Liquid dispersions and powders of cerium-based core-shell particles, methods for producing the same, and their use in polishing.

Abstract

The present invention relates to cerium-based core-shell particles having a core of cerium oxide optionally doped with at least one metal (M) and a shell formed on the surface of the core particle consisting of a plurality of nanoparticles of cerium oxide optionally doped with at least one metal (M'), which may be the same as or different from the metal (M).The present invention also relates to dispersions thereof in liquid media, methods for making same and the use of these particles and dispersions in polishing applications such as chemical mechanical polishing.

Description

[Technical Field]

[0001] This application claims priority to European Patent Application No. 21174022.0, filed on 17 May 2021, and the entire contents of that application are incorporated herein by reference for all purposes.

[0002] The present invention relates to a method for producing dispersions of cerium-based core-shell particles, dispersions and powders that can be obtained by such methods, and their use in the field of polishing, particularly chemical mechanical polishing. [Background technology]

[0003] Cerium oxide is commonly used for polishing applications, particularly for chemical and mechanical polishing. The development of the electronics industry has increasingly necessitated the use of compositions for polishing various processed materials, such as disks or dielectric compounds. Generally in the form of dispersions, these compositions must exhibit a certain number of properties. For example, they must provide a high degree of material removal, reflecting their polishing ability. They must also have the lowest possible defect rate, where the term “defect” specifically refers to the amount of scratches left by a substrate treated with the composition. For reasons of stability and ease of use, these dispersions must contain submicron-sized particles, i.e., generally less than 300 nm. The presence of particles that are too fine in these dispersions reduces the polishing ability of the particles, while particles that are too large can contribute to an increase in defects.

[0004] In this regard, we believe there is a need for cerium-based particles with improved polishing properties when used in chemical mechanical polishing processes. A simple and easily implementable industrial-scale manufacturing method is also required. [Overview of the project]

[0005] These problems are solved by the present invention, which provides particularly novel cerium-based particles having a rough surface for specific core-shell morphology and manufacturing methods thereof.

[0006] Therefore, one object of the present invention is (a) A step of providing an aqueous dispersion containing cerium oxide particles optionally doped with at least one metal (M); a step of providing an aqueous solution containing a cerium(III) salt; a step of providing an aqueous solution containing a peroxygenated salt; and a step of optionally providing an aqueous solution containing at least one metal (M') salt. (b) A step of producing a dispersion of cerium-based core-shell particles by contacting an aqueous dispersion with an aqueous solution provided in step (a) while maintaining a temperature within 0°C to 80°C and a pH of 11 or less, The present invention relates to a method for producing a dispersion of cerium-based core-shell particles in a liquid, including, At least one of step (a) or (b) is carried out in the presence of nitrate ions.

[0007] Furthermore, the present invention relates to cerium-based core-shell particles and dispersions thereof that can be obtained by this method.

[0008] The cerium-based core-shell particles of the present invention can be described as a shell consisting of a core particle of cerium oxide optionally doped with at least one metal (M) and a plurality of nanoparticles of cerium oxide optionally doped with at least one metal (M'), wherein the nanoparticles are formed on the surface of the core particle, and the ratio of the average particle size of the core-shell particles measured by TEM to the average particle size of the core-shell particles measured by BET is at least 1.5.

[0009] Advantageously, the specific core-shell morphology of the particles of the present invention increases their surface roughness and, consequently, their specific surface area compared to smooth cerium oxide particles without a shell according to the present invention. Thus, by increasing the contact surface between the particles and the substrate being polished, the polishing properties of the core-shell particles of the present invention are improved, making it possible to use them advantageously in chemical mechanical polishing processes. The core-shell particle dispersion of the present invention, in particular, allows for a higher removal rate due to their rough surface while maintaining the same defect ratio, due to a comparable particle size distribution compared to a dispersion of smooth cerium oxide particles without a shell according to the present invention.

[0010] As detailed below in this specification, cerium-based core-shell particle dispersions of the present invention can be used to prepare cerium-based core-shell particle powders and abrasive compositions.

[0011] Furthermore, one advantage of the core-shell particles of the present invention is that the nanoparticles from the shell adhere well to the core particles. It has been particularly observed that they remain attached to the core throughout the entire chemical mechanical polishing process. This is increasingly important as the particle shell withstands mechanical stress during the chemical mechanical polishing process. If the nanoparticles from the shell are removed during polishing, these small cerium oxide particles may remain attached to the substrate even after the cleaning process, which is unacceptable to the end user. This would result in unacceptable costs due to substrate loss and frequent replenishment of the polishing composition.

[0012] Another advantage of the core-shell particles of the present invention lies in the fact that they have a particle size range suitable for CMP applications and are monodisperse. [Brief explanation of the drawing]

[0013] [Figure 1] This is a TEM image of a dispersion of core-shell particles of the present invention, having a cerium oxide core and a cerium oxide shell, obtained by the method described in Example 1. [Figure 2]SEM image of a dispersion of cerium oxide particles intended to be used as core particles in the method described in Example 1. [Figure 3] TEM image of a dispersion of the core-shell particles of the present invention obtained by the method described in Example 2, having a cerium oxide core doped with lanthanum and a cerium oxide shell. [Figure 4] TEM image of a dispersion of the core-shell particles of the present invention obtained by the method described in Example 3, having a cerium oxide core and a cerium oxide shell doped with lanthanum.

[0014] Transmission electron microscope (TEM) images were collected using a JEM-1400 (JEOL) apparatus operating at 120 kV. Scanning electron microscope (SEM) images were obtained using an SEMS-5500 apparatus from Hitachi High Technologies Corporation.

[0015] Definitions In the present disclosure, the expression "comprising" should be understood to mean "comprising at least one".

[0016] When referring to the aqueous dispersion or solution provided in steps (a) and (b) of the method of the present invention, the expression "comprising" encompasses embodiments "consisting of" the compounds in relation to which the dispersion and solution are described.

[0017] The expression "contained in... to..." must be understood to include the limit values.

[0018] Throughout this description, the term “cerium-based” encompasses cerium oxide and metal-doped cerium oxide. Cerium oxide generally has a purity of at least 99.8% by weight relative to the weight of the oxide. Cerium oxide is generally crystalline ceric oxide. The term “cerium oxide doped with at least one metal” means that the metal ions partially substitute for the cerium ions in the CeO2 lattice. Thus, it also means a mixed oxide of cerium and at least one metal. It may also mean a solid solution in some embodiments, in which case the metal atoms are well diffused into the cerium oxide crystal structure. Some impurities other than the aforementioned metals may be present in the oxide. The impurities may originate from the raw materials or starting materials used in the preparation process of the metal-doped oxide. The total percentage of impurities is usually less than 0.2% by weight relative to the metal-doped oxide. Residual nitrates are not considered impurities in this application.

[0019] The term "dispersion" in relation to dispersions of cerium-based particles refers to a system consisting of submicron-sized solid fine particles stably dispersed in a liquid medium, and these particles may optionally contain residual amounts of bound or adsorbed ions such as nitrates or ammonium.

[0020] The term "nanoparticles," relating to the multiple small particles that form the shell of the core-shell particles of the present invention, means that these small particles have an average particle size that falls between 1 and 100 nm. This can be determined, among other things, by TEM, as described below.

[0021] Using different parameters, the following particle sizes and particle size distributions can be characterized: - The entire core-shell particle of the present invention; - In particular, core particles by characterizing the particles provided in the dispersion of step (a) of the method of the present invention; - Nanoparticles from the shell.

