Method for producing silica particles, silica particles produced by such methods, compositions and uses of such silica particles - Patents.com

Abstract

The present application relates to a method for producing silica particles, and to silica particles produced by such a method. The present application further relates to compositions comprising silica particles produced by such a method, and to uses of such silica particles and compositions comprising such silica particles.

Description

[Technical field]

[0001] Technical Field The present invention relates to a method for producing silica particles and to silica particles produced by such a method. The present application further relates to compositions comprising silica particles produced by such a method, and to the use of such silica particles and compositions comprising such silica particles. [Background technology]

[0002] background Silica particles can be used in a wide variety of applications: they can be used, for example, as an abrasive, as an additive in paper making and in the paper itself, as a catalyst support, as a drug carrier, in coatings or paints, to name just a few.

[0003] More and more of these applications require the silica particles to be of high purity, i.e., contain low levels of contaminants, such as trace metals and / or organic contaminants. This is the case, for example, in catalysts and catalyst supports, where the absence of contaminants can lead to an increase in the yield of the desired product. Due to modern electronic devices, such as semiconductor devices, memory devices, integrated circuits, etc., becoming smaller, the silica particles used in the manufacture of such modern electronic devices need to meet increasing purity requirements.

[0004] In addition, environmental concerns and political pressures are driving industries to develop and implement more sustainable products and manufacturing processes, which may be more advantageous due to, for example, lower energy consumption or reduced waste. Alternatively, manufacturing processes may be more sustainable if such processes are built on by-products or waste products of a different manufacturing process.

[0005] In a typical conventional "wet" process for producing silica particles, i.e., a process for producing silica particles that is essentially carried out in an aqueous medium, sodium or potassium orthosilicate (Na 4 SiO 4 or K 4 SiO 4 , or more generally SiO 2 xM 2 O (where M is Na or K)) undergoes an ion exchange process to produce orthosilicic acid ("Si(OH) 4 "), which is then polycondensed to give silica particles ("SiO 2 This process, however, has the disadvantage of introducing significant amounts of metal contaminants, such as sodium, into the silica particles (if not removed by the respective purification steps).

[0006] Alternatively, it is known to hydrolyze tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) to produce orthosilicic acid, which is then polycondensed to form silica particles, as disclosed in, for example, US 2007 / 0237701 A1. Although this process can produce silica particles with low levels of metal contaminants, the organic residues from the starting materials as well as the need to use organic solvents in the manufacturing process introduce undesirable organic contaminants into the silica particles.

[0007] As disclosed in US 2012 / 0145950 A1, high purity colloidal silica can be produced by dissolving fumed silica in an aqueous solvent containing an alkali metal hydroxide to produce an alkali silicate, removing the alkali metal via ion exchange to produce a silicic acid solution; and initiating nucleation and particle growth. However, while it can produce high purity silica particles, this method has the disadvantage of relying on fumed silica as a starting material, the production of which already consumes a significant amount of energy.

[0008] As these examples of different manufacturing processes and routes demonstrate, there is a need in industry for improved methods for producing silica particles. The present application therefore aims to provide an improved method for producing silica particles, in particular a method that allows for improved sustainability or high purity, or preferably both improved sustainability and high purity. Summary of the Invention

[0009] overview The inventors have surprisingly found that these objectives can be achieved either individually or in any combination by the present process.

[0010] The present application therefore relates to a method for the manufacture of silica particles, said method comprising the following steps: (a) hydrolyzing silicon chloride in an aqueous solution, thereby producing a gel containing silicic acid and hydrogen chloride, wherein the silicon chloride is represented by the following formula (1'): [ka] R is independently selected at each occurrence from the group consisting of alkyl groups having 1, 2, or 3 carbon atoms; and c is independently selected at each occurrence from the group consisting of 0, 1, 2, and 3; and d is independently selected at each occurrence from the group consisting of 0, 1, 2, and 3; provided that c+d≦3, is represented by; (b) removing at least a portion of the hydrogen chloride from the gel to obtain a purified gel; (c) adjusting the pH of the purified gel to at least 9; and (d) then polycondensing the silicic acid to form silica particles; The method further comprises:

[0011] Additionally, the present application provides silica particles obtainable by such a method, as well as formulations comprising aqueous dispersions of such silica particles.

[0012] Detailed Description Throughout this application, "Me" refers to a methyl group (-CH 3 ), and "Et" is an ethyl group (-CH 2 -CH 3 ), and "nPr" is an n-propyl group (-CH 2 -CH 2 -CH 3 ), and "iPr" is an iso-propyl group (-CH(CH 3 ) 2 ) is intended to indicate For the purposes of this application, the term "silicate" refers to orthosilicic acid (Si(OH) 4 ), as well as their condensation products. It is also noted that a gel or solution of silicic acid is generally understood to also include condensates of silicic acid.

