JP2008019115A - Method for producing silicon fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing silicon fine particles. <P>SOLUTION: The method for producing silicon fine particles comprises forming silicon fine particles by pulverizing at least one portion of single crystal silicon by colliding oxide particles with the single crystal silicon by applying an ultrasonic wave to a dispersion containing the oxide particles and a dispersion medium while bringing the dispersion into contact with the single crystal silicon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing silicon fine particles.

As a method for producing silicon fine particles, a method of reducing silicon tetrachloride with zinc or hydrogen is known, and many other production methods have been proposed.
Patent Document 1 provides a method for producing granular silicon in which chloropolysilane is brought into contact with a moving silicon seed crystal at a temperature of 250 to 1300 ° C. to cause thermal decomposition or hydrogen reduction to deposit silicon on the surface of the seed crystal. Is done.

Patent Document 2 discloses a method for producing high-purity silicon powder by applying pressure to massive silicon to generate microcracks and then pulverizing the massive silicon.
In Patent Document 3, an external heater is installed 50 mm or more away from the lower end of the fluidized bed, is made of polycrystalline silicon particles having an average particle diameter of 100 to 1,000 μm, and the ratio of the stationary bed height to the reactor inner diameter is In a reactor having 2 to 4 fluidized beds, a mixed gas of silane having a silane concentration of 15 to 45% by volume and a dilution gas is supplied to the gas in the fluidized bed under conditions of a reaction temperature of 620 to 750 ° C. and a pressure of 1 to 5 atm. A method of generating seed silicon particles in a gas phase by supplying at a flow rate of 0.3 to 0.9 m / s is disclosed.

  In Patent Document 4, polycrystals are obtained by preparing seed silicon by sequentially cleaning and etching crushed silicon with aqua regia-water-hydrofluoric acid, and performing thermal decomposition or reduction of silanes in the presence of the seed silicon. A method for producing polycrystalline silicon particles characterized by depositing silicon is disclosed.

  Patent Document 5 discloses a method for producing silicon particles, characterized in that silicon particles are obtained by mixing or contacting liquid higher-order silane with liquid alkoxysilane or liquid alkoxysiloxane and then pressurizing. It is disclosed.

  Patent Document 6 discloses a method for producing crystalline silicon particles, in which a silicon raw material is passed through a plasma in which an inert gas and a hydrogen gas as a plasma generating gas are present and heated to form crystalline silicon particles. It is disclosed.

  In Patent Document 7, silicon particles obtained by supplying molten silicon onto a dish-shaped disk rotating at high speed, causing centrifugal force to act as droplets, and quenching in an inert gas atmosphere are contained in a liquid medium. Nanometer-sized spherical polycrystalline or amorphous silicon fine particles obtained by dispersing, pressurizing the dispersion and passing through a small-diameter nozzle are described, and surface oxidation of spherical silicon fine particles and oxidation thereof There is also a description of a method for further miniaturizing the fine particles by repeating film removal.

  Patent Document 8 discloses a step of synthesizing a powder containing silicon oxide particles containing silicon particles by reacting a monosilane gas with an oxidizing gas for oxidizing the monosilane gas, and inerting the powder. And a step of removing the silicon oxide with hydrofluoric acid after holding at 800 to 1400 ° C. in an atmosphere.

In Patent Document 9, an amorphous silicon oxide film is produced on a substrate by a high-frequency sputtering method, the amorphous silicon oxide film is subjected to heat treatment, and a particle size of 3 is formed in the silicon oxide film.
. A nanosilicon having a thickness of 5 nm or less is formed, and then the silicon oxide film is treated with a hydrofluoric acid solution to remove the silicon oxide to expose the nanosilicon, and the nanosilicon is immersed in the solution to perform the solution treatment. After removing the hydrofluoric acid particles adhering to the solution, further stirring the nanosilicon in the solution, separating the nanosilicon from the substrate, separating the nanosilicon into a solution in which the nanosilicon is dispersed in units of particles, A method for producing nanosilicon powder, characterized in that a solution is subjected to filtration to obtain powdered nanosilicon, is disclosed.
JP-A-1-197309 Japanese Patent Laid-Open No. 6-16411 JP-A-6-92617 JP-A-8-48512 Japanese Patent Laid-Open No. 11-49507 JP 2002-104819 A JP 2005-320195 A JP 2005-263522 A JP 2006-70089 A

