Aqueous dispersion containing inorganic particles

Abstract

The inorganic particles contained in the aqueous dispersion according to the present invention are composed of an agglomeration of crystalline and amorphous elementary particles, and are spherical and have a smooth surface. The spherical appearance, low crystallinity and narrow particle size distribution of the inorganic particles are more advantageous in reducing scratch defects in the CMP process. In addition, the elementary particles on the surface of the inorganic particles provide more active sites, resulting in an excellent polishing rate, and are therefore advantageous as a next-generation CMP abrasive. In addition, the aqueous dispersion according to the present invention further contains an amino acid, which is adsorbed on the surface of the silicon oxide wafer to strengthen the electrical attraction between the silicon oxide wafer and the inorganic particles, thereby further improving the polishing rate.

Description

[Technical Field]

[0001] The present invention relates to an aqueous dispersion of ceria-based particles suitable as a polishing slurry used in the manufacture of semiconductor devices, and in particular to an aqueous dispersion of ceria-based fine particles suitable for planarizing a film to be polished formed on a substrate by chemical mechanical polishing (CMP). [Background technology]

[0002] Higher performance is being achieved through the miniaturization and densification of semiconductor substrates, wiring boards, and other semiconductor elements. Chemical mechanical polishing (CMP) is used in the semiconductor manufacturing process, and is an essential technology for shallow trench isolation, planarization of interlayer insulating films, and the formation of contact plugs and Cu damascene wiring.

[0003] Generally, CMP polishing slurries are composed of abrasive particles and chemical components. The chemical components accelerate polishing by oxidizing and corroding the target film. Meanwhile, the abrasive particles polish through mechanical action, and colloidal silica, fumed silica, and ceria (CeO2) particles are used as abrasive particles. Ceria particles, in particular, are used in polishing shallow trench isolation processes because they exhibit a particularly high polishing rate for silicon oxide films.

[0004] In the shallow trench isolation process, not only the silicon oxide film but also the silicon nitride film is polished. To facilitate isolation, it is desirable that the polishing rate of the silicon oxide film is fast and that of the silicon nitride film is slow, so the polishing rate ratio (selectivity) is also important.

[0005] Meanwhile, inorganic particles are used as raw materials or final products in a variety of fields, particularly in a wide range of applications such as chemical catalysts, biotechnology, semiconductor processes, and tempered glass processing.

[0006] There are many different processes for synthesizing these inorganic particles. Depending on the manufacturing approach, methods can be divided into bottom-up (assembling atoms) and top-down (reducing large particles), and depending on the synthesis principle, they can be divided into physical, mechanical, and chemical methods. Among chemical methods, the liquid-phase reaction method, which uses a chemical reaction in a liquid phase, is the most widely used method for synthesizing ceramic raw material powders. Known powder manufacturing processes using liquid-phase chemical reactions include the sol-gel method, pyrolysis method, polymerized complex method, precipitation method, and hydrothermal method.

[0007] Generally, inorganic particles grow during synthesis due to the inherent assembly characteristics of atoms, and the final shape of the inorganic particles is thereby crystallized. In other words, since the shape of an inorganic particle is an inherent property of the inorganic particle, it is very difficult to produce inorganic particles of the same components in other shapes.

[0008] For example, ceria (CeO2) crystals have a fluorite particle shape with a hexagonal structure. When ceria particles are used as abrasive particles in the slurry used in the CMP process in semiconductor manufacturing, the angular structure of the ceria particles causes scratches and other defects. Therefore, to solve this problem, methods to manufacture spherical ceria particles are being researched. However, it is extremely difficult to synthesize ceria particles that are uniform in size and well-dispersed while changing the shape of ceria with a hexagonal fluorite structure to a spherical shape.

[0009] In addition, changes in the shape of inorganic particles can cause differences in the specific surface area of ​​the particles, which can affect the degree of chemical reaction on the particle surface. For example, when inorganic particles are used as catalysts, the specific surface area of ​​the particles is directly related to the catalytic active sites, and particles with a larger specific surface area have better reactivity than particles with the same volume.

[0010] Another issue with inorganic particles is their dispersion stability. Nano-sized inorganic particles (hereinafter also referred to as "nanoparticles") are generally thermodynamically unstable in aqueous solutions and have the drawback of being difficult to stably disperse due to their high surface area. Therefore, particle aggregation occurs during storage, which can cause changes in shape and properties. Therefore, a method for improving the dispersibility of nanoparticles is needed.

[0011] Therefore, a technique for controlling the surface charge of nanoparticles is needed to improve their dispersibility. In particular, the dispersion of ceria or silica nanoparticles, which are used as abrasive particles in the slurry during semiconductor CMP processes, in aqueous solutions is extremely important. Therefore, attempts have been made to improve the efficiency of the polishing process by adjusting the pH of the aqueous slurry solution to create an environment that generates stronger attractive forces between the abrasive particles and the film. Summary of the Invention [Problem to be solved by the invention]

[0012] The problem to be solved by the present invention is to provide an aqueous dispersion containing inorganic particles that have a spherical shape, not angular, but have excellent water dispersibility, particularly excellent polishing ability for silicon films, and at the same time cause little scratch damage. [Means for solving the problem]

[0013] In order to solve the above-mentioned technical problems, the present invention provides an aqueous dispersion containing inorganic particles formed by aggregation of a plurality of elementary particles, wherein the elementary particles are a mixture of a crystalline phase and an amorphous phase, and have a crystallinity of 90% or less.

[0014] According to one embodiment, the aqueous dispersion may further comprise an amino acid.

[0015] According to one specific example, the content of the amino acid is 0.01 to 5% by weight, and the content of the inorganic particles is 0.01 to 5% by weight, based on the total weight of the aqueous dispersion.

[0016] According to one specific example, the weight ratio of the inorganic particles to the amino acid is 100:50-200.

[0017] According to one embodiment, the amino acids are one or more selected from the group consisting of tyrosine, phenylalanine, and tryptophan.

[0018] According to one specific example, the elementary particles have a particle size of 1 to 50 nm.

[0019] According to one specific example, the inorganic particles have a density of 3.0 to 5.0 g / ml, an average particle size of 30 to 1000 nm, and a standard deviation of particle size of 20 or less.

[0020] According to one specific example, the inorganic particles have an isoelectric point of pH 5-7, and the pH of the aqueous dispersion is 3-7.

[0021] According to one specific example, the inorganic particles may have a zeta potential of +30 to +50 mV or −30 to −50 mV in a pH 4 aqueous dispersion state.

[0022] According to one embodiment, the inorganic particles consist of an oxide of one or more elements selected from the group consisting of Ga, Sn, As, Sb, Ce, Si, Al, Co, Fe, Li, Mn, Ba, Ti, Sr, V, Zn, La, Hf, Ni, and Zr.

[0023] According to one embodiment, the inorganic particles are CeO2 particles, and Ce 3+ / Ce 4+ Ion ratio is 5 to 60 % is.

[0024] According to one embodiment, the aqueous dispersion is used as a slurry for CMP.

[0025] According to one specific example, the inorganic particles are produced by a method including the steps of: (a) dissolving a self-assembling surfactant in water or a mixed solvent of water and a water-compatible solvent; (b) dissolving or dispersing an inorganic precursor in the solvent before, after, or simultaneously with carrying out step (a) to prepare an inorganic precursor solution; and (c) forming elementary particles having a mixture of a crystalline phase and an amorphous phase within a shell formed by the surfactant through a self-assembly reaction between the inorganic precursor and the surfactant, and agglomerating a plurality of elementary particles to form the inorganic particles.

