Polishing cloth

Abstract

To provide a polishing cloth capable of sufficiently reducing roughness of a surface-to-be-polished of an object-to-be-polished.SOLUTION: A polishing cloth 10 according to the present invention comprises a nonwoven fabric and a resin with which the nonwoven fabric is impregnated. The polishing cloth 10 has a polishing surface 10a. The minimum autocorrelation length Sal of the polishing surface 10a is 70 μm or less. The minimum autocorrelation length Sal, which is a kind of surface roughness parameter, expresses a horizontal distance in a direction in which an autocorrelation value decays to a specific value (s=0.2).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polishing cloth. More specifically, the present invention relates to a polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as a polishing cloth for polishing an object to be polished such as a silicon wafer, a polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric has been known (for example, Patent Document 1 below).

[0003] Polishing of the workpiece with the abrasive cloth is carried out, for example, using a polishing machine equipped with a disk-shaped head and a disk-shaped lower platen arranged opposite the head, according to the following procedure. (1) A disk-shaped workpiece is attached to the lower surface of the head of the polishing machine via a disk-shaped holding material, and a disk-shaped polishing cloth is attached to the upper surface of the lower platen of the polishing machine. (2) The head is moved downward and the lower platen is moved upward so that the workpiece attached to the lower surface of the head is brought into contact with the polishing surface (upper surface) of the polishing cloth attached to the lower platen. (3) With the workpiece in contact with the polishing cloth, the head and the lower platen are rotated while supplying a polishing slurry to the polishing surface (upper surface) of the polishing cloth, thereby polishing the workpiece with the polishing pad. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-43811 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been an increasing demand for sufficiently reducing the roughness of the polished surface of the object to be polished. However, as described above, when the polished surface of the object to be polished is polished using the abrasive cloth, the roughness of the polished surface may not be sufficiently reduced. However, it cannot be said that sufficient research has been done yet to sufficiently reduce the roughness of the polished surface of the object to be polished.

[0006] In view of the above circumstances, an object of the present invention is to provide a polishing cloth capable of sufficiently reducing the roughness of the polished surface of an object to be polished. [Means for solving the problem]

[0007] The polishing cloth according to the present invention is A polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric, It has a polished surface, The minimum autocorrelation length Sal of the polished surface is 70 μm or less.

[0008] In addition, the polishing cloth according to the present invention is A polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric, It has a polished surface, The ratio Sal / Sa of the minimum autocorrelation length Sal of the polished surface to the arithmetic mean height Sa of the polished surface is 2.5 or less. Effect of the Invention

[0009] According to the present invention, it is possible to provide a polishing cloth capable of sufficiently reducing the roughness of the polished surface of an object to be polished. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic cross-sectional view showing a state in which the polishing cloth according to the embodiment is used. [Diagram 2] 1 is a schematic cross-sectional view showing a state in which a polishing cloth according to an embodiment of the present invention is attached to a platen of a polishing machine via an adhesive layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, one embodiment of the present invention will be described. In the following, one embodiment of the present invention may be simply referred to as the present embodiment.

[0012] The polishing cloth 10 according to this embodiment is used to polish an object 20 in a polishing machine 1000 including a platen (lower platen) 100 and a head 200, as shown in FIG. In this embodiment, the polishing machine 1000 includes, in addition to the platen 100 and the head 200, a slurry supplying unit 300 for supplying polishing slurry. In this embodiment, the head 200 of the polisher 1000 includes a holder (upper platen) 200a for holding the object 20 to be polished. The polishing cloth 10 of this embodiment is attached to a base plate 100 as shown in FIG. 1, and then used to polish a polishing surface 20a of a polished object 20 attached to a holding material 200a of a head 200 with the polishing surface 10a of the polishing cloth 10. In addition, Figure 1 illustrates an example in which the abrasive cloth 10 of this embodiment is attached to a single-sided polisher for polishing one side of the workpiece 20, but the abrasive cloth 10 of this embodiment may also be attached to a double-sided polisher for use. More specifically, the polishing cloth 10 according to this embodiment may be attached to each of a pair of platens arranged opposite each other in a double-sided polisher. The polishing cloth 10 according to this embodiment is a concept that encompasses the polishing cloth 10A according to a first embodiment and the polishing cloth 10B according to a second embodiment, which will be described below.

[0013] In this embodiment, the polishing cloth 10 polishes the polished surface 20a by interposing a polishing slurry containing abrasive grains between the polishing surface 10a and the exposed surface of the workpiece to be polished (polished surface 20a) and bringing the polishing surface 10a and the polished surface 20a into sliding contact with each other. The object 20 to be polished may be an optical material, a semiconductor device, a hard disk, a glass plate, a semiconductor wafer such as a silicon wafer, or the like.

