Method for manufacturing a silica fine particle dispersion for polishing.

Abstract

To provide a method for producing a silica fine particle dispersion liquid for polishing that exhibits excellent polishing speed and can suppress scratch generation on a substrate to be polished when applied to polishing applications. 【Solution means】A method for producing a silica fine particle dispersion liquid for polishing, comprising steps 1 to 4. (Step 1) Introduce an acidic silicic acid solution and an alkali into a reaction vessel (X) maintained in a non-heated state to obtain a first blended liquid. Subsequently, heat to a predetermined temperature and, while maintaining the same temperature range, add an acidic silicic acid solution, age, and obtain a precursor dispersion liquid. (Step 2) Introduce the precursor dispersion liquid and pure water into a reaction vessel (Y) maintained in a non-heated state to obtain a second blended liquid. (Step 3) Add an acidic silicic acid solution and an alkali to the second blended liquid, and while proceeding with the reaction, concurrently extract a part of the solution. (Step 4) Age the remaining solution, solution A, at a predetermined temperature, and mix solution A with solution B, which is the solution extracted in Step 3.

Description

Technical Field

[0001] The present invention relates to a method for producing a silica fine particle dispersion suitable for polishing various electronic materials such as silicon wafers, silicon carbide wafers, sapphire wafers, compound semiconductor wafers, or magnetic disks.

Background Art

[0002] Conventionally, silica sols, fumed silica, fumed alumina, etc. have been used as polishing particles. In the production of a substrate with an integrated circuit of a semiconductor, an aluminum wiring is formed on a silicon wafer, and an oxide film such as silica is provided thereon as an insulating film. In this case, unevenness is caused by the wiring, so this oxide film is polished and planarized. In the polishing of such a substrate, the surface after polishing is flat without steps or unevenness, and is smooth without micro scratches, and a high polishing rate is required.

[0003] As a method for obtaining a high polishing rate, it is common to use abrasive grains of a large size. However, if the particle size of the abrasive grains becomes too large, the flatness of the surface of the substrate after polishing tends to deteriorate. Therefore, in order to obtain a high polishing rate without deteriorating the flatness of the surface, it is known that it is effective to make the abrasive grains non-spherical, that is, to make the abrasive grains into particles of a non-regular shape (irregular particles). As a method for obtaining irregularly shaped particles of a large size, as in Patent Document 1, porous silica gel is pulverized by a bead mill or the like to prepare irregular porous gel, and this irregular porous gel is grown into particles by silicic acid or the like, whereby a method for obtaining irregularly shaped particles having a large size and a high degree of irregularity is known.

[0004] Also, as another method of obtaining a high polishing rate, it is known that applying particles with a wide particle size distribution is also useful. As a method of manufacturing particles with a wide particle size distribution, as in Patent Document 2, while continuously adding a predetermined silica sol to a stirred and heated reaction vessel and adding silicic acid to the reaction vessel to grow particles, a production method is carried out in which the reaction solution is continuously withdrawn from an overflow line, and a method of obtaining a silica sol with a broad particle size distribution is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The异形particles (non-spherical particles) described in Patent Document 1 have a relatively high polishing rate when applied to polishing applications compared to spherical particles. However, the异形particles described in Patent Document 1 have problems that the surface roughness and surface undulation of the polished substrate after polishing are likely to deteriorate, and scratches are likely to occur. In addition, when attempts were made to manufacture异形particles a plurality of times by the manufacturing method described in Patent Document 1, it was found that there are problems in that the reproducibility of the particle size is poor and the polishing performance is likely to vary.

[0007] The perfectly spherical silica nanoparticles with a broad particle size distribution described in Patent Document 2 exhibit superior polishing speed compared to perfectly spherical silica nanoparticles with a sharp particle size distribution. However, it was known that even silica nanoparticles with a broad particle size distribution could not match the polishing speed of silica nanoparticles with irregular shapes. Furthermore, the method for producing perfectly spherical silica nanoparticles with a broad particle size distribution described in Patent Document 2 requires the simultaneous and strict control of three elements (seed particles (or seed particle dispersion), acidic silicic acid solution, and alkaline components) in a reaction vessel, resulting in a heavy equipment load and complicated production management. In addition, when the authors actually conducted trace experiments, they found that although the particle size distribution was broad, the distribution was tailed, with larger particles being more prominent. Therefore, even if the average particle size was of a desirable size, the silica nanoparticles contained some extremely large particles ranging from several hundred nanometers to microns in size, resulting in a high degree of scratching.

[0008] The present invention aims to provide a method for producing a silica fine particle dispersion for polishing that exhibits excellent polishing speed and suppresses scratch generation on the substrate to be polished when applied to polishing applications. [Means for solving the problem]

[0009] According to one aspect of the present invention, a method for producing a silica fine particle dispersion for polishing is provided, comprising the following steps 1 to 4. (Process 1) The process involves introducing an acidic silica solution and an alkali into a reaction vessel (X) kept unheated, stirring uniformly to obtain a first preparation solution, then heating to a temperature of 40°C to 98°C and maintaining that temperature range, and then continuously or intermittently adding the acidic silica solution while maintaining that temperature range, followed by aging at a temperature of 40°C to 98°C for 20 minutes to 120 minutes to obtain a silica nanoparticle precursor dispersion. (Process 2) The process involves introducing the silica nanoparticle precursor dispersion obtained in step 1 and pure water into a reaction vessel (Y) that is kept unheated to obtain a second preparation solution (silica concentration of 0.3% by mass or more and 4.6% by mass or less). (Step 3) Following step 2, the second preparation solution in the reaction vessel (Y) is maintained at a temperature of 40°C to 98°C, and acidic silica solution and alkali are added thereto continuously or intermittently, stirring is performed to allow the reaction to proceed, while simultaneously a portion of the solution in the reaction vessel (Y) is continuously or intermittently withdrawn. (Step 4) After the completion of step 3, the solution A remaining in the reaction vessel (Y) is aged at a temperature of 40°C to 98°C for 20 minutes to 120 minutes, and then the solution A and the solution B extracted in step 3 are mixed to obtain a silica fine particle dispersion for polishing. [Effects of the Invention]

[0010] According to one aspect of the present invention, a method for producing a silica fine particle dispersion for polishing is provided that exhibits excellent polishing speed and suppresses scratch generation on the substrate to be polished when applied for polishing purposes. [Modes for carrying out the invention]

[0011] [Silica particle dispersion for polishing] First, the abrasive silica fine particle dispersion obtained by the method for producing the abrasive silica fine particle dispersion according to this embodiment will be described. The silica fine particle dispersion for polishing obtained in this embodiment consists of a group of particles containing silica fine particles dispersed in a solvent, which are used as abrasive particles. Furthermore, it is preferable that the particle group satisfies all of the following requirements 1 to 7. In this specification, "dispersion of silica microparticles for polishing" may sometimes be simply referred to as "dispersion." Similarly, "group of particles containing silica microparticles" dispersed in the dispersion of silica microparticles for polishing may sometimes be simply referred to as "group of particles." The silica fine particle dispersion for polishing obtained in this embodiment exhibits excellent polishing speed and suppresses scratch generation when applied to polishing applications. The reason for this performance is not entirely clear, but the inventors speculate as follows.

[0012] In other words, the particle group obtained in this embodiment has a broad particle size distribution. Therefore, the polishing speed can be improved compared to conventional abrasive grains. Furthermore, the particle size distribution has a peak on the larger particle size side, meaning that the larger particle size side does not tail, and therefore extremely large particles are not included. In addition, because the shape is perfectly spherical, the surface roughness is improved and the occurrence of scratches can be suppressed. Moreover, the particle group obtained in this embodiment mainly consists of perfectly spherical silica fine particles, while containing a small amount of irregularly shaped silica fine particles. These irregularly shaped silica fine particles improve the polishing speed, and since these irregularly shaped silica fine particles are present in only a small amount, their impact on surface roughness or scratches is small. In addition, the particle group obtained in this embodiment contains irregularly shaped silica fine particles on the smaller diameter side, and almost none on the larger diameter side. If irregularly shaped silica fine particles are included on the larger diameter side, the polishing speed can be improved, but the surface roughness deteriorates and scratches occur. Because most of the irregularly shaped silica microparticles are located on the smaller diameter side, the polishing speed can be improved compared to broad particles that do not contain irregularly shaped silica microparticles, and the adverse effect on surface roughness or scratches is minimal. Furthermore, the method for producing the silica fine particle dispersion for polishing according to this embodiment involves adding an acidic silicic acid solution to a non-heated reaction vessel during preparation. Therefore, drying of the acidic silicic acid solution can be prevented, and since seed particles are not added during the preparation in step 3, the load on the manufacturing equipment can be reduced, the burden of process control can be reduced, and it becomes possible to efficiently produce the silica fine particle dispersion for polishing. The inventors surmise that the above-mentioned effects of the present invention are achieved in this manner.

[0013] In this specification, the properties or characteristics of a substance may be disclosed in parentheses following its name. For example, the description "silica microparticle dispersion (silica concentration 0.05% by mass, pH 7.6)" indicates that the silica concentration of the silica microparticle dispersion is 0.05% by mass and the pH is 7.6. In addition, the characteristics or dimensions of various devices may be disclosed in parentheses following their names.

[0014] (Particle diameter based on specific surface area) The specific surface area-based particle diameter of the particle group obtained in this embodiment is preferably in the range of 5 nm to 200 nm. If the specific surface area-based particle diameter is within the above range, using the silica fine particle dispersion obtained in this embodiment as polishing silica fine particles for polishing silicon wafers, magnetic disks, or semiconductor substrates allows for a high polishing speed, suppresses scratch generation on the object being polished, and makes the surface of the object being polished smoother. If the particle diameter is less than 5 nm, it tends to become more difficult to achieve a practically sufficient polishing speed. If the particle diameter exceeds 200 nm, it tends to become more prone to scratching on the substrate being polished. The specific surface area-based particle diameter of the particle group is preferably in the range of 10 nm to 150 nm, and more preferably in the range of 20 nm to 100 nm.

[0015] (Average sphericity) The average sphericity of the particle group obtained in this embodiment is preferably in the range of 0.70 to 0.90 (Requirement 1). The average sphericity can be calculated by determining the short and long axes of individual silica nanoparticles from the observation results of electron microscope images described later, and then taking their simple average. When the average sphericity of the particle group is in the range of 0.70 to 0.90, applying the silica fine particle dispersion obtained in this embodiment, in which such a particle group is dispersed in a solvent, to polishing applications can smooth the surface roughness of the polished substrate and further suppress the occurrence of scratches. If the average sphericity is less than 0.70, there are more irregularly shaped particles, which increases the polishing speed but also increases the amount of scratches. If the average sphericity exceeds 0.90, there are more spherical particles, and the polishing speed tends to decrease. The average sphericity of the particle group is preferably in the range of 0.75 to 0.89, and more preferably in the range of 0.80 to 0.88. The specific method for measuring the average sphericity of the particle group according to this embodiment is described below.

[0016] The aforementioned particle group preferably contains particles with a sphericity of less than 0.63 in an amount of 1.0% to 10% (Requirement 2). Particles with a sphericity of less than 0.63 are particularly irregular particles (hereinafter also referred to as "high irregular particle"), and such highly irregular particles generally exhibit high polishing speeds but tend to generate scratches on the substrate surface. However, if the high irregular particle ratio (number of irregular particles / total number of particles × 100) is in the range of 1.0 percent or more and 10.0 percent or less, when the particle group obtained in this embodiment is used as polishing abrasive grains, the irregular particles included in the aforementioned percent range contribute to a high polishing speed, while the remaining spherical particles suppress the generation of scratches on the substrate surface, and further reduce the scratches that do occur. Therefore, it is possible to achieve both a high polishing speed and smoothness of the polished substrate surface after polishing. When the percentage of highly irregular particles in the particle group is less than 1.0 percent, no effect of improving the polishing speed due to highly irregular particles is observed. When the percentage of highly irregular particles in the particle group exceeds 10.0 percent, the tendency for increased scratches due to highly irregular particles becomes stronger. The content of highly irregular particles in the polishing silica fine particle dispersion obtained in this embodiment is preferably in the range of 1.0 percent to 6.0 percent, and more preferably in the range of 1.0 percent to 3.0 percent.

