Silica particles, method for producing silica particles, silica sol, polishing composition, polishing method, method for producing semiconductor wafer, and method for producing semiconductor device

Abstract

The purpose of the present invention is to provide silica particles in which the metal content, particularly the specific metal content, is significantly reduced. The main purpose of the present invention is as follows. Silica particles satisfying at least one of the following characteristics (a)-(c). (a) The sodium content is 15 ppb by mass or less. (b) The potassium content is 5 ppb by mass or less. And (c) the calcium content is 9 ppb by mass or less.

Description

Technical Field

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

[0002] As a method for polishing the surface of materials such as metals and inorganic compounds, a polishing method using a polishing liquid is known. Among them, for the final fine polishing of virgin silicon wafers for semiconductors, their recycled silicon wafers, and the planarization of interlayer insulating films, the formation of metal plugs, and the formation of buried wirings during the manufacture of semiconductor devices in chemical mechanical polishing (CMP), since their surface states have a great influence on semiconductor characteristics, it is required to polish the surfaces and end faces of these components with extremely high precision.

[0003] In such precision polishing, a polishing composition containing silica particles is used. As the abrasive grains that are the main component of the polishing composition, colloidal silica is widely used. Depending on the manufacturing method, colloidal silica is known to include colloidal silica based on the thermal decomposition of silicon tetrachloride (such as fumed silica), colloidal silica based on the deionization of silicate alkalis such as water glass, and colloidal silica based on the hydrolysis reaction and condensation reaction of alkoxysilanes (generally referred to as the "sol-gel method").

[0004] Regarding the method for manufacturing silica particles, many studies have been conducted so far. For example, methods for manufacturing silica particles by the hydrolysis reaction and condensation reaction of alkoxysilanes are disclosed in Patent Documents 1 to 3.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: International Publication No. 2008 / 015943

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2018-80331

[0009] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2010-83744 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] If silica particles with a high metal content are used in grinding, the metal contained in the silica particles will adhere to the surface of the object to be ground, thereby contaminating the object to be ground. In addition, the contamination of the object to be ground will have an adverse effect on the performance of the object to be applied. Therefore, especially in semiconductor applications, the metal content of silica particles is required to be reduced to a high level.

[0012] Although the silica particles disclosed in Patent Documents 1 to 3 suppress the metal content to a low level, it cannot be considered that the reduction level is sufficient. In particular, for metals such as sodium and potassium that are likely to be mixed from the environment, and metals that are likely to chemically react with the polished object during semiconductor polishing or in the process after polishing, it is expected to be further reduced compared with the existing silica particles.

[0013] An object of the present invention is to provide silica particles having a significantly reduced metal content, particularly a specific metal content.

[0014] Solutions to the problem

[0015] Conventional silica particles, particularly silica particles obtained by hydrolysis reaction / condensation reaction of alkoxysilane, cannot be considered to have a sufficient reduction in metal content.

[0016] The present inventors have conducted intensive studies and, as a result, have discovered silica particles having an extremely low metal content, thereby completing the present invention.

[0017] The gist of the present invention is as follows.

[0018] [1] A silicon dioxide particle that satisfies at least one of the following characteristics (a) to (c):

[0019] (a) The sodium content is 15 ppb or less,

[0020] (b) Potassium content is 5 ppb by mass or less,

[0021] (c) The calcium content is 9 mass ppb or less.

[0022] [2] The silica particles according to [1], which satisfy at least two of the above characteristics (a) to (c).

[0023] [3] The silica particles according to [2], which satisfy all of the above characteristics (a) to (c).

[0024] [4] The silica particles according to any one of [1] to [3], wherein the metal content is 50 mass ppb or less.

[0025] [5] The silica particles according to any one of [1] to [4], wherein,

[0026] The above silica particles are amorphous.

[0027] [6] The silica particles according to any one of [1] to [5], which have an alkoxysilane condensate as the main component.

[0028] [7] A method for manufacturing silica particles, the silica particles being the silica particles according to any one of [1] to [6], the method comprising:

[0029] A step of subjecting tetraalkoxysilane to a hydrolysis reaction and a condensation reaction in a reaction tank having a fluororesin coating on the inner wall surface.

[0030] [8] The method for manufacturing silica particles according to [7], wherein,

[0031] The above reaction tank is a reaction tank in which the contact area of the reaction solution per unit volume in the hydrolysis reaction and the condensation reaction with the reaction tank is 5 m -1 or less.

[0032] [9] The method for manufacturing silica particles according to [7] or [8], wherein,

[0033] The metal content rate of the above tetraalkoxysilane is 50 mass ppb or less.

[0034]

[10] A silica sol containing the silica particles according to any one of [1] to [6].

[0035]

[11] The silica sol according to

[10] , wherein,

[0036] In 100% by mass of the total amount of the above silica sol, the content rate of the above silica particles is 2% to 50% by mass.

[0037]

[12] A polishing composition containing the silica sol according to

[10] or

[11] .

[0038]

[13] A polishing method using the polishing composition according to

[12] for polishing.

[0039]

[14] The polishing method according to

[13] , wherein,

[0040] The polishing using the above polishing composition is the final polishing in the polishing step.

[0041]

[15] A method for manufacturing a semiconductor wafer, the method comprising:

[0042] A step of polishing using the polishing composition described in

[12] .

[0043]

[16] A method for manufacturing a semiconductor device, the method comprising:

[0044] A step of polishing using the polishing composition described in

[12] .

[0045] Effects of the Invention

[0046] The silica particles of the present invention have an extremely low metal content rate, and even when used for polishing, metal adhesion to the surface of the object to be polished can be suppressed. Therefore, contamination of the object to be polished and adverse effects on the performance of the application object of the object to be polished can be reduced. Detailed Description of the Invention

[0047] Hereinafter, the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist thereof.

[0048] When the expression "~" is used in this specification, it is used as an expression including the numerical values or physical property values before and after it.

[0049] (Silica Particles)

[0050] The silica particles of the present invention are silica particles satisfying at least one of the following characteristics (a) to (c).

[0051] (a) The sodium content rate is 15 mass ppb or less.

[0052] (b) The potassium content rate is 5 mass ppb or less.

[0053] (c) The calcium content rate is 9 mass ppb or less.

[0054] 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).

[0055] In the silica particles of the present invention satisfying the above characteristic (a), the sodium content rate is 15 mass ppb or less.

[0056] By making the sodium content rate of the silica particles 15 mass ppb or less, when used for polishing, the contamination caused by sodium adhering to the surface of the object to be polished and the influence on the performance of the application object of the object to be polished are reduced, and thus it is preferable. Especially in semiconductor applications, quality deterioration caused by sodium diffusing into the object to be polished from the surface of the object to be polished and performance degradation of semiconductor devices manufactured from such objects to be polished can be reduced, and thus it is preferable.

[0057] From the aspect of more significantly excellent performance as described above, the sodium content rate of the silica particles is preferably 12 mass ppb or less, more preferably 10 mass ppb or less. In addition, the sodium content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0058] In the silica particles of the present invention satisfying the above characteristic (b), the potassium content rate is 5 mass ppb or less.

[0059] By making the potassium content rate of the silica particles 5 mass ppb or less, when used for polishing, the contamination caused by potassium adhering to the surface of the workpiece to be polished and the resulting influence on the performance of the application object of the workpiece to be polished are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by potassium diffusing into the interior of the workpiece to be polished due to potassium adhering to the surface of the workpiece to be polished, and the performance degradation of semiconductor devices manufactured from such workpieces to be polished, so it is preferred.

[0060] From the aspect of more significantly excellent performance as described above, the potassium content rate of the silica particles is preferably 2 mass ppb or less, more preferably 0.5 mass ppb or less. In addition, the potassium content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0061] In the silica particles of the present invention satisfying the above characteristic (c), the calcium content rate is 9 mass ppb or less.

