JP2010111524A - Silica container and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica container which ensures cost reduction, high dimensional precision and high durability, and a method of manufacturing the same. <P>SOLUTION: The method of manufacturing the silica container includes a step of: (1) preparing first raw material powder which is a silica particle, spherical second raw material powder comprising amorphous silica and having small average particle diameter, third raw material powder comprising silica as a main component and containing Al element and/or OH or a crystal seed material and forth raw material powder comprising high purity crystalline silica; and (2) forming the second raw material powder into granule bodies; a step of: (3) mixing the granular bodies of the first raw material powder and the second raw material powder; and (4) introducing the mixed powder into the inner wall of an outer mold form to form into a prescribed shape; a step of: (5) pressing the mixed powder to form a base body; (6) firing the base body and eliminating distortion; (7) forming an intermediate layer on the inner surface of the base body by spreading, supplying and melting the third raw material powder from the inside of the base body; and (8) forming an inner side layer on the inner surface of the intermediate layer by spreading, supplying and melting the forth raw material powder from the inside of the base body on which the intermediate layer is formed, wherein (6), (7) and (8) are carried out in random order. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silica container mainly composed of silica and a method for producing the same, and more particularly to a low-cost, high dimensional accuracy, high durability silica container and a method for producing the same.

Silica glass is a lens for projection exposure equipment (lithography equipment) for manufacturing large-scale integrated circuits (LSIs), prisms, photomasks and TFT substrates for displays, lamp tubes, window materials, reflectors, semiconductor industry cleaning containers, and semiconductor industry. It is used as a material for jigs and silicon semiconductor melting containers. However, as raw materials for these silica glasses, expensive compounds such as silicon tetrachloride and highly purified quartz powder must be used, and the silica glass melting temperature and processing temperature are extremely high, about 2000 ° C. Therefore, a large amount of energy is consumed, and a large amount of carbon dioxide, which is considered as one of the global warming gases, is caused.
Therefore, as one of the countermeasures, conventionally, a method for producing silica glass using a relatively inexpensive powder raw material or silica compound has been considered.

For example, Patent Document 1 discloses a method (sol-gel method) in which silicon alkoxide is hydrolyzed to form a silica sol, then gelled to form a wet gel, dried to a dry gel, and finally a transparent glass body by high-temperature firing. ing. Patent Document 2 discloses a method for obtaining transparent silica glass by a sol-gel method from a silica sol mixed solution composed of tetramethoxysilane or tetraethoxysilane and a silica sol solution containing silica fine particles. In Patent Document 3, in a method for producing transparent silica glass using silicon alkoxide and silica fine particles as main raw materials, heat treatment at 200 ° C. to less than 1300 ° C. is performed in an oxygen gas-containing atmosphere, and the temperature is further raised to 1700 ° C. or higher. It is shown that the heat treatment to be performed is performed in an atmosphere containing hydrogen gas, and the reduced-pressure atmosphere heat treatment is performed between the two heat treatments.
However, these conventional sol-gel methods not only have problems in the dimensional accuracy and durability of the produced silica glass, but also require a baking process at a high temperature, so they are not so cheap in terms of energy cost. It was.

Also, for example, in Patent Document 4, at least two different silica glass particles, for example, silica glass fine powder and silica glass particles are mixed to form a water-containing suspension, then press-molded, and dried and sintered at a high temperature. A method (slip casting method) for obtaining a silica-containing composite is shown. In Patent Document 5, opaque silica is produced by preparing a mixed aqueous solution (slip) containing silica glass particles having a size of 100 μm or less and silica glass granules having a size of 100 μm or more, injecting the mixture into a mold, and then drying and sintering. A method of making a glass composite is shown.
However, these conventional slip casting methods have a large shrinkage of the molded product due to mass evaporation of moisture in the drying process and the sintering process, and it has not been possible to produce a thick silica glass molded product with high dimensional accuracy.

JP-A-7-206451 Japanese Patent Laid-Open No. 7-277743 JP-A-7-277744 JP 2002-362932 A JP 2004-131380 A

  The present invention has been made in view of the above-described problems. A silica container mainly composed of silica having high dimensional accuracy and high durability is used as a main raw material. An object of the present invention is to provide a method for producing a silica container for producing at low cost with a small amount of input energy, and to provide such a silica container.

The present invention was made in order to solve the above problems, and is a method for producing a silica container having silica as a main component and having rotational symmetry,
(1) First raw material powder that is silica particles to be an aggregate, second raw material powder that is made of amorphous silica and has an average particle size smaller than the average particle size of the first raw material powder and is spherical. And a third raw material satisfying at least one of the main component being silica, containing an aluminum element and / or an OH group, and containing a compound powder serving as a crystal nucleus material for crystallization of silica glass. A step of preparing a fourth raw material powder consisting of powder and crystalline silica and having a higher silica purity than the first raw material powder and the second raw material powder;
(2) A step of preparing a binder-coated granule by mixing the second raw material powder with at least an organic binder and pure water to form a mixed slurry, and drying the mixed slurry;
(3) a step of preparing a mixed powder by mixing the first raw material powder and a granule prepared from the second raw material powder;
(4) introducing the mixed powder into an inner wall of an outer mold frame having rotational symmetry, and making the mixed powder a predetermined shape according to the outer mold frame while rotating the outer mold frame; ,
(5) A pressure forming step of forming the base by sandwiching the mixed powder having the predetermined shape between the outer mold frame and the inner mold frame, and pressing the mixed powder;
(6) The base body is made of an opaque silica layer by firing the base body in an oxygen-containing atmosphere, and the fired base body is gradually cooled at least in the temperature range from the slow cooling point to the strain point to remove the strain. Process,
(7) An intermediate layer made of silica glass is melted on the inner surface of the substrate by melting with a heating source disposed inside the substrate while the third raw material powder is dispersed and supplied from the inside of the substrate. Forming a step;
(8) While the fourth raw material powder is dispersed and supplied from the inside of the substrate on which the intermediate layer is formed, the intermediate material is melted by a heating source disposed on the inside of the substrate on which the intermediate layer is formed. Forming an inner layer made of transparent silica glass on the inner surface of the layer, and after the step (5), the step (6) and the steps (7) and (8) A method for producing a silica container is provided, wherein the steps are performed in any order (Claim 1).

  If it is a manufacturing method of a silica container by such a process, it has the ability to sufficiently prevent impurities contamination to the contents to be stored, a silica container having high dimensional accuracy, high durability, particularly heat distortion resistance, With low energy consumption, it can be manufactured with high productivity and low cost.

  In this case, the total concentration of aluminum elements and OH groups contained in the third raw material powder is 50 to 5000 wt. It is preferable to set it as ppm (Claim 2). Moreover, the ratio of the compound powder used as the crystal nucleus material contained in said 3rd raw material powder is 50-5000 wt. It is preferable to set it as ppm (Claim 3).

  Thus, when the third raw material powder contains an aluminum element and / or OH group, the total concentration of the aluminum element and OH group contained in the third raw material powder is 50 to 5000 wt. In the case of containing the compound powder that becomes the crystal nucleus material for crystallization of silica glass, the ratio of the compound powder that becomes the crystal nucleus material contained in the third raw material powder is 50 to 5000 wt. If it is set as ppm, when using the manufactured silica container, the spreading | diffusion of the impurity contained in a silica container, especially a base | substrate can be prevented more effectively. As a result, it is possible to more effectively prevent impurity contamination of the contents accommodated in the silica container.

In any one of the above-described methods for producing a silica container, it is preferable that the method further includes a step of applying a solution containing at least one of calcium, strontium, and barium to the surface of the inner layer. And in this case, calcium solution is applied to the surface of the inner layer, strontium, the total concentration of the barium, it is preferable that the 5~500μg / cm ² (Claim 5).

  Thus, in the method for producing a silica container of the present invention, if the step of applying a solution containing at least one of calcium, strontium, and barium is applied to the surface of the inner layer, these elements are added to the surface of the inner layer. A coating layer containing is formed. With such a coating layer, the transparent silica glass layer constituting the inner layer can be recrystallized at a temperature of about 1300 to 1600 ° C., and the contamination of the contents contained therein can be further reduced, and the silica glass surface Etching and dissolution can be suppressed. In particular, the above concentration is more effective.

  Moreover, in the manufacturing method of the silica container which concerns on this invention, it is preferable to have a process which makes the said 4th raw material powder contain at least 1 type of calcium, strontium, and barium (Claim 6). In this case, the total concentration of calcium, strontium, and barium contained in the fourth raw material powder is 50 to 5000 wt. It is preferable to set it as ppm (Claim 7).

  As described above, if the fourth raw material powder has a step of containing at least one of calcium, strontium, and barium, these elements can be contained in the inner layer of the manufactured silica container. Also by this, the transparent silica glass layer which comprises an inner layer can be recrystallized under the temperature of about 1300-1600 degreeC. In particular, the above concentration is more effective.

