JP2017206411A - Silica-based composite fine particle dispersion, method for producing the same and polishing slurry containing silica-based composite fine particle dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silica-based composite fine particle dispersion capable of polishing a silica film, a Si-wafer or even a hard-to-work material at high speed while achieving high face accuracy.SOLUTION: There are provided silica-based composite fine particles dispersion having an average particle diameter of 50-350 nm which have daughter particles containing crystalline ceria as main components on a surface of mother particles containing amorphous silica as main components and have the following characteristics [1] to [3]. [1] The silica-based composite fine particles have a silica to ceria mass ratio of 100:11 to 316. [2] When subjecting the silica-based composite fine particles to X-ray diffraction, only a crystalline phase of ceria is detected. [3] The weight ratio of binding particles in which two or three primary particles are linked contained in the silica-based composite fine particles is 60% or more.SELECTED DRAWING: None

Description

  The present invention relates to a silica-based composite fine particle dispersion suitable as an abrasive used in semiconductor device production, and in particular, a film to be polished formed on a substrate is planarized by 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 slurry containing the silica-based composite fine particle dispersion.

  Semiconductor devices such as semiconductor substrates and wiring boards achieve high performance through high density and miniaturization. In this semiconductor manufacturing process, so-called chemical mechanical polishing (CMP) is applied. Specifically, this technology is indispensable for shallow trench isolation, planarization of interlayer insulating films, formation of contact plugs and Cu damascene wiring, etc. It has become.

In general, an abrasive for CMP comprises 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 high polishing rate specifically with respect to a silicon oxide film, they are applied to polishing in a shallow trench element separation step.
In the shallow trench isolation process, not only the silicon oxide film but also the silicon nitride film is polished. 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, and this polishing rate ratio (selection ratio) is also important.

Conventionally, as a polishing method for such a member, after performing a relatively rough primary polishing process, and then performing a precise secondary polishing process, a smooth surface or a highly accurate surface with few scratches such as scratches can be obtained. The way to get done.
Conventionally, for example, the following methods have been proposed for the abrasive used for the secondary polishing as the finish polishing.

  For example, in Patent Document 1, an aqueous solution of cerium nitrate and a base are stirred and mixed in 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 cerium oxide ultrafine particles (average particle size of 10 to 80 nm) composed of a single crystal of cerium oxide characterized by the following is described. Further, according to this production method, the particle size is highly uniform and the particle shape It is described that ultrafine cerium oxide particles can be provided.

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

  Furthermore, Patent Document 2 discloses that the surface of the amorphous silica particles A has at least one selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium. A silica-based composite particle characterized by having a crystalline oxide layer B containing an element is described. As a preferred embodiment, an amorphous oxide layer containing an element such as aluminum on the surface of the amorphous silica particles A, which is different from the amorphous silica layer A crystalline oxide layer having C and further containing one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum, and strontium Silica-based composite particles characterized by having B are described. And since such a silica type composite particle has the crystalline oxide layer B on the surface of the amorphous silica particle A, it can improve a grinding | polishing speed and pre-process on a silica particle. By suppressing the sintering of particles during firing, the dispersibility in the polishing slurry can be improved, and further, the amount of cerium oxide used can be greatly reduced without containing cerium oxide. Therefore, it is described that it is possible to provide an abrasive that is inexpensive and has high polishing performance. Further, it is described that those having an amorphous oxide layer C between the silica-based particles A and the oxide layer B are particularly excellent in the effect of suppressing the sintering of particles and the effect of improving the polishing rate.

Japanese Patent No. 2746861 JP 2013-119131 A

Seung-Ho Lee, Zhenyu Lu, S .; V. Babu and Egon Matijevic, "Chemical mechanical polishing of thermal oxide filming using silicon part 27, the second of the two", Journal of Mathematics, 27

However, the cerium oxide ultrafine particles described in Patent Document 1 were actually manufactured and examined by the inventor, and the polishing rate was low. Further, the surface of the polishing base material had defects (deterioration of surface accuracy, increased scratches, It has been found that the residue of the abrasive on the surface of the polishing substrate tends to occur.
This is because the method for producing ultrafine cerium oxide particles described in Patent Document 1 does not include a firing step as compared with a method for producing ceria particles including a firing step (the degree of crystallinity of ceria particles is increased by firing). Since the cerium oxide particles are only crystallized from the aqueous solution containing cerium nitrate (the aqueous solution containing cerium nitrate), the cerium oxide particles that are produced have a relatively low degree of crystallinity, and the cerium oxide does not solidify with the mother particles because it does not undergo a firing treatment. The inventor presumes that the main factor is that cerium oxide does not adhere and remains on the surface of the polishing substrate.

  In addition, since the ceria-coated silica described in Non-Patent Document 1 is not fired, it is considered that the actual polishing rate is low, and there is a concern that particles remain on the surface of the polishing substrate.

  Furthermore, when polishing 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 found out.

  An object of the present invention is to solve the above problems. That is, the present invention can polish silica films, Si wafers and difficult-to-process materials at high speed, and at the same time, can achieve high surface accuracy (low scratch, etc.), and can be used for semiconductor devices such as semiconductor substrates and wiring boards. An object of the present invention is to provide a silica-based composite fine particle dispersion that can be preferably used for surface polishing, a method for producing the same, and a polishing slurry containing the silica-based composite fine particle dispersion.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (11).
(1) An average particle diameter of 50 to 350 nm, having child particles mainly composed of crystalline ceria on the surface of mother particles mainly composed of amorphous silica and having the following features [1] to [4] A silica-based composite fine particle dispersion containing the silica-based composite fine particles.
[1] The silica-based composite fine particles have a mass ratio of silica and 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 weight ratio of the bonded particles in which two or three primary particles are directly or indirectly connected in the silica-based composite fine particles is 60% or more.
(2) The silica-based composite fine particle dispersion described in (1) above, wherein the content of impurities contained in the silica-based composite fine particles is as shown in the following (a) and (b).
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 5 ppm or less.
(3) The silica-based composite fine particle dispersion described in (1) or (2) above, further having a silica coating on the surface of the child particles.
(4) The silica-based composite fine particles according to any one of (1) to (3) above, wherein the flow potential before titration when the pH value is in the range of 3 to 8 is a negative potential. Dispersion.
(5) Ratio of Si atom% to Ce atom% obtained by EDS measurement in which an electron beam is selectively applied to a portion of the silica film that can be observed using a transmission electron microscope. (Si atom number% / Ce atom number%) is 0.9 or more, and the silica-based composite fine particle dispersion according to any one of (1) to (4) above.
(6) When cationic colloid titration is performed, the ratio (ΔPCD / V) between the change in flow potential (ΔPCD) represented by the following formula (1) and the addition amount (V) of the cationic colloid titrant in the knick The silica-based composite fine particle dispersion according to any one of claims 1 to 5, wherein a streaming potential curve having a value of -110.0 to -15.0 is obtained.
ΔPCD / V = (I−C) / V (1)
C: Streaming potential (mV) at the nick
I: Streaming potential (mV) at the starting point of the streaming potential curve
V: Amount of the colloid titration solution added in the nick (ml)
(7) A polishing slurry containing the silica-based composite fine particle dispersion described in any one of (1) to (6) above.
(8) The polishing slurry according to (7), which is a polishing slurry for planarizing a semiconductor substrate on which a silica film is formed.
(9) A method for producing a silica-based composite fine particle dispersion, comprising the following steps 1 to 4.
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 a temperature at 5 to 98 ° C. and a pH within a range of 7.0 to 9.0. The process of adding the precursor particle | grain dispersion liquid which adds regularly or intermittently and contains a precursor particle.
Step 2: The precursor particle dispersion is dried and fired at 400 to 1,200 ° C., and the fired body obtained is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion liquid. Obtaining.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and the mixture is crushed and pulverized by a wet process.
Step 3: A step of obtaining a supernatant by subjecting the calcined dispersion liquid to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more and subsequently removing a sediment component.
Step 4: A step of subjecting the supernatant to a centrifugal treatment at a relative centrifugal acceleration of 300 G or more, and subsequently recovering a sediment component to obtain a silica-based composite fine particle dispersion.
(10) The method for producing a silica-based composite fine particle dispersion as described in (9) above, wherein the content ratio of impurities contained in the silica fine particles is as shown in the following (a) and (b).
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 5 ppm or less.
(11) In the above (9) or (10), (ii) in the above step 2 is a treatment of adding a solvent and crushing and crushing in a wet condition in the range of pH 9.0 to 10.6. The manufacturing method of the silica type composite fine particle dispersion of description.

According to the present invention, even a silica film, Si wafer or difficult-to-process material can be polished at high speed, and at the same time, high surface accuracy (low scratch, etc.) can be achieved. A silica-based composite fine particle dispersion that can be preferably used for surface polishing, a method for producing the same, and a polishing slurry containing the silica-based composite fine particle dispersion can be provided.
The silica-based composite fine particle dispersion of the present invention is effective for planarizing the surface of a semiconductor device, and is particularly suitable for polishing a substrate on which a silica insulating film is formed.

