JP6616795B2 - Polishing abrasive dispersion containing silica composite fine particles - Google Patents

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). In particular, the present invention relates to a polishing abrasive dispersion containing silica composite fine particles.

  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 Document 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 present inventors. 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 the cerium oxide does not adhere and falls off 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, the crystallinity of ceria is low. Therefore, it is considered that the actual polishing rate is low. There is also concern about residual particles.

  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 a silica film, a Si wafer or a difficult-to-process material at high speed, and at the same time has high surface accuracy (low scratch, little abrasive grains remaining on the substrate, and improved substrate Ra value. It is an object of the present invention to provide a polishing abrasive dispersion containing silica-based composite fine particles that can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate.

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 (5).
(1) The following [1] which has the child particle which has crystalline ceria as a main component on the surface of the mother particle which has amorphous silica as the main component, and also has the silica coat on the surface of the child particle To [3], a silica-based composite fine particle having an average particle diameter of 50 to 350 nm, and further containing an acidic compound having an acid dissociation constant (pKa) of 1.5 or more.
[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 silica-based composite fine particles have a crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.
(2) The polishing abrasive dispersion according to (1) above, wherein the content of the acidic compound is 0.0002 to 0.1% by mass.
(3) The polishing abrasive dispersion according to (1) or (2) above, wherein the acidic compound is acetic acid.
(4) The polishing abrasive dispersion according to any one of (1) to (3), which is used for planarizing a semiconductor substrate on which a silica film is formed.
(5) The polishing abrasive dispersion according to (4) above, wherein the pH is 3-8.

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, low surface roughness (Ra) of substrate to be polished, etc.) And a polishing abrasive dispersion containing silica-based composite fine particles that can be preferably used for polishing the surface of a semiconductor device such as a semiconductor substrate or a wiring substrate.
The polishing abrasive 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.

1A is an SEM image obtained in Example 1, and FIGS. 1B and 1C are TEM images obtained in Example 1. FIG. 2 is an X-ray diffraction pattern obtained in Example 1. FIG.

The present invention will be described.
The present invention has child particles mainly composed of crystalline ceria on the surface of mother particles mainly composed of amorphous silica, and further has a silica coating on the surface of the child particles [1] ] To [3] a silica-based composite fine particle having an average particle size of 50 to 350 nm having the characteristics of [3], and further containing an acidic compound having an acid dissociation constant (pKa) of 1.5 or more. It is.
[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 silica-based composite fine particles have a crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.
Hereinafter, such a polishing abrasive dispersion is also referred to as “the polishing abrasive dispersion of the present invention”.
The silica-based composite fine particles contained in the polishing abrasive dispersion of the present invention are also referred to as “composite fine particles of the present invention” below.

  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 containing the base particles (silica fine particles) (the polishing abrasive dispersion of the present invention) is dried and then ground using a mortar. For example, a conventionally known X-ray diffractometer (for example, Rigaku Corporation) When an X-ray diffraction pattern is obtained by RINT 1400), a crystalline silica peak 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 preferably 50 ppm or less, more preferably 25 ppm or less, still more preferably 5 ppm or less, and even more preferably 1 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 size of the mother particles is the same as the average particle size of the silica fine particles contained in the silica fine particle dispersion used in Step 1 included in the production method of the present invention described later. Silica-based composite fine particles having an average particle diameter of 30 to 330 nm are preferably used.
When the average particle diameter of the mother particles is within the above range, scratches are reduced when the abrasive dispersion for polishing of the present invention is used as an abrasive. When the average particle diameter of the mother particles is smaller than 30 nm, the polishing rate tends to be insufficient. If the average particle size is larger than 330 nm, the polishing rate tends to decrease. In addition, the surface accuracy of the substrate tends to deteriorate.

The average particle diameter of the mother particles (silica fine particles) in the present invention means a value measured by a dynamic light scattering method or a laser diffraction scattering method. Specifically, it means a value obtained by measurement by the following method. After the silica fine particles are dispersed in water or the like to obtain a silica fine particle dispersion, the silica fine particle dispersion is used as a particle size measuring device by a known dynamic light scattering method (for example, Microtrack UPA device manufactured by Nikkiso Co., Ltd., Measured by 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 particle size distribution. Specifically, PAR-III is used for monodispersed 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 micronometer is obtained by crushing. In the pulverization process in which the particle diameter varies widely from nanometer to nanometer, a known particle diameter measuring apparatus using a dynamic light scattering method or a measuring apparatus using a known laser diffraction scattering method (preferably Microtrac UPA or LA-950) is used. It is preferable.

