Holding material

Abstract

To provide a holding material capable of suppressing variation in polishing amount on a surface to be polished of an object to be polished.SOLUTION: A porous layer having a holding surface in contact with an object to be polished, wherein the porous layer has a plurality of developed pores extending between a first baseline and a second baseline when a predetermined first baseline and a predetermined second baseline are defined in a CT image of a cross section parallel to a thickness direction of the porous layer, wherein, when a rectangle having a pair of first sides parallel to the thickness direction and a pair of second sides orthogonal to the thickness direction is defined for each of the plurality of development pores so as to circumscribe the development pore, the plurality of development pores include a predetermined number of conformable pores that satisfy both of a condition (1) (length of the second side) / (length of the first side)<0.5 and a condition (2) (area of the development pore) / (area of the rectangle)≥0.5.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a holding material, and more particularly to a holding material used to hold an object to be polished in a polishing apparatus. [Background technology]

[0002] Conventionally, chemical mechanical polishing (CMP) is performed on semiconductor wafers, etc., in the manufacture of semiconductor devices, etc. A known polishing apparatus used for CMP includes, for example, a rotary head that rotates a disk-shaped object to be polished in a circumferential direction and a holder that holds the object to be polished on the rotary head.

[0003] One known holding material of this type uses a porous layer formed from a resin. Typically, the porous layer forms a holding surface that contacts the surface of the workpiece opposite to the surface to be polished, and has multiple pores that open to the holding surface. This holding material can hold the workpiece by adsorbing it to the holding surface using the surface tension of a liquid such as water absorbed into the porous layer.

[0004] As described in Patent Document 1, it is generally considered preferable to make the pores teardrop-shaped (a shape that increases in diameter as it moves away from the holding surface in the thickness direction) in order to ensure the performance of the holding material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-50253 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the inventors have discovered that polishing using a holder having many teardrop-shaped pores results in variations in the amount of polishing on the polished surface of the workpiece. For example, when polishing a disc-shaped semiconductor wafer, there is a problem in that the amount of polishing decreases from the center to the periphery of the circular polished surface.

[0007] In view of the above circumstances, an object of the present invention is to provide a holder that can suppress variations in the amount of polishing on the surface of an object to be polished. [Means for solving the problem]

[0008] The inventors of the present invention have considered that the above-mentioned problem is caused by the fact that when a porous layer having many teardrop-shaped pores is pressed in the thickness direction through an object to be polished and deformed, the direction of the stress acting on the resin walls forming these pores deviates from the thickness direction. They have found that the above-mentioned problem can be solved by forming as many pores as possible so that the direction of the stress acting on the resin walls is more likely to be along the thickness direction, and have completed the present invention.

[0009] The retaining material according to the present invention is It is used to hold an object to be polished in a polishing device, a porous layer having a holding surface in contact with the object to be polished and formed of a resin; In a CT image of a cross section parallel to the thickness direction of the porous layer, a top line and a bottom line for determining the thickness of the porous layer are defined, and a first baseline and a second baseline are defined that are located inward from the porous layer by a thickness that is 12.8% of the thickness of the porous layer relative to the top line and the bottom line, respectively. the porous layer has a plurality of developed pores extending between the first baseline and the second baseline; When a rectangle having a pair of first sides parallel to the thickness direction and a pair of second sides perpendicular to the thickness direction is defined for each of the plurality of developed pores and circumscribing the developed pore, the plurality of developed pores include conforming pores that satisfy both the following conditions (1) and (2): Condition (1): (length of the second side) / (length of the first side)<0.5 Condition (2): (area of ​​the developed pore) / (area of ​​the rectangle)≧0.5 The number of the conforming pores is 21% or more of the number of the developed pores.

