Silica particle, silica sol and production method thereof, polishing composition, polishing method, production method of semiconductor wafer, and production method of semiconductor device

Abstract

To solve the problem in which weak repulsive force between silica particles causes the silica particles to easily aggregate, exhibiting poor dispersion stability, and weak interaction between the silica particles and an object to be polished during polishing causes poor polishing properties.SOLUTION: A silica particle has a surface silanol group density as measured by the Sears method of 2 / nm2 or more and a surface silanol group concentration of 1.5% or more. A production method of the silica particle includes a hydrolytic reaction and a condensation reaction of tetraalkoxysilane to produce the silica particle.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to silica particles, silica sol and its manufacturing method, polishing composition, polishing method, and semiconductor wafer. The present invention relates to a wafer manufacturing method and a semiconductor device manufacturing method. [Background technology]

[0002] A method using a polishing liquid is known as a method for polishing the surfaces of materials such as metals and inorganic compounds. Among these, prime silicon wafers for semiconductors and recycled silicon wafers final polishing of semiconductor devices, planarization of interlayer insulating films during semiconductor device manufacturing, formation of metal plugs, In chemical mechanical polishing (CMP) for forming buried wiring, the surface condition changes to semiconductor properties. Since this has a significant impact on the product, the surfaces and edges of these components must be polished with extremely high precision. is required.

[0003] In such precision polishing, a polishing composition containing silica particles is used. Colloidal silica is widely used as the main abrasive grain. Depending on the manufacturing method, they are produced by thermal decomposition of silicon tetrachloride (fumed silica, etc.), Deionization of alkali silicates such as water glass, hydrolysis reaction of alkoxysilanes, and Known methods include those based on condensation reactions (generally called "sol-gel methods").

[0004] It is known that the physical properties of colloidal silica affect its performance as a polishing liquid. Many studies have been carried out. Among them, the silanol groups on the surface of colloidal silica particles have been shown to have abrasive properties. The effects of this on the performance and stability of polishing solutions are not limited to silicon wafer polishing, but are also applicable to semiconductor Much research has also been done on chemical mechanical polishing during device manufacturing.

[0005] For example, Patent Document 1 discloses a method for producing silica by hydrolysis and condensation of alkoxysilane. A method for producing a sol is disclosed. In addition, Patent Document 2 discloses a method for producing a sol by silanol-based surface sol. It is disclosed that the density of the cobalt group affects the polishing performance of the cobalt film. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2008 / 015943 [Patent Document 2] Japanese Patent Application Publication No. 2018-107293 Summary of the Invention [Problem to be solved by the invention]

[0007] The amount of silanol groups on the surface of silica particles has a significant effect on the polishing performance and stability of the polishing solution when used for polishing. It is known that silica particles have a significant effect on the polishing process. It is known that silanol groups on the surface and the surface of the object to be polished undergo dehydration condensation to form siloxane bonds. If polishing proceeds through this mechanism, a certain amount of silanol exists on the surface of the silica particles. Furthermore, if there are not enough silanol groups, the repulsive force between particles will be weak. In particular, small particles with an average primary particle size of less than 40 nm tend to aggregate easily. On the other hand, if there are too many silanol groups, the silanol groups will be easily disintegrated. The water molecules hydrogen-bonded to the nol groups form a film that covers the surface of the silica particles, The chances of contact between the blade and the object being polished decrease, making polishing impossible. If there is an excess of silanol groups, the siloxane bond becomes strong and the amount of silicon remaining on the surface of the object to be polished increases. The amount of silanol groups increases, which deteriorates the quality of the polished object. These become reactive sites and also deteriorate the dispersion stability. It is also required that the content of alkyl groups be kept below a certain amount.

[0008] As a method for evaluating the amount of silanol groups present on the surface of silica particles, There are known methods for measuring the silanol group density and the surface silanol group concentration. The surface silanol group density reflects the amount of silanol groups per unit area, and The surface silanol group concentration is related to the interparticle repulsion and the thickness of the hydration layer. It reflects the amount of silanol groups relative to the amount of silica particles, and the amount of water of hydration and chemical reactivity of silica particles. is related to.

[0009] In the method for producing silica sol disclosed in Patent Document 1, the silica particles present on the surface are Furthermore, Patent Document 2 does not mention anything about silanol groups. Although it has been disclosed that the density of silanol groups affects polishing performance, As described above, the conventional silica sol and silica particles In the manufacturing method, both the surface silanol group density and the surface silanol group concentration of the silica particles are sufficiently controlled. It cannot be said that the concentration is adequately controlled, and the polishing properties and dispersion stability of these particles are insufficient.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a polishing agent having excellent polishing properties, To provide silica particles with excellent dispersion stability, a method for producing the same, a silica sol, and a polishing composition Another object of the present invention is to provide a polishing method that is excellent in suppressing scratches on the object to be polished and in productivity. The present invention aims to provide a polishing method, a semiconductor wafer manufacturing method, and a semiconductor device manufacturing method. Let's say. [Means for solving the problem]

[0011] As a result of extensive research, the inventors of the present invention have found that the surface silanol groups measured by the Sears method By optimizing both the concentration and the surface silanol group density, the polishing properties and dispersion stability of silica particles can be improved. The present inventors have found that the quality of the resulting mixture is improved, and have completed the present invention.

[0012] That is, the gist of the present invention is as follows. [1] The surface silanol group density measured by the Sears method is 2 / nm 2 Above and surface Silica particles having a lanol group concentration of 1.5% or more. [2] The average primary particle diameter measured by the BET method is 40 nm or less, as described in [1] above. of silica particles. [3] The above [1] or [1], wherein the average secondary particle diameter measured by DLS method is 100 nm or less. [2] Silica particles according to the present invention. [4] The silica according to any one of [1] to [3] above, wherein the silica particles are amorphous. particle. [5] A silica sol containing the silica particles according to any one of [1] to [4] above. [6] The method according to the above, comprising a step of subjecting tetraalkoxysilane to hydrolysis and condensation reaction. 5] A method for producing a silica sol according to the present invention. [7] The step of carrying out the hydrolysis reaction and the condensation reaction includes adding, to a liquid (A) containing an alkali catalyst, A liquid (B) containing tetraalkoxysilane and a liquid (C) containing water were added to the mixture, and the hydrolysis reaction and and subjecting the resulting mixture to a condensation reaction. [8] A step of replacing the dispersion medium of the silica sol with water, wherein the time for the step is 3 hours or more; The method for producing a silica sol according to [6] or [7] above, wherein the time is 20 hours or less. [9] A polishing composition containing the silica sol described in [5] above.

[10] A polishing method using the polishing composition according to [9] above.

[11] A method for manufacturing a semiconductor wafer, comprising a step of polishing the semiconductor wafer using the polishing composition according to [9]. Construction method.

[12] A method for polishing a semiconductor device, comprising the step of polishing using the polishing composition according to [9]. Manufacturing method. [Effects of the Invention]

[0013] The silica particles of the present invention, the silica particles obtained by the production method of the present invention, The polishing composition of the present invention has excellent polishing properties and dispersion stability. The method for producing a semiconductor wafer and the method for producing a semiconductor device of the present invention are carried out by polishing a surface of a polished object. Excellent clutch suppression and productivity. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below, but the present invention is not limited to the following embodiments. The present invention can be practiced with various modifications within the scope of its gist. When an expression is used, it is used as an expression including the numerical values ​​or physical property values ​​before and after it.

[0015] <Silica particles> The silica particles of the present invention have a surface silanol group density of 2 / nm as measured by the Sears method. 2 or more, preferably 2.2 / nm 2 More preferably, 2.5 particles / nm 2 That's all This allows the silica particles to have an appropriate surface repulsion, resulting in excellent dispersion stability of the silica sol. Furthermore, the hydration layer on the silica surface becomes thicker, resulting in excellent scratch reduction.