The shape of the base particle (silica fine particle) is not particularly limited, and for example, spherical, bowl-shaped, tetrahedral (triangular pyramid), hexahedral, octahedral, plate-like, and irregular-shaped projections on the surface It may be a saccharide, a confetti-like one, or a porous one, but a spherical one is preferred. The term “spherical” means that the ratio of the number of particles having a minor axis / major axis ratio of 0.8 or less is 10% or less. The 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, the child particles that are entirely covered by the silica coating may be bonded to the mother particles via 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 means that, for example, the abrasive abrasive dispersion of the present invention is dried and then pulverized using a mortar, for example, a conventionally known X-ray diffractometer (for example, Rigaku Electric Co., Ltd.). It can be confirmed from the fact that only the ceria crystal phase is detected in the X-ray diffraction pattern obtained by RINT 1400 manufactured by the company. 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 such as 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.

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

The crystallite diameter of crystalline ceria is determined from the full width at half maximum of the maximum peak of the X-ray diffraction pattern. For example, the average crystallite diameter of the (111) plane is 10 to 25 nm (full width at half maximum is 0.86 to 0.34 °), and 11 to 23 nm (full width at half maximum is 0.78 to 0.37 °). In particular, it is more preferably 12 to 20 nm (full width at half maximum is 0.79 to 0.43 °). In many cases, the peak intensity of the (111) plane is maximized, but the crystal plane is not limited to the (111) plane (near 2θ = 28 degrees), and other crystal planes such as (100) The peak peak intensity may be maximum. In that case, the calculation can be performed in the same manner, and the average crystallite diameter in that case may be the same as the average crystallite diameter of the (111) plane.
The method for measuring the average crystallite diameter of the child particles will be described below by taking the case of the (111) plane (around 2θ = 28 degrees) as an example.
First, the composite fine particles of the present invention are pulverized using a mortar, and an X-ray diffraction pattern is obtained 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 (here, K = 0.94)
λ: X-ray wavelength (1.7789 Å, 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 determined by measuring the average particle size of any 50 child particles in a photograph projection view (for example, FIG. 1C described later) enlarged 300,000 times using a transmission electron microscope. It means a value obtained by simple average of these.

<Silica coating>
The composite fine particles of the present invention 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, the child particles may be bonded to the surface of the mother particles, and may further have a silica coating covering them. That is, the silica coating may cover a part or the whole of the composite particles formed by bonding the child particles to the surface of the mother particles. Therefore, a silica coating is present on the outermost surface of the composite fine particles of the present invention.

In the image (TEM image) obtained by observing the composite fine particles of the present invention using a transmission electron microscope, the image of the child particles appears dark on the surface of the mother particle, but the outside of the child particles, that is, the composite of the present invention. A silica coating appears as a relatively thin image on the surface side of the fine particles. Further, there may be a mode in which 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 particles are bonded to the mother particles through the silica coating. You may do it.
Further, when the composite fine particles of the present invention are subjected to EDS analysis to obtain an element distribution, a portion with a high Ce concentration appears on the surface side of the particles, but a portion with a high Si concentration appears on the outer side.
Further, when EDS measurement is 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 are 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 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 polishing abrasive dispersion of the present invention, the silica-based composite fine particles obtained by baking are subjected to wet crushing to obtain a silica-based composite fine particle dispersion. The coating is considered to have an effect of preventing the child particles (ceria crystal particles) from being detached 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 process.
With such a structure, it is considered that when the abrasive grain dispersion liquid of the present invention is used as an abrasive, the polishing rate is high, and the surface accuracy and scratches are hardly 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.
Further, in the composite fine particles of the present invention, at least a part of the surface of the child particles is covered with a silica layer, so that the OH group of silica is present on the outermost surface (outermost shell) of the composite fine particles of the present invention. Become. For this reason, when used as an abrasive, the composite fine particles of the present invention are repelled by charges due to —OH groups on the surface of the polishing substrate, and as a result, adhesion to the surface of the polishing substrate is considered to be reduced.
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, even if the ceria particles of the child particles fall off during polishing, the surface is covered with silica and thus has a negative charge. In addition, there is 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 base material and the polishing pad due to the difference in the magnitude of the electric potential and the difference in polarity, and tends to remain on the polishing base material and the polishing pad. On the other hand, in the silica-based composite fine particles of the present invention, since ceria as a child particle is at least partially covered with a silica coating, the pH is maintained at a negative potential from alkaline to acidic. It is difficult for abrasive grains to remain on the pad.

