Polishing slurry

Abstract

To provide a polishing slurry capable of more efficiently obtaining a polished surface having good surface characteristics at a high polishing speed, even for an object to be polished having relatively low mechanical strength.SOLUTION: There is provided a polishing slurry containing α-alumina as a polishing particle in an aqueous medium, wherein the α-alumina has a mean particle diameter (D50) of 80 to 120 nm at 50% volumetric integrated value in the particle size distribution determined by a laser diffraction scattering method and a specific surface area (BET) of 20 m2 / g or more as measured in accordance with JIS-Z8830(2013), the ratio (BET / D50) of the specific surface area (BET) to the mean particle diameter (D50) is 1.5 m / g×108 or more and the ratio (TBD / LBD) of the light bulk density (LBD) to the heavy bulk density (TBD) measured in accordance with JIS-R9301-2-3 (1999) is 1.00 to 1.35.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polishing slurry, and more particularly to a polishing slurry that can be used for precision machining of the surface of an interlayer insulating film formed in a semiconductor device, such as an optical component, an electronic component, a precision instrument component, or a semiconductor package substrate mounted on these components. [Background technology]

[0002] In recent years, with the increasing integration and performance of semiconductor package substrates that contain semiconductor integrated circuits, microfabrication technologies such as finer wiring and multi-layering have been developed. Chemical mechanical polishing (hereinafter also referred to as "CMP (Chemical Mechanical Polishing) method") is one of these technologies, and is a technology that is frequently used in the manufacturing process of semiconductor integrated circuits, especially in the process of forming fine multi-layer wiring.

[0003] However, miniaturization and multi-layering hinder the speedup of semiconductor integrated circuits due to signal delays caused by increased capacitance between wiring. Therefore, to meet the demands of high-speed processing, low-dielectric-constant insulating film materials that satisfy various characteristics such as low dielectric constant, low dielectric loss tangent, and high heat resistance are being developed. The advantage of using low-dielectric-constant insulating film materials is that the smaller the dielectric constant, the faster the propagation speed. In particular, organic insulating materials mainly composed of polyimide resin are known to improve transmission speed by lowering the dielectric constant.

[0004] It is expected that by applying the CMP method to polishing the surface of resin films such as polyimide resin, it will be possible to form high-quality interlayer insulating films with low surface roughness, and a process is being investigated in which the CMP method can be used to polish and remove excess parts of objects that contain resin.

[0005] Patent Document 1 discloses a polishing composition as a means for polishing a resin having high rigidity and strength at a high polishing rate, the polishing composition comprising an abrasive grain and a dispersion medium, the abrasive grain having a Mohs hardness of 8 or more, and a surface acid amount of the abrasive grain having a surface acid amount of 0.05 mmol / g or more as measured by ammonia temperature programmed desorption method (NH3-TPD method).

[0006] Patent Document 2 discloses a method for polishing an interlayer insulating material consisting of inorganic particles and a resin material, comprising the steps of polishing the interlayer insulating material with a first polishing slurry containing first abrasive particles having an average particle diameter equal to or larger than the average particle diameter of the inorganic particles and a dispersant, and further polishing the interlayer insulating material polished with the first polishing slurry with a second polishing slurry containing second abrasive particles having an average particle diameter smaller than the average particle diameter of the inorganic particles and a dispersant. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2016-183212 A [Patent Document 2] JP 2021-141213 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, organic interlayer insulating films made of polymer compounds such as polyimide resins have lower mechanical strength than conventional inorganic interlayer insulating films such as SiO2. If such an object to be polished that has low mechanical strength is simply physically treated using abrasive grains with high hardness, film defects such as cracks and scratches are likely to occur, and sufficient polishing speed may not be obtained. If two-stage polishing is performed to compensate for this, problems such as a decrease in process throughput or an increase in the size of the polishing device due to differences in the table (platen) of the polishing device may occur.