Transmission electron micrograph of the silica-based composite fine particle dispersion obtained in Example 1 (magnification 100,000 times) Transmission electron micrograph of the silica-based composite fine particle dispersion obtained in Example 2 (magnification 100,000 times) 2 is an element distribution diagram obtained by EDS measurement of silica-based composite fine particles obtained in Example 1. FIG. It is the photograph (TEM image) obtained by observing the silica type composite fine particle obtained in Example 1 using the transmission electron microscope. It is the EDS measurement result which applied the electron beam selectively to the part of the silica coating of the silica type composite fine particle obtained in Example 1.

The present invention will be described.
The present invention has child particles mainly containing crystalline ceria on the surface of mother particles mainly containing amorphous silica (hereinafter referred to as “silica fine particles”). A silica-based composite fine particle dispersion containing silica-based composite fine particles having an average particle size of 50 to 350 nm having the following features [1] to [3].
[1] The silica-based composite fine particles have a mass ratio of silica and 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 weight ratio of the bonded particles in which two or three primary particles are directly or indirectly connected in the silica-based composite fine particles is 60% or more.
Hereinafter, such a silica-based composite fine particle dispersion is also referred to as “the dispersion of the present invention”.
Further, the silica-based composite fine particles contained in the dispersion of the present invention are also referred to as “composite fine particles of the present invention” below.

Moreover, this invention is a manufacturing method of the silica type composite fine particle dispersion characterized by including the following process 1-process 4.
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 a temperature at 5 to 98 ° C. and a pH within a range of 7.0 to 9.0. The process of adding the precursor particle | grain dispersion liquid which adds regularly or intermittently and contains a precursor particle.
Step 2: The precursor particle dispersion is dried and fired at 400 to 1,200 ° C., and the fired body obtained is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion liquid. Obtaining.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and the mixture is crushed and pulverized by a wet process.
Step 3: A step of obtaining a silica-based composite fine particle dispersion by subjecting the calcined dispersion to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more and subsequently removing a sediment component.
Step 4: A step of subjecting the supernatant to a centrifugal treatment at a relative centrifugal acceleration of 300 G or more, and subsequently recovering a sediment component to obtain a silica-based composite fine particle dispersion.
The relative centrifugal acceleration is expressed as a ratio of the earth's gravitational acceleration as 1G.
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.

  In the following, the simple description of “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.

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

  It can be confirmed, for example, by the following method that the silica contained in the mother particles in the present invention is amorphous. The dispersion liquid (silica microparticle dispersion liquid) containing the mother particles (silica microparticles) is dried and then pulverized using a mortar. For example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Corporation) is used. When an X-ray diffraction pattern is obtained, the peak of crystalline silica such as Cristobalite does not appear. From this, it can be confirmed that the silica contained in the mother particles (silica fine particles) is amorphous.

The “main component” means that the content is 90% by mass or more. That is, in the mother particles, the content of amorphous silica is 90% by mass or more. The content is preferably 95% by mass or more, more preferably 98% by mass or more, and more preferably 99.5% by mass or more.
In the following description of the present invention, the term “main component” is used in this sense.

The mother particles are mainly composed of amorphous silica and may contain other materials such as crystalline silica and impurity elements.
For example, in the mother particle (silica fine particle), 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. Furthermore, it is preferable that it is 90 ppm or less. The content of each element of U, Th, Cl, NO ₃ , SO ₄ and F (hereinafter sometimes referred to as “specific impurity group 2”) in the base particles (silica fine particles) is 5 ppm or less, respectively. Preferably there is.
Generally, silica fine particles prepared using water glass as a raw material contain about a few thousand ppm in total of the specific impurity group 1 and the specific impurity group 2 derived from the raw water glass.
In the case of such a silica fine particle dispersion in which silica fine particles are dispersed in a solvent, it is possible to reduce the contents 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 several ppm to several hundred ppm in total. Therefore, when silica particles made from water glass are used, impurities are also reduced by acid treatment or the like.
On the other hand, in the case of a silica fine particle dispersion 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 Are each 20 ppm or less.
In the present invention, Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ , SO ₄ in the mother particles (silica fine particles) are used. Each of the contents of F and F is a value determined by measurement using the following method.
Na and K: atomic absorption spectroscopic analysis Ag, Al, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, Zr, U and Th: ICP (inductively coupled plasma emission spectroscopic analysis)
・ Cl: Potentiometric titration method ・ NO ₃ , SO ₄ and F: Ion chromatograph

As will be described later, 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 mother particles is necessarily smaller than 350 nm. In the present application, the average particle diameter of the mother 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 later. Silica-based composite fine particles having an average particle diameter of 30 to 200 nm are preferably used.
When the average particle diameter of the mother 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 mother particles is too small, the polishing rate will be insufficient. If the average particle size is too large, the polishing rate is lowered. 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. Silica fine particles are dispersed in water or the like to obtain a silica fine particle dispersion, and then the silica fine particle dispersion is separated from a particle size measuring device by a known dynamic light scattering method (for example, Microtrack UPA device manufactured by Nikkiso Co., Ltd., Measurement is performed using a measurement apparatus (PAR-III manufactured by Otsuka Electronics Co., Ltd.) or a laser diffraction scattering method (for example, LA-950 manufactured by HORIBA).
In addition, a measuring apparatus is selectively used according to the objective of each process, the assumed particle diameter, and a particle size distribution. Specifically, PAR-III is used for the raw material monodisperse silica fine particles having a uniform particle size of about 100 nm or less, and monodisperse raw silica fine particles having a large size of 100 nm or more are measured with LA-950, and the micrometer is obtained by crushing. It is preferable to use Microtrac UPA or LA-950 in the crushing process in which the particle diameter varies widely from 1 to nanometer.

The shape of the mother particle (silica fine particle) is not particularly limited, and for example, the surface other than spherical, bowl-shaped, short fiber-shaped, tetrahedral (triangular pyramid), hexahedral, octahedral, plate, and indefinite It may have a ridge-like protrusion, or it may be confetti-like, or may be porous, but is preferably spherical. 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 mother particles preferably have a minor axis / major axis ratio of 0.8 or less and a number ratio of particles of 5% or less, more preferably 0%.
The minor axis / major axis ratio is measured by the same method as the measuring method (image analysis method) of the minor axis / major axis ratio of the composite fine particles of the present invention described later.

<Child particles>
The composite fine particles of the present invention have child particles on the surface of the mother particles as described above. Here, it is preferable that the child particle is bonded to the surface of the mother particle. Further, for example, the child particles that are entirely covered with the silica coating may be bonded to the mother particles through the silica coating. Even such an embodiment is an embodiment in which child particles are present on the surface of the mother particle, and is included in the technical scope of the present invention.

  In the composite fine particles of the present invention, the child particles are mainly composed of crystalline ceria.

  The fact that the child particles are crystalline ceria is, for example, that the dispersion liquid of the present invention is dried and then pulverized using a mortar, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Corporation). In the X-ray diffraction pattern obtained by (1), only the ceria crystal phase is detected. Examples of the ceria crystal phase include Ceriaite.

The child particles are mainly composed of crystalline ceria (crystalline Ce oxide), 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. That is, even if a crystal phase other than ceria is included, its content is small, and thus it is outside the detection range by X-ray diffraction.
The definition of “principal component” is as described above.

  If the said child particle is crystalline ceria, it can be used conveniently. As such crystalline ceria, for example, the crystallite diameter of the (111) plane (around 2θ = 28 degrees) of the crystalline ceria measured by subjecting the composite fine particles of the present invention to X-ray diffraction is 10 to 25 nm. A range is preferred.

The crystallite diameter of the (111) plane of crystalline ceria (around 2θ = 28 degrees) means a value obtained by the method described below.
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained by using, for example, a conventionally known X-ray diffractometer (for example, RINT1400 manufactured by Rigaku Corporation). Then, the half width of the peak of the (111) plane in the vicinity of 2θ = 28 degrees in the obtained X-ray diffraction pattern is measured, and the crystallite diameter can be obtained by the following Scherrer equation.
D = Kλ / βcos θ
D: Crystallite diameter (angstrom)
K: Scherrer constant λ: X-ray wavelength (1.7789 angstrom, Cu lamp)
β: Half width (rad)
θ: Reflection angle

  The size of the child particles is smaller than that of the mother particles, preferably an average particle diameter of 11 to 26 nm, and more preferably 12 to 23 nm. The size of the child particles is a value obtained by measuring the average particle diameter of any 50 child particles in a photograph projection view enlarged 300,000 times using a transmission electron microscope, and simply averaging them. means.

<Silica coating>
The composite fine particles of the present invention preferably have the child particles on the surface of the mother particles, and further have a silica coating on the surface of the child particles. Here, it is more preferable that the child particles are bonded to the surface of the mother particles and further have a silica coating covering them. That is, it is more preferable that a silica coating covers part or all of the composite particles formed by bonding the child particles to the surface of the mother particles. Therefore, it is more preferable that a silica coating is present on the outermost surface of the composite fine particles of the present invention.
Moreover, a mother particle (primary particle) and another one or two mother particles (primary particles) may be indirectly connected via a child particle and a silica coating to constitute a bonded particle.
Further, the mother particles (primary particles) and one or two other mother particles (primary particles) are directly bonded (that is, directly connected) and cover all or part of them. Thus, the binding particles having the child particles and the silica coating may be formed.

