JP2006206371A - Manufacturing method of silicon fine particle and manufacturing method of titanium oxide fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of manufacturing simply and with good productivity silicon fine particle and titanium oxide fine particle which can be preferably used in a light receiving element, a light emitting element or the like. <P>SOLUTION: The manufacturing method of silicon fine particle comprises dissociating silicon from a silicon hydride by bringing a raw material gas containing the silicon hydride into contact with a heated catalyst comprising either one of tungsten, tantalum, carbon, molybdenum and titanium or a compound thereof, and at the same time aggregating the dissociated silicon by raising the pressure of the raw material gas to high pressure capable of aggregating the dissociated silicon to form silicon fine particle. Whereby the aggregation of silicon is promoted and silicon fine particle is efficiently formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing silicon fine particles and a method for producing titanium oxide fine particles that can be suitably used for light receiving elements, light emitting elements, and the like.

  Conventionally, fine particles having a particle size of about 10 nm or less generally show electrical and optical properties different from the bulk state due to the quantum size effect. For example, in a few nanometer-sized fine particles made of silicon, it has been confirmed that the light absorption edge is not observed in bulk silicon and the emission intensity is increased due to the change of the electron transition type. Application to a light receiving element (photodiode: PD), a light emitting element (light emitting diode: LED, semiconductor laser: LD) of fine particles (silicon nanoparticles) is expected.

  Such fine particle production methods are roughly classified into wet chemical methods and dry processes. As an example of the former, there is a method in which an organosilane is used as a raw material and is prepared by an electrode reduction method using a reactive electrode (for example, see Patent Document 1 below).

  This method for producing silicon ultrafine particles is a method for producing silicon ultrafine particles by an electrode reduction method using a reactive electrode using a material containing silicon as a raw material, and the energization amount is from 0.5 F per mole. By setting it to 2.0F, it is possible to produce silicon ultrafine particles having a diameter in the range of 1.0 nm to 5.0 nm, which is necessary for developing the quantum size effect. Further, the present invention is a method for producing ultrafine silicon particles produced by an electrode reduction method using a reactive electrode using one substance or a plurality of substances among tetrachlorosilane, tetrafluorosilane, and tetrabromosilane as raw materials. By this manufacturing method, it is possible to provide ultrafine silicon particles that are small and have no restrictions on the installation location, and are manufactured by an inexpensive manufacturing apparatus.

On the other hand, as an example of the latter, there is a method of producing silicon single crystal fine particles in a gas phase using SiH ₄ gas as a raw material in VHF plasma (for example, see Patent Document 2 below).

In this method of laminating Si single crystal particles, Si single crystal particles are formed using SiH ₄ gas as a raw material in VHF plasma, Si single crystal particles are deposited on a substrate, and the deposited Si single crystal particles are formed. in Si single crystal fine particle layer obtained by forming a SiO ₂ film on the surface, Si in the SiO ₂ film of Si single crystal fine particles the surface of the single crystal particle layer is melted by heat treatment by doping P (phosphorus) in the Si single crystal The Si single crystal fine particles in the fine particle layer are closely rearranged with each other. By this method, the voids in the Si single crystal fine particle layer are reduced, the electron tunneling probability is increased, the applied electric field distribution becomes uniform, and the external quantum efficiency of the electron gun is increased.

  In addition, a method of forming fine particles such as silicon on a powder such as ceramics has been proposed (see, for example, Patent Document 3 below).

The method of Patent Document 3 is a method of applying ultrafine particles of silicon, silicon oxide, silicon nitride, or an alloy thereof to a core powder such as ceramics, and (a) in a reactive gas to a CVD reaction chamber. A step of uniformly suspending the core powder from the core powder bed, and (b) ultra-fine particles of silicon, silicon oxide, silicon nitride or alloys thereof in the gas phase by uniform decomposition of the reactive feed gas mixture. A step of selectively forming and simultaneously suppressing the growth of the core powder by CVD on the surface of the suspended core powder; and (c) ultrafine particles of silicon, silicon oxide, silicon nitride, or an alloy thereof on the core powder. The process of apply | coating. By this method, ultrafine particles of silicon base can be uniformly applied to the powder.
JP 2002-154817 A JP 2003-81691 A JP-A-5-246786

  However, the wet chemical method described in Patent Document 1 can easily produce silicon fine particles using an inexpensive apparatus, but is not suitable for mass production, Problems such as low purity and low energization in order to control the particle size of the silicon fine particles, resulting in a slow generation rate of the silicon fine particles, and the like.

