Patent Application
20250065468
The present disclosure relates to a polishing pad and a polishing apparatus.
A polishing pad is bonded to a base and is used for polishing processing to be performed in a finishing process for semiconductor substrates and optical lenses. In polishing processing, it may be desirable to perform the finishing process to make the entire surface of a workpiece to be processed uniform to eliminate unevenness in thickness. There are various sizes of semiconductor substrates and optical lenses, which range from several millimeters (mm) to several meters (m). In the finishing process for a large workpiece to be processed, it may be difficult to make the entire surface of the workpiece uniform due to an uneven contact of a part of the polishing pad because of warpage of the workpiece or the like. Accordingly, it may be desirable to improve the followability of the polishing pad to the shape of each workpiece and prevent the occurrence of an uneven contact, to thereby make the entire surface of the workpiece uniform in the finishing process. As techniques that are effective in improving the followability, a laminated polishing pad discussed in Japanese Patent Application Laid-Open No. 2003-220550 and fluid support polishing discussed in Japanese Patent Application Laid-Open No. 2004-358591 are known.
The laminated polishing pad refers to a pad including layers with different hardnesses and different elastic moduli in a thickness direction within a single pad. An upper layer of the laminated polishing pad is a hard layer with high hardness to hold a slurry on a polishing surface. A lower layer of the laminated polishing pad is a soft layer with low hardness to follow the warpage of a workpiece. In such a laminated polishing pad, there is no need to bond the layers with an adhesive, which is advantageous in preventing deterioration in the followability due to an uneven thickness of the adhesive.
The fluid support polishing is a processing method in which a support surface of the polishing pad is supported by a fluid. The fluid is filled at a predetermined pressure depending on the warpage of a workpiece, resulting in an increase in the followability.
According to an aspect of the present disclosure, a polishing pad includes a polishing layer including a polishing surface, and a sealed layer including a support surface, wherein the polishing layer and the sealed layer are sequentially ordered, wherein the polishing surface is provided as a front surface and the support surface is provided as a back surface, wherein the support surface has a water contact angle of 90° or more, wherein the water contact angle of the polishing surface is smaller than the water contact angle of the support surface, and wherein the polishing pad is formed of a resin molded body.
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The fluid storage portion 6 functions to store liquid or gas as a fluid to be supplied to the support surface of the polishing pad 10 at a predetermined pressure from the sealed layer side of the polishing pad 10. The type of the fluid is not particularly limited. Examples of the fluid in the form of gas include air, compressed air, and nitrogen. Examples of the fluid in the form of liquid include pure water and polishing solution. The magnitude of the pressure to be applied to the polishing pad 10 may be about a pressure at which the polishing pad 10 can be supported, and is not particularly limited. For example, the pressure is in a range from 3 kPa to 40 kPa. The pressure is desirably in a range from 5 kPa to 20 kPa.
As illustrated in
In
The polishing layer 11 includes the polishing surface 11S. The polishing surface 11S is a portion of the polishing pad 10 that contacts the workpiece 3, and includes a resin 7. The water contact angle of the polishing surface 11S is smaller than the water contact angle of the support surface 13S. The polishing surface 11S has higher wettability than the support surface 13S. Accordingly, the slurry S is likely to be wet-out on the polishing surface 11S. If the slurry S is likely to wet-out on the polishing surface 11S, the surface roughness of the workpiece 3 can be reduced, compared to a case where the slurry S is not sufficiently wet-out on the polishing surface 11S. The water contact angle of the polishing surface 11S is desirably less than 90°. More desirably, the water contact angle of the polishing surface 11S is less than 75°, and still more desirably less than 25°.
Cells 8 are desirably located in the polishing surface 11S. The cells 8 located in the polishing surface 11S enable the polishing surface 11S to hold the slurry S on the front surface thereof. If the polishing surface 11S can hold the slurry S, the slurry S can be supplied to a space between the polishing pad 10 and the workpiece 3 even when the polishing pad 10 and the workpiece 3 contact each other during polishing processing. The polishing layer 11 has a predetermined hardness and functions to prevent the polishing pad 10 from following the shape of a portion of the workpiece 3 that is to be removed by polishing, for example, an undulated portion with a high spatial frequency. A desired hardness for the polishing layer 11 can be obtained by controlling the amount of the cells 8 (average cell density). For example, if the amount of the cells 8 is increased by increasing the content of hollow particles, cavity portions of which can be used as the cells 8, the hardness of the polishing layer 11 can be decreased, and if the amount of the cells 8 is reduced by reducing the content of the hollow particles, the hardness of the polishing layer 11 can be increased. The hardness refers to an indentation hardness represented by Pa. The average cell density in the polishing layer 11 is not particularly limited and is, for example, in a range from 40% to 80%.
The polishing layer 11 desirably contains metal oxide particles 24 having hydrophilicity in the resin 7. Having hydrophilicity indicates that a hydrophilization rate is more than or equal to 0.50. Metal oxide particles having hydrophilicity indicate that the hydrophilization rate on the front surface of the particles is more than or equal to 0.50. A method for measuring the hydrophilization rate will be described below. The particles having hydrophilicity on the front surface thereof have a large free energy. Accordingly, if the polishing layer 11 contains the metal oxide particles 24, the polishing surface 11S is more likely to hold polishing solution or slurry. In other words, if the polishing layer 11 contains the metal oxide particles 24 having hydrophilicity, the roughness on the polishing surface of the workpiece 3 is likely to decrease. The type of the metal oxide is not particularly limited. In terms of a large front surface free energy, silica and alumina are desirably used. Silica and alumina may be singly used or may be used in combination. If the content of the metal oxide particles 24 in the polishing layer 11 is less than 20% by mass, the water contact angle increases, which may make it difficult to obtain sufficient polishing characteristics. On the other hand, if the content of the metal oxide particles 24 exceeds 50% by mass, the hardness of the polishing layer 11 increases, which may make it difficult to obtain sufficient followability. Therefore, the content of the metal oxide particles 24 in the polishing layer 11 is desirably in a range from 20% by mass to 50% by mass.
The intermediate layer 12 is a portion located between the polishing layer 11 and the sealed layer 13 and includes the resin 7. In the polishing pad 10 according to the present disclosure, the intermediate layer 12 may be omitted. The intermediate layer 12 may include the cells 8 and the metal oxide particles 24 in the resin 7, like the polishing layer 11. The intermediate layer 12 may include the cells 8 and fluororesin particles 9 in the resin 7, like the sealed layer 13 to be described below. In terms of facilitating the polishing pad 10 to follow the shape of the workpiece 3, the hardness of the intermediate layer 12 is desirably lower than the hardness of the polishing layer 11. Therefore, the average cell density in the intermediate layer 12 is desirably lower than the polishing layer 11.
The sealed layer 13 includes the support surface 13S of the polishing pad 10. The support surface 13S is located on an opposite side of the polishing surface 11S in the polishing pad 10. The support surface 13S is a surface to which a fluid is applied from the fluid storage portion 6 at a predetermined pressure in fluid support polishing, and is supported by the fluid during a polishing work. When the support surface 13S is supported by liquid, the support surface 13S also includes a function for preventing immersion of liquid into the polishing surface 11S.