[0026] According to one embodiment, the inorganic particles contained in the aqueous dispersion have a controlled surface charge by further treating the inorganic particles obtained in step (c) with an acid and a base.

[0027] According to one embodiment, the self-assembling surfactant is one or more selected from cationic surfactants, anionic surfactants, and amphoteric surfactants having a charge capable of forming an ionic bond with the inorganic precursor, and has a functional group capable of undergoing a condensation reaction or a crosslinking reaction.

[0028] According to one embodiment, the functional group capable of undergoing a condensation or crosslinking reaction is one or more selected from the group consisting of an amide group, a nitro group, an aldehyde group, and a carbonyl group.

[0029] According to one embodiment, the self-assembling surfactant is a polymer represented by the following formula 1: Chemical formula 1: [ka]

[0030] In the above formula 1, R1 and R3 are independently a hydrogen atom, C1 to C 10 It is an alkyl group or an alkoxy group, R2 is a substituent of the following chemical formula 2, and n is a number of 2 or more. Chemical formula 2: [ka]

[0031] In Chemical Formula 2, R4 and R5 are independently a hydrogen atom, C1 to C 10 R6 is an alkyl group or an alkoxy group, and R6 is a C1-C 10 an alkylene group or a single covalent bond, * indicates a connecting part.

[0032] According to another aspect of the present invention, there is provided inorganic particles formed by agglomeration of a plurality of elementary particles having a mixture of a crystalline phase and an amorphous phase, which satisfy one or more of the following (i) to (v): (i) the elementary particles have a crystallinity of 90% or less; (ii) The inorganic particles have an aspect ratio (minor axis / major axis) of 0.8 or more; (iii) The particle diameter of the elementary particles is 20 nm or less; (iv) the standard deviation of the particle size of the inorganic particles is 20 nm or less; (v) The inorganic particles are CeO2 particles, and Ce 3+ / Ce 4+ Ion ratio is 40 % That which is more than that. [Effects of the Invention]

[0033] The dispersion according to the present invention uses inorganic particles formed by the aggregation of a plurality of elementary particles having a crystallinity of 90% or less, with a mixture of crystalline and amorphous phases. The inorganic particles have a shape in which the elementary particles form surface protrusions, thereby providing a large specific surface area and facilitating control of the surface charge by adjusting the pH. As a result, the contact area with the silicon film is increased, improving the polishing rate, and the abrasive particles cause less scratch damage, resulting in excellent polishing efficiency when used as a polishing particle in a CMP polishing slurry. Furthermore, when the aqueous dispersion according to the present invention is further added with an amino acid and used as a CMP polishing slurry, the amino acid can be adsorbed onto the silicon oxide wafer surface, strengthening the electrical attraction between the silicon oxide wafer and the inorganic particles, thereby further improving the polishing rate. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a diagram schematically illustrating the shape of inorganic particles according to the present invention. [Figure 2] 1 shows scanning electron microscope images and high-resolution transmission electron microscope (HR-TEM) images of CeO2 particles according to Preparation Example 1 and Reference Example 1. [Figure 3] 1 is a scanning electron microscope image of a sample according to Reference Example 2. [Figure 4] 1 is a histogram showing the particle size distribution of CeO 2 particles of Production Example 1 and Reference Example 1. [Figure 5] 1 shows the results of XRD analysis of CeO2 particles of Production Example 1 and Reference Example 1. [Figure 6] 1 shows HR-TEM images and selected area electron diffraction (SAED) patterns of CeO2 particles according to Preparation Example 1 and Reference Example 1. [Figure 7] 1 shows the results of X-ray photoelectron spectroscopy (XPS) of CeO2 particles according to Production Example 1 and Reference Example 1. [Figure 8] 1 shows the results of measuring the zeta potential of aqueous dispersions of CeO2 particles according to Production Example 1 and Reference Example 1. [Figure 9] 1 shows the results of comparing removal rates of silicon films using slurries of CeO 2 particles according to Preparation Example 1 and Reference Example 1. [Figure 10A] 10A and 10B are atomic force microscope images of a wafer surface after a CMP test was performed using CeO 2 particles according to Preparation Example 1 (A) and particles according to Reference Example 1 (B). [Figure 10B] 10A and 10B are atomic force microscope images of a wafer surface after a CMP test was performed using CeO 2 particles according to Preparation Example 1 (A) and particles according to Reference Example 1 (B). DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will now be described in more detail with reference to various embodiments. However, it should be understood that this is not intended to limit the invention to the particular embodiments, but rather to include any modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0036] Terms such as first, second, A, B, etc. are used to describe various components, but the components are not limited by the terms and are used only to distinguish one component from another.

[0037] The term "and / or" includes any one or inclusive combination of the listed items.

[0038] It should be understood that when a component is described as being "coupled" or "connected" to another component, it may be directly coupled or connected to the other component, or there may be other components in between.

[0039] Unless otherwise specified, singular expressions include plural expressions.

[0040] Terms such as "comprise," "include," or "have" refer to the presence of features, values, steps, operations, components, parts, or combinations thereof stated in the specification, but do not exclude the presence or possibility of other features, values, steps, operations, components, parts, or combinations thereof not stated.

[0041] According to the present invention, by reacting a self-assembling surfactant with an inorganic precursor in an aqueous solvent, inorganic particles having shapes other than those inherent to the atomic assembly properties of inorganic materials can be synthesized. For example, ceria (CeO2) inorganic particles, which can only be formed as angular fluorite hexagonal structures due to their inherent atomic assembly structure, can be produced into spherical particles with protrusions.

[0042] According to the present invention, a crystalline phase and an amorphous phase are mixed, and a plurality of elementary particles having a crystallinity of 90% or less are aggregated to form inorganic particles. The crystallinity can refer to the crystallinity of the elementary particles, but since the elementary particles aggregate to form inorganic particles in the form of nanoclusters, it can also be referred to as the crystallinity of the inorganic particles. The crystallinity also refers to the ratio of the crystalline phase to the total phase. That is, a crystallinity of 90% or less means that the crystalline phase accounts for 90% or less and the amorphous phase accounts for 10% or more. The crystallinity of the elementary particles or inorganic particles is 90% or less, 85% or less, 80% or less, or 75% or less, or 50% or more, 60% or more, 65% or more, or 70% or more.

[0043] Since the crystalline phase and amorphous phase are mixed at a certain ratio, when used as a polishing slurry in the CMP process, it can minimize defects such as scratches and dishing on the substrate.

[0044] Fig. 1 shows a schematic diagram of the structure of inorganic particles according to the present invention. That is, the inorganic particles according to the present invention are composed of an aggregate of very small elementary particles, and the elementary particles have a very unique surface due to the mixture of crystalline and amorphous phases and the formation of surface protrusions.

[0045] As shown in Figure 1, both the inorganic particles and the elementary particles are substantially spherical. Here, "spherical" means that the aspect ratio, expressed as the ratio of the minor axis to the major axis, is 0.8 or more, 0.9 or more, or 0.95 or more, and the reciprocal thereof is 1.2 or less, 1.1 or less, or 1.05 or less. Therefore, when referring to the inorganic particles according to the present invention, they are also referred to as "spherical-projection inorganic particles" or "spherical-projection particles" hereinafter.