[0014] First embodiment A polishing cloth 10A according to a first embodiment of the present invention is a polishing cloth including a nonwoven fabric and a resin impregnated in the nonwoven fabric. As described above, the polishing pad 10A according to the first embodiment has a polishing surface 10a. In the polishing pad 10A according to the first embodiment, the minimum autocorrelation length Sal of the polishing surface 10a is 70 μm or less.

[0015] Here, the minimum autocorrelation length Sal is a type of surface roughness parameter, and represents the horizontal distance in the direction in which the autocorrelation value attenuates to a specific value (s=0.2). In other words, in a coordinate system in which the height direction is the Z direction and the horizontal directions are the X and Y directions on a surface having an uneven shape, the overlapping portion between area A1 defined by a convex shape and area A2 defined by the area A1 defined by a convex shape when the area A1 is shifted in the horizontal direction (X and Y directions) (the overlapping portion between area A1 and area A2) becomes small and the overlapping portion reaches a certain value, and Sal is the minimum distance in the horizontal direction (X and Y directions). That is, on the surface (polished surface 10a) where Sal is large, a gentle uneven shape predominates, whereas on the surface (polished surface 10a) where Sal is small, a steep uneven shape predominates.

[0016] As described above, in the polishing pad 10A according to the first embodiment, the minimum autocorrelation length Sal of the polishing surface 10a is a small value of 70 μm or less. That is, on the polishing surface 10a of the polishing pad 10A according to the first embodiment, a steep uneven shape is dominant. Therefore, in the polishing cloth 10A of the first embodiment, the contact area of ​​the polishing surface 10a with the polished surface 20a of the workpiece 20 (the convex portion in the uneven shape) can be increased compared to a polishing surface 10a whose minimum autocorrelation length Sal is outside the above numerical range. This makes it possible to more thoroughly grind away any convex portions occurring on the polishing surface 20a of the polishing object 20, thereby enabling the roughness of the polishing surface 20a of the polishing object 20 to be sufficiently reduced.

[0017] In the polishing pad 10A according to the first embodiment, the minimum autocorrelation length Sal of the polishing surface 10a may be 60 μm or less, or may be 55 μm or less. Since the minimum autocorrelation length Sal of the polishing surface 10a is 55 μm or less, the contact area of ​​the polishing surface 10a with the polishing surface 20a of the workpiece 20 can be further increased, so that the roughness of the polishing surface 20a of the workpiece 20 can be particularly sufficiently reduced.

[0018] In the polishing pad 10A according to the first embodiment, the minimum autocorrelation length Sal of the polishing surface 10a may be 10 μm or more, 15 μm or more, or 20 μm or more.

[0019] The minimum autocorrelation length Sal of the polished surface 10a can be measured in a non-contact manner using a shape analysis laser microscope (Keyence Corporation, model "VK-X1000"). Specifically, a polishing cloth 10A having planar dimensions of 40 mm x 40 mm is prepared, and the polishing cloth 10A is attached to the measurement stage of the shape analysis laser microscope using a pressure-sensitive adhesive (PSA) so that the polishing surface 10a is exposed.Then, measurements are performed on the central region (7 mm x 7 mm area) of the polishing surface 10a under the following measurement conditions. Here, the polishing cloth 10A used is one that has been thoroughly dried. In addition, when attaching the polishing cloth 10A to the measurement table, sufficient care must be taken to prevent air from being trapped between the measurement table and the polishing cloth 10A, and to prevent warping of the polishing cloth 10A after attachment. The reason why the measurement is performed on the central region of the polishing surface 10a is to eliminate as much as possible the influence of warping that inevitably occurs in the polishing cloth 10A. Moreover, the measurement of the central region of the polished surface 10a is performed within the entire region of 7 mm×7 mm, and the obtained Sal is regarded as the measured value. The central region is made up of 12 pieces of measurement data in the width direction of the measurement table and 16 pieces of measurement data in the length direction of the measurement table (that is, 12 pieces x 16 pieces of measurement data). Measurement conditions Scan mode: Laser confocal RPD(Real Peak detection):ON Lighting Filter: 100% ·Coaxial epi-irradiation: 100 Ring lighting: OFF ·Z-axis measurement upper limit: 10000μm ·Z-axis measurement lower limit: 10500μm ·Z-axis measurement distance fixed: OFF ·Z-axis measurement distance: 500μm ·Automatic upper and lower limits ·Automatic brightness: ON Lens magnification: 20x (1 pixel = 2.72 μm) NA: 0.13 Working distance: 22.5mm

