Method of evaluating abrasive grains, method of inspecting abrasive gains, and method of producing abrasive grains

Abstract

To provide an abrasive grain evaluation method that enables quantitative evaluation of microscale friability of abrasive grains.SOLUTION: An abrasive grain evaluation method of the present invention comprises a compression step of applying a compressive load to an evaluation target, and a measurement step of acquiring deformation properties exhibited by the evaluation target during the compression step, and involves evaluating the evaluation target based on the deformation property. In this evaluation method, the evaluation target is an abrasive grain and the deformation properties include micro-fractures in the abrasive grain.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating abrasive grains, a method for inspecting abrasive grain clusters, and a method for manufacturing abrasive grains. [Background technology]

[0002] Generally, tools such as grinding wheels that use abrasive grains have the problem that the grains wear down during the processing process, reducing the cutting edge and reducing processing efficiency. To reduce this problem, abrasive grains that are easy to break, that is, abrasive grains with high friability, are used.

[0003] For example, when processing a semiconductor wafer made of silicon using a grinding wheel, particularly when the semiconductor wafer is made of SiC, which is a highly hard material that is difficult to grind and polish, diamond abrasive grains, a type of superabrasive grain, can be used, as disclosed in Patent Document 1. If these abrasive grains have high friability, the durability of processing will improve. Therefore, abrasive grains with high friability are required to generate a sustainable cutting edge.

[0004] Evaluation of the microfracture behavior of diamond using a nano-polycrystalline diamond (NPD) spherical indenter has been known (Non-Patent Document 1). Patent Document 2 also describes a study in which abrasive grains are crushed in a container using media, and toughness values ​​are calculated by comparing the change in grain size before and after crushing. Non-Patent Document 2 also evaluates the strength of single abrasive grains using a compression test on CBN (Cubic Boron Nitride). Furthermore, JIS R1639-5, "Fine Ceramics - Measurement Methods for Granule Properties - Part 5: Single Granule Crushing Strength," specifies a method for measuring the crushing strength of granules. JIS Z3844, "Method for Measuring the Fracture Strength and Deformation Strength of Microparticles," specifies a method for measuring the fracture of microparticles and deformation due to elastic-plastic or ductile properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-80847 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-146817 [Non-patent literature]

[0006] [Non-Patent Document 1] "Internal strain distribution and microfracture behavior of various single crystal diamonds for cutting tools," by Hitoshi Kadotani et al., Proceedings of the 2019 Japan Society for Precision Engineering Spring Meeting Academic Lectures, pp. 644-645 [Non-patent document 2] "Study on the grindability of CBN abrasive grains (1st report)", Masaki Takahashi et al., Precision Machinery, Vol. 50, No. 2, pp. 54-58 Summary of the Invention [Problem to be solved by the invention]

[0007] However, friability is due to fracture on a microscopic scale, and none of the above prior art techniques quantitatively evaluates the friability of abrasive grains.

[0008] That is, the evaluation method of Non-Patent Document 1 requires a flat plate-shaped sample, and the abrasive grains actually used in the manufacturing method of the grinding wheel cannot be used as the sample. Also, the toughness value used in the evaluation method of Patent Document 2 cannot necessarily be said to evaluate friability on a microscale. Furthermore, the evaluation method of Non-Patent Document 2 does not allow for quantitative evaluation of friability on a microscale. Moreover, the measurement methods of JIS R1639-5 and JIS Z3844 do not anticipate evaluation of friability on a microscale of abrasive grains.

[0009] The present invention has been made in consideration of the above-mentioned conventional circumstances, and aims to provide a method for evaluating abrasive grains that can quantitatively evaluate the friability of abrasive grains on a microscale. Another aim is to provide a method for inspecting abrasive grain clusters using sample abrasive grains sampled from the abrasive grain clusters. A further aim is to provide a method for manufacturing abrasive grains that includes the method for evaluating abrasive grains or the method for inspecting abrasive grain clusters. [Means for solving the problem]

[0010] Generally, when a hard material such as abrasive grains is compressed under a compressive load, it undergoes brittle fracture with a very small amount of displacement, fragmenting, and the compressive load is no longer applied. However, if the abrasive grains have the characteristic of breaking down on a microscopic scale, gradually compressing the abrasive grains will cause them to continuously deform and break down under the compressive load, accompanied by the generation of microscopic fragments and cracks. The amount of displacement at this time is overwhelmingly greater than the amount of displacement expected from the elasticity or plasticity of the abrasive grain material. The inventor discovered this phenomenon and completed the present invention.

[0011] The first teaching method for evaluating an abrasive grain includes a compression step of applying a compressive load to an evaluation object, and a measurement step of acquiring a deformation characteristic exhibited by the evaluation object during the compression step, and is a method for evaluating the evaluation object based on the deformation characteristic, The evaluation object is an abrasive grain, The deformation characteristic is characterized by microfracturing of the abrasive grains.

[0012] According to the abrasive grain evaluation method of the first teaching, the abrasive grain is the evaluation object, and micro-fracture of the abrasive grain is included in the deformation characteristics, so that the fracturability of the abrasive grain on a micro-scale can be quantitatively evaluated. Here, micro-fracture refers to a phenomenon in which, when a compressive load is applied to the abrasive grain, the abrasive grain undergoes displacement while undergoing a compressive load, accompanied by at least one of fracture and crack generation, before the abrasive grain breaks down. Micro-fracture is a phenomenon that occurs before the abrasive grain breaks down, and once the abrasive grain breaks down, the abrasive grain breaks down into fragments and is no longer subjected to a compressive load.

[0013] Therefore, the evaluation method of abrasive grains of the first teaching quantitatively indicates the friability of abrasive grains on a microscopic scale based on deformation characteristics, and the friability of abrasive grains can be determined. Therefore, this evaluation method makes it possible to predict with high accuracy the polishing ability or grinding ability of tools such as grinding wheels that use abrasive grains.

