Polishing pad and method for polishing object to be polished

Abstract

This polishing pad is provided with a polishing layer that contains a hydrolyzable resin and abrasive grains. The pencil hardness at 25°C and 60% RH of the polishing layer after immersion in ion exchange water at 80°C for 3 hours is lower than the pencil hardness at 25°C and 60% RH of the polishing layer before the immersion, and the difference in pencil hardness at 25°C and 60% RH of the polishing layer before and after the immersion is three or more grades.

Description

Polishing Pad and Method for Polishing a Workpiece to be Polished

[0001] The present invention relates to a polishing pad and a method for polishing a workpiece to be polished.

[0002] In the polishing process of a substrate used for semiconductor devices and the like, a method using a fixed abrasive grain polishing pad having a polishing layer containing a binder resin and abrasive grains fixed thereby is known. Conventionally, as the binder resin, a cured product of a curable resin such as a phenolic resin, an epoxy resin, or an acrylic phenolic resin has been used (see, for example, Patent Document 1).

[0003] In recent years, from the viewpoint of reducing environmental pollution, when disposing of a used polishing pad, attempts have been made to decompose it by microorganisms by simply burying the polishing pad in the ground. Therefore, polishing pads using biodegradable resins as binder resins have been studied (see, for example, Patent Documents 2 and 3).

[0004] Japanese Patent Application Laid-Open No. 2018-51733, US Patent Application Publication No. 200501012, Japanese Patent Application Laid-Open No. 2005-305570

[0005] By the way, rough polishing with a fixed abrasive grain polishing pad (sometimes simply referred to as "polishing") proceeds by abrasive grains exposed on the surface of the polishing pad. During polishing, if the abrasive grains fall off from the polishing pad or the abrasive grains are consumed by friction, clogging (a state where the tips of the abrasive grains are worn and flattened) occurs, resulting in a decrease in the number of abrasive grains contributing to polishing and a reduction in the polishing ability of the polishing pad. Therefore, on the polishing surface of the polishing pad, it is desirable to have a structure in which the binder resin disappears moderately, so that the abrasive grains fall off moderately, while new abrasive grains protrude and abrasive grains without clogging are always exposed.

[0006] However, according to the studies of the present inventors, it has been revealed that in the polishing pads of Patent Documents 2 and 3, even if the binder resin decomposes, the decomposed binder resin is difficult to be removed from the polishing surface of the polishing pad. Therefore, a problem has been found that new abrasive grains without clogging are difficult to be exposed and the polishing speed is likely to decrease.

[0007] This invention has been made in view of the above circumstances, and aims to provide a polishing pad in which the binder resin after disassembly is easily removed and the reduction in polishing speed is minimal, as well as a method for polishing an object to be polished using the same.

[0008] The present invention relates to the following polishing pads and polishing methods for workpieces.

[0009] [1] A polishing pad comprising a polishing layer containing a hydrolyzable resin and abrasive grains, wherein the pencil hardness of the polishing layer at 25°C and 60% RH after immersion in ion-exchanged water at 80°C for 3 hours is lower than the pencil hardness of the polishing layer at 25°C and 60% RH before immersion, and the difference between the pencil hardness of the polishing layer at 25°C and 60% RH before and after immersion is 3 levels or more. [2] The polishing pad according to [1], wherein the pencil hardness of the polishing layer at 25°C and 60% RH before immersion is 2H or higher. [3] The polishing pad according to [1] or [2], wherein when a pencil hardness test is performed on the polishing layer after immersion in ion-exchanged water at 80°C for 3 hours using a pencil with a hardness higher than the pencil hardness of the polishing layer at 25°C and 60% RH after immersion, the resulting scratch is cohesive failure. [4] The polishing pad according to any one of [1] to [3], wherein the median diameter of the abrasive grains is less than 30 μm. [5] The polishing pad according to any one of [1] to [4], wherein the content of the abrasive grains in the polishing layer is 1% by mass or more and 55% by mass or less with respect to the total mass of the polishing layer. [6] The polishing pad according to any one of [1] to [5], wherein the content of the hydrolyzable resin in the polishing layer is 20% by mass or more and 98.5% by mass or less with respect to the total mass of the polishing layer. [7] The polishing pad according to any one of [1] to [6], wherein the hydrolyzable resin is mainly composed of a glycolic acid polymer. [8] The polishing pad according to any one of [1] to [7], wherein the polishing layer further comprises a hydrolysis accelerator. [9] The polishing pad according to [8], wherein the hydrolysis accelerator comprises at least one selected from the group consisting of carboxylic acid anhydrides, phosphorus compounds, cyclic esters, and basic metal oxides.

[10] The polishing pad according to any one of [1] to [9], wherein the thickness of the polishing layer is 0.1 mm or more and 30 mm or less.

[11] The density of the polishing layer is 1.57 g / cm³. ３ 3.00g / cm or more３ A polishing pad according to any of [1] to

[10] below. A method for polishing an object to be polished, comprising the step of polishing the object to be polished by sliding the polishing pad and the object to be polished relative to each other while supplying a polishing liquid containing water to the surface of the polishing layer of the polishing pad according to any of [1] to

[11] .

[0010] According to the present invention, it is possible to provide a polishing pad in which the binder resin after disassembly is easily removed and the reduction in polishing speed is minimal, as well as a method for polishing an object to be polished using the same.

[0011] Figure 1 is a schematic cross-sectional view showing a polishing method for an object to be polished according to one embodiment of the present invention. Figure 2 is a laser microscope image of the surface of a test piece after a pencil hardness test at each hardness level for a test piece before immersion of the polishing pad 1 and after immersion in ion-exchanged water at 80°C for 3 hours. Figure 3 is a laser microscope image of the surface of a test piece after a pencil hardness test at each hardness level for a test piece before immersion of the polishing pad 7 and after immersion in ion-exchanged water at 80°C for 3 hours. Figure 4 is an explanatory diagram illustrating the observation area by laser microscopy. Figure 5A is a measurement image before image processing, and Figure 5B is a measurement image after image processing. Figures 6A to 6C are schematic diagrams showing the image processing procedure. Figure 7 is a measurement result showing the profile on a straight line passing through the origin O and point A in Figure 5B.

[0012] From the viewpoint of stably retaining abrasive grains and obtaining desired polishing performance, it is desirable for the polishing layer to have a hardness of a predetermined level or higher. On the other hand, the inventors have found that in order to facilitate the removal of decomposed hydrolyzable resin (binder resin), it is desirable for the surface hardness of the polishing layer to decrease and become brittle after contact with the polishing liquid for a predetermined time.

[0013] Specifically, we found that if the difference in pencil hardness at 25°C and 60% RH before and after immersing the abrasive layer in 80°C deionized water for 3 hours is three levels or more, the abrasive grains are stably retained during polishing, and the decomposed hydrolyzable resin is easily removed by the shear force during polishing, resulting in less reduction in polishing speed. The pencil hardness of the abrasive layer before and after immersion can be adjusted by the type and content of the hydrolyzable resin, the type and content of the hydrolysis accelerator, the median diameter of the abrasive grains, etc., as described later.

