Silica particles, compositions comprising such particles, and uses of such particles and compositions

Abstract

The present invention relates to surface-modified silica particles comprising a nitrogen- or phosphorus-containing group or compound, to compositions comprising such particles, and to the use of such surface-modified silica particles and compositions comprising such silica particles.

Description

Technical Field

[0001] This invention relates to modified silica particles containing nitrogen- or phosphorus-containing groups or compounds, compositions containing such particles, and the use of such modified silica particles and compositions containing such silica particles. Background Technology

[0002] Modern semiconductor devices, memory devices, integrated circuits, etc., alternately comprise conductive layers, semiconductor layers, and dielectric (or insulating) layers, wherein the dielectric layers insulate the conductive layers from each other. Connections between conductive layers can be established, for example, through metal vias. The production of such devices is a complex, multi-step process in which conductive, semi-conductive, and / or dielectric materials are continuously deposited onto the underlying surface, and then can be partially or sometimes even completely removed again.

[0003] Over time, the performance of semiconductor devices, memory devices, integrated circuits, and the like has improved while simultaneously becoming smaller. To ensure that such devices operate reliably and as expected, the requirements for manufacturing processes, such as precision, have also increased despite their increasing complexity. Therefore, the surfaces on which subsequent layers are deposited must have very high planarity. Since the required planarity cannot be achieved by depositing the corresponding material, it is necessary to planarize the wafer (and consequently, the device to be manufactured) by removing some, or in some cases, all of these layers.

[0004] Chemical mechanical polishing (CMP) is a widely used method for planarizing or removing parts or all of a layer in processes such as the production of semiconductor devices. In CMP, abrasives and / or corrosive chemical slurries, such as slurries of silica particles, are used with a polishing pad. The pad and a substrate or surface, such as a wafer, are pressed together and typically rotated non-coaxially, i.e., with different axes of rotation, thereby grinding and removing material from the surface or substrate.

[0005] CMP can be used to polish a wide range of materials, such as metals or metal alloys (e.g., aluminum, copper, or tungsten), metal oxides, silica, or even polymers. For each material, the polishing slurry needs to be specifically formulated to optimize its performance. For example, if a tungsten layer deposited on a silica layer is to be polished, the polishing slurry preferably has a high tungsten removal rate but a lower silica removal rate to effectively remove the tungsten while leaving the silica layer largely intact.

[0006] Furthermore, since polishing is preferably performed through a combination of mechanical polishing and chemical etching, the silica particles need to meet certain requirements to ensure adequate compatibility with the formulation. For example, the composition of the silica particles needs to be modified depending on whether the particles are anionic or cationic.

[0007] However, not only are the semiconductor and related industries under ongoing cost pressures, but also, given the rising pressure for sustainability, there is a need to reduce the amount of waste requiring treatment, such as post-use CMP slurry. Furthermore, there remains an industrial need for silica particles that offer improved removal rates and / or allow good selectivity on the one hand between conductive and / or semiconductor materials, and on the other hand between conductive and / or semiconductor materials and dielectric materials.

[0008] Therefore, the present invention aims to provide silica particles and compositions comprising such silica particles, which allow good selectivity between one or more conductive layers and one or more dielectric layers, said conductive layers comprising any one or more of metals, metal alloys, polycrystalline silicon and any other suitable materials, preferably while allowing for a reduction in the silica concentration in the CMP slurry at the point of use. Summary of the Invention

[0009] The inventors have now surprisingly discovered that the above-mentioned objectives can be achieved individually or in any combination by means of the modified silica particles, compositions and methods of the present invention.

[0010] Therefore, the present invention provides modified silica particles, which (i) contain nitrogen- or phosphorus-containing groups or compounds, and (ii) have a zeta potential of up to +15 mV, as determined in deionized water at 25 °C as 3 wt% of modified silica particles.

[0011] The present invention further provides compositions comprising water and such modified silica particles as defined herein, wherein the compositions are acidic, preferably wherein the compositions have a pH of up to 3.5.

[0012] Furthermore, the present invention provides a method for preparing modified silica particles as defined herein, the method comprising the following steps:

[0013] (a) Provide an aqueous dispersion of unmodified silica particles and a nitrogen- or phosphorus-containing compound;

[0014] (b) Heating the aqueous dispersion provided in step (a), preferably to boiling;

[0015] (c) Adding silica to deposit a silica shell containing a modifier onto silica particles and produce an alkaline aqueous dispersion of modified silica particles as defined herein;

[0016] (d) Pass the alkaline aqueous dispersion of the modified silica particles obtained in step (c) through a cation exchanger to produce an acidic aqueous dispersion of the modified silica particles.

