JP7436268B2 - Silica-based particle dispersion and its manufacturing method - Google Patents

Description

The present invention relates to a silica-based particle dispersion and the like. Specifically, it includes silica-based particles having a particle size, particle size distribution, degree of irregularity, etc. that are preferable as an abrasive, and is particularly used for chemical-mechanical polishing of NiP-plated substrates and silica-based substrates in the manufacture of magnetic disks. The present invention relates to a silica-based particle dispersion suitable as a polishing abrasive dispersion for planarization by chemical mechanical polishing (CMP).

In manufacturing processes for magnetic disks, semiconductors, etc., chemical mechanical polishing (CMP) is applied to flatten substrates such as Si wafers, glass HDs, and aluminum HDs. This chemical-mechanical polishing uses a so-called polishing slurry in which abrasive grains such as silica or ceria are dispersed in water, and chemical components are added to control the polishing performance. In particular, abrasive grains are known to have a large effect on polishing performance, and the performance required of abrasive grains is to be able to obtain a high polishing rate and to avoid defects such as scratches (streaks) on the polished surface. One example is that no defects (defects) occur.

A common method for obtaining a high polishing rate is to use abrasive grains with large particle diameters. However, if the particle diameter of the abrasive grains becomes too large, the number of abrasive grains per mass decreases, and the polishing rate tends to decrease, and the number of scratches also tends to increase. Therefore, in order to obtain a high polishing rate without increasing scratches, it is known that it is effective to make the abrasive grains non-spherical, that is, to make the abrasive grains irregularly shaped particles (deformed particles).

Methods for preparing silica particle groups containing irregularly shaped silica particles having a particle size suitable for abrasives include a method in which silica particles are agglomerated during nucleation using water glass as a raw material, and irregularly shaped seed particles prepared by this method. A method (Patent Document 1) in which a silicic acid solution is added to grow the particle size to a large size is conventionally known.

Patent No. 5127452

Regarding irregularly shaped particles, the degree of irregularity (ratio of weight average particle diameter to projected area equivalent particle diameter) also greatly affects polishing performance. Specifically, particles with a large degree of irregularity tend to have a high polishing rate. On the other hand, particles with a small degree of irregularity are particles that are close to true spheres or ellipses, and therefore the polishing rate tends to be low. However, since irregularly shaped particles are non-spherical in shape, they are usually more prone to scratches than spherical or approximately spherical particles (non- irregularly shaped particles), especially when the degree of irregularity is high. The trend becomes noticeable.

In addition, it is generally known that the particle size and particle size distribution of abrasive grains greatly affect polishing performance, and abrasive grains with large particle diameters have a high polishing speed, but the surface accuracy of the polished substrate (surface roughness, waviness, scratches, etc.) tend to worsen. On the other hand, abrasive grains with a small particle size can finish the substrate surface smoothly and are less likely to cause scratches, but the polishing rate becomes slower. This applies not only to spherical particles but also to irregularly shaped particles.
Although irregularly shaped particles have a wide variety of particle size distributions, particles with relatively large particle sizes usually have a high polishing rate, so if a high polishing rate is required, the average particle size should be as large as possible. Irregularly shaped particles are used. However, in the case of irregularly shaped particles with a relatively large average particle size, the tail of the particle size distribution tends to widen greatly toward the large particle size side, so they often contain a small amount of particles that are coarse compared to the average particle size. Such coarse particles tend to cause scratches on the polished substrate and worsen the surface roughness and waviness of the substrate. Therefore, as abrasive grains used for polishing that requires high polishing speeds, we use irregularly shaped abrasive grains that have a relatively large average particle diameter and very few coarse grains or excessively large grains (these are collectively called "coarse grains"). Particles are desired.

Furthermore, particles with relatively small particle diameters, regardless of whether they are spherical particles or irregularly shaped particles, tend to have a low polishing rate because the amount of polishing per abrasive grain is small. Furthermore, if the particle size is relatively small, the abrasive grains tend to remain on the substrate after polishing (this is called "remaining abrasive grains"). This abrasive grain residue tends to be difficult to remove even in a cleaning process after polishing. This tendency is also seen in irregularly shaped particles with a relatively large average particle diameter, and even for irregularly shaped particles with a relatively large average particle diameter, the tail of the particle size distribution seems to have broadened toward the smaller particle diameter side. It can be said that irregularly shaped particles with such a distribution are more likely to leave abrasive grain residue.
Therefore, in order to achieve suitable chemical-mechanical polishing that achieves both high polishing speed and high surface precision, it is necessary to use abrasive grains that contain relatively large irregularly shaped particles, and the number of abrasive grains per mass is large, reducing polishing performance. It is desirable to have abrasive grains that contain as little coarse particles as possible that cause the abrasive particles to deteriorate, and also contain as little as possible relatively small particles that cause abrasive grain residue.

However, with the method of agglomerating silica particles during nucleation using water glass as a raw material, it has been difficult to obtain irregularly shaped silica particles having a specific surface area equivalent particle diameter of 100 nm or more. Furthermore, in this method, during the silica particle aggregation process during nucleation, some of the core particles may cause a runaway reaction, resulting in the formation of coarse aggregates, which may cause scratches. There was a problem. In addition, in the method of using irregularly shaped silica particles with a specific surface area equivalent particle diameter of 100 nm or less as seed particles and growing the particle size by adding a silicic acid solution to the seed particles, the specific surface area equivalent particle diameter When particles are grown using a silicic acid solution so that the particle diameter is 100 nm or more, the seed particles grow into a spherical or approximately spherical shape. Therefore, by growing irregularly shaped seed particles as they are, relatively large irregularly shaped silica particles can be obtained. That was difficult.

Furthermore, the present inventors investigated a method of obtaining irregularly shaped silica particles by crushing wet silica as another method for preparing a group of silica particles containing irregularly shaped silica particles, and found that although irregularly shaped silica particles were obtained, , wet silica with a gel structure has a weak particle strength to control the particle size and particle size distribution by crushing or crushing, and the obtained irregularly shaped silica particles also have a weak particle strength. When silica particles were used as abrasive grains, it was not possible to obtain the required polishing rate.

Therefore, when the present invention is applied to polishing, for example, a silica-based particle group (compared to a silica-based particle group containing irregularly-shaped particles that exhibit a specific particle size distribution and have necessary particle strength; a silica-based particle dispersion containing this silica-based particle group; It is an object of the present invention to provide a method for manufacturing this silica-based particle group.

In order to solve the above problems, the present inventors used irregularly shaped porous silica obtained by crushing porous silica gel under specific conditions as seed particles instead of irregularly shaped seed particles obtained from conventional water glass. We investigated a method of growing seed particles by using particles made of gel and adding a silicic acid solution. The particles made of this irregularly shaped porous silica gel are obtained by wet crushing a soft porous silica gel under alkaline conditions, and have a relatively uniform particle size with almost no coarse particles. The internal pore structure of the raw material porous silica gel is generally maintained.

By using particles made of such irregularly shaped porous silica-based gel as seed particles and growing the seed particles in the coexistence of a silicic acid solution, silicic acid grows in the pores (concavities between the primary particles) between the primary particles of the seed particles. Since it is preferentially deposited from the surface layer, the interior of the seed particle has a porous structure, while silicic acid is deposited at a constant rate, although the deposition rate is slow, on the convex portions of the surface. I was able to grow it while maintaining its strange shape. In addition, since particles made of irregularly shaped porous silica gel with few coarse particles are used as seed particles, the coarse particles are preferentially crushed during crushing of the obtained silica particles containing irregularly shaped silica particles. contains almost no coarse particles. It was discovered that by using this silica-based particle group as an abrasive grain, the polishing speed is relatively high, the occurrence of scratches on the polished surface is significantly suppressed, and a polished surface with small surface roughness and waviness can be obtained. Ta. The irregular shaped silica particles with a porous structure included in this silica particle group that can obtain such a high polishing rate have a relatively low density compared to dense particles. The number of particles in the silica particle group containing particles increases. On the other hand, since the neck portion between the primary particles in the surface layer is reinforced, the particle strength exceeds a certain level. In other words, it can be said that the particle strength is increased to the extent that it can withstand the pressure during polishing.

Based on the above findings, the present inventor has developed a silica-based particle group consisting of irregularly shaped silica particles and non- irregularly shaped silica particles having a particle size, particle size distribution, degree of irregularity, and particle strength suitable for use as an abrasive, and a silica-based particle group containing the same. The present invention, which is a method for efficiently producing a silica-based particle dispersion and a silica-based particle group, has been completed.
The present invention includes the following (1) to (15).

(1) A silica-based particle dispersion containing a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles,
The irregularly shaped silica particles have a core having pores inside and a covering silica layer covering the core,
The silica-based particle group is a silica-based particle dispersion that satisfies the following [1] to [3].
[1] The weight average particle diameter (D ₁ ) is 60 to 600 nm, and the specific surface area equivalent particle diameter (D ₂ ) is 15 to 300 nm.
[2] The degree of irregularity D (D=D ₁ /D ₃ ) expressed as the ratio of the weight average particle diameter (D ₁ ) to the projected area equivalent particle diameter (D ₃ ) is in the range of 1.1 to 5.0. What's in it.
[3] Waveform separation of the volume-based particle size distribution results in a multimodal distribution in which three or more separated peaks are detected.
(2) The silica-based particle dispersion according to (1) above, wherein the average pore diameter of the internal pores of the core is 30 nm or less.
(3) The silica-based particle dispersion according to (1) or (2) above, wherein the coating silica layer has an average thickness in the range of 1 to 50 nm and contains silica as a main component.
(4) The silica-based particle group according to any one of (1) to (3) above, wherein the silica-based particle group has a skewness in the range of -20 to 20 in its volume-based particle size distribution. Particle dispersion.
(5) The above-mentioned (1) to (1) characterized in that the volume ratio of the largest particle component among the separated peaks obtained as a result of waveform separation of the volume-based particle size distribution of the silica-based particle group is 75% or less. The silica-based particle dispersion liquid according to any one of 4).
(6) The above (1) characterized in that, in the number-based particle size distribution obtained by SEM image analysis of the silica-based particle group, the aspect ratio of the small particle side component is in the range of 1.05 to 5.0. The silica-based particle dispersion according to any one of (5) to (5).
(7) The silica-based particle dispersion according to any one of (1) to (6) above, characterized in that the particle size variation coefficient of the volume-based particle size distribution of the silica-based particle group is 30% or more. .
( ₈ ) Smoothness S ( _S =S ₂ /S ₁ ) is in the range of 1.1 to 5.0, the silica-based particle dispersion according to any one of (1) to (7) above.
(9) In the volume-based particle size distribution of the silica-based particles, the ratio Q (Q=Q ₂ /Q _{1 ) of the volume (Q 2 )} of particles of 0.7 μm or more to the total volume (Q ₁ ) is 5. The silica-based particle dispersion according to any one of (1) to (8) above, characterized in that the silica-based particle dispersion is 0% or less.
(10) A polishing abrasive dispersion containing the silica-based particle dispersion according to any one of (1) to (9) above.
(11) A silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles,
The irregularly shaped silica particles have a core having pores inside and a coating silica layer covering the core, and satisfy the following [1] to [3].
[1] The weight average particle diameter (D ₁ ) is 60 to 600 nm, and the specific surface area equivalent particle diameter (D ₂ ) is 15 to 300 nm.
[2] The degree of irregularity D (D=D ₁ /D ₃ ) expressed as the ratio of the weight average particle diameter (D ₁ ) to the projected area equivalent particle diameter (D ₃ ) is in the range of 1.1 to 5.0. What's in it.
[3] Waveform separation of the volume-based particle size distribution results in a multimodal distribution in which three or more separated peaks are detected.