[0010] In one embodiment of the retaining material according to the present invention, the porous layer is formed by a wet solidification method. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a holder that can suppress variations in the amount of polishing on the surface to be polished of an object to be polished. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic view of a polishing apparatus according to an embodiment; [Figure 2] FIG. 1 is an explanatory diagram showing a method for acquiring one set of CT images of a porous layer. [Figure 3] This is a CT image of a retaining material, showing a cross section parallel to the thickness direction. [Figure 4] FIG. 2 is a schematic diagram illustrating conforming and non-conforming pores that may be present in a porous layer. [Figure 5] 1 is a graph comparing the variation in the amount of polishing on the surface to be polished when Example 1 and Comparative Example 1 are incorporated into a polishing apparatus and a semiconductor wafer is polished. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, with reference to the drawings, a holder according to one embodiment of the present invention will be described, exemplifying an application in which the holder is incorporated into a polishing apparatus for polishing semiconductor wafers.

[0014] As shown in FIG. 1, the polishing apparatus 1 according to this embodiment includes a disk-shaped abrasive 10 for polishing a polished surface w1, which is one surface of a disk-shaped semiconductor wafer W; a surface plate 20 for holding and rotating the abrasive 10 in a horizontal plane; a rotary head 30 for rotating the semiconductor wafer W in a horizontal plane; and a disk-shaped holding member 40 for holding the semiconductor wafer W on the rotary head 30. The rotary head 30 is disposed above the surface plate 20 and has a lower end surface serving as a front end surface 31 to which the holding member 40 is attached. The holding member 40 has a holding surface 41 that contacts the surface of the semiconductor wafer W opposite the polished surface w1 to hold the semiconductor wafer W, and an adhesive surface that is attached to the front end surface 31 of the rotary head 30.

[0015] In CMP using the polishing apparatus 1, a polishing slurry containing abrasive grains is supplied to an abrasive 10 such as a polishing pad while the abrasive 10 is rotated, and the semiconductor wafer W is rotated by a rotary head 30. The polished surface w1 of the semiconductor wafer W is brought into contact with the polishing surface 11 of the abrasive 10, thereby planarizing the polished surface w1. The object to be polished is not limited to a semiconductor wafer, but may be any object having a polished surface that requires planarization. Examples of such objects to be polished include semiconductor elements such as transistors, LCD substrates, sapphire substrates, and SiC substrates.

[0016] The retaining material includes a sheet-like substrate having a pair of surfaces, a first surface and a second surface, and a porous layer formed on the first surface of the substrate. The retaining material has an adhesive surface that contacts the tip surface of the rotary head and a retaining surface that contacts the surface to be polished. The adhesive surface may be formed, for example, by applying an adhesive composition to the second surface of the substrate, or by attaching a double-sided tape having adhesive properties on both sides to the second surface.

[0017] The substrate may be, for example, a resin film such as a PET film, or may be a woven fabric, knitted fabric, or nonwoven fabric, etc. The thickness of the substrate is, for example, 100 to 650 μm.

[0018] The porous layer has the support surface. The porous layer is a layer formed on the first surface of the base material by a wet solidification method using a resin such as polyurethane. When a cross section parallel to the thickness direction of the porous layer is observed, the porous layer has a plurality of pores formed by a plurality of resin walls extending along the thickness direction. The plurality of pores can be classified into several types according to their shape and size using the method described below. When the porous layer is compressed by the object to be polished, the more resin walls among the plurality of resin walls the direction of action of the stress generated during compression is along the thickness direction, the more evenly the porous layer can apply a pushing force across the entire surface to be polished.

[0019] The CT image shown in Figure 3 was acquired using the following imaging method and shows a cross section parallel to the thickness direction of the porous layer. The horizontal direction D1 of the CT image is parallel to the extension direction of the substrate. The vertical direction D2 of the CT image is parallel to the thickness direction perpendicular to the extension direction (horizontal direction D1) of the substrate. Hereinafter, this thickness direction will be referred to as the direction corresponding to the thickness direction of the porous layer.

