JP7020865B2 - Abrasive grain dispersion for polishing containing ceria-based composite fine particle dispersion, its manufacturing method, and ceria-based composite fine particle dispersion. - Google Patents

Description

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

Semiconductor devices such as semiconductor boards and wiring boards have achieved high performance by increasing the density and miniaturization. So-called chemical mechanical polishing (CMP) is applied in the manufacturing process of this semiconductor. Specifically, it is an essential technology for separating shallow trench elements, flattening an interlayer insulating film, and forming contact plugs and Cu damascene wiring. It has become.

Generally, an abrasive for CMP is composed of abrasive grains and a chemical component, and the chemical component plays a role of promoting polishing by oxidizing or corroding the 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, ceria particles show a specifically high polishing rate with respect to the silicon oxide film, and are therefore applied to polishing in the shallow trench element separation step.
In the shallow trench element separation step, not only the silicon oxide film is polished, but also the silicon nitride film is polished. In order to facilitate element separation, 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, and this polishing rate ratio (selection ratio) is also important.

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

For example, in Patent Document 1, an aqueous solution of first cerium nitrate and a base are stirred and mixed at an amount ratio of 5 to 10 and then rapidly heated to 70 to 100 ° C. and aged at that temperature. A method for producing ultrafine particles of cerium oxide (average particle diameter of 10 to 80 nm) made of a cerium oxide single crystal is described, and further, according to this production method, the particle size is highly uniform and the particle shape is high. It is stated that cerium oxide ultrafine particles having high uniformity can be provided.

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

Further, in Patent Document 2, one or more kinds selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanium, and strontium are formed on the surface of the amorphous silica particles A. Described are silica-based composite particles characterized by having a crystalline oxide layer B containing an element. Further, as a preferred embodiment, an amorphous oxide layer containing an element such as aluminum on the surface (of the amorphous silica particles A), which is an amorphous oxide different from the amorphous silica layer. A crystalline oxide having layer C and further containing one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, ittrium, calcium, magnesium, fluorine, lanthanum, and strontium. Silica-based composite particles characterized by having layer B are described. Since such silica-based composite particles have a crystalline oxide layer B on the surface of the amorphous silica particles A, the polishing speed can be improved and the silica particles are pretreated. By doing so, it is possible to suppress the sintering of particles during firing and improve the dispersibility in the abrasive slurry, and further, it is possible to significantly reduce the amount of cerium oxide contained or the amount of cerium oxide used. It is stated that it is possible to provide an abrasive material that is inexpensive and has high polishing performance. Further, it is described that those having an amorphous oxide layer C between the silica-based particles A and the oxide layer B are particularly excellent in the effect of suppressing the sintering of the particles and the effect of improving the polishing rate.

Japanese Patent No. 2,746,861 Japanese Unexamined Patent Publication No. 2013-119131

Sung-Ho Lee, Zhenyu Lu, S.M. V. Babu and Egon Matijevic, "Chemical mechanical polishing of thermal oxide films sillica particles coated with 27 seria", Journal of

However, when the present inventor actually manufactured and examined the cerium oxide ultrafine particles described in Patent Document 1, the polishing speed was low, and further, defects on the surface of the polishing substrate (deterioration of surface accuracy, increase in scratches, It was found that the residual abrasive material on the surface of the polishing substrate) is likely to occur.
This is because the method for producing cerium oxide ultrafine particles described in Patent Document 1 does not include a firing step and is a liquid phase, as compared with a method for producing ceria particles including a firing step (the degree of crystallization of ceria particles is increased by firing). Since the cerium oxide particles are only crystallized from (an aqueous solution containing primary cerium nitrate), the degree of crystallization of the generated cerium oxide particles is relatively low, and since the cerium oxide particles are not fired, the cerium oxide is solidified with the mother particles. The present inventor presumes that the main factor is that cerium oxide remains on the surface of the polished substrate without being attached.

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

Further, when the silica-based composite particles having the oxide layer C described in Patent Document 2 are used for polishing, impurities such as aluminum may remain on the surface of the semiconductor device and adversely affect the semiconductor device. , The present inventor has found.
Further, the ceria particles described in these documents are attached on the mother particles and are not strongly fixed, so that they are easily dropped from the mother particles.
Further, when polishing is performed using abrasive grains in which crystalline ceria particles are formed on the spherical silica mother particles described in Patent Document 2, the silica film is formed by a chemical reaction that occurs at the same time as the mechanical action during polishing of the ceria particles. Although the polishing rate is high, under high pressure conditions, the contact area between the substrate and ceria may decrease due to the ceria crystals falling off, abrasion, or disintegrating, and the polishing rate may decrease.

An object of the present invention is to solve the above problems. That is, the present invention can polish a silica film, a Si wafer, or a difficult-to-process material at high speed, and at the same time, it has high surface accuracy (low scratch, less abrasive residue on the substrate, and improvement of the substrate Ra value. Etc.) and can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring substrates when they can achieve and do not contain impurities. It is an object of the present invention to provide an abrasive grain dispersion liquid for polishing containing.

The present inventor has diligently studied to solve the above problems and completed the present invention.
The present invention is the following (1) to (14).
(1) A ceria-based composite fine particle dispersion liquid containing ceria-based composite fine particles having an average particle diameter of 30 to 1000 nm and having the following characteristics [1] to [5].
[1] The ceria-based composite fine particles have a mother particle, a cerium-containing silica layer on the surface of the mother particle, and child particles dispersed inside the cerium-containing silica layer, and the mother particle is Amorphous silica is the main component, and the child particles are mainly composed of crystalline ceria.
[2] The surface coverage of the child particles in the ceria-based composite fine particles is 40% or more.
[3] The ceria-based composite fine particles have a mass ratio of silica to ceria of 100: 50 to 400.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, only the crystal phase of ceria is detected.
[5] The ceria-based composite fine particles have an average crystallinity diameter of 10 to 50 nm, which is measured by subjecting them to X-ray diffraction.
(2) The ceria-based composite fine particle dispersion liquid according to (1) above, wherein the geometric mean particle diameter of the child particles is 10 to 60 nm.
(3) The ceria-based composite fine particle dispersion liquid according to (1) or (2) above, which further comprises the ceria-based composite fine particles having the following characteristics of [6].
[6] A silicon atom is dissolved in the crystalline ceria contained in the child particles.
(4) Regarding the cerium atom and the silicon atom contained in the child particles, the relationship of R ₁ <R ₂ is satisfied when the cerium-silicon atom distance is R ₁ and the cerium-cerium atom distance is R ₂ . , Cerium-based composite fine particle dispersion liquid according to (3) above.
(5) When cationic colloid titration is performed, the ratio (ΔPCD / V) of the flow potential change amount (ΔPCD) represented by the following formula (1) to the addition amount (V) of the cationic colloid titration solution in the knick. The ceria-based composite fine particle dispersion liquid according to any one of (1) to (4) above, wherein a flow potential curve having a value of -150.0 to -15.0 can be obtained.
ΔPCD / V = (IC) / V ... Equation (1)
C: Flow potential (mV) in the knick
I: Flow potential (mV) at the start point of the flow potential curve
V: Addition amount (ml) of the cationic colloid titration solution in the knick
(6) The ceria-based composite fine particle dispersion liquid according to (5) above, wherein the flow potential before titration is a negative potential when the pH value is in the range of 3 to 8.
(7) The above-mentioned (1) to (6), wherein the number of the ceria-based composite fine particles having coarse particles of 0.98 μm or more is 100 million / cc or less in terms of dryness. Ceria-based composite fine particle dispersion.
(8) The ceria according to any one of (1) to (7) above, wherein the content ratio of impurities contained in the ceria-based composite fine particles is as shown in the following (a) and (b). System composite fine particle dispersion.
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively.
(9) A polishing abrasive grain dispersion liquid containing the ceria-based composite fine particle dispersion liquid according to any one of (1) to (8) above.
(10) The polishing abrasive grain dispersion liquid according to (9) above, wherein the polishing abrasive grain dispersion liquid is for flattening a semiconductor substrate on which a silica film is formed.
(11) A method for producing a ceria-based composite fine particle dispersion, which comprises the following steps 1 to 3.
Step 1: Stir the silica fine particle dispersion liquid in which the silica fine particles are dispersed in the solvent, and maintain the temperature at 0 to 20 ° C., the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV. A step of continuously or intermittently adding a metal salt of hecerium to obtain a precursor particle dispersion liquid containing precursor particles.
Step 2: The precursor particle dispersion is dried, calcined at 800 to 1,200 ° C., a solvent is added to the obtained calcined product, and the mixture is crushed in a wet manner in the range of pH 8.6 to 10.8. A process of processing to obtain a calcined body crushed dispersion.
Step 3: A step of centrifuging the fired body crushed dispersion at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component to obtain a ceria-based composite fine particle dispersion.
(12) In the step 1, the silica 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 redox potential is maintained at 50 to 500 mV. The cerium is added continuously or intermittently, and then the cerium is maintained at a temperature of more than 20 ° C. and 98 ° C. or lower, a pH of 7.0 to 9.0, and a redox potential of 50 to 500 mV. The method for producing a ceria-based composite fine particle dispersion liquid according to (11) above, which is a step of continuously or intermittently adding the metal salt of the above to obtain the precursor particle dispersion liquid.
(13) In the step 1, the silica fine particle dispersion is stirred, and the temperature is maintained at more than 20 ° C. and 98 ° C. or lower, the pH is 7.0 to 9.0, and the oxidation-reduction potential is 50 to 500 mV. The metal salt of the cerium is continuously or intermittently added, and then the cerium is maintained here at a temperature of 0 to 20 ° C., a pH of 7.0 to 9.0, and an oxidation-reduction potential of 50 to 500 mV. The method for producing a ceria-based composite fine particle dispersion liquid according to (11) or (12) above, which is a step of continuously or intermittently adding the metal salt of the above to obtain the precursor particle dispersion liquid.
(14) Described in any one of (11) to (13) above, wherein the content ratio of impurities contained in the silica fine particles in the step 1 is as shown in the following (a) and (b). Method for producing a ceria-based composite fine particle dispersion.
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively.

When a chemical component is added to the ceria-based composite fine particle dispersion of the present invention and used as a polishing slurry, or when the polishing abrasive grain dispersion of the present invention is used as it is as a polishing slurry, the target is a silica film, a Si wafer, or the like. Even a difficult-to-process material containing the above can be polished at high speed, and 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 liquid of the present invention, impurities contained in the ceria-based composite fine particles can be significantly reduced and the purity can be increased. Since 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 does not contain impurities, the surface of semiconductor devices such as semiconductor substrates and wiring boards is polished. Can be preferably used for.
Further, the ceria-based composite fine particle dispersion of the present invention is effective for flattening the surface of a semiconductor device when used as an abrasive grain dispersion for polishing, and is particularly suitable for polishing a substrate on which a silica insulating film is formed. be.

It is a schematic diagram of the cross section of the composite fine particle of this invention. FIG. 2A is an SEM image of the composite fine particles of Example 1, and FIG. 2B is a TEM image of the composite fine particles of Example 2. It is an X-ray diffraction pattern of Example 1. FIG. 4A is an SEM image of the composite fine particles of Example 2, and FIG. 4B is a TEM image of the composite fine particles of Example 2. It is an X-ray diffraction pattern of Example 2. FIG. 6A is an SEM image of the composite fine particles of Comparative Example 3, and FIG. 6B is a TEM image of the composite fine particles of Comparative Example 3. It is a titration diagram of a flow potential.

The present invention will be described.
The present invention is a ceria-based composite fine particle dispersion liquid containing ceria-based composite fine particles having an average particle diameter of 30 to 1000 nm and having the following characteristics [1] to [5].
[1] The ceria-based composite fine particles have a mother particle, a cerium-containing silica layer on the surface of the mother particle, and child particles dispersed inside the cerium-containing silica layer, and the mother particle is Amorphous silica is the main component, and the child particles are mainly composed of crystalline ceria.
[2] The surface coverage of the child particles in the ceria-based composite fine particles is 40% or more.
[3] The ceria-based composite fine particles have a mass ratio of silica to ceria of 100: 50 to 400.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, only the crystal phase of ceria is detected.
[5] The ceria-based composite fine particles have an average crystallinity diameter of 10 to 50 nm, which is measured by subjecting them to X-ray diffraction.

The ceria-based composite fine particles having the characteristics of [1] to [5] and having an average particle diameter of 30 to 1000 nm are hereinafter also referred to as "composite fine particles of the present invention".
Further, the ceria-based composite fine particle dispersion liquid containing the composite fine particles of the present invention is also referred to as "dispersion liquid of the present invention" below.

Further, the present invention is a method for producing a ceria-based composite fine particle dispersion liquid, which comprises the following steps 1 to 3.
Step 1: Stir the silica fine particle dispersion liquid in which the silica fine particles are dispersed in the solvent, and maintain the temperature at 0 to 20 ° C., the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV. A step of continuously or intermittently adding a metal salt of hecerium to obtain a precursor particle dispersion liquid containing precursor particles.
Step 2: The precursor particle dispersion is dried, calcined at 800 to 1,200 ° C., a solvent is added to the obtained calcined product, and the mixture is crushed in a wet manner in the range of pH 8.6 to 10.8. A process of processing to obtain a calcined body crushed dispersion.
Step 3: A step of centrifuging the fired body crushed dispersion at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component to obtain a ceria-based composite fine particle dispersion.
The relative centrifugal acceleration is expressed by the ratio of the gravitational acceleration of the earth as 1G.
Such a manufacturing method is also referred to as "the manufacturing method of the present invention" below.

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

In the following, when the term "invention" is simply used, it means any of the dispersion liquid 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 both schematic views of a cross section of the composite fine particles of the present invention. FIG. 1 (a) is a buried type in which all the child particles are not exposed to the outside, and FIG. 1 (b) is a type in which a part of the child particles is exposed to the outside.
As shown in FIG. 1, the composite fine particles 20 of the present invention include the mother particles 10, the cerium-containing silica layer 12 on the surface of the mother particles 10, and the child particles 14 dispersed inside the cerium-containing silica layer 12. The child particles 14 are present on the mother particle 10 at a high density (inside the cerium-containing silica layer 12) and are coated.
Note that ▲ in FIG. 1 is an example of measurement points X to Z for performing TEM-EDS analysis described later.