(12) A method for producing a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles, which comprises the following steps a to c.
(Step a) A step of wet-pulverizing the porous silica gel under alkaline conditions to obtain a solution containing particles of irregularly shaped porous silica gel.
(Step b) A silicic acid solution is added and heated under alkaline conditions to a solution containing particles made of the irregularly shaped porous silica gel, and the pores between the primary particles of the irregularly shaped porous silica gel are A step of growing particles with irregular shapes while filling them by a reaction with silicic acid contained in a silicic acid solution to produce irregularly shaped silica particles having a smaller weight average particle diameter than the particles made of the irregularly shaped porous silica gel .
(Step c) A step of concentrating and recovering the silica-based particles containing the grown irregularly shaped silica-based particles.
(13) In step a, the porous silica gel with a specific surface area of 50 to 800 m ² /g is made into particles of the irregularly shaped porous silica gel with a weight average particle diameter of 60 to 550 nm;
In step b, the pores between the primary particles of the particles made of the irregularly shaped porous silica gel are filled by reaction with the silicic acid so that the specific surface area of the particles made of the irregularly shaped porous silica gel is 182 m ² /g or less. The method for producing a group of silica-based particles comprising irregular-shaped silica-based particles and non-irregular-shaped silica-based particles according to (12) above, which comprises growing the irregular-shaped silica-based particles into irregularly shaped silica-based particles.
(14) In step a, the porous silica gel is wet-pulverized under alkalinity at pH 8.0 to 11.5 , and the irregularly shaped porous silica gel has a weight average particle diameter of 167 to 200 nm or 208 to 225 nm. to a solution containing particles consisting of a system gel,
In step b, the SiO ₂ concentration of the solution containing particles made of the irregularly shaped porous silica gel is set to 1 to 10% by mass, heated to 60° C. to 170° C., and under alkaline pH of 9 to 12.5. The silicic acid solution is added continuously or intermittently to fill the pores between the primary particles of the particles made of the irregularly shaped porous silica gel by reaction with the silicic acid, thereby reducing the specific surface area of the particles. If the particles made of the irregularly shaped porous silica gel have a weight average particle diameter of 167 to 200 nm, the irregularly shaped silica particles having a weight average particle diameter of 101 to 164 nm, the irregularly shaped porous silica gel When the weight average particle diameter of the gel particles is 208 to 225 nm, the irregularly shaped silica particles have a weight average particle diameter of 128 to 203 nm,
The irregular shape according to (12) or (13) above, wherein in the step c, a solution containing the grown irregularly shaped silica particles is concentrated to recover a group of silica particles containing the irregularly shaped silica particles. A method for producing a silica-based particle group consisting of silica-based particles and non-irregular silica-based particles.
(15) In step b, the amount of the silicic acid solution added is such that the SiO ₂ molar concentration of the silicic acid solution is 0.5 to 0.5 _to The method for producing a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles according to any one of (12) to (14) above, characterized in that the amount is in a range of 20 moles.

The silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles of the present invention has a particle size, particle size distribution, degree of irregularity, and particle strength suitable for use as an abrasive. When the particle dispersion is used, for example, as a polishing abrasive dispersion, or when this polishing abrasive dispersion is directly used as a polishing slurry, the target is a NiP-plated coating to be polished and a silica-based substrate. It can also be polished at high speed, without the abrasive grains penetrating the base material, and at the same time, high surface precision (fewer scratches, small surface roughness (Ra) and waviness (Wa) of the substrate to be polished, etc.). can be achieved.
In addition, the silica particles of the present invention, which are made up of irregularly shaped silica particles and non- irregularly shaped silica particles, have a porous surface that is not smooth and has minute protrusions, so polishing debris generated during polishing can be removed. It also has a scavenger effect that adsorbs ionic components, oligomer components, organic substances, etc. Therefore, redeposition of these components to the polished substrate can be prevented, and a polished surface with less residue can be achieved.

Furthermore, in the method for producing a silica particle group consisting of irregularly shaped silica particles and non- irregularly shaped silica particles of the present invention, particles that have undergone external shape adjustment of irregularly shaped porous silica gel are used as seed particles. In the adding step, the seed particles can be grown to a large size while maintaining their irregular shape, and the strength of the particles can also be increased. As a result, it is possible to efficiently obtain a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles that have a particle size, particle size distribution, degree of irregularity, and particle strength suitable for use as an abrasive.

Illustration of kurtosis in particle size distribution Illustration of skewness in particle size distribution Cross-sectional TEM photograph of irregularly shaped silica particles of Example 3

A silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles of the present invention, and a silica-based particle dispersion containing the same will be specifically explained. In addition, in the present invention, the term "particle group" means a collection of a large number of particles.

<Weight average particle diameter (D ₁ )>
The weight average particle diameter (D ₁ ) of the silica-based particles of the present invention is 60 to 600 nm, preferably 70 to 400 nm, and most preferably 80 to 300 nm. When silica-based particles having a weight average particle diameter in the range of 60 to 600 nm are used as abrasive grains, a high polishing rate can be obtained and scratches are less likely to occur. Note that when silica-based particles having a weight average particle diameter of less than 60 nm are used as abrasive grains, it is difficult to obtain the necessary polishing rate, and smaller particles tend to remain on the substrate after polishing. Furthermore, when silica-based particles with a weight average particle diameter of more than 600 nm are used as abrasive grains, scratches tend to occur easily, and even if the weight average particle diameter is increased further, the amount of abrasive particles per mass Because the number decreases, the polishing rate may not improve.

Here, in the present invention, the weight average particle diameter (D ₁ ) refers to the silica particle dispersion to be measured, diluted with a 0.05% by mass sodium dodecyl sulfate aqueous solution, and the solid content concentration is 2% by mass. 0.1 ml was injected with a syringe into a conventional disk centrifugal particle size distribution analyzer (for example, manufactured by CPS Instrument), and the mixture was heated at 18,000 rpm in a density gradient solution of 8% to 24% sucrose. This is the average particle diameter determined from the weight-based particle diameter distribution obtained by measurement. That is, in the present invention, this weight average particle diameter means "average particle diameter of weight-equivalent particle diameter distribution."

<Specific surface area equivalent particle diameter (D ₂ )>
The specific surface area equivalent particle diameter (D ₂ ) of the silica-based particles of the present invention is 15 to 300 nm, preferably 20 to 250 nm, more preferably 24 to 200 nm, and most preferably 26 to 150 nm. When silica-based particles having a specific surface area equivalent particle diameter (D ₂ ) in the range of 15 to 300 nm are used as abrasive grains, a high polishing rate can be obtained and scratches are less likely to occur. In addition, when using silica-based particles with a specific surface area equivalent particle diameter (D ₂ ) of less than 15 nm as abrasive grains, it is difficult to obtain the required polishing rate, and smaller particles tend to remain on the substrate after polishing. It is in. Furthermore, when silica-based particles with a specific surface area equivalent particle diameter (D ₂ ) of more than 300 nm are used as abrasive grains, scratches tend to occur and the surface roughness of the substrate after polishing tends to worsen. . Furthermore, even if the particle diameter in terms of specific surface area is increased further, the number of abrasive grains per mass decreases, so the polishing rate tends to decrease.

In addition, in the present invention, the specific surface area-converted particle diameter (D ₂ ) means the average particle diameter in terms of specific surface area, and the specific surface area (SA: m ² /g) measured by the BET method and the particle density (D 2 ) ρ) [ρ=2.2 in the case of silica] is used, and is calculated from the formula D ₂ =6000/(SA×ρ).
Here, the BET method is the following method.
First, the pH of 50 ml of silica sol (silica-based particle dispersion) to be measured was adjusted to 3.5 with nitric acid, 40 ml of 1-propanol was added to this, and the sample was dried at 110°C for 16 hours, and the sample was ground in a mortar. Thereafter, the sample was fired at 500° C. for 1 hour in a muffle furnace to obtain a measurement sample. Then, using a known specific surface area measuring device (for example, manufactured by Yuasa Ionics, model number Multisorb 12, etc.), the specific surface area is calculated from the amount of nitrogen adsorbed using the BET one-point method using the nitrogen adsorption method (BET method). In the specific surface area measuring device, 0.5 g of the sample after firing is placed in a measurement cell, degassed for 20 minutes at 300°C in a mixed gas flow of 30 vol% nitrogen/70 vol% helium, and then the sample is exposed to the above mixed gas. It is kept at liquid nitrogen temperature in an air flow to allow equilibrium adsorption of nitrogen onto the sample. Next, the sample temperature is gradually raised to room temperature while flowing the above-mentioned mixed gas, and the amount of nitrogen desorbed during this time is detected, and the specific surface area (SA) of the silica fine particles in the sample is calculated using a calibration curve prepared in advance. .

In addition, if the specific surface area of the silica-based particles is high, sintering will proceed during firing in the BET method, so if the specific surface area (SA) is 100 m ² /g or more, the specific surface area can be reduced by the titration method. Find (SA).
Here, the titration method is the following method.
First, collect a sample equivalent to 1.5 g of SiO ₂ in a beaker, transfer it to a constant temperature reaction tank (25 ° C), and add pure water to make the liquid volume 90 ml (the following operation is carried out at 25 °C). (Carried out in a constant temperature reactor kept at ℃). Next, 0.1 mol/L hydrochloric acid aqueous solution is added thereto to adjust the pH to 3.6. Furthermore, 30 g of sodium chloride is added, diluted to 150 ml with pure water, and stirred for 10 minutes. Then, a pH electrode is set, and while stirring, 0.1 mol/L sodium hydroxide solution is added dropwise to adjust the pH to 4.0. Furthermore, the sample adjusted to pH 4.0 was titrated with 0.1 mol/L sodium hydroxide solution, and the titration amount and pH value in the range of pH 8.7 to 9.3 were recorded at 4 or more points. Create a calibration curve by setting the titration amount of 1 mol/L sodium hydroxide solution as X and the pH value at that time as Y. From the formula V=(A×f×100×1.5)/(W×C), 0.1 mol/L sodium hydroxide is required to reach pH 4.0 to 9.0 per 1.5 g of SiO ₂ The consumption volume V (ml) of the solution is determined, and using this, the specific surface area is determined according to the formula SA=29.0V-28.
In the above formula, A is the titration amount (ml) of 0.1 mol/L sodium hydroxide solution required to reach pH 4.0 to 9.0 per 1.5 g of SiO ₂ , and f is 0.1 mol/L. The titer of the sodium hydroxide solution, C means the SiO ₂ concentration of the sample (%), and W means the amount of sample collected (g).

<Degree of abnormality>
The degree of irregularity is expressed by dividing the above-mentioned weight average particle diameter (D ₁ ) by the projected area equivalent particle diameter (D ₃ ).
Incidentally, the projected area equivalent particle diameter (D ₃ ) is measured and calculated by the following method.
First, using a scanning electron microscope (SEM), 15 fields of view are photographed at an arbitrary location on the surface of the silica-based particles at a magnification of 3000 times with an area of 1.1×10 ^-3 mm ² per field of view. Then, for all the silica particles included in each image taken in each field of view, the projected area of each particle is measured by an image analysis method using an image analysis system, and the area corresponding to each measured area is measured. The particle diameter (diameter of a circle) of the circular particles is calculated, and the number average (arithmetic mean diameter) thereof is defined as the particle diameter equivalent to projected area (D ₃ ).
The silica-based particles of the present invention have an irregularity D (D=D ₁ /D ₃ ) in the range of 1.1 to 5.0, preferably in the range of 1.1 to 4.0, and in the range of 1.1 to 4.0. The range of 3.5 is more preferable, and the range of 1.1 to 3.3 is more preferable. A silica-based particle group with a high degree of irregularity means that the average aspect ratio of the particle group (the average value of the "longest axis / shortest axis ratio of the minimum inscribed square") is high, and if this average aspect ratio is high During polishing, the long axis of the particles mainly contacts the substrate, which increases the contact area with the substrate and increases the polishing rate, which is preferable. However, if the degree of irregularity exceeds 5.0, the degree of irregularity cannot be increased any further. However, the polishing speed does not improve, and scratches and waviness tend to occur more easily. In addition, when this degree of irregularity is less than 1.1, it indicates that the shape of the particles is close to a true sphere, and polishing is performed using a silica-based particle dispersion containing such a group of silica-based particles. If this is done, the polishing rate tends to decrease.
Note that the aspect ratio here means the ratio of the long side to the short side (long side/short side) of the rectangle (including square) in which the particle is inscribed and has the smallest area. Further, the average aspect ratio means a simple average value of aspect ratios of a certain number or more particles.