When the composite fine particle of the present invention has a silica coating on the surface of the child particle, an image (TEM image) obtained by observation using a transmission electron microscope has a dark image of the child particle on the surface of the mother particle. Although it appears, a silica coating appears as a relatively thin image outside the child particle, that is, on the surface side of the composite fine particle of the present invention. Further, it is preferable that the child particles (ceria fine particles) are bonded to the mother particles (silica fine particles), and the child particles whose silica coating covers all or part of the mother particles are interposed via the silica coating. May be bonded to.
Further, when the composite fine particles of the present invention have a silica coating on the surface of the child particles, when the composite fine particles of the present invention are subjected to EDS analysis and the element distribution is obtained, a portion with a high Ce concentration is present on the surface side of the particles. Although it appears, a portion with a high Si concentration appears further outside.
Further, when EDS measurement was performed by selectively applying an electron beam to the silica coating portion specified by the transmission electron microscope as described above, the Si atom number% and Ce atom number% of the part were obtained. It can be confirmed that several percent is very high. Specifically, the ratio of Si atom number% to Ce atom number% (Si atom number% / Ce atom number%) is preferably 0.9 or more.

Such a silica coating is considered to promote the bond (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 particles obtained by firing are crushed and pulverized by a wet process to obtain a silica-based composite fine particle dispersion. It is considered that there is an effect of preventing the child particles (ceria crystal particles) from coming off from the mother particles (silica fine particles). In this case, local dropout of the child particles is not a problem, and the entire surface of the child particles may not be covered with the silica coating. It is sufficient that the child particles are strong enough not to be separated from the mother particles in the crushing / grinding process.
When such a structure is provided, it is considered that when the dispersion liquid of the present invention is used as an abrasive, the polishing rate is high, and the surface accuracy and scratch are less deteriorated. Further, since it is crystallized, there are few —OH groups on the surface of the particles, and there is little interaction with the —OH groups on the surface of the polishing substrate.
For example, when the substrate to be polished is a silica-based material, silanol groups (SiOH) are also present on the surface of the substrate to be polished, but when SiOH is also present on the surfaces of the abrasive particles (silica), both silanol groups react. Thus, it is considered that the abrasive particles may remain on the surface of the substrate to be polished. In addition, free ceria has a positive charge and is likely to adhere to the substrate. When the composite fine particles of the present invention have a silica coating on the surface of the child particles, the silica coating on the surface of the ceria particles imparts a negative charge to the ceria particles, and thus has an effect of reducing adhesion to the substrate. .
In addition, ceria has a potential different from that of silica, a polishing substrate, and a polishing pad, and the pH decreases from a negative zeta potential in the vicinity of neutral to neutral, and has a reverse positive potential in a weakly acidic region. For this reason, it adheres to the polishing substrate or polishing pad due to the difference in the magnitude of the potential or the polarity, and tends to remain on the polishing substrate or the polishing pad. On the other hand, when the composite fine particle of the present invention has a silica coating on the surface of the child particle, the silica-based composite fine particle of the present invention is such that the ceria which is the child particle is at least partially covered with the silica coating. In addition, since the pH is maintained at a negative potential from alkaline to acidic, it is difficult for abrasive grains to remain on the polishing substrate and polishing pad.

  When the composite fine particles of the present invention have a silica coating on the surface of the child particles, the thickness of the silica coating is roughly determined from the TEM image or SEM image by the degree of coverage of the ceria child particles on the mother particles by the silica coating. It is done. That is, as described above, in the TEM image, a child particle having a particle size of about 20 nm appears on the surface of the mother particle, and a silica coating appears as a relatively thin image outside the child particle. The thickness of the silica coating can be roughly determined by comparing with the size of. If the child particles can be clearly confirmed as irregularities from the SEM image and irregularities are seen in the outline of the silica-based composite fine particles from the TEM image, the thickness of the silica coating may be much less than 20 nm. It is done. On the other hand, if the irregularities of the child particles are not clear from the SEM image and the contours of the silica composite fine particles are not seen from the TEM image, the thickness of the silica coating is considered to be about 20 nm.

  When the composite fine particles of the present invention have a silica coating on the surface of the child particles, as described above, the silica coating of the outermost layer (the layer opposite to the mother particle side) is a child particle (ceria fine particles). It is not necessary to completely cover the whole. That is, when the composite fine particle of the present invention has a silica coating on the surface of the child particle, the silica coating is present on the outermost surface of the composite fine particle of the present invention, but the portion where the silica coating is not present is present. There may be. Further, there may be a portion where the base particle of the silica-based composite fine particle is exposed.

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

In the composite fine particles of the present invention, the mass ratio of silica and ceria is 100: 11 to 316, preferably 100: 30 to 230, more preferably 100: 30 to 150, and more preferably 100: 60 to More preferably, it is 120. The mass ratio between silica and ceria is considered to be approximately the same as the mass ratio between the mother particles and the child particles. If the amount of the child particles relative to the mother particles is too small, the mother particles may be bonded to generate coarse particles. In this case, the abrasive (polishing slurry) containing the dispersion of the present invention may cause defects (decrease in surface accuracy such as an increase in scratches) on the surface of the polishing substrate. Further, if the amount of ceria relative to silica is too large, not only is the cost high, but the resource risk increases. Furthermore, the fusion of the particles proceeds. As a result, the roughness of the substrate surface increases (deterioration of the surface roughness Ra), scratches increase, free ceria remains on the substrate, and causes such as adhesion to the waste liquid piping of the polishing apparatus. It's easy to get along.
In addition, the silica used as the object in calculating the mass ratio includes both the following (I) and (II).
(I) Silica component included in the silica coating that covers the composite fine particles formed by binding the child particles (ceria component) to the silica particles (II) constituting the mother particles (II)

The content (mass%) of silica (SiO ₂ ) and ceria (CeO ₂ ) in the composite fine particles of the present invention is determined by first determining the solid content concentration of the dispersion of the composite fine particles of the present invention (dispersion of the present invention) at 1000 ° C. Calculate the weight loss after losing heat.
Next, the content (mass%) of cerium (Ce) contained in a predetermined amount of the composite fine particles of the present invention is determined by ICP plasma emission analysis, and converted to CeO ₂ mass%. Then, assuming that the components other than CeO ₂ constituting the composite fine particles of the present invention are SiO ₂ , SiO ₂ mass% can be calculated.
In the production method of the present invention, the mass ratio of silica and ceria can be calculated from the amount of silica source material and ceria source material used when the dispersion of the present invention is prepared. This can be applied when ceria and silica are not dissolved and removed, and in such a case, the amount of ceria or silica used and the analytical value are in good agreement.

The composite fine particles of the present invention have irregular surface shapes because particulate crystalline ceria (child particles) are bonded to the surface of silica fine particles (mother particles) by sintering or the like.
That is, it is preferable that at least one (preferably both) of the mother particle and the child particle is sinter-bonded and firmly bonded at their contact points. However, the child particles covered with the silica coating may be bonded to the mother particles through the silica coating.

The shape of the composite fine particles of the present invention is not particularly limited, but may be a particle-linked type in practice. The particle connection type means that two or more mother particles are partially bonded to each other. It is considered that at least one (preferably both) of the mother particles are welded at their contact points, and preferably, both are firmly bonded together. Here, in addition to the case where the child particles are bonded to the surface after the mother particles are bonded to each other, and the case where the child particles are bonded to the surface of the mother particle and then bonded to the other particles, And
Since the contact type can increase the contact area with the substrate, 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, there is little scratching.

In the composite fine particles of the present invention, the weight ratio of the combined particles in which two or three primary particles are directly or indirectly connected contained in the silica-based composite fine particles is 60% or more.
Here, the following (A) to (D) are mentioned as main aspects of each particle which is a constituent element of the composite fine particle of the present invention.
(A) A composite fine particle (one) of the present invention in which a child particle is attached to a mother particle.
(A) The composite fine particles of the present invention (one piece) having child particles attached to the mother particles and a silica coating.
(C) Silica so that one primary particle in which child particles are attached to the mother particle and another one or two similar primary particles are directly bonded and cover all or part of them. A bonded particle composed of a coating.
(D) A bonded particle in which one primary particle having a mother particle attached to a child particle and another one or two similar primary particles are indirectly bonded via a silica coating.

  In the composite fine particles of the present invention, the weight ratio of the bound particles corresponding to the above (c) or (d) in which two or three primary particles are connected directly or indirectly is 60% or more. In this case, the composite fine particles of the present invention have a low content of particles having a three-dimensional structure, which is preferable in that the generation of scratches can be further suppressed when used as an abrasive. Here, when three primary particles are connected, there are a case where these three particles are connected in a straight chain and a case where these three particles are connected in a ring shape.

