JP2020050571A - Ceria-based composite fine particle dispersion, method for producing the same, and abrasive grain dispersion for polishing containing the same - Google Patents

Abstract

To provide a ceria-based composite fine particle dispersion capable of: even polishing a silica film, an Si wafer and a hardly-processing material rapidly; and simultaneously achieving high face accuracy.SOLUTION: A ceria-based composite fine particle dispersion has the following characteristics, wherein a minor diameter/major diameter ratio and an average particle diameter are within a specific range: a ceria-based composite fine particle 20 has a mother particle 10, a cerium-containing coating layer 12 on a surface thereof, and a child particle 14 dispersed in the cerium-containing coating layer, wherein the mother particle mainly comprises a crystalline inorganic oxide, and the child particle mainly comprises a crystalline ceria; variation coefficient in a particle size distribution of the child particle is within a specific range; and in the ceria-based composite fine particle, a mass ratio of ceria and compositions other than the ceria is within a specific range, an average crystallite diameter of the crystalline ceria, measured by using X-ray diffraction, is 10-25 nm, and a crystal phase of ceria and a crystal phase of the crystalline inorganic oxide are detected when using the X-ray diffraction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ceria-based composite fine particle dispersion suitable as an abrasive used in the manufacture of semiconductor devices and the like, and more particularly, to flatten a film to be polished formed on a substrate by chemical mechanical polishing (Chemical Mechanical Polishing: CMP). The present invention relates to a ceria-based composite fine particle dispersion, a method for producing the same, and a polishing abrasive dispersion containing the ceria-based composite fine particle dispersion.

  2. Description of the Related Art Semiconductor devices such as semiconductor substrates and wiring substrates achieve high performance by increasing the density and miniaturization. In the manufacturing process of this semiconductor, so-called chemical mechanical polishing (CMP) is applied. Specifically, a technique essential for shallow trench element isolation, flattening of an interlayer insulating film, formation of contact plugs and Cu damascene wiring, and the like. It has become.

Generally, the CMP polishing slurry is composed of abrasive grains and a chemical component, and the chemical component plays a role of promoting polishing by oxidizing or corroding a target film. On the other hand, abrasive grains have a 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 specifically high polishing rate for a silicon oxide film, they are applied to polishing in a shallow trench element isolation step.
In the shallow trench element isolation step, not only polishing of a silicon oxide film but also polishing of a silicon nitride film is performed. In order to facilitate element isolation, it is desirable that the polishing rate of the silicon oxide film is high and the polishing rate of the silicon nitride film is low. The polishing rate ratio (selectivity) is also important.

Conventionally, as a method of polishing such a member, a relatively rough primary polishing process is performed, and then a precise secondary polishing process is performed, whereby a smooth surface or an extremely high-precision surface with few scratches or the like is obtained. The way to get is done.
Conventionally, for example, the following methods have been proposed for the polishing agent used for the secondary polishing as the finish polishing.

  For example, Patent Literature 1 discloses that an aqueous solution of cerous nitrate and a base are mixed under stirring at an amount ratio of pH 5 to 10, followed by rapid heating to 70 to 100 ° C and aging at that temperature. A method for producing ultrafine cerium oxide fine particles (average particle diameter: 10 to 80 nm) comprising a cerium oxide single crystal characterized by the following characteristics is further described. According to this production method, the particle diameter is high and the particle shape is high. It is described that cerium oxide ultrafine particles having high uniformity can be provided.

  Non-Patent Document 1 discloses a method for producing ceria-coated silica including a production step similar to the method for producing cerium oxide ultrafine particles described in Patent Document 1. This method for producing ceria-coated silica does not include a firing-dispersion step as included in the production method described in Patent Document 1.

  Further, Patent Document 2 has child particles mainly composed of crystalline ceria on the surface of mother particles mainly composed of amorphous silica, and further has a silica coating on the surface of the child particles. A silica-based composite fine particle dispersion containing silica-based composite fine particles having an average particle diameter of 50 to 350 nm and having the following features [1] to [3] is described. [1] The silica-based composite fine particles have a mass ratio of ceria to a component other than ceria of 100: 11 to 316. [2] When the silica-based composite fine particles are subjected to X-ray diffraction, a ceria crystal phase and a crystalline inorganic oxide crystal phase are detected. [3] The silica-based composite fine particles have a crystallite diameter of (111) plane of the crystalline ceria of 10 to 25 nm, as measured by X-ray diffraction. According to such silica-based composite fine particles, even a silica film, a Si wafer, or a difficult-to-process material can be polished at high speed, and at the same time, high surface accuracy (low scratch, low surface roughness of the substrate to be polished ( Ra) is low, and a silica-based composite fine particle dispersion liquid that can be preferably used for polishing a surface of a semiconductor device such as a semiconductor substrate or a wiring substrate because it does not contain impurities can be provided. Are listed.

Patent No. 2,746,861 WO 2016/159167 pamphlet

See Seung-Ho Lee, Zhenyu Lu, S.M. V. Babu and Egon Matijevik, "Chemical mechanical polishing of thermal oxide films using silicone particles coated with each cereal, 27th edition of 200th memorial, and 27th edition of Journal of the United States.

However, when the present inventors actually manufactured and examined the cerium oxide ultrafine particles described in Patent Document 1, the polishing rate was low, and the surface of the polishing substrate had defects (deterioration of surface accuracy, increase in scratches, (Residual polishing material on the surface of the polishing base material).
This is because the method for producing ultrafine cerium oxide particles described in Patent Literature 1 does not include the sintering step, and the liquid phase Since the cerium oxide particles are only crystallized from the (aqueous solution containing cerous nitrate), the cerium oxide particles to be produced have relatively low crystallinity, and the cerium oxide solidifies with the base particles because it does not undergo a calcination treatment. The present inventors presume that the main factor is that cerium oxide does not adhere and remains on the surface of the polishing substrate.

  In addition, since the ceria-coated silica described in Non-Patent Document 1 is not calcined, it is considered that the actual polishing rate is low. In addition, since the silica is not fixed and integrated with the silica particles, it easily falls off and the polishing rate decreases. In addition, there is a concern that particles may not remain on the surface of the polishing substrate due to lack of polishing stability.

  Further, the silica-based composite fine particle dispersion described in Patent Document 2 can exhibit excellent polishing performance (polishing speed, high surface accuracy, etc.) in polishing applications, but further increases the density of semiconductor devices. -With the increase in the degree of integration, there has been a demand for an abrasive dispersion liquid that exhibits better polishing performance for semiconductor substrates.

  An object of the present invention is to solve the above problems. That is, the present invention is capable of polishing at high speed even with a silica film, a Si wafer, or a difficult-to-process material, and at the same time, achieves high surface accuracy (low scratches, little abrasive grains remaining on the substrate, improvement of the substrate Ra value). And the like, and further containing no impurities, a ceria-based composite fine particle dispersion that can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate, a method for producing the same, and a ceria-based composite fine particle dispersion. It is an object of the present invention to provide an abrasive dispersion liquid for polishing.

The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and have completed the present invention.
The present invention includes the following (1) to (9).
(1) including ceria-based composite fine particles having the following features [1] to [5], having a minor axis / major axis ratio in the range of 0.2 to 1.0, and having an average particle diameter of 50 to 1000 nm; Ceria-based composite fine particle dispersion.
[1] The ceria-based composite fine particles include base particles, a cerium-containing coating layer on the surface of the base particles, and child particles dispersed inside the cerium-containing coating layer. A crystalline inorganic oxide is a main component, and the child particles are a crystalline ceria as a main component.
[2] The coefficient of variation (CV value) in the particle size distribution of the child particles is 14 to 60%.
[3] The ceria-based composite fine particles have a mass ratio of a component other than ceria to ceria in the range of 100: 11 to 316.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, a ceria crystal phase and a crystal phase of the crystalline inorganic oxide are detected.
[5] The ceria-based composite fine particles have an average crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.
(2) The ceria-based composite fine particle dispersion according to (1), wherein the crystalline inorganic oxide is at least one selected from the group consisting of alumina, titania, and zirconia.
(3) The ceria-based composite fine particle dispersion according to (1) or (2), wherein the cerium-containing coating layer contains the same element and cerium as the base particles.
(4) The ceria-based composite fine particle dispersion according to any one of (1) to (3), wherein the cerium-containing coating layer contains silica.
(5) The ceria-based composite fine particle dispersion according to any one of (1) to (4), wherein the base particles have a compressive breaking strength of 1.0 to 3.0 MPa.
(6) A polishing abrasive dispersion containing the ceria-based composite fine particle dispersion according to any one of (1) to (5).
(7) The polishing abrasive dispersion according to the above (6), which is for flattening a semiconductor substrate on which a silica film is formed.
(8) A method for producing a ceria-based composite fine particle dispersion, comprising the following steps 1 to 3.
Step 1: Stir a crystalline inorganic oxide fine particle dispersion in which a crystalline inorganic oxide fine particle having a minor axis / major axis ratio of 0.1 or more and less than 1.0 is dispersed in a solvent, and adjust the temperature to 0 to 20. While maintaining the pH at 7.0 to 9.0 and the oxidation-reduction potential at 50 to 500 mV, a metal salt of cerium is continuously or intermittently added thereto, and a precursor particle dispersion liquid containing precursor particles is added. The step of obtaining
Step 2: The precursor particle dispersion is dried and fired at 700 to 1,200 ° C., and a solvent is added to the fired body, and the mixture is wet-crushed in a pH range of 8.6 to 10.8. A step of performing a treatment to obtain a fired body disintegrated dispersion.
Step 3: a step of subjecting the crushed dispersion of the fired body to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently removing a settling component to obtain a ceria-based composite fine particle dispersion.
(9) In the step 1, the crystalline inorganic oxide fine particle dispersion is stirred, the temperature is maintained at 0 to 20 ° C., the pH is maintained at 7.0 to 9.0, and the oxidation-reduction potential is maintained at 50 to 500 mV. The method for producing a ceria-based composite fine particle dispersion according to the above (8), wherein the step of adding the metal salt of cerium and a component containing silicon to the mixture continuously or intermittently to obtain the precursor particle dispersion. .

When the ceria-based composite fine particle dispersion of the present invention is used for polishing purposes, for example, as a polishing abrasive dispersion, polishing is performed at a high speed even if the target is a difficult-to-process material including a silica film, a Si wafer, or the like. At the same time, high surface accuracy (low scratch, low surface roughness (Ra) of the substrate to be polished, etc.) can be achieved. The method for producing a ceria-based composite fine particle dispersion of the present invention provides a method for efficiently producing a ceria-based composite fine particle dispersion exhibiting such excellent performance.
In the method for producing a ceria-based composite fine particle dispersion of the present invention, impurities contained in the ceria-based composite fine particles can be significantly reduced and the ceria-based composite fine particles can be highly purified. The highly purified ceria-based composite fine particle dispersion obtained by the preferred embodiment of the method for producing a ceria-based composite fine particle dispersion of the present invention contains no or almost no impurities. It can be preferably used for polishing the surface of a semiconductor device.
Further, the ceria-based composite fine particle dispersion of the present invention, when used as a polishing abrasive dispersion, is effective for flattening the surface of a semiconductor device, and is particularly suitable for polishing a substrate on which a silica insulating film is formed. is there.

FIG. 2 is a schematic view of a cross section of the composite fine particles of the present invention.

The present invention will be described.
The present invention includes the ceria-based composite fine particles having the following features [1] to [5], having a minor axis / major axis ratio in the range of 0.2 to 1.0, and having an average particle diameter of 50 to 1000 nm. And a ceria-based composite fine particle dispersion.
[1] The ceria-based composite fine particles include base particles, a cerium-containing coating layer on the surface of the base particles, and child particles dispersed inside the cerium-containing coating layer. A crystalline inorganic oxide is a main component, and the child particles are a crystalline ceria as a main component.
[2] The coefficient of variation (CV value) in the particle size distribution of the child particles is 14 to 60%.
[3] The ceria-based composite fine particles have a mass ratio of a component other than ceria to ceria in the range of 100: 11 to 316.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, a ceria crystal phase and a crystal phase of the crystalline inorganic oxide are detected.
[5] The ceria-based composite fine particles have an average crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.

The ceria-based composite fine particles having the characteristics of [1] to [5] and having an average particle diameter of 50 to 1000 nm having a minor axis / major axis ratio in the range of 0.2 to 1.0 are hereinafter referred to as “composite of the present invention”. Also referred to as "fine particles".
Further, such a ceria-based composite fine particle dispersion is hereinafter also referred to as “dispersion of the present invention”.

Further, the present invention is a method for producing a ceria-based composite fine particle dispersion, comprising the following steps 1 to 3.
Step 1: Stir a crystalline inorganic oxide fine particle dispersion in which a crystalline inorganic oxide fine particle having a minor axis / major axis ratio of 0.1 or more and less than 1.0 is dispersed in a solvent, and adjust the temperature to 0 to 20. While maintaining the pH at 7.0 to 9.0 and the oxidation-reduction potential at 50 to 500 mV, a metal salt of cerium is continuously or intermittently added thereto, and a precursor particle dispersion liquid containing precursor particles is added. The step of obtaining
Step 2: The precursor particle dispersion is dried and fired at 700 to 1,200 ° C., and a solvent is added to the fired body, and the mixture is wet-crushed in a pH range of 8.6 to 10.8. A step of performing a treatment to obtain a fired body disintegrated dispersion.
Step 3: a step of subjecting the crushed dispersion of the fired body to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently removing a settling component to obtain a ceria-based composite fine particle dispersion.
Hereinafter, such a production method is also referred to as a “production method of the present invention”.

  The dispersion of the present invention is preferably produced by the production method of the present invention.

  Hereinafter, the term “the present invention” simply means any of the dispersion of the present invention, the composite fine particles of the present invention, and the production method of the present invention.

<Composite fine particles of the present invention>
The composite fine particles of the present invention will be described.
The composite fine particles of the present invention have the structure illustrated in FIG. 1 (a) and 1 (b) are each a schematic diagram of a cross section of the composite fine particles of the present invention. FIG. 1A is a type in which a part of the child particles are exposed to the outside, and FIG. 1B is a buried type in which all the child particles are not exposed to the outside.
As shown in FIG. 1, the composite fine particles 20 of the present invention include a base particle 10, a cerium-containing coating layer 12 on the surface of the base particle 10, Having. It should be noted that ▲ in FIG. 1 is an example of measurement points X to Z at which STEM-EDS analysis described later is performed.