[0017] In addition, the present invention provides a method for chemical mechanical polishing, comprising the following steps:

[0018] (A) Provide substrate;

[0019] (B) Provide a composition as defined herein,

[0020] (C) Provide chemical mechanical polishing pads with polished surfaces;

[0021] (D) Contacting the polishing surface of the chemical mechanical polishing pad and the composition provided in step (B) with the substrate; and

[0022] (E) Polish the substrate to remove at least a portion of the substrate.

[0023] Detailed Explanation

[0024] Throughout this invention, "Me" represents methyl (CH3) and "Et" represents ethyl (CH2-CH3).

[0025] As used herein, the term "water glass" is generally used to refer to alkali metal salts of silicate Si(OH)4 (also referred to as "basic silicates" in this invention), preferably sodium and potassium salts of silicate Si(OH)4. Correspondingly, sodium and potassium salts of silicate Si(OH)4 can be derived, for example, from formula M 2x Si y O 2y+x Or (M2O) x (SiO2) y Let M = Na or K, and for example, x = 1 and y is an integer from 2 to 4.

[0026] As used herein, the term "water glass-based" is used to indicate that the silica particles of the present invention are preferably prepared from such basic silica salts as starting materials.

[0027] As used herein, the term “TMOS / TEOS-based” is generally used to refer to silica particles prepared using Si(OMe)4 (“TMOS”) and / or Si(OEt)4 (“TEOS”) as starting materials.

[0028] As used herein, the term "silicate" is generally used to refer to salts and esters of silicic acid (Si(OH)4), which may also be referred to as "ortho-silicic acid" and its condensation products throughout this invention. It should also be noted that gels or solutions of silicic acid should be understood to generally also contain condensates of silicic acid.

[0029] As used herein, the term "colloid" is used to refer to particles dispersed in a medium having a size between 1 nm and 1 μm in at least one direction (see also Compendium of Chemical Terminology, Gold Book, International Union of Pure and Applied Chemistry, Version 2.3.3, 2014-02-24, page 295).

[0030] In this invention, the term "point of use" refers to a chemical mechanical polishing (CMP) method. For example, the expression "composition at the point of use" is used to refer to a composition used in a chemical mechanical polishing (CMP) method.

[0031] Unless otherwise specified, wt% is relative to the total weight of the corresponding solution, dispersion or composition.

[0032] Typically, silica particles can be obtained in a wet process in an alkaline medium by the condensation of silicic acid (Si(OH)4) with an alkaline compound used as a catalyst. This method is well known to those skilled in the art, for example, as disclosed in RK Iler, “The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties and Biochemistry of Silica”, Wiley, 1979.

[0033] Starting from basic silicates, such as sodium silicate and / or potassium silicate, basic silicates undergo an ion exchange process, for example by using a cation exchanger or by adding a sufficient amount of strong acid, to form silicic acid (Si(OH)4), and after adding a base and making the solution alkaline, the silicic acid reacts (condenses) in the presence of a basic catalyst to form silica particles.

[0034] As an alternative to using basic silicates as starting materials, tetraalkyl orthosilicate (Si(OR)4, where R is an alkyl group, preferably methyl or ethyl) can be hydrolyzed to form silicic acid, which is then polycondensed as described above to form silica particles.

[0035] For the purposes of this invention, the basic compound used as a catalyst in the polycondensation of silicic acid differs from the modifiers defined herein. Preferably, the basic compound used in the polycondensation of silicic acid is sodium hydroxide or potassium hydroxide, with potassium hydroxide being a more preferred choice.

[0036] In this wet process, the production of silica particles can be carried out in a single step, starting with a solution / dispersion of silicic acid, or it can be done using so-called seed particles on which silica is then further deposited to grow the silica particles to the desired size.

[0037] Generally, the present invention relates to particles comprising (i) modified groups or compounds and (ii) a specific zeta potential (as described below for determination).

[0038] The modifying groups or compounds of the present invention, which are also generally referred to herein as "modifiers", are selected from nitrogen-containing groups and phosphorus-containing groups or nitrogen-containing compounds and phosphorus-containing compounds.

[0039] Such nitrogen-containing and phosphorus-containing groups, or nitrogen-containing and phosphorus-containing compounds, can be selected from amines, ammonium compounds, phosphine and phosphonium compounds, preferably organic amines, organic ammonium compounds, organic phosphine and organic phosphonium compounds, which can be represented by the following chemical formulas (Ia) to (Id).