[0020] In addition, in order to correct the effect of the warping that inevitably occurs in the central region of the polished surface 10a as much as possible, the Sal value is obtained for the central region of the polished surface 10a processed using the analysis software Mountain map (manufactured by Digital Surf). The analysis software processes the central region of the polished surface 10a according to the following procedure. procedure (1) Removal of abnormal points in the central region of the polished surface 10a (2) Processing of non-measurement points in the central region of the polished surface 10a (selection of a processing method for the portion where abnormal points have been deleted) (3) Shape treatment of the central region of the polished surface 10a (removal of effects of warping, etc.) (4) Leveling the central region of the polished surface 10a (removing tilt)

[0021] The minimum autocorrelation length Sal of the polishing surface 10a can be adjusted by the modulus value of the fibers that make up the nonwoven fabric. Here, a fiber has the property that the higher the modulus value, the less stretchable (harder) the material is, and the lower the modulus value, the easier it is to stretch (softer) the material is. Furthermore, the nonwoven fabric is often produced by entangling a plurality of fibers that have been subjected to a drawing process such as spinning and drawing. Therefore, in the nonwoven fabric, the thinner the fibers to be entangled are, the greater the number of fibers that can be arranged per unit area, whereas the thicker the fibers to be entangled are, the fewer the number of fibers that can be arranged per unit area. The greater the number of fibers arranged per unit area, the narrower the spacing between adjacent fibers, and therefore the smaller the value of the minimum autocorrelation length Sal. Conversely, the fewer the number of fibers arranged per unit area, the wider the spacing between adjacent fibers, and therefore the larger the value of the minimum autocorrelation length Sal. In other words, the lower the modulus value of the fibers used, the thinner the fibers can be made by sufficiently stretching the fibers in the longitudinal direction during stretch molding, and therefore, a nonwoven fabric can be obtained in which a large number of fibers are arranged per unit area, in other words, a nonwoven fabric with a small value of the minimum autocorrelation length Sal can be obtained. On the other hand, the higher the modulus value of the fibers used, the greater the thickness of the fibers will be because the fibers cannot be sufficiently stretched in the longitudinal direction during stretch molding, and therefore a nonwoven fabric with a small number of fibers arranged per unit area, in other words, a nonwoven fabric with a large value of the minimum autocorrelation length Sal, can be obtained.

[0022] The minimum autocorrelation length Sal of the polishing surface 10a can also be adjusted by changing the type (fiber species) of the fibers constituting the nonwoven fabric. Specifically, since the modulus value differs depending on the type of fiber, the value of the minimum autocorrelation length Sal of the polishing surface 10a can be adjusted by changing the modulus value. Furthermore, the minimum autocorrelation length Sal of the polishing surface 10a can also be adjusted by changing the basis weight of the nonwoven fabric. Specifically, by increasing the basis weight of the nonwoven fabric and increasing the number of fibers present per unit area, the minimum autocorrelation length Sal of the polishing surface 10a can be reduced, and by decreasing the basis weight of the nonwoven fabric and decreasing the number of fibers present per unit volume, the minimum autocorrelation length Sal of the polishing surface 10a can be reduced. The minimum autocorrelation length Sal of the polishing surface 10a can also be adjusted by the thickness of the fibers constituting the nonwoven fabric. The thickness of the fibers constituting the nonwoven fabric may be the thickness of fibers that have not been subjected to the above-mentioned stretch molding (unstretched fibers). In other words, the thickness of the fibers constituting the nonwoven fabric may be determined independently of the modulus value of the fibers.

[0023] Examples of the fibers constituting the nonwoven fabric include polyester fibers, nylon fibers, polypropylene fibers, acrylic fibers, polyvinyl alcohol fibers, and polyamide fibers. Examples of the polyester fiber include polyethylene terephthalate fiber, polymethylene terephthalate fiber, polybutylene terephthalate fiber, polyethylene naphthalate fiber, and polybutylene naphthalate fiber.

[0024] The thickness of the fiber (fiber thickness) may be 10.0 dtex or less, 8.0 dtex or less, 5.0 dtex or less, 4.0 dtex or less, or 3.5 dtex or less. In addition, the fiber thickness may be 0.5 dtex or more, 1.0 dtex or more, 1.5 dtex or more, 2.0 dtex or more, or 2.5 dtex or more.

[0025] The nonwoven fabric has a basis weight of 200 g / m 2 More preferably, it is equal to or greater than this. The nonwoven fabric has a basis weight of 300 g / m 2 It may be more than 400 g / m 2 It may be more than that. The nonwoven fabric has a basis weight of 600 g / m 2 It is preferable that: The nonwoven fabric has a basis weight of 500 g / m 2 It may be the following.