As described above, various methods have been proposed as a method for producing silicon fine particles. However, it is desired to develop a method for producing silicon fine particles having a relatively small particle size more easily.
An object of the present invention is to provide a method for efficiently producing silicon fine particles, particularly a method for easily producing silicon fine particles having a relatively small particle size.

Another object of the present invention is to provide a production method for preparing silicon fine particles using single crystal silicon as a raw material.
Furthermore, an object of the present invention is to provide a method for producing silicon fine particles having a more uniform particle size distribution.

  In the method for producing silicon fine particles according to the present invention, an oxide particle dispersion containing oxide particles and a dispersion medium is brought into contact with single crystal silicon, and ultrasonic waves are applied to the dispersion to thereby separate the oxide particles. It is characterized by colliding with crystalline silicon and pulverizing at least a part of the single crystal silicon to generate silicon fine particles.

In the method for producing silicon fine particles, the oxide particles are converted into single crystals by applying ultrasonic waves to the dispersion while immersing the single crystal silicon in the oxide particle dispersion containing the oxide particles and the dispersion medium. Preferably, the method includes a step of colliding with silicon and pulverizing at least a part of the single crystal silicon to generate silicon fine particles and dispersing the silicon fine particles in the dispersion.
An oxide particle dispersion containing oxide particles and a dispersion medium is dropped onto single crystal silicon, and ultrasonic waves are applied to the dispersion to cause the oxide particles to collide with the single crystal silicon. It is also preferable to include a step of pulverizing at least part of silicon to produce silicon fine particles and dispersing the silicon fine particles in the dispersion.

The pH of the oxide particle dispersion is preferably in the range of 2-11.
The oxide particle dispersion may further contain a dispersion stabilizer for oxide particles and / or a dispersion stabilizer for silicon fine particles.

The step of separating the silicon fine particles includes a step (a) of adding a dissolving agent to the liquid containing the silicon fine particles to dissolve the oxide particles, and a solution obtained by the step (a) by heating and drying. Preferably, step (c) is included.

  The step of separating the silicon fine particles includes a step of removing the dissolution agent and / or the dissolved oxide particles by ultrafiltration of the silicon fine particle-containing liquid before the step (c) ( It is preferable to further include b).

The method for producing silicon fine particles may further include a step of removing coarse silicon fine particles and adjusting the average particle size of the silicon fine particles to a range of 5 to 100 nm.
The method for producing silicon fine particles may further include a step of adjusting the particle size of the silicon fine particles by performing the following operations (1) and (2) one or more times;
(1) An oxidant is added to the liquid containing the silicon fine particles to form an oxide film on the surface of the silicon fine particles.
(2) Next, an oxide film solubilizer is added to the liquid containing the silicon fine particles on which the oxide film is formed to dissolve and remove the oxide film.

According to the production method of the present invention, silicon fine particles can be produced efficiently.
According to the production method of the present invention, silicon fine particles having a relatively small particle size can be produced more easily.

According to the manufacturing method of the present invention, silicon fine particles can be manufactured using single crystal silicon as a raw material.
Further, according to the production method of the present invention, silicon fine particles having a uniform particle size distribution can be produced.

  Therefore, the method for producing silicon fine particles of the present invention has high practicality.

Hereinafter, the method for producing silicon fine particles of the present invention will be described in more detail.
In the method for producing silicon fine particles of the present invention, the oxide particles are collided with the single crystal silicon by applying ultrasonic waves to the dispersion while bringing the oxide particle dispersion into contact with the single crystal silicon. It is characterized in that at least a part of single crystal silicon is pulverized to generate silicon fine particles.