  Further, in the method using the dry process described in Patent Document 2, since VHF such as 144 MHz is used as an excitation frequency, a problem that a large amount of discharge is difficult due to difficulty in large-area discharge. In addition, there is a problem in that the silicon single crystal fine particles are charged while staying in the plasma region and easily aggregate.

  Furthermore, the technique described in Patent Document 3 has a problem that the adhesive strength is weak and the substantial carrier mobility is low because of the point contact form of powder and fine particles.

  Accordingly, the present invention has been completed in view of the above-mentioned problems in the prior art, and an object of the present invention is to easily produce silicon fine particles and titanium oxide fine particles that can be suitably used for a light receiving element, a light emitting element, and the like. It is to provide a manufacturing method that can be manufactured well.

  In the method for producing silicon fine particles of the present invention, a source gas containing a hydride of silicon is brought into contact with a heating catalyst made of any one of tungsten, tantalum, carbon, molybdenum, and titanium, or a compound thereof. In addition to dissociating silicon from the compound, the dissociated silicon is aggregated to form silicon fine particles by setting the pressure of the source gas to a high pressure that allows the dissociated silicon to aggregate.

  Further, the method for producing fine titanium oxide particles of the present invention comprises heating a raw material gas containing a chloride or fluoride of titanium and an oxygen gas from any one of tungsten, tantalum, carbon, molybdenum and titanium or a compound thereof. Titanium is dissociated from the chloride or fluoride of titanium by contacting with the catalyst, and the pressure of the source gas is set to a high pressure at which dissociated titanium can be agglomerated, so that the dissociated titanium is agglomerated and oxidized. Titanium fine particles are formed.

  In the method for producing silicon fine particles of the present invention, a source gas containing a hydride of silicon is brought into contact with a heating catalyst made of any one of tungsten, tantalum, carbon, molybdenum and titanium, or a compound thereof, and a hydride of silicon. Since the silicon is dissociated from the silicon and the pressure of the source gas is set to a high pressure at which the dissociated silicon can be agglomerated, the dissociated silicon is agglomerated to form silicon fine particles. Silicone particles used in light-emitting elements, light-receiving elements, etc. can be produced easily and easily by using a method that can agglomerate silicon in the apparatus and obtain silicon particles of a desired size. It becomes possible to manufacture with good properties.

  In the method for producing fine titanium oxide particles of the present invention, a raw material gas containing a chloride or fluoride of titanium and an oxygen gas is used as a heating catalyst made of any one of tungsten, tantalum, carbon, molybdenum and titanium or a compound thereof. Titanium is dissociated from the chloride or fluoride of titanium by bringing it into contact, and the pressure of the source gas is set to a high pressure at which dissociated titanium can be agglomerated, so that the dissociated titanium is agglomerated while being oxidized to form titanium oxide particles. Therefore, by using a technique (contact CVD method) in which the raw material gas is brought into contact with the heating catalyst and titanium can be aggregated in the apparatus to obtain titanium oxide fine particles having a desired size, a light emitting device is obtained. In addition, it is possible to easily produce titanium oxide fine particles used for a light receiving element or the like with high productivity.

  BEST MODE FOR CARRYING OUT THE INVENTION The best embodiment of the method for producing silicon fine particles and the method for producing titanium oxide fine particles of the present invention will be described in detail below.

  In the method for producing silicon fine particles of the present invention, a source gas containing silicon hydride is brought into contact with a heating catalyst made of any one of tungsten, tantalum, carbon, molybdenum, and titanium, or a compound thereof. Silicon is dissociated from the chemical compound, and the pressure of the raw material gas is set to a high pressure at which dissociated silicon can be agglomerated, thereby aggregating the dissociated silicon to form silicon fine particles.