The present inventor presumes the mechanism by which the cerium-containing silica layer is formed in the composite fine particles of the present invention and the mechanism by which the child particles are dispersed and exist inside the cerium-containing silica layer as follows. ..
For example, an alkali is added to a silica sol obtained by adding ammonia to tetraethyl orthosilicate (Si (OC _{2H 5 ) 4} ) and hydrolyzing and decomposing it while adding a solution of a salt containing cerium. To neutralize the solution of the salt containing cerium while maintaining the redox potential of the formulation at 50 to 500 mV and the reaction temperature at 0 to 20 ° C. Then, cerium hydroxide, cerium compound, etc. are attached to the surface of the fine particles (silica fine particles) of the silica sol, and the surface of the silica fine particles reacts with the cerium hydroxide or the cerium compound, via cerium hydroxide, cerium compound, and silicic acid. As an example, a layer containing CeO ₂ , SiO ₂ , SiOH and CeO ₂ ultrafine particles (particle size is 2.5 nm or more and less than 10 nm) (hereinafter, also referred to as “CeO ₂ ultrafine particle-containing layer”, CeO ₂ ultrafine particles and cerium silicate). A layer consisting of layers) is formed on the outside of the silica fine particles. It is presumed that the CeO ₂ ultrafine particle-containing layer was formed by reacting with cerium hydroxide or a cerium compound to dissolve the surface of the silica fine particles and then solidifying the surface due to the influence of oxygen or the like. When such a reaction proceeds, a CeO ₂ ultrafine particle-containing layer is formed.
Then, when it is dried and fired at about 1,000 ° C., the CeO ₂ ultrafine particles having a particle size of 2.5 nm or more existing inside the formed CeO ₂ ultrafine particle-containing layer are formed in the cerium silicate layer. The cerium atom existing in the cerium atom is taken in to grow the particle size, and as a result, cerium that cannot be completely diffused with silica remains in the cerium silicate layer. Finally, the crystalline ceria particles are grown to a particle size of about 10 to 20 nm by firing. Therefore, the crystalline ceria particles exist in a state of being dispersed in the cerium-containing silica layer and in a state of being coated with the mother particles at a high density. That is, since the periphery of the ceria crystal is covered (dispersed) with the Ce-containing silica layer, the ceria crystal becomes a single crystal having no grain boundary. Further, cerium atoms that could not be completely formed into crystalline ceria particles remain in the layer.

When the reaction temperature exceeds 20 ° C. and the redox potential is kept within a predetermined range, the reactivity between cerium hydroxide and the like and the silica fine particles increases, the elution amount of the silica fine particles remarkably increases, and the elution amount of the silica fine particles remarkably increases. For example, the particle size of the silica fine particles after preparation is reduced by about 1/2, and the volume is reduced by 80 to 90%. The dissolved silica is contained in the CeO ₂ ultrafine particle-containing layer, and in the case of the above example, the composition of the CeO ₂ ultrafine particle-containing layer is that the silica concentration is about 40%, the ceria concentration is about 60%, and the CeO ₂ ultrafine particle content is contained. The proportion of silica in the layer increases. Then, when the cerium particles are crystal-grown to 10 to 25 nm by firing, the cerium atoms separated from the cerium silicate layer are deposited and grown on the cerium particles, and the silica resulting from the diffusion of the cerium atoms is ceria. The particles will be coated, and the ceria particles will be adhered to the silica fine particles, and the ceria particles will be covered with the silica film.
When the redox potential is not maintained within a predetermined range, the formation of highly reactive cerium hydroxide or the like is suppressed, or the dissolution of silica fine particles is suppressed, so that ceria or cerium hydroxide is deposited on the silica fine particles. However, the cerium silicate layer is difficult to form. In such a case, even if the ceria is crystal-grown to 10 to 20 nm by firing, the ceria particles easily fall off during polishing because there is no cerium-containing silica layer or silica layer for immobilizing the ceria particles.

In the schematic diagram of FIG. 1, the mother particle 10, the cerium-containing silica layer 12, and the child particles 14 are clearly distinguished for easy understanding, but the composite fine particles of the present invention are formed by the above mechanism. In reality, they exist as one, and the mother particle 10, the cerium-containing silica layer 12, and the child particles 14 are clearly defined except for the contrast or EDS analysis in the STEM / SEM image. It is difficult to distinguish between.
However, when the cross section of the composite fine particles of the present invention is subjected to STEM-EDS analysis and the element concentrations of Ce and Si are measured, it can be confirmed that the structure is as shown in FIG.
That is, EDS analysis is performed by selectively irradiating a spot specified by a scanning transmission electron microscope (STEM) with an electron beam, and the elements of Ce and Si at the measurement point X of the cross section of the composite fine particles of the present invention shown in FIG. When the concentration is measured, the ratio (percentage) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration (Ce / (Ce + Si) × 100) is less than 3%. Further, when the elemental concentrations of Ce and Si at the measurement point Z were measured, the ratio (percentage) (Ce / (Ce + Si) × 100) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration was more than 50%. Become. Then, when the elemental concentrations of Ce and Si at the measurement point Y are measured, the ratio (percentage) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration (Ce / (Ce + Si) × 100) is 3 to 50%. Will be.
Therefore, in the element map obtained by STEM-EDS analysis, the mother particles 10 and the cerium-containing silica layer 12 in the composite fine particles of the present invention are the ratio of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration ( It can be distinguished by the line where the percentage) (Ce / (Ce + Si) × 100) is 3%. Further, in the element map obtained by STEM-EDS analysis, the cerium-containing silica layer 12 and the child particles 14 in the composite fine particles of the present invention are the ratio of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration ( It can be distinguished by the line where the percentage) (Ce / (Ce + Si) × 100) is 50%.

In the present specification, the STEM-EDS analysis shall be performed by observing at 800,000 times.

Since the composite fine particles of the present invention have the embodiment shown in FIG. 1, when STEM-EDS analysis is performed on the cross section and element mapping is performed, the mother particles (mainly amorphous silica) from the outermost shell to the center are obtained. On the way to the component), it has at least one layer (consisting of ceria fine particles) having a relatively high concentration of ceria.

<Mother particle>
The mother particle will be described.
As described above, when the composite fine particles of the present invention are subjected to STEM-EDS analysis and the elemental concentrations of Ce and Si in the cross section of the composite fine particles of the present invention shown in FIG. 1 are measured, the mother particles have a Ce molar concentration. It is a portion where the ratio (percentage) (Ce / (Ce + Si) × 100) of the Ce molar concentration to the total with the Si molar concentration is less than 3%.

Since the average particle size of the composite fine particles of the present invention is in the range of 30 to 1000 nm, the upper limit of the average particle size of the mother particles is inevitably smaller than 1000 nm. In the present application, the average particle size of the mother particles is the same as the average particle size of the silica fine particles contained in the silica fine particle dispersion used in step 1 included in the production method of the present invention described later. The composite fine particles of the present invention in which the average particle size of the mother particles is in the range of 30 to 980 nm are preferably used.
When the dispersion liquid of the present invention obtained by using the mother particles having an average particle diameter in the range of 30 to 980 nm as a raw material is used as an abrasive, the generation of scratches due to polishing is reduced. When the average particle size of the mother particles is less than 30 nm, the polishing rate tends not to reach a practical level when a dispersion obtained by using such mother particles is used as an abrasive. Further, when the average particle diameter of the mother particles exceeds 980 nm, the polishing rate also tends to not reach a practical level, which tends to reduce the surface accuracy of the substrate to be polished. The mother particles are more preferably those showing monodispersity.

The average particle size of the mother particle shall be measured as follows.
First, observe at 800,000 times by STEM-EDS analysis, and identify the line where the ratio (percentage) (Ce / (Ce + Si) x 100) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration is 3%. By doing so, the mother particle is identified. Next, the maximum diameter of the mother particle is set as the major axis, the length is measured, and the value is defined as the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the particle diameter of the mother particle.
In this way, the particle diameters of 50 mother particles are measured, and the value obtained by simple averaging them is taken as the average particle diameter.

The shape of the mother particle is not particularly limited, and is, for example, spherical, bale-shaped, short-fibrous, cocoon-shaped, tetrahedral-shaped (trigonal pyramidal-shaped), hexahedral, octahedral, plate-shaped, amorphous, porous, etc. It may be okoshi-like, gold-flat sugar-like, or raspberry-like (a state in which protrusions or granular parts are scattered on the surface of spherical particles or substantially spherical particles).

The mother particle may be spherical. The spherical shape means that the particle number ratio of the above-mentioned minor axis (DS) / major axis (DL) ratio of 0.8 or less is 10% or less with respect to the total number of particles. Here, the particle number ratio is a value obtained by measuring 50 mother particles. For example, when the minor axis / major axis ratio is obtained for 50 particles and the number of particles having a minor axis / major axis ratio of 0.8 or less is 4, the particle number ratio (%) is 0.8 or less. ) Is calculated to be 8%, so that the particle is judged to be a spherical particle.
The mother particles have a minor axis / major axis ratio of 0.8 or less and a particle number ratio of 5% or less, more preferably 0% or less.

The mother particles are mainly composed of amorphous silica and are usually silica fine particles. Silica fine particles that are spherical and have the same particle size can be easily prepared, and those having various particle sizes can be prepared, so that they can be preferably used.

It can be confirmed, for example, that the mother particle contains amorphous silica as a main component by the following method.
After the dispersion liquid of the present invention or the dispersion liquid containing the composite fine particles of the present invention is dried, it is pulverized using a dairy pot, and X is X-rayed by, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). When a linear diffraction pattern is obtained, the peak of crystalline silica such as Cristobalite does not appear. From this, it can be confirmed that the mother particles contain amorphous silica as a main component. Further, in such a case, it is assumed that the mother particles contain amorphous silica as a main component.
Further, the dispersion liquid of the present invention is dried, embedded in a resin, and then sputter coated with Pt to prepare a cross-sectional sample using a conventionally known focused ion beam (FIB) device. For example, when an FFT pattern is obtained by using a conventionally known TEM device for a prepared cross-sectional sample and using a fast Fourier transform (FFT) analysis, a diffraction pattern of crystalline silica such as Cristobalite does not appear. From this, it can be confirmed that the mother particles contain amorphous silica as a main component. Further, in such a case, it is assumed that the mother particles contain amorphous silica as a main component.
Another method is to observe the presence or absence of lattice fringes due to the atomic arrangement of the mother particles by using a conventionally known TEM analysis for the cross-sectional sample similarly prepared. If it is crystalline, plaids corresponding to the crystal structure are observed, and if it is amorphous, no plaids are observed. From this, it can be confirmed that the mother particles contain amorphous silica as a main component. Further, in such a case, it is assumed that the mother particles contain amorphous silica as a main component.

The mother particle contains amorphous silica as a main component, and may contain other substances such as La, Ce, and Zr in an amount of 10% by mass or less, and may contain crystalline silica or an impurity element.
For example, the mother particles contain elements of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn (hereinafter, may be referred to as “specific impurity group 1”). The ratio is preferably 100 ppm or less. Further, it is preferably 50 ppm or less, more preferably 25 ppm or less, further preferably 5 ppm or less, and even more preferably 1 ppm or less.
Further, the content of each element of U, Th, Cl, NO ₃ , SO ₄ and F (hereinafter, may be referred to as “specific impurity group 2”) in the mother particles is preferably 5 ppm or less. ..

Here, the content of the specific impurity group 1 or the specific impurity group 2 in the mother particles (silica fine particles) and the composite fine particles of the present invention described later means the content with respect to the dry amount.
The content rate with respect to the dry amount is the ratio of the weight of the object to be measured (specific impurity group 1 or specific impurity group 2) to the mass of the solid content contained in the object (mother particles (silica fine particles) or the composite fine particles of the present invention). It shall mean the value of (percentage). The impure content of the mother particles is almost the same as the impure content of the silica-based fine particles if there is no contamination due to contamination or the like.

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

In the present invention, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, U, Th, Cl, NO ₃ , SO ₄ and F are contained in the mother particles. The rate shall be a value obtained by measuring using the following methods.
-Na and K: Atomic absorption spectroscopic analysis-Ag, Al, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, U and Th: ICP-MS (inductively coupled plasma emission spectroscopic mass spectrometry)
・ Cl: Potentiometric titration method ・ NO ₃ , SO ₄ and F: Ion chromatograph

<Child particles>
As described above, when STEM-EDS analysis was performed on the composite fine particles of the present invention and the elemental concentrations of Ce and Si in the cross section of the composite fine particles of the present invention shown in FIG. 1 were measured, the child particles had a Ce molar concentration and Si. This is the portion where the ratio (percentage) (Ce / (Ce + Si) × 100) of the Ce molar concentration to the total with the molar concentration is more than 50%.

The child particles containing crystalline ceria as a main component in the present invention (hereinafter, also referred to as “ceria child particles”) are dispersed at a high density in the cerium-containing silica layer arranged on the mother particles, and the child particles are dispersed. The surface coverage of the composite fine particles of the present invention is 40% or more. That is, the coverage of the child particles in the composite fine particles of the present invention is high. When the dispersion of the present invention having the ceria particles whose surface is coated with such a high coverage is used as the abrasive grain dispersion for polishing, the surface of the composite fine particles of the present invention is covered with the ceria particles at a high coverage. Since it is coated, the contact area between the child particles and the substrate to be polished can be kept high. Therefore, a high polishing rate can be efficiently obtained. Furthermore, since the number of ceria particles that come into contact with the substrate increases, the load applied to one ceria particle becomes smaller, and the depth of pushing into the polishing substrate becomes shallower, so that scratches are less likely to occur and the surface roughness of the polishing substrate is rough. A smooth polished surface with a small particle size can be obtained.
Further, the child particles are not particularly limited as long as the surface coverage of the composite fine particles of the present invention is 40% or more, but the child particles may be bonded to each other, and the child particles are in an independent island shape. However, it may be a mixture of these. In order to keep the surface coverage high, it is desirable that the child particles are bonded to each other. Further, the bonding between the child particles may be an agglomerate of a single crystal via a different phase or a polycrystal having a grain boundary, but from the mechanism for producing composite fine particles of the present invention, the bonding is via a different phase. It is presumed to be an aggregate of single crystals.
Further, the child particles may be coated with a single layer or may be coated with a multilayer. When coated with multiple layers, even if the ceria particles in the first layer are worn or dropped during polishing, the polishing is performed with the child particles in the second and subsequent layers, so the ceria particles must be coated in multiple layers. Is desirable.

In the present invention, the surface coverage of the child particles dispersed in the cerium-containing silica layer in the composite fine particles of the present invention is preferably 40% or more, more preferably 50%, and 55%. The above is more preferable, and 60% or more is most preferable.
This is because when the surface coverage is less than 40%, the contact area between the substrate and the ceria particles is not sufficiently high, so that the polishing rate is lowered.

In the present invention, the surface coverage of the child particles in the composite fine particles of the present invention shall be measured as follows.
First, the line was observed at 800,000 times by STEM-EDS analysis, and the line where the ratio (percentage) (Ce / (Ce + Si) x 100) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration was 50% was specified. By doing so, the child particles are identified.
Next, the projected area of the specified child particles is calculated by image analysis. Further, the projected area of the composite fine particles of the present invention is also calculated, and the projected area of the child particles is divided by the projected area of the composite fine particles of the present invention and multiplied by 100 to cover the surface of the ceria child particles in one composite fine particle of the present invention. The rate is calculated.
(Surface coverage (%) = projected area of child particles / projected area of composite fine particles of the present invention x 100)
Similarly, the surface coverage of 20 or more composite fine particles of the present invention is measured, and the average number thereof is taken as the surface coverage of the composite fine particles of the present invention.

