JP6648064B2 - Silica-based composite fine particle dispersion, method for producing the same, and polishing abrasive dispersion containing silica-based composite fine particle dispersion - Google Patents

Description

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

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

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

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

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

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

  Further, Patent Document 2 discloses that at least one kind selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium is provided on the surface of amorphous silica particles A. A silica-based composite particle having a crystalline oxide layer B containing an element is described. Further, as a preferred embodiment, an amorphous oxide layer containing an element such as aluminum, which is different from the amorphous silica layer, is provided on the surface of the amorphous silica particles A. C is a crystalline oxide layer further containing at least one element selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium B-containing silica-based composite particles are described. Since such a silica-based composite particle has a crystalline oxide layer B on the surface of the amorphous silica particle A, the polishing rate can be improved, and the silica particle is pretreated. By doing so, sintering of particles during firing is suppressed, dispersibility in the polishing slurry can be improved, and further, cerium oxide is not contained, or the use amount of cerium oxide can be significantly reduced. It is described that the method can provide an inexpensive abrasive having 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 sintering of the particles and the effect of improving the polishing rate.

Japanese Patent No. 2748661 JP 2013-119131 A

See Seung-Ho Lee, Zhenyu Lu, S.M. V. Babu and Egon Matijevic, "Chemical mechanical polishing of thermal oxide films using silicone particles coated with each cereal, 27th edition of the joint venture, and 27th edition of the journal."

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

  In addition, the ceria-coated silica described in Non-Patent Document 1 is not calcined, so the ceria crystallinity is low, and therefore, it is considered that the actual polishing rate is low, and the ceria drops off and the surface of the polishing base material is removed. There is also a concern that particles may remain on the surface.

  Furthermore, when polishing is performed using the silica-based composite particles having the oxide layer C described in Patent Document 2, impurities such as aluminum remain on the surface of the semiconductor device, which may adversely affect the semiconductor device. The inventor has found out.

  An object of the present invention is to solve the above problems. That is, the present invention is capable of polishing at high speed even with a silica film, a Si wafer, or a difficult-to-process material, and at the same time, achieves high surface accuracy (low scratches, little abrasive grains remaining on the substrate, improvement of the substrate Ra value). And the like, a silica-based composite fine particle dispersion that can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate, a method for producing the same, and a polishing abrasive dispersion containing the silica-based composite fine particle dispersion. The purpose is to provide.

The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and have completed the present invention.
The present invention is the following (1) to (8).
(1) A mother particle having amorphous silica as a main component, a child particle having crystalline ceria as a main component on a surface thereof, and a silica coating on a part of the surface of the child particle. A silica-based composite fine particle dispersion containing silica-based composite fine particles having an average particle diameter of 50 to 350 nm and having the features of [1] to [4].
[1] The silica-based composite fine particles have a mass ratio of silica to ceria of 100: 11 to 316.
[2] When the silica-based composite fine particles are subjected to X-ray diffraction, only the ceria crystal phase is detected.
[3] The silica-based composite fine particles have a crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.
[4] A silicon atom is dissolved in crystalline ceria which is a main component of the child particles.
(2) Regarding cerium atoms and silicon atoms contained in the above-mentioned child particles, when the distance between adjacent cerium-silicon atoms is R ₁ and the distance between adjacent cerium-cerium atoms is R ₂ , R ₁ <R ₂ The silica-based composite fine particle dispersion according to the above (1), which satisfies the following relationship:
(3) The silica-based composite fine particles according to the above (1) or (2), wherein the content ratio of impurities contained in the silica-based composite fine particles is as shown in the following (a) and (b). Dispersion.
(A) The content of each of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.
(4) A polishing abrasive dispersion containing the silica-based composite fine particle dispersion according to any one of the above (1) to (3).
(5) The polishing abrasive dispersion according to the above (4), which is used for flattening a semiconductor substrate on which a silica film is formed.
(6) The abrasive grain dispersion for polishing according to the above (5), wherein the pH is 3 to 8.
(7) A method for producing a silica-based composite fine particle dispersion, comprising the following steps 1 to 3, wherein the silica-based composite fine particle dispersion according to any one of the above (1) to (3) is obtained. .
Step 1: A silica fine particle dispersion in which silica fine particles are dispersed in a solvent is stirred, and a cerium metal salt is continuously added thereto while maintaining the temperature at 5 to 98 ° C and the pH within a range of 7.0 to 9.0. A step of obtaining the precursor particle dispersion liquid containing the precursor particles by adding the precursor particles intermittently or intermittently.
Step 2: the precursor particle dispersion is dried, and calcined at 400～1,200 ° C., the resulting fired body, as engineering to obtain a sintered body disintegration dispersion was processed in the following (ii) .
( Ii) A solvent is added and the mixture is wet-crushed in a pH range of 8.6 to 10.8.
Step 3: a step of obtaining a silica-based composite fine particle dispersion by subjecting the fired body crushed dispersion to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component.
(8) The method for producing a silica-based composite fine particle dispersion according to the above (7), wherein the content ratio of the impurities contained in the silica fine particles is as follows (a) and (b).
(A) The content of each of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.

ADVANTAGE OF THE INVENTION According to this invention, even if it is a silica film, a Si wafer, or a difficult-to-machine material, it can be polished at high speed, and at the same time, has high surface accuracy (low scratch, low surface roughness (Ra) of the substrate to be polished, etc.). The present invention provides a silica-based composite fine particle dispersion which can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate and a wiring substrate, a method for producing the same, and a polishing abrasive dispersion including the silica-based composite fine particle dispersion. can do.
The silica-based composite fine particle dispersion of the present invention is effective for flattening the surface of a semiconductor device, and is particularly suitable for polishing a substrate on which a silica insulating film is formed.

FIG. 1A is an SEM image obtained in Example 4, and FIG. 1B is a TEM image obtained in Example 4. 9 is an X-ray diffraction pattern obtained in Example 4. FIG. 3A is an SEM image obtained in Comparative Example 2, and FIG. 3B is a TEM image obtained in Comparative Example 2. 9 is an X-ray diffraction pattern obtained in Comparative Example 2. FIG. 5A is a TEM obtained in Example 4, and FIG. 5B is a TEM image in which a part of FIG. 5A is enlarged. FIG. 4 is a titration diagram of streaming potential.

The present invention will be described.
The present invention has child particles mainly composed of crystalline ceria on the surface of base particles mainly composed of amorphous silica (hereinafter, the “base particles” are also referred to as “silica fine particles”), further comprising by silica coating on a part of the surface of the daughter particles, further from the following [1] including the average particle diameter 50~350nm of silica composite particles comprising the features of [4], a silica-based composite fine particles dispersion is there.
[1] The silica-based composite fine particles have a mass ratio of silica to ceria of 100: 11 to 316.
[2] When the silica-based composite fine particles are subjected to X-ray diffraction, only the ceria crystal phase is detected.
[3] The silica-based composite fine particles have a crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.
[4] A silicon atom is dissolved in crystalline ceria which is a main component of the child particles.
Hereinafter, such a silica-based composite fine particle dispersion is also referred to as “dispersion of the present invention”.
In addition, the silica-based composite fine particles contained in the dispersion of the present invention are hereinafter also referred to as “composite fine particles of the present invention”.

Further, the present invention is a method for producing a silica-based composite fine particle dispersion, which comprises the following steps 1 to 3 and obtains the dispersion of the present invention.
Step 1: A silica fine particle dispersion obtained by dispersing silica fine particles in a solvent is stirred, and while maintaining the temperature at 5 to 98 ° C. and the pH range at 7.0 to 9.0, a cerium metal salt is continuously added thereto. A step of obtaining the precursor particle dispersion liquid containing the precursor particles by adding the precursor particles intermittently or intermittently.
Step 2: the precursor particle dispersion is dried, and calcined at 400～1,200 ° C., the resulting fired body, as engineering to obtain a sintered body disintegration dispersion was processed in the following (ii) .
( Ii) A solvent is added and the mixture is wet-crushed in a pH range of 8.6 to 10.8.
Step 3: a step of obtaining a silica-based composite fine particle dispersion by subjecting the fired body crushed dispersion to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component. The relative centrifugal acceleration is expressed by a ratio of the gravitational acceleration of the earth to 1 G.
Hereinafter, the method for producing such a silica-based composite fine particle dispersion is also referred to as “the production method of the present invention”.

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

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

  The composite fine particles of the present invention will be described.

<Base particles>
In the composite fine particles of the present invention, the base particles are mainly composed of amorphous silica.

  The fact that the silica contained in the base particles in the present invention is amorphous can be confirmed, for example, by the following method. After drying the dispersion liquid (silica fine particle dispersion) containing the base particles (silica fine particles), the mixture is pulverized using a mortar, for example, using a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). When an X-ray diffraction pattern is obtained, a peak of crystalline silica such as Cristoballite does not appear. From this, it can be confirmed that the silica contained in the base particles (silica fine particles) is amorphous.

The term “main component” means that the content is 90% by mass or more. That is, the content of the amorphous silica in the base particles is 90% by mass or more. This content is preferably at least 95% by mass, more preferably at least 98% by mass, and even more preferably at least 99.5% by mass.
In the following description of the present invention, the term "main component" is used in such a meaning.

The base particles contain amorphous silica as a main component, and may contain other materials, for example, crystalline silica or an impurity element.
For example, in the base particles (silica fine particles), each element of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr (hereinafter, referred to as “specific impurity group 1”). In some cases) is preferably 100 ppm or less. Further, it is preferably at most 50 ppm, more preferably at most 25 ppm, further preferably at most 5 ppm, still more preferably at most 1 ppm. The content of each of the elements U, Th, Cl, NO ₃ , SO _4, and F (hereinafter sometimes referred to as “specific impurity group 2”) in the base particles (fine silica particles) is 5 ppm or less, respectively. Preferably, there is.
In general, silica fine particles prepared using water glass as a raw material contain the specific impurity group 1 and the specific impurity group 2 derived from the raw water glass in the order of several thousand ppm in total.
In the case of a silica fine particle dispersion 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 ion exchange treatment. However, the specific impurity group 1 and the specific impurity group 2 remain in a few ppm to a few hundred ppm in total. Therefore, when using silica particles made from water glass, impurities are also reduced by acid treatment or the like.
On the other hand, in the case of a silica fine particle dispersion in which silica fine particles synthesized using alkoxysilane as a raw material are dispersed in a solvent, the content of each element and each anion in the specific impurity group 1 and the specific impurity group 2 is usually used. Is 20 ppm or less in each case.
In the present invention, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ and SO _{4 in the base} particles (silica fine particles) are used. And the content of each of F is a value determined by measurement using the following method.
-Na and K: Atomic absorption spectroscopy-Ag, Al, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, Zr, U and Th: ICP (inductively coupled plasma emission spectroscopy)
· Cl: potentiometric titration · NO _3, SO ₄ and F: ion chromatograph

As described below, since the average particle size of the silica-based composite fine particles in the present invention is in the range of 50 to 350 nm, the average particle size of the base particles is necessarily smaller than 350 nm. In the present application, the average particle diameter of the base particles is the same as the average particle diameter 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 below. Silica-based composite fine particles having an average particle diameter of the base particles in the range of 30 to 330 nm are preferably used.
When the average particle diameter of the base particles is in the above range, scratches are reduced when the dispersion of the present invention is used as an abrasive. If the average particle size of the base particles is smaller than 30 nm, the polishing rate tends to be insufficient. If the average particle diameter is larger than 330 nm, the polishing rate tends to decrease. In addition, the surface accuracy of the substrate tends to deteriorate.

