Composite ceria-based composite microparticle dispersion and method for producing same

Abstract

To provide a composite type ceria based composite fine particle liquid dispersion that can polish silica film, a Si wafer and a difficult-to-polish material at a high speed and can suitably be used in polishing the surface of a semiconductor device such as semiconductor substrate and a wiring board.SOLUTION: The composite type ceria based composite fine particle liquid dispersion is formed by dispersing composite type ceria based composite fine particles in a solvent, with the composite type ceria based composite fine particle being formed of a ceria based composite fine particle supported by a heteromorphic inorganic oxide fine particle, the heteromorphic inorganic oxide fine particle having a specific shape, and the ceria based composite fine particle comprising a mother particle whose main component is amorphous silica, a cerium-containing silica layer disposed on the surface of the mother particle, and sub particles whose main component is crystalline silica, dispersed in the cerium-containing silica layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a ceria-based composite microparticle dispersion suitable as an abrasive used in the manufacture of semiconductor devices and the like, and in particular to a ceria-based composite microparticle dispersion for planarizing a film to be polished formed on a substrate by chemical mechanical polishing (CMP), a method for producing the same, and a polishing abrasive dispersion containing the ceria-based composite microparticle dispersion. [Background technology]

[0002] Semiconductor devices such as semiconductor substrates and wiring boards have achieved high performance through higher density and miniaturization. In the manufacturing process of semiconductors, so-called chemical mechanical polishing (CMP) is applied, and is an essential technology for shallow trench isolation, planarization of interlayer insulating films, and formation of contact plugs and Cu damascene wiring.

[0003] Generally, CMP polishing agents consist of abrasive grains and chemical components, and the chemical components play a role in promoting polishing by oxidizing or corroding the target film. On the other hand, the abrasive grains perform polishing through mechanical action, and colloidal silica, fumed silica, and ceria particles are used as abrasive grains. Ceria particles in particular have a particularly high polishing speed for silicon oxide films, and are therefore used for polishing in the shallow trench isolation process. In the shallow trench isolation process, not only the silicon oxide film but also the silicon nitride film is polished. To facilitate isolation, it is desirable that the polishing rate of the silicon oxide film is high and that of the silicon nitride film is low, and the polishing rate ratio (selectivity) is also important.

[0004] Conventionally, the method of polishing such components involves a relatively rough primary polishing process followed by a precise secondary polishing process to obtain a smooth surface or an extremely high-precision surface with few scratches or other imperfections. Regarding the abrasive used in the secondary polishing as the finish polishing, the following methods have been proposed.

[0005] For example, Patent Document 1 describes a method for producing cerium oxide ultrafine particles (average particle size: 10 to 80 nm) made of cerium oxide single crystals, which comprises mixing and stirring an aqueous solution of cerous nitrate and a base in a ratio such that the pH is 5 to 10, followed by rapidly heating to 70 to 100°C and maturing at that temperature. It further describes that this production method can provide cerium oxide ultrafine particles that are highly uniform in particle size and shape.

[0006] Furthermore, Patent Document 2 describes silica-based composite particles characterized in that the surface of an amorphous silica particle A has a crystalline oxide layer B containing one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium. In addition, as a preferred embodiment, a silica-based composite particle is described, which is characterized in that the surface of the amorphous silica particle A has an amorphous oxide layer C that is an amorphous oxide layer containing elements such as aluminum, which is different from the amorphous silica layer, and further has a crystalline oxide layer B containing one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium on top of the amorphous silica particle A. And, such silica-based composite particles can improve the polishing rate because they have a crystalline oxide layer B on the surface of the amorphous silica particle A, and by pretreating the silica particles, the sintering of particles during firing is suppressed, and the dispersibility in the polishing slurry can be improved, and further, it is described that it is possible to provide an inexpensive polishing material with high polishing performance because it does not contain cerium oxide or the amount of cerium oxide used can be greatly reduced. Also, it is described that those having an amorphous oxide layer C between the silica-based particle A and the oxide layer B are particularly excellent in the effect of suppressing sintering of particles and the effect of improving polishing rate.

[0007] Furthermore, Patent Document 3 describes a silica-based composite microparticle dispersion liquid containing silica-based composite microparticles having an average particle size of 50 to 350 nm and the following characteristics [1] to [3], in which child particles mainly made of crystalline ceria are present on the surface of mother particles mainly made of amorphous silica, and the surfaces of the child particles are further coated with silica. [1] The silica-based composite microparticles have a mass ratio of silica to ceria of 100:11 to 316. [2] When the silica-based composite microparticles are subjected to X-ray diffraction, only the crystalline phase of ceria is detected. [3] The silica-based composite microparticles have a crystallite size of 10 to 25 nm in the (111) plane of the crystalline ceria, as measured by X-ray diffraction. It is also described that such silica-based composite microparticles can be used to polish even silica films, Si wafers, and other difficult-to-process materials at high speeds, while at the same time achieving high surface precision (low scratches, low surface roughness (Ra) of the substrate to be polished, etc.), and furthermore, since they do not contain impurities, it is possible to provide a silica-based composite microparticle dispersion that can be preferably used for polishing the surfaces of semiconductor devices such as semiconductor substrates and wiring substrates. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 2,746,861 [Patent Document 2] JP 2013-119131 A [Patent Document 3] International Publication No. 2016 / 159167 Summary of the Invention [Problem to be solved by the invention]

[0009] However, when the present inventors actually produced and examined the cerium oxide ultrafine particles described in Patent Document 1, they found that the polishing rate was low and that the particles were prone to cause defects on the surface of the polishing substrate (deterioration of surface accuracy, increased scratches, and residue of abrasive on the surface of the polishing substrate). The inventors believe that the main reason for this is that, compared to methods for producing ceria particles that include a calcination step (calcination increases the crystallinity of the ceria particles), the method for producing cerium oxide ultrafine particles described in Patent Document 1 does not include a calcination step and simply crystallizes cerium oxide particles from a liquid phase (an aqueous solution containing cerium nitrate), so the crystallinity of the cerium oxide particles produced is relatively low; further, because no calcination process is performed, the cerium oxide does not adhere to the base particles, and so the cerium oxide remains on the surface of the polishing substrate.

[0010] Furthermore, the present inventors have found that when polishing is performed using silica-based composite particles having an oxide layer C described in Patent Document 2, impurities such as aluminum may remain on the surface of the semiconductor device, which may adversely affect the semiconductor device. Furthermore, the ceria particles described in these documents are attached to the base particles, but are not strongly fixed and therefore tend to fall off from the base particles. Furthermore, when polishing is performed using an abrasive in which crystalline ceria particles are formed on spherical silica mother particles as described in Patent Document 2, the removal rate of the silica film is high due to the chemical reaction that occurs simultaneously with the mechanical action of the ceria particles during polishing. However, under high pressure conditions, the ceria crystals may fall off, wear down, or collapse, reducing the contact area between the substrate and the ceria, which may result in a slow removal rate.

[0011] Furthermore, the silica-based composite microparticle dispersion (containing ceria as a main component and essentially ceria-based composite microparticles) described in Patent Document 3 is capable of exhibiting excellent polishing performance (polishing rate, high surface accuracy, etc.) particularly when used to polish the surfaces of semiconductor devices such as semiconductor substrates and wiring substrates. However, with the ever-increasing density and integration of semiconductor devices, there is a demand for polishing abrasives or polishing abrasive dispersions that exhibit even better polishing performance for semiconductor substrates. In addition, in Patent Document 3, when a silica-based composite microparticle dispersion is used as an abrasive dispersion, it is preferable that the shape of the silica-based composite microparticles is of a particle-linked type. When particle-linked silica-based composite microparticles that have grown in two dimensions are used as polishing abrasives, it is expected that it is easy to ensure a dynamic contact area, and furthermore, it is possible to reduce the generation of scratches on the polishing substrate due to stress dispersion during the polishing process, but there is a limit to the number of linked particles and the length of the major axis of the particles due to the process.

[0012] The present invention aims to solve the above-mentioned problems. That is, the present invention aims to provide a composite ceria-based composite microparticle dispersion that can polish, for example, silica films, Si wafers, and difficult-to-process materials at high speed and can also be preferably used for polishing the surfaces of semiconductor devices such as semiconductor substrates and wiring substrates, a method for producing the same, and a polishing abrasive dispersion containing the composite ceria-based composite microparticle dispersion. [Means for solving the problem]

[0013] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention relates to the following (1) to (7). (1) A composite ceria-based composite microparticle dispersion in which composite ceria-based composite microparticles are dispersed in a solvent, The composite ceria-based composite fine particles are those in which ceria-based composite fine particles are supported on irregularly shaped inorganic oxide fine particles, The irregular shaped inorganic oxide fine particles have an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3; The ceria-based composite microparticles are a composite ceria-based composite microparticle dispersion having mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer. (2) The composite ceria-based composite microparticle dispersion according to (1) above, wherein the ceria-based composite microparticles have an average particle size in the range of 50 nm to 600 nm as determined by an image analysis method using a scanning electron microscope photograph. (3) The composite ceria-based composite microparticle dispersion according to (1) or (2) above, wherein the average number of the ceria-based composite microparticles supported on the irregular shaped inorganic oxide microparticles is 1 to 200 per 100 nm in the major axis direction of the irregular shaped inorganic oxide microparticles. (4) The composite ceria-based composite microparticle dispersion according to any one of the above (1) to (3), wherein the irregular-shaped inorganic oxide microparticles are at least one selected from the group consisting of sepiolite, particle-linked silica microparticles, and non-spherical silica microparticles. (5) A polishing abrasive dispersion comprising the composite ceria-based composite microparticle dispersion according to any one of (1) to (4) above. (6) A method for producing the composite ceria-based composite microparticle dispersion according to any one of (1) to (4) above, comprising the following steps [1], [2], [3] and [4]: Step [1]: Depositing irregularly shaped inorganic oxide fine particles having an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3; A process of mixing mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particles, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer, with a ceria-based composite microparticle dispersion in which ceria-based composite microparticles with an average particle size of 50 to 600 nm are dispersed in a solvent, to obtain a raw material dispersion. Step [2]: A step of adding a buffer solution to the raw material dispersion and stirring to obtain a precursor dispersion having a pH of 2.0 to 7.0. Step [3]: A step of heating the precursor dispersion to 40 to 98° C., maintaining the temperature for one hour or more, and then allowing to cool to obtain a reaction dispersion. Step [4]: ​​A step of bringing the reaction dispersion into contact with an anion exchange resin for ion exchange to obtain a composite ceria-based composite microparticle dispersion according to any one of the above (1) to (4). (7) The method for producing a composite ceria-based composite microparticle dispersion according to (6) above, wherein in the step [1], a mixing ratio (solid content equivalent) of the irregular shaped inorganic oxide microparticles to the ceria-based composite microparticles in the mixed liquid is 100:500 to 100:8,000 (parts by mass). Effect of the Invention