[0016] There is no particular upper limit to the surface silanol group density of the silica particles of the present invention. In order to improve the removability from the polished object during cleaning, 2 below It is preferable that the number of particles is 10 / nm 2 More preferably, it is 8 or less per nm. 2 Below It is more preferable that the temperature is lower than the reference temperature.

[0017] The surface silanol group density of silica particles is measured by the Sears method. Measure and calculate under the conditions shown below. A silica sol equivalent to 1.5 g of silica particles was collected and purified water was added to make the liquid volume 90 mL. In an environment of 25°C, add 0.1 mol / L hydrochloric acid solution until the pH reaches 3.6. Add 30g of sodium chloride, and gradually add pure water until the sodium chloride is completely dissolved. Finally, add purified water until the total volume of the test solution becomes 150 mL to obtain the test solution. The obtained test solution was placed in an automatic titrator and 0.1 mol / L sodium hydroxide solution was added. Add 0.1 mol / L of sodium hydroxide dropwise to change the pH from 4.0 to 9.0. Measure the titer A (mL) of the aqueous solution.

[0018] Using the following formula (1), the pH per 1.5 g of silica particles changes from 4.0 to 9.0. Calculate the amount of 0.1 mol / L sodium hydroxide solution consumed (V (mL)) and calculate the following: Using equation (2), the surface silanol group density ρ (particles / nm 2 ) is calculated. V = (A × f × 100 × 1.5) / (W × C SiO2 ) (1) A: The time required for the pH to change from 4.0 to 9.0 per 1.5g of silica particles is 0.1 Titration volume (mL) of mol / L sodium hydroxide solution f: Potency of the 0.1 mol / L sodium hydroxide solution used C SiO2 : Concentration of silica particles in silica sol (mass%) W: Amount of silica sol collected (g) ρ=(B×N A ) / (10 18 ×m×S BET ) (2) The pH per 1.5g of silica particles calculated from B:V changes from 4.0 to 9.0. Amount of sodium hydroxide required (mol) N A : Avogadro's number (units / mol) m: Silica particle amount (1.5g) S BET : The specific surface area (m) of silica particles measured when calculating the average primary particle diameter 2 / g )

[0019] The surface silanol group concentration of the silica particles of the present invention is 1.5% or more, preferably 1.6% or more. The surface repulsion of the silica particles is preferably 1.7% or more, and more preferably 1.7% or more. The dispersion stability of the silica sol is excellent. This improves the polishing performance through chemical action.

[0020] There is no particular upper limit to the surface silanol group concentration of the silica particles of the present invention. In order to improve the removability from the polished object during cleaning when polished, the content is 5.0% or less. It is preferable that the content of the saturation gas is 4.0% or less, more preferably 3.0% or less. More preferable.

[0021] The surface silanol group concentration of silica particles was measured by the Sears method in the same way as the surface silanol group density. Specifically, measurements and calculations are performed under the conditions shown below. A silica sol equivalent to 1.5 g of silica particles was collected and purified water was added to make the liquid volume 90 mL. In an environment of 25°C, add 0.1 mol / L hydrochloric acid solution until the pH reaches 3.6. Next, add 30 g of sodium chloride, and gradually add pure water to completely remove the sodium chloride. After dissolving, add pure water until the total volume of the test solution becomes 150 mL to obtain the test solution.

[0022] The obtained test solution was placed in an automatic titrator and 0.1 mol / L sodium hydroxide solution was added. Add 0.1 mol / L of sodium hydroxide dropwise to change the pH from 4.0 to 9.0. Measure the titer A (mL) of the aqueous solution.

[0023] Using the following formula (1), the pH per 1.5 g of silica particles changes from 4.0 to 9.0. Calculate the amount of 0.1 mol / L sodium hydroxide solution consumed (V (mL)) and calculate the following: Using equation (3), the surface silanol group concentration C of the silica particles is calculated. OH Calculate (%). V = (A × f × 100 × 1.5) / (W × C SiO2 ) (1) A: The time required for the pH to change from 4.0 to 9.0 per 1.5g of silica particles is 0.1 Titration volume (mL) of mol / L sodium hydroxide solution f: Potency of the 0.1 mol / L sodium hydroxide solution used C SiO2 : Concentration of silica particles in silica sol (mass%) W: Amount of silica sol collected (g) C OH =(B×M OH ) / m×100 (3) The pH per 1.5g of silica particles calculated from B:V changes from 4.0 to 9.0. Amount of sodium hydroxide required (mol) M OH Molar mass of OH (17 g / mol) m: Silica particle amount (1.5g)

[0024] The method for measuring and calculating the surface silanol group density and surface silanol group concentration of the silica particles is as follows: , “GWSears, Jr., Analytical Chemistry, Vol. .28, No.12, pp.1981-1983(1956).," Shinichi Haba, Semiconductor Development of abrasives for integrated circuit processing, Doctoral dissertation, Kochi University of Technology, pp.39-45, 2004 March 2018, "Patent No. 5967118", and "Patent No. 6047395" do. The surface silanol group density and surface silanol group concentration of silica particles were measured using various silica particles. By controlling the manufacturing conditions, the desired range can be set. For example, Set by controlling the drop rate of tetraalkoxysilane and the ratio of components in the reaction solution. It is possible to do this.

[0025] The silica particles of the present invention have a surface silanol group density of 2 / nm 2 More than that and the surface Cyrano The concentration of hydroxyl groups is 1.5%. The thickness of the hydration layer on the surface and chemical reactivity have been improved, resulting in excellent dispersion stability, scratch reduction, and polishing performance. do.

[0026] The silica particles of the present invention are preferably amorphous. By this, there are an adequate amount of silanol groups on the surface of the silica particles, which allows polishing of the object to be polished. During the polishing process, a chemical reaction occurs between the silica particles and the object to be polished via the silanol groups. , polishing proceeds smoothly. The amorphous nature of the silica particles is confirmed by the halo pattern observed in wide-angle X-ray scattering measurements. It can be confirmed.

[0027] The metal impurity content of the silica particles of the present invention is preferably 5 ppm or less, and more preferably 2 ppm or less. It is more preferable that the length is m or less. When the metal impurity content of silica particles is 5 ppm or less, the silicon When polishing wafers, metal impurities can adhere to the surface of the object to be polished, causing contamination. This is preferable because it reduces the influence of particles adhering to the surface of the object to be polished on the wafer characteristics. Metallic impurities diffuse into the wafer, deteriorating its quality. This is preferable because it reduces degradation in the performance of the manufactured semiconductor device.

[0028] Furthermore, when the metal impurity content of silica particles is 5 ppm or less, the surface silica exhibits acidity. This reduces the occurrence of coordination interactions between the silanols and metal impurities, and promotes the formation of surface silanols. This prevents the chemical properties of the alkyl groups from changing and affecting the acidity, etc., and maintains the three-dimensional structure of the silica particle surface. This prevents the silica particles from agglomerating due to changes in the environment, reducing the impact on the polishing rate. Therefore, it is preferable.

[0029] In this specification, the metal impurity content of silica particles is determined by high frequency inductively coupled plasma mass spectrometry. This is a value measured by ICP-MS. Accurately weigh out the silica sol, add sulfuric acid and hydrofluoric acid, heat, dissolve, and evaporate it. The test solution was prepared by adding pure water to the acid droplets so that the total amount was exactly 10 g. Measurements are performed using a Zuma mass spectrometer. The target metals are sodium, potassium, iron, and aluminum. Sodium, calcium, magnesium, zinc, cobalt, chromium, copper, manganese, lead, titanium The total content of these metals is the metal impurity content.

[0030] The metal impurity content of silica particles is determined by the hydrolysis reaction and By carrying out a condensation reaction to obtain silica particles, the concentration can be reduced to 5 ppm or less. In the method of deionizing alkali silicate such as water glass, sodium etc. derived from the raw material remains. Therefore, it is extremely difficult to reduce the metal impurity content of silica particles to 5 ppm or less. .