[0013] For the purposes of this application, the terms "silica particle" and "silica particles" are preferably used to denote colloidal silica particles. The term "colloidal" is used to denote particles dispersed in a medium having a dimension between 1 nm and 1 μm in at least one direction (Compendium of Chemical Terminology, Gold Book, International Union of Pure and Applied Chemistry, Version 2.3.3, 2014-02-24, page 295).

[0014] Generally described, the present application provides a method for the production of silica particles, the method comprising the following steps: (a) hydrolyzing silicon chloride in an aqueous solution, thereby producing a gel containing silicic acid and hydrogen chloride; (b) removing at least a portion of the chloride and, if present, the fluoride from the gel to obtain a purified gel; (c) adjusting the pH of the purified gel; and (d) then polycondensing the silicic acid to form silica particles; The present invention relates to the method comprising the steps of:

[0015] The silicon chloride hydrolyzed in step (a) of the present process has the following formula (1'): [ka] wherein R, c and d are as defined herein. It can be represented by:

[0016] R is, independently at each occurrence, selected from the group consisting of alkyl groups having 1, 2, or 3 carbon atoms. Thus, R is, independently at each occurrence, selected from the group consisting of methyl (-CH 3 ), ethyl (-CH 2 -CH 3 ), n-propyl (-CH 2 -CH 2 -CH 3 ), and iso-propyl (-CH(CH 3 ) 2 Preferably, R is, independently at each occurrence, methyl or ethyl. Most preferably, R is methyl. c is independently selected from the group consisting of 0, 1, 2, and 3 in each application. d is independently selected from the group consisting of 0, 1, 2, and 3 in each application.

[0017] c and d are selected in any case with the rule that c+d≦3. Thus, when c is 0, d can be selected from the group consisting of 0, 1, 2, and 3; and when c is 1, d can be selected from the group consisting of 0, 1, and 2; and when c is 2, d can be either 0 or 1; and when c is 3, d is 0.

[0018] Preferably, the silicon chloride hydrolyzed in step (a) of the present process has the following formula (1): [ka] wherein R and a are as defined herein. It can be represented by: a, independently at each occurrence, is an integer selected from the group consisting of 0, 1, 2, and 3. Preferably, independently at each occurrence, a is 0 or 1. Most preferably, a is 0.

[0019] Expressed differently, the silicon chloride hydrolyzed in step (a) is preferably SiCl 4 , MeSiCl 3 , Me 2 SiCl 2 , Me 3 SiCl, EtSiCl 3 , Et 2 SiCl 2 , Et 3 SiCl, nPrSiCl 3 ,NPR 2 SiCl 2 ,NPR 3 SiCl, iPrSiCl 3 , iPr 2 SiCl 2 , iPr 3 From the group consisting of SiCl, and any blends thereof; more preferably, SiCl 4 , MeSiCl 3 , Me 2 SiCl 2 , Me 3 SiCl, EtSiCl 3 , Et 2 SiCl 2 , Et 3 and any blends thereof; even more preferably SiCl 4 , MeSiCl 3 , Me 2 SiCl 2 , Me 3and any blends thereof; even more preferably, SiCl 4 or MeSiCl 3 and most preferably SiCl 4 It is.

[0020] SiCl as starting material for this process 4 The selection of SiCl is particularly advantageous because it is a by-product or waste product of silicon wafer manufacturing and is therefore available in high purity and significant volumes. 4 can also be obtained by chlorination in the presence of a reducing agent, such as carbon, to give SiO 2 can be obtained from

[0021] It is noted that the silicon chloride of step (a) can be a mixture of various silicon chlorides, such as a mixture of any one or more of the silicon chlorides defined above.However, it is preferred that the silicon chloride comprises only one of these, in wt% relative to the total weight of silicon chloride, at least 90 wt%, more preferably at least 95 wt%, even more preferably at least 97 wt%, even more preferably at least 99.0 wt%, and most preferably at least 99.5 wt%.

[0022] The hydrolysis of silicon chloride in step (a) is preferably carried out at a temperature of at least 0°C, such as at least 5°C or 10°C, more preferably at least 20°C, even more preferably at least 30°C, even more preferably at least 40°C, and most preferably at least 50°C.

[0023] The hydrolysis of silicon chloride in step (a) is preferably carried out at a temperature of up to 120° C., more preferably up to 110° C., even more preferably up to 100° C., and most preferably up to 90° C. In general, the hydrolysis of silicon chloride in step (a) is carried out under atmospheric pressure. However, it is also possible to carry out the hydrolysis of silicon chloride in step (a) at elevated pressure, for example up to 10 bar, thereby allowing the hydrolysis of silicon chloride in step (a) to be carried out at a higher temperature, for example up to 150° C.