[0040]

[0041] Where R 1 R 2 R 3 and -if it exists-R 4 Each time it appears, it can be independently selected from hydrogen, alkyl groups having 1 to 10 carbon atoms, arylalkyl groups having 7 to 16 carbon atoms, and aryl groups having 6 to 10 carbon atoms, provided that R 1 R 2 R 3 and -if it exists-R 4 At least one of them is not hydrogen.

[0042] Preferably, R 1 R 2 R 3 and -if it exists-R 4 All are alkyl groups having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. Suitable alkyl groups are preferably selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl and n-hexyl; more preferably methyl and ethyl, and most preferably ethyl.

[0043] The modifier of the present invention is preferably a nitrogen-containing group or a nitrogen-containing compound, more preferably an ammonium group or an ammonium compound, and even more preferably a tetraalkylammonium group or a tetraalkylammonium compound.

[0044] Particularly suitable nitrogen-containing groups or nitrogen-containing compounds are tetramethylammonium (“TMA”), tetraethylammonium (“TEA”), tetramethylammonium hydroxide (“TMAH”), and tetraethylammonium hydroxide (“TEAH”). Tetraethylammonium hydroxide (“TEAH”) is particularly preferred.

[0045] For the purposes of this invention, there are no particular limitations on the choice of (unmodified) silica particles as the starting material. The silica particles used herein can be, for example, any type of colloidal silica particles. They can be prepared from any suitable starting material and can be, for example, water glass-based or TMOS / TEOS-based as described above. Preferably, they are water glass-based colloidal silica particles or TEOS / TMOS-based colloidal silica particles, more preferably water glass-based colloidal silica particles.

[0046] The shape and size of the silica particles used in this article are not particularly limited, provided that the silica particles are suitable for CMP applications. The silica particles may be, for example, spherical, elliptical, curved, bent, elongated, branched, or cocoon-shaped.

[0047] For spherical silica particles, the average diameter is preferably at least 5 nm, more preferably at least 10 nm, and most preferably at least 15 nm. For spherical particles, the average diameter is preferably at most 200 nm, more preferably at most 150 nm or 100 nm, even more preferably at most 90 nm or 80 nm or 70 nm or 60 nm, still even more preferably at most 50 nm or 45 nm or 40 nm or 35 nm or 30 nm, and most preferably at most 25 nm. For example, particularly preferred silica particles have an average diameter of at least 15 nm and at most 25 nm.

[0048] For elongated, curved, bent, branched, and elliptical silica particles, the average diameter is preferably as described above for spherical colloidal silica particles. Preferably, the elongated or elliptical colloidal silica particle has an aspect ratio, i.e., the ratio of length to average diameter, of at least 1.1, more preferably at least 1.2, 1.3, 1.4, or 1.5, even more preferably at least 1.6, 1.7, 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, 8, 7, or 6, and most preferably at most 5.

[0049] The modified silica particles of the present invention are prepared by depositing a silica shell containing a modifier onto unmodified silica particles.

[0050] Therefore, the modified silica particles of the present invention can be produced by a production method including the following steps:

[0051] (a) Provide an aqueous dispersion of (unmodified) silica particles as defined above and a modifier as defined above.

[0052] To prepare the modified silica particles of the present invention, an aqueous dispersion of silica particles and a modifier is heated, preferably to boiling, and then silicic acid is added, preferably over time, thereby depositing a silica shell containing the modifier onto the silica particles, thus obtaining an alkaline aqueous dispersion of modified silica particles as defined herein. This step is carried out with the modifier acting as an alkaline catalyst, without further addition of an alkaline catalyst different from the modifier, such as sodium hydroxide or potassium hydroxide. The alkaline aqueous dispersion of such modified silica particles is then passed through a cation exchanger to make the dispersion acidic, thereby producing an acidic aqueous dispersion of modified silica particles as defined herein.

[0053] It should be noted that when in an alkaline (or alkaline) medium, silica particles are anionic, i.e., negatively charged, while when in an acidic medium, silica particles are cationic, i.e. positively charged.

[0054] Therefore, the method for producing modified silica particles according to the present invention further includes the following steps, preferably including the following steps in sequence:

[0055] (b) Heating the aqueous dispersion provided in step (a), preferably to boiling;

[0056] (c) Adding silica to deposit a silica shell containing a modifier onto silica particles and produce an alkaline aqueous dispersion of modified silica particles as defined herein;

[0057] (d) Pass the alkaline aqueous dispersion of the modified silica particles obtained in step (c) through a cation exchanger to produce an acidic aqueous dispersion of the modified silica particles.