Note that the proportion of irregularly shaped silica particles contained in the silica particle dispersion containing a silica particle group consisting of irregularly shaped silica particles and non- irregularly shaped silica particles according to the present invention is as specified in [1] and [2] above. And as long as the requirements of [3] are met, there is no particular restriction, but the number of irregularly shaped silica particles with an aspect ratio of 1.1 or more accounts for 30% of the total (the silica particle group). It is preferably 40% or more, and more preferably 40% or more.
Note that the method for measuring the number ratio of irregularly shaped silica-based particles having an aspect ratio of 1.1 or more is as shown in Examples described later.

<Kurtosis>
The kurtosis in the volume-based particle size distribution of the silica-based particles of the present invention is preferably -20 to 20, more preferably -10 to 10, and most preferably -5 to 7. When silica-based particles with kurtosis within this range are used as abrasive grains, a higher polishing rate can be obtained, and a smoother surface (lower surface roughness (Ra) and less waviness of the substrate) can be obtained after polishing. (Wa) is also small and there are few scratches).

Here, kurtosis is calculated only from the particle size distribution, regardless of the shape or size of the particle, and if the kurtosis is close to zero (normal distribution), the particle size distribution is close to the normal distribution. It shows that. In addition, a particle size distribution with a kurtosis value larger than zero indicates that the center of the peak is sharper than in a normal distribution, and the left and right tails of the distribution are wider (Figure 1 (a)). A particle size distribution with a kurtosis smaller than zero indicates a shape in which the peak is flat and the left and right sides of the distribution tail are not wide (FIG. 1(b)).

In the present invention, the kurtosis in the volume-based particle size distribution of the silica-based particles may be a negative value. When the kurtosis is negative, it indicates that the peak is flat, there are few small particles and large particle components on the left and right sides of the distribution, and the particle size distribution is relatively uniform with a flat peak. When such a silica-based particle group containing few small particle components and large particle components is used as an abrasive grain, it is preferable because there is little abrasive grain residue and the polishing rate is high.

<Distortion>
The skewness in the volume-based particle size distribution of the silica-based particles of the present invention is preferably -20 to 20, more preferably -15 to 15, and most preferably -10 to 10. When silica-based particles with a distortion degree in this range are used as abrasive grains, a higher polishing rate can be obtained, and the surface roughness (Ra) is small and the waviness of the substrate is reduced. (Wa) is also small and there are few scratches).

Here, skewness, like kurtosis, is calculated only from the particle size distribution, regardless of the shape or size of the particles, and if the skewness is close to zero, the particle size distribution is close to a normal distribution. It shows that. In addition, a particle size distribution with a skewness value larger than zero has a peak on the left side of the distribution (the side where the particle size is small) and has a long tail on the right (Figure 2 (a) )) In contrast, a particle size distribution with a skewness value smaller than zero has a peak on the right side of the distribution (the side where the particle size is large) and has a long tail on the left. (Figure 2(b)).

Normally, the skewness in the volume-based particle size distribution of silica-based particles obtained by crushing and pulverization methods often takes a positive value, and particles obtained by the build-up method tend to have a normal distribution, so the skewness is It often takes values close to zero. When the skewness is positive, the particle size distribution has a peak at a position where the particle size is slightly smaller and has a wider tail on the larger particle size side. When a silica-based particle group having a particle size distribution with a peak on the small particle size side is used as an abrasive grain, a smooth surface tends to be easily obtained after polishing because there are many components with a small particle size. On the other hand, silica-based particles with extremely high skewness have a particle size distribution that widens toward the large particle size side, and depending on the average particle size, they tend to cause scratches when used as abrasive grains. .

In the present invention, the skewness in the volume-based particle size distribution of the silica-based particles may be a negative value. Silica-based particles with a negative skewness value have a peak at a position where the particle size is large, and the particle size distribution has a wide tail toward the small particles, but the particle size distribution is sharp on the large particle side. (i.e., there are few significantly large particles), scratches are less likely to occur even when used as abrasive grains. However, silica-based particles with a skewness of less than -20 have a particle size distribution with too wide a tail on the small particle side, and the small particle component increases, so when used as abrasive grains, there is a tendency for abrasive grain residue to occur. be.

<Measurement of volume-based particle size distribution and calculation method of kurtosis/skewness>
In the present invention, the volume-based particle size distribution of silica-based particles is measured by centrifugal sedimentation. For example, a silica-based particle dispersion liquid is diluted with a 0.05% by mass aqueous sodium dodecyl sulfate solution, the solid content concentration is adjusted to 2% by mass, and the silica-based particle dispersion is diluted with a 0.05% by mass aqueous solution of sodium dodecyl sulfate, and the solid content is adjusted to 2% by mass. ) can be used to measure the volumetric particle size distribution.
Kurtosis and skewness are calculated from the average value, standard deviation, etc. of the volume-based particle size distribution thus obtained using conventionally known formulas. For example, JMP Ver. manufactured by SAS Institute Japan. 13.2 can be used to calculate kurtosis and skewness. In addition, in the volume-based particle size particle size distribution, the frequency of a predetermined particle size may rarely take a negative value, but in such a case, the frequency is calculated as zero.

<Multimodal distribution>
When the volume-based particle size distribution of the silica-based particles of the present invention is waveform-separated by the method described below, it becomes a multimodal distribution in which three or more separated peaks are detected. In the case of particles with a unimodal distribution, the polishing speed and waviness will occur depending on the particle size; if the particle size is large, the polishing speed will be high but the waviness will be large, and if the particle size is small, the waviness will be improved. However, the polishing speed will be lower. On the other hand, in the case of a particle group having a multimodal distribution, polishing proceeds while leaving polishing marks according to the particle diameter of each component, and the sum of these marks becomes the waviness and the polishing rate. Therefore, a distribution in which the small particle component exhibits a sufficient polishing rate at the same time as the large particle component (for example, a trapezoidal distribution that contains many small particles and large particles, and a distribution that becomes multimodal when the waveforms are separated) ), both polishing speed and waviness can be achieved.

Waveform separation was performed by analyzing the volume-based particle size distribution obtained with the aforementioned disk centrifugal particle size distribution measuring device using the peak analyzer of the graph creation and data analysis software Origin (manufactured by OriginLab Corporation). conduct. First, set the baseline to 0 and the peak type to Gaussian, select the maximum point of the particle size distribution as the peak position, perform peak fitting without weighting, and check whether the calculated peak deviates from conditions 1 and 2 below. If there is a deviation, repeat peak fitting by shifting the peak position to an arbitrary position within the distribution range until conditions 1 and 2 below are satisfied. Thereafter, if the corrected R-squared value is 0.99 or less, a peak is added to any position within the distribution range, and peak fitting is repeated until the corrected R-squared value becomes 0.99 or more. The number of separated peaks at this time is defined as the number of peaks.
Condition 1: Each calculated peak does not take a value larger than the original distribution.
Condition 2: Each calculated peak does not take a negative value.
Such a silica-based particle group having a multimodal volume-based particle size distribution has a wide distribution (broad distribution) from large particles to small particles, and has more suitable polishing performance.
Specifically, it is desirable that the volume ratio of the maximum peak after waveform separation is 75% or less of the total volume. This is because if the volume ratio of the maximum peak is 75% or less, the distribution becomes broad, and when waveform separation is performed, there is a tendency for a multimodal distribution with three or more separated peaks.
If the volume ratio of this maximum peak exceeds 75%, the distribution is substantially close to a unimodal distribution, and even if such a volume-based particle size distribution is separated into waveforms, the number of separated peaks tends to be less than 3. be.

Furthermore, in the silica-based particle group of the present invention, it is preferable that the volume ratio of the largest particle component among the separated peaks detected when the volume-based particle size distribution is waveform separated is 75% or less, and 73%. It is more preferable that it is below. When such a silica-based particle group is used as an abrasive grain, the surface roughness and waviness of the substrate are improved during polishing due to the small amount of large particle components. Here, in the present invention, the "largest particle component" means a particle component included in the separation peak on the particle side with the largest particle size when waveform separation is performed on the volume-based particle size distribution of the silica-based particle group. .

<Aspect ratio>
In the silica-based particle group of the present invention, the aspect ratio of the small particle side component is preferably in the range of 1.05 to 5.0 in the number-based particle size distribution obtained as a result of SEM image analysis. It is more preferably in the range of ~3.0, more preferably in the range of 1.05 to 2.0, even more preferably in the range of 1.05 to 1.5. Note that the aspect ratio of the small particle side component in the number-based particle size distribution obtained by SEM image analysis is measured and calculated by the following method. First, the total number of particles in the silica-based particle group is counted using a known scanning electron microscope (SEM) and a known image analysis system. Further, the area of each particle is calculated, and the diameter of a circle having an area equal to the calculated area is determined, and this is defined as the particle diameter. Then, arrange the obtained particle diameters in order of size, count up to 1/3 of the particles from the small side as the small particle side component, and for each particle of the small particle side component, the aspect ratio (minimum inscribed square The long axis/breadth axis ratio) is determined, and their simple average value is defined as the "aspect ratio of the small particle side component."
The aspect ratio of the small particle side component of the silica-based particle group of the present invention is usually smaller than the average aspect ratio of the silica-based particle group. When the aspect ratio of the small particle side component is less than 1.05, such particles are substantially equivalent to spherical particles, so the polishing rate is low, and the polishing rate of the silica-based particles also tends to be low. However, when a silica-based particle group whose small particle side component has an aspect ratio of 1.05 or more is used as an abrasive grain, the small particle side component also exhibits a high polishing rate, so the polishing rate of the silica-based particle group is increased. Therefore, defects are less likely to occur, and high surface accuracy tends to be obtained. In addition, if the aspect ratio of the small particle side component is larger than 5.0, the average aspect ratio of the entire silica-based particle group also becomes higher, so although the polishing rate increases, defects are more likely to occur on the substrate, and the substrate surface The roughness of the substrate and the waviness of the substrate surface also tend to worsen.

Here, methods for producing particles with a high aspect ratio in which single particles are combined include, for example, a method of increasing the aspect ratio by associating particles of several tens of nanometers using ionic strength adjustment or polymers, or a method of increasing the aspect ratio by combining particles of several tens of nm. Sometimes, there is a method of associating particles by adjusting ionic strength, etc. simultaneously with nucleation, and then growing the generated irregularly shaped seed particles to obtain particles with a high aspect ratio. However, in these methods, while particles with a high aspect ratio are generated, unassociated particles also tend to remain, so particles with a small particle size tend to be close to spherical and have a small aspect ratio, and spherical particles Since the polishing rate is low, the polishing rate of the entire particle group tends to be low. On the other hand, the silica-based particle group containing irregularly shaped silica-based particles of the present invention can obtain a high polishing rate because the small particle side component also contains irregularly shaped particles due to the densification effect of the crushing process. .

<Coefficient of variation (CV value)>
The particle diameter variation coefficient of the volume-based particle diameter distribution of the silica-based particles according to the present invention is preferably 30% or more, more preferably 50% or more. By setting the coefficient of variation within a predetermined range, the volume-based particle size distribution becomes broad, that is, the silica-based particles have a wide particle size distribution, and more suitable polishing performance is exhibited. In the present invention, the "coefficient of variation (CV value)" is a value obtained by dividing the standard deviation by the average value, expressed as a percentage, and indicates relative variation.
Note that the CV value of the present invention is determined from a volume-based particle size distribution using a disk centrifugal particle size distribution measuring device (manufactured by CPS Instrument).

<Smoothness S>
Smoothness S (S _{= S 2} /S ₁ ) is preferably in the range of 1.1 to 5.0, more preferably in the range of 1.2 to 4.0. When the S value is higher than 1.0, it indicates that the surface of the irregularly shaped silica particles included in the silica particle group is not smooth but has minute irregularities. This irregularly shaped seed particle is an aggregate of primary particles, and since it is porous, the surface of this seed particle also has minute protrusions. This is because the shape of the protrusion is maintained. Furthermore, when a silica-based particle group containing irregular-shaped silica-based particles having appropriate microprotrusions on the surface of the irregular-shaped silica-based particles is used as polishing abrasive grains, polishing pressure is concentrated on the protrusions, so a high polishing rate can be obtained. Note that if there are too many protrusions on the surface of the particles, the surface roughness and waviness of the substrate surface after polishing will not worsen, but the abrasive grains will be easily worn and the polishing rate will tend to decrease.