[0014] The second teaching inspection method for abrasive grain groups includes a compression step of applying a compressive load to an evaluation object, and a measurement step of acquiring deformation characteristics exhibited by the evaluation object during the compression step, and is a method of inspecting the evaluation object based on the deformation characteristics, The evaluation object is a sample abrasive grain sampled from a group of abrasive grains, The deformation characteristics include micro-fracture of the sample abrasive grains. In this case, it is possible to predict with high accuracy the polishing or grinding ability of a tool such as a grinding wheel using a group of abrasive grains sampled from the sample abrasive grains.

[0015] The manufacturing method of the abrasive grains of the third teaching is characterized by including an abrasive grain inspection step according to the abrasive grain evaluation method of the first teaching, or an abrasive grain inspection step according to the abrasive grain group inspection method of the second teaching. In this case, it is possible to manufacture the desired abrasive grains. [Effects of the Invention]

[0016] The first teaching's method for evaluating abrasive grains allows for quantitative evaluation of the friability of abrasive grains on a microscopic scale. The second teaching's method for inspecting abrasive grain groups allows for quantitative evaluation of the friability of abrasive grain groups on a microscopic scale. The third teaching's method for manufacturing abrasive grains allows for the production of desired abrasive grains. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a schematic cross-sectional view showing the main parts of a compression tester used in Test 1 of Examples 1 and 2. [Figure 2]10 is a graph showing a first relationship between test force and displacement, a second relationship between stress and displacement, a third relationship between test force and relative displacement, a fourth relationship between stress and relative displacement, a fifth relationship between breaking point test force and breaking point displacement, a sixth relationship between breaking point stress and breaking point displacement, a seventh relationship between breaking point test force and breaking point relative displacement, and an eighth relationship between breaking point stress and breaking point relative displacement, relating to Test 1 of Example 1. [Figure 3] 10 is a graph showing the relationship between the amount of wear of abrasive grains and the cumulative amount of processing of a wafer in Test 3 of Example 1. [Figure 4] 10 is a graph showing the relationship between test force and displacement amount in Test 1 of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0018] The material of the abrasive grains to be evaluated is not particularly limited, but examples include diamond, CBN, silicon carbide, alumina, zirconia, ceria, chromium oxide, iron oxide, silica, titania, etc., as well as mixtures of these. In particular, when used for polishing semiconductor wafers, the abrasive grains can be diamond or CBN.

[0019] When the abrasive grain material is diamond, the diamond preferably contains a metal. In this case, there is a tendency for the diamond to be highly micro-fracturable, and tools such as grinding wheels can exhibit high processing durability. The metal contained in the diamond is not particularly limited, but it is preferable that it has a thermal expansion greater than that of the diamond crystal, such as transition metals, particularly Fe, Ni, Co, Mn, etc. Furthermore, the metal may be derived from the diamond manufacturing process or may be intentionally introduced. The metal contained in the diamond may exist as metal particles in the diamond crystal, may react with the diamond crystal to form a chemical bond, or may be diffused in the diamond crystal lattice.

[0020] The content of metal contained in diamond is not particularly limited, but for the high friability of abrasive grain, it is preferably 0.1 mass% or more, more preferably 0.2 mass% or more, even more preferably 0.3 mass% or more, particularly preferably 0.5 mass% or more.On the other hand, if the content of metal contained in diamond is too large, the hardness and strength of abrasive grain will decrease, so it is preferably 10 mass% or less, more preferably 5 mass% or less, even more preferably 3 mass% or less, particularly preferably 1 mass% or less.

[0021] In the measurement step, it is preferable to obtain the test force acting on the abrasive grain due to the compressive load and the displacement of the abrasive grain due to the compressive load. The deformation characteristics preferably include a first relationship consisting of the test force and the displacement. In this case, the abrasive grain can be evaluated based on the shape of the graph of the first relationship between the test force and the displacement.

[0022] The compression tester preferably includes a sample stage having a mounting surface on which abrasive grains are placed, an indenter that pressurizes the abrasive grains, a drive unit that applies a test force between the sample stage and the indenter under predetermined conditions after the abrasive grains on the mounting surface come into contact with the indenter, and a measurement unit that obtains deformation characteristics. The conditions preferably allow for adjustment of the displacement amount per unit time or the test force. The inventors have perfected the present invention using this type of compression tester. Adjusting the displacement amount per unit time or the test force makes it easy to confirm micro-fracture properties. The inventors have perfected the present invention using this type of compression tester.

[0023] The surface on which the indenter presses the abrasive grains is preferably a plane perpendicular to the pressure direction. Furthermore, the diameter of the indenter is preferably at least 1 time the grain size of the abrasive grains, more preferably at least 1.5 times, and particularly preferably at least 2 times, in order to apply an appropriate compressive load to the abrasive grains. Furthermore, if the diameter of the indenter is too large, the indenter may come into contact with abrasive grains other than those scattered on the sample stage. Therefore, the diameter of the indenter is preferably no more than 10 times the grain size of the abrasive grains, more preferably no more than 7 times, even more preferably no more than 5 times, and particularly preferably no more than 3 times.

[0024] The method of applying test force in a compression testing machine is not particularly limited, and either displacement control or test force control may be used. Displacement control is a control method in which the test force is increased so as to enable the displacement to be increased by a constant value every predetermined time. Test force control is a control method in which the test force is increased by a constant value every predetermined time while the displacement is measured.