[0024] It is further noted that the hydrolysis of silicon chloride in step (a) can be accelerated by increasing the temperature of the aqueous medium.However, this is not advantageous for commercial production, as it requires a significant amount of energy, thereby making the process unsustainable.It is also noted that the hydrolysis of silicon chloride is exothermic, thus leading to an increase in the temperature of the aqueous medium, which means that separate heating may not be required.Furthermore, for further process steps, the resulting gel needs to be cooled, thus again requiring energy and / or additional time.

[0025] At the start of step (b), the aqueous solution is preferably at a temperature of at least 0° C., more preferably at a temperature of at least 10° C., or equivalently the lowest temperature at which the solution is still liquid. At the start of step (b), the aqueous solution is at a temperature of up to 50° C., more preferably up to 40° C., even more preferably up to 30° C., and most preferably up to 20° C. Thus, at the start of step (b), the aqueous solution may preferably be in the range of 0° C. to 50° C., or 0° C. to 40° C., or 0° C. to 30° C., or 0° C. to 20° C.

[0026] Preferably, in step (a), the silicon chloride is, for example, SiCl 4The weight ratio of water to silicon chloride, e.g., SiCl, is at least 5, more preferably at least 6. 4 The weight ratio of water to silicon chloride, e.g., SiCl, is at most 20 (e.g., at most 19, or at most 18, or at most 17, or at most 16), and most preferably at most 15 (e.g., at most 14, or at most 13, or at most 12, or at most 11, or at most 10). 4 The weight ratio of water to ethanol may be in the range of 5-20, in the range of 6-20, and most preferably in the range of 5-15 or in the range of 6-15.

[0027] Optionally, a solubilizing agent may be added to the aqueous solution to aid in dissolving the silicic acid produced in step (a) of the process. Such a solubilizing agent may be, for example, hydrogen fluoride (HF).

[0028] Without wishing to be bound by theory, it is believed that the hydrolysis of silicon chlorides as defined above where a is selected from the group consisting of 1, 2, and 3, proceeds initially via hydrolysis of the chloride followed by a condensation reaction, thus resulting in a siloxane intermediate as illustrated by the following equation where a=3, which is then further hydrolyzed to silicic acid: [ka] The hydrolysis of silicon chloride in step (a) produces significant amounts of hydrogen chloride (HCl), at least a portion of which is removed from the gel in the subsequent step (b) of the process to obtain a purified gel.

[0029] Thus, in step (b) of the process, the total content of both chloride and (if present, for example due to the need to use a solubilizing agent as defined herein) fluoride is reduced by 100% by weight of silica ("SiO 2"), preferably to up to 40,000 ppm (e.g., to up to 30,000 ppm, or to up to 20,000 ppm); more preferably to up to 10,000 ppm (e.g., to up to 9,000 ppm, or to up to 8,000 ppm, or to up to 7,000 ppm, or to up to 6,000 ppm, or to up to 5,000 ppm, or to up to 4,000 ppm, or to up to 3,000 ppm, or to up to 2,000 ppm); even more preferably to up to 1,000 ppm (e.g., to up to 900 ppm, or to up to 800 ppm, or to up to 700 ppm, or to up to 600 ppm); and most preferably to up to 500 ppm (e.g., to up to 400 ppm, or to up to 300 ppm, or to up to 200 ppm, or to up to 100 ppm). It is noted that the maximum total amount of chloride and fluoride (if present) may be selected based on the requirements of the application in which the silica particles so produced are to be used.

[0030] The removal of at least a portion of the chlorides and (if present) fluorides from the gel in step (b) of the process to obtain a purified gel may be done by any suitable method. However, it is preferred that step (b) comprises a step (b1) of washing the gel with water, i.e. washing the gel by adding and subsequently removing water, preferably deionized water, more preferably ultrapure water. Preferably, each washing is done with a large volume of water, the volume being preferably 50% to 200%, more preferably 70% to 150%, and most preferably 80% to 120% of the reaction volume in which the gel is prepared. The washing water and the gel may be separated again by filtration or by distilling at least a portion of the water from the gel. Depending on the chloride and fluoride content to be achieved, step (b1) may be repeated as often as necessary.