[0009] In view of the above problems, the present invention provides a polishing slurry that can efficiently obtain a polished surface having good surface characteristics at a high polishing rate even on an object to be polished that has a relatively low mechanical strength. [Means for solving the problem]

[0010] In order to solve the above problems, in one aspect, the polishing slurry according to the present invention contains α-alumina as abrasive particles in an aqueous medium, and the α-alumina has an average particle diameter (D50) of 80 to 120 nm at a volume-based integrated value of 50% in a particle size distribution determined by a laser diffraction scattering method, and a specific surface area (BET) measured according to the provisions of JIS-Z8830 (2013) is 20 m 2 / g or more, and the ratio of the specific surface area (BET) to the average particle size (D50) (BET / D50) is 1.5m / g×10 -4 The above is the polishing slurry.

[0011] In one embodiment, the polishing slurry according to the present invention has a ratio (TBD / LBD) of the loose bulk density (LBD) to the packed bulk density (TBD) measured in accordance with JIS-R9301-2-3 (1999) of 1.5 or less.

[0012] In another embodiment, the polishing slurry according to the present invention has a specific surface area (BET) of 25 m 2 / g or more, and the ratio of the specific surface area (BET) to the average particle size (D50) (BET / D50) is 2.0 m / g × 10 -4 That's all.

[0013] In still another embodiment of the polishing slurry according to the present invention, the content of abrasive particles is 0.01 to 10 mass %, and the polishing slurry contains 0.0001 to 1 mass % of nitric acid as a dispersant.

[0014] In yet another embodiment, the polishing slurry according to the present invention is a free abrasive polishing slurry used for polishing an insulating material containing a polyimide resin. Effect of the Invention

[0015] According to the present invention, there can be provided a polishing slurry which can efficiently obtain a polished surface having good surface characteristics at a high polishing rate even on an object to be polished which has a relatively low mechanical strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described. (Object to be polished) The object to be polished is not particularly limited, but the polishing slurry according to the embodiment of the present invention is suitable for free abrasive polishing of insulating films (particularly interlayer insulating films) formed in semiconductor devices and the like.

[0017] Interlayer insulating films are used as insulating films for filling and insulating fine wiring made of copper, aluminum, etc., and for multi-layering circuit patterns. When multi-layering circuit patterns, the interlayer insulating film formed on the semiconductor substrate is flattened by the CMP method, and then new wiring is optically exposed on the interlayer insulating film by photolithography to form a circuit. By repeating this operation, a predetermined circuit is laminated. Specifically, a conductive layer is formed as a circuit on the surface of a base substrate (for example, a Bakelite substrate, a glass epoxy substrate, a resin substrate such as epoxy or polyester, or a composite substrate of these), and an interlayer insulating film is laminated on the conductive layer. Then, the interlayer insulating film on the substrate is polished to flatten the substrate surface so as to expose the conductive layer.

[0018] As materials used for such interlayer insulating films, for example, polyimide resin, polyester resin, epoxy resin, etc. can be suitably used. Among them, in this embodiment, a polyimide film mainly composed of polyimide resin (50 wt% or more) can be suitably processed. The polyimide film is generally mainly composed of aromatic polyimide obtained by imidizing (dehydrating and cyclizing) polyamic acid by high-temperature heating, and may be one in which fluorine atoms or alicyclic groups are introduced as a substituent to reduce the dielectric constant, one made nanoporous to reduce the film density, one to which a low dielectric constant additive is physically added, one to which the linearity of the main chain skeleton is increased to reduce the thermal expansion coefficient, one to which low-expansion fibers, whiskers, particles are added, etc.

[0019] The polyimide film used as such an interlayer insulating material has a relatively low mechanical strength compared to SiO2 films and the like. However, with the polishing slurry according to the embodiment of the present invention, even with such materials having low mechanical strength, a polished surface with good surface characteristics can be obtained at a higher polishing rate.

[0020] Although not limited thereto, the interlayer insulating film that can be polished using the polishing slurry according to the embodiment of the present invention preferably has a Young's modulus of 0.1 to 20.0 GPa, more preferably 1.0 to 10.0 GPa, and even more preferably 3.0 to 8.0 GPa. The Young's modulus can be evaluated based on JIS-Z2255 (2003).

