Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
  • C01B33/141—Preparation of hydrosols or aqueous dispersions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09G—POLISHING COMPOSITIONS; SKI WAXES
  • C09G1/00—Polishing compositions
  • C09G1/02—Polishing compositions containing abrasives or grinding agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
  • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
  • B24B37/042—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor
  • B24B37/044—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor characterised by the composition of the lapping agent
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/14—Anti-slip materials; Abrasives
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/14—Anti-slip materials; Abrasives
  • C09K3/1409—Abrasive particles per se
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/14—Anti-slip materials; Abrasives
  • C09K3/1436—Composite particles, e.g. coated particles
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P52/00—Grinding, lapping or polishing of wafers, substrates or parts of devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P90/00—Preparation of wafers not covered by a single main group of this subclass, e.g. wafer reinforcement
  • H10P90/12—Preparing bulk and homogeneous wafers
  • H10P90/129—Preparing bulk and homogeneous wafers by polishing
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/02—Amorphous compounds
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P52/00—Grinding, lapping or polishing of wafers, substrates or parts of devices
  • H10P52/40—Chemomechanical polishing [CMP]
  • H10P52/402—Chemomechanical polishing [CMP] of semiconductor materials

Definitions

• the present invention relates to silica particles, a method for producing silica particles, a silica sol, a polishing composition, a polishing method, a method for producing a semiconductor wafer, and a method for producing a semiconductor device.
• a method of polishing the surfaces of materials such as metals and inorganic compounds using polishing liquids is known.
• the surface condition has a significant effect on the semiconductor characteristics, so the surfaces and end faces of these parts must be polished with extremely high precision.
• polishing compositions containing silica particles are used.
• Colloidal silica is widely used as the abrasive grains, which are the main component of this polishing composition.
• Colloidal silica is known to be produced by a variety of methods, including those produced by the thermal decomposition of silicon tetrachloride (fumed silica, etc.), those produced by the deionization of alkali silicate such as water glass, and those produced by the hydrolysis and condensation reaction of alkoxysilanes (commonly known as the "sol-gel method").
• Patent Documents 1 to 3 disclose methods for producing silica particles by hydrolysis and condensation reactions of alkoxysilanes.
• silica particles with a high metal content When silica particles with a high metal content are used for polishing, the metal contained in the silica particles adheres to the surface of the object being polished, contaminating the object. This contamination of the object being polished has a negative effect on the performance of the object to which it is applied. For this reason, particularly in semiconductor applications, there is a demand for silica particles with a high level of reduced metal content.
• the silica particles disclosed in Patent Documents 1 to 3 have a low metal content, but the level of reduction is not sufficient.
• metals such as sodium and potassium, which are likely to be mixed in from the environment, and metals that are likely to react chemically with the object being polished during and after semiconductor polishing, even more than with conventional silica particles.
• the object of the present invention is to provide silica particles in which the metal content, particularly the content of a specific metal, is significantly reduced.
• silica particles particularly silica particles obtained by hydrolysis and condensation reactions of alkoxysilanes, have not been able to be said to have a sufficiently reduced metal content.
• the present inventors discovered silica particles having an extremely low metal content, leading to the completion of the present invention.
• the gist of the present invention is as follows.
• a method for producing silica particles according to any one of [1] to [6], comprising a step of subjecting tetraalkoxysilane to a hydrolysis reaction and a condensation reaction in a reaction vessel having a fluororesin coating on the inner wall surface.
• reaction vessel is a reaction vessel in which the contact area of the reaction solution per unit volume during the hydrolysis reaction and the condensation reaction with the reaction vessel is 5 m ⁇ 1 or less.
• a silica sol containing silica particles according to any one of [1] to [6].
• a method for manufacturing a semiconductor wafer comprising a step of polishing the wafer with the polishing composition described in [12].
• a method for manufacturing a semiconductor device comprising a step of polishing using the polishing composition described in [12].
• the silica particles of the present invention have an extremely low metal content, and when used for polishing, they can prevent metal from adhering to the surface of the object being polished. This reduces contamination of the object being polished and the adverse effects on the performance of the object to which the object is being polished.
• the silica particles of the present invention are silica particles that satisfy at least one of the following characteristics (a) to (c): (a) The sodium content is 15 ppb by mass or less. (b) the potassium content is 5 ppb by mass or less; (c) The calcium content is 9 ppb by mass or less.
• the silica particles of the present invention preferably satisfy at least two of the above characteristics (a) to (c), and more preferably satisfy all of the above characteristics (a) to (c).
• the silica particles of the present invention that satisfy the above characteristic (a) have a sodium content of 15 ppb by mass or less.
• the sodium content of the silica particles is preferably 15 mass ppb or less, since when used for polishing, contamination caused by sodium adhering to the surface of the polished object and the influence of the contamination on the performance of the object to which the polished object is applied are reduced.
• the sodium adhering to the surface of the polished object is preferably prevented from diffusing into the polished object, resulting in deterioration of the quality, and the deterioration of the performance of the semiconductor device manufactured by the polished object is preferably reduced.
• the sodium content of the silica particles is preferably 12 ppb by mass or less, and more preferably 10 ppb by mass or less, because the above-mentioned performance is significantly superior. Also, the sodium content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more, because it is easy to manufacture.
• the silica particles of the present invention that satisfy the above characteristic (b) have a potassium content of 5 ppb by mass or less.
• the potassium content of the silica particles is preferably 5 mass ppb or less, since it reduces contamination caused by potassium adhering to the surface of the object to be polished when used for polishing, and the influence of the contamination on the performance of the object to be polished.
• the potassium content of the silica particles is preferably 2 ppb by mass or less, and more preferably 0.5 ppb by mass or less, because the above-mentioned performance is significantly superior. Also, the potassium content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more, because it is easy to manufacture.
• the silica particles of the present invention that satisfy the above characteristic (c) have a calcium content of 9 ppb by mass or less.
• the calcium content of the silica particles is preferably 9 mass ppb or less, since when used for polishing, contamination caused by calcium adhering to the surface of the polished object and the influence of the contamination on the performance of the object to which the polished object is applied are reduced.
• the calcium adhering to the surface of the polished object diffuses into the polished object, which reduces quality deterioration such as pit formation caused by catalytic chemical reaction between calcium and the polished object, and reduces the deterioration of the performance of the semiconductor device manufactured by the polished object.