  The thickness of the silica coating is generally determined from the TEM image or SEM image in terms of how the ceria child particles on the mother particles are covered with the silica coating. 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.

  As described above, the silica coating of the outermost layer (opposite to the mother particle side) may not completely cover the entire child particles (ceria fine particles). That is, the silica film is present on the outermost surface of the composite fine particles of the present invention, but there may be a portion where the silica film is not present. 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 abrasive dispersion) containing the abrasive abrasive 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. is there. 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 surface roughness of the substrate increases (deterioration of the surface roughness Ra), scratches increase, and free ceria remains on the substrate, causing problems 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 all of the following (I) to (III).
(I) Silica component constituting the mother particle (II) Composite fine particles obtained by bonding child particles (ceria component) to the mother particles are fixed in the silica component (III) ceria particles contained in the covering silica coating. Dissolved silica component

The content (mass%) of silica (SiO ₂ ) and ceria (CeO ₂ ) in the composite fine particles of the present invention is determined based on the solid content concentration of the composite fine particle dispersion of the present invention (the polishing abrasive dispersion of the present invention). Is obtained by weighing after 1000 ° C. ignition loss.
Next, the content (mass%) of cerium (Ce) contained in a predetermined amount of the composite fine particles of the present invention is obtained 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 preparing the polishing abrasive dispersion of the present invention. it can. This can be applied when ceria and silica are not dissolved and removed, and in such a case, the amount of ceria and silica used agrees well with the analytical value.

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

The particle size distribution of the composite fine particles of the present invention may be “particle-linked type” or “monodispersed type”, but the contact area with the substrate can be kept high, and the polishing rate is fast, A particle-linked type is desirable. The particle connection type is one in which two or more composite fine particles are partially bonded to each other, and the connection is preferably 3 or less. It is considered that at least one (preferably both) of the mother particles are firmly bonded by being welded at their contact points or having a history of solidification due to the presence of ceria. Here, in addition to the case where the cerium-containing silica layer is formed on the surface after the mother particles are bonded to each other, the case where the cerium-containing silica layer is formed on the surface of the mother particle and then bonded to the other particles. However, it is a particle-linked type.
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 number ratio of particles having a minor axis / major axis ratio measured by an image analysis method of 0.80 or less (preferably 0.67 or less) is preferably 45% or more.
Here, particles having a minor axis / major axis ratio measured by an image analysis method of 0.80 or less are considered to be of a particle-binding type in principle.
The shape of the composite fine particles of the present invention is not particularly limited, and may be particle-linked particles or single particles (non-connected particles), and is usually a mixture of both.
Here, when the composite fine particle dispersion containing the composite fine particles is used for polishing and when importance is attached to the improvement of the polishing rate for the substrate to be polished, the minor diameter measured by the image analysis method of the composite fine particles / The ratio of the number of particles having a major axis ratio of less than 0.80 (preferably 0.67 or less) is preferably 45% or more (more preferably 51% or more).
Similarly, when importance is attached to the low level of surface roughness on the substrate to be polished, the minor axis / major axis ratio measured by the image analysis method of the composite fine particles is 0.80 or more (preferably 0.9). The number ratio of the particles is preferably 40% or more, and more preferably 51% or more.
In addition, the said particle | grain connection type | mold particle | grain means the particle | grains (condensation particle | grains) formed by the chemical bond of the grade which cannot be re-dispersed between particle | grains produced. The single particle means a particle that is not a plurality of particles connected but not agglomerated regardless of the particle morphology.
As the composite fine particle dispersion of the present invention when importance is attached to the polishing rate improvement for the substrate to be polished, the following embodiment 1 can be mentioned.
[Aspect 1] The composite fine particles of the present invention are characterized in that the number ratio of particles having a minor axis / major axis ratio of less than 0.8 measured by an image analysis method is 45% or more. Dispersion.
In addition, as a composite fine particle dispersion of the present invention when importance is attached to the low level of surface roughness on the substrate to be polished, the following aspect 2 can be exemplified.
[Aspect 2] The composite fine particle of the present invention is further characterized in that the number ratio of particles having a minor axis / major axis ratio of 0.8 or more measured by an image analysis method is 40% or more. Dispersion.

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

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

The composite fine particles of the present invention preferably have a specific surface area of 4 to 100 m ² / g, and more preferably ^{20 to} 70 m ² / g.