For example, when a tungsten wire heated to 1800 ° C. is used as the heating catalyst, when SiH ₄ molecules collide with this under the pressure of a predetermined raw material gas, the SiH ₄ molecules are dissociated with a probability of about 40%. The main feature of the method of the present invention using the catalytic reaction with the heating catalyst is that the utilization efficiency of the raw material gas is about one order of magnitude higher than that of general plasma CVD, and the same amount of fine particles is formed when forming the same amount of fine particles. The usage is greatly reduced.

  Here, as the heating catalyst, it is preferable to use a material having a high melting point and excellent workability that can be easily processed into a linear shape, such as tungsten, tantalum, carbon, molybdenum and titanium, or these. By using this compound, the above high gas decomposition efficiency can be realized.

  In addition, in the example using a tungsten wire heated to 1800 ° C. as the heating catalyst, it has been found that a silicon atom is generated by a primary reaction, and a silicon atom having a short lifetime is rapidly increased to form a fine particle nucleus. The formation rate of silicon fine particles is considered to be high because of the formation.

  In the present invention, the pressure of the raw material gas (atmosphere gas in the production apparatus) is set to a higher pressure (about 0.1 to 5 kPa) than a low pressure (about 0.1 to 50 Pa) as in the conventional catalytic CVD method. The aggregation rate of the dissociated silicon atoms is remarkably increased, and the generation rate of silicon fine particles can be improved. When the pressure of the raw material gas is lower than 0.1 kPa, the radical density in the gas phase is lowered, and the polymerization reaction rate is lowered, so that the production rate of silicon fine particles is extremely lowered. If it exceeds 5 kPa, on the contrary, the collision reaction rate of radical species in the gas phase increases excessively, making it difficult to control the particle size.

  In order to increase the generation amount of silicon fine particles, it is also effective to increase the surface area of the heating catalyst, and there is an advantage that there is no difficulty in increasing the discharge electrode area as in the high-frequency plasma CVD method. . In order to increase the surface area of the heating catalyst, it is preferable that the heating catalyst has a winding shape, a twisted shape, a saddle shape, a shape having surface irregularities, a ladder (ladder) shape, or the like.

  In addition, when silicon fine particles are produced by plasma CVD, the probability of charge adhesion increases as the particle diameter increases, and as a result, the charged silicon aggregates into silicon fine particles, so that silicon tends to repel each other. In addition, a phenomenon such as electrostatic adsorption to a substrate or the like is likely to occur. Therefore, it has a problem that it becomes difficult to handle silicon fine particles. In contrast, in the production method of the present invention, radicals in the gas phase are almost neutral, and the generated silicon fine particles are obtained in an uncharged state. Therefore, silicon fine particles having a particle size of 10 nm or less, in which the manifestation of the quantum size effect is remarkable, can be obtained with high yield.

As hydride of silicon contained in the source gas, Si ₂ H ₆ , Si ₃ H ₉ , SiCl _4-m H _m , SiF _4-m H _m (m is an integer of 0 to 3) in addition to SiH _4. Can be used. These gases have high decomposition efficiency and can realize a high aggregation rate.

In addition, when forming silicon compound fine particles, a raw material gas obtained by mixing the following gas with SiH ₄ may be used. That is, when forming SiC fine particles, CH ₄ (H includes deuterium D), C ₂ H ₂ , C _n H _{2n + 2} (n is a positive integer, the same shall apply hereinafter), C _n H _2n , CX ₄ (X is a halogen element) is preferable. When forming SiN fine particles, N ₂ , NO _n , N ₂ O, and NH ₃ are preferable. In the case of forming SiO fine particles and SiO ₂ fine particles, O ₂ , CO, CO ₂ , NO _n , N ₂ O, H ₂ O and the like are preferable.