• the calcium content of the silica particles is preferably 7 ppb by mass or less, and more preferably 6 ppb by mass or less, because the above-mentioned performance is significantly superior. Also, the calcium content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more, because it is easy to manufacture.
• the silica particles of the present invention preferably have a cobalt content of 1 ppb by mass or less, more preferably 0.7 ppb by mass or less, and even more preferably 0.5 ppb by mass or less.
• the cobalt content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by cobalt adhering to the surface of the object to be polished and the resulting effect on the performance of the object to which the object is to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by cobalt adhering to the surface of the object to be polished diffusing into the object to be polished and reduces the deterioration in performance of semiconductor devices manufactured using such objects to be polished.
• the cobalt content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a magnesium content of 1.5 mass ppb or less, and more preferably 0.5 mass ppb or less.
• the magnesium content of the silica particles within the above range is preferable because it reduces contamination caused by magnesium adhering to the surface of the object to be polished when used for polishing, and the resulting impact on the performance of the object to which the object is to be polished.
• the magnesium adhering to the surface of the object to be polished diffuses into the object to be polished, thereby reducing quality deterioration such as pit formation caused by catalytic chemical reactions between magnesium and the object to be polished, and reducing the performance of semiconductor devices manufactured using such objects to be polished.
• the magnesium content of the silica particles is preferably 0 mass ppb or more, and is preferably 0.0001 mass ppb or more because it is easy to manufacture.
• the silica particles of the present invention preferably have an aluminum content of 2 ppb by mass or less, and more preferably 1.2 ppb by mass or less.
• the aluminum content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by aluminum adhering to the surface of the object to be polished and the resulting effect on the performance of the object to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by aluminum adhering to the surface of the object to be polished diffusing into the object to be polished, and a decrease in the performance of semiconductor devices manufactured using such objects to be polished.
• the aluminum content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a chromium content of 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the chromium content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by chromium adhering to the surface of the object to be polished and the resulting effect on the performance of the object to which the object is to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by chromium adhering to the surface of the object to be polished diffusing into the object to be polished and reduces a decrease in the performance of semiconductor devices manufactured using such objects to be polished.
• the chromium content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because of ease of manufacture.
• the silica particles of the present invention preferably have a manganese content of 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the manganese content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by manganese adhering to the surface of the object to be polished and the resulting effect on the performance of the object to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by manganese adhering to the surface of the object to be polished diffusing into the object to be polished, and reduces a decrease in the performance of semiconductor devices manufactured using such objects to be polished.
• the manganese content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because of ease of manufacture.
• the silica particles of the present invention preferably have an iron content of 1 ppb by mass or less, and more preferably 0.6 ppb by mass or less.
• the iron content of the silica particles within the above range is preferable because it reduces contamination caused by iron adhering to the surface of the object to be polished when used for polishing, and the resulting impact on the performance of the object to which the object is to be polished.
• the iron content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a nickel content of 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the nickel content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by nickel adhering to the surface of the object to be polished and the resulting effect on the performance of the object to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by nickel adhering to the surface of the object to be polished diffusing into the object to be polished, and a decrease in the performance of semiconductor devices manufactured using such objects to be polished.
• the nickel content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a zinc content of 15 mass ppb or less, and more preferably 12 mass ppb or less.
• the zinc content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by zinc adhering to the surface of the object to be polished and the resulting effect on the performance of the object to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by zinc adhering to the surface of the object to be polished diffusing into the object to be polished, and a decrease in the performance of semiconductor devices manufactured using such objects to be polished.
• the zinc content of the silica particles is preferably 0 mass ppb or more, and is preferably 0.0001 mass ppb or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a copper content of 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the copper content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by copper adhering to the surface of the object to be polished and the resulting effect on the performance of the object to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by copper adhering to the surface of the object to be polished diffusing into the object to be polished, and a decrease in the performance of semiconductor devices manufactured using such objects to be polished.
• the copper content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a lead content of 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the lead content of the silica particles within the above range is preferable because it reduces contamination caused by lead adhering to the surface of the object to be polished when used for polishing, and the resulting impact on the performance of the object to be polished.
• the lead content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a titanium content of 2 ppb by mass or less, and more preferably 1.2 ppb by mass or less.
• the titanium content of the silica particles within the above range is preferable because it reduces contamination caused by titanium adhering to the surface of the object to be polished when used for polishing, and the resulting impact on the performance of the object to which the object is to be polished.
• the titanium content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silver content of the silica particles of the present invention is preferably 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the silver content of the silica particles within the above range is preferable because it reduces contamination caused by silver adhering to the surface of the object to be polished when used for polishing, and the resulting effect on the performance of the object to be polished.
• the silver content of the silica particles is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silica particles of the present invention preferably have a metal content of 50 ppb by mass or less, more preferably 40 ppb by mass or less, and even more preferably 35 ppb by mass or less.
• the metal content of the silica particles within the above range is preferable because, when used for polishing, contamination caused by metal adhering to the surface of the object to be polished and the resulting effect on the performance of the object to which the object is to be polished are reduced. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by metal adhering to the surface of the object to be polished diffusing into the object to be polished, and a decrease in the performance of semiconductor devices manufactured using such objects to be polished.
• the metal content of the silica particles is preferably 0 ppb by mass or more, and is easy to manufacture, so it is preferable that the metal content is 0.0001 ppb by mass or more.
• the metal content of the silica particles is 50 ppb by mass or less, the effects on the polishing rate caused by changes in the chemical properties (acidity, etc.) of the surface silanol groups due to the occurrence of coordination interactions between the acidic surface silanol groups and the contained metals, and changes in the three-dimensional environment of the silica particle surface (ease of aggregation of silica particles, etc.) are reduced, which is preferable.
• the content of each metal in silica particles is a value measured by inductively coupled plasma mass spectrometry (ICP-MS). Specifically, 0.4 g of silica particles or silica sol containing 0.4 g of silica particles is accurately weighed out, sulfuric acid and hydrofluoric acid are added, and the mixture is heated, dissolved, and evaporated. Pure water is added to the remaining sulfuric acid droplets so that the total amount is exactly 10 g to create a test solution, which is then measured using an inductively coupled plasma mass spectrometer.
• the target metals are sodium, potassium, cobalt, magnesium, aluminum, calcium, chromium, manganese, iron, nickel, zinc, copper, lead, titanium, and silver, and the sum of the contents of these metals is the metal content.