The average particle diameter of the base particles (silica fine particles) in the present invention means a value measured by a dynamic light scattering method or a laser diffraction scattering method. Specifically, it means a value obtained by measurement by the following method. After dispersing the silica fine particles in water or the like to obtain a silica fine particle dispersion, the silica fine particle dispersion is subjected to a particle diameter measuring device using a known dynamic light scattering method (for example, a Microtrack UPA device manufactured by Nikkiso Co., Ltd., The measurement is performed using a measuring apparatus (for example, LA-950 manufactured by HORIBA) using a laser diffraction scattering method (PAR-III manufactured by Otsuka Electronics Co., Ltd.).
In addition, the measuring device is properly used according to the purpose of each step, the assumed particle diameter and the particle size distribution. Specifically, monodisperse silica fine particles of a raw material having a uniform particle size of about 100 nm or less use PAR-III, and monodisperse raw silica fine particles having a large size of 100 nm or more are measured by LA-950. In the disintegration step in which the particle diameter varies widely from to nanometers, a particle diameter measuring device using a known dynamic light scattering method or a measuring device using a known laser diffraction scattering method (preferably, Microtrack UPA or LA-950) is used. Is preferred.

The shape of the base particles (silica fine particles) is not particularly limited, and examples thereof include a spherical surface, a bale shape, a short fiber shape, a tetrahedral shape (triangular pyramid shape), a hexahedral shape, an octahedral shape, a plate shape, and an irregular shape. May have a wart-like protrusion, a spine-like one, or a porous one, but a spherical one is preferred. The term “spherical” means that the ratio of the number of particles having a minor axis / major axis ratio of 0.8 or less is 10% or less. The base particles preferably have a minor axis / major axis ratio of 0.8 or less and a particle number ratio of 5% or less, and more preferably 0%.
The minor axis / major axis ratio is measured by the same method as the below-described method of measuring the minor axis / major axis ratio (image analysis method) of the composite fine particles of the present invention.

<Child particle>
The composite fine particles of the present invention have child particles on the surface of the above-described base particles. Here, the child particles whose entirety is covered with the silica coating may be bonded to the base particles via the silica coating. Even such an embodiment is an embodiment in which the child particles are present on the surface of the base particle, and is included in the technical scope of the present invention.

  In the composite fine particles of the present invention, the sub-particles mainly contain crystalline ceria.

  The fact that the child particles are crystalline ceria means that, for example, the dispersion of the present invention is dried and then crushed using a mortar, for example, using a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Denki Co., Ltd.). This can be confirmed from the fact that only the ceria crystal phase is detected in the X-ray diffraction pattern obtained by the method (1). In addition, as the ceria crystal phase, Cerianite and the like can be mentioned.

The secondary particles have crystalline ceria (crystalline Ce oxide) as a main component, and may contain other elements, for example, elements other than cerium.
However, as described above, when the composite fine particles of the present invention are subjected to X-ray diffraction, only the ceria crystal phase is detected. In other words, even if a crystal phase other than ceria is included, the content is small, and therefore, is out of the detection range by X-ray diffraction.
The definition of “principal component” is as described above.

  Regarding the child particles, the crystallite diameter of the crystalline ceria measured by subjecting the composite fine particles of the present invention to X-ray diffraction is 10 to 25 nm, preferably 11 to 23 nm, and more preferably 12 to 20 nm. More preferred.

The crystallite diameter of crystalline ceria is determined from the full width at half maximum of the maximum peak of the X-ray diffraction pattern. For example, the average crystallite diameter of the (111) plane is 10 to 25 nm (full width at half maximum is 0.86 to 0.34 °), and 11 to 23 nm (full width at half maximum is 0.78 to 0.37 °). More preferably, it is 12 to 20 nm (the full width at half maximum is 0.79 to 0.43 °). In many cases, the intensity of the peak of the (111) plane is maximized. However, the crystal plane is not limited to the (111) plane (around 2θ = 28 degrees), and is not limited to another crystal plane, for example, (100). The peak intensity of the surface may be maximum. In this case, the average crystallite diameter can be calculated in the same manner. In this case, the average crystallite diameter may be the same as the average crystallite diameter of the (111) plane.
The method of measuring the average crystallite diameter of the child particles will be described below by taking, as an example, the case of the (111) plane (around 2θ = 28 °).
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained using, for example, a conventionally known X-ray diffractometer (for example, RINT1400, manufactured by Rigaku Denki Co., Ltd.). Then, the half-value width of the peak of the (111) plane near 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the crystallite diameter can be obtained by the following Scherrer equation.
D = Kλ / βcosθ
D: crystallite diameter (angstrom)
K: Scherrer constant (here, K = 0.94)
λ: X-ray wavelength (1.7889 angstroms, Cu lamp)
β: half width (rad)
θ: reflection angle

  The size of the child particles is smaller than that of the base particles, preferably has an average particle diameter of 11 to 26 nm, more preferably 12 to 23 nm. The size of the child particles was determined by measuring the average particle diameter of arbitrary 50 child particles in a photograph projection view (for example, FIG. 1 (C) described later) magnified 300,000 times using a transmission electron microscope. It means the value obtained by simply averaging these.

<Silica coating>
The composite fine particles of the present invention have the child particles on the surface of the base particles, and further have a silica coating on the surface of the child particles. Here, the child particles may be bonded to the surface of the base particles, and further have a silica coating covering them. That is, the part of the composite particles in which the child particles are attached to the surface of the mother particle silica film covers. Therefore, the silica coating is present on the outermost surface of the composite fine particles of the present invention.

In the image (TEM image) obtained by observing the composite fine particles of the present invention using a transmission electron microscope, an image of the child particles appears dark on the surface of the base particles, but outside the child particles, that is, the composite of the present invention. On the surface side of the fine particles, a silica coating appears as a relatively thin image. Further, an embodiment in which the child particles (ceria fine particles) are bonded to the base particles (silica fine particles) may be adopted, in which the child particles partially covered by the silica coating are bonded to the base particles via the silica coating. It may be.
When the composite fine particles of the present invention are subjected to EDS analysis to obtain an element distribution, a portion having a high Ce concentration appears on the surface side of the particles, and a portion having a high Si concentration appears further outside.
Further, when the EDS measurement in which the electron beam is selectively applied to the portion of the silica coating specified by the transmission electron microscope as described above is performed to determine the Si atom number% and the Ce atom%, the Si atom It can be seen that a few percent are very high. Specifically, the ratio of the number of Si atoms to the number of Ce atoms (% of Si atoms /% of Ce atoms) is 0.9 or more.

Such a silica coating is considered to promote the bonding (force) between the child particles (ceria crystal particles) and the mother particles (silica fine particles). Thus, for example, in the step of obtaining the dispersion of the present invention, the silica-based composite fine particle dispersion is obtained by subjecting the silica-based composite fine particles obtained by firing to wet disintegration to obtain a silica-based composite fine particle dispersion. It is considered that the particles (ceria crystal particles) have an effect of preventing the particles from deviating from the base particles (silica fine particles). In this case, there is no problem that the child particles locally fall off, and the entire surface of the child particles does not have to be covered with the silica coating. It suffices that the particles have such a rigidity that the particles do not separate from the base particles in the crushing step.
When such a structure is provided, it is considered that when the dispersion of the present invention is used as an abrasive, the polishing rate is high, and the deterioration of surface accuracy and scratches is small.
Further, in the composite fine particles of the present invention, since a part of the surface of the child particles is covered with the silica layer, the OH group of silica exists on the outermost surface (outermost shell) of the composite fine particles of the present invention. . For this reason, when used as an abrasive, the composite fine particles of the present invention are repelled by the charge due to the -OH group on the surface of the polishing substrate, and as a result, it is thought that the adhesion to the surface of the polishing substrate is reduced.
In addition, free ceria has a positive charge and thus easily adheres to the substrate. When the composite fine particles of the present invention have a silica coating on the surface of the child particles, even if the ceria particles of the child particles fall off during polishing, the surface has a negative charge because it is covered with silica. This also has the effect of reducing adhesion to the substrate.
Further, ceria has a different potential from silica, a polishing substrate and a polishing pad, and has a negative zeta potential decreasing from alkaline to near neutral pH, and has an opposite positive potential in a weakly acidic region. Therefore, it adheres to the polishing base 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 or the polishing pad. On the other hand, in the silica-based composite fine particles of the present invention, the ceria, which is a child particle, is partially covered with a silica coating, so that the pH maintains a negative potential from alkaline to acidic. Less abrasive particles remain on the surface.

  The thickness of the silica coating is generally determined from the TEM image and the SEM image by the degree of coverage of the ceria child particles on the base particles with the silica coating. That is, as described above, in the TEM image, an image of a child particle having a particle diameter of about 20 nm appears densely on the surface of the base particle, and a silica coating appears as a relatively thin image outside the child particle. By comparing with the size of the silica film, the thickness of the silica coating can be approximately determined. As for this thickness, if the child particles can be clearly confirmed as irregularities from the SEM image, and if the irregularities are seen in the outline of the silica-based composite fine particles from the TEM image, it is considered that the thickness of the silica film is much less than 20 nm. Can be On the other hand, if the irregularities of the child particles are not clear from the SEM image and no irregularities are seen in the outline of the silica-based composite fine particles from the TEM image, it is considered that the thickness of the silica coating is about 20 nm.

  In addition, as described above, the silica coating of the outermost layer (opposite to the base particle side) may not completely cover the entirety of the child particles (ceria fine particles). That is, although the silica coating is present on the outermost surface of the composite fine particles of the present invention, there may be a portion where the silica coating is not present. Further, there may be a portion where the base particles of the silica-based composite fine particles are exposed.

<Composite fine particles of the present invention>
As described above, the composite fine particles of the present invention have the above-described child particles on the surface of the base particles.