The weight ratio of the binding particles contained in the silica-based composite fine particles means a value obtained by measuring the number ratio of particles by an image analysis method and then converting this to a weight ratio.
Specifically, the composite fine particle dispersion sufficiently diluted and dispersed is dried to prepare the composite fine particle sample of the present invention, and photographed with a transmission electron microscope at a magnification of 250,000 times (or 500,000 times) Then, a photograph projection view is obtained, and the number of particles for each of 50 arbitrary independent particles to be visually observed is measured. After determining the particle number ratio from the result, the combined particles are converted into weight ratios. The ratio of In addition, the method of calculating | requiring a weight ratio conversion value calculated | required weight with the formula described below for every particle | grain number, and calculated | required in percentage with respect to the total weight of all the particle | grain numbers.
Formula: (Average particle diameter of composite fine particle ÷ 2) ³ × True specific gravity of composite fine particle × Number of particles Note that in the electron micrograph, the particles may gather and aggregate when the sample is dried. The validity of the method was confirmed.
First, the particle size distribution was measured with a particle size distribution measuring apparatus (for example, Disc Certifge DC18000 manufactured by CPS) for the sintered body pulverized dispersion of Synthesis Example described later. In the particle size distribution measuring apparatus, a plurality of peaks were confirmed. The peak top of the peak with the smallest particle diameter was defined as one individual particle diameter (D1), and the subsequent peaks were defined as D2, D3, and D4. Next, the particle diameter of a sphere having a volume equal to twice the volume of one individual particle was assumed to be two individuals, and D2 ′ was calculated. The volume of the sphere equal to 3 times or 4 times was similarly determined as D3 ′ and D4 ′. As a result, D2 and D2 ′, D3 and D3 ′, and D4 and D4 ′ were in good agreement. From this, it was considered that the measurement of 1 to 4 balls with a particle size distribution measuring device was appropriate. And this particle size distribution measurement result was peak-separated, and the weight ratio of 1-4 individuals was computed.
Next, from the electron micrograph, the number of particles of 1 to 4 individuals was measured, converted into a weight ratio, and compared with the weight ratio of the particle size distribution measuring apparatus. As a result, since both showed good agreement, it was judged that the image analysis method of the electron microscope was appropriate.
In the present application, a single primary particle not connected to other particles is “one ball”, a particle in which two primary particles are connected directly or indirectly is “two balls”, and a primary particle is directly Particles in which three particles are connected either directly or indirectly are also referred to as “three balls”, and particles in which four primary particles are directly or indirectly connected are also referred to as “four balls”.

The composite fine particles of the present invention preferably have a specific surface area of 4 to 100 m ² / g, and 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 in a measurement cell, degassed in a nitrogen gas stream at 250 ° C. for 40 minutes, and then the sample is a mixed gas of 30% by volume of nitrogen and 70% by volume of helium. Liquid nitrogen temperature is maintained in a stream of air, and nitrogen is adsorbed to the sample by equilibrium. Next, the temperature of the sample is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area of the sample is measured using a calibration curve prepared in advance.
Such a BET specific surface area 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 obtained by such a method unless otherwise specified.

The average particle size of the composite fine particles of the present invention is preferably 50 to 350 nm, and more preferably 170 to 260 nm. When the average particle size of the composite fine particles of the present invention is in the range of 50 to 350 nm, it is preferable because the polishing rate becomes high when applied as an abrasive.
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 used as a particle size measuring device by a known dynamic light scattering method (for example, Nikkiso Co., Ltd. Microtrac UPA device or Otsuka Electronics PAR-III). ) Or a measurement apparatus using a 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. Furthermore, it is preferable that it is 50 ppm or less, and it is more preferable that it is 45 ppm or less. Moreover, it is preferable that the content rate of each element of the said specific impurity group 2 in the composite fine particle of this invention is 5 ppm or less, respectively. As the 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 mother particles (silica fine particles) can be applied.
Note that 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 measurement using an ICP (inductively coupled plasma emission spectrometer).

  The composite fine particle dispersion according to the present invention is characterized in that each element content of the specific impurity group 1 is 100 ppm or less and each element content of the specific impurity group 2 is 5 ppm or less. There are cases where it is a liquid and composite oxide fine particles that do not necessarily satisfy this condition. Among these, the former can be suitably used as an abrasive in applications where application of high-purity abrasives is required, for example, polishing applications such as semiconductor devices such as semiconductor substrates and wiring substrates. Moreover, the latter is applied to applications where application of a high-purity abrasive is not required, such as glass polishing. (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 liquid of the present invention will be described.
The dispersion liquid of the present invention is such that 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. For example, water such as pure water, ultrapure water, or ion exchange water is preferably used as the dispersion solvent. Furthermore, the dispersion of the present invention may contain one or more selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster, and a pH buffer as an additive.

  Examples of the dispersion solvent provided with 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, ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxy Glycol ether acetates such as ethyl acetate; esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and 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 content concentration contained in the dispersion of the present invention is preferably in the range of 0.3 to 50% by mass.

When the dispersion of the present invention was subjected to cationic colloid titration, the ratio of the change in flow potential (ΔPCD) represented by the following formula (1) to the addition amount (V) of the cationic colloid titrant in the knick ( It is preferable that a streaming potential curve having ΔPCD / V) of −110.0 to −15.0 is obtained.
ΔPCD / V = (I−C) / V (1)
C: Streaming potential (mV) at the nick
I: Streaming potential (mV) at the starting point of the streaming potential curve
V: Amount of the colloid titration solution added in the nick (ml)

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

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

  When the value of ΔPCD / V is −110.0 to −15.0, when the dispersion liquid of the present invention is used as an abrasive, the polishing rate of the abrasive is further improved. 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. When the value of ΔPCD / V is within the above range, the present inventor presumes that the child particles are hardly detached at the time of wet pulverization / pulverization and the polishing rate is high. Conversely, if the absolute value of ΔPCD / V is larger than −110.0, the surface of the composite fine particles is entirely covered with a silica coating, so that it is difficult for the child particles to fall off during the crushing and pulverization process. Sometimes the silica is difficult to desorb and the polishing rate decreases. On the other hand, when the absolute value is smaller than -15.0, it is considered that dropout is likely to occur. The inventor presumes that within the above range, the surface of the child particles is appropriately exposed at the time of polishing so that the child particles are not dropped off 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 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 flow potential is negative. Is preferred. This is because when this flow potential is maintained at a negative potential, it is difficult for abrasive grains (silica-based composite fine particles) to remain on the polishing substrate that also exhibits a negative surface potential.

  Although the manufacturing method of the dispersion liquid of this invention is not specifically limited, It is preferable to manufacture with the manufacturing method of this invention demonstrated below.

<Production method of the present invention>
The production method of the present invention will be described.
The manufacturing method of the present invention includes steps 1 to 4 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.
When preparing a silica-based composite fine particle dispersion to be applied to polishing of semiconductor devices and the like by the production method of the present invention, silica fine particles produced by hydrolysis of alkoxysilane are dispersed in a solvent as the silica fine particle dispersion. It is preferable to use a silica fine particle dispersion. When a conventionally known silica fine particle dispersion (such as a silica fine particle dispersion prepared from water glass as a raw material) is used as a raw material, the silica fine particle dispersion is preferably acid-treated and further deionized. . In this case, the content 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 This is because it can be reduced to 100 ppm or less.
Specifically, those satisfying the following conditions (a) and (b) are preferably used as the silica fine particles in the silica fine particle dispersion, which is the raw material used in step 1.
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 5 ppm or less.

  In step 1, the silica fine particle dispersion in which the silica fine particles are dispersed in a solvent as described above is stirred, and the temperature is maintained at 5 to 98 ° C. and the pH range is maintained at 7.0 to 9.0. A salt is added continuously or intermittently to obtain a precursor particle dispersion containing precursor particles.

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

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

  Also, extract impurities with cation exchange resin or anion exchange resin, mineral acid, organic acid, etc., and perform deionization treatment of silica fine particle dispersion as necessary using ultrafiltration membrane etc. Can do. A silica fine particle dispersion from which impurity ions and the like are removed by deionization treatment is more preferable because a hydroxide containing silicon is easily formed on the surface. The deionization process is not limited to these.

In Step 1, the silica fine particle dispersion as described above is stirred, and the cerium metal salt is continuously or intermittently added thereto while maintaining the temperature at 5 to 98 ° C. and the pH range at 7.0 to 9.0. Add to.
The metal salt of cerium is not limited, but cerium chloride, nitrate, sulfate, acetate, carbonate, metal alkoxide, and the like can be used. Specific examples include cerium nitrate, cerium carbonate, cerium sulfate, and cerium chloride. Of these, ceric nitrate and ceric chloride are preferred. Crystalline cerium oxides are formed from a solution that becomes supersaturated at the same time as neutralization, and they quickly adhere to the silica fine particles by an agglomeration and deposition mechanism. However, sulfate ions, chloride ions, nitrate ions, etc. contained in these metal salts are corrosive. For this reason, it is necessary to wash it in a post-process after preparation and remove it to 5 ppm or less. On the other hand, carbonate is released during the preparation as carbon dioxide, and alkoxide is decomposed to become 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 an aqueous cerium metal salt solution obtained by adding water or an aqueous solvent to the cerium metal salt. The ceria concentration of the cerium metal salt aqueous solution is not particularly limited, but the ceria concentration is preferably in the range of 1 to 40% by mass in consideration of workability and the like.

The temperature at the time of stirring after adding the cerium metal salt to the silica fine particle dispersion is 5 to 98 ° C, and preferably 10 to 95 ° C. Moreover, it is preferable that the temperature at the time of stirring is 1-30 degreeC. If the temperature is too low, the solubility of the silica is remarkably reduced, so that ceria crystallization is not controlled, and coarse ceria crystalline oxides are formed, making it difficult to adhere to silica fine particles (mother particles). Things can be considered.
On the other hand, if this temperature is too high, the solubility of silica is remarkably increased, and the formation of crystalline ceria oxide is considered to be suppressed. Furthermore, scale and the like are likely to occur on the reactor wall surface, which is not preferable.