[0021] (Abrasive slurry) The polishing slurry according to the embodiment of the present invention contains α-alumina as polishing particles (abrasive grains) in an aqueous medium. The aqueous medium is not particularly limited as long as it is an aqueous medium capable of dispersing abrasive grains, but is preferably water containing no impurities, and for example, pure water, ultrapure water, distilled water, etc. are preferably used. The α-alumina dispersed in the aqueous medium preferably has an average particle size (D50) of 80 to 120 nm at a volume-based integrated value of 50% in the particle size distribution obtained by a laser diffraction scattering method. For example, an organic interlayer insulating film such as a polyimide resin has a lower mechanical strength than a conventional inorganic interlayer insulating film such as SiO2, so that even if α-alumina with high hardness is simply used as an abrasive grain, it is likely to cause film defects such as cracks and scratches. By adjusting the average particle size (D50) of the α-alumina dispersed in the aqueous medium to a relatively small particle size of 80 to 120 nm, the polishing speed can be improved while preventing film defects from occurring even in the case of a polishing object with low mechanical strength. The average particle size (D50) of α-alumina is more preferably from 90 to 120 nm, and even more preferably from 95 to 110 nm.

[0022] When polishing resin materials with low mechanical strength, such as organic interlayer insulating films made of polyimide resin, simply using α-alumina, which has a small average particle size (D50) and a large specific surface area (BET), may not provide a sufficient polishing speed or a polished surface with good surface properties. By increasing the specific surface area within the appropriate particle size range where film damage is unlikely to occur, a polished surface with good surface properties can be obtained at a high polishing speed.

[0023] In this embodiment, the specific surface area (BET) of α-alumina is 20 m 2 / g or more, and 25m 2 / g or more is more preferable, and 30m 2 If the specific surface area (BET) of α-alumina is too high, dispersion becomes difficult, which may increase the load of the dispersion process, cause undispersed matter, and ultimately cause scratches on the object to be polished. 2 / g or less, and 2 / g or less is more preferable, and 50m 2 It is even more preferable that the specific surface area (BET) is equal to or less than 1 / g. The specific surface area (BET) can be measured based on the standard of JIS-Z8830 (2013).

[0024] Furthermore, by adjusting the ratio (BET / D50) of the specific surface area (BET) and the average particle size (D50) of the α-alumina used as the abrasive particles to an appropriate range, it is possible to suitably polish resin materials with low mechanical strength, such as organic interlayer insulating films using polyimide resin. BET / D50 is 1.5 m / g×10 -4 It is preferable that the concentration is 2.0 m / g×10 or more. -4 More preferably, it is 2.5 m / g×10 or more. -4 It is even more preferable that the BET / D50 is 15.0 m / g×10 or more to ensure a suitable surface roughness and a sufficient polishing rate. -4 It is preferable that the concentration is 10.0 m / g×10 or less. -4 More preferably, it is 6.3 m / g×10 or less. -4 Even more preferably, it is:

[0025] If the light bulk density (LBD) of α-alumina is too high, the proportion of large primary particles increases, causing the surface properties after polishing to deteriorate, while if it is too low, the proportion of alumina with a low α conversion rate increases, which can cause the polishing speed to decrease. The LBD is 0.6 g / cm 3 It is preferable that the content is 0.7 g / cm or more. 3More preferably, it is 0.8 g / cm or more. 3 The upper limit of LBD is preferably 1.7 g / cm or more. 3 It is preferable that the concentration is 1.3 g / cm or less. 3 It is more preferable that:

[0026] In addition, if the packed bulk density (TBD) of α-alumina is too high, the proportion of large primary particles increases, causing the surface properties to deteriorate after polishing, while if it is too low, the proportion of alumina with a low α conversion rate increases, which can cause the polishing speed to decrease. TBD is 0.8 g / cm 3 It is preferable that the content is 0.9 g / cm or more. 3 More preferably, it is 1.0 g / cm or more. 3 The upper limit of TBD is not particularly limited, but is preferably 2.0 g / cm. 3 It is preferable that the density is 1.5 g / cm or less. 3 It is more preferable that the light packed bulk density (LBD) and the heavy packed bulk density (TBD) are measured based on JIS-R9301-2-3 (1999).