The geometric mean particle diameter of the child particles is preferably 10 to 60 nm, more preferably 10 to 50 nm, and even more preferably 12 to 40 nm.
When the geometric mean particle diameter of the child particles exceeds 50 nm, the precursor particles having such ceria child particles tend to be sintered or condensed after firing and difficult to be crushed in step 2. Such a ceria-based composite fine particle dispersion is not preferable because it causes scratches on the object to be polished even if it is used for polishing. When the geometric mean particle diameter of the child particles is less than 10 nm, it tends to be difficult to obtain a practically sufficient polishing rate when the particles are also used for polishing.

In the present invention, the geometric mean particle diameter of the child particles shall be measured as follows.
First, the line was observed at 800,000 times by STEM-EDS analysis, and the line where the ratio (percentage) (Ce / (Ce + Si) x 100) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration was 50% was specified. By doing so, the child particles are identified. Next, the maximum diameter of the mother particle on the image obtained by STEM-EDS analysis is set as the major axis, the length is measured, and the value is defined as the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the geometric mean particle diameter of the child particles.
In this way, the particle size of 100 or more child particles can be measured, and the number average value thereof can be obtained.
In the present invention, the geometric mean particle diameter of the child particles means the number average diameter in the particle size distribution obtained as described above.

The ceria particles are preferably single crystals, but may be aggregates of single crystals (that is, aggregates in which different phases are present between ceria crystals). This is because, in the crushing step, in the case of a polycrystal, the crystal is damaged because it is destroyed from the grain boundaries, but in the case of a single crystal aggregate, it is destroyed from a different phase, so that the crystal is less likely to be damaged. Because. If the crystals are not damaged, the polishing speed tends to be less likely to decrease during polishing.
The single crystal can be confirmed by showing a numerical value in which the average crystallite diameter obtained by X-ray diffraction and the geometric mean diameter measured by STEM substantially match. Further, although polycrystals (aggregates in which no different phase exists between ceria crystals) may be contained in a part, the composite fine particles of the present invention are considered to be aggregates via different phases from the mechanism.

The child particles may be laminated. That is, a plurality of cerium-containing silica layers may be present on a radial line from the center of the mother particles.
Further, the child particles may be buried in the cerium-containing silica layer or may be partially exposed to the outside of the cerium-containing silica layer, but when the child particles are buried in the cerium-containing silica layer, the child particles may be buried in the cerium-containing silica layer. Since the surface of the composite fine particles of the present invention is closer to the silica surface, storage stability and polishing stability are improved, and since the amount of abrasive particles remaining on the substrate after polishing is reduced, the child particles are a cerium-containing silica layer. It is desirable to be buried in.

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

The child particles dispersed in the cerium-containing silica layer arranged on the surface of the mother particles may be in a monodispersed state as long as the surface coverage of the composite fine particles of the present invention is within a predetermined range. May be in a laminated state (that is, a state in which a plurality of child particles are stacked and exist in the thickness direction of the cerium-containing silica layer), or a state in which a plurality of child particles are connected may be used.

In the present invention, the child particles contain crystalline ceria as a main component.
The fact that the child particles contain crystalline ceria as a main component is, for example, that the dispersion liquid of the present invention is dried and then the obtained solid substance is pulverized using a mortar, for example, a conventionally known X-ray diffractometer ( For example, it can be confirmed by X-ray analysis using RINT1400) manufactured by Rigaku Denki Co., Ltd., and only the crystal phase of ceria is detected in the obtained X-ray diffraction pattern. In such a case, it is assumed that the child particles contain crystalline ceria as a main component. The crystal phase of ceria is not particularly limited, and examples thereof include Ceriaite and the like.

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

The average crystallite diameter of the ceria particle is calculated using the full width at half maximum of the maximum peak appearing in the chart obtained by subjecting the composite fine particles of the present invention to X-ray diffraction. Then, for example, the average crystallite diameter of the (111) plane is 10 to 50 nm (full width at half maximum is 0.86 to 0.17 °) and 12 to 30 nm (full width at half maximum is 0.72 to 0.28 °). It is preferably 14 to 25 nm (half width is 0.62 to 0.34), and more preferably. In many cases, the intensity of the peak of the (111) plane is the maximum, but the intensity of the peak of another crystal plane, for example, the (100) plane may be the maximum. In that case, the calculation can be performed in the same manner, and the size of the average crystallite diameter in that case may be the same as the average crystallite diameter of the (111) plane described above.

The method for measuring the average crystallite diameter of the child particles is shown below by taking the case of the (111) plane (near 2θ = 28 degrees) as an example.
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained, for example, by 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 angstrom, Cu lamp)
β: Full width at half maximum (rad)
θ: Reflection angle

The composite fine particles of the present invention preferably have a silicon atom dissolved in crystalline ceria, which is the main component of the child particles. In general, solid solution means that two or more kinds of elements (which may be metal or non-metal) are dissolved in each other to form a uniform solid solution as a whole, and a solid solution obtained by solid solution is , It is classified into a substitution type solid solution and an intrusive type solid solution. Substituted solid solutions can easily occur in atoms with similar atomic radii, but since Ce and Si have significantly different atomic radii, at least substituted solid solutions are unlikely to occur. Further, in the crystal structure of Cerianite, the coordination number of Ce seen from the center of Ce is 8, but for example, when Si is replaced with Ce on a one-to-one basis, the coordination number of Ce should be 7. However, in the analysis result of the preferred embodiment of the composite fine particles of the present invention, the average coordination number of Ce seen from the center of Ce is 8.0, and the average coordination number of Si is 1.2. It is presumed that the preferred embodiment of the composite fine particles is the invasive type. Moreover, from the analysis results of the preferred embodiments of the composite fine particles of the present invention, the interatomic distance of the adjacent Ce—Si is smaller than the interatomic distance of the adjacent Ce—Ce. Is presumed to be an intrusive solid solution. That is, it is preferable that the relationship of R ₁ <R ₂ is satisfied when the cerium-silicon atom distance is R ₁ and the cerium-cerium atom distance is R ₂ for the cerium atom and the silicon atom contained in the child particles. ..
Conventionally, it is known that when a substrate with a silica film or a glass substrate is polished using ceria particles as abrasive particles, a specifically higher polishing rate is exhibited as compared with the case where other inorganic oxide particles are used. .. One of the reasons why the ceria particles show a particularly high polishing rate with respect to the substrate with a silica film is that the trivalent cerium contained in the ceria particles has a high chemical reactivity with the silica film on the substrate to be polished. It has been pointed out. Cerium in cerium oxide can have trivalent and tetravalent valences, but when calcined at a high temperature exceeding 700 ° C, it tends to become tetravalent cerium oxide, and even if it contains trivalent cerium, its content. Is not enough.
In a preferred embodiment of the composite fine particles of the present invention, it is considered that Si atoms are infiltrated into the CeO ₂ crystal in the child particles (ceria fine particles) existing on the outer surface side thereof. Due to the solid dissolution of Si atoms, crystal strain of CeO ₂ crystals occurs, so that oxygen defects increase even when fired at _high temperature, and a large amount of trivalent cerium chemically active with respect to SiO ₂ is generated. As a result of promoting chemical reactivity, it is presumed that the above-mentioned high polishing rate is exhibited. The content of trivalent cerium with respect to the total number of moles of cerium is preferably 5 to 30%, more preferably 10 to 25%.
The interatomic distances of cerium atoms, silicon atoms, and oxygen atoms such as R ₁ and R ₂ described above mean the average interatomic distances obtained by measuring by the method described in Examples described later. ..
Further, as the element that is solid-solved in the ceria child particles, La, Al, Zr or the like may be solid-dissolved in addition to the silicon atom. This is because the solid solution of these elements increases the trivalent cerium content.

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

By adopting such a structure, it is difficult for the child particles to fall off due to the crushing process at the time of manufacturing or the pressure at the time of polishing, and even if some of the child particles are missing, many of the child particles can be dropped. Since it is present in the cerium-containing silica layer, it does not deteriorate the polishing function.

As described above, when STEM-EDS analysis was performed on the composite fine particles of the present invention and the element concentrations of Ce and Si in the cross section of the composite fine particles of the present invention shown in FIG. 1 were measured, the cerium-containing silica layer had a Ce molar concentration. This is the portion where the ratio (percentage) (Ce / (Ce + Si) × 100) of the Ce molar concentration to the total of the Si molar concentration is 3 to 50%.

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

The average thickness of the cerium-containing silica layer is preferably 10 to 70 nm, more preferably 12 to 35 nm.
The average thickness of the cerium-containing silica layer can be obtained by drawing a straight line at any 12 points from the center of the mother particle of the composite fine particles of the present invention to the outermost shell and performing STEM-EDS analysis as described above. The line in which the ratio (percentage) (Ce / (Ce + Si) × 100) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration specified from the elemental map is 3%, and the most of the composite fine particles of the present invention. The distance to the outer shell (distance on the line passing through the center of the mother particle) is measured, and they are simply averaged to obtain the distance. The center of the mother particle is assumed to mean the intersection of the long axis and the short axis described above.

It is considered that the cerium-containing silica layer in the composite fine particles of the present invention promotes the bonding force between the child particles (ceria fine particles containing crystalline ceria as a main component) and the mother particles dispersed and grown in the cerium-containing silica layer during the firing process. .. Therefore, for example, in the step of obtaining the dispersion liquid of the present invention, if necessary, the fired body crushed dispersion obtained by firing is pre-crushed by a dry method, then crushed by a wet method, and further. A ceria-based composite fine particle dispersion can be obtained by performing the centrifugation treatment, and it is considered that the cerium-containing silica layer has an effect of preventing the child particles from coming off from the mother particles. In this case, there is no problem in local shedding 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 silica layer. It suffices if the child particles are strong enough not to be separated from the mother particles in the crushing process.
Due to such a structure, when the dispersion liquid of the present invention is used as an abrasive, it is considered that the polishing speed is high and the surface accuracy and scratches are not deteriorated.

Further, since at least a part of the surface of the child particles of the composite fine particles of the present invention is usually covered with a cerium-containing silica layer, the outermost surface (outermost shell) of the composite fine particles of the present invention has a —OH group of silica. Will exist. Therefore, when used as an abrasive, the composite fine particles of the present invention are considered to repel each other due to the electric charge of the −OH group on the surface of the polishing substrate, and as a result, the adhesion to the surface of the polishing substrate is reduced.

In general, ceria has a different potential from silica, a polishing substrate, and a polishing pad, and the negative zeta potential decreases as the pH shifts from alkaline to near neutral, and the opposite positive potential in the weakly acidic region. have. Therefore, in the acidic pH at the time of polishing, ceria adheres to the polishing base material or the polishing pad due to the difference in the magnitude of the potential or the difference in the polarity, and tends to remain on the polishing base material or the polishing pad. On the other hand, since silica is usually present in the outermost shell of the composite fine particles of the present invention as described above, the potential becomes a negative charge due to silica, so that the pH maintains a negative potential from alkaline to acidic. However, as a result, it is difficult for abrasive grains to remain on the polishing substrate or the polishing pad. When crushing while maintaining the pH of 8.6 to 10.8 during the crushing process of step 2 in the production method of the present invention, a part of silica (silica in the cerium-containing silica layer) on the surface of the composite fine particles is dissolved. If the dispersion liquid of the present invention produced under the above conditions is adjusted to pH <7 when applied to a polishing application, the dissolved silica is deposited on the composite fine particles (abrasive particles) of the present invention. The surface will have a negative potential. If the potential is low, silicic acid may be added to appropriately reinforce the cerium-containing silica layer.
In order to adjust the potential of the child particles, it is possible to adjust the potential with a polymer organic substance such as polyacrylic acid, but in the present invention, the silica softly attached to the surface adjusts the potential, so that the use of organic substances is reduced. , Defects caused by organic substances (residue of organic substances, etc.) on the substrate are unlikely to occur.

In the dispersion liquid of the present invention, there are various aspects in which silica is present, and the composite fine particles of the present invention are not formed, and are dispersed or dissolved in a solvent or adhered to the surface of the composite fine particles of the present invention. It may exist in the state of being used.

<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 are [1] the ceria-based composite fine particles are dispersed inside the mother particles, the cerium-containing silica layer on the surface of the mother particles, and the cerium-containing silica layer. The mother particles are mainly composed of amorphous silica, the child particles are mainly composed of crystalline ceria, and [2] the surface coverage of the child particles in the ceria-based composite fine particles is 40. % Or more, [4] when the ceria-based composite fine particles are subjected to X-ray diffraction, only the crystal phase of ceria is detected, and [5] the ceria-based composite fine particles are measured by being subjected to X-ray diffraction. , The average crystallite diameter of the crystalline ceria is 10 to 50 nm.
Further, the composite fine particles of the present invention further include [3] the ceria-based composite fine particles having a mass ratio of silica and ceria of 100: 50 to 400, and ceria having an average particle diameter of 30 to 1000 nm. It is a system composite fine particle.

In the composite fine particles of the present invention, the mass ratio of silica (SiO ₂ ) to ceria (CeO ₂ ) is 100: 50 to 400, preferably 100: 70 to 350, and preferably 100: 100 to 330. Is more preferable, and 100: 110 to 300 is even more preferable. The mass ratio of silica and ceria is considered to be approximately the same as the mass ratio of mother particles and child particles. If the amount of child particles is too small with respect to the mother particles, the mother particles may be bonded to each other to generate coarse particles. In this case, the polishing agent (polishing slurry) containing the dispersion liquid of the present invention may cause defects (decrease in surface accuracy such as increase in scratches) on the surface of the polishing base material. Moreover, if the amount of ceria for silica is too large, not only the cost becomes high, but also the resource risk increases. Further, the fusion of the particles progresses. As a result, the roughness of the surface of the substrate increases (deterioration of the surface roughness Ra), scratches increase, free ceria remains on the substrate, and the polishing equipment adheres to the waste liquid piping, etc. Easy to get along with.
The silica that is the target for calculating the mass ratio of the silica (SiO ₂ ) and the ceria (CeO ₂ ) means all the silica (SiO ₂ ) contained in the composite fine particles of the present invention. Therefore, it means the total amount of the silica component constituting the mother particle, the silica component contained in the cerium-containing silica layer arranged on the surface of the mother particle, and the silica component that can be contained in the child particles.

The content (% by mass) of silica (SiO ₂ ) and ceria (CeO ₂ ) in the composite fine particles of the present invention is first determined by weighing the solid content concentration of the dispersion liquid of the present invention by burning at 1000 ° C.
Next, the content (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 converted into an oxide mass% (CeO ₂ % by mass, etc.). Then, it is possible to calculate SiO ₂ mass%, assuming that the component other than CeO ₂ constituting the composite fine particles of the present invention is SiO ₂ .
In the production method of the present invention, the mass ratio of silica and ceria can also be calculated from the amount of the silica source substance and the ceria source substance used when preparing the dispersion liquid of the present invention. This can be applied when the process is not such that ceria or silica is dissolved and removed, in which case the amount of ceria or silica used and the analytical value show good agreement.

In the composite fine particles of the present invention, a cerium-containing silica layer is formed on the surface of the mother particles and is firmly bonded, and particulate crystalline ceria (child particles) are dispersed in the cerium-containing silica layer. Has a surface shape of.