[0031] Depending on the intended use and the respective requirements, e.g. as regards purity, the total chloride and / or fluoride content (if present) may be less than or equal to the silica ("SiO 2"), to achieve a reduced chloride and / or fluoride (if present) content of up to 500 ppm, preferably up to 400 ppm or 300 ppm or 200 ppm, more preferably up to 100 ppm, and most preferably up to 50 ppm,

[0032] Optionally, step (b) of the process further comprises step (b2), following step (b1), of contacting the gel with an anion exchanger, e.g., an anion exchange resin, to obtain a purified gel. This can be done, for example, by contacting the anion exchange resin and the gel with each other, preferably under mixing in a batch reactor. Alternatively, this can be done, for example, by passing the gel through an anion exchange resin to obtain a purified gel.

[0033] The water used in steps (b1) and (b2), or depending on the method used, generally in step (b), is deionized water. Although generally practicable, it is preferred that after any one of steps (a) and (b) the silicic acid is not dried.

[0034] Following step (b), the process comprises step (c) of adjusting the pH of the purified gel to preferably at least 9, more preferably to at least 10, and most preferably to at least 11. Preferably, in step (c) of the process the pH is adjusted to a maximum of 13, and preferably to a maximum of 12.

[0035] Preferably, in step (c), the pH of the gel is adjusted by adding a base to the purified gel. Such base may be any suitable base. However, such base is preferably selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide, cesium hydroxide, rubidium hydroxide, ammonia, organic amines, and any blends thereof. Of these, potassium hydroxide and ammonia are especially preferred. Suitable organic amines may be selected from the group consisting of alkylamines, alkanolamines, and any blends thereof, with alkanolamines being preferred.

[0036] Examples of suitable alkylamines include those represented by the following formula (2): [ka] wherein b is, independently at each occurrence, an integer selected from the group consisting of 1, 2, and 3; and 1 is an alkyl group having 1, 2, or 3 carbon atoms; A preferred alkylamine is methylamine (H 2 NMe, dimethylamine (HNMe 2 ), trimethylamine (NMe 3 ), ethylamine (H 2 NEt), diethylamine (HNEt 2 ), triethylamine (NEt 3 ), and any blends thereof.

[0037] Examples of suitable alkanolamines include those represented by formula (3): [ka] In the formula, R 2 is, independently at each occurrence, an alkanediyl having at least 1 and at most 5 carbon atoms; Therefore, R 2 is independently defined for each occurrence as methylene (-CH2 -), ethanediyl (-CH 2 -CH 2 -), propanediyl (-(CH 2 -) 3 ), butanediyl (-(CH 2 -) 4 ), and propanediyl (-(CH 2 -) 5 ) may be selected from the group consisting of Preferred alkanolamines may be selected from the group consisting of 2-aminoethanol, 3-aminopropanol, and 4-aminobutanol, with 2-aminoethanol being most preferred.

[0038] Depending on the type of base added, the method advantageously allows the production of silica particles characterized by low trace metal content or low organic residue content or both. For example, selecting a base different from potassium hydroxide allows the production of silica particles with low potassium content and / or low organic residue content and other trace metal contaminants present in potassium hydroxide. An example of a base different from potassium hydroxide that can be preferably selected is ammonia. Thus, the selection of the base in step (c) can be made depending on the requirements of the targeted application. A blend of bases can also be preferred depending on the requirements of the application and to achieve the desired effect while minimizing the trace metal contaminants typically present in different bases.

[0039] After step (c), the purified silicic acid is polycondensed to form silica particles, which can be carried out according to the following generalized reaction scheme (I): [ka] It can be represented by: Optionally, in step (d), so-called seed particles may be introduced, onto which silicic acid is then polycondensed to form silica particles. Alternatively, the formation of silica particles can be started "in situ", i.e. directly from purified silica particles without the introduction of seed particles.

[0040] The shape and dimensions of the silica particles produced according to this process are not specifically limited, provided that such particles are suitable for the intended application. They have an average diameter of at least 2 nm and at most 200 nm when spherical. Such silica particles can be, for example, spherical, elliptical, curved, bent, elongated, branched or cocoon-shaped. Elongated or elliptical silica particles can have an aspect ratio of at least 1.1. The shape and dimensions of the silica particles can depend on the intended application and can also include silica particles of different dimensions and / or sizes.

[0041] For spherical silica particles, the average diameter is preferably at least 5nm, more preferably at least 10nm, and most preferably at least 15nm.For spherical particles, the average diameter is preferably at most 200nm, more preferably at most 150nm or 100nm, even more preferably at most 90nm or 80nm or 70nm or 60nm, even more preferably at most 50nm or 45nm or 40nm or 35nm or 30nm, and most preferably at most 25nm.For example, particularly preferred silica particles have an average diameter of at least 15nm and at most 25nm.

