Cerium oxide particles, their manufacturing process, and their use in chemical mechanical polishing.

Abstract

The present invention provides a roughness index (RI) of at least 5. [0010] TIFF2024513308000012.tif13170, its manufacturing process and its use in chemical mechanical polishing applications.

Description

[Technical Field]

[0001] This invention relates to cerium oxide particles and abrasive compositions, particularly their use as components of chemical mechanical polishing (CMP) compositions. The invention also relates to a method for preparing cerium oxide particles.

[0002] More specifically, the present invention provides cerium oxide particles having good polishing properties when implemented in a CMP composition, and a method for preparing such particles that is simple, economical, and easily implementable on an industrial scale. [Background technology]

[0003] Cerium oxide is commonly used for polishing applications. The development of the electronics industry necessitates the use of increasingly diverse compositions for polishing various components, such as disks or dielectric compounds. These compositions, typically commercialized in the form of dispersions, must exhibit certain 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 stability and ease of use, these dispersions typically contain submicron-sized particles, i.e., generally less than 300 nm. In addition, the presence of particles that are too fine in these dispersions reduces their polishing ability, while particles that are too large can contribute to an increase in defects.

[0004] Therefore, several types of cerium oxide particles specifically formulated for CMP applications are known from the prior art.

[0005] International Publication No. 2015 / 197656 discloses metal-doped cerium oxide particles.

[0006] International Publication No. 08043703 discloses a suspension of cerium oxide particles in a liquid phase, wherein the particles are secondary particles having an average size of at most 200 nm, and the secondary particles include primary particles having an average size of at most 100 nm and a standard deviation of at most 30% of the average size of the primary particles.

[0007] International Publication No. 2015 / 091495 discloses a suspension of cerium oxide particles in a liquid phase, wherein the particles include secondary particles, the secondary particles having an average size D50 in the 105-1000 nm range, with a standard deviation in the 10-50% range of the average size of the secondary particles, and the primary particles having an average size D50 in the 100-300 nm range, with a standard deviation in the 10-30% range of the average size of the primary particles.

[0008] There is still room for improvement to provide new cerium oxide particles that exhibit improved performance in CMP, and a method for preparing such particles that is simple, economical, and easily implementable on an industrial scale. [Overview of the project]

[0009] The applicant has created novel cerium oxide particles that can solve the aforementioned problems.

[0010] One subject of the present invention is therefore cerium oxide particles exhibiting a roughness index (RI) of at least 5. More specifically, the roughness index of the particles is given by the following formula:

number

number

[0011] To the best of the inventors' knowledge, the roughness index achieved by the particles of this subject matter of the present invention is higher than that of cerium oxide particles of the prior art. This is thought to contribute to achieving greater polishing efficiency when such particles are used as abrasive particles in a CMP composition or process.

[0012] The present invention relates to a process for producing cerium oxide particles, comprising at least the following steps: (a) Under an inert atmosphere, (i) an aqueous solution of a base, (ii) NO3 - Ce III , optionally Ce IV (iii) a step of contacting an aqueous solution containing and an organic acid or a salt thereof to obtain a mixture, wherein the organic acid is a substituted or unsubstituted aryl or heteroarylcarboxylic acid; (b) A step of subjecting the mixture obtained in step (a) to heat treatment; (c) Optionally, a step of acidifying the mixture obtained in step (b); (d) Optionally, a step of washing the solid material obtained at the end of step (b) or (c) with water; (e) Optionally, subject the solid material obtained at the end of step (d) to mechanical treatment to deaggregate the particles. This also relates to processes that include this.

[0013] Advantageously, this process allows for the preparation of the cerium oxide particles of the present invention in a simple manner.

[0014] The present invention also relates to cerium oxide particles obtainable or obtained by the above-described process, a dispersion of the cerium oxide particles of the present invention in a liquid medium, the use of said dispersion or the particles of the present invention for preparing a CMP composition, a CMP composition comprising said dispersion or said particles, a polishing process in which said CMP composition is used to remove a part of a substrate, and a semiconductor substrate polished thereby.

Brief Description of Drawings

[0015] [Figure 1-4] An image of the particles of the present invention observed by transmission electron microscopy. [Figure 5] An image of conventional cerium oxide particles observed by transmission electron microscopy.

Embodiments for Carrying Out the Invention

[0016] The photograph was obtained with a JEM-1400 (JEOL) apparatus operating at 120 kV.

[0017] In the present disclosure, the expression "comprised in ~" should be understood to include both ends.