The present inventors presume as follows about the mechanism in which the cerium-containing coating layer is formed in the composite fine particles of the present invention and the mechanism in which the child particles are dispersed inside the cerium-containing coating layer. .
As described later, typical examples of the crystalline inorganic oxide constituting the crystalline inorganic oxide fine particles include alumina, titania, and zirconia, and further include a case where silica is included. The case where the material is alumina will be described.
For example, a crystalline inorganic oxide obtained by adding ammonia to aluminum isopropoxide, performing an operation of hydrolysis and polycondensation, and further drying and calcining the crystalline inorganic oxide fine particles obtained in a solvent. When an alkali is added in parallel with the cerium salt solution to the oxide particle dispersion, the cerium salt solution is neutralized. Then, the hydroxyl group on the surface of the crystalline inorganic oxide fine particles reacts with a product (cerium hydroxide or the like) obtained by neutralizing the solution of the cerium salt, for example, such as Ce (OH) .Al (OH) -like. A layer containing CeO ₂ .Al ₂ O ₃ .Al (OH) and CeO ₂ ultrafine particles (particle size of 2.5 nm or more and less than 10 nm) on the surface of the crystalline inorganic oxide fine particles via the compound ( Hereinafter, it is also referred to as a “CeO ₂ ultrafine particle-containing layer”, which means a layer composed of CeO ₂ ultrafine particles and cerium aluminate). In the firing step, cerium atoms phase-separated from cerium aluminate are deposited on the CeO ₂ ultrafine particles, so that the CeO ₂ ultrafine particles formed on the surface of the crystalline inorganic oxide fine particles grow. In order to achieve the required ceria particle crystal size (10 to 25 nm) to achieve the required polishing rate, if the crystallite diameter obtained by the preparation is less than 2.5 nm, higher temperature firing is required. It is said. However, when the treatment is carried out at a high temperature, the alumina produced by the phase separation becomes an adhesive, and the single-crystal ceria-based composite fine particles of the present invention cannot be obtained by crushing in a later step.
In this case, since the crystalline inorganic oxide is alumina, the CeO ₂ ultrafine particle-containing layer is a layer composed of CeO ₂ ultrafine particles and cerium aluminate. If it is titania, the CeO ₂ ultrafine particle-containing layer is a layer composed of CeO ₂ ultrafine particles and cerium titanate, and if the crystalline inorganic oxide is zirconia instead of alumina, the CeO ₂ ultrafine particle-containing layer is , A layer composed of CeO ₂ ultrafine particles and cerium zirconate.

In order to obtain CeO ₂ ultrafine particles having an average particle diameter of 2.5 nm or more in the compounding step (step 1), a crystalline inorganic oxide is added when the cerium salt is added to suppress the reaction between the cerium salt and alumina. The temperature of the fine particle dispersion is preferably 20 ° C. or lower. At this time, some CeO ₂ ultrafine particles have already been crystallized without heating and aging by keeping the oxidation-reduction potential during preparation in a predetermined range. On the other hand, even if the mixture is prepared at a temperature of more than 20 ° C., and then heat-treated and matured in the liquid phase, the CeO ₂ ultrafine particles do not grow to 2.5 nm or more, and crystallization does not easily occur.

The CeO ₂ ultrafine particle-containing layer reacts with the surface hydroxyl groups of the crystalline inorganic oxide fine particles and a product (cerium hydroxide or the like) obtained by neutralizing the solution of the cerium salt to form a surface of the crystalline inorganic oxide fine particles. It is presumed that it was eluted and was formed by solidification due to the influence of oxygen and the like (derived from the blown air and the like).
Thereafter, dried, and baked at about 700 to 1200 ° C., the CeO ₂ is present inside the ultrafine particle-containing layer, the particle diameter is 2.5nm or more, CeO ₂ ultrafine particles of less than 10 nm, cerium aluminum Crystalline ceria particles (ceria particles) are grown by taking in cerium atoms contained in the silicate and growing the particle size, and finally growing to an average crystallite diameter of about 10 to 25 nm. Cerium aluminate becomes a cerium-containing coating layer by thermal decomposition or thermal diffusion. Therefore, the crystalline ceria particles exist in a dispersed state in the cerium-containing coating layer. Further, in the crystalline ceria particles (child particles) formed by such a mechanism, coalescence of the particles hardly occurs. Note that a part of the cerium contained in the cerium silicate layer cannot remain as crystalline ceria particles and remains, so that a cerium-containing coating layer is formed.

When the compounding temperature is higher than 20 ° C. and the oxidation-reduction potential is kept within a predetermined range, the reactivity between cerium hydroxide or the like and the crystalline inorganic oxide fine particles increases, and the elution amount of the crystalline inorganic oxide fine particles increases. The particle size of the crystalline inorganic oxide fine particles after blending is remarkably increased, for example, the particle diameter is reduced to about 1/2 and the volume is reduced by 80 to 90%. The dissolved alumina contained in the CeO ₂ ultrafine particles-containing layer, the preceding example, CeO ₂ the composition of ultrafine particles-containing layer is an alumina concentration of about 40%, the ceria concentration is about 60%, CeO ₂ containing ultrafine particles The proportion of alumina in the layer increases. When the ceria particles are grown to a thickness of 10 to 25 nm by calcination, cerium atoms separated from the cerium aluminate layer are deposited and grown on the ceria particles, resulting in phase separation (diffusion) of the cerium atoms. The generated alumina covers the ceria particles, and is fixed to the mother particle alumina, so that the ceria child particles are covered with the alumina coating. At this time, if the sintering temperature is high, the alumina coated on the ceria-coated base particles becomes an adhesive, and promotes coalescence of the particles. Can not. If the firing temperature is low, the pulverization becomes easy, but the polishing rate cannot be obtained because the ceria particles do not grow.

  Further, when the preparation temperature is higher than 20 ° C. and the oxidation-reduction potential is kept in a predetermined range, the crystallite diameter of the ceria particles after preparation becomes as small as 2.5 nm or less, and the ceria particles are crystallized to a predetermined size by firing. For the growth, diffusion of more cerium atoms from cerium aluminate is required, and as a result, the alumina concentration in cerium aluminate increases, and the alumina coating covering the child particles tends to increase.

When the compounding temperature during the reaction between the crystalline inorganic oxide fine particle dispersion and the cerium metal salt is 0 to 20 ° C. and the oxidation-reduction potential is kept within a predetermined range, cerium hydroxide or the like and the crystalline inorganic oxide fine particles are mixed. Is suppressed, the crystalline inorganic oxide fine particles do not dissolve much, and the prepared crystalline inorganic oxide fine particles have a particle diameter of about 1 to 5% and a volume of about 3 to 15%. Can be suppressed. Therefore, in the case of the above-described example, the composition of the CeO ₂ ultrafine particle-containing layer has an alumina concentration of about 10% and a ceria concentration of about 90%, and the ratio of ceria in the CeO ₂ ultrafine particle-containing layer increases. A coating layer is formed. In addition, since the crystal size of ceria after blending is about 2.5 nm or more and less than 10 nm (for example, 6 to 8 nm), the amount of diffusion of cerium atoms for growing ceria particles to a predetermined size by firing is small. As a result, a large amount of cerium remains in the cerium aluminate, crystal growth occurs at low temperature firing, and ceria particles having an average particle diameter of 10 to 25 nm are obtained. Therefore, when prepared at 0 to 20 ° C., a cerium-containing coating layer is formed on the surface of the base particle, and the ceria particles are dispersed in this layer.

  In addition, when the ceria particles have an average particle diameter of 10 nm or more at the compounding stage, coalescence of the ceria particles occurs, and uniform ceria particles are not monodispersely arranged on the surface of the base particles, so that excellent polishing characteristics tend not to be obtained. is there.

In the schematic diagram of FIG. 1, the base particles 10, the cerium-containing coating layer 12, and the child particles 14 are clearly distinguished for easy understanding. However, the composite fine particles of the present invention are formed by the above-described mechanism. Therefore, in reality, they exist integrally, and the base particles 10, the cerium-containing coating layer 12, and the child particles 14 are clearly defined except for the contrast in the STEM / SEM image or the EDS analysis. Difficult to distinguish.
However, when the cross section of the composite fine particles of the present invention is subjected to STEM-EDS analysis to measure the element concentration of Ce, it can be confirmed that the structure has the structure shown in FIG.

That is, an EDS analysis in which a spot specified by a scanning transmission electron microscope (STEM) is selectively irradiated with an electron beam is performed, and the element concentration of Ce at a measurement point X on the cross section of the composite fine particle of the present invention shown in FIG. 1 is measured. Then, it becomes less than 3%. Further, when the element concentration of Ce at the measurement point Z is measured, it is over 50%. Then, when the element concentration of Ce at the measurement point Y is measured, it becomes 3 to 50%.
Therefore, in the element map obtained by performing the STEM-EDS analysis, the base particles 10 and the cerium-containing coating layer 12 in the composite fine particles of the present invention can be distinguished from each other by a line having a Ce molar concentration of 3%. In the element map obtained by performing the STEM-EDS analysis, the cerium-containing coating layer 12 and the child particles 14 in the composite fine particles of the present invention can be distinguished from each other by the line where the Ce molar concentration becomes 50%.

  In this specification, STEM-EDS analysis is performed by observing at 800,000 times.

  Since the composite fine particles of the present invention are in the form as shown in FIG. 1, the cross section thereof is subjected to STEM-EDS analysis and element mapping. On the way to the main component), at least one layer having a relatively high ceria concentration (comprising ceria fine particles) is often provided.

<Base particles>
The base particles in the composite fine particles of the present invention will be described.
As described above, when the STEM-EDS analysis is performed on the composite fine particles of the present invention and the Ce element concentration (molar concentration) in the cross section of the composite fine particles of the present invention shown in FIG. 1 is measured, the portion is less than 3%. .

The substance constituting the base particles is not particularly limited as long as it is a crystalline inorganic oxide, and may include a plurality of types of elements.
The crystalline inorganic oxide constituting the base particles is preferably at least one selected from the group consisting of alumina, titania and zirconia.

As described later, since the average particle diameter of the composite fine particles of the present invention is in the range of 50 to 1000 nm, the average particle diameter of the mother particles in the composite fine particles of the present invention is necessarily smaller than 1000 nm. The composite fine particles of the present invention in which the average particle size of the base particles in the composite fine particles of the present invention is in the range of 30 to 700 nm are preferably used.
When the dispersion of the present invention obtained by using base particles having an average particle diameter in the range of 30 to 700 nm as a raw material is used as an abrasive, scratches due to polishing are reduced. When the average particle diameter of the base particles is less than 30 nm, when a dispersion obtained using such base particles is used as an abrasive, the polishing rate tends not to reach a practical level. Also, when the average particle diameter of the base particles exceeds 700 nm, the polishing rate also tends not to reach a practical level, and the surface accuracy of the substrate to be polished tends to be reduced. Note that the base particles more preferably show monodispersity.

The average particle diameter of the base particles in the composite fine particles of the present invention is measured as follows.
First, the sample is observed at a magnification of 800,000 by STEM-EDS analysis, and a line having a Ce molar concentration of 3% is specified to specify a mother particle. Next, the maximum diameter of the base particles is taken as the major axis, the length is measured, and the value is taken as the major axis (DL). In addition, a point on the long axis that bisects the long axis is determined, two points where a straight line (short axis) orthogonal to the long axis intersects the outer edge of the base particle are determined, the distance between the two points is measured, and the short diameter ( DS). Then, a geometric mean value of the major axis (DL) and the minor axis (DS) is determined, and this is defined as the particle diameter of the base particle.
In this way, the particle diameters of the 50 base particles are measured, and a value obtained by simply averaging the measured values is defined as the average particle diameter.

Although the shape of the base particles in the composite fine particles of the present invention is not particularly limited, specifically, the ratio of the minor axis / major axis of the mother particles in the composite fine particles of the present invention is 0.2 or more. It is preferably 0 or less.
The minor axis / major axis ratio of the base particles in the composite fine particles of the present invention is measured as follows.
First, the sample is observed at a magnification of 800,000 by STEM-EDS analysis, and a line having a Ce molar concentration of 3% is specified to specify a mother particle. Next, the maximum diameter of the base particles is taken as the major axis, the length is measured, and the value is taken as the major axis (DL). Further, a point on the major axis that bisects the major axis is determined, two points where a straight line perpendicular to the major axis intersects the outer edge of the base particle are determined, and a distance between the two points is measured to obtain a minor axis (DS). . Then, the ratio (DS / DL) between the major axis (DL) and the minor axis (DS) is determined, and this is defined as the minor axis / major axis ratio of the base particles. The ratio of the minor axis / major axis is preferably 0.25 or more and 1.0 or less.

  The base particles are mainly composed of a crystalline inorganic oxide, and are usually fine particles of a crystalline inorganic oxide. The crystalline inorganic oxide fine particles are preferably used because they can be easily prepared as non-spherical or spherical particles having a uniform particle diameter, and various particle diameters can be prepared.

The fact that the base particles contain a crystalline inorganic oxide as a main component can be confirmed, for example, by the following method. After drying the dispersion containing the composite fine particles of the present invention, the mixture is pulverized using a mortar and, for example, an X-ray diffraction pattern is obtained by a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). For example, since the crystalline phase of α-alumina, crystalline phase of anatase titania, crystalline phase of cubic zirconia, and the like, it is considered that the base particles are mainly composed of a crystalline inorganic oxide. You can check. In such a case, the base particles are mainly composed of a crystalline inorganic oxide.
Further, the dispersion of the present invention is dried, embedded in a resin, and then subjected to sputter coating with Pt, and a cross-sectional sample is prepared using a conventionally known focused ion beam (FIB) apparatus. For example, when a FFT pattern is obtained from a prepared cross-sectional sample using a conventional Fourier Transform (FFT) analysis using a conventionally known TEM device, the base particle is also made of a crystalline inorganic material because a diffraction pattern corresponding to the crystal structure of the base particle appears. It can be confirmed that an oxide is a main component. In such a case, the base particles are mainly composed of a crystalline inorganic oxide.

The base particles contain a crystalline inorganic oxide as a main component, and may contain other substances such as an amorphous substance (eg, amorphous silica) and a compound other than the oxide.
For example, in the base particles, the content of each element of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, and Zn (hereinafter, may be referred to as “specific impurity group 1”) is respectively It is desirably 5000 ppm or less, desirably 1000 ppm or less, and preferably 100 ppm or less. Further, it is preferably at most 50 ppm, more preferably at most 25 ppm, further preferably at most 5 ppm, still more preferably at most 1 ppm. Further, the content of each of the elements U, Th, Cl, NO ₃ , SO _4, and F (hereinafter, may be referred to as “specific impurity group 2”) in the base particles is preferably 5 ppm or less. .

Here, the content of the specific impurity group 1 or the specific impurity group 2 in the base particles, the composite fine particles of the present invention described later, and the crystalline inorganic oxide fine particles described later means the content relative to the dry amount.
The content relative to the dry amount refers to the measurement target (specific impurity group 1 or specific impurity group 2) with respect to the mass of the solid content contained in the target object (base particles, composite fine particles of the present invention, or crystalline inorganic oxide fine particles described later). ) Means the value of the weight ratio (percentage). In addition, the impurity content of the base particles substantially coincides with the impurity content of the crystalline inorganic oxide fine particles if there is no contamination due to contamination or the like.