[0025] When controlling the amount of displacement, if the speed at which the test force is applied, i.e., the loading rate, is too fast, the abrasive grains will deform suddenly, making it difficult to accurately evaluate their deformation behavior. Therefore, the speed at which the test force is applied, where the initial height is the distance between the mounting surface of the sample table in the compression tester and the indenter at the moment it contacts the abrasive grains, is preferably equal to or less than the initial height / second, more preferably equal to or less than (initial height / 2) / second, even more preferably equal to or less than (initial height / 5) / second, even more preferably equal to or less than (initial height / 10) / second, and particularly preferably equal to or less than (initial height / 20) / second. Furthermore, if the speed at which the test force is applied is too slow, the inspection efficiency will decrease. Therefore, a speed of equal to or more than (initial height / 500) / second is preferred, more preferably equal to or more than (initial height / 200) / second, even more preferably equal to or more than (initial height / 100) / second, even more preferably equal to or more than (initial height / 50) / second, and particularly preferably equal to or more than (initial height / 30) / second.

[0026] In the measurement step, the test force and displacement are acquired, and the test force can be converted into stress based on a specific value related to the size and / or height of the abrasive grain before the compression step. The deformation characteristics preferably include a second relationship between stress and displacement. In this case, the abrasive grain can be evaluated based on the shape of the stress-displacement graph of the second relationship.

[0027] The size (initial size) and height (initial height) of the abrasive grains before the compression step are not particularly limited, as long as the test force and displacement of the compression tester can be controlled and the measurement accuracy and range are sufficient for the purpose. However, if the initial size or height is too small, the measurement accuracy generally decreases. Therefore, for example, the initial height is preferably 0.03 μm or more, more preferably 0.1 μm or more, even more preferably 0.3 μm or more, even more preferably 1 μm or more, even more preferably 2 μm or more, and particularly preferably 5 μm or more.

[0028] The initial size of the abrasive grain can be the grain size, and more specifically, the minor axis, major axis, Feret diameter, equivalent circle diameter, etc., as well as various values ​​obtained by observing the abrasive grain or by image analysis, and various values ​​obtained by using these. For example, when the minor axis x major axis is used as the specific value, the cross-sectional area of ​​the abrasive grain is assumed to be the minor axis x major axis, and the stress can be obtained by dividing the test force by the cross-sectional area.

[0029] Furthermore, if the particle size of the abrasive grains is defined as the average of the minor axis and the major axis, a large particle size will require a large test force. Therefore, the particle size is preferably 10,000 μm or less, more preferably 1,000 μm or less, even more preferably 500 μm or less, even more preferably 200 μm or less, and particularly preferably 100 μm or less.

[0030] If the particle size of the abrasive grains is too small, the abrasive grains tend to aggregate, making it difficult to compress the abrasive grains as individual grains. Therefore, the particle size is preferably 0.03 μm or more, more preferably 0.1 μm or more, even more preferably 0.3 μm or more, even more preferably 1 μm or more, even more preferably 2 μm or more, and particularly preferably 5 μm or more.

[0031] For the same reason, the median diameter of the particle size distribution based on the number of abrasive grains and abrasive grain groups obtained by laser diffraction is preferably 0.03 μm or more, more preferably 0.1 μm or more, even more preferably 0.3 μm or more, even more preferably 1 μm or more, even more preferably 2 μm or more, and particularly preferably 5 μm or more. Also, this median diameter is preferably 10,000 μm or less, more preferably 1,000 μm or less, even more preferably 500 μm or less, even more preferably 200 μm or less, and particularly preferably 100 μm or less.

[0032] In the measurement step, the test force and displacement are acquired, and the displacement can be converted into a relative displacement based on a specific value related to the size and / or height of the abrasive grain before the compression step. The deformation characteristics preferably include a third relationship between the test force and the relative displacement. In this case, the abrasive grain can be evaluated based on the shape of the graph of the third relationship between the test force and the relative displacement.

[0033] In the measurement process, the test force and displacement are acquired, and the test force can be converted into stress, and the displacement into relative displacement. The deformation characteristics preferably include a fourth relationship between stress and relative displacement. In this case, the abrasive grains can be evaluated based on the shape of the graph of the fourth relationship between stress and relative displacement.

[0034] It is preferable to perform the compression and measurement steps until the abrasive grains are broken. This is because the abrasive grains can be evaluated based on the breaking point test force, breaking point displacement, breaking point stress, and breaking point relative displacement, which will be described later. The inventors have confirmed that even for the same type of abrasive grains, differences in breaking point test force, etc. occur when different manufacturing methods are used. The more micro-friable the abrasive grain, the greater the breaking point test force, etc.

[0035] In the measurement process, the test force and displacement are acquired, and the breaking point test force, which is the test force at which the abrasive grain breaks, and the breaking point displacement, which is the displacement at which the abrasive grain breaks, can also be acquired. The deformation characteristics preferably include a fifth relationship consisting of the breaking point test force and the breaking point displacement. In this case, the abrasive grain can be evaluated based on the coordinates of the fifth relationship (breaking point test force, breaking point displacement).

[0036] In the measurement step, the test force and displacement are acquired, and the breaking point test force and breaking point displacement are obtained. The breaking point test force can be converted to breaking point stress based on a specific value related to the size and / or height of the abrasive grain before the compression step. The deformation characteristics preferably include a sixth relationship consisting of the breaking point stress and the breaking point displacement. In this case, the abrasive grain can be evaluated based on the coordinates (breaking point stress, breaking point displacement) of the sixth relationship.

[0037] In the measurement step, the test force and displacement are acquired, and the fracture point test force and fracture point displacement are obtained, and the fracture point displacement can be converted to the fracture point relative displacement based on a specific value related to the size and / or height of the abrasive grain before the compression step. The deformation characteristics preferably include a seventh relationship consisting of the fracture point test force and the fracture point relative displacement. In this case, the abrasive grain can be evaluated based on the coordinates of the seventh relationship (fracture point test force, fracture point relative displacement).