Moreover, in the manufacturing method of the silica container which concerns on this invention, said 1st raw material powder shall be produced by grind | pulverizing and sizing a silica lump (Claim 8).
Thus, if the first raw material powder is prepared by pulverizing and sizing the silica lump, the first raw material powder can be manufactured from a cheaper silica raw material to form a low-cost silica container.
Moreover, even if the silica powder produced by pulverizing and sizing the silica lump is used as a raw material, the method for producing a silica container of the present invention sufficiently prevents impurity contamination in the contents contained in the container. can do.

Moreover, in the manufacturing method of the silica container of this invention, the silica purity of said 1st raw material powder is 99.5-99.999 wt. % (Claim 9).
Thus, in the case of the method for producing a silica container of the present invention, the silica purity of the first raw material powder as a raw material is 99.5 to 99.999 wt. %, It is possible to sufficiently prevent impurities from being contained in the contents to be contained.

  Moreover, in the manufacturing method of the silica container of this invention, it is preferable that the particle size of said 1st raw material powder shall be 0.05-5 mm (Claim 10). Moreover, it is preferable that the particle diameter of said 2nd raw material powder shall be 0.1-10 micrometers (Claim 11).

  Thus, if the particle diameter of the first raw material powder is set to 0.05 to 5 mm or the particle diameter of the second raw material powder is set to 0.1 to 10 μm, high dimensional accuracy and high durability can be achieved at low cost. The silica container having advantages such as properties can be more reliably produced.

Moreover, it is preferable to perform the pressure molding of the mixed powder in a range of a pressure of 0.1 to 1 MPa and a temperature of 50 to 300 ° C. (Claim 12).
Thus, if the pressure molding of mixed powder is performed in the range of pressurization pressure 0.1-1 MPa and temperature 50-300 degreeC, manufacture of the silica container based on this invention can be performed more reliably.

Further, the mixing ratio of the first raw material powder and the second raw material powder when the mixed powder is produced is (second raw material powder) / {(first raw material powder) + (second Raw material powder)} is 5 wt. % Or more and 50 wt. It is preferable to make it less than% (claim 13).
Thus, the mixing ratio of the first raw material powder and the second raw material powder when producing the mixed powder is (second raw material powder) / {(first raw material powder) + (second Raw material powder)} is 5 wt. % Or more and 50 wt. If it is less than%, dimensional accuracy and durability can be sufficiently ensured while sufficiently reducing the manufacturing cost of the silica container.

  Moreover, in the manufacturing method of the silica container of this invention, it is preferable to form the thickness of the said intermediate | middle layer as 0.1-5 mm (Claim 14). Moreover, it is preferable to form the inner layer with a thickness of 0.1 to 5 mm.

  In this way, if the thickness of the intermediate layer and the thickness of the inner layer are formed to be 0.1 mm or more, contamination of the contents to be stored can be sufficiently prevented. Further, if the thickness of the intermediate layer and the thickness of the inner layer are 5 mm or less, the silica container can be manufactured at a sufficiently low cost without the input energy required for manufacturing being excessively increased.

The organic binder may be a paraffin binder or a stearic acid binder.
By using such an organic binder, it is possible to construct a substrate having high dimensional accuracy and high durability at a low cost. As a result, the production of the silica container can be carried out with high dimensional accuracy and high durability, more reliably at low cost.

Further, the silica container can be used as a crucible for pulling up a silicon single crystal.
Thus, the silica container manufactured by the method for manufacturing a silica container of the present invention can be suitably used as a crucible for pulling up a silicon single crystal. As a result, the total input energy and the total cost for manufacturing the silicon single crystal can be reduced.

The fourth raw material powder has an impurity amount of 10 wt. For ppb or less, titanium, vanadium, chromium, manganese, zirconium, niobium, molybdenum, tantalum, tungsten, and gold are each 1 wt. It is preferable to use a material having a ppb or less (claim 18).
Thus, if the fourth raw material powder has an impurity amount as described above, impurity diffusion from the silica container to the contents accommodated can be effectively prevented. It can be suitably used as a silicon single crystal pulling crucible (for solar, for solar cells).

Moreover, this invention provides the silica container manufactured by the manufacturing method of one of said silica containers (Claim 19).
Thus, if it is a silica container manufactured by one of the above-mentioned manufacturing methods of a silica container, it is a silica container manufactured with low energy consumption, high productivity, and low cost, to the contents to be stored. It is possible to make a silica container having the ability to sufficiently prevent the contamination of impurities and having high dimensional accuracy and high durability.

The present invention is also a silica container having rotational symmetry, which contains at least bubbles, is white and opaque, has a bulk density of 1.90 to 2.09 g / cm ³ , and has a silica purity of 99. 5 to 99.999 wt. % Of a non-transparent silica layer, and the inside of the substrate contains an aluminum element and / or an OH group and a compound component that becomes a crystal nucleus material for crystallization of silica glass. And an intermediate layer having a thickness of 0.1 to 5 mm, and a transparent silica glass layer substantially free of bubbles on the inner surface of the intermediate layer. A silica container having an inner layer having a bulk density of 2.20 to 2.21 g / cm ³ and a thickness of 0.1 to 5 mm is provided (claim 20).

  If it is such a silica container, it is a low-cost silica container, but it has the ability to sufficiently prevent the contamination of the contents to be contained, and is an inexpensive silica container having high dimensional accuracy and high durability. It can be.

  In this case, the total concentration of aluminum elements and OH groups contained in the intermediate layer is 50 to 5000 wt. Preferably, it is ppm (claim 21). Further, the concentration of the compound component serving as a crystal nucleus material contained in the intermediate layer is 50 to 5000 wt. It is preferably ppm (claim 22).

  Thus, when the intermediate layer contains an aluminum element and / or OH group, the total concentration of the aluminum element and OH group is 50 to 5000 wt. Preference is given to ppm. When the intermediate layer contains a compound component that becomes a crystal nucleus material, the concentration of the compound component that becomes the crystal nucleus material is 50 to 5000 wt. Preference is given to ppm. By setting it as such a value, the spreading | diffusion of the impurity to the silica container inner surface can be prevented more effectively.

In addition, the content of bubbles having a diameter of 20 μm or more in the substrate is preferably 10,000 / cm ³ or more, and the content of bubbles having a diameter of 20 μm or more in the inner layer is preferably 30 / cm ³ or less (claims). 23).
Thus, if the content of bubbles having a diameter of 20 μm or more in the substrate is 10,000 / cm ³ or more and the content of bubbles having a diameter of 20 μm or more in the inner layer is 30 / cm ³ or less, the substrate The durability of the inner surface of the silica container (surface of the inner layer) can be suppressed, and the resistance to etching and dissolution of the inner surface of the silica container can be increased.

Further, the total concentration of lithium, sodium, potassium, magnesium and calcium of the substrate is 10 to 100 wt. Preferably, it is ppm (claim 24).
Thus, the total concentration of lithium, sodium, potassium, magnesium and calcium of the substrate is 10 to 100 wt. If it is set as ppm, the heat-resistant deformation property of a silica container can further be improved.

The OH group concentration of the inner layer is 100 wt. It is preferably at most ppm (claim 25).
Thus, the OH group concentration of the inner layer is 100 wt. If it is ppm or less, the resistance to etching and dissolution of the inner surface of the silica container can be further increased.

  The inner layer preferably contains at least one of calcium, strontium, and barium. In this case, the total concentration of calcium, strontium and barium contained in the inner layer is 50 to 5000 wt. It is preferably ppm (claim 27).

  In this way, the inner layer contains at least one of calcium, strontium, and barium, and the transparent silica glass that constitutes the inner layer at a temperature of about 1300 to 1600 ° C., particularly if the total concentration is as described above. The layer can be recrystallized. In particular, it is more effective if the concentration is as described above.

In addition, a coating layer containing at least one of calcium, strontium, and barium can be further provided inside the inner layer (claim 28). In this case, the total concentration of calcium, strontium, and barium contained in the coating layer is preferably 5 to 500 μg / cm ² .

  Thus, if the inner layer further has a coating layer containing at least one of calcium, strontium, and barium, the inner layer can be formed at a temperature of about 1300 to 1600 ° C. by such a coating layer. The transparent silica glass layer constituting the material can be recrystallized to further reduce impurity contamination of the contents to be contained, and to suppress etching and dissolution of the silica glass surface. In particular, it is more effective if the concentration is as described above.

Further, the base is made of 30 to 3000 wt. It is preferable that it contains ppm (Claim 30).
Thus, the substrate is made of 30 to 3000 wt. As long as it contains ppm, the substrate can be imparted with an impurity diffusion preventing effect, and the contamination of the contents to be contained can be further reduced.