  Moreover, it is preferable that the time at the time of stirring is 0.5 to 24 hours, and it is more preferable that it is 0.5 to 18 hours. If this time is too short, crystalline cerium oxide cannot be formed sufficiently, which is not preferable. Conversely, even if this time is too long, the formation of crystalline cerium oxide is uneconomical because the reaction does not proceed any further. In addition, after adding the said cerium metal salt, you may age at 5-98 degreeC if desired. By aging, the reaction in which the cerium compound is deposited on the mother particles can be further promoted.

  Moreover, the pH range of the silica fine particle dispersion when adding a cerium metal salt to the silica fine particle dispersion and stirring is 7.0 to 9.0, but is preferably 7.6 to 8.6. . If the pH is too high or too low, the stability tends to decrease. At this time, it is preferable to adjust the pH by adding an alkali or the like. A publicly known alkali can be used as an example of such an alkali. Specific examples include aqueous ammonia, alkali hydroxide, alkaline earth metal, and aqueous amines, but are not limited thereto.

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

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

  In addition, it is preferable that the solid content concentration in a precursor particle dispersion is 1-27 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.

  More preferably, in step 1, the temperature of the silica fine particle dispersion is set to 48 to 52 ° C., and the pH range is maintained at 7.0 to 9.0, and the metal salt of cerium is added continuously or intermittently. Then, a precursor particle dispersion is prepared, and the precursor particle dispersion is aged at a temperature of 90 to 98 ° C. When Step 1 is performed under such conditions, it is possible to prevent cerium oxide having a low crystallinity from uniformly attaching to the surface of the silica fine particles and forming an aggregate of cerium oxides.

<Process 2>
In 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. It can be dried using a conventionally known dryer. Specifically, a box-type dryer, a band dryer, a spray dryer or the like can be used.
In addition, it is recommended that the pH of the precursor particle dispersion before drying is preferably 6.0 to 7.0. It is because surface activity can be suppressed when the pH of the precursor particle dispersion before drying is 6.0 to 7.0.
After drying, the firing temperature is 400 to 1200 ° C, preferably 800 to 1100 ° C, and more preferably 1000 to 1090 ° C. When firing in such a temperature range, crystallization of ceria proceeds sufficiently, and the silica film present on the surface of the ceria fine particles is appropriately thickened so that the mother particles and the child particles are firmly bonded. If this temperature is too high, the ceria crystals will grow abnormally or the silica coating on the ceria particles will become thicker and the bonding with the mother particles will proceed, but it is also expected that the ceria child particles will be covered thickly, forming the mother particles There is a possibility that the amorphous silica to be crystallized or the fusion between the particles proceeds.

In step 2, the fired body obtained by firing is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and the mixture is crushed and pulverized by a wet process.
As the dry crushing / pulverizing apparatus, conventionally known apparatuses can be used, and examples thereof include an attritor, a ball mill, a vibration mill, and a vibration ball mill.
Conventionally known apparatus can be used as a wet crushing / pulverizing apparatus. For example, a batch type bead mill such as a basket mill, a horizontal type, a vertical type or an annular type continuous bead mill, a sand grinder mill, a ball mill, etc. , Rotor-stator type homogenizer, ultrasonic dispersion type homogenizer, and wet medium stirring mill (wet crusher) such as an impact pulverizer that collides fine particles in the dispersion. Examples of the beads used in the wet medium stirring mill include beads made of glass, alumina, zirconia, steel, flint stone, and the like.
In both the processes (i) and (ii), water and / or an organic solvent are used as the solvent. For example, it is preferable to use water such as pure water, ultrapure water, or ion exchange water. Moreover, although the solid content concentration of the baked body disintegration dispersion liquid obtained by the process of (i) or (ii) is not specifically limited, For example, it exists in the range of 0.3-50 mass%. Is preferable, and it is more preferable to set it as 10-30 mass%. Of the treatments (i) or (ii), the wet treatment of (ii) is more preferably used in practice.

In addition, when performing the crushing and grinding | pulverization by wet of said (ii), it is preferable to perform crushing and grinding | pulverization by wet, maintaining the pH of a solvent at 9.0-10.6. When the pH is maintained in this range, when the cationic colloid titration is performed, the change in streaming potential (ΔPCD) represented by the above formula (1) and the addition amount (V) of the cationic colloid titrant in the knick A silica-based composite fine particle dispersion in which a flow potential curve having a ratio (ΔPCD / V) of -110.0 to -15.0 is obtained can be finally obtained more easily.
That is, it is preferable to perform pulverization and pulverization to such an extent that the dispersion liquid of the present invention corresponding to the above-mentioned preferable embodiment can be obtained. This is because, as described above, when the dispersion liquid of the present invention corresponding to a preferred embodiment is used as an abrasive, the polishing rate is further improved. About this, the inventor is that the silica coating on the surface of the composite fine particles of the present invention is moderately thin, and / or the child particles are exposed to a part of the surface of the composite fine particles, the polishing rate is further improved, In addition, it is estimated that the falling of ceria particles can be controlled. Further, since the silica coating is thin or peeled off, it is estimated that the child particles are easily detached 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 step 3, the fired body disintegrated dispersion obtained in step 2 is subjected to a centrifugal separation process at a relative centrifugal acceleration of 300 G or more, and then the sediment component is removed to obtain a supernatant.

  Specifically, the calcination dispersion liquid is classified by a centrifugal separation process. The relative centrifugal acceleration in the centrifugation process is set to 300 G or more. After centrifugation, the sediment component is removed and a supernatant can be obtained. 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, the time for performing the centrifugation treatment is preferably 1 to 30 minutes, and more preferably 3 to 10 minutes.
Note that step 3 (centrifugation treatment) may be performed once or a plurality of times as desired. When the step 3 is performed a plurality of times, the supernatant is separated from the sedimented product, and the supernatant is recovered each time, and the supernatant is subjected to the step 3.

<Step 4>
In step 4, the supernatant obtained in step 3 is centrifuged at a relative centrifugal acceleration of 300 G or higher, and then the sediment component is recovered to obtain a silica-based composite fine particle dispersion.

  Specifically, the supernatant is classified by centrifugation. The relative centrifugal acceleration in the centrifugation process is set to 300 G or more. After the centrifugal separation treatment, the precipitated component can be recovered and obtained as 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 4, the time for performing the centrifugation treatment is preferably 1 to 30 minutes, and more preferably 3 to 10 minutes.
Note that step 4 (centrifugation treatment) may be performed once or a plurality of times as desired. When the step 4 is performed a plurality of times, the supernatant is separated from the sedimented product, and the sedimented product is recovered each time, and the sedimented product is supplied to the step 4.

  In the production method of the present invention, as described above, the centrifugal treatment is performed in Step 3 and Step 4. However, another centrifugal treatment may be performed, and this case is also within the scope of the production method of the present invention. .

In step 3 and step 4, it is necessary to provide a centrifugal separation process that satisfies the above conditions. If the centrifugal acceleration (and preferably the processing time) does not satisfy the above conditions, the silica-based composite fine particle dispersion obtained in Step 4 has a three-dimensional structure (that is, a combination of four or more primary particles). As a result, a relatively large amount of remains, causing scratches when used in polishing applications such as abrasives using silica-based composite fine particle dispersions. According to the production method of the present invention, it is possible to obtain a dispersion liquid of the present invention containing a large number of bonded particles in which two or three primary particles are connected. In such a dispersion liquid of the present invention, there are few particles having a three-dimensional structure. Therefore, scratches are unlikely to occur when used as an abrasive.
In the present invention, the silica-based composite fine particles can be obtained by further drying the silica-based composite fine particle dispersion obtained by the above production method. The drying method is not particularly limited, and for example, it can be dried using a conventionally known dryer.

The dispersion of the present invention can be obtained by the production method of the present invention.
In addition, when the cerium metal salt is added to the silica fine particle dispersion, it is desirable that the reduction potential of the preparation liquid takes 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 plates and rods are generated. Examples of a method for keeping the oxidation-reduction potential positive include a method of adding an oxidizing agent such as hydrogen peroxide and a method of blowing air, but is not limited thereto.

<Slurry for polishing>
The liquid containing the dispersion of the present invention can be preferably used as a polishing slurry (hereinafter also referred to as “the polishing slurry of the present invention”). In particular, it can be suitably used as a polishing slurry for planarizing a semiconductor substrate on which a SiO ₂ insulating film is formed.

  The polishing slurry of the present invention has a high polishing rate when polishing a semiconductor substrate and the like, and is excellent in effects such as few scratches (scratches) on the polishing surface and little residual abrasive grains on the substrate during polishing.

  The polishing slurry of the present invention contains water and / or an organic solvent as a dispersion solvent. For example, water such as pure water, ultrapure water, or ion exchange water is preferably used as the dispersion solvent. Furthermore, the polishing slurry of the present invention may contain one or more selected from the group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster and a pH buffer as an additive.

<Polishing accelerator>
In the polishing slurry according to the present invention, a conventionally known polishing accelerator can be used as necessary, although it varies depending on the type of material to be polished. Examples of such include hydrogen peroxide, peracetic acid, urea peroxide and mixtures thereof. When such an abrasive composition containing a polishing accelerator such as hydrogen peroxide is used, the polishing rate can be effectively improved when the material to be polished is a metal.

  Other examples of polishing accelerators include inorganic acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid and hydrofluoric acid, organic acids such as acetic acid, or 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 consisting of composite components, the polishing rate is accelerated for a specific component of the material to be polished, thereby finally achieving flat polishing. You can get a plane.