Single crystal silicon;
In the manufacturing method of the present invention, single crystal silicon is used as a raw material for silicon fine particles. Examples of the single crystal silicon include a CZ silicon substrate cut out from single crystal silicon grown by the Czochralski method (CZ method), an epitaxial wafer in which a single crystal silicon layer is formed on the CZ silicon substrate by a vapor phase epitaxial growth method, and the like. Can be, but is not limited to.

The shape of the single crystal silicon is not particularly limited, but in the manufacturing method of the present invention, the oxide particles are made to collide with the single crystal silicon by the action of ultrasonic waves, so that it is, for example, plate-shaped and has an area of 1 to 300 cm on one side. Single crystal silicon which is ² is preferred.

Such plate-like single crystal silicon can be obtained, for example, by cutting a silicon wafer.
Oxide particle dispersion;
In the method for producing silicon fine particles of the present invention, at least a part of the surface of the single crystal silicon is ground by causing the oxide particles to collide with the single crystal silicon by the action of ultrasonic waves.
Silicon fine particles are generated.

  Therefore, the oxide particles used in the present invention are required to have such a hardness that the silicon particles can be released by colliding with the surface of the single crystal silicon by the action of ultrasonic waves.

In the present invention, the oxide particles are used in the state of an oxide particle dispersion in which the oxide particles are dispersed in a solvent (dispersion medium).
Examples of the oxide particles include oxide particles selected from SiO ₂ particles, alumina fine particles, titania fine particles, or ceria fine particles, a mixture of these oxide particles, and composite oxide particles of these oxides. . Of these, SiO ₂ particles are particularly preferable because they are high in hardness, excellent in economic efficiency, and suitable for separating silicon fine particles.

  The average particle diameter of the oxide particles depends on the size of the silicon fine particles to be obtained, but is, for example, 100 nm to 300 μm, preferably 500 nm to 100 μm. If the average particle size is less than 100 nm, the impact energy given to the single crystal silicon by the oxide particles is small. Therefore, it may be difficult to scrape the surface of the single crystal silicon, and silicon fine particles may not be generated sufficiently. The average particle size is 300 μm. If it exceeds, ultrasonic energy may not be transmitted to the oxide particles. In general, the larger the average particle size of the oxide particles, the larger the average particle size of the obtained silicon fine particles, and the smaller the average particle size of the oxide particles, the smaller the average particle size of the obtained silicon fine particles.

  In the present invention, the average particle size of the silicon fine particles is a value measured by the following method (TEM observation method), and the average particle size of the oxide particles is measured by the BET method or the centrifugal sedimentation type measurement method. it can.

<TEM observation method>
(1) A measurement sample is prepared by dropping and drying sol-like particles to be measured on a TEM measurement mesh.
(2) Using a transmission electron microscope (model number H-800, manufactured by Hitachi, Ltd.), photograph a measurement sample at a magnification of 200,000 to 500,000.
(3) Next, 250 particles are randomly selected from the captured images, and the particle size on those images is measured with calipers. The actual particle size is determined from the measured value and the imaging magnification. calculate. When the particle shape on the image is not a perfect circle, the major axis is the particle diameter.
(4) The average value of the actual particle diameter is adopted as the average particle diameter.

<Centrifuge sedimentation method>
When the average particle diameter of oxide particles such as SiO ₂ particles is measured by a centrifugal sedimentation measurement method, specifically, a natural / centrifugal precipitation particle size distribution analyzer CAPA-700 (manufactured by Horiba, Ltd.) Can be measured.

  The density | concentration of the oxide particle in an oxide particle dispersion liquid becomes like this. Preferably it is 10-90 mass%, More preferably, it is 40-70 mass%. If the oxide particle concentration is less than 10% by mass, the particle density is low, and it tends to be difficult to transmit ultrasonic impact energy to the single crystal silicon through the oxide particles. The oxide particle dispersion tends to dry or the oxide particles tend to aggregate due to the heat generated by.

As a dispersion medium for oxide particle dispersion, a substance that does not deteriorate single crystal silicon, does not inhibit the formation of silicon fine particles, and does not have reactivity with a solubilizer that may be added after the formation of silicon fine particles Desirable water, water-soluble alcohol, and the like are preferable, and pure water is particularly preferable from the viewpoint of economy. Examples of the water-soluble alcohol include ethanol, ethylene glycol, propylene glycol, and glycerin.