[0046] The inorganic particles have spherical protrusions on their surfaces, which has the effect of increasing the specific surface area of ​​the particles per mass. The diameter of the elementary particles forming the spherical protrusions is 2 to 25% of the diameter of the inorganic particles. The particle size of the elementary particles is 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 8 nm or less, 6 nm or less, or 5 nm or less, and is 1 nm or more, 2 nm or more, 3 nm or more, or 4 nm or more. The particle size of the elementary particles is preferably 20 nm.

[0047] The spherical-protrusion inorganic particles used in the aqueous dispersion according to the present invention have a particle size distribution of 30 to 1000 nm and are formed to a uniform size. The size of the spherical-protrusion inorganic particles is preferably 50 nm or more, 100 nm or more, 110 nm or more, or 120 nm or more, and 800 nm or less, 500 nm or less, 300 nm or less, 200 nm or less, or 150 nm or less, based on the number average particle size. The standard deviation of the inorganic particle particle size is 20 nm or less, 18 nm or less, 16 nm or less, 14 nm or less, 12 nm or less, or 11 nm or less.

[0048] FIG. 1 shows a schematic diagram of the structure of ceria particles prepared by Preparation Example 1 of the present invention, showing that CeO2 units (size 0.54 nm) assemble to form elementary particles (particle size 4.4 nm), and the elementary particles assemble to form ceria particles (particle size 108 nm).

[0049] The spherical protrusion inorganic particles used in the aqueous dispersion of the present invention can be produced by a self-assembling reaction between a self-assembling surfactant and an inorganic precursor, resulting in a density of 3.0 to 5.0 g / ml. The density can be measured using the TAP density measurement method (ASTM B527). The density of the inorganic particles is 3.2 g / ml or more, 3.3 g / ml or more, 3.4 g / ml or more, or 3.5 g / ml or more, and 4.5 g / ml or less, or 4.0 g / ml or less.

[0050] According to one embodiment, the primary particles and secondary particles are each independently made of an oxide of one or more elements selected from the group consisting of Ga, Sn, As, Sb, Ce, Si, Al, Co, Fe, Li, Mn, Ba, Ti, Sr, V, Zn, La, Hf, Ni, and Zr. According to a preferred embodiment, the primary particles and secondary particles are made of an oxide of one or more elements selected from the group consisting of cerium (Ce), silicon (Si), and aluminum (Al). According to a preferred embodiment, the inorganic particles may be made of ceria (CeO).

[0051] According to one specific example, the spherical-protruding inorganic particles may have a surface charge of at least +30 mV or -30 mV in an aqueous dispersion state, and in particular, exhibit a high absolute value of surface charge (zeta potential) of +30 to +50 mV or -30 to -50 mV under pH 4. Here, the term "surface charge" is used to mean the same as "zeta potential."

[0052] The isoelectric point of the inorganic particles is pH 5 to 7. Preferably, the isoelectric point is pH 5.5 or higher and 6.5 or lower. The lower the isoelectric point in an aqueous system, the more -OH groups there are on the particle surface, which directly means that there are more active sites on the particle surface, which is advantageous in terms of improving polishing performance in the CMP process.

[0053] When inorganic particles according to the present invention are used as abrasive particles in a slurry in a semiconductor CMP process, they have a spherical shape without corners and contain an amorphous phase, which can compensate for scratch defects, and the various protrusions on the particle surface increase the specific surface area, increasing the probability of contact with the film to be polished, and the change in particle surface properties can improve the polishing rate. For example, in the case of spherical protrusion ceria particles prepared by the method proposed in the present invention, the elemental defects on the particle surface result in more Ce(III) than existing hexagonal fluorite ceria particles, which can improve the polishing rate.

[0054] The ceria particles produced by the present invention contain Ce 3+ / Ce 4+ Ion ratio is 5 to 60 % Ce 3+ / Ce 4+ The higher the ion ratio, the higher the polishing rate. % That's it, 10 % That's it, 20 % That's it, 30 % Over 40 % That's it, 42 % That's it, 44 % or more than 46 % The ion ratio of 40 or more was obtained. % The ion ratio is preferably 60 or more. % Below, 55 % Below or 50 % The following is the result.

[0055] In addition, by utilizing the method of controlling the surface charge of inorganic particles through pH adjustment proposed in the present invention, the surface charge of the spherical-projection inorganic particles can be more easily controlled, and by utilizing this, a pH environment of the aqueous solution that can exhibit optimal interaction between the abrasive particles and the film quality in the CMP process can be created, thereby enabling more efficient and stable polishing.

[0056] The method for producing spherical-projection inorganic particles using a liquid phase synthesis method will be described in more detail below.

[0057] A method for producing spherical protrusion inorganic particles using a liquid phase synthesis method The spherical protruding inorganic particles according to the present invention can be produced by a method comprising the following steps: (a) dissolving a self-assembling surfactant in a solvent; (b) dissolving or dispersing an inorganic precursor in the solvent before, after, or simultaneously with carrying out step (a) to prepare an inorganic precursor solution; and (c) forming elementary particles having a mixture of crystalline and amorphous phases within a shell formed by the surfactant through a self-assembly reaction between the inorganic precursor and the surfactant, and a plurality of elementary particles agglomerating to form inorganic particles.

[0058] In the process for producing spherically protruded inorganic particles using the liquid phase synthesis method proposed in the present invention, the particle formation process in step (c) includes: (i) a step in which elementary particles are formed as an inorganic precursor is reduced together with a self-assembling surfactant; and (ii) a step in which a plurality of elementary particles are aggregated as the self-assembling reaction of the self-assembling surfactant progresses, growing into spherical inorganic particles with protrusions on their surfaces. Although the two steps of inorganic particle formation and surface protrusion formation are described separately, the reactions occur consecutively, so it can also be interpreted that spherically protruded inorganic particles are formed in a single synthesis step.

[0059] inorganic precursor First, a precursor solution of the inorganic material to be prepared is prepared by mixing the inorganic precursor, a self-assembling surfactant, and a solvent. In this case, the surfactant may be dissolved in the solvent first and then the inorganic precursor is added, or the inorganic precursor may be dissolved in the solvent first and then the surfactant is added and mixed, or the inorganic precursor and the self-assembling surfactant may be added to the solvent simultaneously and then mixed. During this process, a weak bond is formed between the inorganic precursor and the surfactant.

[0060] The inorganic precursor is a substance that contains one or more elements selected from the group consisting of Ga, Sn, As, Sb, Ce, Si, Al, Co, Fe, Li, Mn, Ba, Ti, Sr, V, Zn, La, Hf, Ni, and Zr and is capable of forming an oxide. The inorganic precursor used in the present invention is preferably in the form of a compound that can form an ionic bond with a surfactant that is charged in an aqueous solution. For example, the inorganic precursor may be a nitrate, bromide, carbonate, chloride, fluoride, hydroxide, iodide, oxalate, or sulfate, which may be in the form of a hydrate or anhydrous form.

[0061] More specifically, salts containing cerium such as ammonium cerium(IV) nitrate, cerium(III) bromide anhydrous, cerium(III) carbonate hydrate, cerium(III) chloride anhydrous, cerium(III) chloride heptahydrate, cerium(III) fluoride anhydrous, cerium(IV) fluoride, cerium(IV) hydroxide, cerium(III) iodide anhydrous, cerium(III) nitrate hexahydrate, cerium(III) oxalate hydrate, cerium(III) sulfate, cerium(III) sulfate hydrate, cerium(III) sulfate octahydrate, and cerium(IV) sulfate hydrate are used.