As described above, if the method for producing a silica container according to the present invention, an inexpensive, relatively low-grade silica powder is used as a raw material, and this is molded and fired to obtain a silica container having a predetermined shape. A highly productive and low-cost production method and silica container having dimensional accuracy, high durability, and low energy consumption can be obtained.
In addition, if the silica container according to the present invention is a silica container obtained at low cost and low energy consumption, it has not only the ability to sufficiently prevent impurity contamination to the contents to be stored, but also at a high temperature. Even if it is used for a long time, it is difficult to be thermally deformed, and it is possible to obtain an inexpensive silica container having high dimensional accuracy and high durability with little etching and dissolution of the inner surface of the container.

  In particular, silica crucibles used in the production of silicon crystals for photovoltaic power generation (for solar cells and solar) require large-diameter crucibles as the silicon crystals increase in size, preventing crucibles from softening and deformation when melting metal silicon. This is considered as a first problem. Further, not only impurity metal elements and alkali metal elements Li, Na, and K contained in the silica crucible at the time of forming the silicon crystal, but particularly Ta, Mo, Nd, Zr, W, Ti, V, Au, Cr, Mn When Co, Fe, Pb, Ag, Al, Ni, Cu or the like is taken into the silicon crystal, the photoelectric conversion efficiency is lowered. Accordingly, it is considered that the second problem is to give the silica crucible a shielding action (shielding action) of the impurity metal element so that the metal impurities contained in the silica crucible do not diffuse into the silicon melt. Further, when the silica crucible is dissolved in the silicon melt at the time of forming the silicon crystal and the oxygen element is contained in the silicon crystal, the photoelectric efficiency may be greatly lowered. Therefore, it is considered that the third problem is to form a silica crucible surface that is difficult to dissolve in the silicon melt (having etching resistance).

  Hereinafter, although the present invention is explained in detail, referring to drawings, the present invention is not limited to these. In particular, as an example to which the present invention can be preferably applied mainly below, a silica container that can be used as a metal silicon (Si) melting container (crucible) used as a material for solar cells (solar power generation, solar power generation). However, the present invention is not limited to this and can be widely applied to silica containers containing silica as a main constituent.

  As described above, the silica crucible used to make solar silicon crystals satisfies the three characteristics of heat-resistant deformation, impurity metal element shielding (shielding) and silicon melt etching resistance simultaneously. It is required to make it.

FIG. 1 shows a schematic cross-sectional view of an example of a silica container according to the present invention.
The silica container 71 according to the present invention has rotational symmetry, and its basic structure is a three-layer structure including an outermost layer base 51, an intermediate layer 56, and an inner layer 58. In each of these layers, the substrate 51 is mainly used as a layer responsible for durability such as heat-resistant deformation, the intermediate layer 56 is used as an impurity shield layer, and the inner layer 58 is used as a layer responsible for etching resistance to the contents. Positioned.

  In the substrate 51, the main component is silica, but the total value of the alkali metal elements Li, Na, K and the alkaline earth elements Ca, Mg is 10 wt. ppm to 100 wt. It is preferable to contain ppm. At the same time, 30 wt. ppm to 3000 wt. You may make it contain ppm. As a result, a large amount of silica-based or aluminosilicate-based microcrystals such as cristobalite are produced in the silica substrate 51 at a temperature of about 1500 ° C. at the time of forming the silicon crystal, and the heat distortion resistance of the substrate 51 is greatly increased. It becomes possible to improve.

In the intermediate layer 56 that should have an impurity diffusion preventing effect (impurity shielding effect), as one embodiment, a silica glass layer containing an aluminum (Al) element and / or an OH group is used. In this case, the total concentration of aluminum element and OH group is 50 to 5000 wt. It is preferable to set it as ppm. The idea of an impurity shield containing Al element is shown in the literature (Japanese Patent No. 3764776) as an example of a silicon single crystal pulling crucible for LSI. It is recognized to some extent that silica glass doped only with Al element has an impurity shielding property. However, when a relatively high concentration of impurity metal element is present, complete shielding is difficult with only the Al element. In this case, the silica glass containing the OH group simultaneously with the Al element can greatly improve the impurity shielding characteristics.
This impurity shielding effect is recognized for either Al element or OH group, but a great effect is produced by containing Al element and OH group simultaneously.

As another aspect, the intermediate layer 56 is formed of a silica glass layer having silica microcrystals, that is, glass ceramics. A method for producing glass ceramics is described in the literature (Japanese Patent No. 2931742). Crystal nucleating agent consisting of heat-resistant ceramic particles in silica glass, preferably silica glass containing OH groups, for example, oxides such as Al ₂ O ₃ , CaO, MgO, BeO, ZrO ₂ , HfO ₂ , boride ZrB ₂ , HfB ₂ , TiB ₂ , LaB ₆ , carbides containing ZrC, HfC, TiC, TaC, and nitrides containing at least one of ZrN, HfN, TiN, TaN. After that, when used as a container, it is heat-treated at 1400-1500 ° C., or when used as a container and placed at a temperature around 1500 ° C., cristobalite, opal, etc. Microcrystals are generated and an impurity shielding effect is exhibited.

In the transparent silica glass layer of the inner layer 58 that is resistant to silicon melt etching, at least one of the alkaline earth metal elements Ba, Sr, and Ca having an ionic radius larger than that of silicon is 50 to 5000 wt. ppm uniformly either leave doped, or it is possible to achieve the object by coating with 5~500μg / cm ² on the surface. The crystallization accelerator is described in the literature (Patent No. 3100836, Patent No. 3046545).

  However, in the present invention, in particular, the viscosity of the glass into the inner layer is obtained by forming an inner layer 58 made of a transparent silica glass layer resistant to silicon melt etching on the surface of the impurity shield layer of the intermediate layer 56. It is possible to prevent the diffusion of an alkali metal element that lowers the temperature and to maintain higher silicon melt etching resistance. And OH group contained in this inner layer is 100 wt. ppm or less, preferably 10 wt. By setting it to ppm or less, it becomes possible to maintain the silicon melt etching resistance for a long time.

  As described above, each of the substrate 51, the intermediate layer 56, and the inner layer 58 has a separate function, so that there are three heat resistance, impurity shielding, and silicon melt etching resistance required as a silica container. The characteristics can be fully satisfied at the same time.

Below, the manufacturing method of the above silica containers is demonstrated.
In FIG. 2, an example of the manufacturing method of the silica container which concerns on this invention is shown.

(Step 1: Preparation of each raw material powder)
First, as shown to (1) of FIG. 2, the silica powder used as a raw material in preparing a silica container is prepared. In addition, what is necessary is just to prepare each raw material powder before the process of using this raw material powder at least.
The raw material powder prepared here is as follows.
(A) first raw material powder 11 which is silica particles to be an aggregate;
(B) a second raw material powder 12 made of amorphous silica and having an average particle size smaller than the average particle size of the first raw material powder and having a spherical shape;
(C) A third component in which the main component is silica and satisfies at least one of containing an aluminum element and / or an OH group and containing a compound powder serving as a crystal nucleus material for crystallization of silica glass. Raw material powder 13,
(D) Fourth raw material powder 14 made of crystalline silica and having a silica purity higher than that of the first raw material powder and the second raw material powder.
In the present specification, the silica purity (SiO ₂ purity) means the proportion of silica (SiO ₂ ) in the material. However, metal elements are impurities, but gas components such as OH groups, O ₂ gas, and N ₂ gas are not considered as impurities.
Below, preparation of each of 1st, 2nd, 3rd, and 4th raw material powder is demonstrated one by one.

(First raw material powder)
The first raw material powder 11 is an aggregate of a base made of an opaque silica layer in the silica container according to the present invention, and is a main constituent material of the base.
The first raw material powder can be produced, for example, by pulverizing and sizing the silica lump as follows, but is not limited thereto.

  First, a natural silica lump (naturally produced crystal, quartz, silica, siliceous rock, opal stone, etc.) having a diameter of about 5 to 50 mm is heated in a temperature range of 600 to 1000 ° C. for about 1 to 10 hours in an air atmosphere. To do. Next, the natural silica mass is poured into water, taken out after rapid cooling, and dried. This process facilitates the subsequent crushing and sizing process by a crusher or the like, but the process may proceed to the pulverization process without performing the heating and quenching process.

Next, the natural silica lump is pulverized and sized by a crusher or the like, and the particle size is preferably adjusted to 0.05 to 5 mm, more preferably 0.1 to 1 mm to obtain natural silica powder.
Next, this natural silica powder is put into a rotary kiln composed of a silica glass tube having an inclination angle, and the inside of the kiln is made into an atmosphere containing hydrogen chloride (HCl) or chlorine (Cl ₂ ) gas at 700 to 1100 ° C. High purity treatment is performed by heating for about 1 to 100 hours. However, in a product application that does not require high purity, the process may proceed to the next process without performing the purification process.