[0027] In this embodiment, the ratio (TBD / LBD) of the loose bulk density (LBD) and the loaded bulk density (TBD) measured based on JIS-R9301-2-3 (1999) is preferably 1.5 or less. A small difference between the values ​​of TBD and LBD means that the porosity does not change significantly even after tapping, and the bulk density of each secondary particle (agglomerated particle) contained in the average particle size (D50) of α-alumina is high, that is, the cohesive force of the secondary particles is high. Since there are many particles that maintain the form of agglomerated particles even after dispersion to a moderate particle size, a polished surface with good surface characteristics can be obtained at a high polishing rate in the range of a relatively small moderate particle size. It is more preferable that TBD / LBD is 1.00 to 1.50, and even more preferably 1.00 to 1.35.

[0028] The content of the abrasive particles in the aqueous medium can be set arbitrarily depending on the application. Although not particularly limited, in order to obtain a sufficient polishing rate while maintaining good surface characteristics, the content is preferably 0.01 to 10 mass%, more preferably 0.05 to 5 mass%, and even more preferably 0.1 to 1 mass%.

[0029] The α-alumina used as the abrasive grains may have an α-conversion rate of, but not limited to, 40 to 65%, preferably 45 to 60%, from the viewpoint of polishing a material with relatively poor mechanical properties at a sufficient polishing rate. The α-alumina α-conversion rate can be determined from the integrated intensity ratio of the (113) plane diffraction line by X-ray diffraction measurement.

[0030] The polishing slurry is preferably prepared to contain abrasive particles and a dispersant. By containing a dispersant in the polishing slurry, the effect of efficiently dispersing the abrasive particles and quickly supplying the abrasive particles into the interlayer insulating film can be obtained. As the dispersant, a known dispersant can be used, for example, one that utilizes the steric hindrance of the molecular chain in the surfactant, or one that improves dispersion by the electrical repulsion of the particle surface potential can be used. In particular, in this embodiment, since α-alumina, which is an oxide with high polarity, is used as the abrasive particles, for example, an ionic polymer surfactant such as polyacrylate or polystyrene sulfonate, or an acid such as hydrochloric acid, nitric acid, citric acid, or acetic acid can be used. From the viewpoint of avoiding surface contamination of the semiconductor package substrate, etc. (ease of cleaning), and obtaining a moderate erosion property to the resin material contained in the interlayer insulating material, it is preferable to use an acid as the dispersant. In particular, in the case of an organic interlayer insulating film using a polyimide resin, nitric acid can be preferably used as the dispersant. The content of nitric acid is not particularly limited, but can be, for example, 0.0001 to 1 mass %, preferably 0.001 to 0.1 mass %, and more preferably 0.002 to 0.05 mass %.

[0031] The polishing slurry is preferably prepared to further contain a thickener. In one embodiment, α-alumina with TBD / LBD of 1.5 or less is preferably used, and the bulk density of each secondary particle (agglomerated particle) contained in the polishing particle is high. Therefore, by further containing a thickener in the polishing slurry, it is possible to prevent the precipitation of the agglomerated particle of α-alumina with high bulk density, and to improve the dispersion stability of the polishing particle.

[0032] Examples of the thickener include a surfactant or a water-soluble polymer. In particular, the water-soluble polymer is preferably used to prevent the precipitation of aggregated particles of α-alumina and to improve the dispersion stability.

[0033] As the water-soluble polymer, a polycarboxylic acid-based water-soluble polymer can be used as an anionic (negative) one, for example, a polyacrylic acid-based water-soluble polymer such as polyacrylic acid or its salt, an acrylic acid-(meth)acrylic acid ester copolymer or its salt, alginate, cellulose derivatives such as carboxymethyl cellulose, etc. As the nonionic (non-ionic) one, a cellulose derivative such as hydroxyethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, polyacrylamide, etc. As the cationic (cationic) water-soluble polymer, polyethyleneimine can be used.