Here, a method for measuring the specific surface area (BET specific surface area) will be described.
First, a dried sample (0.2 g) is put in a measurement cell, degassed in a nitrogen gas stream at 250 ° C. for 40 minutes, and then the sample is mixed with 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 by 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 measurement 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, the polishing rate becomes high when applied as an abrasive, which is preferable.
The average particle diameter of the composite fine particles of the present invention means a value measured by a dynamic light scattering method or a laser diffraction scattering method. Specifically, it means a value obtained by measurement by the following method. The composite fine particles of the present invention are dispersed in water, and this composite fine particle dispersion is 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 preferably 50 ppm or less, more preferably 25 ppm or less, still more preferably 5 ppm or less, and even more preferably 1 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).

<Polishing abrasive dispersion of the present invention>
The polishing abrasive dispersion of the present invention will be described.
The polishing abrasive dispersion 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 polishing abrasive 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 abrasive dispersion for polishing of the present invention includes at least one selected from the group consisting of a polishing accelerator, a surfactant, a pH adjuster and a pH buffer as an additive for controlling polishing performance. By doing so, it is suitably used as a polishing slurry.

The polishing abrasive dispersion of the present invention contains the composite fine particles of the present invention, and further contains an acidic compound having an acid dissociation constant (pKa) of 1.5 or more. Here, in the polishing abrasive dispersion of the present invention, the content of the acidic compound is preferably 0.0002 to 0.1% by mass. The polishing abrasive dispersion of the present invention may contain components other than the composite fine particles of the present invention as long as it contains an acidic compound having an acid dissociation constant (pKa) of 1.5 or more. Examples of such an additive include various additives such as ionic strength adjusting additives, polishing accelerators, surfactants, hydrophilic compounds, heterocyclic compounds, pH adjusting agents, and pH buffering agents described later. .
When the polishing abrasive dispersion contains an acidic compound having an acid dissociation constant (pKa) of 1.5 or more, the polishing rate is improved.
Examples of the acidic compound having an acid dissociation constant (pKa) of 1.5 or more include acetic acid, lactic acid, formic acid, malic acid, benzoic acid, citric acid, tartaric acid, phosphoric acid, and carbonic acid.
Conversely, examples of acidic compounds having an acid dissociation constant (pKa) of less than 1.5 include nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, hydrobromic acid, and trichloroacetic acid.
In addition, in this invention, an acid dissociation constant shall mean the acid dissociation constant in case a solvent is water and 25 degreeC.

The polishing abrasive dispersion for use in the present invention can be suitably used as an abrasive dispersion for polishing a semiconductor substrate on which a SiO ₂ insulating film is formed. Here, when the semiconductor substrate on which the silica film is formed is planarized using the polishing abrasive dispersion of the present invention, the polishing abrasive dispersion of the present invention preferably has a pH of 3-8.
The polishing abrasive dispersion of the present invention has a high polishing rate when polishing a semiconductor substrate, etc., and has excellent effects such as few scratches (scratches) on the polishing surface and little residual abrasive on the substrate during polishing. ing.

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

The polishing abrasive dispersion of the present invention, when cation colloid titration is performed, the change in flow potential (ΔPCD) represented by the following formula (1) and the addition amount (V) of the cation colloid titration liquid in the knick. It is preferable that a streaming potential curve having a ratio (ΔPCD / V) to -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 abrasive grain 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. Other measurement conditions are performed by a method suitable for the literature and the standard method recommended by the manufacturer.

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 as the X axis and the flow potential (mV) of the abrasive dispersion of the present invention is taken as 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. Specifically, it is an inflection point of the streaming potential curve, and this point (inflection point) is a nick. The flow potential at this point (inflection point) is C (mV), and the addition amount of the cation colloid titrant at this point (inflection point) is V (ml).
The starting point of the streaming potential curve is the streaming potential in the polishing abrasive dispersion of the present invention before titration. Specifically, the starting point is the point where the addition amount of the cationic colloid titrant in the flow potential curve is zero. The streaming potential at this point is I (mV).

  When the ΔPCD / V value is −110.0 to −15.0, the polishing rate of the abrasive is further improved when the abrasive dispersion for polishing of the present invention is used as an abrasive. This ΔPCD / V is considered to reflect the degree of coating of the silica coating on the surface of the composite fine particles of the present invention and / or the degree of exposure of the child particles on the surface of the composite fine particles or the presence of silica that is easily detached. 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 pulverization by wet and the polishing rate is high. On the contrary, when the absolute value of ΔPCD / V is larger than −110.0, the composite fine particle surface is entirely covered with the silica coating, so that the child particles are not easily dropped in the crushing process, but the silica during polishing 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.