• silica particles by a sol-gel method in order to make the content of each of the above-mentioned metals in the obtained silica particles not exceed the above-mentioned upper limit and to make the total content not exceed 50 ppb by mass, for example, the following measures may be appropriately selected and adopted.
• the tetraalkoxysilane used as the raw material has a metal content of 50 ppb by mass or less.
• the hydrolysis reaction and condensation reaction of tetraalkoxysilane are carried out in a reaction vessel having an inner wall surface coated with a fluororesin or a glass layer.
• a reaction vessel is used in which the contact area of the reaction solution per unit volume during the hydrolysis reaction and the condensation reaction is 5 m ⁇ 1 or less. These may also be used in combination of two or more.
• a method for producing silica particles by deionizing an alkali silicate such as water glass, sodium and the like derived from the raw material remain, making it extremely difficult to reduce the metal impurity content of the silica particles to 50 ppb by mass or less.
• the average primary particle diameter of the silica particles of the present invention is preferably 5 nm to 100 nm, and more preferably 15 nm to 60 nm.
• the storage stability of the silica sol is excellent.
• the average primary particle diameter of the silica particles is 100 nm or less, the surface roughness and scratches of the polished object, such as a silicon wafer, can be reduced, and the settling of the silica particles can be suppressed.
• the average primary particle size of the silica particles can be set within the desired range by adjusting the manufacturing conditions of the silica particles.
• the average secondary particle diameter of the silica particles of the present invention is preferably 10 nm to 200 nm, and more preferably 30 nm to 100 nm.
• the average secondary particle diameter of the silica particles is 10 nm or more, the removability of particles and the like during cleaning after polishing is excellent, and the storage stability of the silica sol is excellent.
• the average secondary particle diameter of the silica particles is 200 nm or less, the surface roughness and scratches on the polished object, such as a silicon wafer, can be reduced during polishing, particles and the like can be removed easily during cleaning after polishing, and sedimentation of the silica particles can be suppressed.
• the average secondary particle size of silica particles is measured by the DLS method. Specifically, it is measured using a dynamic light scattering particle size measuring device.
• the average secondary particle size of the silica particles can be set within the desired range by adjusting the manufacturing conditions of the silica particles.
• the cv value of the silica particles of the present invention is preferably 10% to 50%, more preferably 15% to 40%, and even more preferably 20% to 35%.
• the polishing rate for the workpiece, such as a silicon wafer is excellent, and the productivity of the silicon wafer is excellent.
• the cv value of the silica particles is 50% or less, the surface roughness and scratches on the workpiece, such as a silicon wafer, during polishing can be reduced, and the removal of particles and the like during cleaning after polishing is excellent.
• the association ratio of the silica particles of the present invention is preferably 1.0 to 4.0, and more preferably 1.1 to 3.0.
• the association ratio of the silica particles is 1.0 or more, the polishing rate for the object to be polished, such as a silicon wafer, is excellent, and the productivity of the silicon wafer is excellent.
• the association ratio of the silica particles is 4.0 or less, the surface roughness and scratches on the object to be polished, such as a silicon wafer, during polishing can be reduced, and the aggregation of the silica particles can be suppressed.
• association ratio average secondary particle size / average primary particle size (3)
• the surface silanol group density of the silica particles of the present invention is preferably 1 group/nm 2 to 8 groups/nm 2 , and more preferably 4 groups/nm 2 to 7 groups/nm 2 .
• the surface silanol group density of the silica particles is 1 group/nm 2 or more, the silica particles have appropriate surface repulsion, and the dispersion stability of the silica sol is excellent.
• the surface silanol group density of the silica particles is 8 groups/nm 2 or less, the silica particles have appropriate surface repulsion, and the aggregation of the silica particles can be suppressed.
• the surface silanol group density of the silica particles is measured by the Sears method, specifically, under the following conditions.
• a silica sol equivalent to 1.5 g of silica particles is collected, and pure water is added to make the liquid volume 90 mL.
• a 0.1 mol/L aqueous hydrochloric acid solution is added to this in an environment of 25° C. until the pH becomes 3.6, 30 g of sodium chloride is added, and pure water is gradually added to completely dissolve the sodium chloride. Finally, pure water is added until the total volume of the test liquid becomes 150 mL, to obtain a test liquid.
• the obtained test solution is placed in an automatic titrator, and a 0.1 mol/L aqueous solution of sodium hydroxide is added dropwise to measure the titration amount A (mL) of the 0.1 mol/L aqueous solution of sodium hydroxide required to change the pH from 4.0 to 9.0.
• the amount V (mL) of 0.1 mol/L aqueous sodium hydroxide solution required to change the pH from 4.0 to 9.0 per 1.5 g of silica particles is calculated using the following formula (4), and the surface silanol group density ⁇ (number/ nm2 ) of the silica particles is calculated using the following formula (5).
• V (A x f x 100 x 1.5) / (W x C) ... (4)
• B The amount (mol) of sodium hydroxide required to change the pH of 1.5 g of silica particles from 4.0 to 9.0 calculated from V N A : Avogadro's number (pieces/mol) M: Amount of silica particles (1.5 g) S BET : specific surface area (m 2 /g) of silica particles measured when calculating the average primary particle size
• the silica particles of the present invention are preferably amorphous because they combine the suppression of scratches on the object to be polished with an excellent polishing rate, are less likely to adhere to the object to be polished, and have an appropriate hardness.
• the fact that the silica particles are amorphous can be confirmed by a halo pattern in wide-angle X-ray scattering measurement.
• the silica particles of the present invention have a low content of metal impurities and excellent mechanical strength and storage stability, so that they preferably contain an alkoxysilane condensate as the main component, more preferably a tetraalkoxysilane condensate as the main component, and even more preferably a tetramethoxysilane condensate as the main component.
• the main component refers to a component that accounts for 50% by mass or more of the total 100% by mass of all components that make up the silica particles.
• silica particles whose main component is an alkoxysilane condensate it is preferable to use an alkoxysilane as the main raw material.
• silica particles whose main component is a tetraalkoxysilane condensate it is preferable to use a tetraalkoxysilane as the main raw material.
• silica particles whose main component is a tetramethoxysilane condensate it is preferable to use tetramethoxysilane as the main raw material.
• the main raw material refers to a raw material that accounts for 50% by mass or more of the total 100% by mass of the raw materials that make up the silica particles.
• the silica particles of the present invention can be obtained by a process including a step of subjecting tetraalkoxysilane to a hydrolysis reaction and a condensation reaction.