  When the polishing slurry according to the present invention contains a polishing accelerator, the content thereof is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass.

<Surfactant and / or hydrophilic compound>
In order to improve the dispersibility and stability of the polishing slurry, a cationic, anionic, nonionic or amphoteric surfactant or a hydrophilic compound can be added. Both the surfactant and the hydrophilic compound have an action of reducing a contact angle to the surface to be polished and an action of promoting uniform polishing. As the surfactant and / or the hydrophilic compound, for example, those selected from the following groups can be used.

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

  As cationic surfactant, aliphatic amine salt, aliphatic quaternary ammonium salt, benzalkonium chloride salt, benzethonium chloride, pyridinium salt, imidazolinium salt; as amphoteric surfactant, carboxybetaine type, sulfobetaine type, Mention may be made of aminocarboxylates, imidazolinium betaines, lecithins, alkylamine oxides.

  Nonionic surfactants include ether type, ether ester type, ester type and nitrogen-containing type. Ether type includes polyoxyethylene alkyl and alkylphenyl ether, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene poly Examples include oxypropylene block polymer, polyoxyethylene polyoxypropylene alkyl ether, ether ester type, glycerin ester polyoxyethylene ether, sorbitan ester polyoxyethylene ether, sorbitol ester polyoxyethylene ether, 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. In addition, a fluorine-type surfactant etc. are mentioned.

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

  Further, other surfactants and hydrophilic compounds include 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, 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, aminopolyacrylamide, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, Polycarboxylic acids such as lyamidic acid, polyamic acid ammonium salt, polyamic acid sodium salt and polyglyoxylic acid and their salts; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; methyl tauric acid ammonium salt, methyl tauric acid sodium salt , Methyl sulfate sodium salt, ethyl ammonium sulfate salt, butyl ammonium sulfate salt, vinyl sulfonic acid sodium salt, 1-allyl sulfonic acid sodium salt, 2-allyl sulfonic acid sodium salt, methoxymethyl sulfonic acid sodium salt, ethoxymethyl sulfonic acid ammonium salt Salts, sulfonic acids such as 3-ethoxypropylsulfonic acid sodium salt and the salts thereof; propionamide, acrylamide, methylurea, nicotinamide, succinic acid amide and sulfite Examples thereof include amides such as an amide.

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

  When the polishing slurry according to the present invention contains a surfactant and / or a hydrophilic compound, the total content is preferably 0.001 to 10 g in 1 L of the polishing slurry. It is more preferable to set it as 01-5g, and it is especially preferable to set it as 0.1-3g.

  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, and preferably 10 g or less from the viewpoint of preventing the polishing rate from being lowered.

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

<Heterocyclic compound>
Regarding the polishing slurry of the present invention, when a metal is contained in the substrate to be polished, a heterocyclic compound is formed for the purpose of suppressing the erosion of the substrate to be polished by forming a passive layer or a dissolution suppressing layer on the metal. May be included. Here, the “heterocyclic compound” is a compound having a heterocyclic ring containing one or more heteroatoms. A hetero atom means an atom other than a carbon atom or a hydrogen atom. A heterocycle means a cyclic compound having at least one heteroatom. A heteroatom means only those atoms that form part of a heterocyclic ring system, either external to the ring system, separated from the ring system by at least one non-conjugated single bond, Atoms that are part of a further substituent of are 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 can be mentioned, but is not limited thereto.

  About content in the case of mix | blending a heterocyclic compound with the slurry for polishing which concerns on this invention, it is preferable that it is 0.001-1.0 mass%, and it is more that it is 0.001-0.7 mass%. Preferably, it is 0.002-0.4 mass%.

<PH adjuster>
In order to enhance the effects of the above additives, an acid or a base can be added as necessary to adjust the pH of the polishing composition.

  When adjusting the polishing slurry to pH 7 or higher, an alkaline one is used as a pH adjuster. Desirably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, tetramethylamine are used.

  When the polishing slurry is adjusted to a pH of less than 7, an acidic one is used as a pH adjuster. For example, mineral acids such as hydrochloric acid and nitric acid such as hydroxy acids such as acetic acid, lactic acid, citric acid, malic acid, tartaric acid and glyceric acid are used.

<PH buffering agent>
In order to keep the pH value of the polishing slurry constant, a pH buffer may be used. Examples of the pH buffering agent that can be used include phosphates and borates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate, and organic acids.

  Examples of the dispersion solvent for the polishing slurry 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, ethylene glycol dimethyl ether; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-but Glycol ether acetates such as ciethyl 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 and isooctane Aliphatic hydrocarbons such as cyclohexane; halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, 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 content concentration contained in the polishing slurry of the present invention is preferably in the range of 0.3 to 50 mass%. If this solid content concentration is too low, the polishing rate may decrease. Conversely, even if the solid content concentration is too high, the polishing rate is rarely improved further, which can be uneconomical.

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

  First, details of each measurement method and test method in Examples and Comparative Examples will be described. For each example and comparative example, the following measurement results and test results are shown in Table 1.

[Analysis of ingredients]
[Silica fine particles (mother 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 a raw material, the amount was reduced by 1000 ° C. and measured by weighing. 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 composite fine particles]
The content rate of each element shall be measured with the following method.
First, about 1 g (solid content: 20% by mass) of a sample composed of a silica-based composite fine particle dispersion is collected in a platinum dish. Add 3 ml of phosphoric acid, 5 ml of nitric acid and 10 ml of hydrofluoric acid and heat on a sand bath. Once dry, add a small amount of water and 50 ml of nitric acid to dissolve and place in a 100 ml volumetric flask and add water 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 liquid separation from the solution in 100 ml into the 20 ml volumetric flask is repeated 5 times to obtain 5 10 ml of the liquid separation. Using this, standard addition method for Al, Ag, Ca, Cr, Cu, Fe, Mg, Ni, Ti, Zn, Zr, U and Th with an ICP plasma emission spectrometer (for example, SPS5520 manufactured by SII) Measure with. Here, a blank is also measured by the same method, and the blank is subtracted and adjusted to obtain measured values for each element.
Hereinafter, unless otherwise specified, the content (content) of the components of Na, Al, Ag, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U and Th in the present invention is as follows. The value obtained by measurement by such a method is meant.

The content rate of each anion shall be measured by the following method.
<Cl>
Acetone is added to a 20 g sample (solid content of 20% by mass) composed of a silica-based composite fine particle dispersion to adjust to 100 ml, and 5 ml of acetic acid and 4 ml of 0.001 molar sodium chloride solution are added to this solution to form a 0.002 molar silver nitrate solution. The analysis is carried out by potentiometric titration (Kyoto Electronics: potentiometric titrator AT-610).
Separately, as a blank measurement, 5 ml of acetic acid and 4 ml of 0.001 molar sodium chloride solution were added to 100 ml of acetone, and titration was performed when titrating with 0.002 molar silver nitrate solution, and titration when using a sample. Was subtracted from the sample to obtain a titration amount of the sample.

<NO ₃ , SO ₄ , F>
A 5 g sample (solid content of 20% by mass) composed of a silica-based composite fine particle dispersion is diluted with water to 100 ml, and centrifuged at 4000 rpm for 20 minutes in a centrifuge (HIMAC CT06E manufactured by Hitachi), and the precipitated components are separated. The liquid obtained by the removal was analyzed with an ion chromatograph (ICS-1100, manufactured by DIONEX).

<SiO ₂ , CeO ₂ >
When obtaining the content of silica and ceria in the silica-based composite fine particles, first, the solid content concentration of the dispersion of the silica-based composite fine particles is determined by weighing at 1000 ° C. and by weight reduction. Next, Ce is measured by a standard addition method using an ICP plasma emission spectrometer (for example, SPS5520 manufactured by SII) in the same manner as Al to Th and the like, and CeO ₂ mass% is calculated from the obtained Ce content. . Then, assuming that the components other than CeO ₂ constituting the composite fine particles of the present invention are SiO ₂ , SiO ₂ mass% is calculated.
The content of each element or each anion in the silica fine particles (mother particles) is determined by using the silica fine particle dispersion instead of the silica composite fine particle dispersion in the method for analyzing silica-based composite fine particles. went.

[X-ray diffraction method, measurement of crystallite diameter]
In accordance with 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 pulverized in a mortar for 10 minutes, and X-ray diffraction was performed. An X-ray diffraction pattern was obtained by an apparatus (RINT1400, manufactured by Rigaku Corporation), and a crystal form was specified.
Further, as described above, the half width of the peak of the (111) plane (2θ = 28 degrees) near 2θ = 28 degrees in the obtained X-ray diffraction pattern was measured, and the crystallite diameter was calculated according to Scherrer's equation. Asked.

<Average particle size>
For the silica fine particle dispersions and silica-based composite fine particle dispersions obtained in the examples and comparative examples, the average particle size of the particles contained therein was measured by the method described above. Specifically, PAR-III manufactured by Otsuka Electronics Co., Ltd. and LA950 manufactured by HORIBA Co., Ltd. were used as the silica mother particles, and a Microtrac UPA apparatus manufactured by Nikkiso Co., Ltd. was used for the silica composite fine particles.