Here, the measurement and calculation of the average area (S ₁ ) using the image analysis method and the area of a circle equivalent to the average outer circumference length (S ₂ ) using the image analysis method in a group of silica-based particles will be described.
These were measured and calculated using the following methods. First, using a known scanning electron microscope (SEM), 15 fields of view are photographed at an arbitrary location on the particle surface at a magnification of 3000 times, each field having an area of 1.1×10 ⁻³ mm ² . For all the silica fine particles included in each image taken in each field of view, the area and outer circumference of each particle are measured using a known image analysis system, and based on the measured area and outer circumference data, Calculate the average area (S ₁ ) (simple average value) and average perimeter length (simple average value), and then from this average perimeter length, calculate a circle equivalent to the average perimeter length (a circle with the same circumference as the average perimeter length) The area (S ₂ ) of is calculated.

<Q ₂ /Q ₁ >
The silica-based particles of the present invention have a volume-based particle size distribution in which the ratio Q (Q=Q ₂ /Q ₁ ) of the volume (Q ₂ ) of particles of 0.7 μm or more to the total volume (Q ₁ ) is expressed as a percentage. (indication) is preferably 5.0% or less, more preferably 4.5% or less. Since such a silica-based particle group has a small proportion of coarse particles, defects such as scratches are less likely to occur during polishing, and the surface roughness of the polished substrate can be further reduced.

In addition, the total volume (Q ₁ ) in the volume-based particle size distribution of the silica-based particles of the present invention, the volume ratio of each component of the separated peak obtained as a result of waveform separation, the volume ratio of the largest particle component, and 0. The volume (Q ₂ ) of particles of 7 μm or more can also be measured by the method using the disk centrifugal particle size distribution measuring device described above.

<Internal pores and covering silica layer>
The irregularly shaped silica particles included in the silica particles of the present invention are obtained by using particles made of irregularly shaped porous silica gel as seed particles and growing the seed particles using a silicic acid solution. During this particle growth, the neck portions between the primary particles in the seed particles are preferentially filled with silicic acid, but some pores remain. Therefore, the irregularly shaped silica-based particles of the present invention have minute internal pores inside the particles (core), and have a lower particle density than silica-based particles with a denser interior, but they have less strength. expensive. The average pore diameter of the internal pores is preferably 30 nm or less. This is because if the internal pore diameter becomes too large, the strength of the particles tends to decrease.
The particle surface is provided with a covering silica layer that covers the core having the above-mentioned minute internal pores. This coating silica layer preferably has few internal pores, has an average thickness in the range of 1 to 50 nm, and has silica as its main component. If this average thickness is less than 1 nm, it is difficult to improve the strength of the particles, and if this average thickness exceeds 50 nm, the internal pores of the particles will decrease, and the degree of irregularity will also decrease, resulting in a low polishing rate.
Furthermore, if there is no coating silica layer or if it is thinner than 1 nm, the strength is weak and the particles will disintegrate during polishing, making it difficult to improve the polishing rate and increasing the variation in polishing rate when polishing is repeated. There is a tendency.
Further, the pore volume of the particles having pores inside is not particularly limited, but it is desirable that the pore volume be within a range where the tendency of the particles to collapse during polishing is not noticeable. Note that a range of 0.01 to 1.00 ml/g is usually desirable. When the pore volume is less than 0.01 ml/g, since there are substantially no pores inside, it is difficult to obtain the effect of improving the polishing rate by increasing the number of particles in the particle group. Furthermore, if the pore volume exceeds 1.00 ml/g, the strength of the particles will be insufficient, the particles may collapse during polishing, and the polishing rate will tend to decrease.
Here, in the present invention, the term "main component" means that the content is 90% by mass or more. That is, the content of silica in the coating silica layer is preferably 90% by mass or more. This content is more preferably 95% by mass or more, even more preferably 98% by mass or more, and most preferably 99.5% by mass or more.

The method for measuring the average pore diameter of the core internal pores and the average thickness of the covering silica layer of the irregularly shaped silica particles included in the silica particles of the present invention is as follows.
A cross-sectional TEM photograph obtained by embedding silica-based fine particles in resin and slicing it (observe the silica-based particle image at 100,000 times (or 200,000 times), and set the maximum diameter of one particle where pores are confirmed as the major axis. Then, determine the point on the long axis that divides the long axis into two equal parts, find the two points where a straight line perpendicular to it intersects the outer edge of this particle, and define the short axis between these two points.Then, this long axis and Determine the thickness of the covering silica layer on both sides of the minor axis, and simply average these to determine the average thickness of the covering silica layer for one particle.Similarly, determine the thickness of the covering silica layer for any 20 particles, The simple average of these values is defined as the average thickness of the coating silica layer in the irregularly shaped silica particles.
Furthermore, the diameters of pores existing on the long axis and the short axis are determined, and the average thereof is taken as the average pore diameter of one particle. Similarly, the pore diameters are determined for 20 particles in which pores are confirmed, and the simple average of these is taken as the average pore diameter of the irregularly shaped silica particles. Note that in the silica-based particle image in the cross-sectional TEM photograph, spots with a lower density than the surroundings are internal pores.
In addition, if there are no pores on the long axis or short axis, find the pore diameter of any pore, find the pore diameter of 20 arbitrary particles, and calculate the simple average of these pore diameters. This is the average pore diameter in the particles.
The method for measuring the cross-sectional TEM photograph is as follows.
1) Place dry powder particles on a silicon wafer and harden with epoxy resin.
2) Cut the obtained wafer into strips of 700 μm using a diamond wheel (model: SBT650, manufactured by South Bay Technology).
3) Next, place the cut wafer on a polishing sample stage and cut it to a thickness of 100 μm.
(Note that the Si wafer is removed in step 2) or 3). )
4) A hole was made in the cut sample using an ion slicer (manufactured by JEOL, model: EM-09100IS), and the area around the hole with a thickness of several nm was observed using a TEM.

By providing the irregularly shaped silica particles of the present invention with a core having micropores inside and a covering silica layer covering the core, the number of pores replaced by water is reduced, and the particle density is low. Become. When the particle density decreases, the number of particles per mass increases, so the contact area with the substrate increases and the polishing rate increases. Furthermore, as the number of particles increases, the load applied to each particle becomes smaller. Therefore, since the particles shallowly grind the substrate, the surface roughness and waviness of the substrate tend to improve. Furthermore, although the inside has pores, the outer layer has a dense covering silica layer, which increases the strength of the particles and prevents the particles from breaking due to polishing pressure. Therefore, the polishing rate increases. On the other hand, in the case of porous silica-based particles not provided with such a coating silica layer, the particles are destroyed by the polishing pressure, so that the polishing rate is significantly reduced.

<Abrasive grain dispersion liquid for polishing>
A silica-based particle dispersion in which the silica-based particles of the present invention are dispersed in a dispersion solvent (silica-based particle dispersion containing the silica-based particles of the present invention) is a polishing abrasive dispersion (hereinafter referred to as "abrasive particle dispersion of the present invention"). It can be preferably used as an abrasive grain dispersion (also referred to as "abrasive grain dispersion liquid"). In particular, it can be preferably used for polishing magnetic disks. Furthermore, it can be suitably used as a polishing abrasive dispersion liquid for planarizing a semiconductor substrate on which a SiO ₂ insulating film is formed. Further, in order to control the polishing performance, a chemical component can be added and it can be suitably used as a polishing slurry.

The polishing abrasive grain dispersion of the present invention has a high polishing speed when polishing magnetic disks, semiconductor substrates, etc., and has effects such as fewer scratches on the polished surface and less residual abrasive grains on the substrate during polishing. It has excellent polishing properties and can greatly improve the efficiency of polishing work.

The polishing abrasive dispersion liquid of the present invention contains water and/or an organic solvent as a dispersion solvent. As the dispersion solvent, it is preferable to use water such as pure water, ultrapure water, or ion-exchanged water. Furthermore, a group consisting of a polishing accelerator, a surfactant, a heterocyclic compound, a pH adjuster, a pH buffer, and a sedimentation inhibitor may be added to the polishing abrasive dispersion of the present invention for controlling polishing performance. By adding one or more selected from the above, it can be more suitably used as a polishing slurry.

<Polishing accelerator>
The abrasive grain dispersion of the present invention can be used as a polishing slurry by adding a conventionally known polishing accelerator as necessary, although this varies depending on the type of material to be polished. Such examples include hydrogen peroxide, peracetic acid, urea peroxide, etc. and mixtures thereof. When a polishing agent composition containing such a polishing accelerator such as hydrogen peroxide is used, the polishing rate can be effectively improved when the material to be polished is 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; and sodium salts, potassium salts, ammonium salts, and amine salts of these acids. Examples include mixtures of. In the case of polishing compositions containing these polishing accelerators, when polishing a workpiece made of composite components, by accelerating the polishing rate of a specific component of the workpiece, it is possible to achieve flat polishing in the end. You can get a face.

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

<Surfactant and/or hydrophilic compound>
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 a hydrophilic compound can be added. Both the surfactant and the hydrophilic compound have the effect of lowering the contact angle with the surface to be polished, and have the effect of promoting uniform polishing. As the surfactant and/or hydrophilic compound, for example, those selected from the following group can be used.

Examples of anionic surfactants include carboxylates, sulfonates, sulfate ester salts, and phosphate ester salts; examples of carboxylates include soaps, N-acylamino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carbonate; Acid salts, acylated peptides; as sulfonates, alkyl sulfonates, alkylbenzene and alkylnaphthalene sulfonates, naphthalene sulfonates, sulfosuccinates, α-olefin sulfonates, N-acylsulfonates; sulfuric esters As salts, sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfates, alkyl amide sulfates; as phosphoric acid ester salts, alkyl phosphates, polyoxyethylene or polyoxyethylene sulfates; Mention may be made of oxypropylene alkyl allyl ether phosphate.

As cationic surfactants, aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, imidazolinium salts; as amphoteric surfactants, carboxybetaine type, sulfobetaine type, Mention may be made of aminocarboxylic acid salts, imidazolinium betaine, lecithin, and alkylamine oxides.

Examples of nonionic surfactants include ether type, ether ester type, ester type, and nitrogen-containing type. Ether types include polyoxyethylene alkyl and alkylphenyl ether, alkylaryl formaldehyde condensed polyoxyethylene ether, and polyoxyethylene polyester. Examples include oxypropylene block polymer, polyoxyethylene polyoxypropylene alkyl ether, and as ether ester type, polyoxyethylene ether of glycerin ester, polyoxyethylene ether of sorbitan ester, polyoxyethylene ether of sorbitol ester, and as ester type, Examples of the polyethylene glycol fatty acid ester, glycerin ester, polyglycerin ester, sorbitan ester, propylene glycol ester, sucrose ester, and nitrogen-containing type include fatty acid alkanolamide, polyoxyethylene fatty acid amide, and polyoxyethylene alkyl amide. Other examples include fluorine-based surfactants.

The surfactant is preferably an anionic surfactant or a nonionic surfactant, and the salt includes ammonium salts, potassium salts, sodium salts, etc., with ammonium salts and potassium salts being particularly preferred.

Furthermore, other surfactants, hydrophilic compounds, etc. 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 glycol, alkyl polypropylene glycol alkyl ether , alkyl polypropylene glycol alkenyl ether, alkenyl polypropylene glycol and other ethers; polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, curdlan and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; polyaspartic acid, polyglutamic acid, Polylysine, polymalic acid, polymethacrylic acid, polyammonium methacrylate, polysodium methacrylate, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly(p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, amino Polycarboxylic acids and their salts such as polyacrylamide, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, polyamic acid, polyamic acid ammonium salt, polyamic acid sodium salt, and polyglyoxylic acid; polyvinyl alcohol, polyvinylpyrrolidone, polyacrolein, etc. Vinyl polymer; ammonium methyl taurate, sodium methyl taurate, sodium methyl sulfate, ethyl ammonium sulfate, butylammonium sulfate, sodium vinyl sulfonate, sodium 1-allylsulfonate, 2-allylsulfonic acid Sulfonic acids and their salts such as sodium salt, methoxymethylsulfonic acid sodium salt, ethoxymethylsulfonic acid ammonium salt, 3-ethoxypropylsulfonic acid sodium salt; propionamide, acrylamide, methylurea, nicotinamide, succiamide and sulfanilamide Amides such as these can be mentioned.