[0038] In the measurement step, the test force and displacement are acquired, and the breaking point test force and breaking point displacement are obtained. The breaking point test force can be converted into a breaking point stress based on a specific value related to the size and / or height of the abrasive grain before the compression step, and the breaking point displacement can be converted into a breaking point relative displacement based on the specific value. The deformation characteristics preferably include an eighth relationship consisting of the breaking point stress and the breaking point relative displacement. In this case, the abrasive grain can be evaluated based on the coordinates of the eighth relationship (breaking point stress, breaking point relative displacement).

[0039] Even in the case of test force control, if the speed at which the test force is applied is too fast, the abrasive grains will deform all at once, making it impossible to accurately evaluate the deformation behavior. Therefore, in terms of the stress applied to the abrasive grains, a speed of 10 GPa / sec or less is preferable, 5 GPa / sec or less is more preferable, 2 GPa / sec or less is even more preferable, 1 GPa / sec or less is even more preferable, and 0.5 GPa / sec or less is particularly preferable. Furthermore, if the speed at which the test force is applied is too slow, the inspection efficiency decreases. Therefore, a speed of 0.005 GPa / sec or more is preferable, 0.01 GPa / sec or more is more preferable, 0.02 GPa / sec or more is even more preferable, 0.05 GPa / sec or more is even more preferable, and 0.1 GPa / sec or more is particularly preferable. Here, stress = test force / (π × (abrasive grain diameter / 2) 2.

[0040] When controlling the test force, the speed at which the test force is applied should be determined based on the breaking point stress. If the test force is applied too quickly, the abrasive grains will break in a short time, making it difficult to accurately evaluate the deformation behavior. Therefore, a speed of (breaking point stress x 2) / second or less is preferable, (breaking point stress) / second or less is more preferable, (breaking point stress / 2) / second or less is even more preferable, (breaking point stress / 5) / second or less is even more preferable, and (breaking point stress / 10) / second or less is particularly preferable. Furthermore, if the test force is applied too slowly, the inspection efficiency will decrease. Therefore, a speed of (breaking point stress / 200) / second or more is preferable, (breaking point stress / 100) / second or more is more preferable, (breaking point stress / 50) / second or more is even more preferable, (breaking point stress / 30) / second or more is even more preferable, and (breaking point stress / 20) / second or more is particularly preferable.

[0041] According to the inventor's test results, it is preferable that the relative displacement of the fracture point is 0.05 or more. If the relative displacement of the fracture point is 0.05 or more, it can be said that the abrasive grain has a certain level of micro-friability or more, and this evaluation method can provide a highly reliable evaluation. It is preferable that the relative displacement of the fracture point is 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, or 0.3 or more. In other words, it is preferable that the test object has a certain level of micro-friability or more.

[0042] Preferably, five or more sample abrasive grains are selected from the abrasive grain group. The friability of the abrasive grain group is preferably determined based on whether the average value of the relative displacement of the fracture point is 0.05 or greater. The inventors determined the friability of the abrasive grain group in this manner. If the average value of the relative displacement of the fracture point is less than 0.05, there is significant variation within the abrasive grain group, resulting in insufficient reliability. More preferably, the friability of the abrasive grain group is determined based on whether the average value of the relative displacement of the fracture point is 0.1 or greater, even more preferably 0.15 or greater, even more preferably 0.20 or greater, even more preferably 0.25 or greater, and particularly preferably 0.30 or greater. In other words, it is preferable for the abrasive grains to have a certain level of micro-friability, and the reliability of the test is higher than when testing abrasive grain groups with low micro-friability.

[0043] It is preferable that the abrasive grains are primarily composed of a material with a Young's modulus of 50 GPa or more. The inventors have confirmed the effects of the present invention using abrasive grains primarily composed of a material with a Young's modulus of 50 GPa or more in the literature. The material primarily comprising the abrasive grains preferably has a Young's modulus of 70 GPa or more, more preferably 100 GPa or more, even more preferably 200 GPa or more, even more preferably 400 GPa or more, even more preferably 600 GPa or more, and particularly preferably 800 GPa or more. In these cases, the abrasive grains are less susceptible to elastic deformation, making it possible to suitably evaluate micro-friability.

[0044] The material that primarily constitutes the abrasive grains preferably accounts for 60% by mass or more of the abrasive grains, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and particularly preferably 99% by mass or more.

[0045] The material that mainly constitutes the abrasive grains is not particularly limited, but includes diamond, CBN, silicon carbide, alumina, zirconia, ceria, chromium oxide, iron oxide, silica, titania, etc., as well as mixtures thereof. In particular, when used to polish semiconductor wafers, the material that mainly constitutes the abrasive grains is preferably diamond or CBN superabrasive grains. These are abrasive grains used to process difficult-to-process materials, so the effect of internal stress control is preferably exerted.

[0046] It is preferable that the abrasive grains contain impurities. The inclusion of impurities improves micro-fracturability. The metals that can be impurities are not particularly limited, but are preferably those with a larger thermal expansion than the material that mainly constitutes the abrasive grains, such as transition metals, particularly Fe, Ni, Co, Mn, etc. In particular, when the abrasive grains are diamond, it is preferable that these metals are contained. Furthermore, the metal may be derived from the manufacturing process of the abrasive grains or may be intentionally introduced. The metal contained in the abrasive grains may exist as metal particles in the crystals of the abrasive grains, may react with the crystals of the abrasive grains to form chemical bonds, or may be diffused in the crystal lattice of the abrasive grains.

[0047] The content of impurities contained in the abrasive grains is not particularly limited, but in order to ensure high friability of the abrasive grains, it is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more. On the other hand, if the content of impurities contained in the abrasive grains is too high, the hardness and strength of the abrasive grains will decrease, so it is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less.

[0048] The abrasive grains can be used to polish semiconductor wafers. The inventors have confirmed this effect in tests using SiC wafers. In this case, the need for the present invention is high.