[0014] The composite ceria-based composite microparticles in the composite ceria-based composite microparticle dispersion of the present invention have a unique structure in which specific ceria-based composite microparticles (corresponding to the silica-based composite microparticles in Patent Document 3) are supported on irregular inorganic oxide microparticles whose external shape is classified as chain-like, elongated, rod-like, needle-like, etc. More specifically, the composite ceria-based composite microparticles have a unique structure in which specific ceria-based composite microparticles ..., whose average major axis (L) is in the range of 200 nm to 6,000 nm, whose average minor axis (S) is in the range of 10 to 1,800 nm, and whose ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) is in the range of 0.005 to 0.3. As described above, the ceria composite fine particles show excellent polishing performance in polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates, but by supporting the ceria composite fine particles on the irregular inorganic oxide fine particles, the polishing performance is improved compared to when the ceria composite fine particles are used as a single particle polishing abrasive. In general, the contact area between the polishing pad and the substrate is said to be only a few percent, and similarly, only a few percent of the polishing abrasive particles contribute to polishing. Therefore, it is known that most particles do not contribute to polishing. In addition, even if the irregular inorganic oxide fine particles, which are the raw material of the present invention, are used for polishing, a high polishing rate cannot be obtained. However, the composite particles of the present invention, in which a large number of ceria composite fine particles are supported on the irregular inorganic oxide fine particles, are easily held by the polishing pad because the irregular inorganic oxide fine particles are large in size, and when the composite fine particles of the present invention are held by the polishing pad, the supported ceria composite fine particles are also held by the polishing pad. Therefore, it is considered that the proportion of the ceria composite fine particles that contribute to polishing is increased, that is, the contact area and contact probability with the substrate are improved, and the polishing rate is improved. In addition, since the contact area between the abrasive grains and the substrate is increased, the stress applied to the abrasive grains is dispersed, and polishing scratches tend not to occur easily. The present invention also provides a method for producing the composite ceria-based composite fine particle dispersion. [Brief description of the drawings]

[0015] [Figure 1]1 is a scanning electron microscope photograph (magnification: 100,000 times) of the composite ceria-based composite microparticle dispersion of Example 1. The lower part is a transmission electron microscope photograph (magnification: 100,000 times) of the composite ceria-based composite microparticle dispersion of Example 1. [Diagram 2] 1 is a scanning electron microscope photograph (magnification: 10,000 times) of the composite ceria-based composite microparticle dispersion of Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will now be described. The present invention provides a composite ceria-based composite microparticle dispersion in which composite ceria-based composite microparticles are dispersed in a solvent, the composite ceria-based composite microparticles being comprised of irregular inorganic oxide microparticles carrying ceria-based composite microparticles, the irregular inorganic oxide microparticles having an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3, and the ceria-based composite microparticles having mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and child particles mainly composed of crystalline ceria dispersed within the cerium-containing silica layer. Such a composite ceria-based composite fine particle dispersion is hereinafter also referred to as "the dispersion of the present invention." Moreover, the composite ceria-based composite fine particles dispersed in the dispersion of the present invention are also referred to as "composite particles of the present invention" hereinafter.

[0017] The present invention also relates to a method for producing the dispersion of the present invention, comprising the following steps [1], [2], [3] and [4]: Step [1]: Depositing irregularly shaped inorganic oxide fine particles having an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3; A process of mixing mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particles, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer, with a ceria-based composite microparticle dispersion in which ceria-based composite microparticles with an average particle size of 50 to 600 nm are dispersed in a solvent, to obtain a raw material dispersion. Step [2]: A step of adding a buffer solution to the raw material dispersion and stirring to obtain a precursor dispersion having a pH of 2.0 to 7.0. Step [3]: A step of heating the precursor dispersion to 40 to 98° C., maintaining the temperature for one hour or more, and then allowing to cool to obtain a reaction dispersion. Step [4]: ​​A step of bringing the reaction dispersion into contact with an anion exchange resin to carry out ion exchange, thereby obtaining the dispersion of the present invention. Such a production method will be hereinafter referred to as the "production method of the present invention."

[0018] Hereinafter, when the term "the present invention" is simply mentioned, it means any of the dispersion liquid of the present invention, the composite particle of the present invention, and the production method of the present invention.

[0019] In this specification, the expression "image of composite ceria-based composite particles" means "electron microscope photograph of composite ceria-based composite particles" unless otherwise specified. Electron micrograph means a scanning electron micrograph (image) or a transmission electron micrograph (image). Note that scanning electron micrographs (images) are sometimes abbreviated as "SEM" and transmission electron micrographs (images) as "TEM." Furthermore, the expression "ceria-based composite fine particles in an electron microscope photograph" means "ceria-based composite fine particles in an electron microscope photograph" unless otherwise specified.

[0020] <Composite particles of the present invention> The composite particles of the present invention are described below. The composite particles of the present invention have a structure in which ceria-based composite particles (hereinafter also referred to as "ceria-based composite particles of the present invention") are supported on irregularly shaped inorganic oxide particles (hereinafter also referred to as "irregularly shaped inorganic oxide particles of the present invention").

[0021] [Non-circular inorganic oxide particles of the present invention] The irregular inorganic oxide fine particles of the present invention have an external shape in which the average major axis (L) is in the range of 200 nm to 6,000 nm, the average minor axis (S) is in the range of 10 to 1,800 nm, and the ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) is in the range of 0.005 to 0.3. Typical examples of the external shape of such irregular inorganic oxide fine particles of the present invention include chain-like, elongated, rod-like, and needle-like shapes. Typical examples of the configuration of the irregular inorganic oxide fine particles of the present invention include particle-linked fine particles, irregular particles obtained by growth of core particles without particle linkage, and non-spherical particles obtained by crushing particles. The external shape of the irregularly shaped inorganic oxide fine particles of the present invention is suitable for supporting one or more of the ceria-based composite fine particles of the present invention.

[0022] When the average major axis (L) of the irregular inorganic oxide particles is less than 200 nm, when a dispersion containing particles supported by ceria composite particles is applied to a polishing application, the length of the irregular inorganic oxide particles is insufficient, so that a sufficient dynamic contact area is not obtained, and it is difficult to obtain a practical polishing rate.Also, when the average major axis (L) exceeds 6,000 nm, the major axis is too long for filtration, and foreign matter other than abrasive grains cannot be removed, so that the application to a polishing application is not suitable. The average major axis (L) of the irregular shaped inorganic oxide fine particles of the present invention is preferably in the range of 400 to 2,000 nm, more preferably 400 to 1,000 nm. The average minor axis (S) of the irregular shaped inorganic oxide fine particles of the present invention is preferably in the range of 10 to 1,800 nm, and more preferably in the range of 15 to 1,000 nm.

[0023] When the ratio of the average minor axis (S) to the average major axis (L) of the anisotropic inorganic oxide fine particles of the present invention (average minor axis (S) / average major axis (L)) is less than 0.005, when a dispersion liquid containing particles on which ceria-based composite fine particles are supported is applied to polishing use, since the strength of the anisotropic inorganic oxide fine particles is insufficient, it is likely to break during polishing and become foreign matter, which is not desirable. Also, when the ratio of the average minor axis (S) to the same average major axis (L) exceeds 0.3, since the structure of the anisotropic inorganic oxide fine particles deviates from an elongated shape, even when a dispersion liquid containing the same is applied to polishing use, it may not be possible to obtain a sufficient dynamic contact area and a sufficient polishing rate may not be obtained.

[0024] The anisotropic inorganic oxide fine particles of the present invention have an average major axis (L) in the range of 200 to 6,000 nm, an average minor axis (S) in the range of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) in the range of 0.005 to 0.3. Examples of such anisotropic inorganic oxide fine particles include at least one selected from the group consisting of sepiolite, particle-connected silica fine particles, and non-spherical silica fine particles. Note that the anisotropic inorganic oxide fine particles of the present invention may have a branched structure. In the anisotropic inorganic oxide fine particles having a branched structure, the average major axis (L), the average minor axis (S), etc. can be obtained by taking the longest diameter connecting two points on the outer edge of the anisotropic inorganic oxide fine particle image in the micrograph as the major axis.

[0025] The method for measuring the average major axis (L) and the average minor axis (S) of the anisotropic inorganic oxide fine particles of the present invention will be described later.

[0026] [Ceria-based Composite Fine Particles of the Present Invention] The ceria-based composite fine particles of the present invention have mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particles, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer. Typical properties of such ceria-based composite fine particles of the present invention will be described below.

[0027] The ceria-based composite fine particles of the present invention preferably have an average particle size of 50 to 600 nm. The average particle size is determined by an image analysis method using a scanning electron microscope photograph, and will be described in detail later. When the average particle size of the ceria-based composite fine particles of the present invention is within this range, the composite particles of the present invention exhibit good polishing performance when used for polishing. On the other hand, when the average particle size is less than 50 nm, it is difficult to obtain a sufficient polishing rate. When the average particle size exceeds 600 nm, the occurrence of scratches on the polishing substrate becomes significant, which is not preferable. The average particle size of the ceria-based composite fine particles of the present invention is preferably recommended to be within the range of 170 to 260 nm. The shape of the ceria-based composite fine particles of the present invention is not particularly limited, and may be spherical or non-spherical.

[0028] <Mother particle> The base particle in the ceria-based composite microparticle of the present invention is a portion where, when the composite particle of the present invention is subjected to STEM-EDS analysis to measure the elemental concentrations of Ce and Si in a cross section of the ceria-based composite microparticle of the present invention, the ratio (percentage) of the Ce molar concentration to the sum of the Ce molar concentration and the Si molar concentration (Ce / (Ce+Si)×100) is less than 3%.

[0029] The average particle size of the base particles in the ceria-based composite microparticles of the present invention is not particularly limited, but is preferably 15 nm to 330 nm, and more preferably 120 to 240 nm. When the average particle diameter of the mother particles is less than 15 nm, the average particle diameter of the composite microparticles obtained by using such mother particles is difficult to reach 15 nm, and when such particles are used as an abrasive, the polishing rate may not reach a practical level.When the average particle diameter of the mother particles is more than 330 nm, the average particle diameter of the composite microparticles obtained by using such mother particles is often more than 330 nm, and when the dispersion of such composite microparticles is used as an abrasive, the polishing rate may not reach a practical level, and the surface accuracy of the substrate to be polished may be reduced.In addition, it is more preferable that the mother particles are monodisperse.

[0030] The average particle size of the base particles in the ceria-based composite microparticles of the present invention is measured as follows. The composite particle of the present invention is subjected to STEM-EDS analysis, and the base particle is identified on the obtained image. The maximum diameter of the base particle is taken as the major axis, and the length is measured and this value is taken as the major axis (DL). A point is also determined on the major axis that divides the major axis in half, and two points where a straight line perpendicular to this intersects with the outer edge of the base particle are found, and the distance between these two points is measured and taken as the minor axis (DS). The geometric mean value of the major axis (DL) and minor axis (DS) is then calculated and taken as the particle diameter of the base particle. In this manner, the particle sizes of 50 base particles are measured, and the value obtained by simple averaging is regarded as the average particle size.

[0031] The base particles are mainly composed of amorphous silica and are usually made of silica fine particles or silica-based fine particles, which are preferably used because they are easy to prepare spherical particles with a uniform particle size and can also be prepared with a variety of particle sizes.