[0014] One embodiment of the present invention will be described in detail below. However, the present invention is not limited to this embodiment. Furthermore, in this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit.

[0015] 1. Polishing Pad The polishing pad of this embodiment comprises a polishing layer containing a hydrolyzable resin and abrasive grains. That is, the polishing layer comprises a base material containing a hydrolyzable resin and abrasive grains fixed by the base material.

[0016] 1-1. Polishing layer As described above, the pencil hardness of the polishing layer at 25°C and 60% RH after immersion in 80°C deionized water for 3 hours is lower than the pencil hardness of the polishing layer at 25°C and 60% RH before immersion. Furthermore, the difference in pencil hardness before and after immersion in 80°C deionized water for 3 hours is three levels or more.

[0017] When the difference in pencil hardness before and after immersion is three levels or more, the abrasive grains are stably held during polishing, and the brittle layer caused by the decomposed hydrolyzable resin is easily removed by the shear force during polishing. Therefore, the decrease in polishing speed can be minimized. From a similar viewpoint, the difference in pencil hardness of the polishing layer before and after immersion in ion-exchanged water at 80°C for three hours is preferably six levels or more, and more preferably eight levels or more. The upper limit of the difference in pencil hardness before and after immersion is, for example, 13 levels or less.

[0018] In this specification, pencil hardness is evaluated on a scale of 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, and 6H. Here, if the pencil hardness before immersion is 6H and the pencil hardness after immersion is F, the difference in pencil hardness before and after immersion (before immersion - after immersion) is the difference between 6H and F, resulting in 6 scales. Specifically, if the pencil hardness before immersion is 6H and the pencil hardness after immersion is F, the pencil hardness after immersion is set to 1, and numbers (scales) are assigned in increments of 1 up to the pencil hardness before immersion: F (1), H (2), 2H (3), 3H (4), 4H (5), 5H (6), 6H (7). Then, the value 7 - 1 = 6, obtained by subtracting the scale number "1" assigned to the pencil hardness after immersion from the scale number "7" assigned to the pencil hardness before immersion, is taken as the "difference in pencil hardness".

[0019] When performing a pencil hardness test in the range of 6B to 6H, the pencil hardness of the abrasive layer before immersion at 25°C and 60% RH is not particularly limited as long as it satisfies the above-mentioned difference in pencil hardness, but it is preferable that it be 2H or higher (i.e., 2H or a hardness higher than 2H). If the pencil hardness of the abrasive layer before immersion is 2H or higher, the retention of abrasive grains by the hydrolyzable resin is better, and better polishing performance can be obtained as an abrasive pad. From a similar viewpoint, the pencil hardness of the abrasive layer before immersion is preferably 4H or higher, and more preferably 6H. For example, it is preferable that the pencil hardness of the abrasive layer before immersion is 4H or higher and 6H or lower (any of the pencil hardnesses of 4H, 5H, or 6H).

[0020] On the other hand, the pencil hardness of the polishing layer at 25°C and 60% RH after immersion in ion-exchanged water at 80°C for 3 hours is not particularly limited as long as it satisfies the above-mentioned difference in pencil hardness, but it is preferable that it be 3H or less (i.e., 3H or a hardness lower than 3H). After immersion, an embrittlement layer of decomposed hydrolyzable resin is formed near the surface of the polishing layer. If the pencil hardness of the embrittlement layer is 3H or less, it is more easily removed by the shear force during polishing, so that abrasive grains without deformation are more easily exposed, and the decrease in polishing speed can be further suppressed. From a similar viewpoint, it is more preferable that the pencil hardness of the polishing layer after immersion be F or less, and even more preferable that it be B or less. The lower limit of the pencil hardness of the polishing layer after immersion can be 6B or higher from the viewpoint of suppressing excessive collapse due to decomposition being too fast. For example, it is preferable that the pencil hardness of the polishing layer after immersion be 6B or more and F or less (any of the pencil hardness of 6B, 5B, 4B, 3B, 2B, B, HB and F).

[0021] The pencil hardness before and after immersion can be measured using the following procedure. Specifically, the center of the polishing pad is defined as O, and the distance (radius) from the center O to the edge of the polishing pad (polishing layer) is defined as 1. Next, a circle is drawn at a radius of 0.6 from the center O. Two points on the circumference of this circle are set to divide the circumference into two equal parts, and two test pieces are prepared by cutting out 10 mm x 10 mm pieces with each point as the center. However, if grooves exist in the polishing pad, it is preferable to cut out the test pieces so as to avoid the grooves, as this may affect the pencil hardness test results. The pencil hardness (h0) of one of these test pieces before immersion is measured under conditions of 25°C and 60% RH. Next, the other test piece is immersed in ion-exchanged water at 80°C for 3 hours, and then dried in a dry room with a dew point of -40°C for 1 hour. The pencil hardness (h1) of the surface of the dried test piece after immersion is measured in the same manner as above.

[0022] The above pencil hardness test can be performed in general accordance with JIS K5600-5-4:1999, except for the following points: (1) Since the test piece has thickness, a plate-like member equivalent to its thickness should be placed under the testing machine and secured with double-sided tape so that the pencil lead is positioned at the same height as the test piece. (2) The observation position for the scratch should be the starting position of the test. (3) To ensure that the scratch remains clear and is easy to observe, the pencil hardness test should be performed two minutes after setting the pencil.

[0023] The pencil hardness of the abrasive layer can be adjusted by the type and content of the hydrolyzable resin, the type and content of the hydrolysis accelerator, and the median diameter of the abrasive grains. For example, if glycolic acid polymer is used as the hydrolyzable resin, the pencil hardness before immersion tends to be high, while the pencil hardness after immersion tends to be low. Also, if carboxylic acid anhydrides are used as hydrolysis accelerators, or if the content of the hydrolysis accelerator is increased, or if the median diameter of the abrasive grains is increased, the pencil hardness after immersion tends to be low.

[0024] Furthermore, it is preferable that the scratches observed when performing the same pencil hardness test as described above using a pencil with a harderness higher than the pencil hardness after immersion in 80°C deionized water for 3 hours are cohesive fracture. For example, if the pencil hardness after immersion in the polishing layer is B, then the hardness higher than that is HB. In this case, it is preferable to check the scratches when performing the pencil hardness test using a pencil with an HB hardness. By performing the pencil hardness test using a pencil with a harderness higher than the pencil hardness after immersion in the polishing layer and checking the scratches, it is possible to determine the form of fracture.

[0025] Cohesive failure refers to the marks left by the abrasion and removal of resin, and is different from plastic deformation, which is merely the deformation of the resin. Here, the pencil hardness test is performed at least twice, and cohesive failure is defined as the observation of marks indicating cohesive failure in 80% or more of the test trials (or all trials if the number of trials is 2 to 4). When the marks indicate cohesive failure, the surface of the polished layer becomes brittle due to the formation of an embrittlement layer, and is therefore easily removed by the shear force during polishing. The marks can be observed by visually inspecting the marks at the starting position of the pencil hardness test.