[0018] In relation to the particles of the present invention, the term "cerium oxide" means cerium (IV) oxide, also known as ceric oxide. Cerium oxide generally has a purity of at least 99.8% by weight based on the weight of the oxide. Cerium oxide is generally crystalline ceric oxide. Some impurities other than cerium may be present in the oxide. The impurities may be derived from the raw materials or starting materials used in the preparation process of cerium oxide. The total proportion of impurities is generally less than 0.2% by weight relative to cerium oxide. Residual nitrates are not considered impurities in the present application.

[0019] The expression "dispersion" in relation to the dispersion of cerium oxide particles of the present invention refers to a system consisting of fine, submicron-sized solid cerium oxide particles stably dispersed in a liquid medium, wherein the particles may optionally contain residual amounts of bound or adsorbed ions, such as nitrates or ammonium ions.

[0020] Herein, the present invention will be described in more detail according to its different embodiments.

[0021] As previously described, one subject of the present invention is cerium oxide particles exhibiting a roughness index (RI) of at least 5. More specifically, the roughness index of the particles of the present invention may be in the range of 5 to 20, particularly 6 to 17, and more particularly 7 to 14.

[0022] The particle roughness index (RI) is given by the following formula:

number

number

[0023] TEM size is the effective average size of the particles, such as being measured with respect to a large number of particles, at least 80, preferably at least 90, and more preferably at least 100, in order to obtain statistical analysis. Measurement is usually performed with respect to one or more photographs of the same sample of cerium oxide particles. The particles retained are preferably those whose images are clearly visible in the photographs. The number of particles retained corresponds to preferably at least 80.0%, more particularly at least 90.0%, and even more particularly at least 95.0% of the particles. Some particles may exhibit slight defects on their surface and / or on one of their corners. These particles can nevertheless be retained for statistical analysis.

[0024] Specific surface area (SSA) can be measured for cerium oxide particle 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)". Specific surface area can be measured automatically using Micromeritics' TriStar 3000 instrument, according to the manufacturer's guidelines. Prior to measurement, the powder sample should be degassed under static air by heating to a maximum temperature of 210°C to remove adsorbed chemical species.

[0025] Measuring the BET specific surface area allows for the calculation of the SSA size according to the formula given above. Given an SSA, the formula gives the theoretical size of cerium(IV) oxide particles, assuming the particles are spherical. The ratio TEM size / SSA size is therefore an indicator of particle roughness. A higher ratio indicates higher particle roughness. Cerium oxide particles with an increased roughness index are thought to have improved efficiency when used in polishing processes such as CMP.

[0026] According to one preferred embodiment, the cerium oxide particles of the present invention are substantially cubic. To the best of our knowledge, the combination of the specific roughness index of the particles and their specific cubic morphology contributes to achieving improved results in CMP using them compared to conventional cerium oxide particles (i.e., not cubic and not exhibiting the required roughness index).

[0027] To recognize their cubic shape, the particles can be observed in photographs obtained by TEM (transmission electron microscopy). The photographic observation must be performed with a size and apparatus that allows for clear identification of the particle shape. Therefore, it is preferable to clearly identify each particle individually. The size used for observation may be, for example, in the range of 25K to 250K. 150K magnification may be used. The Jeol Model JEM 1400, operating at 120kV, is particularly suitable.

[0028] Images obtained by TEM of such "cubic" cerium oxide particles show four sides of substantially equal length. Furthermore, the images are such that adjacent sides of these four sides form angles that are substantially equal to 90°. The angles formed by adjacent sides of these four sides may fall within the range of 88°–92° or 89°–91°.

[0029] According to one embodiment, the cerium oxide particles of the present invention may exhibit an average size of 30 nm or more. In many cases, the particle size is 70 nm or more. The cerium oxide particles of the present invention may exhibit an average size of 500 nm or less. In many cases, the particle size is 300 nm or less, particularly 150 nm or less. In one embodiment, the cerium oxide particles of the present invention may exhibit an average size that falls within 120-300 nm, particularly 125-270 nm, more particularly 130-250 nm, and even more particularly 140-240 nm. The average size is preferably measured from a TEM image. This measurement is preferably performed for at least 80 particles.

[0030] According to one embodiment, the cerium oxide particles of the present invention may exhibit a specific surface area when contained in a concentration of 35-100 m² / g, more particularly 38-80 m² / g, more particularly 40-70 m² / g, and even more particularly 42-60 m² / g. The specific surface area is measured with respect to the powder by nitrogen adsorption using the Brunauer-Emmett-Teller method (BET method).

[0031] In certain embodiments, the specific surface area is 15–100 m² / g, and more particularly 22–70 m² / g.

[0032] According to one embodiment, the cerium oxide particles of the present invention may exhibit a carbon weight ratio in the range of 0.001% to 5% by weight, particularly 0.1% to 2.5% by weight. The carbon trace may be the footprint of a synthesis method used to prepare the particles, which requires a specific organic acid. Dosing of elemental carbon can be performed by using a carbon and sulfur analyzer such as the Horiba EMIA 320-V2.