[0042] For elongated, curved, bent, branched and ellipsoidal silica particles, their average diameter is preferably as described above for spherical colloidal silica particles.Preferably, such elongated or ellipsoidal colloidal silica particles have an aspect ratio, i.e., the ratio of length to average diameter, of at least 1.1, more preferably at least 1.2 or 1.3 or 1.4 or 1.5, even more preferably at least 1.6 or 1.7 or 1.8 or 1.9, and most preferably at least 2.0.The aspect ratio is preferably at most 10, more preferably at most 9 or 8 or 7 or 6, and most preferably at most 5.

[0043] The silica particles produced according to the present method may be included in a composition, which further comprises water. Thus, such a composition comprises the present silica particles and water. Preferably, the water is deionized water. Such compositions may be provided as concentrates, which may then be diluted with water, preferably deionized water, prior to their use in the intended application. Such concentrates may contain the silica particles in a weight percent of up to 20 wt.%, preferably up to 25 wt.%, more preferably up to 30 wt.%, even more preferably up to 35 wt.%, even more preferably up to 40 wt.%, and most preferably up to 50 wt.%, based on the total weight of the composition or concentrate.

[0044] Alternatively, when used at point of use, for example in chemical mechanical polishing process, the composition preferably comprises modified silica particles in at least 0.1 wt% (for example, at least 0.2 wt% or 0.3 wt% or 0.4 wt%), more preferably at least 0.5 wt%, even more preferably at least 1.0 wt%, even more preferably at least 1.5 wt%, and most preferably at least 2.0 wt% in wt% based on the total weight of the composition.In this case, the composition preferably comprises modified silica particles in up to 40 wt%, more preferably at most 30 wt%, even more preferably at most 20 wt%, even more preferably at most 15 wt%, and most preferably at most 10 wt%, in wt% based on the total weight of the composition.The concentration or amount of silica particles in the composition at point of use may depend on the intended application and implementation requirements. The concentration or amount of silica particles in the composition at the point of use may be easily modified by diluting the composition or concentrate, preferably with deionized water.

[0045] Optionally, the composition further comprises any one or more of the group consisting of biocides, pH adjusters, pH buffers, oxidizers, chelating agents, corrosion inhibitors, surfactants, and any other additives that may be required to achieve or modify performance as required by the intended use.

[0046] Such oxidizing agent may be any suitable oxidizing agent for one or more metals or metal alloys of the substrate to be polished using the composition. For example, the oxidizing agent may be selected from the group consisting of bromates, bromites, chlorates, chlorites, hydrogen peroxide, hypochlorites, iodates, monoperoxysulfates, monoperoxysulfites, monoperoxyphosphates, monoperoxyhypophosphites, monoperoxypyrophosphates, organic-halo-oxy compounds, periodates, permanganates, peroxyacetic acid, iron nitrates, and any blends thereof. Such oxidizing agents may be added to the composition in suitable amounts, for example, between 0.1 wt% and up to 6.0 wt%, based on the total weight of the composition at the point of use.

[0047] Such a corrosion inhibitor, which may be, for example, a film former, may be any suitable corrosion inhibitor. For example, the corrosion inhibitor may be glycine, which may be added in an amount of at least 0.001 wt% to 3.0 wt% based on the total weight of the composition at the point of use.

[0048] Such chelating agents can be any suitable chelating or complexing agent, alternatively or in combination, to increase the removal rate of the respective material to be removed, preferably metal or metal alloy, or to capture trace metal contaminants that may give unfavorable performance in the polishing process or in the finished device. For example, the chelating agent can be a compound that contains one or more functional groups that contain oxygen (e.g., carbonyl, carboxyl, hydroxyl, etc.) or one or more functional groups that contain nitrogen (e.g., amine or nitrate, etc.). Examples of suitable chelating agents include, but are not limited to, acetylacetonates, acetates, arylcarboxylates, glycolates, lactates, gluconates, gallates, oxalates, phthalates, citrates, succinates, tartrates, malates, ethylenediaminetetraacetic acid and their salts, ethylene glycol, pyrogallol, phosphonates, ammonia, amino alcohols, di- and tri-amines, nitrates (e.g., iron nitrate), and any blends thereof.

[0049] Such biocide can be selected from any suitable biocide.As an example of suitable biocide, mention can be made of biocides that contain isothiazolin derivatives.Such biocide is generally added in an amount of at least 1 ppm and up to 100 ppm of active compound, based on the total weight of the composition at point of use.The amount of biocide added can be adapted, for example, depending on the composition and the planned storage period.