[0020] To distinguish the multiple pores, 120 CT images are first acquired for each holding material. As shown in FIG. 2, the 120 images are extracted by arbitrarily selecting three linear length ranges of 1600 μm on the holding surface 41, and acquiring 40 CT images at 40 μm intervals for each length range. That is, when 40 CT images in one length range are considered as one set, three sets of CT images are acquired. In this case, the width of each CT image is set to 1980 μm. The height of each CT image may be set so that the porous layer is visible throughout the entire thickness direction. When selecting the length ranges, it is preferable to select them so that the length ranges do not intersect on the holding surface 41.

[0021] Next, as shown in Figure 3, a top line TL and a bottom line BL are defined in each CT image to determine the thickness d of the porous layer. The top line TL is defined based on the tip of the resin wall that is located outermost in the vertical direction D2 among the multiple resin walls. The bottom line BL is defined based on the bottom surface that is located closest to the substrate in the vertical direction D2 among the bottom surfaces forming each pore. Naturally, the top line TL and the bottom line BL are lines that are parallel to each other and to the horizontal direction D1 of the CT image.

[0022] The thickness d of the porous layer is, for example, 100 to 1000 μm, and preferably 200 to 600 μm.

[0023] Next, as shown in FIG. 3, a first baseline L1 is defined that is parallel to the top line TL and located inward of the porous layer by a thickness equal to 12.8% of the thickness d of the porous layer relative to the top line TL. That is, the first baseline L1 is a line obtained by translating the top line TL toward the bottom line BL by a thickness equal to d × 0.128. A second baseline L2 is defined that is parallel to the bottom line BL and located inward of the porous layer by a thickness equal to 12.8% of the thickness d of the porous layer relative to the bottom line BL. That is, the second baseline L2 is a line obtained by translating the bottom line BL toward the top line TL by a thickness equal to d × 0.128. The region from the support surface of the porous layer to a position approximately 10% inward in the thickness direction is the region where the tip of the resin wall is located and is likely to be subjected to pressure from the wafer. The tip of the resin wall located in this region is prone to lateral deformation, making it difficult for compression stress to act along the thickness direction. Furthermore, this region is generally called a micropore layer, and is a region where pores cannot fully develop. For these reasons, this region is considered to contribute little to the uniform application of the pushing force over the entire polished surface, and therefore must be excluded when distinguishing between multiple pores.

[0024] 3, the pores can be divided into a plurality of developed pores 401 extending between a first baseline L1 and a second baseline L2, and a plurality of undeveloped pores 402 other than the developed pores 401. The number of the developed pores is preferably 750 to 1000 in the 120 CT images. This allows the retention material to exhibit appropriate compressibility and density.

[0025] Furthermore, the average number of the developed pores in each set (number of developed pores in the 40 CT images constituting one set / 40) is preferably 2 or more, more preferably 2.5 or more, and even more preferably 3 or more. Furthermore, the difference in the average number of developed pores between sets is preferably 1 or less. This allows the force of the porous layer pushing back the object to be polished to be uniform across the surface to be polished.

[0026] It is preferable that 90% or more of the plurality of developed pores are open at the support surface, and it is more preferable that all of the pores are open at the support surface.

[0027] Next, as shown in Fig. 4, a plurality of rectangles R circumscribing each of the plurality of developed pores are defined in each CT image. Each rectangle R is defined to have a pair of first sides s1 parallel to the thickness direction and a pair of second sides s2 perpendicular to the thickness direction.

[0028] The developed pores include conforming pores that satisfy both conditions (1) and (2) of the compatibility condition A below, and nonconforming pores that do not satisfy at least one of conditions (1) and (2). As shown in FIG. 4, condition (1) can be used to eliminate nonconforming pores with a large width (length in the horizontal direction D1) that may reduce the number of resin walls (the two nonconforming pores on the left side of the group in FIG. 4(a)) and nonconforming pores that are significantly inclined relative to the thickness direction (vertical direction D2) that may reduce the number of linear resin walls (the nonconforming pore on the right side of the group in FIG. 4(a)). Furthermore, condition (2) can be used to eliminate nonconforming pores with relatively small diameters that are far from linear (for example, teardrop-shaped as shown on the right side of FIG. 4(b) , which widens with increasing diameter as they move away from the support surface). Compared to these nonconforming pores, conforming pores that satisfy both conditions (1) and (2) have a long, thin, linear shape extending along the thickness direction. (Compatibility Condition A) Condition (1): (length of the second side) / (length of the first side)<0.5 Condition (2): (area of ​​the developed pore) / (area of ​​the rectangle)≧0.5