[Polishing test method]
<Polishing of SiO ₂ film>
A slurry (polishing slurry) containing the silica-based composite fine particle dispersion obtained in each of Examples and Comparative Examples was prepared. Here, the solid content concentration was 0.6% by mass, and nitric acid was added to adjust the pH to 5.0.
Next, as a substrate to be polished, a SiO ₂ insulating film (thickness 1 μm) substrate prepared by a thermal oxidation method was prepared.
Next, 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 a polishing slurry at a rotation speed of 90 rpm at a rate of 50 ml / min for 1 minute.
And the grinding | polishing speed | rate was calculated by calculating | requiring the weight change of the to-be-polished base material before and behind grinding | polishing.
Moreover, the smoothness (surface roughness Ra) of the surface of the polishing substrate was measured using an atomic force microscope (AFM, manufactured by Hitachi High-Tech Science Co., Ltd.).
The polishing scratches were observed by observing the insulating film surface using an optical microscope.

<Aluminum hard disk polishing>
A slurry (polishing slurry) containing the silica-based composite fine particle dispersion obtained in each of Examples and Comparative Examples was prepared. Here, the solid content concentration was 9% by mass and the pH was adjusted to 2.0 by adding nitric acid.
A substrate for aluminum hard disk is set in a polishing apparatus (NF300, manufactured by Nano Factor Co., Ltd.), and a polishing pad (“Polytex φ12” manufactured by Nitta Haas Co., Ltd.) is used. Polishing is performed by supplying at a rate of 20 ml / min for 5 minutes, and using an ultra-fine defect / visualization macro apparatus (manufactured by VISION PSYTEC, product name: Micro-Max), the entire surface is observed with a Zoom 15, 65.97 cm ² The number of scratches (linear traces) present on the polished substrate surface corresponding to No. 1 was counted and totaled and evaluated according to the following criteria.
Number of linear marks Evaluation Less than 50 “Very few”
Less than 80, 50 or more
80 or more "Many"
* At least 80 and so many that the total number cannot be counted "*"

<Flow potential>
About each silica type composite fine particle dispersion liquid obtained by the Example and the comparative example, the measurement of the streaming potential and the cation colloid titration were performed. As a titration apparatus, automatic titration apparatus AT-510 (manufactured by Kyoto Electronics Co., Ltd.) equipped with a streaming potential titration unit (PCD-500) was used.
First, a silica-based composite fine particle dispersion whose solid content concentration was adjusted to 1% by mass was adjusted to pH 6 by adding a 0.05% hydrochloric acid aqueous solution. An amount corresponding to 0.8 g as the solid content of the liquid was taken in a cell of a streaming potential measuring device, and the streaming potential was measured. Next, titration was performed by adding a cationic colloid titration solution (0.0025N polydiallyldimethylammonium chloride solution). Then, the addition amount (ml) of the cation 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, In addition, the flow potential C (mV) at the nick and the addition amount V (ml) of the cation colloid titrant were determined, and ΔPCD / V = (I−C) / V was calculated. The results are shown in Table 1.
Moreover, about each silica type composite fine particle dispersion liquid obtained by the Example and the comparative example, the measurement of the streaming potential and the cation colloid titration were performed. As a titration apparatus, automatic titration apparatus AT-510 (manufactured by Kyoto Electronics Co., Ltd.) equipped with a streaming potential titration unit (PCD-500) was used.
First, a silica-based composite fine particle dispersion whose solid content concentration was adjusted to 1% by mass was adjusted to pH 6 by adding a 0.05% hydrochloric acid aqueous solution. An amount corresponding to 0.8 g as the solid content of the liquid was taken in a cell of a streaming potential measuring device, and the streaming potential was measured. Next, titration was performed by adding a cationic colloid titration solution (0.0025N polydiallyldimethylammonium chloride solution). Then, the addition amount (ml) of the cation 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, In addition, the flow potential C (mV) at the nick and the addition amount V (ml) of the cation colloid titrant were determined, and ΔPCD / V = (I−C) / V was calculated. The results are shown in Table 1.

<Synthesis example>
<Preparation of High-Purity Silicic Acid Solution> An aqueous sodium silicate solution having an SiO ₂ concentration of 24.06% by mass and an Na ₂ O concentration of 7.97% by mass was prepared. Then, pure water was added so that SiO ₂ concentration of 5.0 wt% to the aqueous solution of sodium silicate.

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

[High purity silicic acid solution]
Next, the acidic silicic acid 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 silicic acid solution having a pH of 2.7. The high-purity silicic acid solution obtained had a SiO ₂ concentration of 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 is added to 42 g of pure water while stirring, and then 1,584.6 g of 15% ammonia water is added. Thereafter, the temperature was raised to 83 ° C. and held for 30 minutes.
Next, 13,700 g of high-purity silicic acid solution was added over 18 hours. After completion of the addition, aging was performed while maintaining 83 ° C. to obtain a 25 nm silica fine particle dispersion.
The obtained silica fine particle dispersion was cooled to 40 ° C., and the SiO ₂ concentration was concentrated to 12% by mass with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei).

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

<Preparation of Silica Fine Particle Dispersion (Silica Fine Particle Average Particle Diameter: 70 nm)> Silica Fine Particle Dispersion (SiO ₂ Concentration: 12% by Mass) Dispersed in 705 g of pure water with silica fine particles having an average particle diameter of 45 nm dispersed in a solvent 705 g) was added. Next, 50 g of 15% aqueous ammonia was added, and then the temperature was raised to 87 ° C. and held for 30 minutes.
Next, 7,168 g of high-purity silicic acid solution is added over 18 hours, and after completion of the addition, aging is performed while maintaining 87 ° C. to obtain a silica fine particle dispersion in which silica fine particles having an average particle diameter of 70 nm are dispersed in a solvent. It was.
The obtained silica fine particle dispersion was cooled to 40 ° C., and the SiO ₂ concentration was concentrated to 12% by mass with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei).

Preparation of << silica fine particle dispersion (silica fine particle average particle diameter: 96 nm) >> Dispersion formed by dispersing silica fine particles having an average particle diameter of 70 nm in a solvent while stirring in 1,081 g of pure water (SiO ₂ concentration: 12 mass) %) Was added. Next, 50 g of 15% aqueous ammonia was added, and then the temperature was raised to 87 ° C. and held for 30 minutes.
Next, 6,143 g of high-purity silicic acid solution was added over 18 hours. After completion of the addition, aging was carried out while maintaining 87 ° C., and the dynamic light scattering method (dynamic light scattering particle size measuring device: PAR-III) was used. A silica fine particle dispersion obtained by dispersing silica fine particles having a measured average particle diameter of 96 nm in a solvent was obtained.
The obtained silica fine particle dispersion was cooled to 40 ° C., and the SiO ₂ concentration was concentrated to 12% by mass with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei). Anion exchange resin SANUP B manufactured by Mitsubishi Chemical Corporation was added to the silica fine particle dispersion after concentration to remove anions.
Ultrapure water was added to the resulting silica fine particle dispersion to obtain 6,000 g of Liquid A having a SiO ₂ solid content concentration of 3% by mass. (Hereinafter, in the production process of the silica-based composite fine particle dispersion, the silica fine particle dispersion into which the B liquid described later is introduced is referred to as “liquid A”.)

Next, ion-exchanged water was added to cerium (III) nitrate hexahydrate (manufactured by Kanto Chemical Co., Inc., 4N high-purity reagent) to obtain 2.5 mass% B liquid in terms of CeO ₂ . (Hereinafter, the cerium metal salt dispersion is referred to as “Liquid B”.)

Next, the liquid A (6,000 g) was heated to 50 ° C. and stirred, while the liquid B (8,453 g, 100 parts by mass of SiO _{2) was} equivalent to 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% ammonia water was added as necessary to maintain pH 7.85.
And when addition of B liquid was complete | finished, the liquid temperature was raised to 93 degreeC and ageing | curing | ripening was performed for 4 hours. After aging, the product was allowed to cool by allowing it to stand indoors, and after cooling to room temperature, washing was performed while supplying ion-exchanged water with an outer membrane. The precursor particle dispersion obtained after the washing was finished had a solid content concentration of 7% by mass, a pH of 9.1 (at 25 ° C.), and an electric conductivity of 67 μs / cm (at 25 ° C.). .

  Next, 5% by mass acetic acid was added to the obtained precursor particle dispersion to adjust the pH to 6.5, followed by drying in a 120 ° C. dryer for 16 hours, and then using a 1090 ° C. muffle furnace. Firing was performed for 2 hours to obtain a powder (fired body).

  After adding 375 g of ion-exchanged water to 125 g of the obtained powder and further adjusting the pH to 9 using a 3% aqueous ammonia solution, it was wetted with high-purity silica beads of φ0.22 mm (manufactured by Daiken Chemical Co., Ltd.). Crushing and pulverization were carried out to obtain 540 g of a fired product pulverized dispersion having a solid content concentration of 20% by mass.

<Example 1>
The pulverized dispersion with a solid content of 20% by mass obtained in the above synthesis example was centrifuged at 2000 rpm (620 G) for 3 minutes in a centrifugal separator CR21G (rotor type R21A) manufactured by HITACHI, The supernatant and sediment were separated and the supernatant was recovered.
Next, the collected supernatant was centrifuged at 2500 rpm (980 G) for 3 minutes to separate the supernatant and the sediment, and the supernatant was collected.
Subsequently, the collected supernatant was centrifuged at 2800 rpm (1250 G) for 5 minutes to separate the supernatant and the sediment, and the sediment was collected.
When the average particle diameter of the silica-based composite fine particles contained in the resulting silica-based composite fine particle dispersion was measured, it was 280 nm, ΔPCD / V was −51, and the initial flow potential was −550 mV.
Moreover, the ratio of 1-4 balls was measured by the image analysis method of an electron microscope observation photograph. Further, the above-described two kinds of polishing tests were performed, and the polishing rate and the number of scratches were measured.
The results are shown in Table 1.
A transmission electron micrograph (magnification 100,000 times) of the silica-based composite fine particle dispersion obtained in Example 1 is shown in FIG.