  Further, an inert gas may be contained in the raw material gas. This inert gas has a function as a carrier gas for silicon fine particles and contributes to an improvement in the yield of silicon fine particles. In addition, when the heated inert gas comes into contact with the silicon fine particles, It has the function of activating the surface reaction. As this inert gas, He, Ne, Ar, or the like can be used. In addition, the residence time of the silicon hydride gas is an extremely important parameter for controlling the particle size of the silicon fine particles, and it is important to adjust the flow rate of the inert gas according to the desired particle size. For example, in order to set the particle size of the silicon fine particles to about 5 to 20 nm, it is preferable to adjust the flow rate such that the flow rate of the inert gas is about 15 to 50 times the flow rate of the silicon-based gas.

In addition, when it is desired to change the surface morphology of the silicon fine particles, a gas for dilution such as hydrogen (H ₂ ) may be included in the raw material gas.

  In the method for producing fine titanium oxide particles of the present invention, the raw material gas containing a chloride or fluoride of titanium and oxygen gas is any one of tungsten, tantalum, carbon, molybdenum and titanium or a compound thereof. Titanium oxide is agglomerated while oxidizing the dissociated titanium by contacting the heating catalyst to dissociate titanium from the chloride or fluoride of titanium, and by setting the pressure of the source gas to a high pressure at which dissociated titanium can agglomerate. Form fine particles.

  In this case, fine particles of titanium oxide can be obtained using a raw material gas containing titanium chloride such as titanium tetrachloride or titanium fluoride such as titanium tetrafluoride and oxygen gas.

For example, when a tungsten wire heated to 1800 ° C. is used as the heating catalyst, when TiCl ₄ molecules collide with this under the pressure of a predetermined raw material gas, the TiCl ₄ molecules are dissociated with a probability of about 10 to 30%. To do. The main feature of the method of the present invention using the catalytic reaction with the heating catalyst is that the utilization efficiency of the raw material gas is about one order of magnitude higher than that of general plasma CVD, and the same amount of fine particles is formed when forming the same amount of fine particles. The usage is greatly reduced.

  Here, as the heating catalyst, it is preferable to use a material having a high melting point and excellent workability that can be easily processed into a linear shape, such as tungsten, tantalum, carbon, molybdenum and titanium, or these. By using this compound, the above high gas decomposition efficiency can be realized.

  In addition, in the example using a tungsten wire heated to 1800 ° C as the heating catalyst, it has been found that a titanium atom is generated by a primary reaction, and a titanium atom having a short life is rapidly increased in order and oxidized. Therefore, it is considered that the production rate of titanium oxide fine particles is high because fine particle nuclei are formed.

  In the present invention, the pressure of the raw material gas (atmosphere gas in the production apparatus) is set to a higher pressure (0.1 to 5 kPa) than a low pressure (about 0.1 to 50 Pa) as in the conventional catalytic CVD method, The aggregation rate of the dissociated titanium atoms is dramatically increased, and the generation rate of the titanium oxide fine particles can be improved. When the pressure of the raw material gas is lower than 0.1 kPa, the radical density in the gas phase is lowered, and the polymerization reaction rate is lowered, so that the production rate of titanium oxide fine particles is extremely lowered. If it exceeds 5 kPa, on the contrary, the collision reaction rate of radical species in the gas phase increases excessively, making it difficult to control the particle size.

  In order to increase the amount of titanium oxide fine particles generated, it is also effective to increase the surface area of the heating catalyst, and there is an advantage that there is no difficulty in increasing the discharge electrode area as in the high-frequency plasma CVD method. is there. In order to increase the surface area of the heating catalyst, it is preferable that the heating catalyst has a winding shape, a twisted shape, a saddle shape, a shape having surface irregularities, a ladder shape, or the like.

  In addition, when producing titanium oxide fine particles by the plasma CVD method, the probability of charge adhesion increases as the particle diameter increases, and as a result, the charged titanium aggregates into titanium oxide fine particles. It tends to be repelled, and a phenomenon such as electrostatic adsorption to the substrate or the like is likely to occur. Therefore, there has been a problem that it becomes difficult to handle the titanium oxide fine particles. On the other hand, in the production method of the present invention, radicals in the gas phase are almost neutral, and the produced titanium oxide fine particles are obtained in an uncharged state. Accordingly, titanium oxide fine particles having a particle size of 10 nm or less that exhibits a significant quantum size effect can be obtained with high yield.

