JP5130323B2 - Square silica container for producing polycrystalline silicon ingot and method for producing the same - Google Patents

Description

  The present invention relates to a square (square tank type) silica container for producing a polycrystalline silicon ingot by solidifying after containing a silicon melt and a method for producing the same.

  In recent years, the demand for solar cells (solar power generation devices) has increased rapidly, and there is a demand for solar cells having higher conversion efficiency at lower costs.

  One of the materials constituting the photovoltaic part of a solar cell is polycrystalline silicon. Polycrystalline silicon is often produced as polycrystalline silicon ingots by cooling and solidifying a silicon melt. Silica (silicon dioxide) containers and graphite containers are used as containers for containing a silicon melt and solidifying to produce a polycrystalline silicon ingot.

In a container for solidifying in a container to produce a polycrystalline silicon ingot, its inner surface is used to prevent the polycrystalline silicon ingot from fusing (adhering) to the container when the silicon melt is solidified. It is known to form a release layer in advance. Various materials are used as a release agent for forming the release layer. For example, in Patent Document 1, a release agent slurry containing Si, Si ₃ N ₄ , Si ₃ N ₄ + SiO ₂ or Si + Si ₃ N ₄ + SiO ₂ is used as a release agent in an inner layer of a silicon melting container made of quartz glass. It is described that a layer is formed. Further, Patent Document 2 describes a silicon casting mold made of silicon dioxide in which a release material layer containing silicon nitride is formed on the inner surface.

Japanese Patent Laying-Open No. 2005-271058 JP 2005-125380 A

  As described above, in a container for producing a polycrystalline silicon ingot by solidifying in a container, a release layer is generally formed on the inner surface in advance. However, when a material that becomes an impurity in the polycrystalline silicon ingot is used as a mold release agent, the impurity in the polycrystalline silicon ingot is removed because the release layer is peeled off and taken into the silicon melt. There was a problem that mixing was inevitable.

  On the other hand, if the release agent is not used, the polycrystalline silicon ingot is fused to the container when the silicon melt is solidified, and the surface portion of the polycrystalline silicon ingot is damaged during cooling or removal. There was a problem. As a result, for example, when a solar cell is manufactured from a polycrystalline silicon ingot, the quality of the manufactured solar cell is deteriorated and the cost of the manufactured solar cell is reduced due to a decrease in yield.

  The present invention has been made in view of such problems, has the ability to sufficiently prevent impurity contamination to silicon melt and polycrystalline silicon ingot, and excellent in releasability, It is an object of the present invention to provide a low-cost rectangular silica container for producing a polycrystalline silicon ingot and to provide a method for producing such a rectangular silica container for producing a polycrystalline silicon ingot.

The present invention has been made to solve the above problems, and is a rectangular silica container for producing a polycrystalline silicon ingot by solidifying after containing a silicon melt, and the rectangular silica container is at least porous. The porous silica substrate has a bulk density of 1.80 to 2.10 g / cm ³ and an Al concentration of 5 to 500 wt. ppm, and the OH group concentration is 5 to 500 wt. Polycrystalline silicon, characterized in that a release accelerator for promoting release of the polycrystalline silicon ingot is contained in at least a part of the inner surface portion of the porous silica substrate. A square silica container for producing an ingot is provided.

With such a silica container, a low-cost polycrystalline silicon ingot having the ability to sufficiently prevent impurity contamination of the silicon melt and the polycrystalline silicon ingot and having excellent releasability It can be set as the square silica container for manufacture. That is, in a rectangular silica container, the bulk density is set to 1.80 to 2.10 g / cm ³ , the amount of bubbles is relatively increased, and a mold release accelerator is included in the inner surface portion, thereby allowing silicon fusion. Fusion of the polycrystalline silicon ingot with the rectangular silica container when the liquid is solidified can be suppressed. In addition, by making the content of Al and OH groups in the square silica container as described above, even when an inexpensive raw material is used, impurities are diffused into the contained silicon (silicon melt and polycrystalline silicon ingot). It can be sufficiently prevented.

  In this case, one or more of Ca, Sr, and Ba as the mold release accelerator is included in at least a part of the inner surface portion of the porous silica substrate, and the total value of each element from the inner surface to a depth of 2 mm. As 50 to 5000 wt. It is preferable that it is added at a concentration of ppm.

