KR20100067724A - Method of preparing ceria powder and slurry composite using the same - Google Patents

Abstract

PURPOSE: A method for preparing cerium oxide of high purity and a slurry composition using the same are provided to suppress generation of temperature variation and to reduce microscopic scratch. CONSTITUTION: A method for preparing cerium oxide comprises: a step of inputting cerium carbonate and pure water to a reactor; and a step of maintaining reactor at 300-900°C and 200-400 pressure for 1-4 minutes to plasticize. A slurry composition for chemical mechanical polishing contains 0.1-40 weight% of cerium oxide, 0.001-10 weight% of dispersing agent, and remaining amount of pure water.

Description

Method for preparing cerium oxide and slurry composition using same {Method of preparing ceria powder and slurry composite using the same}

The present invention relates to a method for preparing cerium oxide and a slurry composition using the same, and more particularly, to a method for preparing cerium oxide having a high purity and uniform particle size and a slurry composition using the same, which can reduce fine scratches in a chemical mechanical polishing process. It is about.

Recently, as the degree of integration of semiconductor devices increases, a wide area flattening process is required to secure a margin for a high-performance exposure process. Chemical mechanical polishing (CMP) is a process used for wide-area leveling of such semiconductor devices, and has an advantage of superior planarization capability and simple process compared to other planarization methods. The polishing slurry used in the chemical mechanical polishing process generally includes abrasive particles, deionized water and additives. Colloidal silica particles or fumed silica particles are mainly used as the abrasive particles. Is not high enough, and the polishing selectivity of the oxide film and the nitride film is low, and thus, there is a problem in that various steps of the process must be further performed.

In order to supplement the above problem, the use of a slurry containing cerium oxide particles used in the existing glass processing process is contemplated. Although cerium oxide particles have a high polishing rate and high polishing selectivity of oxide films and nitride films, a large amount of fine scratches are generated by agglomeration between particles during a chemical mechanical polishing process. In particular, during the chemical mechanical polishing process, in the shallow trench isolation (STI) process, when the trench is thin and a large amount of fine scratches are generated, serious results are caused in terms of performance and production yield of the semiconductor device.

Since most of these fine scratches are known to be caused by the shape and size of the abrasive particles, in order to use the cerium oxide particles as abrasive particles in the chemical mechanical polishing process, the high selectivity of the oxide oxide and the nitride film, which are inherent characteristics of the cerium oxide particles, It should have a uniform shape and size to maintain fast polishing speeds and reduce fine scratches during the polishing process.

Hitachi's Korean Patent No. 10-2007-0087037 discloses particle characteristics and additive types required for the method of synthesizing cerium oxide particles and slurry properties for STI CMP, and KC Tech's Korean Patent No. 10-2007-0087840 describes a slurry. A method for reducing fine scratches through a aging process after preparation is disclosed. However, the above methods still have a problem of causing fine scratches because they are not a solution to the abrasive particles themselves to reduce fine scratches. In addition, Korean Patent No. 10-2007-0023163 of Hanwha Chemical discloses a method of preparing cerium oxide by reacting an aqueous metal salt solution containing cerium salt with ammonia-containing fluid using supercritical water.

It is an object of the present invention to provide a high purity and uniform particle size cerium oxide production method and slurry composition using the same which can reduce fine scratches in chemical mechanical polishing processes.

Another object of the present invention is to provide a cerium oxide production method suitable for STI chemical mechanical polishing process and a slurry composition using the same.

In order to achieve the above object, the present invention comprises the steps of adding cerium carbonate and pure water to the reactor; And maintaining the temperature of the reactor at 300 to 900 ° C., the pressure at 200 to 400 atmospheres, and calcining for 1 minute to 4 hours.

Here, the cerium carbonate is 1 to 80% by weight relative to the total reactants, the remaining components are preferably pure water, 0.01 to 10% by weight relative to the total reactants in the step of adding cerium carbonate and pure water to the reactor It is preferable to add an oxidizing agent, and the oxidizing agent is preferably selected from the group consisting of hydrogen peroxide, ozone, oxygen and mixtures thereof, and the cerium oxide is the half width of the main peak by X-ray diffraction (FWHM). It is preferably 28 to 34 ° and an average particle size of 10 to 50 nm.