[0026] The density of the nonwoven fabric is 0.1 g / cm 3 More preferably, it is equal to or greater than this. The density of the nonwoven fabric is 0.3 g / cm 3 It may be less than 0.2 g / cm 3 It may be the following. The density of the nonwoven fabric was determined by preparing a nonwoven fabric having a certain area and a certain thickness, and calculating the volume V (cm) of the nonwoven fabric by multiplying the certain area by the certain thickness. 3 ) and the mass W (g) of the nonwoven fabric having a certain area and thickness is measured, and then the mass can be calculated using the following formula. Density of nonwoven fabric = W / V

[0027] Examples of the resin include polyurethane resin, acrylic resin, melamine resin, phenol resin, and epoxy resin.

[0028] The thickness of the polishing cloth 10A according to the first embodiment is preferably 0.8 mm or more, and more preferably 1.0 mm or more. Moreover, the thickness of the polishing cloth 10A according to the first embodiment is preferably 2.0 mm or less, and more preferably 1.5 mm or less.

[0029] The polishing cloth 10A according to the first embodiment preferably has an Asker C hardness of 55 or more, more preferably an Asker C hardness of 70 or more, and even more preferably an Asker C hardness of 80 or more. The Asker C hardness may be 95 or less, 90 or less, or 85 or less. When the Asker C hardness is within the above numerical range, the polishing pad 10A according to the first embodiment can have an appropriate hardness. As a result, when the polishing surface 20a of the workpiece 20 is polished using the polishing cloth 10A of the first embodiment, excessive indentations are not formed in the polishing cloth 10A, which prevents uneven grinding on the polishing surface 20a of the workpiece 20. That is, the roughness of the polished surface 20a of the polished object 20 can be sufficiently reduced. The Asker C hardness is a value measured according to the standard SRIS0101 (the Society of Rubber Industry, Japan Standard). Moreover, the Asker C hardness is a value measured on the polishing surface 10a of the polishing cloth 10A according to the first embodiment.

[0030] The polishing pad 10A according to the first embodiment preferably has a compressibility of 5.0% or less. The polishing cloth 10A according to the first embodiment may have a compressibility of 4.0% or less, or may have a compressibility of 3.5% or less. Furthermore, in the first embodiment, the polishing cloth 10A may have a compression ratio of 1.0% or more, may have a compression ratio of 2.0% or more, may have a compression ratio of 2.5% or more, or may have a compression ratio of 3.0% or more. By having the compression rate within the above numerical range, excessive compression of the polishing cloth 10A in the first embodiment can be prevented when polishing the polished surface 20a of the workpiece 20. This makes it possible to suppress the occurrence of grinding unevenness on the polished surface 20a of the polished object 20, and therefore the roughness of the polished surface 20a of the polished object 20 can be sufficiently reduced. The compression ratio was measured using a compression elasticity tester (surface area of ​​the indenter: 50 mm 2 ) can be used to measure it. Specifically, first, the compression elasticity tester is used to test the specimen at a pressure of 300 gf / cm 2 While applying a pressure of 100 mm, the polishing cloth 10A according to the first embodiment is pressed in the thickness direction for 60 seconds, and then the thickness T1 of the polishing cloth 10A according to the first embodiment is measured. Next, using the compression elasticity tester, the pressure was measured at 1800 gf / cm 2 While applying a pressure of 100 mm, the polishing cloth 10A according to the first embodiment is pressed in the thickness direction for 60 seconds, and then the thickness T2 of the polishing cloth 10A according to the first embodiment is measured. Then, the compression ratio is calculated based on the following formula: Compression ratio = (T1-T2) / T1 x 100

[0031] The polishing cloth 10A according to the first embodiment has a powder density of 0.20 g / cm 3 It is preferable that the apparent density is 0.30 g / cm or more. 3 It is more preferable that the apparent density is 0.35 g / cm or more. 3 It is more preferable that the apparent density is equal to or greater than this. The polishing cloth 10A according to the first embodiment has a powder density of 0.55 g / cm 3 It is preferred that the apparent density is less than 0.50 g / cm 3 More preferably, it has an apparent density of 0.45 g / cm 3 More preferably, it has an apparent density of: The apparent density of the polishing cloth 10A can be measured based on JIS K7222:2005. Furthermore, the apparent density of the polishing cloth 10A being within the above numerical range means that the apparent density values ​​measured in two non-overlapping areas of one polishing cloth 10A are both within the above range. By having the apparent density of the polishing cloth 10A within the above range, the polishing cloth 10A has a density of 1 cm 3 ) can contain a moderate amount of fiber and resin. This makes it possible to suitably adjust the area of ​​the convex portions on the polishing surface 10a of the polishing cloth 10A, and as a result, it is possible to adjust the Sal of the polishing surface 10a of the polishing cloth 10A to a suitable value.