The first raw material powder obtained after the above steps is crystalline silica, but amorphous silica glass scrap can be used as the first raw material powder depending on the purpose of use of the silica container.
As described above, the particle diameter of the first raw material powder is preferably 0.05 to 5 mm, and more preferably 0.1 to 1 mm.
The silica purity of the first raw material powder is 99.5 wt. % Or more, preferably 99.99 wt. % Or more is more preferable. Moreover, if it is the manufacturing method of the silica container of this invention, even if the silica purity of the 1st raw material powder is 99.999% or less and a thing with comparatively low purity, the manufactured silica container is to the contents to accommodate. Impurity contamination can be sufficiently prevented. Therefore, a silica container can be manufactured at a lower cost than before.

(Second raw material powder)
The 2nd raw material powder 12 becomes a material which comprises the base | substrate which consists of an opaque silica layer with the 1st raw material powder 11 among the silica containers which concern on this invention. The necessary conditions for the second raw material powder 12 are that it is made of amorphous silica and is spherical (spherical amorphous silica powder), and that the average particle size is smaller than the average particle size of the first raw material powder. is there.

In the method for producing a silica container of the present invention, the preferred particle diameter of the second raw material powder 12 for constituting the substrate is 0.1 to 10 μm, more preferably 0.2 to 5 μm. The method for producing the spherical amorphous silica powder as the second raw material powder 12 is not particularly limited, but is roughly divided into a wet method sol-gel method (alkoxide method) and a dry method melting method (spraying method, combustion method). And is prepared by various known methods (for example, the outline is described in “Application Technology of High-Purity Silica” (CMC Co., Ltd., issued on March 1, 1991, PP. 306-310)). be able to. In addition, as the second raw material powder 12, silica glass fine powder produced by a flame hydrolysis method of a silicon compound raw material such as silicon tetrachloride (SiCl ₄ ), so-called soot powder, can be used. The particle size of the soot powder in this case is also preferably about 0.1 to 10 μm.

When the first raw material powder 11 or the second raw material powder 12 contains (dope), for example, the metal element aluminum (Al), the base made of an opaque silica layer of the silica container to be manufactured contains aluminum. can do. When aluminum is contained, as in the case of containing an OH group in the silica glass layer described later, the diffusion of the impurity metal element is reduced, and the container of the impurity metal element with respect to the object to be processed contained in the manufactured silica container This is preferable because it has an effect of preventing diffusion to the inner surface.
The method for containing aluminum is not particularly limited, and it is possible to use a method in which the raw material powder is immersed and impregnated in a solution containing a soluble aluminum compound, and then pulled up at a constant speed and dried.
The dope of aluminum may be performed after a first raw material powder and a second raw material powder (a granule thereof) described later are mixed powder. The dope concentration is 30 to 3000 wt. ppm is preferred.

(Third raw material powder)
As the third raw material powder 13, a raw material powder whose main component is silica is prepared. This third raw material powder 13 is a silica powder for forming a shielding silica glass layer that prevents the diffusion of impurity metal elements, and therefore does it contain an aluminum element (Al element) and / or an OH group? It is necessary to satisfy at least one of the following: containing compound powder that becomes a crystal nucleus material for crystallization of silica glass.

  The material of the third raw material powder 13 may be natural quartz powder, natural crystal powder, synthetic cristobalite powder, or synthetic silica glass powder that has been subjected to high-purification treatment. These contain the above-mentioned Al element and / or OH group, or compound powder which becomes a crystal nucleus material for crystallization of silica glass. The particle size is 10 to 500 μm, preferably 50 to 200 μm.

  When the third raw material powder 13 contains Al element and / or OH group, the total concentration of Al element and OH group contained in the third raw material powder is 50 to 5000 wt. In the case of containing the compound powder that becomes the crystal nucleus material for crystallization of silica glass, the ratio of the compound powder that becomes the crystal nucleus material contained in the third raw material powder is 50 to 5000 wt. It is preferable to set it as ppm.

  Although the method of making the 3rd raw material powder 13 contain Al element and OH group is not specifically limited, For example, it can be as follows. That is, in order to contain Al element, it can be prepared by preparing an aqueous solution or alcohol solution of Al nitrate, chloride or carbonate, immersing high purity silica powder in the solution, and drying. Further, when the third raw material powder 13 is a synthetic powder, the OH group is adjusted to 10 to 1000 wt. About 3 ppm can be contained in the third raw material powder 13. And the density | concentration of the Al element and OH group which are contained in the third raw material powder in these manners is 50 to 5000 wt. It is preferable to set it as ppm.

Examples of compound powders that serve as crystal nuclei for crystallization of silica glass (hereinafter sometimes simply referred to as crystal nucleating agents) include fine powders of compounds having a high melting point such as about 2000 ° C. or higher. For example, Al ₂ O ₃ , CaO, MgO, BeO, ZrO ₂ , HfO ₂ as oxides, ZrB ₂ , HfB ₂ , TiB ₂ , LaB ₆ as borides, ZrC, HfC, TiC, TaC as carbides, The nitride can be produced by uniformly mixing at least one of ZrN, HfN, TiN, and TaN.

  In this way, when the silica container 71 is manufactured by containing the Al element and / or OH group or the crystal nucleus material in the third raw material powder 13, the intermediate layer 56 is particularly included in the base 51. It is possible to more effectively prevent the diffusion of impurities. As a result, it is possible to more effectively prevent impurity contamination of the contents stored in the silica container 71.

(Fourth raw material powder)
As the fourth raw material powder 14, a high-purity silica powder for the inner layer is prepared.
As a material of the fourth raw material powder 14, highly purified natural quartz powder, natural quartz powder, synthetic cristobalite powder, or synthetic silica glass powder can be considered. For the purpose of reducing the amount of bubbles in the transparent silica glass layer, crystalline silica powder is preferred. In addition, synthetic silica glass powder and synthetic cristobalite powder are preferable for the purpose of obtaining a higher-purity transparent silica glass layer. The particle size is 10 to 500 μm, preferably 50 to 200 μm.

Further, as the fourth raw material powder 14, the purity of the silica (SiO ₂ ) component is 99.9999 wt. % Or more is preferable. Preferably, each of the alkali metal elements lithium (Li), sodium (Na), and potassium (K) is 10 wt. below ppb, titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), zirconium (Zr), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), gold ( Au) is 1 wt. It is below ppb.

  Further, when the silica container produced according to the present invention is used as a silicon metal melting container that requires high durability, such as a container for continuously pulling a silicon single crystal (multi-pling) in solar cell production, it is accommodated. For the purpose of reducing the etching dissolution of the transparent silica glass layer by the silicon melt of the material, at least one of group 2 (group 2A) calcium (Ca), strontium (Sr), and barium (Ba) is used as the fourth raw material powder 14 It is preferable to have the process of making it contain. The group 2 element to be contained is more preferably Sr or Ba, and particularly preferably Ba from the point that it is difficult to incorporate into the silicon single crystal. For the fourth raw material powder containing these Group 2 elements, select a Group II element chloride, nitrate or carbonate that dissolves in water or alcohol, and prepare an aqueous solution or alcohol solution of this compound. It can be obtained by immersing silica raw material powder and then drying it. The total concentration of calcium, strontium and barium contained in the fourth raw material powder 14 is 50 to 5000 wt. It is preferable to set it as ppm.

(Step 2: Step of making second raw material powder into binder-coated granules)
Next, as shown in (2) of FIG. 2, the second raw material powder 12 prepared in the above-described step 1 is made into a binder-coated granule. The second raw material powder can be made into a binder-coated granule, for example, by the following procedure.

  First, the second raw material powder 12 is mixed with at least an organic binder and pure water to obtain a mixed slurry. Specifically, a paraffinic binder (melting point: 40 to 70 ° C.) or a stearic acid binder (melting point: 70 to 150 ° C.) is added to the second raw material powder 12 that is a spherical amorphous silica powder that becomes the core of the granule 22. Is preferably 1 to 10 wt. %, More preferably 2 to 5 wt. % Pure water is added so that the viscosity value is 10 to 100 mPa · s (the water content is about 20 to 60% by weight), and then the foreign matter is removed by a mesh filter set to 20 to 30 μm. A mixed slurry (silica slurry, suspension) is prepared.

The organic binder is not limited to the above-mentioned paraffinic binder and stearic acid binder, but with these, the granules 22 can be stably produced under a relatively low temperature heat treatment while being inexpensive. Is preferable.
In addition, as for the organic binder, other types of polyvinyl alcohol, polyvinyl acetal, acrylic binder, glycerin and the like may be appropriately mixed.

  The mixed slurry is dried to produce a binder-coated granule 22. The method for drying the mixed slurry is not particularly limited, and for example, it can be put into a spray drier (spray dryer) to produce spherical amorphous silica powder granules on which the binder is coated. This spray dryer was installed in a cylindrical hopper-type chamber, a device (atomizer) for spraying the mixed slurry installed in the upper part of the chamber, a hot air supply duct installed beside the chamber, and a lower part of the chamber It consists of a granule collection port. The temperature of the air flowing out from the hot air supply duct needs to be set higher than the melting point of the binder to be used, and is set in the range of 100 to 250 ° C. The granules 22 thus produced are aggregates of spherical amorphous silica powders whose surfaces are coated with a binder, and can be set to a predetermined average particle size within a particle size range of 20 to 200 μm. .