[0022] In relation to particle dispersions: - The average particle size of n(>100) particles can be measured using photographs of their dispersions obtained by transmission electron microscopy (TEM); - The standard deviation referred to in this application is also determined by the TEM method. It has its usual mathematical meaning. It is the square root of the variance, and the formula is:

number

number

[0023] In relation to powdered particles (dry particles): - The average particle size can be determined by X-ray diffraction (XRD) techniques. The value measured by XRD corresponds to the size of the coherent range calculated using the Scherrer model, based on the widths of the two strongest diffraction lines. - The specific surface area can be determined on the powder by nitrogen adsorption using the Brunauer-Emmett-Teller method (BET method). This method is disclosed in standard ASTM D 3663-03 (re-approved in 2015). This method is also described in the periodical "The Journal of the American Chemical Society, 60, 309 (1938)". The specific surface area can be automatically measured using Micromeritics' TriStar 3000 instrument, according to the manufacturer's guidelines. Prior to measurement, the sample in powder form should be degassed under static air by heating to a maximum temperature of 210°C to remove adsorbed chemical species. - The average particle size estimated by BET is the theoretical average particle size obtained from the specific surface area measured by the BET method, and the particles are assumed to be non-porous spherical particles of cerium oxide with a density of 7.2.

[0024] The distribution of particle sizes can be characterized by various parameters, which are based on distributions independent of volume and number: - The hydrodynamic mean diameter Dh, which is equal to the median diameter D50 of the particles, can be determined by dynamic light scattering (DLS). This technique allows for the measurement of the hydrodynamic mean diameter Dh of solid objects, whose value is affected by the presence of particle aggregates. Therefore, the measurement is usually performed for dispersions of particles in water. Dh is determined using Malvern's Zetasizer Nano-ZS instrument, according to the manufacturer's guidelines. The sample usually needs to be diluted with deionized water. A dilution factor of 30,000 times may be applied; - Laser diffraction can also be used to measure the size distribution of particles. Laser particle size analyzers such as the Horiba LA-910 can be used according to the manufacturer's guidelines. A relative refractive index of 1.7 can be used for measurement. From the volume distribution obtained by laser diffraction, various parameters commonly used in statistics, such as D10, D50, D90, and the dispersion index, can be estimated.

[0025] D10 is the diameter determined from the distribution obtained by laser diffraction, where 10% of the particles have a diameter smaller than D10.

[0026] D50 is the median diameter measured from the distribution obtained by laser diffraction.

[0027] D90 is a diameter determined from the distribution obtained by laser diffraction, where 90% of the particles have a diameter smaller than D90.

[0028] The "variance index" is defined by the following formula: σ / m = (D90 - D10) / 2D50 [Modes for carrying out the invention]

[0029] The present invention (a) A step of providing an aqueous dispersion containing cerium oxide particles optionally doped with at least one metal (M); a step of providing an aqueous solution containing a cerium(III) salt; a step of providing an aqueous solution containing a peroxygenated salt; and a step of optionally providing an aqueous solution containing at least one metal (M') salt. (b) A step of producing a dispersion of cerium-based core-shell particles by contacting an aqueous dispersion with the aqueous solution provided in step (a) while maintaining a temperature within 0°C to 80°C and a pH of 11 or less. The present invention relates to a method for producing a dispersion of cerium-based core-shell particles in a liquid, preferably water, containing the following: At least one of step (a) or (b) is carried out in the presence of nitrate ions.

[0030] Aqueous dispersion provided in step (a) Particles of cerium oxide optionally doped with at least one metal (M) are provided to serve as core particles for cerium-based core-shell particles produced by the method of the present invention.

[0031] In the following detailed description of process (a), these particles will be referred to as "cerium particles" unless otherwise specified.

[0032] The starting dispersion used in step (a) can be prepared by dispersing a commercially available powder of cerium particles in water. Alternatively, a commercially available dispersion of cerium particles can be used. If necessary, these dispersions can be concentrated or diluted and / or transferred from their original organic phase to water in order to carry out step (a) by methods that are essentially known.

[0033] The dispersion used in step (a) may contain at least 3% by weight, particularly at least 5% by weight, at least 10% by weight, at least 15% by weight, and more specifically at least 20% by weight of cerium-based particles relative to the total weight of the dispersion. The yield of the reaction will be further improved. The dispersion used in step (a) may contain less than 50% by weight, particularly less than 40% by weight, and more specifically less than 35% by weight of cerium-based particles relative to the total weight of the dispersion.

[0034] According to one embodiment, the cerium-based particles used in step (a) are cerium oxide particles, particularly ceria particles. Such particles can be advantageously manufactured by one of the methods described by the applicant in International Publication No. 2008 / 043703, International Publication No. 2010 / 020466, and International Publication No. 2015 / 091495.

[0035] Such cerium oxide particles (and therefore core particles) can exhibit the following characteristics: - Average particle size measured by TEM, up to 250 nm, particularly up to 200 nm, more specifically up to 170 nm; average particle size measured by TEM, at least 30 nm, particularly at least 40 nm, more specifically at least 50 nm. The standard deviation of the average particle size value may be up to 30%, particularly up to 20%, more specifically up to 15%; and / or - Average grain size of up to 120 nm, especially up to 110 nm, calculated from measurements of the BET surface; average grain size of at least 15 nm, especially at least 19 nm, especially at least 30 nm, especially at least 40 nm, calculated from measurements of the BET surface; and / or - The median diameter D50 determined from the distribution obtained by laser diffraction, which is included in 60nm~170nm, particularly 70nm~160nm, more specifically 80nm~150nm, and even more specifically 90nm~150nm, and / or - A dispersion index determined from the distribution obtained by laser diffraction, with a maximum value of 0.5, particularly a maximum of 0.4, and more specifically a maximum of 0.3.

[0036] According to another embodiment, the cerium-based particles used in step (a) are cerium oxide particles doped with at least one metal (M). Such particles can be advantageously produced by one of the methods described by the applicant in International Publication No. 2015 / 197656 and International Publication No. 2018 / 229005.

[0037] According to this embodiment, the metal (M) may be selected more specifically from the group consisting of alkali metal elements, alkaline earth metal elements, rare earth elements, actinide elements, transition metal elements, and post-transition metal elements from the periodic table.

[0038] The expression "rare earth elements" is understood to mean elements from the group consisting of yttrium and elements of the periodic table with atomic numbers from 57 to 71 (including 57 and 71). Transition metal elements are defined as any elements in the d-block of the periodic table, including groups 3 through 12. Post-transition metal elements, also known as poor metals, are defined as metallic elements in the p-block of the periodic table, including, in particular, aluminum, gallium, indium, thallium, tin, lead, bismuth, and polonium.

[0039] Preferably, the at least one metal (M) is selected from the group consisting of transition metal elements such as Zr; post-transition metal elements such as Al; rare earth elements such as La, Pr, Nd, and Y; and alkaline earth metal elements such as Sr. More preferably, the at least one metal (M) is selected from the group consisting of lanthanum, praseodymium, neodymium, and zirconium. Even more preferably, the at least one metal (M) is selected from the group consisting of lanthanum, praseodymium, and neodymium. Even more preferably, the at least one metal (M) is lanthanum.

[0040] Furthermore, according to this embodiment, the molar ratio M / M+Ce in the metal (M)-doped cerium oxide particles used in step (a) may be in the range of 0.01 to 0.15, more specifically 0.01 to 0.13, and particularly 0.01 to 0.12.