[0026] Whether or not cohesive failure has occurred can be determined by whether there is substantial bulging from the surface of the polished layer, similar to that seen in plastic deformation, around the scratch caused by the pencil hardness test at the test start position. For example, if D is the depth of the deepest part of the pencil scratch and H is the height of the highest point of the bulge from the surface of the polished layer, then cohesive failure can be determined when H / D is less than 1.0. D, H, and H / D can be measured using a laser microscope (e.g., Keyence VK-X260).

[0027] Figure 4 is an explanatory diagram illustrating the observation area using a laser microscope. Figure 5A is the measurement image before image processing, and Figure 5B is the measurement image after image processing. Figures 6A to 6C are schematic diagrams showing the image processing procedure. Figure 7 is the measurement result showing the profile on the straight line passing through the origin O and point A in Figure 5B. Specifically, when the field of view is divided into two equal parts vertically, the lower half includes the scratch at the start of the test, and observation is performed using a laser microscope with a magnification of 20x and an objective lens with N.A. = 0.46 (for example, manufactured by Nikon) (see Figures 4, 5A, and 6A). In Figure 4, the area enclosed by the outermost thin line shows the observation field, and the width of the observation field (length in the x-axis direction, described later) is approximately 700 μm. Next, a plane is estimated for the entire observation field using the least squares method, and a reference plane is set. Then, the entire height data is rotated so that the reference plane is horizontal, and adjusted so that the height of the reference plane is 0 (see Figures 5B and 6B). The setting of the reference plane using the least squares method, and the adjustment to set the height of the reference plane to 0, can be performed by analyzing the measurement results using image processing software (for example, a multi-file analysis application (such as Keyence VK-H1XM)). Here, the deepest point in the scratch at the start of the test is defined as the origin O, the x-axis is a straight line passing through the origin O and perpendicular to the direction of pencil hardness test progression, and the y-axis is a straight line passing through the origin O and perpendicular to the x-axis (see Figure 4), and the absolute value of the height from the origin O to the reference plane is defined as D (see Figure 6C). Furthermore, the highest point in the area (enclosed by a thick line) that lies on the y-axis and includes the scratch observation area (filled area) and the area extending approximately 200 μm from that area in the direction of pencil progression (unfilled area) is defined as point A (see Figure 4), and the absolute value of the height from the reference plane to point A is defined as H (see Figure 6C). Furthermore, if the area of ​​the wound is wide and has a depth similar to that of the wound at the start of the test, and the wound and raised area cannot be observed at the same time, D and H can be determined by image stitching and performing the same measurements as described above. In addition, if cracks are observed on the surface with the naked eye after immersion in ion-exchanged water at 80°C for 3 hours, it can be determined that the wound is cohesive fracture because the surface has clearly formed an embrittlement layer and become brittle.

[0028] If a brittle layer of decomposed hydrolyzable resin forms on the polished layer after immersion, scratches are likely to result in cohesive failure. In particular, if cracks or fissures are observed on the surface of the polished layer after immersion, it indicates that the molecular weight of the hydrolyzable resin forming the polished layer has decreased, and a brittle layer has formed on the surface, making scratches likely to result in cohesive failure. For example, if glycolic acid polymer is used as the hydrolyzable resin, a brittle layer is likely to form on the polished layer after immersion, and scratches are likely to result in cohesive failure. Furthermore, if carboxylic acid anhydrides are used as hydrolysis accelerators, or if the content of hydrolysis accelerators is increased, or if the median diameter of the abrasive grains is increased, a brittle layer is likely to form on the polished layer after immersion, and scratches are likely to result in cohesive failure.

[0029] The following describes each component contained in the polishing layer.

[0030] 1-1-1. Hydrolyzable Resins Hydrolyzable resins are not particularly limited as long as they are resins that exhibit hydrolysis. Examples of hydrolyzable resins include polyester, polycarbonate, and polyamide. Among these, polyester is preferred because it exhibits good hydrolysis properties, and aliphatic polyester is more preferred.

[0031] Aliphatic polyesters may be polyesters obtained by homopolymerization or copolymerization of oxycarboxylic acids and / or lactones, esterification reactions of aliphatic dicarboxylic acids and aliphatic diols, or copolymerization of aliphatic dicarboxylic acids, aliphatic diols and oxycarboxylic acids and / or lactones.

[0032] Examples of oxycarboxylic acids include aliphatic hydroxycarboxylic acids having 2 to 8 carbon atoms, such as glycolic acid, lactic acid, malic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid, and hydroxyoctanoic acid.

[0033] Examples of lactones include propiolactone, butyrolactone, valerolactone, and ε-caprolactone, which have 3 to 10 carbon atoms.

[0034] Examples of aliphatic dicarboxylic acids include aliphatic saturated dicarboxylic acids with 2 to 8 carbon atoms, such as oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid, and aliphatic unsaturated dicarboxylic acids with 4 to 8 carbon atoms, such as maleic acid and fumaric acid.

[0035] Examples of aliphatic diols include alkylene glycols with 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, butanediol, and hexanediol, and polyalkylene glycols with 2 to 4 carbon atoms, such as polyethylene glycol, polypropylene glycol, and polybutylene glycol.

[0036] These components may be used individually or in combination of two or more. Furthermore, the aliphatic polyester may further contain constituent units derived from aromatic dicarboxylic acids such as terephthalic acid, aromatic diols such as bisphenol A, aromatic hydroxycarboxylic acids such as hydroxybenzoic acid, etc., provided that they are hydrolyzable.

[0037] Among these, polymers containing structural units derived from oxycarboxylic acids are preferred, and lactic acid polymers and glycolic acid polymers are more preferred. Of these, glycolic acid polymers are preferred from the viewpoint of having high strength, being easily reduced in molecular weight by hydrolysis, and easily forming an embrittlement layer. That is, hydrolyzable resins preferably contain glycolic acid polymers as a main component. Containing glycolic acid polymers as a main component means that the content of glycolic acid polymers relative to the total mass of the hydrolyzable resin is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0038] Glycolic acid polymers are composed of constituent units derived from glycolic acid (-(-O-CH ２ It is a polymer containing -CO-). The glycolic acid polymer may be a homopolymer of glycolic acid, or a copolymer of glycolic acid and a monomer copolymerizable with it.

[0039] Examples of the monomers that can be copolymerized include the above-mentioned oxycarboxylic acids other than glycolic acid, the above-mentioned lactones, aliphatic dicarboxylic acids, aliphatic diols, aromatic dicarboxylic acids, aromatic diols, and aromatic hydroxycarboxylic acids.