The composite fine particles of the present invention may be either a "particle-connected type" or a "monodisperse type", but since the contact area with the substrate can be kept high and the polishing speed is high, the particle-connected type is used. Is desirable. The particle connection type is a type in which two or more mother particles are partially bonded to each other, and the connection is preferably 3 or less. It is considered that the mother particles are firmly bonded to each other by having a history in which at least one (preferably both) is welded at their contact point or solidified by the intervention of ceria. Here, there is a case where a cerium-containing silica layer is formed on the surface of the mother particles after they are bonded to each other, and a case where a cerium-containing silica layer is formed on the surface of the mother particles and then bonded to another particle. However, it is a particle-connected type.
In the case of the connected type, a large contact area with the substrate can be taken, so that polishing energy can be efficiently transmitted to the substrate. Therefore, the polishing speed is high.

The composite fine particles of the present invention are of a particle-connected type, and the number ratio of particles having a minor axis / major axis ratio of less than 0.80 (preferably 0.67 or less) measured by an image analysis method is 45%. The above is preferable.
Here, the particles having a minor axis / major axis ratio of less than 0.80 measured by the image analysis method are considered to be of the particle connection type.
The shape of the composite fine particles of the present invention is not particularly limited, and may be particle-connected particles or single particles (non-connected particles), and is usually a mixture of both.
Here, when the dispersion liquid of the present invention containing the composite fine particles of the present invention is used for polishing and the improvement of the polishing rate for the substrate to be polished is emphasized, the measurement is performed by the image analysis method of the composite fine particles of the present invention. The number ratio of the particles having a minor axis / major axis ratio of less than 0.80 (preferably 0.67 or less) is preferably 45% or more (more preferably 51% or more).
Similarly, when it is important that the surface roughness on the substrate to be polished is at a low level, the minor axis / major axis ratio measured by the image analysis method of the composite fine particles of the present invention is 0.80 or more (preferably 0). The number ratio of the particles of (0.9 or more) is preferably 40% or more, more preferably 51% or more.
The particle-connected particles mean particles (condensed particles) in which chemical bonds that cannot be redispersed are generated between the particles and the particles are connected. Further, the single particle means a particle in which a plurality of particles are not connected and is not aggregated regardless of the morphology of the particles.
The following aspect 1 can be mentioned as the composite fine particle dispersion liquid of the present invention in the case where the improvement of the polishing rate for the substrate to be polished is emphasized.
[Aspect 1] The present invention is characterized in that the composite fine particles of the present invention further have a number ratio of particles having a minor axis / major axis ratio of less than 0.8 as measured by an image analysis method of 45% or more. Dispersion solution.
Further, as the composite fine particle dispersion liquid of the present invention in the case where it is important that the surface roughness on the substrate to be polished is at a low level, the following aspect 2 can be mentioned.
[Aspect 2] The present invention is characterized in that the composite fine particles of the present invention further have a number ratio of particles having a minor axis / major axis ratio of 0.8 or more as measured by an image analysis method of 40% or more. Dispersion solution.

The method of measuring the minor axis / major axis ratio by the image analysis method will be described. In a photographic projection drawing obtained by taking a photograph of the composite fine particles of the present invention at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope, the maximum diameter of the particles is set as the major axis, and the length thereof is measured. , Let the value be the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). From this, the minor axis / major axis ratio (DS / DL) is obtained. Then, in any 50 particles observed in the photographic projection drawing, the number ratio (%) of the particles having a minor axis / major axis ratio of less than 0.80 and 0.80 or less is obtained.

The composite fine particles of the present invention are more preferably of the above-mentioned particle connection type, but may contain other shapes such as spherical particles.

The number of coarse particles of 0.98 μm or more that can be contained in the composite fine particle dispersion liquid of the present invention is preferably 100 million particles / cc or less in terms of dryness. The number of coarse particles is preferably 100 million particles / cc or less, more preferably 80 million particles / cc or less, and most preferably 60 million particles / cc. Coarse particles of 0.98 μm or more may cause polishing scratches and further deteriorate the surface roughness of the polishing substrate. Normally, when the polishing speed is high, the polishing speed is high, but on the other hand, 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-connected type, a high polishing rate can be obtained, while when the number of coarse particles of 0.98 μm or more is 100 million / cc or less, there are few polishing scratches and the surface surface. Roughness can be kept low.

The method for measuring the number of coarse particles that can be contained in the composite fine particle dispersion liquid of the present invention is as follows.
After diluting and adjusting the sample to 0.1% by mass with pure water, 5 ml is collected and injected into a conventionally known coarse particle number measuring device. Then, the number of coarse particles of 0.98 μm or more is obtained. This measurement is performed three times to obtain a simple average value, and the value is multiplied by 1000 to obtain a value having a coarse particle number of 0.98 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 6 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 placed in 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. Keep the liquid nitrogen temperature in the air stream and allow nitrogen to equilibrate and adsorb to the sample. Next, the temperature of the sample is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that period is detected, and the specific surface area of the sample is measured by a calibration curve prepared in advance.
Such a BET specific surface area measuring method (nitrogen adsorption method) can be performed, for example, by using a conventionally known surface area measuring device.
In the present invention, the specific surface area means a value obtained by measuring by such a method unless otherwise specified.

The average particle size of the composite fine particles of the present invention is preferably 30 to 1000 nm, more preferably 50 to 700 nm.
When the average particle size of the composite fine particles of the present invention is in the range of 30 to 1000 nm, the polishing rate becomes high when applied as an abrasive, which is preferable.
The average particle size of the composite fine particles of the present invention means the number average value of the average particle size measured by the image analysis method.
The method of measuring the average particle size by the image analysis method will be described. In a photographic projection drawing obtained by taking a photograph of the composite fine particles of the present invention at a magnification of 300,000 times (or 500,000 times) with a transmission electron microscope, the maximum diameter of the particles is set as the major axis, and the length is measured. , Let the value be the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the average particle diameter of the composite fine particles.
In this way, the average particle size of 50 or more composite particles is measured, and the average number of them is calculated. The value thus obtained is taken as the average particle size of the composite fine particles of the present invention.

In the composite fine particles of the present invention, the content of each element in the specific impurity group 1 is preferably 100 ppm or less. Further, it is preferably 50 ppm or less, more preferably 25 ppm or less, further preferably 5 ppm or less, and even more preferably 1 ppm or less.
Further, 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 for reducing the element content of each 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 the case where the specific impurity group 1 and the specific impurity group 2 contained in the mother particles are measured. It can be measured by the same method as.

<Dispersion liquid of the present invention>
The dispersion liquid of the present invention will be described.
The dispersion liquid 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 liquid of the present invention contains water and / or an organic solvent as the dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Further, the dispersion liquid of the present invention is polished by adding one or more selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster and a pH buffer as an additive for controlling the polishing performance. It is suitably used as a slurry.

Further, as the dispersion solvent provided with the dispersion liquid of the present invention, alcohols such as methanol, ethanol, isopropanol, n-butanol, methylisocarbinol and the like; acetone, 2-butanone, ethyl amylketone, diacetone alcohol, isophorone and cyclohexanone. Ketones such as; amides such as N, N-dimethylformamide, N, N-dimethylacetamide; ethers such as diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran. Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol and ethylene glycol dimethyl ether; glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate and 2-butoxyethyl acetate; acetic acid Ethers such as methyl, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as hexane, heptane, isooctane and cyclohexane; chloride Halogenated hydrocarbons such as methylene, 1,2-dichloroethane, dichloropropane, chlorbenzene; sulfoxides such as dimethylsulfoxide; organics such as pyrrolidones such as N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone A solvent can be used. These may be mixed with water and used.

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

In the dispersion liquid of the present invention, the ratio (V) of the flow potential change amount (ΔPCD) represented by the following formula (1) and the addition amount (V) of the cationic colloid titration solution in the knick when the cationic colloid titration is performed. It is preferable that a flow potential curve having a ΔPCD / V) of −150.0 to −5.0 can be obtained.
ΔPCD / V = (IC) / V ... Equation (1)
C: Flow potential (mV) in the knick
I: Flow potential (mV) at the start point of the flow potential curve
V: Addition amount (ml) of the cationic colloid titration solution in the knick

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

The flow potential curve obtained by this cation colloid titration is a graph in which the addition amount (ml) of the cation titration solution is taken on the X-axis and the flow potential (mV) of the dispersion liquid of the present invention is taken on the Y-axis.
The knick is a point (inflection point) where the flow potential changes abruptly in the flow potential curve obtained by cationic colloid titration. Then, the flow potential at the inflection is C (mV), and the amount of the cationic colloid titration solution added at the inflection is V (ml).
The starting point of the flow potential curve is the flow potential in the dispersion liquid of the present invention before titration. Specifically, the starting point is the point where the addition amount of the cationic colloid titration solution is 0. Let the flow potential at this starting point be I (mV).

When the above-mentioned value of ΔPCD / V is −150.0 to −5.0, the polishing speed of the abrasive is further improved when the dispersion of the present invention is used as the abrasive. It is considered that this ΔPCD / V reflects the covering condition of the child particles with the cerium-containing silica layer on the surface of the composite fine particles and / or the exposure condition of the child particles on the surface of the composite fine particles or the presence of silica which is easily desorbed. Will be. The present inventor estimates that when the value of ΔPCD / V is within the above range, the child particles are less likely to be desorbed during crushing by a wet method and the polishing rate is high. On the contrary, when the value of ΔPCD / V is larger than -150.0, the surface of the composite fine particles is entirely covered with the cerium-containing silica layer, so that the child particles are unlikely to fall off in the crushing step, but polishing. Sometimes silica is hard to remove and the polishing speed decreases. On the other hand, if the absolute value is smaller than -5.0, it is considered that dropout is likely to occur. Within the above range, the present inventor presumes that the surface of the child particles is appropriately exposed during polishing, the child particles are less likely to fall off, and the polishing speed is further improved. ΔPCD / V is more preferably -145.0 to -10.0, and even more preferably -140.0 to -20.0.

When the pH value of the dispersion of the present invention is in the range of 3 to 8, the flow potential before starting the cationic colloid titration, that is, when the titration amount is zero, becomes a negative potential. Is preferable. This is because when the flow potential maintains a negative potential, it is difficult for abrasive grains (ceria-based composite fine particles) to remain on the polishing substrate, which also exhibits a negative surface potential.

<Manufacturing 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 silica fine particle dispersion liquid in which silica fine particles are dispersed in a solvent is prepared.
In this specification, "step 1" may be referred to as "blending step".

The aspect of the silica fine particles is not particularly limited, but it is preferable that the silica fine particles have the same average particle size and shape as the above-mentioned mother particles. Further, the silica fine particles are mainly composed of amorphous silica, like the above-mentioned mother particles. Here, the definition of the principal component is the same as that of the mother particle.

The average particle size of the silica fine particles shall be measured as follows.
First, by STEM-EDS analysis, the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion obtained by the production method of the present invention were collected and observed at 800,000 times, and the Ce molar concentration and the Si molar concentration were measured. Silica fine particles are specified by specifying a line in which the ratio (percentage) of the Ce molar concentration to the total (Ce / (Ce + Si) × 100) is 3%. Next, the maximum diameter of the silica fine particles is set as the major axis, the length is measured, and the value is defined as the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the particle diameter of the silica fine particles.
In this way, the particle size of 50 silica fine particles is measured, and the value obtained by simple averaging is taken as the average particle size of the silica fine particles.
If it is clear from the composition of the raw material to be charged and the composition of the composite fine particles that there is no line in which (Ce / (Ce + Si) × 100) is 3% or more, the EDS analysis may be omitted.

When the dispersion liquid of the present invention to be applied to polishing of semiconductor devices and the like is to be prepared by the production method of the present invention, the silica fine particles produced by hydrolysis of alkoxysilane are dispersed in a solvent as the silica fine particle dispersion liquid. It is preferable to use a silica fine particle dispersion liquid. When a conventionally known silica fine particle dispersion other than the above (such as a silica fine particle dispersion prepared from water glass as a raw material) is used as a raw material, the silica fine particle dispersion is acid-treated and further deionized before use. Is preferable. In this case, the content of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, U, Th, Cl, NO ₃ , SO ₄ and F contained in the silica fine particles is small. This is because, specifically, it can be 100 ppm or less.
Specifically, as the silica fine particles in the silica fine particle dispersion liquid as a raw material, those satisfying the following conditions (a) and (b) are preferably used.
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively.

As the silica fine particles, those having an appropriate reactivity with cerium (dissolved weight of silica fine particles per weight of ceria) are preferably used. In step 1 of the production method of the present invention, by adding a metal salt of cerium to the silica fine particle dispersion, a part of silica is dissolved by the cerium compound, the size of the silica fine particles is reduced, and the surface of the dissolved silica fine particles is reduced. A precursor of a cerium-containing silica layer containing CeO ₂ ultrafine particles is formed in. At this time, in the case of silica having high reactivity with cerium, the precursor of the cerium-containing silica layer becomes thick, the cerium-containing silica layer generated by firing becomes a thick film, or the silica ratio of the layer becomes excessively high. This is because the crushing process in No. 2 becomes difficult. Further, when the reactivity with cerium is extremely low, the cerium-containing silica 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 silica is suppressed, the cerium-containing silica layer becomes an appropriate thickness and prevents the child particles from falling off, and the strength becomes larger than the strength between the composite fine particles. Since it is possible, it is desirable because it is easy to crush.

In step 1, the silica fine particle dispersion liquid in which the silica fine particles are dispersed in a solvent is stirred, and the temperature is maintained at 0 to 20 ° C., the pH range is 7.0 to 9.0, and the redox potential is maintained at 50 to 500 mV. , A metal salt of cerium is continuously or intermittently added thereto to neutralize the metal salt of cerium to obtain a precursor particle dispersion liquid containing the precursor particles.

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

The solid content concentration in the silica fine particle dispersion is preferably 1 to 40% by mass based on the SiO ₂ conversion standard. If this solid content concentration is too low, the silica concentration in the manufacturing process may be low and the productivity may be deteriorated.

In the method for producing ceria-based composite fine particles of the present invention, for example, when the reaction temperature between the silica fine particles and the metal salt of cerium in step 1 is 40 to 50 ° C., the precursor obtained by drying in the intermediate step of step 2. The particle size of the CeO ₂ ultrafine particles in the body particles can be less than 2.5 nm. This is because when silica reacts with ceria in a liquid phase in the high temperature region, silica inhibits the crystal growth of ceria, so that the average particle size of the dried CeO ₂ ultrafine particles tends to be smaller than 2.5 nm. Is shown.
Even with such precursor particles, it is possible to set the average crystallite diameter of the ceria particles to 10 nm or more by setting the firing temperature to 1200 ° C. or higher, but in this case, the silica layer is used. Since the tendency to firmly coat the ceria particles becomes stronger, there is a problem in that crushing becomes difficult. Therefore, by keeping the reaction temperature at 0 to 20 ° C and appropriately suppressing the reaction between silica and ceria in the liquid phase, the average particle size of the CeO ₂ ultrafine particles in the dried precursor particles can be increased to 2.5 nm or more. , The particles are easy to crush. Further, since the average crystallite diameter after drying is large, the firing temperature for setting the average crystallite diameter of the ceria particles to 10 nm or more can be lowered, and the thickness of the cerium-containing silica layer formed by firing becomes excessive. It does not thicken and can be easily crushed.