• the method for producing silica particles of the present invention is preferably a method in which a solution (B) containing a tetraalkoxysilane and a solution (C) containing an alkali catalyst are added to a solution (A) containing water, and the tetraalkoxysilane is subjected to a hydrolysis reaction and a condensation reaction.
• This method makes it easier to control the hydrolysis reaction and condensation reaction, can increase the reaction rates of the hydrolysis reaction and condensation reaction, prevents gelation of the silica particle dispersion, and produces silica particles with a uniform particle size.
• Solution (A) contains water.
• solution (A) contains a solvent other than water, since this provides excellent dispersibility of tetraalkoxysilane in the reaction solution.
• Examples of the solvent other than water in solution (A) include methanol, ethanol, propanol, isopropanol, ethylene glycol, etc. These solvents may be used alone or in combination of two or more. Among these solvents, alcohol is preferred, methanol and ethanol are more preferred, and methanol is even more preferred. These alcohols dissolve tetraalkoxysilanes easily, and the alcohols used in the hydrolysis reaction and the condensation reaction and the by-products are the same, which provides excellent manufacturing convenience.
• solution (A) contains an alkali catalyst, since this can increase the reaction rate of the hydrolysis reaction and condensation reaction of tetraalkoxysilane.
• alkaline catalyst in solution (A) examples include ethylenediamine, diethylenetriamine, triethylenetetraamine, ammonia, urea, ethanolamine, and tetramethylammonium hydroxide. These alkaline catalysts may be used alone or in combination of two or more. Among these alkaline catalysts, ammonia is preferred. Ammonia has excellent catalytic action, is easy to control the particle shape, can suppress the inclusion of metal impurities, is highly volatile, and is easily removable after the hydrolysis reaction and condensation reaction.
• the concentration of water in solution (A) is preferably 3% by mass to 50% by mass, and more preferably 5% by mass to 40% by mass, based on 100% by mass of solution (A).
• concentration of water in solution (A) is 3% by mass or more, it is easy to control the hydrolysis reaction rate of tetraalkoxysilane.
• concentration of water in solution (A) is 50% by mass or less, the reaction balance between the hydrolysis reaction and the condensation reaction is good, and the particle shape is easy to control.
• the concentration of the alkaline catalyst in solution (A) is preferably 0.5% by mass to 2.0% by mass, and more preferably 0.6% by mass to 1.5% by mass, based on 100% by mass of solution (A).
• concentration of the alkaline catalyst in solution (A) is 0.5% by mass or more, aggregation of silica particles is suppressed, and the dispersion stability of the silica particles in the dispersion is excellent.
• concentration of the alkaline catalyst in solution (A) is 2.0% by mass or less, the reaction does not proceed excessively quickly, and the reaction controllability is excellent.
• the concentration of the solvent other than water in solution (A) is preferably the balance of water and the alkali catalyst.
• Solution (B) contains tetraalkoxysilane.
• Examples of the tetraalkoxysilane in solution (B) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetraisopropoxysilane. These tetraalkoxysilanes may be used alone or in combination of two or more. Among these tetraalkoxysilanes, tetramethoxysilane and tetraethoxysilane are preferred, and tetramethoxysilane is more preferred. These have a fast hydrolysis reaction, are less likely to leave unreacted materials, are highly productive, and can easily produce a stable silica sol.
• the raw material for the silica particles may be a raw material other than tetraalkoxysilane, such as a low condensation product of tetraalkoxysilane.
• tetraalkoxysilane is 50% by mass or more and raw materials other than tetraalkoxysilane are 50% by mass or less, and it is more preferable that tetraalkoxysilane is 90% by mass or more and raw materials other than tetraalkoxysilane are 10% by mass or less. If the proportion of tetraalkoxysilane in the raw material is above the above lower limit, the reactivity is excellent.
• the sodium content of the tetraalkoxysilane is preferably 15 mass ppb or less, more preferably 12 mass ppb or less, and even more preferably 10 mass ppb or less.
• the sodium content of the tetraalkoxysilane is within the above range, the sodium content of the resulting silica particles is reduced, and when used for polishing, contamination caused by sodium adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces quality deterioration caused by sodium adhering to the surface of the polished object diffusing into the polished object and the performance degradation of semiconductor devices manufactured using such objects.
• the sodium content of the tetraalkoxysilane is 0 mass ppb or more, and is preferably 0.0001 mass ppb or more because it is easy to manufacture.
• the potassium content of the tetraalkoxysilane is preferably 5 ppb by mass or less, more preferably 2 ppb by mass or less, and even more preferably 0.5 ppb by mass or less.
• the potassium content of the tetraalkoxysilane is within the above range, the potassium content of the resulting silica particles is reduced, and when used for polishing, contamination caused by potassium adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable.
• the potassium content of the tetraalkoxysilane is 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the calcium content of the tetraalkoxysilane is preferably 9 ppb by mass or less, more preferably 7 ppb by mass or less, and even more preferably 6 ppb by mass or less.
• the calcium content of the tetraalkoxysilane is within the above range, the calcium content of the resulting silica particles is reduced, and when used for polishing, contamination caused by calcium adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable.
• the calcium content of the tetraalkoxysilane is 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the tetraalkoxysilane preferably has a cobalt content of 1 ppb by mass or less, more preferably 0.7 ppb by mass or less, and even more preferably 0.5 ppb by mass or less.
• the cobalt content of the tetraalkoxysilane within the above range reduces the cobalt content of the resulting silica particles, and when used for polishing, reduces contamination caused by cobalt adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied.
• the cobalt content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is easy to manufacture, so it is preferably 0.0001 ppb by mass or more.
• the magnesium content of the tetraalkoxysilane is preferably 1.5 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the magnesium content of the tetraalkoxysilane is within the above range, the magnesium content of the resulting silica particles is reduced, and when used for polishing, contamination caused by magnesium adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by magnesium adhering to the surface of the polished object diffusing into the polished object, and decreases in the performance of semiconductor devices manufactured using such objects.
• the magnesium content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is easy to manufacture, so it is preferable that the magnesium content is 0 ppb by mass or more, and is 0.0001 ppb by mass or more.
• the tetraalkoxysilane preferably has an aluminum content of 2 ppb by mass or less, more preferably 1.2 ppb by mass or less.