[0029] It is important that the number of conforming pores in the porous layer conforming to conformity condition A is 21% or more of the number of the plurality of developed pores. Preferably, the number of conforming pores is 50% or more of the number of the plurality of developed pores. A porous layer having such a proportion of developed pores can be said to have a relatively large number of resin walls that form the conforming pores and extend in the thickness direction. When the porous layer is compressed by the workpiece, the direction of the stress that may occur in the resin walls during compression is more likely to be along the thickness direction. Furthermore, by having a large number of such acting resin walls, the porous layer can apply a pushing force evenly across the entire polished surface. It is believed that by providing such a porous layer, the retaining material can suppress variations in the amount of polishing on the polished surface of the workpiece.

[0030] In the porous layer, the number of the conforming pores that conform to the following conforming condition B may be 43% or more of the number of the plurality of developed pores. (Compatibility Condition B) Condition (1): (length of the second side) / (length of the first side)<0.6 Condition (2): (area of ​​the developed pore) / (area of ​​the rectangle)≧0.5

[0031] The porous layer may have a number of conforming pores that conform to the following conforming condition C that is 62% or more of the number of the plurality of developed pores. (Compatibility condition C) Condition (1): (length of the second side) / (length of the first side)<0.7 Condition (2): (area of ​​the developed pore) / (area of ​​the rectangle)≧0.4

[0032] The number of the plurality of suitable pores is preferably 150 or more in total, and more preferably 350 or more, in the 120 CT images under any of the compatibility conditions A to C. Particularly under the compatibility condition A, the number of the plurality of suitable pores is preferably 150 or more in total, and more preferably 350 or more. This number is usually 1000 or less under any of the compatibility conditions A to C. Furthermore, under the compatibility condition A, the number may be 500 or less.

[0033] Furthermore, under all of the compatibility conditions A to C, the average number of the multiple compatible pores in each set (the number of compatible pores in the 40 CT images constituting one set / 40) is preferably 2 or more, more preferably 2.5 or more, and even more preferably 3 or more. Particularly under compatibility condition A, the number of the multiple compatible pores is preferably 2 or more, more preferably 2.5 or more, and even more preferably 3 or more. Furthermore, under all of the compatibility conditions A to C, the difference in the average number of the compatible pores between sets is preferably 1 or less, and more preferably 0.5 or less. This allows the force of the porous layer pushing back the object to be polished to be uniform across the surface to be polished.