The water contact angle of the support surface 13S is 90° or more. The water contact angle of the support surface 13S is greater than the water contact angle of the polishing surface 11S. This makes it possible to provide a structure for preventing a fluid in the form of liquid from entering the polishing pad 10. In other words, the support surface 13S has higher hydrophobicity than the polishing surface 11S. The water contact angle of the support surface 13S is desirably in a range from 90° to 150°. To obtain a water contact angle greater than 150°, the support surface 13S may desirably contain a large amount of the fluororesin particles 9 to be described below, which may result in an increase in hardness.
The sealed layer 13 includes the resin 7 and the cells 8. The average cell density in the sealed layer 13 is not particularly limited and is, for example, in a range from 40% to 80%. If the average cell density in the sealed layer 13 is extremely high, the cells 8 are likely to connect to each other. In this case, a fluid supplied from the fluid storage portion 6 can reach the workpiece 3 via the support surface 13S, the sealed layer 13, the intermediate layer 12, the polishing layer 11, and the polishing surface 11S. The thickness (length in the z-direction in
In terms of increasing the hydrophobicity of the sealed layer 13, the sealed layer 13 desirably contains the fluororesin particles 9. As a type of fluororesin particles to be used, for example, at least one type selected from the group consisting of polytetrafluoroethylene (PTFE=Tetra Fluoro Ethylene), tetrafluoroethylene-perfluoroethylene copolymer resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkoxyethylene copolymer resin (EPE), ethylene-tetrafluoroethylene copolymer resin (ETFE), poly(chlorotrifluoroethylene) resin (PCTFE), ethylene chlorotrifluoroethylene copolymer resin (ECTFE), poly(vinylidene fluoride) resin (PVDF), and vinyl fluoride resin (PVE) can be used. In this group, polytetrafluoroethylene (PTFE) is desirably used. PTFE is a substance that is superior in heat resistance and chemical resistance and has a small front surface free energy of 18.5 mN/m. PTFE is effective in increasing the hydrophobicity of the sealed layer 13 and enhancing the function of preventing immersion of liquid into the polishing surface 11S. The content of the fluororesin particles 9 in the sealed layer 13 is desirably in a range from 20% by mass to 50% by mass. The content of the fluororesin particles 9 within this range permits the water contact angle and the hardness to be well-balanced, so that sufficient followability can be obtained.
As illustrated in
The polishing pad 10 is a resin molded body. Specifically, the polishing surface 11S, the polishing layer 11, the intermediate layer 12, the sealed layer 13, and the support surface 13S are integrally formed without using adhesive. The resin molded body is desirably a foam. In this case, the polishing surface 11S has an uneven shape. A raw material for a resin material to be used as a cured material to form the resin molded body is not particularly limited. For example, polyurethane, polyethylene, polypropylene, polystyrene, polyester, nylon, poly(vinyl chloride), poly(vinylidene chloride), polybutene, polyacetal, polyphenylene oxide, poly(vinyl alcohol), poly(methyl methacrylate), polysulfone, polyether sulfone, polyether ketone, polyetheretherketone, polyamide-imide, polycarbonate, polyarylate, liquid crystal polymer, aromatic polysulfone resin, biodegradable polyester resin, polyamide resin, polyimide resin, fluorinated resin, ethylene-propylene resin, ethylene-ethyl acrylate resin, epoxy resin, acrylic resin, norbornene-based resin, styrene copolymer (e.g., vinyl-polyisoprene-styrene copolymer, butadiene-styrene copolymer, acrylonitrile-styrene copolymer, or acrylonitrile-butadiene-styrene copolymer), natural rubber, synthetic rubber, or thermoplastic elastomer can be used.
These examples of the resin material may be singly used or may be mixed or copolymerized. It is desirable to use polyurethane as a main component in terms of being superior in wear resistance, or in terms of facilitating manufacturing processes to be described below. The term “main component of the resin molded body” as used herein refers to a component with the largest mass in resin materials contained in the resin molded body when the resin molded body is formed of a plurality of resin material. A ratio of polyurethane in the resin molded body is more than or equal to 50% by mass, desirably more than or equal to 70% by mass, and more desirably more than or equal to 90% by mass. A manufacturing method for the resin molded body will be described below.
The water vapor permeability of the polishing pad 10 is desirably 25 g/m2·24 hr or less. If the water vapor permeability is less than or equal to this value, the fluid supplied from the fluid storage portion 6 to the support surface 13S of the polishing pad 10 is less likely to reach the polishing surface 11S, which facilitates the polishing pad 10 to follow the shape of the workpiece 3. On the other hand, if the water vapor permeability is more than this value, the fluid is likely to reach the polishing layer 11. The leakage of the fluid makes it difficult for the polishing pad 10 to follow the shape of the workpiece 3. If it is difficult for the polishing pad 10 to follow the shape of the workpiece 3, the polishing processing cannot fully proceed, which may make it difficult to reduce the surface roughness of the workpiece 3. The water vapor permeability is more desirably 13 g/m2·24 hr or less.
The thickness (length in the z-direction in
The polishing pad 10 according to the present disclosure is formed of a resin molded body having a structure in which the polishing layer 11 including the polishing surface 11S with a smaller water contact angle than the support surface 13S and the sealed layer 13 including the support surface 13S with a water contact angle of 90° or more are sequentially laminated. This structure makes it possible to prevent a fluid from reaching the polishing surface 11S even when the polishing pad 10 is used for fluid support polishing and a fluid pressure is applied. Further, since the polishing pad 10 is formed of the resin molded body without including any adhesive layer made of adhesive, higher followability to the shape or warpage of the workpiece 3 can be maintained. Accordingly, the polishing pad 10 according to the present disclosure makes it possible to sufficiently reduce the surface roughness of the workpiece 3 as compared with the polishing pad for fluid support polishing according to related art.
Next, a manufacturing method for the polishing pad 10 will be described. The manufacturing method for the polishing pad 10 according to the present disclosure is not particularly limited. A preferred mode will be described with reference to
First, in step S1, a sealed layer precursor is placed in a mold 20 and then the sealed layer precursor is heated to be temporarily cured as illustrated in
Next, in step S2, an intermediate layer precursor is placed above the sealed layer precursor 13A temporary cured in the mold 20, and then the intermediate layer precursor is heated to be temporarily cured as illustrated in
Next, in step S3, a polishing layer precursor is placed above the intermediate layer precursor 12A temporary cured in the mold 20, and then the polishing layer precursor is heated to be temporarily cured as illustrated in
In step S4, the inside of the mold 20 is compressed while the sealed layer precursor 13A, the intermediate layer precursor 12A, and the polishing layer precursor 11A are heated to be subjected to main-curing, and each precursor is held until it no longer flows as illustrated in
By the above-described steps, the polishing pad 10 according to the present disclosure can be manufactured.
The manufacturing method for the polishing pad 10 according to the present disclosure described above does not include any process using an adhesive, and thus can provide a polishing pad capable of maintaining high followability to the shape or warpage of the workpiece 3. Consequently, the manufacturing method for the polishing pad 10 according to the present disclosure can provide a polishing pad capable of minimizing the surface roughness of the workpiece 3 as compared with the polishing pad for fluid support polishing according to related art.