[0033] In another embodiment, the present invention provides cerium oxide particles exhibiting a roughness index RI of at least 2.4, particularly at least 3.5, where RI is given by formula:

number

number

[0034] In certain embodiments, the roughness index RI in this embodiment is less than 5.

[0035] To the best of our knowledge, the carbon weight ratio in the cerium oxide particles according to this embodiment contributes to the compatibility of the cerium oxide particles with other components of dispersions and polishing compositions commonly used for CMP applications.

[0036] The cerium oxide particles according to this embodiment are generally characterized in that the particles are substantially cubic. The characterization of the cubic shape, particle size, and specific surface area in this embodiment is as described above.

[0037] The present invention relates to a process for producing cerium oxide particles, comprising at least the following steps: (a) Under an inert atmosphere, (i) an aqueous solution of a base, (ii) NO3 - Ce III , optionally Ce IV (iii) a step of contacting an aqueous solution containing and an organic acid or a salt thereof to obtain a mixture, wherein the organic acid is a substituted or unsubstituted aryl or heteroarylcarboxylic acid; (b) A step of subjecting the mixture obtained in step (a) to heat treatment; (c) Optionally, a step of acidifying the mixture obtained in step (b); (d) Optionally, a step of washing the solid material obtained at the end of step (b) or (c) with water; (e) Optionally, a step of subjecting the solid material obtained at the end of step (d) to mechanical treatment to deflocculate the particles also relates to a process comprising.

[0038] It is advantageous to use high purity salts and components. The purity of the salt can be at least 99.5% by weight, more particularly at least 99.9% by weight.

[0039] An aqueous solution (i) of a base is used 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 also be pre-degassed by bubbling with an inert gas.

[0040] The amount of base used in step (a), expressed as the molar ratio base / total Ce, is preferably included in the range of 4 to 10, preferably 5 to 8.

[0041] NO3 - , Ce III and optionally Ce IV An aqueous solution (ii) containing is used in step (a). Nitrate or cerium can be particularly used for preparing the solution. When Ce IV is present in the aqueous solution, the Ce IV / total Ce molar ratio is preferably included in the range of 1 / 500000 to 1 / 4000. This molar ratio can particularly be 1 / 6000 to 1 / 4000. The Ce IV / total Ce molar ratio used in the examples can be used.

[0042] <s An aqueous cerium nitrate solution obtained by the reaction of nitric acid and cerium sesquioxide can be used in the preparation method. Cerium sesquioxide is the Ce III cation to Ce IVIt is conventionally prepared by the reaction of a solution of cerium mononitrate with an aqueous ammonia solution in the presence of aqueous hydrogen peroxide for conversion to a cation. It is also particularly advantageous to use a solution of cerium nitrate obtained by a method of electrochemical oxidation of a solution of cerium mononitrate, as disclosed in French Patent No. 2570087. A solution of cerium nitrate obtained according to the teachings of French Patent No. 2570087 may exhibit an acidity of approximately 0.6 N.

[0043] Ce IV If present in step (a), it may be provided by a salt which may be cerium nitrate IV or cerium ammonium nitrate.

[0044] NO3 - / Ce III The amount of nitrate ions in the aqueous solution used in step (a), expressed as a molar ratio, is generally 1 / 3 to 5 / 1. The acidity of the aqueous solution used in step (a) is preferably in the range of 0.8 N to 12.0 N.

[0045] A specific organic acid (iii) or a salt thereof, which is a substituted or unsubstituted aryl or heteroarylcarboxylic acid, is used in step (a). The substituted or unsubstituted aryl group is preferably a substituted or unsubstituted phenyl group. The substituted or unsubstituted heteroaryl group is preferably a substituted or unsubstituted heterophenyl group.

[0046] According to one embodiment, the organic solvent is substituted. Examples of substituents include halogens, lower alkyls (i.e., alkyl groups having fewer than six carbon atoms), aryls, alkoxys, hydroxyls, aminos, alkylaminos, arylaminos, alkylsulfinyls, alkylsulfonyls, arylsulfinyls, and arylsulfonyls. A preferred substituent is a hydroxyl group. One or more substituents may be present in the aryl or heteroaryl group. Preferably, only one substituent is present, preferably a hydroxyl group. According to another alternative embodiment, the organic acid is unsubstituted.