[0031] The average primary particle diameter of the silica particles of the present invention is preferably 2 nm or more, more preferably 3 nm or more. The average primary particle diameter of the silica particles is preferably 2 nm or more, and more preferably 4 nm or more. This provides excellent particle removal properties during cleaning after polishing, and the dispersion stability of the silica sol is also excellent. The average primary particle size of the silica particles is preferably 40 nm or less, more preferably 30 nm or less. The average primary particle diameter of the silica particles is 40 nm or less, and more preferably 20 nm or less. This reduces the surface roughness and scratches on the polished object, typically a silicon wafer, during polishing, and the silica particles This can suppress the sedimentation of the children.

[0032] The average primary particle size of silica particles is measured by the BET method. The specific surface area of ​​the silica particles was measured using a measuring device, and the average primary particle diameter was calculated using the following formula (4). Calculate. Average primary particle diameter (nm) = 6000 / (specific surface area (m 2 / g) x density (g / cm 3 )) (4)

[0033] The average primary particle size of the silica particles is set within a desired range depending on the manufacturing conditions of the silica particles. It is possible.

[0034] The average secondary particle diameter of the silica particles is preferably 4 nm or more, more preferably 7 nm or more, It is more preferable that the average secondary particle diameter of the silica particles is 4 nm or more. It has excellent particle removal properties when cleaning after polishing, and excellent dispersion stability of silica sol. The average secondary particle diameter of the silica particles is preferably 100 nm or less, more preferably 90 nm or less, It is more preferable that the average secondary particle diameter of the silica particles is 100 nm or less. This can reduce the surface roughness and scratches of the object being polished, such as silicon wafers, during polishing. It has excellent particle removal properties in subsequent washing and can prevent the sedimentation of silica particles.

[0035] The average secondary particle diameter of silica particles is measured by the DLS method. Measure using a diameter measuring device.

[0036] The average secondary particle size of the silica particles is set within a desired range depending on the manufacturing conditions of the silica particles. It is possible.

[0037] The cv value of the silica particles of the present invention is preferably 10% or more, more preferably 15% or more. The cv value of the silica particles is more preferably 20% or more. It has an excellent polishing rate for the object to be polished, typified by C, and is excellent in productivity of silicon wafers. The cv value of the silica particles of the present invention is preferably 50% or less, more preferably 40% or less. If the cv value of the silica particles is 50% or less, the silica particles can be polished more easily. It can reduce the surface roughness and scratches of the object being polished, such as silicon wafers, and eliminates particles during cleaning after polishing. Excellent ability to remove dirt and other particles.

[0038] The cv value of silica particles is calculated using a dynamic light scattering particle size analyzer. The diameter is measured and calculated using the following formula (5). cv value = (standard deviation (nm) / average secondary particle size (nm)) × 100 (5)

[0039] The association ratio of the silica particles is preferably 1.0 or more, and more preferably 1.1 or more. When the molecular association ratio is 1.0 or more, the polishing level of the object to be polished, typically a silicon wafer, is low. It has excellent adhesion and excellent productivity for silicon wafers. In addition, the association ratio of silica particles is 4.0 or less. When the association ratio of the silica particles is 4.0 or less, the abrasive grains can be easily polished. It can reduce the surface roughness and scratches of the object being polished, such as silicon wafers, and prevents the agglomeration of silica particles. This can suppress the accumulation of bacteria.

[0040] The association ratio of silica particles is calculated by dividing the average primary particle diameter measured by the above-mentioned measurement method by the The average secondary particle diameter is calculated using the following formula (6). Association ratio = average secondary particle diameter / average primary particle diameter (6)

[0041] The silica particles of the present invention have a low content of metal impurities and are excellent in mechanical strength and storage stability. Therefore, it is preferable to use an alkoxysilane condensate as the main component, and It is more preferable that the main component is a silane condensate, and it is more preferable that the main component is a tetramethoxysilane condensate. The main component is 5% by mass of the total components constituting the silica particles. 0% by mass or more. In order to obtain silica particles mainly composed of alkoxysilane condensates, It is preferable to use tetraalkoxysilane condensate as the main raw material. To obtain the desired product, it is preferable to use tetraalkoxysilane as the main raw material. To obtain silica particles mainly composed of silane condensate, tetramethoxysilane is used as the main component. It is preferable to use it as a raw material.

[0042] <Silica sol> The silica sol of the present invention refers to a dispersion of the silica particles of the present invention in an arbitrary dispersion medium. cormorant.

[0043] The silica sol may be a dispersion of the silica particles of the present invention as it is, or a dispersion of the silica particles of the present invention. Even if unnecessary components are removed or necessary components are added to the particle dispersion liquid, good.

[0044] The silica sol of the present invention preferably contains silica particles and a dispersion medium. The dispersion medium in the silica sol is, for example, water, methanol, ethanol, propanol, isopropanol, or the like. Examples of the dispersion medium in these silica sols include propanol, ethylene glycol, etc. One of these dispersion media may be used alone, or two or more of these dispersion media may be used in combination. Among these, water and alcohol are preferred because they have excellent affinity with silica particles, with water being the most preferred. More preferable.

[0045] The content of silica particles in the silica sol is 3% by mass or more out of 100% by mass of the total amount of silica sol. is preferable, more preferably 4% by mass or more, and even more preferably 5% by mass or more. When the content of silica particles in the polishing powder is 3 mass % or more, the polishing powder is The content of silica particles in the silica sol is 50% by mass. The content is preferably 40% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. When the content of silica particles in the polishing composition is 50 mass % or less, the silica particles in the polishing composition are It is possible to suppress the aggregation of silica particles, and the dispersion stability of silica sol and polishing composition is excellent. do.

[0046] The content of the dispersion medium in the silica sol is 50% by mass or more out of the total amount of silica sol (100% by mass). It is preferably 60% by mass or more, more preferably 70% by mass or more. When the content of the dispersion medium in the sol is 50 mass % or more, the silica particles in the silica sol and the polishing composition This can suppress the aggregation of particles, and the dispersion stability of the silica sol and polishing composition is excellent. The content of the dispersion medium in the silica sol is preferably 97% by mass or less, more preferably 96% by mass or less. The content of the dispersion medium in the silica sol is preferably 97% by mass or less, and more preferably 95% by mass or less. When the content is not more than 100%, the polishing rate for the object to be polished, typically a silicon wafer, is excellent.

[0047] The content of silica particles and dispersion medium in the silica sol is determined by the components in the obtained dispersion of silica particles. By removing unnecessary components and adding necessary components, the desired range can be achieved. This can be done.

[0048] Silica sol contains silica particles and a dispersion medium, but any other necessary components are required within the range that does not impair its performance. If necessary, oxidizing agents, preservatives, antifungal agents, pH adjusters, pH buffers, surfactants, chelating agents The composition may also contain other ingredients such as antibacterial and biocide agents. In particular, since silica sol has excellent storage stability, it is possible to use silica sol containing no antibacterial or biocide. It is preferable to do so.

[0049] Antimicrobial biocides include, for example, hydrogen peroxide, ammonia, quaternary ammonium hydroxide, substances, quaternary ammonium salts, ethylenediamine, glutaraldehyde, p-hydroxyammonium These antibacterial biocides include methyl benzoate and sodium chlorite. They may be used alone or in combination of two or more. Among these antibacterial and biocide agents, silica Hydrogen peroxide is preferred because it has excellent affinity with the sol. Antimicrobial biocides also include those commonly referred to as disinfectants.

[0050] The content of the antibacterial biocide in the silica sol is 0.000% of the total amount of silica sol (100% by mass). The content of the antibacterial agent in the silica sol is preferably 1% by mass or more, and more preferably 0.001% by mass or more. When the content of the biological agent is 0.0001% by mass or more, the storage stability of the silica sol is excellent. The content of the antibacterial biocide in the silica sol is preferably 10% by mass or less, and more preferably 1% by mass or less. When the content of the antibacterial biocide in the silica sol is 10% by mass or less, Does not impair the original performance of Rikasol.