[0034] The proportion of the number of conforming pores can be determined by the following procedure. (Creating test specimens) A test piece measuring 5 mm wide x 30 mm long x any thickness is cut out from the holding material in a dry state (meaning normal storage conditions; pre-treatment by drying is not required). (X-ray CT scan) The test piece is placed in an X-ray CT device (three-dimensional measurement X-ray CT device, TDM1000H-1, manufactured by Yamato Scientific Co., Ltd.) and an X-ray CT scan is performed. (X-ray CT measurement conditions) Views per rotation: 1500 Frames / Views: 10 Magnification axis position [mm]: 5.448 Reconstruction pixel size X [mm]: 0.003876 Reconstruction pixel size Y [mm]: 0.003876 Reconstruction pixel size Z [mm]: 0.003876 (Acquisition of X-ray CT images) The CT image processing software used is VGStudio Max 2.1, manufactured by Japan Visual Science Volume Graphics Co., Ltd. Each measurement area is subjected to binarization processing to classify it into pores and parts other than the pores (resin layer and substrate). The specific steps in the binarization process are as follows: First, the image is filtered. The filtering conditions are adaptive Gaussian (smoothing: 0.8, edge threshold: 0.1, number of iterations: 2, multiplier: 1). Next, using the image processing software VGStudio Max, the contrast of the image of the measurement area is adjusted to classify the pores from non-pore areas (areas where the forming material is present). Contrast adjustment is performed in inverse ramp mode. In VGStudio Max, contrast adjustment is referred to as "opacity adjustment." The contrast histogram shows peaks for the pores and areas where the material is present. In contrast adjustment, the gray value is adjusted so that these two peaks are clearly visible in the CT image. Specifically, the lower limit of the gray value is set to the valley between the two peaks (= zero), and the upper limit of the gray value is set so that it exceeds the peak of the area where the material is present. Note that the conditions vary depending on the type of substrate, so contrast adjustment may not necessarily be limited to this. A slice image of the measurement area is obtained from the contrast-adjusted image. The field of view (length x width x height) is 1.984553 mm x 1.984553 mm x 1.984553 mm, and the height is adjusted so that the side of the support material is at least half the field of view during measurement. (Calculation of each area) The image analysis software used can be WinROOF, manufactured by Mitani Shoji Co., Ltd. Processing is performed by using the ROI as the inner region of interest (ROI) for each of the 12.8% area above and below the thickness direction of the cross section of the support material. The processing items are as follows: (1) Calibration 2.061900μm / pixel (2) Grayscale imaging (3) Setting ROI (4) Binarization using two thresholds (threshold: 239 to 255) (5) Isolated point removal (target of removal: bright points) (6) Thinning (number of times: 1) (7) Exclusive Expansion (Number of Times: 1) (8) Shape characteristics (ferret, area) This allows all pores to be analyzed.

[0035] The retaining material preferably has a compressibility of 30% or more. A retaining material that requires high adsorption power and has a high compressibility is prone to variations in the amount of polishing, so it is preferable that the porous layer, which has a predetermined number or more of the matching pores, makes the pushing-back force uniform. The compressibility of the retaining material is, for example, 40% or less. The compressibility of the retaining material is measured using a compression elasticity tester (indenter diameter: 5 mm, indenter area: 19.6 mm) specified in JIS L1096:2010. 2 Specifically, a pressure of 300 gf / cm is applied to the holding surface of the holding material. 2 While applying a pressure of 1800 gf / cm2 to the holding surface of the holding material, the holding material is pressed in the thickness direction and held for 60 seconds, and then the thickness T1 of the holding material is measured. 2 While applying a pressure of 1000 kJ / cm, the holding material is pressed in the thickness direction and held for 60 seconds, after which the thickness T2 of the holding material is measured. The compression ratio (%) is calculated as follows: (T1-T2) x 100 / T1.

[0036] The holding material exhibits an adhesive force of 5 kgf / 80 mmΦ or more, and can exhibit an adhesive force of 5.5 kgf / 80 mmΦ or more. The adhesive force here can be measured using an autograph (AG-IS 1 kN) manufactured by Shimadzu Corporation. First, a test piece with a diameter of 90 mm is cut out from the holding material, and the entire holding surface is immersed in pure water. A glass plate (diameter 80 mm) is placed on the holding material, and a weight is placed on top of that, and a weight of 139.5 g / cm is applied. 2 The test piece is left to stand for 10 seconds with this pressure applied. The weight is then removed and measurement is started under the following conditions, with the maximum test force being taken as the measured value. The measurement is repeated 10 times, and the average of the 10 measurements is taken as the suction force. (Measurement conditions) Test type: Tensile Control: Stroke Sampling interval: 10 msec High-speed sampling: 5 msec Test speed 1:150 Test speed 2:1 Test speed 3:1 Pulling speed: 300m / min