[0032] The fact that the base particles are mainly composed of amorphous silica can be confirmed, for example, by the following method: After drying the dispersion of the present invention, the dispersion is pulverized in a mortar, and an X-ray diffraction pattern is obtained using, for example, a conventionally known X-ray diffractometer (e.g., RINT1400, manufactured by Rigaku Corporation). If no peaks of crystalline silica such as cristobalite appear, the base particles are deemed to be mainly composed of amorphous silica. In addition, the dispersion of the present invention is dried, embedded in resin, and then sputter-coated with Pt, and a cross-sectional sample is prepared using a conventionally known focused ion beam (FIB) device. For example, when the prepared cross-sectional sample is subjected to a conventionally known TEM device and an FFT pattern is obtained using fast Fourier transform (FFT) analysis, a diffraction pattern of crystalline silica such as Cristobalite does not appear. From this, it can be confirmed that the silica contained in the base particles is amorphous. In addition, in such a case, the base particles are considered to be mainly composed of amorphous silica. Another method is to use a conventionally known TEM device to observe the presence or absence of lattice fringes due to the atomic arrangement of the base particles on a cross-sectional sample prepared in a similar manner. If the material is crystalline, lattice fringes according to the crystal structure are observed, and if the material is amorphous, lattice fringes are not observed. From this, it can be confirmed that the silica contained in the base particles is amorphous. In such a case, the base particles are considered to be mainly composed of amorphous silica.

[0033] <Child Particle> In the ceria-based composite fine particle of the present invention, the child particles contain crystalline ceria as a main component, and the child particles are dispersed in a cerium-containing silica layer disposed on the mother particle.

[0034] In the ceria-based composite microparticles of the present invention, when the composite particles of the present invention are subjected to STEM-EDS analysis to measure the elemental concentrations of Ce and Si in a cross section of the ceria-based composite microparticles of the present invention, the child particles are those portions where the ratio (percentage) of the Ce molar concentration to the sum of the Ce molar concentration and the Si molar concentration (Ce / (Ce+Si)×100) exceeds 50%.

[0035] The average particle size of the child particles is smaller than that of the mother particles, and is, for example, preferably 10 to 25 nm, and more preferably 14 to 23 nm. When the average particle size of the child particles exceeds 25 nm, the ceria-based composite microparticle dispersion containing the child particles is not preferable because it causes scratches on the object to be polished when used for polishing purposes.When the average particle size of the child particles is less than 10 nm, it tends to be difficult to obtain a polishing rate sufficient for practical use.

[0036] The average particle size of the child particles in the ceria-based composite fine particles of the present invention is measured as follows. The composite particle of the present invention is subjected to STEM-EDS analysis, and a child particle is identified on the obtained image. The maximum diameter of the child particle is taken as the major axis, and the length is measured and the value is taken as the major axis (DL). A point is also determined on the major axis that divides the major axis in half, and two points where a straight line perpendicular to the major axis intersects with the outer edge of the child particle are found, and the distance between the two points is measured and taken as the minor axis (DS). The geometric mean value of the major axis (DL) and minor axis (DS) is then calculated and taken as the particle diameter of the child particle. In this way, the particle diameters of 50 child particles are measured, and the value obtained by simply averaging them is taken as the average particle diameter.

[0037] The child particles may be stacked in the cerium-containing silica layer, i.e., a plurality of child particles may be present inside the cerium-containing silica layer on radial lines from the center of the mother particle. The child particles may be embedded in the cerium-containing silica layer, or may be partially exposed to the outside of the cerium-containing silica layer. When the child particles are embedded in the cerium-containing silica layer, the surface of the ceria-based composite fine particles of the present invention is closer to the silica surface, so that the storage stability and polishing stability are improved, and the amount of abrasive grains remaining on the substrate after polishing is reduced. Therefore, it is preferable that the child particles are embedded in the cerium-containing silica layer.

[0038] The shape of the child particles is not particularly limited. For example, they may be spherical, elliptical, or rectangular. When the dispersion of the present invention is used for polishing purposes and a high polishing rate is to be obtained, the child particles are preferably non-spherical, and more preferably rectangular.

[0039] In the ceria-based composite fine particles of the present invention, the child particles contain crystalline ceria as a main component. The fact that the child particles are mainly composed of crystalline ceria can be confirmed, for example, by drying the dispersion of the present invention, pulverizing the obtained solid matter in a mortar, etc. to obtain the composite particles of the present invention, and then subjecting the composite particles to X-ray analysis using, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Corporation), and only the crystalline phase of ceria is detected in the obtained X-ray diffraction pattern. In such a case, the child particles are considered to be mainly composed of crystalline ceria. The crystalline phase of ceria is not particularly limited, but examples thereof include cerianite, etc.

[0040] The child particles are mainly composed of crystalline ceria (crystalline Ce oxide), and may contain other substances, such as elements other than cerium, and may also contain a cerium hydrate compound as a polishing promoter. However, as described above, when the composite particles of the present invention are subjected to X-ray diffraction, only the crystalline phase of ceria is detected. That is, even if a crystalline phase other than ceria is contained, the content of the crystalline phase other than ceria is low or the crystalline phase is dissolved in the ceria crystal, so that the crystalline phase is outside the detection range by X-ray diffraction.

[0041] The average crystallite diameter of the child particles is calculated using the full width at half maximum of the maximum peak appearing in the chart obtained by subjecting the composite particles of the present invention to X-ray diffraction. For example, the average crystallite diameter of the (111) plane is 10 to 25 nm (full width at half maximum is 0.86 to 0.34°), and preferably 14 to 23 nm (full width at half maximum is 0.62 to 0.37°). In many cases, the peak intensity of the (111) plane is the maximum, but the peak intensity of other crystal planes, for example, the (100) plane, may be the maximum. In that case, it can be calculated in the same way, and the size of the average crystallite diameter in that case may be the same as the average crystallite diameter of the (111) plane.

[0042] The method for measuring the average crystallite size of the child particles is shown below using the (111) plane (2θ=approximately 28 degrees) as an example. First, the composite particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained using, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). Then, the full width at half maximum of the peak of the (111) plane near 2θ=28 degrees in the obtained X-ray diffraction pattern is measured, and the average crystallite size can be calculated using the following Scherrer formula. D=Kλ / βcosθ D: average crystallite size (angstroms) K: Scherrer constant (K=0.94 in the present invention) λ: X-ray wavelength (1.5419 angstroms, Cu lamp) β: Full width at half maximum (rad) θ: reflection angle

[0043] In the ceria-based composite fine particles of the present invention, the child particles are mainly composed of crystalline ceria, and it is preferable that silicon atoms are dissolved in the crystalline ceria, which is the main component. In general, a solid solution means that two or more elements (which may be metals or nonmetals) are dissolved in each other to form a uniform solid phase, and the solid solutions obtained by solid solution are classified into substitutional solid solutions and interstitial solid solutions. Substitutional solid solutions can easily occur in atoms with similar atomic radii, but since the atomic radii of Ce and Si are significantly different, it is considered that at least substitutional solid solutions are difficult to occur. In addition, in the crystal structure of cerianite, the coordination number of Ce from the Ce center is 8, but when Si is substituted for Ce in a 1:1 ratio, for example, the coordination number of Ce should be 7. However, in the analysis results of a preferred embodiment of the ceria-based composite fine particles of the present invention, the average coordination number of Ce from the Ce center is 8.0, and the average coordination number of Si is 1.2, so it is estimated that the preferred embodiment of the ceria-based composite fine particles of the present invention is an interstitial type. Moreover, from the analysis results of the preferred embodiment of the ceria-based composite microparticles of the present invention, the interatomic distance of Ce-Si is smaller than the interatomic distance of Ce-Ce, so that the preferred embodiment of the ceria-based composite microparticles of the present invention is presumed to be an interstitial solid solution. 1 and the cerium-cerium atom distance is R 2When R 1 <R 2 It is preferable that the following relationship is satisfied.

[0044] It has been known that the use of ceria particles as abrasive grains to polish a silica-coated substrate or a glass substrate shows a specifically high polishing rate compared to the use of other inorganic oxide particles. One of the reasons why ceria particles show a particularly high polishing rate for a silica-coated substrate is that the trivalent cerium contained in the ceria particles has a high chemical reactivity with the silica coating on the substrate to be polished.

[0045] <Cerium-containing silica layer> The ceria-based composite fine particles of the present invention have a cerium-containing silica layer on the surface of the mother particle, and child particles are dispersed inside the cerium-containing silica layer.

[0046] By adopting such a structure, the child particles are less likely to fall off due to the crushing process during production or the pressure during polishing, and even if some of the child particles are chipped off, most of the child particles do not fall off and remain in the cerium-containing silica layer, so that the polishing function is not reduced.

[0047] In the ceria-based composite microparticles of the present invention, the cerium-containing silica layer is a portion where the ratio (percentage) of the Ce molar concentration to the sum of the Ce molar concentration and the Si molar concentration (Ce / (Ce+Si)×100) is 3 to 50% when the composite particles of the present invention are subjected to STEM-EDS analysis to measure the elemental concentrations of Ce and Si in a cross section of the ceria-based composite microparticles of the present invention.

[0048] The average thickness of the cerium-containing silica layer is not particularly limited, but is preferably 10 to 40 nm, more preferably 12 to 30 nm. Note that the ceria-based composite fine particles of the present invention may have a portion on the periphery where the cerium-containing silica layer is not present. The average thickness of the cerium-containing silica layer is determined by drawing straight lines at any 12 locations from the center of the parent particles of the ceria-based composite fine particles of the present invention to the outermost shell, and measuring the distance (distance on the line passing through the center of the parent particles) between the line at which the ratio (percentage) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration (Ce / (Ce+Si)×100) identified from the elemental map obtained by performing STEM-EDS analysis as described above is 3% and the outermost shell of the ceria-based composite fine particles of the present invention, and simply averaging them. Note that the center of the parent particles means the intersection of the major axis and the minor axis described above.

[0049] In the cerium-containing silica layer in the ceria-based composite fine particles of the present invention, it is considered that the bonding force between the daughter particles (ceria fine particles mainly composed of crystalline ceria) dispersed and grown in the cerium-containing silica layer and the parent particles during the firing process is promoted. Therefore, for example, in the process of obtaining the ceria-based composite fine particles of the present invention, if necessary, after performing preliminary crushing by dry method on the fired body pulverized dispersion obtained by firing, crushing by wet method is performed, and further centrifugation treatment is performed if necessary. However, it is considered that the cerium-containing silica layer has the effect of preventing the daughter particles from detaching from the parent particles. In this case, local detachment of the daughter particles is not a problem, and it is not necessary for all of the surface of the daughter particles to be covered by a part of the cerium-containing silica layer. It is sufficient that the daughter particles have a strength such that they do not detach from the parent particles during the crushing process. Due to such a structure, when the dispersion of the present invention is used as an abrasive, it is considered that the polishing rate is high and the deterioration of surface accuracy and scratches is small.

[0050] Further, in the ceria-based composite fine particles of the present invention, since a cerium-containing silica layer exists on at least a part of the outermost surface, -OH groups of silica exist on the outermost surface (outermost shell) of the ceria-based composite fine particles of the present invention. Therefore, when used as an abrasive, it is considered that the ceria-based composite fine particles of the present invention repel each other due to the charge of the -OH groups on the surface of the polished substrate, and as a result, the adhesion to the surface of the polished substrate is reduced.