In addition, impurities are extracted with a cation exchange resin or anion exchange resin, mineral acid, organic acid, etc., and the silica fine particle dispersion is deionized as necessary using an ultrafiltration membrane or the like. Can be done. A silica fine particle dispersion liquid from which impurity ions and the like have been removed by a deionization treatment is more preferable because a hydroxide containing silicon is likely to be formed on the surface. The deionization treatment is not limited to these.

In step 1, the silica fine particle dispersion as described above is stirred, and the temperature is maintained at 0 to 20 ° C., the pH range is 7.0 to 9.0, and the redox potential is 50 to 500 mV. Metal salts are added continuously or intermittently. When the redox potential is low, crystals such as rods are formed, so that they are difficult to deposit on silica fine particles.

The type 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 thereof include first cerium nitrate, cerium carbonate, first cerium sulfate, and first cerium chloride. Of these, trivalent cerium salts such as primary cerium nitrate, primary cerium chloride, and cerium carbonate are preferable. Crystalline cerium oxides (CeO ₂ ultrafine particles) are formed from the solution that is supersaturated at the same time as neutralization, and they are rapidly aggregated and deposited on the silica fine particles, and finally ceria is formed in a monodisperse. be. Further, the trivalent cerium salt and the compound produced from the trivalent cerium salt react appropriately with the silica fine particles, and a cerium-containing silica layer is likely to be 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 are corrosive. Therefore, if desired, it is necessary to wash the mixture in a post-process after preparation and remove it to 5 ppm or less. On the other hand, the carbonate is released as carbon dioxide gas during preparation, and the alkoxide is decomposed into an alcohol, so that it can be preferably used.

The amount of the metal salt of cerium added to the silica fine particle dispersion is such that the mass ratio of silica and ceria in the obtained composite fine particles of the present invention is in the range of 100: 50 to 400 as described above.

The temperature at the time of stirring after adding the metal salt of cerium to the silica fine particle dispersion is preferably 0 to 20 ° C, more preferably 3 to 18 ° C. If this temperature is too low, the reactivity between ceria and silica will decrease, and the solubility of silica will decrease significantly, so that the crystallization of ceria will not be controlled. As a result, coarse crystalline oxide of cerium is generated, abnormal growth of ceria particles on the surface of silica fine particles occurs, it becomes difficult to be crushed after firing, and the amount of silica dissolved by the cerium compound decreases, so that cerium The amount of silica supplied to the contained silica layer will be reduced. For this reason, it is conceivable that the silica that serves as a binder between the silica mother particles and the ceria child particles is insufficient (the silica that is laminated on the mother particles is insufficient), and the immobilization of the ceria child particles to the silica mother particles is difficult to occur. On the contrary, if this temperature is too high, the solubility of silica may be remarkably increased and the formation of crystalline ceria oxide may be suppressed. It may not be possible, and moreover, scale or the like is likely to occur on the wall surface of the reactor, which is not preferable. Further, the silica fine particles to be the mother particles are preferably those that are difficult to dissolve in a cerium compound (neutralized product of a cerium salt). In the case of silica fine particles that are easily dissolved, the crystal growth of ceria is suppressed by silica, and the particle size of the CeO ₂ ultrafine particles at the compounding stage tends to be less than 2.5 nm.
If the particle size of the CeO ₂ ultrafine particles at the compounding 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 that case, the cerium-containing silica layer Etc. may cover the mother particles firmly, making it difficult to crush them. When silica fine particles that are easily dissolved are dried or fired at 100 ° C. or higher and then used as a raw material, the solubility can be easily suppressed.

The time for stirring the silica fine particle dispersion is preferably 0.5 to 24 hours, more preferably 0.5 to 18 hours. If this time is too short, crystalline cerium oxide aggregates and becomes difficult to react with silica on the surface of the silica fine particles, which is not preferable in that composite fine particles that are difficult to be crushed tend to be formed. On the contrary, even if this time is too long, the formation of crystalline cerium oxide is uneconomical because the reaction does not proceed any further. After the addition of the cerium metal salt, it may be aged 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 liberated CeO ₂ ultrafine particles on the silica fine particles without adhering to the silica fine particles.

Further, the pH range of the silica fine particle dispersion liquid when the metal salt of cerium is added to the silica fine particle dispersion liquid and stirred is set to 7.0 to 9.0, but preferably 7.2 to 8.6. .. At this time, it is preferable to add an alkali or the like to adjust the pH. As an example of such an alkali, a known alkali can be used. Specific examples thereof include, but are not limited to, an aqueous solution of ammonia, an alkali hydroxide, an alkaline earth metal, and an aqueous solution of amines.

Further, a metal salt of cerium is added to the silica fine particle dispersion, and the redox potential of the fine particle dispersion at the time of stirring is adjusted to 50 to 500 mV. The redox potential is preferably 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 liquid decreases during preparation. Further, by keeping the redox potential in this range, the crystallization of the produced _CeO2 ultrafine particles is promoted. When the redox potential becomes negative, the cerium compound may not be deposited on the surface of the silica fine particles, and a plate-shaped or rod-shaped cerium compound or cerium single particles may be generated. Further, the reactivity of cerium hydroxide or the like with respect to the silica fine particles is lowered, the CeO ₂ ultrafine particle-containing layer is not formed, and even if it is formed, the ratio of silica in the CeO ₂ ultrafine particle layer is extremely low. Therefore, the cerium-containing silica layer that coats the ceria child particles is not formed after firing, and the ceria child particles tend to be exposed and arranged on the mother particles after firing.
Examples of the method of keeping the redox 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.

By such step 1, a dispersion liquid (precursor particle dispersion liquid) containing particles (precursor particles) which are precursors of the composite fine particles of the present invention can be obtained. In this step, it is possible to obtain particles having an average crystallite diameter of 2.5 nm to less than 10 nm of CeO ₂ ultrafine particles contained in the precursor particles. If the reactivity between silica and ceria is too high, particles having an average crystallite diameter of less than 2.5 nm of CeO ₂ ultrafine particles contained in the precursor particles can be obtained. It is necessary to bake at high temperature. As a result, the adhesion between the particles becomes strong, which may make crushing difficult.

As described above, in step 1, the silica 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 redox potential is maintained at 50 to 500 mV. The metal salt of the above is continuously or intermittently added, and then, while maintaining the temperature above 20 ° C. and 98 ° C. or lower, the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV, the above-mentioned It is preferable to continuously or intermittently add a metal salt of cerium to obtain the precursor particle dispersion.
That is, in step 1, the treatment is carried out at a temperature of 0 to 20 ° C., and then the treatment is carried out by changing the temperature to over 20 ° C. and 98 ° C. or lower to obtain the precursor particle dispersion liquid.
This is because when such step 1 is performed, it is easy to obtain the dispersion liquid of the present invention containing the composite fine particles of the present invention in which the coefficient of variation in the particle size distribution of the child particles is a suitable value (14 to 50%).
The pH and redox potential in the case of treatment at a temperature of more than 20 ° C. and 98 ° C. or lower, the adjustment method and the like are the same as in the case of treatment at a temperature of 0 to 20 ° C.

On the contrary, it is preferable to obtain the precursor particle dispersion liquid by performing the treatment at a temperature of more than 20 ° C. and 98 ° C. or lower before performing the treatment at a temperature of 0 to 20 ° C. That is, the silica fine particle dispersion is stirred, and the metal salt of cerium is added thereto while maintaining the temperature above 20 ° C. and 98 ° C. or lower, the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV. The metal salt of the cerium is continuously or intermittently added, and then the metal salt of the cerium is continuously added thereto while maintaining the temperature at 0 to 20 ° C., the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV. Alternatively, it is preferably added intermittently to obtain the precursor particle dispersion liquid.
This is because when such step 1 is performed, it is easy to obtain the dispersion liquid of the present invention containing the composite fine particles of the present invention in which the coefficient of variation in the particle size distribution of the child particles is a suitable value (14 to 50%).
The pH and redox potential in the case of treatment at a temperature of more than 20 ° C. and 98 ° C. or lower, the adjustment method and the like are the same as in the case of treatment at a temperature of 0 to 20 ° C.

Here, the particle size distribution of the child particles shall be measured as follows.
First, the line was observed at 800,000 times by STEM-EDS analysis, and the line where the ratio (percentage) (Ce / (Ce + Si) x 100) of the Ce molar concentration to the total of the Ce molar concentration and the Si molar concentration was 50% was specified. By doing so, the child particles are identified. Next, the maximum diameter of the child particles is set as the major axis, the length is measured, and the value is defined as the major axis (DL). Further, a point that divides the long axis into two equal parts is determined on the long axis, two points where a straight line orthogonal to the point intersects the outer edge of the particle are obtained, and the distance between the two points is measured and used as the minor axis (DS). Then, the geometric mean value of the major axis (DL) and the minor axis (DS) is obtained, and this is used as the particle diameter of the child particles.
In this way, the particle size of 100 or more child particles can be measured and the particle size distribution can be obtained.

For the coefficient of variation (CV value) in the particle size distribution of child particles, the standard deviation and the number mean value are obtained using the particle size distribution obtained as described above as a population, and then the standard deviation is divided by the number mean value. Then, it is calculated by multiplying by 100 (that is, standard deviation / number mean value × 100).

When the reaction is carried out in the range of 0 to 20 ° C, the reactivity of cerium with silica is suppressed, so that large-sized CeO ₂ ultrafine particles are produced. When the salt is added, the reactivity of cerium with silica is increased and the dissolution of silica is promoted, so that the silica inhibits the crystal growth of cerium and produces CeO ₂ ultrafine particles having a small size. In this way, the reaction temperature in the compounding step (step 1) is essential to be 0 to 20 ° C., the reaction temperature is changed to more than 20 ° C. and 98 ° C. or less, and a metal salt of cerium is added to obtain CeO ₂ ultrafine particles and. The particle size distribution of ceria particles can be widened. If there is a step of adding a metal salt of cerium in the mixing temperature range of 0 to 20 ° C., the reaction at a temperature of more than 20 ° C. and 98 ° C. or lower may be performed before or after the reaction at 0 to 20 ° C. However, the temperature may be changed three or more times.
Even when the compound is prepared by changing the temperature during the compounding as described above, the composite fine particles have the same formation mechanism as described above as long as the step of performing the compounding at a temperature of 0 to 20 ° C. is included. ..
Further, the amount of the cerium metal salt added in the step of reacting at 0 to 20 ° C. when the reaction temperature is carried out in two or more steps shall be in the range of 10 to 90% by mass with respect to the total amount of the cerium metal salt added. Is preferable. If it exceeds this range, the proportion of large (or small) CeO ₂ ultrafine particles and ceria particles is small, so that the particle size distribution is not so wide.

The precursor particle dispersion obtained in step 1 may be further diluted or concentrated with pure water, ion-exchanged water, or the like before being subjected to step 2, and then subjected to the next step 2.

The solid content concentration in the precursor particle dispersion is preferably 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. Alternatively, a cake may be formed on the filter cloth and washed with ion-exchanged water.

<Step 2>
In step 2, the precursor particle dispersion is dried and then calcined at 800 to 1,200 ° C.

The method of drying is not particularly limited. It can be dried using a conventionally known dryer. Specifically, a box-type dryer, a band dryer, a spray dryer, or the like can be used.
It is preferable that the pH of the precursor particle dispersion before drying is 6.0 to 7.0. This is because the surface activity can be suppressed when the pH of the precursor particle dispersion liquid before drying is set to 6.0 to 7.0.
After drying, the firing temperature is 800 to 1200 ° C, preferably 850 to 1100 ° C, more preferably 900 to 1090 ° C. When fired in such a temperature range, the crystallization of cerium progresses sufficiently, the cerium-containing silica layer in which the ceria particles are dispersed has an appropriate film thickness, and the cerium-containing silica layer is firmly formed into the mother particles. The particles that are bonded and dispersed in the cerium-containing silica layer are less likely to fall off. Further, by firing in such a temperature range, cerium hydroxide and the like are less likely to remain. If this temperature is too high, ceria crystals may grow abnormally, the cerium-containing silica layer may become too thick, the amorphous silica constituting the mother particles may crystallize, and the particles may be fused together. ..

Further, when calcined in such a temperature range, the silicon atom is dissolved in the crystalline ceria which is the main component of the child particles. Therefore, for the cerium atom and silicon atom contained in the child particles, the relationship of R ₁ <R ₂ is satisfied when the cerium-silicon atom distance is R ₁ and the cerium-cerium atom distance is R ₂ . obtain.

In step 2, a solvent is added to the calcined body obtained by calcining, and the calcined body is crushed in a wet manner in the range of pH 8.6 to 10.8 to obtain a calcined body crushed dispersion.

A conventionally known device can be used as the wet crushing device, but for example, a batch type bead mill such as a basket mill, a horizontal / vertical / annual type continuous bead mill, a sand grinder mill, a ball mill, or the like, and a rotor. -A wet medium stirring type mill (wet crusher) such as a stator type homogenizer, an ultrasonic dispersion type homogenizer, and an impact crusher that collides fine particles in a dispersion liquid with each other can be mentioned. Examples of the beads used in the wet medium stirring mill include beads made of glass, alumina, zirconia, steel, flint stone, organic resin and the like.
Water and / or an organic solvent is used as the solvent for the wet crushing treatment. 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 crushed dispersion is not particularly limited, but is preferably in the range of, for example, 0.3 to 50% by mass.

Here, after the fired body obtained by firing is crushed by a dry method, a solvent may be added and crushed by a wet method in the range of pH 8.6 to 10.8.
As the dry crushing device, a conventionally known device can be used, and examples thereof include an attritor, a ball mill, a vibration mill, a vibration ball mill, and a bead mill.

In the case of wet crushing, it is preferable to carry out wet crushing while maintaining the pH of the solvent at 8.6 to 10.8. When the pH is maintained in this range, when cationic colloid titration is performed, the flow potential change amount (ΔPCD) represented by the above formula (1) and the addition amount (V) of the cationic colloid titrator in the knick are set. Finally, a ceria-based composite fine particle dispersion liquid having a flow potential curve having a ratio (ΔPCD / V) of −150.0 to −5.0 can be obtained more easily.
That is, it is preferable to carry out crushing to the extent that the dispersion liquid of the present invention corresponding to the above-mentioned preferable embodiment can be obtained. This is because, as described above, when the dispersion liquid of the present invention corresponding to the preferred embodiment is used as the polishing agent, the polishing speed is further improved. Regarding this, the present inventor further improves the polishing speed by appropriately thinning the cerium-containing silica layer on the surface of the composite fine particles of the present invention and / or appropriately exposing the child particles to a part of the surface of the composite fine particles. Moreover, it is presumed that the shedding of ceria particles can be controlled. In addition, since the cerium-containing silica layer is thin or peeled off, it is estimated that the child particles are likely to be detached to some extent during polishing. ΔPCD / V is more preferably -145.0 to −5.0, and even more preferably -140.0 to -20.0.