[0051] The pH of the silica sol is preferably 6.0 or higher, more preferably 6.5 or higher. When the pH is 6.0 or more, the dispersion stability is excellent and aggregation of silica particles can be suppressed. The pH of the silica sol is preferably 8.0 or less, and more preferably 7.8 or less. If the pH of the silica sol is 8.0 or less, dissolution of the silica particles is prevented, and long-term storage stability is maintained. Excellent in. The pH of the silica sol can be adjusted to the desired range by adding a pH adjuster. do.

[0052] <Method of producing silica particles and silica sol containing silica particles> The method for producing silica particles and silica sol containing silica particles of the present invention is By controlling various manufacturing conditions, including the process of subjecting silane to hydrolysis and condensation reactions, Therefore, the surface silanol group density measured by the Sears method was 2 / nm 2 Above and surface Silica particles with a hydroxyl group concentration of 1.5% or more can be obtained. The polymerization reaction is easy to control, and the reaction rates of the hydrolysis reaction and condensation reaction can be increased. This prevents gelation of the dispersion of alkali particles and allows for the production of silica particles with uniform particle size. The catalyst-containing solution (A) is mixed with the tetraalkoxysilane-containing solution (B) and, if necessary, water. and subjecting the tetraalkoxysilane to hydrolysis and condensation reactions. The method is preferred. The pH during the reaction, reaction temperature, reaction time, catalyst concentration, raw material supply rate, etc. By adjusting the particle manufacturing conditions and subjecting the manufactured silica particles to post-treatments such as pressure and heat treatment, The surface silanol group density and surface silanol group concentration of the silica particles are set within a desired range. This can be done.

[0053] Liquid (A) increases the reaction rate of the hydrolysis reaction and condensation reaction of tetraalkoxysilane. Since it is possible to do so, an alkali catalyst is included.

[0054] Examples of the alkali catalyst in the liquid (A) include ethylenediamine, diethylenetriamine, amine, triethylenetetramine, ammonia, urea, ethanolamine, tetramethyl water These alkali catalysts may be used alone. Among these alkali catalysts, the one having excellent catalytic activity and particle shape is It is easy to control the shape, can suppress the contamination of metal impurities, is highly volatile, and has a high hydrolysis reaction rate. Ammonia is preferred because it is easy to remove after the condensation reaction.

[0055] The liquid (A) preferably contains water.

[0056] Liquid (A) has excellent dispersibility in the reaction liquid of tetraalkoxysilane, so it is possible to use any liquid other than water. It is preferred that the solvent contains: Examples of the solvent other than water in the liquid (A) include methanol, ethanol, and propanol. , isopropanol, ethylene glycol, etc. These solvents can be used alone. Among these solvents, tetraalkoxysilane ... It easily dissolves silanes, and the by-products used in the hydrolysis and condensation reactions are the same as those produced in the reaction. Alcohol is preferred because of its ease of production, and methanol and ethanol are preferred. is more preferred, and methanol is even more preferred.

[0057] The concentration of the alkali catalyst in the liquid (A) is 0.05 mass% or more in 100 mass% of the liquid (A). The concentration of the alkali catalyst in the liquid (A) is preferably 0.0% by mass or more, and more preferably 0.1% by mass or more. When the content is 5% by mass or more, aggregation of silica particles is suppressed, and dispersion stability of silica particles in the dispersion liquid is improved. The concentration of the alkali catalyst in the liquid (A) is preferably 2.0% by mass or less, and The concentration of the alkali catalyst in the liquid (A) is preferably 2.0% by mass or less. When present, the reaction does not proceed excessively quickly, resulting in excellent reaction controllability.

[0058] The concentration of water in the liquid (A) is preferably 3% by mass or more, and more preferably 5% by mass or more, based on 100% by mass of the liquid (A). When the concentration of water in the liquid (A) is 3 mass % or more, the tetraalkoxysilane The hydrolysis reaction rate of silane is easily controlled. In addition, the concentration of water in liquid (A) is 90 mass %. % or less, and more preferably 50% or less by mass. When the amount is less than 1000 ppm, the reaction balance between the hydrolysis reaction and the condensation reaction is good, and the particle shape is easily controlled. Furthermore, the concentration of silicic acid produced by the hydrolysis of tetramethoxysilane increases, The concentration of silanol groups contained in the silicon particles increases.

[0059] The concentration of the solvent other than water in the liquid (A) is preferably the balance of water and the alkali catalyst.

[0060] The liquid (B) contains a tetraalkoxysilane.

[0061] The tetraalkoxysilane in the liquid (B) may be, for example, tetramethoxysilane, tetramethyl ... Examples of suitable silane include tetraethoxysilane, tetrapropoxysilane, and tetraisopropoxysilane. These tetraalkoxysilanes may be used alone or in combination of two or more. Among these tetraalkoxysilanes, the tetraalkoxysilanes having a fast hydrolysis reaction and no unreacted compounds are preferred. It is difficult to leave residue, has excellent productivity, and can easily produce stable silica sol. Tetramethoxysilane and tetraethoxysilane are preferred, and tetramethoxysilane is more preferred. It's nice.

[0062] The raw material for silica particles is a tetraalkoxysilane such as a low condensate of tetraalkoxysilane. Although raw materials other than silane may be used, the entire composition of silica particles is preferred due to its excellent reactivity. Tetraalkoxysilane is 50% by mass or more of 100% by mass of raw materials, and tetraalkoxysilane is It is preferable that the amount of raw materials other than lan is 50 mass % or less, and tetraalkoxysilane is 90 mass % or less. % by mass or more, and the amount of raw materials other than tetraalkoxysilane is more preferably 10% by mass or less. Desirable.

[0063] Liquid (B) may be tetraalkoxysilane only without a solvent, but the tetraalkoxysilane in the reaction liquid may be It is preferable to contain a solvent, as this provides excellent dispersibility of the alkoxysilane. Examples of the solvent in the liquid (B) include methanol, ethanol, propanol, isopropyl alcohol, and the like. These solvents can be used alone. Among these solvents, those suitable for the hydrolysis reaction and the condensation reaction may be used. The by-products and the products used in the process are the same, making it convenient for manufacturing. is preferred, methanol and ethanol are more preferred, and methanol is even more preferred.

[0064] The concentration of tetraalkoxysilane in liquid (B) is 60% by mass or more in 100% by mass of liquid (B). The concentration of the tetraalkoxysilane in the liquid (B) is preferably 70 mass % or more, and more preferably 70 mass % or more. When the concentration is 60% by mass or more, the reaction solution tends to be homogeneous. The concentration of the coxysilane is preferably 95% by mass or less, and more preferably 90% by mass or less. When the concentration of the tetraalkoxysilane (B) is 95% by mass or less, the formation of a gel-like substance is suppressed. It can be controlled.

[0065] The concentration of the solvent in the liquid (B) is preferably 5% by mass or more in 100% by mass of the liquid (B). When the concentration of the solvent in the liquid (B) is 5% by mass or more, the formation of a gel-like substance is difficult. In addition, the concentration of the solvent in the liquid (B) is preferably 40% by mass or less. When the concentration of the solvent in the liquid (B) is 40% by mass or less, the reaction The liquid tends to become uniform.