(Process 3: Mixing of the first raw material powder and the granule of the second raw material powder)
Next, as shown in FIG. 2 (3), the first raw material powder 11 and the granule 22 made from the second raw material powder 12 are uniformly mixed to produce a mixed powder 31.
As a method for mixing the granule of the first raw material powder and the second raw material powder, a V-type mixer or the like can be used when the amount is relatively small, but is not limited thereto.

As a mixing ratio of the first raw material powder 11 and the second raw material powder 12 when the mixed powder 31 is produced, (second raw material powder) / {(first raw material powder) + (second Raw material powder)} is 5 wt. % Or more and 50 wt. %, Preferably 10 wt. % Or more and 30 wt. % Or less is more preferable. This is due to the following reasons.
That is, for the purpose of reducing the manufacturing cost, it is preferable to make the first raw material powder as much as possible. The mixing ratio of the second raw material powder in the mixed powder is 5 wt. If it is at least%, the void density of the silica container substrate after molding and firing will not increase too much, and the bulk density can be made sufficiently high. As a result, the dimensional accuracy and heat resistance of the silica container can be ensured.
Also, the higher the mixing ratio of the second raw material powder, the smaller the voids of the silica container substrate after molding and firing, and the bulk density can be made relatively high, so that the dimensional accuracy and heat resistance of the silica container can be increased. And the mixing ratio is 50 wt. If it is less than%, the manufacturing cost can be kept sufficiently low.

(Process 4: Introduction of mixed powder into outer mold)
Next, as shown in (4) of FIG. 2, the mixed powder 31 is introduced into an outer mold frame having rotational symmetry for molding.
A state of this process is schematically shown in FIG.
First, as shown in FIG. 4A, the mixed powder 31 is gradually put into the inner wall portion of the rotating outer mold frame 101, and the mixed powder 31 is put into the outer mold frame 101 while utilizing the centrifugal force generated by the rotation. It is set as the predetermined shape according to the shape of the inner wall. At this time, the inner shape of the mixed powder 31 may be adjusted using the inner molding frame 102 or the like.
The method for supplying the mixed powder 31 to the outer mold 101 is not particularly limited. For example, a hopper 103 including a stirring screw 104 and a measuring feeder 105 can be used. In this case, the mixed powder 31 filled in the hopper 103 is stirred by the stirring screw 104 and supplied while adjusting the supply amount by the measuring feeder 105.

(Process 5: Pressure molding of mixed powder)
Next, as shown in FIG. 2 (5), the mixed powder 31 having a predetermined shape is sandwiched between the outer mold frame and the inner mold frame, and the mixed powder 31 is pressed to form the base.
The state of this process is schematically shown in FIGS. 4 (b) and 4 (c).
First, as shown in FIG. 4B, the plunger 111 serving as the inner mold frame is inserted into the mixed powder 31 having a predetermined shape in the above step 4, and the rotation of the outer mold frame 101 is stopped. Thereafter, the plunger 111 is pressurized and adjusted to a predetermined pressure of 0.1 to 1 MPa until the temperature of the mixed powder 31 reaches a predetermined temperature of 50 to 300 ° C. Hold until welded.
Next, as shown in FIG. 4 (c), the plunger 111 is pulled out and allowed to cool to room temperature to obtain a base body 51 on which the mixed powder 31 is pressure-molded. The material of the plunger is a metal such as stainless steel or a ceramic such as graphite, but is not limited thereto.

(Step 6: Firing of substrate by atmospheric heat treatment)
In this step, first, the base 51 is made of an opaque silica layer by firing the base 51 in an oxygen-containing atmosphere.
This will be described with reference to FIG.
The base 51 is taken out from the outer mold 101, and installed in an electric resistance heating furnace 301 using a high-purity alumina board as a heat insulating material and molybdenum disilicide as a heater 306. The electric resistance heating furnace 301 has a gas supply port 302 that supplies atmospheric gas, a gas discharge port 303 that discharges atmospheric gas, a gas supply port 302, and an open / close valve that controls gas passing through the gas discharge port 303, respectively. 304, 305 and the like.
In the case where Step 7 (intermediate layer formation) and Step 8 (inner layer formation) described later are performed prior to Step 6 (substrate baking, strain removal), the intermediate layer 56 is already formed on the substrate 51 of FIG. And the inner layer 58 is formed.

  Next, in an oxygen gas-containing atmosphere, the temperature is increased from room temperature to 1000 ° C. at a temperature increase rate of 50 ° C./hour to 200 ° C./hour to oxidize and burn organic substances such as binder contained in the substrate. ,Remove. Subsequently, the temperature is increased from 1000 ° C. to 1200 to 1500 ° C. at 20 ° C./hour to 100 ° C./hour, and then continuously at a predetermined temperature in the range of 1200 to 1500 ° C., preferably 1300 to 1400 ° C. The mixed powder 31 of the silica aggregate which is the first raw material powder 11 in the silica substrate 51 and the granule 22 of the second raw material powder 12 is sintered for a time. The atmosphere in the electric resistance heating furnace 301 during sintering may be an oxygen gas-containing atmosphere or may be a nitrogen gas 100% atmosphere, and is arbitrarily selected according to the characteristics of the raw material powder. I can do it.

Next, the baked substrate 51 is gradually cooled at least in the temperature range from the annealing point to the strain point to remove the strain.
For example, after completion of firing, the temperature is lowered to a temperature range of 1100 to 1200 ° C. (near the cooling point of silica glass) and then gradually increased to about 900 ° C. (below the strain point of silica glass) at 5 ° C./hour to 20 ° C./hour. The temperature is lowered to remove the residual strain of the silica container base 51 and allowed to cool to room temperature.

(Step 7: Formation of intermediate layer on inner surface of temporary molded body (hereinafter referred to as silica substrate) by electric discharge melting method)
In this step, an intermediate layer 56 is formed on the inner surface of the substrate 51 by melting and supplying the third raw material powder 13 from the inside of the substrate 51 with a heating source disposed inside the substrate 51. To do. The basic forming method follows the contents shown in, for example, Japanese Patent Publication No. 4-22861 and Japanese Patent Publication No. 7-29871. This will be described with reference to FIG.
The apparatus for forming the intermediate layer on the inner surface of the silica substrate includes a rotatable outer frame 201 having rotational axis symmetry, a rotary motor (not shown), and the third raw material powder 13 for forming the intermediate layer 56. , A stirring screw 234 for stirring the third raw material powder 13 in the hopper 233, a measuring feeder 235, a carbon electrode 212 serving as a heat source for discharge melting (arc melting), an electric wire, a high-voltage power supply unit 211, etc. Consists of.
The outer mold 201 used in this process may be the same as the outer mold 101 in the process 5.

  As the intermediate layer forming means, first, the outer mold 201 is set to a predetermined rotation speed, and a high voltage is gradually applied from the high-voltage power supply unit, and at the same time, a third intermediate layer is gradually formed from the raw material hopper 233. The raw material powder 13 is sprayed from the upper part of the base body 51. At this time, the discharge is started between the carbon electrodes, and the inside of the silica substrate is in the melting temperature range of silica powder (estimated to be about 1800 to 2000 ° C.), so the dispersed third raw material powder 13 (silica powder) is It becomes fused silica particles and adheres to the inner surface of the substrate 51. The carbon electrode, the raw material powder inlet, and the lid 213 installed in the upper opening of the base 51 have a mechanism capable of changing the position to some extent with respect to the base 51. By changing these positions, the base 51 The intermediate layer 56 can be formed with a uniform thickness on the entire inner surface. The intermediate layer 56 has less bubbles and is colorless and translucent to colorless and transparent.

  The intermediate layer 56 is preferably formed with a thickness of 0.1 to 5 mm. If the thickness of the intermediate layer is 0.1 mm or more, impurity diffusion to the inside of the silica container can be sufficiently suppressed, and contamination of the contents to be contained can be sufficiently prevented. Further, if the thickness of the intermediate layer is 5 mm or less, the silica container can be produced at a sufficiently low cost without the input energy necessary for production becoming too large.

In order to reduce the consumption of the carbon electrode, the atmosphere gas inside the silica substrate during discharge melting generally uses 100% nitrogen gas (N ₂ ). However, when the atmosphere containing hydrogen gas (H ₂ ) is used, the atmosphere gas has higher purity with fewer bubbles. An intermediate layer 56 is obtained. Further, the OH group concentration in the intermediate layer 56 can be set to a predetermined value by controlling the water vapor content concentration in the atmospheric gas. As an effect of containing an OH group, for example, by reducing the diffusion of an impurity metal element such as an alkali metal element contained in a substrate, contamination of a material to be treated when it is used as a silica container is prevented. I can do it.