  In the polishing abrasive dispersion of the present invention, when the pH value is in the range of 3 to 8, the flow potential before starting the cationic colloid titration, that is, when the titer is zero, becomes a negative potential. It is preferable. 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.

<Polishing accelerator>
In the polishing abrasive dispersion of 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 abrasive dispersion of the present invention contains a polishing accelerator, its content is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass. .

<Surfactant and / or hydrophilic compound>
In order to improve the dispersibility and stability of the polishing abrasive dispersion of the present invention, a cationic, anionic, nonionic or amphoteric surfactant or 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 abrasive dispersion of the present invention contains a surfactant and / or a hydrophilic compound, the content is 0.001 to 10 g in 1 L of the polishing abrasive dispersion as a total amount. Is preferable, 0.01 to 5 g is more preferable, and 0.1 to 3 g is particularly preferable.

  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 liter of the abrasive dispersion for polishing, and is preferably 10 g or less from the viewpoint of preventing reduction in the polishing rate. .

  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>
In the case where a metal is contained in the substrate to be polished to which the polishing abrasive dispersion of the present invention is applied, in order to suppress erosion of the substrate to be polished by forming a passive layer or a dissolution inhibiting layer on the metal, A heterocyclic compound may be contained in the polishing abrasive dispersion of the invention. 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 and the like can be mentioned, but are not limited thereto.

  About content in the case of mix | blending a heterocyclic compound with the abrasive grain dispersion liquid of this invention, it is preferable that it is 0.001-1.0 mass%, and it is 0.001-0.7 mass%. Is more preferable, and it is further more preferable that it is 0.002-0.4 mass%.

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

  When the polishing abrasive dispersion of the present invention is adjusted 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 adjusting the polishing abrasive dispersion of the present invention to less than pH 7, an acidic one is used as a pH adjuster. Acids having an acid dissociation constant of 1.5 or more, such as lactic acid, formic acid, malic acid, benzoic acid, citric acid, tartaric acid, and phosphoric acid carbonate, are used.

<PH buffering agent>
In order to keep the pH value of the polishing abrasive dispersion of the present invention constant, a pH buffering agent 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.

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

<Production method of the present invention>
Although the manufacturing method of the abrasive grain dispersion liquid of this invention is not specifically limited, It is preferable to manufacture with the manufacturing method of this invention demonstrated below.
The production method of the present invention is a method for producing a polishing abrasive dispersion, comprising the following steps 1 to 3.
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 of 5 to 98 ° C. and a pH of 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 is performed by a dry method, and a solvent is added to carry out a solvent dispersion treatment.
(Ii) A solvent is added and pulverized in a wet manner in the range of pH 8.6 to 10.8.
Step 3: The fired body disintegrated dispersion is subjected to a centrifugal separation process at a relative centrifugal acceleration of 300 G or more, subsequently, a sediment component is removed, and an acidic compound having an acid dissociation constant (pKa) of 1.5 or more is added. To obtain a polishing abrasive dispersion.
By the production method of the present invention, the polishing abrasive dispersion of the present invention can be produced.

The production method of the present invention will be described.
The manufacturing method of the present invention includes steps 1 to 3 described below.

<Production method of the present invention>
<Step 1>
In step 1, a silica fine particle dispersion in which silica fine particles are dispersed in a solvent is prepared.
When preparing a silica-based composite fine particle dispersion (polishing abrasive dispersion for polishing) to be applied to polishing of semiconductor devices or the like by the production method of the present invention, the silica fine particle dispersion is produced by hydrolysis of alkoxysilane. It is preferable to use a silica fine particle dispersion in which the silica fine particles are dispersed in a solvent. 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.

The temperature at the time of stirring after adding the metal salt of cerium to the silica fine particle dispersion is preferably 5 to 98 ° C, more preferably 10 to 95 ° C. 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 can be suppressed. Furthermore, scale and the like are easily generated 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. . 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 cerium metal salt is added continuously or intermittently while maintaining the temperature range of the silica fine particle dispersion at 5 to 52 ° C. and the pH range of 7.0 to 9.0. Then, a precursor particle dispersion is prepared, and the precursor particle dispersion is aged at a temperature of 5 to 52 ° C. When Step 1 is performed under such conditions, the metal salt of cerium or cerium hydroxide reacts with silica in a liquid phase to produce a cerium silicate compound, which inhibits ceria crystal growth. At the same time, ceria microcrystals are generated, and cerium silicate compound and ceria microcrystals are formed on the mother particles.