<Process 3>
In step 3, the calcined body crushed dispersion obtained in step 2 is subjected to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and then the sedimentation component is removed to obtain a ceria-based composite fine particle powder.
Specifically, the fired body crushed dispersion is classified by centrifugation. The relative centrifugal acceleration in the centrifugation process is 300 G or more. After the centrifugation treatment, the sedimentation component can be removed to obtain a ceria-based composite fine particle dispersion. The upper limit of the relative centrifugal acceleration is not particularly limited, but is practically used at 10,000 G or less.
In step 3, it is necessary to provide a centrifugation treatment satisfying the above conditions. If the centrifugal acceleration does not meet the above conditions, coarse particles will remain in the ceria-based composite fine particle dispersion, and scratches will occur when used for polishing applications such as abrasives using the ceria-based composite fine particle dispersion. It causes the occurrence.
In the present invention, the ceria-based composite fine particle dispersion obtained by the above-mentioned production method can be further dried to obtain ceria-based composite fine particles. The drying method is not particularly limited, and for example, it can be dried using a conventionally known dryer.

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

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

The polishing abrasive grain dispersion liquid of the present invention has excellent effects such as high polishing speed when polishing a semiconductor substrate, less scratches (scratches) on the polished surface during polishing, and less residual abrasive grains on the substrate. ing.

The abrasive grain dispersion liquid for polishing of the present invention contains water and / or an organic solvent as a dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Further, the polishing abrasive grain dispersion liquid of the present invention is selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer as an additive for controlling the polishing performance1. It is suitably used as a polishing slurry by adding seeds or more.

<Abrasive accelerator>
Although it depends on the type of the material to be polished, it can be used as a polishing slurry by adding a conventionally known polishing accelerator to the abrasive grain dispersion liquid for polishing of the present invention, if necessary. Examples of such include hydrogen peroxide, peracetic acid, urea peroxide and the like, and mixtures thereof. When such an abrasive composition containing 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 polishing accelerators include inorganic acids such as sulfuric acid, nitrate, phosphoric acid, oxalic acid and hydrofluoric acid, organic acids such as acetic acid, or sodium salts, potassium salts, ammonium salts, amine salts and the like of these acids. And the like. In the case of a polishing composition containing these polishing accelerators, when polishing a material to be polished composed of a composite component, by accelerating the polishing rate for a specific component of the material to be polished, finally flat polishing is performed. You can get a face.

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

<Surfactant and / or hydrophilic compound>
Cationic, anionic, nonionic, amphoteric surfactants or hydrophilic compounds can be added to improve the dispersibility and stability of the abrasive grain dispersion for polishing. Both the surfactant and the hydrophilic compound have an action of lowering the contact angle with the surface to be polished and have an action of promoting uniform polishing. As the surfactant and / or the hydrophilic compound, for example, those selected from the following groups can be used.

Examples of the anionic surfactant include carboxylates, sulfonates, sulfates and phosphates, and the carboxylates include soaps, N-acylamino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carboxylics. Acid salts, acylated peptides; as sulfonates, alkyl sulfonates, alkylbenzene and alkyl naphthalene sulfonates, naphthalene sulfonates, sulfosuccinates, α-olefin sulfonates, N-acyl sulfonates; sulfate esters. As salts, sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkylallyl ether sulfates, alkylamide sulfates; as phosphate ester salts, alkyl phosphates, polyoxyethylene or poly Oxypropylene alkyl allyl ether phosphate can be mentioned.

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

Examples of the nonionic surfactant include an ether type, an ether ester type, an ester type, and a nitrogen-containing type, and examples of the ether type are polyoxyethylene alkyl and alkylphenyl ether, alkylallyl formaldehyde condensed polyoxyethylene ether, and polyoxyethylene poly. Examples thereof include oxypropylene block polymer and polyoxyethylene polyoxypropylene alkyl ether, and examples of the ether ester type include polyoxyethylene ether for glycerin ester, polyoxyethylene ether for sorbitan ester, polyoxyethylene ether for sorbitol ester, and ester type. Examples of polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester, sucrose ester, and nitrogen-containing type include fatty acid alkanolamide, polyoxyethylene fatty acid amide, and polyoxyethylene alkylamide. In addition, a fluorine-based surfactant and the like can be mentioned.

As the surfactant, an anionic surfactant or a nonionic surfactant is preferable, and examples of the salt include an ammonium salt, a potassium salt, a sodium salt and the like, and an ammonium salt and a potassium salt are particularly preferable.

Further, as other surfactants, hydrophilic compounds and the like, 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 glycol, alkyl polypropylene glycol alkyl ether , Alkyl Polypropylene Glycols Alkenyl Ethers, Ethers such as Alkenyl Polypropylene Glycols; Polysaccharides such as Arginic Acid, Pectinic Acid, Carboxymethyl Cellulose, Cardolan and Purulane; Amino Acid Salts such as Glycinammonium Salt and Glycin Sodium Salt; Polylysine, polyapple acid, polymethacrylic acid, polyammonium methacrylate, sodium polymethacrylate, polyamic acid, polymaleic acid, polyitaconic acid, polyfumarate, poly (p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, amino Polycarboxylic acids such as polyacrylamide, ammonium polyacrylic acid salt, sodium polyacrylic acid salt, polyamic acid, ammonium polyamic acid salt, sodium polyamic acid salt and polyglioxylic acid and salts thereof; Vinyl-based polyma; ammonium methyltaurate, sodium methyltaurate, methylsodium sulfate, ethylammonium sulfate, butylammonium sulfate, sodium vinylsulfonic acid, sodium 1-allylsulfonic acid, 2-allylsulfonic acid Sulphonic acids and salts thereof such as sodium salt, sodium methoxymethylsulfonic acid salt, ammonium ethoxymethylsulfonic acid salt, sodium 3-ethoxypropylsulfonic acid salt; propionamide, acrylamide, methylurea, nicotineamide, succinic acid amide and sulf Examples thereof include amides such as ananyl amides.

When the substrate to be polished is a glass substrate or the like, any surfactant can be preferably used, but in the case of a silicon substrate for a semiconductor integrated circuit or the like, alkali metal or alkaline soil can be used. When the influence of contamination by metals or halides is disliked, it is desirable to use an acid or an ammonium salt-based surfactant thereof.

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

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

Only one type of surfactant or hydrophilic compound may be used, two or more types may be used, or different types may be used in combination.

<Heterocyclic compound>
The abrasive grain dispersion liquid for polishing of the present invention has the purpose of forming a passivation layer or a dissolution suppressing layer on the metal when the base material to be polished contains a metal to suppress erosion of the base material to be polished. Heterocyclic compounds may be contained. Here, the "heterocyclic compound" is a compound having a heterocycle containing one or more heteroatoms. Heteroatom means an atom other than a carbon atom or a hydrogen atom. The heterocycle means a cyclic compound having at least one heteroatom. Heteroatoms refer only to the atoms that form the constituents of the heterocyclic ring system, and may be located outside the ring system, separated from the ring system by at least one unconjugated single bond, or the ring system. It does not mean an atom that is part of a further substituent of. Preferred heteroatoms include, but are not limited to, nitrogen atoms, sulfur atoms, oxygen atoms, selenium atoms, tellurium atoms, phosphorus atoms, silicon atoms, and boron atoms. As an example 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 can be mentioned, but the present invention is not limited thereto.

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

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

When adjusting the polishing abrasive grain dispersion of the present invention to pH 7 or higher, an alkaline pH adjusting agent is used. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, tetramethylamine and the like are used.

When adjusting the abrasive grain dispersion for polishing to a pH of less than 7, an acidic one is used as the pH adjuster. 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>
A pH buffer may be used to keep the pH value of the abrasive grain dispersion for polishing constant. As the pH buffer, for example, phosphates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammo tetrahydrate tetrahydrate, and borates or organic acid salts can be used.

Further, as the dispersion solvent of the abrasive grain dispersion liquid for polishing of the present invention, for example, alcohols such as methanol, ethanol, isopropanol, n-butanol, methyl isocarbinol; acetone, 2-butanone, ethyl amylketone, diacetone alcohol, etc. Ketones such as isophorone and cyclohexanone; amides such as N, N-dimethylformamide, N, N-dimethylacetamide; diethyl ether, isopropyl ether, tetrahydrofuran, 1,4-dioxane, 3,4-dihydro-2H-pyran and the like. Ethers; Glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ethylene glycol dimethyl ether; Glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate Kind; Ethers such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethylene carbonate; Fragrant hydrocarbons such as benzene, toluene, xylene; Fat group hydrocarbons such as hexane, heptane, isooctane, cyclohexane Classes; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, chlorbenzene; sulfoxides such as dimethylsulfoxide; pyrrolidones such as N-methyl-2-pyrrolidone, N-octyl-2-pyrrolidone. And other organic solvents can be used. These may be mixed with water and used.

The solid content concentration contained in the abrasive grain dispersion liquid for polishing of the present invention is preferably in the range of 0.3 to 50% by mass. If this solid content concentration is too low, the polishing rate may decrease. On the contrary, even if the solid content concentration is too high, the polishing rate is rarely improved further, which may be uneconomical.

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

<Experiment 1>
First, the details of each measurement method and test method in Examples and Comparative Examples will be described. For each Example and Comparative Example, the following measurement results and test results are shown in Tables 1 to 3.

[Analysis of ingredients]
[Measurement of SiO ₂ content]
Regarding the content of SiO ₂ in the silica fine particle dispersion liquid, when sodium silicate was used as a raw material, the silica fine particle dispersion liquid was weighed by burning at 1000 ° C., and the content was determined assuming that all of the obtained products were SiO ₂ . I asked. When alkoxysilane was used as a raw material, the silica fine particle dispersion was dried at 150 ° C. for 1 hour and then weighed, and the content thereof was determined assuming that all of the obtained substances were SiO ₂ . Here, the solid content concentration of the silica fine particle dispersion can also be determined.
The SiO ₂ content in the ceria-based composite fine particles is the case where the ceria-based composite fine particle dispersion is subjected to a burning weight reduction of 1000 ° C. to determine the mass of the solid content, and then the content of Al to Th, etc., which will be described later, is measured. Similarly, the Ce content is measured by the standard addition method using an ICP plasma emission analyzer (for example, SII, SPS5520) to calculate CeO ₂ % by mass, and the solid component other than CeO ₂ is SiO ₂ . If there is, the content of SiO ₂ was determined. The SiO ₂ content, CeO ₂ content, and mass portion of ceria with respect to 100 parts by mass of silica in the ceria-based composite fine particles were calculated based on the CeO ₂ content and SiO ₂ content obtained here. Here, the solid content concentration of the ceria-based composite fine particle dispersion can also be determined.
In the measurement of the content of the specific impurity group 1 and the specific impurity group 2 described below, the content of each component with respect to the dry amount was determined based on the mass of the solid content thus determined.

[Component analysis of ceria-based composite fine particles or silica fine particles]
The content of each element shall be measured by the following method.
First, about 1 g of a sample consisting of a ceria-based composite fine particle or a ceria-based composite fine particle dispersion (adjusted to a solid content of 20% by mass) is collected in a platinum dish. Add 3 ml of phosphoric acid, 5 ml of nitric acid and 10 ml of hydrofluoric acid and heat on a sand bath. After drying, add a small amount of water and 50 ml of nitric acid to dissolve and put in a 100 ml volumetric flask, and add water to make 100 ml. In this solution, Na and K are measured by an atomic absorption spectrophotometer (for example, Z-2310 manufactured by Hitachi, Ltd.). Next, the operation of collecting 10 ml of the separated solution in a 20 ml volumetric flask from the solution contained in 100 ml is repeated 5 times to obtain 5 10 ml of the separated solution. Then, using this, Al, Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, U and Th are measured by an ICP plasma emission spectrometer (for example, SII, SPS5520) by a standard addition method. I do. Here, the blank is also measured by the same method, and the blank is subtracted and adjusted to obtain the measured value for each element.
Then, based on the mass of the solid content obtained by the above-mentioned method, the content ratio of each component with respect to the dry amount was determined.

The content of each anion shall be measured by the following method.
<Cl>
Add acetone to 20 g of a sample consisting of ceria-based composite fine particles or ceria-based composite fine particles dispersion (adjusted to a solid content of 20% by mass) to adjust the volume to 100 ml, and add 5 ml of acetic acid and 4 ml of 0.001 mol sodium chloride solution to this solution. Is added and analyzed with a 0.002 mol silver nitrate solution by a potentiometric titration method (manufactured by Kyoto Electronics: Potentiometric Titration Device AT-610).
As a separate blank measurement, 5 ml of acetic acid and 4 ml of 0.001 mol sodium chloride solution are added to 100 ml of acetone, and titration is performed with 0.002 mol silver nitrate solution. It was subtracted from the sample and used as the titration amount of the sample.
Then, based on the mass of the solid content obtained by the above-mentioned method, the content ratio of each component with respect to the dry amount was determined.

<NO ₃ , SO ₄ , F>
A sample consisting of ceria-based composite fine particles or a ceria-based composite fine particle dispersion (adjusted to a solid content of 20% by mass) is diluted with water to 100 ml, and a centrifuge (HIMAC CT06E manufactured by Hitachi) is used at 4000 rpm for 20. The liquid obtained by centrifuging and removing the sedimentation component was analyzed by an ion chromatograph (ICS-1100 manufactured by DIONEX).
Then, based on the mass of the solid content obtained by the above-mentioned method, the content ratio of each component with respect to the dry amount was determined.

[X-ray diffraction method, measurement of average crystallite diameter]
The ceria-based composite fine particle dispersion or silica-based composite fine particles obtained in Examples and Comparative Examples were dried using a conventionally known dryer, and the obtained powder was pulverized in a dairy pot for 10 minutes, and an X-ray diffractometer was used. An X-ray diffraction pattern was obtained by (RINT1400, manufactured by Rigaku Denki Co., Ltd.), and the crystal type was specified.
Further, the full width at half maximum of the peak of the (111) plane (near 2θ = 28 degrees) near 2θ = 28 degrees in the obtained X-ray diffraction pattern was measured by the above-mentioned method, and the average crystallite was measured by Scherrer's equation. The diameter was calculated.

<Average particle size>
With respect to the silica fine particle dispersions and the ceria-based composite fine particle dispersions obtained in Examples and Comparative Examples, the average particle size of the particles contained therein was measured by the above-mentioned image analysis method.

<Geometric mean particle diameter of child particles>
The geometric mean particle diameter of the child particles is a value obtained from the image obtained by the STEM-EDS analysis as described above.

<Measurement of minor axis / major axis ratio>
The minor axis / major axis ratio of the silica fine particles and the ceria-based composite fine particles is determined by the image analysis method as described above.

<Specific surface area>
As described above, the specific surface area of the ceria-based composite fine particles is measured by the BET specific surface area measurement method.

