JP2022116977A - Particle-linked ceria-based composite particulate dispersion, method for producing the same, and abrasive dispersion containing particle-linked ceria-based composite particulate dispersion - Google Patents

Abstract

To provide ceria-based composite particulates, which can polish silica films, Si wafers and even difficult-to-process materials at high-speed, can achieve high surface accuracy at the same time, and can be particularly suitable in a dispersion for high-speed polishing.SOLUTION: A ceria-based composite particulate, which is characterized in that (i) it includes a plurality of specific silica primary fine particles connected via a cerium-containing silica layer, (ii) it has mother particles having on their surfaces a cerium-containing silica layer, and child particles dispersed inside the cerium-containing silica layer, and (iii) it has the following characteristics (1) to (3): (1) The ratio of short diameter/long diameter is in the range of 0.1 to 0.9. (2) The ratio of the projected area (T) of the stereoscopic portion of the particulate and the projected area (S) of the entire particulate, determined from scanning electron micrograph, satisfy a specific relationship. (3) Neither of the two sites α nor β on the outer edge and on the long axis of the particulate, identified from the scanning electron micrograph, has a sharp-edged projection structure.SELECTED DRAWING: Figure 1

Description

The present invention relates to a ceria-based composite fine particle dispersion suitable as a polishing agent for use in the manufacture of semiconductor devices, etc., and in particular, a film to be polished formed on a substrate is flattened by chemical mechanical polishing (CMP). The present invention relates to a ceria-based composite fine particle dispersion for polishing, a method for producing the same, and an abrasive dispersion for polishing containing the ceria-based composite fine particle dispersion.

Semiconductor devices, such as semiconductor substrates and wiring substrates, have achieved high performance through high density and miniaturization. So-called chemical mechanical polishing (CMP) is applied in the manufacturing process of these semiconductors. Specifically, it is an essential technology for shallow trench isolation, flattening of interlayer insulating films, formation of contact plugs and Cu damascene wiring, etc. It has become.

Generally, CMP polishing agents are composed 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, abrasive grains have the role of polishing by mechanical action, and colloidal silica, fumed silica, and ceria particles are used as abrasive grains. In particular, since ceria particles exhibit a high polishing rate specifically for silicon oxide films, they are applied to polishing in the shallow trench isolation process.
In the shallow trench isolation process, not only the silicon oxide film is polished, but also the silicon nitride film is polished. In order to facilitate device isolation, it is desirable that the silicon oxide film is polished at a high polishing speed and the silicon nitride film is polished at a low speed, and the polishing speed ratio (selection ratio) is also important.

Conventionally, as a method of polishing such members, a relatively rough primary polishing process is performed, and then a precise secondary polishing process is performed. There is a way to get
Conventionally, the following methods, for example, have been proposed with respect to the abrasive used for secondary polishing as such final polishing.

For example, in Patent Document 1, an aqueous solution of cerous nitrate and a base are stirred and mixed in a quantity ratio that gives a pH of 5 to 10, followed by rapid heating to 70 to 100° C., and aging at that temperature. A method for producing cerium oxide ultrafine particles (average particle size 10 to 80 nm) composed of cerium oxide single crystals characterized by It is described that cerium oxide ultrafine particles having high uniformity can be provided.

In addition, Non-Patent Document 1 discloses a method for producing ceria-coated silica, which includes a production process similar to the method for producing cerium oxide ultrafine particles described in Patent Document 1. This method for producing ceria-coated silica does not have the firing-dispersion step included in the production method described in Patent Document 1.

Further, in Patent Document 2, one or more selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium is added to the surface of amorphous silica particles A. Silica-based composite particles are described which are characterized by having a crystalline oxide layer B containing elements. Further, as a preferred embodiment, an amorphous oxide layer containing an element such as aluminum is formed on the surface of the amorphous silica particles A, and the amorphous oxide layer is different from the amorphous silica layer. A crystalline oxide layer having C and containing thereon at least one element selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum and strontium Silica-based composite particles characterized by having B are described. Since such silica-based composite particles have the crystalline oxide layer B on the surface of the amorphous silica particles A, the polishing rate can be improved, and the silica particles are pretreated By doing so, it is possible to suppress sintering of particles during firing, improve dispersibility in the polishing slurry, and furthermore, do not contain cerium oxide, or significantly reduce the amount of cerium oxide used Therefore, it is possible to provide an inexpensive abrasive with high polishing performance. In addition, it is described that those having an amorphous oxide layer C between the silica-based particles A and the oxide layer B are particularly excellent in the effect of suppressing sintering of particles and the effect of improving the polishing rate.

Further, in Patent Document 3, child particles containing crystalline ceria as a main component are provided on the surfaces of mother particles containing amorphous silica as a main component, and the surfaces of the child particles are coated with silica. , a silica-based composite fine particle dispersion liquid containing silica-based composite fine particles having an average particle diameter of 50 to 350 nm having the following characteristics [1] to [3]. [1] The silica-based composite fine particles have a mass ratio of silica to ceria of 100:11 to 316. [2] When the silica-based composite fine particles are subjected to X-ray diffraction, only the crystalline phase of ceria is detected. [3] In the silica-based composite fine particles, the crystallite diameter of the (111) plane of the crystalline ceria measured by X-ray diffraction is 10 to 25 nm. And, according to such silica-based composite fine particles, even silica films, Si wafers, and difficult-to-process materials can be polished at high speed, and at the same time, high surface accuracy (low scratches, surface roughness of the substrate to be polished ( Ra) is low, etc.), and since it does not contain impurities, it is possible to provide a silica-based composite fine particle dispersion that can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates. Have been described.

Patent No. 2,746,861 JP 2013-119131 A International Publication No. 2016/159167 pamphlet

Seung-Ho Lee, Zhenyu Lu, S.P. V. Babu and Egon Matijevic, "Chemical mechanical polishing of thermal oxide films using silica particles coated with ceria", Journal of Materials Research, Vol.

However, when the inventors of the present invention actually produced and examined the cerium oxide ultrafine particles described in Patent Document 1, the polishing rate was low, and defects on the surface of the polishing substrate (deterioration of surface precision, increase in scratches, residual abrasive on the surface of the polishing substrate).
This is because the method for producing cerium oxide ultrafine particles described in Patent Document 1 does not include a sintering step, and the liquid phase is Since the cerium oxide particles are only crystallized from (aqueous solution containing cerous nitrate), the degree of crystallinity of the cerium oxide particles produced is relatively low. The present inventor presumes that the main reason is that the cerium oxide remains on the surface of the polishing base material.

In addition, since the ceria-coated silica described in Non-Patent Document 1 is not fired, it is considered that the actual polishing rate is low, and since it is not fixed and integrated with the silica particles, it easily falls off, reducing the polishing rate. Also, the stability of polishing is lacking, and there is concern that particles may remain on the surface of the polishing base material.

Furthermore, it has been found that when the silica-based composite particles having the oxide layer C described in Patent Document 2 are used for polishing, impurities such as aluminum remain on the surface of the semiconductor device, which may adversely affect the semiconductor device. , the inventors have found.
In addition, the ceria particles described in these documents are adhered to the mother particles and are not strongly fixed, so they tend to fall off from the mother particles.
Furthermore, when polishing is performed using abrasive grains in which crystalline ceria particles are formed on spherical silica base particles described in Patent Document 2, a silica film is formed by a chemical reaction that occurs simultaneously with the mechanical action of the ceria particles during polishing. Although the polishing rate is high under high pressure conditions, the ceria crystals may come off, wear away, or collapse, reducing the contact area between the substrate and the ceria, resulting in a lower polishing rate.

In addition, the silica-based composite fine particle dispersion described in Patent Document 3 is capable of exhibiting excellent polishing performance (polishing speed, high surface accuracy, etc.) in polishing applications. - Along with the high integration, there is a demand for an abrasive dispersion with further improved polishing performance, especially polishing speed, for semiconductor substrates.

An object of the present invention is to solve the above problems. That is, according to the present invention, even silica films, Si wafers, and difficult-to-process materials can be polished at high speed, and at the same time, high surface accuracy (low scratches, few residual abrasive grains on the substrate, improvement of the substrate Ra value) can be achieved. etc.), and if it does not contain impurities, it can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates, and is particularly suitable for high-speed polishing. An object of the present invention is to provide a dispersion, a method for producing the same, and an abrasive dispersion for polishing containing a particle-linked ceria-based composite fine particle dispersion.

The present inventor has made intensive studies to solve the above problems and completed the present invention.
The present invention is the following [1] to [12].
[1] A plurality of silica primary fine particles having a particle diameter in the range of 50 to 600 nm as measured by STEM-EDS analysis are connected via a cerium-containing silica layer, and the cerium-containing silica is also formed on the surface thereof. a base particle having a layer;
Child particles dispersed within the cerium-containing silica layer;
Particle-linked ceria-based composite fine particles having the following characteristics (1) to (3).
(1) The ratio of minor axis to major axis of the particle-linked ceria-based composite fine particles is in the range of 0.1 to 0.9.
(2) The projected area (T) of the three-dimensional portion of the particle and the projected area (S) of the entire particle obtained from the scanning electron micrograph of the particle-linked ceria-based composite fine particles are related by the following general formula (I): to meet
T / S × 100 = 0: general formula (I)
(3) Two sites α and β located on the outer edge of the particle and on the long axis, which are specified from the scanning electron micrograph of the particle-linked ceria-based composite fine particles, both have a pointed structure. do not take
[2] The particle-linked ceria-based composite fine particles according to [1] above, wherein the particle-linked ceria-based composite fine particles have a non-kurtosis in the range of 0.85 to 1.0.
[3] The particle-linked ceria-based composite fine particles according to [1] or [2] above, which have the base particles in which 4 to 10 silica primary fine particles are linked via the cerium-containing silica layer.
[4] A particle-linked ceria-based composite fine particle dispersion obtained by dispersing the particle-linked ceria-based composite fine particles according to any one of [1] to [3] above in a solvent.
[5] A group of linked particles containing the particle-linked ceria-based composite fine particles according to any one of the above [1] to [3] and having the characteristics described in the following (4) to (7) dispersed in a solvent A particle-linked ceria-based composite fine particle dispersion liquid.
(4) The average particle size of the linked particle group measured by a dynamic light scattering method is 100 to 600 nm.
(5) The average particle diameter of the silica primary fine particles in the linked particle group as measured by STEM-EDS analysis is in the range of 50 to 600 nm.
(6) The short axis/long axis ratio of the linked particle group is in the range of 0.1 to 0.9.
(7) The total projected area (T') of the three-dimensional portions of the particles and the total projected area (S') of the entire particles obtained from the scanning electron micrograph of the linked particle group are represented by the following general formula (II ) relationship.
T'/S'×100≦30: general formula (II)
[6] The particle-linked ceria-based composite microparticle dispersion liquid according to [5] above, wherein the non-kurtosis of the linked-type particle group is in the range of 0.85 to 1.0.
[7] The above [5] or [6], wherein the base particles of the particles constituting the linked particle group are 4 to 10 silica primary fine particles linked via the cerium-containing silica layer. The particle-linked ceria-based composite fine particle dispersion described above.
[8] Among the particles having the mother particles in which the four or more silica primary fine particles are linked via the cerium-containing silica layer in the linked particle group, the silica primary fine particles extend in a planar manner The particle-linked ceria-based composite fine particle dispersion liquid according to any one of [5] to [7] above, wherein the number ratio of those having the linked mother particles is 60% or more.
[9] The particle-linked ceria-based composite fine particle dispersion according to any one of the above [5] to [8], characterized in that the linked particle number distribution of the particles constituting the linked-type particle group has a plurality of peaks. liquid.
[10] A polishing abrasive dispersion containing the particle-linked ceria-based composite fine particle dispersion according to any one of [6] to [9] above.
[11] Silica primary fine particles, a cerium-containing silica layer on the surface of the silica primary fine particles, and child particles dispersed inside the cerium-containing silica layer, wherein the silica primary fine particles are amorphous silica is a main component, and the child particles are mainly composed of crystalline ceria, and ceria-based composite fine particles having an average particle diameter of 50 to 350 nm as measured by a dynamic light scattering method are dispersed in a solvent, solid content concentration A method for producing a particle-linked ceria-based composite fine particle dispersion, comprising a step of maintaining a dispersion having a pH of 2.0 to 6.0 and a temperature of 50 to 180°C.
[12] After holding the dispersion having a solid content concentration of 1 to 20% by mass in the range of pH 2.0 to 6.0 and the temperature in the range of 50 to 180°C, the pH range of 10.0 or more, A step of maintaining the temperature in the range of 50 to 98 ° C., and then continuously or intermittently adding a silicic acid solution to prepare the particle-linked silica-based fine particle dispersion in which particles have grown. The method for producing the particle-linked ceria-based composite fine particle dispersion according to [11] above.

The particle-linked ceria-based composite fine particle dispersion liquid of the present invention contains planarly elongated particle-linked ceria-based composite fine particles as a main component. When planarly elongated particle-linked ceria-based composite fine particles are used as abrasive grains, compared to spherical ceria-based composite fine particles that do not have a linked structure or particle-linked ceria-based composite fine particles that have a three-dimensional branched structure, Since the stress is easily dispersed at a plurality of contact points with the polishing substrate, the occurrence of polishing scratches can be suppressed. In addition, by having the connecting structure, it is possible to effectively obtain a dynamic contact area due to the rotational movement of the abrasive grains, thereby achieving excellent polishing characteristics. Therefore, the particle-linked ceria-based fine particle dispersion containing the particle-linked ceria-based fine particles of the present invention is useful, for example, as a raw material for an abrasive dispersion and a polishing composition, and is particularly excellent in the high polishing rate effect. is.

In the particle-linked ceria-based fine particles of the present invention, particle-linked silica-based fine particles in which silica primary fine particles are bound together exist as mother particles. With regard to such particle-linked silica-based fine particles, it is preferable that the primary silica fine particles are bonded to each other through a cerium-containing silica layer described below.
The particle-linked ceria-based fine particle dispersion of the present invention exhibits excellent polishing performance as an abrasive dispersion, as described later. In addition, in the case of particle-linked ceria-based composite fine particles of a type that does not contain components other than silica and ceria in the component of particle-linked ceria-based fine particles, even if it is applied as abrasive grains for polishing applications related to electronic parts, semiconductors There is no problem of contamination of the substrate, etc., and it can be said that the usefulness is much higher.