[0049] A plurality of sample abrasive grains can be sampled from the abrasive grain group. In the measurement process, it is preferable to obtain an average deformation characteristic by averaging the deformation characteristics exhibited by each sample abrasive grain, and then inspect the abrasive grain group based on the average deformation characteristic. In this case, the friability of a plurality of abrasive grain groups manufactured by the same manufacturing method can be evaluated.

[0050] The abrasive grains preferably have internal stress. In this case, the abrasive grains tend to have a certain degree of microfracture resistance, resulting in high reliability of the test. The Raman spectrum of diamonds is particle size dependent, and when the particle size is below 10 μm, it shifts to the low wavenumber side. Therefore, the particle size of the abrasive grains is determined as the circle equivalent diameter obtained by image analysis of a microscope image. In this case, if the abrasive grains are diamond, Raman spectra are obtained from at least one location per abrasive grain with a particle size of 10 μm or more selected from 100 or more abrasive grains. The average peak position (Raman shift) of the Raman peaks (peaks with a peak position of 1320-1335 / cm and a half-width of 10 / cm or less) obtained for a total of 500 or more abrasive grains is preferably 1332.0 / cm or less, more preferably 1331.5 / cm or less, even more preferably 1331.0 / cm or less, even more preferably 1330.5 / cm or less, and particularly preferably 1330.0 / cm or less. Since the Raman peak position (Raman shift) of diamond crystal is 1333.0 / cm, it can be said that such abrasive grains have internal tensile stress. [Example]

[0051] The present teachings are illustrated below by Tests 1 to 3 in Example 1. (1) Test 1 The following abrasive grain groups, Samples A to C, were prepared. Sample A: Abrasive grains made of pseudo-polycrystalline diamond ("FRM-DN40-60" manufactured by Global Diamond Co., Ltd.) This abrasive grain group was purchased commercially. The D50 of this abrasive grain group was 45 μm in the volume-based particle size distribution obtained by laser diffraction (dispersion medium: water). Furthermore, according to component analysis by XRF, this abrasive grain group contained 0.176 mass% Ni and 0.389 mass% Mn.

[0052] Sample B: The abrasive grains of Sample A were heated in air at a rate of 100°C / hour, held at 500°C for 3 hours, and then cooled to room temperature at a rate of 100°C / hour. The weight loss of the abrasive grains due to the heat treatment was less than 1%.

[0053] Sample C: The abrasive grains of Sample A were heated at 100°C / hour in a nitrogen atmosphere containing 3% hydrogen, held at 1000°C for 3 hours, and then cooled to room temperature at 100°C / hour. The weight loss of the abrasive grains due to the heat treatment was less than 1%.

[0054] Also, a compression tester (Shimadzu Corporation, "Micro Autograph MST-1HR") 10 was prepared. As shown in FIG. 1, this compression tester 10 has a sample stage 1, an indenter 3, a drive unit 5, and a measurement unit 7.

[0055] The sample stage 1 has a hardness of 700 and has a horizontal mounting surface 1a on which the abrasive grains S are placed. The indenter 3 is made of diamond and applies pressure to the abrasive grains S. The lower surface 3a of the indenter 3, which applies pressure to the abrasive grains S, is parallel to the mounting surface 1a and perpendicular to the pressure direction. The diameter of the indenter 3 is 200 μm, which is 3 to 5 times the grain size of the abrasive grains S in order to apply an appropriate compression load to the abrasive grains S.

[0056] After the abrasive grains S on the mounting surface 1a come into contact with the indenter 3, the driving unit 5 applies a test force under predetermined conditions between the sample stage 1 and the indenter 3 by controlling the amount of displacement. The condition is adjustable in terms of the amount of displacement (μm) per unit time. Note that a compression testing machine that can adjust the test force per unit time can also be used.

[0057] The measurement unit 7 has a load cell and can measure deformation characteristics, including the amount of displacement (μm) over a certain time period until the abrasive grain S breaks and the test force (N). The measurement unit 7 has a stereomicroscope positioned perpendicular to the pressure direction. The stereomicroscope monitors the side of the abrasive grain S, and the grain size d is determined by measuring the maximum horizontal length (perpendicular to the pressure direction) displayed on the monitor using a micrometer attached to the XY stage. The measurement unit 7 also has a displacement sensor and can measure the distance between the mounting surface 1a and the bottom surface 3a of the abrasive grain S at the moment of contact as the initial height T (μm) of the abrasive grain S.

[0058] Five abrasive grains (sample abrasive grains) S were randomly selected from the abrasive grain groups of samples A to C, and each abrasive grain S was placed one by one on the mounting surface 1a of the sample stage 1, and a compression fracture test was performed under the following conditions (compression step).

[0059] Load cell capacity: 500N (50N range) Load speed (constant speed): 2μm / sec Stroke origin test force: 0.02N

[0060] In the measurement section 7, the test force (N) acting on the abrasive grain S due to the compressive load until the abrasive grain S breaks and the displacement (μm) of the abrasive grain due to the compressive load were obtained as deformation characteristics (measurement process).

[0061] As a result of the compression fracture test, the displacement was determined in increments of 0.02 μm for one abrasive grain S in each of the abrasive grain groups of samples A to C, and a graph showing the relationship between the test force and the displacement (test force-displacement graph) was obtained, as shown in Figure 2. The test force at the time when the abrasive grain S broke is the fracture point test force, and the displacement at that time is the fracture point displacement.

[0062] Also, assuming that the abrasive grain S is cylindrical with a base of radius r (= d / 2), the cross-sectional area of ​​each abrasive grain S before the compression process (πr 2 ) was defined as the first specific value. The test force was divided by the first specific value to obtain a graph (stress-displacement graph) showing the relationship between stress and displacement, as shown in Figure 3. The stress at the time when the abrasive grain S broke was the breaking point stress.