<Step 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. This is because when the pH of the precursor particle dispersion before drying is 6.0 to 7.0, it is possible to suppress the formation of strong aggregates.
The temperature for firing after drying is 400 to 1200 ° C, preferably 800 to 1100 ° C, and more preferably 1000 to 1090 ° C. When firing in such a temperature range, cerium diffuses from the cerium silicate compound on the mother particle and crystallization of ceria proceeds sufficiently, and as a result, the ceria particles are coated with a silica layer. In addition, 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 is performed by a dry method, and a solvent is added to carry out a solvent dispersion treatment.
(Ii) A solvent is added, and pulverization is performed in a wet manner in the range of pH 8.6 to 10.8 (preferably 9.0 to 10.6).
Conventionally known devices can be used as the dry crushing device, and examples thereof include an attritor, a ball mill, a vibration mill, and a vibration ball mill.
Conventionally known devices can be used as wet crushing devices. For example, batch-type bead mills such as basket mills, horizontal, vertical and annular continuous bead mills, sand grinder mills, ball mills, etc. -Stator type homogenizers, ultrasonic dispersion type homogenizers, and wet medium stirring mills (wet crushers) such as an impact crusher that collides fine particles in a dispersion. Examples of the beads used in the wet medium agitation 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 preferred. Of the treatments (i) or (ii), the wet treatment of (ii) is more preferably used in practice.

In addition, when performing the crushing by wet of said (ii), crushing by wet may be performed, maintaining the pH of a solvent at 8.6-10.8 (preferably 9.0-10.6). preferable. 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 The polishing abrasive dispersion of the present invention that can provide a streaming potential curve with a ratio (ΔPCD / V) of -110.0 to -15.0 can be finally obtained more easily.
That is, it is preferable to perform crushing to such an extent that the abrasive grain dispersion liquid of the present invention corresponding to the above-mentioned preferred embodiment is obtained. As described above, this is because the polishing rate is further improved when the abrasive dispersion for polishing of the present invention corresponding to a preferred embodiment is used as an abrasive. 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 appropriately exposed on 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, followed by removal of sediment components, and an acid dissociation constant (pKa) of 1.5. The above acidic compound is added to obtain a polishing abrasive dispersion.
Specifically, coarse particles such as agglomerates and abnormally grown particles are removed from the fired body pulverized dispersion by centrifugation. The relative centrifugal acceleration in the centrifugation process is set to 300 G or more. After the centrifugal separation treatment, the precipitated components are removed, and a specific acidic compound is further added to obtain a silica-based composite fine particle dispersion (polishing abrasive dispersion). The upper limit of the relative centrifugal acceleration is not particularly limited, but is practically used at 10,000 G or less.
Here, the relative centrifugal acceleration is expressed as a ratio of the earth's gravitational acceleration as 1G.

In step 3, it is necessary to provide a centrifugal separation process that satisfies the above conditions. When the centrifugal acceleration does not satisfy the above conditions, coarse particles remain in the polishing abrasive dispersion, so when used for polishing applications such as abrasives using the abrasive dispersion, Cause it to occur.
In the present invention, the polishing abrasive dispersion obtained by the above production method can be further dried to obtain silica-based composite fine particles. The drying method is not particularly limited, and for example, it can be dried using a conventionally known dryer.

By such a production method of the present invention, the abrasive grain dispersion liquid of the present invention can be obtained.
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 does not deposit 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.

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

<Experiment 1>
First, details of each measurement method and test method in Examples and Comparative Examples will be described. 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 the silica 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 by 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, the 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 the potentiometric titration method (manufactured by 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 (Hitachi HIMAC CT06E). 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.
In the present example and the comparative example, the peak of the (111) plane near 2θ = 28 degrees (2θ = 28 degrees) in the obtained X-ray diffraction pattern has the maximum intensity. The crystallite diameter was determined by the Scherrer equation.

<Average particle size>
With respect to the silica fine particle dispersions and silica-based composite fine particle dispersions obtained in Examples and Comparative Examples, the average particle 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>
An abrasive dispersion (polishing abrasive dispersion for polishing) containing the silica-based composite fine particle dispersion obtained in each of Examples and Comparative Examples was prepared. Here, the solid content concentration of the polishing abrasive dispersion was 0.6% by mass, and an acid having a different acid dissociation constant 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, with a substrate load of 0.5 MPa, a table Polishing was performed by supplying a polishing abrasive dispersion 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.