[0062] Other examples include silicon precursors such as tetraethyl orthosilicate (TEOS), diethoxydimethylsilane (DEMS), and vinyltriethoxysilane (VTES), titanium precursors having the Ti(OR) structure, zirconium precursors having the Zr(OR) structure, and aluminum precursors having the Al(OR) structure. Here, R represents a functional group that can be hydrated or alcoholized with water or alcohol, such as a lower alkyl group such as a methyl group or an ethyl group. Alternatively, precursors capable of forming oxides of Ga, Sn, As, Sb, Mn, or V can also be used.

[0063] Self-assembling surfactants The surfactants that form self-assembly can be any of anionic, cationic, and amphoteric surfactants, and are capable of bonding with inorganic precursors, dissolving in a solvent, and possessing a functional group that can induce particle formation through a crosslinking reaction and has a positive or negative charge, or both. Examples of such functional groups include amide, nitro, aldehyde, and carbonyl groups.

[0064] According to the present invention, particles with different surface charges can be produced by selecting the type of self-assembling surfactant used in the synthesis reaction. That is, the self-assembling surfactant can be selectively selected depending on the surface charge of the inorganic particles to be produced. For example, when producing negatively charged spherical protrusion inorganic particles, a cationic surfactant can be used. The positively charged portion of the cationic surfactant binds with the ions of the inorganic precursor to form elementary particles. As the reaction progresses, a self-assembled shell is formed, and the inorganic particles grow into a spherical shape with protrusions on the surface. Using a similar principle, an anionic surfactant can be used to produce positively charged spherical protrusion inorganic particles. Thus, to produce inorganic particles with a desired surface charge, a surfactant shell with a specific ionic charge is required. Depending on the type of self-assembling surfactant used, particles with different surface charges can be produced.

[0065] One or more surfactants can be mixed during the synthesis process, if necessary. Among self-assembling materials, surfactants can form crosslinks while dissolved in a solvent, and self-assemble by reacting at a certain temperature for a certain period of time. During this process, the particles grow as the spacing between the particles bound to the surfactant narrows and they aggregate. As the particles grow, the inorganic particles are formed into solid spherical particles surrounded by a shell of self-assembled surfactants, and simultaneously develop a shape with various protrusions on the surface. The protrusions may grow simultaneously on the surface of the spherical particles, or protrusions that have grown independently may appear on the surface of the spherical particles.

[0066] Anionic surfactants include alkylbenzene sulfonates, alkyl sulfates, alkyl ether sulfates, and soaps.

[0067] As cationic surfactants, alkyl quaternary nitrogen compounds, quaternary ammonium compounds such as esterquats, etc. are used.

[0068] In addition, the cationic quaternary ammonium ion group and the anionic carboxylate (-COO - )sulfate(-SO4 2- ) or sulfonate(-SO3 - ) groups are used.

[0069] Not only that, but also Picolinic acid, (carboxymethyl)dimethyl-3-[(1-oxododecyl)amino]propylammonium hydroxide, lauryl betaine, betaine citrate, sodium lauroamphoacetate, sodium hydroxymethylglycinate, (carboxymethyl)dimethyloleylammonium hydroxide, cocamidopropyl betaine, (carboxylate) methyl)dimethyl(octadecyl)ammonium, PEO-PPO block copolymer, anionic siloxanes and dendrimers, poly(sodium 10-undecylenate), poly(sodium 10-undecenylsulfate), poly(sodium polyvinylpyrrolidone, polyvinylalcohol, 2-acrylamide-2-methyl-1-propanesulfonic acid, alkyl methacrylamide, alkyl acrylate, poly(allylamine)-supported Phases, poly(ethyleneimine), poly(N-isopropylacrylamide), n-hydroxysuccinimide, etc. are used.

[0070] Preferably, the self-assembling surfactant is a polymer represented by the following formula 1. In addition, the polymer represented by the following formula 1 can be said to be an amphoteric surfactant having both (+) and (-) properties within the molecule. Chemical formula 1: [ka]

[0071] In the above formula 1, R1 and R3 are independently a hydrogen atom, C1 to C 10 It is an alkyl group or an alkoxy group, n is a number of 2 or more, and R2 is a substituent having the structure of the following chemical formula 2. Chemical formula 2: [ka]

[0072] In Chemical Formula 2, R4 and R5 are independently a hydrogen atom, C1 to C 10 R6 is an alkyl group or an alkoxy group, and R6 is a C1-C 10 an alkylene group or a single covalent bond, * indicates a connecting part.

[0073] The polymer of Formula 1 preferably has a molecular weight of 500 to 100,000 g / mol. Here, the molecular weight is a weight-average molecular weight, and the weight-average molecular weight refers to a polystyrene-equivalent molecular weight measured by a GPC method. The molecular weight is 1,000 or more, 5,000 or more, 10,000 or more, 20,000 or more, or 30,000 or more, and 95,000 or less, 90,000 or less, 85,000 or less, 80,000 or less, 70,000 or less, 60,000 or less, 50,000 or less, or 40,000 or less.

[0074] The amount of the self-assembling surfactant used is 30 to 150 parts by weight per 100 parts by weight of the inorganic precursor. The amount of the surfactant used is 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, or 90 parts by weight or more, and 140 parts by weight or less, 130 parts by weight or less, 120 parts by weight or less, or 110 parts by weight or less, per 100 parts by weight of the inorganic precursor.

[0075] solvent The solvent used in the synthesis reaction of the spherical-projection inorganic particles is water or a mixed solvent of water and a solvent compatible with water.

[0076] According to one embodiment, the water-compatible solvent is one or more selected from the group consisting of alcohol, chloroform, ethylene glycol, propylene glycol, diethylene glycol, glycerol, and butyl glycol.

[0077] When a solvent compatible with water is used in combination with water, the volume ratio of water to compatible solvent is 100:50-200, or 100:60-150, or 100:70-120.

[0078] When adding and dissolving the inorganic precursor and / or the self-assembling surfactant in water or a mixture of water and a water-compatible solvent, it is recommended to use a stirrer and proceed with the reaction only after complete dissolution, as failure to do so may hinder the formation of particles with uniform morphology.

[0079] Synthesis reaction of spherical protrusion inorganic particles In the synthesis of the spherical-protrusion inorganic particles, the inorganic precursor solution prepared above is introduced into a reactor, where a synthesis reaction with a self-assembling surfactant takes place. The synthesis of the spherical-protrusion inorganic particles is carried out at a temperature range of 60 to 250°C for 1 to 24 hours. Preferably, the temperature range is 70°C or higher, 80°C or higher, or 90°C or higher, and 220°C or lower, 200°C or lower, 180°C or lower, or 160°C or lower, for 2 hours or more, 3 hours or more, or 4 hours or more, and 20 hours or less, 10 hours or less, or 8 hours or less.