The oxide particle dispersion may further contain additives such as a dispersion stabilizer for oxide particles, a dispersion stabilizer for silicon fine particles, a polishing accelerator, a surfactant, a stabilizer, and a buffer.
Examples of the dispersion stabilizer for oxide particles include alkali metal hydroxides, alkali metal hydroxide salts, organic acids, organic acid salts, inorganic acids, inorganic acid salts, and the like. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide, examples of alkali metal hydroxide salts include sodium nitrate, potassium nitrate, sodium sulfate, and potassium sulfate, and examples of organic acids include citric acid. Examples of the organic acid salt include sodium citrate, potassium citrate, and ammonium citrate, examples of the inorganic acid include hydrochloric acid, and examples of the inorganic acid salt include sodium chloride and potassium chloride.

  Examples of the dispersion stabilizer for silicon fine particles include hydrogen peroxide, alkali metal hydroxide, alkali metal hydroxide salt, organic acid, and organic acid salt. Examples of alkali metal hydroxides include sodium hydroxide and potassium hydroxide, examples of alkali metal hydroxide salts include sodium nitrate, potassium nitrate, sodium sulfate, and potassium sulfate, and examples of organic acids include citric acid. Examples of the organic acid salt include sodium citrate, potassium citrate and ammonium citrate, examples of the inorganic acid include hydrochloric acid, and examples of the inorganic acid salt include sodium chloride and potassium chloride.

  Examples of the polishing accelerator include metal hydroxides such as potassium hydroxide and sodium hydroxide, metal carbonates such as sodium carbonate and ammonium carbonate, amines such as ammonia, monoethanolamine and piperazine, and tetramethylammonium. A quaternary ammonium hydroxide can be used, and hydrogen peroxide can be used as an oxide-based polishing accelerator.

As the surfactant, anionic, cationic, nonionic or amphoteric surfactants can be used.
Examples of the stabilizer include celluloses such as carboxymethyl cellulose and hydroxyethyl cellulose, water-soluble polymers such as polyvinyl alcohol, water-soluble alcohols such as ethanol, ethylene glycol, propylene glycol and glycerin, and sodium alkylbenzene sulfonate. Examples thereof include surfactants, organic polyanionic substances such as polyacrylates, inorganic salts such as magnesium chloride and potassium acetate.

  The ions used as a buffering agent depend on the pH range to be adjusted, but at least one selected from quaternary ammonium ions and alkali metal ions if cations are used, and carbonate ions and carbonates if anions are used. At least one selected from hydrogen ions and borate ions is preferable, and a mixture of carbonate ions and hydrogen carbonate ions, or borate ions are particularly preferable.

  The dispersant for oxide particles, the dispersant for silicon fine particles, the polishing accelerator, the surfactant and the stabilizer are each usually used in the range of 0.01 to 3% by mass in the oxide particle dispersion. However, it is not limited to this range.

The oxide particle dispersion may be liquid, gel, slurry, or paste.
The pH of the oxide particle dispersion is preferably in the range of 2-11. If the pH is less than 2, the dispersion stability of the abrasive and the silicon fine particles may be lowered. If the pH exceeds 11, the generated silicon fine particles may be dissolved. For pH adjustment, a sodium hydroxide aqueous solution, a hydrochloric acid aqueous solution, a citric acid aqueous solution or the like is preferably used.

Sonication;
The ultrasonic wave applied to the method for producing silicon fine particles of the present invention is not particularly limited as long as it has energy capable of generating silicon fine particles by colliding oxide particles with single crystal silicon. Ultrasound generated by a known ultrasonic generator can be applied. Examples of such an ultrasonic generator include a magnetostrictive ultrasonic generator and an electrostrictive ultrasonic generator. In these ultrasonic generators, a high-frequency fluctuating electric field or magnetic field is applied to a vibrator made of an electrostrictive material or a magnetostrictive material to generate mechanical vibration at an ultrasonic band frequency, and the vibration is expanded. For this purpose, vibration is guided to a desired position using a horn and a waveguide tube, and ultrasonic waves are emitted into an external medium.

