When the inorganic particles according to the present disclosure are used as polishing particles in a slurry in a semiconductor CMP process, scratch defects can be compensated because they are spherical without sharp angles and contain an amorphous phase, and the numerous protrusions on the surface of the particle increase the specific surface area, which not only increases the probability of contact with the film to be polished, but also improves the polishing speed due to changes in the surface properties of the particle. For example, in the case of spherical protruding ceria particles prepared by the method proposed in the present disclosure, Ce(III) increases compared to existing hexagonal fluorite ceria particles due to elemental defects on the particle surface, thereby improving the polishing speed.

The ceria particles prepared according to the present disclosure may have a Ce³⁺/Ce⁴⁺ ion ratio of 5 to 60. The higher the Ce³⁺/Ce⁴⁺ ion ratio, the higher the polishing speed, and according to the present disclosure, an ion ratio of 5 or more, 10 or more, 20 or more, 30 or more, 40 or more, 42 or more, 44 or more, or 46 or more may be obtained, and is preferably 40 or more. The ion ratio may be 60 or less, 55 or less, or 50 or less.

In addition, by using the method of controlling the surface charge of inorganic particles through pH control proposed in the present disclosure, the surface charge of spherical protruding inorganic particles may be more easily controlled, and by using this to create an aqueous solution pH environment that may achieve optimal interaction between the polishing particles and the film material in the CMP process, more efficient and stable polishing is possible.

Hereinafter, a method for preparing spherical protruding inorganic particles using a liquid phase synthesis method will be described in more detail.

Method for Preparing Spherical Protruding Inorganic Particles Using a Liquid Phase Synthesis Method

The spherical protruding inorganic particles according to the present disclosure may be prepared by a method including the following steps.

- (a) dissolving a self-assembling surfactant in a solvent;
- (b) preparing an inorganic precursor solution by dissolving or dispersing an inorganic precursor in the solvent before, after, or simultaneously with step (a); and
- (c) forming elementary particles having a mixed phase of a crystalline phase and an amorphous phase in a shell formed by the surfactant through a self-assembly reaction of the inorganic precursor and the surfactant, and forming inorganic particles by aggregation of a plurality of the elementary particles.

In the process of preparing spherical protruding inorganic particles using the liquid-phase synthesis method proposed in the present disclosure the particle formation process of step (c) includes (i) a step in which elementary particles are formed as the inorganic precursor is reduced with a self-assembling surfactant; and (ii) a step in which a plurality of elementary particles aggregate and grow into spherical inorganic particles with protrusions on the surface as the self-assembly reaction of the self-assembling surfactant progresses. Although the two steps of inorganic particle formation and surface protrusion formation are explained separately, since the reactions occur continuously, it may be seen that spherical protruding inorganic particles are formed through one synthesis step.

Inorganic Precursor

First, a precursor solution of the inorganic material to be prepared is prepared. It is prepared by mixing an inorganic precursor, a self-assembling surfactant, and a solvent, and at this time, the surfactant may first be dissolved in the solvent and then the inorganic precursor may be added, the inorganic precursor may first be dissolved in the solvent and then mixed with the surfactant, or the inorganic precursor and the self-assembling surfactant may be simultaneously added to the solvent and mixed. In this process, a weak bond is formed between the inorganic precursor and the surfactant.

Here, the inorganic precursor includes 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 a material capable of forming an oxide. The inorganic precursor used in the present disclosure is preferably in the form of a compound capable of ionic bonding with a charged surfactant in an aqueous solution. For example, it may be may be a nitrate, bromide, carbonate, chloride, fluoride, hydroxide, iodide, oxalate or sulfate, which may be in hydrated or anhydrous form.

More specifically, for example, 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, cerium(IV) sulfate hydrate may be used.

As another example, silicone precursors such as tetraethyl orthosilicate (TEOS), diethoxydimethylsilane (DEMS) and vinyltriethoxysilane (VTES), titanium precursors with the Ti(OR)₄structure, zirconium precursors with the Zr(OR)₄structure, aluminum precursors with the Al(OR)₄structure, etc., may be used. Here, R refers to a functional group that may be hydrated or alcoholized with water or alcohol, and may be, for example, a lower alkyl group such as a methyl group or an ethyl group. In addition, it is also possible to use a precursor that may form oxides of Ga, Sn, As, Sb, Mn, or V.