[0017] (Ratio of particle projected area (s) to particle area (S) calculated from maximum Ferret diameter) Generally, when a projected particle image is sandwiched between two parallel lines in a fixed direction, the length of the perpendicular line is called the Ferret diameter. In this embodiment, it is preferable that the area ratio (s / S) of the projected area s of the particles captured by the electron microscope to the area S of a circle whose diameter is the maximum Ferret diameter of the particles captured by the electron microscope is in the range of 0.68 to 0.80 (Requirement 3). Here, the area ratio (s / S) indicates the degree of irregularity and unevenness of the particles. It is presumed that in the manufacturing process of the particles of the present invention, some of the generated nucleus particles aggregate to form aggregates with shapes such as two or three particles. Using such aggregates as nuclei, particle growth is carried out by the subsequent addition of acidic silica solution, and the connecting parts of the aggregates, i.e., the recesses, are filled. At this time, particles whose recesses are completely filled become elliptical irregular particles, and particles whose recesses are not completely filled become irregular particles with irregularities. Furthermore, perfectly spherical particles formed from non-aggregating nuclei also coexist, but as the proportion of irregularly shaped particles increases, (s / S) becomes smaller. Therefore, (s / S) can be said to be a parameter that indicates the degree of irregularity and unevenness of the particles. If the area ratio (s / S) is less than 0.68, there will be more irregularly shaped particles, which will increase the polishing speed but also increase scratches, which is undesirable. If the area ratio (s / S) is greater than 0.80, there will be more perfectly spherical particles, which tends to decrease the polishing speed. Preferably, the area ratio (s / S) is recommended to be in the range of 0.69 to 0.79, and more preferably, in the range of 0.70 to 0.78.

[0018] (Percentage of particles within a specific area ratio range) The closer the area ratio (s / S) is to 1, the closer the particle is to a perfect sphere. Conversely, the smaller the area ratio (s / S) is to 1, the more irregularly shaped the particle is. The particle group preferably contains particles with a value of the area ratio (s / S) in the range of 0.40 or more and 0.75 or less in the range of 30% by number or more and 60% by number or less (Requirement 4). Here, the particles with a value of the area ratio (s / S) in the range of 0.40 or more and 0.75 or less are irregularly shaped particles, and it can be said that they have the function of improving the polishing rate and are suitable. When the proportion of particles with a value of the area ratio (s / S) in the particle group in the range of 0.40 or more and 0.75 or less is less than 30% by number, there is a concern that there are many spherical particles and the polishing rate will be low. Also, when it exceeds 60% by number, there are many irregularly shaped particles, and although an improvement in the polishing rate can be expected, an increase in scratches or deterioration of the surface quality is a concern. Regarding the proportion of the particle group containing particles with a value of the area ratio (s / S) in the range of 0.40 or more and 0.75 or less, preferably, a range of 31% by number or more and 60% by number or less is recommended, and more preferably, a range of 32% by number or more and 55% by number or less is recommended. If the number ratio of the particles satisfying the area ratio (s / S) is within the above range, that is, if Requirement 4 is satisfied, the particle group of the present invention is likely to satisfy Requirement 3.

[0019] (Weight-converted cumulative particle size distribution) In the weight-converted cumulative particle size distribution of the particle group according to the present embodiment, the cumulative 10% particle size (D 10 ), the cumulative 90% particle size (D 90 ) and the cumulative 50% particle size (D 50 ) preferably satisfy the following mathematical formula (F1) (Requirement 5). 0.5 ≦ (D 90 - D 10 ) / D 50 ≦ 3.0 ··· (F1) The value of (D 90 - D 10 ) / D 50 in the mathematical formula (F1) indicates the width of the particle size distribution, and the larger the value of (D 90 - D 10 ) / D 50 , the wider the particle size distribution. That is, (D 90 - D 10 ) / D 50A large value indicates that the dispersion contains both small and large particles. Here, the larger particles exhibit a high polishing rate, while the smaller particles reduce scratches. Therefore, a silica fine particle dispersion with this particle size distribution can achieve both a high polishing rate and suppression of scratch generation. (D 90 -D 10 ) / D 50 If the value is in the range of 0.5 to 3.0, it can be said that the particle size distribution is sufficiently broad and contains appropriate amounts of small and large particles. Generally, the larger the particle size, the higher the polishing speed, but on the other hand, a problem arises in that scratches are more likely to occur on the substrate when the size is large. However, if the particle size distribution satisfies the above range, the balance between the content of large and small particles is good, and scratches generated on the polished substrate by polishing with large particles are reduced by polishing with small particles, which is preferable. (D 90 -D 10 ) / D 50 If the value is less than 0.5, the particle size distribution is sharp, making it difficult to achieve both a high polishing speed and suppression of scratch generation. (D 90 -D 10 ) / D 50 If the value is greater than 3.0, the particle size distribution is quite broad and includes coarse particles, resulting in a large gap between large and small particles. Scratches caused by large particles are difficult to reduce with small particles. ((D 90 -D 10 ) / D 50 The value of ) is preferably in the range of 0.6 or more and 2.0 or less, and more preferably in the range of 0.8 or more and 1.8 or less.

[0020] (Peak in particle size distribution) In the weight-based particle size distribution of the particle group obtained in this embodiment, it is preferable to have a distribution peak on the larger particle size side (Requirement 6). Here, having a distribution peak on the larger particle diameter side means that the weight-reduced particle diameter distribution is D 60This means that the distribution peak is shown on the side of larger particle diameters than the cumulative 60% of particle diameters (calculated from the smallest particle diameters). When the particle size distribution has a peak on the larger particle size side, the distribution does not tail on the larger particle size side. On the other hand, a distribution that tails on the larger particle size side contains extremely large particles. Generally, the larger the particle size, the faster the polishing speed, but scratches are more likely to occur and the surface roughness tends to worsen. However, extremely large particles tend to cause scratches that cannot be reduced. Therefore, particles with a distribution that has a peak on the larger particle size side but does not tail on the larger particle size side tend to suppress critical scratches. Furthermore, by combining requirement 2 and requirement 6, scratches generated by the peaks on the larger particle diameter side are reduced by the smaller particles, which have the function of smoothing the surface despite the slower polishing speed. This makes it possible to achieve both improved polishing speed and improved surface roughness.

[0021] (Number of separated waveforms) The weight-based particle size distribution of the particle group preferably has four or more separated waveforms, and furthermore, among these four or more separated waveforms, the separated waveform with the second smallest most frequent diameter preferably has a full width at half maximum (FWHM) of 0.022 or more (Requirement 7). Generally, between spherical particles and irregularly shaped particles with the same weight-average diameter, irregularly shaped particles have a wider particle size distribution. A FWHM of 0.022 or more for the separated waveform with the second smallest most frequent diameter indicates that a desired amount of irregularly shaped particles are included on the small particle size side, and a higher polishing speed can be expected compared to spherical particles. If the FWHM is less than 0.022, the small particle size side is substantially spherical, and no improvement in polishing speed can be expected. Here, the waveform separation for the weight-based particle size distribution of the particle group can be obtained by analyzing the weight-based particle size distribution measurement data using the curve_fit function of the Scipy numerical analysis library in Python. Details are described later. The weight-based particle size distribution of the aforementioned particle group means that the separated waveforms obtained by waveform separation decompose the particle size distribution, which contains multiple component waveforms, into a sum of component waveforms. If there are four or more separated waveforms, the particle size distribution is broad, and as described in requirement 6 above, it is possible to achieve both polishing speed and surface roughness improvement. If the number of separated waveforms is less than four, the particle size distribution is sharp, which is undesirable because it is not possible to achieve both polishing speed and surface roughness improvement. The half-width of the separated waveform with the second smallest value of the most frequent diameter is preferably in the range of 0.0225 to 1.0, and more preferably in the range of 0.023 to 0.1. The reason for selecting the distribution waveform with the second smallest most frequent diameter value is that the particles in this region are moderately large in size, and the proportion and degree of irregularity of the particles are relatively high, thus having a significant impact on the polishing performance of the particle group of the present invention. The particles in the region with the smallest most frequent diameter have a high proportion and degree of irregularity of the particles, but their small size means that their impact on the polishing performance of the particle group of the present invention is relatively small. The particles in the regions with the third and subsequent most frequent diameter values ​​are close to perfect spheres, so their impact on polishing performance is relatively small.

[0022] (Coefficient of variation of particle size distribution area) The abrasive silica fine particle dispersion obtained in this embodiment preferably further satisfies the following requirement 8. In the weight-based particle size distribution of the aforementioned particle group, the cumulative 1% particle size (D1) to the cumulative 99% particle size (D 99 The particle size range up to ) is divided into six equal parts, and when these particle size ranges are designated as S1, S2, S3, S4, S5, and S6, the CV value [unit: %] of the particle size distribution area corresponding to each particle size range must be in the range of 20.0% or more and 70.0% or less (Requirement 8). The particle size distribution of typical silica sol exhibits a normal distribution, resulting in a high CV value exceeding 70.0%. In contrast, when the CV value is in the range of 20.0% to 70.0%, it indicates that the areas from S1 to S6 are relatively uniform, and the shape of the particle size distribution is generally trapezoidal or rectangular, although it has a peak on the larger particle size side. Such a particle size distribution contains relatively uniform amounts of large particles for fast polishing, small particles to suppress scratches, and medium particles that offer a good balance between polishing speed and scratch suppression. Therefore, it is possible to achieve both high polishing speed and scratch suppression. When the CV value is less than 20.0%, it tends to be practically difficult to obtain such a particle size distribution. On the other hand, when the CV value exceeds 70.0%, it approaches a normal distribution, and therefore tends to result in a slower polishing speed. The CV value is more preferably in the range of 22.0% to 65.0%, and particularly preferably in the range of 25.0% to 62.0%.

[0023] (Average sphericity for each individual average Ferret diameter range) The abrasive silica fine particle dispersion obtained in this embodiment preferably further satisfies the following requirement 9. When the average of the multiple Ferret diameter lengths of each individual silica microparticle included in the particle group is defined as the individual average Ferret diameter (R), the particle size distribution of the individual average Ferret diameter (R) of the silica microparticles in the particle group is divided into six equal parts, from the smallest to the largest individual average Ferret diameter, and these are designated as N1, N2, N3, N4, N5, and N6, respectively, and the average sphericity of the silica particle group included in the individual average Ferret diameter range Nx is expressed as (Ex), the following relationship holds (Requirement 9). N1;0.70 <E1≦0.85 N2;0.80 <E2≦0.90 N3;0.90 <E3≦1.00 N4;0.90 <E4≦1.00 N5;0.90 <E5≦1.00

[0024] Generally, when a projected particle image is enclosed by two parallel lines, the length of the perpendicular between these two parallel lines is called the Ferret diameter. In this embodiment, for each individual silica nanoparticle, the average of its multiple Ferret diameter lengths was defined as the individual average Ferret diameter (R). In this embodiment, the individual average Ferret diameter (R) was determined for each individual particle using image analysis software. Specifically, in this embodiment, an electron microscope image or photograph (magnification 200,000x, but containing 200 or more silica microparticles in the same field of view) of a dispersion of abrasive silica microparticles was prepared. The length of the individual average ferret diameter of 200 randomly selected silica microparticles was determined using image analysis software. A particle size distribution of the individual average ferret diameters of these 200 silica microparticles was created. The range from the minimum to the maximum individual average ferret diameter of this particle size distribution was divided into six equal parts, and these were designated as N1, N2, N3, N4, N5, and N6, from smallest to largest individual average ferret diameter. The average sphericity (Ex) of the silica particle group included in the individual average ferret diameter range Nx was then determined.

[0025] In this embodiment, it is preferable that the relationship described in requirement 9 above be satisfied. When this relationship is satisfied, most of the particles with low sphericity are located on the smaller diameter side, and most of the particles on the larger diameter side are spherical, which is suitable for achieving both increased polishing speed and good surface roughness. If the average sphericity Ex is below the range mentioned above, there are many particles with low sphericity, which increases the polishing speed but tends to worsen surface roughness or scratching. Also, if the average sphericity Ex exceeds the range mentioned above, there are many spherical particles, and the improvement in polishing speed tends to saturate.