  If it is a square silica container for producing a polycrystalline silicon ingot in which Ca, Sr, and Ba as mold release accelerators are added to the inner surface portion of the porous silica substrate at such a concentration, the mold release property is more effective. The impurity contamination of the silicon melt and the polycrystalline silicon ingot can be sufficiently prevented.

Further, at least one of Ca, Sr, and Ba as the release accelerator is applied at a concentration of 50 to 5000 μg / cm ² as a total value of each element on at least a part of the inner surface portion of the porous silica substrate. It is also preferable that it is what is done.

  It is also possible to more effectively release a rectangular silica container for producing a polycrystalline silicon ingot in which Ca, Sr, and Ba as release accelerators are applied to the inner surface portion of the porous silica substrate at such a concentration. The moldability can be increased and impurity contamination of the silicon melt and the polycrystalline silicon ingot can be sufficiently prevented.

  The concentration of Li, Na, and K contained in the porous silica substrate is 5 wt. It is preferably at most ppm.

  If the concentration of each of Li, Na, and K contained in the porous silica substrate is set in this manner, impurity contamination to the silicon melt and the polycrystalline silicon ingot can be more effectively prevented. A square silica container can be used.

The present invention also relates to a method for producing a rectangular silica container for producing a polycrystalline silicon ingot by solidifying after containing a silicon melt, and at least a first raw material powder having a particle size of 0.03. A step of producing a silica powder of ˜3.0 mm, a step of producing a silica powder having a particle size of 0.1 to 10 μm as the second raw material powder, the first raw material powder, and the second raw material powder, A step of preparing a mixed slurry containing water, a step of dehydrating and drying the mixed slurry in a square mold to prepare a temporary molded body of a porous silica substrate, and a step of temporarily forming the porous silica substrate. A fired step of firing the molded body at a temperature of 1200 to 1500 ° C. in an atmosphere containing an inert gas as a main component and containing O ₂ gas to form a porous silica substrate, the first raw material powder , The second raw material powder, and the mixed powder Al element is added to at least one of the leas so that the porous silica substrate contains Al element, and the release of the polycrystalline silicon ingot is performed on at least a part of the inner surface portion of the porous silica substrate. Provided is a method for producing a rectangular silica container for producing a polycrystalline silicon ingot, characterized by containing a demolding accelerator to be promoted.

  If it is a manufacturing method of such a square silica container for polycrystalline silicon ingot manufacture, it has the ability to fully prevent impurity contamination to a silicon melt and a polycrystalline silicon ingot, and it is in mold release nature. An excellent rectangular silica container for producing a polycrystalline silicon ingot can be produced at low cost.

The present invention also relates to a method for producing a rectangular silica container for producing a polycrystalline silicon ingot by solidifying after containing a silicon melt, wherein the first raw material powder has a particle size of 0.03 to 3 A step of producing a 0.0 mm silica powder, a step of producing a silica powder having a particle size of 0.1 to 10 μm as a second raw material powder, the first raw material powder, the second raw material powder, and an organic binder To prepare a mixed powder, and the mixed powder is introduced into a square formwork and heated to 50 to 200 ° C. to melt the organic binder, thereby forming a porous silica substrate temporary molded body. The step of producing and the temporary molded body of the porous silica substrate are baked at a temperature of 1200 to 1500 ° C. in an atmosphere containing an inert gas as a main component and an O ₂ gas to obtain a porous silica substrate. Firing step, the first Al element is added to at least one of the raw material powder, the second raw material powder, and the mixed powder, so that the porous silica substrate contains Al element, and at least the inner surface portion of the porous silica substrate A method for producing a rectangular silica container for producing a polycrystalline silicon ingot, characterized in that a release accelerator that promotes the release of the polycrystalline silicon ingot is included in a part thereof.

  Even with such a method for producing a rectangular silica container for producing a polycrystalline silicon ingot, it has the ability to sufficiently prevent impurity contamination of the silicon melt and the polycrystalline silicon ingot, and release. A rectangular silica container for producing a polycrystalline silicon ingot having excellent properties can be produced at low cost.

  Further, in the method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to the present invention, after the temporary forming step, the content of the release accelerator is applied to at least a part of the inner surface of the temporary molded body, Drying, adding the release accelerator to at least a portion of the inner surface portion of the temporary molded body and / or after the firing step, the release accelerator is added to the porous silica substrate. It is preferable to carry out by applying to at least a part of the inner surface.