[0062] By making the calcium content rate of the silica particles 9 mass ppb or less, when used for polishing, the contamination caused by calcium adhering to the surface of the workpiece to be polished and the resulting influence on the performance of the application object of the workpiece to be polished are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce quality deterioration such as the formation of pits caused by catalytic chemical reactions between calcium and the workpiece to be polished due to calcium diffusing into the interior of the workpiece to be polished from the surface of the workpiece to be polished, and the performance degradation of semiconductor devices manufactured from such workpieces to be polished, so it is preferred.

[0063] From the aspect of more significantly excellent performance as described above, the calcium content rate of the silica particles is preferably 7 mass ppb or less, more preferably 6 mass ppb or less. In addition, the calcium content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0064] The cobalt content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.7 mass ppb or less, and still more preferably 0.5 mass ppb or less. By making the cobalt content rate of the silica particles within the above range, during grinding, the contamination caused by cobalt adhering to the surface of the object to be ground and the influence on the performance of the application object of the object to be ground are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by cobalt diffusing into the object to be ground from the surface of the object to be ground and the performance degradation of semiconductor devices manufactured from such objects to be ground, so it is preferred. In addition, the cobalt content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0065] The magnesium content rate of the silica particles of the present invention is preferably 1.5 mass ppb or less, more preferably 0.5 mass ppb or less. By making the magnesium content rate of the silica particles within the above range, during grinding, the contamination caused by magnesium adhering to the surface of the object to be ground and the influence on the performance of the application object of the object to be ground are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration such as the formation of pits caused by the catalytic chemical reaction between magnesium and the object to be ground due to magnesium diffusing into the object to be ground from the surface of the object to be ground and the performance degradation of semiconductor devices manufactured from such objects to be ground, so it is preferred. In addition, the magnesium content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0066] The aluminum content rate of the silica particles of the present invention is preferably 2 mass ppb or less, more preferably 1.2 mass ppb or less. By making the aluminum content rate of the silica particles within the above range, during grinding, the contamination caused by aluminum adhering to the surface of the object to be ground and the influence on the performance of the application object of the object to be ground are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by aluminum diffusing into the object to be ground from the surface of the object to be ground and the performance degradation of semiconductor devices manufactured from such objects to be ground, so it is preferred. In addition, the aluminum content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0067] The chromium content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the chromium content rate of the silica particles within the above range, when used for polishing, the contamination caused by chromium adhering to the surface of the object to be polished and the resulting influence on the performance of the application object of the object to be polished are reduced, which is thus preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by chromium adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, which is thus preferred. In addition, the chromium content rate of the silica particles is 0 mass ppb or more, and preferably 0.0001 mass ppb or more from the aspect of easy manufacturing.

[0068] The manganese content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the manganese content rate of the silica particles within the above range, when used for polishing, the contamination caused by manganese adhering to the surface of the object to be polished and the resulting influence on the performance of the application object of the object to be polished are reduced, which is thus preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by manganese adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, which is thus preferred. In addition, the manganese content rate of the silica particles is 0 mass ppb or more, and preferably 0.0001 mass ppb or more from the aspect of easy manufacturing.

[0069] The iron content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.6 mass ppb or less. By making the iron content rate of the silica particles within the above range, when used for polishing, the contamination caused by iron adhering to the surface of the object to be polished and the resulting influence on the performance of the application object of the object to be polished are reduced, which is thus preferred. Especially in semiconductor applications, it is possible to reduce quality deterioration such as the formation of pits caused by the catalytic chemical reaction between iron and the object to be polished due to iron adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, which is thus preferred. In addition, the iron content rate of the silica particles is 0 mass ppb or more, and preferably 0.0001 mass ppb or more from the aspect of easy manufacturing.

[0070] The nickel content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the nickel content rate of the silica particles within the above range, when used for polishing, the contamination caused by nickel adhering to the surface of the object to be polished and the resulting influence on the performance of the object to which the object to be polished is applied are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by nickel adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, so it is preferred. In addition, the nickel content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0071] The zinc content rate of the silica particles of the present invention is preferably 15 mass ppb or less, more preferably 12 mass ppb or less. By making the zinc content rate of the silica particles within the above range, when used for polishing, the contamination caused by zinc adhering to the surface of the object to be polished and the resulting influence on the performance of the object to which the object to be polished is applied are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by zinc adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, so it is preferred. In addition, the zinc content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0072] The copper content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the copper content rate of the silica particles within the above range, when used for polishing, the contamination caused by copper adhering to the surface of the object to be polished and the resulting influence on the performance of the object to which the object to be polished is applied are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by copper adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, so it is preferred. In addition, the copper content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0073] The lead content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the lead content rate of the silica particles within the above range, when used for polishing, the contamination caused by lead adhering to the surface of the workpiece to be polished and the resulting influence on the performance of the application object of the workpiece to be polished are reduced, which is thus preferred. Especially in semiconductor applications, it is possible to reduce the quality degradation caused by lead diffusing from the surface of the workpiece to be polished into the interior of the workpiece to be polished and the performance degradation of semiconductor devices manufactured from such workpieces to be polished, which is thus preferred. In addition, the lead content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0074] The titanium content rate of the silica particles of the present invention is preferably 2 mass ppb or less, more preferably 1.2 mass ppb or less. By making the titanium content rate of the silica particles within the above range, when used for polishing, the contamination caused by titanium adhering to the surface of the workpiece to be polished and the resulting influence on the performance of the application object of the workpiece to be polished are reduced, which is thus preferred. Especially in semiconductor applications, it is possible to reduce the quality degradation caused by titanium diffusing from the surface of the workpiece to be polished into the interior of the workpiece to be polished and the performance degradation of semiconductor devices manufactured from such workpieces to be polished, which is thus preferred. In addition, the titanium content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0075] The silver content rate of the silica particles of the present invention is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the silver content rate of the silica particles within the above range, when used for polishing, the contamination caused by silver adhering to the surface of the workpiece to be polished and the resulting influence on the performance of the application object of the workpiece to be polished are reduced, which is thus preferred. Especially in semiconductor applications, it is possible to reduce the quality degradation caused by silver diffusing from the surface of the workpiece to be polished into the interior of the workpiece to be polished and the performance degradation of semiconductor devices manufactured from such workpieces to be polished, which is thus preferred. In addition, the silver content rate of the silica particles is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0076] The metal content rate of the silica particles of the present invention is preferably 50 mass ppb or less, more preferably 40 mass ppb or less, and still more preferably 35 mass ppb or less. By making the metal content rate of the silica particles within the above range, during grinding, the contamination caused by metal adhering to the surface of the object to be ground and the resulting impact on the performance of the application object of the object to be ground are reduced, which is thus preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by the diffusion of metal adhering to the surface of the object to be ground into the interior of the object to be ground and the performance degradation of semiconductor devices manufactured from such objects to be ground, which is thus preferred. In addition, the metal content rate of the silica particles is 0 mass ppb or more, and from the aspect of ease of manufacture, it is preferably 0.0001 mass ppb or more.

[0077] In addition, when the metal content rate of the silica particles is 50 mass ppb or less, it is possible to reduce the influence of the change in the chemical properties (acidity, etc.) of the surface silanol groups and the change in the spatial environment on the surface of the silica particles (ease of aggregation of the silica particles, etc.) on the grinding rate due to the coordination interaction occurring between the acidic surface silanol groups and the contained metals, which is thus preferred.

[0078] The content rate of each metal in the silica particles in this specification refers to the value obtained by measurement using high-frequency inductively coupled plasma mass spectrometry (ICP-MS). Specifically, accurately measure 0.4 g of silica particles or a silica sol containing 0.4 g of silica particles, add sulfuric acid and hydrofluoric acid, heat, dissolve, and evaporate, and add pure water to the remaining sulfuric acid drop to make the total amount accurately reach 10 g to prepare a test solution, and use a high-frequency inductively coupled plasma mass spectrometry device for measurement. 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 content rates of these metals is taken as the metal content rate.