In the manufacturing method described above, temporary curing and main-curing are performed by sequentially placing the sealed layer precursor 13A, the intermediate layer precursor 12A, and the polishing layer precursor 11A in the mold 20. Alternatively, temporary curing and main-curing may be performed by sequentially placing the polishing layer precursor 11A, the intermediate layer precursor 12A, and the sealed layer precursor 13A in the mold 20. Further, in the manufacturing method described above, the hardness of each layer is adjusted by changing the size or content of hollow particles. The method for adjusting the hardness of each layer is not limited to this example. For example, the hardness of each layer may be controlled by intentionally foaming the precursors in each layer when the precursors are mixed.
In the case of manufacturing the polishing pad 10 that does not include the intermediate layer 12, step S2 may be omitted. In this case, the polishing layer precursor 11A is directly placed on the temporarily cured sealed layer precursor 13A.
Examples of the present disclosure will be described in more detail below. However, the present disclosure is not limited by the following examples.
Prior to the description of manufactured examples, a method for evaluating each example and each comparative example will be described.
Measuring Instrument: Contact angle meter (VCA-2500XE manufactured by AST Products, Inc.)
Test Method: The water contact angle was measured immediately after dropping pure water (1 μL) onto the polishing surface and the support surface of the polishing pad from a microsyringe coated with polytetrafluoroethylene (PTFE) with an inside diameter of 0.1 mm.
Measuring Instrument: Fourier-transform infrared spectroscopic analyzer (FT-IR-NIRA manufactured by PerkinElmer, Inc.)
Test Method: The percentage hydrophilicity of silica particles was calculated by dividing the absorbance at 7300 cm−1 representing Si—OH in an infrared radiation (IR) spectrum on the front surface thereof by the absorbance at 4500 cm−1 representing SiO2. The percentage hydrophilicity of alumina particles was calculated by dividing the absorbance at 3690 cm−1 representing Al-OH in an IR spectrum on the front surface thereof by the absorbance at 7425 cm−1 representing Al2O3.
Measuring Instrument: Gas permeation tester (PERMATRAN-W1/50 manufactured by Mocon, Inc.)
Test Method: An evaluation was performed in accordance with JIS Z 0208: a water vapor permeability test method (cup method) (test conditions: temperature of 40° C., humidity of 90% RH).
Measuring Instrument: Color 3D laser microscope (VK-9700 manufactured by Keyence Corporation)
Test Method: The average cell density was calculated by measuring a section of a test piece (10 mm×10 mm) with a 10-power objective lens, converting a resin portion and a cell portion into grayscales by image processing, and binarizing the obtained information in 125 grayscales.
Measuring Instrument: Color 3D laser microscope (VK-9700 manufactured by Keyence Corporation)
Test Method: The average cell diameter was calculated by performing a stitching measurement on the entire front surface of the polishing surface of a test piece (10 mm×10 mm) with a 10-power objective lens, and adding up cell diameters in an image obtained by converting a resin portion and a cell portion into grayscales by image processing and binarizing the obtained information in 125 grayscales.
Measuring Instrument: Color 3D laser microscope (VK-9700 manufactured by Keyence Corporation)
Test Method: The thickness of each cell in the lamination direction was measured from an image obtained by measuring a section of a test piece (10 mm×10 mm) with a 10-power objective lens, converting a resin portion and a cell portion into grayscales by image processing, and binarizing the obtained information in 125 grayscales.
Measuring Instrument: Color 3D laser microscope (VK-9700 manufactured by Keyence Corporation)
Test Method: The thickness of each layer was measured from a section of a test piece (10 mm×10 mm) also with a 10-power objective lens.
Measuring Instrument: White interferometer (CP300 manufactured by Zygo, Inc.)
Test Method: A stitching measurement was performed with a 5-power objective lens on an area of a test workpiece (φ80 mm) that is 35 mm rightward from the center from a position that is 35 mm leftward from the center, and the roughness Rz (JIS B 0601-2001) on the entire measured area was evaluated. The resolution was 0.01 nm.
Test Method: Polishing processing was performed for 30 minutes by adding a cerium oxide (K30-9 manufactured by Mirek Corporation), as a slurry, using a workpiece of a glass substrate having a surface roughness of 50 nmRz and a diameter of φ80 mm, and a maximum roughness Rz was evaluated. In this case, a maximum roughness of 1 nmRz was set as a determination value to determine whether the polishing pad can follow the shape of the workpiece. This is because if the polishing pad cannot follow the shape of the workpiece and polishing processing cannot be uniformly performed, an unprocessed portion is left and the roughness less than or equal to the determination value cannot be obtained. A result showing that the roughness was less than or equal to 1 nmRz was evaluated as “A”, and a result showing that the roughness was more than 1 nmRz was evaluated as “B”.
Measuring Instrument: FE-SEM (Product Name: JSM-IT500HR/LA manufactured by JEOL Ltd.)
Test Method: A method for measuring the content of metal oxide particles will be described. A first observation region obtained by arbitrarily selecting a square area with a side of 1 mm (stitching measurement on an image size of 260 um×190 um) in a range from the polishing surface to a position at a depth of 5 μm from the polishing surface on a section in the thickness direction taken along a line parallel to the longitudinal direction of the polishing layer was set. In the first observation region, an Energy-dispersive X-ray spectroscopy (EDS) image was obtained under conditions of a power of 500 and 10 kV, and binarization processing was performed with numerical calculation software (Product Name: MATLAB® manufactured by MathWorks, Inc.), to thereby obtain a binarized image. In the obtained binarized image, the ratio of the number of pixels in a region corresponding to hydrophilic metal oxide particles to the number of pixels (resolution of 2083 in length×2083 in width) in the entire measured region was calculated.
A method for measuring the content of fluororesin particles will be described. A second observation region obtained by arbitrarily selecting a square area with a side of 50 μm (stitching measurement on an image size of 260 um×190 um) in a range from the support surface to a position at a depth of 5 μm from the support surface on a section in the thickness direction taken along a line parallel to the longitudinal direction of the sealed layer was set. In the second observation region, an EDS image was obtained under conditions of a power of 500 and 10 kV, and binarization processing was performed with numerical calculation software (Product Name: MATLAB® manufactured by MathWorks, Inc.), to thereby obtain a binarized image. In the obtained binarized image, the ratio of the number of pixels in a region corresponding to fluororesin particles to the number of pixels (resolution of 2083 in length×2083 in width) in the entire measured region was calculated.
In Example 1, 28.98 g of methylene diphenyl diisocyanate (MDI) type polyurethane elastomer Coronate 4370 (manufactured by TOSOH CORPORATION), which is thermoplastic resin, was weighed as a resin material for the sealed layer, and 20.28 g of polyol-based curing agent Nipporan 4479 (manufactured by TOSOH CORPORATION) was weighed as a curing agent, and these materials were mixed. In this mixture, 0.78 g of Matsumoto Microsphere FN-78D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and 3.06 g of polytetrafluoroethylene particles ALGOFLON L203R (manufactured by Solvay Corporation) were weighed as the first hollow particles, and the sealed layer precursor was prepared by mixing the particles using an Auto Mixer (2-913-01 Auto Mixer AS100 manufactured by AS ONE Corporation and having a rotational speed of 3000 rpm) for 16 seconds as one set, which is less heat-affected, by three sets (48 seconds in total).