[0041] Such metal (M)-doped cerium oxide particles can exhibit the following characteristics: - Average particle size measured by TEM, up to 250 nm, particularly up to 200 nm, more specifically up to 170 nm; average particle size measured by TEM, at least 30 nm, particularly at least 40 nm, more specifically at least 50 nm. The standard deviation of the average particle size value may be up to 30%, particularly up to 20%, more specifically up to 15%; and / or - Average grain size of up to 120 nm, especially up to 110 nm, calculated from measurements of the BET surface; average grain size of at least 15 nm, especially at least 19 nm, at least 30 nm, especially at least 40 nm, calculated from measurements of the BET surface; and / or - The median diameter D50, which is determined from the distribution obtained by laser diffraction and is contained in 60 nm to 700 nm, especially 70 nm to 200 nm; and / or - A variance index determined from the distribution obtained by laser diffraction, with a maximum value of 0.6, particularly a maximum of 0.4, and more specifically a maximum of 0.3.

[0042] According to one sub-embodiment, the cerium-based particles used in step (a) are lanthanum-doped cerium oxide particles. Such particles may be as follows: - The hydrodynamic mean diameter Dh, determined by the distribution obtained by DLS, which is included in 100nm to 1000nm, more specifically 100nm to 500nm, even more specifically 100nm to 250nm, and even more specifically 150nm to 250nm, and / or - The median diameter D50, determined from the distribution obtained by laser diffraction, which is included in 100nm to 700nm, and especially in 100nm to 200nm, and / or - A variance index determined from the distribution obtained by laser diffraction, with a maximum value of 0.6, particularly a maximum of 0.4, and more specifically a maximum of 0.3.

[0043] Such particles can be manufactured, in particular, as described in International Publication No. 2018 / 229005.

[0044] The temperature of the cerium-based particle dispersion provided in step (a) may be set before step (b) to a value within the range of 0°C to 80°C, preferably 10°C to 60°C, more preferably 15°C to 45°C, particularly 20°C to 40°C, more specifically 25°C to 35°C, and even more specifically 30°C to 35°C. It is preferable to set the required temperature while stirring the dispersion. Stirring can be started before adjusting the temperature.

[0045] Similarly, the pH of the dispersion of cerium particles provided in step (a) may be set before step (b) to a value of 11 or less, preferably 3 to 11, preferably 4 to 11, preferably 8 to 11, more preferably 8 to 10, and particularly 8 to 9, more specifically about 9. A pH adjuster can be used in this regard. Depending on the initial pH of the dispersion, the pH adjuster may be an acid or a base. Suitable acids include nitric acid, hydrochloric acid, sulfonic acid, carbonic acid, picolinic acid, propionic acid, and mixtures thereof, with nitric acid being preferred. Suitable bases include alkali metal and alkaline earth metal hydroxides and aqueous ammonia. Secondary, tertiary, or quaternary amines can also be used. Ammonia water is preferred. According to a preferred embodiment, the pH adjuster is a base, preferably aqueous ammonia.

[0046] Preparation of core particles provided in step (a) According to one embodiment, the cerium-based particles used in step (a) are prepared by a method based on the precipitation of cerium(III) and cerium(IV) salts. This method includes the following steps: (a') Under an inert atmosphere, an aqueous solution of a base and NO3 -A step of contacting an aqueous solution containing Ce(III), Ce(IV), and optionally at least one metal (M); (b') A step of heat-treating the mixture obtained in step (a') under an inert atmosphere; (c') The mixture obtained at the end of step (b') may be optionally acidified; (d') The solid material obtained at the end of step (b') or step (c') may be optionally washed with water; (e') The solid material obtained at the end of step (d') can be optionally subjected to mechanical treatment to deaggregate the particles.

[0047] The Ce(IV) / total Ce molar ratio in process (a') can fall within the range of 1 / 500000 to 1 / 4000. It may also typically be between 1 / 90000 and 1 / 100000.

[0048] If at least one metal (M) is provided in step (a'), a suitable amount thereof is determined to obtain a molar ratio M / M+Ce of metal (M)-doped cerium oxide particles produced according to this embodiment, which is contained in 0.01 to 0.15, more specifically 0.01 to 0.12.

[0049] When present in the aqueous solution of step (a'), metal (M) is provided by a salt that may be a nitrate, chloride, sulfate, phosphate, acetate, or carbonate of metal (M), or a mixture of these salts such as a mixed nitrate / chloride. It is preferably a metal (M) nitrate. Metal (M) is as defined in the above description relating to step (a) of the method of the present invention.

[0050] NO3 - The amount of nitrate ions in the aqueous solution used in process (a'), expressed by the molar ratio of / Ce(III), is typically between 1 / 3 and 5 / 1.

[0051] The acidity of the aqueous solution used in step (a') is selected so that cerium(III) is completely present in the solution. It is preferably in the range of 0.8N to 12.0N.

[0052] Cerium(IV) can be provided in step (a') by salts that may be cerium(IV) nitrate, sulfate, cerium ammonium nitrate, or cerium ammonium sulfate. It is preferably cerium(IV) nitrate. A cerium nitrate solution can be advantageously obtained by the electrochemical oxidation method of a cerium nitrate solution as disclosed in French Patent No. 2570087. A cerium nitrate solution obtained according to the teachings of French Patent No. 2570087 may exhibit an acidity of about 0.6 N.

[0053] Cerium(III) may be provided in step (a') by salts that may be cerium(III) nitrate, chloride, sulfate, phosphate, acetate or carbonate, or mixtures of these salts such as mixed nitrate / chloride. It is preferably cerium(III) nitrate.

[0054] The amount of free oxygen in the starting solution in step (a') should be carefully controlled and minimized. For this purpose, the starting solution may be degassed by bubbling with an inert gas. The term “inert gas” or “inert atmosphere” is intended to mean an atmosphere or gas that does not contain oxygen, and the gas may be, for example, nitrogen or argon.

[0055] In step (a'), hydroxide-type products can be particularly used as the base. Examples include alkali metal or alkaline earth metal hydroxides and aqueous ammonia. Secondary, tertiary, or quaternary amines can also be used. The aqueous solution of the base can be pre-degassed by bubbling with an inert gas. The amount of base used in step (a'), expressed as the molar ratio of base / (Ce+ optional M), is preferably in the range of 8.0 to 30.0. This ratio may preferably be greater than 9.0.

[0056] Process (a') is typically carried out at a temperature within the range of 5°C to 50°C. This temperature may also be 20°C to 25°C.

[0057] Step (b') is the heat treatment of the reaction medium obtained at the end of the previous step. This consists of (i) a heating sub-step and (ii) an aging sub-step. The heating sub-step (i) consists of heating the medium at a temperature typically in the range of 75°C to 95°C, more specifically 80°C to 90°C, and even more specifically 85°C to 90°C.

[0058] The aging sub-process (ii) consists of maintaining the medium at a temperature within the range of 75°C to 95°C, more specifically 80°C to 90°C, and even more specifically 85°C to 90°C. The duration of the aging sub-process (ii) is 2 to 20 hours. The higher the temperature of the aging process, the shorter the duration of the aging sub-process. For example, if the temperature of the maturation sub-process is 85°C to 90°C, for example 88°C, the duration of the maturation sub-process may be 2 to 15 hours, more particularly 4 to 15 hours. If the temperature of the maturation sub-process is 75°C to 85°C, for example 80°C, the duration of the maturation sub-process may be 15 to 30 hours.

[0059] During step (b'), oxidation of Ce(III) to Ce(IV) occurs. This step may be carried out under an inert atmosphere. The description of the atmosphere for step (a') applies here.