[0032] Below, the manufacturing method of the polishing cloth 10A of the first embodiment will be explained using as an example a method of performing a two-stage impregnation process in which a first polyurethane resin is wet-impregnated into a nonwoven fabric and then a second polyurethane resin is dry-impregnated into the nonwoven fabric.

[0033] In the wet impregnation, first, a first polyurethane resin is dissolved in a water-soluble organic solvent to obtain a first impregnation liquid. Next, the nonwoven fabric is immersed in the first impregnation liquid, and then the nonwoven fabric that has been immersed in the first impregnation liquid is further immersed in water. As a result, the water-soluble organic solvent in the first impregnation liquid attached to the nonwoven fabric is replaced with water, and the first polyurethane resin solidifies on the surface of the nonwoven fabric. As a result, the first polyurethane resin adheres to the surface of the nonwoven fabric.

[0034] Examples of the water-soluble organic solvent include dimethylformamide, methyl sulfoxide, tetrahydrofuran, and dimethylacetamide. The first impregnation liquid may include a filler. The filler includes carbon black. The first impregnation liquid may contain a surfactant as a dispersion stabilizer.

[0035] In the dry impregnation, a urethane prepolymer having an isocyanate group as a terminal group, an organic compound having active hydrogen, and an organic solvent are mixed to obtain a second impregnation liquid. The organic compound having active hydrogen functions as a curing agent. Next, the nonwoven fabric that has been subjected to the wet impregnation is immersed in the second impregnation liquid, and then the nonwoven fabric that has been immersed in the second impregnation liquid is dried in a drying oven. As a result, the organic solvent is volatilized, and the urethane prepolymer and the organic compound having active hydrogen undergo a curing reaction to form a second polyurethane resin. As a result, the second polyurethane resin is further adhered to the surface of the nonwoven fabric.

[0036] Examples of the organic solvent include methyl ethyl ketone, acetone, alcohol, and ethyl acetate. Examples of the organic compound having active hydrogen include an isocyanate-based crosslinking agent.

[0037] Second Embodiment The polishing cloth 10B according to the second embodiment of the present invention is also a polishing cloth including a nonwoven fabric and a resin impregnated into the nonwoven fabric. As described above, the polishing pad 10B according to the second embodiment also has a polishing surface 10a. In the polishing pad 10B according to the second embodiment, the ratio Sal / Sa of the minimum autocorrelation length Sal of the polishing surface 10a to the arithmetic mean height Sa of the polishing surface 10a is 2.5 or less.

[0038] The minimum autocorrelation length Sal of the polished surface 10a can be measured according to the procedure described above in the first embodiment. Moreover, the arithmetic mean height Sa on the polished surface 10a can also be measured in accordance with the procedure described in the first embodiment above, except that the minimum autocorrelation length Sal is replaced with the arithmetic mean height Sa.

[0039] As described above in the section on the first embodiment, the minimum autocorrelation length Sal of the polishing surface 10a can be adjusted by changing the modulus value of the fibers constituting the nonwoven fabric, by changing the type of fibers constituting the nonwoven fabric, by changing the basis weight of the nonwoven fabric, or by changing the thickness of the fibers constituting the nonwoven fabric.

[0040] The arithmetic mean height Sa is a type of surface roughness parameter, and is a parameter that extends the arithmetic mean height Ra of a line to a surface. That is, in the second embodiment, the arithmetic mean height Sa represents the average of the absolute values ​​of the differences in height of each point with respect to the reference plane. The reference surface means the average surface of the polished surface 10a (surface) in the measurement range.