[0058] The modifier is added in an amount such that the modified silica particles have a specific zeta potential as defined herein. The amount of such modifier added can be readily determined by those skilled in the art.

[0059] Preferably, the amount of modifier added relative to the amount of SiO2 added can be at least 1.0 wt%, more preferably at least 1.5 wt%, even more preferably at least 2.0 wt%, and most preferably at least 2.5 wt% (see step (c) of the method above).

[0060] Preferably, the amount of modifier added relative to the amount of SiO2 added can be up to 4.5 wt%, more preferably up to 4.4 wt% or 4.3 wt%, even more preferably up to 4.2 wt%, and even more preferably up to 4.1 wt% (see step (c) of the method above).

[0061] Without being bound by theory, the inventors have discovered that typically about 40% to about 60%, for example about 50%, of the added modifier will actually be incorporated into the silica shell produced in this method (see step (c) of the method above).

[0062] It should be noted that any modifiers incorporated into the surface of the modified silica particles contained in the alkaline aqueous dispersion prepared in step (c) of this method will be removed at least partially or substantially partially or even completely by the cation exchanger in step (d) of this method.

[0063] When in an acidic aqueous dispersion, i.e. in a composition comprising modified silica particles as defined herein and water, the modified silica particles of the present invention are cationic, i.e. carrying a permanent positive charge.

[0064] Preferably, the zeta potential of the modified silica particles of the present invention is at most +15mV, more preferably at most +10mV, and is measured at 25°C in deionized water containing 3wt% modified silica particles, as described in detail below.

[0065] Preferably, the zeta potential of the modified silica particles of the present invention is at least +2mV, more preferably at least +3mV, even more preferably at least +4mV, and most preferably at least +5mV, as measured at 25°C in deionized water containing 3wt% modified silica particles, as described in detail below.

[0066] The modified silica particles of the present invention can be used in a composition that further comprises water. Therefore, such a composition comprises the modified silica particles of the present invention and water. The water is preferably deionized water.

[0067] The composition of the present invention, comprising water and the above-described modified silica particles, is acidic, i.e., characterized by an acidic pH. The pH of the composition of the present invention is preferably at most 3.5 (e.g., at most 3.4, or at most 3.3, or at most 3.2, or at most 3.1), more preferably at most 3.0.

[0068] Although there is no practical limitation on the lower limit of the pH of the compositions of the present invention, it is preferred that such pH be at least 1.0, more preferably at least 1.5, even more preferably at least 2.0, and most preferably at least 2.5.

[0069] If supplied as a concentrate, it can be diluted with water, preferably deionized water, before being used in a chemical mechanical polishing process. The composition of the present invention may contain up to 20% by weight, preferably up to 25% by weight, more preferably up to 30% by weight, even more preferably up to 35% by weight, even more preferably up to 40% by weight, and most preferably up to 50% by weight of modified silica particles, wherein the weight percentage is relative to the total weight of the composition of the present invention.

[0070] Alternatively, at the point of use, i.e., when used in a chemical mechanical polishing method, the composition of the present invention preferably contains at least 0.1 wt% (e.g., at least 0.2 wt%, 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% of modified silica particles, wherein the wt% is relative to the total weight of the composition of the present invention. In this case, the composition of the present invention preferably contains at most 10 wt%, more preferably at most 5.0 wt%, even more preferably at most 4.0 wt%, even more preferably at most 3.5 wt%, and most preferably at most 3.0 wt% of modified silica particles, wherein the wt% is relative to the total weight of the composition of the present invention.

[0071] Optionally, the compositions of the present invention further comprise any one or more of the group consisting of: biocides, pH adjusters, pH buffers, oxidants, chelating agents, corrosion inhibitors, and surfactants.

[0072] This oxidant can be any suitable oxidant of one or more metals or metal alloys used for polishing the substrate to which the composition of the present invention is to be used. For example, the oxidant can be selected from the group consisting of: bromates, bromates, chlorates, chlorites, hydrogen peroxide, hypochlorites, iodates, monoperoxysulfates, monoperoxysulfites, monoperoxyphosphates, monoperoxyhypophosphates, monoperoxypyrophosphates, organohaloxy compounds, periodates, permanganates, peracetic acid, ferric nitrate, and any blends thereof. This oxidant can be added to the composition of the present invention in a suitable amount, for example, at least 0.1% by weight and at most 6.0% by weight, wherein the weight percentage is relative to the total weight of the composition of the present invention at the point of use.