When the particle-linked ceria-based composite fine particle dispersion of the present invention is used for polishing purposes, for example, as an abrasive dispersion for polishing, even if the object is a difficult-to-process material such as a silica film or a Si wafer, it can be processed at high speed. It can be polished, and at the same time, high surface precision (low scratches, low surface roughness (Ra) of the substrate to be polished, etc.) can be achieved.
The method for producing a particle-linked ceria-based composite fine particle dispersion of the present invention provides a method for efficiently producing a particle-linked ceria-based composite fine particle dispersion exhibiting such excellent performance.

1 is a schematic diagram of a cross section of composite fine particles of the present invention. FIG. FIG. 4 is a diagram (schematic diagram) for explaining the neck depth; FIG. 3 is another schematic diagram of the cross section of the composite fine particle of the present invention. It is a figure for demonstrating non-kurtosis.

The present invention will be described.
In the present invention, a plurality of primary silica fine particles having a particle diameter in the range of 50 to 600 nm as measured by STEM-EDS analysis are connected via a cerium-containing silica layer, and the surface of the silica primary fine particles also contains the cerium. Particle-linked ceria-based composite fine particles having mother particles having a silica layer and child particles dispersed inside the cerium-containing silica layer, and having the following features (1) to (3): .
(1) The ratio of minor axis to major axis of the particle-linked ceria-based composite fine particles is in the range of 0.1 to 0.9.
(2) The projected area (T) of the three-dimensional portion of the particle and the projected area (S) of the entire particle obtained from the scanning electron micrograph of the particle-linked ceria-based composite fine particles are related by the following general formula (I): to meet
T / S × 100 = 0: general formula (I)
(3) Two sites α and β located on the outer edge of the particle and on the long axis, which are specified from the scanning electron micrograph of the particle-linked ceria-based composite fine particles, both have a pointed structure. do not take
Such particle-linked ceria-based composite fine particles are hereinafter also referred to as "composite fine particles of the present invention" or "ceria-based composite fine particles of the present invention".

The present invention also provides a dispersion of particle-linked ceria-based composite fine particles, which contains the composite fine particles of the present invention and in which linked particle groups having the characteristics described in the following (4) to (7) are dispersed in a solvent. is.
(4) The average particle size of the linked particle group measured by a dynamic light scattering method is 100 to 600 nm.
(5) The average particle diameter of the silica primary fine particles in the linked particle group as measured by STEM-EDS analysis is in the range of 50 to 600 nm.
(6) The short axis/long axis ratio of the linked particle group is in the range of 0.1 to 0.9.
(7) The total projected area (T') of the three-dimensional portions of the particles and the total projected area (S') of the entire particles obtained from the scanning electron micrograph of the linked particle group are represented by the following general formula (II ) relationship.
T'/S'×100≦30: general formula (II)
Such a particle-linked ceria-based composite fine particle dispersion is hereinafter also referred to as "the dispersion of the present invention".
Further, the particles contained in the dispersion of the present invention are hereinafter also referred to as "connected particle group of the present invention".

The linked particle group of the present invention includes the composite fine particle of the present invention, but the linked particle group of the present invention may include other particles that do not correspond to the composite fine particle of the present invention.

Further, the present invention has silica primary fine particles, a cerium-containing silica layer on the surface of the silica primary fine particles, and child particles dispersed inside the cerium-containing silica layer, and the silica primary fine particles are non- Ceria-based composite fine particles containing crystalline silica as a main component, the child particles containing crystalline ceria as a main component, and having an average particle diameter of 50 to 350 nm as measured by a dynamic light scattering method are dispersed in a solvent. A particle-linked ceria-based composite fine particle dispersion liquid comprising a step of maintaining a dispersion liquid having a solid content concentration of 1 to 20% by mass at a pH range of 2.0 to 6.0 and a temperature range of 30 to 180 ° C. manufacturing method.
Such a manufacturing method is hereinafter also referred to as "the manufacturing method of the present invention".

The dispersion of the invention is preferably produced by the method described above.

In the following description, simply referring to the "present invention" means any of the fine composite particles of the present invention, the dispersion liquid of the present invention, the linked particle group of the present invention, and the production method of the present invention.

In the present specification, unless otherwise specified, the term "ceria-based composite fine particles" simply means single-particle ceria-based composite fine particles. Such single-particle ceria-based composite fine particles do not have a connecting structure of a plurality of ceria-based composite fine particles. Such single-particulate ceria-based composite fine particles can be turned into "particle-linked ceria-based composite fine particles" through the production method specified in the present application.
The single-particle ceria-based composite fine particles have an average particle diameter of 50 to 350 nm as measured by a dynamic light scattering method, and are composed of primary silica fine particles, a cerium-containing silica layer on the surface of the primary silica fine particles, child particles dispersed inside the cerium-containing silica layer, the silica primary fine particles are composed mainly of amorphous silica, and the child particles are particles composed mainly of crystalline ceria.
Likewise, unless otherwise specified, the term "ceria-based composite fine particle dispersion" simply means a dispersion in which the single-particle ceria-based composite fine particles are dispersed in a solvent.

The base particles of the particle-linked ceria-based composite fine particles in the present invention are composed of a plurality of silica primary fine particles having an average particle diameter in the range of 50 to 600 nm measured by the STEM-EDS analysis method as described above, and a cerium-containing silica layer. It is a linked body of silica primary fine particles (particle-linked silica fine particles) formed by linking via vias, and the mother particles also have the cerium-containing silica layer on the surface thereof. In addition, in this application, the said base particle may be called "particle connection type silica microparticles|fine-particles."

<Composite Fine Particles of the Present Invention and Linked Particle Group of the Present Invention>
The composite microparticles of the present invention will be described.
The composite fine particles of the present invention are particle-linked ceria-based composite fine particles elongated in a plane. When a dispersion or slurry containing planarly elongated particle-linked ceria-based composite fine particles is used as abrasive grains, when spherical particles or particle-linked ceria-based composite fine particles having a three-dimensional branched structure are used as abrasive grains In comparison, the inventors have found that a higher polishing rate can be obtained.

In the present application, the particle-linked ceria-based composite fine particles having a three-dimensional branched structure refers to the three-dimensional portion of the particles obtained from scanning electron micrographs (including scanning transmission electron micrographs) of the particle-linked ceria-based composite fine particles. and the projected area (S) of the entire grain satisfy the following relational expression.
T/S×100>0
In such particles, the particle-linked ceria-based composite fine particles can be said to have a significant three-dimensional structure. Specifically, when the particle-linked ceria-based composite fine particles have a plurality of branched structures, and the branched structures are in a twisted positional relationship, or when they have only one branched structure and a bent structure, and the bent structure is bent in a three-dimensional direction with respect to the branched structure.

In contrast, the planarly elongated particle-linked ceria-based composite fine particles in the present application are particle-linked ceria-based composite fine particles that do not have a three-dimensional branched structure. Examples of such particle-linked ceria-based composite fine particles include particle-linked ceria-based composite fine particles having only one curved structure, and particle-linked ceria-based composite fine particles having a branched structure that does not correspond to three-dimensional branching. can.
Regarding the presence or absence of three-dimensional branching, the projected area (T) of the three-dimensional part of the particle and the projected area of the whole particle ( When S) satisfies the relationship of the following general formula (I), the particle-linked ceria-based composite fine particles can be regarded as extending in a plane without having a three-dimensional branched structure.
T / S × 100 = 0: general formula (I)
When a dispersion or slurry containing planarly elongated particle-linked ceria-based composite fine particles is used as abrasive grains, the planarly-extended particle-linked ceria-based composite fine particles have a larger contact surface with the substrate to be polished. Therefore, it is presumed that performance such as improvement of the polishing rate is exhibited.

FIG. 1 illustrates the structure of the composite fine particles of the present invention. FIG. 1 shows an embodiment in which the primary silica fine particles constituting the base particles (particle-linked fine silica particles) are bonded via a cerium-containing silica layer.

The silica primary fine particles forming the base particles are connected in a plane. In other words, it does not constitute a three-dimensional structure. The degree is represented by formula (I) or formula (II). The details of formula (II) will be described later.

In addition, the embodiment shown in FIG. 1 is a type in which a part of the child particles is exposed to the outside, but in the composite fine particles of the present invention, all the child particles may be exposed to the outside, or all of the child particles may be exposed to the outside. may not be exposed to

As shown in FIG. 1, composite fine particles 20 of the present invention have base particles 10 in which a plurality of silica primary fine particles 1 are connected via cerium-containing silica layers 12 . Moreover, the cerium-containing silica layer 12 is also provided on the surface of the mother particle 10 . Further, the composite fine particle 20 of the present invention has child particles 14 dispersed inside the cerium-containing silica layer 12 . In FIG. 1, .tangle-solidup.

In the schematic diagram of FIG. 1, the mother particles 10, the cerium-containing silica layer 12, and the child particles 14 are clearly distinguished for ease of understanding. , the cerium-containing silica layer 12 and the child particles 14 are present together, and the mother particles 10, the cerium-containing silica layer 12 and the child particles 14 can be clearly distinguished except for contrast in STEM-EDS or EDS analysis. is difficult.
However, when the STEM-EDS analysis is performed on the cross section of the composite fine particles of the present invention to measure the elemental concentrations of Ce and Si, it can be confirmed that the structure is shown in FIG.

The STEM-EDS analysis in this application is described below.
[STEM-EDS analysis]
A sample containing the composite fine particles of the present invention was subjected to EDS analysis by selectively irradiating an electron beam at a specified location with a scanning transmission electron microscope (STEM). When the element concentrations of and are measured, the ratio (percentage) of the Ce molar concentration to the sum of the Ce molar concentration and the Si molar concentration (percentage) (Ce/(Ce+Si)×100) is less than 3%.
In addition, when the elemental concentrations of Ce and Si at the measurement point Z are measured, the ratio (percentage) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration (percentage) (Ce / (Ce + Si) × 100) exceeds 50%. Become.
Then, when the element concentrations of Ce and Si at the measurement point Y are measured, the ratio (percentage) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration (percentage) (Ce / (Ce + Si) × 100) is 3 to 50% becomes.
Therefore, in the elemental map obtained by STEM-EDS analysis, the silica primary fine particles 1 and the cerium-containing silica layer 12 constituting the base particles 10 in the composite fine particles of the present invention are the sum of the Ce molar concentration and the Si molar concentration A distinction can be made by the line where the ratio (percentage) of Ce molar concentration to (Ce/(Ce+Si)×100) is 3%. In addition, in the elemental map obtained by STEM-EDS analysis, the cerium-containing silica layer 12 and the child particles 14 in the composite fine particles of the present invention have a ratio of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration ( Percentage) (Ce/(Ce+Si)×100) can be distinguished by the line where 50%.

STEM-EDS analysis is performed in this way to obtain an elemental map, and the shape of each of the mother particles, child particles and cerium-containing silica layer in the particles constituting the linked particle group of the present invention or the composite fine particles of the present invention, Understanding the size and the like is hereinafter also referred to as "elemental mapping method".
In the present invention, the STEM-EDS analysis is performed by observing at a magnification of 200,000 unless otherwise specified.

<Mother particle>
The base particles in the particles constituting the linked particle group of the present invention and the base particles in the composite fine particles of the present invention will be described.
The silica primary fine particles contained in the base particles in the particles constituting the linked particle group of the present invention and the silica primary fine particles constituting the base particles in the composite fine particles of the present invention have a Ce molar concentration of and Si molar concentration (percentage) (Ce/(Ce+Si)×100) is less than 3%.

If an elemental map is obtained, it can be understood from the shape (contour) of the base particles that the base particles of the composite fine particles of the present invention are formed by connecting a plurality of silica primary fine particles. In addition, since it is possible to grasp the outline of the primary silica fine particles that constitute the base particles in the particles that constitute the linked particle group of the present invention or the base particles of the composite fine particles of the present invention, it is possible to grasp the primary silica fine particles that constitute the base particles. , the particle diameter of each silica primary fine particle, and the like can also be measured.

The number (connection number) of the primary silica fine particles contained in the base particles of the particles constituting the linked particle group of the present invention and the primary silica fine particles constituting the base particles of the composite fine particles of the present invention (the number of connections) is not particularly limited. It is preferably 4 to 10, more preferably 4 to 8, per mother particle. This is because polishing with the dispersion of the present invention containing such fine composite particles of the present invention results in a higher polishing rate.

In the linked particle group of the present invention, among the particles having mother particles in which four or more silica primary fine particles are linked, the number ratio of particles having mother particles in which silica primary fine particles are extended and linked in a plane (Number of particles having base particles in which silica primary fine particles are connected while extending in a plane/Number of particles having base particles in which four or more silica primary fine particles are connected × 100) is 60% or more. It is preferably 70% or more, more preferably 80% or more. The reason for this is that it is easy to reduce polishing scratches due to stress dispersion and to obtain a polishing speed due to dynamic contact.

A method for measuring this ratio will be described.
First, with respect to the linked particle group of the present invention, the silica primary fine particles constituting the base particles are specified by the above-mentioned STEM-EDS method, and further the base particles are specified from the shape thereof to form one base particle. Measure the number of connections. Then, 50 particles including base particles in which four or more silica primary fine particles are connected are specified. Next, among the particles having mother particles in which four or more silica primary fine particles are connected, the number ratio (percentage) of the particles having mother particles in which the silica primary fine particles are connected while extending in a plane ).
In addition, in the case where the silica primary fine particles are not elongated on the plane, that is, as the base particles contained in the particle-linked ceria-based composite fine particles having a three-dimensional branched structure, the base particles have a plurality of branched structures, and the branched structures are twisted. Particles in a closed positional relationship, particles having a unique branched structure and a bent structure, the bent structure being bent in a three-dimensional direction with respect to the branched structure, and aggregated particles (pyramidal or irregular shape), and single particles (having no connected structure). The details of the measuring method are described in "Physical Property Test 7" below.