  In this way, after the provisional molding step, the release accelerator is applied to at least a part of the inner surface of the temporary molded body and dried to release at least a part of the inner surface portion of the temporary molded body. By adding an accelerator or by applying a mold release accelerator to at least a part of the inner surface of the porous silica substrate after the firing step, the porous silica substrate can be more efficiently A mold release accelerator can be contained in the inner surface portion of the.

  In the method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to the present invention, the release accelerator is preferably one or more of Ca, Sr, and Ba.

  As described above, when the mold release accelerator is Ca, Sr, or Ba, the mold release property can be increased more effectively and impurity contamination to the silicon melt and the polycrystalline silicon ingot can be sufficiently prevented. be able to.

  Further, in the method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to the present invention, before the mixed slurry or the mixed powder is produced, the second raw material powder is collected from the second raw material powder. It is preferable to prepare a granule having a particle size of 5 to 500 μm and to prepare the mixed slurry or the mixed powder by using the granule of the second raw material powder.

  Thus, if the mixed slurry or mixed powder is prepared after making the second raw material powder into granules, handling of the second raw material powder having a small particle size can be simplified.

In the method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to the present invention, in the firing step, the inert gas is at least one of N ₂ gas, He gas, and Ar gas, and contains O ₂ gas. The amount is 1-30 vol. % Is preferable.

  If the composition of the inert gas in the firing step is thus done, a rectangular silica container for producing a polycrystalline silicon ingot can be produced at a lower cost.

  If it is a square silica container for producing a polycrystalline silicon ingot of the present invention, it has the ability to sufficiently prevent impurity contamination to the silicon melt and the polycrystalline silicon ingot, and has excellent releasability, A low-cost rectangular silica container for producing a polycrystalline silicon ingot can be obtained. By using such a rectangular silica container for producing a polycrystalline silicon ingot, a polycrystalline silicon ingot in which impurity contamination is sufficiently prevented can be produced, and the total cost for producing the polycrystalline silicon ingot is reduced. be able to.

  Further, the method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to the present invention has the ability to sufficiently prevent impurity contamination of the silicon melt and the polycrystalline silicon ingot, and the mold release A rectangular silica container for producing a polycrystalline silicon ingot having excellent properties can be produced at low cost.

  Thus, according to the present invention, a high-quality and low-cost rectangular polycrystalline ingot can be provided, which is particularly suitable for a solar cell.

(A) is a schematic top view of the rectangular silica container for manufacturing a polycrystalline silicon ingot according to the present invention, and (b) is a schematic cross-sectional view of the rectangular silica container for manufacturing a polycrystalline silicon ingot according to the present invention. It is a flowchart which shows the outline of an example of the manufacturing method of the square silica container for polycrystalline silicon ingot manufacture which concerns on this invention. It is a flowchart which shows the outline of another example of the manufacturing method of the square silica container for polycrystalline silicon ingot manufacture based on this invention.

  As described above, in the present invention, for example, a rectangular silica container for producing a polycrystalline silicon ingot that can be used to obtain a rectangular polycrystalline silicon ingot suitable for a solar cell has the following problems.

  The first is to make a square silica container having excellent releasability (improvement of releasability). In other words, when a polycrystalline silicon ingot is produced by solidification of a silicon melt contained in a rectangular silica container, the fusion (adhesion) of the polycrystalline silicon ingot to the rectangular silica container is suppressed. The silicon ingot should be easily removed from the square silica container.

  Secondly, a rectangular silica container capable of preventing impurity contamination is used. This means that various impurity metal elements contained in the square silica container move and diffuse to the contained silicon (silicon melt, polycrystalline silicon ingot, etc.) even at high temperatures during the production of polycrystalline silicon. As a result, impurity contamination of the silicon melt and the polycrystalline silicon ingot is sufficiently prevented.

  Thirdly, it is possible to realize the above-mentioned excellent releasability and prevention of impurity contamination at a low cost. This means that an inexpensive silica raw material can be used for the production of a rectangular silica container, and the silica raw material is melted and sintered at a relatively low temperature to produce a rectangular silica container. It is to reduce energy consumption at the time.

  Hereinafter, although the present invention is explained in detail, referring to drawings, the present invention is not limited to these.

  FIG. 1 shows an outline of an example of a rectangular silica container for producing a polycrystalline silicon ingot according to the present invention. Fig.1 (a) is a schematic top view of the square silica container of this invention, FIG.1 (b) is a schematic sectional drawing of the square silica container of this invention.

  As shown in FIGS. 1 (a) and 1 (b), the shape of the silica container 10 of the present invention is a square (also called a square tank type). The square silica container 10 includes a side wall part 11 and a bottom part 21.