In addition, the present invention, the total slurry composition, 0.1 to 40% by weight of the cerium oxide; 0.0001 to 10 weight percent dispersant; And it provides a slurry composition for chemical mechanical polishing comprising the remaining pure water. Here, the dispersant is preferably selected from the group consisting of polyvinyl alcohol, ethylene glycol, glycerin, polyethylene glycol, polyacrylic acid, ammonium polyacrylate salt, polyacrylic maleic acid and mixtures thereof.

The method for producing cerium oxide and the slurry composition using the same according to the present invention, unlike the conventional firing method in which the particles of cerium oxide grow unevenly due to the temperature difference depending on the position in the kiln, is characterized by the supercritical or subcritical fluid Due to the permeability, temperature deviation does not occur during the firing process so that cerium particles grow uniformly. In addition, the cerium oxide particles can be produced at a lower temperature and a shorter time than a conventional firing method due to the high oxidizing power having supercritical water or subcritical water. The slurry composition of the present invention comprising cerium oxide having a uniform particle size prepared by the above production method maintains the high selectivity of the oxide film and the nitride film in the chemical mechanical polishing process, and maintains a high polishing rate and fine scratches during the polishing process. It can also be used for STI chemical mechanical polishing processes that are sensitive to fine scratches.

Hereinafter, the present invention will be described in detail.

According to the cerium oxide manufacturing method of the present invention, by using the high permeability and thermal conductivity of a supercritical or subcritical fluid, cerium oxide having a uniform particle size with high purity is produced, and the rate of generation of cerium oxide is accelerated through rapid oxidation. Cerium carbonate with pure water is calcined in a supercritical or subcritical atmosphere.

Generally, in order to manufacture cerium oxide, the firing method which manufactures cerium oxide by heating cerium salts, such as cerium carbonate, to baking temperature is used. In a conventional firing method, cerium carbonate is decarbonized at a temperature near 300 ° C., whereby the carbonic acid of cerium carbonate is removed in the form of carbon dioxide, which is converted into a cerium oxide crystal and at a higher temperature. The cerium oxide crystals grow to form cerium oxide having a specific particle size and shape. The most important factor that determines the particle formation, size and shape of the cerium oxide is temperature. When the temperature difference between the cerium carbonate occurs during the firing of cerium carbonate, the shape and size of the cerium oxide crystals are not uniform, and if the temperature difference between the crystals occurs even during the growth of the cerium oxide crystals, the cerium oxide crystals grow unevenly, It is important to eliminate temperature variations during the firing process. The firing according to the invention is carried out under pure water in a supercritical or subcritical atmosphere (temperature and pressure to be supercritical or subcritical), so that cerium carbonate is of uniform shape and size through a decarbonization reaction. Formed with cerium oxide crystals and growing uniformly at the same time to form cerium oxide, the formed cerium oxide has the strength possible as abrasive particles, and the particle shape and size are uniform.

The supercritical fluid refers to a fluid that exists above a critical point (the maximum temperature-pressure limit at which a liquid and gas phase can be distinguished), which is one of the intrinsic properties of a substance. Supercritical fluids are characterized by a molecular density close to liquid but similar to gas. As a result, the fluid diffusion speed is high, and the permeability and thermal conductivity is high, thereby eliminating the temperature variation of the reactants. The subcritical refers to a fluid present in the temperature and pressure near the critical point, and has properties similar to those of the supercritical fluid. Supercritical or subcritical water means water in a supercritical or subcritical state. Supercritical water or subcritical water is characterized by rapid oxidation of the material due to the high permeability characteristic of supercritical or subcritical fluids and elimination of temperature variations of the reactants.