[0040] The content of the structural unit derived from glycolic acid in the glycolic acid polymer is preferably 50% by mass or more, more preferably 75% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 99% by mass or more, based on the total mass of the structural units constituting the glycolic acid polymer. When the content of the structural unit derived from glycolic acid is 50% by mass or more, the strength of the glycolic acid polymer can be increased, and thus more sufficient strength can be obtained when used as a polishing pad.

[0041] The weight average molecular weight of the hydrolyzable resin preferably ranges from 70,000 to 500,000, although it depends on the type. When the weight average molecular weight of the hydrolyzable resin is 70,000 or more, the strength of the hydrolyzable resin can be increased, so that the retention of abrasive grains and the durability of the polishing pad can be enhanced. Also, more sufficient strength for handling, such as when removing the polishing pad from the mold during molding or attaching the polishing pad to the surface plate of the polishing apparatus, can be obtained. Furthermore, when a load is applied by bringing the polishing pad into contact with the workpiece to be polished, it is possible to prevent the abrasive grains protruding from the surface from being pushed back into the base material. Thereby, even when using fine abrasive grains, it is possible to make it difficult to reduce the polishing rate. When the weight average molecular weight of the hydrolyzable resin is 500,000 or less, not only can the moldability be further maintained, but the time until it collapses by hydrolysis can be shortened. From the same perspective, the weight average molecular weight of the hydrolyzable resin is more preferably from 110,000 to 400,000.

[0042] The weight average molecular weight of the hydrolyzable resin can be measured by gel permeation chromatography (GPC). The measurement conditions can be as follows. (Measurement conditions) Device: "Shodex-104" manufactured by Showa Denko KK Column: Two HFIP-606M columns and one HFIP-G column connected in series as a pre-column Column temperature: 40 °C Eluent: HFIP solution dissolved with 5 mM sodium trifluoroacetate Flow rate: 0.6 mL / min Detector: RI (differential refractive index) detector Molecular weight calibration: Five standard polymethyl methacrylates with different molecular weights

[0043] The content of the hydrolyzable resin is preferably 20% by mass or more and 98.5% by mass or less, more preferably 50% by mass or more and 94% by mass or less, and even more preferably 70% by mass or more and 89% by mass or less, based on the total mass of the polishing layer. When the content of the hydrolyzable resin is 20% by mass or more, the strength of the polishing layer containing abrasive grains becomes higher. When the content of the hydrolyzable resin is 98.5% by mass or less, the proportion of abrasive grains does not become too small, so the polishing rate does not become too small. When the content of the hydrolyzable resin is within the above range, it is easy to obtain a more stable polishing rate due to the dressing effect while suppressing excessive disintegration of the polishing layer.

[0044] 1-1-2. Abrasive grains The material of the abrasive grains is not particularly limited, and examples include diamond, silicon carbide, boron carbide, boron nitride, silicon nitride, cerium oxide, aluminum oxide, zirconium oxide, silicon oxide, iron oxide, manganese oxide, magnesium oxide, calcium oxide, barium oxide, zinc oxide, titanium oxide, chromium oxide, barium carbonate, and calcium carbonate. Among these, from the viewpoint of increasing the polishing rate, diamond, boron carbide, and boron nitride are preferable, and from the viewpoint of facilitating the processing of substrates with high hardness such as SiC substrates, diamond is more preferable.

[0045] The upper limit of the median diameter of the abrasive grains depends on the desired degree of polishing, but is preferably less than 30 μm, more preferably 20 μm or less, even more preferably 10 μm or less, particularly preferably 5 μm or less, very preferably 3 μm or less, and extremely preferably 1 μm or less. The lower limit of the median diameter of the abrasive grains is not particularly limited as long as a polishing speed of a predetermined level or higher can be achieved, but is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more.

[0046] The median diameter of the abrasive grains can be determined from the particle size distribution measured according to particle size analysis - laser diffraction and scattering method (ISO 13320:2020). Specifically, it can be measured using a laser diffraction particle size analyzer (e.g., Malvern Mastersizer 3000) under the following conditions: measurement temperature of 21°C, dispersion medium of deionized water, dispersion medium refractive index of 1.330, and light scattering model of Mie theory. The abrasive grains can be obtained by heating and melting the polishing layer, passing the resulting molten material through a filter, and separating the abrasive grains from the remaining hydrolyzable resin.

[0047] The abrasive content is not particularly limited, but is preferably 1% by mass or more and 55% by mass or less relative to the total mass of the polishing layer, and more preferably 5% by mass or more and 40% by mass or less. When the abrasive content is 1% by mass or more, the polishing speed can be increased. When the abrasive content is 55% by mass or less, the moldability or machinability of the polishing pad can be increased. In particular, when the median diameter of the abrasive is less than 1 μm, the abrasive content is preferably 5% by mass or more and 15% by mass or less relative to the total mass of the polishing layer, and when the median diameter of the abrasive is 1 μm or more, the abrasive content is preferably 9% by mass or more and 30% by mass or less relative to the total mass of the polishing layer.

[0048] The abrasive content can be measured using a thermogravimetric analysis (TGA) apparatus. Specifically, on the surface of the polishing layer of an unused polishing pad, let L be an arbitrary straight line passing through the center O of the polishing layer, and let M be a straight line perpendicular to L and passing through the center O of the polishing layer. Let a1 and a2 be the midpoints between the center O and the edge of the polishing layer on line L, and b1 and b2 be the midpoints between the center O and the edge of the polishing layer on line M. Take a sample of 100 mg or more from the polishing layer from each measurement point, within the range including each measurement point O, a1, a2, b1, and b2, and crush it as appropriate to obtain the measurement sample from each measurement point. Place 20 mg ± 2 of the measurement sample in a platinum pan, heat it from room temperature at a rate of 10°C / min to 800°C in an air atmosphere, hold it at 800°C for 30 minutes to burn off components other than abrasive grains, and divide the remaining sample weight by the mass of the measurement sample to determine the abrasive content in the polishing layer at each measurement point. In this application, the arithmetic mean of the abrasive content of each of the five points is used as a representative value for the abrasive content of the polishing layer.

[0049] 1-1-3. Other Components The polishing layer may further contain other components besides hydrolyzable resins and abrasive grains. Other components include other resins besides hydrolyzable resins and hydrolysis accelerators. In particular, from the viewpoint of further improving the removal of decomposed hydrolyzable resins, it is preferable that the polishing layer further contains hydrolysis accelerators. One type of hydrolysis accelerator may be used alone, or two or more types may be used in combination.

[0050] A hydrolysis accelerator is a compound that promotes the hydrolysis reaction of a hydrolyzable resin. Preferably, it is a compound that promotes the penetration of the solution into the hydrolyzable resin by dissolving in the polishing solution, and more preferably a compound that generates an acid or alkali in the presence of water. Examples of such hydrolysis accelerators include carboxylic acid anhydrides, phosphorus compounds, cyclic esters, and basic metal oxides.