Generally, crystalline inorganic oxide fine particles prepared from water glass as a raw material contain the specific impurity group 1 and the specific impurity group 2 derived from the raw water glass in the order of several thousand ppm in total.
In the case of a dispersion liquid in which such crystalline inorganic oxide 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 ion exchange treatment, Even in that case, the specific impurity group 1 and the specific impurity group 2 remain in a few ppm to a few hundred ppm in total. For this reason, when using crystalline inorganic oxide fine particles made of water glass as a raw material, impurities are also reduced by acid treatment or the like.
In contrast, in the case of a dispersion obtained by dispersing crystalline inorganic oxide fine particles synthesized from alkoxysilane as a raw material in a solvent, the content of each element in the specific impurity group 1 is usually 100 ppm or less. 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, the respective contents of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Zn, U, Th, Cl, NO ₃ , SO ₄ and F in the base particles are respectively The value shall be determined by measurement using the following method.
-Na and K: Atomic absorption spectroscopy-Ag, Ca, Cr, Cu, Fe, Mg, Ni, Zn, U and Th: ICP-MS (inductively coupled plasma emission mass spectrometry)
· Cl: potentiometric titration · NO _3, SO ₄ and F: ion chromatograph

The base particles preferably have a compressive breaking strength of 1.0 to 3.0 MPa. The reason is that when the compressive fracture strength is within this range, it is possible to prevent the collapse of the composite fine particles during polishing, further suppress the stress relaxation due to the deformation of the composite fine particles, and effectively transmit the pressure to the substrate. And a high polishing rate can be obtained.
Here, the compressive breaking strength of the base particles is measured by the following method.
The dispersion of the present invention is crushed by a sand mill, and classified by a centrifugal separator to obtain base particles in which ceria particles are dropped from the base particles. The compression breaking strength was measured using a machine (MCT-W500).

<Child particle>
In the composite fine particles of the present invention, child particles containing crystalline ceria as a main component (hereinafter also referred to as “ceria child particles”) are dispersed in a cerium-containing coating layer disposed on the base particles.
The base particles in the composite fine particles of the present invention preferably have a ratio of minor axis / major axis in the range of 0.2 to 0.7, and preferably have irregularities on the surface. That is, it is preferable to provide a concave portion and a convex portion. In the composite fine particles of the present invention, the child particles mainly have the following forms (a), (b) and (c).
(A) A form in which child particles are bonded to the projections of the base particles via a part of the cerium-containing coating layer.
(B) A form in which child particles are bonded to both the projections and depressions of the base particles via a part of the cerium-containing coating layer.
(C) Form in which child particles are bonded to concave portions of base particles via a part of the cerium-containing coating layer It is desirable that these forms (a), (b) and (c) exist simultaneously. This is because, when the dispersion of the present invention is used as an abrasive dispersion for polishing, since the base particles have a step, the sub-particles in the form (a) are firstly polished during polishing. And polishing is performed. Even if the child particles in the form (a) come off, wear or break due to the polishing pressure, then the ceria child particles in the form (b) and (c) come into contact with the substrate to be polished to reduce the contact area. This is because the polishing rate can be kept high, so that polishing with a stable polishing rate is efficiently performed.
According to the production method of the present invention to be described later, it is easy to obtain the dispersion of the present invention containing the composite fine particles of the present invention in which the child particles of the form (a), (b) or (c) are simultaneously present.

Further, the ceria particles may be laminated in the cerium-containing coating layer, and the shape thereof is not particularly limited to a true spherical shape, an elliptical shape, a rectangular shape, and the like. Alternatively, a step may occur in the ceria child particles due to the base particles having projections or non-smooth shapes.
The ceria particles may be buried in the cerium-containing coating layer, or may be partially exposed from the cerium-containing coating layer.

  As described above, when the STEM-EDS analysis is performed on the composite fine particles of the present invention and the Ce element concentration in the cross section of the composite fine particles of the present invention shown in FIG. 1 is measured, the child particles have a Ce molar concentration of more than 50%. Part.

  The child particles mainly composed of crystalline ceria in the present invention are dispersed in the cerium-containing coating layer disposed on the base particles, and the coefficient of variation (CV value) in the particle diameter distribution of the child particles is 14 to 60%. That is, the width of the particle size distribution of the child particles is large. When the dispersion of the present invention having such a ceria child particle having a large particle size distribution width is used as a polishing abrasive particle dispersion, the child particle having a large particle diameter comes into contact with the substrate to be polished in the initial stage of polishing. Polishing is performed. Then, even if the child particles come off due to the polishing pressure or are worn or broken, the child particles having the smaller particle diameter come into contact with the substrate to be polished, so that the contact area can be kept high. Therefore, polishing with a stable polishing rate is performed efficiently.

  In the present invention, the coefficient of variation (CV value) in the particle size distribution of the child particles dispersed in the cerium-containing coating layer is 14 to 60%, preferably 17 to 50%, and more preferably 20 to 40%. More preferably, there is.

In the present invention, the particle size distribution of the child particles is measured as follows.
First, the composite fine particles of the present invention are observed at a magnification of 800,000 by STEM-EDS analysis, and child particles are specified by specifying a line where the Ce molar concentration becomes 50%. Next, the maximum diameter of the child particles is taken as the major axis, the length is measured, and the value is taken as the major axis (DL). In addition, a point on the long axis that bisects the long axis is determined, two points where a straight line perpendicular to the long axis intersects the outer edge of the child particle are determined, and the distance between the two points is measured to obtain a short diameter (DS). . Then, a geometric mean value of the major axis (DL) and the minor axis (DS) is determined, and this is defined as the particle diameter of the child particle.
In this way, the particle size of 100 or more child particles can be measured to obtain a particle size distribution.

  In the present invention, the coefficient of variation (CV value) in the particle size distribution of the child particles is obtained by obtaining the standard deviation and the number average value using the particle size distribution obtained as described above as a population, and then calculating the standard deviation by the number average value. , And multiplying by 100 (that is, standard deviation / number average value × 100).

The average particle diameter of the child particles is preferably from 10 to 25 nm, more preferably from 14 to 23 nm.
When the average particle diameter of the child particles exceeds 25 nm, in step 2, the precursor particles having such ceria child particles tend to undergo sintering or coagulation after firing and become difficult to disintegrate. Such a ceria-based composite fine particle dispersion is not preferable because it causes scratches on the object to be polished even when used for polishing. When the average particle diameter of the secondary particles is less than 10 nm, there is a tendency that it is difficult to obtain a practically sufficient polishing rate when the particles are used for polishing.

  In the present invention, the average particle diameter of the child particles means the number average diameter in the particle diameter distribution obtained as described above.

The child particles may be stacked. That is, a plurality of cerium-containing coating layers may exist on a radial line from the center of the base particle.
Further, the child particles may be buried in the cerium-containing coating layer or may be partially exposed to the outside of the cerium-containing coating layer. Since the surface becomes the containing coating layer, the storage stability and the polishing stability are improved, and the abrasive particles remaining on the substrate after polishing are reduced. Therefore, it is preferable that the child particles are buried in the cerium-containing coating layer. .

  The shape of the child particles is not particularly limited. For example, the shape may be true 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 and more preferably rectangular.

  The child particles dispersed in the cerium-containing coating layer disposed on the surface of the base particles may be in a monodispersed state, or in a state in which the child particles are stacked (that is, a plurality of the child particles are arranged in the thickness direction of the cerium-containing coating layer). (A state in which child particles are stacked and present) or a state in which a plurality of child particles are connected.

In the present invention, the child particles contain crystalline ceria as a main component.
That the child particles are mainly composed of crystalline ceria, for example, after drying the dispersion of the present invention, the obtained solid is crushed using a mortar or the like to obtain the composite fine particles of the present invention After that, this was subjected to X-ray analysis using, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). In the obtained X-ray diffraction pattern, the ceria crystal phase and the crystalline inorganic oxidation This can be confirmed by detecting the crystalline phase of the product. In such a case, it is assumed that the child particles have crystalline ceria as a main component. Note that the ceria crystal phase is not particularly limited, and examples thereof include Cerianite.

The child particles contain crystalline ceria (crystalline Ce oxide) as a main component, and may contain other elements, for example, elements other than cerium. Further, a hydrated cerium compound may be contained as a polishing promoter.
However, as described above, when the composite fine particles of the present invention are subjected to X-ray diffraction, the ceria crystal phase and the crystalline inorganic oxide crystal phase are detected. That is, even if a crystal phase other than ceria is contained, its content is small or the solid phase is dissolved in the ceria crystal, so that it is out of the detection range by X-ray diffraction.

  The average crystallite diameter of ceria particles is calculated using the full width at half maximum of the maximum peak appearing in a chart obtained by subjecting the composite fine particles of the present invention to X-ray diffraction. For example, the average crystallite diameter of the (111) plane is 10 to 25 nm (full width at half maximum is 0.86 to 0.34 °), and 14 to 23 nm (full width at half maximum is 0.62 to 0.37 °). It is more preferably 15 to 22 nm (full width at half maximum is 0.58 to 0.38). In many cases, the peak intensity of the (111) plane is maximum, but the peak intensity of another crystal plane, for example, the (100) plane may be maximum. In that case, it can be calculated in the same manner, and the size of the average crystallite diameter in that case may be the same as the above-mentioned average crystallite diameter of the (111) plane.

The method of measuring the average crystallite diameter of the child particles will be described below by taking, as an example, the case of the (111) plane (around 2θ = 28 °).
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained using, for example, a conventionally known X-ray diffractometer (for example, RINT1400, manufactured by Rigaku Denki Co., Ltd.). Then, the full width at half maximum of the peak of the (111) plane near 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the average crystallite diameter can be obtained by the following Scherrer equation.
D = Kλ / βcosθ
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: reflection angle

In the composite fine particles of the present invention, it is preferable that atoms (aluminum, titanium, zirconium, etc.) contained in the crystalline inorganic oxide are dissolved in crystalline ceria which is a main component of the child particles. Generally, solid solution means that two or more types of elements (in some cases, metal or non-metal) are dissolved with each other to form a uniform solid phase as a whole. , And are classified into substitutional solid solutions and interstitial solid solutions. It is known that a substitutional solid solution can easily occur at an atom having a close atomic radius. For example, Zr is known to form a solid solution while maintaining a Cerianite crystal structure, and Al is a CeAlO ₃ composition. Perovskite structures are known. Further, it may be an interstitial solid solution.
Conventionally, it is known that when a silica film-coated substrate or a glass substrate is polished using ceria particles as abrasive grains, it exhibits a specifically high polishing rate as compared with the case where other inorganic oxide particles are used. . One of the reasons that ceria particles exhibit a particularly high polishing rate with respect to a substrate with a silica film is that trivalent cerium contained in the ceria particles has a high chemical reactivity with respect to a silica film on a substrate to be polished. It is pointed out that it has. Cerium in cerium oxide can have trivalent and tetravalent valences, but high-purity cerium oxide particles used as abrasives for semiconductors can be obtained by converting high-purity cerium salts such as cerium carbonate at a high temperature of about 700 ° C. It has undergone a firing process. Therefore, the valence of cerium in the fired ceria particles is mainly tetravalent, and even if trivalent cerium is contained, its content is not sufficient.
In a preferred embodiment of the composite fine particles of the present invention, in the child particles (ceria fine particles) existing on the outer surface side, it is considered that atoms such as Al are in an interstitial solid solution in the CeO ₂ crystal. The solid solution of atoms such as Al causes crystal distortion of the CeO ₂ crystal, so that even when fired at a high temperature, oxygen vacancies increase and a large amount of trivalent cerium chemically active with respect to SiO ₂ is generated. As a result of promoting the chemical reactivity of No. ₂ , it is supposed that the above high polishing rate is exhibited. In order to increase the trivalent cerium content, La or Zr may be doped.

The ceria-based composite fine particles of the present invention have the following features because the base particles are mainly composed of a crystalline inorganic oxide.
1) The general shape of the ceria-based composite fine particles can also take a shape such as a cube, a column, a plate, or a needle, reflecting the crystal habit of the base particles. By having such a shape, when used as abrasive grains, when the semiconductor substrate or the like to be polished comes into contact with a portion corresponding to the apex of the abrasive grains, the contact area becomes smaller, resulting in stress concentration, Deep cutting and polishing proceeds, and a high polishing rate can be obtained. Further, when the contact is made at a portion corresponding to the surface or the side of the abrasive grain, the contact area increases, and as a result, greater friction occurs, and a higher polishing rate can be obtained.
2) Since the base particles have high physical stability and chemical stability, contamination of the polished substrate due to elution of the base particle components and impurities contained in the base particles can be prevented.
3) By having high rigidity, stress relaxation due to deformation of abrasive grains during polishing hardly occurs, stress concentration on the substrate proceeds, and a higher polishing rate can be obtained. In addition, a higher polishing rate can be obtained because the particles are less likely to collapse.

<Cerium-containing coating layer>
The composite fine particles of the present invention have a cerium-containing coating layer on the surface of the base particles. Then, the child particles are dispersed inside the cerium-containing coating layer.

  By adopting such a structure, it is difficult for the child particles to fall off due to the crushing process during production or the pressure during polishing, and even if some of the child particles are missing, many child particles cannot fall off. In the cerium-containing coating layer, the polishing function does not deteriorate.

Preferably, the cerium-containing coating layer contains silica.
For example, when the base particles contain crystalline alumina as a main component, the cerium-containing coating layer preferably contains Ce and Si.
Further, for example, when the mother particles are mainly composed of crystalline titania, the cerium-containing coating layer preferably contains Ce and Si.
Further, for example, when the base particles are mainly composed of crystalline zirconia, the cerium-containing coating layer preferably contains Ce and Si.

The cerium-containing coating layer preferably contains the same element as the base particles.
For example, when the base particles contain crystalline alumina as a main component, the cerium-containing coating layer preferably contains Al and Ce.
Further, for example, when the base particles are mainly composed of crystalline titania, the cerium-containing coating layer preferably contains Ti and Ce.
Further, for example, when the base particles are mainly composed of crystalline zirconia, the cerium-containing coating layer preferably contains Zr and Ce.

It is preferable that the cerium-containing coating layer further contains silica.
For example, when the base particles contain crystalline alumina as a main component, the cerium-containing coating layer preferably contains Ce, Al, and Si.
Further, for example, when the mother particles are mainly composed of crystalline titania, the cerium-containing coating layer preferably contains Ce, Ti and Si.
Further, for example, when the base particles contain crystalline zirconia as a main component, the cerium-containing coating layer preferably contains Ce, Zr and Si.