• the aluminum content of the tetraalkoxysilane is within the above range, the aluminum content of the resulting silica particles is reduced, and when used for polishing, contamination caused by aluminum adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by aluminum adhering to the surface of the polished object diffusing into the interior of the polished object and decreases in the performance of semiconductor devices manufactured using such objects.
• the aluminum content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the tetraalkoxysilane preferably has a chromium content of 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the chromium content of the tetraalkoxysilane is within the above range, the chromium content of the resulting silica particles is reduced, and when used for polishing, contamination caused by chromium adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable.
• the chromium content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is easy to manufacture, so it is preferable that the chromium content is 0 ppb by mass or more, and is 0.0001 ppb by mass or more.
• the manganese content of the tetraalkoxysilane is preferably 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the manganese content of the resulting silica particles is reduced, and when used for polishing, contamination caused by manganese adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable.
• this is preferable because it reduces quality deterioration caused by manganese adhering to the surface of the polished object diffusing into the polished object and the decrease in performance of semiconductor devices manufactured using such objects.
• the manganese content of the tetraalkoxysilane is 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the iron content of the tetraalkoxysilane is preferably 1 ppb by mass or less, and more preferably 0.6 ppb by mass or less.
• the iron content of the tetraalkoxysilane is within the above range, the iron content of the resulting silica particles is reduced, and when used for polishing, contamination caused by iron adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by iron adhering to the surface of the polished object diffusing into the polished object, and decreases in the performance of semiconductor devices manufactured using such objects.
• the iron content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the nickel content of the tetraalkoxysilane is preferably 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the nickel content of the tetraalkoxysilane is within the above range, the nickel content of the resulting silica particles is reduced, and when used for polishing, contamination caused by nickel adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces the deterioration of quality caused by nickel adhering to the surface of the polished object diffusing into the interior of the polished object and the decrease in performance of semiconductor devices manufactured using such objects.
• the nickel content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is easy to manufacture, so it is preferable that the nickel content is 0 ppb by mass or more and is 0.0001 ppb by mass or more.
• the zinc content of the tetraalkoxysilane is preferably 15 ppb by mass or less, and more preferably 12 ppb by mass or less.
• the zinc content of the tetraalkoxysilane is within the above range, the zinc content of the resulting silica particles is reduced, and when used for polishing, contamination caused by zinc adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by zinc adhering to the surface of the polished object diffusing into the interior of the polished object and decreases in the performance of semiconductor devices manufactured using such objects.
• the zinc content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the copper content of the tetraalkoxysilane is preferably 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the copper content of the tetraalkoxysilane is within the above range, the copper content of the resulting silica particles is reduced, and when used for polishing, contamination caused by copper adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable.
• the copper content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is easy to manufacture, so it is preferable that the copper content is 0 ppb by mass or more and is 0.0001 ppb by mass or more.
• the tetraalkoxysilane preferably has a lead content of 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the lead content of the tetraalkoxysilane is within the above range, the lead content of the resulting silica particles is reduced, and when used for polishing, contamination caused by lead adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces quality deterioration caused by lead adhering to the surface of the polished object diffusing into the polished object and the decrease in performance of semiconductor devices manufactured using such objects.
• the lead content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is easy to manufacture, so it is preferable that the lead content is 0 ppb by mass or more, and is 0.0001 ppb by mass or more.
• the titanium content of the tetraalkoxysilane is preferably 2 ppb by mass or less, and more preferably 1.2 ppb by mass or less.
• the titanium content of the resulting silica particles is reduced, and when used for polishing, contamination caused by titanium adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable.
• this is preferable because it reduces deterioration in quality caused by titanium adhering to the surface of the polished object diffusing into the interior of the polished object and decreases in the performance of semiconductor devices manufactured using such objects.
• the titanium content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the silver content of the tetraalkoxysilane is preferably 1 ppb by mass or less, and more preferably 0.5 ppb by mass or less.
• the silver content of the tetraalkoxysilane is within the above range, the silver content of the resulting silica particles is reduced, and when used for polishing, contamination caused by silver adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable. In particular, in semiconductor applications, this is preferable because it reduces deterioration in quality caused by silver adhering to the surface of the polished object diffusing into the polished object and a decrease in the performance of semiconductor devices manufactured using such objects.
• the silver content of the tetraalkoxysilane is preferably 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the metal content of the tetraalkoxysilane is preferably 50 ppb by mass or less, more preferably 40 ppb by mass or less, and even more preferably 35 ppb by mass or less.
• the metal content of the tetraalkoxysilane is within the above range, the metal content of the resulting silica particles is reduced, and when used for polishing, contamination caused by metal adhering to the surface of the polished object and the resulting impact on the performance of the object to which the polished object is applied are reduced, which is preferable.
• the metal content of the tetraalkoxysilane is 0 ppb by mass or more, and is preferably 0.0001 ppb by mass or more because it is easy to manufacture.
• the content of each metal in tetraalkoxysilane is a value measured by inductively coupled plasma mass spectrometry (ICP-MS).
• the target metals are sodium, potassium, cobalt, magnesium, aluminum, calcium, chromium, manganese, iron, nickel, zinc, copper, lead, titanium, and silver, and the total content of these metals is the metal content.
• the solution (B) may contain only tetraalkoxysilane without containing a solvent, but it is preferable to contain a solvent since this provides excellent dispersibility of the tetraalkoxysilane in the reaction liquid.
• Examples of the solvent in solution (B) include methanol, ethanol, propanol, isopropanol, and ethylene glycol. These solvents may be used alone or in combination of two or more. Among these solvents, alcohol is preferred, methanol and ethanol are more preferred, and methanol is even more preferred. These alcohols are the same as those used in the hydrolysis reaction and the condensation reaction and are by-produced, which provides excellent manufacturing convenience.
• the concentration of the tetraalkoxysilane in solution (B) is preferably 60% by mass to 95% by mass, and more preferably 70% by mass to 90% by mass, in 100% by mass of solution (B).
• concentration of the tetraalkoxysilane in solution (B) is 60% by mass or more, the reaction liquid tends to become homogeneous.
• concentration of the tetraalkoxysilane in solution (B) is 95% by mass or less, the formation of a gel-like substance can be suppressed.
• the concentration of the solvent in solution (B) is preferably 5% by mass to 40% by mass, and more preferably 10% by mass to 30% by mass, in 100% by mass of solution (B).
• concentration of the solvent in solution (B) is 5% by mass or more, the formation of a gel-like substance can be suppressed.