[0026] The abrasive silica fine particle dispersion obtained in this embodiment preferably further satisfies the following requirement 10. In each particle size range from N1 to N6, the average area ratio (s / S) of N1 is greater than 0.60 and 0.75 or less, the average area ratio (s / S) of N2 is greater than 0.75 and 0.82 or less, and the average area ratio (s / S) of N3, N4, N5, and N6 is greater than 0.82 and 1.00 or less (Requirement 10). When this relationship is satisfied, most irregularly shaped particles are located on the smaller particle size side, and most perfectly spherical particles are located on the larger particle size side. This distribution of irregularly shaped and perfectly spherical particles is considered suitable for achieving both improved polishing speed and surface roughness. If the average area ratio (s / S) falls below the aforementioned range, there are too many irregularly shaped particles, so while the polishing speed improves, the surface roughness or scratches tend to worsen. Conversely, if the average area ratio (s / S) exceeds the aforementioned range, there are too many perfectly spherical particles, and the polishing speed does not improve.

[0027] (Silica microparticles) Furthermore, the fact that the silica nanoparticles obtained in this embodiment consist of silica can be confirmed, for example, using an ICP (Inductively Coupled Plasma Atomic Emission Spectrometer) as follows. Specifically, 1 g of an aqueous dispersion containing the silica nanoparticles obtained in this embodiment is placed in a 30 mL lidded zirconia ball, dried (200°C, 20 minutes), and then 22 g of Na2O and 1 g of NaOH are added and dissolved for 15 minutes. After that, 10 mL of 98% by mass sulfuric acid and 10 mL of pure water are added and dissolved, and then diluted with pure water to a total volume of 500 mL to obtain a sample. The silicon content of the obtained sample can be measured using an ICP instrument (Shimadzu Corporation, ICPS-8100, analysis software ICPS-8000).

[0028] The particle group obtained in this embodiment consists of silica, but may contain 10% by mass or less of components other than silica. Examples of components other than silica include Al, Ti, Fe, Ca, Mg, Cr, Ni, Cu, Zn, K, or Na, or oxides thereof. As mentioned above, the fact that the particle group obtained in this embodiment consists of silica can be confirmed, for example, using an ICP apparatus. Furthermore, the content of components other than silica that may be present in the particle group obtained in this embodiment can be identified and quantified, for example, using an inductively coupled plasma emission spectrometer. Ni, Cu, K, and Na can be identified and quantified using an atomic absorption spectrophotometer.

[0029] (solvent) As described above, the dispersion obtained in this embodiment is made by dispersing the particle group obtained in this embodiment in a solvent. Examples of solvents include water, alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, ethers, esters, and water-soluble organic solvents such as ketones. A mixed solvent consisting of water and an organic solvent may also be used.

[0030] The content of the particle group in the dispersion obtained in this embodiment is preferably in the range of 1% by mass or more and 50% by mass or less, and more preferably in the range of 10% by mass or more and 50% by mass or less. Here, the content of the particle group was determined by subjecting the silica fine particle dispersion to a loss of volume at 1000°C, weighing the resulting solid content, and subtracting the alkali content, which was calculated separately and converted to oxides (such as Na2O), to the concentration of the particle group according to this embodiment.

[0031] [Polishing composition] Next, a polishing composition using the abrasive silica fine particle dispersion obtained in this embodiment will be described. The polishing composition contains a dispersion or group of polishing silica fine particles obtained in this embodiment and a solvent, and further contains components that impart necessary properties, including polishing performance. The components that impart the necessary performance include polishing accelerators, surfactants, hydrophilic compounds, heterocyclic compounds, pH adjusters, and pH buffers. The polishing composition may contain only one of these components, or two or more, as components that impart the necessary performance. The polishing composition obtained in this embodiment is also referred to as a "polishing slurry."

[0032] A silica fine particle dispersion or polishing composition for polishing can be used, for example, as a CMP slurry to polish semiconductor wafers such as silicon wafers, or to polish hard disk drive substrates, liquid crystal glass, sapphire substrates, compound semiconductors, GaN substrates, or SiC substrates.

[0033] Examples of polishing accelerators include acids such as sulfuric acid, nitric acid, phosphoric acid, oxalic acid, and hydrofluoric acid, or sodium salts, potassium salts, ammonium salts of these acids, and mixtures thereof. When the polishing composition obtained in this embodiment contains these polishing accelerators, a flat polished surface can be obtained by accelerating the polishing rate of specific components of the material to be polished when polishing a material made of complex components. If the polishing composition obtained in this embodiment contains a polishing accelerator, its content is preferably in the range of 0.1% by mass or more and 10% by mass or less, and more preferably in the range of 0.5% by mass or more and 5% by mass or less.

[0034] To improve the dispersibility and stability of the polishing composition, at least one of the surfactant and hydrophilic compound may be a cationic, anionic, nonionic, or amphoteric surfactant or hydrophilic compound.

[0035] Both surfactants and hydrophilic compounds have the effect of reducing the contact angle with the surface to be polished, thereby promoting uniform polishing. As at least one of the surfactant and hydrophilic compound, for example, those selected from the following group can be used.

[0036] Examples of anionic surfactants include carboxylates, sulfonates, sulfate esters, and phosphate esters. Examples of carboxylates include soaps, N-acyl amino acid salts, polyoxyethylene or polyoxypropylene alkyl ether carboxylates, and acylated peptides. Examples of sulfonates include alkyl sulfonates, alkylbenzene and alkylnaphthalene sulfonates, naphthalene sulfonates, sulfosuccinates, α-olefin sulfonates, and N-acyl sulfonates. Examples of sulfate ester salts include sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or polyoxypropylene alkylallyl ether sulfates, and alkylamide sulfates. Examples of phosphate ester salts include alkyl phosphates, polyoxyethylene or polyoxypropylene alkylallyl ether phosphates.

[0037] Examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium chloride salts, benzethonium chloride, pyridinium salts, and imidazolinium salts. Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate salts, imidazolinium betaine, lecithin, and alkylamine oxides.

[0038] Nonionic surfactants include ether-type, ether-ester-type, ester-type, and nitrogen-containing types. Examples of ether-type surfactants include polyoxyethylene alkyl and alkylphenyl ethers, alkylallylformaldehyde condensed polyoxyethylene ethers, polyoxyethylene polyoxypropylene block polymers, and polyoxyethylene polyoxypropylene alkyl ethers. Examples of ether-ester-type surfactants include polyoxyethylene ethers of glycerin esters, polyoxyethylene ethers of sorbitan esters, and polyoxyethylene ethers of sorbitol esters. Examples of ester-type surfactants include polyethylene glycol fatty acid esters, glycerin esters, polyglycerin esters, sorbitan esters, propylene glycol esters, and sucrose esters. Examples of nitrogen-containing surfactants include fatty acid alkanolamides, polyoxyethylene fatty acid amides, and polyoxyethylene alkylamides. Other examples include fluorine-based surfactants.

[0039] As the surfactant, anionic surfactants or nonionic surfactants are preferred. As the salt, examples include ammonium salts, potassium salts, and sodium salts, with ammonium salts and potassium salts being particularly preferred.

[0040] Furthermore, other surfactants and hydrophilic compounds include esters (glycerin esters, sorbitan esters and alanine ethyl esters, etc.), ethers (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, and alkenyl polypropylene glycol, etc.), polysaccharides (alginic acid, pectinic acid, carboxymethylcellulose, curdlan and pullulan, etc.), amino acid salts (glycine ammonium salt and (Sodium glycine salt, etc.), polycarboxylic acids and their salts (polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polyammonium methacrylate salt, sodium methacrylate salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly(p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, ammonium polyacrylate salt, sodium polyacrylate salt, polyamic acid, ammonium polyamic acid salt, sodium polyamic acid salt, and polyglycerides) Oxyl acids, etc.), vinyl polymers (polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein, etc.), sulfonic acids and their salts (ammonium methyltaurate, sodium methyltaurate, sodium methyl sulfate, ethylammonium sulfate, butylammonium sulfate, sodium vinylsulfonate, sodium 1-allylsulfonate, sodium 2-allylsulfonate, sodium methoxymethylsulfonate, ammonium ethoxymethylsulfonate, sodium 3-ethoxypropylsulfonate, etc.),Examples include amides (such as propionamide, acrylamide, methylurea, nicotinamide, succinamide, and sulfanilamide).

[0041] Furthermore, while any surfactant can be suitably used when the substrate to be polished is a glass substrate, in the case of silicon substrates for semiconductor integrated circuits, where contamination by alkali metals, alkaline earth metals, or halides is undesirable, it is preferable to use an acid-based or ammonium salt-based surfactant.

[0042] If the polishing composition contains at least one surfactant and a hydrophilic compound, the total amount thereof is preferably in the range of 0.001 g to 10 g per liter of the polishing composition obtained in this embodiment, more preferably in the range of 0.01 g to 5 g, and particularly preferably in the range of 0.1 g to 3 g.

[0043] The surfactant or hydrophilic compound may be used alone, or two or more types may be used, and different types may be used in combination.

[0044] For polishing compositions, if the substrate to be polished contains metal, a heterocyclic compound may be included for the purpose of forming a passivation layer or dissolution-inhibiting layer on the metal to suppress erosion of the substrate. Here, "heterocyclic compound" refers to a compound having a heterocycle containing one or more heteroatoms. A heteroatom means an atom other than a carbon atom or a hydrogen atom. A heterocycle means a cyclic compound having at least one heteroatom. A heteroatom refers only to an atom that forms a component of the ring system of a heterocycle, and does not refer to an atom located outside the ring system, separated from the ring system by at least one non-conjugated single bond, or part of a further substituent of the ring system. Preferred heteroatoms include, but are not limited to, nitrogen, sulfur, oxygen, selenium, tellurium, phosphorus, silicon, and boron atoms. Examples of heterocyclic compounds that can be used include imidazole, benzotriazole, benzothiazole, and tetrazole. More specifically, examples include, but are not limited to, 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, and 3,5-diamino-1,2,4-triazole.

[0045] When a polishing composition contains a heterocyclic compound, its content is preferably in the range of 0.001% by mass or more and 1.0% by mass or less, more preferably in the range of 0.001% by mass or more and 0.7% by mass or less, and even more preferably in the range of 0.002% by mass or more and 0.4% by mass or less.

[0046] To enhance the effects of the above-mentioned additives, the pH of the polishing composition can be adjusted by adding an acid or base as needed.

[0047] When adjusting the pH of an abrasive composition to 7 or higher, an alkaline pH adjuster should be used. Preferably, amines such as sodium hydroxide, aqueous ammonia, ammonium carbonate, ethylamine, methylamine, triethylamine, and tetramethylamine should be used.

[0048] When adjusting the pH of an abrasive composition to less than 7, an acidic pH adjuster is used. For example, hydroxy acids such as lactic acid, citric acid, malic acid, tartaric acid, and glyceric acid are used.

[0049] To maintain a constant pH value in the polishing composition, a pH buffer may be used. Examples of pH buffers include phosphates and borates such as ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium tetraborate tetrahydrate, or organic acids.

[0050] The concentration of abrasive particles in the abrasive composition is preferably in the range of 0.5% by mass or more and 50% by mass or less, and more preferably in the range of 5% by mass or more and 30% by mass or less. If the concentration is less than 0.5% by mass, depending on the type of substrate and insulating film, the concentration may be too low, resulting in a slow polishing speed and productivity problems. If the concentration of abrasive particles exceeds 50% by mass, the stability of the abrasive material becomes insufficient, and the polishing speed and polishing efficiency will not improve further. Also, dried material may be generated and adhere during the process of supplying the dispersion liquid for the polishing treatment, which may cause scratches.

[0051] [Method for producing a dispersion of silica fine particles for polishing] Next, a method for producing the silica fine particle dispersion for polishing according to this embodiment will be described. The method for producing the silica fine particle dispersion for polishing according to this embodiment requires the inclusion of the following steps 1 to 4.

[0052] (Process 1) In step 1, an acidic silica solution and an alkali are introduced into a reaction vessel (X) that is kept unheated and mixed uniformly (hereinafter, the mixed solution of acidic silica solution and alkali after mixing will be referred to as the "first preparation"), then heated to between 40°C and 98°C and maintained within that temperature range, and then the acidic silica solution is added continuously or intermittently while maintaining that temperature range, followed by maturation at a temperature of between 40°C and 98°C for between 20 minutes and 120 minutes to obtain a silica nanoparticle precursor dispersion.

[0053] In step 1, first, acidic silica solution and alkali are introduced as raw materials into a reaction vessel (X) kept unheated, and a solvent is added as needed to prepare the first mixture. In this specification, "reaction vessel" means a vessel into which each component can be introduced and subjected to processes such as stirring, mixing, or heating, and as long as it has such a function, its name is not limited, and it may also be called a mixing tank, reaction tank, or tank, for example.