Similarly, 28.98 g of methylene diphenyl diisocyanate (MDI) type polyurethane elastomer Coronate 4370 (manufactured by TOSOH CORPORATION), which is thermoplastic resin, was weighed as a resin material for the polishing layer, and 20.28 g of polyol-based curing agent Nipporan 4479 (manufactured by TOSOH CORPORATION) was weighed as a curing agent, and then these materials were mixed. In this mixture, 0.99 g of Matsumoto Microsphere F-80DE (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) was weighed as the third hollow particles, and the polishing layer precursor was prepared by mixing the particles using Auto Mixer (2-913-01 Auto Mixer AS100 manufactured by AS ONE Corporation and having a rotational speed of 3000 rpm) for 16 seconds as one set, which is less heat-affected, by three sets (48 seconds in total). In a square mold with a lower surface of 200 mm×200 mm, 2.67 g of sealed layer precursors were placed and were temporarily cured for 10 minutes in an electric furnace at 120° C. Next, 8.00 g of polishing layer precursors were placed above the sealed layer precursors temporarily cured, and the polishing layer precursors were primarily cured for one hour in an electric furnace at 120° C. After that, the temporarily cured precursors of the polishing pad were released from the mold. Then, the precursors of the polishing pad were secondarily cured under the temperature condition of 120° C. for eight hours. Thus, the polishing pad according to Example 1 was obtained.
In the polishing pad according to Example 1, the thickness of the sealed layer was 0.11 mm and the thickness of the polishing layer was 0.21 mm. The water contact angle of the support surface was 90.6° and the cell density in the sealed layer was 62%. The water contact angle of the polishing surface was 73.9° and the cell density in the polishing layer was 61%. The water vapor permeability was 18.6 g/m2·24 h.
Table 1 illustrates a list of the water contact angle of the polishing surface, the water contact angle of the support surface, the content of fluororesin particles, the water vapor permeability, the workpiece roughness, and the followability evaluation result. As seen from Table 1, it was confirmed that in Example 1, the roughness was less than or equal to 1 nmRz and thus the polishing pad can fully follow the shape of the workpiece.
In Example 2, the amount of polytetrafluoroethylene particles to be added was increased to 7.5 g so as to increase the water contact angle of the sealed layer. In the subsequent procedure from degassing to curing, the polishing pad was prepared in the same manner as Example 1. In the mold, 16.8 g of sealed layer precursors were placed and 42.8 g of polishing layer precursors were placed above the sealed layer precursors temporarily cured, and then the precursors were subjected to main-curing.
In the polishing pad according to Example 2, the thickness of the sealed layer was 0.63 mm and the thickness of the polishing layer was 1.07 mm. The water contact angle of the support surface was 149.5° and the cell density in the sealed layer was 59%. The water contact angle of the polishing surface was 74.7° and the cell density in the polishing layer was 62%. The water vapor permeability was 12.1 g/m2·24 h.
As seen from Table 1, it was confirmed that in Example 2, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. Although the water contact angle of the sealed layer in Example 2 was greater than that in Example 1, it was confirmed that the effect of the water contact angle on the maximum roughness was small.
In Example 3, the precursors were prepared in the same procedure as that for Example 2. However, in Example 3, 0.47 g of hydrophilic silica AEROXIDE® 380PE (manufactured by NIPPON AEROSIL CO., LTD.) with a hydrophilization rate of 0.51 was added to the polishing layer precursors. In the subsequent procedure from degassing to curing, the polishing pad according to Example 3 was prepared in the same manner as Example 1. In the mold, 12.53 g of sealed layer precursors were placed and temporarily cured, and then 38.00 g of polishing layer precursors were placed above the sealed layer precursors and were subjected to main-curing.
In the polishing pad according to Example 3, the thickness of the sealed layer was 0.47 mm and the thickness of the polishing layer was 0.95 mm. The water contact angle of the support surface was 120.8° and the cell density in the sealed layer was 59%. The water contact angle of the polishing surface was 49.5° and the cell density in the polishing layer was 60%. The water vapor permeability was 15.3 g/m2·24 h.
As seen from Table 1, it was confirmed that in Example 3, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. As compared with Example 2, the polishing pad according to Example 3 contains hydrophilic metal oxide particles, so that the polishing solution is likely to be held on the polishing surface, resulting in a reduction in roughness.
In Example 4, the precursors were prepared in the same procedure as that for Example 3. Further, in Example 4, 0.24 g of hydrophilic alumina AEROXIDE® Alu130 (manufactured by NIPPON AEROSIL CO., LTD.) with a hydrophilization rate of 0.52 was added to the polishing layer precursors. In the subsequent procedure from degassing to curing, the polishing pad according to Example 4 was prepared in the same manner as Example 1. In the mold, 12.53 g of sealed layer precursors were placed and temporarily cured, and then 38.00 g of polishing layer precursors were placed above the sealed layer precursors and were subjected to main-curing.
In the polishing pad according to Example 4, the thickness of the sealed layer was 0.47 mm and the thickness of the polishing layer was 0.95 mm. The water contact angle of the support surface was 121.9° and the cell density in the sealed layer was 59%. The water contact angle of the polishing surface was 49.8° and the cell density in the polishing layer was 60%. The water vapor permeability was 15.3 g/m224 h.
As seen from Table 1, it was confirmed that in Example 4, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. It is also confirmed that even when hydrophilic alumina is used, a polishing accuracy equivalent to that when hydrophilic silica is used can be obtained as compared with Example 3.
In Example 5, the precursors were prepared in the same procedure as that for Example 3. Further, in Example 5, 1.15 g of hydrophilic silica AEROXIDE® 380PE (manufactured by NIPPON AEROSIL CO., LTD.) with a hydrophilization rate of 0.51 were added to the polishing layer precursors. In the subsequent procedure from degassing to curing, the polishing pad according to Example 5 was prepared in the same manner as Example 1. In the mold, 12.53 g of sealed layer precursors were placed and temporarily cured, and then 43.60 g of polishing layer precursors were placed above the sealed layer precursors and were subjected to main-curing.
In the polishing pad according to Example 5, the thickness of the sealed layer was 0.47 mm and the thickness of the polishing layer was 1.09 mm. The water contact angle of the support surface was 120.8° and the cell density in the sealed layer was 60%. The water contact angle of the polishing surface was 49.5° and the cell density in the polishing layer was 62%. The water vapor permeability was 14.8 g/m2·24 h.
As seen from Table 1, it was confirmed that in Example 5, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece and thus the polishing pad can fully follow the shape of the workpiece. Unlike in Example 2, the polishing pad according to Example 5 contains hydrophilic metal oxide particles and thus the polishing solution is likely to be held on the polishing surface, which leads to a reduction in roughness.