Self-Assembling Surfactant

Surfactants that form self-assembly may include anionic, cationic, and amphoteric surfactants, and may possess a functional group that may combine with an inorganic precursor, dissolve in a solvent, have a (+) or (−) charge, or both, and may induce a particle formation reaction through a cross-linking reaction. Examples of such functional groups include amide group, nitro group, aldehyde group, carbonyl group, etc.

According to the present disclosure, particles with different surface charges may be prepared depending on the type of self-assembling surfactant used in the synthesis reaction. In other words, the self-assembling surfactant may be selectively used depending on the surface charge of the inorganic particles to be synthesized and prepared. For example, when it is to prepare spherical protruding inorganic particles with a (−) charge, a cationic surfactant may be used. The (+) charged part of the cationic surfactant combines with the ion of the inorganic precursor to form elementary particles, and as the reaction progresses, a self-assembling shell is formed, and the inorganic particles within it grow into a spherical shape with protrusions on the surface. According to the same principle, when it is to prepare spherical protruding inorganic particles with an opposite (+) charge, an anionic surfactant may be used. As such, in order to prepare inorganic particles with the target surface charge, a surfactant shell with specific ionic properties is required, and it is possible to prepare particles with different surface charges depending on the type of self-assembling surfactant used.

In addition, if necessary, one or more surfactants may be mixed and used during the synthesis process. Among self-assembling materials, surfactants may form crosslinks while dissolving in a solvent, and self-assemble as the reaction progresses at a certain temperature and over a certain time. At this time, the gap between the elementary particles bound to the surfactant becomes closer and the particles grow as they aggregate, and inorganic particles are formed into solid spherical particles as they grow surrounded by a shell of self-assembled surfactant, and at the same time grow into a shape containing numerous protrusions on the surface. Protrusions may grow simultaneously on the surface of a spherical particle, or independently grown protrusions may appear on the surface of a spherical particle to form a protrusion.

As anionic surfactants, alkylbenzene sulfonates, alkyl sulfates, alkyl ether sulfates, soaps, and the like may be used.

As cationic surfactants, alkyl quaternary nitrogen compounds and quaternary ammonium compounds such as esterquats and the like may be used.

In addition, an amphoteric surfactant containing both a cationic quaternary ammonium ion group and an anionic carboxylate (—COO⁻)

sulfate
(

-

SO
4

2
-

)

group may be used.

In addition, 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 undeconylvalinate), polyvinylpyrrolidone, polyvinylalcohol, 2-acrylamide-2-methyl-1-propanesulfonic acid, alkyl methacrylamide, alkyl acrylate, poly(allylamine)-supported phases, poly(ethyleneimine), poly(N-isopropylacrylamide), n-hydroxysuccinimide, and the like may be used.

Preferably, the self-assembling surfactant may be a polymer of the following Formula 1. In addition, the polymer of Formula 1 below may be said to be an amphoteric surfactant that has both (+) and (−) properties within the molecule.

[Image Omitted]

In Formula 1, R₁and R₃are independently hydrogen atoms, C₁-C₁₀alkyl groups, or alkoxy groups, n is a number of 2 or more, and R₂is a substituent of Formula 2 below.

[Image Omitted]

In Formula 2, R₄and R₅are independently hydrogen atoms, C₁-C₁₀alkyl groups, or alkoxy groups, R₆is a C₁-C₁₀alkylene group or a single covalent bond, and * represents a connection site.

The polymer of Formula 1 preferably has a molecular weight of 500 or more and 100,000 g/mol or less. Here, the molecular weight is the weight average molecular weight, and the weight average molecular weight means the polystyrene conversion molecular weight measured by GPC method. The molecular weight may be 1000 or more, 5000 or more, 10,000 or more, 20,000 or more, or 30,000 or more, and may be 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.