[0050] Such pH adjuster may be selected as required, and may be any suitable acid or base. Suitable acid may be selected, for example, but not limited to, from the group consisting of hydrochloric acid, nitric acid or sulfuric acid, with nitric acid or sulfuric acid being preferred, and nitric acid being especially preferred. Suitable base may be selected, for example, from the group consisting of alkali metal hydroxides as defined above, ammonia, organic amines, and any blends thereof. For alkali metal hydroxides, the alkali metal may be selected from the group consisting of Li, Na, K, and Cs, preferably from the group consisting of Li, Na, and K; and most preferably, the alkali metal is K.

[0051] Such surfactants can be selected from any suitable surfactant, such as cationic, anionic and nonionic surfactants. A particularly preferred example is an ethylenediamine polyoxyethylene surfactant. In general, surfactants can be added in an amount of 100 ppm to 1 wt % based on the total weight of the composition at the point of use.

[0052] Some of these compounds may be present in the form of a salt, such as a metal salt, an acid, or as a partial salt. Similarly, some of these compounds may fulfill more than one function when included in a composition suitable for chemical mechanical polishing. For example, iron nitrate, specifically Fe(NO 3 ) 3 may act as a chelating agent and / or an oxidizing agent and / or a catalytic agent.

[0053] Such compositions as defined herein can be prepared by standard methods well known to those skilled in the art. Generally, such preparations include a mixing and stirring phase. They can be carried out either in a continuous or batch manner.

[0054] The silica particles produced by this method, as well as compositions containing such silica particles, may be used in any application, as silica produced via sodium or potassium silicate by conventional wet manufacturing processes.Thus, the silica particles produced by this method may be used, for example, as an abrasive, as an additive in paper making and in the paper itself, as a catalyst support, as a drug carrier, in coatings or paints, to name just a few.

[0055] Preferably, the silica particles and compositions comprising such silica particles can be used in modern semiconductor devices, memory devices, integrated circuits, etc., which contain alternating layers of conductive, semiconductive, and dielectric (insulating) layers (the dielectric layers insulate the conductive layers from each other). The connections between the conductive layers can be established, for example, by metal vias. In the manufacture of such devices, conductive, semiconductive, and / or dielectric materials are successively deposited on the surface of a semiconductive wafer and partially removed again from the surface of the semiconductive wafer.

[0056] Chemical mechanical polishing (CMP) is a widely used method to planarize or partially remove some or all of the layers in the process of manufacturing semiconductor devices and the like. In the CMP process, an abrasive and / or corrosive chemical slurry, such as a slurry of silica particles, is used in conjunction with a polishing pad. The pad and substrate or surface, e.g., a wafer, are pressed together and rotated, typically non-concentrically, i.e., with different axes of rotation, thereby polishing and removing material from the surface or substrate.

[0057] CMP can be used to polish a wide range of materials, such as metals or metal alloys (such as aluminum, copper, or tungsten), metal oxides, silicon dioxide, or even polymeric materials. For each material, the polishing slurry needs to be specifically formulated to optimize its performance. For example, when a tungsten layer that is deposited on a silicon dioxide layer is polished, the polishing slurry preferably has a high removal rate for tungsten but a low removal rate for silicon dioxide, so as to efficiently remove tungsten but leave the majority of the silicon dioxide layer intact.

[0058] Furthermore, since the polishing is preferably done by a combination of mechanical polishing and chemical etching, the silica particles need to meet certain requirements to be fully compatible with the formulation, for example, the composition of the silica particles needs to be modified depending on whether the silica particles are anionic or cationic.

[0059] The compositions as described herein may preferably be used in a chemical mechanical polishing (CMP) process in which a substrate is polished. The method for chemical mechanical polishing thus comprises the following steps: (A) providing a substrate to be polished; and (B) providing a composition as defined herein; Includes.

[0060] In the CMP process, a polishing pad having a polishing surface is used for the actual polishing of the substrate. Such a polishing pad may be, for example, a woven or non-woven polishing pad, and may comprise or consist essentially of a suitable polymer. Exemplary polymers include, by way of example only, polyvinyl chloride, polyvinyl fluoride, nylon, poly-propylene, polyurethane, and any blends thereof. The polishing pad and the substrate to be polished are generally placed on a polishing apparatus, pressed together, and generally rotated non-concentrically, i.e., with different axes of rotation, thereby polishing the surface or substrate and removing material from the surface or substrate. Thus, the CMP process includes the following steps: (C) providing a chemical mechanical polishing pad having an abrasive surface; (D) contacting the polishing surface of the chemical mechanical polishing pad with the substrate; and (E) polishing the substrate such that at least a portion of the substrate is removed; Further includes:

[0061] The CMP process can be applied in the manufacture of flat panel displays, integrated circuits (ICs), memory or rigid disks, metals, interlayer dielectric devices (ILDs), semiconductors, microelectromechanical systems, ferroelectrics, and magnetic heads. In other words, the substrate polished in the CMP process can be selected from the group consisting of flat panel displays, integrated circuits (ICs), memory or rigid disks, metals, interlayer dielectric devices (ILDs), semiconductors, microelectromechanical systems, ferroelectrics, and magnetic heads.