[0079] In the manufacture of silica particles by the sol-gel method, in order to make the content rate of each of the above metals in the obtained silica particles not exceed the above upper limit and make its total content rate 50 mass ppb or less, for example, the following methods can be appropriately selected and adopted.

[0080] (1) As the starting material tetraalkoxysilane, use tetraalkoxysilane with a metal content rate of 50 mass ppb or less.

[0081] (2) Conduct the hydrolysis reaction and condensation reaction of tetraalkoxysilane in a reaction tank with a fluororesin coating or a glass layer on the inner wall surface.

[0082] (3) As the reaction tank, use a reaction tank such that the contact area between the reaction solution in the hydrolysis reaction and the condensation reaction and the reaction tank is 5 m per unit volume on average. -1 The following reaction tank.

[0083] It is also possible to combine and adopt two or more of the above solutions.

[0084] It should be noted that in the method for manufacturing deionized silica particles using silicate alkalis such as water glass, sodium and the like derived from the raw materials will remain. Therefore, it is extremely difficult to make the metal impurity content rate of the silica particles 50 mass ppb or less.

[0085] The average primary particle diameter of the silica particles of the present invention is preferably 5 nm to 100 nm, more preferably 15 nm to 60 nm. When the average primary particle diameter of the silica particles is 5 nm or more, the storage stability of the silica sol is excellent. When the average primary particle diameter of the silica particles is 100 nm or less, it is possible to reduce the surface roughness and damage of the object to be polished represented by a silicon wafer, and to suppress the sedimentation of the silica particles.

[0086] The average primary particle diameter of the silica particles is measured by the BET method. Specifically, the specific surface area of the silica particles is measured using a specific surface area automatic measuring device, and the average primary particle diameter is calculated using the following formula (1).

[0087] Average primary particle diameter (nm) = 6000 / (specific surface area (m 2 / g) × density (g / cm 3 )) ··· (1)

[0088] The average primary particle diameter of the silica particles can be set to a desired range by the manufacturing conditions of the silica particles.

[0089] The average secondary particle diameter of the silica particles of the present invention is preferably 10 nm to 200 nm, more preferably 30 nm to 100 nm. When 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. When the average secondary particle diameter of the silica particles is 200 nm or less, it is possible to reduce the surface roughness and damage of the object to be polished represented by a silicon wafer during polishing, the removability of particles and the like during cleaning after polishing is excellent, and the sedimentation of the silica particles can be suppressed.

[0090] The average secondary particle diameter of the silica particles is measured by the DLS method. Specifically, it is measured using a dynamic light scattering particle size measuring device.

[0091] The average secondary particle diameter of the silica particles can be set to a desired range by the manufacturing conditions of the silica particles.

[0092] The CV value of the silica particles of the present invention is preferably 10% to 50%, more preferably 15% to 40%, and further preferably 20% to 35%. When the CV value of the silica particles is 10% or more, the polishing rate for the workpieces to be polished represented by silicon wafers is excellent, and the productivity of silicon wafers is excellent. When the CV value of the silica particles is 50% or less, the surface roughness and damage of the workpieces to be polished represented by silicon wafers during polishing can be reduced, and the removability of particles and the like during cleaning after polishing is excellent.

[0093] The average secondary particle size of the silica particles is measured using a dynamic light scattering particle size measuring device, and the CV value of the silica particles is calculated using the following formula (2).

[0094] CV value = (standard deviation (nm) / average secondary particle size (nm)) × 100 ··· (2)

[0095] The association ratio of the silica particles of the present invention is preferably 1.0 to 4.0, more preferably 1.1 to 3.0. When the association ratio of the silica particles is 1.0 or more, the polishing rate for the workpieces to be polished represented by silicon wafers is excellent, and the productivity of silicon wafers is excellent. When the association ratio of the silica particles is 4.0 or less, the surface roughness and damage of the workpieces to be polished represented by silicon wafers during polishing can be reduced, and the aggregation of silica particles can be suppressed.

[0096] Based on the average primary particle size measured by the above measurement method and the average secondary particle size measured by the above measurement method, the association ratio of the silica particles is calculated using the following formula (3).

[0097] Association ratio = average secondary particle size / average primary particle size ··· (3)

[0098] The surface silanol group density of the silica particles of the present invention is preferably 1 per nm 2 ~8 per nm 2 and more preferably 4 per nm 2 ~7 per nm 2 . When the surface silanol group density of the silica particles is 1 per nm 2 or more, the silica particles have appropriate surface repulsion, and the dispersion stability of the silica sol is excellent. When the surface silanol group density of the silica particles is 8 per nm 2 or less, the silica particles have appropriate surface repulsion, and the aggregation of silica particles can be suppressed.

[0099] The surface silanol group density of the silica particles is measured by the Sears method. Specifically, the measurement / calculation is performed under the conditions shown below.

[0100] Collect silica sol equivalent to 1.5 g of silica particles, add pure water to make the liquid volume reach 90 mL. In an environment of 25 °C, add 0.1 mol / L hydrochloric acid aqueous solution thereto until the pH reaches 3.6, add 30 g of sodium chloride, gradually add pure water while completely dissolving sodium chloride, and add pure water until the total amount of the test solution finally reaches 150 mL to obtain a test solution.

[0101] Add the obtained test solution to an automatic titrator, dropwise add 0.1 mol / L sodium hydroxide aqueous solution, and measure the titration volume A (mL) of 0.1 mol / L sodium hydroxide aqueous solution required for the pH to change from 4.0 to 9.0.

[0102] Use the following formula (4) to calculate the consumption volume V (mL) of 0.1 mol / L sodium hydroxide aqueous solution required for the pH to change from 4.0 to 9.0 per 1.5 g of silica particles on average, and use the following formula (5) to calculate the surface silanol group density ρ (pieces / nm 2 ) of the silica particles.

[0103] V = (A × f × 100 × 1.5) / (W × C) ··· (4)

[0104] A: Titration volume (mL) of 0.1 mol / L sodium hydroxide aqueous solution required for the pH to change from 4.0 to 9.0 per 1.5 g of silica particles on average

[0105] f: Titration degree of 0.1 mol / L sodium hydroxide aqueous solution used

[0106] C: Concentration (mass%) of silica particles in the silica sol

[0107] W: Sampling amount (g) of the silica sol

[0108] ρ = (B × N A ) / (10 18 × M × S BET ) ··· (5)

[0109] B: Amount of sodium hydroxide required for the pH to change from 4.0 to 9.0 per 1.5 g of silica particles on average calculated based on V (mol)

[0110] N A : Avogadro's constant (pieces / mol)

[0111] M: Amount of silica particles (1.5 g)

[0112] S BET : Specific surface area of silica particles measured when calculating the average primary particle size (m 2 / g)

[0113] From the aspects of taking into account the suppression of damage to the material to be polished, excellent polishing rate, not easily adhering to the material to be polished, and having appropriate hardness, the silica particles of the present invention are preferably amorphous. The fact that the silica particles are amorphous can be confirmed by the halo pattern in wide-angle X-ray scattering measurement.

[0114] From the aspects of low content of metal impurities, excellent mechanical strength, and excellent storage stability, the silica particles of the present invention preferably have an alkoxysilane condensate as the main component, more preferably have a tetraalkoxysilane condensate as the main component, and further preferably have a tetramethoxysilane condensate as the main component. The main component means a component that is 50% by mass or more in 100% by mass of all the components constituting the silica particles.

[0115] In order to obtain silica particles having an alkoxysilane condensate as the main component, it is preferable to use an alkoxysilane as the main raw material. In order to obtain silica particles having a tetraalkoxysilane condensate as the main component, it is preferable to use a tetraalkoxysilane as the main raw material. In order to obtain silica particles having a tetramethoxysilane condensate as the main component, it is preferable to use a tetramethoxysilane as the main raw material. The main raw material means a raw material that is 50% by mass or more in 100% by mass of all the raw materials constituting the silica particles.