[0080] After dissolving in a solvent, a self-assembling surfactant reacts with inorganic precursor ions at a certain temperature and time. Here, "self-assembly" refers to the spontaneous formation of an organized structure or morphology as the surfactant's (+) and (-) functional groups combine. For example, if a surfactant contains an amide group in its molecular structure, the nitrogen atom has a (+) functional group and the oxygen atom has a (-) functional group, forming a network structure. At the same time, the particles dissolved in the solvent along with the self-assembling material grow as they aggregate and the spacing between them narrows (nanocluster formation). During this process, the particles grow surrounded by a surfactant shell, forming spherical particles and protrusions on their surfaces. The protrusions may grow simultaneously on the surface of the spherical particles, or they may form as protrusions that grow independently and emerge on the surface of the spherical particles.

[0081] Method for controlling the surface charge of spherically protruded inorganic particles According to the present invention, the inorganic particles obtained by the synthesis reaction can be treated with an acid and / or a base to control the surface charge of the inorganic particles.

[0082] The method for controlling the surface charge of spherically protruding inorganic particles proposed in this invention basically involves controlling the pH of the aqueous dispersion containing the particles. For example, if there are positively charged particles in the aqueous dispersion, the more acidic substance is added, the stronger the positive charge the particles will take on. Conversely, the more basic substance is added, the weaker the surface charge of the particles will gradually become, until they reach a point where they are neutral. If an excessive amount of base is added continuously, they will take on a negative charge. Using this principle, the surface charge of the inorganic particles can be controlled by adjusting the pH of the aqueous solution.

[0083] As an acidic pH adjuster for lowering the pH of an aqueous solution, one or more acidic substances such as phosphoric acid, hydrochloric acid, nitric acid, sulfuric acid, etc. can be used in combination, while as a basic pH adjuster for raising the pH, one or more basic substances such as sodium hydroxide, aqueous ammonia, etc. In this case, accurate pH measurement can only be performed by adjusting the pH and uniformly mixing the aqueous solution using a stirrer.

[0084] The spherical-protruding inorganic particles according to the present invention are inorganic particles having a surface charge of at least +30mV or -30mV, and include a method for controlling the surface charge so that they can exist in a stable state in an aqueous solution and more effectively exhibit surface properties. The particles thus manufactured have excellent bonding strength with various media such as glass and silicon, and can be used as abrasive particles.

[0085] In particular, the inorganic particles according to the present invention have a surface charge of +30 to +50 mV or -30 to -50 mV in an aqueous dispersion at pH 4. That is, the particles have a high absolute value of zeta potential under given pH conditions, which further improves the polishing rate. Here, the term "surface charge" is used to mean the same as "zeta potential."

[0086] According to the present invention, there is provided an aqueous dispersion in which the above-mentioned inorganic particles are dispersed in water and which contains an amino acid as an additive.

[0087] In metal oxide inorganic particles, the metal element bonds with the silicon oxide surface, resulting in polishing. For example, ceria particles polish through Ce-O-Si bonds with the SiO2 surface, but amino acids can increase the polishing rate by strengthening the electrical attraction between the SiO2 wafer and the ceria particles. In other words, amino acids increase the polishing rate by adsorbing to the SiO2 surface without directly reacting with ceria.

[0088] Specific examples of amino acids include glycine, α-alanine, β-alanine, N-methylglycine, N,N-dimethylglycine, 2-aminobutyric acid, norvaline, valine, leucine, norleucine, isoleucine, phenylalanine, proline, sarcosine, ornithine, lysine, taurine, serine, threonine, homoserine, tyrosine, bicine, tricine, 3,5-diiodo-tyrosine, β-(3,4-dihydroxyphenyl)-alanine, and thyroxine. , 4-hydroxy-proline, cysteine, methionine, ethionine, ethionine, cystathionine, cystine, cysteic acid, aspartic acid, glutamic acid, S-(carboxymethyl)-cysteine, 4-aminobutyric acid, asparagine, glutamine, azaserine, arginine, canavanine, citrulline, delta-hydroxy-lysine, creatine, histidine, 1-methyl-histidine, 3-methyl-histidine, tryptophan, and the like.

[0089] Among these, aromatic amino acids such as tyrosine, phenylalanine, and tryptophan are more desirable because they have a strong tendency to be adsorbed onto the surface of the silicon oxide wafer without reacting directly with the ceria particles.

[0090] The amino acid content is 0.01 to 5 wt% based on the total weight of the aqueous dispersion. If the amino acid content is less than 0.01 wt%, it will not be effective in increasing the polishing rate by adsorbing to the SiO2 surface, while if it exceeds 5 wt%, it will undesirably form a thick passivation layer on the SiO2 surface. The amino acid content, based on the total weight of the dispersion, is, for example, 0.05 wt% or more, 0.06 wt% or more, 0.07 wt% or more, 0.08 wt% or more, and 4 wt% or less, 3 wt% or less, 2 wt% or less, 1 wt% or less, or 0.5 wt% or less.

[0091] The content of the inorganic particles is 0.01 to 5 wt % based on the total weight of the aqueous dispersion. Preferably, it is 0.05 wt % or more, 0.06 wt % or more, 0.07 wt % or more, 0.08 wt % or more, and 4 wt % or less, 3 wt % or less, 2 wt % or less, 1 wt % or less, or 0.5 wt % or less. If it is less than 0.01 wt %, the polishing effect on the SiO2 wafer surface is minimal, and if it exceeds 5 wt %, the polishing action is undesirably inhibited by the presence of excessive inorganic particles.

[0092] Additionally, an aqueous dispersion with optimal polishing efficiency can be prepared by adjusting the weight ratio of amino acid to inorganic particles. For example, 50 to 200 parts by weight of amino acid can be used per 100 parts by weight of inorganic particles. Desirably, the amino acid content is 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, or 90 parts by weight or more, 180 parts by weight or less, 160 parts by weight or less, 140 parts by weight or less, or 120 parts by weight or less per 100 parts by weight of inorganic particles. If the amino acid content is below this range, the effect of adding the amino acid on improving polishing efficiency is minimal. If the amino acid content exceeds this range, an undesirable thick amino acid passivation layer is formed on the SiO2 surface.

[0093] Furthermore, the inventors have found through their research that the polishing rate of the aqueous dispersion containing inorganic particles according to the present invention can be further increased when the pH of the aqueous dispersion is adjusted to a range of 3 to 7 after adding an amino acid. The pH of the aqueous dispersion is 3 or more, 3.5 or more, 4 or more, 4.2 or more, 4.4 or more, and 7 or less, 6.5 or less, 6 or less, 5.5 or less, 5 or less, or 4.9 or less.

[0094] A pH adjuster can be used to adjust the pH of the aqueous dispersion to a desired value. The pH adjuster used may be any acid or alkali, or any inorganic or organic compound. The pH adjuster may be used alone or in combination of two or more. When a substance having a pH adjusting function (e.g., various acids) is used as one of the various additives described above, the additive may be used as at least a part of the pH adjuster.

[0095] The aqueous dispersion according to the present invention may further contain various additives depending on its intended use. For example, when used as a polishing slurry, it may contain various additives that can further improve the polishing rate, such as organic acids, nitrile compounds, and other chelating agents.

[0096] Specific examples of organic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, etc. Instead of or in combination with an organic acid, a salt such as an alkali metal salt of an organic acid can also be used.

[0097] Specific examples of the nitrile compound include acetonitrile, aminoacetonitrile, propionitrile, butyronitrile, isobutyronitrile, benzonitrile, glutarodinitrile, and methoxyacetonitrile.