[0051] Examples of carboxylic acid anhydrides include hexanoic anhydride, octanoic anhydride, decanoic anhydride, lauric anhydride, myristic anhydride, palmitic anhydride, stearic anhydride, benzoic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, tetrahydrophthalic anhydride, butanetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, diphenylsulfonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, ethylene glycol bis-anhydrotrimellitate, and glycerin bis-anhydrotrimellitate monoacetate.

[0052] As phosphorus compounds, organophosphorus compounds such as phosphate esters and phosphite esters are preferred, and organophosphorus compounds having at least one selected from the group consisting of a long-chain alkyl group having 8 to 24 carbon atoms, an aromatic ring, and a pentaerythritol skeleton are more preferred.

[0053] Examples of phosphate esters having long-chain alkyl groups with 8 to 24 carbon atoms include mono- or di-stearyl acid phosphates or mixtures thereof, and di-2-ethylhexyl acid phosphate. Examples of phosphite esters having aromatic rings include tris(nonylphenyl) phosphite. Examples of phosphite esters having a pentaerythritol skeleton include cyclic neopentanetetraylbis(2,6-di-tert-butyl-4-methylphenyl) phosphite, cyclic neopentanetetraylbis(2,4-di-tert-butylphenyl) phosphite, and cyclic neopentanetetraylbis(octadecyl) phosphite.

[0054] Examples of cyclic esters include glycosides, lactides, ε-caprolactone, γ-valerolactone, δ-valerolactone, diglycolic anhydride, and glutaric anhydride.

[0055] Examples of basic metal oxides include magnesium oxide, zinc oxide, calcium oxide, sodium oxide, and copper oxide.

[0056] Among these, carboxylic acid anhydrides are preferred from the viewpoint of being relatively stable during molding and further promoting the hydrolysis of hydrolyzable resins in the polished layer where water has penetrated, with phthalic anhydride, trimellitic anhydride, benzoic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and pyromellitic dianhydride being more preferred, and pyromellitic dianhydride being particularly preferred.

[0057] When the polishing layer contains a hydrolysis accelerator, the content of the hydrolysis accelerator is preferably, for example, 1% to 50% by mass, more preferably 3% to 15% by mass, and even more preferably 5% to 9% by mass, based on the total mass of the polishing layer. When the above content of the hydrolysis accelerator is 1% by mass or more, it not only further accelerates the decomposition of the hydrolyzable resin but also makes it easier to form an embrittlement layer, thereby improving the removeability of the hydrolyzable resin after decomposition. When the above content of the hydrolysis accelerator is 50% by mass or less, it not only makes the bleed-out of the hydrolysis accelerator less likely to occur but also further suppresses excessive collapse due to excessive hydrolysis.

[0058] From a similar viewpoint, the content of the hydrolysis accelerator is preferably 0.5% by mass or more and 45% by mass or less, more preferably 2% by mass or more and 14% by mass or less, and even more preferably 4% by mass or more and 8% by mass or less, based on the total mass of the hydrolyzable resin.

[0059] The content of hydrolysis accelerators in the polishing layer can be measured by gas chromatography (GC). Specifically, a sample is taken from the polishing layer in the same way as for measuring the content of abrasive grains. The sample is dissolved in a solvent of choice along with p-chlorobenzophenone, which is an internal standard. The solution is then filtered to obtain the measurement sample. When the hydrolyzable resin is a glycolic acid polymer, DMSO (dimethyl sulfoxide) is preferred as the solvent. The GC measurement conditions are as follows: Apparatus: Shimadzu GC-2010 Carrier gas: Helium, Flow rate: 1.08 mL / min Column: RESTEK Rxi-5ms Column temperature: Held at 150°C for 5 minutes → (Increased temperature at 20°C / min) → Held at 270°C for 3 minutes Detector: FID (Flame Ionization Detector) Detector temperature: 300°C Injection temperature: 180°C GC measurement determines the content of hydrolysis accelerators in the polishing layer at each measurement point. In this application, the arithmetic mean of the abrasive content at the measurement point is used as a representative value for the hydrolysis accelerator content of the polishing layer.

[0060] 1-1-4. Physical Properties (Tensile Strength) The tensile strength of the base material that fixes the abrasive grains at 25°C is not particularly limited, but is preferably 55 MPa or higher. When the abrasive pad is brought into contact with the workpiece and a load is applied, the abrasive grains protruding from the surface are less likely to be pushed back into the base material. From a similar viewpoint, the tensile strength of the base material is more preferably 60 MPa or higher. There is no particular upper limit to the tensile strength of the base material, but it can be, for example, 1000 MPa or less. The tensile strength can be measured in accordance with ISO 527.

[0061] (Tensile Modulus) The tensile modulus of the base material at 25°C is not particularly limited, but is preferably 1 GPa or higher. When the tensile modulus is 1 GPa or higher, when the polishing pad is brought into contact with the workpiece and a load is applied, the abrasive grains protruding from the surface are less likely to be pushed back into the base material. As a result, even when using minute abrasive grains, the reduction in polishing speed can be minimized. In addition, edge rounding of the workpiece after polishing (a phenomenon in which the edges are concentrated and the dimensional accuracy is reduced) can be reduced. From a similar viewpoint, the tensile modulus of the base material is more preferably 3 GPa or higher, and even more preferably 5 GPa or higher. There is no particular upper limit to the tensile modulus of the base material, but it can be, for example, 50 GPa or lower. The tensile modulus can be measured in accordance with ISO 527.

[0062] The tensile strength and tensile modulus of the above-mentioned base material can be adjusted by the type and content of the hydrolyzable resin, the type and content of the hydrolysis accelerator, the weight-average molecular weight, the cooling process during molding, etc. For example, if the content of the hydrolysis accelerator is low, the above-mentioned tensile strength and tensile modulus tend to be higher.

[0063] (Density) The density of the abrasive layer is not particularly limited, but is 1.57 g / cm³. ３ 3.00g / cm or more ３ Preferably, it is 1.60 g / cm³. ３ 2.00g / cm or more ３ The following is more preferable: The density of the polished layer can be measured in accordance with JIS K0061:2001 at 20°C and 65% RH. The test specimens can be prepared in the same manner as test specimens for pencil hardness testing.

[0064] The density of the abrasive layer can be adjusted by the abrasive grain content, for example. The higher the abrasive grain content, the higher the density of the abrasive layer can be.

[0065] (Thickness) The thickness of the polishing layer is not particularly limited, but for example, when used for processing substrates of semiconductor devices, it is preferably 0.1 mm or more and 30 mm or less, more preferably 0.3 mm or more and 10 mm or less, and even more preferably 0.5 mm or more and 5 mm or less. When the thickness of the polishing layer is 0.1 mm or more, the abrasive grains can be held more sufficiently.

[0066] 1-2. Other Layers The polishing pad may consist only of a polishing layer, or it may further include other layers. Examples of other layers include a base layer and an adhesive layer. The base layer may be, for example, a resin film. If the polishing pad includes a base layer, the polishing layer may be uniformly arranged on the base layer or arranged in a pattern. The adhesive layer may be an adhesive layer for attaching the polishing pad 100 to a polishing plate (a surface plate 210 described later).