In order to make the reaction conditions into a supercritical or subcritical atmosphere (i.e., to make the pure water into a supercritical or subcritical water), the temperature of the reactor is 300 to 900 ° C, preferably 400 to 850 ° C, more preferably The pressure is maintained at 600 to 800 ° C., and the pressure is maintained at 200 to 400 atm, preferably at 220 to 350 atm, more preferably at 250 to 300 atm. If the temperature is less than 300 ° C, the pure water may not be a supercritical water or subcritical water, and there is a fear that cerium oxide having an irregular particle size may be formed. If the temperature exceeds 900 ° C, the particle size of cerium oxide is excessively excessive. There is a fear that the fine scratches increase due to the increase. If the pressure is less than 200 atm, the pure water may not be a supercritical water or subcritical water, and there is a fear that cerium oxide having an uneven particle size may be formed. If the pressure exceeds 400 atm, the particle size of cerium oxide is excessively large. There is a fear that the polishing rate is reduced due to being small.

The firing is carried out for 1 minute to 4 hours, preferably for 30 minutes to 2 hours. If the firing time is less than 1 minute, the particle size of cerium oxide may not grow sufficiently to be used as abrasive particles, and thus the polishing rate may be reduced. If it exceeds 4 hours, the cerium oxide particle size becomes excessively large and uneven. There is a fear that fine scratches increase during polishing.

With respect to the total reactants, the cerium carbonate is 1 to 80% by weight, preferably 10 to 70% by weight, more preferably 10 to 50% by weight, and the remaining components are pure water. If the cerium carbonate is less than 1% by weight, the amount of cerium oxide produced is not economical, and if the amount of cerium carbonate is more than 80% by weight, cerium oxide having an irregular particle size may be formed.

In order to more effectively calcinate the cerium carbonate, an oxidizing agent may be added in the step of introducing cerium carbonate and pure water into the reactor, and the amount of the oxidizing agent is added in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight. can do. If the oxidant exceeds 10% by weight, there is a fear of serious corrosion in the reactor.

The oxidizing agent can be used a wide range of conventional oxidizing agent, preferably hydrogen peroxide, ozone, oxygen or a mixture thereof, more preferably hydrogen peroxide.

The cerium oxide according to the present invention has high purity and uniform particle size, and has a full width at half maximum (FWHM) of 28-34 °, preferably 29-34 by the X-ray diffraction method. 33 ° and an average particle size of 10 to 50 nm, preferably 20 to 40 nm. The average particle size can be obtained by substituting the half value width into a Scherrer equation. If the half width and the average particle size of the main peak is less than 10 nm, the particle size may be small for use as abrasive particles, and thus, the polishing rate may be reduced, and if it exceeds 50 nm, fine scratches may be caused during polishing.

In addition, the slurry composition for chemical mechanical polishing of the present invention, using the cerium oxide prepared from cerium carbonate having a high purity and uniform particle size, even in the chemical mechanical polishing process, especially fine scratches, the performance and production yield of the semiconductor device It is suitable for a large falling STI process, 0.1 to 40% by weight of the cerium oxide, preferably 0.5 to 10% by weight, 0.0001 to 10% by weight, preferably 0.005 to 5% by weight, based on the total slurry composition. And the remaining pure water. If the cerium oxide is less than 0.1% by weight, cerium oxide may not fully function as the abrasive particles, and thus the polishing rate and the removal rate may be reduced. If the cerium oxide is more than 40% by weight, dispersibility may occur and precipitation may occur. There is no particular advantage, only fine scratches are generated. When the dispersant is less than 0.0001% by weight, cerium oxide in the slurry composition may not be sufficiently dispersed and may be entangled or aggregated. When the dispersant is more than 10% by weight, the dispersant may act as an impurity to reduce the polishing rate. Is not.

The dispersant may be used in a wide range of dispersants used in conventional slurry compositions using cerium oxide, for example, anionic dispersants, nonionic dispersants, cationic dispersants may be used, specifically, polyvinyl alcohol ( polyvinylalcohol, PVA), ethylene glycol (ethyleneglycol, EG), glycerin, polyethylene glycol (polyethyleneglycol, PEG), polyacrylic acid, polyacrylic acid ammonium salt, polyacrylic maleic acid or mixtures thereof may be used.