In the composite fine particles of the present invention, the mass ratio of silica to ceria is 100: 11-316, preferably 100: 30-230, more preferably 100: 30-150, and 100: 60- More preferably, it is 120. It is considered that the mass ratio between silica and ceria is approximately the same as the mass ratio between the mother particles and the child particles. If the amount of the child particles is too small relative to the base particles, the base particles may be bonded to each other to generate coarse particles. In this case, the abrasive (polishing abrasive particle dispersion) containing the dispersion of the present invention may cause defects (decrease in surface accuracy such as increase in scratches) on the surface of the polishing base material. Also, if the amount of ceria relative to silica is too large, not only is it costly, but also resource risk increases. Further, fusion of the particles proceeds. As a result, the causes of troubles such as an increase in the roughness of the substrate surface (deterioration of the surface roughness Ra), an increase in scratches, the release of ceria remaining on the substrate, and adhesion to waste liquid piping of a polishing apparatus. It is easy to become.
The silica to be used in calculating the mass ratio includes all of the following (I) to (III).
(I) Silica component constituting mother particles (II) Composite fine particles obtained by bonding child particles (ceria component) to mother particles are solidified in silica component (III) ceria child particles contained in a covering silica coating. Dissolved silica component

The content (% by mass) of silica (SiO ₂ ) and ceria (CeO ₂ ) in the composite fine particles of the present invention is determined by first setting the solid content concentration of the dispersion of the composite fine particles of the present invention (the dispersion of the present invention) to 1000 ° C. The weight loss is determined by igniting.
Next, the content (% by mass) of cerium (Ce) contained in a predetermined amount of the composite fine particles of the present invention is determined by ICP plasma emission analysis, and is converted to ₂ % by mass of CeO. Then, assuming that the component other than CeO ₂ constituting the composite fine particles of the present invention is SiO ₂ , the SiO ₂ mass% can be calculated.
In the production method of the present invention, the mass ratio of silica to ceria can also be calculated from the amounts of the silica source substance and the ceria source substance used when preparing the dispersion of the present invention. This can be applied when the process is not such that ceria or silica is dissolved and removed, and in such a case, the used amount of ceria and silica and the analysis value show good agreement.

The composite fine particles of the present invention may be those in which particulate crystalline ceria (child particles) are bonded to the surface of silica fine particles (base particles) by sintering or the like. In this case, the composite fine particles of the present invention have an uneven surface shape.
That is, at least one (preferably both) of the base particle and the child particle may be sinter-bonded and strongly bonded at their contact points. However, the child particles covered with the silica coating may be bonded to the base particles via the silica coating.

The composite fine particles of the present invention are characterized in that silicon atoms are dissolved in crystalline ceria which is a main component of the above-mentioned child particles. Further, an element other than silicon may be dissolved in crystalline ceria. Generally, solid solution means that two or more types of elements (which may be metallic or non-metallic) are dissolved together and form a uniform solid phase as a whole. , Are classified into substitutional solid solutions and interstitial solid solutions. A substitutional solid solution can easily occur at an atom having a close atomic radius, but it is considered that at least a substitutional solid solution is unlikely to be formed because Ce and Si have greatly different atomic radii. In the crystal structure of Cerianite, the coordination number of Ce as viewed from the center of Ce is 8. For example, when Si is substituted with Ce in a one-to-one correspondence, the coordination number of Ce should be 7. However, according to the analysis results of the composite fine particles of the present invention, the average coordination number of Ce from the center of Ce is 7.9, and the average coordination number of Si is 1.1. Presumed to be type. In addition, from the analysis results of the composite fine particles of the present invention, the interatomic distance between adjacent Ce-Si is smaller than the interatomic distance between adjacent Ce-Ce. Therefore, the composite fine particles of the present invention are interstitial solid solutions. It is presumed that there is. That is, for the cerium atom and the silicon atom contained in the child particles, it is preferable to satisfy the relationship of R ₁ <R ₂ when the distance between cerium and silicon atoms is R ₁ and the distance between cerium and cerium atoms is R _2. .
Conventionally, it has been known that polishing a substrate with a silica film or a glass substrate using ceria particles as abrasive grains shows a specifically high polishing rate as compared with the case of using other inorganic oxide particles. . It is pointed out that one of the reasons why ceria particles exhibit a particularly high polishing rate with respect to a substrate with a silica film is that the ceria particles have high chemical reactivity with respect to a silica coating on a substrate to be polished.
In the composite fine particles of the present invention, in the child particles (ceria fine particles) present on the outer surface side, it is considered that Si atoms form an interstitial solid solution in the CeO ₂ crystal. It is presumed that the solid solution of Si atoms causes crystal distortion of the CeO ₂ crystal, thereby promoting the chemical reactivity of CeO ₂ , resulting in the high polishing rate described above.
The interatomic distance between cerium atom and silicon atom, such as R ₁ and R ₂ , means an average bonding distance obtained by a method described in Examples described later.

The shape of the composite fine particles of the present invention is not particularly limited, but is preferably a particle-connected type in practical use. The particle-coupled type means one in which two or more base particles are partially bonded to each other. It is considered that at least one (preferably both) of the base particles is welded at their contact point, and preferably both are firmly bonded by being fixed. Here, in addition to the case where the child particles are bonded to the surface after the mother particles are bonded to each other, even if the child particles are bonded to the surface of the base particle and then bonded to other particles, the particle connection type And
The connection type allows a large contact area with the substrate, so that the polishing energy can be efficiently transmitted to the substrate. Therefore, the polishing rate is high. Further, since the polishing pressure per particle is lower than that of a single particle, scratches are small.

In the composite fine particles of the present invention, the number ratio of particles having a ratio of minor axis / major axis of 0.80 or less (preferably 0.67 or less) measured by an image analysis method is preferably 50% or more.
Here, particles having a minor axis / major axis ratio of 0.80 or less measured by the image analysis method are considered to be of a particle-bound type in principle.

  A method of measuring the ratio of minor axis / major axis by image analysis will be described. In a photographic projection image obtained by photographing the composite fine particles of the present invention with a transmission electron microscope at a magnification of 250,000 (or 500,000), the maximum diameter of the particles is taken as the major axis, and the length is measured. , And its value is defined as the major axis (DL). Further, a point on the long axis that bisects the long axis is determined, two points where a straight line perpendicular to the long axis intersects the outer edge of the particle are determined, and the distance between the two points is measured to obtain the short diameter (DS). From this, the ratio of minor axis / major axis (DS / DL) is determined. Then, the number ratio (%) of particles having a ratio of minor axis / major axis of 0.80 or less is obtained for any 50 particles observed in the photographic projection.

  In the composite fine particles of the present invention, the number ratio of particles having a minor axis / major axis ratio of 0.80 or less (preferably 0.67 or less) is preferably 55% or more, more preferably 65% or more. . The composite fine particles of the present invention in this range have a high polishing rate when used as an abrasive, and are therefore preferable.

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

The composite fine particles of the present invention preferably have a specific surface area of 4 to 100 m ² / g, more preferably 30 to 60 m ² / g.

Here, a method for measuring the specific surface area (BET specific surface area) will be described.
First, a dried sample (0.2 g) is put into a measurement cell, degassed at 250 ° C. for 40 minutes in a nitrogen gas stream, and then the sample is mixed with 30% by volume of nitrogen and 70% by volume of helium. The liquid nitrogen temperature is maintained in an air stream, and nitrogen is equilibrium-adsorbed to the sample. Next, the temperature of the sample is gradually raised to room temperature while flowing the above-mentioned mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area of the sample is measured by a previously prepared calibration curve.
Such a BET specific surface area measurement method (nitrogen adsorption method) can be performed using, for example, a conventionally known surface area measurement device.
In the present invention, the specific surface area means a value measured by such a method unless otherwise specified.

The average particle diameter of the composite fine particles of the present invention is preferably from 50 to 350 nm, more preferably from 170 to 260 nm. When the average particle diameter of the composite fine particles of the present invention is in the range of 50 to 350 nm, the polishing rate is high when applied as an abrasive, which is preferable.
The average particle diameter of the composite fine particles of the present invention means a value measured by a dynamic light scattering method or a laser diffraction scattering method. Specifically, it means a value obtained by measurement by the following method. The composite fine particles of the present invention are dispersed in water, and this composite fine particle dispersion is subjected to a particle diameter measurement apparatus using a known dynamic light scattering method (for example, a Microtrack UPA apparatus manufactured by Nikkiso Co., Ltd., or a PAR-III manufactured by Otsuka Electronics Co., Ltd.). ) Or using a measuring device by laser diffraction scattering method (for example, LA-950 manufactured by HORIBA).

In the composite fine particles of the present invention, the content of each element of the specific impurity group 1 is preferably 100 ppm or less. Further, it is preferably at most 50 ppm, more preferably at most 25 ppm, further preferably at most 5 ppm, still more preferably at most 1 ppm. The content of each element of the specific impurity group 2 in the composite fine particles of the present invention is preferably 5 ppm or less. As a method for reducing the content of each element of the specific impurity group 1 and the specific impurity group 2 in the composite fine particles of the present invention, the method described for the base particles (silica fine particles) can be applied.
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 a value obtained by measuring using ICP (inductively coupled plasma emission spectroscopy).

  The composite fine particles of the present invention are characterized in that the content of each element of the specific impurity group 1 is 100 ppm or less and the content of each element of the specific impurity group 2 is 5 ppm or less, respectively. In some cases, there are cases where the composite oxide fine particles do not necessarily satisfy this condition. Among them, the former can be suitably used as an abrasive in applications requiring the application of a high-purity abrasive, for example, in polishing of semiconductor devices such as semiconductor substrates and wiring boards. In addition, the latter is applied to applications where application of a high-purity abrasive is not required, such as glass polishing. Of course, the former can naturally be applied to applications where application of a high-purity abrasive is not required.

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

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

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

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

In the dispersion of the present invention, when cationic colloid titration is performed, the ratio of the flow potential change (ΔPCD) represented by the following formula (1) to the addition amount (V) of the cationic colloid titrant in a knick ( It is preferable that a streaming potential curve in which ΔPCD / V) is −110.0 to −15.0 can be obtained.
ΔPCD / V = (IC) / V Equation (1)
C: streaming potential (mV) in the knick
I: streaming potential (mV) at the starting point of the streaming potential curve
V: Amount of the cationic colloid titrant added in the knick (ml)

  Here, the cationic colloid titration is performed by adding the cationic colloid titrant to 80 g of the dispersion of the present invention in which the solid content concentration is adjusted to 1% by mass. A 0.001N polydiallyldimethylammonium chloride solution is used as a cationic colloid titrant. Other measurement conditions are measured by a suitable method according to a literature or an ordinary method recommended by a manufacturer.

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

  When the value of ΔPCD / V is from -110.0 to -15.0, the polishing rate of the abrasive is further improved when the dispersion of the present invention is used as the abrasive. This ΔPCD / V is considered to reflect the degree of coating of the silica coating on the surface of the composite fine particles of the present invention and / or the degree of exposure of the child particles on the surface of the composite fine particles or the presence of silica that is easily detached. The present inventor estimates that when the value of ΔPCD / V is within the above range, the detachment of the child particles during wet pulverization is small and the polishing rate is high. Conversely, if the absolute value of ΔPCD / V is larger than -110.0, the composite fine particle surface is entirely covered with the silica coating, so that it is difficult for child particles to fall off in the crushing step, but the silica particles are polished during polishing. Is difficult to be removed, and the polishing rate decreases. On the other hand, if the absolute value is smaller than -15.0, it is considered that dropout is likely to occur. The present inventors presume that when the content is in the above range, the surface of the child particles is appropriately exposed during polishing, the falling of the child particles is small, and the polishing rate is further improved. ΔPCD / V is more preferably -100.0 to -15.0, and further preferably -100.0 to -20.0.