[0066] The addition rate of solution (B) was 17g silica / hour / kg solution to 150g silica / hour / kg solution. A solution of 50 g silica / hour / kg solution to 130 g silica / hour / kg solution is preferred, and a solution of 50 g silica / hour / kg solution to 130 g silica / hour / kg solution is more preferred. When the addition rate of solution (B) is equal to or higher than the lower limit, the reaction time is shortened and productivity is excellent. Furthermore, the generation of fine particles can be suppressed by the hydrolysis of tetramethoxysilane. The concentration of silicic acid produced by this process increases, and the concentration of silanol groups contained in the silica particles also increases. Furthermore, if the addition rate of solution (B) is below the upper limit, the tetraalkoxy group in the reaction solution may be increased. Excellent dispersibility of silane, suppressing the generation of fine particles. Silica / hour / kg solution The quantity of tetraalkoxysilane added per hour to 1 kg of solution (A) is The amount is expressed as the mass of silica.

[0067] The liquid (C) preferably contains water and further contains an alkali catalyst.

[0068] The alkali catalyst contained in the liquid (C) is, for example, ethylenediamine, diethylenetriamine, amine, triethylenetetraamine, ammonia, urea, ethanolamine, tetramethyl These alkali catalysts may be used alone. Among these alkali catalysts, the one with excellent catalytic activity and particle size is It is easy to control the shape, can suppress the contamination of metal impurities, is highly volatile, and is suitable for hydrolysis reactions. Ammonia is preferred because it is easily removable after the reaction and condensation reactions.

[0069] Examples of the solvent contained in the liquid (C) other than water include methanol, ethanol, propanol, etc. Examples of solvents other than water include alcohol, isopropanol, and ethylene glycol. They may be used alone or in combination of two or more. In addition, the by-products and the compounds used in the condensation reaction are the same, which makes it convenient to manufacture. , water alone, or a combination of water and alcohol is preferred, with water alone being more preferred.

[0070] The concentration of the alkali catalyst in the liquid (C) is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. When the concentration of the alkali catalyst in the liquid (C) is 0.05% by mass or more, the reaction The concentration of the alkali catalyst in the reaction solution can be easily adjusted from the start to the end of the reaction. In order to minimize the fluctuation in the concentration of the alkali catalyst, the concentration of the alkali catalyst in liquid (C) is It is preferably 10% by mass or less, and more preferably 6% by mass or less.

[0071] The concentration of water in the liquid (C) is preferably 99.5% by mass or less, more preferably 99% by mass or less. When the concentration of water in the liquid (C) is 99.5 mass % or less, the reaction proceeds smoothly from the start to the end of the reaction. It is easy to adjust the concentration of the alkaline catalyst in the reaction solution. From the viewpoint of minimizing fluctuations, the concentration of water in the liquid (C) is preferably 90 mass % or more, and 94 mass % or more. % or more by volume is more preferable.

[0072] The concentration of the solvent other than water in the liquid (C) is preferably the same as the concentration of the balance of water and the alkali catalyst. It's nice.

[0073] The addition of the liquid (B) and the liquid (C) is preferably carried out into the liquid (A). By adding liquid (C) to liquid (A), highly volatile alkalis such as ammonia can be dissolved. When you want to use a potassium catalyst and proceed with the hydrolysis and condensation reactions at high temperatures, In this case, the mixing of each component in the reaction solution is improved, and abnormal reactions in the air can be suppressed. Adding into the liquid means adding below the liquid surface, and By setting the supply outlet of liquid (B) and the supply outlet of liquid (C) below the liquid level of liquid (A), The liquid (C) can be added to the liquid (A).

[0074] The timing of adding the liquid (B) and the liquid (C) to the liquid (A) may be the same or alternate. However, the reaction composition is less variable and the operation is less complicated. , are preferably the same.

[0075] The pH in the process of hydrolysis and condensation of tetraalkoxysilane is 8.0. Preferably, it is 8.2 or more, more preferably 8.5 or more. It is preferable that the pH in the above step is 8.0 or higher. The reaction rate is excellent, and the aggregation of silica particles can be suppressed. is preferably 14, more preferably 13 or less, and even more preferably 12 or less. When the pH in the above step is 14 or less, the shape of the silica particles can be easily controlled, and the silica particles can be easily formed. Excellent surface smoothness.

[0076] The temperature in the process of hydrolysis and condensation of tetraalkoxysilane is 0°C or less. Preferably, the temperature is 5°C or higher, more preferably 5°C or higher, and even more preferably 10°C or higher. If the temperature in the above step is 0°C or higher, the hydrolysis and condensation reactions are accelerated, and the reaction is strongly In addition, the temperature in the above process is set to 70°C or less. Preferably, the temperature is less than 60°C, more preferably less than 50°C. If the temperature in this step is less than 70°C, excessive condensation of the silanol groups is suppressed, and the surface silanol groups are not condensed. The amount of nol groups can be increased.

[0077] The concentration of water in the reaction system of the hydrolysis reaction and the condensation reaction is, based on the total amount in the reaction system (100 mass%), It is preferable to maintain it at 3% by mass or more, and more preferable to maintain it at 5% by mass or more, It is more preferable to maintain the water concentration in the reaction system at 3% by mass or more. In this case, it is easy to control the hydrolysis reaction rate of tetraalkoxysilane. The concentration is preferably maintained at 50% by mass or less, and more preferably maintained at 30% by mass or less. It is more preferable to maintain the water concentration in the reaction system at 20 mass % or less. When the content is 50 mass % or less, the reaction balance between the hydrolysis reaction and the condensation reaction is good, and the surface silanols The amount of alkyl groups is easy to control.

[0078] The concentration of the alkali catalyst in the reaction system for the hydrolysis reaction and the condensation reaction is 100% of the total amount in the reaction system. In mass %, it is preferable to maintain it at 0.5 mass % or more, and it is preferable to maintain it at 0.6 mass % or more. When the concentration of the alkali catalyst in the reaction system is 0.5 mass % or more, the silica It suppresses particle aggregation and provides excellent dispersion stability of silica particles in the dispersion liquid. The concentration of the alkali catalyst is preferably maintained at 2.0% by mass or less, and more preferably at 1.5% by mass or less. It is more preferable to maintain the concentration of the alkali catalyst in the reaction system at 2.0 mass % or less. In this case, the reaction does not proceed excessively quickly, resulting in excellent reaction controllability.

[0079] The method for producing silica sol allows for the removal of unnecessary components and the addition of necessary components. Therefore, the obtained silica sol was further concentrated and the dispersion medium was added to replace the dispersion medium. It is preferable to include a step of:

[0080] In the above-mentioned dispersing medium substitution step, it is necessary to decide which of the silica sol concentration and the dispersing medium addition should be performed first. Alternatively, the dispersing medium in the silica sol may be entirely replaced. It is not necessary to remove a part of the dispersion medium, and the silica sol is concentrated. The body should be added.

[0081] The method for concentrating the silica sol is not particularly limited, and examples thereof include a heat concentration method and a membrane concentration method. Among these, from the viewpoint of promoting the surface condensation of silica particles, the silica sol is concentrated by the heat concentration method. It is preferable that To concentrate silica sol by the heat concentration method, the silica sol is heated under normal pressure or under reduced pressure. This can be concentrated by heating.

[0082] The dispersion medium substitution step for silica sol is preferably carried out over 3 hours or more, and more preferably over 5 hours or more. If the dispersion medium substitution step is carried out for 3 hours or more, the silica particle surface The silanol groups in the compound condense, making it easy to remove from the object being polished during cleaning after polishing. The dispersion medium replacement step for silica sol is preferably carried out within 20 hours, and more preferably within 15 hours. If the dispersion medium substitution step is completed within 20 hours, the remaining silanol groups will be Because the amount of silica particles increases, the silica particles have a moderate surface repulsion, and the dispersion stability of the silica sol is excellent. Furthermore, the hydration layer on the silica surface becomes thicker, resulting in excellent scratch reduction.

[0083] To concentrate silica sol by the membrane concentration method, membrane separation by ultrafiltration is preferred. The main purpose of ultrafiltration is to remove unnecessary components such as intermediate products. The molecular weight cutoff of the ultrafiltration membrane used here is determined according to the intermediate product in the dispersion. Select a product that can be filtered and removed. Ultrafiltration membranes are made of polysulfone, polyacrylonitrile, sintered metal, and ceramic. Examples of ultrafiltration membranes include spiral and tube types. Examples include a hollow fiber type and a hollow fiber type.