In the chemical mechanical polishing slurry composition, it is preferable to use a dispersing device to more effectively disperse when dispersing the cerium oxide in the pure water, and the dispersing device may use a conventional stirrer and a disperser, and specific examples. Examples include bead mills, ultrasonic dispersers, shakers, homogenizers, paint shakers, roll mills, apex mills, vibrating ball mills, jet mills, and dispersers using these.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples are intended to illustrate the invention, and the invention is not limited by the following examples.

Example 1 Preparation of Cerium Oxide

After 2 kg of pure water was added to the reactor, 1 kg of cerium carbonate and 50 g of hydrogen peroxide were added, heated to 400 ° C., and then pressurized to 220 atm. Firing while maintaining a supercritical state for 30 minutes yielded 500 g of cerium oxide having an average particle size of about 12 nm. The average particle size was obtained by spray drying the reaction solution after the completion of the reaction and substituting the half value width of the main peak by the powder X-ray diffraction method into the Scherer equation.

Example 2 Preparation of Cerium Oxide

After 2 kg of pure water was added to the reactor, 1 kg of cerium carbonate and 50 g of hydrogen peroxide were added, heated to 700 ° C., and then pressurized to 220 atm. Firing while maintaining a supercritical state for 1 hour yielded 500 g of cerium oxide having an average particle size of about 25 nm. The average particle size was obtained by spray drying the reaction solution after completion of the reaction and substituting the half-value width of the main peak by the powder X-ray diffraction method into the Scherker equation. A scanning electron microscope (SEM) photograph of the cerium oxide powder was shown in FIG. 1. Shown in

Example 3 Preparation of Cerium Oxide

After 2 kg of pure water was added to the reactor, 1 kg of cerium carbonate was added, heated to 700 ° C., and then pressurized to 220 atm. Firing while maintaining a supercritical state for 1 hour yielded 400 g of cerium oxide having an average particle size of about 33 nm. The average particle size was obtained by spray drying the reaction solution after the completion of the reaction and substituting the half value width of the main peak by the powder X-ray diffraction method into the Scherer equation.

Comparative Example Preparation of Cerium Oxide

1 kg of cerium carbonate was calcined at 750 ° C. for 4 hours to obtain 500 g of cerium oxide having an average particle size of about 30 nm. The average particle size was obtained by substituting the half value width of the main peak by the powder X-ray diffraction method into the Scherker equation. The SEM image of the cerium oxide powder is shown in FIG. It was.

Preparation Examples 1 to 4 Preparation of Cerium Oxide Slurry Composition

10 kg of pure water and 10 g of ammonium polyacrylate salt solution were gradually added to the premixing vessel, followed by mixing, followed by Example 1 (Preparation Example 1), Example 2 (Preparation Example 2), Example 3 (Preparation Example 3) or Comparative Example 100 g of cerium oxide of Preparation Example 4 was added thereto, followed by stirring for 30 minutes to prepare a cerium oxide slurry. The prepared slurry was dispersed using a bead mill to prevent particle agglomeration.

Example 4 Preparation of Cerium Oxide

Using the prepared slurry compositions (Preparation Examples 1 to 4), an 8-inch diameter blanket silicon wafer having a 1.0 μm silicon oxide film layer coated by TEOS (Tetra Ethyl Ortho Silicate) precursor chemical vapor deposition was applied to the AVANTI 472 device of IPEC. Polishing using Polishing conditions were polished for 1 minute at a slurry flow rate of 150 cc / min at a falling pressure of 4 psi, a table speed of 60 rpm, and a head speed of 50 rpm. After completion of the polishing, washing with pure water and drying, the amount of silicon oxide film and nitride film remaining on the wafer was measured by an optical interferometer to measure the removal rate of the oxide film and the nitride film. The number of scratches was measured using Negev's inspection equipment, and the number of scratches in the 8-inch wafer was 0.3-2.5 μm. The results are shown in Table 1.