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

  The method for producing the dispersion of the present invention is not particularly limited, but is preferably produced by the production method of the present invention described below.

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

<Production method of the present invention>
<Step 1>
In step 1, a silica fine particle dispersion in which silica fine particles are dispersed in a solvent is prepared.
According to the production method of the present invention, when attempting to prepare a silica-based composite fine particle dispersion applied to polishing of a semiconductor device or the like, silica fine particles produced by hydrolysis of alkoxysilane are dispersed in a solvent as a silica fine particle dispersion. It is preferable to use a dispersion liquid of silica fine particles. When a conventionally known silica fine particle dispersion (such as a silica fine particle dispersion prepared using water glass as a raw material) is used as a raw material, the silica fine particle dispersion is preferably subjected to an acid treatment and further deionized. . In this case, the contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ , SO ₄ and F contained in the silica fine particles Is, specifically, 100 ppm or less.
Specifically, as the silica fine particles in the silica fine particle dispersion, which is a raw material used in step 1, those satisfying the following conditions (a) and (b) are preferably used.
(A) The content of each of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.

  The silica fine particles preferably have an average particle diameter in the range of 30 to 330 nm and a ratio of minor axis / major axis measured by the image analysis method in the range of 0.95 to 1.0.

  In Step 1, the silica fine particle dispersion liquid in which the silica fine particles are dispersed in a solvent as described above is stirred, and while maintaining the temperature at 5 to 98 ° C. and the pH range at 7.0 to 9.0, the cerium metal is added thereto. The salt is added continuously or intermittently to obtain a precursor particle dispersion containing the precursor particles.

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

The solid content concentration in the silica fine particle dispersion is preferably 1 to 40% by mass in terms of SiO ₂ . If this solid content is too low, the silica concentration in the production process will be low, and the productivity may be poor.

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

In step 1, the cerium metal salt is continuously or intermittently added to the silica fine particle dispersion as described above, while maintaining the temperature at 5 to 98 ° C. and the pH range at 7.0 to 9.0. To be added.
The metal salt of cerium is not limited, but chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide and the like of cerium can be used. Specific examples include cerous nitrate, cerium carbonate, cerous sulfate, cerous chloride and the like. Of these, cerous nitrate and cerous chloride are preferred. Crystalline cerium oxide is generated from the solution that has become supersaturated at the same time as the neutralization, and these are quickly attached to the silica fine particles by a coagulation deposition mechanism. However, sulfate ions, chloride ions, nitrate ions and the like contained in these metal salts show corrosiveness. Therefore, it is necessary to wash it in a post-process after the preparation to remove it to 5 ppm or less. On the other hand, carbonates are released during the preparation as carbon dioxide gas, and alkoxides are decomposed into alcohol, which is preferable.

The amount of the cerium metal salt added to the silica fine particle dispersion is such that the mass ratio of silica to ceria in the obtained composite fine particles of the present invention is in the range of 100: 11 to 316, as described above.
In the method for producing a silica-based composite fine particle dispersion of the present invention, the cerium metal salt is usually a cerium metal salt obtained by adding water or an aqueous solvent, an acid, etc. to form a cerium metal salt aqueous solution. . The ceria concentration of the cerium metal salt aqueous solution is not particularly limited, but in consideration of workability and the like, the ceria concentration is preferably in the range of 1 to 40% by mass.

After the addition of the cerium metal salt to the silica fine particle dispersion, the temperature at the time of stirring is preferably from 5 to 98 ° C, more preferably from 10 to 95 ° C. If the temperature is too low, the solubility of silica is remarkably reduced, so that the crystallization of ceria is not controlled, and coarse ceria crystalline oxide is generated, so that adhesion to silica fine particles (base particles) becomes difficult to occur. Things are possible.
Conversely, if the temperature is too high, the solubility of silica will increase significantly, and the generation of crystalline ceria oxide may be suppressed. Further, scale and the like are easily generated on the wall surface of the reactor, which is not preferable.

  The time for stirring is preferably 0.5 to 24 hours, more preferably 0.5 to 18 hours. If the time is too short, crystalline cerium oxide cannot be formed sufficiently, which is not preferable. Conversely, if this time is too long, the formation of crystalline cerium oxide will not proceed further and will be uneconomical. After the addition of the cerium metal salt, aging may be performed at 5 to 98 ° C. if desired. The aging can further promote the reaction of depositing the cerium compound on the base particles.

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

  By such a process 1, a dispersion liquid (precursor particle dispersion liquid) containing particles (precursor particles) which are precursors of the composite fine particles of the present invention is obtained.

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

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

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

  In the step 1, more preferably, the metal salt of cerium is added continuously or intermittently while keeping the temperature range of the silica fine particle dispersion at 5 to 52 ° C and maintaining the pH range at 7.0 to 9.0. Then, a precursor particle dispersion is prepared, and the precursor particle dispersion is aged at a temperature of 5 to 52 ° C. When Step 1 is performed under such conditions, the metal salt of cerium or cerium hydroxide reacts with silica in a liquid phase to generate a cerium silicate compound, and inhibits ceria crystal growth. At the same time, ceria microcrystals are generated, and cerium silicate compounds and ceria microcrystals are formed on the mother particles.

<Step 2>
In the step 2, the precursor particle dispersion is dried and then fired at 400 to 1,200 ° C.

The method for drying is not particularly limited. Drying can be performed using a conventionally known dryer. Specifically, a box dryer, a band dryer, a spray dryer, or the like can be used.
Preferably, it is further recommended that the pH of the precursor particle dispersion before drying is 6.0 to 7.0. This is because when the pH of the precursor particle dispersion before drying is set to 6.0 to 7.0, it is possible to suppress the formation of a strong aggregate.
After drying, the temperature for baking is 400 to 1200 ° C, preferably 800 to 1100 ° C, and more preferably 1000 to 1090 ° C. When baking is performed in such a temperature range, cerium diffuses from the cerium silicate compound on the base particles, and crystallization of ceria sufficiently proceeds. As a result, the ceria particles are covered with a silica layer. In addition, the silica coating present on the surface of the ceria fine particles is appropriately thickened, and the mother particles and the child particles are firmly bonded. Further, when firing is performed in such a temperature range, silicon atoms form a solid solution in crystalline ceria which is a main component of the child particles. Accordingly, the cerium atom and a silicon atom contained in the daughter particles, cerium - between silicon atoms distance and R _1, cerium - between cerium atom distance is taken as R _2, it will satisfy the relationship of R ₁ <R ₂ obtain. If this temperature is too high, the ceria crystals will grow abnormally, and the silica coating on the ceria particles will become thicker and bond with the mother particles. The resulting amorphous silica may crystallize or the fusion of particles may proceed.

In step 2, the fired body obtained by firing is subjected to the following process ( ii) to obtain a fired body crushed dispersion .
( Ii) A solvent is added, and the mixture is wet-crushed in a pH range of 8.6 to 10.8 (preferably 9.0 to 10.6) .
Can also be used conventionally known devices as wet-type crushing device, for example, a batch-type bead mill such as a basket mill, horizontal, vertical, annular type continuous type bead mill, sand grinder mill, ball mill, Examples thereof include a wet medium stirring mill (wet crusher) such as a rotor-stator type homogenizer, an ultrasonic dispersion type homogenizer, and an impact crusher that crushes fine particles in a dispersion liquid. Examples of the beads used in the wet medium stirring mill include beads made of glass, alumina, zirconia, steel, flint stone, or the like.
Before Symbol Te processing smell (ii), as the solvent, water and / or organic solvent is used. For example, it is preferable to use water such as pure water, ultrapure water, and ion-exchanged water. Moreover, the solid concentration of the sintered body disintegration dispersion obtained by the process of (ii) are, but are not particularly limited, for example, has preferably in the range of 0.3 to 50 wt% .

In the case of performing the wet disintegration of (ii), the wet disintegration may be performed while maintaining the pH of the solvent at 8.6 to 10.8 (preferably 9.0 to 10.6). preferable. When the pH is maintained in this range, when the cationic colloid titration is performed, the flow potential change (ΔPCD) represented by the above formula (1) and the addition amount (V) of the cationic colloid titrant in the knick are determined. Finally, a silica-based composite fine particle dispersion having a streaming potential curve with a ratio (ΔPCD / V) of −110.0 to −15.0 can be obtained more easily.
That is, it is preferable to carry out crushing to such an extent that the dispersion liquid of the present invention corresponding to the above-mentioned preferred embodiment is obtained. This is because, as described above, when the dispersion of the present invention, which corresponds to a preferred embodiment, is used as an abrasive, the polishing rate is further improved. In this regard, the present inventors have found that the silica coating on the surface of the composite fine particles of the present invention is appropriately thin, and / or that the child particles are appropriately exposed on a part of the surface of the composite fine particles, whereby the polishing rate is further improved, In addition, it is estimated that shedding of ceria child particles can be controlled. In addition, it is estimated that since the silica coating is thin or peeled off, the child particles are likely to detach to some extent during polishing. ΔPCD / V is more preferably -100.0 to -15.0, and further preferably -100.0 to -20.0.

<Step 3>
In the step 3, the fired body disintegrated dispersion obtained in the step 2 is subjected to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently, the sediment component is removed to obtain a silica-based composite fine particle dispersion.
Specifically, coarse particles and connected particles having a minor axis / major axis ratio of less than 0.8 are removed from the fired body crushed dispersion by classification by centrifugation. The relative centrifugal acceleration in the centrifugal separation process is 300 G or more. After the centrifugation treatment, the sediment components are removed to obtain a silica-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 centrifugal separation process satisfying the above conditions. When the centrifugal acceleration is less than the above conditions, coarse particles remain in the silica-based composite fine particle dispersion, so that when used for polishing applications such as an abrasive using the silica-based composite fine particle dispersion, scratches may occur. This will cause it to occur.
In the present invention, the silica-based composite fine particle dispersion obtained by the above production method can be further dried to obtain silica-based composite fine particles. The drying method is not particularly limited, and for example, drying can be performed using a conventionally known dryer.

The dispersion of the present invention can be obtained by such a production method of the present invention.
Further, when the cerium metal salt is added to the silica fine particle dispersion, it is desirable that the reduction potential of the preparation has a positive value. This is because when the oxidation-reduction potential becomes negative, the cerium compound is not deposited on the surface of the silica particles, and cerium single particles such as plate-like and rod-like particles are generated. Examples of a method for maintaining the oxidation-reduction potential at a positive value include a method of adding an oxidizing agent such as hydrogen peroxide and a method of blowing air, but are not limited thereto.

