KR20010074200A - Manufacturing of Cerium Oxide Nanoparticles Using Chelating Agents in Solution - Google Patents

Abstract

PURPOSE: A method for preparing cerium(II) oxides-fine granules is provided to obtain the granules having less than 100 nm of diameter and uniform distribution of particle size useable to effect as catalyst or polishing material. CONSTITUTION: The method comprises the following steps of adding a chelating agent into a water solution to prepare the first solution(I); dissolving salts such as Ce(NO3)3 or Ce(NO3)4·2NH4NO3 in water to prepare the second solution(II); blending both of the first(I) and second(II) solutions to generate cerium ions and form ligands; producing a precipitate by adding determined amount of organic solvent; and heat-treating the precipitate to produce fine cerium oxide granules having less than 100nm of diameter and in the spherical form. The chelating agent is ammonium acetate or propionate ammonium salt alone and/or in combination with two compounds.

Description

Manufacturing method of cerium oxide microparticles using chelating agent in solution {Manufacturing of Cerium Oxide Nanoparticles Using Chelating Agents in Solution}

When the particle size is reduced to fine units (100 nm or less) in the particle utilization technology, the physical properties and performance of the particle are very different from those when the particle size is larger than or equal to μm. This is due to the increase in the surface-to-mass ratio of the particles, which increases the surface area per unit mass, which improves the performance of the particles, decreases the melting point of the particles, and changes the properties of the particles. Has different properties.

In addition, it is also very important to make the size of the particles formed as small as the particles in the technology of particle utilization. If the particle size is non-uniform, the performance and physical properties of each particle is different, so the research to manufacture a small and uniform size of the particles are actively conducted.

In the present invention, a complexing agent having a carboxyl group such as ammonium acetate, propionate ammonium salt, oxalate, oxal acetate, and citrate is used for coordination with cerium ions. This is a chelating effect, which prevents fusion between nuclei and delays or prevents nuclear growth after fusion, thereby producing a uniform, spherical cerium oxide particle with a uniform size distribution. The particles produced in this way are small in size, uniform in size distribution, and close in shape to sphere. In addition, the manufacturing method is very simple and no special apparatus is required, so it is economical and excellent in yield.

Particularly, when metal nitrate is used, carboxyl groups of nitrate ions and complexing agents are calcined by self-propagating combustion behavior by heating, and thus, homogeneous and fine particles can be easily produced by instant exothermic reaction. At this time, the metal nitrate is an oxidizing agent, and the acetate of ammonium acetate acts as a fuel for ignition while preventing the precipitation of the metal nitrate.

Therefore, this method is very suitable for preparing monocomponent oxides as well as multicomponent oxide powders with a uniform chemical composition.

Considering the problems of conventional cerium oxide particle production, it is possible to economically mass-produce mass, develop particle manufacturing method that has small particle size (less than 100nm), uniform size distribution and spherical shape, and has large specific surface area and high temperature. It is an object of the present invention to develop a method for producing fine cerium oxide particles which is stable even in the form of a catalyst or a catalyst support and excellent as a raw material for a slurry for semiconductor polishing. Fine cerium oxide particles are used for STI (Shallow Trench Isolation) CMP slurry and show high selectivity in device design with minimum line width of 0.17㎛.

Fine cerium oxide particles have a lot of experience in lens polishing, CMP polishing rate is very fast, can be used in neutral. In the case of fine cerium oxide particle abrasives, many companies are developing slurries for the next generation, and the market is expected to change. However, due to the polygonal morphology of the existing fine cerium oxide particles, scratches appear on the wafer surface during the CMP process. Therefore, the purpose of the fine cerium oxide particles are not only spherical in morphology but also 50-100 nm in size, narrow particle size distribution, excellent dispersion stability and storage stability of the slurry.