Slurry Composition (cerium oxide) Preparation Example 1
(Example 1) Preparation Example 2
(Example 2) Preparation Example 3
(Example 3) Preparation Example 4
(Comparative Example) Cerium Oxide Average Particle Size 12nm 25 nm 33 nm 30 nm Oxide removal rate (Å / min) 2102 2717 2521 2494 Nitride removal rate (Å / min) 40 42 49 51 Scratch count 168 153 210 305

As can be seen in Table 1 above, the slurry composition of the present invention has a removal rate of 2000 nm / min or more and a removal rate of 50 nm / min or less of the oxide film, so that the polishing selectivity of the high oxide film and the nitride film, which is an inherent property of the cerium oxide slurry composition, And while maintaining a high polishing rate, the number of scratches (fine scratches) was reduced as much as 50% (Preparation Example 2) to 31% (Preparation Example 3) as compared to the slurry composition of Preparation Example 4 (Comparative Example).

Since the cerium oxide of the present invention has a uniform particle size, when the particles are smaller than the cerium oxide produced by the conventional method (comparative example) (Example 1), the polishing rate is lowered but the fine scratches are reduced by about 1/2. Therefore, when the STI chemical mechanical polishing process, which is sensitive to fine scratches, and the particle size is similar (Example 2), the polishing rate is increased, and the fine scratch is also reduced by about 1/2, and the chemical including the STI process is reduced. It can be more usefully used in mechanical polishing process. In the case of cerium oxide prepared without the addition of an oxidizing agent (Example 3), if the particle size is similar, the polishing rate is increased and the fine scratches are reduced by about one third, which is suitable for the STI chemical mechanical polishing process.

Comparing FIG. 1, which is a scanning electron microscope (SEM) photograph of cerium oxide prepared according to Example 2, to FIG. 2, which is a scanning electron microscope (SEM) photograph of cerium oxide prepared by a conventional method (comparative example) , It can be seen that the size and shape of the cerium oxide particles prepared according to Example 2 are more uniform, and the particles do not aggregate and have a uniform distribution. Because of this, the cerium oxide slurry of the present invention has a fast polishing rate, a small number of fine scratches as shown in Table 1, and can be used more effectively in a chemical mechanical polishing process including an STI process.

1 is a SEM photograph of the cerium oxide particles prepared in Example 2 of the present invention.

Figure 2 is a SEM photograph of the cerium oxide particles prepared in the comparative example of the present invention.

Claims (7)

Injecting cerium carbonate and pure water into the reactor; And Maintaining the temperature of the reactor 300 to 900 ℃ pressure to 200 to 400 atm, and firing for 1 minute to 4 hours. The method for producing cerium oxide according to claim 1, wherein the cerium carbonate is 1 to 80% by weight, and the remaining pure water, based on the total reactants. The method of claim 1, wherein in the step of introducing cerium carbonate and pure water into the reactor, 0.01 to 10% by weight of an oxidizing agent is added to the total reactants. The method of claim 3, wherein the oxidant is selected from the group consisting of hydrogen peroxide, ozone, oxygen, and mixtures thereof. The method for producing cerium oxide according to claim 1, wherein the cerium oxide has a half width (FWHM) of the main peak by X-ray diffraction of 28 to 34 ° and an average particle size of 10 to 50 nm. 0.1-40% by weight of cerium oxide, relative to the total slurry composition; 0.0001 to 10 weight percent dispersant; And Contains the remaining pure water, The cerium oxide, the step of introducing cerium carbonate and pure water into the reactor; And maintaining the temperature of the reactor at 300 to 900 ° C., maintaining the pressure at 200 to 400 atm, and firing for 1 minute to 4 hours. The slurry of claim 6, wherein the dispersant is selected from the group consisting of polyvinyl alcohol, ethylene glycol, glycerin, polyethylene glycol, polyacrylic acid, ammonium polyacrylate, polyacrylic maleic acid, and mixtures thereof. .

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