The amount of self-assembling surfactant used may be 30 to 150 parts by weight per 100 parts by weight of the inorganic precursor. The amount of surfactant used may be 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, per 100 parts by weight of the inorganic precursor, 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.

Solvent

The solvent used in the synthesis reaction of the spherical protruding inorganic particles may be water or a mixed solvent of a solvent compatible with water and water.

According to an embodiment, the solvent compatible with water may be one or more selected from alcohol, chloroform, ethylene glycol, propylene glycol, diethylene glycol, glycerol, and butyl glycol.

When a solvent compatible with water is used by being mixed with water, the mixing volume ratio of water:compatible solvent may be 100:50-200, 100:60-150, or 100:70-120.

When using water or a mixture of water and a solvent compatible with water as a solvent to add and dissolve inorganic precursors and/or self-assembling surfactants, it is best to use a stirrer and proceed with the reaction after complete dissolution. Otherwise, it may interfere with the formation of particles with uniform morphology.

Spherical Protruding Inorganic Particle Synthesis Reaction

In the spherical protruding inorganic particle synthesis step, the previously prepared inorganic precursor solution is introduced into the reactor and a synthesis reaction with the self-assembling surfactant is performed. Synthesis of spherical protruding inorganic particles is carried out at a temperature range of 60 to 250° C. for 1 to 24 hours. Preferably, it may be carried out 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, and in the range of 70° C. or higher, 80° C. or higher, or 90° C. or lower, and 220° C. or lower, 200° ° C. or lower, 180° C. or lower, or 160° C. or lower.

Self-assembling surfactants are dissolved in a solvent and then combine with the ions of the inorganic precursor as the reaction proceeds at a certain temperature and time. Here, self-assembly means spontaneously forming an organized structure or form by combining the part with (+) properties of the surfactant with the part with (−) properties. For example, if a surfactant has an amide group in its molecular structure, the nitrogen atom part has (+) properties and the oxygen atom part has (−) properties, so that they may form a network structure by themselves. At the same time, the distance between the elementary particles dissolved in the solvent with these self-assembling materials becomes closer and the particles grow as they aggregate (nanocluster formation). In this process, the particles grow surrounded by a surfactant shell, forming spherical particles, and protrusions are formed on the surface of the particles. At this time, protrusions may grow simultaneously on the surface of the spherical particle, or independently grown protrusions may be exposed on the surface of the spherical particle to form protrusions.

Method for Controlling Surface Charge of Spherical Protruding Inorganic Particles

According to the present disclosure, the surface charge of the inorganic particles obtained from the above synthesis reaction may be controlled by treating the inorganic particles with an acid and/or a base.

The method for controlling the surface charge of spherical protruding inorganic particles proposed in the present disclosure is basically controlling the pH of the aqueous dispersion containing the particles. For example, when there are positively charged particles in an aqueous dispersion, as more acidic substances are added, the particles will have a stronger positive charge, and conversely, as more basic substances are added, the surface charge of the particle will gradually become slightly positive and then reach a point where it becomes neutral. If more base is added continuously, it will become negatively charged. Using this principle, the surface charge of inorganic particles may be controlled by adjusting the pH in the aqueous solution.

As an acidic pH adjuster to lower the pH of an aqueous solution, one or more acidic substances such as phosphoric acid, hydrochloric acid, nitric acid, and sulfuric acid may be used in combination, and on the other hand, as a basic pH adjuster to increase pH, one or more basic substances such as sodium hydroxide and ammonia water may be used in combination. At this time, accurate pH measurement may be achieved only by adjusting the pH and evenly mixing the inside of the aqueous solution using a stirrer at the same time.

The spherical protruding inorganic particles according to the present disclosure are inorganic particles having a surface charge of +30 mV or more or −30 mV or less at least once, and a surface charge control method that can more effectively express surface properties by existing in a stable state in an aqueous solution is included. The particles prepared in this way have excellent bonding power with various media such as glass and silicon, so they may be used as polishing particles.

In particular, the inorganic particles according to the present disclosure may have a surface charge of +30 to +50 mV or −30 to −50 mV in an aqueous dispersion state of pH 4. In other words, since it has a zeta potential with a high absolute value under given pH conditions, the removal rate may be further improved. Here, the term ‘surface charge’ is used interchangeably with ‘zeta potential’.