[0054] Normally, when raw materials such as acidic silica solution and alkali are introduced into a reaction vessel, splashing occurs at the bottom or inner wall of the vessel or at the liquid surface (the surface of the introduced acidic silica solution and alkali). When introduced into a heated reaction vessel, these splashed raw materials tend to dry out, leading to the formation of coarse aggregates, which can be problematic. If the raw materials are introduced gradually to avoid splashing, the mixing time becomes long, which is undesirable both practically and economically. Furthermore, as in the process described in Patent Document 2, when the seed particle dispersion and alkali are added to a heated reaction vessel, the seed particle dispersion and alkali are heated from the moment of addition, which can lead to the problem of seed particle aggregation occurring at an early stage. The aforementioned "non-heating state" means that no operations are performed to raise the temperature of the reaction vessel. However, if the temperature of the reaction vessel exceeds 40°C in the non-heating state due to seasonal high temperatures or other reasons, it is recommended to cool the reaction vessel so that its temperature falls below 40°C. It is preferable that the temperatures of both the acidic silica solution and the alkali introduced into the reaction vessel be below 40°C.

[0055] (Acidic silica solution) As the acidic silicic acid solution, one obtained by dealkalizing an alkaline silicate aqueous solution with a cation exchange resin can be used. The concentration of the acidic silicic acid solution is preferably in the range of 0.1% to 10% by mass, more preferably in the range of 1% to 7% by mass, and particularly preferably in the range of 2% to 6% by mass, based on SiO2. The pH of the acidic silicic acid solution is preferably 1.0 to 3.0.

[0056] The amounts of acidic silicic acid solution and alkali used should be such that the molar ratio of silica to alkali (in oxide terms) in the first preparation solution is between 0.5 and 10, and it is desirable to further adjust the silica concentration in the first preparation solution by adding solvent as needed, so that it is between 0.1% by mass and 15% by mass. Here, the molar ratio of silica to alkali (in oxide terms) is expressed as molar ratio = [number of moles of SiO2] / [number of moles of A2O] (where A represents alkali metals, ammonia, organic alkalis, or alkali metals in water glass). If the molar ratio of silica to alkali (in oxide terms) is less than 0.5, the amount of alkali is excessive, causing the ionic strength in the first preparation solution to become excessively high. This leads to the aggregation of silica microparticles produced in subsequent steps 2 and 3, making it impossible to obtain perfectly spherical particles, and making it easier for precipitates to form. Even if sedimentation does not occur, the increase in aggregates of silica microparticles makes it difficult to obtain a monodisperse silica sol. On the other hand, if the molar ratio of silica to alkali (in oxide terms) exceeds 10, the amount of silica is too large, resulting in only small particles being obtained, making it difficult to adjust to the desired size. Also, because the alkali is relatively low, when the acidic silicic acid solution is added in the subsequent step 2, the pH of the reaction solution becomes significantly lower. As a result, the added acidic silicic acid solution does not deposit on the surface of the generated silica fine particles, and self-nucleation by silicic acid occurs, ultimately making it difficult to obtain a silica sol with the desired particle size. The molar ratio of silica to alkali is preferably in the range of 1.75 to 8, and more preferably in the range of 1.0 to 7.0.

[0057] As mentioned earlier, it is desirable to adjust the silica concentration in the first formulation to be in the range of 0.1% by mass or more and 15% by mass or less. If the silica concentration in the first formulation is less than 0.1% by mass, monodisperse silica fine particles are easily obtained, but because the silica concentration in the first formulation is low, production is not efficient and is uneconomical. If the silica concentration exceeds 15% by mass, the silica fine particles tend to aggregate during formulation, making it difficult to obtain monodisperse silica fine particles. It is more preferable that the silica concentration in the first formulation be 0.2% by mass or more and 10% by mass or less, and particularly preferable that be 0.3% by mass or more and 8% by mass or less. Furthermore, if the molar ratio of silica to alkali (in oxide terms) and the silica concentration in the first formulation are set within the aforementioned range, most silica fine particles will avoid aggregation, but some will aggregate and grow into irregularly shaped particles (sphericity less than 0.63). As a result, the particle group containing silica fine particles obtained in this embodiment will contain between 1.0% and 10% of such irregularly shaped particles. In the first formulation, when the flocculant described below is not used, a suitable silica concentration is preferably 2.0% by mass or more and 15% by mass or less. This is because, when the flocculant is not used, if the silica concentration of the first formulation is less than 2.0% by mass, it is difficult to obtain the desired irregularly shaped particles. When the flocculant is not used, the silica concentration of the first formulation is more preferably 2.0% by mass or more and 10% by mass or less, and particularly preferably 2.0% by mass or more and 7.0% by mass or less. If the silica concentration of the first formulation exceeds 15% by mass, flocculation may proceed too much, resulting in a failure to obtain the desired particles and the formation of coarse precipitates.

[0058] (alkali) Examples of alkalis added in step 1 include alkali silicates such as sodium silicate (water glass) and potassium silicate, as well as alkali hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, ammonia, and organic alkalis such as organic amines. Here, the alkali is usually added as an alkaline aqueous solution. There are no particular restrictions on the alkali concentration of the alkaline aqueous solution, but it is usually used in the range of 1% by mass to 50% by mass. In this embodiment, metal salts are not included in the alkali range. For example, metal salts such as potassium chloride are not included in the alkali range. Although potassium chloride is not included in the alkali range, it can be used in step 1 as a flocculant.

[0059] (solvent) Examples of solvents that may be added as needed in step 1 include water, deionized water, pure water, ultrapure water, and mixed solvents containing water and water-soluble organic solvents, as well as water-soluble organic solvents.

[0060] (Holding temperature and holding time) In step 1, the first formulation is heated to a temperature of 40°C to 98°C while being stirred, and maintained at this temperature range for a certain period of time. The holding time is preferably 10 minutes to 120 minutes, and more preferably 20 minutes to 90 minutes. This temperature maintenance allows the formulation to be sufficiently homogenized. If the holding time is less than 10 minutes, homogenization is insufficient, and the subsequent addition of the acidic silicic acid solution tends to result in uneven generation of silica fine particles and particle growth. If the holding time exceeds 120 minutes, the homogenization of the formulation does not progress further, and the longer holding time actually reduces production efficiency and worsens economic viability.

[0061] (Addition of acidic silica solution) Next, while maintaining the temperature of the first preparation solution within a range of 40°C to 98°C, the acidic silicic acid solution is added continuously or intermittently to generate silica nanoparticle precursors. More specifically, in this initial stage of acidic silicic acid solution addition, core particles (polymers of silicic acid) are formed first, and these core particles grow continuously with the subsequently added acidic silicic acid solution to produce a dispersion of silica nanoparticle precursors. Here, the silica nanoparticle precursors are particles preceding the silica nanoparticles of a predetermined particle size range obtained by the dispersion production method according to this embodiment, and usually consist of even finer silica nanoparticles. The addition time for the acidic silica solution is preferably between 3 hours and 48 hours. If the addition time is less than 3 hours, the addition rate of the acidic silica solution is too fast, which can lead to self-nucleation by the added acidic silica solution itself, in addition to the generation of desired silica nanoparticles through particle growth of the silica nanoparticle precursor. When such self-nucleation occurs, the particles do not have the desired particle size distribution, the balance between large and small particles becomes poor, and it may become impossible to achieve both a high polishing speed and suppression of scratch generation. On the other hand, if the addition time for the acidic silica solution exceeds 48 hours, self-nucleation of the acidic silica solution does not occur, but the preparation time becomes too long, which tends to reduce practicality and economic efficiency. The particle size distribution of the silica nanoparticle precursor produced in this step 1 shows a normal distribution and is a relatively sharp particle size distribution.

[0062] In step 1, as described above, it is preferable to further add a flocculant to the first preparation solution in a reaction vessel (X) which is kept unheated if desired. The flocculant here has the effect of generating cations or anions in the first preparation solution and increasing the ionic strength in the preparation solution. The addition of such a flocculant makes some of the nucleus particles more likely to aggregate, and after step 1, a silica nanoparticle precursor containing irregularly shaped silica nanoparticles can be obtained. Examples of the aforementioned flocculants include alkali metal salts and alkaline earth metal salts.

[0063] Examples of alkali metal salts include alkali metal halides, hydrochlorides, nitrates, sulfates, phosphates, and organic acid salts. Examples of alkaline earth metal salts include alkaline earth metal halides, hydrochlorides, sulfates, phosphates, and organic acid salts. As the flocculant, alkali metal halides are more preferably recommended. Of these, potassium chloride is particularly preferred.

[0064] The amount of the flocculant added is equal to the number of moles of silica in the acidic silicic acid solution in the first preparation solution (MN). SiO2 ) and the number of moles of flocculant (MN) MX ) molar ratio (MN SiO2 / MN MX It is preferable that the value is in the range of 0.1 to 100. The aforementioned molar ratio (MN) SiO2 / MN MX If the ratio (MN) is less than 0.1, particle aggregation may progress too much, resulting in the generation of many coarse particles, which may cause scratches when used as an abrasive. On the other hand, if the ratio (MN) is less than 0.1, SiO2 / MN MX If the ratio exceeds 100, the particle aggregation effect is small, and silica particles with the desired irregular shape may not be obtained. For this reason, sufficient polishing performance may not be obtained when used as an abrasive. The aforementioned molar ratio (MN) SiO2 / MN MX The range of ) is preferably between 0.5 and 40.

[0065] Furthermore, in step 1, a flocculant is added to the first preparation liquid, such that the number of moles of silica in the acidic silicic acid solution in the first preparation liquid is equal to the number of moles (MN). SiO2 ) and the number of moles of flocculant (MN) MX ) molar ratio (MN SiO2 / MN MX In a method for producing a silica fine particle dispersion for polishing, in which the amount of additives is in the range of 0.1 to 100, the silica concentration of the first preparation solution may be in the range of 0.1% by mass to 15% by mass. This is because the flocculating effect of the flocculant on the silica fine particle precursor makes it easier to generate irregularly shaped silica particles with a sphericity of less than 0.63.

[0066] (Process 2) In step 2, the silica nanoparticle precursor dispersion obtained in step 1 and pure water are introduced into a reaction vessel (Y) that is kept unheated to obtain a second formulation (silica concentration of 0.3% by mass or more and 4.6% by mass or less). The purpose of diluting the silica microparticle precursor dispersion with water to a silica concentration of 0.3% by mass or more and 4.6% by mass or less is to control the particle size distribution. If the silica concentration after dilution is less than 0.5% by mass, there are few silica microparticles in the reaction vessel (Y), and when the acidic silicic acid solution is added in the subsequent step 3, the particle growth cannot keep up with the addition, resulting in self-nucleation, making it difficult to control the particle size distribution. In this case, if the rate of addition of the acidic silicic acid solution is slowed down to prevent self-nucleation, the process time increases, reducing practicality. If the silica concentration of the silica microparticle precursor dispersion exceeds 4.6% by mass, there are an excess of silica microparticles in the reaction vessel (Y), and the surface area of ​​the silica microparticles increases. As a result, the particle growth rate in the subsequent step 3 slows down, and relatively small particles are more likely to be generated. Therefore, the particle size distribution of the polishing silica microparticle dispersion finally obtained after step 4 may be biased towards the small particle size side. The silica concentration of the silica nanoparticle precursor dispersion is preferably in the range of 0.3% by mass to 4.5% by mass. In this specification, the silica nanoparticle precursor dispersion after water dilution in step 2 is also referred to as the "second preparation solution."

[0067] As described above, in step 2, the silica nanoparticle precursor dispersion obtained in step 1 and pure water are introduced into a reaction vessel (Y) that is kept unheated. The reason for using a reaction vessel (Y) that is kept unheated is the same as when a reaction vessel (X) that is kept unheated is used in step 1. Step 2 also includes the case where the reaction vessel (X) that has completed Step 1 is cooled to a non-heated state (temperature below 40°C), and then diluted with pure water in the reaction vessel (X). In this case, from the cooling stage onward, the reaction vessel (X) shall be treated as the reaction vessel (Y).