[0073] This corrosion inhibitor (which may be, for example, a film-forming agent) can 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% by weight to 3.0% by weight, wherein the weight percentage is relative to the total weight of the composition of the invention at the point of use.

[0074] Such chelating agents can be any suitable chelating or complexing agent used to increase the removal rate of the corresponding material, preferably the metal or metal alloy to be removed, or alternatively or in combination, to capture trace amounts of metallic contaminants that may adversely affect the performance of the polishing process or finished device. For example, chelating agents can be compounds containing one or more oxygen-containing functional groups (e.g., carbonyl, carboxyl, hydroxyl) or nitrogen-containing functional groups (e.g., amino or nitrate). Examples of suitable chelating agents include, in a non-limiting manner, acetylacetonates, acetates, aryl carboxylates, glycolates, lactates, gluconates, gallic acid, oxalates, phthalates, citrates, succinates, tartrates, malates, ethylenediaminetetraacetic acid and its salts, ethylene glycol, pyrogallol, phosphates, ammonia, amino alcohols, diamines and triamines, nitrates (e.g., ferric nitrate), and any blends thereof.

[0075] This biocide can be selected from any suitable biocide, such as those comprising isothiazolino derivatives. This biocide is typically added in an amount of at least 1 ppm and at most 100 ppm, where ppm is relative to the total weight of the composition at the point of use. The amount of biocide added can be adjusted, for example, according to the composition and the planned shelf life.

[0076] This pH adjuster can be selected from suitable acids, such as hydrochloric acid, nitric acid or sulfuric acid, with nitric acid or sulfuric acid being preferred, and nitric acid being particularly preferred.

[0077] This surfactant can be selected from any suitable surfactant, such as cationic, anionic, and nonionic surfactants. A particularly preferred example is an ethylenediamine polyoxyethylene surfactant. Typically, the surfactant can be added in an amount from 100 ppm to 1% by weight, where ppm and % by weight are relative to the total weight of the composition of the invention at the point of use.

[0078] Some of these compounds may exist as salts, such as metal salts, as acids, or as partial salts. Similarly, some of these compounds may fulfill more than one function if included in a composition suitable for chemical mechanical polishing. For example, ferric nitrate, particularly Fe(NO3)3, can be used as a chelating agent and / or an oxidizing agent and / or a catalyst.

[0079] The compositions of the present invention can be prepared by standard methods well known to those skilled in the art. Typically, such preparation involves mixing and stirring the phases. This can be carried out continuously or in batches.

[0080] The composition described above can be used in a chemical mechanical polishing (CMP) method, in which a substrate is polished. In the CMP method of the present invention, the substrate to be polished comprises (i) at least one layer comprising silicon oxide, preferably substantially composed of silicon oxide, and (ii) at least one layer comprising one or more metals or metal alloys, preferably substantially composed of one or more metals or metal alloys.

[0081] Therefore, the chemical mechanical polishing method of the present invention includes the following steps:

[0082] (A) A substrate is provided, the substrate comprising: (i) at least one layer comprising silicon oxide, preferably substantially composed of silicon oxide; and preferably thereon, (ii) at least one layer comprising one or more metals or metal alloys, preferably substantially composed of one or more metals or metal alloys; and

[0083] (B) Provide a composition as defined herein.

[0084] As used herein, the term "on top of" is used to indicate that a layer containing metal or a metal alloy is substantially placed on top of / located on top of a layer containing silicon oxide. In contrast, and in relation to chemical mechanical polishing, the layer on top is the layer closer to the polishing pad mounted on the CMP polisher before polishing begins.

[0085] As used herein, the term “consistently of” is used to indicate that the layer may contain small amounts of one or more different materials, for example, in amounts of up to 5% by weight (e.g., in amounts of up to 4% by weight, 3% by weight, 2% by weight, 1% by weight, 0.5% by weight, or 0.1% by weight), where the weight percentage is relative to the total weight of the layer.

[0086] Preferably, the silicon oxide contained in the layer (which is in turn contained in the substrate) may be selected from the group consisting of: bromophosphosilicate glass (BPSG), plasma-enhanced tetraethyl orthosilicate (PETEOS), thermal oxide, undoped silicate glass, high-density plasma (HDP) oxide, and silane oxide.