According to the present disclosure, an aqueous dispersion is provided wherein the above-described inorganic particles are dispersed in water and contain amino acids as additives.

Metal oxide-based inorganic particles are polished by combining metal elements with the silicon oxide plane. For example, ceria particles are polished through SiO₂planes and Ce—O—Si bonds, and amino acids may increase the removal rate by strengthening the electrical attraction between the SiO₂wafer and ceria particles. In other words, amino acids have the effect of increasing the removal rate by adsorbing onto the SiO₂surface without directly reacting with ceria.

Specific examples of amino acid may 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, thyroxine, 4-hydroxy-proline, cysteine, methionine, ethionine, lathionine, cystathionine, cystine, cysteic acid, aspartic acid, glutamic acid, S-(carboxymethyl)-cysteine, 4-aminobutyric acid, asparagine, glutamine, azaserine, arginine, canavanine, citrulline, δ-hydroxy-lysine, creatine, histidine, 1-methyl-histidine, 3-methyl-histidine, tryptophan, etc.

Among these, aromatic amino acids such as tyrosine, phenylalanine, and tryptophan are more preferable because they have a greater tendency to adsorb to the surface of the silicon oxide wafer without direct reaction with the ceria particles.

In addition, the content of the amino acid may be 0.01 to 5% by weight based on the total weight of the aqueous dispersion. If the amino acid content is less than 0.01% by weight, the effect of increasing the removal rate by adsorbing on the SiO₂surface is minimal, and if it exceeds 5% by weight, a thick passivation layer may be formed on the SiO₂surface, which is not desirable. The content of amino acids may be, for example, based on the total weight of the dispersion, 0.05% by weight or more, 0.06% by weight or more, 0.07% by weight or more, 0.08% by weight or more, and 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less.

In addition, the content of the inorganic particles may be 0.01 to 5% by weight based on the total weight of the aqueous dispersion. Preferably it may be 0.05% by weight or more, 0.06% by weight or more, 0.07% by weight or more, 0.08% by weight or more, and 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. If it is less than 0.01% by weight, the polishing effect on the SiO₂wafer surface is minimal, and if it exceeds 5% by weight, the polishing action may be inhibited due to the presence of excessive inorganic particles, which is not desirable.

In addition, by adjusting the weight ratio of amino acids to inorganic particles, an aqueous dispersion with optimal polishing efficiency may be prepared. For example, 50 to 200 parts by weight of amino acids may be used based on 100 parts by weight of inorganic particles. Preferably, it may be 60 or more, 70 or more, 80 or more, 90 or more, 180 or less, 160 or less, 140 or less, or 120 or less based on 100 parts by weight of the inorganic particles. If the amino acid content is less than the above range, the effect of improving polishing efficiency due to the addition of amino acids is minimal, and if it exceeds the above range, a thick amino acid passivation layer may be formed on the SiO₂surface, which may be undesirable.

In addition, according to the research of the present inventors, it was discovered that the removal rate may be further increased when the pH of the aqueous dispersion containing the inorganic particles according to the present disclosure is adjusted to the range of 3 to 7 after adding amino acids. The pH of the aqueous dispersion may be 3 or higher, 3.5 or higher, 4 or higher, or 4.2 or higher, 4.4 or higher, and 7 or lower, 6.5 or lower, 6 or lower, 5.5 or lower, 5 or lower, or 4.9 or lower.

A pH adjuster may be used to adjust the pH of the aqueous dispersion to a desired value. The pH adjuster to be used may be either an acid or an alkali, or may be an inorganic or organic compound. In addition, pH adjusters may be used alone or in combination of two or more types. In addition, when using the above-mentioned various additives having a pH adjusting function (for example, various acids, etc.), the additive may be used as at least a part of the pH adjuster.

In addition, the aqueous dispersion according to the present disclosure may further include various additives depending on its use. For example, when used as a polishing slurry, it may contain various additives that may further improve the polishing speed, such as organic acids, nitrile compounds, and other chelating agents.