[0060] In step (c'), the mixture obtained at the end of step (b') may be optionally acidified. This step (c') can be carried out using nitric acid. The reaction mixture can be acidified with HNO3 to a pH lower than 3.0, more particularly in the range of 1.5 to 2.5.

[0061] In step (d'), the solid material obtained at the end of step (b') or step (c') is washed with water, preferably deionized water. This operation reduces the amount of residual anions, particularly nitrates, in the dispersion and allows the target conductivity to be obtained. This step may be carried out by filtering the solid from the mixture and redispersing the solid in water. Filtration and redispersion may be performed several times as needed.

[0062] In step (e'), the solid material obtained at the end of step (d) can be subjected to mechanical treatment to deaggregate the particles. This step can be carried out by double-jet treatment or ultrasonic deaggregation. This step typically results in a sharp particle size distribution and a reduction in the number of large aggregated particles. According to one embodiment, the cerium-based particles have undergone mechanical deaggregation treatment. According to another embodiment, the cerium-based particles have not undergone mechanical deaggregation treatment.

[0063] After step (e'), the solid material can be dried to obtain the cerium-based particles provided in step (a) in powder form. Alternatively, after step (e'), water can be added to directly obtain an aqueous dispersion of the cerium-based particles provided in step (a).

[0064] The aqueous solution provided in step (a) The purpose of aqueous solutions containing cerium(III) salt, peroxygen aqueous solution, and optional aqueous solutions containing at least one metal(M') salt is to form nanoparticles of the shell of the cerium-based core-shell particles to be manufactured.

[0065] Cerium(III) salts can be cerium(III) nitrate, chloride, sulfate, phosphate, or carbonate, or mixtures of these salts, such as mixed nitrates / chlorides. It is preferably cerium(III) nitrate.

[0066] Nitrate ions can be provided in either step (a) or (b). Molar ratio NO3 - The amount of nitrate ions, represented as / Ce(III), is generally between 1 / 3 and 5 / 1.

[0067] The acidity of the aqueous solution containing the cerium(III) salt provided in step (a) is selected such that the cerium(III) is completely present in the solution. It is preferably in the range of 0.8 N to 12.0 N. In this regard, suitable acids such as nitric acid, hydrochloric acid, sulfonic acid, carbonic acid, picolinic acid, propionic acid, and mixtures thereof can be used, and it is preferably nitric acid.

[0068] It is advantageous to use high-purity salts and ingredients. The purity of the salt may be at least 99.5% by weight, and more specifically, at least 99.9% by weight.

[0069] According to one embodiment in which it is desirable to obtain a metal (M')-doped cerium oxide shell, an aqueous solution containing at least one metal (M') salt is also provided in step (a). The metal (M') salt may be a metal (M') nitrate, chloride, sulfate, phosphate, acetate or carbonate, and also a mixture of these salts such as a mixed nitrate / chloride. It is preferably a metal (M') nitrate. When it is desirable to produce cerium-based core-shell particles in which both the core and shell are doped, metal (M') may be the same as or different from metal (M) above. More specifically, metal (M') may be selected from the group consisting of alkali metal elements, alkaline earth metal elements, rare earth elements, actinide elements, transition metal elements and post-transition metal elements from the periodic table. The definitions of these groups of elements shown in relation to metal (M) apply equally. Preferably, the at least one metal (M') is selected from the group consisting of transition metal elements such as Zr; post-transition metal elements such as Al; rare earth elements such as La, Pr, Nd, and Y; and alkaline earth metal elements such as Sr. More preferably, the at least one metal (M') is selected from the group consisting of lanthanum, praseodymium, neodymium, and zirconium. Even more preferably, the at least one metal (M') is selected from the group consisting of lanthanum, praseodymium, and neodymium. Even more preferably, the at least one metal (M') is lanthanum.

[0070] According to this embodiment, the amount of metal (M') salt can be determined to obtain a molar ratio M' / M'+Ce in the shell of core-shell particles contained in 0.01 to 0.15, more specifically 0.01 to 0.12.

[0071] In step (a), a peroxygenated aqueous solution is also provided. In this invention, peroxygen is Ce 3+ Ions to Ce 4+ It is used as an oxidizing agent that converts substances into ions.

[0072] The peroxygen used in this invention can be selected from hydrogen peroxide, water-soluble peracids, and any other water-soluble molecule containing a peroxygen group of formula -OO-. Hydrogen peroxide is preferred.

[0073] The amount of peroxygen in the peroxygenated aqueous solution used may be in the range of 5 to 70% by weight, particularly 20 to 50% by weight, and more specifically 30 to 40% by weight, relative to the total weight of the peroxygenated aqueous solution.

[0074] Process (b) Step (b) is to produce a dispersion of cerium-based core-shell particles by reacting an aqueous dispersion containing cerium oxide particles optionally doped with at least one metal (M), an aqueous solution containing a cerium(III) salt, an aqueous peroxygenated solution, and an aqueous solution containing at least one metal (M') salt provided in an optional step (a), while maintaining a temperature within 0°C to 80°C and a pH of 11 or less.

[0075] The aqueous dispersion and the aqueous solution can be brought into contact simultaneously or sequentially, in any order or in any combination.

[0076] In particular, an aqueous dispersion containing cerium oxide particles doped with at least one metal (M) in an optional manner may be brought into contact with an aqueous solution containing a cerium(III) salt. The resulting solution may then be brought into contact with an aqueous solution of peroxygen.

[0077] When both are provided, an aqueous solution containing a cerium(III) salt and an aqueous solution containing at least one metal (M') salt can be brought into contact with each other, particularly before step (b), to form an aqueous solution containing the cerium(III) salt and at least one metal (M') salt. Optionally, a dispersion containing particles of cerium oxide doped with at least one metal (M) may be brought into contact with this solution. The resulting solution may then be brought into contact with an aqueous solution of peroxygen.

[0078] The contact step (b) may include a contact substep (i) and a subsequent aging substep (ii). During the contact substep (i), the dispersion and the solution are brought into contact with each other while maintaining the required temperature and pH. During the aging substep (ii), the medium obtained from the contact substep (i) is maintained at the required temperature and pH for a specific period of time.

[0079] The contact sub-step (i) can be carried out by preferably gradually and / or sequentially introducing the solution into the dispersion provided in step (a).

[0080] The molar ratio of cerium oxide to cerium(III) before starting process (b) may be between 1 / 1 and 100 / 1, particularly between 3 / 1 and 30 / 1, and more specifically between 5 / 1 and 15 / 1.

[0081] The molar ratio of peroxygen / cerium(III) before starting step (b) is preferably less than 0.50, particularly less than or equal to 0.40, and more specifically less than or equal to 0.38. This is preferably 0.01 or higher, particularly 0.10 or higher, and more specifically 0.20 or higher.

[0082] The duration of the aging sub-process (ii) can be 2 to 24 hours, particularly 2 to 10 hours, or more specifically 2 to 5 hours.

[0083] The temperature of the medium is maintained for the duration of process (b) within a range of 0°C to 80°C, preferably 10°C to 60°C, more preferably 15°C to 45°C, particularly 20°C to 40°C, more specifically 25°C to 35°C, and even more specifically 30°C to 35°C. It is highly noteworthy that the process can be operated at a lower temperature, thus achieving energy savings.