• concentration of the solvent in solution (B) is 40% by mass or less, the reaction liquid tends to become homogeneous.
• the addition rate of solution (B) per hour relative to the volume of solution (A) is preferably 0.05 kg/hour/L to 1.3 kg/hour/L, and more preferably 0.1 kg/hour/L to 0.8 kg/hour/L.
• the addition rate of solution (B) is 0.05 kg/hour/L or more, the productivity of silica particles is excellent.
• the addition rate of solution (B) is 1.3 kg/hour/L or less, the formation of a gel-like substance can be suppressed.
• the solution (C) contains an alkaline catalyst.
• alkaline catalyst in solution (C) examples include ethylenediamine, diethylenetriamine, triethylenetetraamine, ammonia, urea, ethanolamine, and tetramethylammonium hydroxide. These alkaline catalysts may be used alone or in combination of two or more. Among these alkaline catalysts, ammonia is preferred. Ammonia has excellent catalytic action, is easy to control the particle shape, can suppress the inclusion of metal impurities, is highly volatile, and is easily removable after the hydrolysis reaction and condensation reaction.
• solution (C) contains a solvent, since this can reduce fluctuations in the concentration of the alkaline catalyst in the reaction solution.
• Examples of the solvent in solution (C) include water, methanol, ethanol, propanol, isopropanol, and ethylene glycol. These solvents may be used alone or in combination of two or more. Among these solvents, water and alcohol are preferred, and water is more preferred. Water and alcohol, and especially water, are used in the hydrolysis reaction and the condensation reaction and are produced as a by-product, which provides excellent manufacturing convenience.
• the concentration of the alkaline catalyst in solution (C) is preferably 0.5% to 10% by mass, and more preferably 1% to 6% by mass, in 100% by mass of solution (C).
• concentration of the alkaline catalyst in solution (C) is 0.5% by mass or more, it is easy to adjust the concentration of the alkaline catalyst in the reaction liquid from the start of the reaction to the end of the reaction.
• concentration of the alkaline catalyst in solution (C) is 10% by mass or less, it is possible to reduce fluctuations in the concentration of the alkaline catalyst in the reaction liquid.
• the concentration of the solvent in solution (C) is preferably 90% by mass to 99.5% by mass, and more preferably 94% by mass to 99% by mass, in 100% by mass of solution (C).
• concentration of the solvent in solution (C) is 90% by mass or more, the fluctuation in the concentration of the alkaline catalyst in the reaction liquid can be reduced.
• concentration of the solvent in solution (C) is 99.5% by mass or less, it is easy to adjust the concentration of the alkaline catalyst in the reaction liquid from the start of the reaction to the end of the reaction.
• solutions (B) and (C) is preferably carried out into solution (A).
• solutions (B) and (C) are added into solution (A)
• a highly volatile alkali catalyst such as ammonia
• Adding into the liquid means adding below the liquid level. For example, by making the supply outlet for solution (B) and the supply outlet for solution (C) below the liquid level of solution (A), solution (B) and solution (C) can be added into solution (A).
• the timing of adding solution (B) and solution (C) to solution (A) may be the same or may be different, such as alternating. It is preferable that the timing of adding solution (B) and solution (C) to solution (A) is the same, since this reduces fluctuations in the reaction composition and avoids complicated operations.
• the pH in the process of subjecting tetraalkoxysilane to hydrolysis and condensation reactions is preferably 8 to 14, more preferably 8.2 to 13, and even more preferably 8.5 to 12. If the pH in the process is 8 or higher, the reaction rate of the hydrolysis and condensation reactions is excellent, and aggregation of silica particles can be suppressed. If the pH in the process is 14 or lower, the shape of the silica particles is easily controlled, and the smoothness of the silica particle surface is excellent.
• the reaction temperature for the hydrolysis reaction and condensation reaction is preferably 5°C to 50°C, and more preferably 10°C to 45°C. If the reaction temperature is 5°C or higher, the reaction does not proceed too slowly and is excellent in controllability. If the reaction temperature is 50°C or lower, an excellent balance between the hydrolysis reaction rate and the condensation reaction rate is achieved.
• the concentration of water in the reaction system for the hydrolysis and condensation reactions is preferably maintained at 3% to 30% by mass, and more preferably at 5% to 25% by mass, out of a total of 100% by mass in the reaction system. If the concentration of water in the reaction system is 3% by mass or more, it is easy to control the hydrolysis reaction rate of tetraalkoxysilane. If the concentration of water in the reaction system is 30% by mass or less, the reaction balance between the hydrolysis and condensation reactions is good, and the particle shape is easy to control.
• the concentration of the alkaline catalyst in the reaction system for the hydrolysis reaction and the condensation reaction is preferably maintained at 0.5% to 2.0% by mass, and more preferably at 0.6% to 1.5% by mass, out of a total of 100% by mass in the reaction system.
• concentration of the alkaline catalyst in the reaction system is 0.5% by mass or more, the aggregation of the silica particles is suppressed, and the dispersion stability of the silica particles in the dispersion liquid is excellent.
• the concentration of the alkaline catalyst in the reaction system is 2.0% by mass or less, the reaction does not proceed excessively quickly, and the reaction controllability is excellent.
• the hydrolysis reaction and condensation reaction are preferably carried out in a reaction vessel having a fluororesin coating or a glass layer on the inner wall surface, i.e., a reaction vessel in which a fluororesin coating or a glass layer is formed on the inner wall surface, and are particularly preferably carried out in a reaction vessel in which a fluororesin coating is applied to the inner wall surface.
• the reaction vessel used for the hydrolysis reaction and the condensation reaction is preferably one in which the contact area of the reaction liquid with the reaction vessel per unit volume (1 m 3 ) during the hydrolysis reaction and the condensation reaction is 5 m 2 or less, i.e., the ratio of the contact area with the reaction vessel to the unit volume of the reaction liquid (hereinafter sometimes referred to as the "contact area ratio with the reaction vessel") is 5 m -1 or less, and the contact area ratio with the reaction vessel is more preferably 4 m -1 or less. If the contact area ratio to the reaction vessel is 5 m -1 or less, it is easy to reduce metal contamination of the silica particles from the inner wall of the reaction vessel. On the other hand, from the viewpoint of temperature controllability of the reaction solution during the hydrolysis reaction and the condensation reaction, the contact area ratio to the reaction vessel is preferably 1 m -1 or more, and more preferably 3 m -1 or more.