[0098] Specific examples of chelating agents include iminodiacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, N,N,N-trimethylenephosphonic acid, ethylenediamine-N,N,N',N'-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol ether diaminetetraacetic acid, ethylenediamine orthohydroxyphenylacetic acid, ethylenediamine disuccinic acid (SS form), N-(2-ethyl carboxylate)-L-aspartic acid, β-alaninediacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid, and 1,2-dihydroxybenzene-4,6-disulfonic acid.

[0099] The aqueous dispersion according to the present invention also contains an oxidizing agent. Usable oxidizing agents include hydrogen peroxide, peracetic acid, perbenzoic acid, tert-butyl hydroperoxide, potassium permanganate, potassium dichromate, potassium iodate, potassium periodate, nitric acid, iron nitrate, perchloric acid, hypochlorous acid, potassium ferricyanide, ammonium persulfate, and ozone water. These oxidizing agents can be used alone or in combination of two or more.

[0100] The aqueous dispersion of the present invention may further contain other components, as necessary, such as water, abrasive grains, a metal corrosion inhibitor, a polishing accelerator, a surfactant, an oxoacid, a preservative, a mildew inhibitor, a reducing agent, a water-soluble polymer, and an organic solvent for dissolving poorly soluble organic substances.

[0101] The following examples will further illustrate the structure and operation of the present invention. However, these examples are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way. Furthermore, explanations of content that can be fully understood by those skilled in the art will be omitted.

[0102] Production of spherical protrusion ceria particles <Production Example 1> 2 g of Poly(N-isopropylacrylamide) (Aldrich, Mw: 30,000) as a self-assembling surfactant was added to 160 ml of a 100:100 volumetric mixture of ethylene glycol (99%) and water and stirred with a magnetic stirrer. After confirming complete dissolution, 2 g of Aldrich's cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was added and dissolved to prepare a cerium precursor solution.

[0103] The cerium precursor solution was placed in a temperature-maintaining liquid-phase reactor, and the synthesis reaction was carried out for approximately 165 minutes at a temperature range of 90 to 140°C. After the reaction was completed, the resulting ceria particle solution was centrifuged at 4000 rpm for 1 hour and 30 minutes to separate the precipitate, which was then washed with water (H2O) three times to obtain the resulting ceria particles (hereinafter also referred to as "BOC100").

[0104] <Production Example 2> 2.4 g of Poly(N-isopropylacrylamide) (Aldrich, Mw: 85,000) with a different molecular weight than that used in Preparation Example 1 was added to an aqueous solution of 2.4 g of cerium chloride in 180 ml of water, and the mixture was stirred at 70 to 90°C for 6 hours to react. After that, the mixture was separated and washed in the same manner as in Preparation Example 1, and ceria particles with spherical protrusions were obtained.

[0105] <Reference Example 1> Fluorite hexagonal structured CeO2 particles (manufacturer: Solvay, product name: HC60) were prepared.

[0106] <Reference Example 2> 8g of Aldrich's cerium nitrate hexahydrate (Ce(NO3)3·6H2O) was added to 160ml of water as a cerium precursor, and dissolved to create a cerium precursor solution, which was then stirred with a magnetic stirrer. After confirming complete dissolution, 4g of sodium hydroxide (NaOH) was added to create a basic solution. The mixture was stirred for approximately 1 hour to prepare CeO2 particles synthesized by the precipitation method.

[0107] Morphological and structural analysis The morphology and structure of the ceria particles of Preparation Examples 1 and 2 and Reference Example 1 were analyzed using a scanning electron microscope (FE-SEM, JEOL JSM 7401F), a high-resolution transmission electron microscope (HR-TEM, JEM-2100F), an X-ray diffraction analyzer (Rigaku SmartLab SE X-ray diffractometer with Cu Kα radiation), and an X-ray photoelectron spectrometer (XPS, Thermo ESCALAB 250).

[0108] 2A and 2B are SEM and TEM images showing the shape of the ceria particles (BOC100) produced in Production Example 1. The images show that the ceria particles of Production Example 1 are round and spherical with soft surfaces.

[0109] On the other hand, according to Figures 2D and 2E, the ceria particles (HC60) of Reference Example 1 exhibit a characteristic shape of fluorite crystals having sharp, angular edges and crystal lattice planes.

[0110] Figure 3 is an SEM image of particles prepared by the precipitation method in Reference Example 2. It can be seen that the particles have irregular shapes and are aggregated.

[0111] 4 is a histogram showing the particle size distribution of the ceria particles of Production Example 1 and Reference Example 1. The ceria particles (BOC100) of Production Example 1 have an average particle size of 108 nm and a standard deviation of 10.3, while the ceria particles (HC60) of Reference Example 1 have an average particle size of 117 nm and a standard deviation of 22.5. The fact that the standard deviation of the ceria particles (BOC100) of Production Example 1 is much smaller than that of the ceria particles (HC60) of Reference Example 1 confirms that the ceria particles of Production Example 1 are monodisperse.

[0112] The spherical and monodisperse ceria particles according to the present invention have a rounded and gentle surface without sharp edges, which is more desirable in terms of reducing defects, scratches, or dishing flaws during the CMP process.

[0113] As shown in Figure 1, the ceria particles prepared in Preparation Example 1 have a unique surface because they are composed of very small nanoparticles (approximately 4.4 nm in diameter). In other words, the inorganic particles used in the aqueous dispersion according to the present invention are formed as aggregates of nanoparticles or units, but in the case of Preparation Example 1, CeO2 atoms (0.54 nm) aggregate to form nanoparticles (4.4 nm), and the nanoparticles aggregate to form inorganic particles (108 nm).

[0114] Figure 5 shows the XRD analysis results for the ceria particles of Preparation Example 1 and Reference Example 1. Both particles have peaks at 28.55°, 33.08°, 47.47°, 56.33°, 59.08°, 69.4°, 76.7°, and 79.07°, which correspond to the (111), (200), (220), (311), (222), (400), (331), and (420) lattice planes, which are characteristic of fluorite crystals. However, the peaks of the ceria particles (BOC100) of Preparation Example 1 are much broader, indicating a lower crystallinity than the HC60 particles of Reference Example 1.

[0115] To compare the crystallite size, the crystallite size was calculated based on the (111) peak. The average crystallite size (Lc) was calculated using the Scherrer equation, which uses the full-width-of-half-maximum (FWHM) (Monshi, A., M.R. Foroughi, and M.R. Monshi, Modified Scherrer Equation to Estimate More Accurately Nano-Crystallite Size Using XRD. World Journal of Nano Science and Engineering, 2012.02(03):pp.154-160).

number

[0116] In the above formula, λ is the X-ray wavelength (nm), β is the FWHM (radian), and K is a constant (0.9) related to the crystal shape.

[0117] The crystallinity of the particles was calculated from the area under the XRD peak using the Ruland-Vonk method (Iulianelli, GCV, et al., Influence of TiO2 nanoparticles on the thermal, morphological, and molecular characteristics of PHB matrix, Polymer Testing, 2018.65:pp.156-162).

number

[0118] In the above formula, Ic is the sum of the areas under the crystalline peaks and Ia is the sum of the amorphous halo areas.