  The higher the ultrasonic transmission power is, the better, but it is usually in the range of 10 to 1000 W. The frequency of the ultrasonic wave is preferably in the range of 1 to 300 kHz. Moreover, the time for applying ultrasonic waves is usually 10 to 100 minutes.

In this way, silicon fine particles are obtained in the form of a silicon fine particle dispersion.
Practically, a method including the following step (1) or (2) is preferable as a method of causing the oxide particles to collide with the single crystal silicon by the action of ultrasonic waves.

(1) While immersing single crystal silicon in an oxide particle dispersion containing oxide particles and a dispersion medium, ultrasonic waves are applied to the dispersion to cause the oxide particles to collide with the single crystal silicon. Crushing at least a portion of the single crystal silicon to produce silicon fine particles in the dispersion and dispersing the silicon fine particles in the dispersion;
In this step (1), specifically, as shown in FIG. 1, the single crystal silicon is allowed to stand or be fixed in a container filled with the oxide particle dispersion, and a predetermined distance from the single crystal silicon is set. Set the horn part of the ultrasonic generator and sonicate for 5 to 120 minutes, for example, to generate silicon fine particles from single crystal silicon and disperse the silicon fine particles in the oxide particle dispersion. . The method for fixing the single crystal silicon is not particularly limited, and examples thereof include a method of fixing in a container using a jig.

  In this step (1), it is preferable that the tip of the horn part of the ultrasonic generator and the flat part of the single crystal silicon are separated from each other by about 0.01 mm to 3 mm. If it is less than 0.01 mm, the generated silicon fine particles may be clogged between the horn tip and the single crystal silicon, and the oxide particles may not effectively transmit the ultrasonic shock to the single crystal silicon. If it exceeds 3 mm, the ultrasonic energy transmitted to the oxide particles may be attenuated.

(2) An oxide particle dispersion containing oxide particles and a dispersion medium is dropped on the single crystal silicon, and ultrasonic waves are applied to the dispersion to cause the oxide particles to collide with the single crystal silicon. Crushing at least a part of the single crystal silicon to produce silicon fine particles and dispersing the silicon fine particles in the dispersion;
Specifically, in this step (2), as shown in FIG. 2, the single crystal silicon is allowed to stand or be fixed, and the horn portion of the ultrasonic generator is set at a predetermined interval from the single crystal silicon. Then, the oxide particle dispersion is dropped onto the single crystal silicon, and ultrasonic waves are applied to the dropped oxide particle dispersion. Since the oxide particle dispersion dropped on the single crystal silicon is scattered by the impact of ultrasonic waves, it is recovered from the drain, supplied to the tank, and reused, that is, dropped again on the single crystal silicon.

In this step (2), it is preferable that the tip of the horn part of the ultrasonic generator and the flat part of the single crystal silicon are separated by about 0.01 to 3 mm. If it is less than 0.01 mm, the generated silicon fine particles may be clogged between the horn tip and the single crystal silicon, and the oxide particles may not effectively transmit the ultrasonic shock to the single crystal silicon. If it exceeds 3 mm, the ultrasonic energy transmitted to the oxide particles may be attenuated.

Dissolution of oxide particles;
In the oxide particle dispersion after the ultrasonic treatment, silicon fine particles scraped (generated) from single crystal silicon are dispersed. As a method for recovering the silicon fine particles from this dispersion, a known method can be applied, but a method of recovering the silicon fine particles after adding a dissolving agent to the dispersion to dissolve the oxide particles is preferable.

A solubilizer is a substance that dissolves oxide particles and is substantially non-reactive with silicon fine particles. For example, when the oxide particles are SiO ₂ particles, hydrofluoric acid is preferably used as the dissolving agent. The solubilizer may be diluted with a solvent. In this case, the concentration is preferably 10 to 49% by mass. Examples of the solvent include water and an acetic acid aqueous solution.