Note that when the substrate to be polished is a glass substrate, etc., any surfactant can be suitably used, but in the case of a silicon substrate for semiconductor integrated circuits, an alkali metal, alkaline earth If the influence of contamination by similar metals or halides is to be avoided, it is desirable to use an acid or ammonium salt-based surfactant.

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

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

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

<Heterocyclic compound>
Regarding the polishing abrasive dispersion of the present invention, when the base material to be polished contains metal, for the purpose of forming a passive layer or a dissolution suppressing layer on the metal and suppressing erosion of the base material to be polished, A heterocyclic compound may also be included. Here, the "heterocyclic compound" is a compound having a heterocyclic ring containing one or more heteroatoms. Heteroatom means an atom other than a carbon atom or a hydrogen atom. Heterocycle means a cyclic compound having at least one heteroatom. Heteroatom means only those atoms that form a constituent part of a heterocyclic ring system and are located externally to the ring system or are separated from it by at least one non-conjugated bond; is not meant to be such an atom that it is part of a further substituent. Preferred heteroatoms include, but are not limited to, nitrogen atom, sulfur atom, oxygen atom, selenium atom, tellurium atom, phosphorus atom, silicon atom, and boron atom. Examples of heterocyclic compounds that can be used include imidazole, benzotriazole, benzothiazole, and tetrazole. 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-amino 1,2,4-triazole, 3,5 Examples include, but are not limited to, -diamino-1,2,4-triazole.

When a heterocyclic compound is blended into the polishing abrasive dispersion of the present invention, the content thereof is preferably 0.001 to 1.0% by mass, and preferably 0.001 to 0.7% by mass. is more preferable, and even more preferably 0.002 to 0.4% by mass.

<pH adjuster>
In order to enhance the effects of each of the above-mentioned additives, acids or bases and salt compounds thereof can be added as necessary to adjust the pH of the polishing composition.

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

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

<pH buffer>
A pH buffer may be used to maintain a constant pH value of the polishing abrasive dispersion of the present invention. As the pH buffering agent, for example, phosphates and borates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammo tetraborate water, or organic acid salts can be used.

<Sedimentation inhibitor>
A sedimentation inhibitor may be added to the polishing abrasive dispersion of the present invention for the purpose of suppressing sedimentation and, if sedimentation occurs, to facilitate dispersion. There are no particular restrictions on the sedimentation inhibitor, but polycarboxylic acid surfactants, anionic polymer surfactants, cationic surfactants, sodium polyacrylate, carboxylic acid copolymer sodium salts, carboxylic acid copolymers, etc. copolymer ammonium salt, polyammonium acrylate, polyacrylic acid, sulfonic acid copolymer sodium salt, fatty acid salt, α-sulfo fatty acid ester salt, alkylbenzene sulfonate, alkyl sulfate, alkyl ether sulfate ester, Alkyl triethanolamine sulfate, fatty acid diethanolamide, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, alkyl trimethyl ammonium salt, dialkyl dimethyl ammonium chloride, alkyl pyridium chloride, alkyl carboxybetaine, styrene/maleic anhydride copolymer , formalin bond of naphthalene sulfonate, carboxymethyl cellulose, olefin/maleic anhydride copolymer, sodium alginate, polyvinyl alcohol, polyalkylene polyamine, polyacrylamide, polyoxypropylene/polyoxyethylene block, polymer starch, polyethylene imine, Examples include aminoalkyl acrylate copolymer, polyvinylimidasoline, and satokinsan.
Note that when a sedimentation inhibitor is added to the polishing abrasive dispersion of the present invention, the total content is preferably 0.001 to 10 g in 1 L of the polishing abrasive dispersion, and 0. The amount is more preferably 0.01 to 5 g, and particularly preferably 0.1 to 3 g. This content is preferably 0.001 g or more per liter of the polishing abrasive dispersion in order to obtain a sufficient effect, and is preferably 10 g or less in order to prevent a decrease in polishing speed.

In addition, examples of dispersion solvents for the polishing abrasive dispersion of the present invention include alcohols such as methanol, ethanol, isopropanol, n-butanol, and methylisocarbinol; 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, etc. ethers; glycol ethers such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, and ethylene glycol dimethyl ether; glycol ether acetates such as 2-methoxyethyl acetate, 2-ethoxyethyl acetate, and 2-butoxyethyl acetate; Esters such as methyl acetate, ethyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and ethylene carbonate; Aromatic hydrocarbons such as benzene, toluene, and xylene; Aliphatic hydrocarbons such as hexane, heptane, isooctane, and cyclohexane halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, dichloropropane, and chlorobenzene; sulfoxides such as dimethyl sulfoxide; pyrrolidones such as N-methyl-2-pyrrolidone and N-octyl-2-pyrrolidone Organic solvents such as can be used. These may be used in combination with water.

The solid content concentration contained in the polishing abrasive grain 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. On the other hand, if the solid content concentration is too high, the polishing rate will rarely be improved any further, which may be uneconomical.

<Method for producing a silica particle group consisting of irregularly shaped silica particles and non- irregularly shaped silica particles>
Next, a method for producing a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles of the present invention will be specifically explained.
This involves wet crushing the porous silica gel under alkalinity to make a solution containing particles made of irregularly shaped porous silica gel, and adding an alkaline solution to the solution containing particles made of irregularly shaped porous silica gel. A silicic acid solution is added below and heated, and the pores between the primary particles of the particles made of the irregularly shaped porous silica gel are filled by a reaction with the silicic acid contained in the silicic acid solution, and the particles grow while keeping the irregular shape. Step (b) of forming irregularly shaped silica particles having a smaller weight average particle diameter than the irregularly shaped porous silica gel particles , and concentrating and recovering the silica particles containing the grown irregularly shaped silica particles. This method includes step c.

[Step a]
This process uses porous silica gel as a starting material. The porous silica-based gel is not limited to silica gel, but may be a composite gel such as silica-alumina gel, silica-titania gel, silica-zirconia gel, etc., as long as it is a porous silica-based gel. Further, the gel state may be a hydrogel, a xerogel, or an organogel. Then, such a porous silica-based gel is wet-disintegrated under alkaline conditions to form a solution containing particles of irregularly shaped porous silica-based gel. By pulverizing porous silica-based gel and using it as seed particles, the seed particles also become porous, and the seed particles are rarely truly spherical and are irregularly shaped particles. This tendency is remarkable when seed particles with a large particle size are prepared by pulverization, and when the seed particles are pulverized to a smaller seed size, the degree of irregularity tends to be lowered. In the subsequent step b, the silicic acid solution to be added is deposited while penetrating into the silica surface and several tens of nanometers inside the irregularly shaped porous silica gel particles (seed particles), and the difference in solubility affects the particle size. The silicic acid preferentially reacts with the pores that do not exist, filling the pores, and depositing silica on the outer surface of the particles, promoting particle growth (in the following description, this is referred to as build-up). Due to this build-up, the convex parts on the outer surface of the particle contribute more to the increase in the outer diameter, and the concave parts contribute less to the outer shape, so the strength of the growing particle increases and the irregular shape of the particle is suppressed from collapsing. It is possible to produce irregularly shaped silica particles with large diameters. Note that when building up seed particles with a large particle size (for example, seed particles with a particle size of 60 nm or more), the silicic acid solution can only penetrate into the pores of several nanometers to several tens of nanometers, so it fills the surface several tens of nanometers. After that, silica will only be deposited on the outer surface of the grain, leaving pores inside. Seed particles with a large particle size have a high degree of irregularity, and by buildup, form irregularly shaped silica particles having a structure having a core having pores inside and a covering silica layer covering the core. On the other hand, when seed particles with a small particle size are built up, most of the pores between the primary particles are filled with silica, and there is a strong tendency for the particle to become close to dense silica-based particles.

Further, in the present invention, porous silica gel is used as a manufacturing raw material, but since this silica gel is porous, its strength is weak. Therefore, even if porous silica-based gel is crushed so that the weight average particle diameter is several hundred nm, fine particles of about several tens of nanometers are also generated at the time of crushing. Therefore, when porous silica-based gel is used as a manufacturing raw material, the particles obtained by pulverization range from small particles to large particles. As mentioned above, those that have built up seed particles with a large particle size have a structure with internal pores, while those that have built up seed particles that have a small particle size have a structure that has internal pores. It tends to fill up easily. Therefore, the silica-based particles of the present invention have a large weight-average particle diameter and also contain fine particles, resulting in high skewness and kurtosis.

The porous silica-based gel used as a manufacturing raw material here is preferably a gel that is easily crushed, such as a wet hydrogel obtained by washing a gel by the water glass method, a xerogel, a white carbon, a gel by the alkoxide method, etc. Since the gel produced by the alkoxide method has fewer hydroxyl groups to be dehydrated and condensed, the dry powder thereof is soft and can be used as a dry powder with good productivity. It is preferable that the particle size distribution of the irregularly shaped porous silica gel particles obtained by crushing the porous silica gel is controlled within a certain range. This is not preferable because it takes time to crush and tends to have a wide particle size distribution.

Pore volume and specific surface area are listed as parameters indicating the porosity of porous silica-based gels, and in the case of open pores, the specific surface area and pore volume are approximately proportional if the pore diameters are the same. In the present invention, specific surface area (SA) was used as a parameter indicating the porosity of the porous silica gel.

The porous silica gel used in the present invention preferably has a specific surface area in the range of 50 to 800 m ² /g. When the specific surface area is smaller than 50 m ² /g, there are few pores between the primary particles of the porous silica gel, so a silicic acid solution is added to the solution containing particles of irregularly shaped porous silica gel obtained by crushing. When this happens, the amount of silicic acid that permeates into the pores between the primary particles of particles made of irregularly shaped porous silica gel is small, and these pores become difficult to fill due to the reaction with silicic acid. It tends to be consumed so that the particles grow round, making it difficult to maintain the irregular shape. In addition, if the specific surface area is larger than 800 m ² /g, the particle strength is too weak, and the inside of the particle made of the irregularly shaped porous silica gel obtained by crushing is built up by reaction with silicic acid and partially buried. However, it tends to be difficult to obtain irregularly shaped silica particles with sufficient strength.
The size (particle diameter) of the porous silica gel is preferably in the range of 1 μm to 10 mm.

The porous silica gel is wet-pulverized under alkaline conditions to produce particles of irregularly shaped porous silica gel. In particular, relatively soft silica gel with a specific surface area of about 50 to 800 m ² /g is used. Particles made of irregularly shaped porous silica gel can be suitably prepared by simultaneously performing deformation and crushing under strong shear such as a bead mill. For crushing, it is preferable to use, for example, a sand mill crusher or bead mill containing a glass media. It is preferable to perform crushing multiple times.

Normally, when grinding powder with a bead mill, the particle size of the powder decreases in proportion to the grinding time, but for soft materials with a high surface area such as silica gel, the particle size changes with the grinding time. The process is slow, and the weight average particle diameter is crushed into particles with a weight average particle size of about 60 to 550 nm, and the particles made of this irregularly shaped porous silica gel maintain the specific surface area before crushing, and there are no necks or fine particles between the primary particles. It has a rough structure with many pores. Therefore, even if these particles are used as they are as an abrasive, they tend to crumble due to insufficient strength, and only a very low polishing rate can be obtained. Therefore, in the present invention, in the subsequent step b, a silicic acid solution is added to a solution containing particles made of irregularly shaped porous silica gel to close the pores between the primary particles inside the particles made of irregularly shaped porous silica gel. The strength of the particles is increased by building up and filling them with silicic acid solution. Here, the silicic acid solution used for build-up may be derived from alkoxide, sodium silicate, or silicate amine. Furthermore, the material is not limited to silicic acid as long as it can fill the spaces between primary particles, and silicates such as alkali salts of silicic acid and alkaline earth salts may be used.