[0119] As summarized in Table 1, the crystal size (Lc) of the ceria particles in Production Example 1 was 4.4 nm, and the crystallinity Xc was 70.5%. The nanoparticle size of 4.4 nm in the schematic diagram in Figure 1 is based on these XRD analysis results. [Table 1]

[0120] On the other hand, the particles of Reference Example 1 had a crystal size (Lc) of 45.5 nm and a crystallinity (Xc) of 95.8%. That is, the particles of Preparation Example 1 according to the present invention had a much smaller crystal size and a much lower crystallinity than the particles of Reference Example 1. This indicates that the particles according to the present invention contain a significant amount of amorphous ceria. The amorphous phase is much softer than the crystalline phase and is therefore desirable for reducing scratches and dishing defects during the CMP process.

[0121] Figures 6B and 6C show the HR-TEM image and selected area electron diffraction (SAED) pattern of the particles from Preparation Example 1. The particles from Preparation Example 1 have a d-spacing of 3.10 Å, which corresponds to the (111) lattice plane of ceria. The phase sizes obtained by delineating the phase boundaries in Figure 6C range from 2 to 5 nm. This corresponds to the crystal size of 4.4 nm shown in Figure 1. The diffused SAED pattern, shown in Figure 6D, indicates that the particles from Preparation Example 1 are a mixture of crystalline and amorphous phases (represented by spots and rings).

[0122] 6E to 6G show that the particles of Reference Example 1 have a large crystalline phase represented by unidirectional (111) lattice planes surrounded by boundaries, indicating that the particles of Reference Example 1 are mostly composed of one or two single crystalline phases, which is supported by the crystal size of 45.5 nm and the crystallinity of 95.8%.

[0123] 7 shows the results of elemental analysis of Ce 3d and O 1s by X-ray photoelectron spectroscopy (XPS) for the particles of Production Example 1 and Reference Example 1, as graphs A and B, respectively. 5 / 2 and C3 3d 3 / 2 v0, v1, v2, v3 and v4 are split into Ce 3d 5 / 2 u0, u1, u2, u3 and u4 belong to Ce 3d 3 / 2 (Thromat, N., M. Gautier-Soyer, and G. Bordier, Formation of the CeY2O3 interface: an in situ XPS study, Surface science, 1996. 345(3): pp. 290-302). The v0, v2, u0, and u2 peaks are due to the Ce 3+ The characteristics of the ions are as follows: v1, v3, v4, u1, u3 and u4 peaks are Ce 4+ It exhibits ionic properties (Zhang, C. and J. Lin, Visible-light induced oxo-bridged Zr IV-O-Ce III redox center in tetragonal ZrO 2 -CeO 2 solid solution for degradation of organic pollutants, Physical Chemistry Chemical Physics, 2011.13(9):pp.3896-3905).

[0124] Ce 3+ and Ce 4+ The concentration was calculated as follows: [Ce 3+ ]=v0+v2+u0+u2 [Ce 4+ ]=v1+v3+v4+u1+u3+u4

[0125] Table 2 shows specific information for XPS peak assignments. [Table 2]

[0126] According to the results, the particles of Production Example 1 contain Ce. 3+ The calculated concentration was 32.6%, which was higher than the 28.3% of the particles of Reference Example 1. 3+ / Ce 4+ The ratio of the particles in Production Example 1 was 48.4 % and the particles of Reference Example 1 were 39.5 % The Ce contained in the particles of Production Example 1 3+ It can be seen that the concentration is even higher.

[0127] In aqueous systems, Ce present on the surface of ceria particles 3+ The ions promote the dissociation of H2O to form hydroxyl groups (OH groups) on the CeO2 surface. The hydroxyl groups on the particle surface not only act as active sites but also assist in the physical adsorption of other substances, especially in the CMP process, by forming Ce-O-Si bonds.

[0128] The hydroxyl group concentrations of the particles of Production Example 1 and Reference Example 1 were measured by O 1s XPS analysis (see FIG. 7B). The peak at 528.83 eV is due to lattice oxygen ions O 2- The peak at 530.33 eV is the surface hydroxyl ion OH - (See Table 2) (Van den Brand, J., et al., Correlation between hydroxyl fraction and O / Al atomic ratio as determined from XPS spectra of aluminum oxide layers. Surface and Interface Analysis: An International Journal devoted to the development and application of techniques for the analysis of surfaces, interfaces and thin films, 2004. 36(1): pp. 81-88).

[0129] The particles of Production Example 1 have 69.4% OH on the surface. -which is 47.3% of the OH content of the particles of Reference Example 1. - In addition, the particles of Production Example 1 have a surface containing 30.6% O. 2- This is because the particles of Reference Example 1 have 52.7% O 2- This result indicates that the particles of Production Example 1 have a much higher concentration of Ce than the particles of Reference Example 1. 3+ Therefore, the surface OH - The concentration is Ce 3+ As a result, the particles of Preparation Example 1, which have more Ce-OH active sites than the particles of Reference Example 1, can promote the formation of Ce-O-Si bonds between the SiO2 substrate and the CeO2 particles during the CMP process.

[0130] density The densities of the CeO2 inorganic particles of Production Examples 1 and 2 and Reference Examples 1 and 2 were measured by the TAP density measurement method (ASTM B527). [Table 3]

[0131] Zeta potential measurement The zeta potential was measured using a Malvern zeta potential analyzer (Nano ZS).

[0132] FIG. 8 shows the results of measuring the zeta potential of the spherical-projection CeO2 particle dispersion liquid of Production Example 1 after adjusting the pH to 2 to 10 using a nitric acid solution (acidic pH adjuster) and ammonia water (basic pH adjuster).

[0133] As shown in Figure 5, the slurries of Preparation Example 1 and Reference Example 1 have a high positive charge of about 60 mV at pH 2, and the positive charge gradually weakens as the pH increases. At pH 4 to 4.5, which corresponds to the CMP process conditions, both slurries have a zeta potential of >30 mV, maintaining a stable dispersion state due to electrostatic repulsion. On the other hand, silica particles have a negative zeta potential in the wide range of pH 2 to 10, especially around pH 4, which generates electrostatic attraction due to the opposite charges between the silica substrate and the ceria particles. The isoelectric point (IEP) of the particles of Preparation Example 1 in deionized water is roughly around pH 6, while that of Reference Example 1 is around pH 9. This is because the particles of Preparation Example 1 have no OH group as shown in XPS analysis. - This is thought to be due to the high concentration.

[0134] Polishing performance test Slurries were prepared by dispersing the ceria particles of Preparation Example 1 and Reference Example 1 in deionized water without any other additives at concentrations of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0 and 3 wt % respectively.

[0135] The CMP test was performed for 1 minute using a GnP POLI-400L under the following conditions: slurry flow rate: 150 ml / min, fixed head pressure: 4 psi. The initial SiO2 thickness on the bare wafer was 30,000 Å, and the removal rate (RR) was measured using a refractometer (ST4000-DLX) (see Figure 9).

[0136] It is known that a slurry containing particles of Reference Example 1 generally exhibits the highest polishing performance when the concentration is 0.3 wt %. Accordingly, when the particle concentration is 0.3 wt %, the RR was compared, and it was measured that Preparation Example 1 had an RR of 3546 Å / min and Reference Example 1 had an RR of 2197 Å / min.