The amount of the solubilizer used is not particularly limited as long as it is an amount capable of dissolving the oxide particles. For example, when the oxide particles are SiO ₂ particles and the solubilizer is a solution containing hydrogen fluoride, The amount of the hydrogen fluoride-containing solution used is preferably 5 to 500 parts by mass in terms of hydrogen fluoride with respect to 100 parts by mass of the SiO ₂ fine particles.

Conditions such as the time required for dissolving the oxide particles or the temperature at which the oxide particles are dissolved are not particularly limited, and can be set as appropriate according to the concentration of the oxide particles, the concentration of the dissolving agent, and the like. For example, when the oxide particles are SiO ₂ particles and the dissolving agent is a solution containing hydrogen fluoride, the time can be 0.1 to 2 hours and the temperature can be 5 to 80 ° C.

Separation of silicon particles;
The method for producing silicon fine particles of the present invention may include a step of separating silicon fine particles from a liquid containing silicon fine particles.

  The liquid containing the silicon fine particles after the oxide particles are dissolved contains the generated silicon fine particles, as well as a dispersion medium (dispersion medium, dissolved oxide particles, additives, etc.). Silicon fine particles may be separated from the substrate.

  The step of separating the silicon fine particles includes a step (a) of adding a dissolving agent to the silicon fine particle-containing liquid to dissolve the oxide particles, and a step of heating and drying the liquid obtained by the step (a) ( Preferably c) is included. Moreover, it is preferable to include the process (b) which removes the melt | dissolution of the said dissolving agent and / or the said oxide particle by ultrafiltering the liquid containing the said silicon fine particle before the said process (c).

Examples of the method for separating the silicon fine particles include removal of a dispersion medium and the like. As a method for removing the dispersion medium and the like, a known method can be employed, and examples thereof include methods such as heat drying and filtration. For example, when the oxide particles are SiO ₂ , the dispersion medium is water, and the dissolving agent is hydrofluoric acid, the liquid containing the silicon fine particles is heated to form the oxide particles together with the dispersion medium. The lysate (H ₂ Si ₂ F ₆ ) can also be removed.

In addition, by applying a combination of filtration such as ultrafiltration and dilution with a dispersion medium to the liquid after the dissolution treatment of the oxide particles is completed, dispersion stability for the solubilizer and oxide particles can be applied. Additives such as an agent, a dispersion stabilizer for silicon fine particles, a polishing accelerator, a surfactant, and a stabilizer can be removed to prepare a silicon fine particle-containing liquid substantially composed of silicon fine particles and a dispersion medium. The silicon fine particles may be separated from the silicon fine particle-containing liquid by removing the dispersion medium by heat drying or the like.

Thus, although it depends on the conditions of the ultrasonic treatment, silicon fine particles having an average particle diameter in the range of 5 to 100 nm can be usually obtained.
Sizing treatment;
The method for producing silicon fine particles of the present invention may further include a sizing step.

  The sizing method is not particularly limited as long as coarse particles can be excluded from the silicon fine particles, but usually a filtration method or a sedimentation classification method is adopted. The term “coarse particles” refers to silicon fine particles having a particle diameter larger than that of silicon fine particles to be produced (particle diameter is in a specific range).

As the filtration method, a known dehydration filtration method, ultrafiltration membrane method or the like can be used.
The sedimentation classification method is a method in which fine particles are added to water or an aqueous dispersion medium containing an organic solvent such as alcohol, and coarse particles are separated or classified according to the difference in sedimentation speed of the particles.

Particle size adjustment treatment;
The method for producing silicon fine particles of the present invention may further include a step of adjusting the particle size of the produced silicon fine particles.

Examples of the step of adjusting the particle diameter include a step of performing the following operations (1) and (2) once or a plurality of times;
(1) An oxidant is added to the liquid in which the silicon fine particles are dispersed to form an oxide film on the surface of the silicon fine particles.
(2) Next, an oxide film solubilizer is added to the liquid containing silicon fine particles on which the oxide film is formed, and the oxide film is dissolved and removed.