[0034] In this embodiment, the thickener can be suitably used as a nonionic water-soluble polymer, because it prevents the precipitation of the aggregated particles of α-alumina as abrasive particles, enhances the dispersion stability, and ensures the function of suppressing the polishing inhibition such as the decrease in the polishing speed of the polishing object due to the excessive increase in viscosity. The content of the water-soluble polymer is 0.01-1 mass %, preferably 0.1-0.9 mass %, based on the total polishing slurry.

[0035] The polishing slurry according to the embodiment of the present invention is preferably used for polishing an interlayer insulating material mainly composed of polyimide resin, but when polishing an interlayer insulating material, it may be necessary to planarize metal wiring made of copper, aluminum, etc. together with the interlayer insulating film by the CMP method. In this case, an oxidizing agent, a complexing agent, an antioxidant, a pH adjusting agent, etc. may be appropriately added as necessary.

[0036] The oxidizing agent has the function of moderately oxidizing and ionizing a metal film such as copper, and the complexing agent promotes the ionization of a metal film such as copper, etc. The antioxidant can suppress excessive etching of the metal film by the oxidizing agent or the complexing agent, and by adjusting the concentrations of these agents, the polishing rate for the metal film can be adjusted within a suitable range.

[0037] As the oxidizing agent, for example, peroxides such as H2O2, Na2O2, Ba2O2, (C6H5C)2O2, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, peracetic acid, nitrobenzene, and other organic peroxides can be used. Among them, hydrogen peroxide (H2O2) is preferably used because it does not contain metal components and does not generate harmful by-products. The content of the oxidizing agent is 0.01 to 15 mass % relative to the entire polishing slurry, preferably 0.1 to 10 mass %.

[0038] As the complexing agent, organic acids such as known carboxylic acids and amino acids can be used. Examples of organic acids include glycine, alanine, valine, serine, threonine, cysteine, phenylalanine, proline, asparagine, aspartic acid, lysine, histidine, arginine, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, and salts thereof such as ammonium salts and alkali metal salts, or mixtures thereof. Among them, glycine, an amino acid having both an amino group and a carboxyl group, can be suitably used to dissolve metals that are difficult to dissolve. The content of the complexing agent is 0.01 to 5 mass %, preferably 0.05 to 3 mass %, and more preferably 0.1 to 1 mass % based on the total polishing slurry.

[0039] As the antioxidant, for example, benzotriazole, 1,2,3-triazole, 1,2,4-triazole, benzofuroxan, 2,1,3-benzothiazole, o-phenylenediamine, m-phenylenediamine, catechol, o-aminophenol, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, melamine, and derivatives thereof can be used. The content of the antioxidant is 0.001-1 mass% relative to the entire polishing slurry, preferably 0.01-0.1 mass%.

[0040] The pH of the polishing slurry is suitable from the viewpoint of polishing speed, slurry viscosity, dispersion stability of polishing particles, etc., pH 3 to 8, preferably pH 4 to 7. The pH of the polishing slurry can be adjusted by a known method. When nitric acid is used as the dispersant of the polishing slurry, it is preferable to use an alkali, and can use alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, alkali metal carbonate such as sodium carbonate, potassium carbonate, ammonia, amine, etc., and among them, it is suitable to add ammonia to adjust the pH to a suitable range.

[0041] (Method of manufacturing polishing slurry) The manufacturing method of the polishing slurry according to the embodiment of the present invention can be produced by, for example, stirring and mixing abrasive particles and dispersant in aqueous solvent, and diluting.For example, water and dispersant such as nitric acid are added to abrasive particles, and then, by using a bead mill or the like, the average particle diameter (D50) of abrasive particles is 80-120nm, the mixture is stirred and mixed, and then, the content of abrasive particles is 0.01-10 mass%, and the pH is further adjusted, thereby producing a polishing slurry (free abrasive polishing slurry) suitable for polishing insulating materials including polyimide resin.