[0084] Examples of the dispersion medium to be added to the silica sol include water, methanol, ethanol, and propane. These dispersion media include alcohol, isopropanol, and ethylene glycol. The species may be used alone or in combination of two or more. Water and alcohol are preferred, and water is more preferred, due to their excellent affinity with particles.

[0085] <Polishing composition> The polishing composition of the present invention comprises the silica sol of the present invention. The polishing composition of the present invention preferably contains a water-soluble polymer in addition to the silica sol of the present invention. stomach.

[0086] The water-soluble polymer improves the wettability of the polishing compound to the object to be polished, such as a silicon wafer. The water-soluble polymer is preferably a polymer having a functional group with high water affinity. The affinity between this functional group with high water affinity and the surface silanol group of silica particles is high, and the polishing composition The silica particles and the water-soluble polymer are dispersed more closely in the composition. When polishing objects such as silicon wafers, the effects of silica particles and water-soluble polymers are synergistic. It functions effectively.

[0087] Examples of water-soluble polymers include cellulose derivatives, polyvinyl alcohol, polyvinyl copolymers with polyvinylpyrrolidone skeletons, polyoxyalkylene structures Examples of the polymer include a polymer having the following formula:

[0088] Examples of cellulose derivatives include hydroxyethyl cellulose, hydrolyzed cellulose, Hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose ethyl cellulose, hydroxypropyl methylcellulose, methylcellulose, ethylcellulose Examples of suitable cellulose include cellulose, ethylhydroxyethyl cellulose, and carboxymethyl cellulose. do.

[0089] Examples of copolymers having a polyvinylpyrrolidone skeleton include polyvinyl alcohol. and a graft copolymer of polyvinylpyrrolidone.

[0090] Examples of polymers having a polyoxyalkylene structure include polyoxyethylene, poly Examples of the copolymer include propylene oxide, copolymer of ethylene oxide and propylene oxide, etc. can be done.

[0091] These water-soluble polymers may be used alone or in combination of two or more. Among these water-soluble polymers, the one with the highest affinity for the surface silanol groups of silica particles has a synergistic effect. Cellulose derivatives are preferred because they act on the surface of the object to be polished to give it good hydrophilicity. Hydroxyethyl cellulose is more preferred.

[0092] The mass average molecular weight of the water-soluble polymer is preferably 1,000 or more, more preferably 5,000 or more. The mass average molecular weight of the water-soluble polymer is preferably 1,000 or more, and more preferably 10,000 or more. When the mass average molecular weight of the water-soluble polymer is 00 or more, the hydrophilicity of the polishing composition is improved. The amount is more preferably 3,000,000 or less, more preferably 2,000,000 or less. The mass average molecular weight of the water-soluble polymer is preferably 3,000,000 or less. When the molecular weight is 0,000 or less, it has excellent affinity with silica sol and is suitable for substrates such as silicon wafers. Excellent polishing rate for polishing body.

[0093] The mass average molecular weight of the water-soluble polymer is 0.1 mol / L in terms of polyethylene oxide. The measurement is carried out by size exclusion chromatography using a mobile phase of NaCl solution.

[0094] The content of the water-soluble polymer in the polishing composition is 0.02 mass % of the total amount of the polishing composition. The water-soluble polymer in the polishing composition is preferably 0.05 mass % or more, and more preferably 0.05 mass % or more. When the content is 0.02% by mass or more, the hydrophilicity of the polishing composition is improved. The content of the water-soluble polymer in the composition is preferably 10% by mass or less, more preferably 5% by mass or less. When the content of the water-soluble polymer in the polishing composition is 10 mass % or less, This can suppress the aggregation of silica particles during the process.

[0095] The polishing composition of the present invention may contain, in addition to the silica sol and the water-soluble polymer, any other additives within the range that do not impair the performance of the composition. In the range, basic compounds, polishing accelerators, surfactants, hydrophilic compounds, anti- Preservatives, antifungals, pH adjusters, pH buffers, surfactants, chelating agents, antibacterial and biocides, etc. It may contain the component: In particular, chemical polishing is performed by applying chemical action to the surface of the object to be polished, such as a silicon wafer. (chemical etching) can be performed, and the synergistic effect with the surface silanol groups of the silica particles Since it is possible to improve the polishing speed of the object to be polished, which is typified by silicon wafers, It is preferable to include a basic compound in the composition.

[0096] Examples of basic compounds include organic basic compounds, alkali metal hydroxides, alkali metal hydroxides, and the like. Metal hydrogen carbonates, alkali metal carbonates, ammonia, etc. These basic compounds may be used alone or in combination of two or more. Among these, ammonia is preferred because of its high water solubility and excellent affinity with silica particles and water-soluble polymers. Nia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ammonium bicarbonate Ammonium and ammonium carbonate are preferred, and ammonia, tetramethylammonium hydroxide, More preferred is ammonium hydroxide, and tetraethylammonium hydroxide, and even more preferred is ammonia.

[0097] The content of the basic compound in the polishing composition is 0.001% by mass relative to the total amount of the polishing composition (100% by mass). The content of the basic compound in the polishing composition is preferably 0.01% by mass or more, and more preferably 0.01% by mass or more. If the content of the substance is 0.001 mass % or more, it is difficult to polish the object to be polished, such as a silicon wafer. The polishing rate can be improved. In addition, the content of the basic compound in the polishing composition is 5% or more. The content of the basic compound in the polishing composition is preferably 1% by mass or less, and more preferably 3% by mass or less. When the proportion is 5% by mass or less, the polishing composition has excellent stability.

[0098] The pH of the polishing composition is preferably 8.0 or higher, and more preferably 9.0 or higher. When the pH is 8.0 or more, aggregation of silica particles in the polishing composition can be suppressed, The polishing composition has excellent dispersion stability. The pH of the polishing composition is preferably 12.0 or less. When the pH of the polishing composition is 12.0 or less, the silica particles This can suppress dissolution of the polishing agent, resulting in excellent stability of the polishing composition. The pH of the polishing composition can be adjusted to a desired range by adding a pH adjuster. do.

[0099] The polishing composition contains the silica sol of the present invention, a water-soluble polymer, and, if necessary, other components. However, in consideration of storage and transportation, it is recommended to prepare it at a high concentration and then mix it with water etc. just before polishing. It may be diluted with

[0100] <Polishing method> The polishing method of the present invention is a polishing method using a polishing composition containing the silica sol of the present invention. do. The polishing composition used is preferably the polishing composition described above. As a specific polishing method, for example, the surface of a silicon wafer is pressed against a polishing pad. The polishing composition of the present invention is dropped onto a polishing pad to polish the surface of a silicon wafer. Examples include:

[0101] <Semiconductor wafer manufacturing method> The method for producing a semiconductor wafer of the present invention includes a step of polishing the wafer using the polishing composition of the present invention. The specific polishing composition and polishing method are as described above. Examples of semiconductor wafers include silicon wafers and compound semiconductor wafers. .

[0102] <Semiconductor device manufacturing method> The method for producing a semiconductor device of the present invention includes a step of polishing using the polishing composition of the present invention. The specific polishing composition and polishing method are as described above.

[0103] Other materials that can be polished include Si, Cu, W, Ti, Cr, Co, Zr, Hf, Mo, Metals such as Ta, Ru, Au, Pt, Ag, Al, and Ni; oxides, nitrides, and silicon dioxide of the above metals; Among these polishing targets, metal compounds, intermetallic compounds, etc. It can be suitably used for metal oxides, and can be particularly suitably used for metal oxides.