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, and citric acid. Instead of the organic acid, or in combination with the organic acid, salts such as alkali metal salts of the organic acid may be used.

Specific examples of nitrile compounds include acetonitrile, aminoacetonitrile, propionitrile, butyronitrile, isobutyronitrile, benzonitrile, glutarodinitrile, and methoxyacetonitrile.

Specific examples of a chelating agent may include iminodiacetic acid, nitrilotriacetic acid, diethylenetriaminetetraacetic acid, ethylenediaminetetraacetic acid, N,N,N-trimethylenephosphonic acid, Ethylenediamine-N,N,N′,N′-tetramethylenesulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropanetetraacetic acid, glycol etherdiaminetetraacetic acid, ethylenediamineorthohydroxyphenylacetic acid, ethylenediaminedisuccinic acid (SS form), N-(2-carboxylate ethyl)-L-aspartic acid, β-alanine diacetic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid, 1,2-dihydroxybenzene-4,6-disulfonic acid, etc.

In addition, the aqueous dispersion according to the present disclosure may contain an oxidizing agent. Available oxidizing agents may 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, ozone water, etc. These oxidizing agents may be used individually or in combination of two or more types.

The aqueous dispersion according to the present disclosure may further include other ingredients such as water, abrasives, metal anticorrosives, polishing accelerators, surfactants, oxoacids, preservatives, anti-fungal agents, reducing agents, water-soluble polymers, and organic solvents for dissolving poorly soluble organic substances.

MODES FOR CARRYING OUT THE INVENTION

The configuration and operation of the present disclosure will be described in more detail through the following examples. However, this is presented as a preferred example of the present disclosure and should not be construed as limiting the present disclosure in any way. In addition, descriptions of content that may be sufficiently technically inferred by those skilled in this technical field will be omitted.

Preparation of Spherical Protruding Ceria Particles

Preparation Example 1

To 160 ml of solvent in which ethylene glycol (99%) and water is mixed at a volume ratio of 100:100, 2 g of poly(N-isopropylacrylamide) (Aldrich, Mw: 30,000) as a self-assembling surfactant was added and stirred with a magnetic stirrer. After confirming that it is completely dissolved, as a cerium precursor, 2 g of cerium nitrate hexahydrate (Ce(NO₃)₃·6H₂O) from Aldrich was added and dissolved to prepare a cerium precursor solution.

The cerium precursor solution was placed in a liquid reactor where the temperature was maintained, and the synthesis reaction was performed for about 165 minutes at a temperature range of 90 to 140° C. After completion of the reaction, the obtained ceria particle solution was centrifuged at 4000 rpm for 1 hour and 30 minutes using a centrifuge, and after separating the precipitate, the washing process with water (H₂O) was repeated three times to obtain the resulting ceria particles (hereinafter also referred to as “BOC100”).

Preparation Example 2

To an aqueous solution of 2.4 g of cerium chloride dissolved in 180 ml of water, 2.4 g of poly(N-isopropylacrylamide) (Aldrich, Mw: 85,000) which has a different molecular weight than that used in Preparation Example 1, was added and stirred for 6 hours at 70-90° C. to react. Thereafter, by separating and washing in the same manner as in Preparation Example 1 above, the ceria particles having spherical protrusions were obtained.

Reference Example 1

CeO₂particles with a fluorite hexagonal structure (manufacturer: Solvay, product name: HC60) were prepared.

Reference Example 2

To 160 ml of water, 8 g of Aldrich's cerium nitrate hexahydrate (Ce(NO₃)₃·6H₂O) as a cerium precursor was added and dissolved to create a cerium precursor solution and stirred with a magnetic stirrer. After confirming complete dissolution, 4 g of sodium hydroxide (NaOH) was added to prepare a basic solution. CeO₂particles synthesized by the precipitation method were prepared by stirring for about 1 hour.

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 diffractometer (Rigaku SmartLab SE X-ray diffractometer with Cu Kα radiation) and an X-ray photoelectron spectrometer (XPS, Thermo ESCALAB 250).