In Example 6, the precursors were prepared in the same procedure as that for Example 5. Further, in Example 6, Matsumoto Microsphere FN-78D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) was added to the polishing layer precursors as the third hollow particles. To perform the compression process, 18.98 g of sealed layer precursors were placed in the mold and were temporarily cured, and then 66.06 g of polishing layer precursors, the amount of which was increased, were placed above the sealed layer precursors. After that, a vent hole formed in a side surface of the mold and having a diameter of φ3 mm was opened and the top lid was covered on the upper surface of the mold. The top lid was moved to compress the inside of the mold until the thickness became 66% of the original thickness before compression while heating the precursors for main-curing. This state was maintained until the resin no longer flows. Extra resin was discharged from the vent hole.
In the polishing pad according to Example 6, the thickness of the sealed layer was 0.47 mm and the thickness of the polishing layer was 1.09 mm. The thickness in the lamination direction of each cell in the sealed layer was 0.42 mm at maximum, the thickness in the lamination direction of each cell in the polishing layer was 0.98 mm, and the average cell diameter in the polishing surface was 300 μm. The cell diameter was 1.8 mm at maximum and each cell had a flat shape in the lamination direction. The water contact angle of the support surface was 120.6° and the cell density in the sealed layer was 60%. The water contact angle of the polishing surface was 49.5° and the cell density in the polishing layer was 62%. The water vapor permeability was 9.2 g/m2·24 h.
As seen from Table 1, it was confirmed that in Example 6, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. As compared with Example 5, the cells each have a flat shape and thus the cells in each layer do not connect to each other, which leads to an increase in followability and a decrease in roughness.
In Example 7, the precursors were prepared in the same procedure as that for Example 5. In Example 7, Matsumoto Microsphere FN-78D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) was added to the polishing layer precursors as the third hollow particles. To perform the compression process, 25.06 g of sealed layer precursors were placed in the mold and were temporarily cured, and then 87.20 g of polishing layer precursors, the amount of which was increased, were placed above the sealed layer precursors. After that, a vent hole formed in a side surface of the mold and having a diameter of φ3 mm was opened and the top lid was covered on the upper surface of the mold. The top lid was moved to compress inside of the mold until the thickness became 50% of the original thickness before compression while heating the precursors for main-curing. This state was maintained until the resin no longer flows. Extra resin was discharged from the vent hole.
In the polishing pad according to Example 7, the thickness of the sealed layer was 0.47 mm and the thickness of the polishing layer was 1.09 mm. The thickness in the lamination direction of each cell in the sealed layer was 0.30 mm at maximum, the thickness in the lamination direction of each cell in the polishing layer was 0.74 mm, and the average cell diameter in the polishing surface was 300 μm. The cell diameter was 2.1 mm at maximum and each cell had a flat shape in the lamination direction. The water contact angle of the support surface was 120.6° and the cell density in the sealed layer was 60%. The water contact angle of the polishing surface was 49.5° and the cell density in the polishing layer was 62%. The water vapor permeability was 8.4 g/m2·24 h.
As seen from Table 1, it was confirmed that in Example 7, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. Although the thickness of each cell was smaller than that in Example 6, it was confirmed that the effect of the thickness of each cell on the maximum roughness was small.
In Example 8, the precursors were prepared in the same procedure as that for Example 5. In Example 6, Matsumoto Microsphere F-65DE (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) was added to the polishing layer precursors as the third hollow particles. To perform the compression process, 18.98 g of sealed layer precursors were placed in the mold and were temporarily cured, and then 66.06 of polishing layer precursors, the amount of which was increased, were placed above the sealed layer precursors. After that, a vent hole formed in a side surface of the mold and having a diameter of φ3 mm was opened and the top lid was covered on the upper surface of the mold. The top lid was moved to compress the inside of the mold until the thickness became 66% of the original thickness before compression while heating the precursors for main-curing. This state was maintained until the resin no longer flows. Extra resin was discharged from the vent hole.
In the polishing pad according to Example 5, the thickness of the sealed layer was 0.47 mm and the thickness of the polishing layer was 1.09 mm. The thickness in the lamination direction of each cell in the sealed layer was 0.42 mm at maximum, and the thickness in the lamination direction of each cell in the polishing layer was 0.98 mm, and the average cell diameter in the polishing surface was 50 μm. The cell diameter was 1.8 mm at maximum and each cell had a flat shape in the lamination direction. The water contact angle of the support surface was 120.6° and the cell density in the sealed layer was 60%. The water contact angle of the polishing surface was 49.5° and the cell density in the polishing layer was 62%. The water vapor permeability was 9.2 g/m2·24 h.
As seen from Table 1, it was confirmed that in Example 5, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. Although the average cell diameter was smaller than that in Example 6, the effect of the average cell diameter on the maximum roughness was small.
In Example 9, the amount of polytetrafluoroethylene particles was increased to 8.15 g so as to increase the water contact angle of the sealed layer. In the subsequent procedure from degassing to curing, the polishing pad according to Example 6 was prepared in the same manner as Example 1.
In the polishing pad according to Example 9, the thickness of the sealed layer was 0.51 mm and the thickness of the polishing layer was 0.86 mm. The water contact angle of the support surface was 150.6° and the cell density in the sealed layer was 59%. The water contact angle of the polishing surface was 71.8° and the cell density in the polishing layer was 60%. The water vapor permeability was 9.2 g/m2·24 h.
As seen from Table 1, it was confirmed that in Example 9, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. Although the contact angle of the sealed layer was larger than that in Example 1, it was confirmed that the effect of the water contact angle of the sealed layer on the maximum roughness was small.
In Comparative Example 1, the precursors were prepared in the same procedure as that for Example 3. After that, 12.53 g of sealed layer precursors were first placed in the mold and were cured in a furnace at 120° C. for four hours. After that, the cured sealed layer precursors were released from the mold. Next, 43.60 g of polishing layer precursors were placed in the mold and were primarily cured at 120° C. for four hours, and then the cured polishing layer precursors were released from the mold. Then, the sealed layer precursors and the polishing layer precursors were bonded together with 1.1 g of adhesive (Cemedine Super X). Thus, the polishing pad according to Comparative Example 1 was prepared.
In the polishing pad according to Comparative Example 1, the thickness of the sealed layer was 0.47 mm, the thickness of the polishing layer was 0.95 mm, and the thickness of the adhesive was 0.09 mm. The water contact angle of the support surface was 120.8° and the cell density in the sealed layer was 60%. The water contact angle of the polishing surface was 15.10 and the cell density in the polishing layer was 62%. The water vapor permeability was 15.1 g/m2·24 h.
The roughness was evaluated in the same manner as Example 1. As seen from Table 1, the roughness in Comparative Example 1 was larger than 1.0 nmRz. This result indicates that a gap formed during bonding resulted in uneven adhesion. When air, polishing solution, or the like enters the gap, it causes a distribution in the fluid pressure. This leads to deterioration in the followability of the polishing pad to the shape of an object to be polished, which make it difficult to obtain high surface accuracy.
In Comparative Example 2, the polishing pad was prepared in the same procedure as that for Example 1. In this case, polytetrafluoroethylene particles were not blended in the sealed layer precursors. In the subsequent procedure from degassing to curing, the polishing pad was prepared in the same manner as Example 1.