[0116] (Method for manufacturing silica particles)

[0117] The silica particles of the present invention can be obtained by including a step of subjecting a tetraalkoxysilane to a hydrolysis reaction and a condensation reaction.

[0118] The method for manufacturing the silica particles of the present invention is preferably a method in which a solution (B) containing a tetraalkoxysilane and a solution (C) containing a base catalyst are added to a solution (A) containing water to subject the tetraalkoxysilane to a hydrolysis reaction and a condensation reaction.

[0119] In the case of this method, it is easy to control the hydrolysis reaction and the condensation reaction, the reaction rate of the hydrolysis reaction and the condensation reaction can be increased, the gelation of the dispersion of the silica particles can be prevented, and silica particles having a uniform particle size can be obtained.

[0120] Solution (A) contains water.

[0121] From the aspect of excellent dispersibility of the tetraalkoxysilane in the reaction solution, it is preferable that solution (A) contains a solvent other than water.

[0122] As solvents other than water in solution (A), examples include: methanol, ethanol, propanol, isopropanol, ethylene glycol, etc. These solvents can be used alone, or two or more of them can be used in combination. Among these solvents, alcohols are preferred, methanol and ethanol are more preferred, and methanol is further preferred. These alcohols easily dissolve tetraalkoxysilane, and the alcohol used in the hydrolysis reaction and the condensation reaction is the same as the alcohol generated as a by-product, and the manufacturing convenience is excellent.

[0123] From the aspect of being able to increase the reaction rate of the hydrolysis reaction and the condensation reaction of tetraalkoxysilane, it is preferred that solution (A) contains a base catalyst.

[0124] As the base catalyst in solution (A), examples include: ethylenediamine, diethylenetriamine, triethylenetetramine, ammonia, urea, ethanolamine, tetramethylammonium hydroxide, etc. These base catalysts can be used alone, or two or more of them can be used in combination. Among these base catalysts, ammonia is preferred. In the case of ammonia, the catalytic action is excellent, the particle shape is easy to control, the mixing of metal impurities can be suppressed, the volatility is high, and the removability after the hydrolysis reaction and the condensation reaction is excellent.

[0125] The concentration of water in solution (A) is preferably 3% by mass to 50% by mass, more preferably 5% by mass to 40% by mass in 100% by mass of solution (A). When the concentration of water in solution (A) is 3% by mass or more, the hydrolysis reaction rate of tetraalkoxysilane is easily controlled. When the concentration of water in solution (A) is 50% by mass or less, the reaction equilibrium between the hydrolysis reaction and the condensation reaction is good, and the particle shape is easy to control.

[0126] The concentration of the base catalyst in solution (A) is preferably 0.5% by mass to 2.0% by mass, more preferably 0.6% by mass to 1.5% by mass in 100% by mass of solution (A). When the concentration of the base catalyst in solution (A) is 0.5% by mass or more, the aggregation of silica particles can be suppressed, and the dispersion stability of silica particles in the dispersion liquid is excellent. When the concentration of the base catalyst in solution (A) is 2.0% by mass or less, the reaction does not proceed too fast, and the reaction controllability is excellent.

[0127] The concentration of the solvent other than water in solution (A) is preferably set to the remainder of water and the base catalyst.

[0128] Solution (B) contains tetraalkoxysilane.

[0129] Examples of the tetraalkoxysilane as the solution (B) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, etc. These tetraalkoxysilanes can be used alone or in combination of two or more. Among these tetraalkoxysilanes, tetramethoxysilane and tetraethoxysilane are preferred, and tetramethoxysilane is more preferred. These tetraalkoxysilanes have a fast hydrolysis reaction, and unreacted substances are not likely to remain, with excellent productivity, and can easily obtain a stable silica sol.

[0130] As the raw material of the silica particles, raw materials other than tetraalkoxysilane such as low condensates of tetraalkoxysilane can be used. Among them, in all the raw materials of the silica particles by 100% by mass, it is preferred that the tetraalkoxysilane is 50% by mass or more and the raw materials other than tetraalkoxysilane are 50% by mass or less, and more preferably the tetraalkoxysilane is 90% by mass or more and the raw materials other than tetraalkoxysilane are 10% by mass or less. When the proportion of tetraalkoxysilane in the raw materials is above the above lower limit, the reactivity is excellent.

[0131] The sodium content rate of the tetraalkoxysilane is preferably 15 mass ppb or less, more preferably 12 mass ppb or less, and further preferably 10 mass ppb or less. By making the sodium content rate of the tetraalkoxysilane within the above range, the sodium content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by sodium adhering to the surface of the object to be polished and the resulting influence on the performance of the application object of the object to be polished are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by sodium diffusing into the object to be polished from the surface of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, so it is preferred. In addition, the sodium content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0132] The potassium content rate of the tetraalkoxysilane is preferably 5 mass ppb or less, more preferably 2 mass ppb or less, and further preferably 0.5 mass ppb or less. By making the potassium content rate of the tetraalkoxysilane within the above range, the potassium content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by potassium adhering to the surface of the object to be polished and the resulting influence on the performance of the application object of the object to be polished are reduced, so it is preferred. Especially in semiconductor applications, it is possible to reduce the quality deterioration caused by potassium diffusing into the object to be polished from the surface of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished, so it is preferred. In addition, the potassium content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0133] The calcium content rate of the tetraalkoxysilane is preferably 9 mass ppb or less, more preferably 7 mass ppb or less, and still more preferably 6 mass ppb or less. By making the calcium content rate of the tetraalkoxysilane within the above range, the calcium content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by calcium adhering to the surface of the object to be polished and the influence on the performance of the object to which the object to be polished is applied are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by calcium diffusing from the surface of the object to be polished into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the calcium content rate of the tetraalkoxysilane is 0 mass ppb or more, and preferably 0.0001 mass ppb or more from the viewpoint of easy manufacturing.

[0134] The cobalt content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.7 mass ppb or less, and still more preferably 0.5 mass ppb or less. By making the cobalt content rate of the tetraalkoxysilane within the above range, the cobalt content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by cobalt adhering to the surface of the object to be polished and the influence on the performance of the object to which the object to be polished is applied are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by cobalt diffusing from the surface of the object to be polished into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the cobalt content rate of the tetraalkoxysilane is 0 mass ppb or more, and preferably 0.0001 mass ppb or more from the viewpoint of easy manufacturing.

[0135] The magnesium content rate of the tetraalkoxysilane is preferably 1.5 mass ppb or less, more preferably 0.5 mass ppb or less. By making the magnesium content rate of the tetraalkoxysilane within the above range, the magnesium content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by magnesium adhering to the surface of the object to be polished and the influence on the performance of the object to which the object to be polished is applied are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by magnesium diffusing from the surface of the object to be polished into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the magnesium content rate of the tetraalkoxysilane is 0 mass ppb or more, and preferably 0.0001 mass ppb or more from the viewpoint of easy manufacturing.