[0084] The pH of the medium is maintained at a value of 11 or less during the time of step (b), preferably 3 to 11, preferably 4 to 11, preferably 8 to 11, more preferably 8 to 10, particularly 8 to 9, and more specifically about 8. Depending on the initial pH of the medium, the pH adjuster may be an acid or a base. Suitable acids include nitric acid, hydrochloric acid, sulfonic acid, carbonic acid, picolinic acid, propionic acid, and mixtures thereof, with nitric acid being preferred. Suitable bases include alkali metal and alkaline earth metal hydroxides and aqueous ammonia. Secondary, tertiary, or quaternary amines can also be used. Ammonia water is preferred. According to a preferred embodiment, the pH adjuster is a base, preferably aqueous ammonia water.

[0085] Process (b) can be advantageously carried out at atmospheric pressure (i.e., at approximately 1,013.25 millibars).

[0086] Step (b) may be carried out in an inert atmosphere or a non-inert atmosphere. The term “inert atmosphere” has the same meaning as described above. According to one embodiment, the reaction is carried out in an oxidizing atmosphere. “Oxidizing atmosphere” has the meaning common to those skilled in the art, i.e., an atmosphere containing free oxygen. It may be air or any oxygen-containing atmosphere such as a molecular oxygen-rich atmosphere.

[0087] The medium may be stirred during the time of step (b).

[0088] According to one embodiment, no Ce(IV) salt is introduced in either step (a) or (b). In conventional cerium precipitation-based methods, cerium(IV) ions are used as crystalline species to promote nucleation in solution. However, in the method of the present invention, the cerium-based particles provided from the dispersion in step (a) and intended to be core particles already fulfill this role. The presence of additional Ce(IV) salts can lead to the formation of small cerium oxide particles independently of core-shell particles, thus increasing the dispersion index of the resulting particle dispersion, which is undesirable for the target polishing application.

[0089] Optional process (c) In step (c), the mixture obtained at the end of step (b) or step (d), which will be described in detail later, may be optionally acidified. Step (c) can be carried out using a suitable acid such as nitric acid, picolinic acid, propionic acid, hydrochloric acid, sulfonic acid, carbonic acid, and mixtures thereof, preferably nitric acid. The reaction mixture may be acidified to a pH lower than 3.0, more specifically to a pH in the range of 1.5 to 2.5.

[0090] Optional process (d) In step (d), the solid material obtained at the end of step (b) or step (c) may be washed with water, preferably deionized water. When both are carried out, steps (c) and (d) may be carried out in any order. This operation reduces the amount of residual anions, particularly nitrates, in the dispersion and allows the target conductivity to be obtained. This step can be carried out by filtering the solid from the mixture and redispersing the solid in water. Filtration and redispersion may be carried out several times as needed.

[0091] Optional step (e) In step (e), the solid material obtained at the end of steps (b), (c), or (d) can be subjected to mechanical treatment to deaggregate the core-shell particles. This step can be carried out by double-jet treatment or ultrasonic deaggregation. This step typically results in a sharp particle size distribution and a reduction in the number of large aggregated particles. According to one embodiment, the cerium-based core-shell particles are subjected to mechanical treatment for deaggregation. According to another embodiment, the cerium-based core-shell particles are not subjected to mechanical treatment for deaggregation.

[0092] After step (e), the solid material can be dried in step (f) to obtain the cerium-based core-shell particles of the present invention in powder form. After step (e), water can also be added to obtain an aqueous dispersion of the cerium-based core-shell particles according to the present invention. Dispersions according to the present invention can be prepared using liquids other than water, such as water / water miscible, compatible solvent mixtures or organic solvents. Such dispersions can be prepared from the aqueous dispersion obtained by the method of the present invention by methods that are essentially known. The pH of the dispersion can also be adjusted to a value of 4 to 6.

[0093] According to one embodiment, cerium-based core-shell particles are produced having a cerium oxide core and a shell made of La-doped cerium oxide nanoparticles. To this end, in order to carry out the method described above, an aqueous dispersion of cerium oxide particles, preferably an aqueous solution containing a cerium(III) salt, which is cerium(III) nitrate, and preferably an aqueous solution containing a lanthanum salt, which is lanthanum nitrate, are provided in step (a).

[0094] According to another embodiment, cerium oxide core-shell particles are produced, having a core of cerium oxide and a shell made of cerium oxide nanoparticles. To this end, in order to carry out the method described above, an aqueous dispersion of cerium oxide particles and an aqueous solution containing a cerium(III) salt, preferably cerium(III) nitrate, are provided in step (a).

[0095] particle The present invention relates to cerium-based core-shell particles that can or can be obtained by the methods described above.

[0096] The present invention particularly relates to cerium-based core-shell particles, wherein each cerium-based core-shell particle comprises a core particle manufactured from cerium oxide optionally doped with at least one metal (M), and a shell consisting of a plurality of nanoparticles of cerium oxide optionally doped with at least one metal (M'), wherein the nanoparticles are formed on the surface of the core particle, and the ratio of the average particle size of the core-shell particle measured by TEM to the average particle size of the core-shell particle measured by BET is at least 1.5.

[0097] Such cerium-based core-shell particles may also exhibit the following characteristics: - The average core-shell particle size, as measured by TEM, is up to 200 nm, particularly up to 190 nm; it can also be up to 180 nm, particularly up to 150 nm, particularly up to 140 nm, particularly up to 130 nm, and even further up to 120 nm. Cerium oxide particles may exhibit an average particle size of at least 30 nm, particularly at least 40 nm, more specifically at least 50 nm, as measured by TEM. The standard deviation of the average particle size value can be up to 30%, particularly up to 25%, particularly up to 20%, more specifically up to 15%; and / or - Average core-shell particle size of up to 120 nm, particularly up to 100 nm, and up to 85 nm, calculated from BET surface measurements. Cerium oxide particles may exhibit an average particle size of at least 15 nm, particularly at least 19 nm, particularly at least 20 nm, and particularly at least 30 nm, calculated from BET surface measurements; and / or - The ratio of the average particle size of core-shell particles measured by TEM to the average particle size of core-shell particles measured by BET is at least 1.7, at least 1.9, more specifically at least 2.0; and / or - The hydrodynamic mean diameter Dh, determined by DLS, and included in the range of 50 nm to 300 nm, particularly 70 nm to 280 nm, particularly 80 nm to 250 nm, particularly 90 nm to 230 nm. - The median diameter D50, determined from the distribution obtained by laser diffraction, and included in the range of 30 nm to 180 nm, particularly 60 nm to 160 nm, more specifically 80 nm to 150 nm, even more specifically 90 nm to 145 nm; and / or - The median diameter D10, determined from the distribution obtained by laser diffraction, and included in the range of 10 nm to 160 nm, particularly 40 nm to 130 nm, more specifically 60 nm to 120 nm, even more specifically 70 nm to 110 nm; and / or - The median diameter D90, determined from the distribution obtained by laser diffraction, and included in the range of 45 nm to 250 nm, particularly 90 nm to 220 nm, more specifically 100 nm to 210 nm, even more specifically 110 nm to 200 nm; and / or - The dispersion index, determined from the distribution obtained by laser diffraction, and with a maximum of 0.5, particularly a maximum of 0.4, a maximum of 0.3; and / or - The ratio of the average particle size of the nanoparticles from the shell measured by TEM to the average particle size of the core particles measured by TEM, with a maximum of 1 / 2, particularly a maximum of 1 / 3, particularly a maximum of 1 / 4; and / or - Determined by BET, and included in the range of 8 - 60 m 2 / g, particularly included in the range of 8 - 4 m 2 / g, particularly included in the range of 8 - 30 m 2 / g, particularly 10 - 28 m 2 / g, particularly 14 - 25 m 2 / g, more specifically 15 - 22 m 2 / g of the specific surface area; and / or - The average microcrystalline size, included in the range of 60 - 120 nm, particularly 60 - 80 nm. It is calculated from the FWHM of the (111) plane by applying the Scherrer model using a Scherrer constant equal to 0.94.