• the volume of the reaction tank in which the hydrolysis reaction and the condensation reaction are carried out is preferably 1000 L or more, more preferably 2000 L or more.
• the volume of the reaction tank is 1000 L or more, the metal ratio per unit volume when metal is mixed into the reaction solution is reduced, and the metal content of the obtained silica particles is easily reduced.
• the volume of the reaction tank is preferably 20,000 L or less.
• the method for producing silica particles preferably further includes the following step (1) since it is possible to remove unnecessary components and add necessary components.
• Step (1) Concentrating the resulting dispersion of silica particles and adding a dispersion medium.
• step (1) either the concentration of the silica particle dispersion or the addition of the dispersion medium can be carried out first.
• the method for concentrating the silica particle dispersion is not particularly limited, and examples include a heat concentration method and a membrane concentration method.
• the dispersion can be heated and concentrated under normal pressure or reduced pressure.
• the main purpose of the ultrafiltration method is to remove unnecessary components such as intermediate products.
• the molecular weight cutoff of the ultrafiltration membrane used here is selected according to the intermediate products in the dispersion, so that the intermediate products can be filtered and removed.
• the material of the ultrafiltration membrane include polysulfone, polyacrylonitrile, sintered metal, ceramic, carbon, etc.
• the form of the ultrafiltration membrane include a spiral type, a tubular type, a hollow fiber type, etc.
• dispersion medium to be added to the dispersion liquid of silica particles examples include water, methanol, ethanol, propanol, isopropanol, ethylene glycol, etc. These dispersion media may be used alone or in combination of two or more. Among these dispersion media, water and alcohol are preferred, and water is more preferred, because they have excellent affinity with silica particles.
• the silica sol of the present invention contains the silica particles of the present invention.
• the silica sol of the present invention may be produced by using the dispersion liquid of the silica particles of the present invention as is, or by removing unnecessary components from the dispersion liquid of the silica particles of the present invention and adding necessary components.
• the silica sol of the present invention preferably contains silica particles and a dispersion medium.
• dispersion medium in the silica sol examples include water, methanol, ethanol, propanol, isopropanol, and ethylene glycol. These dispersion media in the silica sol may be used alone or in combination of two or more. Among these dispersion media in the silica sol, water and alcohol are preferred, and water is more preferred, because they have excellent affinity with the silica particles.
• the content of silica particles in the silica sol is preferably 2% to 50% by mass, more preferably 4% to 40% by mass, and even more preferably 5% to 30% by mass, based on the total amount of silica sol (100% by mass).
• the content of silica particles in the silica sol is 2% by mass or more, the polishing rate for a workpiece such as a silicon wafer is excellent.
• the content of silica particles in the silica sol is 50% by mass or less, the aggregation of silica particles in the silica sol or polishing composition can be suppressed, and the storage stability of the silica sol or polishing composition is excellent.
• the content of the dispersion medium in the silica sol is preferably 50% to 98% by mass, more preferably 60% to 96% by mass, and even more preferably 70% to 95% by mass, out of a total amount of 100% by mass of the silica sol. If the content of the dispersion medium in the silica sol is 50% by mass or more, aggregation of silica particles in the silica sol or polishing composition can be suppressed, and the storage stability of the silica sol or polishing composition is excellent. If the content of the dispersion medium in the silica sol is 98% by mass or less, the polishing rate for the object to be polished, such as a silicon wafer, is excellent.
• the content of silica particles and dispersion medium in the silica sol can be set to the desired range by removing unnecessary components from the resulting dispersion of silica particles and adding necessary components.
• the silica sol may contain other components such as oxidizing agents, preservatives, antifungal agents, pH adjusters, pH buffers, surfactants, chelating agents, and antibacterial and biocide agents, as necessary, to the extent that the performance of the silica sol is not impaired.
• an antibacterial biocide in the silica sol, since the storage stability of the silica sol is excellent.
• Hydrogen peroxide is preferred as an antibacterial biocide because it has excellent affinity with silica sol.
• Antibacterial biocides also include those generally known as disinfectants.
• the content of the antibacterial biocide in the silica sol is preferably 0.0001% to 10% by mass, and more preferably 0.001% to 1% by mass, out of a total amount of 100% by mass of the silica sol.
• the content of the antibacterial biocide in the silica sol 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 10% by mass or less, the original performance of the silica sol is not impaired.
• the pH of the silica sol is preferably 6.0 to 8.0, and more preferably 6.5 to 7.8. If the pH of the silica sol is 6.0 or higher, it has excellent dispersion stability and can suppress aggregation of silica particles. If the pH of the silica sol is 8.0 or lower, it prevents dissolution of silica particles and has excellent long-term storage stability.
• the pH of the silica sol can be set to the desired range by adding a pH adjuster.
• the polishing composition of the present invention comprises the silica sol of the present invention.
• the polishing composition of the present invention may contain, in addition to the silica sol of the present invention, other components such as water-soluble polymers, basic compounds, polishing accelerators, surfactants, hydrophilic compounds, preservatives, fungicides, pH adjusters, pH buffers, surfactants, chelating agents, and antibacterial and biocide agents, as necessary, to the extent that the performance of the composition is not impaired.
• other components such as water-soluble polymers, basic compounds, polishing accelerators, surfactants, hydrophilic compounds, preservatives, fungicides, pH adjusters, pH buffers, surfactants, chelating agents, and antibacterial and biocide agents, as necessary, to the extent that the performance of the composition is not impaired.
• the polishing composition can be obtained by mixing the silica sol of the present invention and, if necessary, other components.
• the polishing composition of the present invention can be prepared at a high concentration and then diluted with water or the like immediately before polishing.
• the polishing method of the present invention is a polishing method using a polishing composition containing the silica sol of the present invention.
• the polishing composition used is preferably the polishing composition described above.
• a specific polishing method is, for example, a method in which the surface of a silicon wafer is pressed against a polishing pad, the polishing composition of the present invention is dropped onto the polishing pad, and the surface of the silicon wafer is polished.
• the method for producing a semiconductor wafer of the present invention is a method comprising a step of polishing the wafer with the polishing composition of the present invention. Specific examples of the polishing composition and the polishing method are as described above.
• Semiconductor wafers include, for example, silicon wafers and compound semiconductor wafers.
• the method for producing a semiconductor device of the present invention is a method comprising a step of polishing with the polishing composition of the present invention. Specific polishing compositions and polishing methods are as described above.