<Abrasive dispersion liquid for polishing>
The liquid containing the dispersion of the present invention can be preferably used as a polishing abrasive dispersion (hereinafter also referred to as “polishing abrasive dispersion of the present invention”). In particular, it can be suitably used as a polishing abrasive dispersion for planarizing a semiconductor substrate on which an SiO ₂ insulating film is formed.
Here, when the semiconductor substrate on which the silica film is formed is flattened using the polishing slurry dispersion liquid of the present invention, the pH of the polishing slurry dispersion liquid of the present invention is preferably set to 3 to 8.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

<PH adjuster>
The pH of the polishing composition can be adjusted by adding an acid or a base as needed to enhance the effect of each of the above additives.

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

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

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

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

  It is preferable that the solid content concentration contained in the abrasive grain dispersion liquid of the present invention is in the range of 0.3 to 50% by mass. If the solid content is too low, the polishing rate may decrease. Conversely, even if the solid content concentration is too high, the polishing rate is rarely further improved, 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, details of each measurement method and test method in Examples and Comparative Examples will be described. Table 1 shows the following measurement results and test results for each example and comparative example.

[Analysis of components]
[Silica fine particles (base particles)]
Regarding the SiO ₂ weight of the silica fine particle dispersion described later, in the case of silica fine particles using sodium silicate as the raw material, the weight was determined by igniting at 1000 ° C. In the case of silica fine particles using alkoxysilane as a raw material, the silica fine particle dispersion was dried at 150 ° C. for 1 hour and then weighed.

[Silica-based composite fine particles]
The content of each element shall be measured by the following method.
First, about 1 g (solid content: 20% by mass) of a sample composed of the silica-based composite fine particle dispersion is collected in a platinum dish. 3 ml of phosphoric acid, 5 ml of nitric acid and 10 ml of hydrofluoric acid are added and heated on a sand bath. After drying, a small amount of water and 50 ml of nitric acid are added and dissolved, put in a 100 ml measuring flask, and water is added to make 100 ml. In this solution, Na and K are measured with an atomic absorption spectrometer (for example, Z-2310 manufactured by Hitachi, Ltd.).
Next, the operation of collecting 10 ml of the separated solution from the solution contained in the 100 ml measuring flask into a 20 ml measuring flask is repeated five times to obtain 5 10 ml of separated solutions. Using this, Al, Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, Zr, U and Th are standardly added by an ICP plasma emission spectrometer (eg, SII, SPS5520). Measure with. Here, a blank is also measured by the same method, and the blank is subtracted for adjustment, to obtain a measured value for each element.
Hereinafter, unless otherwise specified, the contents (contents) of the components of Na, Al, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U and Th in the present invention are as follows. Means a value obtained by such a method.

The content of each anion shall be measured by the following method.
<Cl>
Acetone was added to 20 g (solid content 20% by mass) of a sample composed of the silica-based composite fine particle dispersion to adjust the volume to 100 ml. The analysis is performed by a potentiometric titration method (manufactured by Kyoto Electronics: potentiometric titrator AT-610).
Separately, as a blank measurement, a titer was determined by adding 5 ml of acetic acid and 4 ml of a 0.001 mol sodium chloride solution to 100 ml of acetone and titrating with a 0.002 mol silver nitrate solution, and then titrating with a sample. To obtain the titer of the sample.

<NO ₃ , SO ₄ , F>
A 5 g sample (solid content: 20% by mass) composed of a silica-based composite fine particle dispersion was diluted with water, placed in a 100 ml volumetric flask, placed in a 50 ml centrifuge tube, and centrifuged at 4000 rpm with a centrifuge (HIMAC CT06E manufactured by Hitachi). The solution obtained by removing the sedimented components by centrifugation at for 20 minutes was analyzed by ion chromatography (ICS-1100 manufactured by DIONEX).

<SiO ₂ , CeO ₂ >
When determining the content of silica and ceria in the silica-based composite fine particles, first, the solid content concentration of the silica-based composite fine particle dispersion liquid is determined by weighing at 1000 ° C. after loss on ignition. Next, Ce is measured by a standard addition method using an ICP plasma emission spectrometer (for example, SII, SPS5520) in the same manner as Al to Th and the like, and CeO ₂ mass% is calculated from the obtained Ce content. . Then, the components other than CeO ₂ constituting the composite fine particles of the present invention are assumed to be SiO ₂ , and the SiO ₂ mass% is calculated.

  The content of each element or each anion in the silica fine particles (base particles) can be determined by using the silica fine particle dispersion instead of the sample in the above-described method of analyzing the silica fine particles. went.

[X-ray diffraction method, measurement of crystallite diameter]
According to the method described above, the silica-based composite fine particle dispersions obtained in Examples and Comparative Examples were dried using a conventionally known dryer, and the obtained powder was crushed in a mortar for 10 minutes, and subjected to X-ray diffraction. An X-ray diffraction pattern was obtained with an apparatus (RINT1400, manufactured by Rigaku Denki Co., Ltd.), and the crystal form was identified.
Further, as described above, the full width at half maximum of the peak of the (111) plane near 2θ = 28 ° (near 2θ = 28 °) in the obtained X-ray diffraction pattern was measured, and the crystallite diameter was calculated by Scherrer's equation. I asked.

<Average particle size>
With respect to the silica fine particle dispersions and silica-based composite fine particle dispersions obtained in Examples and Comparative Examples, the average particle diameter of the particles contained therein was measured by the above-described method. Specifically, PAR-III manufactured by Otsuka Electronics Co., Ltd. was used for the silica fine particle dispersion, and LA950 apparatus manufactured by HORIBA was used for the silica-based composite fine particle dispersion.
Here, the measurement conditions of PAR-III are as follows.
Ammonia water having a concentration of 0.56% by mass prepared in advance was added to the silica fine particle dispersion to adjust the solid content concentration to 1.0% by mass, and filled in a plastic measuring cell. At the time of measurement, the amount of light was adjusted so that the scattering intensity was 8000 to 12000 by PINHOLE SELECTOR and ATTENATOR FILTER, and the refractive index of the solvent was measured using the value of water.
The LA-950 measurement conditions are as follows.
Version of LA-950V2 is 7.02, algorithm option is standard operation, refractive index of solid is 1.450, refractive index of solvent (pure water) is 1.333, number of repetitions is 15 times, circulation speed of sample input bath is 5 The stirring speed was set to 2, and measurement was performed using a measurement sequence in which these were set in advance. Then, the measurement sample was put into the sample inlet of the apparatus as it was in the form of a stock solution using a dropper. Here, it was charged so that the numerical value of the transmittance (R) became 90%. Then, after the numerical value of the transmittance (R) was stabilized, ultrasonic waves were irradiated for 5 minutes to measure the particle diameter.

<Short diameter / long diameter ratio>
Magnification of each particle contained in the silica fine particle dispersion and the silica-based composite fine particle dispersion obtained in Examples and Comparative Examples using a transmission electron microscope (Transmission Electron Microscope; manufactured by Hitachi, Ltd., model number: S-5500). In a photographic projection obtained by photographing at a magnification of 250,000 (or 500,000), the maximum diameter of the particles was taken as the major axis, the length was measured, and the value was taken as the major diameter (DL). In addition, a point on the long axis that bisects the long axis was determined, two points where a straight line perpendicular to the long axis intersected the outer edge of the particle were determined, and the distance between the two points was measured to obtain the short diameter (DS). Then, the ratio (DS / DL) was determined. This measurement was performed on arbitrary 50 particles, and the number ratio (%) of particles having a minor axis / major axis ratio of 0.8 or less as a single particle was determined.

[Polishing test method]
<Polishing of SiO ₂ film>
Dispersions (polishing abrasive dispersions) containing the silica-based composite fine particle dispersions obtained in each of the examples and comparative examples were prepared. Here, the solid content concentration was 0.6% by mass, and nitric acid was added to adjust the pH to 5.0.
Next, as a substrate to be polished, an SiO ₂ insulating film (thickness: 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, the substrate to be polished is set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and a polishing pad ("IC-1000 / SUBA400 concentric type", manufactured by Nitta Haas) is used. Polishing was performed by supplying the abrasive dispersion liquid for polishing at a rotation speed of 90 rpm at a rate of 50 ml / min for 1 minute.
Then, the change in weight of the substrate to be polished before and after polishing was obtained, and the polishing rate was calculated.
The surface smoothness (surface roughness Ra) of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Corporation).
The polishing scratches were observed by polishing five substrates and observing the surface of the insulating film using an optical microscope. The evaluation criteria are as follows.
・ Observing 5 sheets, there are too many linear marks and cannot be counted visually ... "very much"
・ Observation of 5 sheets showed linear marks even on 1 sheet ... "Yes"
・ Observation of 5 sheets, no linear marks were observed .... "Not clearly observed"

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

<Preparation process 1>
Preparation of << High Purity Silicate Solution >> An aqueous solution of sodium silicate having an SiO ₂ concentration of 24.06% by mass and a Na ₂ O concentration of 7.97% by mass was prepared. Then, pure water was added to the aqueous sodium silicate solution so that the SiO ₂ concentration became 5.0% by mass.

[Acid silicic acid solution]
18 kg of the obtained 5.0 mass% aqueous sodium silicate solution was passed through 6 L of a strongly acidic cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to adjust the pH to 2.7. 18 kg of an acidic silicic acid solution was obtained.
The SiO ₂ concentration of the obtained acidic silicate solution was 4.7% by mass.

[High purity silicate liquid]
Next, the acidic silicate solution was passed through a strongly acidic cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h ^-1 to obtain a high-purity silicate solution having a pH of 2.7. The SiO ₂ concentration of the obtained high-purity silica solution was 4.4% by mass.

Preparation of << Silica Fine Particle Dispersion (Average Particle Diameter of Silica Fine Particles: 25 nm) >> 514.5 g of high-purity silicic acid solution was added to 42 g of pure water while stirring, and then 15% aqueous ammonia was added to 1,584 g of 1,584. Then, the temperature was raised to 83 ° C. and maintained for 30 minutes.
Next, 13,700 g of a high-purity silicic acid solution was further added over 18 hours, and after completion of the addition, aging was performed while maintaining the temperature at 83 ° C., to obtain a 25-nm silica fine particle dispersion.
The obtained silica fine particle dispersion was cooled to 40 ° C., and concentrated with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei) to a SiO ₂ concentration of 12% by mass.