[0042] (polishing method) The polishing slurry according to the embodiment of the present invention can be used to suitably perform free abrasive polishing of the insulating film containing polyimide resin formed on the substrate of a semiconductor device. The polishing device is not particularly limited, and various general polishing devices can be used, and it can be a single-sided polishing device or a double-sided polishing device. For example, when using a single-sided polishing device, the semiconductor substrate is held by a holder such as a carrier, and the polishing slurry according to the embodiment of the present invention is supplied to the surface of the insulating film containing polyimide resin formed on the semiconductor substrate. Then, the surface of the insulating film is polished at a predetermined polishing speed or higher by pressing a surface plate with a predetermined polishing pad attached to the surface plate against the object to be polished and rotating the surface plate.

[0043] According to the polishing method using the polishing slurry of the embodiment of the present invention, even for materials with relatively low mechanical strength such as insulating materials containing polyimide resin, a polished surface with good surface characteristics can be obtained at a high polishing rate by a single polishing process without repeating the polishing process step by step. This allows for efficient polishing.

[0044] According to the polishing method of the embodiment of the present invention, the polishing speed can be 200 nm / min or more, further 300 nm / min or more, and further 350 nm / min or more. The upper limit of the polishing speed is not particularly specified, but if the polishing speed is too fast, it may be difficult to adjust the desired amount of removal, so it is typically 3000 nm / min or less, and further 1500 nm / min or less is preferable. Although not limited to the following, the polishing load on the insulating film containing a polyimide resin can be, for example, 0.1 to 10.0 psi, and preferably 1.0 to 5.0 psi. By carrying out such a treatment, the surface of the insulating film has a surface roughness (center line average roughness Ra) based on Appendix JB of JIS-B0601 (2013). 75 ) is 10 nm or less, further 5.0 nm or less, and even more preferably 2.0 nm or less, and a polished surface having good flatness characteristics can be obtained. EXAMPLES

[0045] The following examples of the present invention are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

[0046] <Polishing slurry> Using various abrasive particles shown in Table 1, 0.2 mass% of nitric acid was added to an abrasive particle / water mixture with an abrasive particle content of 30 mass%, dispersed in a bead mill, and then diluted with water to prepare abrasive slurries with an abrasive particle content (abrasive concentration) of 0.5 mass% and average particle diameter (D50) of the abrasive particles shown in Table 1. The pH of the abrasive slurries was adjusted to pH = 6 by adding ammonia.

[0047] <Particle size measurement> The particle size of the abrasive particles contained in the polishing slurry was measured using a laser diffraction / scattering type particle size distribution analyzer (LA-960, manufactured by Horiba, Ltd.) The particle size value was the average particle size (D50) at 50% of the volume-based cumulative value in the particle size distribution obtained by the laser diffraction scattering method.

[0048] <Object to be polished> A polyimide (photosensitive positive type, manufactured by Advanced Materials Technology Corp.) was coated onto a silicon wafer having a diameter of φ200 mm using a spin coater, and then thermally cured to produce a polyimide film having a thickness of 10 μm on the silicon wafer.

[0049] <Polishing conditions> The polishing was performed using a Mirra CMP device manufactured by Applied Materials under the following conditions: A polishing pad (IC1400 manufactured by Nitta DuPont Co., Ltd.) was attached to the platen of the polishing device. Down Force = 2.0 psi Head Speed ​​ / Platen Speed ​​= 120 / 117 rpm Slurry Flow = 200ml / min Polish Time = 30 sec

[0050] <Measurement of polishing speed> The polishing rate was measured by measuring the change in film thickness of the object (polyimide film) before and after polishing using a filmTec1000 manufactured by SCI Corporation to measure the amount of film thickness reduction per polishing time, and then calculating the polishing rate.

[0051] <Surface roughness measurement> The surface roughness was measured using a scanning probe microscope (Nanoscope V, manufactured by Bruker Japan Co., Ltd.). The surface roughness value was the center line average roughness Ra defined in Annex JB of JIS-B0601 (2013). 75 was used.