  As described above, when the STEM-EDS analysis was performed on the composite fine particles of the present invention and the elemental concentration of Ce in the cross section of the composite fine particles of the present invention shown in FIG. 1 was measured, the Ce molar concentration of the cerium-containing coating layer was 3%.部分 50%.

  In the image (TEM image) obtained by observing the composite fine particles of the present invention using a transmission electron microscope, the images of the child particles appear densely on the surface of the base particles. A part of the cerium-containing coating layer also appears as a relatively thin image on the surface side of the composite fine particles. STEM-EDS analysis was performed on this portion, and when the molar concentration of Al, Ti, Zr, etc. and Ce molar concentration contained in the crystalline inorganic oxide of the portion were determined, it was confirmed that the molar concentration of Al, etc. was very high. can do.

The average thickness of the cerium-containing coating layer is not particularly limited, but is preferably, for example, 10 to 40 nm, and more preferably 12 to 30 nm.
The average thickness of the cerium-containing coating layer was obtained by performing a STEM-EDS analysis as described above by drawing a straight line at any 12 points from the center of the mother particles of the composite fine particles of the present invention to the outermost shell. The distance (the distance on the line passing through the center of the base particle) between the line where the Ce molar concentration specified by the element map becomes 3% and the outermost shell of the composite fine particles of the present invention is measured, and these are simply averaged. Shall be sought. Note that the center of the base particle means the intersection of the aforementioned major axis and minor axis.

It is considered that the cerium-containing coating layer in the composite fine particles of the present invention promotes the bonding force between the parent particles (ceria fine particles mainly composed of crystalline ceria) dispersed and grown in the cerium-containing coating layer during the firing process. . Thus, for example, in the step of obtaining the dispersion of the present invention, if necessary for the fired body disintegrated dispersion obtained by firing, after performing preliminary disintegration in a dry method, then performing wet disintegration, Although the ceria-based composite fine particle dispersion is obtained by performing the centrifugation treatment, it is considered that the cerium-containing coating layer has an effect of preventing the child particles from coming off from the base particles. In this case, there is no problem of local falling off of the child particles, and the entire surface of the child particles does not have to be covered with a part of the cerium-containing coating layer. It suffices that the secondary particles have such a rigidity that they do not separate from the mother particles in the crushing step.
With such a structure, when the dispersion liquid of the present invention is used as an abrasive, it is considered that the polishing rate is high and the surface accuracy and scratches are hardly deteriorated.

  In the composite fine particles of the present invention, at least a part of the surface of the child particles is coated with the cerium-containing coating layer. Therefore, when the cerium-containing coating layer contains Si, the outermost surface of the composite fine particles of the present invention (the outermost surface) The (shell) will have the -OH groups of the silica. For this reason, when used as an abrasive, when the cerium-containing coating layer of the composite fine particles of the present invention contains Si, they repel each other with charges due to -OH groups on the polishing substrate surface, and as a result, adhesion to the polishing substrate surface is reduced. It is considered to be.

  In general, ceria has a different potential from silica, a polishing substrate, and a polishing pad. The negative zeta potential decreases as the pH moves from alkaline to near neutral, and the opposite positive potential decreases in a weakly acidic region. have. Therefore, at acidic pH during polishing, ceria adheres to the polishing substrate or polishing pad and tends to remain on the polishing substrate or polishing pad due to the difference in the magnitude of the potential or the difference in polarity at the time of polishing. On the other hand, when the cerium-containing coating layer of the composite fine particles of the present invention contains Si, since the silica is present in the outermost shell as described above, the potential becomes a negative charge due to the silica, and the pH becomes alkaline. A negative potential is maintained until the polishing base material and the polishing pad remain as a result. When crushing while maintaining the pH of 8.6 to 10.8 during the crushing treatment in Step 2 in the production method of the present invention, when silica is used as a part of the raw material in Step 1, the silica on the surface of the composite fine particles of the present invention is Part of the silica (cerium-containing coating layer) dissolves. If the pH of the dispersion of the present invention produced under such conditions is adjusted to pH <7 when applied to polishing applications, the dissolved silica is deposited on the composite fine particles (abrasive grains) of the present invention. The surface will have a negative potential. When the potential is low, silicic acid may be added to moderately reinforce the cerium-containing coating layer.

In order to adjust the potential of the particles, it is possible to adjust the potential with a high molecular organic material such as polyacrylic acid. Adjusts the electric potential, the use of organic substances is reduced, and defects due to organic substances (residual organic substances, etc.) on the substrate are less likely to occur. Further, the silica adhered to the soft is a low-density, soft and easily soluble silica layer because it has not been subjected to the firing step. This easily soluble silica layer has an adhesive action with the substrate, and is effective in improving the polishing rate. This easily soluble silica layer can be confirmed by keeping the dispersion of the present invention at pH 9 and measuring the concentration of silica in the solid-liquid separated solution.
In the dispersion of the present invention in which the cerium-containing coating layer contains the composite fine particles of the present invention containing Si, the mode in which silica is present is various, and the silica does not constitute the composite fine particles of the present invention and is dispersed in a solvent. Alternatively, it may be dissolved or present in a state of being attached to the surface of the composite fine particles of the present invention.

<Composite fine particles of the present invention>
The composite fine particles of the present invention will be described.
As described above, the composite fine particles of the present invention [1] are obtained by dispersing the ceria-based composite fine particles inside the base particles, the cerium-containing coating layer on the surface of the base particles, and the cerium-containing coating layer. [2] a coefficient of variation (CV value) in the particle size distribution of the child particles, wherein the mother particles are mainly composed of a crystalline inorganic oxide, and the child particles are mainly composed of crystalline ceria. ) Is 14 to 60%, and [4] when the ceria-based composite fine particles are subjected to X-ray diffraction, a ceria crystal phase and a crystalline inorganic oxide crystal phase are detected; The fine particles have an average crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.
The composite fine particles of the present invention further include [3] the ceria-based composite fine particles, wherein the mass ratio of the component other than ceria to ceria is 100: 11 to 316. The ceria-based composite fine particles have a ratio in the range of 0.2 or more and 1.0 or less and have an average particle diameter of 50 to 1000 nm.

In the composite fine particles of the present invention, the mass ratio between the component other than ceria and ceria (CeO ₂ ) is from 100: 11 to 316, preferably from 100: 30 to 230, and more preferably from 100: 30 to 150. More preferably, the ratio is more preferably from 100: 60 to 100: 120. It is considered that the mass ratio between the component other than ceria and ceria is approximately the same as the mass ratio between the base particles and the child particles. If the amount of the child particles is too small relative to the mother particles, the mother particles or the composite fine particles may be bonded to each other to generate coarse particles. In this case, the abrasive (polishing slurry) containing the dispersion of the present invention may cause defects (decrease in surface accuracy such as increase in scratches) on the surface of the polishing substrate. Further, if the amount of ceria relative to components other than ceria is too large, not only is cost increased, but also resource risk increases. Further, the fusion of the particles proceeds. As a result, the causes of troubles such as an increase in the roughness of the substrate surface (deterioration of the surface roughness Ra), an increase in scratches, the release of ceria remaining on the substrate, and adhesion to waste liquid piping of a polishing apparatus. It is easy to become.
When calculating the mass ratio between the component other than ceria and ceria (CeO ₂ ), if the component other than ceria contains silica, the silica is used as all silica (SiO ₂ ) contained in the composite fine particles of the present invention. ₂ ) means. Therefore, it means the total amount of the silica component constituting the base particles, the silica component contained in the cerium-containing coating layer disposed on the surface of the base particles, and the silica component contained in the child particles.

The content (% by mass) of the component other than ceria and ceria (CeO ₂ ) in the composite fine particles of the present invention is determined by first weighing the solid content of the dispersion of the present invention by performing a burning loss at 1000 ° C.
Next, the content (% by mass) of cerium (Ce) contained in a predetermined amount of the composite fine particles of the present invention is determined by ICP plasma emission spectrometry, and is converted into an oxide mass% (CeO ₂ mass% or the like). Then, components other than CeO ₂ constituting the composite fine particles of the present invention can be calculated.
In the production method of the present invention, the mass ratio between the component other than ceria and ceria is calculated from the amounts of the ceria source material and the material that can constitute the base particles that were added when preparing the dispersion of the present invention. You can also. This can be applied when the process that dissolves and removes substances that can form ceria and mother particles is not performed, and in such cases, the usage amount and analysis value of the substances that can form ceria and mother particles are good. Indicates a match.

  The composite fine particles of the present invention have a cerium-containing coating layer formed on the surface of the base particles and are firmly bound, and the crystalline cerium (child particles) are dispersed in the cerium-containing coating layer. Surface shape.

The ratio of minor axis / major axis of the composite fine particles of the present invention is 0.2 to 1.0.
Since the ratio of the minor axis to the major axis of the composite fine particles of the present invention is in a specific range, when the dispersion of the present invention is used for polishing, the polishing rate of the substrate to be polished can be improved, and at the same time, on the substrate to be polished, Can have a low surface roughness.

Here, the minor axis / major axis ratio is measured by the following image analysis method.
First, in a photographic projection image obtained by photographing the composite fine particles of the present invention with a transmission electron microscope at a magnification of 300,000 (or 500,000), the maximum diameter of the particles is taken as the major axis, and the length is measured. Then, the value is defined as the major axis (DL). In addition, a point on the major axis that bisects the major axis is determined, two points at which a straight line perpendicular to the major axis intersects the outer edge of the particle are determined, and the distance between the two points is measured to obtain the minor axis (DS). From this, the ratio of minor axis / major axis (DS / DL) is determined. Then, for any 50 particles observed in the photographic projection view, the minor / major ratio (DS / DL) of each composite fine particle is determined, and the average value is calculated as the minor / major ratio value of the composite fine particle. did.

As described above, the shape of the composite fine particles of the present invention needs to have a minor axis / major axis ratio in the range of 0.2 to 1.0. As long as the ratio is in the range of the minor axis / major axis ratio, the composite fine particles of the present invention may be a “particle connected type” in which a plurality of particles are bonded, or a “single particle type” composed of independent particles. It does not matter. Among these, the particle-connected type is more preferable because the contact area with the substrate can be kept high and a high polishing rate can be exhibited. More specifically, the particle-connected type is one in which two or more base particles are partially bonded to each other, and the number of connected particles is preferably three or less. In the particle-coupled type composite fine particles, at least one (preferably both) of the base particles is strongly bonded by providing a history of being welded at their contact point or solidified by the interposition of ceria. Conceivable. Here, in addition to the case where the cerium-containing coating layer is formed on the surface after the mother particles are bonded to each other, the case where the cerium-containing coating layer is formed on the surface of the base particles and then bonded to another one. In this case, the particles are connected.
The connection type allows a large contact area with the substrate, so that the polishing energy can be efficiently transmitted to the substrate. Therefore, the polishing rate is high.
In addition, the particle-connected particles mean particles formed by forming chemical bonds to such an extent that they cannot be re-dispersed (aggregated particles). In addition, a single particle means one in which a plurality of particles are not connected and is not aggregated regardless of the morphology of the particles.

When the composite fine particles of the present invention are applied to, for example, polishing, they are preferably of a particle-connected type, and the ratio of minor axis / major axis measured by an image analysis method is preferably from 0.2 to 1.0. And 0.65 or less.
Here, the particle connection type usually has a minor axis / major axis ratio of 0.2 to 1.0 as measured by an image analysis method.
The shape of the composite fine particles of the present invention is not particularly limited, and may be particle-connected particles or single-particle (unconnected particles), and usually a mixture of both. .

  When the dispersion of the present invention is applied to polishing, the composite having a minor axis / major axis ratio of 0.2 to 1.0 in all the composite fine particles of the present invention contained in the dispersion of the present invention. The number ratio of the fine particles is preferably 60% or more, and more preferably 70% or more.

  The number of coarse particles having a size of 0.51 μm or more that can be contained in the dispersion of the present invention is preferably 100 million particles / cc or less on a dry basis. The number of coarse particles is preferably 100 million / cc or less, more preferably 80 million / cc or less. Coarse particles of 0.51 μm or more may cause polishing scratches and may further deteriorate the surface roughness of the polished substrate. Usually, when the polishing rate is high, the polishing rate is high, but polishing scratches occur frequently and the surface roughness of the substrate tends to deteriorate. However, when the composite fine particles of the present invention are of the particle-coupled type, a high polishing rate can be obtained. On the other hand, when the number of coarse particles of 0.51 μm or more is 100 million / cc or less, polishing scratches are small, and The roughness can be kept low.

The method for measuring the number of coarse particles that can be contained in the dispersion of the present invention is as follows.
After diluting the sample to 0.1% by mass with pure water, 5 ml of the sample is collected and injected into a conventionally known coarse particle counting apparatus. Then, the number of coarse particles of 0.51 μm or more is determined. This measurement is performed three times, a simple average value is obtained, and the value is multiplied by 1000 to obtain a value of the number of coarse particles of 0.51 μm or more.

The composite fine particles of the present invention preferably have a specific surface area of 4 to 100 m ² / g, more preferably ^{20 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) is put into a measurement cell, degassed at 250 ° C. for 40 minutes in a nitrogen gas stream, and then the sample is mixed with 30% by volume of nitrogen and 70% by volume of helium. The liquid nitrogen temperature is maintained in an air stream, and nitrogen is equilibrium-adsorbed to the sample. Next, the temperature of the sample is gradually raised to room temperature while flowing the above-mentioned mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area of the sample is measured by a previously prepared calibration curve.
Such a BET specific surface area measurement method (nitrogen adsorption method) can be performed using, for example, a conventionally known surface area measurement device.
In the present invention, the specific surface area means a value measured by such a method unless otherwise specified.

The average particle diameter of the composite fine particles of the present invention is preferably from 50 to 1000 nm, more preferably from 100 to 300 nm. When the average particle diameter of the composite fine particles of the present invention is in the range of 50 to 1000 nm, the polishing rate is high when applied as an abrasive, which is preferable.
The average particle diameter of the composite fine particles of the present invention means the number average value of the average particle diameter measured by the image analysis method.
A method for measuring the average particle size by the image analysis method will be described. In a photographic projection image obtained by photographing the composite fine particles of the present invention with a transmission electron microscope at a magnification of 300,000 (or 500,000), the maximum diameter of the particles is taken as the major axis, and the length is measured. , And its value is defined as the major axis (DL). In addition, a point on the major axis that bisects the major axis is determined, two points at which a straight line perpendicular to the major axis intersects the outer edge of the particle are determined, and the distance between the two points is measured to obtain the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is determined, and this is defined as the average particle diameter of the composite fine particles.
In this way, the average particle diameter of 50 or more composite particles is measured, and their number average value is calculated.