[0067] 1-3. Grooves may be arranged on the surface of the abrasive layer. This makes it easier for the abrasive liquid to spread throughout the entire surface of the abrasive layer through the grooves, and also makes it easier for the chips (decomposed hydrolyzable resin, abrasive material, etc.) generated by the hydrolysis of the hydrolyzable resin to be discharged to the outside through the grooves.

[0068] The grooves should be arranged to allow for the supply or discharge of polishing fluid and the discharge of hydrolyzable resin chips generated by hydrolysis. The plan view shape of the grooves may be annular, radial, grid-like, or linear. The protrusions of the uneven pattern formed by the grooves may also be arranged in an island-like manner.

[0069] 2. Method for Manufacturing Polishing Pads The polishing pad according to this embodiment can be manufactured by any method. For example, a polishing pad can be manufactured by 1) obtaining a composition containing a hydrolyzable resin and abrasive grains, and 2) molding the obtained composition to form an polishing layer.

[0070] 1) The composition containing the hydrolyzable resin and abrasive grains can be obtained by any method. For example, the composition can be obtained by kneading the hydrolyzable resin and abrasive grains. As a kneader, for example, a roll, kneader, Banbury mixer, extruder (single-screw, multi-screw), etc. can be used.

[0071] From the viewpoint of improving processability, kneading is preferably carried out under heating. The heating temperature can be, for example, 150°C to 270°C. In particular, if the above composition contains a hydrolysis accelerator, the heating temperature is preferably such that the hydrolysis accelerator can be dispersed in a stable state.

[0072] The form of the resulting composition is not particularly limited and may be, for example, pellets, powder, or filaments.

[0073] 2) Next, the obtained composition is molded into a predetermined shape to form an abrasive layer. The molding method is not particularly limited and may be any of the following: injection molding, melt extrusion molding, solidification extrusion molding, vacuum molding, transfer molding, and compression molding. Molding may also be performed using a 3D printer.

[0074] When manufacturing a molded product by compression molding, pellets of the above composition are supplied into the mold. The mold temperature is set to 150°C or higher and 270°C or lower, and press molding is performed to obtain a polishing pad containing the molded product. Furthermore, by performing the compression molding method in a dry room (under dry conditions) with a dew point temperature of -40°C, hydrolysis of the resin can be prevented, and the strength of the pad can be maintained.

[0075] Grooves may be formed on the surface of the molded article of the obtained composition. The method for forming the grooves is not particularly limited; grooves may be formed by cutting the surface of the molded article of the composition, or grooves may be formed by molding the composition using a mold or template with a pattern corresponding to the grooves. Furthermore, annealing may be performed as needed from the viewpoint of improving the dimensional stability of the molded article.

[0076] 3. Polishing Method for the Workpiece Figure 1 is a schematic diagram showing a polishing apparatus 100 using a polishing pad according to this embodiment. Detailed illustration of the polishing pad 110 is omitted in this figure.

[0077] As shown in Figure 1, the polishing apparatus 100 includes a polishing pad 110, a disc-shaped base plate 120 that supports the polishing pad 110, a disc-shaped polishing head 130 that holds the workpiece 200 to be polished, a carrier 140 that holds the polishing head 130, a weight 150, and a supply nozzle 160 that supplies polishing fluid W. The base plate 120 is rotatable by a rotating shaft (not shown), and the polishing head 130 is rotatable by a rotating shaft 130A.

[0078] In this embodiment, the polishing pad 110 is polished by supplying a polishing liquid W containing water to the surface of the polishing pad 110 and sliding the polishing pad 110 and the workpiece 200 relative to each other.

[0079] Specifically, first, a polishing pad 110 is attached to the surface plate 120. Next, the workpiece 200 held by the polishing head 130 is pressed against the polishing surface of the polishing pad 110, and while supplying polishing fluid W from the supply nozzle 160, the surface plate 120 and / or the polishing head 130 are rotated. This causes the polishing pad 110 and the workpiece 200 to slide relative to each other, polishing the machined surface (polished surface) of the workpiece 200.

[0080] The material of the workpiece 200 is not particularly limited and may be a ceramic material, a glass material, etc. Examples of ceramic materials include Si (silicon), SiC (silicon carbide), GaN (silicon nitride), GaAs (gallium arsenide), sapphire, etc., with SiC and GaN being preferred. Specifically, the workpiece 200 can be a material for semiconductor devices or electronic components, particularly Si substrates, SiC substrates, GaAs substrates, glass, or substrates for hard disks and LCDs (liquid crystal displays). Among these, semiconductor wafers are preferred, SiC substrates, sapphire substrates, or GaN substrates used in power devices are more preferred, and SiC substrates or GaN substrates are even more preferred.

[0081] The polishing solution W contains at least water. When the polishing pad 110 contains a glycolic acid polymer as a hydrolyzable resin, it is preferable that the polishing solution W be an alkaline or acidic aqueous solution in order to promote the hydrolysis of the glycolic acid polymer and further enhance the dressing effect. In an alkaline aqueous solution, the carboxylic acid terminals produced by hydrolysis remain as carboxylate ions, and the oligomers of the polymer produced by hydrolysis easily dissolve into the liquid, thus promoting hydrolysis.

[0082] An alkaline aqueous solution contains water and an alkaline substance. Examples of alkaline substances include alkali metal hydroxides such as sodium hydroxide (NaOH) and potassium hydroxide (KOH), and organic alkalis such as tetramethylammonium hydroxide. From the viewpoint of further promoting the hydrolysis of glycolic acid polymers, the pH of the alkaline aqueous solution is preferably 9 or higher, more preferably 12 or higher, and even more preferably 13 or higher. The upper limit of the pH can be, for example, 14. The pH is measured by a pH meter at 20°C in accordance with JIS Z 8802:2011. The pH of the alkaline aqueous solution can be adjusted by the amount of alkaline substance.

[0083] The temperature of the polishing solution W is not particularly limited, but it can be between 1°C and 60°C.

[0084] Polishing solution W may further contain other components besides those mentioned above, such as hydrolysis accelerators.

[0085] The present disclosure will be described below with reference to examples. The scope of the present disclosure shall not be limited by the examples.

[0086] 1. Materials 1-1. Hydrolyzable resins: PGA (hybrid polymer of glycolic acid, weight-average molecular weight 298,000, tensile strength 112.8 MPa), PLA (Natureworks 7000D, manufactured by Natureworks, Inc., polylactic acid, weight-average molecular weight 246,000)

[0087] The weight-average molecular weight and tensile strength of the above PGA were measured by the following method.

[0088] (Measurement of weight-average molecular weight) The weight-average molecular weight was measured by gel permeation chromatography (GPC). The measurement conditions were as follows: Apparatus: Showa Denko K.K. "Shodex-104" Column: Two HFIP-606M columns connected in series with one HFIP-G column as a pre-column Column temperature: 40°C Eluent: HFIP solution with 5 mM sodium trifluoroacetate dissolved in it Flow rate: 0.6 mL / min Detector: RI (differential refractive index) detector Molecular weight calibration: Five types of standard polymethyl methacrylate with different molecular weights

[0089] (Measurement of tensile strength) The tensile strength of the above PGA was measured in accordance with ISO 527.