In the polishing pad according to Comparative Example 2, the thickness of the sealed layer was 0.38 mm and the thickness of the polishing layer was 0.95 mm. The water contact angle of the support surface was 71.1° and the cell density in the sealed layer was 62%. The water contact angle of the polishing surface was 72.3° and the cell density in the polishing layer was 60%. The water vapor permeability was 300 g/m2·24 h.
The roughness was evaluated in the same manner as Example 1. As seen from Table 1, it was confirmed that the roughness in Comparative Example 2 was larger than 1.0 nmRz. This result indicates that since the water contact angle of the support surface was less than 90°, liquid flowed from holes, which made it difficult to obtain high surface accuracy.
In Comparative Example 3, the polishing pad was prepared in the same procedure as Example 5. However, the polishing layer was not prepared and only the sealed layer was formed to thereby prepare the polishing pad according to Comparative Example 3.
In the polishing pad according to Comparative Example 3, the thickness of the sealed layer was 0.94 mm. The water contact angle of the support surface was 122.0° and the cell density in the sealed layer was 60%. The water vapor permeability was 10.9 g/m2·24 h.
The roughness was evaluated in the same manner as Example 1. As seen from Table 1, the roughness in Comparative Example 3 was larger than 1.0 nmRz. This result indicates that the polishing solution cannot be sufficiently held due to a lack of a hydrophilic surface, such as the polishing surface, which made it difficult to obtain high surface accuracy.
As seen from the above results, it was confirmed that in the polishing pad according to the present disclosure that is formed of a resin molded body having a structure in which a polishing layer including a polishing surface with a water contact angle smaller than that of a support surface and a sealed layer including the support surface with a water contact angle of 90° or more are sequentially laminated, a fluid is less likely to reach the polishing surface even when the polishing pad is used for fluid support processing and a fluid pressure is applied. It is also confirmed that since the polishing pad is formed of the resin molded body without including any adhesive layer made of adhesive, high followability to the shape or warpage of a workpiece can be maintained. Consequently, in the polishing pad according to the present disclosure, the surface roughness of the workpiece can be sufficiently reduced as compared with the polishing pad for fluid support polishing according to related art.
In
The polishing surface 11S is a portion of the polishing pad 10 that contacts the workpiece 3. First cells 8A are desirably located in the polishing surface 11S. The first cells 8A located in the polishing surface 11S enable the polishing surface 11S to hold the slurry S on the front surface thereof. If the polishing surface 11S can hold the slurry S, the slurry S can be supplied to a space between the polishing pad 10 and the workpiece 3 even when the polishing pad 10 and the workpiece 3 contact each other during polishing processing.
The first region 12 includes the resin 7 and the first cells 8A, and has a first hardness. The front surface of the first region 12 corresponds to the polishing surface 11S, and functions to prevent the polishing pad 10 from following the shape of a portion of the workpiece 3 that is to be removed by polishing, for example, an undulated portion with a high spatial frequency. A desired first hardness can be obtained by controlling the amount of the first cells 8A (average cell density). If the content of the first hollow particles, the cavity portions of which can be used as the first cells 8A, is increased, the first hardness can be decreased, and if the content of the first hollow particles is reduced, the first hardness can be increased. However, if the first hardness is extremely high, deformation to follow the shape of the workpiece 3 can be insufficient. To increase the degree of freedom of deformation to the workpiece 3 or prevent the polishing pad 10 from excessively following the shape of the workpiece 3, the average cell density in the first region 12 is desirably in a range from 10% to 40%. A method for measuring the average cell density will be described below. From the same point of view, the value of the first hardness is desirably in a range from 0.016 GPa to 0.06 GPa. A method for measuring the hardness will be described below.
The second region 13 includes the resin 7 and second cells 8B, and has a second hardness lower than the first hardness. The second region 13 having the second hardness lower than the first hardness facilitates the polishing pad 10 to follow the shape of the workpiece 3. A desired second hardness can be obtained by controlling the amount of the second cells 8B (average cell density). If the content of the second hollow particles, the cavity portions of which can be used as the second cells 8B, is increased, the second hardness can be decreased, and if the content of the second hollow particles is decreased, the second hardness can be increased. To set the second hardness to be lower than the first hardness, the average cell density in the second region 13 is desirably higher than the average cell density in the first region 12. Further, since the average equivalent circle diameter of the second cells 8B is desirably greater than the average equivalent circle diameter of the first cells 8A, the average particle diameter of the second hollow particles is desirably greater than the average particle diameter of the first hollow particles. Similarly, the coefficient of linear expansion of the second hollow particle is desirably greater than the coefficient of linear expansion of the first hollow particles. The second hardness is lower than the first hardness. As the difference between the second hardness and the first hardness increases, the polishing pad 10 is more likely to follow the shape of the workpiece 3. However, if the second hardness is extremely low, the possibility that the reproducibility of polishing may deteriorate or that the workpiece 3 may be damaged depending on the material of the workpiece 3 can be increased. Therefore, in terms of increasing the followability of the polishing pad 10 to the shape of the workpiece 3 and securing the reproducibility of polishing processing, the value of the average cell density in the second region 13 is desirably in a range from 40% to 80%. From the same point of view, the value of the second hardness is desirably more than or equal to 0.003 GPa and less than 0.016 GPa. To follow warpage or the like of the workpiece 3, the thickness (length in the z-direction in
The sealed layer 14 includes the resin 7 and the support surface of the polishing pad. The average cell density in the sealed layer 14 is lower than the average cell density in the first region 12 and the second region 13. The value of the average cell density in the sealed layer 14 is not particularly limited, but is desirably 10% or less. If the average cell density in the sealed layer 14 is extremely high, the cells are more likely to connect to each other. In this case, there is a possibility that a fluid supplied from the fluid storage portion 6 may reach the workpiece 3 via the sealed layer 14, the second region 13, the first region 12, and the polishing surface 11S. The hardness of the sealed layer 14 is desirably higher than the first hardness and the second hardness. The thickness (length in the z-direction in
The polishing pad 10 is a resin molded body. Specifically, the polishing surface 11S, the first region 12, the second region 13, and the sealed layer 14 are integrally formed without using adhesive. A raw material for a resin material to be used as a cured material to form the resin molded body is not particularly limited. For example, polyurethane, polyethylene, polypropylene, polystyrene, polyester, nylon, polyvinyl chloride, polyvinylidene chloride, polybutene, polyacetal, polyphenylene oxide, polyvinyl alcohol, polymethyl methacrylate, polysulfone, polyether sulfone, polyether ketone, polyether ether ketone, polyamide-imide, polycarbonate, polyarylate, liquid crystal polymer, aromatic polysulfone resin, biodegradable polyester resin, polyamide resin, polyimide resin, fluorinated resin, ethylene-propylene resin, ethylene-ethyl acrylate resin, epoxy resin, acrylic resin, norbornene-based resin, styrene copolymer (e.g., vinyl polyisoprene-styrene copolymer, butadiene-styrene copolymer, acrylonitrile-styrene copolymer, or acrylonitrile-butadiene-styrene copolymer), natural rubber, synthetic rubber, or thermoplastic elastomer can be used. These examples of the resin materials may be singly used or may be mixed or copolymerized. In terms of being superior in wear resistance and facilitating manufacturing processes to be described below, it is desirable to use polyurethane as a main component. The term “main component of the resin molded body” as used herein refers to a component with the largest mass in resin materials contained in the resin molded body when the resin molded body is formed of a plurality of resin material. A ratio of polyurethane in the resin molded body is more than or equal to 50% by mass, desirably more than or equal to 70% by mass, and more desirably more than or equal to 90% by mass. A manufacturing method for the resin molded body will be described below.