[0104] (Application) The silica particles and the silica sol of the present invention can be suitably used for polishing purposes, For example, polishing of semiconductor materials such as silicon wafers, polishing of electronic materials such as hard disk substrates , polishing in the planarization process when manufacturing integrated circuits (chemical mechanical polishing), photomasks It can be used for polishing synthetic quartz glass substrates used in liquid crystal displays, and magnetic disk substrates. Among these, it can be particularly suitably used for polishing silicon wafers and chemical mechanical polishing. [Example]

[0105] The present invention will be explained in more detail below using examples. However, the present invention is not limited to the above examples. Unless otherwise stated, the following examples are not intended to be limiting.

[0106] <Measurement method> (Measurement of surface silanol group density and surface silanol group concentration) The silica sol obtained in the examples and comparative examples was added in an amount equivalent to 1.5 g of silica particles to 20 The solution was collected in a 0 mL tall beaker and purified water was added to bring the liquid volume to 90 mL. In a 25°C environment, a pH electrode was inserted into a tall beaker and stirred with a magnetic stirrer. The test solution was stirred for 5 minutes. While stirring with a magnetic stirrer was continued, A 0.1 mol / L aqueous solution of hydrochloric acid was added until the pH reached 3.6. The electrodes were removed and the sodium chloride was added while continuing to stir with a magnetic stirrer. 30 g of sodium chloride was added, and pure water was gradually added to completely dissolve the sodium chloride. Add pure water until the total volume of the test solution becomes 150 mL, and stir the test solution with a magnetic stirrer. The mixture was stirred for 5 minutes to obtain a test solution. The tall beaker containing the obtained test solution was placed in an automatic titration device "COM-1600" (Hiranuma (manufactured by Sangyo Co., Ltd.) and insert the pH electrode and burette that came with the device into the tall beaker. While stirring the test solution with a magnetic stirrer, 0 Add 1 mol / L sodium hydroxide solution dropwise until the pH changes from 4.0 to 9.0. The titer A (mL) of 0.1 mol / L sodium hydroxide solution required for this was measured. Using the following formula (1), the pH per 1.5 g of silica particles changes from 4.0 to 9.0. Calculate the amount of 0.1 mol / L sodium hydroxide solution consumed (V (mL)) and calculate the following: Using equation (2), the surface silanol group density ρ (particles / nm 2 ) and calculate the following Using equation (3), the surface silanol group concentration C of the silica particles is calculated. OH (%) was calculated. V = (A × f × 100 × 1.5) / (W × CSiO2 ) (1) A: The time required for the pH to change from 4.0 to 9.0 per 1.5g of silica particles is 0.1 Titration volume (mL) of mol / L sodium hydroxide solution f: Potency of the 0.1 mol / L sodium hydroxide solution used C SiO2 : Concentration of silica particles in silica sol (mass%) W: Amount of silica sol collected (g) ρ=(B×N A ) / (10 18 ×m×S BET ) (2) C OH =(B×M OH ) / m×100 (3) The pH per 1.5g of silica particles calculated from B:V changes from 4.0 to 9.0. Amount of sodium hydroxide required (mol) N A : Avogadro's number (units / mol) M OH Molar mass of OH (17 g / mol) m: Silica particle amount (1.5g)

[0107] (Measurement of average primary particle size) The silica sols obtained in the examples and comparative examples were dried at 150°C and measured using an automatic specific surface area measuring device. BELSORP-MR1" (model name, Microtrack BEL Corporation) The specific surface area of ​​the particles was measured, and the density was calculated as 2.2 g / cm using the following formula (4). 3 With an average of 1 The primary particle size was calculated. Average primary particle diameter (nm) = 6000 / (specific surface area (m 2 / g) x density (g / cm 3 )) (4)

[0108] (Measurement of average secondary particle size) The average secondary particle diameter of the silica particles in the silica sols obtained in the examples and comparative examples was Using a light scattering particle size measuring device "Zetersizer Nano ZS" (model name, manufactured by Malvern Instruments) and measured.

[0109] (Calculation of association ratio) The association ratio was calculated from the measured average primary particle size and average secondary particle size using the following formula (6): did. Association ratio = average secondary particle diameter / average primary particle diameter (6)

[0110] [Example 1] A mixture of 85% by mass of tetramethoxysilane and 15% by mass of methanol (B) and 0. A 3 mass % aqueous ammonia solution (C) was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and Ammonia mixed liquid (A) was charged. The concentration of methanol in liquid (A) was 92.4 mass %. The concentration of water in solution (A) is 7.5% by mass, and the concentration of ammonia in solution (A) is 0.1 It is expressed as mass %.

[0111] The temperature of the reaction solution was set to 66°C, and the mixture was 62% by mass of liquid (A), 30% by mass of liquid (B) and liquid (C). 45% by mass was added at a constant rate over 97 minutes, and the silica particle content was approximately 10% by mass. % dispersion of silica particles was obtained. The obtained dispersion of silica particles was diluted with water so that the content of silica particles became about 20% by mass. The temperature was increased while adjusting the volume by adding pure water to remove methanol and ammonia. Over time, an aqueous dispersion of silica particles with a silica particle content of about 20% by mass was obtained.

[0112] [Example 2] A mixture of 85% by mass of tetramethoxysilane and 15% by mass of methanol (B) and 0. A 1% by mass aqueous solution of ammonia (C) was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and Ammonia mixed liquid (A) was charged. The concentration of methanol in liquid (A) was 81.7 mass %. The concentration of water in liquid (A) is 17.5% by mass, and the concentration of ammonia in liquid (A) is 0.8 It is expressed as mass %.

[0113] The temperature of the reaction solution was set to 40°C, and the mixture was 81% by mass of liquid (A), 14% by mass of liquid (B) and liquid (C). 5% by mass was added at a constant rate over 180 minutes, and the silica particle content was approximately 4% by mass. A dispersion of silica particles was obtained. The obtained dispersion of silica particles was diluted with water so that the content of silica particles became about 10% by mass. The temperature was increased while adjusting the volume by adding pure water to remove methanol and ammonia. Over time, an aqueous dispersion of silica particles with a silica particle content of about 10% by mass was obtained.

[0114] [Example 3] A mixture of 75% by mass of tetramethoxysilane and 25% by mass of methanol (B) and 2. A 3 mass % aqueous ammonia solution (C) was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and Ammonia mixed liquid (A) was charged. The concentration of methanol in liquid (A) was 81.7 mass %. The concentration of water in liquid (A) is 17.5% by mass, and the concentration of ammonia in liquid (A) is 0.8 It is expressed as mass %.

[0115] The temperature of the reaction solution was set to 30°C, and the mixture was 81% by mass of liquid (A), 14% by mass of liquid (B) and liquid (C). 5% by mass was added at a constant rate over 180 minutes, and the silica particle content was approximately 4% by mass. A dispersion of silica particles was obtained. The obtained dispersion of silica particles was added to the liquid in an amount of 100 ml so that the content of silica particles became about 5% by mass. By adjusting the temperature by adding pure water, the temperature was increased to remove methanol and ammonia. Over time, an aqueous dispersion of silica particles with a silica particle content of about 5 mass % was obtained.

[0116] [Example 4] A mixture of 85% by mass of tetramethoxysilane and 15% by mass of methanol (B) and 1. A solution (C) of 0 mass % aqueous ammonia solution was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and A solution (A) containing ammonia was added. The concentration of methanol in the solution (A) was 79.6%. The concentration of water in liquid (A) is 20% by mass, and the concentration of ammonia in liquid (A) is 0.4% by mass. The percentage was expressed as a percentage by volume.

[0117] The temperature of the reaction solution was set to 40°C, and the mixture was mixed with 58% by mass of liquid (A), 30% by mass of liquid (B) and liquid (C). 13% by mass was added at a constant rate over 104 minutes, and the silica particle content was approximately 10% by mass. A dispersion of silica particles of % by weight was obtained. The obtained dispersion of silica particles was diluted with water so that the content of silica particles became about 10% by mass. The temperature was increased while adjusting the amount of pure water added to remove methanol and ammonia. Over this time, an aqueous dispersion of silica particles with a silica particle content of about 10 mass % was obtained.