As the oxidizing agent, a dispersion medium of silicon fine particles, that is, a substance having high solubility in the inert liquid is preferable, and examples thereof include HNO ₃ , H ₂ O ₂ , HIO ₃ , and O ₃ . The amount used is usually 1 to 100 parts by mass with respect to 100 parts by mass of the silicon fine particles. If the amount is less than 1 part by mass, the silicon fine particles may not be oxidized sufficiently. If the amount exceeds 100 parts by mass, the oxide film tends to be excessively thick and fine adjustment of the particle diameter tends to be difficult.

As the solubilizer, those capable of dissolving the oxide film and substantially not dissolving silicon fine particles are used, and examples thereof include hydrofluoric acid.
After the oxide film is formed on the silicon fine particles, a dissolving agent is added to remove the oxide film. Although the addition amount of a solubilizing agent is based also on the kind of solubilizing agent, it is 30-200 mass parts normally with respect to 100 mass parts of silicon microparticles. If the amount is less than 30 parts by mass, the oxide film may not be sufficiently removed. If the amount exceeds 200 parts by mass, the step of removing the dissolving agent may be lengthened.

[Example]
Hereinafter, the present invention will be described in more detail with reference to examples.
[Example 1]
As shown in FIG. 2, the single crystal silicon 2 is fixed to the sample stage 7 at the bottom of the container 4, and the horn 1 of the ultrasonic generator (horn type ultrasonic device C-5281 manufactured by Kaijo Corporation) is placed on the single crystal silicon 2. (Horn tip diameter; 7 mmφ) was installed vertically. The distance between the single crystal silicon 2 and the horn part 1 of the ultrasonic generator was set to 0.5 mm.

  The single crystal silicon 2 was cut from a 200 mmφ single crystal silicon wafer (manufactured by Fujimi Electronics Co., Ltd.) and fixed so that the (100) mirror surface of 20 mm × 20 mm was horizontal and upward.

  The oxide particle dispersion 3 is supplied from the nozzle 8 onto the single crystal silicon 2 at a rate of 0.5 ml / min so that the space between the tip of the horn 1 and the upper surface of the single crystal silicon 2 is always filled with droplets. The ultrasonic waves were applied to the single crystal silicon 2 from the horn unit 1 of the ultrasonic generator while maintaining the state where the dropped liquid droplets were in contact with the single crystal silicon 2 and the horn unit 1. This sonication was performed for 40 minutes. All of the dispersed oxide particle dispersion 3 was collected in the drain 5, circulated through the pump 6, and again supplied onto the single crystal silicon 2 from the nozzle 8.

The details of this ultrasonic treatment are as follows.
Single crystal silicon;
Single crystal silicon of size 200 mm [specifications of 200 mmφ wafer substrate (single crystal silicon); CZ manufacturing method B-doped P type (resistivity: 0.1 to 100 Ωcm)]
Oxide particle dispersion;
The details of the prepared oxide particle dispersion are as follows.

Oxide particles = Silica fine particles Average particle size of oxide particles = 500 nm (natural / centrifugal sedimentation particle size distribution analyzer
CAPA-700 (measured by HORIBA, Ltd.)
Dispersion medium = pure water Silica particle concentration = 20% by mass
pH = 9.5 (adjusted with 5% by mass aqueous sodium hydroxide solution)
Dispersion stabilizer of oxide particles = 1: 1 mixture of 10 mass% hydrochloric acid and 10 mass% sodium hydroxide aqueous solution (0.1 mass% in the dispersion)
Liquid volume = 20ml
Sonication;
The details of the ultrasonic treatment conditions are as follows.

Ultrasonic output: 150W
Ultrasonic frequency: 19.5 kHz
Ultrasonic horn tip diameter: 7mm
After the ultrasonic treatment is completed, 20 ml of 49% hydrofluoric acid solution is added to the particle dispersion to dissolve all the SiO ₂ particles, followed by drying at 90 ° C. for 10 hours to obtain about 1 g of silicon fine particles. Got.