The particle size of the silica primary fine particles constituting the base particles of the composite fine particles of the present invention is 50 to 600 nm, preferably 60 to 400 nm. The particle diameter of the silica primary fine particles is determined by the elemental map of the composite fine particles of the present invention obtained by the elemental mapping method using STEM-EDS as described above. The concentration ratio (percentage) (the portion where Ce/(Ce+Si)×100) is less than 3% is specified, and the silica primary fine particles constituting the base particles are specified from the shape thereof, and the length and length of the silica primary fine particles are specified. The short diameter is measured, and the average value is defined as the particle diameter of the silica primary fine particles (see FIG. 1).
In addition, the particle diameters of 50 particles constituting the linked particle group of the present invention were measured by the same method, and the value obtained by simple averaging was calculated as the primary silica fine particle in the linked particle group of the present invention. It was taken as the average particle size. The details of the measuring method are described in "Physical Property Test 1" below.

In addition, in an elemental map obtained by an elemental mapping method or an enlarged image (including photographs and images) obtained by a scanning electron microscope (SEM) or a transmission electron microscope (TEM), the straight line indicating the maximum diameter of the particle is the long axis. Measure its length, set the value as the major axis (DL), set a point on the major axis that bisects the major axis, and set two points where a straight line orthogonal to that bisects the outer edge of the particle The method of determining the major diameter (DL) and minor diameter (DS) of the particle by measuring the distance between the two points and making it the minor diameter (DS) is hereinafter also referred to as the "major and minor diameter measurement method". .

It can be confirmed, for example, by the following method that the silica primary fine particles constituting the base particles are mainly composed of amorphous silica. After drying the dispersion of the present invention, it is pulverized using a mortar and, for example, an X-ray diffraction pattern is obtained with a conventionally known X-ray diffraction device (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.), and Cristobalite is obtained. No crystalline silica peak appears. From this, it can be confirmed that the silica contained in the base particles is amorphous. In such a case, the silica primary fine particles forming the base particles are mainly composed of amorphous silica.
After drying the dispersion of the present invention and embedding it in resin, it is sputter-coated with Pt, and a cross-sectional sample is prepared using a conventionally known focused ion beam (FIB) apparatus. For example, when an FFT pattern is obtained by fast Fourier transform (FFT) analysis of a prepared cross-sectional sample using a conventionally known TEM apparatus, a diffractogram of crystalline silica such as Cristobalite does not appear. From this, it can be confirmed that the silica contained in the silica primary fine particles forming the base particles is amorphous. In such a case, the main component of the mother particles is amorphous silica.
As another method, there is a method of observing the presence or absence of lattice fringes due to the atomic arrangement of the mother particles using a conventionally known TEM apparatus on a cross-sectional sample prepared in the same manner. If it is crystalline, lattice fringes corresponding to the crystal structure will be observed, and if it is amorphous, no lattice fringes will be observed. From this, it can be confirmed that the silica contained in the base particles is amorphous. In such a case, the silica primary fine particles forming the base particles are mainly composed of amorphous silica.

The particles constituting the linked particle group of the present invention or the composite fine particles of the present invention may have necks, and thicker ones are preferable. The reason for this is that it is possible to prevent the particles from collapsing due to the stress during polishing and to suppress the deterioration of the polishing properties.
In addition, in the composite microparticles of the present invention, the neck refers to the peripheral portion corresponding to the bonding portion between the adjacent primary silica microparticles in the base particle.

Also, the average neck depth (Lm) is preferably 5 to 200 (unit: nm), more preferably 5 to 100 (unit: nm).

The average neck depth shall mean a value obtained by measuring as follows.
[Measuring method of average neck depth]
As shown in FIG. 2, two adjacent silica primary fine particles (P and Q ) is obtained, and a line segment γ perpendicular to the straight line R is obtained from the junction outer layer point D of the portion corresponding to the two silica primary fine particles ( The perpendicular point is E), and the length between DE is neck depth (L). When a plurality of straight lines R are obtained, the straight line R is determined so that the value of the neck depth (L) is maximized.
The neck depth (L) [nm] is determined at three arbitrary locations on the same composite fine particle of the present invention, and the average value (Ls) [nm] thereof is calculated.
Calculation of Ls is performed for 50 particles, and the average value is taken as the average neck depth (Lm) [nm] of the particles constituting the linked particle group of the present invention.

<child particles>
The child particles in the particles constituting the linked particle group of the present invention and the child particles in the composite fine particles of the present invention will be described.
In the elemental map obtained by the elemental mapping method, the child particles in the particles constituting the linked particle group of the present invention and the child particles in the composite fine particles of the present invention show the Ce molar concentration with respect to the sum of the Ce molar concentration and the Si molar concentration. This is the portion where the ratio (percentage) (Ce/(Ce+Si)×100) exceeds 50%.

In the composite fine particles of the present invention, the child particles containing crystalline ceria as a main component (hereinafter also referred to as "ceria child particles") are dispersed in the cerium-containing silica layer arranged on the mother particles.

Further, in the composite fine particles of the present invention, it is preferable that the mother particles have recesses and protrusions on the surface thereof, and the child particles of the mother particles are in the form of the following (a), (b) or (c). preferably present.
(a) A form in which child particles are bonded to convex portions of mother particles via a part of the cerium-containing silica layer.
(b) A form in which child particles are bonded to both the convex and concave portions of the mother particle via a part of the cerium-containing silica layer.
(c) A form in which the child particles are bound to the recesses of the mother particles via a part of the cerium-containing silica layer.
It is desirable that these forms (a), (b) or (c) exist simultaneously. This is because when the dispersion of the present invention is used as an abrasive dispersion for polishing, the base particles have steps, so that the child particles of the form (a) are first deposited on the substrate to be polished during polishing. Polishing takes place in contact with the Even if the child particles in the form of (a) are dislodged, worn out, or destroyed by the polishing pressure, the ceria child particles in the form of (b) and (c) are brought into contact with the substrate to be polished, and the contact area is increased. This is because the polishing can be efficiently performed with a stable polishing rate because it can be kept high.
According to the production method of the present invention, which will be described later, it is easy to obtain the dispersion liquid of the present invention containing the composite fine particles of the present invention in which child particles of the form (a), (b) or (c) are present at the same time.

In addition, the ceria particles may be stacked in the cerium-containing silica layer, and the shape thereof is not particularly limited, such as spherical, elliptical, or rectangular, and the particle size distribution may be uniform or sharp. Alternatively, the ceria child particles may have steps due to mother particles having projections or uneven shapes.
Some of the ceria child particles are embedded in the cerium-containing silica layer, while others are partially exposed from the cerium-containing silica layer.

The average particle size of the child particles is preferably 10 to 25 nm, more preferably 12 to 23 nm.
When the average particle diameter of the child particles exceeds 25 nm, in the production method of the present invention, the precursor particles having such ceria child particles tend to be sintered or aggregated after firing, making it difficult to crush them. . Such a dispersion of the present invention is not preferable because it causes scratches on the object to be polished even 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 practically sufficient polishing rate when used for polishing.

The average particle size of the child particles is obtained by specifying the child particles based on the elemental map obtained by the elemental mapping method, then obtaining the major diameter (DL) and the minor diameter (DS) of the child particles by the major diameter and minor diameter measurement method. The value obtained by calculating the geometric mean value is defined as the particle diameter of the child particles, and the particle diameters of 50 child particles are measured in this way, and the measured values are simply averaged to obtain the value.

Child particles may be stacked. That is, they may be present in plurality on radial lines from the center of the base particle inside the cerium-containing silica layer.
Further, 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. Since the surface of the system composite fine particles is closer to the silica surface, storage stability and polishing stability are improved, and since less abrasive grains remain on the substrate after polishing, the child particles are buried in the cerium-containing silica layer. It is desirable to have

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

The child particles dispersed in the cerium-containing silica layer may be in a monodispersed state, or in a state in which the child particles are stacked (that is, a plurality of child particles are stacked in the thickness direction of the cerium-containing silica layer. state), or a state in which a plurality of child particles are connected.

In the present invention, the child particles preferably contain crystalline ceria as a main component.
The reason why the child particles contain crystalline ceria as a main component is that the composite fine particles of the present invention are obtained by, for example, drying the dispersion liquid of the present invention and pulverizing the obtained solid matter using a mortar. After that, for example, X-ray analysis is performed using a conventionally known X-ray diffraction apparatus (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.), and only the ceria crystal phase is detected in the obtained X-ray diffraction pattern. You can check from In such a case, the child particles are mainly composed of crystalline ceria. The crystal phase of ceria is not particularly limited, but includes, for example, Cerianite.

The child particles preferably contain crystalline ceria (crystalline Ce oxide) as a main component, and may contain other elements such as elements other than cerium. A hydrous cerium compound may also be included as a co-catalyst for polishing.
However, as described above, when the fine composite particles of the present invention are subjected to X-ray diffraction, it is preferable that only the crystalline phase of ceria is detected. That is, even if a crystal phase other than ceria is contained, the content is small, or it is dissolved in the ceria crystal, so it is out of the detection range by X-ray diffraction.

The average crystallite diameter of the ceria particles is calculated using the full width at half maximum of the maximum peak appearing in the chart obtained by subjecting the particles contained in the linked particle group of the present invention or the composite fine particles of the present invention to X-ray diffraction. For example, the average crystallite diameter of the (111) plane is preferably 10 to 25 nm (full width at half maximum is 0.86 to 0.34°), and 12 to 23 nm (full width at half maximum is 0.72 to 0.37° ), more preferably 15 to 22 nm (full width at half maximum of 0.58 to 0.38°). In many cases, the intensity of the peak of the (111) plane is the maximum, but the intensity of the peak of another crystal plane, for example, the (100) plane, may be the maximum. In that case, it can be similarly calculated, and the average crystallite size in that case may be the same as the average crystallite size of the (111) plane described above.

A method for measuring the average crystallite diameter of the child particles will be described below using the case of the (111) plane (2θ=around 28 degrees) as an example.
First, the particles contained in the linked particle group of the present invention or the composite fine particles of the present invention are pulverized using a mortar, for example, by a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). A line diffraction pattern is obtained. Then, the full width at half maximum of the peak of the (111) plane in the vicinity of 2θ=28 degrees in the obtained X-ray diffraction pattern is measured, and the average crystallite diameter can be obtained from the following Scherrer's formula.
D=Kλ/β cos θ
D: Average crystallite diameter (Angstrom)
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: angle of reflection The measuring method is described in physical property test 12 below.

<Cerium-containing silica layer>
The cerium-containing silica layer in the particles constituting the linked particle group of the present invention and the cerium-containing silica layer in the composite fine particles of the present invention will be described.

The composite fine particles of the present invention have a cerium-containing silica layer between a plurality of silica primary fine particles and on the surface of the base particles. Child particles are dispersed inside the cerium-containing silica layer.
By adopting such a structure, it is difficult for the child particles to fall off due to the crushing treatment during manufacturing or the pressure during polishing, and even if some child particles are lost, many child particles will not fall off. Since it is present in the cerium-containing silica layer without deteriorating the polishing function.

The cerium-containing silica layer in the particles constituting the linked particle group of the present invention and the cerium-containing silica layer in the composite fine particles of the present invention are shown in the elemental map obtained by the elemental mapping method with respect to the total of the Ce molar concentration and the Si molar concentration. This is the portion where the Ce molar concentration ratio (percentage) (Ce/(Ce+Si)×100) is 3 to 50%.

In the image (TEM image) obtained by observing the composite fine particles of the present invention using a transmission electron microscope, the image of the child particles appears densely on the surface of the mother particle, but the surrounding and outside of the child particles, that is, the present invention Part of the cerium-containing silica layer also appears as a relatively thin image on the surface side of the composite fine particles. When STEM-EDS analysis is performed on this portion to determine the Si molar concentration and Ce molar concentration of the portion, it can be confirmed that the Si molar concentration is very high. Specifically, the ratio (percentage) of Ce molar concentration to the sum of Ce molar concentration and Si molar concentration (Ce/(Ce+Si)×100) is 3 to 50%.

The average thickness of the cerium-containing silica layer is preferably 10-40 nm, more preferably 12-30 nm.
The average thickness of the cerium-containing silica layer can be obtained by drawing a straight line at any 12 points from the center of the base particle of the composite fine particle of the present invention to the outermost shell, and performing STEM-EDS analysis as described above. A line where the ratio (percentage) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration specified from the element map (percentage) (Ce / (Ce + Si) × 100) is 3%, and the maximum of the composite fine particles of the present invention. The distance to the outer shell (distance on a line passing through the center of the base particle) is measured, and a simple average is obtained. Note that the center of the base particle means the intersection of the above-described long axis and short axis.

It is believed that the cerium-containing silica layer in the composite fine particles of the present invention promotes the bonding force between the child particles (ceria fine particles containing crystalline ceria as a main component) dispersed and grown in the cerium-containing silica layer during the firing process and the mother particles. . Therefore, for example, in the production method of the present invention, if necessary, the fired body pulverized dispersion obtained by sintering is pre-pulverized by a dry method, then wet pulverized, and then centrifuged. A ceria-based composite fine particle dispersion can be obtained by performing the above, and it is considered that the cerium-containing silica layer has the effect of preventing child particles from coming off from the mother particles. In this case, there is no problem with the child particles falling off locally, and the entire surface of the child particles may not be partially covered with the cerium-containing silica layer. It suffices if the child particles are strong enough not to separate from the mother particles during the pulverization step.
Due to such a structure, when the dispersion of the present invention is used as a polishing agent, it is believed that the polishing rate is high and deterioration of surface precision and scratches is small.

In addition, in the composite fine particles of the present invention, since at least a part of the surface of the child particles is coated with a cerium-containing silica layer, the outermost surface (outermost shell) of the composite fine particles of the present invention has —OH groups of silica. will exist. For this reason, when used as a polishing agent, the fine composite particles of the present invention are thought to repel each other due to the charges of the —OH groups on the surface of the polishing substrate, resulting in less adhesion to the surface of the polishing substrate.