[0063] On the other hand, the breaking strength Cs (GPa) was calculated using the following formula (JIS-R1639-5), where Pf is the test force at the breaking point (N), which is the test force at the time when each abrasive grain S broke, and d (μm) is the grain size of the abrasive grain S. Breaking strength Cs = 2.48 × Pf / (πd 2 )

[0064] In addition, the breaking point stress Ps (GPa), which is the stress at which the abrasive grain S breaks, was calculated using the following formula. Breaking point stress Ps=Pf / (πr 2 )

[0065] Furthermore, the initial height T was set as a second specific value, and the displacement (μm) was divided by the second specific value to obtain the relative displacement, and the breaking point relative displacement Pd2 was calculated using the following formula. Breaking point relative displacement Pd2 = Breaking point displacement Pd1 / Initial height T

[0066] A graph showing the relationship between the test force and the relative displacement (test force-relative displacement graph) is also shown in FIG. 3, and a graph showing the relationship between the stress and the relative displacement (stress-relative displacement graph) is also shown in FIG.

[0067] In addition, the slope t of the stress-relative displacement graph was calculated using the following formula: Stress-relative displacement graph slope t = breaking point stress Ps / breaking point relative displacement Pd2

[0068] Tables 1 to 3 show the initial height T, particle size d, fracture point displacement Pd1, fracture point test force Pf, fracture point stress Ps, fracture point relative displacement Pd2, slope t of the line connecting the origin and the fracture point on the stress-relative displacement graph, and fracture strength Cs for each abrasive grain S of Samples A to C. Table 1 shows the results for each abrasive grain S of Sample A, Table 2 shows the results for each abrasive grain S of Sample B, and Table 3 shows the results for each abrasive grain S of Sample C.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] The graph in Figure 2 shows the coordinates (fracture point test force, fracture point displacement), coordinates (fracture point stress, fracture point displacement), coordinates (fracture point test force, fracture point relative displacement), and coordinates (fracture point stress, fracture point relative displacement).

[0073] From the average values ​​in Tables 1 to 3, it can be seen that the abrasive grain S sampled from the abrasive grain group of sample B has the largest fracture point displacement Pd1, fracture point test force Pf, fracture point stress Ps, and fracture strength Cs, followed by the abrasive grain S sampled from the abrasive grain group of sample A, and the abrasive grain S sampled from the abrasive grain group of sample C has the smallest of the three.

[0074] On the other hand, the abrasive grain S sampled from the abrasive grain group of sample B has the largest relative displacement of the fracture point Pd2, followed by the abrasive grain S sampled from the abrasive grain group of sample C, and the abrasive grain S sampled from the abrasive grain group of sample A has the smallest of the three.

[0075] It can also be seen that the abrasive grain S sampled from the abrasive grain group of sample A has the largest slope t of the stress-displacement graph, followed by the abrasive grain S sampled from the abrasive grain group of sample B, and the abrasive grain S sampled from the abrasive grain group of sample C has the smallest slope t of the three.

[0076] 2, it can be seen that the abrasive grain groups of Samples A to C each produce a different line diagram. Note that this line diagram is for one abrasive grain from each of Samples A to C, and it is preferable to draw the line diagram using an average value obtained using multiple abrasive grains, as shown in Tables 1 to 3.

[0077] (2) Test 2 Using a microscopic laser Raman spectrometer (Horiba, Ltd.'s "LabRAM HR Evolution"), Raman spectra were obtained at five measurement points for each of the 100 abrasive grains in the abrasive grain group for Samples A to C under the following conditions, and the average value of the diamond peak position was calculated. The equivalent circle diameter calculated from the microscopic images of all analyzed abrasive grains was within the range of 25 to 75 μm.

[0078] Measurement room temperature: 24°C Calibration sample: Si Excitation wavelength: 532 nm Grating: 1800gr / mm Exposure time: 8 seconds Number of times accumulated: 2 times

[0079] The obtained Raman spectrum was subjected to baseline correction, peak search, and fitting using software (Horiba, Ltd. "Labspec6"). The results are shown in Table 4.

[0080] [Table 4]

[0081] From Table 4, it can be seen that the average value of the Raman peak position is smallest for Sample C, followed by Sample B and Sample A. It is known that the Raman peak position changes depending on the internal stress. When the abrasive material is diamond, the original Raman peak position is about 1333 / cm, but the larger the difference from this value, the higher the internal stress is, and the amount of change per unit internal stress is 2cm. -1 / GPa. In the case of the abrasive grains in Samples A to C, the Raman peak position shifts to the lower wavenumber side, indicating the presence of tensile stress. The magnitude of tensile stress increases in the order of Sample C, Sample B, and Sample A.

[0082] It is known that the presence of internal stress affects the friability of diamonds, with greater internal stress resulting in higher friability. In other words, the Raman spectra suggest that the order of friability is highest for Sample C, followed by Sample B and then Sample A.

[0083] (3) Test 3 Glass powder (TOMATEC Corporation "TMX-501F") was prepared and a paste of the glass powder was printed on three alumina substrates. Several abrasive grains were randomly selected from the abrasive grain groups of Samples A to C above and scattered on the paste, respectively, to obtain three types of unfired test pieces.

[0084] After drying the paste for each unsintered test piece, it was fired in air at 570°C for two hours to soften the glass powder, and then each unsintered test piece was cooled to room temperature. In this way, the abrasive grains of Samples A to C were fixed to the substrate with glass, yielding three types of fired test pieces. Excess abrasive grains were removed from each fired test piece, yielding multiple test pieces A to C, each with one abrasive grain fixed to the substrate. Test piece A had the abrasive grains of Sample A, test piece B had the abrasive grains of Sample B, and test piece C had the abrasive grains of Sample C. The protruding height of the abrasive grains in Test pieces A to C was 18 to 30 μm.

[0085] Using four test pieces A to C each, SiC wafers were ground under the following conditions, and the height of the abrasive grains before and after processing, as well as the depth of the SiC grinding, were measured using a laser microscope. This processing process was repeated two to four times. The average depth of each grinding mark was taken as the average. This test was performed four times for each sample, and the average results are shown in Figure 3.