[0047] According to one embodiment, the organic acid is a heteroarylcarboxylic acid. Examples of heteroatom portions of the heteroaryl group include, in particular, S, O, and / or N atoms. One or more heteroatoms may constitute the heteroaryl group. The heteroaryl group preferably has at least one N atom, more preferably only one N atom. A pyridyl group is a suitable heteroaryl group within the framework of the present invention. According to another alternative embodiment, the organic acid is an arylcarboxylic acid.

[0048] According to one particular embodiment, the organic acid is an unsubstituted heteroarylcarboxylic acid, preferably an unsubstituted heterophenylcarboxylic acid. Examples of heteroatom portions of the unsubstituted heteroaryl group include S, O, and / or N atoms. One or more heteroatoms may be part of the heteroaryl group. The heteroaryl group preferably has at least one N atom, more preferably only one N atom, and preferably a pyridyl group. Picolinic acid is particularly suitable as an unsubstituted heteroarylcarboxylic acid for carrying out the process of the present invention.

[0049] According to another specific embodiment, the organic acid is a substituted arylcarboxylic acid, preferably a substituted phenylcarboxylic acid. Examples of substituents on the aryl group include halogens, lower alkyls (i.e., alkyls having fewer than six carbon atoms), aryls, alkoxys, hydroxyl, aminos, alkylaminos, arylaminos, alkylsulfinyls, alkylsulfonyls, arylsulfinyls, and arylsulfonyls. A preferred substituent on the aryl group is hydroxyl. One or more substituents may be present in the aryl group. Preferably, only one substituent is present, preferably a hydroxyl group. Among suitable substituted arylcarboxylic acids for carrying out the process of the present invention is 4-hydroxybenzoic acid.

[0050] Ammonium salts can be cited as suitable salts of the above-mentioned organic acids.

[0051] According to one embodiment, the organic acid is in the form of an aqueous solution. The concentration of the organic acid in the aqueous solution may be, for example, in the range of 1 to 20% by weight, particularly 2 to 10% by weight, and more particularly 3 to 7% by weight. According to another embodiment, a pure, i.e., undiluted organic acid is used.

[0052] The components (i), (ii), and (iii) that are brought into contact in step (a) to form the mixture can be brought into contact in any order. In particular according to one embodiment, an aqueous solution of a base (i) and an organic acid (iii) are brought into contact with each other, and the resulting mixture is brought into contact with an aqueous solution (ii) containing cerium nitrate. In such a case, since the solution of the base (i) is already in the form of an aqueous solution, a pure (i.e., undiluted) organic acid (iii) can be used. The contact of the mixture of (i) and (iii) with (ii) may preferably involve adding (ii) to the mixture under stirring and / or bubbling of an inert gas.

[0053] In an alternative embodiment, an aqueous solution (ii) containing cerium nitrate and an aqueous solution (i) of a base are brought into contact with each other, and the resulting mixture is brought into contact with an organic acid (iii). In such a case, the organic acid (iii) can be used in the form of an aqueous solution. The contact between (ii) and (i) may preferably involve adding (ii) to (i) under stirring and / or inert gas bubbling.

[0054] The organic acid (iii) can be used at concentrations ranging from 0.11 to 245 mmol / L, particularly 0.5 to 150 mmol / L, more particularly 1 to 100 mmol / L, and more particularly 2 to 50 mmol / L, relative to the total volume of the mixture obtained in step (a). This range is particularly suitable for forming well-defined particles.

[0055] The amount of free oxygen in the mixture should be carefully controlled and minimized. For this purpose, one or more of the components (i), (ii), and (iii) used, and / or the resulting mixture, 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.

[0056] Step (a) includes reacting components (i), (ii), and (iii). Step (a) is preferably carried out under an inert atmosphere, particularly in either a closed reactor or a semi-closed reactor with sweeping of an inert gas. Contact is generally carried out in a stirred reactor.

[0057] Process (a) is generally carried out at a temperature that falls within the range of 5°C to 50°C. This temperature can be 20 to 25°C.

[0058] Step (b) is the heat treatment of the reaction medium obtained at the end of the preceding step. This may include (i) a heating sub-step and (ii) a maturation sub-step.

[0059] The heating sub-step (i) may generally include heating the medium to a temperature in the range of 75°C to 95°C, and more particularly 80°C to 90°C.

[0060] The aging sub-process (ii) may include maintaining the medium at a temperature within 75°C to 95°C, more particularly 80°C to 90°C. The duration of the aging sub-process (ii) is 2 to 20 hours. As a rule of thumb, the higher the temperature of the aging process, the shorter the duration of the aging sub-process. For example, if the temperature of the aging sub-process is 85°C to 90°C, e.g., 88°C, the duration of the aging sub-process may be 2 to 15 hours, more particularly 4 to 15 hours. If the temperature of the aging sub-process is 75°C to 85°C, e.g., 80°C, the duration of the aging sub-process may be 15 to 30 hours.