[0051] In addition, ceria generally has a different potential from silica, polishing substrates, and polishing pads, and as the pH goes from alkaline to near neutral, the negative zeta potential decreases, and in the weak acid region, it has a positive potential. Therefore, at an acidic pH during polishing, ceria adheres to the polishing substrate or polishing pad due to differences in the magnitude and polarity of the potential, and is likely to remain on the polishing substrate or polishing pad. On the other hand, since the ceria-based composite fine particles of the present invention have silica in the outermost shell as described above, the potential becomes negative due to silica, so that the ceria-based composite fine particles maintain a negative potential from alkaline to acidic pH, and as a result, abrasive grains are less likely to remain on the polishing substrate or polishing pad. When the ceria-based composite fine particles of the present invention are obtained by crushing while maintaining a pH of 8.6 to 10.8 during the crushing treatment, part of the silica (silica in the cerium-containing silica layer) on the surface of the ceria-based composite fine particles of the present invention is dissolved. If the dispersion of the present invention produced under such conditions is adjusted to pH<7 when applied to polishing applications, the dissolved silica will be deposited on the ceria-based composite fine particles (abrasive grains) of the present invention, and the surfaces of the ceria-based composite fine particles of the present invention will have a negative potential. If the potential is low, silicic acid may be added to appropriately reinforce the cerium-containing silica layer.

[0052] The composite particles of the present invention have a specific surface area of ​​9 to 60 m 2 / g, and 10 to 43 m 2 It is more preferable that the molecular weight is / g.

[0053] Here, a method for measuring the specific surface area (BET specific surface area) will be described. First, a dried sample (0.2 g) is placed in a measurement cell and degassed in a nitrogen gas flow at 250°C for 40 minutes, then the sample is kept at liquid nitrogen temperature in a mixed gas flow of 30% nitrogen by volume and 70% helium by volume to allow the nitrogen to be adsorbed in equilibrium on the sample. Next, the temperature of the sample is gradually raised to room temperature while the mixed gas is being passed through, and the amount of nitrogen desorbed during this period is detected, and the specific surface area of ​​the sample is measured using a calibration curve created in advance. Such a BET specific surface area measurement method (nitrogen adsorption method) can be carried out using, for example, a conventionally known surface area measurement device. In the present invention, the specific surface area means a value obtained by measurement in this manner, unless otherwise specified.

[0054] [Composite particles of the present invention] As described above, the composite particles of the present invention are obtained by supporting the ceria-based composite particles of the present invention on the irregular inorganic oxide particles of the present invention, and the irregular inorganic oxide particles of the present invention have an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3. The ceria-based composite particles of the present invention comprise mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer.

[0055] The average number of the ceria-based composite fine particles supported on the irregular inorganic oxide fine particles of the present invention is preferably 1 to 200 particles per 100 nm in the major axis direction of the irregular inorganic oxide fine particles of the present invention. When the dispersion of the present invention is used for polishing, good polishing performance is exhibited when the average number of particles is within the above range. It is practically difficult to prepare particles having an average number of particles exceeding 200. Even if such particles can be prepared, they are huge agglomerates, and when used for polishing, polishing scratches occur frequently. The average number of particles supported is more preferably 1 to 100, and further preferably 1 to 30. The chemical form in which the ceria-based composite microparticles of the present invention are supported on the irregular inorganic oxide microparticles of the present invention is not particularly limited as long as sufficient polishing performance can be exhibited when the composite particles of the present invention are used as polishing abrasive grains, but is usually such that the ceria-based composite microparticles of the present invention are adsorbed or chemically bonded to the irregular inorganic oxide microparticles of the present invention. The structural form of the ceria-based composite fine particles of the present invention supported on the irregular inorganic oxide fine particles of the present invention may be such that the ceria-based composite fine particles of the present invention are directly supported on the irregular inorganic oxide fine particles of the present invention, or the ceria-based composite fine particles of the present invention supported on the irregular inorganic oxide fine particles of the present invention may further support one or more other ceria-based composite fine particles of the present invention. When the ceria-based composite fine particles of the present invention are further supported on the ceria-based composite fine particles of the present invention, the number of the ceria-based composite fine particles of the present invention supported on the irregular inorganic oxide fine particles of the present invention increases, which is preferable.

[0056] <Dispersion of the Present Invention> The dispersion of the present invention will now be described. The dispersion of the present invention is one in which the composite particles of the present invention as described above are dispersed in a dispersion solvent.

[0057] The dispersion of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Furthermore, the dispersion of the present invention can be suitably used as a polishing slurry by adding at least one additive selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster, and a pH buffer as an additive for controlling the polishing performance.

[0058] In addition, as the dispersion solvent containing the dispersion liquid of the present invention, for example, alcohols such as methanol and ethanol; amides such as acetone and 2-butanone; ethers such as diethyl ether and isopropyl ether; glycol ethers such as 2-methoxyethanol and 2-ethoxyethanol; glycol ether acetates such as 2-methoxyethyl acetate and 2-ethoxyethyl acetate; esters such as methyl acetate and ethyl acetate; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane and heptane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; pyrrolidones such as N-methyl-2-pyrrolidone and N-octyl-2-pyrrolidone, and other organic solvents can be used. These may be mixed with water and used.

[0059] The solid content concentration in the dispersion of the present invention is preferably in the range of 0.3 to 50% by mass.

[0060] <Production Method of the Present Invention> The manufacturing method of the present invention will now be described. The manufacturing method of the present invention includes steps [1], [2], [3] and [4] which will be described below.

[0061] <Process [1]> In step [1], irregularly shaped inorganic oxide microparticles having an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3 are mixed with a ceria-based composite microparticle dispersion in which ceria-based composite microparticles having an average particle diameter of 50 to 600 nm are dispersed in a solvent, the ceria-based composite microparticles having mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particles, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer, are mixed with each other to obtain a raw material dispersion.

[0062] The mixture can be obtained, for example, by mixing a dispersion of irregular shaped inorganic oxide fine particles (solid content concentration: 0.5 to 30% by mass) and a dispersion of ceria-based composite fine particles (solid content concentration: 0.5 to 30% by mass). The mixing means is not particularly limited.

[0063] The solvent for the irregular shaped inorganic oxide fine particle dispersion and the ceria-based composite fine particle dispersion is preferably water or a mixed solvent containing water and a water-soluble organic solvent.

[0064] The mixing ratio of the irregular shaped inorganic oxide fine particle dispersion and the ceria-based composite fine particle dispersion is preferably within a range of 100:500 to 100:8000 (parts by mass) calculated as solid content.

[0065] The temperature during mixing is preferably from room temperature to 40°C.

[0066] Furthermore, the irregular inorganic oxide microparticles are mixed with a ceria-based composite microparticle dispersion liquid in which the ceria-based composite microparticles are dispersed in a solvent to prepare a raw material dispersion liquid. Here, it is preferable to prepare the raw material dispersion liquid by subjecting the mixed liquid containing the irregular inorganic oxide microparticles and the ceria-based composite microparticles to ultrasonic treatment. The ultrasonic treatment is preferable because it allows the irregular inorganic oxide microparticles and the ceria-based composite microparticles to be uniformly dispersed and mixed. Regarding the output and frequency of the ultrasonic waves, any commercially available ultrasonic disperser having an ultrasonic treatment function can be used.

[0067] The ceria-based composite fine particle dispersion can be obtained, for example, by a production method including the following steps A, B, and C. <Process A> In step A, a silica fine particle dispersion in which silica fine particles are dispersed in a solvent is prepared. As the silica fine particle dispersion liquid, it is preferable to use a silica fine particle dispersion liquid in which silica fine particles produced by hydrolysis of alkoxysilane are dispersed in a solvent. When using a silica fine particle dispersion liquid prepared from water glass as a raw material, it is preferable to use the silica fine particle dispersion liquid after acid treatment and further deionization treatment. In this case, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO contained in the silica fine particles. 3 , S.O. 4 This is because the content of F is reduced, specifically, it can be 100 ppm or less. Specifically, the silica fine particles in the silica fine particle dispersion liquid, which is the raw material used in the step A, preferably satisfy the following conditions (a) and (b). (a) The content of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is each 100 ppm or less. (b) U, Th, Cl, NO 3 , S.O. 4 and F content is 5 ppm or less.

[0068] In step A, a silica microparticle dispersion liquid in which the above-mentioned silica microparticles are dispersed in a solvent is stirred, and a metal salt of cerium is added thereto continuously or intermittently while maintaining the temperature at 5 to 98°C and the pH range at 7.0 to 9.0, to obtain a precursor particle dispersion liquid containing precursor particles.

[0069] The dispersion medium in the silica fine particle dispersion preferably contains water, and it is preferable to use an aqueous silica fine particle dispersion (aqueous sol).

[0070] The solid content concentration in the silica fine particle dispersion is SiO 2 The solid content is preferably 1 to 40 mass % converted into a solid content of 1. If the solid content is too low, the silica concentration in the production process will be low, which may result in poor productivity.

[0071] Furthermore, impurities can be extracted using a cation exchange resin or an anion exchange resin, or a mineral acid, an organic acid, or the like, and the silica fine particle dispersion can be deionized, if necessary, using an ultrafiltration membrane, etc. A silica fine particle dispersion from which impurity ions have been removed by deionization is more preferable because it is easier to form hydroxides containing silicon on the surface. However, the deionization treatment is not limited to these.

[0072] In step A, the silica fine particle dispersion as described above is stirred, and a metal salt of cerium is added thereto continuously or intermittently while maintaining the temperature at 5 to 98° C. and the pH range at 7.0 to 9.0. The metal salt of cerium is not limited, but cerium chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide, etc. can be used. Specific examples include cerium (I) nitrate, cerium carbonate, cerium (I) sulfate, and cerium (I) chloride. Among them, cerium (I) nitrate and cerium (I) chloride are preferred. Crystalline cerium oxide is generated from the solution that becomes supersaturated at the same time as neutralization, and these are quickly attached to the silica fine particles by a coagulation and deposition mechanism, so that the efficiency of forming a bonded oxide is high and it is preferred. However, sulfate ions, chloride ions, nitrate ions, etc. contained in these metal salts are corrosive. Therefore, it is necessary to remove them to 5 ppm or less in a post-process after preparation by washing. On the other hand, carbonate is released as carbon dioxide gas during preparation, and alkoxide is decomposed to alcohol, so it is preferred.

[0073] The amount of the metal salt of cerium added to the silica fine particle dispersion is preferably an amount such that the mass ratio of silica to ceria in the resulting composite fine particles of the present invention falls within the range of 100:11-316.

[0074] After the cerium metal salt is added to the silica microparticle dispersion, the temperature during stirring is preferably 5 to 98° C., and more preferably 10 to 95° C. If the temperature is too low, the solubility of silica decreases significantly, making it difficult to control the crystallization of ceria, resulting in the formation of coarse crystalline oxides of ceria, which may make it difficult for the oxides to adhere to the silica microparticles (base particles). On the other hand, if the temperature is too high, the solubility of silica increases significantly, which may inhibit the formation of crystalline ceria oxide, and further, scale tends to form on the reactor wall, which is undesirable.

[0075] The stirring time is preferably 0.5 to 24 hours, and more preferably 0.5 to 18 hours. If this time is too short, crystalline cerium oxide cannot be sufficiently formed, which is not preferable. Conversely, if this time is too long, the reaction to form crystalline cerium oxide does not proceed any further, which is uneconomical. After the addition of the cerium metal salt, the mixture may be aged at 5 to 98°C as desired. Aging can further promote the reaction of depositing the cerium compound on the base particles.

[0076] In addition, when the metal salt of cerium is added to the silica microparticle dispersion and stirred, the pH range of the silica microparticle dispersion is 7.0 to 9.0, preferably 7.6 to 8.6. In this case, it is preferable to adjust the pH by adding an alkali or the like. Examples of such alkali include known alkalis. Specific examples include an aqueous ammonia solution, an alkali hydroxide, an alkaline earth metal, and an aqueous solution of amines, but are not limited thereto.