<Surface coverage>
As for the surface coverage of the child particles in the ceria-based composite fine particles, as described above, the child particles are specified by STEM-EDS analysis, the projected area thereof and the projected area of the ceria-based composite fine particles are obtained by image analysis, and the projected area of the child particles is obtained. / The work of calculating the projected area of the ceria-based composite fine particles × 100 is performed for 20 or more ceria-based composite fine particles, and the average value thereof is obtained.

<Number of coarse particles>
The number of coarse particles of the composite fine particles was measured using an Accusizer 780 APS manufactured by Particle sizing system Inc. After adjusting the measurement sample to 0.1% by mass with pure water, inject 5 mL into the measuring device, measure under the following conditions, measure 3 times, and then obtain 0. The average value of the values of the number of coarse particles of 98 μm or more was calculated. Further, the average value was multiplied by 1000 to obtain the dry-equivalent coarse particle number of the ceria-based composite fine particles. The measurement conditions are as follows.
<System Setup>
・ Stir Speed Control / Low Speed Factor 1500 / High Speed Factor 2500
<System Menu>
・ Data Collection Time 60 Sec.
・ Syringe Volume 2.5ml
-Sample Line Number: Sum Mode
・ Initial 2nd ^-Stage Dilution Factor 350
・ Vessel Fast Flush Time 35 Sec.
・ System Flush Time / Before Measurement 60 Sec. / After Measurement 60 Sec.
・ Sample Equilibration Time 30 Sec./Sample Flow Time 30 Sec.

[Polishing test method]
<Polishing of SiO ₂ film>
The abrasive grain dispersion liquid for polishing containing the ceria-based composite fine particle dispersion liquid obtained in each of the examples and the comparative examples was prepared. Here, the solid content concentration was 0.6% by mass, and nitric acid was added to adjust the pH to 5.0.
Next, as a substrate to be polished, a SiO ₂ insulating film (thickness 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, this substrate to be polished is set in a polishing device (Nanofactor Co., Ltd., NF300), and a polishing pad (“IC-1000 / SUBA400 concentric circle type” manufactured by Nitta Hearth Co., Ltd.) is used, and the substrate load is 0.5 MPa, the table. Polishing was performed by supplying a polishing abrasive grain dispersion at a rotation speed of 90 rpm for 1 minute at a rate of 50 ml / min.
Then, the polishing rate was calculated by obtaining the weight change of the substrate to be polished before and after polishing.
Further, the smoothness (surface roughness Ra) of the surface of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Co., Ltd.). Since the smoothness and the surface roughness are generally in a proportional relationship, the surface roughness is shown in Table 3.
The polishing scratches were observed by observing the surface of the insulating film using an optical microscope.

<Aluminum hard disk polishing>
The abrasive grain dispersion liquid for polishing containing the ceria-based composite fine particle dispersion liquid obtained in each of the examples and the comparative examples was prepared. Here, the solid content concentration was 9% by mass, and nitric acid was added to adjust the pH to 2.0.
Set the substrate for the aluminum hard disk in the polishing device (Nanofactor Co., Ltd., NF300), and use the polishing pad (Nitta Hearth Co., Ltd. "Polytex φ12") to prepare the polishing slurry at a substrate load of 0.05 MPa and a table rotation speed of 30 rpm. Polishing is performed by supplying at a rate of 20 ml / min for 5 minutes, and the entire surface is observed with Zoom15 using an ultrafine 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 few"
50 to less than 80 "less"
80 or more "many"
At least 80 or more, too many to count the total number "*"

Examples are described below. The term "solid content concentration" simply means the concentration of fine particles dispersed in a solvent regardless of the chemical species.

[Preparation step 1]
Preparation of << silica fine particle dispersion (average particle size of silica fine particles: 331 nm) >> (seed particle preparation step)
First, water, alcohol and a catalyst for hydrolysis were added to prepare a mixed solvent. Here, 4424 g of water, 3702 g of ethyl alcohol (manufactured by Kanto Chemical Co., Inc.), and 762 g of an aqueous ammonia solution having an ammonia concentration of 28% by mass (manufactured by Kanto Chemical Co., Inc.) were placed in a glass reactor having a capacity of 2 L and stirred. The liquid temperature of this solution was adjusted to 35 ± 0.5 ° C., and 157.6 g of tetraethoxysilane (manufactured by Tama Chemical Co., Ltd.) was added to the reactor at once. Then, it was stirred for 1 hour. By stirring for 1 hour, tetraethoxysilane was hydrolyzed and condensed to obtain a dispersion of silica fine particles having an average particle size of 83 nm.

In order to adjust the pH of the dispersion liquid of silica fine particles having an average particle diameter of 83 nm, 1222 g of an aqueous ammonia solution having an ammonia concentration of 28% by weight and 200 g of water were added, and the liquid temperature was adjusted to 35 ± 0.5 ° C. with stirring.

(Particle growth process / aging process)
10676 g of tetraethoxysilane was placed in the first dropping device. 8820 g of aqueous ammonia having a concentration of 8% by mass was placed in the second dropping device. Then, tetraethoxysilane and aqueous ammonia were added dropwise to the silica fine particle dispersion (liquid temperature 35 ± 0.5 ° C.) obtained in the previous step over 12 hours using a first dropping device and a second dropping device. After completion of the dropping, the liquid temperature was adjusted to 60 ± 0.5 ° C., and the mixture was stirred for 1 hour for aging.

(Filtration / water replacement process)
The aging liquid thus obtained was filtered through a 0.5 μm nylon filter to remove aggregated particles of silica particles. Further, it was replaced with an aqueous solvent using a distillation apparatus.
114 g of a cation exchange resin (SK-1BH manufactured by Mitsubishi Chemical Corporation) was gradually added to 1,053 g of the obtained silica fine particle dispersion, and the mixture was stirred for 30 minutes to separate the resin. The pH at this time was 4.8.
Further, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, U, Th, of the particles contained in the silica fine particle dispersion after the treatment with the cation exchange resin. The contents of Cl, NO ₃ , SO ₄ and F (the content of each component with respect to the amount of dry) were all 1 ppm or less.
Then, it concentrated until the silica concentration became 35% by mass, and the silica fine particle dispersion liquid was obtained. At this time, the average particle size of the silica fine particles was 331 nm.

[Preparation step 2]
Preparation of << Silica fine particle dispersion (average particle size of silica fine particles: 189 nm) >> Preparation except that the amount of tetraethoxysilane to be put into the first dropping device in the particle growth and aging step of preparation step 1 was 1855 g. It was carried out in the same manner as in step 1.
The average particle size of the obtained silica fine particles was 189 nm.

[Preparation step 3]
Preparation of << High-Purity Silicic Acid Solution >> An aqueous sodium silicate solution having a SiO ₂ concentration of 24.06% by mass and a Na _2O concentration of 7.97% by mass was prepared. Then, pure water was added to the sodium silicate aqueous solution so that the SiO ₂ concentration was 5.0% by mass.

[Acid silicic acid solution]
18 kg of the obtained aqueous sodium silicate solution having a SiO ₂ concentration of 5.0% by mass was passed through a 6 L strong acid cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at an air velocity of 3.0 h ^-1 to have a pH of 2. 18 kg of the acidic silicic acid solution of 0.7 was obtained.
The SiO ₂ concentration of the obtained acidic silicic acid solution was 4.7% by mass.

[High-purity silicic acid solution]
Next, this acidic silicic acid solution (SiO ₂ concentration is 4.7% by mass) is passed through a chelate type ion exchange resin (CR11, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 , and the pH is 2. The high-purity silicic acid solution of No. 7 was obtained. The SiO ₂ concentration of the obtained high-purity silicic acid solution was 4.4% by mass.

Preparation of << Silica fine particle dispersion liquid (average particle diameter of silica fine particles: 25 nm) >> A part (514.5 g) of a high-purity silicate liquid having a SiO ₂ concentration of 4.4% by mass obtained here is stirred. While adding the particles to 42 g of pure water, 1,584.6 g of an aqueous ammonia solution having an ammonia concentration of 15% by mass was added, and then the temperature was raised to 83 ° C. and maintained for 30 minutes.
Then, another part (13,700 g) of a high-purity silicic acid solution having a SiO ₂ concentration of 4.4% by mass was further added over 18 hours, and after the addition was completed, aging was performed while maintaining 83 ° C., and the average was increased. A silica fine particle dispersion having a particle size of 25 nm was obtained.
The obtained silica fine particle dispersion was cooled to 40 ° C., and the SiO ₂ concentration was concentrated to 12% by mass with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei Corporation).

Preparation of << Silica fine particle dispersion (average particle diameter of silica fine particles: 45 nm) >> 963 g of silica fine particle dispersion (average particle diameter of silica fine particles 25 nm) having a SiO ₂ concentration of 12% by mass in 991 g of pure water with stirring. added. Next, 1,414 g of an aqueous ammonia solution having an ammonia concentration of 15% by mass was added, and then the temperature was raised to 87 ° C. and maintained for 30 minutes.
Next, another part (12,812 g) of a high-purity silica solution having a SiO ₂ concentration of 4.4% by mass was further added over 18 hours, and after the addition was completed, aging was performed while maintaining 87 ° C. A silica fine particle dispersion having an average particle diameter of 45 nm was obtained.
The obtained silica fine particle dispersion was cooled to 40 ° C., and the SiO ₂ concentration was concentrated to 12% by mass with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei Corporation).

Preparation of << Silica fine particle dispersion (average particle diameter of silica fine particles: 70 nm) >> Silica fine particle dispersion (SiO ₂ concentration) in which silica fine particles with an average particle diameter of 45 nm are dispersed in a solvent while stirring in 705 g of pure water. 12% by mass) was added in an amount of 705 g. Then, 50 g of a 15% aqueous ammonia solution was added, and then the temperature was raised to 87 ° C. and maintained for 30 minutes.
Next, another part (7,168 g) of a high-purity silica solution having a SiO ₂ concentration of 4.4% by mass was further added over 18 hours, and after the addition was completed, aging was performed while maintaining 87 ° C. A silica fine particle dispersion was obtained by dispersing silica fine particles having an average particle diameter of 70 nm in a solvent.
The obtained silica fine particle dispersion was cooled to 40 ° C., and the SiO ₂ concentration was concentrated to 12% by mass with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei Corporation).

Preparation of << Silica Fine Particle Dispersion (Average Particle Diameter of Silica Fine Particles: 96 nm) >> A dispersion liquid (SiO ₂ concentration) in which silica fine particles having an average particle diameter of 70 nm are dispersed in a solvent while stirring in 1,081 g of pure water. : 12% by mass) was added in an amount of 1,081 g. Then, 50 g of an aqueous ammonia solution having an ammonia concentration of 15% by mass was added, and then the temperature was raised to 87 ° C. and maintained for 30 minutes.
Next, another part (6,143 g) of a high-purity silicic acid solution having a SiO ₂ concentration of 4.4% by mass was added over 18 hours, and after the addition was completed, aging was performed while maintaining 87 ° C. A silica fine particle dispersion was obtained by dispersing silica fine particles having an average particle diameter of 96 nm in a solvent.
The obtained silica fine particle dispersion was cooled to 40 ° C., and the SiO ₂ concentration was concentrated to 12% by mass with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei Corporation). Anion exchange resin SANUP B manufactured by Mitsubishi Chemical Corporation was added to the concentrated silica fine particle dispersion to remove anions.

<Example 1>
Ultrapure water is added to the silica fine particle dispersion obtained in the above preparation step 1 having an average particle diameter of 331 nm, and 6,000 g (SiO ₂ dry 180 g) of the dispersion having a SiO ₂ solid content concentration of 3% by mass is added. A-1 liquid) was obtained.

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

Next, while keeping 6,000 g of the A-1 solution at 15 ° C. and stirring, the B solution (7,186.7 g, CeO ₂ dry215.6 g) was added over 18 hours. During this period, the liquid temperature was maintained at 15 ° C., and if necessary, an aqueous ammonia solution having an ammonia concentration of 3% was added to maintain the pH at 7.8 to 8.1. Then, after the addition was completed, aging was carried out at a liquid temperature of 15 ° C. for 4 hours. During the addition and aging of the liquid B, the liquid was prepared while blowing air into the liquid, and the redox potential was maintained at 100 to 200 mV.
Then, washing was performed while replenishing ion-exchanged water with an ultrafiltration membrane. The precursor particle dispersion obtained after washing has a solid content concentration of 5.5% by mass, a pH of 5.7 (at 25 ° C), and a conductivity of 27 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 calcined for 2 hours in a muffle furnace at 960 ° C. to obtain a powder (firing body).

300 g of ion-exchanged water was added to 100 g of the powder (calcined body) obtained after firing, and the pH was adjusted to 9.3 using an aqueous ammonia solution (ammonia concentration 3% by mass). Wet crushing (batch type tabletop sand mill manufactured by Kampe Co., Ltd.) was performed at Daiken Kagaku Kogyo Co., Ltd. for 210 minutes.
Then, after crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained calcined body crushed dispersion was 8.0% by mass, and the weight was 1175 g. During crushing, an aqueous ammonia solution (ammonia concentration 3% by mass) was added to keep the pH at 9.3.

Further, the crushed dispersion was treated with a centrifuge (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at 1700 G for 102 seconds, and the light liquid was recovered to obtain a ceria-based composite fine particle dispersion. The average particle size of the obtained ceria-based composite fine particle dispersion was measured. The measurement method is the image analysis method as described above. Table 3 shows the measurement results of the average particle size.

In addition, the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion obtained in Example 1 were observed using SEM and TEM. FIG. 2A shows an SEM image, and FIG. 2B shows a TEM image. From FIG. 2, it can be seen that the composite fine particles are covered with ceria particles, and the surface coverage of the ceria particles with respect to the composite fine particles is very high.

Further, it was measured by an X-ray diffraction method of the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion obtained in Example 1. The obtained X-ray diffraction pattern is shown in FIG. As shown in FIG. 3, a fairly sharp Ceriante crystal pattern was observed in the X-ray diffraction pattern.

<Example 2>
In Example 1, silica particles having an average particle diameter of 331 nm obtained in the preparation step 1 were used as the silica fine particle dispersion liquid, but in Example 2, silica fine particles having an average particle diameter of 189 nm obtained in the preparation step 2 were used. The same operation as in Example 1 was carried out except that the dispersion was used and the firing temperature was set to 1020 ° C.

In addition, the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion obtained in Example 2 were observed using SEM and TEM. FIG. 4A shows an SEM image, and FIG. 4B shows a TEM image. From FIG. 4, it can be seen that the composite fine particles are covered with the ceria particles, although some parts are not covered with the ceria particles, and the surface coverage of the ceria particles with respect to the composite fine particles is very high.

Further, it was measured by the X-ray diffraction method of the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion obtained in Example 2. The obtained X-ray diffraction pattern is shown in FIG. As shown in FIG. 5, a fairly sharp Ceriante crystal pattern was observed in the X-ray diffraction pattern.

<Example 3>
Ultrapure water is added to the silica fine particle dispersion having an average particle diameter of 96 nm obtained in the preparation step 3, and 2,083.3 g (SiO ₂ dry62.5 g) of the dispersion having a SiO ₂ solid content concentration of 3% by mass is added. , Also referred to as A-2 liquid).