Preparation of << Silica Fine Particle Dispersion (Silica Fine Particle Average Particle Diameter: 45 nm) >> 963 g of 12% by mass of 25 nm silica fine particle dispersion was added to 991 g of pure water while stirring. Next, 1,414 g of 15% aqueous ammonia was further added, and then the temperature was raised to 87 ° C. and maintained for 30 minutes.
Next, 12,812 g of a high-purity silicic acid solution was further added over 18 hours, and after completion of the addition, aging was performed while maintaining the temperature at 87 ° C., to obtain a 45 nm silica fine particle dispersion.
The obtained silica fine particle dispersion was cooled to 40 ° C., and concentrated with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei) to a SiO ₂ concentration of 12% by mass.

Preparation of << Silica Fine Particle Dispersion (Average Particle Diameter of Silica Fine Particles: 70 nm) >> 705 g of a silica fine particle dispersion (SiO ₂ concentration: 12% by mass) prepared by dispersing silica fine particles having an average particle diameter of 45 nm in a solvent is prepared. Was added to 705 g of pure water while stirring. Next, 50 g of 15% aqueous ammonia was further added, and then the temperature was raised to 87 ° C. and maintained for 30 minutes.
Next, 7,168 g of a high-purity silicic acid solution is further added over 18 hours, and after completion of the addition, aging is performed while maintaining at 87 ° C., and a silica fine particle dispersion in which silica fine particles having an average particle diameter of 70 nm are dispersed in a solvent. I got Here, the average particle size of the silica fine particles is a value obtained by measurement by a dynamic light scattering method (dynamic light scattering method particle size measuring apparatus: PAR-III).
The obtained silica fine particle dispersion was cooled to 40 ° C., and concentrated with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei) to a SiO ₂ concentration of 12% by mass.

<< Preparation of Silica Fine Particle Dispersion (Silica Fine Particle Average Particle Diameter: 96 nm) >> 1,081 g of a dispersion liquid (SiO ₂ concentration: 12% by mass) prepared by dispersing silica fine particles having an average particle diameter of 70 nm in a solvent is prepared. This was added to 1,081 g of pure water while stirring. Next, 50 g of 15% aqueous ammonia was further added, and then the temperature was raised to 87 ° C. and maintained for 30 minutes.
Next, 6,143 g of a high-purity silicate solution is further added over 18 hours, and after completion of the addition, aging is performed while maintaining the temperature at 87 ° C., and a silica fine particle dispersion in which silica fine particles having an average particle diameter of 96 nm are dispersed in a solvent. I got Here, the average particle size of the silica fine particles is a value obtained by measurement by a dynamic light scattering method (dynamic light scattering method particle size measuring apparatus: PAR-III).
The obtained silica fine particle dispersion was cooled to 40 ° C., and concentrated with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei) to a SiO ₂ concentration of 12% by mass. Anion exchange resin SANUP B manufactured by Mitsubishi Chemical Corporation was added to the concentrated silica fine particle dispersion to remove anions.

<Preparation process 2>
Ultrapure water was added to the 96-nm silica fine particle dispersion obtained in the preparation step 1 to obtain 6,000 g of the solution A having a SiO ₂ solid content concentration of 3% by mass.

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

Next, the temperature of the liquid A (6,000 g) was raised to 50 ° C., and while stirring, the liquid B (8,453 g, 100 parts by mass of SiO ₂ ) was mixed with 117.4 parts by mass of CeO _2. Was added over 18 hours. During this time, the liquid temperature was maintained at 50 ° C., and 3% aqueous ammonia was added as needed to maintain the pH at 7.85.
When the addition of the solution B was completed, the temperature of the solution was raised to 93 ° C. and aging was performed for 4 hours. After completion of ripening, it was allowed to cool by standing in a room and cooled to room temperature, and then washed while supplying ion-exchanged water with an ultramembrane to wash the electric conductivity to 75 μS / cm. The precursor particle dispersion liquid A obtained after the completion of the washing had a solid content concentration of 7% by mass, and the particle diameter by laser diffraction / scattering method (LA-950, manufactured by HORIBA) was 4.6 μm [median diameter]. .

<Preparation process 3>
Next, 3% by mass acetic acid was added to the precursor particle dispersion liquid A obtained in the preparation step 2 to adjust the pH to 6.5, followed by drying in a dryer at 120 ° C. for 15 hours. Firing was performed for 2 hours using a muffle furnace to obtain a powdered fired body.

To 100 g of the obtained fired body, 300 g of ion-exchanged water was added, and the pH was adjusted to 9.2 with a 3% aqueous ammonia solution. Crushing (batch type desktop sand mill manufactured by Campe Co., Ltd.) was performed for 120 minutes. After crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained fired body disintegrated dispersion was 7% by mass, and the recovered weight was 1200 g. During the crushing, an aqueous ammonia solution was added to maintain the pH at 9.2.
Next, the obtained fired body disintegrated dispersion is treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at 675 G for 3 minutes to recover a light liquid (supernatant from which settled components have been removed). Thus, a silica-based composite fine particle dispersion was obtained. The average particle diameter (median diameter) of the silica-based composite fine particle dispersion was measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA) and found to be 0.208 μm (208 nm).

<Example 1>
In Example 1, the second disintegration treatment and centrifugation treatment were performed on the silica-based composite fine particle dispersion obtained in the preparation step 3. The method will be described below. In addition, the silica-based composite fine particle dispersion obtained by performing the second crushing treatment and the centrifugation treatment naturally corresponds to the dispersion of the present invention.
1 kg of a liquid whose solid content concentration was adjusted to 20% by mass by adding ion-exchanged water to the silica-based composite fine particle dispersion obtained in the preparation step 3 was prepared. This liquid was crushed using a crusher (LMZ-06, manufactured by Ashizawa Finetech Co., Ltd.). Here, crushing was performed using quartz beads having a diameter of 0.25 mm, a filling rate of 85%, a peripheral speed of 10 m / s, and circulation under the conditions of 1 L / min. The concentration at the time of crushing was 10% by mass because ion-exchanged water remained in the crushing chamber and piping of the crusher. During the crushing, the pH was maintained at 9.2 by adding 3% ammonia. After the disintegration, the solid content recovered by water-pressing the pulverizing chamber was 9.3% by mass.
Subsequently, the disintegrated dispersion liquid was treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at a relative centrifugal acceleration of 1700 G for 102 seconds. Then, the light liquid was recovered to obtain a silica-based composite fine particle dispersion. When the average particle diameter (median diameter) of the obtained silica-based composite fine particle dispersion was measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA), it was 0.196 μm (196 nm).

  When the silica-based composite fine particles contained in the obtained dispersion liquid of silica-based composite fine particles were measured by an X-ray diffraction method, a Cerianite diffraction pattern was observed.

Next, a polishing test was performed using the silica-based composite fine particle dispersion. Further, the ratio of the minor axis / major axis of the silica-based composite fine particles contained in the polishing slurry dispersion liquid was measured.
The average particle diameter of the silica fine particles contained in the silica fine particle dispersion liquid used as the raw material, the content of impurities in the silica fine particles, the mass of ceria with respect to 100 parts by mass of silica in the silica composite fine particles, and the firing during the preparation of the silica composite fine particles Temperature, crystallite diameter of silica-based composite fine particles, crystal form, content of impurities contained in silica-based composite fine particles, average particle diameter of silica-based composite fine particles, ratio of minor axis / major axis of silica-based composite fine particles of 0.8 or less Tables 1 to 3 show the measurement results of the particle number ratio and the polishing performance (polishing speed, surface roughness, observation results of polishing scratches in polishing a SiO ₂ film, and the number of scratches in polishing of an aluminum hard disk). The same applies to the following examples and comparative examples.

<Example 2>
In Example 2, the second disintegration treatment and centrifugation treatment were performed on the silica-based composite fine particle dispersion obtained in the preparation step 3. The method will be described below. In addition, the silica-based composite fine particle dispersion obtained by performing the second crushing treatment and the centrifugation treatment naturally corresponds to the dispersion of the present invention.
Ion-exchanged water was added to the silica-based composite fine particle dispersion obtained in Preparation Step 3 to adjust the solid content concentration to 5% by mass. Next, using a 4 L rotor with a high-speed centrifugal separator H-660 manufactured by KOKUSAN, the liquid was passed under the conditions of a relative centrifugal acceleration of 10,000 G and a liquid passing speed of 1 L / min, followed by centrifugation. The silica fine particle dispersion obtained after centrifugation had a solid content of 1.8% and an average particle diameter of 0.200 μm (200 nm) [median diameter] measured by a laser diffraction scattering method.

<Example 3>
4.0 kg of the precursor particle dispersion liquid A obtained in the preparation step 2 was prepared. This was crushed using a crusher (LMZ-06, manufactured by Ashizawa Finetech Co., Ltd.). Here, crushing was performed using quartz beads having a diameter of 0.25 mm, a filling rate of 60%, a peripheral speed of 8 m / s, and 20 passes at 2 L / min. During the disintegration of the precursor particle dispersion A, no aqueous ammonia or the like was added thereto. The pH of the precursor fine particle dispersion A after crushing was 9.0. Further, the average particle diameter (median diameter) of the crushed precursor fine particle dispersion liquid A measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA) was 0.225 μm.
Next, 3% by mass acetic acid was added to the crushed precursor fine particle dispersion A to adjust the pH to 6.5, and the mixture was dried in a dryer at 120 ° C. for 15 hours. For 2 hours to obtain a powdered fired body.
300 g of ion-exchanged water was added to 100 g of the obtained fired body, and the pH was adjusted to 9.2 with a 3% aqueous ammonia solution. For 60 minutes. In the crushing treatment, quartz beads having a diameter of 0.25 mm (manufactured by Daiken Chemical Industry Co., Ltd.) were used. During the crushing, an aqueous ammonia solution was added to maintain the pH at 9.2. Thus, 1020 g of a crushed dispersion of the fired body having a solid content of 2.4% by mass was obtained.
Further, the crushed dispersion of the calcined body is treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at a relative centrifugal acceleration of 1700 G for 102 seconds, and the light liquid is recovered. I got The average particle diameter (median diameter) of the obtained silica-based composite fine particle dispersion was measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA), and was found to be 0.198 μm (198 nm).

<Example 4>
Ultrapure water was added to the silica fine particle dispersion obtained in the preparation step 1 to obtain 6,000 g of the solution A having a SiO ₂ solid content concentration of 3% by mass.

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

  Next, 6,000 g (dry 180 g) of the solution A was kept at 18 ° C., and while stirring this, 8,453 g (dry 211.3 g) of the solution B was added thereto over 18 hours. During this time, the liquid temperature was maintained at 18 ° C., and 3% aqueous ammonia was added as needed to maintain the pH at 7.7. After completion of the addition, aging was performed at a liquid temperature of 18 ° C. for 4 hours. Thereafter, washing was performed while supplying ion-exchanged water with an ultramembrane. The precursor particle dispersion obtained after the completion of the washing has a solid content of 4.3% by mass, a pH of 4.3 (at 25 ° C.), and an electric conductivity of 170 μs / cm (at 25 ° C.). there were.