[0136] The aluminum content rate of the tetraalkoxysilane is preferably 2 mass ppb or less, more preferably 1.2 mass ppb or less. By making the aluminum content rate of the tetraalkoxysilane within the above range, the aluminum content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by aluminum adhering to the surface of the object to be polished and the influence on the performance of the object to be polished due to this are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by aluminum adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance reduction of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the aluminum content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0137] The chromium content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the chromium content rate of the tetraalkoxysilane within the above range, the chromium content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by chromium adhering to the surface of the object to be polished and the influence on the performance of the object to be polished due to this are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by chromium adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance reduction of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the chromium content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0138] The manganese content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the manganese content rate of the tetraalkoxysilane within the above range, the manganese content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by manganese adhering to the surface of the object to be polished and the influence on the performance of the object to be polished due to this are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by manganese adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance reduction of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the manganese content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0139] The iron content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.6 mass ppb or less. By making the iron content rate of the tetraalkoxysilane within the above range, the iron content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by iron adhering to the surface of the object to be polished and the influence on the performance of the application object of the object to be polished caused thereby are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by iron adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance reduction of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the iron content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0140] The nickel content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the nickel content rate of the tetraalkoxysilane within the above range, the nickel content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by nickel adhering to the surface of the object to be polished and the influence on the performance of the application object of the object to be polished caused thereby are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by nickel adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance reduction of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the nickel content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0141] The zinc content rate of the tetraalkoxysilane is preferably 15 mass ppb or less, more preferably 12 mass ppb or less. By making the zinc content rate of the tetraalkoxysilane within the above range, the zinc content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by zinc adhering to the surface of the object to be polished and the influence on the performance of the application object of the object to be polished caused thereby are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by zinc adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance reduction of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the zinc content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0142] The copper content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the copper content rate of the tetraalkoxysilane within the above range, the copper content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by copper adhering to the surface of the object to be polished and the influence on the performance of the object to be polished due to this can be reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by copper adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the copper content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0143] The lead content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the lead content rate of the tetraalkoxysilane within the above range, the lead content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by lead adhering to the surface of the object to be polished and the influence on the performance of the object to be polished due to this can be reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by lead adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the lead content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0144] The titanium content rate of the tetraalkoxysilane is preferably 2 mass ppb or less, more preferably 1.2 mass ppb or less. By making the titanium content rate of the tetraalkoxysilane within the above range, the titanium content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by titanium adhering to the surface of the object to be polished and the influence on the performance of the object to be polished due to this can be reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by titanium adhering to the surface of the object to be polished diffusing into the interior of the object to be polished and the performance degradation of semiconductor devices manufactured from such objects to be polished can be reduced, so it is preferred. In addition, the titanium content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0145] The silver content rate of the tetraalkoxysilane is preferably 1 mass ppb or less, more preferably 0.5 mass ppb or less. By making the silver content rate of the tetraalkoxysilane within the above range, the silver content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by silver adhering to the surface of the workpiece to be polished and the influence on the performance of the application object of the workpiece to be polished are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by silver diffusing from the surface of the workpiece to be polished into the interior of the workpiece to be polished and the performance reduction of semiconductor devices manufactured from such workpieces to be polished can be reduced, so it is preferred. In addition, the silver content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0146] The metal content rate of the tetraalkoxysilane is preferably 50 mass ppb or less, more preferably 40 mass ppb or less, and further preferably 35 mass ppb or less. By making the metal content rate of the tetraalkoxysilane within the above range, the metal content rate of the obtained silica particles can be reduced. When used for polishing, the contamination caused by metal adhering to the surface of the workpiece to be polished and the influence on the performance of the application object of the workpiece to be polished are reduced, so it is preferred. Especially in semiconductor applications, the quality deterioration caused by metal diffusing from the surface of the workpiece to be polished into the interior of the workpiece to be polished and the performance reduction of semiconductor devices manufactured from such workpieces to be polished can be reduced, so it is preferred. In addition, the metal content rate of the tetraalkoxysilane is 0 mass ppb or more, and from the aspect of easy manufacturing, it is preferably 0.0001 mass ppb or more.

[0147] The content rate of each metal in the tetraalkoxysilane in this specification refers to the value obtained by measurement using 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 sum of the content rates of these metals is used as the metal content rate.

[0148] Solution (B) may contain no solvent and consist only of tetraalkoxysilane, and from the aspect of excellent dispersibility of tetraalkoxysilane in the reaction solution, it preferably contains a solvent.

[0149] Examples of the solvent in Solution (B) include: methanol, ethanol, propanol, isopropanol, ethylene glycol, etc. These solvents can be used alone or in combination of two or more. Among these solvents, alcohols are preferred, methanol and ethanol are more preferred, and methanol is further preferred. For these alcohols, the alcohol used in the hydrolysis reaction and the condensation reaction is the same as the alcohol generated as a by-product, and the manufacturing convenience is excellent.

[0150] The concentration of the tetraalkoxysilane in solution (B) is preferably 60% by mass to 95% by mass, more preferably 70% by mass to 90% by mass, based on 100% by mass of solution (B). When the concentration of the tetraalkoxysilane in solution (B) is 60% by mass or more, the reaction solution is likely to become uniform. When the concentration of the tetraalkoxysilane in solution (B) is 95% by mass or less, the formation of gel-like substances can be suppressed.

[0151] The concentration of the solvent in solution (B) is preferably 5% by mass to 40% by mass, more preferably 10% by mass to 30% by mass, based on 100% by mass of solution (B). When the concentration of the solvent in solution (B) is 5% by mass or more, the formation of gel-like substances can be suppressed. When the concentration of the solvent in solution (B) is 40% by mass or less, the reaction solution is likely to become uniform.

[0152] The addition rate of solution (B) per hour, on average, relative to the volume of solution (A) is preferably 0.05 kg / hour / L to 1.3 kg / hour / L, more preferably 0.1 kg / hour / L to 0.8 kg / hour / L. When the addition rate of solution (B) is 0.05 kg / hour / L or more, the productivity of silica particles is excellent. When the addition rate of solution (B) is 1.3 kg / hour / L or less, the formation of gel-like substances can be suppressed.

[0153] Solution (C) contains a base catalyst.

[0154] Examples of the base catalyst in solution (C) include: ethylenediamine, diethylenetriamine, triethylenetetramine, ammonia, urea, ethanolamine, tetramethylammonium hydroxide, etc. These base catalysts can be used alone, or two or more of them can be used in combination. Among these base catalysts, ammonia is preferred. Ammonia has excellent catalytic activity, is easy to control the particle shape, can suppress the mixing of metal impurities, has high volatility, and excellent removability after hydrolysis reaction and condensation reaction.

[0155] From the aspect of being able to reduce the variation in the concentration of the base catalyst in the reaction solution, it is preferred that solution (C) contains a solvent.

[0156] Examples of the solvent in solution (C) include: water, methanol, ethanol, propanol, isopropanol, ethylene glycol, etc. These solvents can be used alone, or two or more of them can be used in combination. Among these solvents, water and alcohol are preferred, and water is more preferred. For water, alcohol, especially water, the solvent used in the hydrolysis reaction and condensation reaction is the same as that generated as a by-product, and the manufacturing convenience is excellent.

[0157] The concentration of the base catalyst in solution (C) is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 6% by mass, based on 100% by mass of solution (C). When the concentration of the base catalyst in solution (C) is 0.5% by mass or more, it is easy to adjust the concentration of the base catalyst in the reaction solution from the start to the end of the reaction. When the concentration of the base catalyst in solution (C) is 10% by mass or less, the variation in the concentration of the base catalyst in the reaction solution can be reduced.

[0158] The concentration of the solvent in solution (C) is preferably 90% by mass to 99.5% by mass, more preferably 94% by mass to 99% by mass, based on 100% by mass of solution (C). When the concentration of the solvent in solution (C) is 90% by mass or more, the variation in the concentration of the base catalyst in the reaction solution can be reduced. When the concentration of the solvent in solution (C) is 99.5% by mass or less, it is easy to adjust the concentration of the base catalyst in the reaction solution from the start to the end of the reaction.

[0159] The addition of solution (B) and solution (C) is preferably carried out in the liquid of solution (A). By adding solution (B) and solution (C) to the liquid of solution (A), in the case where a highly volatile base catalyst represented by ammonia is to be used and in the case where the hydrolysis reaction and the condensation reaction are to be carried out at a high reaction temperature, the miscibility of the respective components in the reaction solution is increased, abnormal reactions in the gas can be suppressed, and the particle shape can be easily controlled.

[0160] Adding to the liquid means adding below the liquid surface. For example, by setting the supply outlet of solution (B) and the supply outlet of solution (C) below the liquid surface of solution (A), solution (B) and solution (C) can be added to the liquid of solution (A).