In step a, the porous silica gel is wet-disintegrated under alkaline conditions, and the alkalinity is preferably in the range of pH 8.0 to 11.5. As the pH falls below the alkaline range, the negative potential gradually decreases, and the particles become unstable in the neutral to acidic ranges, so particles generated by disintegration cannot exist stably and tend to aggregate immediately. Furthermore, if the pH is over 11.5, the dissolution of silica is promoted, so there is a tendency for silica to aggregate. The pH during the wet crushing is preferably in the range of 8.5 to 11.0.
Note that the method for adjusting the pH here is not particularly limited. For example, it can be adjusted by adding sodium hydroxide or the like.

The weight average particle diameter of the particles made of irregularly shaped porous silica gel obtained by the wet crushing is preferably in the range of 60 to 550 nm. If the weight average particle diameter of the particles made of irregularly shaped porous silica gel is smaller than 60 nm, it may be difficult to make the particles suitable for use as an abrasive material even if a silicic acid solution is subsequently added to grow the particles. be. Furthermore, if the weight average particle diameter of the particles made of irregularly shaped porous silica gel is larger than 550 nm, the particle diameter may exceed a particle diameter suitable for an abrasive material, which is not very preferable. Coarse particles that exceed the particle size suitable for such an abrasive may cause scratches. Although coarse particles and large particles tend to be preferentially crushed by crushing, centrifugation may be performed for the purpose of removing coarse particles remaining in the irregularly shaped porous silica gel. The weight average particle diameter of the particles made of the irregularly shaped porous silica gel is preferably in the range of 60 to 400 nm.

Here, the weight average particle diameter of the particles made of irregularly shaped porous silica gel means the value obtained by measuring by the same method as the weight average particle diameter (D ₁ ) of the silica particle group described above. .

Note that this crushing can be performed in multiple stages using media of different materials and sizes. For example, when a porous silica gel is crushed using a large zirconia media, the first stage crushing can be performed at high speed and in a short time due to the strong shearing force. Next, when a second stage of crushing is performed using a glass media smaller in size than the first stage, crushing proceeds with a moderate shearing force, and the desired particle size can be adjusted. At this time, since the primary particles are destroyed starting from the weaker strength portions, they tend to become smaller and irregularly shaped. In addition, since wet crushing is carried out under alkaline conditions, some of the particles made of irregularly shaped porous silica gel dissolve, preferentially filling the necks between primary particles, so there is no excessive Miniaturization is not progressing.

[Step b]
In this process, a silicic acid solution is added under alkaline conditions to a solution containing particles made of irregularly shaped porous silica gel, and the silicic acid solution is heated to form pores between the primary particles of the irregularly shaped porous silica gel particles. This is a build-up process in which particles are filled in by reaction and grow while maintaining their irregular shape. The SiO ₂ concentration of the solution containing particles made of the irregularly shaped porous silica gel is preferably in the range of 1 to 10% by mass. If the SiO ₂ concentration of the solution containing particles made of irregularly shaped porous silica gel is less than 1% by mass, the efficiency of producing irregularly shaped silica particles tends to decrease. Furthermore, if the SiO ₂ concentration is more than 10% by mass, minute silica nuclei are generated, the irregular shape cannot be maintained, and the particle growth of irregularly shaped silica particles tends to become non-uniform.
Note that this step b may be carried out by adding a silicic acid solution while hydrothermally treating the particles made of irregularly shaped porous silica gel. In this method, the silica becomes supersaturated with the added silicic acid solution, and some of the particles also dissolve, causing silica to deposit and grow. Pores between particles are filled preferentially.

The heating temperature is preferably in the range of 60°C to 170°C. This is because if the temperature is lower than 60°C, the growth of particles made of irregularly shaped porous silica gel tends to be slow, and if it is higher than 170°C, the obtained irregularly shaped silica particles tend to be spherical. The heating temperature is more preferably in the range of 60°C to 100°C.

Further, the pH when adding the silicic acid solution to the solution containing particles of irregularly shaped porous silica gel is preferably in the range of 9 to 12.5. If the pH is less than 9, the solubility of silica is low, so the degree of supersaturation becomes extremely high, and the added silicic acid solution is not consumed by particle growth and tends to be produced as fine particles. Furthermore, since the negative potential becomes low, particles tend to aggregate. Furthermore, since the hydroxyl groups are insufficiently dissociated, the reactivity with primary particles is reduced, and the neck portion is not sufficiently reinforced. Furthermore, if the pH is higher than 12.5, the dissolution of silica may be promoted.

The pH of the solution containing particles made of irregularly shaped porous silica gel is adjusted as necessary to keep the pH within the above-mentioned range. Although there are no particular restrictions on the adjustment means, the adjustment is usually made by adding an alkaline substance. Examples of such alkaline substances include sodium hydroxide and water glass. A pH range of 9.5 to 12.0 is recommended when the silicic acid solution is added to a solution containing particles of irregularly shaped porous silica gel.

The amount of the silicic acid solution added is preferably in a range such that the SiO ₂ molar concentration of the silicic acid solution is 0.5 to 20 times the SiO ₂ molar concentration of the solution containing particles made of the irregularly shaped porous silica gel. If the amount of silicic acid solution added is less than the above range, the strength between the primary particles cannot be sufficiently increased, and the coating silica layer will not have a sufficient thickness, so the strength of the particles will tend to decrease. be. Furthermore, when particles are grown by adding a silicic acid solution, the degree of irregularity and aspect ratio usually decrease, but if the amount of the silicic acid solution added is larger than the above range, the degree of irregularity of the particles decreases significantly, and the desired degree of irregularity is reduced. This is because there is a tendency that the degree of abnormality cannot be maintained. Furthermore, during particle growth, the small particle component grows preferentially compared to the large particle component, so if the amount of silicic acid solution added is greater than the above range, it is difficult to obtain a small particle component with the desired aspect ratio. There is a tendency to
Further, it is desirable to add the silicic acid solution continuously or intermittently.

The silicic acid solution permeates into the inside of the particles made of irregularly shaped porous silica gel through the pores between the primary particles, and is deposited on the neck portions of the particles to reduce the specific surface area, thereby increasing the strength of the particles. In this step b, it is desirable that the specific surface area of the particles made of irregularly shaped porous silica gel is 182 m ² /g or less, more preferably in the range of 9 m ² /g to 136 m ² /g. If the specific surface area of the particles made of irregularly shaped porous silica gel is larger than 182 m ² /g, the obtained irregularly shaped silica particles will lack strength and tend to crumble when used as abrasive grains, resulting in a slow polishing rate. .
The specific surface area of the particles made of irregularly shaped porous silica gel is measured by the BET method as described in "Measurement of Specific Surface Area" in Examples below.

The silicic acid liquid dropped from the outside uniformly falls from the liquid phase onto the surface of the irregularly shaped porous silica gel, binds to the outer surface of the particles made of irregularly shaped porous silica gel, and grows the outer shape of the particle. It is possible to obtain irregularly shaped silica particles with a large particle size while maintaining the irregular shape .
Here, the weight average particle diameter of the irregularly shaped silica particles means a value obtained by measurement using the same method as the weight average particle diameter (D ₁ ) of the silica particle group described above.

[Step c]
This step is a step of concentrating and recovering the silica particles containing the grown irregularly shaped silica particles. Specifically, for example, a solution containing grown irregularly shaped silica particles is cooled to about room temperature to 40°C, concentrated using an ultrafiltration membrane, etc., and further concentrated using an evaporator etc. to remove the remaining silica particles. All you have to do is collect the particle group. In order to further remove coarse particles, centrifugation may be performed. Concentration is preferably performed using an ultrafiltration membrane from the viewpoint that coarse agglomerates are less likely to occur due to drying.

Examples of the present invention will be shown below along with comparative examples. In the Examples and Comparative Examples, the specific surface area of the silica particles was measured, the specific surface area equivalent particle diameter (D ₂ ) was calculated, the weight average particle diameter (D ₁ ) was measured, and the projected area equivalent particle diameter (D ₃ ), calculation of skewness and kurtosis in volume-based particle size distribution, waveform separation of volume-based particle size distribution, measurement of volume in volume-based particle size distribution, calculation of aspect ratio of small particle side component, coefficient of variation calculation, measurement and calculation of the average area (S ₁ ) and the area of a circle equivalent to the average outer circumference (S ₂ ), measurement and calculation of the average pore diameter of the core internal pores of irregularly shaped silica particles, Measurement and calculation of the average thickness of the coated silica layer and polishing test were performed as follows.

[Measurement of specific surface area]
For Examples 1 to 4 and Comparative Examples 3 to 5, the specific surface area was measured and calculated by the BET method. Specifically, 50 ml of the silica sol to be measured was adjusted to pH 3.5 with nitric acid, 40 ml of 1-propanol was added thereto, and the sample was dried at 110°C for 16 hours. After pulverizing in a mortar, the sample was ground in a muffle furnace. The sample was baked at 500° C. for 1 hour to prepare a measurement sample. Then, using a specific surface area measuring device (manufactured by Yuasa Ionics, model number Multisorb 12), the specific surface area was calculated from the amount of nitrogen adsorbed using the BET one-point method using the nitrogen adsorption method (BET method).
In the specific surface area measurement device, 0.5 g of the sample after firing is placed in a measurement cell, degassed for 20 minutes at 300°C in a mixed gas flow of 30v% nitrogen/70v% helium, and then the sample is placed in the above mixed gas. The sample was maintained at liquid nitrogen temperature in an air stream to allow equilibrium adsorption of nitrogen onto the sample. Next, the sample temperature was gradually raised to room temperature while flowing the above-mentioned mixed gas, and the amount of nitrogen desorbed during this time was detected, and the specific surface area of the silica fine particles in the sample was calculated using a calibration curve prepared in advance.
In addition, for Comparative Examples 1, 2, and 6 in which porous silica-based gel was crushed (build-up was not performed), the specific surface area was measured and calculated by the titration method. Specifically, a sample equivalent to 1.5 g of SiO ₂ was collected in a beaker, then transferred to a constant temperature reaction tank (25°C), and purified water was added to make the liquid volume 90 ml (the following operation was carried out at 25°C). (This was carried out in a constant temperature reaction tank maintained at 0.degree. C.), and then a 0.1 mol/L aqueous hydrochloric acid solution was added to adjust the pH to 3.6. Furthermore, 30 g of sodium chloride was added, diluted to 150 ml with pure water, and stirred for 10 minutes. Then, a pH electrode was set, and while stirring, 0.1 mol/L sodium hydroxide solution was added dropwise to adjust the pH to 4.0. Furthermore, the sample adjusted to pH 4.0 was titrated with 0.1 mol/L sodium hydroxide solution, and the titration amount and pH value in the range of pH 8.7 to 9.3 were recorded at 4 or more points. A calibration curve was prepared by setting the titration amount of 1 mol/L sodium hydroxide solution as X and the pH value at that time as Y. Then, the consumption amount of 0.1 mol/L sodium hydroxide solution required for pH 4.0 to 9.0 per 1.5 g of SiO ₂ is determined from the predetermined formula, and using this, the specific surface area is determined according to the predetermined formula. I asked for

[Calculation of specific surface area equivalent particle diameter (D ₂ )]
Using the specific surface area (SA) measured by the above method and the particle density (ρ = 2.2), calculate the specific surface area equivalent particle diameter (D ₂ ) from the formula D ₂ = 6000/(SA x ρ). did.

[Measurement of weight average particle diameter (D ₁ )]
The silica-based particle dispersion was diluted with a 0.05% by mass aqueous sodium dodecyl sulfate solution to give a solid content concentration of 2% by mass, and then transferred to a disk centrifugal particle size distribution analyzer (model number: DC24000UHR, manufactured by CPS instruments). , 0.1 ml was injected with a syringe, and the weight average particle diameter (D ₁ ) was measured at 18,000 rpm in a density gradient solution of 8 to 24 mass % sucrose. Disintegrated products of porous silica gel (particles made of irregularly shaped porous silica gel) were also measured in the same manner.