(Step 8: Formation of inner layer on intermediate layer surface by electric discharge melting method)
In this step, the fourth raw material powder 14 is dispersed and supplied from the inside of the base 51 on which the intermediate layer 56 is formed, and melted by a heating source disposed on the inside of the base 51 on which the intermediate layer 56 is formed. The inner layer 58 is formed on the inner surface of the intermediate layer 56. The basic formation method is the same as in step 7 above.
The inner layer 58 preferably has a thickness of 0.1 to 5 mm, substantially does not contain bubbles, and is colorless and transparent. If the thickness of the inner layer is 0.1 mm or more, contamination of the contents to be contained can be sufficiently prevented. Further, when the thickness of the inner layer is 5 mm or less, the silica container can be manufactured at a sufficiently low cost without the input energy required for the manufacturing being excessively increased.

This will be described with reference to FIG.
The apparatus for forming the inner layer 58 on the inner surface of the intermediate layer 56 includes a rotatable outer mold 201 having rotational axis symmetry, a rotary motor (not shown), and a fourth raw material for forming the inner layer 58. A hopper 243 containing the powder 14, a stirring screw 244 for stirring the fourth raw material powder 14 in the hopper 243, a measuring feeder 245, a carbon electrode 212 serving as a heat source for discharge melting (arc melting), an electric wire, and a high-voltage power supply unit 211.
The hopper 243 for supplying the fourth raw material powder 14, the stirring screw 244 that constitutes a part thereof, and the measuring feeder 245 may be the same as those for the third raw material powder 13 in step 7. However, another one may be prepared or used.

In addition, the said process 6, the process 7, and the process 8 can be performed in random order. A case where Step 7 and Step 8 are performed before Step 6 is shown in FIG.
In this case, since the inner layer 58 and the intermediate layer 56 are fired at a high temperature, it is often preferable to perform the step 6 before the steps 7 and 8.

  Thus, although the silica container 71 of the present invention can be obtained, the silica container is washed as follows as necessary.

(Silica container cleaning and drying)
For example, surface etching is performed for about 5 to 30 minutes with about 1 to 10% hydrofluoric acid aqueous solution (HF), then washed with pure water and dried in clean air to obtain a silica container.

(Formation of coating layer)
Furthermore, in the present invention, a step of applying a solution containing at least one of calcium (Ca), strontium (Sr), and barium (Ba) to the surface of the inner layer 58 can be provided.
The inner surface portion of the manufactured silica container 71 is coated with at least one of Ca, Sr, and Ba as a crystallization accelerator. An aqueous solution or alcohol solution of any of these nitrates, oxides and carbonates of Ca, Sr and Ba is prepared, and this is applied to the inner surface of the inner layer 58 and dried. The total concentration of Ca, Sr, and Ba is preferably 5 to 500 μg / cm ² .
This treatment may not be performed depending on the use of the silica container.

Through the above steps, the silica container 71 according to the present invention shown in FIG. 1 as described above can be manufactured.
Of the layers constituting the silica container 71, the base 51 contains bubbles, is white and opaque, and is made of an opaque silica layer. The bulk density of the base 51 is typically 1.90 to 2.09 g / cm ³ , and with such a bulk density, the heat distortion resistance of the base 51 can be further increased.
In the case of the silica container 71 of the present invention, the substrate 51 has a silica purity of 99.5 to 99.999 wt. Even if it is comparatively low purity like%, the impurity contamination to the content to accommodate can fully be prevented.

  Furthermore, the silica container 71 of the present invention contains at least an aluminum element and / or an OH group inside the substrate 51 and a compound component that becomes a crystal nucleus material for crystallization of silica glass. It has the intermediate | middle layer 56 which consists of silica glass which satisfies one side.

Furthermore, the silica container 71 of the present invention has an inner layer 58 made of a transparent silica glass layer substantially free of bubbles on the inner surface of the intermediate layer 56. The bulk density of the inner layer 58 is typically 2.20 to 2.21 g / cm ³ .

Moreover, according to the manufacturing method of the silica container which concerns on this invention, content of the bubble of diameter 20 micrometers or more in the base | substrate 51 of the silica container 71 can be 10,000 pieces / cm < ³ > or more. If the bubble content in the substrate 51 is such a value, the heat distortion resistance of the substrate 51 can be further increased, and the heat distortion resistance of the silica container 71 can be further increased, which is preferable.
Moreover, according to the manufacturing method of the silica container which concerns on this invention, content of the bubble of diameter 20 micrometers or more in the inner layer 58 of the silica container 71 can be 30 pieces / cm < ³ > or less. If the content of bubbles in the inner layer 58 is such a value that does not substantially include bubbles, the surface of the inner layer 58 (roughness on the inner surface of the silica container 71) is suppressed, and the silica container 71 is suppressed. This is preferable because resistance to etching and dissolution of the inner surface can be increased.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.
Example 1
According to the method for producing a silica container of the present invention shown in FIG. 2, a silica container was produced as follows.

First, the first raw material powder 11 was prepared as follows.
100 kg of natural silica was prepared, heated in an air atmosphere at 1000 ° C. for 10 hours, put into a water tank containing pure water, and rapidly cooled. This was dried and then pulverized using a crusher to obtain a particle size of 50 to 500 μm and a silica (SiO ₂ ) purity of 99.995 wt. %, And a total weight of 80 kg of silica powder (natural silica powder).

Moreover, the 2nd raw material powder 12 was prepared as follows.
Spherical amorphous silica powder (second raw material powder) was synthesized by a melting method. The spherical amorphous silica powder had a particle size of 0.3-2 μm, an average particle size of 0.6 μm, an average specific surface area of 5 m ² / g, and a weight of 20 kg.

Thus, the prepared 2nd raw material powder 12 was used as the granule 22 by which binder coating was carried out as follows.
A paraffinic binder (melting point 55 ° C.) 200 g, a stearic acid binder (melting point 100 ° C.) 200 g, and pure water 5 kg were mixed with the second raw material powder 12 and 20 kg to prepare a mixed slurry. This mixed slurry was dried by a spray dryer to produce a binder-coated granule 22. The granule diameter of the spherical amorphous silica glass coated with the binder was 10 to 100 μm, and the average was 50 μm.

Moreover, the 3rd raw material powder 13 was prepared as follows. First, 2 kg of high-purity natural quartz powder (particle size 50 to 500 μm, silica purity 99.9999 wt.% Or more) was prepared, and then immersed in an aqueous solution containing aluminum chloride (AlCl ₃ ) and dried.
The fourth raw material powder 14 has a particle size of 50 to 300 μm and a silica purity of 99.9999 wt. % Of cristobalite powder subjected to high purity treatment of 2% or more was prepared.

Next, using a V-shaped mixer, the first raw material powder 11 and the granule 22 of the second raw material powder were uniformly mixed to obtain a mixed powder 31.
The mixing ratio was 1st raw material powder 11, 80 wt. % Of the second raw material granule 22, 20 wt. % (That is, weight mixing ratio (second raw material powder) / {(first raw material powder) + (second raw material powder)} = 20 wt.%).

Next, as shown in FIG. 4 (a), the mixed powder 31 is put inside the rotating cylindrical stainless steel outer mold 101, and the thickness becomes uniform according to the shape of the outer mold 101. Thus, the shape of the mixed powder 31 was adjusted.
Next, as shown in FIGS. 4B and 4C, a stainless steel inner mold (plunger) 111 is inserted into the outer mold 101, and the mixed powder 31 is loaded with 0.1 MPa (approx. While pressurizing at a pressure of 1 kgf / cm ² ), the plunger 111 was heated to rise to 100 ° C. and held for 1 hour.
The plunger 111 was pulled out to form a molded body of the mixed powder 31, which was used as the base 51. The substrate 51 had an outer diameter of 300 mm, a height of 300 mm, and a thickness of 10 mm.

Next, as shown in FIG. 7, the base body 51 was subjected to firing and strain removal treatment (annealing treatment) as follows.
The substrate 51 was placed in an electric resistance heating furnace 301 having a molybdenum disilicide heater 306 and made of a heat-resistant material of a high-purity alumina board having an in-furnace size of 1 m × 1 m × 1 m. The temperature was raised from room temperature to 1000 ° C. at a rate of 200 ° C./hour over about 5 hours, raised to 1300 ° C. at a rate of 20 ° C./hour, and then held at 1300 ° C. for 3 hours.
Next, the temperature is lowered from 1300 ° C. to 1150 ° C. at a rate of 100 ° C./hour, held at 1150 ° C. for 1 hour, and the temperature is lowered from 1150 ° C. to 950 ° C. at a rate of 20 ° C./hour. went.
Then it was allowed to cool and returned to room temperature.