[0087] In CMP methods, polishing pads with polished surfaces are used in the actual polishing of the substrate. These polishing pads can be, for example, woven or nonwoven polishing pads and contain or are substantially composed of a suitable polymer. Exemplary polymers include polyvinyl chloride, polyvinyl fluoride, nylon, polypropylene, polyurethane, and blends of these, to name just a few. Typically, the polishing pad and the substrate to be polished are mounted on a polishing apparatus, pressed together, and generally rotated non-coaxially, i.e., with different axes of rotation, thereby abrading and removing material from the surface or substrate together with the composition of the present invention, typically located between the polishing pad and the substrate.

[0088] Therefore, the CMP method of the present invention further includes the following steps:

[0089] (C) Provide chemical mechanical polishing pads with polished surfaces;

[0090] (D) Contact the polishing surface of the chemical mechanical polishing pad and the composition provided in step (B) above with the substrate; and

[0091] (E) Polish the substrate to remove at least a portion of the substrate.

[0092] The CMP method of this invention is applicable to the production of flat panel displays, integrated circuits (ICs), memory or hard disks, metals, interlayer dielectric devices (ILDs), semiconductors, microelectromechanical systems (MEMS), ferroelectric materials, and magnetic heads. In other words, the substrate to be polished in the CMP method of this invention can be selected from the group consisting of: flat panel displays, integrated circuits (ICs), memory or hard disks, metals, interlayer dielectric devices (ILDs), semiconductors, microelectromechanical systems (MEMS), ferroelectric materials, and magnetic heads. Detailed Implementation

[0093] Example

[0094] All materials used in the examples are commercially available. Water glass-based silica particles, obtained as an aqueous dispersion from Merck KGaA, Darmstadt, Germany, with SiO2 content and average particle size as shown in the following examples, are sold under the trade name Klebosol®. Silicic acid was obtained internally in aqueous solution form, with SiO2 content as shown in the examples. Tetraethylammonium hydroxide (denoted as "TEAH"; 35% by weight in water; CAS-nr. 77-98-5) can be obtained, for example, from Sigma-Aldrich, a subsidiary of Merck KGaA, Darmstadt, Germany. The cation exchange resin used is AMBERJET. TM 1200 H, supplied by DuPont de Nemours, Wilmington, Delaware, USA. Kathon ICP II biocide was obtained from DuPont de Nemours, Wilmington, Delaware, USA.

[0095] All the water used is deionized.

[0096] Particle size (indicated as z-average particle size) and zeta potential were determined on a Zetasizer Nano ZSP (available from Malvern Instruments Limited, Worcestershire, UK) by dynamic light scattering (DLS) and electrophoretic light scattering (ELS), respectively.

[0097] To determine the zeta potential, the instrument is first cleaned with ultrapure water (such as Type I water as defined in ASTM D 1193-06, having a resistivity of at least 18.0 MΩ·cm and a total organic carbon (TOC) content of at most 5 ppb), and then the aqueous dispersion of the silica particles to be measured is injected into the instrument intact using a 10 mL syringe.

[0098] Unless otherwise stated, all weight percent are relative to the total weight of the corresponding aqueous dispersion or solution.

[0099] Example 1

[0100] Aqueous dispersion of 7840 g silica particles (23.90 wt% SiO2; average particle size 47.9 nm; specific surface area (SSA) 160.3 m²) was diluted with deionized water. 2 To obtain 12089 g of an aqueous dispersion containing 15.5 wt% SiO2, 17.85 g of TEAH (35 wt% in water) was added to the dispersion at room temperature. The resulting reaction mixture was then heated to boiling. 4004 g of an aqueous silicate solution (5.62 wt% SiO2) was then added to the boiling reaction mixture to obtain approximately 2.78 wt% TEAH relative to the amount of SiO2 added, and the mixture was stirred for approximately 1¾ hours.

[0101] The resulting reaction mixture was stirred at boiling temperature for another 10 minutes, then cooled to room temperature while stirring, to obtain 11621g of an intermediate aqueous dispersion with 18.06% by weight SiO2.

[0102] The intermediate aqueous dispersion thus obtained was then passed through a cation exchange resin column and diluted with deionized water to 13721 g of an aqueous dispersion containing approximately 15 wt% SiO2 and with a pH of 2.42. Then, 12.35 g of the biocide Kathon ICP II was added, followed by filtration through filters with pore sizes of 5 μm, 1.5 μm, and 0.3 μm. The properties of the resulting aqueous dispersion D-1 are given in Table 1 below.