The technical field of the present invention belongs to the manufacturing and utilization of fine metal particles, the conventional method for producing the fine metal particles are largely a technique for producing nanoparticles in the gas phase, such as aerosol method and evaporation / condensation method and a solution containing a reducing agent in the metal ion solution The coprecipitation method for preparing nanoparticles by mixing the nanoparticles has been widely developed. In the case of the coprecipitation method, the metal ions in the solution and the hydroxyl group of the reducing agent are combined to obtain a precipitate in the form of hydroxide. The precipitate is dried and calcined to produce nano ceramic particles.

In the case of the gas phase method, the mass production of nanoparticles is impossible and the cost of producing the particles is too high, and they are not widely used in industrial applications. In addition, the coprecipitation method is simple and economical, but there is a limit to limit the size of the obtained particles to the nanometer range, it is difficult to obtain spherical particles in terms of shape. As an alternative to these two methods, various techniques such as ultrasonic method, microemulsion method, hydrothermal method, spray method, sol-gel method, electrolysis method and cavitation processing and high energy ball milling have been reported in the literature. Despite the industrial importance of nano-ceramic particles due to limitations and manufacturing costs, they are still widely used in the industry. Mechanical grinding, co-precipitation, spraying, hydrothermal, sol-gel, electrolysis, reverse phase microemulsion, etc. exist, but these methods are difficult to control the size of the formed particles or to produce fine metal particles. There is a problem that requires a lot of expenses. For example, the coprecipitation method is similar to the present invention, but by preparing particles in an aqueous solution using a basic hydroxide compound having no chelation effect, it is impossible to control the size, shape, and size distribution of the particles, but metal particles are widely used. Technology. Electrolysis and sol-gel methods are expensive to manufacture and difficult to mass-produce. Reversed-phase microemulsion is easy to control the size, shape, and size distribution of particles, but the manufacturing process is very complicated and not practical.

The technical problem to be achieved by the present invention is the following two.

① Production of economical fine cerium oxide particles

To achieve mass production of fine cerium oxide particles with uniform size distribution in an economical and simple process. Conventional fine metal particle manufacturing technology is very disadvantageous in terms of mass production and cost, but the present invention is a simple process for producing fine cerium oxide particles and the size of the particles formed is the type of cerium salt, the type of chelating agent, the concentration, Easily controlled by simple changes such as sintering temperature, aqueous solution (pH).

②Utilization of fine cerium oxide particles with excellent performance

Cerium oxide can be used as a filler, a binder, a dispersant, a catalyst or catalyst carrier for automobile exhaust gas purification, and has recently been used as a raw material for semiconductor polishing slurries. It is important to have a high specific surface area even at high temperatures when using cerium oxide particles as a catalyst, and despite the excellent selectivity of cerium oxide when used in a slurry for semiconductor polishing, it has been a problem due to scratching. Therefore, this problem is solved by manufacturing cerium oxide particles having a small size, uniform size distribution and spherical shape.

1 is a manufacturing process diagram of the present invention

2 is an XRD graph of cerium oxide particles according to sintering temperature

3 is a SEM photograph of the cerium oxide particles prepared according to the present invention.

Aqueous cerium salt is dissolved in an aqueous solution. In another aqueous solution, one of the complexing agents is dissolved in the aqueous solution, and then slowly added while stirring the solution containing the salt to form a ligand with cerium ions. After the reaction for 2 to 30 hours, an organic solvent such as acetone or alcohol is added at a volume ratio of 1.5 to 5 times and mixed. Reaction for 30 minutes to 30 hours yields a precipitate in the form of a spent acetate. It is recovered by centrifugation or filtering. The recovered precipitate is sintered between 200 and 1000 ° C. through vacuum drying to obtain cerium oxide particles. The firing time can vary within a large range between 1 and 10 hours. At this time, fine oxidized particles having different sizes and size distributions are prepared according to the type, mixing ratio, concentration, and sintering temperature of the complexing agent and cerium salt. Complexing agents which may be added here include carboxylic acid complexes such as ammonium acetate or propionic acid ammonium salts, citrate, oxalate, oxal acetate with weak chelating effects with acetate groups.