[0061] During step (b), Ce IIICe IV Oxidation occurs. This process can also be carried out in an inert atmosphere, and the description of this atmosphere for process (a) also applies here. Similarly, the heat treatment can be carried out in a stirred reactor.

[0062] In step (c), the mixture obtained at the end of step (b) may be optionally acidified. This step (c) may be carried out using nitric acid. The reaction mixture may be acidified with HNO3 to a pH lower than 3.0, more particularly in the range of 1.5 to 2.5.

[0063] 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 nitrates in the dispersion and allows for obtaining the target conductivity. 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.

[0064] In step (e), the solid material obtained at the end of step (d) may be subjected to mechanical treatment to deaggregate the particles. This step may 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 oxide particles are subjected to mechanical deaggregation. According to another embodiment, the cerium oxide particles are not subjected to mechanical deaggregation.

[0065] After step (e), the solid material may be dried to obtain cerium oxide particles in powder form. After step (e), water or a mixture of water and a miscible liquid organic compound may be added to obtain a dispersion of cerium oxide particles in a liquid medium.

[0066] One further object of the present invention is cerium oxide particles that are available or obtained by the process described above.

[0067] The present invention also relates to dispersions of cerium oxide particles in a liquid medium. The dispersion comprises the cerium oxide particles of the present invention and a liquid medium. The liquid medium may be water or a mixture of water and a water-miscible organic liquid. The water-miscible organic liquid should not cause the particles to precipitate or aggregate. The water-miscible organic liquid may be, for example, alcohols such as isopropyl alcohol, ethanol, 1-propanol, methanol, and 1-hexanol; ketones such as acetone, diacetone alcohol, and methyl ethyl ketone; or 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).

[0068] The proportion of cerium oxide particles in the dispersion can range from 1.0% by weight to 40.0% by weight, and this proportion is expressed as the weight of cerium oxide particles divided by the total weight of the dispersion. This proportion can range from 10.0% by weight to 35.0% by weight.

[0069] The dispersion may exhibit conductivity less than 300 μS / cm, more particularly less than 150 μS / cm, and even more particularly less than 100 μS / cm or 50 μS / cm. Conductivity is measured with a Horiba 9382-10D conductivity meter.

[0070] The cerium oxide particles or dispersions of the present invention can be used to prepare abrasive compositions, and more particularly CMP compositions. They are used as components of abrasive compositions, and more particularly CMP compositions.

[0071] The present invention also relates to CMP compositions. CMP compositions (i.e., chemical mechanical polishing compositions) are polishing compositions used for the selective removal of 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 used to fill features and provide a smooth surface for subsequent levels of metallization and processing.

[0072] Substrates that can be polished with the polishing composition or CMP composition may be, for example, silicon dioxide type substrates, glass, semiconductors, or wafers.

[0073] The particles or dispersions of the present invention can be used to prepare CMP compositions. The present invention therefore also relates to CMP compositions comprising cerium oxide particles or dispersions, such as those defined above.

[0074] Polishing compositions or CMP compositions typically contain different components other than cerium oxide particles. Polishing compositions include the following components: - Abrasive particles other than cerium oxide particles of the cerium oxide particles or dispersion of the present invention; and / or - pH adjusters; and / or - Surfactants; and / or - Rheology control agents containing viscosity improvers and coagulants; and / or - Additives selected from nonionic polymers, cationic polymers, anionic polymers, quaternary ammonium compounds, silanes, sulfonated monomers, phosphonated monomers, acrylates, starches, cyclodextrins, and combinations thereof. It may include one or more of the following.

[0075] The pH of abrasive compositions is generally between 1 and 6. Typically, abrasive compositions have a pH of 3.0 or higher. Also, typically, the pH of abrasive compositions is 6.0 or lower.

[0076] The present invention relates to a method for removing a portion of a substrate, which includes the step of polishing the substrate with an abrasive composition such as the one described above.

[0077] Finally, this invention relates to a semiconductor polished by this method.

[0078] If any disclosure of a patent, patent application, or publication incorporated herein by reference conflicts with the description of this application to such an extent that it obscures certain terms, the description herein shall prevail.