[0103] Example 2

[0104] Aqueous dispersion of 7840 g silica particles (23.90 wt% SiO2; average particle size 47.9 nm; specific surface area (SSA) 160.3 m²) was diluted with deionized water. 2To obtain 11711 g of an aqueous dispersion containing approximately 16 wt% SiO2, 21.41 g of TEAH (35 wt% in water) was added to the dispersion at room temperature. The resulting reaction mixture was then heated to boiling. 4004 g of an aqueous silicate solution (5.62 wt% SiO2) was then added to the boiling reaction mixture to obtain approximately 3.33 wt% TEAH relative to the amount of SiO2 added, and the mixture was stirred for approximately 1¾ hours.

[0105] The resulting reaction mixture was stirred at boiling temperature for another 10 minutes, then cooled to room temperature while stirring, to obtain 11507 g of an intermediate aqueous dispersion with 18.24 wt% SiO2.

[0106] The intermediate aqueous dispersion thus obtained was then passed through a cation exchange resin column and diluted with deionized water to 13642 g of an aqueous dispersion containing approximately 15 wt% SiO2 and with a pH of 2.42. Then, 12.35 g of the biocide Kathon ICP II was added, followed by filtration through filters with pore sizes of 5 μm, 1.5 μm, and 0.3 μm. The properties of the resulting aqueous dispersion D-2 are given in Table 1 below.

[0107] Example 3

[0108] Aqueous dispersion of 7840 g silica particles (23.90 wt% SiO2; average particle size 47.9 nm; specific surface area (SSA) 160.3 m²) was diluted with deionized water. 2 To obtain 11711 g of an aqueous dispersion containing approximately 16 wt% SiO2, 24.98 g of TEAH (35 wt% in water) was added to the dispersion at room temperature. The resulting reaction mixture was then heated to boiling. 3828 g of an aqueous silicate solution (5.87 wt% SiO2) was then added to the boiling reaction mixture to obtain approximately 3.89 wt% TEAH relative to the amount of SiO2 added, and the mixture was stirred for approximately 1¾ hours.

[0109] The resulting reaction mixture was stirred at boiling temperature for another 10 minutes, then cooled to room temperature while stirring, to obtain 11593g of an intermediate aqueous dispersion with 18.10% by weight SiO2.

[0110] The intermediate aqueous dispersion thus obtained was then passed through a cation exchange resin column and diluted with deionized water to 13639 g of an aqueous dispersion containing approximately 15 wt% SiO2 and with a pH of 2.46. Then, 12.28 g of the biocide Kathon ICP II was added, followed by filtration through filters with pore sizes of 5 μm, 1.5 μm, and 0.3 μm. The properties of the resulting aqueous dispersion D-3 are given in Table 1 below.

[0111]

[0112] Example 4

[0113] Aqueous dispersions of 7810g of silica particles (24.28 wt% SiO2; average particle size 47.8 nm; specific surface area (SSA) 155.9 m²) were diluted with 3300g of deionized water. 2 12642 g of an aqueous dispersion containing 15 wt% SiO2 was obtained, to which 25.28 g of TEAH (35 wt% in water) was added at room temperature. The resulting reaction mixture was then heated to boiling. 3753 g of an aqueous silicate solution (6.06 wt% SiO2) was then added to the boiling reaction mixture, yielding approximately 3.89 wt% TEAH relative to the amount of SiO2 added, and the mixture was stirred for approximately 1.5 hours.

[0114] The resulting reaction mixture was stirred at boiling temperature for another 10 minutes, then cooled to room temperature while stirring, to obtain the first batch of 11056g of aqueous dispersion with 19.21% by weight SiO2.

[0115] Five more batches were prepared in the same manner and then combined (or blended) to obtain a total of 64,174 g of aqueous dispersion with 19.57 wt% SiO2. The weights and SiO2 contents of these batches and blends are shown in Table 3 below.

[0116]

[0117] The resulting blend 4 was then passed through a cation exchange resin column and diluted to 83465 g with deionized water. An aqueous dispersion (D-4) containing approximately 15% by weight SiO2 and a pH of 2.46 was recovered, followed by the addition of 125.5 g of the biocide Kathon ICP II. The properties of the aqueous dispersion D-4 are given in Table 4 below.

[0118]

[0119] Example 5

[0120] Chemical mechanical polishing was performed using an aqueous composition D-4' equivalent to D-4, diluted with deionized water from approximately 15 wt% SiO2 to 3 wt% SiO2, and without any other additives. The composition could be filtered (0.3 μm pore size) before use for chemical mechanical polishing.