[0041] The arithmetic mean height Sa of the polishing surface 10a can also be adjusted by the modulus value of the fibers constituting the nonwoven fabric. Specifically, if the modulus value of the fiber is reduced, the thickness of the fiber can be reduced by subjecting the fiber to a drawing process. On the other hand, if the modulus value of the fiber is increased, the thickness of the fiber cannot be made thinner than that of a fiber having a lower modulus value even if the fiber is stretched. In other words, the thickness of the fiber becomes thicker. Furthermore, the thinner the fiber, the lower the height of the convex portion formed by intertwining multiple fibers can be relative to the reference plane, and the thicker the fiber, the higher the height of the convex portion can be relative to the reference plane. Furthermore, the arithmetic mean height Sa of the polishing surface 10a, like the minimum autocorrelation length Sal of the polishing surface 10a, can also be adjusted by changing the type of fiber constituting the nonwoven fabric, by changing the basis weight of the nonwoven fabric, or by adjusting the thickness of the fibers constituting the nonwoven fabric. Furthermore, when the polishing surface 10a is ground using abrasive grains, the arithmetic mean height Sa of the polishing surface 10a can also be adjusted by the size of the abrasive grains used for grinding. For example, when the abrasive grains are held on paper and used in the form of sandpaper, the smaller the size of the abrasive grains, the greater the amount of abrasive grains that can be held per unit area of ​​the paper, thereby enabling the polishing surface 10a to be sufficiently ground. That is, the smaller the size of the abrasive grains, the lower the height of the convex portions formed on the polishing surface 10a can be, and as a result, the value of the arithmetic mean height Sa of the polishing surface 10a can be reduced. On the other hand, the larger the size of the abrasive grains, the smaller the amount of the abrasive grains that can be held per unit area of ​​the paper material, making it more difficult to sufficiently grind the polishing surface 10a. That is, the larger the size of the abrasive grains, the higher the height of the convex portions formed on the polishing surface 10a can be, and as a result, the value of the arithmetic mean height Sa of the polishing surface 10a can be increased.

[0042] As described above, by adjusting the value of the minimum autocorrelation length Sal of the polished surface 10a and the value of the arithmetic mean height Sa of the polished surface 10a to achieve a balance, Sal / Sa can be adjusted to be within the above numerical range.

[0043] As described above, in the polishing cloth 10B of the second embodiment, on the polishing surface 10a, the ratio Sal / Sa between the arithmetic mean height Sa, which is a surface roughness parameter in the height direction, and the minimum autocorrelation length Sal, which is a surface roughness parameter in the horizontal direction, is 2.5 or less. In other words, the value of the minimum autocorrelation length Sal is made small and the value of the arithmetic mean height Sa is made large, while the values ​​of Sal and Sa are appropriately balanced so that the ratio between them, Sal / Sa, is equal to or less than a predetermined value (2.5). Therefore, while a steep uneven shape is dominant on the polishing surface 10a of the polishing cloth 10B, the height of the convex portions formed by intertwining multiple fibers can be increased relative to the reference plane. This makes it possible to increase the contact area (the convex portion in the concave-convex shape) of the polishing surface 10a with the polished surface 20a of the object 20 to be polished, while allowing the convex portions to hold a sufficient amount of polishing liquid (polishing slurry). This makes it possible to more thoroughly grind away any convex portions occurring on the surface 20a to be polished of the object 20 to be polished, thereby making it possible to sufficiently reduce the roughness of the surface 20a to be polished of the object 20 to be polished.

[0044] In the polishing cloth 10B according to the second embodiment, Sal / Sa of the polishing surface 10a may be 2.2 or less, 2.0 or less, or 1.9 or less. Furthermore, Sal / Sa of the polishing surface 10a may be 1.2 or more, 1.5 or more, or 1.7 or more. It is particularly preferable that Sal / Sa of the polishing surface 10a be 1.7 or more and 2.0 or less. By having Sal / Sa within the above-mentioned numerical range, the values ​​of Sal and Sa can be particularly appropriately balanced, so that the roughness of the polished surface 20a of the polished object 20 can be particularly sufficiently reduced.

[0045] In the polishing pad 10B according to the second embodiment, the arithmetic mean height Sa of the polishing surface 10a may be 20 μm or more, 25 μm or more, or 30 μm or more. The arithmetic mean height Sa of the polished surface 10a may be 40 μm or less, 35 μm or less, or 32 μm or less. It is particularly preferable that the arithmetic mean height Sa of the polished surface 10a be 20 μm or more and 32 μm or less. When Sal / Sa is 1.7 or more and 2.0 or less, and Sa is 20 μm or more and 32 μm or less, the roughness of the polished surface 20a of the polished object 20 can be reduced particularly sufficiently.

[0046] In the polishing pad 10B according to the second embodiment, the numerical range of the minimum autocorrelation length Sal of the polishing surface 10a may be the same as that described in the first embodiment. Specifically, in the polishing pad 10B according to the second embodiment, the minimum autocorrelation length Sal of the polishing surface 10a is preferably 70 μm or less. Also, in the polishing pad 10B according to the second embodiment, the minimum autocorrelation length Sal of the polishing surface 10a may be 60 μm or less, or 55 μm or less. Furthermore, in the polishing pad 10B according to the second embodiment, the minimum autocorrelation length Sal of the polishing surface 10a may also be 10 μm or more, 15 μm or more, or 20 μm or more.

[0047] The fibers and resin constituting the nonwoven fabric may be the same as those described in the first embodiment. The thickness of the fibers (fiber thickness) may be in the same range as described in the first embodiment, and the basis weight of the nonwoven fabric may be in the same range as described in the first embodiment.