In the composite fine particles of the present invention, the content of each element of the specific impurity group 1 is preferably 100 ppm or less. Further, it is preferably at most 50 ppm, more preferably at most 25 ppm, further preferably at most 5 ppm, still more preferably at most 1 ppm.
The content of each element of the specific impurity group 2 in the composite fine particles of the present invention is preferably 5 ppm or less. The method of reducing the content of each element of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention is as described above.
The content of each element of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention is determined by measuring the specific impurity group 1 and the specific impurity group 2 contained in the base particles. Can be measured by the same method as described above.

<Dispersion of the present invention>
The dispersion of the present invention will be described.
The dispersion of the present invention is one in which the composite fine particles of the present invention as described above are dispersed in a dispersion solvent.

  The dispersion of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, for example, water such as pure water, ultrapure water, or ion-exchanged water is preferably used. Further, the dispersion of the present invention is polished by adding at least one selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster and a pH buffer as an additive for controlling polishing performance. It is suitably used as a slurry.

  Examples of the dispersion solvent including the dispersion of the present invention include alcohols such as methanol, ethanol, isopropanol, n-butanol, and methyl isocarbinol; acetone, 2-butanone, ethyl amyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Ketones such as N; N-dimethylformamide, amides such as N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane and 3,4-dihydro-2H-pyran Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoki Glycol ether acetates such as ethyl acetate; methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, esters such as ethylene carbonate; aromatic hydrocarbons such as benzene, toluene, xylene; hexane, heptane, isooctane; Aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone, N-octyl- Organic solvents such as pyrrolidones such as 2-pyrrolidone can be used. These may be used by mixing with water.

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

In the dispersion of the present invention, when cationic colloid titration is performed, the ratio of the flow potential change (ΔPCD) represented by the following formula (1) to the addition amount (V) of the cationic colloid titrant in a knick ( It is preferable that a streaming potential curve in which ΔPCD / V) is −250.0 to −5.0 is obtained.
ΔPCD / V = (IC) / V Equation (1)
C: streaming potential (mV) in the knick
I: streaming potential (mV) at the starting point of the streaming potential curve
V: Addition amount (ml) of the cationic colloid titrant in the knicks

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

The streaming potential curve obtained by the cationic colloid titration is a graph in which the addition 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) where the streaming potential changes abruptly in the streaming potential curve obtained by cationic colloid titration. The streaming potential at the inflection point is C (mV), and the amount of the cationic colloid titrant at the inflection point is V (ml).
The starting point of the streaming potential curve is the streaming potential of the dispersion of the present invention before titration. Specifically, the point at which the amount of the cationic colloid titrant added is 0 is defined as the starting point. The streaming potential at this start point is defined as I (mV).

  When the value of ΔPCD / V is −250.0 to −5.0, the polishing rate of the abrasive is further improved when the dispersion of the present invention is used as the abrasive. This ΔPCD / V reflects the degree of coating of the child particles by the cerium-containing coating 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 a base particle component that is easily desorbed. it is conceivable that. The present inventor estimates that when the value of ΔPCD / V is within the above range, the detachment of the child particles during wet pulverization is small and the polishing rate is high. On the other hand, when the value of ΔPCD / V is greater than −250.0, the surface of the composite fine particles is entirely covered with the cerium-containing coating layer. At times, the cerium-containing coating layer is hardly detached, and the polishing rate is reduced. On the other hand, if the absolute value is smaller than -5.0, it is considered that dropout is likely to occur. The present inventors presume that when the content is in the above range, the surface of the child particles is appropriately exposed during polishing, the falling of the child particles is small, and the polishing rate is further improved. ΔPCD / V is more preferably from −230.0 to −5.0, and still more preferably from −230.0 to −10.0.

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

<Production method of the present invention>
The manufacturing method of the present invention will be described.
The manufacturing method of the present invention includes Steps 1 to 3 described below.

<Step 1>
In step 1, a crystalline inorganic oxide fine particle dispersion liquid in which crystalline inorganic oxide fine particles are dispersed in a solvent is prepared.
In the present specification, “step 1” may be referred to as “mixing step”.

  The mode of the crystalline inorganic oxide fine particles used in the step 1 is not particularly limited, but it is more preferable if the average particle diameter and the shape are the same as those of the above-mentioned base particles. Further, the crystalline inorganic oxide fine particles have a crystalline inorganic oxide as a main component, similarly to the above-described base particles. Here, the definition of the main component is the same as that of the base particle. That is, after the crystalline inorganic oxide fine particle dispersion is dried, it is pulverized using a mortar, and an X-ray diffraction pattern is obtained by, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). And when only the peak of the crystalline inorganic oxide appears, it means that it is the main component.

The average particle diameter of the crystalline inorganic oxide fine particles in the crystalline inorganic oxide fine particle dispersion used as a raw material in step 1 is the average of the ceria-based composite fine particles in the ceria-based composite fine particle dispersion obtained by the production method of the present invention. Those smaller than the particle size are used. Preferably, crystalline inorganic oxide fine particles in a range of 15 nm or more and less than 350 nm are used.
The average particle diameter of the crystalline inorganic oxide fine particles in the crystalline inorganic oxide fine particle dispersion is an average particle diameter with a value calculated based on a photographic projection obtained by photographing using a transmission electron microscope. can do. A specific measuring method is the same as the above-described method for measuring the average particle diameter of the composite fine particles of the present invention.

The ratio of the minor axis / major axis of the crystalline inorganic oxide microparticles in the crystalline inorganic oxide microparticle dispersion used as the raw material in step 1 may be a minor axis / major axis ratio of 0.1 or more and less than 1.0. desirable. Further, as a more desirable range, a range of a minor axis / major axis ratio of 0.2 or more and 0.7 or less can be mentioned.
The ratio of the minor axis / major axis of the crystalline inorganic oxide fine particles in the crystalline inorganic oxide fine particle dispersion is determined by calculating the minor axis with a value calculated based on a photographic projection obtained by photographing using a transmission electron microscope. / Major axis ratio. A specific measuring method is the same as the above-described measuring method of the minor diameter / major diameter ratio in the composite fine particles of the present invention.

When the dispersion of the present invention to be applied to polishing of a semiconductor device or the like is to be prepared by the production method of the present invention, the dispersion of the crystalline inorganic oxide prepared by hydrolysis of the metal alkoxide is used as the dispersion of the crystalline inorganic oxide fine particles. It is preferable to use a crystalline inorganic oxide fine particle dispersion obtained by dispersing fine particles of the substance in a solvent, but other conventionally known crystalline inorganic oxide fine particle dispersions may be used as a raw material.
Specifically, for example, those satisfying the following conditions (a) and (b) are suitably used as the crystalline inorganic oxide fine particles in the crystalline inorganic oxide fine particle dispersion liquid as a raw material.
(A) The content of each of Na, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni and Zn is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.

  Further, as the crystalline inorganic oxide fine particles, those having an appropriate reactivity with cerium (the dissolved weight of the crystalline inorganic oxide fine particles per weight of ceria) are suitably used. By adding a metal salt of cerium in the preparation step of Step 1 in the production method of the present invention, a part of the crystalline inorganic oxide is dissolved by cerium hydroxide or the like, The size of the oxide fine particles is reduced, and a precursor of the cerium-containing coating layer containing cerium microcrystals is formed on the surfaces of the dissolved crystalline inorganic oxide fine particles. At this time, when the crystalline inorganic oxide fine particles are made of a crystalline inorganic oxide having high reactivity with cerium, the precursor of the cerium-containing coating layer becomes thick, and the cerium-containing coating layer generated by firing becomes thicker, This is because the ratio of the crystalline inorganic oxide in the layer becomes excessively high, and it becomes difficult to crush in the crushing step. Further, when the crystalline inorganic oxide fine particles are made of a crystalline inorganic oxide having extremely low reactivity with cerium, the cerium-containing coating layer is not sufficiently formed, and the ceria particles are likely to fall off. When the reactivity with cerium is appropriate, the dissolution of excess crystalline inorganic oxide is suppressed, the cerium-containing coating layer has an appropriate thickness, prevents falling off of the child particles, and has a strength between the composite fine particles. It is preferable because it is easier to disintegrate.

  In step 1, the crystalline inorganic oxide fine particle dispersion liquid in which the crystalline inorganic oxide fine particles are dispersed in a solvent is stirred, the temperature is set to 0 to 20 ° C., the pH range is set to 7.0 to 9.0, and the oxidation-reduction potential is set. Is maintained at 50 to 500 mV, a cerium metal salt is continuously or intermittently added thereto to neutralize the cerium metal salt, thereby obtaining a precursor particle dispersion liquid containing precursor particles.

Here, it is preferable to add a component containing silicon in addition to the metal salt of cerium.
A typical example of the component containing silicon is a compound containing a silicon atom such as a silicate. In addition, alkoxysilanes such as tetraethoxysilane may be mentioned as components containing silicon.
While stirring the crystalline inorganic oxide fine particle dispersion, maintaining the temperature at 0 to 20 ° C, the pH at 7.0 to 9.0, and the oxidation-reduction potential at 50 to 500 mV, the metal salt of cerium and silicon were added thereto. Is added continuously or intermittently to obtain the composite fine particles of the present invention in which at least a part of the cerium-containing coating layer is made of silica.

  When the crystalline inorganic oxide fine particles have protrusions, the temperature of the crystalline inorganic oxide fine particle dispersion when adding a metal salt of cerium (preferably, a component further containing silicon) is 3 to 20 ° C. Is preferred.

  The dispersion medium in the crystalline inorganic oxide fine particle dispersion preferably contains water, and it is preferable to use an aqueous crystalline inorganic oxide fine particle dispersion (water sol).

  The solid content concentration in the crystalline inorganic oxide fine particle dispersion is preferably 1 to 40% by mass in terms of oxide. If this solid content concentration is too low, the concentration of the inorganic oxide in the production process will be low, and the productivity may be poor.

In the production method of the present invention, for example, when the reaction temperature between the crystalline inorganic oxide fine particles and the metal salt of cerium (preferably a component containing silicon) in Step 1 is set to 40 to 50 ° C., ceria and inorganic oxide And the dissolution of the crystalline inorganic oxide fine particles proceeds. As a result, the particle diameter of the CeO ₂ ultrafine particles in the precursor particles obtained by drying in the intermediate stage of Step 2 is less than 2.5 nm. This means that when the inorganic oxide reacts with ceria in the liquid phase in such a high temperature range, the inorganic oxide inhibits the ceria particle growth, so that the average particle size of the ceria after drying is reduced to less than 2.5 nm. Is shown.
In addition, even with such precursor particles, it is possible to make the average crystallite diameter of ceria particles 10 nm or more by setting the firing temperature to 1200 ° C. or more. In this case, however, the cerium-containing coating is used. A layer of an inorganic oxide is formed without forming a layer, and there is a problem in that crushing is difficult because the inorganic oxide film has a strong tendency to firmly cover the ceria particles. Therefore, by keeping the reaction temperature at 0 to 20 ° C. and appropriately suppressing the reaction between the inorganic oxide and ceria in the liquid phase, the average crystallite diameter of the ultrafine CeO ₂ particles in the dried precursor particles is set to 2.5 nm. The particles can be formed as described above and are easily crushed. Further, since the average crystallite diameter after drying is large, the firing temperature for setting the average crystallite diameter of the ceria child particles to 10 nm or more can be lowered, and the thickness of the cerium-containing coating layer formed by firing becomes excessive. Disintegration is facilitated without thickening.

  In addition, impurities are extracted with a cation exchange resin or an anion exchange resin, or a mineral acid, an organic acid, or the like, and if necessary, deionization of the crystalline inorganic oxide fine particle dispersion is performed using an ultrafiltration membrane or the like. Processing can be performed. A crystalline inorganic oxide fine particle dispersion liquid from which impurity ions and the like have been removed by deionization treatment is more preferable because a hydroxide containing an inorganic oxide is easily formed on the surface. The deionization treatment is not limited to these.

In step 1, while stirring the above-mentioned crystalline inorganic oxide fine particle dispersion liquid, maintaining the temperature at 0 to 20 ° C, the pH range at 7.0 to 9.0, and the oxidation-reduction potential at 50 to 500 mV, Here, a metal salt of cerium (preferably a component further containing silicon) is added continuously or intermittently. When the oxidation-reduction potential is low, rod-like crystals or the like are generated, and thus are not easily deposited on the crystalline inorganic oxide fine particles.
Further, when the oxidation-reduction potential is not adjusted to a predetermined range, the CeO ₂ ultrafine particles generated in the blending step tend to hardly crystallize, and the non-crystallized CeO ₂ ultrafine particles can be crystallized by heating and aging after the blending. Is not promoted. Therefore, in order to crystallize to a predetermined size in the baking in the step 2, baking at a high temperature is required, and crushing becomes difficult.

The kind of the metal salt of cerium is not limited, but chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide and the like of cerium can be used. Specific examples include cerous nitrate, cerium carbonate, cerous sulfate, cerous chloride and the like. Of these, trivalent cerium salts such as cerous nitrate, cerous chloride and cerium carbonate are preferred. Crystallized cerium oxide, cerium hydroxide, etc. are generated from the supersaturated solution at the same time as the neutralization, and these are quickly aggregated and deposited on the crystalline inorganic oxide fine particles, and finally the CeO ₂ ultrafine particles are monodispersed. It is because it is formed by. Further, the trivalent cerium salt reacts moderately with the crystalline inorganic oxide fine particles, and a cerium-containing coating layer is easily formed. Further, trivalent cerium having high reactivity with the silica film formed on the polishing substrate is easily formed in the ceria crystal, which is preferable. However, sulfate ions, chloride ions, nitrate ions and the like contained in these metal salts show corrosiveness. Therefore, if necessary, it is necessary to wash it in a post-process after the preparation to remove it to 5 ppm or less. On the other hand, carbonates are released during the preparation as carbon dioxide gas, and alkoxides are decomposed into alcohols, and thus can be preferably used.

  The amount of the cerium metal salt added to the crystalline inorganic oxide fine particle dispersion is the mass ratio of the component other than ceria and ceria in the obtained ceria-based composite fine particles, as in the case of the above-described composite fine particles of the present invention. , 100: 11 to 316.