[0077] By such step A, a dispersion liquid (precursor particle dispersion liquid) containing particles (precursor particles) which are precursors of the composite fine particles of the present invention is obtained.

[0078] The precursor particle dispersion obtained in step A may be further diluted or concentrated with pure water or ion-exchanged water before being subjected to step B.

[0079] The solid content in the precursor particle dispersion is preferably 1 to 27% by mass.

[0080] If desired, the precursor particle dispersion may be deionized using a cation exchange resin, an anion exchange resin, an ultrafiltration membrane, an ion exchange membrane, centrifugation, or the like.

[0081] <Project B> In Project B, after drying the precursor particle dispersion, it is fired at 400 to 1,200 °C.

[0082] The method of drying is not particularly limited. It can be dried using a conventionally known dryer. Specifically, a box dryer, a band dryer, a spray dryer, etc. can be used. Preferably, it is recommended that the pH of the precursor particle dispersion before drying be 6.0 to 7.0. This is because the surface activity can be suppressed when the pH of the precursor particle dispersion before drying is 6.0 to 7.0. After drying, the firing temperature is 400 to 1200 °C, preferably 800 to 1100 °C, and more preferably 1000 to 1090 °C. When firing in such a temperature range, the crystallization of ceria proceeds sufficiently, and the silica film present on the surface of the ceria fine particles thickens moderately, and the mother particles and the daughter particles are firmly bonded. If this temperature is too high, the crystals of ceria may grow abnormally, or the silica film on the ceria particles may thicken and the bonding with the mother particles may progress, but it is also expected to thickly cover the daughter particles of ceria, and the amorphous silica constituting the mother particles may crystallize or the fusion of the particles may progress.

[0083] In Project B, the fired body obtained by firing is subjected to the following treatment (i) or (ii) to obtain a fired body pulverized dispersion. (i) Dry crushing and pulverization treatment is performed, and a solvent is added for solvent dispersion treatment. (ii) A solvent is added, and wet crushing and pulverization treatment is performed in the range of pH 8.6 to 10.8. As the dry crushing and pulverization device, a conventionally known device can be used. For example, an attritor, a ball mill, a vibration mill, a vibration ball mill, etc. can be mentioned. Conventionally known wet disintegration / grinding devices can be used, including, for example, batch bead mills such as basket mills, horizontal, vertical, and annular continuous bead mills, sand grinder mills, ball mills, rotor-stator homogenizers, ultrasonic dispersion homogenizers, wet media agitation mills (wet disintegrators) such as impact grinders that collide fine particles in a dispersion liquid. Beads used in wet media agitation mills include, for example, beads made from glass, alumina, zirconia, steel, flint, etc. In either the treatment (i) or (ii), water and / or an organic solvent is used as the solvent. For example, it is preferable to use water such as pure water, ultrapure water, or ion-exchanged water. In addition, the solid content concentration of the sintered body crushed dispersion obtained by the treatment (i) or (ii) is not particularly limited, but is preferably in the range of, for example, 0.3 to 50 mass %. Of the treatments (i) and (ii), the wet treatment (ii) is more preferably used in practice.

[0084] In addition, when the wet disintegration / grinding of (ii) is performed, it is preferable to perform the wet disintegration / grinding while maintaining the pH of the solvent at 8.6 to 10.8. This is because the polishing rate is further improved. Regarding this, the present inventors presume that the polishing rate is further improved and the falling off of the child particles of ceria can be controlled by appropriately thinning the silica coating on the surface of the ceria-based composite fine particle of the present invention and / or appropriately exposing the child particles on a part of the surface of the ceria-based composite fine particle of the present invention. In addition, they presume that since the silica coating is thin or peeled off, the child particles are more likely to fall off to some extent during polishing.

[0085] <Process C> In step C, the dispersion of the crushed sintered body obtained in step B is centrifuged at a relative centrifugal acceleration of 300 G or more, and then the precipitated components are removed to obtain a dispersion of silica-based composite fine particles. Specifically, the sintered powder dispersion is classified by centrifugation. The relative centrifugal acceleration in the centrifugation is 300G or more. After the centrifugation, the precipitated components are removed to obtain a silica-based composite microparticle dispersion. There is no particular upper limit to the relative centrifugal acceleration, but in practice, it is used at 10,000G or less. It is necessary to provide a centrifugal separation process that satisfies the above conditions in step C. If the centrifugal acceleration or processing time does not satisfy the above conditions, coarse particles will remain in the silica-based composite microparticle dispersion, which will cause scratches when the silica-based composite microparticle dispersion is used for polishing purposes such as an abrasive.

[0086] By such a production method, the ceria-based composite fine particle dispersion can be obtained.

[0087] <Process [2]> In step [2], a buffer solution is added to the raw material dispersion and stirred to obtain a precursor dispersion having a pH of 2.0 to 7.0. In order to maintain an optimal pH range for the composite formation in the subsequent steps, a pH buffer solution is added to the raw material dispersion to adjust the pH to the range of 2.0 to 7.0.

[0088] Examples of pH buffer solutions that can be used include aqueous ammonium acetate solutions, aqueous ammonium nitrate solutions, phosphates and borates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate, or organic acids. As the pH range, a range of pH 4 to 6 is more preferably recommended.

[0089] <Process [3]> In the step [3], the precursor dispersion is heated to 40 to 98° C., maintained at that temperature for one hour or more, and then allowed to cool to obtain a reaction dispersion. In step 3, the irregular inorganic oxide fine particles and the ceria-based composite fine particles are composited. If the reaction temperature is less than 40°C, the reaction does not proceed smoothly, and the amount of the ceria-based composite fine particles carrying the irregular inorganic oxide fine particles decreases, or a long period of time is required, which is not economically preferable. Conversely, if the reaction temperature is higher than 98°C, it is difficult to control, and excessive reaction occurs, resulting in the generation of coarse aggregated particles, which is not preferable.

[0090] <Process [4]> In the step [4], the reaction dispersion is brought into contact with an anion exchange resin to carry out ion exchange, thereby obtaining the dispersion of the present invention. The pH of the reaction dispersion obtained in step [3] is in an unstable range, and since the ionic strength is high, the stability is poor. Therefore, by lowering the ionic strength by anion exchange and adjusting the pH to a relatively stable range, specifically, pH 8 to 11, a stable composite ceria-based composite microparticle dispersion can be obtained.

[0091] As the anion exchange resin, a known anion exchange resin such as an OH type anion exchange resin can be used. The anion exchange resin may be in any form, such as beads or fibers.

[0092] As a method for the anion exchange treatment, a conventionally known method can be used, such as a method in which an anion exchange resin is added to the reaction dispersion liquid and treated in a batch system, or a method in which an anion exchange resin is packed in a column and the liquid is passed through the column. EXAMPLES

[0093] First, the measurement methods and test methods in the examples and comparative examples will be described in detail. The following measurement results and test results are shown in Tables 1 to 3 for each of the examples and comparative examples.

[0094] [Analysis of ingredients] 1. SiO in silica-based particle dispersion 2 Content measurement Silica content in silica-based fine particle dispersion (SiO 2Content) measurement method and silica concentration (SiO 2 The calculation method for the concentration is as follows: First, the mass of the silica-based particle dispersion is measured. In the case of silica-based particles made from sodium silicate, the silica-based particle dispersion is subjected to ignition at 1000°C to reduce the weight, and the whole of the resultant is weighed. 2 Assuming that SiO 2 The content (mass of solid content) was obtained, and the ratio to the mass of the silica-based fine particle dispersion was calculated to give the silica concentration (mass %). In the case of a silica-based particle dispersion liquid made from alkoxysilane as a raw material, the silica-based particle dispersion liquid was dried at 150°C for 1 hour and then weighed. All of the obtained dispersion was found to be SiO 2 Assuming that SiO 2 The content (mass of solid content) was obtained, and the ratio to the mass of the silica-based fine particle dispersion was calculated to give the silica concentration (mass %).

[0095] 2. SiO in ceria-based composite particles 2 Content and CeO 2 Content measurement SiO in ceria-based composite particles 2 The content was determined by subjecting the ceria-based composite particle dispersion to 1000°C ignition loss, determining the mass of the solid content, and then measuring the Ce content by the standard addition method described later using an ICP plasma emission spectrometer to determine the CeO 2 Calculate the mass% and CeO 2 The other solid components are SiO 2 Assuming that SiO 2 Content (and SiO 2 The content of ceria per 100 parts by mass of silica was also calculated. [Standard addition method] Approximately 0.2 g of a sample (adjusted to a solid content of 20% by mass) made of a ceria-based composite microparticle dispersion is collected on a platinum dish. 1 g of sodium hydroxide and 2 g of sodium peroxide are added, heated on an electric heater, melted with a Bunsen burner, and then cooled to room temperature. 50 ml of hydrochloric acid and 150 ml of water are added to a 300 ml beaker, and a zirconia crucible and lid are placed in the beaker and heated on a water bath to dissolve the molten material, then cooled to room temperature. This solution is placed in a 500 ml measuring flask, water is added to make 500 ml, 10 ml of the solution is taken, placed in a 100 ml measuring flask, 4 ml of hydrochloric acid is added, and the solution is diluted to 100 ml with water. This solution is measured using an ICP plasma emission spectrometer (e.g., SPS5520 made by SII), and the CeO is measured based on a calibration curve created using a cerium standard solution. 2 Calculate the mass percentage.

[0096] [X-ray diffraction method, measurement of average crystallite size] The ceria-based composite microparticle dispersion was dried using a conventional dryer, and the resulting powder was ground in a mortar for 10 minutes. The X-ray diffraction pattern was obtained using an X-ray diffractometer (Rigaku Corporation, RINT1400) to identify the crystal type. In addition, the full width at half maximum of the peak of the (111) plane (near 2θ=28 degrees) in the obtained X-ray diffraction pattern was measured by the above-mentioned method, and the average crystallite size was calculated by Scherrer's formula.

[0097] [Measurement of average particle size] 1. Average particle size of ceria-based composite particles The average particle size of the ceria-based composite fine particles means the number average value of the average particle sizes measured by the image analysis method. Specifically, in the photographic projection diagram obtained by photographing the ceria-based composite fine particles with a scanning electron microscope at a magnification of 300,000 times (or 500,000 times), the maximum diameter of the particle is taken as the major axis, and its length is measured, and this value is defined as the major diameter (DL). Also, a point that bisects the major axis on the major axis is determined, and two points where a straight line orthogonal to it intersects the outer edge of the particle are obtained, and the distance between the two points is measured and defined as the minor diameter (DS). Then, the geometric mean value of the major diameter (DL) and the minor diameter (DS) is obtained, and this is taken as the particle size of the ceria-based composite fine particles. In this way, the particle sizes of 50 or more ceria-based composite particles are measured, and their number average value is calculated. The value thus obtained is taken as the average particle size (nm) of the ceria-based composite fine particles.

