or higher and 180°C or lower for 1 hour or longer. (Method 3) The method for producing a polishing pad according to method 1 or 2, wherein an allophanate bond is formed on the one surface of the resin in the curing step. (Method 4) 10. A method for producing an object to be polished, comprising polishing the object to be polished with the polishing pad according to any one of aspects 1 to 9. [Explanation of symbols]

[0055] 1 Polishing equipment 2 Supply section S Polishing Slurry 3 Work 4 Carrier support stand 5 Base 6 Surface layer 6S polished surface 7 Lower layer 8 Hard Resin 9. Resin 10 Polishing Pads 11 Bubbles

Claims

1. A polishing pad having a resin containing bubbles, a surface layer of the resin including a surface to be polished is made of a hard resin having a higher hardness than other regions of the resin, A polishing pad characterized in that, when the value of the circle equivalent diameter of the bubbles on the polishing surface is defined as the bubble diameter on the surface, and the value of the circle equivalent diameter of the bubbles on the surface of the polishing pad opposite the polishing surface is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is within 15%.

2. 2. The polishing pad according to claim 1, wherein the difference between the bubble diameter on the front surface and the bubble diameter on the back surface is 5% or more and 13% or less.

3. 2. The polishing pad according to claim 1, wherein the hardness of the hard resin is at least 1.2 times the hardness of the other region.

4. 2. The polishing pad according to claim 1, wherein the hardness of the hard resin is at least two times and at most ten times the hardness of the other region.

5. 2. The polishing pad according to claim 1, wherein the thickness of the hard resin is 0.1 μm or more and 100 μm or less.

6. 2. The polishing pad according to claim 1, wherein the average bubble diameter on the surface is 100 μm or more and 500 μm or less.

7. 2. The polishing pad according to claim 1, wherein the ratio of the area of ​​bubbles on the polishing surface to the area of ​​the polishing surface is defined as the bubble area ratio on the front surface, and the ratio of the area of ​​bubbles on the surface opposite the polishing surface to the area of ​​the surface opposite the polishing surface is defined as the bubble area ratio on the back surface, and the difference between the bubble area ratio on the front surface and the bubble area ratio on the back surface is 10% or less.

8. 2. The polishing pad according to claim 1, wherein the hard resin has a hardness of 25 MPa or more and 60 MPa or less.

9. the resin having bubbles is mainly composed of polyurethane, The polishing pad of claim 1 , wherein the hard resin comprises a polyurethane having allophanate linkages.

10. The polishing pad of claim 1; a fixing portion to which the polishing pad is fixed; a holding portion for holding the object to be polished; A polishing apparatus comprising:

11. a preparation step of preparing a resin containing bubbles; a curing process in which a surface layer including one surface of the resin is subjected to a curing treatment to provide a cured resin having a higher hardness than other regions of the resin; Including, A method for manufacturing a polishing pad, characterized in that when the circle equivalent diameter of bubbles on the surface that has been hardened is defined as the bubble diameter on the surface, and the circle equivalent diameter of bubbles on the surface of the resin opposite to the surface that has been hardened is defined as the bubble diameter on the back surface, the difference between the bubble diameter on the surface and the bubble diameter on the back surface is within 15%.

12. The method further includes a heating step of heating the resin before the curing step, The method for producing a polishing pad according to claim 11, wherein the resin is heated at 100°C or higher and 180°C or lower for one hour or longer in the heating step.

13. The method for producing a polishing pad according to claim 11 , wherein an allophanate bond is formed on the one surface of the resin in the curing step.

14. 2. A method for manufacturing an object to be polished, comprising polishing the object with the polishing pad according to claim 1.

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