[Measurement and calculation of projected area equivalent particle diameter (D ₃ )]
The projected area equivalent particle diameter (D ₃ ) of the silica-based particles was measured and calculated by an image analysis method. Specifically, first, using a scanning electron microscope (SEM), arbitrary points on the surface of the silica-based particles were photographed at 3000x magnification, with an area of 1.1 x 10 ^-3 mm ² per field, for 15 fields. . Then, for all the silica particles included in each image taken in each field of view, the projected area of each particle is measured by an image analysis method using an image analysis system, and the area corresponding to each measured area is measured. The particle diameter (diameter of a circle) of the circular particles was calculated, and the number average thereof was defined as the projected area equivalent particle diameter (D ₃ ).

[Calculation of kurtosis and skewness in volume-based particle size distribution]
The volume-based particle size distribution was also measured by the method using the disk centrifugal particle size distribution measuring device described above. Then, using the obtained volume-based particle size distribution data, JMP Ver. Kurtosis and skewness were calculated using 13.2. In addition, in the volume-based particle size particle size distribution, when the frequency of a predetermined particle size was a negative value, the frequency was calculated as zero.

[Waveform separation of volume-based particle size distribution]
The aforementioned volume-based particle size distribution measurement data was analyzed using a peak analyzer of the graph creation/data analysis software Origin (manufactured by OriginLab Corporation). First, set the baseline to 0 and the peak type to Gaussian, select the maximum point of the particle size distribution as the peak position, perform peak fitting without weighting, and check whether the calculated peak deviates from conditions 1 and 2 below. If there was a deviation, the peak position was shifted to an arbitrary position within the distribution range and peak fitting was repeated until Conditions 1 and 2 below were satisfied. Thereafter, if the corrected R-squared value was 0.99 or less, a peak was added at any position within the distribution range, and peak fitting was repeated until the corrected R-squared value became 0.99 or higher. The number of separated peaks at this time was defined as the number of peaks.
Condition 1: Each calculated peak does not take a value larger than the original distribution.
Condition 2: Each calculated peak does not take a negative value.

[Measurement of volume in volume-based particle size distribution]
The total volume (Q ₁ ) in the volume-based particle size distribution of the silica-based particles, the volume ratio of each component of the separated peak obtained as a result of waveform separation, the volume ratio of the largest particle component, and the volume ratio of particles of 0.7 μm or more. The volume (Q ₂ ) was measured using the disk centrifugal particle size distribution measuring device described above.

[Aspect ratio calculation of small particle side component]
The aspect ratio of the small particle side component is determined by counting the total number of particles in the silica particle group using a scanning electron microscope (SEM) and an image analysis system, calculating the area of each particle, and calculating the area equal to that area. Find the diameter of the circle and use it as the particle size. Then, arrange the obtained particle diameters in order of size, count up to 1/3 of the number of particles from the small side as the small particle side component, and average the aspect ratio (length/breadth ratio of the smallest inscribed square). The value was defined as the "aspect ratio of the small particle side component."

[Calculation of coefficient of variation]
The coefficient of variation of the volume ratio of each component of the separation peak obtained as a result of waveform separation of the volume-based particle size distribution of the silica-based particle group, and the coefficient of variation of the particle size of the volume-based particle size distribution are the volume-based particle size described above. The standard deviation and average value were calculated from the distribution measurement data, the standard deviation was divided by the average value, and the result was expressed as a percentage.

[Measurement and calculation of the average area (S ₁ ) and the area of a circle equivalent to the average circumference (S ₂ )]
The average area (S ₁ ) and the area of a circle equivalent to the average outer circumference (S ₂ ) of the silica-based particles were measured by an image analysis method. Specifically, first, using a scanning electron microscope (SEM), arbitrary points on the surface of the silica-based particles were photographed at 3000x magnification, with an area of 1.1 x 10 ^-3 mm ² per field, for 15 fields. . Then, the area and outer circumference of all the silica particles included in each image taken in each field of view are measured by an image analysis method using an image analysis system, and the area and outer circumference of each measured area and each outer circumference are measured. Calculate the average area (S ₁ ) and average perimeter length (simple average value) from the data, and from this average perimeter length, calculate the area ( S ₂ ) was calculated.

[Measurement and calculation of the average pore diameter of the core internal pores of irregularly shaped silica particles and the average thickness of the covering silica layer]
The average pore diameter of the core internal pores of the irregularly shaped silica-based particles and the average thickness of the covering silica layer were measured and calculated as follows. First, the irregularly shaped silica particles were observed using a transmission electron microscope (TEM) at a magnification of 200,000 times. A point for equal division was determined, two points where a straight line perpendicular thereto intersects with the outer edge of the particle were determined, and the short axis was defined between these two points. Then, the thicknesses of the covering silica layers on both sides of the long axis and the short axis were determined, and these were simply averaged to determine the average thickness of the covering silica layer of one particle. Similarly, the thickness of the silica layer was determined for 20 arbitrary particles, and the simple average of these was taken as the average thickness of the covering silica layer in the irregularly shaped silica particles.
Furthermore, the pore diameters existing on the long axis and the short axis were determined, and the average thereof was taken as the average pore diameter of one particle. Similarly, the pore diameters were determined for 20 arbitrary particles, and the simple average of these was determined as the average pore diameter of the irregularly shaped silica particles.
In addition, if there are no pores on the long axis or short axis, find the pore diameter of any pore, find the pore diameter of 20 arbitrary particles, and calculate the simple average of these pore diameters. This is the average pore diameter in the particles.

[Method for measuring the size of porous silica gel]
The size of the porous silica gel was measured using LA-950 manufactured by HORIBA under the following measurement conditions.
LA-950V2 version is 7.02, algorithm options are standard calculation, solid refractive index 1.450, solvent (pure water) refractive index 1.333, number of repetitions is 15, sample input bath circulation speed is 5. , the stirring speed was set to 2, and measurements were performed using a measurement sequence set in advance. Then, the measurement sample was put into the sample input port of the device as an undiluted solution using a dropper. Here, it was added so that the transmittance (R) value was 90%. After the transmittance (R) value became stable, ultrasonic waves were irradiated for 5 minutes and the particle diameter was measured.

[Method for measuring the proportion of irregularly shaped silica particles contained in a silica particle dispersion containing a silica particle group consisting of irregularly shaped silica particles and non- irregularly shaped silica particles]
In a photographic projection diagram obtained by photographing a silica-based particle dispersion at a magnification of 250,000 times (or 500,000 times) using an electron microscope (manufactured by Hitachi, Ltd., model number "S-5500"), any 100 particles The aspect ratio (length/breadth ratio of the smallest inscribed square) of each particle was determined. Particles having an aspect ratio of 1.1 or more are irregularly shaped silica particles. Then, the proportion of the irregularly shaped silica particles was determined from the number of particles having an aspect ratio of 1.1 or more and the number of measured particles (100).
The results are shown in Table 1.

[Polishing test]
Substrate to be polished
A nickel-plated aluminum substrate for hard disks (nickel-plated substrate manufactured by Toyo Kohan Co., Ltd.) was used as the substrate to be polished. This substrate is a donut-shaped substrate (outer diameter 95 mmφ, inner diameter 25 mmφ, thickness 1.27 mm).
Polishing test
344 g of 9% by mass silica-based particle dispersion was prepared, 5.65g of 31% by mass hydrogen peroxide solution was added thereto, and the pH was adjusted to 1.5 with 10% by mass nitric acid to produce a polishing slurry. .
The above-mentioned substrate to be polished was set in a polishing device (NF300 manufactured by NanoFactor), and a polishing pad (Bellatrix NO178 manufactured by FILWEL) was used.The substrate load was 0.05 MPa, the number of rotations of the surface plate was 50 rpm, and the number of head rotations. 1 μm polishing was performed at 50 rpm while supplying the polishing slurry at a rate of 40 g/min.
polishing speed
The polishing rate was calculated from the difference in weight of the polished substrate before and after polishing and the polishing time.
Stability of polishing rate
Polishing was repeated five times under the above conditions, and the coefficient of variation (CV value) of the polishing rate was calculated.
Substrate smoothness
The polished substrate obtained from the polishing test was observed using an ultrafine defect/visualization macro device (manufactured by VISION PSYTEC, product name: Maicro-Max VMX-3100), and the observation conditions were MME-250W white light at 10%. The sample was adjusted and LA-180Me was observed at 0%.
In this observation, if a defect such as a scratch exists on the substrate surface, white light is diffusely reflected, and the defective portion is observed as white. On the other hand, in areas without defects, white light is specularly reflected and the entire area is observed as black. Observations were made in this manner, and the area of defects caused by scratches (linear marks) etc. present on the substrate surface (area where the substrate was observed to be white) was evaluated according to the following criteria.
Defect area evaluation Less than 3% "Very small"
3% or more, less than 20% "Less"
20% or more, less than 40% "Many"
40% or more “Very high”
undulation
Measure an arbitrary point that divides the outer edge and inner edge of the polished donut-shaped aluminum substrate into two halves, measure the two halves on the opposite side of the measured point, and calculate the average value of these values as the measured waviness value. And so. The measurement conditions are as follows.
Equipment: ZygoNewView7200
Lens: 2.5x Zoom ratio: 1.0
Filter: 50-500μm
Measurement area: 3.75mm x 2.81mm

[Example 1]
Preparation of purified silica hydrogel
Pure water was added to 462.5 g of sodium silicate to prepare a 24% by mass sodium silicate aqueous solution in terms of SiO ₂ , and 25% by mass of sulfuric acid was added so that the pH was 4.5 to prepare a solution containing silica hydrogel. Obtained. This silica hydrogel solution was maintained at a temperature of 21° _C in a constant temperature bath, left to stand for 5.75 hours, and then aged. The purified silica hydrogel (porous silica gel) was obtained by washing with pure water until the mass % was reached. The purified silica hydrogel had a SiO ₂ concentration of 5.0% by mass, a specific surface area of 600 m ² /g, and a size of 84 μm.

Preparation of irregularly shaped porous silica gel <Unshaped porous silica gel fine particle dispersion (1)>
500 g of purified silica hydrogel having an SiO ₂ concentration of 5.0% by mass was added to a 2L glass beaker, and the pH was adjusted to 9.8 by adding a 4.8% by mass aqueous sodium hydroxide solution. 2,390 g of zirconia media with a diameter of 1.0 mm was added to this, and crushed using a sand mill until the weight average particle diameter became 530 nm ( _first stage crushing). A silica gel fine particle dispersion (1) was obtained.

<Unshaped porous silica gel particle dispersion (2)>
Next, a 4.8% by mass aqueous sodium hydroxide solution was added to the irregularly shaped silica porous silica-based gel fine particle dispersion (1) (weight average particle diameter 530 nm), the pH was adjusted to 10.0, and a glass media with a diameter of 0.25 mm was added. The dispersion was carried out until the weight average particle diameter became 225 nm to obtain a 3.0% by mass irregularly shaped porous silica gel fine particle dispersion (2).

Preparation of a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles Ion-exchanged water was added to the obtained irregularly shaped porous silica-based gel fine particle dispersion (2) to give an SiO ₂ concentration of 2.76% by mass. 2716 g of solution was obtained. Next, a 4.8% by mass aqueous sodium hydroxide solution and ion-exchanged water were added to adjust the pH to 10.7 and the SiO ₂ concentration to be 2.5% by mass. Then, the temperature was raised to 98°C and held at 98°C for 30 minutes. Next, 5573.1 g of a 4.6% by mass acidic silicic acid solution was added over 20 hours while maintaining the temperature at 98°C, and stirring was continued for 1 hour while maintaining the temperature at 98°C.
After cooling this mixture to room temperature, it was concentrated to an SiO ₂ concentration of 12% by mass using an ultrafiltration membrane (SIP-1013 manufactured by Asahi Kasei Corporation). The mixture was further concentrated to 30% by mass using a rotary evaporator to obtain a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles. The weight average particle diameter of the obtained silica-based particles was 203 nm.

[Example 2 ]
Preparation of irregularly shaped porous silica gel
<Irregular porous silica gel particle dispersion ( 3 )>
A 4.8% by mass aqueous sodium hydroxide solution was added to the irregularly shaped porous silica gel fine particle dispersion (1) obtained in Example 1 (weight average particle diameter 530 nm), the pH was adjusted to 10.0, and a 0.25 mmφ Glass media was added and the mixture was crushed until the weight average particle diameter became 167 nm to obtain a 3.0% by mass irregularly shaped porous silica gel fine particle dispersion ( 3 ).