<Example 2>
The pulverized dispersion with a solid content of 20% by mass obtained in the above synthesis example was centrifuged at 2000 rpm (620 G) for 3 minutes in a centrifugal separator CR21G (rotor type R21A) manufactured by HITACHI, The supernatant and sediment were separated and the supernatant was recovered.
Next, the collected supernatant was centrifuged at 2500 rpm (980 G) for 3 minutes to separate the supernatant and the sediment, and the supernatant was collected.
Subsequently, the collected supernatant was centrifuged at 2800 rpm (1250 G) for 5 minutes to separate the supernatant and the sediment, and the supernatant was collected.
Subsequently, the collected supernatant was centrifuged at 3200 rpm (1650 G) for 5 minutes to separate the supernatant and the sediment, and the sediment was collected.
The average particle diameter of the silica-based composite fine particles contained in the obtained silica-based composite fine particle dispersion as a sediment was measured by the method described later, and was 245 nm, ΔPCD / V was −55, and the initial flow potential was −563 mV. Met.
Moreover, the ratio of 1-4 balls was measured by the image analysis method of an electron microscope observation photograph. Further, the above-described two kinds of polishing tests were performed, and the polishing rate and the number of scratches were measured.
The results are shown in Table 1.
Moreover, the transmission electron micrograph (magnification 100,000 times) of the silica type composite fine particle dispersion obtained in Example 2 is shown in FIG.

The silica composite fine particles contained in the silica composite fine particle dispersion obtained in Example 1 were subjected to energy dispersive X-ray spectrometry (EDS) to obtain an element distribution diagram (FIG. 3).
The measurement conditions for energy dispersive X-ray spectrometry (EDS) are shown below.
For sample preparation, silica-based composite fine particles were dispersed in pure water, and then placed on a Cu mesh with a carbon support film, and measurement was performed with the following measuring device.
Measuring device: manufactured by JEOL Ltd., UTW type Si (Li) semiconductor detector, beam diameter 0.2 nm

  From the element distribution chart shown in FIG. 3, it was confirmed that Si and O (oxygen) existed outside the Ce element (on the surface side of the particles).

Next, with respect to the silica-based composite fine particles contained in the silica-based composite fine particle dispersion obtained in Example 1, transmission electron microscope (manufactured by JEOL Ltd., JEM-2100F, field emission transmission electron microscope (attached to Cs correction), (Acceleration electron: 120 kV, magnification: 50,000 times) is observed, and it is confirmed that a coating is present outside the child particles (ceria crystal particles), and then an electron beam is selectively applied to the coating. The applied EDS measurement was performed.
The measurement conditions for energy dispersive X-ray spectrometry (EDS) are shown below.
After the silica-based composite fine particles were dispersed in pure water, they were placed on a Cu mesh with a carbon support film and measured with the following measuring device.
Measuring device: manufactured by JEOL Ltd., UTW type Si (Li) semiconductor detector Beam system: 0.2 nm

  A photograph (TEM image) obtained by observation using a transmission electron microscope is shown in FIG. FIG. 3 shows an EDS measurement result in which an electron beam is selectively applied to the silica coating portion outside the child particles (ceria crystal particles) confirmed in FIG. As shown in FIG. 3, a Si intensity peak appeared at 1.739 keV, and a Ce intensity peak appeared at 4.839 keV. The calculated atomic percentage of Si was 23.22 atom%, Ce atomic percentage was 25.64 atomic%, and Si atomic percentage / Ce atomic percentage was calculated as 0.9056.

<Comparative Example 1>
The average particle size of the calcined dispersion with a solid content of 20% by mass (without centrifugation) obtained in the above synthesis example was measured to be 211 nm, ΔPCD / V was −53, and the initial flow potential was -575 mV.
Moreover, the ratio of 1-4 balls was measured by the image analysis method of an electron microscope observation photograph. Further, two types of polishing tests described later were performed, and the polishing rate and the number of scratches were measured.
The results are shown in Table 1.

<Comparative example 2>
The calcined dispersion with a solid content of 20% by mass obtained in the synthesis example was centrifuged at 1100 rpm (200 G) for 40 minutes to separate the supernatant and the sediment.
When the average particle size of the silica-based composite fine particles contained in the collected supernatant (silica-based composite fine particle dispersion) was measured, it was 194 nm, ΔPCD / V was −58, and the initial flow potential was −570 mV. Moreover, the ratio of 1-4 balls was measured by the image analysis method of an electron microscope observation photograph. Further, the above-described two kinds of polishing tests were performed, and the polishing rate and the number of scratches were measured.
The results are shown in Table 1.

<Comparative Example 3>
The calcined dispersion with a solid content of 20% by mass obtained in the above synthesis example was run at 2000 rpm (620 G) for 3 minutes to separate the supernatant and the sediment. When the average particle diameter of the obtained sediment was measured by the method described later, it was 208 nm, ΔPCD / V was −50, and the initial flow potential was −567 mV.
Moreover, the ratio of 1-4 balls was measured by the image analysis method of an electron microscope observation photograph. Further, the above-described two kinds of polishing tests were performed, and the polishing rate and the number of scratches were measured.
The results are shown in Table 1.

  Since the composite fine particle of the present invention does not contain impurities, it can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate.

Claims (11)

Silica-based particles having an average particle size of 50 to 350 nm having the following particles [1] to [3] on the surface of the mother particle mainly composed of amorphous silica and having the child particles mainly composed of crystalline ceria A silica-based composite fine particle dispersion containing composite fine particles.
[1] The silica-based composite fine particles have a mass ratio of silica and 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 weight ratio of the bonded particles in which two or three primary particles are directly or indirectly connected in the silica-based composite fine particles is 60% or more. 2. The silica-based composite fine particle dispersion according to claim 1, 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 contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 5 ppm or less.   Furthermore, the silica type composite particle dispersion liquid of Claim 1 or 2 which has a silica film on the surface of the said child particle | grain.   The silica-based composite fine particle dispersion according to any one of claims 1 to 3, wherein the flow potential before titration when the pH value is in the range of 3 to 8 is a negative potential.   About the silica-based composite fine particles, the ratio of the number of Si atoms to the number of Ce atoms% (the number of Si atoms) determined by EDS measurement in which an electron beam is selectively applied to a portion of the silica film that can be observed using a transmission electron microscope % / Ce atom number%) is 0.9 or more, and the silica-based composite fine particle dispersion according to claim 1. When cationic colloid titration is performed, the ratio (ΔPCD / V) between the amount of change in streaming potential (ΔPCD) represented by the following formula (1) and the addition amount (V) of the cationic colloid titrant in the knick is −110. The silica-based composite fine particle dispersion according to any one of claims 1 to 5, wherein a streaming potential curve of 0.0 to -15.0 is obtained.
ΔPCD / V = (I−C) / V (1)
C: Streaming potential (mV) at the nick
I: Streaming potential (mV) at the starting point of the streaming potential curve
V: Amount of the colloid titration solution added in the nick (ml)   A polishing slurry comprising the silica-based composite fine particle dispersion according to claim 1.   The polishing slurry according to claim 7, which is a polishing slurry for planarizing a semiconductor substrate on which a silica film is formed. The manufacturing method of the silica type composite fine particle dispersion characterized by including the following process 1-process 4.
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 a temperature at 5 to 98 ° C. and a pH within a range of 7.0 to 9.0. The process of adding the precursor particle | grain dispersion liquid which adds regularly or intermittently and contains a precursor particle.
Step 2: The precursor particle dispersion is dried and fired at 400 to 1,200 ° C., and the fired body obtained is subjected to the following treatment (i) or (ii) to obtain a fired body crushed dispersion liquid. Obtaining.
(I) Crushing and pulverizing by a dry method, and adding a solvent to carry out a solvent dispersion treatment.
(Ii) A solvent is added and pulverization and pulverization are performed in a wet manner.
Step 3: A step of obtaining a supernatant by subjecting the calcined dispersion liquid to a centrifugal separation treatment at a relative centrifugal acceleration of 300 G or more and subsequently removing a sediment component.
Step 4: A step of subjecting the supernatant to a centrifugal treatment at a relative centrifugal acceleration of 300 G or more, and subsequently recovering a sediment component to obtain a silica-based composite fine particle dispersion. The method for producing a silica-based composite fine particle dispersion according to claim 9, wherein the content ratio of impurities contained in the silica fine particles is as shown in the following (a) and (b).
(A) The contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, and Zr are each 100 ppm or less.
(B) The contents of U, Th, Cl, NO ₃ , SO ₄ and F are each 5 ppm or less.   11. The silica-based composite fine particles according to claim 9 or 10, wherein (ii) in step 2 is a treatment of crushing and pulverizing in a wet manner in a pH range of 9.0 to 10.6 by adding a solvent. A method for producing a dispersion.