[0079] Herein, the present invention is described further in the examples without the intention of limiting it. [Examples]

[0080] Example 1 A cerium nitrate solution was prepared by mixing 111.3 2.87 M cerium(III) nitrate, 16.80 g of 68% HNO3, and 3.27 g of deionized water. This solution was placed in a 250 mL semi-closed container. Subsequently, cerium(IV) nitrate equivalent to a cerium IV / total cerium molar ratio of 1 / 5000 was added to the cerium nitrate solution. An aqueous ammonia solution was prepared by mixing 74.48 g of 13.35 M aqueous ammonia and 620.90 g of deionized water. This solution was placed in a 1 L semi-closed reactor with a jacket and bubbled with N2 gas at a flow rate of 210 L / h under stirring for 1 hour. The above cerium nitrate solution was added to the aqueous ammonia solution after approximately 30 minutes under the same stirring and N2 bubbling conditions. An organic acid solution was prepared by adding 1.04 g of picolinic acid to 23 g of deionized water, bubbling with N2 gas for 1 hour, and then adding it to the reactor. The temperature of the reaction mixture was raised to 85°C in approximately 1 hour and maintained under the same stirring conditions for approximately 4 hours with a reduced N2 bubbling flow rate (less than 10 L / h). The reaction mixture was cooled and acidified to pH 2 using 68% HNO3. After decantation, the supernatant was removed, and NH4OH was added to the slurry to reach pH 8.

[0081] The reaction mixture was washed with deionized water by centrifugation. The washing process was repeated, and the conductivity of the washing solution was less than 0.04 mS / cm.

[0082] The BET specific surface area measured by nitrogen adsorption was 53.9 m² / g. For approximately 80 particles representative of the suspension, the suspension was observed by TEM, and each particle was counted and measured. The average particle size was 157 nm, and the standard deviation was 23 nm, corresponding to 14% of the average particle size. The SSA size, determined as described herein, was equal to 15, giving a roughness index RI of 10.1, also determined as described herein. The carbon percentage was measured with %C = 1.78 wt%. TEM images of the obtained cubic coarse particles are reported in Figure 1.

[0083] Example 2 A cerium nitrate solution was prepared by mixing 113.4 g of 2.87 M cerium(III) nitrate, 16.81 g of 68% HNO3, and 3.29 g of deionized water. This solution was placed in a 250 mL semi-closed container. Subsequently, cerium(IV) nitrate equivalent to a cerium IV / total cerium molar ratio of 1 / 5000 was added to the cerium nitrate solution. An aqueous ammonia solution was prepared by mixing 75.58 g of 13.35 M aqueous ammonia, 641.44 g of deionized water, and 1.05 g of picolinic acid. This solution was placed in a 1 L semi-closed reactor with a jacket and bubbled with N2 gas at a flow rate of 210 L / h under stirring for 1 hour. The above cerium nitrate solution was added to the aqueous ammonia solution after approximately 30 minutes under the same stirring and N2 bubbling conditions. The reaction mixture was heated to 85°C over approximately 1 hour and maintained under the same stirring conditions for approximately 4 hours with a reduced N2 bubbling flow rate (less than 10 L / h). The reaction mixture was cooled and acidified to pH 2 using 68% HNO3. After decantation, the supernatant was removed, and NH4OH was added to the slurry to reach pH 8.

[0084] The reaction mixture was washed with deionized water by centrifugation. The washing process was repeated, and the conductivity of the washing solution was less than 0.04 mS / cm.

[0085] The BET specific surface area, measured by nitrogen adsorption, was 43.1 m² / g. For approximately 80 particles representative of the suspension, the suspension was observed by TEM, and each particle was counted and measured. The average particle size was 212.6 nm, and the standard deviation was 125 nm, corresponding to 60% of the average particle size. The SSA size, determined as described herein, was equal to 19, giving a roughness index RI of 11.0, also determined as described herein. The carbon percentage was measured with %C = 1.19 wt%.

[0086] The TEM images of the obtained cubic coarse particles are shown in Figure 2.

[0087] Example 3 A cerium nitrate solution was prepared by mixing 222.4 g of 2.87 M cerium(III) nitrate with 33.9 g of 68% HNO3. This solution was placed in a 250 mL semi-closed container. Then, cerium(IV) nitrate equivalent to a cerium IV / total cerium molar ratio of 1 / 5000 was added to the cerium nitrate solution. An aqueous ammonia solution was prepared by mixing 133.3 g of 15 M aqueous ammonia, 1298.5 g of deionized water, and 19.9 g of picolinic acid. This solution was placed in a 2 L semi-closed reactor with a jacket and bubbled with N2 gas at a flow rate of 100 L / h under stirring for 1 hour. The above cerium nitrate solution was added to the aqueous ammonia solution after approximately 30 minutes under the same conditions of stirring and N2 bubbling. The temperature of the reaction mixture was raised to 80°C in approximately 1 hour and maintained under the same conditions of stirring with a reduced N2 bubbling flow rate (less than 10 L / h) for approximately 4 hours. The reaction mixture was cooled and acidified to pH 2 using 68% HNO3. After decantation, the supernatant was removed, and NH4OH was added to the slurry to reach pH 8.