Next, as shown in FIG. 5, an intermediate layer 56 having a thickness of about 1.2 mm was formed on the inner surface of the substrate 51 by electric discharge melting (arc melting).
A carbon electrode 212 was inserted into the base 51 contained in the outer mold 201, and a third raw material powder supply port and a lid 213 were set. Thereafter, while the outer mold 201 was rotated, the third raw material powder was gradually added, and discharge heating (electric arc heating) was performed with the carbon electrode 212.

Next, as shown in FIG. 6, an inner layer 58 having a thickness of about 3.2 mm was formed on the inner surface of the intermediate layer 56 by electric discharge melting (arc melting).
A carbon electrode 212 was inserted into the base 51 contained in the outer mold 201, and a fourth raw material powder supply port and a lid 213 were set. Thereafter, while the outer mold 201 was rotated, the fourth raw material powder was gradually added, and discharge heating (electric arc heating) was performed at the carbon electrode 212.

  The silica container 71 thus manufactured was washed with a 5% aqueous hydrofluoric acid solution (HF) for 5 minutes, then washed with pure water and dried.

Next, an aqueous solution of barium nitrate Ba (NO ₃ ) ₂ was prepared, uniformly applied (coated) to the inner surface of the silica container 71, and dried.

(Example 2)
Basically, a silica container was produced in the same manner as in Example 1, but the following points were different.
That is, the fourth raw material powder 14 prepared by doping barium was prepared as follows. First, a particle size of 50 to 300 μm and a silica purity of 99.9999 wt. 2 kg of cristobalite powder having a purity of at least% was prepared. In addition, 100 g of barium nitrate (Ba (NO ₃ ) ₂ ) was added to 50% ethyl alcohol C ₂ H ₅ OH. An aqueous solution containing 5% was added and dissolved to prepare a barium-containing solution. Then, put the cristobalite powder treated with the above high purity in a cylindrical silica glass container, then put the barium-containing solution, stir and dry at 100 ° C. in a clean oven to produce cristobalite powder containing barium The fourth raw material powder 14 was obtained.
Further, no coating layer was formed on the inner surface of the silica container 71.

(Example 3)
The silica container 71 was manufactured in the same manner as in Example 2, except that the manufacturing conditions were changed as follows.
That is, soot powder produced by a flame hydrolysis method using silicon tetrachloride (SiCl ₄ ) as a raw material was used as the spherical silica powder of the second raw material powder 12. Further, zirconia was mixed as the third raw material powder 13. Further, the mixed powder 31 of the first raw material powder and the granule of the second raw material powder was immersed in an aqueous solution containing aluminum chloride (AlCl ₃ ) and dried to dope aluminum. The base body 51 was baked at 1350 ° C. for 3 hours.

Example 4
The silica container 71 was manufactured in the same manner as in Example 3, except that the manufacturing conditions were changed as follows.
That is, magnesia was mixed as the third raw material powder 13. The first raw material powder 11 has a particle size of 100 to 1000 μm and a silica purity of 99.995 wt. % Silica glass scrap powder was used. The base body 51 was baked at 1250 ° C. for 3 hours.

(Comparative Example 1)
In general, a silica container (silica crucible) was prepared according to a conventional method.
It differs from Example 1 as follows.
First, the silica purity of 99.995 wt. % Natural quartz powder (particle size 50-300 μm) having a purity of at least%. In addition, when producing the crucible base (opaque silica layer), only the high-purity-treated natural quartz powder corresponding to the first raw material powder was used without using the one corresponding to the second raw material powder. Moreover, the thing equivalent to a 3rd raw material powder was not used. Also, without firing the crucible substrate independently, the carbon electrode discharge heating from the inner surface at the temperature and atmospheric conditions when forming the transparent silica glass layer corresponding to the inner layer from the raw material powder corresponding to the fourth raw material powder To sinter the substrate.

(Comparative Example 2)
As in Comparative Example 1, except that a step of applying the barium nitrate solution to the inner surface of the transparent silica glass layer corresponding to the inner layer was provided to produce a silica container.

[Evaluation Methods in Examples and Comparative Examples]
The physical properties and characteristics of the silica containers produced in each of the examples and comparative examples were evaluated as follows.

(Measurement method of bubble content)
For the measurement of the bubble content in the substrate of the silica container and the transparent silica glass layer, a sample of size 10 mm × 10 mm × thickness 1.2 mm is cut out from each arbitrary position. Next, the sample is subjected to double-sided parallel mirror polishing to make the dimensions 10 mm × 10 mm × thickness 1 mm. This is observed with a stereomicroscope, and the number of bubbles is counted while scanning the visual field. The number of bubbles per unit volume (cm ³ ) was determined by multiplying the number of bubbles in the sample by 10. At this time, the sample thickness was adjusted according to the amount of the bubble content in the sample so that it could be easily observed.

(Impurity metal element concentration analysis)
The impurity metal element concentration of the substrate composed of the transparent silica glass layer and the opaque silica layer was measured as follows.
When the impurity metal element concentration is relatively low (high purity), plasma emission analysis (ICP-AES, Inductively Coupled Plasma-Atomic Emission Spectroscopy) or plasma mass spectrometry (ICP-MS, Inductively Coupled Plasma Plus) In the case where the impurity metal element concentration is relatively high (low purity), atomic absorption spectrophotometry (AAS) was used.

(Bulk density (specific gravity))
It measured by the Archimedes method using the water tank and the precision weight scale.

(Silicon single crystal continuous pulling (multiple pulling) evaluation)
In a silica container, a purity of 99.99999 wt. % Metal polysilicon was added, the temperature was raised to obtain a silicon melt, and then the silicon single crystal was pulled 10 times repeatedly (multi-pulling), and the success rate of single crystal growth was evaluated. The pulling conditions were such that the inside of the CZ apparatus was a 10 ³ Pa argon (Ar) gas 100% atmosphere, the pulling rate was 0.5 mm / min, the silicon single crystal size, the diameter was 100 mm, and the length was 100 mm. The evaluation classification of the success rate of 10 times of single crystal growth was as follows.
8 times or more ◎ (particularly good)
6 times to less than 8 times ○ (good)
4 times or more and less than 6 times △ (somewhat bad)
Less than 4 times × (defect)

(Effect diffusion prevention effect of transparent silica glass layer of silica container)
The manufactured silica container is set in an electric furnace using a high-purity alumina board as a heat-resistant material and molybdenum disilicide as a heater, and is subjected to heat treatment at 1450 ° C. for 24 hours. Next, 10 μm of the inner surface portion of the container is washed away with a hydrofluoric acid (HF) aqueous solution. Next, 100 μm in thickness of the inner surface portion of the container is subjected to a dissolution etching treatment with a 50% aqueous solution of hydrofluoric acid (HF), and the alkali metal element concentration value of this etching solution is analyzed, whereby the silica purity is low. It was evaluated whether the impurity metal element diffused from the container substrate to the high-purity transparent silica glass layer more or less.
The classification based on the total concentration values of Li, Na, and K in the inner surface thickness of 100 μm was as follows.
1 wt. Less than ppm ○ (Good)
1 to 10 wt. Less than ppm △ (somewhat bad)
10 wt. ppm or more × (defect)

(Internal surface recrystallization effect of silica container)
The manufactured silica container is placed in an electric furnace using high-purity alumina board as a heat-resistant material and molybdenum disilicide as a heater, and subjected to heat treatment at 1450 ° C. for 6 hours. Subsequently, the recrystallization effect was evaluated by visually observing the white devitrification (cristobalite crystal) part of the inner surface part of the container. The evaluation classification of the recrystallization effect was as follows.
More than 80% of total internal surface area is white devitrified ○ (good)
50% to less than 80% of total internal surface area is white devitrified △ (somewhat poor)
Less than 50% of total internal surface area is white devitrified × (defect)

(Method for measuring particle size of each raw material powder)
The shape observation and area measurement of each raw material powder were performed with an optical microscope or an electron microscope, the shape was assumed to be a perfect circle, and the diameter was calculated from the area value. This method was repeated statistically to obtain a value in the particle size range.

(Heat-resistant deformation of silica container)
After the silicon single crystal was continuously pulled 10 times, the amount of collapse of the uppermost silica container into the container was evaluated. The evaluation classification of heat distortion resistance was as follows.
Amount of wall falling down to less than 1 cm ○ (Good)
Amount of wall falling into the inside 1-5cm △ (somewhat bad)
The amount of wall collapse to the inside 5 cm or more × (defect)

  The production conditions, measured physical property values, and evaluation results of the silica containers produced in Examples 1 to 4 and Comparative Examples 1 to 2 are summarized and shown in Tables 1 to 3 below.