After adding the metal salt of cerium to the crystalline inorganic oxide fine particle dispersion, the temperature during stirring is preferably 0 to 20 ° C, more preferably 3 to 20 ° C, and more preferably 3 to 18 ° C. It is more preferred that there be. If the temperature is too low, the reactivity between ceria and the inorganic oxide is reduced, and the solubility of the inorganic oxide is significantly reduced, so that the crystallization of ceria is not controlled. As a result, coarse ceria crystalline oxide is generated, and abnormal growth of CeO ₂ ultrafine particles occurs on the surface of the crystalline inorganic oxide fine particles, which makes it difficult to be crushed after firing, or that the inorganic oxide due to the cerium compound Decreases the amount of inorganic oxide supplied to the cerium-containing coating layer. For this reason, the amount of the inorganic oxide serving as a binder between the base particles and the ceria particles is insufficient (the amount of the inorganic oxide laminated on the base particles is insufficient), and the immobilization of the ceria child particles on the base particles is unlikely to occur. It can be considered. Conversely, if the temperature is too high, the solubility of the inorganic oxide is significantly increased, and it is conceivable that the generation of crystalline ceria oxide is suppressed. Crushing may not be possible, and furthermore, scale or the like is likely to be formed on the reactor wall surface, which is not preferable. In addition, the crystalline inorganic oxide fine particles are preferably those that are hardly dissolved in a cerium compound (neutralized cerium salt). In the case of the crystalline inorganic oxide fine particles that are easily dissolved, the ceria crystal growth is suppressed by the inorganic oxide, and the particle diameter of the CeO ₂ ultrafine particles in the preparation stage becomes less than 2.5 nm.
If the particle size of the CeO ₂ ultrafine particles at the blending stage is less than 2.5 nm, it is necessary to raise the firing temperature in order to make the ceria particle size after firing 10 nm or more, in which case the cerium-containing coating layer May firmly coat the base particles, making it difficult to disintegrate. When the crystalline inorganic oxide fine particles that are easily dissolved are dried at a temperature of 100 ° C. or higher and used as a raw material, the solubility can be suppressed.

Further, the time for stirring the crystalline inorganic oxide fine particle dispersion after adding the cerium metal salt is preferably 0.5 to 24 hours, and more preferably 0.5 to 18 hours. If the time is too short, the CeO ₂ ultrafine particles are aggregated, and it is difficult to react with the inorganic oxide on the surface of the crystalline inorganic oxide fine particles. Absent. Conversely, even if this time is too long, the formation of the CeO ₂ ultrafine particle-containing layer is uneconomic because the reaction does not proceed any further. After the addition of the cerium metal salt, aging may be performed at 0 to 80 ° C. if desired. This is because the aging has the effect of accelerating the reaction of the cerium compound and, at the same time, adhering the CeO ₂ ultrafine particles released without adhering to the crystalline inorganic oxide fine particles onto the crystalline inorganic oxide fine particles.

  The pH range of the crystalline inorganic oxide fine particle dispersion at the time of adding a cerium metal salt to the crystalline inorganic oxide fine particle dispersion and stirring the mixture is set to 7.0 to 9.0, but 7.6 to 9.0. It is preferably set to 8.6. At this time, it is preferable to adjust the pH by adding an alkali or the like. As an example of such an alkali, a known alkali can be used. Specific examples include, but are not limited to, aqueous ammonia solutions, aqueous alkali hydroxides, alkaline earth metals, and aqueous solutions of amines.

Further, a metal salt of cerium (preferably a component further containing silicon) is added to the crystalline inorganic oxide fine particle dispersion, and the oxidation-reduction potential of the fine particle dispersion at the time of stirring is adjusted to 50 to 500 mV. The oxidation-reduction potential is preferably set to 100 to 300 mV. This is because when a trivalent cerium metal salt is used as a raw material, the acid-reduction potential of the fine particle dispersion decreases during the preparation. By keeping the oxidation-reduction potential in this range, crystallization of the generated CeO ₂ ultrafine particles is promoted. When the oxidation-reduction potential is 50 mV or less or becomes negative, the cerium compound may not be deposited on the surface of the crystalline inorganic oxide fine particles, and plate-like or rod-like ceria single particles or composite ceria particles may be generated. Further, the reactivity of cerium hydroxide or the like to the crystalline inorganic oxide fine particles is reduced, and the CeO ₂ ultrafine particle-containing layer is not formed. Even if it is formed, the ratio of the inorganic oxide in the CeO ₂ ultrafine particle layer is extremely low. Lower. Therefore, the cerium-containing coating layer containing the ceria particles is not formed after firing, and the ceria particles tend to be exposed and arranged on the surface of the inorganic oxide base particles.
Examples of a method for keeping the oxidation-reduction potential within the above range include a method of adding an oxidizing agent such as hydrogen peroxide and a method of blowing air, oxygen, and ozone. When these methods are not performed, the oxidation-reduction potential tends to be negative or 50 mV or less.

By such a process 1, a dispersion liquid (precursor particle dispersion liquid) containing particles (precursor particles) which are precursors of the composite fine particles of the present invention is obtained. In this step, it is possible to obtain particles in which the average crystallite diameter of the CeO ₂ ultrafine particles contained in the precursor particles is 2.5 nm or more and less than 10 nm. If the reactivity between the inorganic oxide and ceria is too high, the average crystallite diameter of the CeO ₂ ultrafine particles contained in the precursor particles tends to be less than 2.5 nm. Requires firing at an excessively high temperature. As a result, the adhesion between the particles becomes strong, and there is a possibility that crushing becomes difficult.

As described above, in Step 1, the crystalline inorganic oxide fine particle dispersion is stirred, and the temperature is maintained at 0 to 20 ° C., the pH is maintained at 7.0 to 9.0, and the oxidation-reduction potential is maintained at 50 to 500 mV. The metal salt of cerium (preferably a component further containing silicon) is continuously or intermittently added thereto. Thereafter, the temperature is increased from 20 ° C. to 98 ° C., the pH is 7.0 to 9.0, and the oxidation-reduction is performed. It is preferable to add the metal salt of cerium (preferably, a component containing silicon) continuously or intermittently to obtain the precursor particle dispersion while maintaining the potential at 50 to 500 mV.
That is, in the step 1, the treatment is performed at a temperature of 0 to 20 ° C., and then it is preferable to obtain the precursor particle dispersion by changing the temperature to a temperature higher than 20 ° C. and 98 ° C. or less.
This is because, when such a step 1 is performed, it is easy to obtain the dispersion of the present invention containing the composite fine particles of the present invention whose variation coefficient in the particle size distribution of the child particles is a suitable value.
In addition, when treating at a temperature of more than 20 ° C. and 98 ° C. or less, suitable values of pH and oxidation-reduction potential, adjustment methods, and the like are the same as in the case of treating at a temperature of 0 to 20 ° C.

Conversely, before performing the treatment at a temperature of 0 to 20 ° C., it is preferable to perform the treatment at a temperature higher than 20 ° C. and 98 ° C. or less to obtain the precursor particle dispersion. That is, while stirring the crystalline inorganic oxide fine particle dispersion, the temperature is maintained at more than 20 ° C. to 98 ° C., the pH is maintained at 7.0 to 9.0, and the oxidation-reduction potential is maintained at 50 to 500 mV. Is added continuously or intermittently, and thereafter, the temperature is maintained at 0 to 20 ° C., the pH is maintained at 7.0 to 9.0, and the oxidation-reduction potential is maintained at 50 to 500 mV. Here, it is preferable that the metal salt of cerium (preferably, a component containing silicon) is continuously or intermittently added to obtain the precursor particle dispersion.
This is because, when such a step 1 is performed, it is easy to obtain the dispersion of the present invention containing the composite fine particles of the present invention whose variation coefficient in the particle size distribution of the child particles is a suitable value.
In addition, when treating at a temperature of more than 20 ° C. and 98 ° C. or less, suitable values of pH and oxidation-reduction potential, adjustment methods, and the like are the same as in the case of treating at a temperature of 0 to 20 ° C.
Even in the case of dispensing by changing the temperature during dispensing in this way, if the step of dispensing at a temperature of 0 to 20 ° C is included, the composite fine particles have the same generation mechanism as described above. .

When the reaction is carried out in the range of 0 to 20 ° C., the reactivity of cerium with respect to the inorganic oxide is suppressed, so that large-sized CeO ₂ ultrafine particles are generated. When the metal salt of (1) is added, the reactivity of cerium with respect to the inorganic oxide increases, and the dissolution of the inorganic oxide is promoted. Therefore, the inorganic oxide inhibits ceria crystal growth, and small-sized CeO ₂ Generate. As described above, the reaction temperature during the preparation step (step 1) is essentially 0 to 20 ° C., the reaction temperature is changed from more than 20 ° C. to 98 ° C. or less, and the CeO ₂ ultrafine particles and The particle size distribution of the ceria particles can be widened. In addition, if there is a step of adding a metal salt of cerium at a compounding temperature in the range of 0 to 20 ° C, the reaction at a temperature of more than 20 ° C and 98 ° C or less may be performed before or after the reaction at 0 to 20 ° C. Alternatively, the temperature may be changed three times or more.
In addition, the addition amount of the cerium metal salt in the step of reacting at 0 to 20 ° C. when the reaction temperature is performed in two or more stages is in the range of 10 to 90% by mass based on the total addition amount of the cerium metal salt. Is preferred. If the ratio exceeds this range, the ratio of CeO ₂ ultrafine particles having a large size (or small size) and the ratio of ceria particles are reduced, and the particle size distribution is not so widened.

  Before the precursor particle dispersion obtained in the step 1 is subjected to the step 2, the precursor particle dispersion may be further diluted or concentrated using pure water or ion-exchanged water and then subjected to the next step 2.

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

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

<Step 2>
In the step 2, the precursor particle dispersion is dried and then fired at 700 to 1,200 ° C.

The method of drying is not particularly limited. Drying can be performed using a conventionally known dryer. Specifically, a box dryer, a band dryer, a spray dryer, or the like can be used.
Preferably, it is further recommended that the pH of the precursor particle dispersion before drying is 6.0 to 7.0. This is because surface activity can be suppressed when the pH of the precursor particle dispersion before drying is 6.0 to 7.0.

  After drying, the firing temperature is 700 to 1200 ° C, preferably 710 to 1100 ° C, more preferably 720 to 1090 ° C, and most preferably 730 to 1090 ° C. When calcined in such a temperature range, crystallization of ceria proceeds sufficiently, and the cerium-containing coating layer in which ceria particles are dispersed has an appropriate thickness, and the cerium-containing coating layer is firmly attached to the base particles. Bonding makes it difficult for the child particles dispersed in the cerium-containing coating layer to fall off. Further, by firing in such a temperature range, cerium hydroxide and the like hardly remain. If the temperature is too high, ceria crystals may grow abnormally, the cerium-containing coating layer may become too thick, the crystalline inorganic oxide constituting the base particles may be crystallized, and the fusion of the particles may proceed. is there.

At the time of firing, an alkali metal, an alkaline earth metal, a sulfate, or the like can be added as a flux component to promote the crystal growth of ceria, but the flux component can cause metal contamination and corrosion on the polished substrate. Therefore, the content of the flux component during firing is preferably 100 ppm or less, more preferably 50 ppm or less, and most preferably 40 ppm or less, based on the precursor particles (dry).
The flux component may be brought in from the raw material or used as an alkali to be used for neutralizing the cerium metal salt at the time of blending.However, when an alkali metal or an alkaline earth metal coexists at the time of blending, crystallinity may be reduced. Since polymerization of the inorganic oxide fine particles is promoted and densified, the reactivity between cerium hydroxide or the like and the crystalline inorganic oxide fine particles is reduced. Furthermore, since the surface of the crystalline inorganic oxide fine particles is protected with an alkali metal or an alkaline earth metal, reactivity with cerium hydroxide or the like is suppressed, and a cerium-containing coating layer tends to be not formed. Further, since the dissolution of the inorganic oxide is suppressed during the preparation, the atoms of the inorganic oxide hardly dissolve in the ceria particles.

Further, when firing is performed in such a temperature range, atoms of the inorganic oxide are dissolved in crystalline ceria, which is a main component of the child particles. Therefore, regarding the cerium atom and the inorganic oxide atom contained in the child particles, when the interatomic distance between the cerium and the inorganic oxide is R ₁ and the interatomic distance between the cerium and cerium is R ₂ , R ₁ <R ₂ Can be satisfied.

In step 2, a solvent is added to the fired body obtained by firing, and the mixture is wet-crushed in a pH range of 8.6 to 10.8 to obtain a fired body crushed dispersion.
Here, the fired body may be subjected to a dry-type crushing before the wet-type crushing treatment is performed on the fired body, and then the wet-type crushing may be performed.

A conventionally known apparatus can be used as a dry crushing apparatus, and examples thereof include an attritor, a ball mill, a vibration mill, and a vibration ball mill.
Conventionally known devices can also be used as a wet-type crusher, for example, batch type bead mills such as basket mills, horizontal / vertical / annular type continuous bead mills, sand grinder mills, ball mills, etc. -Wet media stirring mills (wet disintegrators) such as a stator homogenizer, an ultrasonic dispersing homogenizer, and an impact crusher for hitting fine particles in a dispersion liquid. Examples of the beads used in the wet medium stirring mill include beads made of glass, alumina, zirconia, steel, flint stone, an organic resin, or the like.
Water and / or an organic solvent is used as a solvent used when the fired body is wet-crushed. For example, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. The solid content concentration of the fired body disintegrated dispersion is not particularly limited, but is preferably, for example, in the range of 0.3 to 50% by mass.

In the case where the fired body is subjected to wet crushing, it is preferable to perform wet crushing while maintaining the pH of the solvent at 8.6 to 10.8. When the pH is maintained in this range, when the cationic colloid titration is performed, the flow potential change (ΔPCD) represented by the above formula (1) and the addition amount (V) of the cationic colloid titrant in the knick are determined. Finally, a ceria-based composite fine particle dispersion having a streaming potential curve with a ratio (ΔPCD / V) of −110.0 to −15.0 can be obtained more easily.
That is, it is preferable to carry out crushing to such an extent that the dispersion liquid of the present invention corresponding to the above-mentioned preferred embodiment is obtained. This is because, as described above, when the dispersion of the present invention, which corresponds to a preferred embodiment, is used as an abrasive, the polishing rate is further improved. In this regard, the present inventor has found that the cerium-containing coating layer on the surface of the composite fine particles of the present invention is appropriately thinned and / or the child particles are appropriately exposed on a part of the surface of the composite fine particles, whereby the polishing rate is further improved. It is estimated that the falling of ceria particles can be controlled. Further, during the disintegration, the inorganic oxide in the cerium-containing coating layer dissolves and deposits again, forming a soft and easily soluble inorganic oxide layer on the outermost layer. It is presumed that the layer enhances the frictional force due to the adhesive action with the substrate, thereby increasing the polishing rate. Further, it is estimated that since the cerium-containing coating layer is thin or peeled, the child particles are likely to be detached to some extent during polishing. ΔPCD / V is more preferably -100.0 to -15.0, and further preferably -100.0 to -20.0.
In addition, if the crushed powder is loosened without passing through the wet disintegration step as in step 2, the dry disintegration / pulverization alone, or even if the wet disintegration is outside the predetermined pH range, ΔPCD / V is hardly in the range of −100.0 to −15, and a soft and easily soluble cerium-containing coating layer is hardly formed.