[0086] Depth of cut: 2 μm Machining speed: 6mm / sec Processing distance: 5mm / pass x 20

[0087] Figure 3 shows that the machining efficiency of SiC increases in the order of Sample B, Sample A, and Sample C. This suggests that Sample B has the physical properties most suitable for machining SiC, i.e., it has the ability to fracture at an appropriate micro-scale.

[0088] Tables 1 to 3 show that the results of the compression fracture test show that sample B has the largest relative fracture point displacement Pd2. Diamond has a high Young's modulus of approximately 1000 GPa, is hardly subject to elastic deformation, and is known to be difficult to plastically deform. Therefore, this result indicates that sample B has the largest displacement due to microfracture, i.e., the highest microfracture resistance, which is consistent with the fact that sample B, as mentioned above, has the highest SiC processing efficiency.

[0089] On the other hand, sample C was estimated to have the highest friability based on the Raman peak positions shown in Table 4. From Tables 1 to 3, sample C has the lowest fracture strength Cs and the fracture point relative displacement Pd2 is equivalent to that of sample A, so it can be said to be an abrasive grain with high friability (large cracks occur under relatively weak stress) but low micro-friability. In other words, when it comes to the purpose of SiC machining, sample C is thought to have been too brittle, resulting in the lowest SiC machining efficiency, as shown in Figure 3.

[0090] The above results demonstrate that the compression fracture test can be used to evaluate diamond abrasive grains. In particular, the relative fracture point displacement Pd2 can be used to evaluate micro-fracture.

[0091] Therefore, it can be seen that the evaluation method of Example 1 quantitatively indicates the friability of the abrasive grains S on a microscopic scale based on the deformation characteristics, and makes it possible to determine the friability of the abrasive grains S. Therefore, this evaluation method makes it possible to predict with high accuracy the polishing ability or grinding ability of a tool such as a grinding wheel that uses the abrasive grains S.

[0092] Furthermore, if this evaluation method is used as an abrasive grain inspection step in a manufacturing method of abrasive grains, it becomes possible to manufacture desired abrasive grains.Furthermore, if this evaluation method is used as an abrasive grain inspection step in a manufacturing method of a grinding wheel, it becomes possible to manufacture desired grinding wheels. [Example]

[0093] The present teachings are illustrated below by Tests 1 to 3 in Example 2. (1) Test 1 The following abrasive grain groups, Samples D and E, were prepared. Sample D: Diamond abrasive grains (Global Diamond Co., Ltd. "FRM20-30")

[0094] Sample E: The abrasive grains of Sample D were heated in air at a rate of 100°C / hour, held at 500°C for 3 hours, and then cooled to room temperature at a rate of 100°C / hour. The weight loss of the abrasive grains due to the heat treatment was less than 1%.

[0095] A compression tester (Shimadzu Corporation, "Micro Compression Tester MCT-510") 20 was also prepared. This compression tester 20 also had the configuration shown in FIG. 1. However, the lower surface 3a, where the indenter 3 presses the abrasive grain S, was parallel to the mounting surface 1a and had a diameter of 50 μm. The abrasive grain S was monitored from above (in the pressure direction) using a stereomicroscope, and the minor and major axes were measured, and their average value was taken as the grain size d. The side of the sample was monitored from a fixed position using a stereomicroscope from a direction perpendicular to the compression direction, and the maximum length of the abrasive grain S in the vertical direction (compression direction) as seen on the monitor was measured and taken as the initial height T. While the compression tester 10 of Example 1 performed displacement control, the compression tester 20 performed test force control. The other configurations and calculation formulas of the compression tester 20 were the same as those of the compression tester 10 of Example 1.

[0096] Ten abrasive grains S were randomly selected from the abrasive grain groups of samples D and E, and each evaluation grain S was placed one by one on the mounting surface 1a of the sample stage 1, and a compression fracture test was carried out under the following conditions (compression step).

[0097] Load speed: 103.7mN / sec

[0098] Tables 5 and 6 show the initial height T, particle size d, fracture point displacement Pd1, fracture point test force Pf, fracture point stress Ps, fracture point relative displacement Pd2, slope t of the line connecting the origin and the fracture point on the stress-relative displacement graph, and fracture strength Cs for each abrasive grain S of Samples D and E (measurement process). Table 5 shows the results for each abrasive grain S of Sample D, and Table 6 shows the results for each abrasive grain S of Sample E.

[0099] [Table 5]

[0100] [Table 6]

[0101] From the average values ​​in Tables 5 and 6, it can be seen that the abrasive grain group of sample E is larger than the abrasive grain group of sample D in all of the fracture point displacement Pd1, fracture point test force Pf, fracture point stress Ps, fracture point relative displacement, and slope t of the stress-displacement graph.

[0102] (2) Test 2 As in Example 1, Raman spectra were obtained at five measurement points for each of 100 abrasive grains in the abrasive grain groups of Samples D and E, and the average value of the diamond peak position was calculated. The equivalent circle diameters of all analyzed abrasive grains were within the range of 15 to 35 μm. The results are shown in Table 7.

[0103] [Table 7]

[0104] From Table 7, it can be seen that the average value of the Raman peak position is smaller for Sample E than for Sample D. Therefore, it can be said that Sample E has a larger internal stress, and it is estimated that it has a higher crushability.

[0105] From the above, it was shown that there is a reasonable correlation between the relative displacement of the fracture point in the compression fracture test and the Raman spectrum, and it is clear that it is possible to inspect abrasive grains. [Industrial Applicability]

[0106] The present invention can be used in a method for manufacturing a grinding wheel or the like. [Explanation of symbols]

[0107] S...Abrasive grain 10, 20...Compression testing machine 1a...Placement surface 1...Sample stage 3...Indenter 5...Drive unit 7...Measuring section Pd1: Breaking point displacement Pd2: Relative displacement of breaking point

Claims

1. A method for evaluating an evaluation object based on deformation characteristics, the method comprising: a compression step of applying a compressive load to an evaluation object; and a measurement step of acquiring deformation characteristics exhibited by the evaluation object during the compression step, The evaluation object is an abrasive grain, The method for evaluating abrasive grains, wherein the deformation characteristics include microfracture of the abrasive grains.