[0052] <Experimental Results> The polishing results using the polishing slurries containing various abrasive particles are shown in Table 1 below.

[0053] [Table 1]

[0054] The abrasive particles used are α-alumina, with particle diameters in the range of 80 to 120 nm and a specific surface area (BET) of 20 m 2 / g or more, and the ratio of the specific surface area (BET) to the average particle size (D50) (BET / D50) is 1.5m / g×10 -4 In Example 1, a higher polishing rate was obtained compared to Comparative Examples 1 to 4. In addition, the surface roughness of the polyimide film was Ra 75 = 2.0 nm or less, which was good. In Example 1, the ratio (TBD / LBD) of the light bulk density (LBD) to the heavy bulk density (TBD) was 1.5 or less.

[0055] In Comparative Examples 1 to 4, in which α-alumina was used as the abrasive particles, the average particle diameter (D50) was adjusted to the range of 80 to 120 nm, and the surface roughness after polishing was good in all cases. However, the polishing rate was lower than that of Example 1. In Comparative Example 4, the BET was 20 m 2 / g or less, BET / D50 is 1.5m / g x 10 -4 The BET and BET / D50 were not within the preferred ranges, and the TBD / LBD was 1.5 or less, but the polishing rate was lower than that of Example 1. In Comparative Example 3, the BET / D50 was 1.5 m / g×10 -4 That was the case, but the BET was 20m 2 / g, and TBD / LBD was 1.5 or more, resulting in a lower polishing rate than in Example 1. In Comparative Example 2, the BET was small, and the TBD / LBD was also large, resulting in a lower polishing rate. In Comparative Example 1, the BET was small, and the BET / D50 was 1.5 m / g×10 -4The polishing rate was low at less than 1000 mm. Moreover, in Reference Example 1 and Reference Example 2, in which θ-alumina and silica were used as abrasive particles, neither of them could obtain a polishing rate higher than that of Example 1. From these results, it can be seen that α-alumina was used as abrasive particles, and the average particle diameter (D50) at 50% of the volume-based integrated value in the particle size distribution obtained by the laser diffraction scattering method was 80 to 120 nm, and the specific surface area (BET) measured according to the JIS-Z8830 (2013) was 20 m. 2 / g or more, and the ratio of the specific surface area (BET) to the average particle size (D50) (BET / D50) is 1.5m / g×10 -4 It has been found that by satisfying the above requirements, and further preferably by ensuring that the ratio (TBD / LBD) of the loose bulk density (LBD) to the loaded bulk density (TBD) measured based on JIS-R9301-2-3 (1999) is 1.5 or less, sufficiently high speed and excellent planarization can be achieved in polishing materials having low mechanical strength, such as polyimide resins, which are used for interlayer insulating films.

Claims

1. The abrasive particles include α-alumina in an aqueous medium. The α-alumina is The average particle size (D50) at 50% volume-based integrated value in the particle size distribution determined by a laser diffraction scattering method is 80 to 120 nm; The specific surface area (BET) measured according to the JIS-Z8830 (2013) standard is 20 m 2 / g or more, The ratio (BET / D50) of the specific surface area (BET) to the average particle diameter (D50) is 1.5 m / g×10 -4 End The abrasive slurry is

2. 2. The polishing slurry according to claim 1, wherein the ratio (TBD / LBD) of the loose bulk density (LBD) to the loaded bulk density (TBD) measured according to JIS-R9301-2-3 (1999) is 1.5 or less.

3. The specific surface area (BET) is 25 m 2 / g or more, and the ratio (BET / D50) of the specific surface area (BET) to the average particle diameter (D50) is 2.0 m / g×10 -4 The polishing slurry according to claim 1 or 2.

4. 3. The polishing slurry according to claim 1, wherein the content of the abrasive particles is 0.01 to 10% by mass, and the polishing slurry further contains 0.0001 to 1% by mass of nitric acid as a dispersant.

5. 3. The polishing slurry according to claim 1, which is a free abrasive polishing slurry used for polishing an insulating material containing a polyimide resin.

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