  As can be seen from Tables 1 to 3, in Examples 1 to 4 according to the method for producing a silica container according to the present invention, low-purity silica particles that are less expensive than Comparative Example 1 and can be supplied with high productivity are used. Nevertheless, it was possible to produce a silica container capable of producing results comparable to the conventional silica container of Comparative Example 1 in pulling a single crystal.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is a schematic sectional drawing which shows an example of the silica container which concerns on this invention. It is a flowchart figure which shows an example of the manufacturing method of the silica container which concerns on this invention. It is a flowchart figure which shows another example of the manufacturing method of the silica container which concerns on this invention. It is explanatory drawing which shows typically a part of manufacturing process of the manufacturing method of the silica container which concerns on this invention. It is explanatory drawing which shows typically an example of the formation process of the intermediate | middle layer which concerns on this invention. It is explanatory drawing which shows typically an example of the formation process of the inner layer which concerns on this invention. It is explanatory drawing which shows typically an example of the baking process which concerns on this invention.

Explanation of symbols

11 ... First raw material powder, 12 ... Second raw material powder, 13 ... Third raw material powder,
14 ... Fourth raw material powder 22 ... Binder-coated granules,
31 ... Mixed powder of granules of the first raw material powder and the second raw material powder,
51 ... Substrate, 56 ... Intermediate layer, 58 ... Inner layer,
71 ... Silica container,
101 ... Outer mold frame, 102 ... Inner mold frame,
103 ... Hopper, 104 ... Stirring screw, 105 ... Measuring feeder,
111 ... Inner formwork (plunger),
201: outer formwork,
211 ... High voltage power supply unit, 212 ... Carbon electrode, 213 ... Lid,
233 ... Hopper, 234 ... Stirring screw, 235 ... Weighing feeder,
243 ... Hopper, 244 ... Stirring screw, 245 ... Metering feeder,
301 ... Electric resistance heating furnace, 302 ... Gas supply port, 303 ... Gas discharge port,
304, 305 ... Open / close valve, 306 ... Heater.

Claims (30)

A method for producing a silica container having silica as a main constituent and having rotational symmetry, at least,
(1) First raw material powder that is silica particles to be an aggregate, second raw material powder that is made of amorphous silica and has an average particle size smaller than the average particle size of the first raw material powder and is spherical. And a third raw material satisfying at least one of the main component being silica, containing an aluminum element and / or an OH group, and containing a compound powder serving as a crystal nucleus material for crystallization of silica glass. A step of preparing a fourth raw material powder consisting of powder and crystalline silica and having a higher silica purity than the first raw material powder and the second raw material powder;
(2) A step of preparing a binder-coated granule by mixing the second raw material powder with at least an organic binder and pure water to form a mixed slurry, and drying the mixed slurry;
(3) a step of preparing a mixed powder by mixing the first raw material powder and a granule prepared from the second raw material powder;
(4) introducing the mixed powder into an inner wall of an outer mold frame having rotational symmetry, and making the mixed powder a predetermined shape according to the outer mold frame while rotating the outer mold frame; ,
(5) A pressure forming step of forming the base by sandwiching the mixed powder having the predetermined shape between the outer mold frame and the inner mold frame, and pressing the mixed powder;
(6) The base body is made of an opaque silica layer by firing the base body in an oxygen-containing atmosphere, and the fired base body is gradually cooled at least in the temperature range from the slow cooling point to the strain point to remove the strain. Process,
(7) An intermediate layer made of silica glass is melted on the inner surface of the substrate by melting with a heating source disposed inside the substrate while the third raw material powder is dispersed and supplied from the inside of the substrate. Forming a step;
(8) While the fourth raw material powder is dispersed and supplied from the inside of the substrate on which the intermediate layer is formed, the intermediate material is melted by a heating source disposed on the inside of the substrate on which the intermediate layer is formed. Forming an inner layer made of transparent silica glass on the inner surface of the layer, and after the step (5), the step (6) and the steps (7) and (8) A method for producing a silica container, wherein the steps are performed in any order.   The total concentration of aluminum elements and OH groups contained in the third raw material powder is 50 to 5000 wt. It is set as ppm, The manufacturing method of the silica container of Claim 1 characterized by the above-mentioned.   The ratio of the compound powder used as the crystal nucleus material contained in the third raw material powder is 50 to 5000 wt. It is set as ppm, The manufacturing method of the silica container of Claim 1 or Claim 2 characterized by the above-mentioned.   The method for producing a silica container according to any one of claims 1 to 3, further comprising a step of applying a solution containing at least one of calcium, strontium, and barium to the surface of the inner layer. A method for producing a silica container. Calcium solution is applied to the surface of the inner layer, strontium, the total concentration of barium, method for producing a silica container according to claim 4, characterized in that the 5~500μg / cm ^2.   The method for producing a silica container according to any one of claims 1 to 5, further comprising a step of containing at least one of calcium, strontium, and barium in the fourth raw material powder.   The total concentration of calcium, strontium, and barium contained in the fourth raw material powder is 50 to 5000 wt. It is set as ppm, The manufacturing method of the silica container of Claim 6 characterized by the above-mentioned.   The method for producing a silica container according to any one of claims 1 to 7, wherein the first raw material powder is prepared by pulverizing and sizing a silica lump.   The silica purity of the first raw material powder is 99.5 to 99.999 wt. The method for producing a silica container according to any one of claims 1 to 8, wherein the content is%.   The method for producing a silica container according to any one of claims 1 to 9, wherein a particle diameter of the first raw material powder is 0.05 to 5 mm.   The method for producing a silica container according to any one of claims 1 to 10, wherein the particle size of the second raw material powder is 0.1 to 10 µm.   The silica container according to any one of claims 1 to 11, wherein the pressure molding of the mixed powder is performed at a pressure of 0.1 to 1 MPa and a temperature of 50 to 300 ° C. Manufacturing method.   The mixing ratio of the first raw material powder and the second raw material powder in producing the mixed powder is (second raw material powder) / {(first raw material powder) + (second raw material Powder)} is 5 wt. % Or more and 50 wt. The method for producing a silica container according to any one of claims 1 to 12, wherein the silica container is less than%.   The method for producing a silica container according to any one of claims 1 to 13, wherein the intermediate layer is formed with a thickness of 0.1 to 5 mm.   The method for producing a silica container according to any one of claims 1 to 14, wherein the inner layer is formed with a thickness of 0.1 to 5 mm.   The method for producing a silica container according to any one of claims 1 to 15, wherein the organic binder is a paraffin binder or a stearic acid binder.   The method for producing a silica container according to any one of claims 1 to 16, wherein the silica container is used as a crucible for pulling a silicon single crystal.   As the fourth raw material powder, the amount of impurities is 10 wt. For ppb or less, titanium, vanadium, chromium, manganese, zirconium, niobium, molybdenum, tantalum, tungsten, and gold are each 1 wt. The method for producing a silica container according to any one of claims 1 to 17, wherein a ppb or less is used.   A silica container manufactured by the method for manufacturing a silica container according to any one of claims 1 to 18. A silica container having rotational symmetry, at least,
It contains bubbles, is white and opaque, has a bulk density of 1.90 to 2.09 g / cm ³ , and a silica purity of 99.5 to 99.999 wt. % Having a substrate composed of an opaque silica layer,
The inside of the substrate is made of silica glass satisfying at least one of containing an aluminum element and / or OH group and containing a compound component serving as a crystal nucleus material for crystallization of the silica glass. Having an intermediate layer with a thickness of 0.1 to 5 mm,
An inner side consisting of a transparent silica glass layer substantially free of bubbles on the inner surface of the intermediate layer, having a bulk density of 2.20 to 2.21 g / cm ³ and a thickness of 0.1 to 5 mm A silica container comprising a layer.   The total concentration of aluminum elements and OH groups contained in the intermediate layer is 50 to 5000 wt. The silica container according to claim 20, wherein the silica container is ppm.   The concentration of the compound component serving as the crystal nucleus contained in the intermediate layer is 50 to 5000 wt. The silica container according to claim 20 or 21, wherein the silica container is ppm. 21. The content of bubbles having a diameter of 20 μm or more in the substrate is 10,000 / cm ³ or more, and the content of bubbles having a diameter of 20 μm or more in the inner layer is 30 / cm ³ or less. The silica container according to any one of claims 22 to 22.   The total concentration of lithium, sodium, potassium, magnesium and calcium in the substrate is 10 to 100 wt. The silica container according to any one of claims 20 to 23, wherein the silica container is ppm.   The OH group concentration of the inner layer is 100 wt. The silica container according to any one of claims 20 to 24, wherein the silica container is not more than ppm.   The silica container according to any one of claims 20 to 25, wherein the inner layer contains at least one of calcium, strontium, and barium.   The total concentration of calcium, strontium, and barium contained in the inner layer is 50 to 5000 wt. The silica container according to claim 26, wherein the silica container is ppm.   The silica container according to any one of claims 20 to 27, further comprising a coating layer containing at least one of calcium, strontium, and barium inside the inner layer. The silica container according to claim 28, wherein the total concentration of calcium, strontium, and barium contained in the coating layer is 5 to 500 µg / cm ² .   The base is 30 to 3000 wt. 30. The silica container according to any one of claims 20 to 29, which contains ppm.

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