TiCl ₄ or the like can be used as the titanium chloride contained in the source gas, and TiF ₄ or the like can be used as the titanium fluoride. These gases have high decomposition efficiency and can realize a high aggregation rate.

  The source gas contains titanium chloride or fluoride and oxygen gas, but contains oxygen such as carbon monoxide, nitrogen monoxide, carbon dioxide, and nitrogen dioxide other than oxygen gas as a constituent element. An oxygen compound gas may be used.

  Further, an inert gas may be contained in the raw material gas. This inert gas has a function as a carrier gas for the titanium oxide fine particles, and contributes to the improvement of the yield of the titanium oxide fine particles. In addition, the heated inert gas comes into contact with the titanium oxide fine particles, It has a function of activating the surface reaction of titanium oxide fine particles. As this inert gas, He, Ne, Ar, or the like can be used. In addition, the residence time of titanium chloride or fluoride gas is an extremely important parameter for controlling the particle size of the titanium oxide fine particles, and it is important to adjust the flow rate of the inert gas according to the desired particle size. For example, to adjust the particle size of the titanium oxide fine particles to about 5 to 20 nm, it is preferable to adjust the flow rate such that the flow rate of the inert gas is about 15 to 50 times the flow rate of the silicon-based gas.

When it is desired to change the surface morphology of the titanium oxide fine particles, a gas for dilution such as hydrogen (H ₂ ) may be included in the raw material gas.

  Next, the manufacturing apparatus used for the manufacturing method of the present invention will be described below.

  FIG. 1 is a cross-sectional view schematically showing a production apparatus used in the method for producing silicon fine particles and the method for producing titanium oxide fine particles according to the present invention. In the manufacturing apparatus of FIG. 1, 1 is a chamber for generating a predetermined reaction inside by a contact CVD method to form silicon fine particles and titanium oxide fine particles, and 2 is a heating in the shape of a winding made of tungsten or the like. Catalyst, 3 is a DC power source for resistance heating by supplying a predetermined power to the heating catalyst, 4 is a gas introduction port for introducing a raw material gas, and 5 is a silicon fine particle or titanium oxide fine particle that has been formed and dropped in the chamber 1 A fine particle collector 6 collects silicon fine particles and titanium oxide fine particles having a predetermined particle diameter or less.

  In this manufacturing apparatus, the source gas is supplied from the gas inlet 4 provided in the chamber 1 and is decomposed in contact with the heating catalyst 2 heated by the DC power source 3. Next, silicon fine particles and titanium oxide fine particles are generated by a secondary reaction in the gas phase. Here, by providing the mesh window 6 on the entire upper surface of the particulate collector 5 provided on the downstream side of the source gas, it is possible to collect silicon particulates and titanium oxide particulates having a predetermined particle size or less with high yield. It becomes.

  By using a manufacturing apparatus having such a configuration, it is possible to manufacture silicon fine particles and titanium oxide fine particles with a high production rate and high yield.

  Examples of the method for producing silicon fine particles of the present invention will be described below.

  In the forming apparatus of FIG. 1, the chamber 1 is made of SUS (stainless steel), and a hot water jacket is provided on the inner wall in order to suppress the reaction between the adhesion film on the inner wall surface and radical species in the gas phase. A wall structure was adopted. As the heating catalyst 2, a coil-shaped tantalum (Ta) wire having a wire diameter of 0.5 mm was used. By making the heating catalyst 2 into a coil shape, the contact surface area between the heating catalyst 2 and the raw material gas molecules is increased, the generation rate of fine particles is improved, and the substantial dynamics of the heating catalyst 2 against thermal expansion and contraction. There is also an advantage that the service life of the heating catalyst 2 is extended by improving the mechanical strength. The heating catalyst 2 is connected to a DC power source 3 and is energized and heated to about 1800-1950 ° C. by resistance heating. Instead of the DC power supply 3, an AC power supply may be used as a power supply.