[0098] 2. Average particle size of ceria-based composite fine particles supported on irregular inorganic oxide fine particles In the photographic projection diagram obtained by photographing the irregular inorganic oxide fine particles with a scanning electron microscope at a magnification of 100,000 times, the maximum diameter of the particle is taken as the major axis, and its length is measured, and this value is defined as the major diameter (L). Also, a point that bisects the major axis on the major axis is determined, and two points where a straight line orthogonal to it intersects the outer edge of the particle are obtained, and the distance between the two points is measured and defined as the minor diameter (S). Also, the geometric mean value of the major diameter (L) and the minor diameter (S) is obtained, and this is taken as the particle size of the irregular inorganic oxide fine particles. In this way, the particle sizes of 50 or more ceria-based composite particles are measured, and their number average value is calculated. The value thus obtained is taken as the average particle size (nm) of the ceria-based composite fine particles supported on the irregular inorganic oxide fine particles.

[0099] [Average particle sizes of the mother particles and daughter particles in the ceria-based composite fine particles] The average particle sizes of the mother particles and daughter particles of the ceria-based composite fine particles obtained in the examples and comparative examples are taken as the values determined by the image analysis method by STEM-EDS analysis as described above.

[0100] [Average major diameter (L) and average minor diameter (S) / Average major diameter (L)] 1. Average major diameter (L) and average minor diameter (S) / Average major diameter (L) of irregular inorganic oxide fine particles In a photographic projection obtained by photographing a large number of irregular inorganic oxide fine particles at a magnification of 100,000 times with a scanning electron microscope, one irregular inorganic oxide fine particle was selected. The maximum diameter of the particle was taken as the major axis, and its length was measured, and the value was defined as the major axis length (L). Also, a point that bisects the major axis on the major axis was determined, two points where a straight line perpendicular to it intersects the outer edge of the particle were obtained, and the distance between the two points was measured and defined as the minor axis (S). Furthermore, the minor axis / major axis ratio of the one irregular inorganic oxide fine particle was determined. This operation was performed on 50 randomly selected irregular inorganic oxide fine particles, and the average value was obtained to calculate the average major axis length (L) and the average minor axis (S) / average major axis length (L).

[0101] 2. Average major axis length (L) and average minor axis (S) / average major axis length (L) of irregular inorganic oxide fine particles supported by ceria-based composite fine particles In a photographic projection obtained by photographing composite ceria-based composite fine particles at a magnification of 100,000 times with a scanning electron microscope, the maximum diameter of the irregular inorganic oxide fine particles supported by the ceria-based composite fine particles was taken as the major axis, and its length was measured, and the value was defined as the major axis length (L) of the composite ceria-based composite fine particles. Also, a point that bisects the major axis on the major axis was determined, two points where a straight line perpendicular to it intersects the outer edge of the particle were obtained, and the distance between the two points was measured and defined as the minor axis (S) of the composite ceria-based composite fine particles. Also, the geometric mean value of the major axis (L) and the minor axis (S) was determined and defined as the minor axis / major axis ratio of the composite ceria-based composite fine particles. This operation was performed on 50 randomly selected composite ceria-based composite fine particles, and the major axis length (L) and the minor axis length (S) were measured respectively, and the minor axis (S) / major axis length (L) was calculated. The average values were obtained respectively and defined as the average major axis length (L) and the average minor axis (S) / average major axis length (L).

[0102] [Average number of ceria-based composite fine particles supported per 100 nm in the major axis direction of the irregular inorganic oxide fine particles of the ceria-based composite fine particles supported on the irregular inorganic oxide fine particles] In the photographic projection obtained by photographing the composite ceria-based composite microparticles at a magnification of 100,000 times using a scanning electron microscope, the number of ceria-based composite microparticles supported within a range of 100 nm in the major axis direction was measured for 50 randomly selected composite ceria-based composite microparticles, and the average value was calculated to be the average number of ceria-based composite microparticles supported per 100 nm of the major axis of the irregular inorganic oxide microparticles.

[0103] The composite ceria-based composite microparticle dispersions obtained in the examples described below and the particles contained in the dispersions obtained in the comparative examples were subjected to two types of polishing performance tests, which will be described below.

[0104] <Polishing performance test 1: Measurement of polishing speed> Ultrapure water was added as a solvent to the composite ceria-based composite microparticle dispersion obtained in each of the examples and comparative examples to prepare a polishing abrasive dispersion, in which the solid content concentration of the polishing abrasive dispersion was 0.6 mass %, and the pH was adjusted to 5.0 by adding nitric acid. Next, SiO2 prepared by thermal oxidation was used as the substrate to be polished. 2 An insulating film (thickness 1 μm) substrate was prepared. Next, the substrate to be polished was set in a polishing apparatus (NF300, manufactured by Nanofactor Co., Ltd.), and polishing was performed using a polishing pad (IC-1000 / SUBA400 concentric type, manufactured by Nitta Haas Co., Ltd.) with a substrate load of 0.5 MPa, a table rotation speed of 90 rpm, and a polishing abrasive dispersion liquid supplied at a rate of 50 ml / min for 1 minute. The change in weight of the substrate to be polished before and after polishing was then determined, and the polishing rate was calculated. In Comparative Example 1, the obtained dispersion was adjusted to the same solid content concentration and pH, and then the same measurements were carried out.

[0105] <Polishing performance test 2: Measurement of the number of scratches> Ultrapure water was added as a solvent to the composite ceria-based composite microparticle dispersion obtained in each of the examples and comparative examples to prepare a polishing abrasive dispersion, in which the solid content concentration of the polishing abrasive dispersion was 9 mass % and the pH was adjusted to 2.0 by adding nitric acid. Next, the aluminum hard disk substrate was set in a polishing device (NF300, manufactured by Nanofactor Co., Ltd.) and polished using a polishing pad (Polytex φ12, manufactured by Nitta Haas Co., Ltd.) with a substrate load of 0.05 MPa, a table rotation speed of 30 rpm, and a polishing abrasive dispersion liquid for 5 minutes supplied at a rate of 20 ml / min. The substrate was then observed over the entire surface at Zoom 15 using an ultrafine defect visualization macro device (product name: Maicro-Max, manufactured by VISION PSYTEC Co., Ltd.). 2 The number of scratches (linear marks) present on the polished substrate surface corresponding to the number of scratches was counted and totaled, and the result was evaluated according to the following criteria. Number of linear scratches Evaluation Less than 50 "Very few" Between 50 and 80 "Few" 80 or more "Many" At least 80 or more, so many that the total cannot be counted. "*" In Comparative Example 1, the obtained dispersion was adjusted to the same solid content concentration and pH, and then the same measurements were carried out.

[0106] <Synthesis Example 1> <Refining the dispersion of irregularly shaped inorganic oxide particles> [1] Sepiolite (product name "PANGL FF", manufactured by GRUPO TOLSA, powder form, average major axis (L) = 491 nm, average minor axis (S) = 26 nm, average minor axis (S) / average major axis (L) = 0.05) was prepared. Here, the average major axis (L) and the average minor axis (S) were measured using the method described above.

[0107] Next, 44 g of the above sepiolite was added to 700 g of ultrapure water and stirred for 10 minutes to obtain 744 g of an aqueous suspension of sepiolite (irregularly shaped inorganic oxide fine particle dispersion).

[0108] [2] 90 g of cation exchange resin (manufactured by Mitsubishi Chemical Corporation, product number: SK1BH) was added to the aqueous suspension of sepiolite (744 g) obtained in [1] above, and ion exchange was performed by stirring for 90 minutes. The cation exchange resin was then separated using a SUS316 wire mesh (325 mesh) to obtain 613 g of an aqueous suspension of sepiolite (pH 3.1 / 25°C). The aqueous suspension of sepiolite obtained here is hereinafter also referred to as a cation-exchanged product.

[0109] [3] 69 g of anion exchange resin was added to the cation exchange product (613 g) obtained in [2] above, and the mixture was stirred for 50 minutes to perform ion exchange. The anion exchange resin was then separated using a SUS316 wire mesh (325 mesh) to obtain 568 g of an aqueous suspension of sepiolite (pH 5.8 / 25°C). The aqueous suspension of sepiolite obtained here is hereinafter also referred to as an anion exchange product.

[0110] [4] 83 g of cation exchange resin was added again to the anion-exchanged product (568 g) obtained in [3] above, and ion exchange was performed by stirring for 55 minutes. The cation exchange resin was then separated using a SUS316 wire mesh (325 mesh) to obtain 525 g of an aqueous suspension of sepiolite (pH 3.7 / 25°C). The aqueous suspension of sepiolite obtained here is hereinafter also referred to as a recation-exchanged product.

[0111] [5] 525 g of ultrapure water was added to the recation-exchanged product (525 g) obtained in [4] above to obtain a diluted aqueous suspension of sepiolite. The diluted aqueous suspension of sepiolite obtained here is hereinafter also referred to as the diluted product. An aqueous ammonia solution (concentration: 3% by mass) was added to the diluted product (25°C) so that the pH of the diluted product became 10, and then ultrasonic treatment was carried out for 6 hours to obtain an aqueous suspension of ultrasonically treated sepiolite (1055 g). The aqueous suspension of ultrasonically treated sepiolite obtained here is also referred to as the "ultrasonicated product" below. The solid content of the ultrasonically treated product was measured by the ignition reduction method and found to be 1.2% by mass. In the ignition loss method used here, 2 g of sample was weighed into a crucible (capacity 5 ml), dried using a hot plate at 120°C for 1 hour, 200°C for 30 minutes, and 300°C for 30 minutes, in that order, and then the sample was placed in a muffle furnace (1000°C) and dried for 1 hour, and then cooled in a desiccator for 30 minutes and weighed after cooling.The solid content concentration of the ultrasonically treated product was calculated from the weight after cooling and the sample weight (2 g).

[0112] <Synthesis Example 2> <Preparation of silica-based microparticle dispersion (average particle size of silica-based microparticles: 63 nm)> Mix 12,090g of ethanol and 6,363.9g of ethyl orthosilicate to obtain mixed solution a. 1 Next, 6,120 g of ultrapure water and 444.9 g of 29% ammonia water were mixed to obtain mixed solution b. 1 It was decided. Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed to prepare a bed water. Then, adjust the temperature of the water to 75°C while stirring, and add mixed liquid a. 1 and mixture b 1 After the addition was completed, the liquid temperature was kept at 75°C for 3 hours for aging, and then the solid content was adjusted and SiO 2 9,646.3 g of silica sol in which silica-based fine particles having a concentration of 19% by mass and an average particle size of 63 nm were dispersed in a solvent was obtained. Here, the average particle diameter of the silica-based microparticles was determined by preparing an image or photograph taken at 50,000 times magnification using a scanning electron microscope, calculating the area-equivalent particle diameter of 40 silica-based microparticles from the projected area obtained by using image analysis software (e.g., Avizo ver. 6.0 manufactured by Visualization Sciences Group), and then calculating the simple average of these values.

[0113] <Synthesis Example 3> <Preparation of silica-based microparticle dispersion (average particle size of silica-based microparticles: 113 nm)> Mix 2,733.3 g of methanol and 1,822.2 g of ethyl orthosilicate to obtain mixed solution a.2 Next, 1,860.7 g of ultrapure water and 40.6 g of 29% ammonia water were mixed to obtain mixed solution b. 2 It was decided. Next, 59 g of ultrapure water and 1,208.9 g of methanol were mixed to prepare a bed of water, and 922.1 g of the silica sol obtained in Synthesis Example 2 in which silica-based fine particles having an average particle size of 63 nm were dispersed in a solvent was added. The water containing the silica sol was then adjusted to 65°C while stirring, and mixed solution a was added. 2 and mixture b 2 After the addition was completed, the liquid temperature was kept at 65°C for 3 hours to mature, and then the liquid was concentrated using an ultrafiltration and a rotary evaporator to obtain a solids concentration (SiO 2 The solid content concentration was adjusted to 19 mass %, and 3,600 g of a silica-based fine particle dispersion in which silica-based fine particles having an average particle size of 113 nm were dispersed in the solvent was obtained. The average particle size of the silica-based fine particles obtained here was measured and determined in the same manner as in the case of the silica sol in which silica-based fine particles having an average particle size of 63 nm are dispersed in a solvent.