[0137] Furthermore, the particles of Reference Example 1 showed a gradual increase in RR until the concentration increased to 2 wt%, but decreased at 3 wt%. On the other hand, the particles of Preparation Example 1 showed an increase in RR as the concentration increased, achieving an RR of 8904 Å / min at 3 wt%. This is a high value, 233% of the RR of 3823 Å / min achieved by the particles of Reference Example 1 at 2 wt%. This indicates that the particles of Reference Example 1 are saturated at about 2 wt%, but the particles of Preparation Example 1 are not saturated even up to 3 wt%. This result is due to the presence of Ce on the particle surface. 3+ ions and OH - This is thought to be due to the high concentration of ions.

[0138] 10A and 10B show the atomic force microscope images of wafer surfaces after CMP tests using slurries containing 0.3 wt % of the particles of Preparation Example 1 and Reference Example 1 dispersed in deionized water. The CMP test using the slurry containing the particles of Reference Example 1 resulted in deep, large scratches on the wafer surface (FIG. 10B), which can be confirmed by the large number of particles remaining on the surface after the process. In contrast, the slurry containing the particles of Preparation Example 1 did not result in any scratches on the wafer surface even after the CMP process, and the amount of remaining ceria particles was significantly smaller (FIG. 10A).

[0139] These results demonstrate that the inorganic particles produced by the method of the present invention are uniform in size and that the surface charge can be effectively controlled by pH. Furthermore, a CMP test using the slurry showed superior polishing performance compared to commercially available slurries using fluorite hexagonal ceria particles, and also significantly reduced scratch defects on the wafer surface.

[0140] Manufacture of aqueous dispersion containing amino acids Example 1 0.1 wt % (based on the weight of the deionized water) of the ceria particles of Preparation Example 1 was dispersed in deionized water at room temperature, and then nitric acid was added to adjust the pH to 4, 4.2, 4.4, 4.6, and 4.8 to prepare aqueous dispersions.

[0141] Example 2 0.1 wt% of the ceria particles of Preparation Example 1 were dispersed in deionized water at room temperature, and 1000 ppm (0.1 wt%) of tyrosine (based on the weight of the deionized water) was added. Nitric acid was added to the aqueous dispersion to adjust the pH to 4, 4.2, 4.4, 4.6, 4.8, and 5, respectively, to prepare aqueous dispersions.

[0142] The results of measuring the polishing performance using the aqueous dispersions of Examples 1 and 2 are the same as those in Table 4. [Table 4]

[0143] From the above results, it can be seen that the polishing rate of the aqueous dispersion of Example 2 is higher than that of Example 1 and is affected by pH. It can also be seen that the best performance is shown when the pH is 4.6.

[0144] Example 3 From the results in Table 4, it was confirmed that the polishing rate was best when the pH was 4.6. Therefore, aqueous dispersions were prepared with the pH fixed at 4.6 and the amount of amino acid added varied to 0, 600, 800, and 1000 ppm, and the polishing performance was tested. [Table 5]

[0145] The results in Table 5 show that the polishing rate was improved compared to when tyrosine was not added. In particular, the highest polishing rate was observed when the amount added was about 0.1 wt % (1000 ppm). The aqueous dispersion according to a preferred embodiment of the present invention contains an amino acid along with the specific inorganic particles of the present invention. When used as a CMP polishing slurry, the amino acid is adsorbed onto the silicon oxide wafer surface, strengthening the electrical attraction between the silicon oxide wafer and the inorganic particles, thereby further improving the polishing rate.

[0146] Although the present invention has been described above with reference to the preferred embodiments, various modifications and variations may be made by those skilled in the art. Such modifications and variations are within the scope of the present invention as long as they do not deviate from the technical concept of the present invention. Therefore, the scope of the present invention should be determined by the following claims.

Claims

1. An aqueous dispersion containing inorganic particles formed by aggregation of a plurality of elementary particles and an amino acid, the elementary particles are a mixture of a crystalline phase and an amorphous phase, and have a crystallinity of 90% or less; The inorganic particles are CeO ２ containing particles, The inorganic particles have a density of 3.0 to 5.0 g / ml, an average particle size of 30 to 1000 nm, and a standard deviation of particle size of 20 nm or less.

2. 2. The aqueous dispersion according to claim 1, wherein the content of the amino acid is 0.01 to 5 wt % and the content of the inorganic particles is 0.01 to 5 wt %, based on the total weight of the aqueous dispersion.

3. 2. The aqueous dispersion according to claim 1, wherein the weight ratio of the inorganic particles to the amino acid is 100:50 to 200.

4. The aqueous dispersion according to claim 1 , wherein the amino acid is one or more selected from the group consisting of tyrosine, phenylalanine, and tryptophan.

5. 2. The aqueous dispersion according to claim 1, wherein the elementary particles have a particle size of 1 to 50 nm.

6. 2. The aqueous dispersion according to claim 1, wherein the inorganic particles have an isoelectric point of pH 5 to 7, and the aqueous dispersion has a pH of 3 to 7.

7. 2. The aqueous dispersion according to claim 1, wherein the inorganic particles have a surface charge with a zeta potential of +30 to +50 mV or −30 to −50 mV in an aqueous dispersion state at a pH of 4.

8. The inorganic particles include Ce. ３＋ / Ce ４＋ The aqueous dispersion according to claim 1, wherein the ionic ratio is 5 to 60%.

9. The aqueous dispersion according to claim 1 , wherein the aqueous dispersion is a slurry for CMP.

10. An aqueous dispersion containing inorganic particles formed by aggregation of a plurality of elementary particles and an amino acid, the elementary particles are a mixture of a crystalline phase and an amorphous phase, and have a crystallinity of 90% or less; The inorganic particles are CeO ２ 1. A method for producing inorganic particles contained in an aqueous dispersion comprising the particles, the method comprising: (a) dissolving a self-assembling surfactant in water or a mixture of water and a solvent compatible with water; (b) before, after, or simultaneously with carrying out step (a), dissolving or dispersing an inorganic precursor in the solvent to prepare an inorganic precursor solution; (c) forming elementary particles having a mixture of a crystalline phase and an amorphous phase in a shell formed by the surfactant through a self-assembly reaction between the inorganic precursor and the surfactant, and a plurality of elementary particles agglomerating to form inorganic particles; (d) dispersing the inorganic particles in water.

11. The inorganic particles contained in the aqueous dispersion are The method according to claim 10, further comprising treating the inorganic particles obtained in step (c) with an acid and a base to produce inorganic particles having a controlled surface charge.

12. The method of claim 10, wherein the self-assembling surfactant is one or more selected from cationic surfactants, anionic surfactants, and amphoteric surfactants having a charge capable of bonding with the inorganic precursor, and has a functional group capable of undergoing a condensation reaction or a crosslinking reaction.

13. The method according to claim 12, wherein the functional group capable of a condensation reaction or a crosslinking reaction is one or more selected from the group consisting of an amide group, a nitro group, an aldehyde group, and a carbonyl group.

14. 11. The method of claim 10, wherein the self-assembling surfactant has the structure of Formula 1: Chemical formula 1: 【Chemistry 1】 In the above formula 1, R １ and R ３ are independently a hydrogen atom, C １ ~C １０ is an alkyl group or an alkoxy group, and R ２ is a substituent of the following chemical formula 2, where n is a number equal to or greater than 2: Chemical formula 2: 【Chemistry 2】 In Chemical Formula 2, R ４ and R ５ are independently a hydrogen atom, C １ ~C １０ is an alkyl group or an alkoxy group, and R ６ is C １ ~C １０ an alkylene group or a single covalent bond, ＊ indicates a connecting part.

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