<Step 3>
In step 3, the fired body disintegrated dispersion obtained in step 2 is subjected to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently, sediment components are removed to obtain a ceria-based composite fine particle dispersion.
Specifically, the fired compacted dispersion is classified by centrifugation. The relative centrifugal acceleration in the centrifugation process is 300 G or more. After the centrifugation, the sediment components are removed to obtain a ceria-based composite fine particle dispersion. Although the upper limit of the relative centrifugal acceleration is not particularly limited, it is practically used at 10,000 G or less.

  In step 3, it is necessary to provide a centrifugal separation process that satisfies the above conditions. If the centrifugal acceleration is less than the above condition, coarse particles remain in the ceria-based composite fine particle dispersion, so that when used for polishing applications such as an abrasive using the ceria-based composite fine particle dispersion, scratches may occur. Cause it to occur.

  In the present invention, the ceria-based composite fine particle dispersion obtained by the above production method can be further dried to obtain ceria-based composite fine particles. The drying method is not particularly limited, and for example, drying can be performed using a conventionally known dryer.

  The dispersion of the present invention can be obtained by such a production method of the present invention.

<Abrasive dispersion liquid for polishing>
The liquid containing the dispersion of the present invention can be preferably used as a polishing abrasive dispersion (hereinafter also referred to as “polishing abrasive dispersion of the present invention”). In particular, it can be suitably used as a polishing abrasive dispersion for polishing a semiconductor substrate on which an SiO ₂ insulating film is formed. In addition, a chemical component can be added to control the polishing performance, and can be suitably used as a polishing slurry.

  The abrasive dispersion liquid for polishing according to the present invention has excellent effects such as a high polishing rate when polishing a semiconductor substrate and the like, little scratches (scratch) on the polished surface during polishing, and little residual abrasive grains on the substrate. ing.

  The abrasive dispersion liquid for polishing of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, for example, water such as pure water, ultrapure water, or ion-exchanged water is preferably used. Further, as an additive for controlling the polishing performance, the polishing abrasive dispersion of the present invention may further include, as an additive for controlling the polishing performance, a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster, and a pH buffer. By adding more than one kind, it is suitably used as a polishing slurry.

<Polishing accelerator>
The polishing slurry dispersion of the present invention varies depending on the type of the material to be polished, but can be used as a polishing slurry by adding a conventionally known polishing accelerator as needed. Such examples include hydrogen peroxide, peracetic acid, urea peroxide, and the like, and mixtures thereof. When a polishing composition containing such a polishing accelerator such as hydrogen peroxide is used, the polishing rate can be effectively improved when the material to be polished is a metal.

  Other examples of the polishing accelerator include inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid, organic acids such as acetic acid, and sodium, potassium, ammonium, and amine salts of these acids. And the like. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished made of a composite component, the polishing rate for a specific component of the material to be polished is promoted so that a flat polishing is finally achieved. Face can be obtained.

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

<Surfactant and / or hydrophilic compound>
A cationic, anionic, nonionic, amphoteric surfactant or a hydrophilic compound can be added to improve the dispersibility and stability of the abrasive dispersion liquid for polishing of the present invention. Both the surfactant and the hydrophilic compound have a function of reducing the contact angle to the surface to be polished, and a function of promoting uniform polishing. As the surfactant and / or the hydrophilic compound, for example, those selected from the following group can be used.

  Examples of the anionic surfactant include carboxylate, sulfonate, sulfate, and phosphate. As the carboxylate, soap, N-acyl amino acid salt, polyoxyethylene or polyoxypropylene alkyl ether carboxylate Acid sulfonate, acylated peptide; alkyl sulfonate, alkylbenzene and alkyl naphthalene sulfonate, naphthalene sulfonate, sulfosuccinate, α-olefin sulfonate, N-acyl sulfonate; sulfate Salts include sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, and alkyl amide sulfates; phosphate salts such as alkyl phosphates, polyoxyethylene or polyoxyphosphates Can pyrene alkyl allyl ether phosphates.

  As cationic surfactants, aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, imidazolinium salts; carboxybetaine type, sulfobetaine type as amphoteric surfactants, Amino carboxylate, imidazolinium betaine, lecithin, alkylamine oxide can be mentioned.

  Examples of the nonionic surfactant include an ether type, an ether ester type, an ester type, and a nitrogen-containing type. Examples of the ether type include polyoxyethylene alkyl and alkyl phenyl ether, alkyl allyl formaldehyde condensed polyoxyethylene ether, and polyoxyethylene poly. Oxypropylene block polymer, polyoxyethylene polyoxypropylene alkyl ethers, and as the ether ester type, glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, as an ester type Polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester , Sucrose esters, nitrogen-containing type, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amide, and the like. Other examples include a fluorine-based surfactant.

  As the surfactant, an anionic surfactant or a nonionic surfactant is preferable, and as the salt, an ammonium salt, a potassium salt, a sodium salt and the like can be mentioned, and an ammonium salt and a potassium salt are particularly preferable.

  Further, as other surfactants and hydrophilic compounds, esters such as glycerin ester, sorbitan ester and alanine ethyl ester; polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol alkyl ether, polyethylene glycol alkenyl ether, alkyl Polyethylene glycol, alkyl polyethylene glycol alkyl ether, alkyl polyethylene glycol alkenyl ether, alkenyl polyethylene glycol, alkenyl polyethylene glycol alkyl ether, alkenyl polyethylene glycol alkenyl ether, polypropylene glycol alkyl ether, polypropylene glycol alkenyl ether, alkyl polypropylene Ethers such as recall, alkyl polypropylene glycol alkyl ether, alkyl polypropylene glycol alkenyl ether and alkenyl polypropylene glycol; polysaccharides such as alginic acid, pectic acid, carboxymethyl cellulose, curdlan and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; Polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), poly Acrylic acid, polyacrylamide, amino polyacrylamide, ammonium polyacrylate, sodium polyacrylate, Polycarboxylic acids and salts thereof such as rimidic acid, ammonium polyamic acid salt, polyamic acid sodium salt and polyglyoxylic acid; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; ammonium methyltaurate and sodium methyltaurate Sodium methyl sulfate, ethyl ammonium sulfate, butyl ammonium sulfate, sodium vinyl sulfonate, sodium 1-allyl sulfonate, sodium 2-allyl sulfonate, sodium methoxymethyl sulfonate, ammonium ethoxymethyl sulfonate Salts, sulfonic acids such as 3-ethoxypropylsulfonic acid sodium salt, and salts thereof; propionamide, acrylamide, methylurea, nicotinamide, succinamide, and sulf And amides such as phenylamide.

  When the substrate to be polished is a glass substrate or the like, any of the surfactants can be suitably used. However, in the case of a silicon substrate for a semiconductor integrated circuit or the like, an alkali metal or an alkaline earth is used. In the case where the influence of contamination by a class of metal or halide is disliked, it is desirable to use an acid or its ammonium salt-based surfactant.

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

  In order to obtain a sufficient effect, the content of the surfactant and / or the hydrophilic compound is preferably 0.001 g or more in 1 L of the polishing slurry dispersion liquid, and is preferably 10 g or less from the viewpoint of preventing a reduction in polishing rate. .

  One or more surfactants or hydrophilic compounds may be used, or two or more surfactants or hydrophilic compounds may be used in combination.

<Heterocyclic compound>
With respect to the abrasive grain dispersion for polishing of the present invention, when a metal to be polished contains a metal, by forming a passivation layer or a dissolution inhibiting layer on the metal, for the purpose of suppressing erosion of the substrate to be polished, A heterocyclic compound may be contained. Here, the “heterocyclic compound” is a compound having a heterocyclic ring containing one or more hetero atoms. A hetero atom means an atom other than a carbon atom or a hydrogen atom. Heterocycle means a cyclic compound having at least one heteroatom. Heteroatom means only those atoms that form a part of a heterocyclic ring system, which is located external to the ring system, separated from the ring system by at least one non-conjugated single bond, An atom which is part of a further substituent of is not meant. Preferred examples of the hetero atom include, but are not limited to, a nitrogen atom, a sulfur atom, an oxygen atom, a selenium atom, a tellurium atom, a phosphorus atom, a silicon atom, and a boron atom. As examples of the heterocyclic compound, imidazole, benzotriazole, benzothiazole, tetrazole, and the like can be used. More specifically, 1,2,3,4-tetrazole, 5-amino-1,2,3,4-tetrazole, 5-methyl-1,2,3,4-tetrazole, 1,2,3- Triazole, 4-amino-1,2,3-triazole, 4,5-diamino-1,2,3-triazole, 1,2,4-triazole, 3-amino1,2,4-triazole, 3,5 -Diamino-1,2,4-triazole and the like, but are not limited thereto.

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

<PH adjuster>
The pH of the polishing composition can be adjusted by adding an acid or a base and a salt compound thereof as necessary, for example, to enhance the effect of each of the above additives.

  When adjusting the abrasive grain dispersion of the present invention to have a pH of 7 or more, an alkaline one is used as a pH adjuster. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, and tetramethylamine are 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 such as hydroxy acids such as acetic acid, lactic acid, citric acid, malic acid, tartaric acid and glyceric acid are used.

<PH buffer>
In order to keep the pH value of the abrasive dispersion of the present invention constant, a pH buffer may be used. As the pH buffer, for example, phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate, borate, or organic acid salts can be used.

  Further, as a dispersion solvent of the abrasive grain 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; Ketones such as isophorone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran Ethers; glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butane Glycol ether acetates such as xylethyl acetate; esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; aromatic hydrocarbons such as benzene, toluene, xylene; hexane, heptane, isooctane Hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; N-methyl-2-pyrrolidone; N-octyl Organic solvents such as pyrrolidones such as -2-pyrrolidone can be used. These may be used by mixing with water.

  It is preferable that the solid content concentration contained in the abrasive grain dispersion liquid of the present invention is in the range of 0.3 to 50% by mass. If the solid content is too low, the required polishing rate may not be reached. Conversely, even if the solid content concentration is too high, the polishing rate is rarely further improved.

  Hereinafter, the present invention will be described based on examples. The present invention is not limited to these examples.

<Experiment 1>
First, details of each measurement method and test method in Examples and Comparative Examples will be described. Table 1 shows the following measurement results and test results for each example and comparative example.

The compressive breaking strength of the crystalline inorganic oxide fine particles contained in the dispersion liquid of the crystalline inorganic oxide fine particles used as a raw material in Examples and Comparative Examples was measured by the following method.
The composite fine particle dispersion was crushed with a sand mill and classified and separated by a centrifugal separator to obtain mother particles, and the compressive fracture strength was measured using a micro compression tester (MCT-W500) manufactured by Shimadzu Corporation.

<Average particle diameter and minor axis / major axis ratio>
With respect to the ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples, the average particle diameter and the minor axis / major axis ratio of the ceria-based composite fine particles contained therein were measured by the above-described image analysis method.
That is, the average particle diameter and the minor axis / major axis ratio of the ceria-based composite fine particles in the ceria-based composite fine particle dispersion are calculated based on the photographic projections obtained by photographing using a transmission electron microscope as described above. The obtained value was used as the average particle diameter or the ratio of the minor axis / major axis.

[Measurement of CeO ₂ content and other contents]
The ceria-based composite fine particle dispersion is subjected to a burning loss at 1000 ° C. to determine the mass of the solid content.
Next, about 1 g of the ceria-based composite fine particle dispersion (adjusted to a solid content of 20% by mass) is collected in a platinum dish. 3 ml of phosphoric acid, 5 ml of nitric acid and 10 ml of hydrofluoric acid are added and heated on a sand bath. After drying, a small amount of water and 50 ml of nitric acid are added and dissolved, put in a 100 ml measuring flask, and water is added to make 100 ml.
Next, the operation of collecting 10 ml of the separated liquid from the solution contained in 100 ml into a 20 ml measuring flask is repeated five times to obtain five 10 ml of separated liquid.
Then, using this, measurement is performed by a standard addition method using an ICP plasma emission spectrometer (for example, SPS5520 manufactured by SII). Here, a blank is also measured by the same method, and the blank is subtracted to make an adjustment to obtain a Ce measurement value.
Then, a and the CeO ₂ content and content of other than CeO ₂ based on the solid content of the mass of the foregoing, calculating these weight ratios.

[Variation coefficient (CV value)]
The particle size distribution of the child particles is obtained by the above-described method, the standard deviation and the number average value are obtained using the particle size distribution as a population, and then the standard deviation is divided by the number average value and multiplied by 100 (that is, the standard deviation). The deviation coefficient (CV value) in the particle size distribution of the child particles was determined from (deviation / number average value × 100).

[X-ray diffraction method, measurement of average crystallite diameter]
The ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples were dried using a conventionally known dryer, and the obtained powder was pulverized in a mortar for 10 minutes, and an X-ray diffractometer (Rigaku Denki Co., Ltd.) ), RINT1400) to obtain the X-ray diffraction pattern to identify the crystal forms of ceria and the crystalline inorganic oxide.
Further, the full width at half maximum of the peak on the (111) plane near 2θ = 28 degrees (around 2θ = 28 degrees) in the obtained X-ray diffraction pattern was measured by the above-described method, and the average crystallite was calculated by Scherrer's equation. The diameter was determined.

[Polishing test method]
<Polishing of SiO ₂ film>
Polishing abrasive dispersions containing the ceria-based composite fine particle dispersions obtained in each of the examples and comparative examples were prepared. Here, the solid content concentration was 0.6% by mass, and the pH was adjusted to 5.0 by adding nitric acid.
Next, as a substrate to be polished, an SiO ₂ insulating film (thickness: 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, the substrate to be polished is set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and a polishing pad ("IC-1000 / SUBA400 concentric type", manufactured by Nitta Haas) is used. Polishing was performed by supplying an abrasive dispersion liquid for polishing at a rotation speed of 90 rpm at a rate of 50 ml / min for 1 minute.
Then, the change in weight of the substrate to be polished before and after polishing was obtained, and the polishing rate was calculated.
The surface smoothness (surface roughness Ra) of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Corporation). Since the smoothness and the surface roughness are generally in a proportional relationship, Table 1 shows the surface roughness.
Note that the polishing scratches were observed by observing the insulating film surface using an optical microscope.