In addition, ceria generally has a different potential than silica, a polishing substrate, or a polishing pad. have. Therefore, at acidic pH during polishing, ceria adheres to the polishing base material or polishing pad due to the difference in potential magnitude or polarity, and tends to remain on the polishing base material or polishing pad. On the other hand, since silica is present in the outermost shell of the composite fine particles of the present invention as described above, the potential thereof becomes a negative charge due to silica, so that the negative potential is maintained from alkaline to acidic pH, As a result, abrasive grains hardly remain on the polishing substrate or polishing pad. If the pH is maintained at 8.6 to 10.8 during the crushing treatment in the production method of the present invention, part of the silica on the surface of the composite fine particles of the present invention (silica of the cerium-containing silica layer) dissolves. If the dispersion liquid of the present invention produced under such conditions is adjusted to a pH of <7 when applied to polishing, the dissolved silica will deposit on the fine composite particles (abrasive grains) of the present invention. The surface will have a negative potential. If the potential is low, silicic acid may be added to moderately reinforce the cerium-containing silica layer.

In order to adjust the potential of the child particles, it is possible to adjust the potential with a polymer organic substance such as polyacrylic acid, but in the present invention, silica softly attached to the surface adjusts the potential, so the use of organic substances is reduced. , Defects (residual organic matter, etc.) caused by organic substances in the substrate are less likely to occur. In addition, since this softly adhered silica has not undergone a firing process, it is a low-density, soft, and easily soluble silica layer. This readily soluble silica layer has an adhesive action with the substrate, and is recognized to have the effect of improving the polishing rate. This easily soluble silica layer can be confirmed by keeping the dispersion liquid of the present invention at pH 9 and measuring the silica concentration in the solid-liquid separated solution.
In the dispersion liquid of the present invention, silica exists in various forms, does not constitute the composite fine particles of the present invention, is dispersed or dissolved in a solvent, or adheres to the surface of the composite fine particles of the present invention. It may exist in a state where

The fine composite particles of the present invention have the base particles, the cerium-containing silica layer, and the child particles as described above. Moreover, the particles constituting the linked particle group of the present invention include the composite fine particles of the present invention.
The mass ratio of silica (SiO ₂ ) to ceria (CeO ₂ ) in the particles constituting the linked particle group of the present invention and the composite fine particles of the present invention is preferably 100:11 to 316, more preferably 100:30 to 230. is more preferably 100:30 to 150, and even more preferably 100:60 to 120.
The mass ratio of silica and ceria is considered to be approximately the same as the mass ratio of mother particles and child particles. If the amount of child particles relative to the mother particles is too small, the mother particles or composite fine particles may bond together to form coarse particles. In this case, the polishing agent (polishing slurry) containing the dispersion of the present invention may cause defects (decrease in surface precision such as increase in scratches) on the surface of the polishing substrate. Also, if the amount of ceria relative to silica is too large, not only will the cost be high, but resource risk will increase. Further, fusion between particles proceeds. As a result, the roughness of the substrate surface increases (the surface roughness Ra deteriorates), the number of scratches increases, and free ceria remains on the substrate, causing problems such as adhesion to the waste liquid piping of the polishing apparatus. Easy to get along with.
The silica to be used for calculating the mass ratio between silica (SiO ₂ ) and ceria (CeO ₂ ) is the particles constituting the linked particle group of the present invention or included in the composite fine particles of the present invention. means all silica (SiO ₂ ) Therefore, it means the total amount of the silica component that constitutes the mother particle, the silica component contained in the cerium-containing silica layer arranged on the surface of the mother particle, and the silica component that can be contained in the child particles.

The content (% by mass) of silica (SiO ₂ ) and ceria (CeO ₂ ) in the particles constituting the linked particle group of the present invention and the composite fine particles of the present invention is determined by first calculating the solid content concentration of the dispersion of the present invention, 1000° C. ignition loss is performed and weighed.
Next, the content (mass%) of cerium (Ce) contained in a predetermined amount of particles constituting the linked particle group of the present invention is determined by ICP plasma emission spectrometry, and the oxide mass% (CeO ₂ mass%, etc.) Convert to Then, SiO ₂ mass % can be calculated assuming that the component other than CeO ₂ that constitutes the particles that constitute the linked particle group of the present invention is SiO ₂ .
In the production method of the present invention, the mass ratio of silica and ceria can also be calculated from the amounts of the silica source material and the ceria source material used when preparing the dispersion of the present invention. This can be applied when ceria or silica is not dissolved and removed by the process, and in such cases, the amount of ceria or silica used and the analytical value show good agreement.
The measuring method is described in physical property test 11 below.

[Composite Fine Particles of the Present Invention and Linked Particle Group of the Present Invention]
The minor axis/longer axis ratio of the particles constituting the linked particle group of the present invention and the composite fine particles of the present invention is 0.1 to 0.9, preferably 0.1 to 0.7, and 0.1. ~0.65 is more preferred.
With such a short diameter/long diameter ratio, when the dispersion liquid of the present invention containing the composite fine particles of the present invention is used for polishing, the polishing rate for the substrate to be polished can be improved, and at the same time, the substrate to be polished can be improved. The upper surface roughness can be reduced.

Here, the minor axis/longer axis ratio is a photograph obtained by photographing the particles constituting the linked particle group of the present invention or the composite fine particles of the present invention at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope. In the projection view, the major axis (DL) and the minor axis (DS) are determined by the major axis and minor axis measurement method, the minor axis/longer axis ratio (DS/DL) is calculated, and this is determined for arbitrary 50 particles, and they are shall be the value obtained by averaging.

The projected area (T) of the three-dimensional portion of the particle and the projected area (S) of the entire particle obtained from the scanning electron micrograph of the composite fine particle of the present invention satisfy the following general formula (I).
T / S × 100 = 0: general formula (I)
In other words, it means that the fine composite particles of the present invention have a planar structure without a three-dimensional portion of the particles.

Here, the method for measuring the projected area (T) of the three-dimensional portion of the grain and the projected area (S) of the entire grain is the same as in "Physical Property Test 5: Calculation of Formula (II)" below.

Neither of the two sites α and β located on the outer edge of the particle and on the long axis specified from the scanning electron micrograph of the composite fine particle of the present invention has a pointed structure.

The structures of site α and site β will be described with reference to FIG.
FIG. 3 is a schematic cross-sectional view of the fine composite particles of the present invention, showing particles identified from scanning electron micrographs. In FIG. 3, the composite fine particles 20 of the present invention include a base particle 10 formed by connecting a plurality of silica primary fine particles 1, a cerium-containing silica layer 12 between the silica primary fine particles 1 and on the surface of the base particle 10, and a cerium-containing silica and child particles 14 dispersed within the layer 12 .
DL represented by a dotted line in FIG. 3 represents the long axis.
The composite fine particle 20 of the present invention shown in FIG. 3 does not have a peak structure at two sites α and β on the outer edge of the particle and on the long axis DL.
Now, the cusp structure will be described.
First, the long axis DL is determined from scanning electron micrographs.
Next, the intersections of the long axis DL and the outer edge of the composite fine particles of the present invention are determined and designated as α and β, respectively. A portion containing the intersection point α is defined as a portion α, and a portion containing the intersection point β is defined as a portion β.
Next, draw two tangent lines that pass through the intersection α and circumscribe the outer edge of the composite fine particles of the present invention (ie, the outer edge of the cerium-containing silica layer or child particles) (the tangent lines D1 and D2).
Here, for the two tangent lines, the position of the circumscribed outer edge is selected so that the angle formed by the two tangent lines (the angle on the side including the long axis DL. [This angle is assumed to be Fα]) takes the maximum value. do.
Next, similarly for the intersection point β, the angle Fβ formed by the two tangent lines is measured.
When both Fα and Fβ are 120 degrees or more, the fine composite particles of the present invention do not have a peak structure.

The particles constituting the linked particle group of the present invention and the particle-linked ceria-based composite fine particles of the present invention are characterized in that the outer shape of the particles is not sharp. Specifically, the particles constituting the linked particle group of the present invention and the particle-linked ceria-based composite fine particles of the present invention preferably have a non-kurtosis in the range of 0.85 to 1.0, and more A range of 0.87 to 1.0 is preferably recommended.

Non-kurtosis will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view of the composite fine particle of the present invention, which is the same as FIG. A center P of the silica primary fine particles closest to the site α is determined, and a line segment A perpendicular to the tangent line D1 from the center P is determined. Similarly, a line segment B perpendicular to the tangent line D2 from the center P is defined. Also, a line segment C connecting the center P and the intersection point α is determined. Then, the length a of the line segment A, the length b of the line segment B, and the length c of the line segment C are obtained, and the non-spiky value (Nsv) is obtained from the following equation.
(Nsv)=(a+b+c)/3
Next, among the segments A, B and C, the value obtained by dividing (Nsv) by the length (T) of the longest segment is defined as non-custody (Nsd).
(Nsd) = (Nsv)/T
Specifically, the non-kurtosis (Nsd) is obtained for both the part α side and the part β side of one particle, and the average value thereof is taken as the non-custody of the particle.
Regarding the non-kurtosis of the particles constituting the linked particle group of the present invention, the non-kurtosis of 20 particles is determined, and the average value thereof is determined to form the linked particle group of the present invention. Let the non-kurtosis be the non-kurtosis of the particles

The average particle size of the particles constituting the linked particle group of the present invention or the particle size of the composite fine particles of the present invention is preferably 100 to 600 nm, more preferably 100 to 500 nm. When the average particle diameter of the particles constituting the linked particle group of the present invention or the particle diameter of the composite fine particles of the present invention is within such a range, the polishing rate is increased when applied as an abrasive, which is preferable.
The average particle diameter of the composite fine particles of the present invention is obtained by photographing the composite fine particles of the present invention with a transmission electron microscope at a magnification of 300,000 times (or 500,000 times), and in a photographic projection obtained by the major axis and minor axis measurement method. It means a value obtained by obtaining the major axis and the minor axis and calculating the geometric mean value thereof.
Moreover, the average particle diameter of the particles constituting the linked particle group of the present invention is obtained by a dynamic light scattering method. For example, the average particle size can be measured by the cumulant method using a conventionally known particle size measuring device (eg, ELSZ-1000 manufactured by Otsuka Electronics Co., Ltd.). The measuring method is described in physical property test 3 below.

It is preferable that the particles constituting the linked particle group of the present invention contained in the dispersion of the present invention have a plurality of peaks in the distribution of the number of linked particles.
Polishing with an abrasive dispersion is usually performed using a polishing pad. It is known that the surface of a polishing pad has irregularities and pores of various sizes, and if abrasive grains are appropriately retained in the irregularities and pores, the polishing rate can be increased. For example, when the ceria-based composite fine particles in the linked particle group of the present invention have a plurality of peaks in the number distribution of the linked particles, they are likely to be retained in the irregularities and pores, which is desirable for further increasing the polishing rate. . In the present application, the number of linked silica primary fine particles was measured (specifically, the measuring method is described in Physical Property Test 2 below), and the number of peaks in the distribution of the number of linked particles was measured. This measuring method is described in physical property test 8 below.
Further, when the particle size distribution of the linked particle group of the present invention contained in the dispersion of the present invention is determined by the dynamic light scattering method, the particle size distribution is also for the same reason as the above-described linked number distribution: It is preferred to have multiple peaks.

The projected area (T′) of the three-dimensional portion of the particle and the projected area (S′) of the entire particle obtained from the scanning electron micrograph of the particles constituting the linked particle group of the present invention are expressed by the following general formula (II): satisfy the relationship
T'/S'×100≦30: general formula (II)
In other words, it means that the particles have few three-dimensional parts and the particles constituting the linked particle group of the present invention are mainly planar.

In the general formula (II), T'/S'×100 is 0 to 30 (that is, 0≦T'/S'×100≦30), 0.1 to 25 (that is, 0.1≦T' /S'×100≦25), more preferably 3 to 20 (that is, 0.1≦T′/S′×100≦20). This is because, in this case, when the dispersion of the present invention containing the linked particle group of the present invention is applied as an abrasive, the polishing rate is further increased.

Here, the projected area (T') of the three-dimensional portion of the grain and the projected area (S') of the entire grain were obtained by the method described above for 50 grains. The projected area (S) of is determined, and the value obtained by calculating the geometric mean value is used.

The particles constituting the linked particle group of the present invention or the composite fine particles of the present invention preferably have a specific surface area of 4 to 100 m ² /g, more preferably 5 to 70 m ² /g.

Here, a method for measuring the specific surface area (BET specific surface area) will be described.
First, a dried sample (0.2 g) was placed in a measurement cell and subjected to degassing treatment at 250° C. for 40 minutes in a nitrogen gas stream. The temperature of liquid nitrogen is maintained in an air stream, and nitrogen is allowed to equilibrate to the sample. Next, the temperature of the sample is gradually raised to room temperature while the mixed gas is flowed, the amount of nitrogen desorbed during this time is detected, and the specific surface area of the sample is measured using a calibration curve prepared in advance.
Such a BET specific surface area measuring method (nitrogen adsorption method) can be performed using, for example, a conventionally known surface area measuring device.
In the present invention, the specific surface area means the value obtained by measuring by such a method unless otherwise specified.

Each element of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr in the particles constituting the linked particle group of the present invention and the composite fine particles of the present invention (hereinafter referred to as " The content of specific impurity group 1" is preferably 5000 ppm or less, more preferably 1000 ppm or less, more preferably 100 ppm or less, and more preferably 50 ppm or less. It is preferably 25 ppm or less, more preferably 5 ppm or less, and even more preferably 1 ppm or less.
In addition, each element of U, Th, Cl, NO ₃ , SO ₄ and F in the particles constituting the linked particle group of the present invention and the composite fine particles of the present invention (hereinafter sometimes referred to as "specific impurity group 2" ) is preferably 5 ppm or less.

Here, the content of the specific impurity group 1 or specific impurity group 2 in the particles constituting the linked particle group of the present invention, the composite fine particles of the present invention, and the silica-based fine particles described later means the content with respect to the dry amount. do.
The content ratio with respect to the dry amount means the ratio (percentage) of the weight of the measurement object (specific impurity group 1 or specific impurity group 2) to the mass of the solid content contained in the object. The impurities of the base particles are generally the same as those of the silica-based fine particles if there is no contamination due to contamination or the like.