[0068] (Step 3) In step 3, following step 2, the second preparation in reaction vessel (Y) is maintained at a temperature of 40°C to 98°C, and acidic silica solution and alkali hydroxide are added thereto continuously or intermittently, stirring is performed to allow the reaction to proceed, while simultaneously a portion of the solution in reaction vessel (Y) is continuously or intermittently withdrawn. In step 3, the particle growth reaction proceeds immediately upon the addition of the acidic silica solution to the second preparation solution. Therefore, for convenience, the solution in the reaction vessel (Y) from the start of the addition of the acidic silica solution in step 3 onward will also be referred to as the "reaction solution." The term "solution" is a convenient general term for the liquid filling the reaction vessel, and the particle growth reaction proceeds in the second preparation liquid filling the reaction vessel as soon as the acidic silica solution is added. As stated above, the solution at this stage is also referred to as the "reaction liquid" in this specification. Furthermore, in this specification, the silica component contained in the liquid will also be referred to as "silica dry." As will be explained in more detail later, in the following step 4, the reaction liquid (Solution A) remaining in the reaction vessel (Y) after the completion of step 3 is aged at a predetermined temperature, and then the extracted reaction liquid (Solution B) is added and mixed to obtain a silica fine particle dispersion for polishing obtained in this embodiment, which has a broader particle size distribution (wider range of particle size distribution). In step 3, as described above, the solution in the reaction vessel (Y) is continuously withdrawn. However, in order to mix solution A and solution B in step 4, it is necessary to withdraw the reaction solution to the extent that some of the reaction solution (solution A) remains in the reaction vessel (Y).

[0069] As described above, in step 3, acidic silica solution and alkali are added to the second preparation solution to form the reaction solution. In parallel with the addition of the acidic silica solution and alkali, a portion of the reaction solution is withdrawn to form the withdrawal solution (solution B). Here, when the number of moles of silica contained in the reaction solution is M3S and the number of moles of alkali in oxide form contained in the reaction solution is M3A, the value of M3S / M3A is preferably in the range of 20 to 160. If the M3S / M3A value is less than 20, the growth of silica microparticles in the silica microparticle dispersion obtained by the manufacturing method according to this embodiment is slow, and furthermore, the size becomes small and it is difficult to achieve a broad distribution, so the polishing speed tends to be insufficient when used as an abrasive. On the other hand, if the M3S / M3A value exceeds 160, the particle size of the silica microparticles in the silica microparticle dispersion obtained by the manufacturing method according to this embodiment becomes excessively large, and when used as an abrasive, the occurrence of scratches on the substrate to be polished may become significant, which is undesirable. In addition, in such cases, the mixing time becomes very long, and the economic efficiency tends to deteriorate. Furthermore, the M3S / M3A value is more preferably in the range of 40 to 140, even more preferably in the range of 50 to 130, and particularly preferably in the range of 60 to 120. In practical terms, it is desirable to adjust the amount of acidic silica solution and alkali hydroxide added throughout step 3 so that the M3S / M3A value remains constant.

[0070] (Reaction temperature) When adding the acidic silicic acid solution to the second preparation or reaction solution, the temperature of the second preparation or reaction solution is preferably between 40°C and 98°C. If the temperature of the second preparation or reaction solution is below 40°C, the added acidic silicic acid solution will not dissolve easily and will not deposit easily on the surface of the silica nanoparticles. As a result, self-nucleation by silicic acid will occur, and the desired size will not be obtained. If the temperature of the second preparation or reaction solution is above 98°C, the added acidic silicic acid solution will dissolve sufficiently and the silica nanoparticles will grow, but the temperature of the silica nanoparticle dispersion or reaction solution will be excessively high, which poses problems in terms of energy efficiency and also poses problems in terms of safety. When adding the acidic silicic acid solution to the second preparation or reaction solution, the temperature of the second preparation or reaction solution is more preferably between 50°C and 98°C.

[0071] (Addition rate of acidic silica solution) In this embodiment, in step 3, the amount of acidic silicic acid solution added is expressed as the amount of dry silica [g] added per minute in the acidic silicic acid solution when it is added to the reaction vessel filled with the second preparation solution or reaction solution. Here, the rate of addition of the acidic silicic acid solution can be expressed as the amount of acidic silicic acid solution (calculated as silica mass) added per unit time, or as the amount of acidic silicic acid solution (calculated as silica mass) added per unit time relative to the amount of silica contained in the acidic silicic acid solution. In this specification, the former is simply referred to as "addition rate" (unit: [g / min]), and the latter as "addition rate relative to the solution" (unit: [g / (min·g)]).

[0072] The preferred rate of adding the acidic silica solution to the reaction solution is between 0.0001 g / (min·g) and 0.05 g / (min·g). Within this range, the acidic silica solution added for particle growth dissolves in the alkali in the reaction solution and deposits on the surface of the fine silica particles, thereby promoting particle growth of the silica particles. If the rate of adding the acidic silica solution to the reaction solution is less than 0.0001 g / (min·g), the preparation time becomes too long for practical purposes, reducing both practicality and economic efficiency. If the rate of adding the acidic silica solution to the reaction solution exceeds 0.05 g / (min·g), self-nucleation may occur without the silica depositing on the particle surface, which is undesirable. The rate at which the acidic silicate solution is added to the liquid is more preferably in the range of 0.00025 g / (min·g) or more and 0.02 g / (min·g) or less, and particularly preferably in the range of 0.0005 g / (min·g) or more and 0.01 g / (min·g) or less.

[0073] In step 3 of this embodiment, the rate at which the acidic silicic acid solution is added to the liquid can be calculated as the rate (S) of adding the acidic silicic acid solution (in terms of silica dry) relative to the unit mass of silica dry contained in the solution in the reaction vessel, using the following formula. (S) = (Addition rate of acidic silica solution per dry silica) [g / min] / (Mass of dry silica in the solution in the reaction vessel) [g] Here, "(rate of addition of acidic silicic acid solution per dry silica) [g / min]" and "(mass of dry silica in the solution in the reaction vessel) [g]" refer to "(rate of addition of acidic silicic acid solution per dry silica) [g / min]" and "(mass of dry silica in the solution in the reaction vessel) [g]" at any time in step 3.

[0074] Furthermore, the addition rate of the acidic silica solution [g / min] in step 3 is calculated from the amount of acidic silica solution added per unit time (minutes) (in terms of silica dry equivalent), regardless of whether the addition of the acidic silica solution is continuous or intermittent. For example, if the addition rate of the acidic silica solution changes in two stages, the addition rate of the acidic silica solution is calculated using the silica dry mass of the acidic silica solution added in the first and second stages, respectively. If the addition rate does not change, it is calculated using the total silica dry mass of the acidic silica solution added in step 3.

[0075] The addition rate of the acidic silica solution [g / min] is changed at least once, and the nth addition rate is set to L n When expressed as [g / min], L n+1 ≤L n It is preferable that the following relationship is satisfied. Here, n is a positive integer. That is, it is preferable to change the rate of addition of the acidic silicic acid solution during preparation at least once, and gradually decrease the rate of addition. In step 3, the acidic silicic acid solution is added to grow particles to the desired size, but in this embodiment, the reaction solution is continuously withdrawn, so the number of particles decreases. As a result, the acidic silicic acid solution may not deposit on the particle surface, and self-nucleation by silicic acid may occur. By reducing the rate of addition of the acidic silicic acid solution from the second stage onward, the occurrence of self-nucleation can be prevented, and particles can be grown to the desired size.

[0076] (Concentration of alkali) In step 3, it is desirable to add the acidic silica solution to the second mixture or reaction solution simultaneously with the continuous or intermittent addition of alkali for the purpose of controlling the extraction rate ratio, as described later. Here, the alkali concentration is preferably between 0.01% by mass and 48.6% by mass. By changing the alkali concentration, the silica concentration of the entire additive solution can be changed, and thus the extraction rate ratio can be controlled. In addition, the alkali concentration may be uniform throughout step 3 or changed one or more times. If the alkali concentration is less than 0.01% by mass, the silica concentration in the entire additive solution becomes low, and the silica concentration in the reaction solution also becomes low, resulting in inefficient and uneconomical production. In addition, the amount of alkali to be added increases, which tends to worsen work efficiency. When the alkali concentration is higher than 48.6% by mass, the pH may rise locally in the area where the alkali is added, and particles may dissolve or aggregate.

[0077] (Adjusting the pH of the reaction solution) In step 3, it is desirable to add the acidic silica solution to the second preparation solution or reaction solution simultaneously with the continuous or intermittent addition of alkali to maintain the pH of the reaction solution. The rate of alkali addition cannot be uniformly restricted as it depends on the type and concentration of the alkali, but it is desirable to add it so that the pH of the reaction solution is in the range of 8.5 to 13.0. If the pH of the reaction solution is above 13.0, the ionic strength in the reaction solution becomes too high, which tends to cause silica particles to aggregate and settle, or the particles to become deformed, making it difficult to obtain the desired particle size. If the pH is below 8.5, the added acidic silica solution becomes difficult to dissolve, which tends to cause autonucleation by silica. It is more preferable that the pH of the reaction solution is between 9.0 and 12.5.

[0078] (Molar ratio of SiO2 / A2O in the reaction mixture in the reaction vessel) In step 3, acidic silicic acid solution is added to the solution in the reaction vessel continuously or intermittently, while the reaction mixture is continuously or intermittently withdrawn, which tends to lower the pH of the reaction mixture. When the pH decreases, the added acidic silicic acid solution becomes less soluble, which tends to lead to autonucleation by silicic acid. Therefore, it is desirable to adjust the pH by adding alkali to maintain the pH of the solution in the reaction vessel. In this case, the pH can be adjusted to the desired level by adding alkali so that the SiO2 / A2O molar ratio of the solution in the reaction vessel is in the range of 20 to 160.

[0079] (Removal of solution) In step 3, the reaction solution is generated by continuously or intermittently adding the acidic silica solution to the second preparation liquid or reaction solution in the reaction vessel (Y), while simultaneously continuously withdrawing a portion of the reaction solution. Here, the withdrawn reaction solution is also called the "withdrawn solution" or "solution B". The reaction solution remaining in the reaction vessel (Y) after all withdrawals are complete is also called "solution A". In the initial stages of extraction, although the particle growth reaction has begun, the silica nanoparticles have not grown sufficiently, so small silica nanoparticles are extracted. However, in the later stages of extraction, the silica nanoparticles have grown sufficiently, so larger silica nanoparticles (in terms of particle size) are extracted. By continuously extracting the solution in this way, the solution can be made to contain silica nanoparticles with a wide particle size distribution. Furthermore, it is desirable to mix the reaction solution remaining in the reaction vessel with the extraction solution. In step 3, extraction is performed continuously, but it is desirable to perform the extraction under conditions that the preparation solution remains in the reaction vessel. The remaining preparation solution contains the largest particles with the greatest particle growth. By mixing this preparation solution with the extraction solution, particles with a wider distribution can be obtained, and the components of the remaining reaction solution become the components of the large particle side peak of the silica fine particles obtained in this embodiment. The shape of the distribution can also be adjusted to have a distribution shape with a peak on the small particle side by adjusting the extraction rate ratio, and the peak ratio between the small particle side and the large particle side can also be adjusted. Note that if the remaining preparation solution and the extraction solution are not mixed, the distribution shape will not have a peak on the large particle side. Furthermore, when the inventors conducted trace experiments, they found that in a process in which seed particle dispersion and acidic silica solution are continuously added in a reaction vessel equipped with an overflow line, as in the manufacturing method of Patent Document 1, even if the extraction rate ratio is adjusted, a particle size distribution with a peak on the large particle side as in this embodiment cannot be obtained.

[0080] (Extraction speed ratio) The manufacturing method according to this embodiment is characterized by adding an acidic silica solution to the reaction solution to promote particle growth, while simultaneously withdrawing the reaction solution for the purpose of broadening the particle size distribution. When X is the addition rate [g / min] (silica dry equivalent) when adding the acidic silica solution in step 3, and Z is the extraction rate [g / min] (silica dry equivalent) when extracting the reaction solution (extracted liquid) from the reaction vessel in process B of step 3, the extraction rate ratio (X / Z) defined by the following formula is preferably in the range of 0.2 to 15.0, more preferably in the range of 0.4 to 12.0, and particularly preferably in the range of 0.5 to 10.0. Extraction rate ratio (X / Z) = (Silica dry per hour of acidic silica solution [g]) / (Silica dry per hour of extraction solution [g]) In this embodiment, the addition of the acidic silica solution and the withdrawal of the reaction solution are started simultaneously. The withdrawal rate ratio (X / Z) is measured at 10 minutes from the start of the addition of the acidic silica solution and the start of the withdrawal of the reaction solution, and at the end of the addition of the acidic silica solution and the end of the withdrawal of the reaction solution. The values ​​of the withdrawal rate ratio (X / Z) at 10 minutes from the start and at the end are calculated, and this embodiment is included when both of these rate ratios (X / Z) fall within the withdrawal rate ratio range.