  The rectangular silica container 10 according to the present invention is a container for producing a rectangular polycrystalline silicon ingot by containing a silicon melt and then solidifying. If the manufactured polycrystalline silicon ingot is rectangular, it can be sliced to obtain a rectangular polycrystalline silicon wafer. Compared with a cylindrical polycrystalline silicon ingot, the sliced wafer is used as a solar cell. In this case, the light receiving area is not wasted, which is very suitable.

The rectangular silica container 10 of the present invention comprises at least a porous silica substrate 151. The porous silica substrate 151 has a bulk density of 1.80 to 2.10 g / cm ³ . This bulk density is preferably in the range of 1.85 to 1.93 g / cm ³ .

  In order to improve releasability, the bulk density of the porous silica substrate 151 is set to the above range, and the amount of bubbles contained in the porous silica substrate 151 is increased (that is, the porosity is increased). By increasing the amount of bubbles in this manner, the fusion (adhesion) of the polycrystalline silicon ingot with the rectangular silica container 10 when the silicon melt is solidified is suppressed, and the polycrystalline silicon ingot is removed from the rectangular silica container 10. It becomes easy to remove without being damaged.

When the bulk density of the porous silica substrate 151 exceeds 2.10 g / cm ³ , the fusion between the produced polycrystalline silicon ingot and the square silica container becomes strong, and the strength of the square silica container becomes high. The nature will decline. On the other hand, when the bulk density is lower than 1.80 g / cm ³ , the releasability is improved, but the strength of the rectangular silica container itself is excessively lowered.

  In the present invention, a mold release accelerator for promoting mold release of the polycrystalline silicon ingot is contained in at least a part of the inner surface portion of the porous silica substrate 151. The inner surface of the porous silica substrate 151 is the inner surface 12 of the side wall 11 of the porous silica substrate 151 and the inner surface 22 of the bottom 21 of the porous silica substrate 151.

  As the mold release accelerator used for the rectangular silica container 10 of the present invention, the following three types can be used.

First, the recrystallization type, that is, the releasability is improved by finely recrystallizing the surface of the porous silica substrate 151. Specific examples that are particularly suitable for the present invention include alkaline earth metal elements Ba, Ca, and Sr. Of these, Ba is the most preferable. In addition, mullite 3Al ₂ O ₃ .2SiO _{2 to} 2Al ₂ O ₃ .SiO ₂ , spinel MgAl ₂ O _{4 and the} like can be mentioned.

Secondly, the mold release property is improved by reacting with silica at a high temperature such as 1400 ° C. or higher to foam the silica. Specific examples include silicon carbide SiC and silicon nitride Si ₃ N ₄ .

Third, non-reactive type, that is, release property is improved by not reacting with silica or silicon at a high temperature such as 1400 ° C. or higher. Specifically, mention may be made of carbon C, zirconia ZrO _2, beryllia BeO, magnesia MgO, calcia CaO, thoria ThO _2, tungsten W or the like.

Of these three types of mold release accelerators, the recrystallization type is most preferably used in the present invention. In this case, at least one of Ca, Sr, and Ba is at least part of the inner surface portion of the porous silica substrate 151 with a total value of 50 to 5000 wt. It is preferable that it is added at a concentration of ppm. 50 wt. If it is ppm or more, an improvement in releasability is recognized, and 5000 wt. If it is less than ppm, it is preferable because sufficient releasability is recognized and the polycrystalline silicon ingot is not contaminated with a release agent. The total value of each element is 300 to 3000 wt. A range of ppm is more preferred. Further, at least one of Ca, Sr, and Ba as a release accelerator is applied to at least a part of the inner surface portion of the porous silica substrate 151 at a concentration of 50 to 5000 μg / cm ² as a total value of each element. It is also preferable that 50 [mu] g / cm ² or more is improved if the releasability long is recognized, if 5000 [mu] g / cm ² or less, while sufficiently made releasability is observed, and contaminating the polycrystalline silicon ingot with a release agent also It is preferable because it disappears. The total value of each element is more preferably in the range of 300 to 3000 μg / cm ² .