In general, silica-based fine particles prepared using water glass as a raw material contain about several thousand ppm in total of the specific impurity group 1 and the specific impurity group 2 derived from the raw material water glass.
In the case of a dispersion liquid in which particles containing such silica-based fine particles are dispersed in a solvent, it is possible to reduce the content of the specific impurity group 1 and the specific impurity group 2 by performing an ion exchange treatment. Even in that case, the specific impurity group 1 and the specific impurity group 2 remain in total from several ppm to several hundred ppm. Therefore, when silica-based fine particles made from water glass are used, the impurities are reduced by acid treatment or the like.
On the other hand, in the case of a dispersion in which silica-based fine particles synthesized using alkoxysilane as a raw material are dispersed in a solvent, the content of each element in the specific impurity group 1 is preferably 100 ppm or less. It is more preferably 20 ppm or less, and the content of each element and each anion in the specific impurity group 2 is preferably 20 ppm or less, more preferably 5 ppm or less.

In the present invention, each of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, _NO3 , _SO4 and F in the base particles The content of is a value obtained by measuring using the following method.
· Na and K: Atomic absorption spectroscopy · Ag, Al, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, Zr, U and Th: ICP-MS (Inductively Coupled Plasma Emission Spectroscopy Mass Spectrometry)
・Cl: potentiometric titration method ・NO ₃ , SO ₄ and F: ion chromatograph

<Dispersion liquid of the present invention>
The dispersion liquid of the present invention will be explained.
The dispersion liquid of the present invention is obtained by dispersing the above-described linked particle group of the present invention in a solvent.

The dispersion of the invention contains water and/or an organic solvent as solvent. As the solvent, it is preferable to use water such as pure water, ultrapure water, or ion-exchanged water. Furthermore, the dispersion of the present invention contains at least one selected from the group consisting of polishing accelerators, surfactants, pH adjusters and pH buffers as additives for controlling polishing performance. It is preferably used as a slurry.

In addition, as a solvent provided with the dispersion of the present invention, for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, cyclohexanone, etc. ketones; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, and 3,4-dihydro-2H-pyran; 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, glycol ethers such as ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, glycol ether acetates such as 2-butoxyethyl acetate; methyl acetate , Esters such as ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and ethylene carbonate; Aromatic hydrocarbons such as benzene, toluene and xylene; Aliphatic hydrocarbons such as hexane, heptane, isooctane and cyclohexane; Methylene chloride , 1,2-dichloroethane, dichloropropane, halogenated hydrocarbons such as chlorobenzene; sulfoxides such as dimethylsulfoxide; organic solvents such as pyrrolidones such as N-methyl-2-pyrrolidone and N-octyl-2-pyrrolidone can be used. These may be used by mixing with water.

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

When cationic colloid titration is performed on the dispersion of the present invention, the ratio of the amount of change in streaming potential (ΔPCD) represented by the following formula (1) to the amount (V) of the cationic colloid titrant added to the knick ( It is preferable to obtain a streaming potential curve in which ΔPCD/V) is -110.0 to -5.0.
ΔPCD/V=(IC)/V Expression (1)
C: Streaming potential (mV) in the knick
I: streaming potential (mV) at the starting point of the streaming potential curve
V: Amount (ml) of the cationic colloid titrant added to the knick

Here, cationic colloidal titration is performed by adding a cationic colloidal titrant to 80 g of the dispersion liquid of the present invention adjusted to a solid content concentration of 1% by mass. A 0.001N polydiallyldimethylammonium chloride solution is used as a cationic colloid titrant.

The streaming potential curve obtained by this cationic colloid titration is a graph in which the added amount (ml) of the cationic titrant is plotted on the X axis and the streaming potential (mV) of the dispersion of the present invention is plotted on the Y axis.
A knick is a point (inflection point) at which the streaming potential changes abruptly in a streaming potential curve obtained by cationic colloid titration. Let C (mV) be the streaming potential at the point of inflection, and V (ml) be the amount of cation colloid titrant added at the point of inflection.
The starting point of the streaming potential curve is the streaming potential in the dispersion of the invention before titration. Specifically, the starting point is the point at which the amount of the cationic colloid titrant added is zero. Let the streaming potential at this starting point be I (mV).

When the value of .DELTA.PCD/V is -110.0 to -5.0, the polishing rate of the polishing agent is further improved when the dispersion of the present invention is used as the polishing agent. This ΔPCD/V is considered to reflect the degree of coverage of the child particles by the cerium-containing silica layer on the surface of the composite fine particles of the present invention and/or the degree of exposure of the child particles on the surface of the composite fine particles or the presence of silica that is easily detached. be done. The present inventor presumes that when the value of ΔPCD/V is within the above range, the child particles are less likely to be detached during wet pulverization, and the polishing rate is high. Conversely, when the absolute value of ΔPCD/V is greater than −110.0, the surface of the composite fine particles is entirely covered with the cerium-containing silica layer, so child particles are unlikely to fall off in the crushing process, but polishing In some cases, silica is difficult to detach and the polishing rate decreases. On the other hand, if the absolute value is smaller than -5.0, dropout is likely to occur. The present inventor presumes that within the above range, the surfaces of the child particles are appropriately exposed during polishing, less dropout of the child particles occurs, and the polishing rate is further improved. ΔPCD/V is more preferably −100.0 to −5.0, and even more preferably −100.0 to −10.0.

The dispersion of the present invention should have a negative streaming potential before the cationic colloid titration is started, that is, when the titer is zero, when the pH value is in the range of 3 to 8. is preferred. This is because when the streaming potential is maintained at a negative potential, abrasive grains (ceria-based composite fine particles) are less likely to remain on the polishing substrate, which also exhibits a negative surface potential.

<Manufacturing method of the present invention>
A manufacturing method of the present invention will be described.
In the production method of the present invention, for example, a ceria-based composite fine particle dispersion liquid in which single-particle ceria-based composite fine particles are dispersed in a solvent is used as a raw material. The ceria-based composite fine particle dispersion in the present application includes, for example, primary silica fine particles (preferably composed of one silica-based fine particle), a cerium-containing silica layer on the surface of the silica primary fine particles, and the cerium-containing silica layer. child particles dispersed inside, the silica primary fine particles are mainly composed of amorphous silica, and the child particles are ceria-based composite fine particles mainly composed of crystalline ceria (by dynamic light scattering method A dispersion liquid (with a solid content concentration of 1 to 20% by mass) in which the measured average particle diameter is 50 to 350 nm) is dispersed in a solvent in a pH range of 2.0 to 6.0 at a temperature of 30 to 180 ° C. (preferably is obtained by holding in the range of 50 to 180°C).

The dispersion of the invention is preferably produced by the production method of the invention.
In the production method of the present invention, first, a silica-based fine particle dispersion is prepared.

The form of the silica-based fine particles is not particularly limited. The silica-based fine particles are mainly composed of amorphous silica, like the silica primary fine particles described above. Here, the definition of the main component is also the same as in the case of the silica primary fine particles.

Here, the average particle diameter of the silica-based fine particles in the silica-based fine particle dispersion used as a raw material is the average particle size of the particle-linked ceria-based composite fine particles in the particle-linked ceria-based composite fine particle dispersion obtained by the production method of the present invention. A smaller diameter is used. Preferably, silica-based microparticles with a range of 50 to 600 nm are used.
The average particle diameter of the silica-based fine particles in this silica-based fine particle dispersion is obtained by determining the major and minor diameters by measuring the major and minor diameters based on a photographic projection obtained by photographing using a scanning electron microscope. The average value is the particle diameter of the particles, and after measuring the particle diameters of 50 particles, it means a simple average value calculated from them.

In addition, the silica-based fine particles used as a raw material tend to have a higher degree of uniformity in particle size, the durability of the finally obtained particle-linked ceria-based composite fine particles is improved, and this tends to have a good effect on polishing performance. It is in. When the particle diameter of the primary silica fine particles constituting the particle-linked ceria-based composite fine particles varies greatly, for example, when the particle-linked ceria-based composite fine particles are used as abrasive grains, the particle-linked ceria-based composite fine particles In addition, stress concentration on the polishing substrate may cause many polishing scratches.

The coefficient of variation (CV value) in the particle size distribution of the silica-based fine particles is preferably 30% or less, more preferably 20% or less. When silica-based fine particles having a variation coefficient of particle size distribution within this range are used as a raw material, the coefficient of variation of the particle size distribution of the silica primary fine particles in the finally obtained particle-linked ceria-based composite fine particles is about the same as that of the raw material. , is preferable for obtaining better polishing performance. The variation coefficient of the particle size distribution of the silica primary fine particles in the particle-linked ceria-based composite fine particles is preferably 30% or less, more preferably 20% or less.
In addition, when the average particle size of the silica-based fine particles used as the raw material is highly uniform, the particle size distribution of the finally obtained particle-linked ceria-based composite fine particles can be easily converged into multiple peaks.

The short diameter/long diameter ratio of the silica-based fine particles in the silica-based fine particle dispersion liquid used as a raw material is preferably 0.1 or more and less than 1.0, and more preferably 0.1 or more and 0.7 or less. preferable.
The minor axis/longer axis ratio of the silica-based fine particles in this silica-based fine particle dispersion is obtained by determining the major and minor diameters by the major axis and minor axis measurement method based on a photographic projection obtained by photographing using a scanning electron microscope, After measuring the long diameter and short diameter of 50 particles, each simple average value calculated therefrom shall be meant.

When preparing the dispersion liquid of the present invention that is applied to the polishing of semiconductor devices or the like by the production method of the present invention, silica-based fine particles produced by hydrolysis of alkoxysilane are dispersed in a solvent as the silica-based fine particle dispersion liquid. It is preferable to use a silica-based fine particle dispersion liquid consisting of When a conventionally known silica-based fine particle dispersion other than the above (silica-based fine particle dispersion prepared using water glass as a raw material, etc.) is used as a raw material, the raw material water glass or an acidic silicic acid liquid obtained from water glass is used. It is preferable to use it after purifying it by a method, or to use it after acid-treating the resulting silica-based fine particle dispersion and further deionizing it. In this case, the content of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, U, Th, Cl, NO ₃ , SO ₄ and F contained in the silica-based fine particles is This is because it can be reduced, specifically, to 100 ppm or less.
Specifically, as the silica-based fine particles in the raw material silica-based fine particle dispersion, those satisfying the following conditions (a) and (b) are preferably used.
(a) Contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are each 100 ppm or less.
(b) Contents of U, Th, Cl, _NO3 , _SO4 and F are each 5 ppm or less.

In addition, silica-based fine particles having moderate reactivity with cerium (weight of dissolved silica-based fine particles per weight of ceria) are preferably used. By adding a cerium salt aqueous solution to the silica-based fine particles, part of the silica is dissolved by the cerium salt (cerium hydroxide, etc.), the size of the silica-based fine particles is reduced, and cerium fine particles are formed on the surface of the dissolved silica-based fine particles. A precursor of a cerium-containing silica layer containing crystals is formed. At this time, when the silica-based fine particles consist of amorphous silica that is highly reactive with cerium, the precursor of the cerium-containing silica layer becomes thick, and the cerium-containing silica layer formed by firing becomes thick, and the silica in that layer increases. The ratio becomes excessively high, and crushing becomes difficult in the crushing process. Further, when the silica-based fine particles are composed of amorphous silica having extremely low reactivity with cerium, the cerium-containing silica layer is not sufficiently formed, and the ceria particles tend to fall off. When the reactivity with cerium is appropriate, excessive dissolution of silica is suppressed, the cerium-containing silica layer has an appropriate thickness and prevents child particles from falling off, and its strength becomes greater than the strength between composite fine particles. It is desirable because it can be easily crushed.

Next, a cerium salt aqueous solution and an alkaline aqueous solution are added to this silica-based fine particle dispersion. Here, while maintaining the pH of the silica-based fine particle dispersion in the range of 7.0 to 9.0, a cerium salt aqueous solution and an alkaline aqueous solution are added continuously or intermittently to prepare a precursor particle dispersion. .

Here, the type of cerium salt is not limited, but cerium chlorides, nitrates, sulfates, acetates, carbonates, metal alkoxides, and the like can be used. Specific examples include cerous nitrate, cerium carbonate, cerous sulfate, and cerous chloride. Among them, trivalent cerium salts such as cerous nitrate, cerous chloride, and cerium carbonate are preferred. Crystalline cerium oxide, cerium hydroxide, etc. are formed from the solution that becomes supersaturated at the same time as the neutralization, and they quickly aggregate and deposit on the silica _- based fine particles, finally forming monodisperse ultrafine CeO2 particles. This is because that. Furthermore, the trivalent cerium salt moderately reacts with the silica-based fine particles to easily form a cerium-containing silica layer. Moreover, trivalent cerium, which is highly reactive with the silica film formed on the polished substrate, is easily formed in the ceria crystal, which is preferable. However, sulfate ions, chloride ions, nitrate ions, etc. contained in these metal salts are corrosive. Therefore, if desired, it is necessary to wash in a post-process after preparation to remove it to 5 ppm or less. On the other hand, carbonates are released as carbon dioxide gas during preparation, and alkoxides are decomposed into alcohols, so they can be preferably used.

A known alkali can be used as the alkaline aqueous solution added together with the cerium salt aqueous solution. Specific examples include aqueous ammonia solutions, alkali hydroxides, alkaline earth metals, aqueous solutions of amines, and the like.

The amount of the cerium metal salt added to the silica-based fine particle dispersion is such that the mass ratio of silica and ceria in the obtained ceria-based composite fine particles is 100:11 to 316, as in the case of the composite fine particles of the present invention. It is preferable to set the amount within the range.

The amount of the alkaline aqueous solution to be added is such that the pH is maintained at 7.0 to 9.0.

Moreover, the time for adding the cerium salt aqueous solution and the alkaline aqueous solution to the silica-based fine particle dispersion is preferably 0.5 to 24 hours. If this time is too short, the _CeO2 ultrafine particles agglomerate and become difficult to react with silica on the surface of the silica-based fine particles, and in the crushing process after firing, there is a tendency to form particles that are difficult to crush. I don't like it. Conversely, if this time is too long, the formation of the CeO ₂ ultrafine particle-containing layer will not proceed any further, making it uneconomical.
After addition of the cerium metal salt, aging at 0 to 80° C. may be performed if desired. This is because the aging promotes the reaction of the cerium compound and at the same time has the effect of causing free CeO ₂ ultrafine particles that do not adhere to the silica-based fine particles to adhere to the silica-based fine particles.