[0037] The retaining material can also exhibit a breaking strength of 3 kgf / inch or more. The breaking strength here can be measured using an autograph (AG-IS 1kN) manufactured by Shimadzu Corporation and measurement software TRAPEZIUM2 version 2.32. First, a 400 mm x 400 mm sample is cut out from the original (roll) retaining material after buffing. Next, a hot melt sheet is thermocompressed to glass epoxy FR4 (thickness 0.6 mm) using a heat press (130°C, 3000 kgf / cm). 2 , 60 seconds, no spacer), and adjust to a size of 200 mm x 200 mm. Place glass epoxy with the hot melt sheet facing downwards on the holding surface of the sample and heat press (127°C, 1.5 MPa, 60 seconds, 1.30 mm). At this time, align so that the four edges of the sample periphery protrude beyond the periphery of the glass epoxy. Cut out a rectangular test piece 25.4 mm wide x 180 mm long from the sample with the glass epoxy attached. At this time, leave one end of the test piece protruding from the sample. After manually peeling this end 180° to form a tensile allowance, set it in the tensile tester so that it is peeled 180°, and measure the strength at break under the measurement conditions below. (Measurement conditions) Test mode: Single Test type: Peel Test force polarity: Standard Test direction: Up Sampling interval: 150 msec Filter: ON Control: Stroke Stretch origin: From the beginning V1 (pulling speed): 300 mm / min Disconnection detection: Level, 5% / FS Number of divisions: None Sensitivity: 1 First half deletion range: Displacement, 20mm Second half deletion range: Displacement, 30mm

[0038] Next, a method for forming the porous layer will be described.

[0039] The porous layer according to this embodiment can be formed using a wet coagulation method, and for example, film formation conditions known in the technical field of synthetic leather can be used (for example, the method for forming a cylindrical microporous film described in JP-A-7-207052 can be used as a reference).

[0040] In the forming method according to this embodiment, a coating layer is laminated on a first surface of the substrate using a resin solution containing a resin such as polyurethane and a coater. When the substrate is a woven fabric, knitted fabric, or nonwoven fabric, the basis weight of the substrate and the permeability of the resin solution into the substrate may be adjusted so that the coating layer can be laminated on the substrate. Furthermore, for such substrates, a coating layer that can prevent the resin solution from permeating the substrate may be formed on the first surface so that the coating layer can be laminated on the substrate.

[0041] Next, in the forming method, the substrate on which the coating layer has been formed may be immersed in a coagulation liquid to coagulate the resin, thereby forming the porous layer and obtaining the retaining material. The obtained retaining material is usually washed with water. Furthermore, the formed porous layer is buffed so that the multiple pores are appropriately open on the retaining surface.

[0042] The resin solution typically contains a polyurethane resin, an organic solvent, and a surfactant, and the coagulation liquid typically is an aqueous solution containing an organic solvent.

[0043] The polyurethane resin can be obtained, for example, by reacting a diisocyanate, a polyol, and a chain extender. The polyurethane resin is at least one selected from the group consisting of polyester-based polyurethane resins, polyether-based polyurethane resins, and polycarbonate-based polyurethane resins. The polyurethane resin preferably has a 100% modulus of 40 MPa or more and less than 60 MPa, and more preferably 45 MPa or more and less than 53 MPa. The 100% modulus can be measured by preparing a film with a thickness of 40 μm using the resin, cutting a test piece with a width of 2.5 cm from the film, and performing a tensile test using an autograph at 20°C and a tensile speed of 300 mm / min, and then determining the modulus from the resulting SS curve.

[0044] Examples of the diisocyanate include diphenylmethane-4,4'-diisocyanate, tolylene-2,4-diisocyanate, xylylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and hexamethylene diisocyanate.

[0045] Examples of the polyol include polyester polyols such as polyethylene adipate glycol, polypropylene adipate glycol, polyethylene propylene adipate glycol, polybutylene adipate glycol, polyethylene butylene adipate glycol, and polypentamethylene adipate glycol; polyether polyols such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol; and polycarbonate polyols such as polytetramethylene carbonate, polypentamethylene carbonate, and polyhexamethylene carbonate. Among these, polyester polyols are preferred. For example, when a porous layer having many teardrop-shaped pores is formed using a conventional forming method, the number of suitable pores can be increased by using the polyester polyol or increasing the content of the polyester polyol based on the formation conditions of the porous layer.