[0161] The timing of adding solution (B) and solution (C) to solution (A) may be the same or may be different alternately. From the aspect that the change in the reaction composition is small and the operation does not become complicated, it is preferable that the timing of adding solution (B) and solution (C) to solution (A) is the same.

[0162] The pH in the step of subjecting the tetraalkoxysilane to a hydrolysis reaction and a condensation reaction is preferably 8 to 14, more preferably 8.2 to 13, and still more preferably 8.5 to 12. When the pH in the above step is 8 or more, the reaction rates of the hydrolysis reaction and the condensation reaction are excellent, and the aggregation of the silica particles can be suppressed. When the pH in the above step is 14 or less, it is easy to control the shape of the silica particles, and the smoothness of the surface of the silica particles is excellent.

[0163] The reaction temperature of the hydrolysis reaction and the condensation reaction is preferably 5°C to 50°C, more preferably 10°C to 45°C. When the reaction temperature is 5°C or higher, the reaction does not proceed too slowly and the controllability is excellent. When the reaction temperature is 50°C or lower, the balance between the hydrolysis reaction rate and the condensation reaction rate is excellent.

[0164] The concentration of water in the reaction system of the hydrolysis reaction and the condensation reaction is preferably maintained at 3% to 30% by mass, more preferably 5% to 25% by mass, based on the total amount of 100% by mass in the reaction system. When the concentration of water in the reaction system is 3% by mass or higher, it is easy to control the hydrolysis reaction rate of tetraalkoxysilane. When the concentration of water in the reaction system is 30% by mass or lower, the reaction balance between the hydrolysis reaction and the condensation reaction is good and it is easy to control the particle shape.

[0165] The concentration of the base catalyst in the reaction system of the hydrolysis reaction and the condensation reaction is preferably maintained at 0.5% to 2.0% by mass, more preferably 0.6% to 1.5% by mass, based on the total amount of 100% by mass in the reaction system. When the concentration of the base catalyst in the reaction system is 0.5% by mass or higher, the aggregation of silica particles can be inhibited and the dispersion stability of silica particles in the dispersion liquid is excellent. When the concentration of the base catalyst in the reaction system is 2.0% by mass or lower, the reaction does not proceed too fast and the reaction controllability is excellent.

[0166] The hydrolysis reaction and the condensation reaction are preferably carried out in a reaction tank having a fluororesin coating or a glass layer on the inner wall surface, that is, in a reaction tank in which a fluororesin coating or a glass layer is formed on the inner wall surface, and particularly preferably in a reaction tank in which a fluororesin coating is applied to the inner wall surface. By carrying out the hydrolysis reaction and the condensation reaction in a reaction tank having a fluororesin coating or a glass layer on the inner wall surface, it is easy to reduce the contamination of silica particles by metals from the inner wall of the reaction tank.

[0167] The reaction tank used for the hydrolysis reaction and the condensation reaction is preferably such that the contact area between the reaction liquid per unit volume (1 m 3 ) in the hydrolysis reaction and the condensation reaction and the reaction tank is 5 m 2 or less, that is, the ratio of the contact area between the reaction liquid and the reaction tank to the unit volume of the reaction liquid (hereinafter sometimes simply referred to as "contact area ratio with the reaction tank") is 5 m -1 or less, and more preferably the contact area ratio with the reaction tank is 4 m -1 or less.

[0168] When the contact area ratio with the reaction tank is 5 m -1 or less, it is easy to reduce the contamination of silica particles by metals from the inner wall of the reaction tank. On the other hand, from the viewpoint of temperature controllability of the reaction liquid in the hydrolysis reaction and the condensation reaction, the contact area ratio with the reaction tank is preferably 1 m-1 More preferably, it is 3 m or more. -1 or more.

[0169] The volume of the reaction tank for carrying out the hydrolysis reaction and the condensation reaction is preferably 1000 L or more, and more preferably 2000 L or more. When 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 can be reduced, and the metal content rate of the obtained silica particles can be easily reduced.

[0170] On the other hand, from the viewpoint of temperature control of the reaction solution in the hydrolysis reaction and the condensation reaction, the volume of the reaction tank is preferably 20000 L or less.

[0171] In the method for producing silica particles of the present invention, preferably, with respect to such a reaction tank, the reaction is carried out in such a manner that the amount of the reaction solution in the hydrolysis reaction and the condensation reaction is 16000 L or less, particularly 8000 L or less, and 800 L or more.

[0172] From the aspect of being able to remove unnecessary components and add necessary components, it is preferable that the method for producing silica particles further includes the following step (1).

[0173] Step (1): A step of concentrating the dispersion liquid of the obtained silica particles and adding a dispersion medium.

[0174] Either the concentration of the dispersion liquid of the silica particles in step (1) or the addition of the dispersion medium can be carried out first.

[0175] The method for concentrating the dispersion liquid of the silica particles is not particularly limited, and examples thereof include a heating concentration method and a membrane concentration method.

[0176] In order to concentrate the dispersion liquid of the silica particles by the heating concentration method, it is only necessary to heat and concentrate the dispersion liquid under normal pressure or reduced pressure.

[0177] In order to concentrate the dispersion liquid of the silica particles by the membrane concentration method, membrane separation based on the ultrafiltration method is preferably used. Here, the main purpose of the ultrafiltration method is to remove unnecessary components such as intermediate products, for example. The molecular weight cut-off of the ultrafiltration membrane used here can be selected according to the intermediate product in the dispersion liquid to be a molecular weight capable of filtering and separating and removing the intermediate product.

[0178] Examples of the material of the ultrafiltration membrane include polysulfone, polyacrylonitrile, sintered metal, ceramic, carbon, etc. Examples of the form of the ultrafiltration membrane include spiral type, tubular type, hollow fiber type, etc.

[0179] Examples of the dispersion medium added to the dispersion of silica particles include water, methanol, ethanol, propanol, isopropanol, ethylene glycol, etc. These dispersion media can be used alone or in combination of two or more. Among these dispersion media, water and alcohol are preferred from the viewpoint of excellent affinity with silica particles, and water is more preferred.

[0180] (Silica sol)

[0181] The silica sol of the present invention contains the silica particles of the present invention.

[0182] The silica sol of the present invention can directly use the dispersion of the silica particles of the present invention, and can be manufactured by removing unnecessary components from the components in the dispersion of the silica particles of the present invention and adding necessary components.

[0183] The silica sol of the present invention preferably contains silica particles and a dispersion medium.

[0184] Examples of the dispersion medium in the silica sol include water, methanol, ethanol, propanol, isopropanol, ethylene glycol, etc. These dispersion media in the silica sol can be used alone or in combination of two or more. Among these dispersion media in the silica sol, water and alcohol are preferred from the viewpoint of excellent affinity with silica particles, and water is more preferred.

[0185] The content rate of the silica particles in the silica sol is preferably 2 mass% to 50 mass%, more preferably 4 mass% to 40 mass%, and further preferably 5 mass% to 30 mass% in 100 mass% of the total amount of the silica sol. When the content rate of the silica particles in the silica sol is 2 mass% or more, the polishing rate for a polished object represented by a silicon wafer is excellent. When the content rate of the silica particles in the silica sol is 50 mass% or less, aggregation of the silica particles in the silica sol and the polishing composition can be suppressed, and the storage stability of the silica sol and the polishing composition is excellent.

[0186] The content rate of the dispersion medium in the silica sol is preferably 50 mass% to 98 mass%, more preferably 60 mass% to 96 mass%, and further preferably 70 mass% to 95 mass% in 100 mass% of the total amount of the silica sol. When the content rate of the dispersion medium in the silica sol is 50 mass% or more, aggregation of the silica particles in the silica sol and the polishing composition can be suppressed, and the storage stability of the silica sol and the polishing composition is excellent. When the content rate of the dispersion medium in the silica sol is 98 mass% or less, the polishing rate for a polished object represented by a silicon wafer is excellent.