A and B of FIG. 2 are SEM images and TEM images showing the shape of ceria particles (BOC100) prepared in Preparation Example 1. It shows that the ceria particles of Preparation Example 1 have a spherical shape with a round and smooth surface.

Meanwhile, according to D and E of FIG. 2, the ceria particle (HC60) of Reference Example 1 shows the characteristic shape of a fluorite crystal with sharply angled edges and a crystal lattice plane.

FIG. 3 is an SEM image of particles prepared by precipitation method according to Reference Example 2. It may be seen that the shape of the particles is irregular and clumped together.

In addition, FIG. 4 is a histogram showing the particle size distribution of ceria particles of Preparation Example 1 and Reference Example 1. The ceria particles (BOC100) of Preparation Example 1 have an average particle diameter of 108 nm and a standard deviation of 10.3, but the ceria particles (HC60) of Reference Example 1 have an average particle diameter of 117 nm and a standard deviation of 22.5. From the fact that the standard deviation of the ceria particles (BOC100) of Preparation Example 1 is much smaller than that of the ceria particles (HC60) of Reference Example 1, it may be confirmed that the ceria particles of Preparation Example 1 exhibit monodisperse.

The ceria particles according to the present disclosure, which have a spherical shape and are monodisperse, have a round and gentle surface without sharply angled edges, and are therefore more preferable in terms of reducing defects, scratches, or dishing flaws in the CMP process.

As shown in FIG. 1, the ceria particle according to Preparation Example 1 has a very unique surface because it is formed of very small fine nanoparticles (particle diameter is about 4.4 nm). In other words, the inorganic particles used in the aqueous dispersion according to the present disclosure are formed as aggregates of nanoparticles or units, and in the case of Preparation Example 1, it may be said that CeO₂atoms (0.54 nm) gather to form nanoparticles (4.4 nm), and the nanoparticles gather to form inorganic particles (108 nm).

FIG. 5 is an XRD analysis result of 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° corresponding to the (111), (200), (220), (311), (222), (400), (331) and (420) lattice planes, which correspond to the characteristic peaks of fluorite crystals. However, since the peak of the ceria particles (BOC100) of Preparation Example 1 is much wider, it may be seen that the crystallinity is lower than that of the HC60 particles of Reference Example 1.

In addition, for crystal size comparison, the crystal size was calculated based on the (111) peak. The average crystal size (Lc) was calculated by the Scherrer equation using 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): p. 154-160).

L

C

=
 

K
*
λ

β

*
cos
⁢
θ

[

Equation
⁢

1

]

In the above equation, λ is the X-ray wavelength (nm), β is the FWHM (radians), and K is a constant related to the crystal shape (0.9).

The crystallinity of the particles was calculated as the area under the XRD peak using the Ruland-Vonk method (Iulianelli, G. C. V., et al., Influence of TiO2 nanoparticle on the thermal, morphological and molecular characteristics of PHB matrix, Polymer Testing, 2018. 65: p. 156-162).

X
c

⁢

(
%
)

=

I
c

I
c

+

I
a

×
100

[

Equation
⁢

2

]

In the above equation, Ic is the sum of the area under the crystalline peak and Ia is the sum of the amorphous halo area.

As summarized in Table 1, the crystal size (Lc) of the ceria particles of Preparation Example 1 is 4.4 nm and the crystallinity Xc was 70.5%. The nanoparticle size of 4.4 nm in the schematic diagram of FIG. 1 is based on this XRD analysis result.

TABLE 1

FWHM
Crystal
Crystallinity
d-spacing

(degree)
size (nm)
(%)
(Å)

BOC100
1.88
4.4
70.5
3.10

HC60
0.18
45.5
95.8
3.12

Meanwhile, the particles of Reference Example 1 has a crystal size (Lc) of 45.5 nm and a crystallinity (Xc) of 95.8%. In other words, the crystal size of the particles of Preparation Example 1 according to the present disclosure is much smaller and the crystallinity is much lower than that of the particles of Reference Example 1. From this, it may be seen that the particles according to the present disclosure contain a significant amount of amorphous ceria. The amorphous phase is much softer than the crystalline phase and is therefore desirable for mitigating scratching and dishing defects in the CMP process.