Preparation of a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles The obtained irregularly shaped porous silica-based gel fine particle dispersion ( 3 ) was subjected to the same steps as in Example 1 to prepare irregularly shaped silica-based particles and non- irregularly shaped silica-based particles. A silica-based particle group consisting of irregularly shaped silica-based particles was prepared. The weight average particle diameter of the obtained silica-based particles was 164 nm.

[Example 3 ]
<Irregular porous silica gel particle dispersion ( 4 )>
In a 2 L glass beaker, 28 g of silica powder with a SiO ₂ concentration of 90.5% by mass, an average particle diameter of 123 μm, and a specific surface area of 403 m ² /g and 472 g of pure water were added, and a 4.8% by mass aqueous sodium hydroxide solution was added. The pH was adjusted to 10.0. 2,390 g of zirconia media with a diameter of 1.0 mm was added to this, and crushed in a sand mill until the weight average particle diameter became 314 nm (first stage crushing), resulting in irregularly shaped porous particles with a SiO ₂ concentration of 4.0% by mass. A silica gel fine particle dispersion ( 4 ) was obtained.

<Irregular porous silica gel particle dispersion ( 5 )>
Next, 1135 g of glass media with a diameter of 0.25 mm was added to the irregularly shaped porous silica-based gel fine particle dispersion ( 4 ), and crushed until the weight average particle diameter became 208 nm (second stage crushing), and the SiO ₂ concentration was 3. 1900 g of irregularly shaped porous silica-based gel fine particle dispersion ( 5 ) of .5% by mass was obtained.

Preparation of a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles The obtained irregularly shaped porous silica-based gel fine particle dispersion ( 5 ) was subjected to the same process as in Example 1 to prepare irregularly shaped silica-based particles and non- irregularly shaped silica-based particles. A silica-based particle group consisting of irregularly shaped particles was prepared. The weight average diameter of the obtained silica-based particles was 128 nm.

[Example 4 ]
<Irregular porous silica gel particle dispersion ( 6 )>
In a 2 L glass beaker, 28 g of silica powder with a SiO ₂ concentration of 90.7% by mass, an average particle diameter of 12 μm, and a specific surface area of 354 m ² /g and 472 g of pure water were added, and a 4.8% by mass sodium hydroxide aqueous solution was added. The pH was adjusted to 10.0. To this was added 1135 g of glass media with a diameter of 0.25 mm, and the mixture was crushed in a sand mill until the weight average particle diameter became 200 nm, resulting in a dispersion of irregularly shaped porous silica-based gel fine particles with an SiO ₂ concentration of 4.0% by mass ( 6 ) was obtained.

Preparation of a silica-based particle group consisting of irregular-shaped silica-based particles and non-irregular silica-based particles The obtained irregular-shaped porous silica-based gel fine particle dispersion ( 6 ) was subjected to the same process as in Example 1 to prepare irregularly shaped silica-based particles and non-irregular silica-based particles. A silica-based particle group consisting of irregularly shaped particles was prepared. The weight average diameter of the obtained silica-based particles was 101 nm.

[Comparative example 1]
1135 g of glass media with a diameter of 0.25 mm was added to the irregularly shaped silica porous silica gel fine particle dispersion (1) obtained in Example 1, and the mixture was crushed until the weight average particle diameter became 248 nm (second stage crushing). ), Comparative Example 1 was obtained by concentrating a irregularly shaped porous silica gel fine particle dispersion with an SiO ₂ concentration of 3.5% by mass to an SiO ₂ concentration of 9% by weight using an ultrafiltration membrane (SIP-1013 manufactured by Asahi Kasei Corporation). And so.

[Comparative example 2]
The purified silica hydrogel obtained in Example 1 with a SiO ₂ concentration of 5.0% by mass was dried overnight in a dryer at 100°C, ground in an agate mortar, and baked at 550°C for 2 hours to obtain a specific surface area of 200 m ² /g of silica gel was obtained. Pure water was added to this to obtain a 9% by mass silica-based gel dispersion, which was designated as Comparative Example 2.

[Comparative example 3]
“Cataroid SI-80P” (manufactured by JGC Catalysts & Chemicals Co., Ltd.; silica concentration: 40% by mass), which is a dispersion liquid in which fine silica particles are dispersed, was used as Comparative Example 3.

[Comparative example 4]
“SS-160” (manufactured by JGC Catalysts & Chemicals Co., Ltd., silica concentration 20% by mass), which is a dispersion liquid in which fine silica particles are dispersed, was used as Comparative Example 4.

[Comparative example 5]
“SS-300” (manufactured by JGC Catalysts & Chemicals Co., Ltd., silica concentration 20% by mass), which is a dispersion liquid in which fine silica particles are dispersed, was used as Comparative Example 5.

[Comparative example 6]
The purified silica hydrogel with an SiO ₂ concentration of 5.0% by mass obtained in Example 1 was added to a 2 L glass beaker, and a 4.8% by mass aqueous sodium hydroxide solution was added to adjust the pH to 9.8. To this was added 2390 g of zirconia media with a diameter of 1.0 mm, and the mixture was crushed using a sand mill until the average particle diameter was 664 nm. The obtained silica hydrogel fine particle dispersion had a SiO ₂ concentration of 4.0% by mass. This silica hydrogel fine particle dispersion was concentrated to an SiO ₂ concentration of 9% by mass using an ultrafiltration membrane to obtain a silica hydrogel fine particle dispersion (5). This was designated as Comparative Example 6.

The aforementioned measurement and calculation data for Examples 1 to 4 and Comparative Examples 1 to 6 are summarized in Tables 1 and 2 below. The silica-based particle groups of Examples 1 to 4 obtained by a predetermined manufacturing method have a particle size, particle size distribution, and degree of irregularity suitable for use as an abrasive, and silica-based particles containing these silica-based particle groups When the dispersion liquid is used as a polishing abrasive dispersion liquid, a high polishing rate can be obtained, and at the same time, high surface precision can be achieved.

The silica-based particles of the present invention have suitable particle size, particle size distribution, degree of irregularity, and particle strength. It can be preferably used for surface polishing of substrates, etc.

Claims (15)

A silica-based particle dispersion containing a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles,
The irregularly shaped silica particles have a core having pores inside and a covering silica layer covering the core,
The silica-based particle group is a silica-based particle dispersion that satisfies the following [1] to [3].
[1] The weight average particle diameter (D ₁ ) is 60 to 600 nm, and the specific surface area equivalent particle diameter (D ₂ ) is 15 to 300 nm.
[2] The degree of irregularity D (D=D ₁ /D ₃ ) expressed as the ratio of the weight average particle diameter (D ₁ ) to the projected area equivalent particle diameter (D ₃ ) is in the range of 1.1 to 5.0. What's in it.
[3] Waveform separation of the volume-based particle size distribution results in a multimodal distribution in which three or more separated peaks are detected. The silica-based particle dispersion according to claim 1, wherein the average pore diameter of the internal pores of the core is 30 nm or less. The silica-based particle dispersion according to claim 1 or 2, wherein the coating silica layer has an average thickness in the range of 1 to 50 nm and contains silica as a main component. The silica-based particle dispersion according to any one of claims 1 to 3, wherein the silica-based particle group has a skewness in the range of -20 to 20 in its volume-based particle size distribution. According to any one of claims 1 to 4, the volume ratio of the largest particle component among the separated peaks obtained as a result of waveform separation of the volume-based particle size distribution of the silica-based particle group is 75% or less. The silica-based particle dispersion described above. Any one of claims 1 to 5, characterized in that, in the number-based particle size distribution obtained by SEM image analysis of the silica-based particle group, the aspect ratio of the small particle side component is in the range of 1.05 to 5.0. A silica-based particle dispersion liquid described in Crab. The silica-based particle dispersion liquid according to any one of claims 1 to 6, characterized in that the particle size variation coefficient of the volume-based particle size distribution of the silica-based particle group is 30% or more. Smoothness S ₍ S= _{S 2 /} S The silica-based particle dispersion according to any one of claims 1 to 7, characterized in that ₁ ) is in the range of 1.1 to 5.0. In the volume-based particle size distribution of the silica-based particle group, the ratio Q (Q=Q ₂ /Q _{1 ) of the volume (Q 2 )} of particles of 0.7 μm or more to the total volume (Q ₁ ) is 5.0% or less The silica-based particle dispersion according to any one of claims 1 to 8, characterized in that: A polishing abrasive grain dispersion comprising the silica-based particle dispersion according to any one of claims 1 to 9. A silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles,
The irregularly shaped silica particles have a core having pores inside and a coating silica layer covering the core, and satisfy the following [1] to [3].
[1] The weight average particle diameter (D ₁ ) is 60 to 600 nm, and the specific surface area equivalent particle diameter (D ₂ ) is 15 to 300 nm.
[2] The degree of irregularity D (D=D ₁ /D ₃ ) expressed as the ratio of the weight average particle diameter (D ₁ ) to the projected area equivalent particle diameter (D ₃ ) is in the range of 1.1 to 5.0. What's in it.
[3] Waveform separation of the volume-based particle size distribution results in a multimodal distribution in which three or more separated peaks are detected. A method for producing a silica-based particle group consisting of irregularly shaped silica-based particles and non- irregularly shaped silica-based particles, the method comprising the following steps a to c.
(Step a) A step of wet-pulverizing the porous silica gel under alkaline conditions to obtain a solution containing particles of irregularly shaped porous silica gel.
(Step b) A silicic acid solution is added and heated under alkaline conditions to a solution containing particles made of the irregularly shaped porous silica gel, and the pores between the primary particles of the irregularly shaped porous silica gel are A step of growing particles with irregular shapes while filling them by a reaction with silicic acid contained in a silicic acid solution to produce irregularly shaped silica particles having a smaller weight average particle diameter than the particles made of the irregularly shaped porous silica gel .
(Step c) A step of concentrating and collecting the silica-based particles containing the grown irregularly shaped silica-based particles. In step a, the porous silica gel having a specific surface area of 50 to 800 m ² /g is made into particles of the irregularly shaped porous silica gel having a weight average particle diameter of 60 to 550 nm;
In step b, the pores between the primary particles of the particles made of the irregularly shaped porous silica gel are filled by reaction with the silicic acid so that the specific surface area of the particles made of the irregularly shaped porous silica gel is 182 m ² /g or less. 13. The method for producing a silica-based particle group comprising irregular-shaped silica-based particles and non-irregular-shaped silica-based particles according to claim 12 , wherein the irregular-shaped silica-based particles are grown. In step a, the porous silica-based gel is wet-disintegrated under alkalinity at pH 8.0 to 11.5 to obtain the irregularly shaped porous silica-based gel having a weight average particle diameter of 167 to 200 nm or 208 to 225 nm. to a solution containing particles of
In step b, the SiO ₂ concentration of the solution containing particles made of the irregularly shaped porous silica gel is set to 1 to 10% by mass, heated to 60° C. to 170° C., and under alkaline pH of 9 to 12.5. The silicic acid solution is added continuously or intermittently to fill the pores between the primary particles of the particles made of the irregularly shaped porous silica gel by reaction with the silicic acid, thereby reducing the specific surface area of the particles. If the particles made of the irregularly shaped porous silica gel have a weight average particle diameter of 167 to 200 nm, the irregularly shaped silica particles having a weight average particle diameter of 101 to 164 nm, the irregularly shaped porous silica gel When the weight average particle diameter of the gel particles is 208 to 225 nm, the irregularly shaped silica particles have a weight average particle diameter of 128 to 203 nm,
Irregular-shaped silica-based particles according to claim 12 or 13, characterized in that in the step c, a solution containing the grown irregular-shaped silica-based particles is concentrated to recover a silica-based particle group containing the irregular-shaped silica-based particles. and a method for producing a silica-based particle group consisting of non-irregularly shaped silica-based particles. In step b, the amount of the silicic acid solution added is such that the SiO ₂ molar concentration of the silicic acid solution is 0.5 to 20 times the SiO ₂ molar concentration of the solution containing particles made of the irregularly shaped porous silica gel. The method for producing a silica-based particle group comprising irregularly shaped silica-based particles and non- irregularly shaped silica-based particles according to any one of claims 12 to 14, wherein the range is as follows.