[0081] Generally, when the extraction rate ratio is 1.0, the rate at which silica dry is added to the reaction vessel is the same as the rate at which silica dry is extracted. Therefore, the amount of silica dry in the reaction vessel remains constant, and although it depends on the concentration of the raw materials, the liquid level in the reaction vessel is usually roughly constant. When the extraction rate ratio is greater than 1.0, the amount of silica dry in the reaction vessel increases because the amount extracted is small, and the liquid level in the reaction vessel usually gradually rises. On the other hand, when the extraction rate ratio is less than 1.0, the amount of silica dry in the reaction vessel decreases, and the liquid level in the reaction vessel usually gradually falls. In this embodiment, if the extraction rate ratio is less than 0.2, the extraction rate is too fast, causing the reaction vessel to become empty or nearly empty in a short reaction time, forcing the reaction to be terminated, and resulting in a tendency for the particle size distribution not to be sufficiently broadened. On the other hand, if the extraction rate ratio is greater than 10.0, the rate of addition of the acidic silica solution is too fast, making it prone to self-nucleation by the acidic silica solution. In addition, the amount of silica dry in the reaction vessel gradually increases, and the level of the prepared liquid usually rises. As a result, overflow from the reaction vessel may occur. Even if overflow does not occur, it is necessary to increase the size of the reaction vessel, which is not economical.

[0082] (Step 4) After the completion of step 3, the solution remaining in the reaction vessel (Y) (hereinafter referred to as "Solution A") is aged at a temperature of 40°C to 98°C for 20 minutes to 120 minutes. Then, Solution A and the solution extracted in step 3 (hereinafter referred to as "Solution B") are mixed to obtain a silica fine particle dispersion for polishing.

[0083] (heat aging) It is necessary to heat-age the remaining solution A in the reaction vessel (Y). The aging temperature must be in the range of 40°C to 98°C, and more preferably in the range of 60°C to 98°C. The aging time must be in the range of 20 minutes to 120 minutes, and more preferably in the range of 30 minutes to 90 minutes. By performing such heat-age, the reaction can be completed. If heat-age is not performed, the added acidic silicic acid solution may remain without depositing on the particle surface, and the stability of the silica sol may be impaired.

[0084] (Mixing process) In step 4, as described above, continuous extraction is performed, but it is necessary to perform the extraction under conditions that the reaction solution (Solution A) remains in the reaction vessel (Y). The reaction solution (Solution A) remaining in the reaction vessel contains the largest particles with the greatest particle growth. By mixing this reaction solution (Solution A) with the extraction solution (Solution B), particles with a wider distribution can be obtained. Furthermore, when this reaction solution (Solution A) and extraction solution (Solution B) are mixed, the particle size distribution will have a peak on the larger particle side. Here, the shape of the distribution can be adjusted to have a peak on the smaller particle side as well by adjusting the extraction rate ratio, and the peak ratio between the small particle side and the large particle side can also be adjusted. Note that if the reaction solution (Solution A) remaining in the reaction vessel and the extraction solution (Solution B) are not mixed, the distribution will have no peak on the larger particle side. There are no particular restrictions on the temperature at which the reaction solution (Solution A) and the withdrawal solution (Solution B) are mixed, but it is generally preferable to mix Solution A at room temperature by cooling or allowing it to cool.

[0085] (concentration process) The silica fine particle dispersion obtained by the method for producing the abrasive silica fine particle dispersion according to this embodiment, including steps 1 to 4, may be concentrated to a desired concentration after adjusting the temperature to a range of room temperature to about 50°C. The concentration method is not particularly limited, but it can be concentrated using an ultrafiltration membrane or a rotary evaporator. If desired, coarse particles may be removed by filtration using centrifugation or a filter. [Examples]

[0086] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples. Furthermore, unless otherwise specified, the methods for measuring or evaluating various characteristics in the examples and comparative examples were carried out by the methods described below.

[0087] 1. Specific surface area measurement (nitrogen adsorption method) and particle diameter converted to specific surface area The specific surface area-based particle diameter (Ds) of silica nanoparticles can be calculated using the following equation (1). Specific surface area equivalent particle diameter (Ds) [nm]=6,000 / (M SiO2 ×SA)...Equation (1) (Here, M SiO2 The density of silica nanoparticles is (2.2 [g / cm³] 3 ]) represents the specific surface area [m²] of the sample being measured. 2 It represents / g]. Here, the specific surface area (SA) of the silica nanoparticles is determined by the nitrogen adsorption method (BET single-point method). Specifically, 50 mL of the sample (silica nanoparticle dispersion) is mixed with nitric acid to adjust the pH to 3.5, then 40 mL of 1-propanol is added, and the mixture is dried at 110°C for 16 hours to obtain a dried sample. The obtained dried sample is then calcined in an electric furnace at 500°C for 1 hour to obtain the sample for measurement. Approximately 0.3 g of this sample was placed in a measuring cell and subjected to a specific surface area analyzer (Mountec, Macsorb 1201, measuring gas: mixed gas of 30 v% nitrogen gas and 70 v% helium gas). Degassing was performed at 280°C for 20 minutes while flowing nitrogen gas through the sample. The amount of degassing was then determined by the nitrogen adsorption method (BET single-point method), and the sample mass was measured to calculate the specific surface area of ​​the sample. The obtained specific surface area (SA) of the sample was substituted into formula (1) above to determine the particle diameter converted to specific surface area (Ds).

[0088] 2. Sphericity and mean sphericity A silica microparticle dispersion (silica concentration 0.05% by mass, pH 7.6) was prepared as a sample. Images or photographs (containing 200 or more silica microparticles in the same field of view) of the sample were taken with a scanning electron microscope (magnification 200,000x). 200 randomly selected silica microparticles were analyzed using image analysis software (EMSIS Corporation's image analysis software "RADIUS2.0") to determine the sphericity (short side / long side ratio) of each particle. Since the image analysis software calculates the long side / short side ratio as the aspect ratio, the value of (1 / aspect ratio) was further calculated and used as the sphericity. The average value of these values ​​was then calculated and used as the average sphericity. In this specification, a high-resolution field emission scanning electron microscope S-5500 (Hitachi High-Technologies Corporation) was used as the scanning electron microscope.

[0089] 3. Number of particles within a specific sphericity range Of the 200 silica nanoparticles mentioned above, the number (R) of silica nanoparticles with a sphericity of less than 0.63 was determined, and the percentage of silica nanoparticles with a sphericity of less than 0.63 was calculated using the following formula. [Percentage of silica microparticles with a spherical shape less than 0.63] = R / 200 × 100 [percentage]

[0090] 4. Particle projected area (s) For images or photographs (containing 200 or more silica microparticles in the same field of view) obtained by capturing images (magnification 200,000x) using the aforementioned "sphericity and mean sphericity," 200 randomly selected silica microparticles were analyzed using image analysis software (EMSIS Corporation's image analysis software "RADIUS2.0") to determine the projected area (s) of each of the 200 silica microparticles. X ) was sought.

[0091] 5. Length of the maximum Ferret diameter (f) and the equivalent circular area of ​​the maximum Ferret diameter (S) In this specification, the maximum Ferret diameter refers to the longest line segment (F) [whose length is denoted by f] connecting any two points on the outer edge of the particle image. The maximum ferre diameter is the length of the maximum ferre diameter of each of 200 randomly selected silica nanoparticles in an image or photograph (containing 200 or more silica nanoparticles in the same field of view) obtained by imaging (magnification 200,000x) using the aforementioned "sphericity and average sphericity" method (f X The area of ​​each circle with the largest Ferret diameter as its diameter is calculated using image analysis software (EMSIS's image analysis software "RADIUS2.0"). X The area of ​​the circle was calculated using the following formula. (S X ) = π(f X / 2) 2

[0092] 6. Area ratio (s / S) and the number of particles within a specific area ratio range. 1) Area ratio (s / S) For the 200 particles whose areas were calculated using the methods described in "4. Particle Projection Area (s)" and "5. Maximum Ferret Diameter and Equivalent Circular Area (S)" above, the area ratio (s) was determined for each particle. x / S x The values ​​of ) were calculated, and their number average was determined to obtain the area ratio (s / S) of the projected area (s) of the particle to the area of ​​the circle converted to the maximum Ferret diameter. 2) Particle number ratio within a specific area ratio range The area ratio (s / S) of each of the 200 particles obtained in "1) Area ratio (s / S)" above x / Sx ) of which 0.40≦(s x / S x The number of particles (n) in the range ) ≤ 0.75 was determined, and the percentage [%] of particles with an area ratio (s / S) between 0.40 and 0.75 was calculated using the following formula. Percentage [%] = n / 200 × 100

[0093] 7. Weight-equivalent particle size distribution 1) Weight-equivalent particle size distribution The sample (silica microparticle dispersion) was diluted with a 0.05% by mass sodium dodecyl sulfate aqueous solution to a solid content concentration of 2% by mass. 0.1 mL was extracted from this solution and injected into a disk centrifugal particle size analyzer (CPSINSTRUMENTS) using a syringe. The particle size distribution was measured in a sucrose density gradient solution (sucrose concentration 8-24% by mass) at a measurement condition of 18,000 rpm to determine the weight-converted particle size distribution and the weight-average particle size [nm]. 2)(D 10 ), (D 50 ) and (D 90 ) From the obtained weight-converted particle size distribution, the cumulative 10% particle size (D) from the smallest particle size was determined. 10 )[nm], cumulative 10% particle diameter (D 50 )[nm] and cumulative 90% particle size (D 90 Find the value of [nm], (D 90 -D 10 ) / D 50 The value was calculated.

[0094] 8. Confirming the peak position Regarding the weight-converted particle size distribution of the silica fine particle dispersion obtained in "7. Weight-converted particle size distribution" above, D 60 Determine the particle size of the particle that represents 60% of the cumulative particle size (calculated from the smallest particle size), and confirm that a peak in the particle size distribution exists in the particle size range larger than that particle size.

[0095] 9. Waveform separation of weight-based particle size distribution 1) Waveform separation The aforementioned weight-converted particle size distribution measurement data was optimized using the curve_fit function of the SciPy numerical analysis library in Python, adjusting the parameters (height, center, width) of the approximation curve. A Gaussian function was used for the approximation curve. Optimization was performed to minimize the number of waveforms and to ensure a corrected R-squared value of 0.99 or higher. It was confirmed that the calculated peaks did not deviate from the following conditions 1 and 2. If deviations occurred, the optimization was repeated by shifting the peak position to an arbitrary position within the distribution range until conditions 1 and 2 were satisfied. The number of separated peaks at this point was defined as the number of peaks. Condition 1: Each calculated peak must not have a value greater than the original distribution. Condition 2: Each of the calculated peaks must not take a negative value. Then, the weight-converted particle size distribution data (horizontal axis: particle size, vertical axis: particle weight %) including the obtained separation waveforms is examined, and the number of separation waveforms with different most frequent diameters is determined. 2) The half-width of the separated waveform with the second smallest value for the most frequent diameter. For weight-reduced particle size distribution data containing four or more separated waveforms, the half-width was calculated for the separated waveform with the second smallest value for the most frequent diameter using the following formula. FWMH = 2σ(ln(4)) 1 / 2 FWMH: Half-width σ: width

[0096] 10. CV value of particle size distribution area [%] From the weight-based particle size distribution, we obtain the cumulative 1% particle size (D1) [nm] and the cumulative 99% particle size (D 99 )[nm] is determined, followed by the cumulative 1% particle size (D1) and the cumulative 99% particle size (D 99 The particle size range between the particle sizes was divided into six equal parts, and the regions of the weight-converted particle size distribution corresponding to each were designated as S1, S2, S3, S4, S5, and S6 from the smallest particle size side. The particle content (mass%) corresponding to each region was determined, and the coefficient of variation (%) of each particle content was calculated.