B and C of FIG. 6 show HR-TEM images and selected area electron diffraction (SAED) patterns of particles according to Preparation Example 1. The particle of Preparation Example 1 has a d-spacing of 3.10 Å, which corresponds to the (111) lattice plane of ceria.

The size of the phase obtained by drawing the phase boundary in C of FIG. 6 is in the range of 2-5 nm. This corresponds to the crystal size of 4.4 nm shown in FIG. 1. The diffused SAED pattern is shown in D of FIG. 6, showing that the particle of Preparation Example 1 is a mixture of crystalline and amorphous phases (as expressed as spots and rings).

E to G of FIG. 6 show that the particles of Reference Example 1 have a large crystalline phase represented by a unidirectional (111) lattice plane surrounded by boundary lines. This indicates that the particles of Reference Example 1 are formed almost entirely of one or two single crystal phases, which is supported by the crystal size of 45.5 nm and crystallinity of 95.8%.

FIG. 7 shows the results of elemental analysis of Ce 3d and O 1s on the particles of Preparation Example 1 and Reference Example 1 by X-ray photoelectron spectroscopy (XPS) in graphs A and B, respectively. A of FIG. 7 shows that the Ce 3d peak is split into Ce 3d_5/2and C3 3d_3/2. v₀, v₁, v₂, v₃, and v₄belong to Ce 3d_5/2, and u₀, u1, u2, u3 and u4 belong to Ce 3d_3/2(Thromat, N., M. Gautier-Soyer, and G. Bordier, Formation of the CeY203 interface: an in situ XPS study, Surface science, 1996. 345(3): p. 290-302). The peaks v₀, v₂, u₀, and u₂represent the characteristics of Ce³⁺ ions, and the peaks v₁, v₃, v₄, u₁, u₃, and u₄represent the characteristics of Ce⁴⁺ ions (Zhang, C. and J. Lin, Visible-light induced oxo-bridged Zr IV-O-Ce III redox centre in tetragonal ZrO 2-CeO 2 solid solution for degradation of organic pollutants, Physical Chemistry Chemical Physics, 2011. 13(9): p. 3896-3905).

The concentrations of Ce³⁺ and Ce⁴⁺ were obtained as follows.

[

Ce

3
+

]

=

v
0

+

v
2

+

u
0

+

u
2

[

Ce

4
+

]

=

v
1

+

v
3

+

v
4

+

u
1

+

u
3

+

u
4

Table 2 shows specific information of XPS peak assignment.

TABLE 2

Peak Assignment (%)

Ce 3d_3/2
Ce 3d_5/2

Ratio

u₄
u₃
u₂
u₁
u₀
v₄
v₃
v₂
v₁
v₀
O 1s
Ce³⁺
Ce⁴⁺
Ce³⁺/

Ce⁴⁺
Ce⁴⁺
Ce³⁺
Ce⁴⁺
Ce³⁺
Ce⁴⁺
Ce⁴⁺
Ce³⁺
Ce⁴⁺
Ce³⁺
OH⁻
O²⁻
(%)
(%)
Ce⁴⁺

Binding
916.28
907.08
902.08
900.18
898.38
897.53
888.68
884.23
881.83
879.88
530.33
528.83

Energy (eV)

BOC100
13.3
6.99
10.2
9.35
4.60
12.6
11.4
16.0
13.7
1.72
69.4
30.6
32.6
67.4
48.4

HC60
14.7
7.35
8.94
10.1
4.39
13.4
12.0
13.8
14.2
1.13
47.3
52.7
28.3
71.7
39.5

According to the above results, the calculated Ce³⁺ concentration of the particles of Preparation Example 1 is 32.6%, which is higher than 28.3% of the particles of Reference Example 1. In addition, the ratio of Ce³⁺/Ce⁴⁺ is 48.4 for the particles of Preparation Example 1, and 39.5 for the particles of Reference Example 1, and it may be seen that the concentration of Ce³⁺ contained in the particles of Preparation Example 1 is higher.

In aqueous systems, Ce³⁺ ions present on the surface of ceria particles promote the dissociation of H