[0187] Regarding the content ratios of the silica particles and the dispersion medium in the silica sol, the desired ranges can be set by removing the unnecessary components from the components in the obtained dispersion liquid of the silica particles and adding the necessary components.

[0188] In addition to the silica particles and the dispersion medium, the silica sol may contain other components such as oxidants, preservatives, mildew-proof agents, pH adjusters, pH buffers, surfactants, chelating agents, antibacterial biocides, etc. within a range that does not impair its performance as needed.

[0189] Particularly from the aspect of excellent storage stability of the silica sol, it is preferred to include an antibacterial biocide in the silica sol.

[0190] From the aspect of excellent affinity with the silica sol, the antibacterial biocide is preferably hydrogen peroxide. Antibacterial biocides include substances generally referred to as sterilizing agents.

[0191] The content ratio of the antibacterial biocide in the silica sol is preferably 0.0001% by mass to 10% by mass, more preferably 0.001% by mass to 1% by mass in 100% by mass of the total amount of the silica sol. When the content ratio of the antibacterial biocide in the silica sol is 0.0001% by mass or more, the storage stability of the silica sol is excellent. When the content ratio of the antibacterial biocide in the silica sol is 10% by mass or less, the original performance of the silica sol is not impaired.

[0192] The pH of the silica sol is preferably 6.0 to 8.0, more preferably 6.5 to 7.8. When the pH of the silica sol is 6.0 or more, the dispersion stability is excellent and the aggregation of the silica particles can be inhibited. When the pH of the silica sol is 8.0 or less, the dissolution of the silica particles can be prevented and the long-term storage stability is excellent.

[0193] The pH of the silica sol can be set to the desired range by adding a pH adjuster.

[0194] (Polishing composition)

[0195] The polishing composition of the present invention contains the silica sol of the present invention.

[0196] In addition to the silica sol of the present invention, the polishing composition of the present invention may contain other components such as water-soluble polymers, basic compounds, polishing accelerators, surfactants, hydrophilic compounds, preservatives, mildew-proof agents, pH adjusters, pH buffers, surfactants, chelating agents, antibacterial biocides, etc. within a range that does not impair its performance as needed.

[0197] The polishing composition can be obtained by mixing the silica sol of the present invention and other components used as needed. Considering storage and handling, the polishing composition of the present invention can be prepared temporarily at a high concentration and diluted with water or the like immediately before polishing.

[0198] (Polishing method)

[0199] The polishing method of the present invention is a method of polishing using a polishing composition containing the silica sol of the present invention.

[0200] Preferably, the above-mentioned polishing composition is used as the polishing composition.

[0201] As a specific polishing method, for example, there can be mentioned a method of pressing the surface of a silicon wafer onto a polishing pad, dropping the polishing composition of the present invention on the polishing pad, and polishing the surface of the silicon wafer.

[0202] (Method for manufacturing a semiconductor wafer)

[0203] The method for manufacturing a semiconductor wafer of the present invention is a method including a step of polishing using the polishing composition of the present invention. The specific polishing composition and polishing method are as described above.

[0204] As the semiconductor wafer, for example, there can be mentioned: a silicon wafer, a compound semiconductor wafer, etc.

[0205] (Method for manufacturing a semiconductor device)

[0206] The method for manufacturing a semiconductor device of the present invention is a method including a step of polishing using the polishing composition of the present invention. The specific polishing composition and polishing method are as described above.

[0207] (Use)

[0208] The silica particles and the silica sol of the present invention can be suitably used for polishing applications. For example, they can be used for polishing semiconductor materials such as silicon wafers, polishing electronic materials such as hard disk substrates, polishing in the planarization process when manufacturing integrated circuits (chemical mechanical polishing), polishing of photomasks, synthetic quartz glass substrates used for liquid crystals, polishing of disk substrates, etc. Among them, 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.

[0209] Examples

[0210] Hereinafter, the present invention will be described more specifically using examples. The present invention is not limited to the description of the following examples as long as it does not depart from its gist.

[0211] (Measurement of average primary particle size)

[0212] The silica sol (dispersion of silica particles) obtained in the examples and comparative examples was dried at 150 °C, and the BET specific surface area of the silica particles was measured using a specific surface area automatic measuring device (model name "Belsorp MR1", manufactured by Microtrak Bell Co., Ltd.). Assuming that the silica particles are regular spherical, using the following formula (1), with the density set to 2.2 g / cm 3 , the average primary particle size was calculated.

[0213] Average primary particle size (nm) = 6000 / (BET specific surface area (m 2 / g) × density (g / cm 3 )) ··· (1)

[0214] (Measurement of average secondary particle size / cv value)

[0215] For the silica sol (dispersion of silica particles) obtained in the examples and comparative examples, the average secondary particle size of the silica particles was measured using a dynamic light scattering particle size measuring device "Zetasizer Nano ZS" (model name, manufactured by Malvern Co., Ltd.), and the cv value was calculated using the following formula (2).

[0216] cv value = (standard deviation (nm) / average secondary particle size (nm)) × 100 ··· (2)

[0217] (Calculation of association ratio)

[0218] Based on the measured average primary particle size and average secondary particle size, the association ratio was calculated using the following formula (3).

[0219] Association ratio = average secondary particle size / average primary particle size ··· (3)

[0220] (Measurement of surface silanol group density)

[0221] An amount equivalent to 1.5 g of silica particles of the silica sol (dispersion of silica particles) obtained in the examples and comparative examples was collected in a 200 mL tall beaker, and pure water was added to make the liquid volume reach 90 mL.

[0222] In an environment of 25 °C, a pH electrode was inserted into the tall beaker, and the test solution was stirred for 5 minutes by a magnetic stirrer. While continuously stirring using the magnetic stirrer, 0.1 mol / L hydrochloric acid aqueous solution was added until the pH reached 3.6. The pH electrode was removed from the tall beaker, and while continuously stirring using the magnetic stirrer, 30 g of sodium chloride was added. While slowly adding pure water, sodium chloride was completely dissolved, and pure water was added until the total volume of the test solution finally reached 150 mL. The test solution was stirred for 5 minutes by a magnetic stirrer to obtain a test solution.

[0223] The tall beaker containing the obtained test solution was placed in an automatic titrator "COM-1600" (manufactured by Hiranuma Sangyo Co., Ltd.). The pH electrode and burette attached to the device were inserted into the tall beaker. While stirring the test solution using a magnetic stirrer, a 0.1 mol / L aqueous sodium hydroxide solution was added dropwise through the burette, and the titration volume A (mL) of the 0.1 mol / L aqueous sodium hydroxide solution required for the pH to change from 4.0 to 9.0 was measured.

[0224] Using the following formula (4), the consumption volume V (mL) of the 0.1 mol / L aqueous sodium hydroxide solution required for the pH to change from 4.0 to 9.0 per 1.5 g of silica particles on average was calculated. Using the following formula (5), the surface silanol group density ρ (number / nm 2 ) of the silica particles was calculated.

[0225] V = (A × f × 100 × 1.5) / (W × C) ··· (4)

[0226] A: Titration volume (mL) of the 0.1 mol / L aqueous sodium hydroxide solution required for the pH to change from 4.0 to 9.0 per 1.5 g of silica particles on average

[0227] f: Titration factor of the 0.1 mol / L aqueous sodium hydroxide solution used

[0228] C: Concentration (mass%) of silica particles in the silica sol

[0229] W: Sampling amount (g) of the silica sol

[0230] ρ = (B × N A ) / (10 18 × M × S BET ) ··· (5)

[0231] B: Amount of sodium hydroxide required for the pH to change from 4.0 to 9.0 per 1.5 g of silica particles on average calculated based on V (mol)

[0232] N A : Avogadro's constant (number / mol)

[0233] M: Amount of silica particles (1.5 g)

[0234] S BET : Specific surface area of the silica particles measured when calculating the average primary particle size (m 2 / g)

[0235] (Determination of metal impurity content)

[0236] Accurately measure 0.4 g of silica sol containing silica particles obtained in the examples and comparative examples, add sulfuric acid and hydrofluoric acid, heat, dissolve, and evaporate. Add pure water to the remaining sulfuric acid drop to make the total amount accurately reach 10 g, and prepare a test solution. The metal impurity content rate was measured using a high-frequency inductively coupled plasma mass spectrometry device "ELEMENT2" (model name, manufactured by Thermo Fisher Scientific).