Through such treatment, a dispersion (precursor particle dispersion) containing particles (precursor particles) that are precursors of the fine composite particles of the present invention is obtained. It is possible to obtain particles having an average crystallite diameter of 2.5 nm or more and less than 10 nm of the CeO ₂ ultrafine particles contained in the precursor particles.

The obtained precursor particle dispersion may be diluted with pure water, ion-exchanged water, or the like, or concentrated before being subjected to the next treatment.
Further, 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.

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

Next, the obtained precursor particle dispersion is dried and then fired at 800 to 1200.degree.

The drying method is not particularly limited. It can be dried using a conventionally known dryer. Specifically, a box dryer, a band dryer, a spray dryer, or the like can be used.

Although the drying time is not particularly limited, it is preferably 1 to 64 hours, more preferably 3 to 24 hours.

Further, it is recommended that the pH of the precursor particle dispersion before drying is preferably 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 baking temperature is 800 to 1200°C, preferably 1000 to 1100°C, more preferably 1010 to 1090°C, even more preferably 1030 to 1090°C. When fired in such a temperature range, the crystallization of ceria sufficiently progresses, and the cerium-containing silica layer in which the ceria child particles are dispersed has an appropriate thickness, and the cerium-containing silica layer is firmly formed into primary silica fine particles. This is because it is difficult for the child particles dispersed in the cerium-containing silica layer to fall off. Furthermore, sintering in such a temperature range makes it difficult for cerium hydroxide or the like to remain. If this temperature is too high, the ceria crystals will grow abnormally, the cerium-containing silica layer will become too thick, the amorphous silica that constitutes the primary silica fine particles will crystallize, and the fusion between particles will progress. be.

Although the firing time is not particularly limited, it is preferably 1 to 20 hours, more preferably 2 to 10 hours.

After obtaining a roughly powdery sintered body in this way, a solvent is added to the sintered body, and a wet pulverization treatment is performed in the pH range of 8.6 to 10.8 to obtain a pulverized dispersion of the sintered body. get
Here, the sintered body may be dry crushed before being subjected to the wet crushing treatment, and then subjected to the wet crushing treatment.

A conventionally known device can be used as the dry crushing device, and examples thereof include an attritor, a ball mill, a vibrating mill, and a vibrating ball mill.
A conventionally known device can be used as a wet crushing device. - Stator homogenizers, ultrasonic dispersion homogenizers, and wet medium stirring mills (wet pulverizers) such as impact pulverizers in which fine particles in a dispersion collide with each other. Beads used in the wet medium agitating mill include, for example, beads made from glass, alumina, zirconia, steel, flint stone, organic resin, and the like.

Water and/or an organic solvent is used as a solvent for wet pulverization of the sintered body. For example, it is preferable to use water such as pure water, ultrapure water, or ion-exchanged water.

In the wet pulverization, an alkaline aqueous solution such as an aqueous ammonia solution is appropriately added so that the pH is in the range of 8.6 to 10.8.
If the pH is maintained in this range during wet disintegration, the amount of change in streaming potential (ΔPCD) represented by the above formula (1) and the amount of cation colloid titrant added in the knick will be reduced when cation colloid titration is performed. Finally, the dispersion of the present invention, which gives a streaming potential curve in which the ratio (ΔPCD/V) to (V) is from −110.0 to −15.0, can be obtained more easily. When such a dispersion of the present invention is used as a polishing agent, the polishing rate is further improved. With respect to this, the present inventor believes that the cerium-containing silica layer on the surface of the composite fine particles of the present invention is moderately thin, and the child particles are appropriately exposed on a part of the surface of the composite fine particles of the present invention, so that the polishing rate is It is presumed that this is because the separation of the ceria particles can be controlled. Furthermore, during pulverization, the silica in the cerium-containing silica layer dissolves and deposits again, forming a soft and easily soluble silica layer as the outermost layer, and this easily soluble silica layer has an adhesive effect with the substrate. It is presumed that the frictional force is improved in In addition, it is presumed that the cerium-containing silica layer is thin or peeled off, so that the child particles are likely to detach to some extent during polishing. ΔPCD/V is more preferably −100.0 to −15.0, and even more preferably −100.0 to −20.0.

In addition, without going through the wet pulverization process, even if the baked powder is loosened, or after being dispersed in a solvent, it can be stirred or ultrasonically dispersed, dry pulverization / pulverization, or wet pulverization. If it is outside the range, ΔPCD/V is unlikely to be in the range of -110 to -5 (preferably -100.0 to -15), and it is difficult to form a soft and easily soluble silica layer. Also, the ceria particles are not exposed and the polishing rate tends to be low.

The solid content concentration of the fired body pulverization dispersion liquid is not particularly limited, but is preferably in the range of 0.3 to 50% by mass, for example.

Next, it is preferable to perform a centrifugal separation process at a relative centrifugal acceleration of 300 G or more for the fired body pulverized dispersion liquid, and then remove the sediment component.

Specifically, it is preferable to classify the fired body pulverized dispersion liquid by centrifugal separation. The relative centrifugal acceleration in the centrifugation process is preferably 300G or more. After the centrifugation treatment, it is preferable to remove the precipitated components. Although the upper limit of the relative centrifugal acceleration is not particularly limited, it is preferably used at 10,000 G or less in practice.

By such treatment, the silica primary fine particles are mainly composed of amorphous silica, the child particles are mainly composed of crystalline ceria, and the average particle diameter measured by the dynamic light scattering method is 50 to 350 nm. A dispersion liquid in which fine composite particles are dispersed in a solvent and ceria-based fine composite particles are dispersed in a solvent can be obtained.

In the production method of the present invention, a dispersion liquid having a solid content concentration of 1 to 20% by mass in which such ceria-based composite fine particles are dispersed in a solvent is prepared at a pH range of 2.0 to 6.0 at a temperature of 30 to 30%. A particle-linked ceria-based composite fine particle dispersion can be obtained through a treatment including a step of holding at 180° C. (preferably 50 to 180° C.).

The method for adjusting the conditions such as solid content concentration, pH and temperature may be the same as described above.

After holding the dispersion having a solid content concentration of 1 to 20% by mass in this way at a pH range of 2.0 to 6.0 and a temperature range of 30 to 180 ° C. (preferably 50 to 180 ° C.), It is preferred that the pH range is maintained at 10.0 or higher and the temperature is maintained at 50-98° C., and the silicic acid solution is added continuously or intermittently. In this case, the bonding portion (neck portion) of the obtained particle-linked ceria-based composite fine particles grows, and the bonding between the ceria-based composite fine particles constituting the particle-linked ceria-based composite fine particles becomes stronger. In addition, as described above, the alkaline aqueous solution may be added for the purpose of maintaining the pH range.

By such a production method of the present invention, the particle-linked ceria-based composite fine particle dispersion of the present invention can be obtained.

<Abrasive Grain Dispersion for Polishing>
A liquid containing the dispersion of the present invention can be preferably used as an abrasive dispersion for polishing (hereinafter also referred to as "abrasive dispersion for polishing of the present invention"). In particular, it can be suitably used as a polishing abrasive dispersion for flattening a semiconductor substrate having an SiO ₂ insulating film formed thereon. Further, it can be suitably used as a polishing slurry by adding a chemical component to control the polishing performance.

The abrasive grain dispersion for polishing of the present invention has excellent effects such as a high polishing rate when polishing semiconductor substrates, etc., less scratches on the polished surface during polishing, and less residual abrasive grains on the substrate. ing.

The abrasive dispersion for polishing of the present invention contains water and/or an organic solvent as a solvent. As the solvent, it is preferable to use water such as pure water, ultrapure water, or ion-exchanged water. Further, in the abrasive dispersion for polishing of the present invention, an additive for controlling polishing performance is selected from the group consisting of polishing accelerators, surfactants, heterocyclic compounds, pH adjusters and pH buffers. By adding more than seeds, it can be suitably used as a polishing slurry.

<Grinding accelerator>
The abrasive grain dispersion for polishing of the present invention can be used as a polishing slurry by adding a conventionally known polishing accelerator as necessary, although it varies depending on the type of material to be polished. Examples of such include hydrogen peroxide, peracetic acid, urea peroxide, and the like, and mixtures thereof. By using a polishing agent composition containing such a polishing accelerator such as hydrogen peroxide, it is possible to effectively improve the polishing rate when the material to be polished is a metal.

Other examples of polishing accelerators include inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid and hydrofluoric acid, organic acids such as acetic acid, sodium salts, potassium salts, ammonium salts and amine salts of these acids, and and the like. In the case of a polishing composition containing these polishing accelerators, when a material to be polished consisting of multiple components is polished, the polishing rate of specific components of the material to be polished is accelerated, resulting in a flat polishing. face can be obtained.

When the polishing abrasive dispersion of the present invention contains a polishing accelerator, the content thereof is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. .

<Surfactant and/or hydrophilic compound>
Cationic, anionic, nonionic or amphoteric surfactants or hydrophilic compounds can be added to improve the dispersibility and stability of the abrasive grain dispersion of the present invention. Surfactants and hydrophilic compounds both have the effect of reducing the contact angle with the surface to be polished, and have the effect of promoting uniform polishing. As surfactants and/or hydrophilic compounds, for example, those selected from the following group can be used.

Examples of anionic surfactants include carboxylates, sulfonates, sulfate ester salts, and phosphate ester salts. Examples of carboxylates include soaps, N-acylamino acid salts, polyoxyethylene or polyoxypropylene alkyl ether acid salts, acylated peptides; sulfonates such as alkylsulfonates, alkylbenzene and alkylnaphthalenesulfonates, naphthalenesulfonates, sulfosuccinates, α-olefinsulfonates, N-acylsulfonates; sulfate esters As salts, sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkylallyl ether sulfates, alkylamide sulfates; Oxypropylene alkyl allyl ether phosphates may be mentioned.

As cationic surfactants, aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, imidazolinium salts; Mention may be made of aminocarboxylates, imidazolinium betaines, lecithins, alkylamine oxides.

Nonionic surfactants include ether types, ether ester types, ester types, and nitrogen-containing surfactants. Ether types include polyoxyethylene alkyl and alkylphenyl ethers, and ether ester types include glycerin ester polyoxy Examples of ethylene ether and ester type include polyethylene glycol fatty acid ester, and nitrogen-containing type include fatty acid alkanolamide. In addition, fluorine-based surfactants and the like are included.

The surfactant is preferably an anionic surfactant or nonionic surfactant, and the salt includes ammonium salt, potassium salt, sodium salt and the like, with ammonium salt and potassium salt being particularly preferred.

Further, other surfactants, hydrophilic compounds, etc. include esters such as glycerin ester; ethers such as polyethylene glycol; polysaccharides such as alginic acid; amino acid salts such as glycine ammonium salts; salts thereof; vinyl polymers such as polyvinyl alcohol; sulfonic acids such as ammonium methyltaurate and salts thereof; amides such as propionamide.

When the substrate to be polished is a glass substrate or the like, any surfactant can be suitably used. If the influence of contamination by metals or halides is to be avoided, it is desirable to use an acid or its ammonium salt surfactant.

When the abrasive grain dispersion for polishing of the present invention contains a surfactant and/or a hydrophilic compound, the total content thereof should be 0.001 to 10 g per 1 L of the abrasive grain dispersion for polishing. is preferred, 0.01 to 5 g is more preferred, and 0.1 to 3 g is particularly preferred.

The content of the surfactant and/or hydrophilic compound is preferably 0.001 g or more in 1 L of the polishing abrasive dispersion in order to obtain a sufficient effect, and preferably 10 g or less in terms of preventing a decrease in polishing speed. .

Surfactants or hydrophilic compounds may be used alone, or two or more may be used, or different types may be used in combination.

<Heterocyclic compound>
Regarding the abrasive grain dispersion for polishing of the present invention, in the case where the substrate to be polished contains metal, for the purpose of suppressing erosion of the substrate to be polished by forming a passivation layer or a dissolution inhibiting layer on the metal, A heterocyclic compound may be contained. Here, the "heterocyclic compound" is a compound having a heterocyclic ring containing one or more heteroatoms. Heteroatom means an atom other than a carbon atom or a hydrogen atom. Heterocycle means a cyclic compound containing at least one heteroatom. heteroatom means only those atoms which form a constituent part of a heterocyclic ring system and which may be external to the ring system, separated from the ring system by at least one non-conjugated single bond, or Atoms that are part of a further substituent of are not meant. Preferred heteroatoms include, but are not limited to, nitrogen, sulfur, oxygen, selenium, tellurium, phosphorus, silicon, and boron atoms. Examples of heterocyclic compounds that can be used include imidazole, benzotriazole, benzothiazole, tetrazole, and the like. More specific examples include 1,2,3,4-tetrazole and the like, but are not limited to these.

The content of the heterocyclic compound when blended in the abrasive grain dispersion of the present invention is preferably 0.001 to 1.0% by mass, more preferably 0.001 to 0.7% by mass. is more preferable, and 0.002 to 0.4% by mass is even more preferable.

<pH adjuster>
Acids or bases and salt compounds thereof can be added as necessary to adjust the pH of the polishing composition in order to enhance the effect of each of the above additives.

When adjusting the abrasive grain dispersion of the present invention to pH 7 or more, an alkaline pH adjuster is used. Amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine and tetramethylamine are preferably used.

When adjusting the abrasive grain dispersion of the present invention to a pH of less than 7, an acidic pH adjuster is used. For example, mineral acids such as hydrochloric acid and nitric acid are used, such as hydroxy acids such as acetic acid, lactic acid, citric acid, malic acid, tartaric acid and glyceric acid.

<pH buffer>
A pH buffer may be used to keep the pH value of the abrasive dispersion of the present invention constant. Phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium tetraborate tetrahydrate, and borates or organic acid salts can be used as pH buffers.

Examples of solvents for the abrasive grain dispersion of the present invention include alcohols such as methanol and ethanol; ketones such as acetone; amides such as N,N-dimethylformamide; ethers such as diethyl ether; Glycol ethers such as methoxyethanol; Glycol ether acetates such as 2-methoxyethyl acetate; Esters such as methyl acetate and ethyl acetate; Aromatic hydrocarbons such as benzene, toluene and xylene; Hexane, heptane, isooctane, cyclohexane Halogenated hydrocarbons such as methylene chloride; Sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone and other pyrrolidones using organic solvents such as be able to. These may be used by mixing with water.