2. In the measuring step, a test force acting on the abrasive grain due to the compressive load and a displacement amount of the abrasive grain due to the compressive load are obtained; 2. The method for evaluating abrasive grains according to claim 1, wherein the deformation characteristics include a first relationship between the test force and the displacement.

3. In the measuring step, a test force acting on the abrasive grain due to the compressive load and a displacement amount of the abrasive grain due to the compressive load are acquired, and the test force is converted into a stress based on a specific value related to the size and / or height of the abrasive grain before the compressing step is performed; 2. The method for evaluating abrasive grains according to claim 1, wherein the deformation characteristics include a second relationship between the stress and the amount of displacement.

4. In the measuring step, a test force acting on the abrasive grain due to the compressive load and a displacement amount of the abrasive grain due to the compressive load are acquired, and the displacement amount is converted into a relative displacement amount based on a specific value related to the size and / or height of the abrasive grain before the compressing step is performed; 2. The method for evaluating abrasive grains according to claim 1, wherein the deformation characteristics include a third relationship between the test force and the relative displacement.

5. In the measuring step, a test force acting on the abrasive grain due to the compressive load and a displacement amount of the abrasive grain due to the compressive load are acquired, and the test force is converted into a stress based on a specific value relating to the size and / or height of the abrasive grain before the compressing step, and the displacement amount is converted into a relative displacement amount based on the specific value; 2. The method for evaluating abrasive grains according to claim 1, wherein the deformation characteristics include a fourth relationship between the stress and the relative displacement.

6. 2. The method for evaluating abrasive grains according to claim 1, wherein the compressing step and the measuring step are carried out until the abrasive grains are broken.

7. In the measuring step, a test force acting on the abrasive grain due to the compressive load, a displacement amount of the abrasive grain due to the compressive load, a breaking point test force which is the test force when the abrasive grain breaks, and a breaking point displacement amount which is the displacement amount when the abrasive grain breaks are obtained; 7. The method for evaluating abrasive grains according to claim 6, wherein the deformation characteristics include a fifth relationship between the breaking point test force and the breaking point displacement.

8. In the measurement step, a test force acting on the abrasive grain due to the compressive load, a displacement amount of the abrasive grain due to the compressive load, a breaking point test force which is the test force when the abrasive grain breaks, and a breaking point displacement amount which is the displacement amount when the abrasive grain breaks are obtained, and the breaking point test force is converted into a breaking point stress based on a specific value related to the size and / or height of the abrasive grain before the compression step is performed, 7. The method for evaluating abrasive grains according to claim 6, wherein the deformation characteristics include a sixth relationship between the breaking point stress and the breaking point displacement.

9. In the measurement step, a test force acting on the abrasive grain due to the compressive load, a displacement amount of the abrasive grain due to the compressive load, a fracture point test force which is the test force when the abrasive grain breaks, and a fracture point displacement amount which is the displacement amount when the abrasive grain breaks are obtained, and the fracture point displacement amount is converted into a fracture point relative displacement amount based on a specific value related to the size and / or height of the abrasive grain before the compression step is performed, 7. The method for evaluating abrasive grains according to claim 6, wherein the deformation characteristics include a seventh relationship between the breaking point test force and the breaking point relative displacement.

10. In the measuring step, a test force acting on the abrasive grain due to the compressive load, a displacement amount of the abrasive grain due to the compressive load, a breaking point test force which is the test force when the abrasive grain breaks, and a breaking point displacement amount which is the displacement amount when the abrasive grain breaks are obtained, and the breaking point test force is converted into a breaking point stress using a specific value related to the size and / or height of the abrasive grain before the compression step is performed as a reference, and the breaking point displacement amount is converted into a breaking point relative displacement amount using the specific value as a reference, 7. The method for evaluating abrasive grains according to claim 6, wherein the deformation characteristics include an eighth relationship formed by the breaking point stress and the breaking point relative displacement.

11. The method for evaluating abrasive grains according to claim 9 or 10, wherein the relative displacement of the breaking point is 0.05 or more.

12. 10. The method for evaluating abrasive grains according to claim 1, wherein the abrasive grains are mainly made of a material having a Young's modulus of 50 GPa or more.

13. The method for evaluating abrasive grains according to claim 1 or 6, wherein the abrasive grains contain impurities.

14. 10. The method for evaluating abrasive grains according to claim 1, wherein the abrasive grains are used for polishing semiconductor wafers.

15. A method for inspecting an evaluation object based on deformation characteristics, comprising: a compression step of applying a compressive load to an evaluation object; and a measurement step of acquiring deformation characteristics exhibited by the evaluation object during the compression step, The evaluation object is a sample abrasive grain sampled from a group of abrasive grains, The method for inspecting a group of abrasive grains, wherein the deformation characteristics include micro-fracture of the sample abrasive grains.

16. A plurality of sample abrasive grains are sampled from the group of abrasive grains, In the measuring step, an average deformation characteristic is obtained by averaging the deformation characteristics exhibited by each of the sample abrasive grains; The method for inspecting abrasive grains according to claim 15, wherein the abrasive grains are inspected based on the average deformation characteristics.

17. A method for manufacturing abrasive grains, comprising a step of inspecting abrasive grains by the method for evaluating abrasive grains according to claim 1 or 6.

18. A method for manufacturing abrasive grains, comprising a step of inspecting abrasive grains by the method for inspecting abrasive grains according to claim 15 or 16.

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