The gas permeability of the polishing pad 10 is desirably 50 ml/m2·24 hr-atm or less. If the gas permeability is less than or equal to this value, the polishing pad 10 is likely to follow the shape of the workpiece 3 even when a fluid is supplied to the polishing pad 10 from the fluid storage portion 6. On the other hand, if the gas permeability is greater than this value, a fluid pressure to be applied to the polishing pad 10 is extremely large, which may make it difficult for the polishing pad 10 to follow the shape of the workpiece 3. If it is difficult for the polishing pad 10 to follow the shape of the workpiece 3, polishing processing cannot fully proceed, which may make it difficult to reduce the surface roughness of the workpiece 3.
The thickness (length in the z-direction in
As described above, the polishing pad 10 according to the present disclosure is formed of a resin molded body having a structure in which a polishing surface, a first region with a first hardness, a second region with a second hardness lower than the first hardness, and a sealed layer are sequentially laminated. Accordingly, even when the polishing pad is used for fluid support polishing and a fluid pressure is applied, a fluid is less likely to reach the polishing surface. Further, since the polishing pad 10 is formed of the resin molded body that does not include any adhesive layer made of adhesive, high followability to the shape or warpage of the workpiece 3 can be maintained. Consequently, the polishing pad 10 according to the present disclosure makes it possible to sufficiently reduce the roughness on the front surface of a workpiece as compared with the polishing pad for fluid support polishing of related art.
While the present disclosure illustrates an example where the first cells 8A are smaller than the second cells 8B, any other form may be used as long as the second hardness of the second region 13 is lower than the first hardness of the first region 12. Any other member may be provided on the lower surface of the sealed layer 14, as long as the polishing pad 10 is formed of a resin molded body.
Next, a manufacturing method for the polishing pad 10 will be described. The manufacturing method for the polishing pad 10 according to the present disclosure is not particularly limited. A preferred mode will be described with reference to
First, in step S11, a first region precursor is placed in the mold 20 and is then heated to be temporarily cured as illustrated in
Next, in step S12, a second region precursor is placed above the first region precursor 12A temporarily cured in the mold 20, and then the second region precursor is heated to be temporarily cured as illustrated in
Next, in step S13, a sealed layer precursor is placed above the second region precursor temporarily cured in the mold 20, and then the sealed layer precursor is heated to be temporarily cured as illustrated in
In step S14, the first region precursor 12A, the second region precursor 13A, and the sealed layer precursor 14A are heated to be subjected to main-curing as illustrated in
By the above-described steps, the polishing pad 10 according to the present disclosure can be manufactured.
The manufacturing method for the polishing pad 10 according to the present disclosure described above does not include any process of bonding regions together with adhesive, and the regions are integrally formed, thereby making it possible to provide a polishing pad capable of maintaining high followability to the shape or warpage of the workpiece 3. Therefore, the manufacturing method for the polishing pad 10 according to the present disclosure can provide a polishing pad capable of sufficiently reducing the surface roughness of a workpiece as compared with the polishing pad for fluid support polishing according to related art.
In the above-described manufacturing method, temporary curing and main-curing are performed by sequentially placing the first region precursor 12A, the second region precursor 13A, and the sealed layer precursor 14A in the mold 20. Alternatively, temporary curing and main-curing may be performed by sequentially placing the sealed layer precursor 14A, the second region precursor 13A, and the first region precursor 12A in the mold 20. Further, in the above-described manufacturing method, the hardness of the first region 12 and the hardness of the second region 13 are adjusted by changing the size or content of hollow particles. However, the manufacturing method is not limited to this mode. For example, the hardness of each layer may be controlled by intentionally foaming the precursors in each layer when the first region precursor 12A and the second region precursor 13A are mixed.
The present disclosure will be described in more detail below with reference to examples. However, the present disclosure is not limited to the following examples.
Prior to the description of examples to be manufactured, a method for evaluating each example and each comparative example will be described.
Measuring Instrument: Nano Indenter G200 manufactured by TOYO Corporation)
Test Method: A test piece (φ70 mm) was cut out from the polishing pad depending on the thickness to be evaluated, and the test piece was placed on a sample stage, 12 locations on each sample were measured by using a Berkovich indenter and setting an indentation depth of 10 μm in an XR mode, and the average value was calculated.
Measuring Instrument: Gas permeation tester
Test Method: By differential gas chromatography compliant with JIS K 7126-1 (differential pressure method), test nitrogen gas was caused to flow to one side of a film (φ70 mm) of a test piece at an atmospheric pressure and the transmission side, which is the other side of the film, was decompressed, and the measurement on each sample was performed three times, and then the average value was calculated.
Measuring Instrument: Color 3D laser microscope (VK-9700 manufactured by Keyence Corporation)
Test Method: The average cell density was calculated by measuring a section of a test piece (10 mm×10 mm) with a 10-power objective lens, converting a resin portion and a cell portion into grayscales by image processing, and binarizing the obtained information into 125 grayscales.
Measuring Instrument: Color 3D laser microscope (VK-9700 manufactured by Keyence Corporation)
Test Method: The thickness of each layer was measured by measuring a section of a test piece (10 mm×10 mm) with a 10-power objective lens.
Measuring Instrument: White interferometer (CP300 manufactured by Zygo, Inc.)
Test Method: A stitching measurement was performed with a 5-power objective lens on an area of a test workpiece (φ80 mm) that is 35 mm rightward from the center from a position that is 35 mm leftward from the center, and the roughness Rz (JIS B 0601-2001) on the entire measured area was evaluated. The resolution was 0.01 nm.
Test Method: Polishing processing was performed for 30 minutes by adding a cerium oxide (K30-9 manufactured by Mirek Corporation) as a slurry using a workpiece of a glass substrate having a surface roughness of 50 nmRz and a diameter of φ80 mm, and a maximum roughness Rz was evaluated. In this case, a maximum roughness of 1 nmRz was set as a determination value to determine whether the polishing pad can follow the shape of the workpiece. This is because if the polishing pad cannot follow the shape of the workpiece and polishing processing cannot be uniformly performed, an unprocessed portion is left and the roughness less than or equal to the determination value cannot be obtained. A result showing that the roughness was less than or equal to 1 nmRz was evaluated as “A”, and a result showing that the roughness was more than 1 nmRz was evaluated as “B”.
Polyurethane elastomer Coronate 4370 (manufactured by TOSOH CORPORATION), which is thermoplastic resin, was prepared as a resin material and polyol-based curing agent Nipporan 4479 (manufactured by TOSOH CORPORATION) was prepared as a curing agent. Matsumoto Microsphere F-80DE (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) was prepared as the first hollow particles, and Matsumoto Microsphere FN-78D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) having a larger coefficient of linear expansion and a larger particle size than the first hollow particles was prepared as the second hollow particles.