[0062] The practice and advantages of the present application are illustrated in non-limiting examples with the following examples.

[0063] example All materials used in the following examples are commercially available. Silicon chloride (IV) at 99.0%+ purity was obtained from SigmaAldrich, a subsidiary of Merck KGaA, Darmstadt, Germany, or silicon chloride (IV) at 99.8%+ purity was obtained from Acros Organics, a brand of Thermo Fisher Scientific. Water was prepared using a Milli-Q® water purification system available from Merck KGaA, Darmstadt, Germany, and used as ultrapure water. The cation exchange resin used was AMBERJET™ 1200 H, supplied by Rohm and Haas Company, Philadelphia, Pennsylvania, USA.

[0064] Example 1 800 ml of ultrapure water was added to a 1.5 L round-bottom flask at room temperature. Then, 117.5 g of SiCl 4 was taken up in a 100 ml plastic syringe and introduced therefrom into ultrapure water under stirring over a period of about 5 minutes, resulting in an increase in the temperature of the aqueous reaction mixture inside the flask to about 57° C. The aqueous reaction mixture was then allowed to settle without stirring for about 30 minutes, during which time a gel formed. The aqueous reaction mixture containing the gel was then filtered in a Buchner funnel using Whatman filter paper 0965, producing 854 ml of filtrate.

[0065] The gel retained in the Buchner funnel was washed with 800 ml of ultrapure water at room temperature, transferred to a beaker, in which it was treated with 36 ml of potassium hydroxide solution (45.65 wt%) at 70° C. with stirring for 1.5 hours, and diluted with 10 wt% SiO 2 (in wt% relative to the total weight of the potassium silicate solution) and K of 2.23 2 SiO vs O 2 A potassium silicate solution (415 g theoretical yield) was produced having a weight ratio of:

[0066] Example 2 The solution of silicic acid obtained in Example 1 above can then be used to prepare silica particles with a diameter of 9 nm. A stainless steel reactor with a volume of 2.8 l is first filled with approximately 450 ml of deionized water, then with 1155 g of aqueous silicic acid solution with a silica concentration of approximately 5.6 wt% (based on the weight of the aqueous silicic acid solution) and a pH of 2.75. To this, approximately 5.8 g of silica and SiO 2 (obtained by adding KOH to the corresponding volume of the silicic acid solution obtained in Example 1 above, followed by concentration through evaporation to the desired volume) are added. 2 / K 2 Approximately 29 g of an aqueous potassium silicate solution containing a weight ratio of 0.953 is added with stirring. The resulting reaction medium is heated to boiling and maintained at boiling while an additional 2240 g of an aqueous silicic acid solution having a silica concentration of approximately 5.6 wt% (based on the weight of the aqueous silicic acid solution) and a pH of 2.75 is added at a rate of approximately 8 g / min. Once the addition of the aqueous silicic acid solution is complete, heating may be continued for some time, for example 0.5 hours, and then stopped to allow the reaction medium to cool. The resulting aqueous (colloidal) silica composition has a silica concentration of approximately 1.13 g / cm. 3 The specific density of silica is approximately 300m 2 / g surface area, a pH of approximately 10.3, a silica content of approximately 19 wt % (based on the total weight of the silica composition), and a viscosity of approximately 2 mPas.

[0067] Example 3 Applying the procedure of Example 2, silica particles having a diameter of approximately 40 nm were produced and the particle diameters were measured as indicated in Table 1 below.

[0068] Example 4 - Polishing Chemical mechanical polishing was carried out using aqueous compositions of comparative silica particles (designated S-4a) produced by a conventional "wet" process, i.e., commercially available silica particles not produced according to the process of the present application, and silica particles (designated S-4 and S-4c) produced as described above in Example 3 according to the present application. The properties of the aqueous compositions, in wt% relative to the total weight of each aqueous composition, were as indicated in Table 1. Before being used in polishing, the aqueous compositions were filtered (0.3 μm).

[0069] [Table 1] The particle diameters indicated are the z-average particle sizes determined by dynamic light scattering (DLS).