[0237] [Example 1]

[0238] Tetraalkoxysilane was manufactured according to the description in Japanese Patent Laid-Open No. 8-325272. The content rates of various metals in the manufactured tetraalkoxysilane are shown in Table 1.

[0239] A solution (B) prepared by mixing tetramethoxysilane and methanol at a volume ratio of 4.4:1 was prepared. A solution (C) of 3.0 mass% aqueous ammonia solution was prepared separately. In a reaction tank equipped with a thermometer, a stirrer, a supply pipe, and coated with tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin (PFA) on the inner surface, a solution (A) prepared by previously mixing methanol, pure water, and ammonia was added. The water concentration in the solution (A) was set to 11.7 mass%, and the ammonia concentration in the solution (A) was set to 0.73 mass%.

[0240] Over a period of 200 minutes, 100 volume% of solution (B) and 33 volume% of solution (C) were respectively added dropwise to 166 volume% of solution (A) at 22 °C at a constant speed, and a dispersion of silica particles was obtained.

[0241] The contact area ratio of the reaction solution to the reaction tank during the hydrolysis reaction and the condensation reaction was 3.7 m -1 .

[0242] For the obtained dispersion of silica particles, while adjusting the liquid volume by adding pure water so that the content rate of silica particles reaches about 20 mass%, the temperature was raised to remove methanol and ammonia, and a dispersion of silica particles with a silica particle content rate of about 20 mass% was obtained.

[0243] It was confirmed by the halo pattern in wide-angle X-ray scattering measurement that the obtained silica particles were amorphous.

[0244] [Comparative Example 1]

[0245] A commercially available dispersion of silica particles (trade name "PL-3", manufactured by Fuso Chemical Industry Co., Ltd.) was directly used.

[0246] [Comparative Example 2]

[0247] Tetraalkoxysilane was manufactured according to the description in Japanese Patent Laid-Open No. 8-325272. The metal content rates of the manufactured tetraalkoxysilane are shown in Table 1.

[0248] A solution (B) prepared by mixing tetramethoxysilane and methanol at a volume ratio of 4.4:1 was prepared. A solution (C) of 3.0 mass% aqueous ammonia solution was prepared separately. In a glass reaction tank equipped with a thermometer, a stirrer, and a supply pipe, a solution (A) prepared by previously mixing methanol, pure water, and ammonia was added. The water concentration in the solution (A) was set to 11.7 mass%, and the ammonia concentration in the solution (A) was set to 0.73 mass%.

[0249] Over a period of 200 minutes, 100% by volume of solution (B) and 33% by volume of solution (C) were respectively added dropwise to 166% by volume of solution (A) at 22°C at a uniform speed, and a dispersion of silica particles was obtained.

[0250] The contact area ratio of the reaction solution in the hydrolysis reaction and the condensation reaction with the reaction tank was 48.7 m -1 .

[0251] For the obtained dispersion of silica particles, while adjusting the liquid volume by adding pure water so that the silica particle content rate reached about 20 mass%, the temperature was increased to remove methanol and ammonia, and a dispersion of silica particles with a silica particle content rate of about 20 mass% was obtained.

[0252] It was confirmed by the halo pattern in wide-angle X-ray scattering measurement that the obtained silica particles were amorphous.

[0253] The evaluation results of each silica particle are shown in Table 1.

[0254]

[0255] According to Table 1, compared with the silica particles used in Comparative Example 1, the silica particles obtained in Example 1 have substantially the same physical properties such as particle size, but the content rates of most metals are low.

[0256] Compared with the commercially available silica particles of Comparative Example 1, the silica particles obtained in Example 1 have an extremely low metal content rate. Even when used for grinding, it is possible to suppress the adhesion of metals to the surface of the object to be ground, and it is possible to reduce the adverse effects on the performance of the application object of the object to be ground.

[0257] In addition, compared with the silica particles used in Comparative Example 2, the silica particles obtained in Example 1 have substantially the same physical properties such as particle size, but the content rates of all metals are low.

[0258] The silica particles obtained in Example 1 have an extremely low metal content rate compared to the silica particles of Comparative Example 2 obtained using a glass reaction tank under conditions where the contact area ratio between the reaction liquid and the reaction tank is high. Even when used for polishing, it is possible to suppress the adhesion of metals to the surface of the object to be polished, and it is possible to reduce the adverse effects on the performance of the object to be polished to which the present invention is applied.

[0259] The present invention has been described in detail in a specific manner, but those skilled in the art will understand that various modifications can be made within the scope where the effects of the invention can be achieved.

[0260] This application is based on Japanese Patent Application No. 2022-196462 filed on December 8, 2022, and the entire content thereof is incorporated herein by reference.

[0261] Industrial Applicability

[0262] The silica particles of the present invention and the silica sol of the present invention can be suitably used for polishing applications. For example, they can be used for polishing semiconductor materials such as silicon wafers, polishing electronic materials such as hard disk substrates, polishing in the planarization process when manufacturing integrated circuits (chemical mechanical polishing), polishing photomasks, synthetic quartz glass substrates used for liquid crystals, polishing disk substrates, and the like. Among them, they can be suitably used for polishing silicon wafers and chemical mechanical polishing, and in particular, can be particularly suitably used for final polishing of silicon wafers and final polishing of chemical mechanical polishing.

Claims

1. A silica particle that satisfies at least one of the following characteristics (a) to (c), (a) The sodium content rate is 15 mass ppb or less, (b) The potassium content rate is 5 mass ppb or less, (c) The calcium content rate is 9 mass ppb or less.

2. The silica particle according to claim 1, which satisfies at least two of the characteristics (a) to (c).

3. The silica particle according to claim 2, which satisfies all of the characteristics (a) to (c).

4. The silica particle according to any one of claims 1 to 3, wherein the metal content rate is 50 mass ppb or less.

5. The silica particle according to any one of claims 1 to 3, wherein, the silica particle is amorphous.

6. The silica particle according to any one of claims 1 to 3, which has an alkoxysilane condensate as a main component.

7. A method for manufacturing a silica particle, the silica particle being the silica particle according to any one of claims 1 to 3, the method comprising: a step of subjecting a tetraalkoxysilane to a hydrolysis reaction and a condensation reaction in a reaction tank having a fluororesin coating on an inner wall surface.

8. The method for manufacturing a silica particle according to claim 7, wherein, The reaction tank is a reaction tank in which the contact area per unit volume of the reaction solution in the hydrolysis reaction and the condensation reaction with the reaction tank is 5 m -1 or less.

9. The method for manufacturing a silica particle according to claim 7, wherein, the metal content rate of the tetraalkoxysilane is 50 mass ppb or less.

10. A silica sol that contains the silica particle according to any one of claims 1 to 3.

11. The silica sol according to claim 10, wherein, in 100 mass% of the total amount of the silica sol, the content rate of the silica particle is 2 mass% to 50 mass%.

12. A polishing composition that contains the silica sol according to claim 10.

13. A polishing method that polishes using the polishing composition according to claim 12.

14. The polishing method according to claim 13, wherein, the polishing using the polishing composition is the final polishing in a polishing step.

15. A method for manufacturing a semiconductor wafer, the method comprising: a step of polishing using the polishing composition according to claim 12.

16. A method for manufacturing a semiconductor device, the method comprising: a step of polishing using the polishing composition according to claim 12.

Images