[0114] Of the resulting 3,600 g silica-based fine particle dispersion, 1,053 g was gradually added with 114 g of cation exchange resin (SK-1BH manufactured by Mitsubishi Chemical Corporation), and the mixture was stirred for 30 minutes to separate the resin. The pH at this time was 5.1.

[0115] <Synthesis Example 4> <Preparation of ceria-based composite particle dispersion> The silica-based fine particle dispersion (SiO 2 Add ultrapure water to a concentration of 19% by mass and SiO 2 6,000 g of silica-based fine particle dispersion with a concentration of 3% by mass (SiO 2 dry 180g) (hereinafter referred to as “A 1 The resulting solution is referred to as "SiO 2 "Dry" refers to the silica weight.

[0116] Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (Kanto Chemical Co., Ltd., 4N high-purity reagent) to obtain CeO 2 A 3.0 mass% aqueous solution of cerium nitrate (hereinafter referred to as "B 1 The solution was obtained.

[0117] Next is A. 1 Liquid (Silica-based fine particle dispersion liquid (SiO 2 6,000 g of B (concentration 3% by mass) was kept at 10°C and added with stirring. 1 Solution (cerium nitrate solution (CeO 2 7,186.7g (CeO 2 The CeO 2 "Dry" refers to the ceria mass. In addition, A 1 B to liquid 1 During addition of liquid, B 1 A to which liquid was added 1 The temperature of the liquid (hereinafter also referred to as the "mixed liquid") was maintained at 10°C, and an aqueous ammonia solution (ammonia concentration: 3% by mass) was added as necessary to maintain the pH in the range of 8.6 to 8.8. 1 After the entire amount of the liquid had been added, the mixture was aged at a liquid temperature of 10° C. for 4 hours. Also, B 1 During the addition of the liquid (cerium nitrate aqueous solution) and during aging, air was blown into the prepared liquid to maintain the redox potential at 100 to 200 mV. After that, washing was performed by replenishing ion-exchanged water through the ultrafiltration membrane. 1 Dispersion C 1 The solid content was 4.7% by mass, the pH was 8.8 (at 25° C.), and the electrical conductivity was 44 μs / cm (at 25° C.).

[0118] Dispersion C 1 The mixture was dried in a dryer at 120°C for 16 hours, and then calcined in a muffle furnace at 1030°C for 2 hours to obtain a powder (calcined body). 300 g of ion-exchanged water was added to 100 g of this powder (sintered body), and then an aqueous ammonia solution (ammonia concentration 3% by mass) was added to adjust the pH to 9.2, after which wet crushing (batch-type benchtop sand mill manufactured by Kampe Co., Ltd.) was performed for 120 minutes using φ0.25 mm quartz beads (manufactured by Daiken Chemical Industry Co., Ltd.) During crushing, an aqueous ammonia solution (ammonia concentration 30% by mass) was added to maintain the pH at 9.2. After crushing, the beads were separated by passing the mixture through a 44 mesh wire screen to obtain a dispersion liquid of crushed sintered particles (1). The resulting dispersion liquid (1) of pulverized sintered particles had a mass of 1,115 g (solid content concentration: 3.1% by mass).

[0119] Next, the sintered crushed particle dispersion liquid (1) was centrifuged (at 1700 G for 102 seconds) using a centrifuge (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") to separate it into a light liquid and a heavy liquid, and the light liquid was recovered to obtain a ceria-based composite microparticle dispersion liquid (E1). The average particle size of the ceria-based composite fine particles contained in the obtained ceria-based composite fine particle dispersion (E1) was measured by the above-mentioned method using SEM. Moreover, the average particle sizes of the mother particles and the child particles in the ceria-based composite microparticles were measured by the image analysis method using STEM-EDS, as described above. In addition, the SiO in the ceria-based composite fine particle dispersion (E1) obtained by the above-mentioned method 2 Content and CeO 2 The content was calculated, and the parts by mass of ceria per 100 parts by mass of silica was determined. In addition, the average crystallite size of the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion (E1) was measured by the method described above. Furthermore, the ceria-based composite particles contained in the ceria-based composite particle dispersion (E1) were subjected to X-ray diffraction by the method described above to confirm the crystal type. The measurement results are shown in Table 1.

[0120] <Synthesis Example 5> <Preparation of ceria-based composite particle dispersion> Ultrapure water was added to silica-based fine particle dispersion "CATALOID SS-160" (average particle size 160 nm (SEM image analysis method), solid content concentration 14 mass%, manufactured by JGC Catalysts and Chemicals Co., Ltd.) to obtain SiO 2 6,000 g of silica-based fine particle dispersion with a concentration of 3% by mass (SiO 2 dry180g) (hereinafter referred to as “A 2 The solution was obtained.

[0121] Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (Kanto Chemical Co., Ltd., 4N high-purity reagent) to obtain CeO 2 A 3.0 mass% aqueous solution of cerium nitrate (hereinafter referred to as "B 2 The solution was obtained.

[0122] Next is A. 2 Liquid (Silica-based fine particle dispersion liquid (SiO 2 6,000 g of B (concentration 3% by mass) was kept at 10°C and added with stirring. 2 Solution (cerium nitrate solution (CeO 2 7,186.7g (CeO 2 Dry 215.6 g) was added over 18 hours. In addition, A 2 B to liquid 2 During addition of liquid, B 2 A to which liquid was added 2 The temperature of the liquid (hereinafter also referred to as the "mixed liquid") was maintained at 10°C, and an aqueous ammonia solution (ammonia concentration: 3% by mass) was added as necessary to maintain the pH in the range of 8.6 to 8.8. 2 After the entire amount of the liquid had been added, the mixture was aged at a liquid temperature of 10° C. for 4 hours. In addition, B 2 During the addition of the liquid (cerium nitrate aqueous solution) and during aging, air was blown into the prepared liquid to maintain the redox potential at 100 to 200 mV. After that, washing was performed by replenishing ion-exchanged water through the ultrafiltration membrane. 2 Dispersion C 2 The solid content was 7.5% by mass, the pH was 9.0 (at 25° C.), and the electrical conductivity was 30 μs / cm (at 25° C.).

[0123] Dispersion C 2 The mixture was dried in a dryer at 120°C for 16 hours, and then calcined in a muffle furnace at 930°C for 2 hours to obtain a powder (calcined body). 342 g of ion-exchanged water was added to 100 g of this powder (sintered body), and then an aqueous ammonia solution (ammonia concentration 3% by mass) was added to adjust the pH to 9.2, after which wet crushing (batch-type benchtop sand mill manufactured by Kampe Co., Ltd.) was performed for 120 minutes using φ0.25 mm quartz beads (manufactured by Daiken Chemical Industry Co., Ltd.) During crushing, an aqueous ammonia solution (ammonia concentration 30% by mass) was added to maintain the pH at 9.2. After crushing, the beads were separated by passing the mixture through a 44 mesh wire screen to obtain a dispersion liquid of crushed sintered particles (2). The mass of the resulting pulverized sintered particle dispersion (2) was 1,155 g (solid content concentration: 3.1% by mass).

[0124] Next, the sintered crushed particle dispersion liquid (2) was centrifuged (at 1700 G for 102 seconds) using a centrifuge (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") to separate it into a light liquid and a heavy liquid, and the light liquid was recovered to obtain a ceria-based composite microparticle dispersion liquid (E2). The average particle size of the ceria-based composite fine particles contained in the obtained ceria-based composite fine particle dispersion (E2) was measured by the above-mentioned method using SEM. Moreover, the average particle diameters of the mother particles and the child particles in the ceria-based composite microparticles are measured by the image analysis method using STEM-EDS, as described above. In addition, the SiO in the ceria-based composite fine particle dispersion (E2) obtained by the above-mentioned method 2 Content and CeO 2 The content was calculated, and the parts by mass of ceria per 100 parts by mass of silica was determined. In addition, the average crystallite size of the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion (E2) was measured by the method described above. Furthermore, the ceria-based composite particles contained in the ceria-based composite particle dispersion (E2) were subjected to X-ray diffraction by the above-mentioned method to confirm the crystal type. The measurement results are shown in Table 1.

[0125] <Example 1> <Compositing irregularly shaped inorganic oxide particles with ceria-based composite particles> [1] Ultrapure water was added to the ceria-based composite microparticle dispersion (E1) to adjust the concentration to 2.3% by mass, and then the mixture was stirred for 10 minutes. The pH of this diluted ceria-based composite microparticle dispersion (solid content concentration: 2.3% by mass) was 8.9 at 25°C. This diluted ceria-based composite microparticle dispersion is referred to as "diluted ceria-based composite microparticle dispersion (E1)".

[0126] [2] 87 g of the ultrasonically treated product (solid content concentration: 1.2 mass%) obtained in Synthesis Example 1 was added to 870 g of the diluted ceria-based composite microparticle dispersion (E1), and ultrasonic treatment was further performed for 60 minutes to obtain raw material dispersion (1) (pH 9.1 / 25°C). Here, the mixing ratio (solid content equivalent) of the ultrasonically treated product (irregularly shaped inorganic oxide fine particles) to the ceria-based composite fine particles was 100:2000.

[0127] [3] 11 g of an aqueous solution of ammonium acetate (acetic acid concentration: 7% by mass) was added as a buffer solution to 800 g of the raw material dispersion liquid (1), and the mixture was stirred for 10 minutes to obtain a precursor dispersion liquid (1). The pH of the precursor dispersion liquid (1) obtained after stirring at 25°C was 4.6.

[0128] [4] 696 g of precursor dispersion (1) was heated to 85°C, held for 20 hours, and then allowed to cool. The pH of reaction dispersion (1) obtained after cooling was 5.2 at 25°C.

[0129] [5] 32 g of anion exchange resin was added to 630 g of reaction dispersion liquid (1) and stirred for 60 minutes. After that, the anion exchange resin was separated to obtain 596 g of composite ceria-based composite microparticle dispersion liquid (1) (pH 10.6 / 25°C, solid content concentration 2.1% by mass). The solids concentration here was measured by the ignition reduction method, similarly to the solids concentration of the ultrasonically treated product described above.

[0130] The composite ceria-based composite particles dispersed in the obtained composite ceria-based composite particle dispersion (1) were separated and subjected to STEM-EDS analysis. In addition, scanning electron micrographs (SEM images) and transmission electron micrographs (TEM images) were obtained. The upper part of Figure 1 is an SEM image at 100,000 magnification, the lower part is a TEM image at 100,000 magnification (100,000 magnification), and Figure 2 is an SEM image at 10,000 magnification.