[0070] Chemical mechanical polishing was then performed on a 4-inch TEOS (silicon oxide) wafer using an IC1000™ CMP polishing pad (available from DuPont de Nemours, Wilmington, Delaware, USA) on a Bruker CP-4 system (available from Bruker Corporation, Billerica, Massachusetts, USA). Further polishing conditions were as indicated in Table 2 below. [Table 2]

[0071] The results for chemical mechanical polishing are shown in Table 3 below, with PC-1 being the comparative example. [Table 3]

[0072] The polishing performance of silica particles S-4b and S-4c produced according to the method of the present application was further (unexpectedly) improved, as evidenced by the significantly increased removal rates compared to silica particles of similar physical properties produced without the method of the present application.

[0073] In general, the present method for producing silica particles provides the advantage that it allows producing silica particles with lower levels of metal contaminants than silica particles produced by conventional "wet" process, i.e., the process in which sodium silicate is converted into orthosilicic acid using ion exchange process.Furthermore, and this is a great surprise, the silica particles produced according to the present process further have improved polishing performance compared to the silica particles produced by conventional "wet" process.Therefore, it is believed that the silica particles produced using the present method are very well suited for use in chemical mechanical polishing processes, for example in the semiconductor industry.

Claims

1. 1. A method for the production of silica particles, the method comprising the steps of: (a) hydrolyzing silicon chloride in an aqueous solution, thereby producing a gel containing silicic acid and hydrogen chloride, wherein the silicon chloride is represented by the following formula (1'): 【Chemical 1】 R is, independently at each occurrence, selected from the group consisting of alkyl groups having 1, 2, or 3 carbon atoms; and c is, independently at each occurrence, selected from the group consisting of 0, 1, 2, and 3; and d is, independently at each occurrence, selected from the group consisting of 0, 1, 2, and 3; provided that c+d≦3, It is expressed as: (b) removing at least a portion of the hydrogen chloride from the gel to obtain a purified gel; (c) adjusting the pH of the purified gel to at least 9; and (d) then polycondensing the silicic acid to form silica particles; The method comprising:

2. The silicon chloride is represented by the following formula (1): 【Chemistry 2】 R is, independently at each occurrence, selected from the group consisting of alkyl groups having 1, 2, or 3 carbon atoms; and a is, independently at each occurrence, selected from the group consisting of 0, 1, 2, and 3. The method of claim 1, wherein the

3. 2. The method of claim 1, wherein R is independently selected at each occurrence from the group consisting of methyl, ethyl, n-propyl, and iso-propyl; preferably, methyl or ethyl; and most preferably, methyl.

4. 3. The method of claim 2, wherein a is 0 or 1, and preferably a is 0.

5. The silicon chloride may be independently SiCl ４ , MeSiCl ３ , Me ２ SiCl ２ , Me ３ SiCl, EtSiCl ３ , Et ２ SiCl ２ , Et ３ From the group consisting of SiCl, and any blends thereof; preferably SiCl ４ , MeSiCl ３ , Me ２ SiCl ２ , Me ３ SiCl, and any blend thereof; more preferably SiCl ４ or MeSiCl ３ and most preferably SiCl ４ The method of claim 1, wherein

6. 10. The method of claim 1, wherein step (a) is carried out at a temperature of at least 0°C and at most 120°C.

7. In step (b), the combined content of chloride or fluoride or both is reduced to silica ("SiO ２ 10. The method of claim 1, wherein the concentration of HCl is reduced to a maximum of 40,000 ppm.

8. Step (b) comprises the steps of: (b1) washing the gel by adding and then removing water; and (b2) preferably following step (b1), passing the gel through an anion exchange resin to obtain a purified gel; The method of claim 1 , comprising:

9. 2. The method of claim 1, wherein the silicic acid is not dried after step (a) and / or step (b).

10. 2. The method of claim 1, wherein in step (c) the pH of the gel is adjusted by adding a base to the purified gel, the base preferably being selected from the group consisting of potassium hydroxide, sodium hydroxide, lithium hydroxide, cesium hydroxide, rubidium hydroxide, ammonia, organic amines, and any blend thereof.

11. 10. The method of claim 1, wherein in step (c), the pH of the gel is adjusted to at least 10.

12. 10. The method of claim 1, wherein in step (c), the pH of the gel is adjusted to a maximum of 13.

13. 10. The method of claim 1, wherein the silica particles formed in step (d) are colloidal silica particles.

14. 10. The method of claim 1, wherein step (d) also comprises introducing silica seeds onto which silicic acid is polycondensed to form silica particles.

15. 10. The method of claim 1, wherein the silica particles so produced are used in chemical mechanical polishing in the electronics industry, catalyst supports, prime wafer polishing, etc.

16. Silica particles obtainable by the method according to any one of claims 1 to 15.

17. A formulation comprising an aqueous dispersion of silica particles according to claim 16.

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