• the silica particles and silica sol of the present invention can be suitably used for polishing purposes.
• they can be used for polishing semiconductor materials such as silicon wafers, polishing electronic materials such as hard disk substrates, polishing in the flattening process when manufacturing integrated circuits (chemical mechanical polishing), polishing synthetic quartz glass substrates used for photomasks and liquid crystals, and polishing magnetic disk substrates.
• they can be suitably used for polishing silicon wafers and chemical mechanical polishing. They can be particularly suitably used for final polishing of silicon wafers and final polishing of chemical mechanical polishing.
• Association ratio average secondary particle size / average primary particle size (3)
• silica sols (dispersions of silica particles) obtained in the Examples and Comparative Examples, an amount equivalent to 1.5 g of silica particles was placed in a 200 mL tall beaker, and pure water was added to make the liquid volume 90 mL.
• a pH electrode was inserted into the tall beaker, and the test solution was stirred for 5 minutes with a magnetic stirrer. With stirring continued with the magnetic stirrer, 0.1 mol/L aqueous hydrochloric acid solution was added until the pH reached 3.6.
• the pH electrode was removed from the tall beaker, and with stirring continued with the magnetic stirrer, 30 g of sodium chloride was added, and pure water was gradually added to completely dissolve the sodium chloride. Finally, pure water was added until the total amount of the test solution reached 150 mL, and the test solution was stirred for 5 minutes with a magnetic stirrer to obtain a test solution.
• the tall beaker containing the obtained test solution was set in an automatic titration device "COM-1600" (manufactured by Hiranuma Sangyo Co., Ltd.), and the pH electrode and burette included with the device were inserted into the tall beaker.
• A Titration amount (mL) of 0.1 mol/L sodium hydroxide aqueous solution required to change the pH from 4.0 to 9.0 per 1.5 g of silica particles
• f Titer of 0.1 mol/L aqueous sodium hydroxide solution used
• C Concentration (mass%) of silica particles in silica sol
• B The amount (mol) of sodium hydroxide required to change the pH of 1.5 g of silica particles from 4.0 to 9.0 calculated from V N A : Avogadro's number (pieces/mol) M: Amount of silica particles (1.5 g) S BET : specific surface area (m 2 /g) of silica particles measured when calculating the average primary particle size
• the silica sol containing 0.4 g of silica particles obtained in the examples and comparative examples was accurately weighed out, sulfuric acid and hydrofluoric acid were added, and the mixture was heated, dissolved, and evaporated, and pure water was added to the remaining sulfuric acid droplets so that the total amount was exactly 10 g to prepare a test solution.
• the metal impurity content was measured using a high-frequency inductively coupled plasma mass spectrometer "ELEMENT2" (model name, manufactured by Thermo Fisher Scientific).
• Tetraalkoxysilane was produced according to the method described in JP-A-8-325272. The contents of each metal in the produced tetraalkoxysilane are shown in Table 1.
• a solution (B) was prepared by mixing tetramethoxysilane and methanol at a volume ratio of 4.4:1.
• a solution (C) of 3.0% by mass aqueous ammonia was prepared separately.
• the concentration of water in the solution (A) was 11.7% by mass, and the concentration of ammonia in the solution (A) was 0.73% by mass.
• the contact area ratio of the reaction solution to the reaction vessel during the hydrolysis and condensation reactions was 3.7 m -1 .
• the temperature of the obtained dispersion of silica particles was raised to remove methanol and ammonia while adjusting the liquid volume by adding pure water so that the silica particle content was approximately 20 mass %, thereby obtaining a dispersion of silica particles with a silica particle content of approximately 20 mass %.
• the obtained silica particles were confirmed to be amorphous by a halo pattern obtained by wide-angle X-ray scattering measurement.
• Tetraalkoxysilane was produced according to the method described in JP-A-8-325272. The contents of each metal in the produced tetraalkoxysilane are shown in Table 1.
• a solution (B) was prepared by mixing tetramethoxysilane and methanol at a volume ratio of 4.4:1.
• a solution (C) of 3.0% by mass aqueous ammonia was separately prepared.
• a solution (A) of methanol, pure water, and ammonia was previously mixed in a glass reaction vessel equipped with a thermometer, a stirrer, and a supply pipe. The concentration of water in the solution (A) was 11.7% by mass, and the concentration of ammonia in the solution (A) was 0.73% by mass.
• the contact area ratio of the reaction liquid to the reaction vessel during the hydrolysis reaction and the condensation reaction was 48.7 m -1 .
• the temperature of the obtained dispersion of silica particles was raised to remove methanol and ammonia while adjusting the liquid volume by adding pure water so that the silica particle content was approximately 20 mass %, thereby obtaining a dispersion of silica particles with a silica particle content of approximately 20 mass %.
• the obtained silica particles were confirmed to be amorphous by a halo pattern obtained by wide-angle X-ray scattering measurement.
• the silica particles obtained in Example 1 have almost the same physical properties as the silica particles used in Comparative Example 1, such as particle size, but the contents of most of the metals are low.
• the silica particles obtained in Example 1 have an extremely low metal content compared to the commercially available silica particles of Comparative Example 1, and when used for polishing, they can suppress the adhesion of metal to the surface of the object to be polished, thereby reducing the adverse effects on the performance of the object to which they are applied.
• the silica particles obtained in Example 1 have almost the same physical properties as the silica particles used in Comparative Example 2, such as particle size, but the contents of all metals are low.
• the silica particles obtained in Example 1 have an extremely low metal content compared to the silica particles in Comparative Example 2, which were obtained using a glass reaction tank and under conditions of a high contact area ratio of the reaction liquid to the reaction tank. Even when used for polishing, this prevents metal from adhering to the surface of the object to be polished, thereby reducing the adverse effects on the performance of the object to which the object is polished.
• the silica particles and silica sol of the present invention can be suitably used for polishing purposes.
• they can be used for polishing semiconductor materials such as silicon wafers, polishing electronic materials such as hard disk substrates, polishing in the flattening process when manufacturing integrated circuits (chemical mechanical polishing), polishing synthetic quartz glass substrates used for photomasks and liquid crystals, polishing magnetic disk substrates, etc.
• they can be suitably used for polishing silicon wafers and chemical mechanical polishing, and particularly suitable for final polishing of silicon wafers and final polishing of chemical mechanical polishing.

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• 2023
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