The concentration of solids contained in the abrasive grain dispersion for polishing of the present invention is preferably in the range of 0.3 to 50 mass %. If this solid content concentration is too low, the required polishing rate may not be achieved. Conversely, even if the solid content concentration is too high, there are few cases where the polishing rate is further improved.

Particle-linked ceria-based composite fine particle dispersions obtained in Examples described later and particles contained in dispersions obtained in Comparative Examples were subjected to physical property tests and abrasiveness tests described below.

<Physical Property Test 1: Average Particle Size of Silica Primary Fine Particles in Linked Particle Group>
First, element maps were obtained by the above-described elemental mapping method using STEM-EDS for the dispersion liquids obtained in each example and each comparative example.
Next, in the elemental map, the mother particles (parts where the ratio (percentage) of Ce molar concentration to the sum of Ce molar concentration and Si molar concentration (percentage) (Ce / (Ce + Si) × 100) is less than 3%) are specified, Based on the shape, the primary silica fine particles forming the base particles in the elemental map were identified.
Next, the major diameter and minor diameter of the silica primary fine particles were measured by the major diameter and minor diameter measuring method, and the simple average value was taken as the particle diameter of the silica primary fine particles (see FIG. 1).
The particle diameters of the silica primary fine particles in 50 particles contained in the dispersion are measured in this way, and the value obtained by simple averaging is calculated as the particles contained in the dispersion (connected particle group of the present invention). ) was the average particle size of the silica primary fine particles.
In the examples and comparative examples, a STEM-EDS manufactured by JEOL Ltd., product number: JEM2100 was used.
(In Comparative Example 1, single-particle ceria-based composite fine particles were similarly measured.)

<Physical Property Test 2: Number of Linked Primary Silica Fine Particles in Linked Particle Group of the Present Invention>
For the dispersion obtained in each example and each comparative example, the base particles are specified by the elemental mapping method, and the silica primary fine particles constituting the base particles are specified from the shape thereof to form one base particle. The number of connected silica primary fine particles was measured.
Then, the number of connected silica primary fine particles was measured for 50 mother particles, the geometric mean value was obtained, and the obtained value was used as the number of connected silica particles in the dispersion.

<Physical Property Test 3: Average Particle Size Measurement of Linked Particle Group of the Present Invention>
The average particle size of the particle-linked ceria-based composite fine particle dispersions obtained in each of the examples and comparative examples was determined by a dynamic light scattering method. Specifically, using a particle size measuring device, ELSZ-1000 manufactured by Otsuka Electronics Co., Ltd., the average particle size of the particle-linked ceria-based composite fine particles contained in the particle-linked ceria-based composite fine particle dispersion liquid is measured by the cumulant method. did.
In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Physical Property Test 4: Short Diameter/Long Diameter Ratio of Particle-Linked Ceria-Based Composite Fine Particles>
Particles constituting linked particle groups contained in particle-linked ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples were observed with a transmission electron microscope (TEM) at a magnification of 300,000 times (or 500,000 times). In the resulting photographic projection view, the major diameter (DL) and minor diameter (DS) are measured for 50 or more particles by the major diameter and minor diameter measurement method, and the geometric mean value is obtained. The values were defined as the long diameter (DL) and short diameter (DS) of the particle-linked ceria-based composite fine particles. Then, the minor axis/longer axis ratio was determined.
In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Physical Property Test 5: Calculation of Formula (II)>
Prepare an image or photograph of the particles constituting the linked particle group contained in the particle linked ceria-based composite fine particle dispersion liquid obtained in each example and comparative example, obtained by using a scanning electron microscope at a magnification of 50,000. Then, the SEM image is analyzed using image analysis software (for example, Avizo ver. 6.0 manufactured by Visualization Sciences Group) to determine the projected area (S) of the entire particle, and the three-dimensional portion on the particle is visually determined. , the projected area (T) of the three-dimensional portion was determined by the same software by designating only the three-dimensional portion.
Next, for 50 randomly selected particles, the projected area (T) of the three-dimensional portion and the projected area (S) of the entire particle are obtained in the same manner, and the value obtained by calculating the geometric mean value is The projected area (T') of the three-dimensional portion of the particles constituting the connected type particle group and the projected area (S') of the entire particle were used.
Then, the value of T'/S'×100 was calculated.
In Comparative Example 1, the same calculation was performed for single-particle ceria-based composite fine particles.

<Physical Property Test 6: Measurement of Non-Kuspiciousness>
The non-cuspidity value and the non-cuspidity of the particles constituting the linked particle group contained in the particle-linked ceria-based composite fine particle dispersion obtained in each example and comparative example are described in each example and comparative example. Using a scanning electron microscope, prepare an image or photograph of the particles constituting the linked particle group contained in the resulting particle-linked ceria-based composite fine particle dispersion at a magnification of 50,000, and measure by the method described above. did. In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Physical Property Test 7: Proportion of Connected Particles Stretching Planar>
A method for measuring the ratio of planarly elongated connected particles of the particles constituting the connected particle groups contained in the particle-connected ceria-based composite fine particle dispersions obtained in each of Examples and Comparative Examples will be described. Regarding the particles constituting this connected type particle group, the base particles are specified by the STEM-EDS method in the same manner as in the physical property test 1, and the silica primary fine particles constituting the base particles are specified from their shapes, and one base is obtained. The number of connected particles that constitute the particle is measured. Then, 50 particles including base particles in which four or more silica primary fine particles are connected are specified. Next, among the particles having mother particles in which four or more silica primary fine particles are connected, the number ratio (percentage) of the particles having mother particles in which the silica primary fine particles are connected while extending in a plane ).
Whether or not the silica primary fine particles are elongated in a plane was determined according to the aforementioned criteria.

<Physical Property Test 8: Number of Peaks in Linked Number Distribution>
Regarding the particle-linked ceria-based composite fine particle dispersion liquid obtained in each of the examples and comparative examples, the number of linked silica primary fine particles was measured for 50 mother particles in the same manner as described in physical property test 2. The number of peaks in the distribution (X axis: number of connections, Y axis: number of particles having each number of connections) was measured. In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Physical Property Test 9: Measurement of Variation Coefficient of Particle Size Distribution of Silica-based Fine Particles>
The silica-based fine particle dispersion liquid (silica concentration: 0.05% by mass) used as a raw material was photographed with a scanning electron microscope (SEM) at a magnification of 50,000 times, and the average particle diameter of 50 silica-based fine particles was measured. The standard deviation was calculated, and the standard deviation was divided by the average value to calculate the coefficient of variation (CV value) [%] in the particle size distribution of the silica-based fine particles. As the scanning electron microscope, the product number JEM2100 manufactured by JEOL Ltd. was used. In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Physical Property Test 10: Measurement of Average Neck Depth (Lm)>
The average neck depth of the linked particle group of the present invention obtained in each example and comparative example was measured by the method described above.

<Physical Property Test 11: Measurement of Ratio (Parts by Mass) of SiO ₂ Content to CeO ₂ Content>
A method for measuring the CeO ₂ content and the SiO ₂ content in the particles contained in the particle-linked ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples will be described.
First, the particle-linked ceria-based composite fine particle dispersion is subjected to ignition loss at 1000° C., and the mass of the solid content is determined. The content was measured and the _SiO2 mass % was calculated. Next, the CeO ₂ content (% by mass) was obtained assuming that the solid component other than SiO ₂ was CeO ₂ . Then, the ratio (mass part) between the SiO ₂ content and the CeO ₂ content was obtained. In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Physical property test 12: Measurement of crystal type and measurement of average crystallite size>
The particle-linked ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples were dried using a conventionally known dryer, and the resulting powder was pulverized in a mortar for 10 minutes and subjected to X-ray diffraction analysis (Rigaku). An X-ray diffraction pattern was obtained using RINT1400 (manufactured by Denki Co., Ltd.) to identify the crystal type.
In addition, the full width at half maximum of the peak of the (111) plane (near 2θ = 28 degrees) near 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the average crystallite diameter is obtained by the aforementioned Scherrer equation. rice field. In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Polishing Performance Test 1: Measurement of Polishing Rate>
Polishing abrasive dispersions containing the particle-linked ceria-based composite fine particle dispersions obtained in each of Examples and Comparative Examples were prepared. Here, the solid content concentration of the abrasive grain dispersion for polishing was set to 0.6% by mass, and nitric acid was added to set the pH to 5.0.
Next, as a substrate to be polished, a SiO ₂ insulating film (thickness 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, this substrate to be polished is set in a polishing apparatus (NF300, manufactured by Nanofactor Co., Ltd.), and a polishing pad ("IC-1000/SUBA400 concentric type" manufactured by Nitta Haas Co., Ltd.) is used to apply a substrate load of 0.5 MPa and a table. Polishing was performed by supplying the polishing abrasive dispersion at a rate of 50 ml/min for 1 minute at a rotating speed of 90 rpm.
Then, the change in weight of the substrate to be polished before and after polishing was obtained to calculate the polishing rate.
In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

<Polishing Performance Test 2: Number of Scratches>
A polishing abrasive dispersion containing the particle-linked ceria-based composite fine particle dispersion obtained in each of the examples and comparative examples was prepared. Here, the solid content concentration of the abrasive grain dispersion for polishing was set to 9% by mass, and nitric acid was added to adjust the pH to 2.0.
Next, the aluminum hard disk substrate was set in a polishing apparatus (NF300, manufactured by Nanofactor Co., Ltd.), and a polishing pad ("Polytex φ12" manufactured by Nitta Haas Co., Ltd.) was used. Polishing is performed by supplying a polishing abrasive dispersion for 5 minutes at a rate of 20 ml / minute, and using an ultrafine defect / visualization macro device (manufactured by VISION PSYTEC, product name: Micro-Max), the entire surface is zoomed 15. The number of scratches (linear scratches) present on the surface of the polished substrate corresponding to 65.97 cm ² was counted and totaled, and evaluated according to the following criteria.
Number of linear scratches Evaluation Less than 50 "very few"
From 50 to less than 80 "Few"
80 or more "many"
At least 80 or more, so many that the total number cannot be counted "*"
In Comparative Example 1, the same measurement was performed for single-particle ceria-based composite fine particles.

[Example 1]
Preparation of <<silica-based fine particle dispersion (silica-based fine particles have an average particle diameter of 43 nm)>> 12,090 g of ethanol and 6,363.9 g of normal ethyl silicate were mixed to obtain _a mixed solution a1. Next, 6,120 g of ultrapure water and 444.9 g of 29% aqueous ammonia were mixed to obtain a mixture b ₁ .
Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed to prepare a bed water.
Then, the bed water was adjusted to 75° C. with stirring, and mixed solution a ₁ and mixed solution b ₁ were simultaneously added thereto so that the addition was completed in 10 hours. After the addition was completed, the liquid temperature was kept at 75° C. for 3 hours for aging, and then the solid content concentration was adjusted to 19% by mass of SiO ₂ solid content. 9,646.3 g of a silica-based fine particle dispersion was obtained in which silica-based fine particles having an average particle diameter of 43 nm measured by the method were dispersed in a solvent.

Preparation of <<silica-based fine particle dispersion (average particle size of silica-based fine particles: 80 nm)>> 2,733.3 g of methanol and 1,822.2 g of normal ethyl silicate were mixed to obtain a mixed solution _a2 .
Next, _1,860.7 g of ultrapure water and 40.6 g of 29% aqueous ammonia were mixed to obtain a mixed solution b2.
Next, 59 g of ultrapure water and 1,208.9 g of methanol were mixed to obtain a silica-based fine particle dispersion liquid 922.922.1, which was prepared by dispersing silica-based fine particles having an average particle diameter of 60 nm obtained in the previous step in a solvent. 1 g was added.
Then, the bed water containing the silica-based fine particle dispersion is adjusted to 65° C. while stirring, and mixed solution a ₂ and mixed solution b ₂ are added simultaneously so that the addition is completed in 18 hours. gone. After the addition was completed, the liquid temperature was kept at 65° C. for 3 hours for aging, and then the solid content concentration (SiO ₂ solid content concentration) was adjusted to 19% by mass, and 3,600 g of high-purity silica-based fine particles were dispersed. I got the liquid.
The silica-based fine particles contained in this high-purity silica-based fine particle dispersion liquid had an average particle diameter of 80 nm as measured by a major axis and minor axis measurement method using a scanning electron micrograph.

Next, 114 g of a cation exchange resin (SK-1BH manufactured by Mitsubishi Chemical Corporation) was gradually added to 1,053 g of this high-purity silica-based fine particle dispersion (average particle diameter of silica-based fine particles: 108 nm) and stirred for 30 minutes. The resin was separated. The pH at this time was 5.1.
Ultrapure water was added to the obtained silica-based fine particle dispersion to obtain 6,000 g of A-1 liquid having a SiO ₂ solid content concentration of 3% by mass.

Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (manufactured by Kanto Kagaku Co., Ltd., 4N high-purity reagent) to obtain liquid B-1 with a content of 2.5% by mass in terms of CeO ₂ .

Next, the temperature of solution A-1 (6,000 g) was raised to 50° C., and while stirring, solution B-1 (8,453 g, 117 parts of CeO ₂ was added to 100 parts by mass of SiO ₂ ). .4 parts by weight) was added over 18 hours. During this time, the liquid temperature was maintained at 50° C., and 3% aqueous ammonia was added as necessary to maintain the pH at 7.9 to 8.7. During addition of solution B-1 and during aging, preparation was carried out while blowing air into the prepared solution, and the oxidation-reduction potential was maintained at a positive value.
After the addition of solution B-1 was completed, the temperature of the solution was raised to 93° C. and aging was carried out for 4 hours. After the aging was completed, the product was allowed to stand indoors for cooling, and after cooling to room temperature, the product was washed with an ultramembrane while replenishing ion-exchanged water. The precursor particle dispersion obtained after washing had a solid content concentration of 7% by mass, a pH of 9.1 (at 25°C), and an electrical conductivity of 67 μs/cm (at 25°C). .

Next, a 5% by mass acetic acid aqueous solution was added to the obtained precursor particle dispersion to adjust the pH to 6.5, dried in a dryer at 100°C for 16 hours, and then dried in a muffle furnace at 1088°C. Firing was performed for 2 hours to obtain a powder.