[0097] 11. Average sphericity of silica microparticles corresponding to individual average Ferret diameter ranges 1) For images or photographs (containing 200 or more silica microparticles in the same field of view) obtained by imaging with the aforementioned "sphericity and average sphericity" (magnification 200,000x), the length of the individual average Ferret diameter of 200 randomly selected silica microparticles is determined using image analysis software (EMSIS Corporation's image analysis software "RADIUS2.0"), and a particle size distribution of the individual average Ferret diameter of the 200 silica microparticles is created. 2) Next, the range of individual average Ferret diameters from the minimum to the maximum value of the particle size distribution (particle size distribution) is divided into six equal parts, and each of these is designated as individual Ferret diameter range N1, N2, N3, N4, N5, and N6, starting from the smallest individual average Ferret diameter. 3) Determine the average sphericity (Ex) of the silica particle group contained within the individual average Ferret diameter range Nx. Specifically, images or photographs (containing 200 or more silica particles in the same field of view) obtained by photographing silica microparticles (magnification 200,000x) were analyzed using image analysis software (EMSIS Corporation's image analysis software "RADIUS2.0") to determine the sphericity (short side / long side ratio) of each particle. Note that the aforementioned image analysis software calculates the long side / short side ratio as the aspect ratio, so the value of (1 / aspect ratio) was further calculated and this value was used as the sphericity. The average sphericity (Ex) of the silica particle group included in the individual average Ferret diameter range Nx was calculated by dividing the sum of the sphericities of particles with an individual average Ferret diameter range Nx by the number of particles included in Nx. The individual average Ferret diameter was determined for each individual silica microparticle using the image analysis software and defined as the individual average Ferret diameter (R).

[0098] 12. Average area ratio (s / S) of silica microparticles corresponding to the individual average Ferret diameter range. 1) Using image analysis software, determine the length of the individual average Ferret diameter of 200 individual silica microparticles obtained from images or photographs (containing 200 or more silica microparticles in the same field of view) obtained by capturing images (magnification 200,000x) with the aforementioned "sphericity and average sphericity," and create a Ferret diameter particle size distribution for the 200 silica microparticles. 2) Next, the range of individual average ferret diameters from the minimum to the maximum value is divided into six equal parts, and each of these is designated as individual ferret diameter range N1, N2, N3, N4, N5, and N6, starting from the smallest individual average ferret diameter. 3) Determine the average area ratio (NxA) of the silica particle groups contained within the individual average Ferret diameter range Nx. Specifically, images or photographs (containing 200 or more silica particles in the same field of view) obtained by photographing silica microparticles (magnification 200,000x) were analyzed using image analysis software (EMSIS's image analysis software "RADIUS2.0"), and the area ratio (s / S) of the projected area s of each particle and the area S of a circle with the maximum Ferret diameter as its diameter was determined. The sum of the sphericities of the particles whose individual average Ferret diameter range is Nx was divided by the number of particles contained in Nx to determine the average area ratio (NxA) of the silica particle groups contained within the individual average Ferret diameter range Nx.

[0099] 13. The ratio of moles of silica (M3S) to moles of alkali (M3A) in the reaction solution. The ratio of moles of silica (M3S) to moles of alkali (M3A) in the reaction solution was calculated by taking the number of moles of alkali in the second preparation solution, the number of moles of alkali in the second preparation solution, and the total amount of acidic silica solution and alkali added in step 3, and then calculating the value of (M3S) / (M3A). Note that metal salts contained in the second preparation solution were not included as alkali in this calculation.

[0100] 14. Calculation of Addition Rate Ratio When the addition rate of acidic silica solution [g / min] (calculated in silica dry equivalent) is X, and the withdrawal rate of the reaction solution [g / min] (calculated in silica dry equivalent) is Z, the ratio of the addition rate of acidic silica solution to the withdrawal rate of the reaction solution (X / Z) was calculated by simultaneously starting the addition of acidic silica solution and the withdrawal of the reaction solution, measuring the addition rate of acidic silica solution and the withdrawal rate of the reaction solution at 10 minutes after the completion of addition and withdrawal, and then calculating the ratio of the addition rate of acidic silica solution to the withdrawal rate of the reaction solution (X / Z) from these values.

[0101] 15. Polishing Test Method • Polishing of aluminum hard drives The abrasive dispersions obtained in each of the examples and comparative examples were prepared. The solid content concentration was 9% by mass, and the pH was adjusted to 2.0 by adding nitric acid. An aluminum hard disk substrate was set in a polishing machine (NF300, manufactured by Nanofactor Co., Ltd.), and polishing was performed using a polishing pad (Polytex φ12, manufactured by Nitta Haas Co., Ltd.) with a substrate load of 0.05 MPa, a table rotation speed of 30 rpm, and a polishing head rotation speed of 60 rpm. Polishing was carried out by supplying abrasive dispersion liquid at a rate of 20 mL / min for 10 minutes, and the polishing speed was calculated by determining the weight change of the substrate before and after polishing. In addition, the entire surface of the polished substrate was observed using an ultrafine defect visualization macro device (Macro-Max, manufactured by VISION PSYTEC, Inc.) at Zoom 15, and the measurement was taken at 65.97 cm². 2 The number of scratches (linear marks) present on the polished substrate surface corresponding to the specified condition was counted and totaled.

[0102] The raw materials used in the examples and comparative examples are described below.

[0103] [Potassium hydroxide solution] The potassium hydroxide aqueous solution used was "Super Kali R" (KOH concentration 48.6% by mass) manufactured by Toagosei Co., Ltd., either as is or concentrated or diluted as needed.

[0104] [Potassium chloride solution] Potassium chloride was used as an aqueous solution (KCl concentration 20% by mass) by diluting potassium chloride from Takasugi Pharmaceutical Co., Ltd. with pure water.

[0105] [Acidic silica solution] A sodium silicate aqueous solution (silica concentration 24.06% by mass, Na2O concentration 7.97% by mass) was mixed with pure water to obtain a sodium silicate aqueous solution (silica concentration 5% by mass). 18 kg of the obtained sodium silicate aqueous solution was mixed with 6 L of strongly acidic cation exchange resin (SK1BH, manufactured by Mitsubishi Chemical Corporation) at a space velocity of 3.0 h. -1The solution was passed through to obtain an acidic silica solution (18 kg, silica concentration 4.55% by mass, pH 2.7). In the following examples and comparative examples, this acidic silica solution or an equivalent acidic silica solution (silica concentration 4.55% by mass, pH 2.7) was used as a raw material after being appropriately concentrated or diluted.

[0106] [Example 1] ·Process 1 6.700 kg of pure water was poured into a mixing tank (X) (internal volume 200 L), followed by the addition of 314.81 g of potassium hydroxide aqueous solution (KOH concentration 48.6% by mass), and then 8988.8 g of acidic silicic acid solution (SiO2 concentration 4.45%). The mixture was stirred until homogeneous to obtain the first preparation solution (silica concentration 2.50% by mass). After stirring the first preparation solution, the temperature was raised to 90°C and held for 30 minutes. Then, 138.3 kg of acidic silicic acid solution (SiO2 concentration 4.45%) was added to the first preparation solution over 11 hours. The addition rate of the acidic silicic acid solution during this process was 209.55 g / min. After the addition was complete, the mixture was kept at 90°C for 1 hour and then cooled to room temperature to obtain 154.30 kg of silica nanoparticle precursor dispersion, which was then cooled to room temperature. ·Process 2 5.776 kg of pure water was poured into a mixing tank (Y) (internal volume 200 L) that was kept unheated, and 84.22 kg of the silica fine particle precursor dispersion obtained in step 1 was added. The mixture was stirred until homogeneous to obtain the second formulation (silica concentration 4.10 mass%). ·Process 3 The second preparation solution (silica concentration 4.38% by mass) was heated to 90°C, and while maintaining a temperature of 89-91°C, acidic silicic acid solution (silica concentration 4.45% by mass, 566.85 kg) and potassium hydroxide aqueous solution (72.68 kg) were added simultaneously and continuously. The relationship between the addition rate and elapsed time is shown in Table 1. In addition, 602.05 kg of the reaction solution was withdrawn from the mixing tank (Y) at the same time as the addition of the acidic silica solution and the potassium hydroxide aqueous solution. The relationship between the withdrawal rate and the elapsed time is shown in Table 1. The time required for the addition of the acidic silica solution and potassium hydroxide aqueous solution in Step 3 of Example 1 was 90 hours, and the time required for the withdrawal of the reaction solution was also 90 hours. Table 1 also shows the SiO2 concentration of the acidic silica solution, the rate of acidic silica solution addition, the weight of acidic silica solution added, and the concentration, mass, and number of moles of potassium hydroxide for each elapsed time period, in addition to the two addition and withdrawal rates mentioned above. The rate of acidic silica solution addition, potassium hydroxide concentration, potassium hydroxide addition rate, and withdrawal rate were varied for each elapsed time period. The pH of the reaction solution in the mixing tank (Y) during the addition of the acidic silica solution and potassium hydroxide aqueous solution and the simultaneous withdrawal of the reaction solution was in the range of 9.86 to 10.42. After the addition and withdrawal were completed, 127.50 kg of reaction solution remained in the mixing tank. ·Process 4 The reaction solution remaining in the mixing tank (127.50 kg) was kept at 90°C for 1 hour and then cooled to room temperature. This solution, along with the extracted reaction solution B (602.05 kg), was mixed until homogeneous to obtain a dispersion of silica fine particles for polishing. The resulting silica fine particle dispersion for polishing had a specific surface area equivalent particle size of 43.3 nm and an SiO2 concentration of 3.96% by mass. This mixture was concentrated using an Asahi Kasei SIP-2013 ultrafiltration membrane until the SiO2 concentration reached 12.0% by mass.

[0107] [Example 2] ·Process 1 45.250 kg of pure water was added to mixing tank (X) (internal volume 200 L), followed by 289.69 g of potassium hydroxide aqueous solution (KOH concentration 48.6% by mass). Subsequently, 1,839.11 g of potassium chloride aqueous solution (KCl concentration 20% by mass) was added, followed by 6514.9 g of acidic silica solution (SiO2 concentration 4.55%). The mixture was stirred until homogeneous to obtain the first preparation solution. Next, the first preparation solution was heated to 90°C and held for 30 minutes. Then, 126.1 kg of acidic silicic acid solution (SiO2 concentration 4.55%) was added at an addition rate of 191.06 g / min over 11 hours. After the addition was complete, the solution was held at 90°C for 1 hour to obtain a silica nanoparticle precursor dispersion. Subsequently, the obtained silica nanoparticle precursor dispersion was cooled to room temperature. ·Process 2 33.70 kg of silica microparticle precursor dispersion was extracted from the silica microparticle precursor dispersion (180.00 kg) in mixing tank (X), and the entire amount was poured into mixing tank (Y) (internal volume 50 L). Further, 6.304 kg of pure water was added, and the mixture was stirred until homogeneous to obtain the second formulation (silica concentration 3.00 mass%). ·Process 3 The second preparation solution in the mixing tank (Y) was heated to 90°C, and while maintaining a temperature of 89-91°C, acidic silicic acid solution (silica concentration 4.55% by mass, 97.20 kg) and potassium hydroxide aqueous solution (KOH concentration 0.26% by mass, 40.68 kg) were added simultaneously and continuously. The relationship between the addition rate and elapsed time is shown in Table 1. In addition, simultaneously with the addition of the acidic silica solution and the potassium hydroxide aqueous solution, 148.41 kg of the reaction solution was withdrawn from the mixing tank (Y) in total volume. The relationship between the withdrawal rate and the elapsed time is shown in Table 1. The time required for the addition of the acidic silica solution and potassium hydroxide aqueous solution in this step 3 was 75 hours, and the time required for the withdrawal of the reaction solution was also 75 hours. Table 1 also shows the SiO2 concentration of the acidic silica solution, the rate of acidic silica solution addition, the weight of acidic silica solution added, and the concentration, mass, and number of moles of potassium hydroxide for each elapsed time period, in addition to the two addition and withdrawal rates mentioned above. The rate of acidic silica solution addition, potassium hydroxide concentration, potassium hydroxide addition rate, and withdrawal rate were varied for each elapsed time period. The pH of the reaction solution in the mixing tank (Y) during the addition of the acidic silica solution and potassium hydroxide aqueous solution and the simultaneous withdrawal of the reaction solution was in the range of 9.45 to 10.21. After the addition and withdrawal were completed, 29.47 kg of reaction solution remained in the mixing tank. ·Process 4 The reaction solution (29.47 kg) remaining in the mixing tank (Y) was held at 90°C for 1 hour and cooled to room temperature. This solution, along with the extracted reaction solution (148.41 kg), was mixed until homogeneous to obtain a silica fine particle dispersion for polishing. This silica fine particle dispersion had a specific surface area equivalent particle size of 42.6 nm and an SiO2 concentration of 3.19 mass%. This silica fine particle dispersion was then concentrated using an Asahi Kasei SIP-2013 ultrafiltration membrane until the SiO2 concentration reached 12.0 mass%.