[0118] [Example 5] A mixture of 85% by mass of tetramethoxysilane and 15% by mass of methanol (B) and 4. A 3 mass % aqueous ammonia solution (C) was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and Ammonia mixed liquid (A) was charged. The concentration of methanol in liquid (A) was 93.8 mass %. The concentration of water in liquid (A) is 5% by mass, and the concentration of ammonia in liquid (A) is 1.2% by mass. It was decided.

[0119] The temperature of the reaction solution was set to 22°C, and the mixture was 49% by mass of liquid (A), 37% by mass of liquid (B) and liquid (C). 14% by mass was added at a constant rate over 210 minutes, until the silica particle content reached approximately 12. A dispersion of 5% by mass of silica particles was obtained. The obtained dispersion of silica particles was diluted with water so that the content of silica particles became about 20% by mass. The temperature was increased while adjusting the volume by adding pure water to remove methanol and ammonia. Over time, an aqueous dispersion of silica particles with a silica particle content of about 20% by mass was obtained.

[0120] [Comparative Example 1] Commercially available silica sol (product name "PL-1", manufactured by Fuso Chemical Co., Ltd.) was used as is. .

[0121] Comparative Example 2 Commercially available silica sol (trade name "Snowtex OXS", manufactured by Nissan Chemical Co., Ltd.) was used as is. I used it.

[0122] Comparative Example 3 Commercially available silica sol (trade name "Snowtex OS", manufactured by Nissan Chemical Co., Ltd.) was used as is. Used.

[0123] Comparative Example 4 A mixture of 75% by mass of tetramethoxysilane and 25% by mass of methanol (B) and 0. A 3 mass % aqueous ammonia solution (C) was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and Liquid (A) mixed with ammonia was charged. The concentration of methanol in liquid (A) was 82.4 mass %. The concentration of water in liquid (A) is 17.5% by mass, and the concentration of ammonia in liquid (A) is 0.1 It is expressed as mass %.

[0124] The temperature of the reaction solution was set to 70°C, and the mixture was 82% by mass of liquid (A), 14% by mass of liquid (B) and liquid (C). 5% by mass was added at a constant rate over 180 minutes, and the silica particle content was approximately 4% by mass. A dispersion of silica particles was obtained. The obtained dispersion of silica particles was added to the liquid in an amount of 100 ml so that the content of silica particles became about 5% by mass. The temperature was increased while adjusting the temperature by adding pure water to remove methanol and ammonia. This resulted in an aqueous dispersion of silica particles with a silica particle content of about 5 mass %.

[0125] Comparative Example 5 A mixture of 85% by mass of tetramethoxysilane and 15% by mass of methanol (B) and 0. A 1% by mass aqueous solution of ammonia (C) was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and Liquid (A) mixed with ammonia was charged. The concentration of methanol in liquid (A) was 39.9 mass %. The concentration of water in liquid (A) is 60% by mass, and the concentration of ammonia in liquid (A) is 0.1% by mass. %.

[0126] The temperature of the reaction solution was set to 80°C, and the mixture was mixed with 25% by mass of liquid (A), 30% by mass of liquid (B) and liquid (C). 45% by mass was added at a constant rate over 237 minutes, and the silica particle content was approximately 10% by mass. A dispersion of silica particles of % by weight was obtained. The obtained dispersion of silica particles was diluted with water so that the content of silica particles became about 10% by mass. The temperature was increased while adjusting the amount of pure water added to remove methanol and ammonia. Over this time, an aqueous dispersion of silica particles with a silica particle content of about 10 mass % was obtained.

[0127] Comparative Example 6 A mixture of 85% by mass of tetramethoxysilane and 15% by mass of methanol (B) and 4. A 3 mass % aqueous ammonia solution (C) was prepared. A reaction vessel equipped with a thermometer, a stirrer, a supply pipe, and a distillation line was charged with methanol, pure water, and Ammonia mixed liquid (A) was charged. The concentration of methanol in liquid (A) was 93.8 mass %. The concentration of water in liquid (A) is 5% by mass, and the concentration of ammonia in liquid (A) is 1.2% by mass. It was decided.

[0128] The temperature of the reaction solution was set to 22°C, and the mixture was 49% by mass of liquid (A), 37% by mass of liquid (B) and liquid (C). 14% by mass was added at a constant rate over 210 minutes, until the silica particle content reached approximately 12. A dispersion of 5% by mass of silica particles was obtained. The obtained dispersion of silica particles was diluted with water so that the content of silica particles became about 20% by mass. The temperature was increased while adjusting the volume by adding pure water to remove methanol and ammonia. Over time, an aqueous dispersion of silica particles with a silica particle content of about 20% by mass was obtained.

[0129] The evaluation results of the obtained aqueous dispersion of silica particles are shown in Table 1.

[0130] [Table 1]

[0131] As can be seen from Table 1, the silica particles obtained in the examples were obtained by adjusting the component ratios of each solution and the hydrolysis ratio. and controlling various conditions such as the temperature during the condensation reaction, the addition rate of each additive solution, and the time for water replacement. This results in a surface silanol group density of 2 / nm 2 and a surface silanol group concentration of 1.5% or less These silica particles have a primary particle diameter of 1.0 mm or more, compared with the silica particles obtained in the comparative example. Even with small particles, they have a strong interaction with the object being polished, have excellent chemical polishing properties, and are It has high resilience and excellent dispersion stability. [Industrial Applicability]

[0132] The silica sol obtained by the method for producing silica sol according to this embodiment is suitable for polishing purposes. For example, it can be used for polishing semiconductor materials such as silicon wafers, hard disk substrates, etc. Polishing of electronic materials, polishing in the planarization process when manufacturing integrated circuits (chemical mechanical polishing) ), polishing of synthetic quartz glass substrates used in photomasks and liquid crystal displays, polishing of magnetic disk substrates, etc. It can be used for a variety of purposes, and is particularly suitable for polishing silicon wafers and chemical mechanical polishing. It is possible.

Claims

1. The surface silanol group density measured by the Sears method is 2 / nm ２ Above and surface Cyrano Silica particles having a silyl group concentration of 1.5% or more.

2. 2. The silicon dioxide powder according to claim 1, wherein the average primary particle diameter measured by the BET method is 40 nm or less. Ka particle.

3. 2. The sintered body according to claim 1, wherein the average secondary particle diameter measured by DLS is 100 nm or less. Rika particles.

4. 10. The silica particles of claim 1, wherein the silica particles are amorphous.

5. A silica sol comprising the silica particles according to any one of claims 1 to 4.

6. The method according to claim 5, further comprising the step of subjecting tetraalkoxysilane to hydrolysis and condensation reaction. The method for producing the silica sol described above.

7. The step of carrying out the hydrolysis reaction and the condensation reaction is carried out by adding tetrahydrofuran to a solution (A) containing an alkali catalyst. A liquid (B) containing an alkoxysilane and a liquid (C) containing water are added to the mixture, and a hydrolysis reaction and condensation reaction are carried out. The method for producing a silica sol according to claim 6, wherein the step of carrying out a polymerization reaction is

8. The dispersion medium of the silica sol is replaced with water, and the time for the replacement is 3 hours or more, The method for producing a silica sol according to claim 6, wherein the heating time is 1 hour or less.

9. A polishing composition comprising the silica sol according to claim 5 .

10. A polishing method, comprising polishing using the polishing composition according to claim 9.

11. A method for producing a semiconductor wafer, comprising a step of polishing the semiconductor wafer with the polishing composition of claim 9.

12. A method for manufacturing a semiconductor device, comprising a step of polishing with the polishing composition according to claim 9. 。

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