  Next, the obtained precursor particle dispersion was dried in a dryer at 120 ° C. for 16 hours, and then fired for 2 hours using a muffle furnace at 1030 ° C. to obtain a powdery fired body.

After adding 300 g of ion-exchanged water to 100 g of the obtained fired body and further adjusting the pH to 9.2 by adding a 3% aqueous ammonia solution, a wet method was performed using a crusher (manufactured by Campe Co., Ltd., batch-type tabletop sand mill). For 90 minutes. In the crushing treatment, quartz beads having a diameter of 0.25 mm (manufactured by Daiken Chemical Industry Co., Ltd.) were used. After crushing, the beads were separated through a 44 mesh wire mesh. During the crushing, an aqueous ammonia solution was added to maintain the pH at 9.2. Thus, 1115 g of a fired body disintegration dispersion having a solid content of 3.1% by mass was obtained.
Further, the crushed dispersion of the calcined body is treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at a relative centrifugal acceleration of 1700 G for 102 seconds, and the light liquid is recovered. I got When the average particle diameter (median diameter) of the obtained silica-based composite fine particle dispersion was measured by using a laser diffraction scattering method (LA-950, manufactured by HORIBA), it was 0.194 μm (194 nm).

  The silica-based composite fine particles contained in the dispersion liquid of silica-based composite fine particles obtained in Example 4 were observed using SEM and TEM. FIGS. 1A and 1B show an SEM image and a TEM image (magnification: 50,000).

  FIG. 2 shows an X-ray diffraction pattern of the silica-based composite fine particles contained in the dispersion liquid of silica-based composite fine particles obtained in Example 4.

In the X-ray diffraction pattern of FIG. 2, it is a very sharp Cerianite crystal, and it can be seen from the TEM and SEM images that the ceria crystal particles are strongly sintered on the silica surface.
Further, from FIG. 1, it was observed that a thin silica coating was present on the outermost surface of the silica-based composite fine particles so as to cover the silica-based composite fine particles.

<Example 5>
Ion-exchanged water was added to the silica fine particle dispersion obtained in the preparation step 1 to obtain 6,000 g of the solution A having a SiO ₂ solid content concentration of 3% by mass.

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

Next, the temperature of the liquid A (6,000 g) was raised to 50 ° C., and while stirring, the liquid B (8,453 g, 100 parts by mass of SiO ₂ ) was mixed with 117.4 parts by mass of CeO _2. Was added over 18 hours. During this time, the liquid temperature was maintained at 50 ° C., and 3% aqueous ammonia was added as needed to maintain the pH at 7.85.
When the addition of the solution B was completed, the temperature of the solution was raised to 93 ° C. and aging was performed for 4 hours. After ripening, it was allowed to cool by standing in a room and cooled to room temperature, and then washed while supplying ion-exchanged water with an ultramembrane, and washed until the electric conductivity reached 75 μS / cm. The precursor particle dispersion obtained after the completion of the washing has a solid content concentration of 7% by mass, a pH of 9.1 (at 25 ° C.), and a laser diffraction scattering particle size (LA-950 manufactured by HORIBA). It was 4.6 μm.

  Next, a 3% by mass aqueous acetic acid solution is added to the obtained precursor particle dispersion to adjust the pH to 6.5, and after drying in a dryer at 120 ° C. for 15 hours, a muffle furnace at 1062 ° C. is used. For 2 hours to obtain a powdered fired body.

310 g of the obtained fired body and 430 g of ion-exchanged water are put into a 1-L beaker with a handle, a 3% aqueous ammonia solution is added thereto, and ultrasonic waves are irradiated for 10 minutes in an ultrasonic bath with stirring to obtain a pH of 10 ( A temperature of 25 ° C.) was obtained.
Next, 595 g of quartz beads having a diameter of 0.25 mm was charged into a crusher (LMZ06, manufactured by Ashizawa Finetech Co., Ltd.) that had been washed in advance, and a water operation was performed. Further, the above suspension was filled in a charge tank of a crusher (filling rate: 85%). In consideration of the ion-exchanged water remaining in the pulverizing chamber and the pipe of the pulverizer, the concentration at the time of pulverization is 25% by mass. Then, wet crushing was performed under the conditions that the peripheral speed of the disk in the crusher was 12 m / sec, the number of passes was 25, and the residence time per pass was 0.43 minutes. In addition, a 3% aqueous ammonia solution was added for each pass so as to maintain the pH of the suspension at the time of crushing at 10. In this way, a fired body crushed dispersion having a solid content of 22% by mass was obtained.
Next, the obtained fired body disintegrated dispersion liquid was subjected to centrifugal separation at a relative centrifugal acceleration of 675 G for 3 minutes using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number “CR21G”) to remove settled components, A composite fine particle dispersion was obtained. The average particle diameter (median diameter) of the obtained silica-based composite fine particle dispersion was measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA), and was 0.208 μm (208 nm).

<Example 6>
Ion-exchanged water was added to the silica fine particle dispersion having an average particle diameter of 70 nm obtained in the process of the preparation step 1 to obtain 6,000 g of the liquid A having a SiO ₂ solid content concentration of 3.0% by mass. Ion-exchanged water was added to cerium (III) hexahydrate to obtain a liquid B of 3.0 mass% in terms of CeO ₂ .
Next, 6,000 g (dry 180.0 g) of solution A was cooled to 15.5 ° C., and 7044.2 g (dry 211.3 g) of solution B was added thereto over 18 hours while stirring. During this time, the liquid temperature was maintained at 15.5 ° C., and if necessary, 3.0% by mass of aqueous ammonia was added to maintain the pH at 8.3 to 8.6. When the addition of the solution B was completed, aging was performed for 4 hours while maintaining the solution temperature at 15.5 ° C. During the addition of the solution B to the solution A and during the ripening, air was continuously blown into the mixture to keep the oxidation-reduction potential at 100 to 200 mV.
After completion of the aging, the operation of filtering using an ultra-membrane and then supplying ion-exchanged water and washing was repeated up to an electric conductivity of 26 μS / cm to obtain a precursor particle dispersion.
Next, 3.0 mass% of acetic acid was added to the obtained precursor particle dispersion to adjust the pH to 6.5. After drying in a dryer at 120 ° C. for 15 hours, a muffle furnace at 1064 ° C. Was fired for 2 hours to obtain a powdered fired body.
After adding 300 g of ion-exchanged water to 100 g of the obtained fired body and further adjusting the pH to 10.0 by adding a 3.0% by mass aqueous ammonia solution, a crusher (manufactured by Campe Co., Ltd., batch-type desktop sand mill) was used. The crushing treatment was performed for 270 minutes in a wet manner. In the crushing treatment, quartz beads having a diameter of 0.25 mm were used. After crushing, the beads were separated through a 44 mesh wire mesh. During the crushing, an aqueous ammonia solution was added to keep the pH at 10.0. Thus, 1151 g of a fired body disintegrated dispersion having a solid content of 6.6% by mass was obtained.
Further, the fired body disintegrated dispersion liquid was treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at a relative centrifugal acceleration of 1700 G for 102 seconds to obtain a light liquid (a supernatant liquid from which sediment components were removed). This was collected to obtain a silica-based composite fine particle dispersion. Then, the obtained silica-based composite fine particle dispersion was evaluated in the same manner as in Example 1.

<Example 7>
Ultrapure water was added to the 96-nm silica fine particle dispersion obtained in the preparation step 1 to obtain 2,500 g of solution A having a SiO ₂ solid content concentration of 3% by mass.

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

Next, 2,500 g (dry 75 g) of solution A was heated to 18 ° C., and 5,833.3 g (dry 175 g) of solution B was added thereto with stirring over 18 hours. During this time, the liquid temperature was maintained at 18 ° C., and 3% aqueous ammonia was added as needed to maintain the pH at 7.8. When the addition of the solution B was completed, the solution was aged for 4 hours while keeping the solution temperature at 18 ° C. During the addition of the solution B to the solution A and during the ripening, air was continuously blown into the mixture to keep the oxidation-reduction potential at 100 to 200 mV.
After completion of the aging, the operation of filtering using an ultra-membrane and then supplying ion-exchanged water and washing was repeated up to an electric conductivity of 26 μS / cm to obtain a precursor particle dispersion. The average particle diameter (median diameter) of the precursor particle dispersion liquid after washing was measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA), and was 0.33 μm.

  Next, the obtained precursor particle dispersion liquid was adjusted to pH 6.5 by adding 3% by mass acetic acid, dried in a dryer at 120 ° C. for 15 hours, and then dried in a muffle furnace at 1028 ° C. for 2 hours. The firing was performed for a time to obtain a powdered fired body.

300 g of ion-exchanged water was added to 100 g of the obtained fired body, and a 3.0 mass% aqueous ammonia solution was further added to adjust the pH to 10.0. Then, a crusher (manufactured by Campe Co., Ltd., batch-type tabletop sand mill) was used. Crushing treatment was performed for 120 minutes in a wet manner. In the crushing treatment, quartz beads having a diameter of 0.25 mm were used. After crushing, the beads were separated through a 44 mesh wire mesh. During the crushing, an aqueous ammonia solution was added to maintain the pH at 9.2. Thus, 1121 g of a fired body disintegrated dispersion having a solid content of 7.2% by mass was obtained.
Further, the crushed dispersion of the calcined body is subjected to a relative centrifugal acceleration: 675 G for 3 minutes using a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") for 3 minutes to collect a light liquid (a supernatant liquid from which sedimentation components have been removed). Thus, a silica-based composite fine particle dispersion was obtained. Then, the obtained silica-based composite fine particle dispersion was evaluated in the same manner as in Example 1.

<Comparative Example 1>
With respect to the 96-nm silica fine particle dispersion obtained in the preparation step 1, each measurement such as the average particle diameter was performed.

<Comparative Example 2>
With respect to the precursor particle dispersion liquid A obtained in the preparation step 2, each measurement such as the average particle diameter was performed.

<Comparative Example 3>
3.63 kg of 0.7 mass% aqueous ammonia was prepared and heated to 93 ° C. (Solution A). Next, 5.21 kg (solution B) of a 1.6 mass% cerium nitrate solution as CeO ₂ was prepared, and solution B was added to solution A over 1 hour. After completion of the addition, 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, it was centrifuged at a relative centrifugal acceleration of 5000 G, and the supernatant was removed. Then, ion-exchanged water was added to the precipitated cake, and the mixture was stirred and reslurried, and the process of centrifuging again at a relative centrifugal acceleration of 5000 G was repeated until the 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 concentration of 6.0% by mass and dispersed by ultrasonic waves to obtain a ceria fine particle dispersion.
The average particle diameter (median diameter) of the obtained ceria fine particle dispersion was measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA) and found to be 0.116 μm.
When the crystallite size and crystal form were measured by X-ray, the crystallite diameter was 18 nm, indicating a Cerianite crystal form.
The pH of this ceria fine particle dispersion was adjusted to 5.0 with nitric acid to obtain a polishing abrasive dispersion having a solid content of 0.6 mass. The thermal oxide film was polished with this abrasive grain dispersion. The results are shown in Tables 1 to 3.