310 g of the powder obtained after firing and 430 g of ion-exchanged water are placed in a 1 L beaker with a handle, a 3% aqueous ammonia solution is added thereto, and the mixture is irradiated with ultrasonic waves for 10 minutes in an ultrasonic bath while stirring. A suspension of pH 10 (temperature 25° C.) was obtained.
Next, 595 g of quartz beads with a diameter of 0.25 mm were put into a crusher (LMZ06, manufactured by Ashizawa Fine Tech Co., Ltd.) that had been cleaned and water-operated in advance, and the above suspension was added to the charge tank of the crusher. Filled (85% fill factor). Considering the residual ion-exchanged water in the pulverizing chamber and pipes of the pulverizer, the concentration at the time of pulverization was 25% by mass. Then, wet pulverization and pulverization were performed under the conditions of a disk peripheral speed of 12 m/sec, a number of passes of 25, and a residence time of 0.43 minutes per pass. In addition, a 3% aqueous ammonia solution was added in each pass so as to maintain the pH of the suspension at 10.1 during pulverization and pulverization. Thus, a ceria-based composite fine particle dispersion having a solid concentration of 22% by mass was obtained.

The thus-obtained ceria-based composite fine particle dispersion having a solid concentration of 22% by mass is centrifuged for 1 minute at a relative centrifugal acceleration of 1700 G using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G"). Then, the precipitated components were removed to obtain a ceria-based composite fine particle dispersion (average particle diameter (by dynamic light scattering method): 134 nm, solid content: 20.5% by mass).
1178 g of pure water was added to 390 g of this ceria-based composite fine particle dispersion (solid concentration: 20.5% by mass) to dilute to a solid content concentration of 5.1% by mass.
40 g of cation exchange resin SK1BH was added to 1568 g of this ceria-based composite fine particle dispersion, and the mixture was stirred for 60 minutes to carry out cation exchange. After cation exchange, the resin was separated using a mesh to obtain a ceria-based composite fine particle dispersion (cation-exchanged product).
784 g of this ceria-based composite fine particle dispersion (cation exchange product, solid content concentration 5.1% by mass) was subdivided, and 24 g of an ammonium acetate aqueous solution (acetic acid concentration 7% by mass) was added as a pH buffer to adjust the pH. The temperature was adjusted to 4.5 and heat treatment (90° C., 5 hours) was performed to obtain a particle-linked ceria-based composite fine particle dispersion. The average particle size of this particle-linked ceria-based composite fine particle dispersion measured by a dynamic light scattering method was 303 nm.
Subsequently, 500 g of the particle-linked ceria-based composite fine particle dispersion (heat-treated product) was subdivided, 25 g of an anion exchange resin (SANUP B) was added, stirred for 60 minutes, and anion exchange was performed. The resin was separated using a mesh to obtain a particle-linked ceria-based composite fine particle dispersion (anion-exchanged product).

The particle-linked ceria-based composite fine particles contained in the particle-linked ceria-based composite fine particle dispersion (anion exchange product) thus obtained were subjected to STEM-EDS by the method described in [STEM-EDS analysis] above. An elemental map of the analysis (×200,000) was obtained. Then, from this elemental map, the particle-linked ceria-based composite fine particles according to the present example are composed of a mother particle in which a plurality of silica primary fine particles are linked, a cerium-containing silica layer on the surface of the mother particle, and a cerium-containing silica layer It was confirmed that it has child particles dispersed inside.
Further, physical property tests 1 to 12 and polishing performance tests 1 and 2 were performed on the particle-linked ceria-based fine particle dispersion thus obtained. The results are shown in Table 1.

For the dispersion liquid obtained in Example 1, after obtaining an elemental map by the same method as in physical property test 1, the length and breadth of the silica primary fine particles obtained by the length and breadth measuring method were simply averaged. The obtained particle diameter is 101 nm, and the short diameter/short diameter obtained from the long diameter (DL) and short diameter (DS) measured by the long diameter and short diameter measurement method in the photographic projection obtained by the same method as in physical property test 4. The length ratio is 0.8, and the projected area (S ), then visually determine the three-dimensional portion on the same particle, specify only the three-dimensional portion, and obtain the projected area (T) of the three-dimensional portion using the same software. , the presence of particles in which neither site α nor site β has a pointed structure (both Fα and Fβ are 120° or more).

[Example 2]
In the same manner as in Example 1, a ceria-based composite fine particle dispersion (average particle size (according to dynamic light scattering method) of 134 nm, solid content concentration of 20.5% by mass) was obtained.
402 g of pure water was added to 390 g of this ceria-based composite fine particle dispersion (solid content concentration: 20.5 mass %) to dilute the solid content concentration to 10.1 mass %.
40 g of cation exchange resin SK1BH was added to 792 g of this ceria-based composite fine particle dispersion, and the mixture was stirred for 60 minutes to carry out cation exchange. After cation exchange, the resin was separated using a mesh to obtain a ceria-based composite fine particle dispersion (cation-exchanged product).
700 g of this ceria-based composite fine particle dispersion (cation exchange product, solid content concentration 10.1% by mass) was subdivided, and 43 g of an ammonium acetate aqueous solution (acetic acid concentration 7% by mass) was added as a pH buffer. was adjusted to 4.5, heat treatment (90° C., 16 hours) was performed, and a particle-linked ceria-based composite fine particle dispersion was obtained. The average particle diameter of this particle-linked ceria-based composite fine particle dispersion liquid measured by a dynamic light scattering method was 406 nm.

For the dispersion liquid obtained in Example 2, after obtaining an elemental map by the same method as in physical property test 1, the major diameter and minor diameter of the primary silica fine particles obtained by the major diameter and minor diameter measurement method were simply averaged. The obtained particle diameter is 101 nm, and the short diameter/short diameter obtained from the long diameter (DL) and short diameter (DS) measured by the long diameter and short diameter measurement method in the photographic projection obtained by the same method as in physical property test 4. The major axis ratio is 0.5, and the projected area (S ), then visually determine the three-dimensional portion on the same particle, specify only the three-dimensional portion, and obtain the projected area (T) of the three-dimensional portion using the same software. , the presence of particles in which neither site α nor site β has a pointed structure (both Fα and Fβ are 120° or more).

[Comparative Example 1]
[Preparation of silica-based fine particle dispersion]
Add 3986 g of ion-exchanged water to 300 g of fumed silica (AEROSIL50, manufactured by Nippon Aerosil Co., Ltd.), and perform wet decomposition using high-purity silica beads of φ0.25 mm (bead mill LMZ06, manufactured by Ashizawa Finetech Co., Ltd., manufactured by Daiken Chemical Industry Co., Ltd.). Crushing and pulverization were carried out to obtain 4286 g of a silica-based fine particle dispersion having a solid content concentration of 7% by mass.
3387.7 g of ultrapure water and 29.7 g of 3% ammonia were added to 2571 g of the silica-based fine particle dispersion obtained above and mixed, and 6000 g of a dispersion having a SiO ₂ solid content concentration of 3% by mass (hereinafter, also referred to as liquid A-2) ) was obtained. The average particle size of the silica-based fine particles contained in this liquid A-2 (silica-based fine particle dispersion) was 32 nm.

Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (manufactured by Kanto Chemical Co., Ltd., 4N high-purity reagent), and an aqueous cerium nitrate solution of 3.0 mass% in terms of CeO ₂ (hereinafter, liquid B-2) was obtained. ) was obtained.

Next, liquid B-2 (7,186 g, CeO ₂ dry 215.6 g) was added to liquid A-2 (6,000 g) over 18 hours while the mixture was kept at 10° C. and stirred. During this time, the liquid temperature was maintained at 10° C., and 3% aqueous ammonia was added as necessary to maintain the pH at 7.9 to 8.7. After completion of the addition, aging was performed at a liquid temperature of 10° C. for 4 hours. During the addition and aging of solution B-2, the preparation was carried out while blowing air into the prepared solution, and the oxidation-reduction potential was kept at 100 to 300 mV.
After that, washing was performed while replenishing ion-exchanged water with an ultramembrane. The precursor particle dispersion obtained after washing had a solid content concentration of 4.7% by mass, a pH of 8.2 (at 25°C), and an electrical conductivity of 19 μs/cm (at 25°C). there were

Next, the obtained precursor particle dispersion was dried in a drier at 120° C. for 16 hours, and then calcined in a muffle furnace at 1075° C. for 2 hours to obtain a powder (calcined body).

300 g of ion-exchanged water was added to 100 g of the powder (fired body) obtained after firing, and the pH was adjusted to 10.1 using a 3% aqueous ammonia solution. (manufactured by Kanpe Co., Ltd.) for 120 minutes.
After crushing, the beads were separated through a 44-mesh wire mesh. The obtained fired body pulverized dispersion liquid had a solid content concentration of 5.9% by mass and a weight of 1148 g. During the pulverization, an aqueous ammonia solution was added to keep the pH at 10.1.

Further, the crushed dispersion liquid was treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at 1700 G for 102 seconds, and a light liquid was recovered to obtain a ceria-based composite fine particle dispersion liquid.

For the ceria-based composite fine particles contained in the thus-obtained ceria-based composite fine-particle dispersion, an elemental map was obtained by STEM-EDS analysis (200,000 times) in the same manner as in Example 1. From this elemental map, the ceria-based composite fine particle dispersion liquid according to Comparative Example 1 has a cerium-containing silica layer on the surface of the silica primary fine particles and child particles dispersed inside the cerium-containing silica layer. It was confirmed that the ceria-based composite fine particle dispersion liquid was obtained by dispersing single-particle-like ceria-based composite fine particles in a solvent.
Further, physical property tests 1 to 12 and polishing performance tests 1 and 2 were performed on the single-particle ceria-based fine particle dispersion thus obtained. The results are shown in Table 1.

Claims (12)

A plurality of primary silica fine particles having a particle diameter in the range of 50 to 600 nm as measured by STEM-EDS analysis are connected via a cerium-containing silica layer, and the cerium-containing silica layer is also formed on the surface thereof. base particles;
child particles dispersed within the cerium-containing silica layer;
Particle-linked ceria-based composite fine particles having the following characteristics (1) to (3).
(1) The ratio of minor axis to major axis of the particle-linked ceria-based composite fine particles is in the range of 0.1 to 0.9.
(2) The projected area (T) of the three-dimensional portion of the particle and the projected area (S) of the entire particle obtained from the scanning electron micrograph of the particle-linked ceria-based composite fine particles are related by the following general formula (I): to meet
T / S × 100 = 0: general formula (I)
(3) Two sites α and β located on the outer edge of the particle and on the long axis, which are specified from the scanning electron micrograph of the particle-linked ceria-based composite fine particles, both have a pointed structure. do not take The particle-linked ceria-based composite fine particles according to claim 1, wherein the particle-linked ceria-based composite fine particles have a non-kurtosis in the range of 0.85 to 1.0. 3. The particle-linked ceria-based composite fine particles according to claim 1 or 2, wherein said mother particles are linked to said 4 to 10 primary silica fine particles via said cerium-containing silica layer. A particle-linked ceria-based composite fine particle dispersion liquid in which the particle-linked ceria-based composite fine particles according to any one of claims 1 to 3 are dispersed in a solvent. Particle-linked, comprising the particle-linked ceria-based composite fine particles according to any one of claims 1 to 3, wherein linked particle groups having the characteristics of the following (4) to (7) are dispersed in a solvent type ceria-based composite fine particle dispersion.
(4) The average particle size of the linked particle group measured by a dynamic light scattering method is 100 to 600 nm.
(5) The average particle diameter of the silica primary fine particles in the linked particle group as measured by STEM-EDS analysis is in the range of 50 to 600 nm.
(6) The short axis/long axis ratio of the linked particle group is in the range of 0.1 to 0.9.
(7) The total projected area (T') of the three-dimensional portions of the particles and the total projected area (S') of the entire particles obtained from the scanning electron micrograph of the linked particle group are represented by the following general formula (II ) relationship.
T'/S'×100≦30: general formula (II) 6. The particle-linked ceria-based composite fine particle dispersion liquid according to claim 5, wherein the non-kurtosis of the linked-type particle group is in the range of 0.85 to 1.0. 7. The particle-linked ceria according to claim 5, wherein the mother particles of the particles constituting the linked-type particle group are 4 to 10 silica primary fine particles linked via the cerium-containing silica layer. system composite fine particle dispersion. Among the particles having the base particles in which the four or more silica primary fine particles are linked via the cerium-containing silica layer in the linked particle group, the silica primary fine particles are linked while extending in a plane. 8. The particle-linked ceria-based composite fine particle dispersion liquid according to any one of claims 5 to 7, wherein the number ratio of those having the base particles is 60% or more. 9. The particle-linked ceria-based composite fine particle dispersion liquid according to any one of claims 5 to 8, wherein the particle-linked ceria-based composite fine particle dispersion has a plurality of peaks in the linked number distribution of the particles constituting the linked-type particle group. A polishing abrasive dispersion containing the particle-linked ceria-based composite fine particle dispersion according to any one of claims 6 to 9. It has silica primary fine particles, a cerium-containing silica layer on the surface of the silica primary fine particles, and child particles dispersed inside the cerium-containing silica layer, and the silica primary fine particles are mainly composed of amorphous silica. The child particles are mainly composed of crystalline ceria, and ceria-based composite fine particles having an average particle diameter of 50 to 350 nm as measured by a dynamic light scattering method are dispersed in a solvent, and the solid content concentration is 1 to A method for producing a particle-linked ceria-based composite fine particle dispersion, comprising a step of maintaining a 20% by mass dispersion at a pH range of 2.0 to 6.0 and a temperature range of 30 to 180°C. After holding the dispersion having a solid content concentration of 1 to 20% by mass in a pH range of 2.0 to 6.0 and a temperature range of 30 to 180 ° C., a pH range of 10.0 or more and a temperature of 50 to (11) The step of maintaining the temperature in the range of 98°C and then continuously or intermittently adding a silicic acid solution thereto to prepare the particle-linked silica-based fine particle dispersion in which particles have grown. 3. The method for producing the particle-linked ceria-based composite fine particle dispersion according to 1.

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