[0048] Moreover, the thickness of the polishing pad 10B according to the second embodiment can be in the same range as that described in the first embodiment.

[0049] Furthermore, the polishing cloth 10B according to the second embodiment preferably has the same Asker C hardness, compressibility, and apparent density as the polishing cloth 10A according to the first embodiment.

[0050] Moreover, the polishing cloth 10B according to the second embodiment can be produced in the same manner as described for the polishing cloth 10A according to the first embodiment.

[0051] As described above, the polishing cloth 10 according to this embodiment is attached to the surface plate (lower surface plate) 100 of the polisher 1000 when in use. The polishing cloth 10 according to this embodiment may be attached to a platen 100 via an adhesive layer 30, as shown in FIG. The adhesive layer 30 may be, for example, a double-sided tape. The double-sided tape includes a substrate and a pressure-sensitive adhesive layer laminated on each of the two surfaces of the substrate. The substrate may be, for example, a resin film. The resin film may be, for example, a polyethylene terephthalate film. The pressure-sensitive adhesive layer includes a pressure-sensitive adhesive layer containing an acrylic polymer (an acrylic pressure-sensitive adhesive layer).

[0052] The thickness of the adhesive layer 30 may be 0.05 mm or more, 0.08 mm or more, or 0.10 mm or more. Furthermore, the thickness of the adhesive layer 30 may be 0.50 mm or less, 0.30 mm or less, or 0.15 mm or less. In addition, when the adhesive layer 30 is the double-sided tape, the thickness of the adhesive layer 30 means the combined thickness of the substrate and the thicknesses (two layers) of the pressure-sensitive adhesive layers laminated on each side of the substrate.

[0053] The matters disclosed in this specification include the following.

[0054] (1) A polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric, It has a polished surface, The minimum autocorrelation length Sal of the polished surface is 70 μm or less. polishing cloth.

[0055] (2) A polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric, It has a polished surface, The ratio of the minimum autocorrelation length Sal of the polished surface to the arithmetic mean height Sa of the polished surface, Sal / Sa, is 2.5 or less. polishing cloth.

[0056] (3) The arithmetic mean height Sa of the polished surface is 20 μm or more. The polishing cloth described in (2) above.

[0057] (4) The compression ratio is 5% or less The polishing cloth according to any one of (1) to (3) above.

[0058] (5) Apparent density: 0.20g / cm 3 More than 0.55g / cm 3 is less than or equal to The polishing cloth according to any one of (1) to (4) above.

[0059] The polishing cloth according to the present invention is not limited to the above embodiment. Furthermore, the polishing cloth according to the present invention is not limited to the above-mentioned functions and effects. Furthermore, the polishing cloth according to the present invention can be modified in various ways without departing from the spirit and scope of the present invention. EXAMPLES

[0060] The present invention will now be described in more detail with reference to examples and comparative examples. The following examples are provided to further explain the present invention in detail, and are not intended to limit the scope of the present invention.

[0061] Example 1 As the polishing cloth according to Example 1, a nonwoven fabric made of polyethylene terephthalate fibers impregnated with polyurethane resin was prepared. The physical properties of the polishing cloth according to Example 1 and the physical properties of the nonwoven fabric constituting the polishing cloth are as shown in Table 1 below.

[0062] Example 2 As the polishing cloth according to Example 2, a nonwoven fabric made of nylon fibers impregnated with polyurethane resin was prepared. The physical properties of the polishing cloth according to Example 2 and the physical properties of the nonwoven fabric constituting the polishing cloth are as shown in Table 2 below.

[0063] Example 3 As the polishing cloth according to Example 3, a nonwoven fabric made of nylon fibers impregnated with polyurethane resin was prepared. The physical properties of the polishing cloth according to Example 3 and the physical properties of the nonwoven fabric constituting the polishing cloth are as shown in Table 3 below.

[0064] Example 4 As the polishing cloth according to Example 4, a nonwoven fabric made of nylon fibers was soaked in polyurethane resin to prepare the polishing cloth. The physical properties of the polishing cloth according to Example 4 and the physical properties of the nonwoven fabric constituting the polishing cloth are as shown in Table 3 below.

[0065] Example 5 As the polishing cloth according to Example 5, a nonwoven fabric made of nylon fibers impregnated with polyurethane resin was prepared. The physical properties of the polishing cloth according to Example 5 and the physical properties of the nonwoven fabric constituting the polishing cloth are as shown in Table 3 below.

[0066] Comparative Example 1 As the polishing cloth according to Comparative Example 1, a nonwoven fabric made of polyethylene terephthalate fibers impregnated with polyurethane resin was prepared. The physical properties of the polishing cloth according to Comparative Example 1 and the physical properties of the nonwoven fabric constituting the polishing cloth are as shown in Table 1 below.