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

Next, 2,083.3 g (dry62.5 g) of the A-2 solution was heated to 15 ° C., and 6,250 g (dry187.5 g) of the B solution was added thereto over 18 hours while stirring. During this period, the liquid temperature was maintained at 15 ° C., and if necessary, an aqueous ammonia solution having an ammonia concentration of 3% was added to maintain the pH at 7.6 to 8.0. Then, when the addition of the liquid B was completed, aging was carried out for 4 hours while keeping the liquid temperature at 15 ° C. While liquid B was being added to liquid A-2 and during aging, air was continuously blown into the preparation liquid to maintain the redox potential at 50 to 200 mV.
After completion of aging, the work of replenishing ion-exchanged water and washing after filtering using an ultrafiltration membrane was repeated until the electrical conductivity was 51 μS / cm to obtain a precursor particle dispersion.

Next, 3% by mass acetic acid was added to the obtained precursor particle dispersion to adjust the pH to 6.5, and the mixture was dried in a dryer at 120 ° C. for 15 hours and then used in a muffle furnace at 1015 ° C. It was fired for 2 hours to obtain a powdery fired body.

310 g of the obtained fired body and 821 g of ion-exchanged water were placed in a 1 L patterned beaker, a 3% aqueous ammonia solution was added thereto, and ultrasonic waves were irradiated in an ultrasonic bath for 10 minutes with stirring to obtain a pH of 10 ( A suspension having a temperature of 25 ° C.) was obtained.
Next, 595 g of quartz beads having a diameter of 0.25 mm were put into a crusher (LMZ06 manufactured by Ashizawa Finetech Co., Ltd.) whose equipment had been washed in advance, and water operation was performed. Further, the above suspension was filled in the charge tank of the crusher (filling rate 85%). Considering the ion-exchanged water remaining in the crushing chamber and the piping of the crusher, the concentration at the time of crushing is 19% by mass. Then, wet crushing was performed at a peripheral speed of the disk in the crusher at 12 m / sec and a number of passes of 20 times. Further, an aqueous ammonia solution having an ammonia concentration of 3% by mass was added for each pass so that the pH of the suspension at the time of crushing was maintained at 10. In this way, a calcined body crushed dispersion having a solid content concentration of 15% by mass was obtained.
Next, the obtained calcined body crushed dispersion was centrifuged in a centrifuge device (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at a relative centrifugal acceleration of 675 G for 3 minutes to remove sediment components, and ceria was removed. A system composite fine particle dispersion was obtained.

<Comparative Example 1>
The silica fine particle dispersion obtained in the preparation step 1 having an average particle diameter of 331 nm was used as a ceria-based composite fine particle, and the same evaluation as in Example 1 was performed. That is, the silica fine particle dispersion obtained in the preparation step 1 having an average particle diameter of 331 nm was evaluated in the same manner as the ceria-based composite fine particles obtained in Example 1.

<Comparative Example 2>
The silica fine particle dispersion obtained in the preparation step 2 having an average particle diameter of 189 nm was used as a ceria-based composite fine particle, and the same evaluation as in Example 1 was performed. That is, the silica fine particle dispersion obtained in the preparation step 2 having an average particle diameter of 189 nm was evaluated in the same manner as the ceria-based composite fine particles obtained in Example 1.

<Comparative Example 3>
Ultrapure water is added to the silica fine particle dispersion having an average particle diameter of 96 nm obtained in the preparation step 3, and the dispersion having a SiO ₂ solid content concentration of 3% by mass is 5,833.3 g (SiO ₂ dry175 g) (hereinafter referred to as A). -3 liquid) was obtained.

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

Next, 5,833.3 g (SiO ₂ dry 175 g) of the A-3 liquid was heated to 18 ° C., and 2,500 g (dry 75 g) of the B liquid was added thereto while stirring. During this period, the liquid temperature was maintained at 18 ° C., and 3% aqueous ammonia was added as needed to maintain the pH at 7.4 to 7.8. Then, when the addition of the liquid B was completed, aging was carried out for 4 hours while keeping the liquid temperature at 18 ° C. While liquid B was being added to liquid A-3 and during aging, air was continuously blown into the preparation liquid to maintain the redox potential at 50 to 200 mV.
After completion of aging, the work of replenishing ion-exchanged water and washing after filtering using an ultrafiltration membrane was repeated until the electrical conductivity was 50 μS / cm to obtain a precursor particle dispersion.

Next, 3% by mass acetic acid was added to the obtained precursor particle dispersion to adjust the pH to 6.5, and the mixture was dried in a dryer at 120 ° C. for 15 hours and then used in a muffle furnace at 1032 ° C. It was fired for 2 hours to obtain a powdery fired body.
After adding 300 g of ion-exchanged water to 100 g of powder (calcined body) obtained after firing and adjusting the pH to 9.3 using a 3% aqueous ammonia solution, φ0.25 mm quartz beads (Daken Kagaku Kogyo Co., Ltd.) Wet crushing (batch type tabletop sand mill manufactured by Kampe Co., Ltd.) was performed for 300 minutes at (manufactured by the company).
Then, after crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained calcined body crushed dispersion was 8.2% by mass, and the weight was 1078 g. During crushing, an aqueous ammonia solution was added to keep the pH at 9.3.

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

In addition, the ceria-based composite fine particles contained in the ceria-based composite fine particle dispersion obtained in Comparative Example 3 were observed using SEM and TEM. FIG. 6A shows an SEM image, and FIG. 6B shows a TEM image. From FIG. 6, it was found that the ceria child particles existed in the form of islands and had a low surface coverage with respect to the composite fine particles.

<Comparative Example 4>
3.63 kg of 0.7 mass% aqueous ammonia was prepared and heated to 93 ° C. (Liquid A-4). Next, 5.21 kg (Liquid B) of a 1.6 mass% cerium nitrate solution was prepared as CeO ₂ , and Liquid B was added to Liquid A-4 over 1 hour. After the addition was completed, the mixture was aged at 93 ° C. for 3 hours. The pH of the solution after aging was 8.4. After cooling the aged solution, the solution was centrifuged at a relative centrifugal acceleration of 5000 G to remove the supernatant. Then, ion-exchanged water was added to the precipitated cake, and the mixture was stirred to perform a reslurry, and the process of centrifuging at a relative centrifugal acceleration of 5000 G was repeated until the electric conductivity of the slurry became 100 μS / cm or less. The slurry having an electric conductivity of 100 μS / cm or less was adjusted to a solid content concentration of 6.0% by mass and dispersed by ultrasonic waves to obtain a ceria fine particle dispersion.
The average particle size of the obtained ceria fine particle dispersion was measured and found to be 118 nm.
Moreover, when the crystallite diameter and the crystal form were measured by X-ray, the crystallite diameter was 18 nm, and the crystal form of Cerianite was shown.
The pH of this ceria fine particle dispersion was adjusted to 5.0 with nitric acid to obtain a polishing abrasive grain dispersion having a solid content concentration of 0.6 mass. The thermal oxide film was polished with this abrasive grain dispersion liquid for polishing. The results are shown in Tables 1 to 3.

<Experiment 2>
[Measurement of Si solid solution state]
The ceria-based composite fine particle dispersion prepared in Example 1 was measured for X-ray absorption spectrum at the CeL III absorption edge (5727eV) using an X-ray absorption spectroscopy measuring device (R-XAS Looper manufactured by Rigaku). The EXAFS vibration appearing in the X-ray absorption spectrum was obtained. Rigaku software REX-2000 was used for the analysis, and the average number of coordinated atoms N and the average bond length R of oxygen and cerium around cerium were obtained. The results are shown in Table 4.
From the results in Table 4, oxygen, silicon and cerium are present around cerium, and in Example 1, the cerium-oxygen atom distance is 2.4 Å and the cerium-cerium atom distance is 3.8 Å. On the other hand, it was confirmed that the interatomic distance between cerium and silicon was 3.2 Å. In Example 3, it was confirmed that the cerium-oxygen atom distance was 2.4 Å and the cerium-cerium atom distance was 3.9 Å, whereas the cerium-silicon atom distance was 3.2 Å. Was done.
Moreover, from the analysis result of XRD, cerium exists as CeO ₂ in the crystal form of Cerianite.
Therefore, in the case of Example 1 and Example 3, it is considered that Si is dissolved in cerium oxide.
On the other hand, in Comparative Example 1 and Comparative Example 4, the Si coordination at the center of Ce was not detected.

<Experiment 3>
The flow potential of each ceria-based composite fine particle dispersion obtained in Examples 2 and 3 and Comparative Example 4 was measured and cationic colloid titration was performed. As the titration device, an automatic titration device AT-510 (manufactured by Kyoto Electronics Industry Co., Ltd.) equipped with a flow potential titration unit (PCD-500) was used.
First, a 0.05% aqueous hydrochloric acid solution was added to a ceria-based composite fine particle dispersion having a solid content concentration adjusted to 1% by mass to adjust the pH to 6. Next, an amount corresponding to 0.8 g of the solid content of the liquid was placed in a 100 ml tall beaker, and the flow potential was measured. Next, a cationic colloid titration solution (0.001N polydialyldimethylammonium chloride solution) was added at 5-second intervals with an injection volume of 0.2 ml and an injection rate of 2 seconds / ml to 20 ml for titration. Then, the addition amount (ml) of the cation colloid titration solution is plotted on the X-axis, and the flow potential (mV) of the ceria-based composite fine particle dispersion is plotted on the Y-axis. In addition, the flow potential C (mV) in the knick and the addition amount V (ml) of the cationic colloid titrator were determined, and ΔPCD / V = (IC) / V was calculated. The results are shown in Table 5. The flow potential curve is shown in FIG.

The ceria-based composite fine particles contained in the dispersion liquid of the present invention do not contain coarse particles, so that they have low scratches and a high polishing rate. Therefore, the polishing abrasive grain dispersion liquid containing the dispersion liquid of the present invention can be preferably used for polishing the surface of semiconductor devices such as semiconductor substrates and wiring boards. Specifically, it can be preferably used for flattening a semiconductor substrate on which a silica film is formed.

Claims (14)

A ceria-based composite fine particle dispersion liquid containing ceria-based composite fine particles having an average particle diameter of 30 to 1000 nm and having the following characteristics [1] to [5].
[1] The ceria-based composite fine particles have a mother particle, a cerium-containing silica layer on the surface of the mother particle, and child particles dispersed inside the cerium-containing silica layer, and the mother particle is Amorphous silica is the main component, and the child particles are mainly composed of crystalline ceria.
[2] The surface coverage of the child particles in the ceria-based composite fine particles is 60% or more .
[3] The ceria-based composite fine particles have a mass ratio of silica to ceria of 100: 50 to 400.
[4] When the ceria-based composite fine particles are subjected to X-ray diffraction, only the crystal phase of ceria is detected.
[5] The ceria-based composite fine particles have an average crystallinity diameter of 10 to 50 nm, which is measured by subjecting them to X-ray diffraction. The ceria-based composite fine particle dispersion liquid according to claim 1, wherein the geometric mean particle diameter of the child particles is 10 to 60 nm. The ceria-based composite fine particle dispersion liquid according to claim 1 or 2, which further comprises the ceria-based composite fine particles having the following characteristics of [6].
[6] A silicon atom is dissolved in the crystalline ceria contained in the child particles. A claim that the cerium atom and silicon atom contained in the child particles satisfy the relationship of R ₁ <R ₂ when the cerium-silicon atom distance is R ₁ and the cerium-cerium atom distance is R ₂ . 3. The cerium-based composite fine particle dispersion liquid according to 3. When cationic colloid titration is performed, the ratio (ΔPCD / V) of the flow potential change amount (ΔPCD) represented by the following formula (1) to the addition amount (V) of the cationic colloid titration solution in the knick is −150. The ceria-based composite fine particle dispersion liquid according to any one of claims 1 to 4, wherein a flow potential curve of 0 to -15.0 can be obtained.
ΔPCD / V = (IC) / V ... Equation (1)
C: Flow potential (mV) in the knick
I: Flow potential (mV) at the start point of the flow potential curve
V: Addition amount (ml) of the cationic colloid titration solution in the knick The ceria-based composite fine particle dispersion according to claim 5, wherein the flow potential before titration is a negative potential when the pH value is in the range of 3 to 8. The ceria-based composite fine particle dispersion liquid according to any one of claims 1 to 6, wherein the number of the ceria-based composite fine particles having coarse particles of 0.98 μm or more is 100 million / cc or less in terms of dryness. .. The ceria-based composite fine particle dispersion liquid according to any one of claims 1 to 7, wherein the content ratio of impurities contained in the ceria-based composite fine particles is as follows (a) and (b).
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively. An abrasive grain dispersion liquid for polishing containing the ceria-based composite fine particle dispersion liquid according to any one of claims 1 to 8. The polishing abrasive grain dispersion liquid according to claim 9, wherein the polishing abrasive grain dispersion liquid is for flattening a semiconductor substrate on which a silica film is formed. The method for producing a ceria-based composite fine particle dispersion liquid according to any one of claims 1 to 8, which comprises the following steps 1 to 3.
Step 1: Stir the silica fine particle dispersion liquid in which the silica fine particles are dispersed in the solvent, and maintain the temperature at 0 to 20 ° C., the pH at 7.0 to 9.0, and the redox potential at 50 to 500 mV. A step of continuously or intermittently adding a metal salt of hecerium to obtain a precursor particle dispersion liquid containing precursor particles.
Step 2: The precursor particle dispersion is dried, calcined at 800 to 1,200 ° C., a solvent is added to the obtained calcined product, and the mixture is crushed in a wet manner in the range of pH 8.6 to 10.8. A process of processing to obtain a calcined body crushed dispersion.
Step 3: A step of centrifuging the fired body crushed dispersion at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component to obtain a ceria-based composite fine particle dispersion. In step 1, the silica fine particle dispersion is stirred, the temperature is maintained at 0 to 20 ° C., the pH is 7.0 to 9.0, and the redox potential is maintained at 50 to 500 mV. Is continuously or intermittently added, and then the metal salt of the cerium is maintained at a temperature of more than 20 ° C. and 98 ° C. or lower, a pH of 7.0 to 9.0, and a redox potential of 50 to 500 mV. The method for producing a ceria-based composite fine particle dispersion according to claim 11, which is a step of continuously or intermittently adding the above to obtain the precursor particle dispersion. In step 1, the silica fine particle dispersion is stirred, and the temperature is maintained at more than 20 ° C. and 98 ° C. or lower, the pH is 7.0 to 9.0, and the oxidation-reduction potential is 50 to 500 mV. The metal salt of the cerium is added continuously or intermittently, and then 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 11 or 12, which is a step of continuously or intermittently adding the above to obtain the precursor particle dispersion. The ceria-based composite fine particle dispersion according to any one of claims 11 to 13, wherein the content ratio of impurities contained in the silica fine particles in the step 1 is as follows (a) and (b). Liquid manufacturing method.
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti and Zn are 100 ppm or less, respectively.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are 5 ppm or less, respectively.

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