[0046] Examples of the chain extender include glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol; diamines such as ethylenediamine, trimethylenediamine, propylenediamine, and butylenediamine; and amino alcohols.

[0047] Examples of the solvent include hydrophilic solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, and tetrahydrofuran.

[0048] The surfactant is preferably one or more selected from anionic surfactants and nonionic surfactants, and more preferably one or more selected from each of anionic surfactants and nonionic surfactants. For example, when a porous layer having many teardrop-shaped pores is obtained by referring to a conventional formation method, the compatible pores can be increased by using an anionic surfactant or by increasing the content of the anionic surfactant. Examples of such anionic surfactants include alkylbenzene sulfonates. Furthermore, the compatible pores can be increased by using a nonionic surfactant or by increasing the content of the nonionic surfactant. Examples of such nonionic surfactants include silicone oil.

[0049] As described above, one embodiment has been shown as an example, but the retaining material according to the present invention is not limited to the configuration of the above embodiment. Furthermore, the retaining material according to the present invention is not limited by the above-described effects. The retaining material according to the present invention can be modified in various ways without departing from the gist of the present invention. [Example]

[0050] The present invention will be further explained below with reference to examples, but the present invention is not limited to these examples.

[0051] [Manufacturing example] A polyurethane resin and a surfactant were dissolved in DMF to prepare a resin solution. A coating layer was formed on the surface of a resin film as a substrate using the resin solution. The film with the coating layer formed thereon was immersed in a DMF-containing coagulation solution to coagulate the polyurethane resin in the coating layer, thereby forming a porous layer. In other words, a retention material having a porous layer laminated on a film was produced by a wet coagulation method. The surface of the porous layer was buffed to prepare a retention material for evaluation.

[0052] [Evaluation method] A 300 mm silicon wafer was polished using the polishing equipment and polishing conditions shown in Table 1, and the variation in the amount of polishing on the polished surface was evaluated by measuring the GBIR. The results are shown in Table 2.

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] From Table 3 and FIG. 5, it can be seen that in polishing using Example 1, the variation in the amount of polishing on the surface to be polished can be suppressed compared to Comparative Example 1. [Explanation of symbols]

[0057] 1: polishing device, 10: polishing material, 11: polishing surface, 20: surface plate, 30: rotating head, 40: holding material, 41: holding surface, W: object to be polished, w1: surface to be polished, D1: horizontal direction, D2: vertical direction, d: thickness, TL: top line, BL: bottom line, L1: first baseline, L2: second baseline, R: rectangle, s1: first side, s2: second side

Claims

1. It is used to hold an object to be polished in a polishing device, a porous layer having a holding surface in contact with the object to be polished and formed of a resin; In a CT image of a cross section parallel to the thickness direction of the porous layer, a top line and a bottom line are defined to determine the thickness of the porous layer, and a first baseline and a second baseline are defined that are located inward from the porous layer by a thickness that is 12.8% of the thickness of the porous layer relative to the top line and the bottom line, respectively. the porous layer has a plurality of developed pores extending between the first baseline and the second baseline; When a rectangle having a pair of first sides parallel to the thickness direction and a pair of second sides perpendicular to the thickness direction is defined for each of the plurality of developed pores and circumscribing the developed pore, the plurality of developed pores include conforming pores that satisfy both of the following conditions (1) and (2): Condition (1): (length of the second side) / (length of the first side)<0.5 Condition (2): (area of ​​the developed pore) / (area of ​​the rectangle)≧0.5 A retention material, wherein the number of the conforming pores is 21% or more of the number of the plurality of developed pores.

2. The retaining material according to claim 1 , wherein the porous layer is formed by a wet solidification method.

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