<Polishing of aluminum hard disk>
Polishing abrasive dispersions containing the ceria-based composite fine particle dispersions obtained in each of the examples and comparative examples were prepared. Here, the solid concentration was 9% by mass, and the pH was adjusted to 2.0 by adding nitric acid.
The substrate for an aluminum hard disk was set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and the polishing slurry was applied at a substrate load of 0.05 MPa and a table rotation speed of 30 rpm using a polishing pad (“Polytex φ12” manufactured by Nitta Haas). Polishing was performed by supplying the solution at a rate of 20 ml / min for 5 minutes, and the entire surface was observed with a Zoom 15 using a superfine defect / visualization macro device (manufactured by Vision Psytec, product name: Micro-Max), and 65.97 cm ^2. The number of scratches (linear marks) existing on the surface of the polished substrate corresponding to the above was counted and totaled, and evaluated according to the following criteria.
Number of linear marks Evaluation Less than 50 "Very little"
50 to less than 80 "less"
80 or more "many"
At least 80 or more such that the total number cannot be counted.

  Examples will be described below. The term “solid content concentration” simply refers to the concentration of fine particles dispersed in a solvent regardless of chemical species.

<Example 1> α-Al ₂ O ₃ core [Preparation of crystalline inorganic oxide dispersion]
To 180 g of α-Al ₂ O ₃ (Sumitomo Chemical Co., Ltd., Advanced Alumina AA-03), 5815.1 g of ion-exchanged water was added, and ultrasonic treatment was performed for 2 hours. Next, 4.9 g of 3% ammonia was added and mixed to obtain 6000 g of a dispersion having a solid content concentration of Al ₂ O _{3 of} 3% by mass (hereinafter, also referred to as A-1 solution).

Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (4N high-purity reagent manufactured by Kanto Chemical Co., Ltd.), and a 3.0 mass% cerium nitrate aqueous solution in terms of CeO ₂ (hereinafter referred to as B-1 solution) ).

Next, while keeping the A-1 solution (6000 g) at 10 ° C. and stirring, the B-1 solution (7,186 g, CeO ₂ dry 215.6 g) was added thereto over 18 hours. During this period, the liquid temperature was maintained at 10 ° C., and 3% aqueous ammonia was added as needed 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 the B-1 solution, the mixture was prepared while blowing air into the mixture, and the oxidation-reduction potential was maintained at 100 to 300 mV.
Thereafter, washing was performed while supplying ion-exchanged water with an ultramembrane. The precursor particle dispersion obtained after the completion of the washing has a solid content of 4.7% by mass, a pH of 8.2 (at 25 ° C.), and an electric conductivity of 19 μs / cm (at 25 ° C.). there were

  Next, the obtained precursor particle dispersion was dried in a dryer at 120 ° C. for 16 hours, and then fired in a muffle furnace at 750 ° C. for 2 hours to obtain a powder (fired 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 with a 3% aqueous ammonia solution. Wet pulverization (batch type desktop sand mill manufactured by Campe Co., Ltd.) for 30 minutes.
After crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained fired body crushed dispersion was 7.1% by mass, and the weight was 1178 g. During the crushing, an aqueous ammonia solution was added to maintain the pH at 10.1.

  Further, the disintegrated dispersion was treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at 509 G for 60 seconds, and the light liquid was recovered to obtain a ceria-based composite fine particle dispersion.

The average particle diameter and the ratio of minor axis / major axis of the ceria-based composite fine particles contained in the obtained ceria-based composite fine particle dispersion were measured. The measuring method is an image analysis method based on a transmission electron micrograph as described above.
In addition, the ratio of the minor axis to the major axis of the mother particles in the ceria-based composite fine particles was measured using the above-mentioned STEM-EDS analysis.
Further, the coefficient of variation (CV value) in the particle size distribution of the child particles was determined by the method described above.
Further, the mass ratio of ceria to components other than ceria contained in the ceria-based composite fine particle dispersion was determined by the method described above.
Further, the X-ray diffraction pattern of the ceria-based composite fine particles was obtained by the method described above, and the crystal forms of ceria and the crystalline inorganic oxide were identified. Further, the average crystallite diameter of the ceria-based composite fine particles was determined.
The results are shown in Table 1.

Next, a polishing test was performed using the obtained ceria-based composite fine particle dispersion.
The results are shown in Table 1.

<Example 2> α-Al ₂ O ₃ core To 100 g of α-Al ₂ O ₃ used in Example 1, 400 g of ion-exchanged water was added, and the pH was adjusted to 3.8 with a 7% nitric acid aqueous solution. Instead of ultrasonic treatment, quartz beads (0.25 mm in diameter, manufactured by Daiken Kagaku Kogyo Co., Ltd.) were subjected to wet pulverization (batch type desktop sand mill manufactured by Campe Co., Ltd.) for 120 minutes.
After crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained α-Al ₂ O ₃ disintegrated dispersion was 6.6% by mass, and the weight was 1401 g. During the crushing, an aqueous nitric acid solution was added to keep the pH at 4.4. Next, 13 g of an anion exchange resin (SANUP B, manufactured by Mitsubishi Chemical Corporation) was gradually added to 1340 g of the α-Al ₂ O ₃ disintegrated dispersion, and the mixture was stirred for 9 minutes, and the resin was separated using 1200 g of ion exchange water. did. The pH at this time was 8.4.
Next, the same operation as in Example 1 was performed, except that the amount of the A-1 solution to be added was 4000 g and the firing temperature was 760 ° C., and the same evaluation was performed.
The results are shown in Table 1.

<Example 3> The same operation as in Example 1 was performed, except that 1100 g of the A-1 solution to which the α-Al ₂ O ₃ core was added and the firing temperature was 950 ° C, and the same evaluation was performed.
The results are shown in Table 1.

<Example 4> TiO ₂ core The α-Al ₂ O ₃ used in Example 1 was changed to an anatase type TiO ₂ , and the precursor particle dispersion was dried in a dryer at 120 ° C. for 16 hours. Except for setting the firing temperature at 950 ° C., the same operation as in Example 1 was performed, and the same evaluation was performed.
The results are shown in Table 1.

Example 5 ZrO ₂ Core The α-Al ₂ O ₃ used in Example 1 was changed to ZrO _2, and the firing temperature after drying the precursor particle dispersion in a dryer at 120 ° C. for 16 hours. Was set to 900 ° C., and the same operation as in Example 1 was performed, and the same evaluation was performed.
The results are shown in Table 1.

<Comparative Example 1>
"Silica fine particle dispersion (average particle diameter 60nm of the silica fine particles)" were mixed and prepared ethanol 12,090g and ethyl orthosilicate 6,363.9g of was a mixture a _1.
Then mixed with ultrapure water 6,120g and 29% aqueous ammonia 444.9G, was mixed solution b _1.
Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed to form spread water.
Then, the spread water was adjusted to 75 ° C. while stirring, and the mixed solution a ₁ and the mixed solution b ₁ were simultaneously added so that the addition was completed in 10 hours each. When the addition is complete, after the liquid temperature was aged by holding 3 hours while the 75 ° C., to adjust the solid content concentration, SiO ₂ solid content concentration of 19 wt%, a dynamic light scattering method (manufactured by Otsuka Electronics Co., Ltd. PAR- 9,646.3 g of a silica fine particle dispersion obtained by dispersing silica fine particles having an average particle diameter of 60 nm measured in III) in a solvent was obtained.

"Silica fine particle dispersion (average particle diameter of the silica fine particles: 108 nm)" were mixed and prepared methanol 2,733.3g and ethyl orthosilicate 1,822.2g of was a mixture a _2.
Then mixed with ultrapure water 1,860.7g and 29% aqueous ammonia 40.6 g, was mixed solution b _2.
Next, 592.1 g of ultrapure water and 1,208.9 g of methanol were mixed, and as spreading water, 922.1 g of a silica fine particle dispersion obtained by dispersing silica fine particles having an average particle diameter of 60 nm obtained in the previous step in a solvent was used. added.
Then, the spread water containing the silica fine particle dispersion was adjusted to 65 ° C. while stirring, and the mixed solution a ₂ and the mixed solution b ₂ were simultaneously added thereto such that the addition was completed in 18 hours, respectively. Was. After completion of the addition, the solution was kept at 65 ° C. for 3 hours for aging, and then the solid content (SiO ₂ solid content) was adjusted to 19% by mass. I got
The silica fine particles contained in the high-purity silica fine particle dispersion had an average particle diameter of 108 nm as measured by a dynamic light scattering method (PAR-III manufactured by Otsuka Electronics Co., Ltd.). In addition, when the ratio of minor axis / major axis of the silica fine particles was measured based on a transmission electron microscope photograph, the minor axis / major axis ratio was 1.0. The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ , SO ₄ and F are determined by ICP (inductively coupled plasma). All were 1 ppm or less when measured using emission spectroscopy.

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 fine particle dispersion (average particle diameter of silica fine particles: 108 nm), and the mixture was stirred for 30 minutes to remove the resin. separated. At this time, the pH was 5.1.
Ultrapure water was added to the obtained silica fine particle dispersion to obtain 6,000 g of A-2 liquid having a SiO ₂ solid content concentration of 3% by mass.

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

Next, the temperature of the solution A-2 (6,000 g) was raised to 50 ° C., and with stirring, CeO ₂ was added to the solution B-2 (8,453 g, 100 parts by mass of SiO ₂ ). (Corresponding to 0.4 parts by mass) over 18 hours. During this time, the liquid temperature was maintained at 50 ° C., and 3% aqueous ammonia was added as needed to maintain the pH at 7.85. During the addition of the solution B-2 and during the aging, the mixture was prepared while blowing air into the mixture, and the oxidation-reduction potential was maintained at a positive value.
When the addition of solution B-2 was completed, the temperature of the solution was raised to 93 ° C and aging was performed for 4 hours. After completion of the ripening, it was allowed to cool by leaving it in a room, and after cooling to room temperature, washing was performed while supplying ion-exchanged water with an ultramembrane. The precursor particle dispersion obtained after the completion of the washing had a solid content concentration of 7% by mass, a pH of 9.1 (at 25 ° C.), and an electric conductivity of 67 μs / cm (at 25 ° C.). .

  Next, a 5% by mass aqueous solution of acetic acid was added to the obtained precursor particle dispersion to adjust the pH to 6.5, followed by drying in a dryer at 100 ° C. for 16 hours, and then using a muffle furnace at 1090 ° C. For 2 hours to obtain a powder.

310 g of the powder obtained after the calcination and 430 g of ion-exchanged water are put into a 1 L beaker with a handle, a 3% aqueous ammonia solution is added thereto, and ultrasonic waves are irradiated for 10 minutes in an ultrasonic bath with stirring, A suspension with a pH of 10 (temperature 25 ° C.) was obtained.
Next, 595 g of quartz beads having a diameter of 0.25 mm were charged into a crusher (LMZ06, manufactured by Ashizawa Finetech Co., Ltd.) which had been previously washed with equipment and operated with water, and the above suspension was charged into a charge tank of the crusher. Filled (filling rate 85%). In consideration of the ion-exchanged water remaining in the pulverizing chamber and the piping of the pulverizer, the concentration at the time of pulverization is 25% by mass. Then, wet pulverization and pulverization were performed under the conditions that the peripheral speed of the disk in the pulverizer was 12 m / sec, the number of passes was 25 times, and the residence time per pass was 0.43 minutes. A 3% aqueous ammonia solution was added to each pass so that the pH of the suspension during crushing and pulverization was maintained at 10. Thus, a silica-based composite fine particle dispersion having a solid content of 22% by mass was obtained.
Next, the obtained fine particle dispersion liquid was subjected to centrifugal separation at a relative centrifugal acceleration of 675 G for 1 minute using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") to remove sedimentation components and to disperse silica-based composite fine particles. A liquid was obtained.

The same evaluation as in Example 1 was performed on the silica-based composite fine particle dispersion thus obtained.
The results are shown in Table 1.

  The ceria-based composite fine particles contained in the dispersion of the present invention have a low scratch and a high polishing rate. Therefore, the abrasive grain dispersion containing the dispersion of the present invention can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate and a wiring substrate. Specifically, it can be preferably used for flattening a semiconductor substrate on which a silica film is formed.

Claims (9)

A ceria-based composite having the following features [1] to [5], including a ceria-based composite fine particle having a minor axis / major axis ratio in a range of 0.2 to 1.0 and an average particle diameter of 50 to 1000 nm. Fine particle dispersion.
[1] The ceria-based composite fine particles include base particles, a cerium-containing coating layer on the surface of the base particles, and child particles dispersed inside the cerium-containing coating layer. A crystalline inorganic oxide is a main component, and the child particles are a crystalline ceria as a main component.
[2] The coefficient of variation (CV value) in the particle size distribution of the child particles is 14 to 60%.
[3] The ceria-based composite fine particles have a mass ratio of a component other than ceria to ceria in the range of 100: 11 to 316.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, a ceria crystal phase and a crystal phase of the crystalline inorganic oxide are detected.
[5] The ceria-based composite fine particles have an average crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.   The ceria-based composite fine particle dispersion according to claim 1, wherein the crystalline inorganic oxide is at least one selected from the group consisting of alumina, titania, and zirconia.   The ceria-based composite fine particle dispersion according to claim 1, wherein the cerium-containing coating layer contains the same element as the base particles and cerium.   The ceria-based composite fine particle dispersion according to any one of claims 1 to 3, wherein the cerium-containing coating layer contains silica.   The ceria-based composite fine particle dispersion according to any one of claims 1 to 4, wherein the base particles have a compressive breaking strength of 1.0 to 3.0 MPa.   A polishing abrasive dispersion containing the ceria-based composite fine particle dispersion according to claim 1.   The polishing abrasive dispersion according to claim 6, which is used for flattening a semiconductor substrate on which a silica film is formed. A method for producing a ceria-based composite fine particle dispersion, comprising the following steps 1 to 3.
Step 1: Stir a crystalline inorganic oxide fine particle dispersion in which a crystalline inorganic oxide fine particle having a minor axis / major axis ratio of 0.1 or more and less than 1.0 is dispersed in a solvent, and adjust the temperature to 0 to 20. While maintaining the pH at 7.0 to 9.0 and the oxidation-reduction potential at 50 to 500 mV, a metal salt of cerium is continuously or intermittently added thereto, and a precursor particle dispersion liquid containing precursor particles is added. The step of obtaining
Step 2: The precursor particle dispersion is dried and fired at 700 to 1,200 ° C., and a solvent is added to the fired body, and the mixture is wet-crushed in a pH range of 8.6 to 10.8. A step of performing a treatment to obtain a fired body disintegrated dispersion.
Step 3: a step of subjecting the crushed dispersion of the fired body to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently removing a settling component to obtain a ceria-based composite fine particle dispersion.   In the step 1, the crystalline inorganic oxide fine particle dispersion is stirred, the temperature is maintained at 0 to 20 ° C., the pH is maintained at 7.0 to 9.0, and the oxidation-reduction potential is maintained at 50 to 500 mV. The method for producing a ceria-based composite fine particle dispersion according to claim 8, wherein the step of adding the metal salt and the component containing silicon continuously or intermittently to obtain the precursor particle dispersion.