[0088] The reaction mixture was washed with deionized water by centrifugation. The washing process was repeated five times, and the conductivity of the washing solution was less than 0.04 mS / cm.

[0089] The BET specific surface area, measured by nitrogen adsorption, was 72 m² / g. For approximately 200 particles representative of the suspension, the suspension was observed by TEM, and each particle was counted and measured. The average particle size was 71 nm, and the standard deviation was 19 nm, corresponding to 27% of the average particle size. The SSA size, determined as described herein, was equal to 12, giving a roughness index RI of 6.1, also determined as described herein. The carbon percentage was measured with %C = 4.6 wt%. TEM images of the obtained cubic coarse particles are reported in Figure 3.

[0090] Example 4 A cerium nitrate solution was prepared by mixing 222.4 g of 2.87 M cerium(III) nitrate with 33.9 g of 68% HNO3. This solution was placed in a 250 mL semi-closed container. Then, cerium(IV) nitrate equivalent to a cerium IV / total cerium molar ratio of 1 / 5000 was added to the cerium nitrate solution. An aqueous ammonia solution was prepared by mixing 134 g of 15 M aqueous ammonia, 1296.7 g of deionized water, and 1 g of picolinic acid. This solution was placed in a 2 L semi-closed reactor with a jacket and bubbled with N2 gas at a flow rate of 100 L / h under stirring for 1 hour. The above cerium nitrate solution was added to the aqueous ammonia solution after approximately 30 minutes under the same conditions of stirring and N2 bubbling. The temperature of the reaction mixture was raised to 80°C in approximately 1 hour and maintained under the same conditions of stirring with a reduced N2 bubbling flow rate (less than 10 L / h) for approximately 4 hours. The reaction mixture was cooled and acidified to pH 2 using 68% HNO3. After decantation, the supernatant was removed, and NH4OH was added to the slurry to reach pH 8.

[0091] The reaction mixture was washed with deionized water by centrifugation. The washing process was repeated five times, and the conductivity of the washing solution was less than 0.04 mS / cm.

[0092] The BET specific surface area, measured by nitrogen adsorption, was 25 m² / g. For approximately 150 particles representative of the suspension, the suspension was observed by TEM, and each particle was counted and measured. The average particle size was 108 nm, and the standard deviation was 41 nm, corresponding to 33% of the average particle size. The SSA size, determined as described herein, was equal to 30, giving a roughness index RI of 3.6, also determined as described herein. The carbon percentage was measured with %C = 0.8 wt%. TEM images of the obtained cubic coarse particles are reported in Figure 4.

[0093] Example 5 A cerium nitrate solution was prepared by mixing 224.4 g of 2.87 M cerium(III) nitrate with 33.9 g of 68% HNO3. This solution was placed in a 250 mL semi-closed container. Then, cerium(IV) nitrate equivalent to a cerium IV / total cerium molar ratio of 1 / 5000 was added to the cerium nitrate solution. An aqueous ammonia solution was prepared by mixing 132 g of 15.1 M aqueous ammonia, 1298.9 g of deionized water, and 2.2 g of 4-hydroxybenzoic acid. This solution was placed in a 2 L semi-closed reactor with a jacket and bubbled with N2 gas at a flow rate of 100 L / h under stirring for 1 hour. The above cerium nitrate solution was added to the aqueous ammonia solution after approximately 30 minutes under the same stirring and N2 bubbling conditions. The reaction mixture was heated to 80°C over approximately 1 hour and maintained under the same stirring conditions for approximately 4 hours with a reduced N2 bubbling flow rate (less than 10 L / h). The reaction mixture was cooled and acidified to pH 2 using 68% HNO3. After decantation, the supernatant was removed, and NH4OH was added to the slurry to reach pH 8.

[0094] The reaction mixture was washed with deionized water by centrifugation. The washing process was repeated five times, and the conductivity of the washing solution was less than 0.04 mS / cm.

[0095] The BET specific surface area, measured by nitrogen adsorption, was 37 m² / g. For approximately 200 particles representative of the suspension, the suspension was observed by TEM, and each particle was counted and measured. The average particle size was 94 nm, and the standard deviation was 53 nm, corresponding to 56% of the average particle size. The SSA size, determined as described herein, was equal to 23, giving a roughness index RI of 4.2, also determined as described herein. The carbon percentage was measured with %C = 1.12 wt%.