<Example 1>
"Silica fine particle dispersion (average particle diameter 60nm of the silica fine particles)" were mixed and prepared ethanol 12,090g and ethyl orthosilicate 6,363.9g of was a mixture a _1.
Next, 6,120 g of ultrapure water and 444.9 g of 29% ammonia water were mixed to obtain a mixed solution b ₁ .
Next, 192.9 g of ultrapure water and 444.9 g of ethanol were mixed and used as bedding water.
Then, the stirring water was adjusted to 75 ° C. while stirring, and the mixed solution a ₁ and the mixed solution b ₁ were simultaneously added so that the addition was completed in 10 hours each. After the addition was completed, the liquid temperature was kept at 75 ° C. for 3 hours for aging, the solid content concentration was adjusted, the SiO ₂ solid content concentration was 19% by mass, the dynamic light scattering method (PAR-Otsuka Electronics PAR- 9,646.3 g of a silica fine particle dispersion obtained by dispersing silica fine particles having an average particle diameter of 60 nm measured in III) in a solvent was obtained.

"Silica fine particle dispersion (average particle diameter of the silica fine particles: 108 nm)" were mixed and prepared methanol 2,733.3g and ethyl orthosilicate 1,822.2g of was a mixture a _2.
Next, 1,860.7 g of ultrapure water and 40.6 g of 29% ammonia water were mixed to obtain a mixed solution b ₂ .
Next, 922.1 g of a silica fine particle dispersion in which silica fine particles having an average particle diameter of 60 nm obtained in the previous step are dispersed in a solvent is prepared by mixing 59 g of ultrapure water and 1,208.9 g of methanol. added.
Then, the stirring water containing the silica fine particle dispersion is adjusted to 65 ° C. while stirring, and the mixed solution a ₂ and the mixed solution b ₂ are added simultaneously so that the addition is completed in 18 hours each. It was. When the addition is completed, the liquid temperature is kept at 65 ° C. for 3 hours and ripened, and then the solid content (SiO ₂ solid content) is concentrated to 19% by mass, and 3,600 g of high-purity silica fine particle dispersion Got.
The particles contained in the high-purity silica fine particle dispersion had an average particle diameter of 108 nm as measured by a dynamic light scattering method (PAR-III manufactured by Otsuka Electronics Co., Ltd.). Also, the contents of Na, Ag, Al, Ca, Cr, Cu, Fe, K, Mg, Ni, Ti, Zn, Zr, U, Th, Cl, NO ₃ , SO ₄ and F are all 1 ppm or less. there were.

Next, 114 g of a cation exchange resin (SK-1BH manufactured by Mitsubishi Chemical Corporation) was gradually added to 1,053 g of this high-purity silica fine particle dispersion, and the resin was separated by stirring for 30 minutes. The pH at this time was 5.1.
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.

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 .

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% aqueous ammonia was added as necessary to maintain pH 7.85. During addition of B liquid and aging, preparation was performed while air was blown into the preparation liquid, and the oxidation-reduction potential maintained a positive value.
And when addition of B liquid was completed, 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 mass% acetic acid aqueous solution was added to the obtained precursor particle dispersion to adjust the pH to 6.5, followed by drying in a dryer at 100 ° C. for 16 hours, and then using a muffle furnace at 1090 ° C. And baked for 2 hours to obtain a powder.

Put 310 g of powder obtained after firing and 430 g of ion-exchanged water in a 1 L beaker with a handle, add 3% aqueous ammonia solution thereto, and irradiate ultrasonic waves in an ultrasonic bath for 10 minutes while stirring. A suspension with a pH of 10 (temperature is 25 ° C.) was obtained.
Next, 595 g of quartz beads having a diameter of 0.25 mm are put into a pulverizer (manufactured by Ashizawa Finetech Co., Ltd., LMZ06) that has been subjected to equipment cleaning and water operation in advance, and the above suspension is further charged into the charge tank of the pulverizer. Filled (filling rate 85%). In consideration of ion-exchanged water remaining in the pulverization chamber and piping of the pulverizer, the concentration during pulverization is 25% by mass. Then, wet crushing was performed under the conditions that the peripheral speed of the disk in the pulverizer was 12 m / sec, the number of passes was 25, and the residence time per pass was 0.43 minutes. Further, a 3% aqueous ammonia solution was added for each pass so that the pH of the suspension during crushing was maintained at 10. In this way, a silica-based composite fine particle dispersion having a solid concentration of 22% by mass was obtained.
Next, the obtained fine particle dispersion is centrifuged with a centrifugal separator (manufactured by Hitachi Koki Co., Ltd., model number “CR21G”) at a relative centrifugal acceleration of 675 G for 1 minute to remove sediment components, and silica-based composite fine particles are dispersed. A liquid was obtained.