[0108] [Example 3] A dispersion of silica fine particles for polishing was obtained using the same procedure as in Example 2, except that the specific numerical conditions were as described in the column for Example 3 in Table 1. In addition, the time required for adding the acidic silica solution and potassium hydroxide aqueous solution in step 3 of Example 3 was 90 hours, and the time required for withdrawing the reaction solution was also 90 hours.

[0109] [Example 4] A dispersion of silica fine particles for polishing was obtained using the same procedure as in Example 1, except that the specific numerical conditions were as shown in Table 1. In addition, the time required for adding the acidic silica solution and potassium hydroxide aqueous solution in step 3 of Example 4 was 61 hours, and the time required for withdrawing the reaction solution was also 61 hours.

[0110] [Comparative Example 1] 4527g of pure water was added to a mixing tank (internal volume 10L), and then 413.6g of silica fine particle dispersion (JGC Cataloid SI-50, manufactured by JGC Catalysts & Chemicals, SiO2 concentration 48.35% by mass, Na2O concentration 0.49% by mass, specific surface area equivalent particle diameter 26.2nm, liquid temperature 25℃) was added to obtain a diluted silica fine particle dispersion. A potassium hydroxide aqueous solution (KOH concentration 48.7% by mass, Super Kali R, manufactured by Toagosei Co., Ltd.) was diluted with pure water to a KOH concentration of 4.8% by mass. 20.83 g of this potassium hydroxide aqueous solution was added to the diluted silica fine particle dispersion, and the mixture was stirred until homogeneous. After stirring, the temperature was raised to 95°C and held for 30 minutes. Next, while maintaining a temperature of 94°C to 96°C, an acidic silica solution (SiO2 concentration 4.45% by mass, 14.198 kg) and a potassium hydroxide aqueous solution (KOH concentration 1.0% by mass, 1.475 kg) were added over 18 hours. The addition rate of the acidic silica solution (SiO2 concentration 4.45% by mass, pH 2.7) was 14.40 g / min for the first 9 hours after the start of addition, and 11.90 g / min from 9 hours to 18 hours. The addition rate of the potassium hydroxide aqueous solution (KOH concentration 1.0% by mass) was 1.54 g / min for the first 9 hours after the start of addition, and 1.19 g / min from 9 hours to 18 hours. Simultaneously with the addition of the acidic silica solution and the potassium hydroxide aqueous solution, 15.04 kg of the reaction solution was withdrawn from the mixing tank. The withdrawal rate of the withdrawn solution was set at 15.93 g / min for the first 9 hours after the start of withdrawal, and then at 11.92 g / min from 9 hours to 18 hours after the start of withdrawal. After the addition and withdrawal were complete, 5.59 kg of reaction solution remained in the mixing tank. This solution was kept at 95°C for 1 hour and then cooled to room temperature. The reaction solution remaining in the mixing tank (5.59 kg) and the extracted reaction solution (15.04 kg) were mixed until homogeneous to obtain a dispersion of silica microparticles for polishing. This dispersion of silica microparticles had a specific surface area equivalent diameter of 45.5 nm and an SiO2 concentration of 4.03% by mass. This dispersion of silica microparticles was then concentrated to an SiO2 concentration of 12.0% using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation.

[0111] [Comparative Example 2] 304.66 g of pure water was added to a mixing tank (internal volume 10 L), followed by 6.72 g of potassium hydroxide aqueous solution (KOH concentration 48.7% by mass (Super Kali R, manufactured by Toagosei Co., Ltd.)). Furthermore, 160.88 g of acidic silica solution (SiO2 concentration 4.55% by mass) was added, and the mixture was stirred until homogeneous to obtain the first formulation. Next, the first preparation solution was heated to 98°C and held there for 30 minutes. Then, 2.918 kg of acidic silica solution (SiO2 concentration 4.55% by mass) was added over 11 hours. The addition rate was 4.42 g / min. After the addition was complete, 351.27 g of pure water was added to maintain the temperature at 98°C. Next, while maintaining a temperature of 97°C to 99°C, acidic silica solution (SiO2 concentration 4.55% by mass, 14.338 kg) and potassium hydroxide aqueous solution (KOH concentration 0.5% by mass, 3.046 kg) were added over 24 hours. Simultaneously with the addition of the acidic silica solution and potassium hydroxide aqueous solution, 17.24 kg of the reaction mixture was withdrawn from the mixing tank. Table 2 shows the SiO2 concentration of the acidic silica solution, the rate of addition of the acidic silica solution, the weight of the acidic silica solution added, the rate of addition of potassium hydroxide, and the withdrawal rate for each time period during this process. After the addition and withdrawal were completed, 3.89 kg of reaction solution remained in the mixing tank. This solution was held at 98°C for 1 hour and then cooled to room temperature. The reaction solution remaining in the mixing tank (3.89 kg) and the extracted reaction solution (17.24 kg) were mixed until homogeneous to obtain a dispersion of silica microparticles for polishing. This dispersion of silica microparticles had a pH of 10.1, a specific surface area equivalent diameter of 36.9 nm, and an SiO2 concentration of 3.75% by mass. This dispersion of silica microparticles was then concentrated to an SiO2 concentration of 12.0% using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation.

[0112] [Comparative Example 3] 4522g of pure water at 95°C was added to a mixing tank (internal volume 10L), followed by 461.2g of silica fine particle dispersion (Cataloid SI-50, manufactured by JGC Catalysts & Chemicals, SiO2 concentration 48.35% by mass, Na2O concentration 0.49% by mass, specific surface area equivalent particle size 26.2nm, liquid temperature 25°C). Furthermore, 48.6% by mass of NaOH (sodium hydroxide, manufactured by JGC Catalysts & Chemicals) was diluted to 4.8% by mass with pure water, and 16.56g of the sodium hydroxide aqueous solution was added. The mixture was stirred until homogeneous and held for 30 minutes. Subsequently, while maintaining a temperature of 94°C to 96°C, 21.520 kg of acidic silicic acid solution (SiO2 concentration 4.55% by mass, 7.121 kg), sodium hydroxide aqueous solution (NaOH concentration 0.25% by mass, 7.121 kg), and 3.519 kg of a silica microparticle dispersion (JGC Cataloid SI-50, manufactured by JGC Chemical Co., Ltd.) diluted with pure water to a 12% SiO2 concentration were added over 48 hours. During this process, the addition rates for the acidic silicic acid solution were 7.47 g / min, the 0.25% by mass NaOH aqueous solution were 2.47 g / min, and the silica microparticle dispersion was 1.22 g / min. Simultaneously with the addition of the acidic silicic acid solution, sodium hydroxide aqueous solution, and silica microparticle dispersion, 32.47 kg of the reaction solution was withdrawn from the mixing tank. The withdrawal rate was 11.27 g / min. After the addition and withdrawal were complete, 4.69 kg of reaction solution remained in the mixing tank. This solution was kept at 95°C for 1 hour and then cooled to room temperature. The reaction solution remaining in the mixing tank (4.69 kg) and the extracted reaction solution (32.47 kg) were mixed until homogeneous to obtain a dispersion of silica microparticles for polishing. This dispersion of silica microparticles had a pH of 10.3, a specific surface area equivalent diameter of 33.3 nm, and an SiO2 concentration of 4.36% by mass. This dispersion of silica microparticles was then concentrated to an SiO2 concentration of 12.0% using an ultrafiltration membrane SIP-1013 manufactured by Asahi Kasei Corporation.

[0113] [Comparative Example 4] Cataloid SI-45P (silica microparticle dispersion) manufactured by JGC Catalysts & Chemicals Co., Ltd. was used as the silica microparticle dispersion for polishing.

[0114] [Comparative Example 5] 5.830 kg of pure water was added to a mixing tank (internal volume 50 L), and then 393 g of silica fine particle dispersion (JGC Cataloid SI-30, manufactured by JGC Catalysts & Chemicals, SiO2 concentration 30.54% by mass, Na2O concentration 0.41% by mass, specific surface area equivalent particle size 11.0 nm, liquid temperature 25°C) was added to obtain a diluted silica fine particle dispersion. 48.6% by mass of NaOH (sodium hydroxide manufactured by JGC Catalysts & Chemicals Co., Ltd.) was diluted to 4.8% by mass with pure water, and 179 g of this sodium hydroxide aqueous solution was added to the diluted silica fine particle dispersion and stirred until homogeneous. Then, 1100 g of an aqueous solution of polyethyleneimine (PEI-600 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., average molecular weight approximately 600), diluted to 0.3% with pure water, was added to the mixing tank over 20 minutes. The addition rate at this time was 55.00 g / min. After that, the mixture was stirred until homogeneous, and after stirring, the temperature was raised to 90°C and held for 120 minutes. Next, while maintaining a temperature of 89°C to 91°C, an acidic silica solution (SiO2 concentration 4.50% by mass, 41.90 kg) was added over 18 hours. The addition rate of the acidic silica solution (SiO2 concentration 4.50% by mass, pH 2.7) was 38.79 g / min. After the addition was complete, the 49.40 kg of reaction solution in the mixing tank was kept at 90°C for 1 hour, then cooled to room temperature to obtain a silica microparticle dispersion for polishing. This silica microparticle dispersion had a specific surface area equivalent diameter of 53.5 nm and an SiO2 concentration of 4.06% by mass. This silica microparticle dispersion was then concentrated to an SiO2 concentration of 12.0% using an ultrafiltration membrane SIP-2013 manufactured by Asahi Kasei Corporation.

[0115] [Evaluation Results] The conditions for preparing the examples are shown in Table 1. The conditions for preparing the comparative examples are shown in Table 2. Furthermore, the evaluation results of the abrasive silica fine particle dispersions obtained in the examples and comparative examples are shown in Tables 3 and 4.

[0116] [Table 1]

[0117] [Table 2]

[0118] [Table 3]

[0119] Table 4

Claims

1. A method for producing a silica fine particle dispersion for polishing, comprising the following steps 1 to 4. (Step 1) The process involves introducing an acidic silica solution and an alkali into a reaction vessel (X) kept unheated, stirring uniformly to obtain a first preparation solution, then heating to a temperature of 40°C to 98°C and maintaining that temperature range, and then continuously or intermittently adding the acidic silica solution while maintaining that temperature range, followed by aging at a temperature of 40°C to 98°C for 20 minutes to 120 minutes to obtain a silica nanoparticle precursor dispersion. (Step 2) The process involves introducing the silica fine particle precursor dispersion obtained in step 1 and pure water into a reaction vessel (Y) that is kept unheated to obtain a second preparation solution (silica concentration of 0.3% by mass or more and 4.6% by mass or less). (Step 3) Following step 2, the second preparation solution in the reaction vessel (Y) is maintained at a temperature of 40°C to 98°C, and acidic silica solution and alkali are added thereto continuously or intermittently, stirring is performed to allow the reaction to proceed, while simultaneously a portion of the solution in the reaction vessel (Y) is continuously or intermittently withdrawn. (Step 4) After the completion of step 3, the solution A remaining in the reaction vessel (Y) is aged at a temperature of 40°C to 98°C for 20 minutes to 120 minutes, and then the solution A and the solution B extracted in step 3 are mixed to obtain a silica fine particle dispersion for polishing.

2. A method for producing a silica fine particle dispersion for polishing according to claim 1, wherein the addition rate [g / min] (silica dry equivalent) when adding the acidic silica solution in step 3 is X, and the extraction rate [g / min] (silica dry equivalent) when extracting the B solution is Z, and the ratio of the addition rate of the acidic silica solution to the extraction rate of the reaction solution (X / Z) is in the range of 0.2 or more and 15.0 or less.

3. A method for producing a silica fine particle dispersion for polishing according to claim 1 or claim 2, wherein the silica concentration of the first preparation liquid in step 1 is 0.1% by mass or more and 15% by mass or less.

4. In step 1, a flocculant is further added to the first preparation liquid, in order to match the number of moles of silica in the acidic silicic acid solution in the first preparation liquid (MN ＳｉＯ２ ) and the number of moles of flocculant (MN ＭＸ ) molar ratio (MN ＳｉＯ２ / MN ＭＸ A method for producing a silica fine particle dispersion for polishing according to claim 1 or claim 2, wherein the amount of ) is added in a range of 0.1 to 100.

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