<Comparative Example 4>
Next, 3% by mass acetic acid was added to the precursor particle dispersion liquid A obtained in the preparation step 2 to adjust the pH to 6.5, and the mixture was dried in a dryer at 120 ° C. for 15 hours. Firing was performed for 2 hours using a muffle furnace to obtain a powdered fired body.

To 100 g of the obtained fired body, 300 g of ion-exchanged water was added, and the pH was adjusted to 9.2 with a 3% aqueous ammonia solution. Crushing (batch type desktop sand mill manufactured by Campe Co., Ltd.) was performed for 120 minutes. After crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained fired body disintegrated dispersion was 7.1% by mass, and the recovered weight was 1183 g. During the crushing, an aqueous ammonia solution was added to maintain the pH at 9.2.
Next, the obtained fired body disintegrated dispersion is treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at 675 G for 3 minutes to recover a light liquid (supernatant from which settled components have been removed). Thus, a silica-based composite fine particle dispersion was obtained. When the average particle diameter (median diameter) of the silica-based composite fine particle dispersion was measured using a laser diffraction scattering method (LA-950, manufactured by HORIBA), it was 0.221 μm (221 nm).

<Comparative Example 5>
Next, 3% by mass acetic acid was added to the precursor particle dispersion liquid A obtained in the preparation step 2 to adjust the pH to 6.5, and the mixture was dried in a dryer at 120 ° C. for 15 hours. The powder was fired for 2 hours using a muffle furnace to obtain a powdered fired body.

To 100 g of the obtained fired body, 300 g of ion-exchanged water was added, and the pH was adjusted to 9.2 with a 3% aqueous ammonia solution. Crushing (batch type desktop sand mill manufactured by Campe Co., Ltd.) was performed for 120 minutes. After crushing, the beads were separated through a 44 mesh wire mesh. The solid content concentration of the obtained fired body disintegrated dispersion was 7.2% by mass, and the recovered weight was 1167 g. During the crushing, an aqueous ammonia solution was added to maintain the pH at 9.2.
Next, the obtained fired body disintegrated dispersion is treated with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number "CR21G") at 675 G for 3 minutes to recover a light liquid (supernatant from which settled components have been removed). Thus, a silica-based composite fine particle dispersion was obtained. When the average particle diameter (median diameter) of the silica-based composite fine particle dispersion was measured by a laser diffraction scattering method (LA-950, manufactured by HORIBA), it was 0.194 μm (194 nm).

<Comparative Example 6>
To the precursor particles A obtained in the preparation step 2, 3% by mass acetic acid was added to adjust the pH to 6.5, and the mixture was dried in a dryer at 120 ° C for 15 hours. For 2 hours to obtain a powdered fired body.
430 g of ion-exchanged water was added to 310 g of the obtained fired body, and further, ammonia water of 3.0% by mass was added to adjust the pH to 11.0. To obtain a suspension.
Next, 595 g of quartz beads having a diameter of 0.25 mm was put into a crusher (LMZ06, manufactured by Ashizawa Finetech Co., Ltd.) that had been washed in advance, and a water operation was performed. Further, the suspension was filled in a charge tank of a crusher (filling rate: 85%). In consideration of the ion-exchanged water remaining in the pulverizing chamber and the pipe of the pulverizer, the concentration at the time of pulverization is 25% by mass. The wet crushing was performed under the conditions that the peripheral speed of the disk in the crusher was 14 m / sec and the number of passes was 30 times. In addition, a 3% aqueous ammonia solution was added for each pass so that the pH of the suspension at the time of crushing was maintained at 11. Thus, a fired body disintegrated dispersion having a solid content concentration of 20% by mass was obtained.
Next, the obtained fired body disintegrated dispersion was centrifuged at a relative centrifugal acceleration of 675 G for 3 minutes using a centrifugal separator (CR21G, manufactured by Hitachi Koki Co., Ltd.) to remove sedimentation components and to disperse silica-based composite fine particles. A liquid was obtained.

<Experiment 2> EDS composition analysis of coating film The silica-based composite fine particles contained in the dispersion liquid of silica-based composite fine particles obtained in Example 4 were analyzed with a transmission electron microscope (JEM-2100F, JEOL, field emission transmission electron microscope). (Attached to Cs correction), accelerated electron: 120 kV, magnification: 50,000 times), and confirmed that a film was present outside the child particles (ceria crystal particles). EDS measurement was performed by selectively applying an electron beam.
The measurement conditions of energy dispersive X-ray spectrometry (EDS) are shown below.
After the silica-based composite fine particles were dispersed in pure water, the particles were placed on a Cu mesh provided with a carbon support film and measured with the following measuring device.
Measuring device: JEOL Ltd., UTW type Si (Li) semiconductor detector Beam system: 0.2 nm

  FIGS. 5A and 5B show photographs (TEM images) obtained by observation using a transmission electron microscope. 5 (a) and 5 (b), the result of EDS measurement in which an electron beam was selectively applied to a portion of the silica coating on the outside of the child particles (ceria crystal particles) confirmed that the intensity of Si was around 1.74 keV. A peak appeared, and an intensity peak of Ce appeared around 4.84 keV. The atomic% of Si was 0.836 atom%, the atomic% of Ce was 0.277, and the atomic% of Si / the atomic% of Ce was calculated to be 3.018. Similarly, Tables 4 show the results of the same measurements performed on Examples 1 and 7 and Comparative Examples 1 and 3. In Comparative Examples 1 and 3, no coating was confirmed.

<Experiment 3>
For each of the silica-based composite fine particle dispersions obtained in Examples 2, 4, and 7 and Comparative Examples 3 and 6, measurement of streaming potential and titration of cationic colloid were performed. As the titrator, an automatic titrator AT-510 (manufactured by Kyoto Electronics Industry) equipped with a streaming potential titrator (PCD-500) was used.
First, a 0.05% hydrochloric acid aqueous solution was added to a silica-based composite fine particle dispersion having a solid concentration adjusted to 1% by mass to adjust the pH to 6. Next, an amount equivalent to 0.8 g as a solid content of the liquid was placed in a 100 ml tall beaker, and the streaming potential was measured. Next, titration was performed by adding a cationic colloid titrant (0.001 N polydiallyldimethylammonium chloride solution) at an interval of 5 seconds, 20 ml at an injection rate of 0.2 ml and an injection speed of 2 seconds / ml. Then, the addition amount (ml) of the cationic colloid titrant is plotted on the X-axis, and the streaming potential (mV) of the silica-based composite fine particle dispersion is plotted on the Y-axis, and the streaming potential I (mV) at the starting point of the streaming potential curve is plotted. In addition, the streaming potential C (mV) and the addition amount V (ml) of the cationic colloid titrant in the knick were determined, and ΔPCD / V = (IC) / V was calculated. The results are shown in Table 5. FIG. 4 shows a streaming potential curve.

<Experiment 4>
[Measurement of Si solid solution state]
The silica-based composite fine particle dispersion prepared in Example 5 was measured for an X-ray absorption spectrum at a CeL III absorption end (5727 eV) using an X-ray absorption spectrometer (R-XAS Looper manufactured by Rigaku). EXAFS vibrations appearing in the X-ray absorption spectrum were obtained. Rigaku software REX-2000 was used for analysis, and the average number of coordinating atoms N and the average bond distance R of oxygen and cerium around cerium were obtained. The results are shown in Table 6.
From the results in Table 6, oxygen, silicon and cerium exist around cerium, the distance between cerium and oxygen atoms is 2.4 °, and the distance between cerium and cerium atoms is 3.8 °, It was confirmed that the interatomic distance between cerium and silicon was 3.2 °. Also, from the XRD analysis results, it is considered that Si is dissolved in cerium oxide because cerium exists as CeO _{2 in} the crystal form of Cerianite.
The same measurement was performed for Example 1, Example 4, Comparative Example 3, and Comparative Example 4. The results are shown in Table 6.

  Since the composite fine particles of the present invention do not contain impurities, they can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate and a wiring substrate.

Claims (8)

[1] The following [1] in which child particles having crystalline ceria as a main component are provided on the surface of base particles mainly containing amorphous silica, and a silica coating is further provided on a part of the surface of the child particles. A silica-based composite fine particle dispersion containing silica-based composite fine particles having an average particle diameter of 50 to 350 nm and having the characteristics of [4] to [4].
[1] The silica-based composite fine particles have a mass ratio of silica to ceria of 100: 11 to 316.
[2] When the silica-based composite fine particles are subjected to X-ray diffraction, only the ceria crystal phase is detected.
[3] The silica-based composite fine particles have a crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.
[4] A silicon atom is dissolved in crystalline ceria which is a main component of the child particles. For cerium atom and a silicon atom contained in the child particles, adjacent cerium - between silicon atoms distance and R _1, adjacent cerium - between cerium atom distance it is taken as R _2, the relationship of R ₁ <R ₂ The silica-based composite fine particle dispersion according to claim 1, which is filled. The silica-based composite fine particle dispersion according to claim 1 or 2, wherein the content ratio of impurities contained in the silica-based composite fine particles is as shown in the following (a) and (b).
(A) The content of each of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.   A polishing abrasive dispersion containing the silica-based composite fine particle dispersion according to claim 1.   The abrasive grain dispersion for polishing according to claim 4, which is used for flattening a semiconductor substrate on which a silica film is formed.   The abrasive grain dispersion for polishing according to claim 5, which has a pH of 3 to 8. A method for producing a silica-based composite fine particle dispersion, comprising the following steps 1 to 3, wherein the silica-based composite fine particle dispersion according to any one of claims 1 to 3 is obtained.
Step 1: A silica fine particle dispersion in which silica fine particles are dispersed in a solvent is stirred, and a cerium metal salt is continuously added thereto while maintaining the temperature at 5 to 98 ° C and the pH within a range of 7.0 to 9.0. A step of obtaining the precursor particle dispersion liquid containing the precursor particles by adding the precursor particles intermittently or intermittently.
Step 2: the precursor particle dispersion is dried, and calcined at 400～1,200 ° C., the resulting fired body, as engineering to obtain a sintered body disintegration dispersion was processed in the following (ii) .
( Ii) A solvent is added and the mixture is wet-crushed in a pH range of 8.6 to 10.8.
Step 3: a step of obtaining a silica-based composite fine particle dispersion by subjecting the fired body crushed dispersion to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more, and subsequently removing the sedimentation component. The method for producing a silica-based composite fine particle dispersion according to claim 7, wherein the content ratio of impurities contained in the silica fine particles is as follows (a) and (b).
(A) The content of each of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn and Zr is 100 ppm or less.
(B) The content of each of U, Th, Cl, NO ₃ , SO ₄ and F is 5 ppm or less.