[0067] Comparative Example 2 As the polishing cloth according to Comparative Example 2, a nonwoven fabric made of polyethylene terephthalate fibers impregnated with polyurethane resin was prepared. The physical properties of the polishing cloth according to Comparative Example 2 and the physical properties of the nonwoven fabric constituting the polishing cloth are as shown in Table 2 below.

[0068] The physical properties of the polishing cloth in each example and the physical properties of the nonwoven fabric constituting the polishing cloth in each example were determined according to the method described in the above embodiment.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] (Polishing test) The polishing surface of an object to be polished was polished using the polishing cloth according to each example. The polishing cloth according to each example was attached to a single-sided polisher so that the polishing surface was exposed. The polishing was carried out after conditioning the polishing surface of the polishing cloth according to each example in the following procedure. Conditioning Procedure (1) The polishing surface of the polishing cloth in each example is dressed. (2) Using the polishing cloth after the dressing process, the surface to be polished of a dummy wafer (12-inch P-wafer) is dummy polished for 15 minutes. The dummy polishing is performed four times. That is, the polishing was performed using the polishing cloth after four dummy polishings had been performed. The polishing conditions and dressing treatment conditions were as follows. Polishing and dressing conditions ·Polishing machine: Poli762 (manufactured by G&P) Dresser: Dresser #150 (Kinik) Dressing time: 10min Head type: Rubber head Polishing pressure: 300gf / cm 2 Rotational speed (Head / Platen): 40 / 43 rpm Plate temperature: 25℃ ·Polished object (monitor wafer): 12 inch P-wafer Polishing liquid (polishing slurry): Nanopure (registered trademark) NP6610 (Ni 3.2% by mass of pure PET (manufactured by DuPont) was added. What I did Polishing fluid flow rate: 300mL / min

[0073] (Evaluation of the roughness of the polished surface of the object) The surface roughness of the polished surface of the object to be polished (monitor wafer) polished with the polishing cloth of each example was measured. The surface roughness of the polished surface of the polished object was measured in a measurement range of 3500 μm×2700 μm using a non-contact three-dimensional white light interference optical microscope ("Counter GT-X" manufactured by Bruker). Then, the surface roughness value of the polished surface of the workpiece polished with the polishing cloth of Comparative Example 1 was used as a standard to calculate the ratio of the surface roughness value of the polished surface of the workpiece polished with the polishing cloth of each of the other examples (Examples 1 to 5 and Comparative Example 2). That is, in each of the other examples, the smaller the surface roughness value is compared to the surface roughness value of Comparative Example 1, the smaller the calculated value of the ratio becomes. Therefore, the smaller the calculated value of the ratio, the more sufficiently the roughness of the polished surface can be reduced in each of the other examples. The calculated values ​​of the ratios for each example (Examples 1 to 5 and Comparative Examples 1 and 2) are shown in Tables 1 to 3 above.

[0074] Referring to Tables 1 to 3, it can be seen that in Examples 1 to 5, the calculated values ​​of the ratios are all smaller than that in Comparative Example 1. In particular, in Examples 3 to 5, the calculated value of the ratio was 80% or less, which shows that the roughness of the polished surface was particularly sufficiently reduced. From these results, it can be seen that the roughness of the polished surface of the workpiece can be sufficiently reduced by using a polishing cloth whose polishing surface Sal is 70 μm or less and whose Sal / Sa, which is the ratio of the polishing surface Sal to the polishing surface Sa, is 2.5 or less. [Explanation of symbols]

[0075] 10 polishing cloth, 20 object to be polished, 30 adhesive layer, 100 surface plate, 200 head, 300 slurry supply unit, 1000 polishing machine, 10a polished surface, 20a polished surface, 200a holding material.

Claims

1. A polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric, It has a polished surface, The minimum autocorrelation length Sal of the polished surface is 70 μm or less. polishing cloth.

2. A polishing cloth comprising a nonwoven fabric and a resin impregnated in the nonwoven fabric, It has a polished surface, A ratio of the minimum autocorrelation length Sal of the polished surface to the arithmetic mean height Sa of the polished surface, Sal / Sa, is 2.5 or less. polishing cloth.

3. The arithmetic mean height Sa of the polished surface is 20 μm or more. The polishing cloth according to claim 2.

4. The compression rate is 5% or less. The polishing cloth according to any one of claims 1 to 3.

5. Apparent density: 0.20 g / cm ３ 0.55g / cm or more ３ is less than or equal to The polishing cloth according to any one of claims 1 to 3.

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