The first region precursor was obtained by mixing the resin material, the curing agent, and the first hollow particles and removing air bubbles by the deaerator. The second region precursor was obtained by mixing the resin material, the curing agent, and the second hollow particles and removing air bubbles by the deaerator. The sealed layer precursor was obtained by mixing the resin material and the curing agent and removing air bubbles by the deaerator.
In a square mold with a bottom surface of 200×200 mm, the first region precursor was placed and was temporarily cured for 10 minutes in an electric furnace at 120° C. Next, the second region precursor was placed above the first region precursor temporarily cured, and was temporarily cured for 10 minutes in an electric furnace at 120° C. After that, the sealed layer precursor was placed above the second region precursor temporarily cured, and was primarily cured for two hours in an electric furnace at 120° C. After that, the temporarily cured precursors of the polishing pad were released from the mold. Then, the precursors of the polishing pad were secondarily cured under the temperature condition of 120° C. for eight hours. Thus, the polishing pad according to Example 1 was obtained.
In the polishing pad according to Example 1, the thickness of the polishing pad was 1.5 mm, the thickness of the first region was 0.4 mm, the thickness of the second region was 0.8 mm, and the thickness of the sealed layer was 0.3 mm. Table 2 illustrates a list of the indentation hardness, the gas permeability, the cell density, the workpiece roughness, and the followability evaluation result. As seen from Table 2, it was confirmed that in Example 1, the roughness was less than or equal to 1 nmRz and thus the polishing pad can fully follow the shape of the workpiece.
Except that the content of the second hollow particles in Example 2 is less than the content of the second hollow particles in Example 1, the polishing pad according to Example 2 was obtained in the same processes as those for Example 1. As seen from Table 2, it was confirmed that in Example 2, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. It is also confirmed that the hardness of the second region in Example 2 was higher than that in Example 1, and thus the roughness had increased.
Except that the content of the first hollow particles in Example 3 is more than the content of the first hollow particles in Example 1 and the content of the second hollow particles in Example 3 is less than the content of the second hollow particles in Example 1, the polishing pad according to Example 3 was obtained in the same processes as those for Example 1. As seen from Table 2, it was confirmed that in Example 3, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. It was also confirmed that the hardness of the first region in Example 3 was lower than that in Example 1 and the hardness of the second region in Example 3 was higher than that in Example 1, and thus the roughness had increased.
Except that the content of the first hollow particles in Example 4 is less than the content of the first hollow particles in Example 3, the polishing pad according to Example 4 was obtained in the same processes as those for Example 3. As seen from Table 2, it was confirmed that in Example 4, the roughness was less than or equal to 1.0 nmRz and thus the polishing pad can fully follow the shape of the workpiece. It is also confirmed that the hardness of the first region in Example 4 was higher than that in Example 3, and thus the roughness had decreased.
In Comparative Example 1, polyurethaneelastomer Coronate 4370 (manufactured by TOSOH CORPORATION), which is thermoplastic resin, was prepared as the resin material and Nipporan 4479 (manufactured by TOSOH CORPORATION) was prepared as the curing agent. Matsumoto Microsphere F-80DE (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) was prepared as the first hollow particles, and Matsumoto Microsphere FN-78D (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) having a larger coefficient of linear expansion and a larger particle size than the first hollow particles was prepared as the second hollow particles.
A first molded body precursor was obtained by mixing the resin material, the curing agent, and the first hollow particles and removing air bubbles by the deaerator. A second molded body precursor was obtained by mixing the resin material, the curing agent, and the second hollow particles and removing air bubbles by the deaerator. A sealed layer precursor was obtained by mixing the resin material and the curing agent and removing air bubbles by the deaerator.
A first molded body was obtained by placing the first molded body precursor in a square mold with a bottom surface of 200×200 mm and curing the first molded body precursor for 10 minutes in an electric furnace at 120° C. The thickness of the first molded body was 0.4 mm.
A second molded body was obtained by placing the second molded body precursor in a square mold with a bottom surface of 200×200 mm and curing the second molded body precursor for 10 minutes in an electric furnace at 120° C. The thickness of the second molded body was 0.8 mm.
After that, the first molded body and the second molded body were bonded together with an adhesive (Cemedine 575F) to thereby obtain an adherent body. After that, a rubber sheet that is made of nitrile and has a thickness of 0.3 mm was bonded to the second molded body side of the adherent body with an adhesive. In this bonding process, a spatula was used for each of the first molded body and the second molded body, and the polishing pad according to Comparative Example 1 was obtained by bonding the first molded body and the second molded body while uniformly spreading the first molded body and the second molded body.
The roughness was evaluated in the same manner as Example 1. As seen from Table 2, the roughness in Comparative Example 1 was larger than 1.0 nmRz. This is because uneven adhesion occurred during bonding of the polishing pad and the rubber sheet, which made it difficult for the polishing pad to follow the shape of the workpiece and to uniformly perform polishing processing.
Comparative Example 2 differs from Example 3 in that the sealed layer precursor was not placed in the mold and the thickness of the second region in Comparative Example 2 was different from the thickness of the second region in Example 3. Except for the above-described differences, the polishing pad according to Comparative Example 2 was obtained in the same processes as those for Example 3. The thickness of the polishing pad was 1.5 mm, the thickness of the first region was 0.4 mm, and the thickness of the second region was 1.1 mm. As seen from Table 2, it was confirmed that in Comparative Example 2, the roughness was larger than 1.0 nmRz. Due to high gas permeability, the fluid pressure becomes more than or equal to a threshold, which made it difficult for the polishing pad to follow the shape of the workpiece and to fully proceed polishing processing, resulting in an increase in roughness.
As seen from the above results, it was confirmed that in the polishing pad according to the present disclosure formed of a resin molded body having a structure in which a polishing surface, a first region with a first hardness, a second region with a second hardness lower than the first hardness, and a sealed layer are sequentially laminated, a fluid is less likely to reach the polishing surface even when the polishing pad is used for fluid support processing and a fluid pressure is applied. It is also confirmed that since the polishing pad is formed of the resin molded body without including any adhesive layer made of adhesive, high followability to the shape or warpage of a workpiece can be maintained. Consequently, in the polishing pad according to the present disclosure, the surface roughness of the workpiece can be sufficiently reduced as compared with the polishing pad for fluid support polishing according to related art.
The present disclosure is not limited to the above-described exemplary embodiments, and can be modified in various ways within the technical idea of the present disclosure. Advantageous effects described in the exemplary embodiments are merely examples of desirable advantageous effects resulting from the present disclosure, and the advantageous effects of the present disclosure are not limited to those described in the exemplary embodiments.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Applications No. 2023-136104, filed Aug. 24, 2023, No. 2023-136105, filed Aug. 24, 2023, and No. 2024-001513, filed Jan. 9, 2024, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-136104 | Aug 2023 | JP | national |
| 2023-136105 | Aug 2023 | JP | national |
| 2024-001513 | Jan 2024 | JP | national |