[0096] Comparative Example 1 A cerium nitrate solution was prepared by mixing 139.1 g of 2.87 M cerium(III) nitrate, 21.1 g of 68% HNO3, and 4 g of deionized water. This solution was placed in a 250 mL semi-closed container. Then, cerium(IV) nitrate equivalent to a cerium IV / total cerium molar ratio of 1 / 5000 was added to the cerium nitrate solution. An aqueous ammonia solution was prepared by mixing 100.5 g of 13.35 M aqueous ammonia and 795.5 g of deionized water. This solution was placed in a 1 L semi-closed reactor with a jacket and bubbled with N2 gas at a flow rate of 210 L / h under stirring for 1 hour. The above cerium nitrate solution was added to the aqueous ammonia solution after approximately 30 minutes under the same conditions of stirring and N2 bubbling. The temperature of the reaction mixture was raised to 85°C in approximately 1 hour and maintained under the same conditions of stirring with a reduced N2 bubbling flow rate (less than 10 L / h) for approximately 4 hours. The reaction mixture was cooled and acidified to pH 2 using 68% HNO3. After decantation, the supernatant was removed, and NH4OH was added to the slurry to reach pH 8.

[0097] The reaction mixture was washed with deionized water by centrifugation. The washing process was repeated, and the conductivity of the washing solution was less than 0.04 mS / cm.

[0098] The BET specific surface area, measured by nitrogen adsorption, was 16.8 m² / g. For approximately 150 particles representative of the suspension, the suspension was observed by TEM, and each particle was counted and measured. The average particle size was 87 nm, and the standard deviation was 21 nm, corresponding to 24% of the average particle size. The SSA size, determined as described herein, was equal to 50, giving a roughness index RI of 1.7, also determined as described herein. TEM images are reported in Figure 5.

Claims

1. A method for producing cerium oxide particles, comprising the following steps: (a) in an inert atmosphere, (i) aqueous solution of a base, (ii) NO ３ － Ce ＩＩＩ , optionally Ce ＩＶ A step of contacting an aqueous solution containing (iii) an organic acid or a salt thereof to obtain a mixture, wherein the organic acid is a substituted or unsubstituted arylcarboxylic acid, or a substituted or unsubstituted heteroarylcarboxylic acid; (b) A step of subjecting the mixture obtained in step (a) to heat treatment; (c) optionally, a step of acidifying the mixture obtained in step (b); (d) Optionally, washing the solid material obtained at the end of step (b) or (c) with water; (e) Optionally, subject the solid material obtained at the end of step (d) to a mechanical treatment to deaggregate the cerium oxide particles. A method that includes this.

2. The method according to claim 1, wherein the organic acid is a substituted or unsubstituted heteroarylcarboxylic acid.

3. The method according to claim 1 or 2, wherein the organic acid is picolinic acid.

4. The method according to any one of claims 1 to 3, wherein the heat treatment in step (b) is carried out at a temperature in the range of 75°C to 95°C.

5. Cerium oxide particles, wherein the particles are substantially cubic and exhibit a roughness index RI of at least 2.4, and RI is given by the formula: [Math 3] (In the formula, "TEM size" refers to the average size of at least 80 particles as measured in a transmission electron microscope image, and "SSA size" is given by the following formula: [Math 4] (In the formula, SSA represents the BET specific surface area of ​​the particles as measured by nitrogen adsorption, ρ represents the density of cerium(IV) oxide, and is 7.22 g / cm³) ３ (Equivalent to) (This shows the theoretical average size of the aforementioned particles.) Cerium oxide particles characterized by being defined by and having a carbon weight ratio in the range of 0.001% to 5% by weight.

6. The cerium oxide particle according to claim 5, characterized in that the image of the particle obtained by TEM shows four sides having substantially the same length, and adjacent sides of the four sides form an angle substantially equal to 90°.

7. 15-100m ２ The cerium oxide particles according to claim 5 or 6, characterized by showing the specific surface area contained in / g.

8. 22-70m ２ The cerium oxide particles according to claim 7, characterized by showing the specific surface area contained in / g.

9. Cerium oxide particles according to any one of claims 5 to 8, characterized in that they have an average size of 30 to 500 nm, and the average size is measured from a TEM image.

10. The cerium oxide particles according to claim 9, characterized in that they show the average size contained in the 120-300 nm range, and the average size is measured from a TEM image.

11. The method according to any one of claims 1 to 4, wherein the cerium oxide particles are as defined in any one of claims 5 to 10.

12. A dispersion of cerium oxide particles according to any one of claims 5 to 10 in a liquid medium.

13. The dispersion according to claim 12, exhibiting an electrical conductivity of less than 300 μS / cm.

14. A method for preparing an abrasive composition using cerium oxide particles according to any one of claims 5 to 10 or a dispersion according to claim 12 or 13.

15. An abrasive composition comprising cerium oxide particles according to any one of claims 5 to 10 or a dispersion according to claim 12 or 13.

16. A method for removing a portion of a substrate, comprising polishing the substrate with the polishing composition described in claim 15.

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