[0121] Then, IC1000 was used on a Bruker CP-4 (purchased from Bruker Corporation, Billerica, MA, USA). TM CMP polishing pads (purchased from DuPont de Nemours, Wilmington, Delaware, USA) were used to polish 4” TEOS (silicon oxide) wafers. Other polishing conditions are shown in Table 5 below.

[0122]

[0123] Comparative polishing tests were conducted using an aqueous particulate composition D-5 containing conventional silica particles under the same conditions (i.e., with 3% by weight SiO2).

[0124] The results of chemical mechanical polishing are shown in Table 6 below, where Examples D-5 are comparative examples, and the zeta potential was measured at 25°C with 3% by weight silica particles in deionized water.

[0125]

[0126] The data clearly demonstrate that, contrary to current standard knowledge, in the case of this invention, particularly for TEOS, excellent removal rates can be achieved under acidic conditions at low zeta potentials.

Claims

1. Modified silica particles, (i) containing nitrogen-containing groups or phosphorus-containing groups or nitrogen-containing compounds or phosphorus-containing compounds, and (ii) having a zeta potential of up to +15 mV, determined in deionized water at 25 °C as 3% by weight of modified silica particles.

2. The modified silica particles according to claim 1, wherein the modified silica particles are core-shell particles, and the nitrogen-containing group or phosphorus-containing group or nitrogen-containing compound or phosphorus-containing compound is contained in the shell.

3. The modified silica particles according to claim 1 or claim 2, wherein the silica particles are colloidal silica particles.

4. The modified silica particles according to any one of the preceding claims, wherein the silica particles are silica particles based on water glass or silica particles based on tetraalkoxysilane.

5. The modified silica particles according to any one of the preceding claims, wherein the nitrogen-containing compound is an ammonium compound, preferably a tetraalkylammonium compound, more preferably a tetramethylammonium compound or a tetraethylammonium compound, even more preferably a tetramethylammonium hydroxide or a tetraethylammonium hydroxide, and most preferably a tetraethylammonium hydroxide.

6. A composition comprising water and modified silica particles according to any one of claims 1 to 5, wherein the composition is acidic, preferably wherein the composition has a pH of up to 3.

5.

7. The composition according to claim 6, wherein the composition has a pH of at least 1.

0.

8. The composition according to claim 6 or claim 7, wherein the SiO2 content of the composition is at least 0.1% by weight and at most 50% by weight relative to the total weight of the composition.

9. The composition according to any one of claims 6 to 9, wherein the composition has a zeta potential of at most +15 mV, preferably at most +10 mV, as determined in deionized water at 25°C with 3% by weight of modified silica particles.

10. The composition according to any one of claims 6 to 9, wherein the composition has a zeta potential of at least +2 mV, preferably at least +3 mV, more preferably at least +4 mV, and most preferably at least +5 mV, as determined in deionized water at 25°C with 3% by weight of modified silica particles.

11. The composition according to any one of claims 7 to 10, wherein the composition comprises one or more selected from the group consisting of: biocides, pH adjusters, pH buffers, oxidants, chelating agents, corrosion inhibitors, and surfactants.

12. A method for producing modified silica particles according to any one of claims 1 to 5, the method comprising the following steps: (a) Provide unmodified silica particles and an aqueous dispersion containing a nitrogen- or phosphorus-containing compound; (b) Heating the aqueous dispersion provided in step (a), preferably to boiling; (c) Adding silica to deposit a silica shell containing a modifier onto silica particles and produce an alkaline aqueous dispersion of modified silica particles as defined herein; (d) Pass the alkaline aqueous dispersion of the modified silica particles obtained in step (c) through a cation exchanger to produce an acidic aqueous dispersion of the modified silica particles.

13. A method for chemical mechanical polishing, comprising the following steps: (A) Provide substrate; (B) Providing the composition according to any one of claims 6 to 11; (C) Provide chemical mechanical polishing pads with polished surfaces; (D) Contact the polishing surface of the chemical mechanical polishing pad and the composition provided in step (B) with the substrate; and (E) Polish the substrate to remove at least a portion of the substrate.

14. The method of claim 13, wherein the substrate provided in step (A) comprises silicon oxide, preferably composed of silicon oxide.

15. The method of claim 13 or claim 14, wherein the substrate is selected from flat panel displays, integrated circuits (ICs), memory or hard disks, interlayer dielectric devices (ILDs), semiconductors, microelectromechanical systems, ferroelectrics, and magnetic heads.

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