Here, in order to form silicon fine particles, a mixed gas of SiH ₄ and Ar is supplied from the gas inlet 4 as a raw material gas in a flow rate ratio range of 1: 1 to 1:50, and a gas pressure is set to 0.1 to 5 kPa. Hold to the extent. In Example 1, the flow rate ratio of the mixed gas of SiH ₄ and Ar is 1:20, the temperature of the heating catalyst 2 and the pressure of the raw material gas are various values, the yield of silicon fine particles and the time per hour The results of investigating the yield are shown in Table 1. Under the conditions shown in Table 1, silicon fine particles having a particle diameter of about 5 to 8 nm were formed.

  Examples of the method for producing titanium oxide fine particles of the present invention will be described below.

  In the forming apparatus of FIG. 1, the chamber 1 is made of SUS (stainless steel), and a hot water jacket is provided on the inner wall in order to suppress the reaction between the adhesion film on the inner wall surface and radical species in the gas phase. A wall structure was adopted. As the heating catalyst 2, a coil-shaped tantalum (Ta) wire having a wire diameter of 0.5 mm was used. By making the heating catalyst 2 into a coil shape, the contact surface area between the heating catalyst 2 and the raw material gas molecules is increased, the generation rate of fine particles is improved, and the substantial dynamics of the heating catalyst 2 against thermal expansion and contraction. There is also an advantage that the service life of the heating catalyst 2 is extended by improving the mechanical strength. The heating catalyst 2 is connected to a DC power source 3 and is energized and heated to about 1800-1950 ° C. by resistance heating. Instead of the DC power supply 3, an AC power supply may be used as a power supply.

［比較例１］ Here, in order to form the titanium oxide fine particles, a mixed gas of TiCl ₄ , oxygen gas and Ar is supplied from the gas inlet 4 as a raw material gas within a flow ratio of 1: 2: 15 to 1: 4: 20. The gas pressure is supplied and maintained at about 0.1 to 10 kPa. In Example 2, the flow ratio of the mixed gas of TiCl ₄ , oxygen gas, and Ar is 1: 2: 15, the temperature of the heating catalyst 2 and the pressure of the raw material gas are various values, and the titanium oxide fine particles Table 2 shows the results of investigation on the yield and the yield per hour. In addition, under the conditions in Table 2, titanium oxide fine particles having a particle size of about 10 to 50 nm were formed.

[Comparative Example 1]

［比較例２］ Silicon fine particles were produced in the same manner as in Example 1 except that the pressure of the raw material gas was set to a low pressure of 20 to 75 Pa. The results are shown in Table 3.

[Comparative Example 2]

Titanium oxide fine particles were produced in the same manner as in Example 2 except that the pressure of the source gas was changed to a low pressure of 10 to 45 Pa. The results are shown in Table 4.

It is sectional drawing which shows the outline of the manufacturing apparatus of the silicon fine particle of this invention.

Explanation of symbols

1: Chamber 2: Heated catalyst 3: DC power supply 4: Gas inlet 5: Fine particle collector 6: Mesh window

Claims (2)

A source gas containing a hydride of silicon is brought into contact with a heating catalyst made of any one of tungsten, tantalum, carbon, molybdenum and titanium or a compound thereof to dissociate silicon from the hydride of silicon, and the source material A method for producing silicon fine particles, characterized in that silicon fine particles are formed by aggregating the dissociated silicon by setting the gas pressure to a high pressure capable of aggregating the dissociated silicon. Titanium chloride or fluoride is brought into contact with a heating catalyst comprising any one of tungsten, tantalum, carbon, molybdenum and titanium or a compound thereof, and a source gas containing chloride or fluoride of titanium and oxygen gas. Titanium oxide fine particles characterized in that titanium oxide fine particles are formed by agglomerating while dissociating titanium by oxidizing the raw material gas at a high pressure at which the dissociated titanium can be agglomerated while dissociating titanium from Manufacturing method.

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