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

Next, a polishing test was performed using a silica-based composite fine particle dispersion as a polishing abrasive dispersion. In Example 1, polishing was performed using acetic acid having a pKa of 4.7 and adjusting the pH of the polishing abrasive dispersion to 5.0.
Properties of silica fine particles (mother particles) and impurity content, silica content and ceria content in silica-based composite fine particles contained in silica-based composite fine particles (and ceria mass parts relative to 100 parts by mass of silica), silica-based Firing temperature at the time of preparing the composite fine particles, crystallite diameter, crystal type, average particle diameter of the child composite particles, specific surface area of the silica composite fine particles, content of impurities contained in the silica composite fine particles, silica composite Table 1 shows the measurement results of the average particle diameter and the polishing performance (polishing rate) of the fine particles. The same applies to the following examples and comparative examples.
In addition, the acetic acid addition amount used for pH adjustment was 0.0036 mass% with respect to the abrasive grain dispersion liquid.

Further, the silica-based composite fine particles contained in the silica-based composite fine particle dispersion obtained in Example 1 were observed using SEM and TEM. An SEM image and a TEM image (100,000 times) are shown in FIGS.
Further, FIG. 1C shows a transmission electron microscope image (300,000 times) obtained by measuring the particle diameter of the child particles.

  Furthermore, the X-ray diffraction pattern of the silica-based composite fine particles contained in the silica-based composite fine particle dispersion obtained in Example 1 is shown in FIG.

In the X-ray diffraction pattern of FIG. 2, it is a very sharp Ceriaite crystal, and it appears that ceria crystal particles are strongly sintered with the silica surface from TEM and SEM images.
Further, from FIG. 1, it was observed that a thin silica coating was present on the outermost surface of the silica-based composite fine particles.

<Comparative Example 1>
In Example 1, the pH of the polishing abrasive dispersion was adjusted to 5.0 using acetic acid, but in Comparative Example 1, the pH of the polishing abrasive dispersion was adjusted using nitric acid having a pKa of −1.8. Adjusted to 5.0. Otherwise, the same processing as in Example 1 was performed, and the same measurement was performed.
The results are shown in Table 1.

<Comparative Example 2>
In Example 1, the pH of the polishing abrasive dispersion was adjusted to 5.0 using acetic acid, but in Comparative Example 2, the pH of the polishing abrasive dispersion was adjusted using hydrochloric acid having a pKa of −3.7. Adjusted to 5.0. Otherwise, the same processing as in Example 1 was performed, and the same measurement was performed.
The results are shown in Table 1.

<Comparative Example 3>
In Example 1, the pH of the polishing abrasive grain dispersion was adjusted to 5.0 using acetic acid. In Comparative Example 3, the pH of the polishing abrasive grain dispersion was adjusted using sulfuric acid having a pKa of −3.0. Adjusted to 5.0. Otherwise, the same processing as in Example 1 was performed, and the same measurement was performed.
The results are shown in Table 1.

  From Table 1, it was found that the polishing rate was high when the thermal oxide film was polished with the polishing abrasive dispersion of Example 1 whose pH was adjusted with an acid having a pKa of 1.5 or more. It was also found that the polishing rate was not fast when the thermal oxide film was polished with the polishing abrasive dispersions of Comparative Examples 1 to 3 whose pH was adjusted with an acid having a pKa of less than 1.5.

  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 (4)

[3] The following [1] to [3] have child particles mainly containing crystalline ceria on the surface of mother particles mainly containing amorphous silica, and further have a silica coating on the surface of the child particles. comprises silica-based composite fine particles having an average particle size of 50~350nm comprising the features of, seen including a further acid dissociation constant (pKa) of 1.5 or more acidic compounds, wherein the acidic compound is acetic acid, formic acid, benzoic acid, phosphorus A polishing abrasive dispersion, which is at least one selected from the group consisting of an acid and carbonic acid .
[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 silica-based composite fine particles have a crystallite diameter of the crystalline ceria of 10 to 25 nm measured by X-ray diffraction.   The polishing abrasive dispersion according to claim 1, wherein the content of the acidic compound is 0.0002 to 0.1 mass%. The polishing abrasive dispersion according to claim 1 or 2 , which is used for planarizing a semiconductor substrate on which a silica film is formed. pH is 3 to 8, abrasive grains dispersion of claim 3.