[0131] From this STEM-EDS analysis, it was confirmed that the composite ceria-based composite microparticles dispersed in the obtained composite ceria-based composite microparticle dispersion (1) were ceria-based composite microparticles supported on irregular inorganic oxide microparticles. It was also confirmed that the ceria-based composite microparticles have mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer. In addition, the average particle sizes of the parent particles and child particles were measured by the image analysis method using the STEM-EDS analysis described above, and it was confirmed that these were the same as the average particle sizes of the parent particles and child particles of the ceria-based composite microparticles before they were supported on the irregular inorganic oxide microparticles.

[0132] Next, the average particle size of the ceria-based composite microparticles supported on the composite ceria-based composite microparticles dispersed in the composite ceria-based composite microparticle dispersion (1) was measured by the above-mentioned method. The results are shown in Table 3.

[0133] Next, for the irregular inorganic oxide particles in the composite ceria-based composite particles dispersed in the composite ceria-based composite particle dispersion (1) obtained, the average major axis (L) and the average minor axis (S) were determined by the above-mentioned method using the SEM image in Figure 1, and further the value of the average minor axis (S) / average major axis (L) was determined. The results are shown in Table 3.

[0134] Next, the average number of ceria-based composite fine particles supported on the irregular shaped inorganic oxide fine particles was determined by the above-mentioned method using the SEM image of Figure 1. The results are shown in Table 3.

[0135] Next, the polishing rate was measured using the obtained composite ceria-based composite fine particle dispersion (1) by the above-mentioned method, and the number of scratches was also measured. The results are shown in Table 3.

[0136] <Example 2> <Combination of irregularly shaped inorganic oxide particles and ceria-based composite particles> [1] 870 g of the diluted ceria-based composite fine particle dispersion (E1) obtained in Example 1 was prepared.

[0137] [2] 44 g of the ultrasonically treated product (solid content concentration 1.2 mass%) obtained in Synthesis Example 1 was added to 870 g of the diluted ceria-based composite microparticle dispersion (E1), and ultrasonic treatment was further carried out for 60 minutes to obtain raw material dispersion (2) (pH 9.0 / 25°C). Here, the mixing ratio (solid content equivalent) of the ultrasonically treated product (irregularly shaped inorganic oxide fine particles) to the ceria-based composite fine particles was 100:4000.

[0138] [3] 11 g of an aqueous solution of ammonium acetate (acetic acid concentration: 7% by mass) was added as a buffer solution to 800 g of the raw material dispersion liquid (2), and the mixture was stirred for 10 minutes to obtain a precursor dispersion liquid (2). The pH of the precursor dispersion liquid (2) obtained after stirring at 25°C was 4.6.

[0139] [4] 696 g of precursor dispersion (2) was heated to 85°C, held for 20 hours, and then allowed to cool. The pH of reaction dispersion (2) obtained after cooling was 5.1 at 25°C.

[0140] [5] 32 g of anion exchange resin was added to 636 g of reaction dispersion liquid (2) and stirred for 60 minutes. After that, the resin was separated to obtain 602 g of composite ceria-based composite microparticle dispersion liquid (2) (pH 10.6 / 25°C, solid content concentration 2.2% by mass). The solids concentration here was measured by the ignition reduction method, similarly to the solids concentration of the ultrasonically treated product described above.

[0141] The composite ceria-based composite fine particles dispersed in the obtained composite ceria-based composite fine particle dispersion (2) were separated, and STEM-EDS analysis was performed in the same manner as in Example 1.

[0142] From this STEM-EDS analysis, it was confirmed that the composite ceria-based composite fine particles dispersed in the obtained composite ceria-based composite fine particle dispersion (2) were those in which ceria-based composite fine particles were supported on irregular-shaped inorganic oxide fine particles. In addition, it was confirmed that the ceria-based composite fine particles had a mother particle mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and a child particle mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer. Also, the average particle diameters of the mother particle and the child particle were measured by the image analysis method using the aforementioned STEM-EDS analysis, and it was confirmed that these were the same as the average particle diameters of the mother particle and the child particle of the ceria-based composite fine particles before being supported on the irregular-shaped inorganic oxide fine particles.

[0143] Next, the average particle diameter of the ceria-based composite fine particles supported on the composite ceria-based composite fine particles dispersed in the obtained composite ceria-based composite fine particle dispersion (2) was measured by the aforementioned method. The results are shown in Table 3.

[0144] Next, regarding the irregular-shaped inorganic oxide fine particles in the composite ceria-based composite fine particles dispersed in the obtained composite ceria-based composite fine particle dispersion (2), using the SEM image taken at 100,000 times magnification, the average major axis length (L) and the average minor axis length (S) were obtained by the aforementioned method, and further the value of the average minor axis length (S) / average major axis length (L) was obtained. The results are shown in Table 3.

[0145] Next, using the obtained SEM image, the average value of the number of ceria-based composite fine particles supported on the irregular-shaped inorganic oxide fine particles was obtained by the aforementioned method. The results are shown in Table 3.

[0146] Next, using the obtained composite ceria-based composite fine particle dispersion (2), the polishing rate was measured and the number of scratches was measured by the aforementioned method. The results are shown in Table 3.

[0147] <Example 3> <Combination of irregularly shaped inorganic oxide particles and ceria-based composite particles> [1] Ultrapure water was added to the ceria-based composite microparticle dispersion (E2) to adjust the concentration to 2.3% by mass, and then the mixture was stirred for 10 minutes. The pH of this diluted ceria-based composite microparticle dispersion (solid content concentration: 2.3% by mass) was 8.2 at 25°C. This diluted ceria-based composite microparticle dispersion is referred to as "diluted ceria-based composite microparticle dispersion (E2)".

[0148] [2] 40 g of the ultrasonically treated product (solid content concentration: 1.2% by mass) obtained in Synthesis Example 1 was added to 870 g of the diluted ceria-based composite microparticle dispersion (E2), and ultrasonic treatment was further performed for 60 minutes to obtain raw material dispersion (3) (pH 8.9 / 25°C). Here, the mixing ratio (solid content equivalent) of the ultrasonically treated product (irregularly shaped inorganic oxide fine particles) to the ceria-based composite fine particles was 100:4000.

[0149] [3] 11 g of an aqueous solution of ammonium acetate (acetic acid concentration: 7% by mass) was added as a buffer solution to 800 g of the raw material dispersion liquid (3), and the mixture was stirred for 10 minutes to obtain a precursor dispersion liquid (3). The pH of the precursor dispersion liquid (3) obtained after stirring at 25°C was 4.6.

[0150] [4] 696 g of precursor dispersion (3) was heated to 85°C, held for 20 hours, and then allowed to cool. The pH of reaction dispersion (3) obtained after cooling was 4.9 at 25°C.

[0151] [5] 32 g of anion exchange resin was added to 636 g of reaction dispersion liquid (3) and stirred for 60 minutes. After that, the anion exchange resin was separated to obtain 602 g of composite ceria-based composite microparticle dispersion liquid (3) (pH 10.7 / 25°C, solid content concentration 2.1 mass%). The solids concentration here was measured by the ignition reduction method, similarly to the solids concentration of the ultrasonically treated product described above.

[0152] The composite ceria-based composite particles dispersed in the obtained composite ceria-based composite particle dispersion (3) were separated and subjected to STEM-EDS analysis in the same manner as in Example 1.

[0153] From this STEM-EDS analysis, it was confirmed that the composite ceria-based composite microparticles dispersed in the obtained composite ceria-based composite microparticle dispersion (3) were in the form of ceria-based composite microparticles supported on irregular inorganic oxide microparticles. It was also confirmed that the ceria-based composite microparticles have mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer. In addition, the average particle sizes of the parent particles and child particles were measured by the image analysis method using the STEM-EDS analysis described above, and it was confirmed that these were the same as the average particle sizes of the parent particles and child particles of the ceria-based composite microparticles before they were supported on the irregular inorganic oxide microparticles.

[0154] Next, the average particle size of the ceria-based composite microparticles supported on the composite ceria-based composite microparticles dispersed in the composite ceria-based composite microparticle dispersion (3) was measured by the above-mentioned method. The results are shown in Table 3.

[0155] Next, the average major axis (L) and the average minor axis (S) of the irregular inorganic oxide particles in the composite ceria-based composite particles dispersed in the composite ceria-based composite particle dispersion (3) obtained were measured by the above-mentioned method using SEM images taken at 100,000 times magnification, and the value of the average minor axis (S) / average major axis (L) was also measured. The results are shown in Table 3.

[0156] Next, using the obtained SEM images, the average number of ceria-based composite fine particles supported on the irregular shaped inorganic oxide fine particles was calculated by the above-mentioned method. The results are shown in Table 3.

[0157] Next, the polishing rate was measured and the number of scratches was counted by the above-mentioned method using the obtained composite ceria-based composite fine particle dispersion (3). The results are shown in Table 3.

[0158] <Comparative Example 1> Using 870 g of the diluted ceria-based composite fine particle dispersion (E1) obtained in Example 1, a polishing test was carried out in the same manner as in Examples 1 to 3.

[0159] [Table 1]

[0160] [Table 2]

[0161] [Table 3]

Claims

1. A composite ceria-based composite microparticle dispersion in which composite ceria-based composite microparticles are dispersed in a solvent, The composite ceria-based composite fine particles are those in which ceria-based composite fine particles are supported on sepiolite, The sepiolite has an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3; The ceria-based composite microparticles are a composite ceria-based composite microparticle dispersion having mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer.

2. 2. The composite ceria-based composite microparticle dispersion according to claim 1, wherein the ceria-based composite microparticles have an average particle size in the range of 50 nm to 600 nm as determined by image analysis using a scanning electron microscope photograph.

3. 3. The composite ceria-based composite microparticle dispersion according to claim 1, wherein an average number of the ceria-based composite microparticles supported on the sepiolite is 1 to 200 microparticles per 100 nm in the major axis direction of the sepiolite.

4. 4. A polishing abrasive dispersion comprising the composite ceria-based composite microparticle dispersion according to claim 1.

5. A method for producing a composite ceria-based composite microparticle dispersion according to any one of claims 1 to 3, comprising the following steps [1], [2], [3] and [4]: Step [1]: Sepiolite having an average major axis (L) of 200 to 6,000 nm, an average minor axis (S) of 10 to 1,800 nm, and a ratio of the average minor axis (S) to the average major axis (L) (average minor axis (S) / average major axis (L)) of 0.005 to 0.3; A process of mixing mother particles mainly composed of amorphous silica, a cerium-containing silica layer on the surface of the mother particle, and child particles mainly composed of crystalline ceria dispersed inside the cerium-containing silica layer, with a ceria-based composite microparticle dispersion in which ceria-based composite microparticles having an average particle size of 50 to 600 nm are dispersed in a solvent, to obtain a raw material dispersion. Step [2]: A step of adding a buffer solution to the raw material dispersion and stirring to obtain a precursor dispersion having a pH of 2.0 to 7.

0. Step [3]: A step of heating the precursor dispersion to 40 to 98° C., maintaining the temperature for 1 hour or more, and then allowing to cool to obtain a reaction dispersion. Step [4]: ​​A step of contacting the reaction dispersion with an anion exchange resin to carry out ion exchange, thereby obtaining a composite ceria-based composite microparticle dispersion according to any one of claims 1 to 3.

6. 6. The method for producing a composite ceria-based composite microparticle dispersion according to claim 5, wherein in the step [1], a mixing ratio (solid content equivalent) of the sepiolite to the ceria-based composite microparticles in the mixed liquid is 100:500 to 100:8,000 (parts by mass).

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