[0098] In the embodiments of this patent application, the minimum values ​​of D10, D50, and D90 may be selected. In the embodiments of this patent application, the maximum values ​​of D10, D50, and D90 may be selected.

[0099] The metal (M) and / or (M') optionally present in the core-shell particles of the present invention can be selected from the metals described above in relation to the manufacturing process.

[0100] When the core particles are doped with at least one metal (M), the molar ratio M / M+Ce in the core particles can be in the range of 0.01 to 0.15, more specifically 0.01 to 0.13, and in particular 0.01 to 0.12.

[0101] When shell nanoparticles are doped with at least one metal (M'), the molar ratio M' / M'+Ce in the shell particles can range from 0.01 to 0.15, more specifically 0.01 to 0.13, and in particular 0.01 to 0.12.

[0102] According to a specific embodiment of the present invention: - Both the core and shell particles are manufactured from cerium oxide; or - The core particles are made from cerium oxide and the shell particles are made from lanthanum-doped cerium oxide; or - The core particles are made from lanthanum-doped cerium oxide and the shell particles are made from cerium oxide; or - The core particles are manufactured from lanthanum-doped cerium oxide, and the shell particles are manufactured from lanthanum-doped cerium oxide.

[0103] dispersion liquid The present invention also relates to a dispersion of the cerium-based core-shell particles of the present invention in a liquid medium.

[0104] The zeta potential of cerium-based core-shell particles contained in the dispersion of the present invention is preferably positive. It can be measured at the pH value of the dispersion in the range of 4 to 9.5. The zeta potential can be measured for 1 wt% of the dispersion using a Quantachrome zetameter DT300.

[0105] The dispersion of the present invention may advantageously exhibit conductivity of less than 600 μS / cm, less than 300 μS / cm, more specifically less than 150 μS / cm, and even more specifically less than 100 μS / cm.

[0106] The liquid medium may be water or a mixture of water and a water-miscible organic liquid. The water-miscible organic liquid should not precipitate or aggregate particles. Examples of water-miscible organic liquids include alcohols such as isopropyl alcohol, ethanol, 1-propanol, methanol, and 1-hexanol; ketones such as acetone, diacetone alcohol, and methyl ethyl ketone; and esters such as ethyl formate, propyl formate, ethyl acetate, methyl acetate, methyl lactate, butyl lactate, and ethyl lactate. The water / organic liquid ratio may be 80 / 20 to 99 / 1 (wt / wt).

[0107] The proportion of cerium-based core-shell particles in the dispersion may range from 0.5% to 40.0% by weight, and this proportion is expressed as the weight of cerium-based core-shell particles relative to the total weight of the dispersion. This ratio can range from 10.0% to 35.0% by weight.

[0108] Use of cerium-based core-shell particles or dispersions The cerium-based core-shell particles or dispersions of the present invention can be used to prepare abrasive compositions, more specifically CMP compositions. They are used as components of abrasive compositions, and more particularly CMP compositions.

[0109] CMP compositions (or chemical-mechanical polishing compositions) are polishing compositions used to selectively remove material from the surface of a substrate. They are used in the field of integrated circuits and other electronic devices. In fact, in the manufacture of integrated circuits and other electronic devices, multiple layers of conductive, semiconducting, and dielectric materials are deposited on or removed from the surface of a substrate. Because layers of material are deposited on and removed from the substrate sequentially, the top surface of the substrate may become non-planar and require planarization. Surface planarization (or surface "polishing") is the process of removing material from the surface of a substrate to form a generally smooth and flat surface. Planarization is useful for removing undesirable surface topography and surface defects such as rough surfaces, aggregated material, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful for forming features on a substrate by removing excess deposited material that was used to fill in features and provide a smooth surface for subsequent levels of metallization and processing.

[0110] The substrates that can be polished with the polishing composition or CMP composition may be, for example, silicon dioxide type substrates, glass, semiconductors, or wafers.

[0111] Polishing compositions or CMP compositions typically contain different components other than cerium-based core-shell particles. Polishing compositions may contain one or more of the following components: - Abrasive particles other than cerium-based particles (referred to herein as “additional abrasive particles”); and / or - pH adjusters; and / or - Surfactants; and / or - Rheology control agents including viscosity improvers and coagulants; and / or - Anionic copolymers of carboxylic acid monomers, sulfonated monomers, or phosphonic oxide monomers with acrylates, polyvinylpyrrolidone, or polyvinyl alcohol (e.g., copolymer of 2-hydroxyethyl methacrylic acid and methacrylic acid); nonionic polymers which are polyvinylpyrrolidone or polyethylene glycol; silanes which are aminosilane, ureidosilane, or glycidylsilane; N-oxides of functionalized pyridines (e.g., N-oxide picolinate); starch; cyclodextrins (e.g., α-cyclodextrin or β-cyclodextrin); and additives selected from combinations thereof.

[0112] The pH of abrasive compositions generally falls within the range of 1 to 6. Typically, abrasive compositions have a pH of 3.0 or higher. Also, typically, the pH of abrasive compositions is 6.0 or lower.

[0113] The cerium-based core-shell particles of the present invention can be used in the polishing compositions disclosed in the following publications: International Publication No. 2013 / 067696; International Publication No. 2016 / 140968; International Publication No. 2016 / 141259; International Publication No. 2016 / 141260; International Publication No. 2016 / 047725; International Publication No. 2016 / 006553.

[0114] Furthermore, the present invention relates to a method for removing a portion of a substrate, comprising the step of polishing the substrate with an abrasive composition prepared from a dispersion containing cerium-based core-shell particles according to the present invention.

[0115] Finally, the present invention relates to a semiconductor including a substrate polished by this method.

[0116] If any disclosure in any patent, patent application, or publication incorporated herein by reference is inconsistent with the description in this application to such an extent that it obscures the terminology, the description in this application shall prevail. [Examples]

[0117] The present invention will be further illustrated by the following embodiments, but this is not intended to limit the invention.

[0118] Example 1: Particles with a CeO2 core and CeO2 shell - concentration 20% by weight A 20% by weight aqueous dispersion of cerium oxide particles is prepared by adding 895.7 g of Solvay's commercially available CeO2 aqueous dispersion Zenus® (average primary particle size calculated by BET measurement = 60 nm) containing 31.3% by weight to 504.3 g of deionized water. A diluted ammonia solution is prepared by adding 135.1 g of 28% aqueous ammonia to 664.9 g of deionized water. A cerium trivalent nitrate solution is prepared by adding 153.4 g of 2.87 M cerium trivalent nitrate solution to 21.2 g of deionized water.

[0119] A 20 wt% aqueous dispersion of cerium oxide is introduced into a 2 L semi-closed jacketed reactor and then stirred (using a stirrer with four inclined blades at 600 rpm). The reaction mixture is then heated to 35°C under the same stirring conditions. The initial pH of the dispersion is increased to 8 by adding 2.5 M ammonia solution. Next, cerium trivalent nitrate solution is added at a rate of 7 g / min using a peristaltic pump. During this step, the pH is maintained at 8 by controlling the addition of 2.5 M ammonia solution. After the addition is complete, the reaction mixture is maintained at the same temperature and with the same stirring conditions for 3 minutes, and then 10.74 g of commercially available 30.9 wt% H2O2 solution is added over 6 minutes. The reaction mixture is then maintained at the same temperature and stirred for 2 hours and 47 minutes. During this time, the pH is maintained by controlling the addition of 2.5 M ammonia solution. The reaction is then stopped, the dispersion is washed several times by centrifugation, the supernatant is removed, and the cake is redispersed in deionized water. Finally, adjust the dispersion to 10-15% by weight, with a pH of approximately 5 and an ionic conductivity of 0.1 mS.cm. -1 Reduce the concentration to less than 50%. Deagglomerate by continuously passing the dispersion through a dual-impact jet homogenizer.