  The average particle diameter of the silicon fine particles measured by the method described above (TEM observation method) was 40 nm. Note that a transmission electron microscope H-800 (manufactured by Hitachi, Ltd., acceleration voltage 200 KV, resolution: 0.2 nm, photographing magnification 250,000 times) was used for taking a TEM photograph. A TEM photograph (magnification 250,000 times) of the obtained silicon fine particles is shown in FIG.

[Example 2]
About 1 g of silicon fine particles were produced in the same manner as in Example 1 except that the oxide particle dispersion was changed to an oxide particle dispersion in which the concentration of SiO ₂ particles having an average particle diameter of 1000 nm was 20%.

  The average particle diameter of the silicon fine particles measured by the method described above (TEM observation method) was 60 nm.

Silicon fine particles obtained by the production method of the present invention are extremely useful as a semiconductor material, a light emitting material, and the like.
Further, the method for producing silicon fine particles of the present invention can produce silicon fine particles effectively with relatively little energy, and has high practicality.

FIG. 1 is a schematic view showing an embodiment of the present invention. FIG. 2 is a schematic view showing an embodiment of the present invention. FIG. 3 is a TEM photograph of the silicon fine particles produced in Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ultrasonic horn 2 ... Single crystal silicon 3 ... Oxide particle dispersion 4 ... Container 5 ... Drain 6 ... Pump 7 ... Sample stand 8 ... Nozzle

Claims (10)

  While bringing the oxide particle dispersion containing the oxide particles and the dispersion medium into contact with the single crystal silicon, ultrasonic waves are applied to the dispersion to cause the oxide particles to collide with the single crystal silicon, thereby A method for producing silicon fine particles, characterized in that at least a part of crystalline silicon is pulverized to produce silicon fine particles.   While immersing the single crystal silicon in the oxide particle dispersion containing the oxide particles and the dispersion medium, ultrasonic waves are applied to the dispersion to cause the oxide particles to collide with the single crystal silicon. 2. The method for producing silicon fine particles according to claim 1, comprising a step of pulverizing at least a part of the crystalline silicon to produce silicon fine particles and dispersing the silicon fine particles in the dispersion.   An oxide particle dispersion containing oxide particles and a dispersion medium is dropped onto single crystal silicon, and ultrasonic waves are applied to the dispersion to cause the oxide particles to collide with the single crystal silicon. 2. The method for producing silicon fine particles according to claim 1, comprising a step of pulverizing at least a part of silicon to produce silicon fine particles and dispersing the silicon fine particles in the dispersion.   The method for producing silicon fine particles according to any one of claims 1 to 3, wherein the pH of the oxide particle dispersion is in the range of 2 to 11.   The method for producing silicon fine particles according to any one of claims 1 to 4, wherein the oxide particle dispersion further contains a dispersion stabilizer for oxide particles and / or a dispersion stabilizer for silicon fine particles.   6. The method for producing silicon fine particles according to claim 1, further comprising a step of separating the silicon fine particles from the liquid containing the silicon fine particles.   In the step of separating the silicon fine particles, a step (a) of adding a dissolving agent to the silicon fine particle-containing liquid to dissolve the oxide particles, and a solution obtained by the step (a) are heated and dried. The method for producing silicon fine particles according to claim 6, comprising a step (c).   Before the step (c), the method further includes a step (b) of removing the dissolution agent and / or the dissolved oxide particles by ultrafiltration of the silicon fine particle-containing liquid. The method for producing silicon fine particles according to claim 7.   The method for producing silicon fine particles according to any one of claims 1 to 8, further comprising a step of removing coarse silicon fine particles and adjusting the average particle size of the silicon fine particles to a range of 5 to 100 nm. 10. The silicon fine particle-containing liquid according to claim 1, further comprising a step of preparing the particle size of the silicon fine particles by performing the following operations (1) and (2) once or a plurality of times. Manufacturing method of
(1) An oxidant is added to the liquid containing the silicon fine particles to form an oxide film on the surface of the silicon fine particles.
(2) Next, an oxide film solubilizer is added to the silicon fine particle-containing liquid on which the oxide film is formed to dissolve and remove the oxide film.