[0090] 1-2. Abrasive grains Abrasive grain 1: Single-crystal diamond powder FRM (manufactured by Global Diamond, median diameter 0.25 μm, irregular shape) Abrasive grain 2: Single-crystal diamond powder FRM (manufactured by Global Diamond, median diameter 1.0 μm, irregular shape) Abrasive grain 3: Single-crystal diamond powder FRM (manufactured by Global Diamond, median diameter 3.0 μm, irregular shape)

[0091] (Method for measuring median diameter) The median diameter of the abrasive grains was measured using the following method. Specifically, a laser diffraction grain size analyzer Mastersizer3000 (Malvern) was used, with the following conditions set: measurement temperature 21°C, dispersion medium deionized water, dispersion medium refractive index 1.330, light scattering model Mie theory, particle absorptivity of polycrystalline diamond powder 0.100, and particle refractive index 2.418. The amount of abrasive grains added to the dispersion medium was adjusted so that the laser scattering intensity was between 4% and 10%.

[0092] 1-3. Hydrolysis accelerators: Pyromellitic dianhydride (PMDA), Glycolide (GL)

[0093] 2. Preparation and Evaluation of Polishing Pads 2-1. Preparation of Polishing Pads 1 to 9 (Mixing Process) Each component shown in Table 1 was weighed in the proportions shown in Table 1, and the mixture was kneaded using a Laboplast Mill (manufactured by Toyo Seiki Seisakusho) to obtain the composition. The kneading was performed at a predetermined heater temperature, with a preheating time of 1 minute, a kneading time of 5 minutes, and a rotation speed of 50 rpm. The heater temperature was set to 250°C.

[0094] (Molding Process) A stainless steel mold with a 150 mm diameter hole was prepared. The mixed composition was placed in this stainless steel mold and press-molded to produce a polishing pad consisting of a 2.0 mm thick disc-shaped polishing layer. The press machine temperature was set to the same temperature as the heater temperature of the Laboplast Mill. Furthermore, after the pad was made, a triangular knife was used to form a grid pattern of grooves on the surface of the pad.

[0095] 2-2. For each of the polishing pads that were evaluated, the density, pencil hardness, and polishing speed were measured using the following method.

[0096] 2-2-1. Density: The density of the polished layer was measured in accordance with the specific gravity bottle method described in JIS K0061:2001 under conditions of 20°C and 65% RH.

[0097] 2-2-2. Pencil Hardness (1) Preparation of Test Specimens A polishing pad consisting of a disc-shaped polishing layer with a thickness of 3.0 mm was prepared in the same manner as the molding process described above. The center of this polishing pad was defined as O, and the distance (radius) from the center O to the edge of the polishing pad (polishing layer) was defined as 1. Next, a circle was drawn at a radius of 0.6 from the center O. Two points on the circumference of this circle were set to divide the circumference into two equal parts, and two rectangular parallelepiped test specimens measuring 10 mm × 10 mm × 3 mm were cut out with each point as the center, and these were used as test specimens for pencil hardness. In order to facilitate observation of scratches, the portion of the polishing pad without groove processing was cut out.

[0098] (2) Pencil hardness test To prevent the test specimens from moving, double-sided tape was attached to the back of each specimen and fixed to the base. Then, using a pencil hardness tester 054-1 (manufactured by Allgood Co., Ltd.), the test specimens were subjected to pencil hardness tests before and after immersion in ion-exchanged water at 80°C for 3 hours. Specifically, the largest surface of one of the two prepared test specimens was subjected to a pencil hardness test at 25°C and 60% RH (pencil hardness test before immersion). Next, the other of the two prepared test specimens was immersed in ion-exchanged water at 80°C for 3 hours, and then dried in a dry room with a dew point of -40°C for 1 hour. Then, in the same manner as above, the surface of the dried test specimen was subjected to a pencil hardness test (pencil hardness test after immersion).

[0099] The pencil hardness test was conducted in general accordance with JIS K5600-5-4:1999, except for the following points: • Because the test specimen had thickness, a plate-like member equivalent to its thickness was placed under the testing machine and secured with double-sided tape, so that the pencil lead was positioned at the same height as the test specimen. • The observation position for the scratch was the test start position. • To ensure that the scratch remained clear and was easy to observe, the pencil hardness test was performed after leaving the pencil in place for two minutes. • After the test, the pencil lead powder was removed with an eraser to the extent that it did not cause scratches or other damage to the surface. Furthermore, the pencil hardness test was conducted with an upper limit of 6H.

[0100] (3) Determination of pencil hardness The pencil hardness of the test pieces before and after immersion was determined by visually observing the marks left after the pencil hardness test. The observation position for the marks was the test start position. The difference in pencil hardness before and after immersion (h0 - h1) was then calculated.

[0101] (4) Observation of scratches on the test specimens after immersion A pencil hardness test was performed on the test specimens after immersion using a pencil with a hardness one step higher than the pencil hardness of the immersed test specimen (the lowest pencil hardness at which scratches occurred). The scratches after the pencil hardness test were then observed using a laser microscope. The test was performed twice.

[0102] Specifically, the following procedure was followed: 1) When the field of view was divided into two equal parts vertically, the scratch at the test start position was included in the lower half, and the area was observed using a laser microscope (Keyence VK-X260) with a magnification of 20x and an objective lens (Nikon) with N.A. = 0.46. The width of the observation field of view was approximately 700 μm. Subsequently, the plane was estimated using the least squares method for the entire observation field of view, and a reference plane was set. Image processing was performed using a multi-file analysis application (Keyence VK-H1XM). 2) Next, the deepest point in the scratch at the test start position was defined as the origin O, and a straight line passing through the origin O and perpendicular to the direction of the pencil hardness test was defined as the x-axis, and a straight line passing through the origin O and perpendicular to the x-axis was defined as the y-axis. The absolute value of the height from the origin O to the reference plane was defined as D. Furthermore, point A was defined as the highest point among the points located on the y-axis and included in the scar observation area (an area with a width of approximately 100 μm in the direction of pencil advance) and the area extending approximately 200 μm from that area in the direction of pencil advance, and H was defined as the absolute value of the height from the reference plane to point A. Then, H / D was calculated.

[0103] 2-2-3. Polishing Speed ​​(1) Pre-treatment of polishing pads Immediately after molding, the polishing pads had abrasive grains embedded in the resin. Therefore, after sharpening them for 10 minutes with a #1000 diamond dresser (double-sided diamond grinding wheel, round type, manufactured by Fujiwara Sangyo Co., Ltd.) under a pressure of 10.8 kPa, a polishing test was performed.