[0120] The resulting dispersion was observed by TEM (Figure 1). It was observed that cerium salt precipitated on the doped cerium oxide particles, forming a shell with a rough surface. The average particle size was determined after counting 150 particles on the TEM image, yielding an average particle size of 109 nm.

[0121] A portion of the dispersion is dried in an oven at 200°C to obtain a powder for measuring the BET surface. The BET specific surface area determined by nitrogen adsorption is 13 m² for the starting particles. 2 The value is / g, and for core-shell particles, it is 20m 2 The particle size is given by / g, and the average primary particle size is 64 nm and 42 nm, respectively (giving the ratio of average size TEM / size BET 2.6). The secondary particle size is also measured by dynamic light scattering (DLS) at the relative refractive index of CeO2 in water of 1.7. The hydrodynamic diameter is 158 nm for core-shell particles.

[0122] Example 2: Particles in which the core is lanthanum-doped cerium oxide and the shell is cerium oxide. A 20% by weight aqueous dispersion of lanthanum-doped cerium oxide particles is prepared by adding 940.5 g of a 29.8% by weight CeO2:La aqueous dispersion (average primary particle size = 74 nm calculated from BET measurement, La / La+Ce molar ratio of 0.025, synthesized according to Example 1 of International Publication No. 2018 / 229005) to 459.5 g of deionized water. A diluted ammonia solution is prepared by adding 132.7 g of 28% aqueous ammonia to 667.3 g of deionized water. A solution of cerium trivalent nitrate is prepared by adding 70.5 g of 2.87 M cerium trivalent nitrate solution to 41.3 g of deionized water.

[0123] A 20 wt% aqueous dispersion of cerium oxide is introduced into a 2 L semi-closed jacketed reactor and then stirred (using a stirrer with four inclined blades at 600 rpm). The reaction mixture is then heated to 35°C under the same stirring conditions. The initial pH of the dispersion is increased to 8 by adding 2.5 M ammonia solution. Next, cerium trivalent nitrate solution is added at a rate of 3.2 g / min using a peristaltic pump. During this step, the pH is maintained at 8 by the controlled addition of 2.5 M ammonia solution. After the addition is complete, the reaction mixture is maintained at the same temperature and with the same stirring conditions for 3 minutes, and then 4.88 g of commercially available 30.9 wt% H2O2 solution is added over 3 minutes and 20 seconds. The reaction mixture is then maintained at the same temperature and stirred for 2 hours and 46 minutes. During this time, the pH is maintained by the controlled addition of 2.5 M ammonia solution. The reaction is then stopped, the dispersion is washed several times by centrifugation, the supernatant is removed, and the cake is redispersed in deionized water. Finally, the dispersion is adjusted to 10-15% by weight, with a pH of approximately 5 and an ionic conductivity of less than 0.1 mS / cm⁻¹. The dispersion is then deaggregated by continuously passing it through a dual-impact jet homogenizer.

[0124] The resulting dispersion was observed by TEM (Figure 3). It was observed that cerium salt precipitated on the doped cerium oxide particles, forming a shell with a rough surface. The average particle size was determined after counting 150 particles on the TEM image, yielding an average particle size of 137 nm.

[0125] A portion of the dispersion is dried in an oven at 200°C to obtain a powder for measuring the BET surface. The BET specific surface area determined by nitrogen adsorption is 11.3 m² for the starting particles. 2 The value is / g, and for core-shell particles it is 12.9m 2 The particle size is given by / g, and the average primary particle size is 74 nm and 65 nm, respectively (giving the ratio of average size TEM / size BET 2.1). The secondary particle size is also measured by dynamic light scattering (DLS) at a relative refractive index of 1.7 for CeO2 in water. The hydrodynamic diameter is 200 nm for core-shell particles.

[0126] Example 3: Particles in which the core is cerium oxide and the shell is lanthanum-doped cerium oxide A 5% by weight aqueous dispersion of cerium oxide particles is prepared by adding 246.7 g of Solvay's commercially available CeO2 aqueous dispersion Zenus® (average primary particle size calculated by BET measurement = 60 nm) at a concentration of 28.4% by weight to 1153.3 g of deionized water. A diluted ammonia solution is prepared by adding 132.7 g of 28% aqueous ammonia to 667.3 g of deionized water. 2.87 mol / L CeO2 in 87.5 g of deionized water 3+ 22.8 g of cerium trivalent nitrate solution and 2.87 mol / L of La 3+ A solution of cerium trivalent nitrate and lanthanum nitrate is prepared by adding 2.6 g of lanthanum nitrate solution.

[0127] A 5 wt% aqueous dispersion of cerium oxide is introduced into a 2 L semi-closed jacketed reactor and then stirred (using a stirrer with four inclined blades at 600 rpm). The reaction mixture is then heated to 35°C under the same stirring conditions. The initial pH of the dispersion is increased to 8 by adding 2.5 M ammonia solution. Next, cerium trivalent nitrate solution and lanthanum nitrate solution are added at a rate of 4.2 g / min using a peristaltic pump. During this process, the pH is maintained at 8 by controlling the addition of 2.5 M ammonia solution. After the addition is complete, the reaction mixture is maintained at the same temperature and with the same stirring conditions for 3 minutes, and then 1.58 g of commercially available 30.9 wt% H2O2 solution is added over 3 minutes and 20 seconds. The reaction mixture is then maintained at the same temperature and stirred for 2 hours and 23 minutes. During this time, the pH is maintained by controlling the addition of 2.5 M ammonia solution. The reaction is then stopped, the dispersion is washed several times by centrifugation, the supernatant is removed, and the cake is redispersed in deionized water. Finally, adjust the dispersion to 10-15% by weight, with a pH of approximately 5 and an ionic conductivity of 0.1 mS.cm. -1 Reduce the concentration to less than 50%. Deagglomerate by continuously passing the dispersion through a dual-impact jet homogenizer.

[0128] The resulting dispersion was observed by TEM (Figure 4). It was observed that cerium salt precipitated on the doped cerium oxide particles, forming a shell with a rough surface. The average particle size was determined after counting 150 particles on the TEM image, yielding an average particle size of 109 nm.

[0129] A portion of the dispersion is dried in an oven at 200°C to obtain a powder for measuring the BET surface. The BET specific surface area determined by nitrogen adsorption is 13 m² for the starting particles. 2 The value is / g, and for core-shell particles it is 16.7m 2 The particle size is given by / g, and the average primary particle size is 64 nm and 50 nm, respectively (giving the ratio of average size TEM / size BET 2.2). The secondary particle size is also measured by dynamic light scattering (DLS) at a relative refractive index of 1.7 for CeO2 in water. The hydrodynamic diameter is 154 nm for core-shell particles.

[0130] Comparative Example 1: Repeat Example 1, except that the applied temperature is 85°C instead of 35°C. Observe the dispersion by TEM. Note that the starting particles are not covered by small microcrystals (no core-shell structure).