As an example, a method of manufacturing fine cerium oxide particles by the above technique is specifically as follows.

Example 1

As shown in FIG. 1, 0.1 M aqueous solution of cerium nitrate is mixed with 0.5 M aqueous solution of ammonium acetate in a volume ratio of 1: 1. After a certain time of reaction, the mixture is added with stirring acetone. When the reaction occurs, white precipitates in the form of cerium acetate are produced. The precipitates are recovered by centrifugation or filtering and then dried in vacuo. Then, after sintering in an electric furnace in an air atmosphere at 400, 600, and 800 ° C. for 2 hours, XRD (FIG. 2), SEM (FIG. 3), and BET were measured and compared with each other.

As a result, the specific surface area of the product was heat-treated at 800 ° C. for 2 to 4 hours, having a size of 15-25 m 3 / g, a size of 50-100 nm, and a spherical shape.

Example 2

It carried out by the same method as Example 1, but changed by changing the mixing volume ratio of ammonium acetate and a metal nitrate solution.

As a result, the specific surface area of the product was heat-treated at 800 ° C. for 2 to 4 hours, having a value of 15-25 m 3 / g, a size of 50-100 nm, and a spherical shape.

Example 3

The same method or starting material as Example 1 was used as ceric ammonium nitrate.

As a result, the specific surface area of the product was heat-treated at 800 ° C. for 2 to 4 hours, having a value of 15-25 m 3 / g, a size of 50-100 nm, and a spherical shape.

Example 4

Ethanol was used in the same manner as in Example 1 or as a particle generation reaction medium. As a result, the specific surface area of the product was heat-treated at 800 ° C. for 2 to 4 hours, having a size of 15-25 m 3 / g, a size of 50-100 nm, and a spherical shape.

In the effect of the present invention

-Easy to mass production of various fine cerium oxide particles with economical and simple manufacturing process

-The particle size is fine (100 nm or less) and the size distribution is uniform, so the particle performance is excellent.

Even after firing at high and low temperatures, the specific surface is large, making it well suited for catalyst applications such as catalysts or catalyst supports.

-Suppresses the polygonal Molphology of fine cerium oxide particles to create spherical particles to solve the scratch problem in the existing semiconductor CMP process

-The particle size is small and the dispersion stability is large, so it can be used very well for the manufacture of slurry for STI CMP.

Claims (6)

In preparing cerium oxide fine particles, preparing a solution I by adding a chelating agent to an aqueous solution, a water-soluble salt capable of producing ions of the cerium oxide particles to be prepared, namely Ce (NO ₃ ) ₃ or Ce ( NO _{3) 4} · added to 2NH ₄ NO ₃ further comprising: a mixture step of dissolving such a salt in water to prepare a solution ⅱ, the solution I and solution ⅱ at a predetermined volume ratio to form a cerium ion and a ligand, and a suitable amount of an organic solvent Generating a precipitate by heat-treating the obtained precipitate to produce fine cerium oxide particles having a spherical shape and a particle diameter of 100 nm or less. A method of using ammonium acetate or propionate ammonium salt as a chelating agent in claim 1 alone or in combination with other chelating agents. The method for preparing particles according to claim 1, wherein an organic solvent such as ethanol or acetone is used instead of water as a medium for dissolving the chelating agent and the cerium salt. Heat treatment method characterized in that the heat treatment temperature range of 150 to 950 ℃ when heat-treating the complex compound formed between the cerium ion and the chelating agent in claim 1 to convert to cerium oxide particles The method characterized in that the fine cerium oxide particles prepared by the method of claim 1 are used as a raw material in the slurry for semiconductor polishing The method characterized in that the cerium oxide particles prepared by the method of claim 1 are prepared alone or in a mixture of two or more different metal particles and used for the purpose of catalysts, fillers, binders and dispersants.