[0104] (2) Pre-processing of the workpiece The surface of the 20 x 20 mm square SiC substrate, which is the workpiece to be polished, was roughly polished on a cast iron surface plate using a slurry containing polycrystalline diamond with a median diameter of 9 μm, and then lapping was performed.

[0105] (3) Polishing Test The polishing test was performed by attaching a polishing pad to the polishing apparatus 100, as shown in Figure 1. Specifically, the polishing pad was attached to the surface plate 120 (polishing plate) using a double-sided adhesive film (for example, AS ONE OCA50-A4). The double-sided adhesive sheet was attached using a rubber roller or the like to prevent air bubbles from getting trapped when it was attached to the polishing pad and polishing plate.

[0106] Next, the SiC substrate (20 x 20 mm square) that had undergone the above pre-processing was pressed against the rotating polishing pad as the workpiece 200 and polished. The polishing conditions were as follows. At this time, the substrate was subjected to the load of a jig (polishing head 130) and a weight 150. (Polishing conditions) Polishing device: Dialap ML-150P (manufactured by Maruto Co., Ltd.) Polishing disc rotation speed: 100 rpm Polishing disc diameter: 150 mm Forced drive and oscillation of workpiece: None Surface pressure: 250 gf / cm ２ Polishing solution flow rate: 75 mL / h Polishing solution: NaOH aqueous solution with pH = 13 (20°C)

[0107] The polishing speed was then measured using the following method. With the workpiece attached to the jig, the thickness of the workpiece was measured using an electric micrometer Millimar 1240 (manufactured by Mahr). The thickness of the workpiece was measured at five points, and the average value was used. The polishing speed was calculated from the polishing time (min) and the reduction in thickness (amount removed, μm).

[0108] Table 1 shows the evaluation results for polishing pads 1 to 9. Figure 2 shows laser microscope images of the surface of test pieces of polishing pad 1 (Example) before immersion and after immersion in ion-exchanged water at 80°C for 3 hours, for each hardness level after the pencil hardness test. Figure 3 shows laser microscope images of the surface of test pieces of polishing pad 7 (Comparative Example) before immersion and after immersion in ion-exchanged water at 80°C for 3 hours, for each hardness level after the pencil hardness test.

[0109]

[0110] (1) Regarding the pencil hardness test, polishing pad 1 (example) did not show scratches with pencils of 6H or lower before immersion (see left side of Figure 2), indicating that the pencil hardness before immersion was 6H. On the other hand, after immersion, it did not show scratches with pencils of B or lower, but it did show scratches with pencils of HB or higher (see right side of Figure 2), indicating that the pencil hardness after immersion was B. Furthermore, all scratches after immersion were cohesive failure.

[0111] In contrast, polishing pad 7 (comparative example) did not show scratches when the pencil hardness was 2H or less before and after immersion, but it did show scratches when it was 3H or more (see Figure 3). This indicates that the pencil hardness was 2H before and after immersion, and that the pencil hardness did not change before and after immersion. Furthermore, all scratches after immersion were due to plastic deformation. Note that the areas enclosed by white lines in Figure 3 are areas that underwent plastic deformation.

[0112] (2) Regarding the polishing test, as shown in Table 1, polishing pads 1 to 6, in which the difference in pencil hardness of the polishing layer before and after immersion was three levels or more, were all able to maintain a good polishing speed. In contrast, polishing pads 7 and 8, in which the difference in pencil hardness of the polishing layer before and after immersion was less than three levels, showed a significant decrease in polishing speed after 120 minutes, indicating that they could not maintain a polishing speed. Depending on the median diameter of the abrasive grains, for example, a lower abrasive grain content resulted in a larger difference in hardness before and after immersion and less decrease in polishing speed (comparison of polishing pads 1 and 2). Depending on the size of the abrasive grains, this is thought to be because a lower abrasive grain content results in a higher polishing pressure.

[0113] From these findings, it can be seen that polishing pads in which the difference in pencil hardness of the polishing layer before and after immersion is three levels or more allow the decomposed PGA to become an embrittlement layer and be removed effectively, thereby maintaining a good polishing speed.

[0114] This application claims priority under Japanese Patent Application No. 2024-193663, filed on November 5, 2024. All contents described in the specification and drawings of said application are incorporated herein by reference.

[0115] According to the present invention, it is possible to provide a polishing pad in which the binder resin after disassembly is easily removed and the reduction in polishing speed is minimal, as well as a method for polishing an object to be polished using the same.

[0116] 100 Polishing device 110 Polishing pad 120 Surface plate 130 Polishing head 130A Rotating shaft 140 Carrier 150 Weight 160 Supply nozzle 200 Workpiece

Claims

1. A polishing pad comprising a polishing layer containing a hydrolyzable resin and abrasive grains, wherein the pencil hardness of the polishing layer at 25°C and 60% RH after immersion in ion-exchanged water at 80°C for 3 hours is lower than the pencil hardness of the polishing layer at 25°C and 60% RH before immersion, and the difference between the pencil hardness of the polishing layer at 25°C and 60% RH before and after immersion is 3 levels or more.

2. The polishing pad according to claim 1, wherein the pencil hardness of the polishing layer before immersion is 2H or higher at 25°C and 60% RH.

3. The polishing pad according to claim 2, wherein, after immersion in ion-exchanged water at 80°C for 3 hours, a pencil hardness test is performed on the polishing layer using a pencil with a hardness higher than the pencil hardness of the polishing layer after immersion at 25°C and 60% RH, and the resulting scratches are cohesive failure.

4. The polishing pad according to any one of claims 1 to 3, wherein the median diameter of the abrasive grains is less than 30 μm.

5. The polishing pad according to any one of claims 1 to 4, wherein the content of abrasive grains in the polishing layer is 1% by mass or more and 55% by mass or less with respect to the total mass of the polishing layer.

6. The polishing pad according to any one of claims 1 to 5, wherein the content of the hydrolyzable resin in the polishing layer is 20% by mass or more and 98.5% by mass or less with respect to the total mass of the polishing layer.

7. The abrasive pad according to any one of claims 1 to 6, wherein the hydrolyzable resin mainly comprises a glycolic acid polymer.

8. The polishing pad according to any one of claims 1 to 8, wherein the polishing layer further comprises a hydrolysis accelerator.

9. The polishing pad according to claim 8, wherein the hydrolysis accelerator comprises at least one selected from the group consisting of carboxylic acid anhydrides, phosphorus compounds, cyclic esters, and basic metal oxides.

10. The polishing pad according to any one of claims 1 to 9, wherein the thickness of the polishing layer is 0.1 mm or more and 30 mm or less.

11. The density of the abrasive layer is 1.57 g / cm³. ３ 3.00g / cm or more ３ The polishing pad according to any one of claims 1 to 10, as follows:

12. A method for polishing an object to be polished, comprising the step of polishing the object to be polished by sliding the polishing pad and the object to be polished relative to each other while supplying a polishing liquid containing water to the surface of the polishing layer of the polishing pad according to any one of claims 1 to 11.

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