[0131] Comparative Example 2: Repeat Example 1, except that the pH is 12 instead of 8. Observe the dispersion by TEM. Note that the starting particles are aggregated and not covered by small microcrystals (no core-shell structure).

[0132] Comparative example 3: Hydrothermal synthesis A 5% by weight aqueous dispersion of cerium oxide particles is prepared by adding 41.6 g of 30% by weight Solvay's commercially available cerium oxide aqueous dispersion Zenus® (average primary particle size calculated by BET measurement = 60 nm) to 208.4 g of deionized water. A 1N ammonia solution is prepared by adding 28 g of 28% aqueous ammonia to 771 g of deionized water. A cerium trivalent nitrate solution is prepared by adding 0.75 g of 2.87 M cerium trivalent nitrate solution to 249.25 g of deionized water.

[0133] A 5 wt% cerium oxide suspension and a cerium trivalent nitrate solution were introduced into a 2 L semi-closed jacketed reactor and then stirred (using a stirrer with four inclined blades at 300 rpm). The pH of the mixture was adjusted to 11 by adding an appropriate amount of 1 N ammonia solution, and the mixture was stirred for 2 hours. The solution was then transferred to a Teflon bottle and placed in a stainless steel autoclave at 170°C for 12 hours. The dispersion was observed by TEM (Figure 3). It was noted that the starting particles were not covered by small microcrystals (no core-shell structure).

[0134] Evaluation of polishing performance The polishing machine used is a Struers Tegramin. The surface to be polished is made of amorphous silica. An aqueous dispersion of core-shell particles was tested under the following conditions. • Pressure applied to the head: 50N • Rotation speed: 150 rpm; • Pads: Neoprene (MD-Chem) - a new pad for each order; • Dispersion flow rate: 15 mL / min; • Dispersion: The amount of core-shell particles is 1% by weight; The dispersion has a pH of 6.0-6.1, obtained by adding diluted NH4OH; Polishing time: 10 minutes.

[0135] For reference, a 1% by weight aqueous dispersion of cerium oxide (average CeO2 primary particle size = 60 nm, calculated by BET measurement) of Solvay's commercially available Zenus® particles at pH = 6.0 is used.

[0136] The polishing procedure is as follows: 1) Test the reference dispersion. 2) Test the sample. 3) Perform a second test on the sample. Between each step of the procedure, the pad is cleaned with deionized water, and the dispersion to be tested is introduced onto the surface to be polished at a controlled flow rate.

[0137] Record the weight loss of the substrate. Then, calculate the removal rate (RR), expressed in nm / min, as follows:

number

[0138] The efficiency ratio of the removal rate is the ratio of the average removal rate achieved in the dispersion tested for each sequence to the removal rate achieved in the reference dispersion. This is 1.28 for the particles in Example 1 and 1.38 for the particles in Example 2, reflecting the improvement in removal rate compared to the reference used (efficiency ratio of removal rate greater than 1).

[0139] At the end of the polishing test, the substrate and core-shell particles are visually inspected: it is confirmed that the nanoparticles from the shell of the core-shell particles of the present invention are sufficiently fixed and remained attached to the core during polishing.

Claims

1. A method for producing a dispersion of cerium-based core-shell particles in a liquid, (a) A step of providing an aqueous dispersion containing cerium oxide particles or cerium oxide particles doped with at least one metal (M); a step of providing an aqueous solution containing a cerium(III) salt; and a step of providing an aqueous solution of peroxygen, (b) A step of producing a dispersion of cerium-based core-shell particles by contacting the aqueous dispersion with the aqueous solution provided in step (a) while maintaining a temperature within 0°C to 80°C and a pH of 11 or less, A method comprising, wherein at least one of steps (a) and (b) is carried out in the presence of nitrate ions.

2. The method according to claim 1, wherein the aqueous dispersion in step (a) contains at least 3% by weight of cerium oxide particles or cerium oxide particles doped with at least one metal (M), based on the total weight of the aqueous dispersion.

3. The method according to claim 1 or 2, wherein the particles provided to the aqueous dispersion in step (a) are cerium oxide particles.

4. The method according to claim 1 or 2, wherein the particles provided to the aqueous dispersion in step (a) are particles of cerium oxide doped with at least one metal (M) selected from the group consisting of alkali metal elements, alkaline earth metal elements, rare earth elements, actinide elements, transition metal elements and post-transition metal elements from the periodic table.

5. The method according to claim 4, wherein the metal (M) is selected from the group consisting of Zr, Al, La, Pr, Nd, Y, and Sr.

6. The method according to claim 4, wherein the molar ratio M / (M+Ce) of the particles provided to the aqueous dispersion in step (a) is within the range of 0.01 to 0.

15.

7. The method according to claim 1 or 2, wherein the peroxygenated aqueous solution provided in step (a) is a hydrogen peroxide solution.

8. The method according to claim 1 or 2, wherein an aqueous solution containing at least one metal (M') salt is provided in step (a), and the metal (M') is selected from the group consisting of alkali metal elements, alkaline earth metal elements, rare earth elements, actinide elements, transition metal elements and post-transition metal elements from the periodic table.

9. The method according to claim 8, wherein the metal (M') is selected from the group consisting of Zr, Al, La, Pr, Nd, Y, and Sr.

10. The method according to claim 8, wherein the molar ratio M' / (M'+Ce) of the manufactured core-shell particles is within 0.01 to 0.

15.

11. The method according to claim 1 or 2, wherein the temperature in step (b) is maintained at 10°C to 60°C.

12. The method according to claim 1 or 2, wherein the pH in step (b) is maintained between 3 and 11.

13. The method according to claim 1 or 2, wherein the molar ratio of cerium oxide to cerium(III) before commencing step (b) is between 1 / 1 and 100 / 1.

14. The method according to claim 1 or 2, further comprising the steps of (c) acidifying the dispersion of cerium-based core-shell particles and / or washing it (d).

15. The method according to claim 1 or 2, further comprising the step (e) of deaggregating the cerium-based core-shell particles.

16. The method according to claim 1, further comprising the step (f) of drying the cerium-based core-shell particles.

17. A dispersion of cerium-based core-shell particles in a liquid, wherein each cerium-based core-shell particle comprises a core particle manufactured from cerium oxide or cerium oxide doped with at least one metal (M), and a shell consisting of a plurality of nanoparticles of cerium oxide or cerium oxide doped with at least one metal (M'), wherein the nanoparticles are formed on the surface of the core particle, and the ratio of the average particle size of the core-shell particles measured by TEM to the average particle size of the core-shell particles measured by BET is at least 1.

5.

18. A cerium-based core-shell particle powder, wherein each cerium-based core-shell particle comprises a core particle manufactured from cerium oxide or cerium oxide doped with at least one metal (M), and a shell consisting of a plurality of nanoparticles of cerium oxide or cerium oxide doped with at least one metal (M'), wherein the nanoparticles are formed on the surface of the core particle, and the ratio of the average particle size of the core-shell particle measured by TEM to the average particle size of the core-shell particle measured by BET is at least 1.

5.

19. An abrasive composition comprising a dispersion of cerium-based core-shell particles according to claim 17 or a powder of cerium-based core-shell particles according to claim 18.

20. Use of the cerium-based core-shell particle dispersion according to claim 17 or the cerium-based core-shell particle powder according to claim 18 for the preparation of an abrasive composition.

21. A method for removing a portion of a substrate, comprising polishing the substrate with an abrasive composition prepared from a dispersion prepared from the dispersion described in claim 16 or from a dispersion prepared from core-shell cerium oxide particle powder described in claim 18.

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