  By containing the recrystallization type, particularly Ca, Sr, and Ba in the inner surface portion of the porous silica substrate 151 in this way, the silicon melt is accommodated in the rectangular silica container 10 and gradually cooled and solidified. In the manufacturing process of making a polycrystalline silicon ingot, the inner surface layer of the square silica container 10 can be transferred from silica glass to a microcrystalline phase such as cristobalite or opal, thereby causing the generation of microcracks. As a result, since the fusion between the cooled and solidified polycrystalline silicon ingot and the inner surface of the rectangular silica container 10 can be reduced, the polycrystalline silicon ingot is removed when removing the polycrystalline silicon ingot from the rectangular silica container 10. It can be removed without breaking or forming irregularities on the surface portion of the polycrystalline silicon ingot or causing progressive cracks.

  Compared with alkali metal elements such as Li, Na, K, etc., the alkaline earth metal elements Ca, Sr, Ba have a correlation with the segregation coefficient, and are applied to the polycrystalline silicon ingot produced by solidification from the melt. Incorporation is small, that is, process contamination of the polycrystalline silicon ingot can be reduced. In particular, Ba is most preferable as a mold release accelerator because it has less diffusion contamination into the polycrystalline silicon ingot.

  Of the inner surface portion of the porous silica substrate 151, the range in which the mold release accelerator is contained may be at least part of the inner surface portion of the porous silica substrate 151 as described above. Of these, the entire inner surface portion up to a height at which the silicon melt is accommodated and solidified is more preferable, and the entire inner surface portion of the porous silica substrate 151 is more preferable.

  The porous silica substrate 151 has an Al concentration (Al element concentration) of 5 to 500 wt. ppm, and the OH group concentration is 5 to 500 wt. ppm. In order to prevent impurity contamination, the porous silica substrate 151 contains an OH group simultaneously with the Al element. Al concentration is 10-100 wt. It is preferable to set it as ppm, and the OH group concentration is 30 to 300 wt. It is preferable to set it as ppm.

  These Al and OH groups are converted when the impurity metal element in the porous silica substrate 151, especially the carrier lifetime of polycrystalline silicon under light irradiation is reduced, or when the polycrystalline silicon ingot is used as a solar cell material. It prevents migration and diffusion in the silica of alkali metal elements such as Li, Na and K which are considered to reduce the efficiency and transition metal elements such as Ti, Cr, Fe, Ni, Cu, Zn, Mo and Au. The details of the mechanism are unknown, but by replacing the Al atom with the Si atom, the cation (cation) of the impurity metal element is incorporated from the difference in coordination number, and the charge balance in the silica glass network is maintained. Therefore, it is presumed to prevent adsorption and diffusion. In addition, it is presumed that the OH group has an effect of adsorbing or preventing diffusion of these impurity metal elements by substitution of hydrogen ions and impurity metal ions.

Al concentration is 5 wt. If it is less than ppm, the impurity contamination preventing effect is not recognized, and 500 wt. If it exceeds ppm, the effect of preventing impurity contamination is recognized, but Al or Al ₂ O ₃ itself is not preferable because it contaminates the produced polycrystalline silicon ingot.

  Further, the concentration of OH groups is 5 wt. If it is less than ppm, the impurity contamination preventing effect is not recognized, and 500 wt. Exceeding ppm is not preferable because the viscosity of the porous silica substrate at a high temperature is lowered. The OH group serves as a silica glass network structure of Si and O, that is, a terminal portion (network terminator) of the glass network. For this reason, the inclusion of a high concentration of OH groups is considered to easily cause deformation of the porous silica substrate at a high temperature.

The effect of preventing contamination of impurities by Al and OH groups is recognized to some extent with either one of Al or OH groups, but the combination of these two types greatly improves the effect. As a result, the purity of the silica powder used as the raw material for the porous silica substrate 151 is SiO ₂ 99.9 to 99.999 wt. %, It is possible to produce a rectangular silica container 10 that meets the object of the present invention. More specifically, for example, the purity of the silica raw material powder (SiO ₂ purity) is 99.99 wt. %, And the concentration of each of Li, Na, and K is 5 wt. When the content is less than or equal to ppm, it is possible to produce a polycrystalline silicon ingot with sufficient prevention of process contamination by containing appropriate amounts of Al and OH groups simultaneously. Thus, in the polycrystalline silicon ingot in which the process contamination is sufficiently prevented, the size of each crystal grain is more uniform. If a solar power generation device (solar cell) is manufactured from such a polycrystalline silicon ingot, its photoelectric conversion efficiency can be significantly increased.

  Hereinafter, the method for producing the rectangular silica container for producing a polycrystalline silicon ingot according to the present invention, which can produce the above-described square silica container 10, will be described more specifically.

(I) 1st aspect The outline of an example (1st aspect, a wet method) of the manufacturing method of the square silica container 10 which concerns on this invention was shown in FIG.

  First, as shown to (a-1) of FIG. 2, raw material powder is produced. Specifically, silica powder having a particle size of 0.03 to 3.0 mm and silica powder having a particle size of 0.1 to 10 μm are prepared as the first raw material powder. Each of the first raw material powder and the second raw material powder may be prepared before preparing a mixed slurry described later.

Among these, the first raw material powder is a main constituent material of the porous silica substrate 151 of the rectangular silica container 10 (see FIG. 1) according to the present invention. As the first raw material powder, high purity silica raw material powder (high purity quartz powder, high purity quartz powder, ultra high purity synthetic silica glass powder) is not used, and silica purity SiO ₂ 99.9 to 99.999 wt. % Of relatively low purity silica powder raw material is preferably used. This first raw material powder can be produced, for example, by pulverizing and sizing the silica mass as follows, but is not limited thereto.

  First, a natural silica stone block (naturally produced crystal, quartz, quartzite, siliceous rock, opal stone, etc.) having a diameter of about 10 to 100 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 put into water, taken out after rapid cooling, and dried. This process facilitates the subsequent crushing and sizing process using a crusher or the like, but the process may proceed to the crushing process without performing the heating and quenching process.

  Next, the natural silica mass is pulverized and sized by a crusher or the like, and the particle size is adjusted to 0.03 to 3 mm, 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, and is kept at 700 to 1100 ° C. For about 1 to 100 hours. However, in a polycrystalline silicon ingot manufacturing application that does not require high purity, the process may proceed to the next process without performing this high-purification process.

  The first raw material powder obtained after the above steps is crystalline silica powder. From the viewpoint of cost, such natural crystalline silica powder is preferably used as the first raw material powder.

As described above, the particle size of the first raw material powder is 0.03 to 3 mm, preferably 0.1 to 1 mm.
The silica purity of the first raw material powder is 99.9 wt. % Or more, preferably 99.99 wt. % Or more is more preferable. In particular, the concentration of each of Li, Na, and K is 5 wt. It is preferable to set it as ppm or less. Moreover, if it is a manufacturing method of the square silica container of this invention, the silica purity of 1st raw material powder will be 99.999 wt. Even if it has a relatively low purity of not more than%, the manufactured rectangular silica container can sufficiently prevent impurity contamination of the silicon melt and polycrystalline silicon ingot. Therefore, a rectangular silica container for producing a polycrystalline silicon ingot can be produced at a lower cost than before.

  As the first raw material powder, it is sufficient that the particle diameter is 0.03 to 3 mm, and amorphous fused natural quartz glass powder, synthetic silica glass powder, etc. are used in place of or mixed with the above crystalline silica powder. May be. With such a vitreous silica powder, the firing temperature can be lowered.

  The second raw material powder is a material that constitutes the porous silica substrate 151 of the rectangular silica container 10 of the present invention together with the first raw material powder.

As the second raw material powder, silica glass powder having a particle size of 0.1 to 10 μm, preferably 0.2 to 5 μm, preferably spherical silica glass is prepared. The spherical silica glass can be produced by a wet sol-gel method (alkoxide method) and a dry melting method (spraying method). Alternatively, as an alternative material, a silica glass fine powder, so-called soot powder, is produced by flame hydrolysis of a silicon compound raw material such as silicon tetrachloride (SiCl ₄ ). The particle size of the soot powder in this case is 0.1 to 10 μm, preferably 0.2 to 5 μm, as described above.

After producing the second raw material powder, before producing a mixed slurry to be described later, it is possible to produce a granule having a particle diameter of 5 to 500 μm formed by the aggregation of the second raw material powder from the second raw material powder. it can. Thus, it is preferable to use the second raw material powder as a granule because the second raw material powder can be handled easily.
In order to make the second raw material powder into granules, for example, the following procedure can be used.

  First, an organic binder having a melting point of 200 ° C. or lower, for example, a paraffin 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 in a weight ratio of 1 to 10 wt. % Preferably 2 to 5 wt. % Pure water is added so that the viscosity value is 10 to 100 mPa · S at a shear rate of 1 to 10 / sec (about 10 to 40% as a moisture content), and then the mesh filter is set to 20 to 30 μm. Foreign matter is removed to prepare a slurry (suspension) for preparing granules.

  This granule-prepared mixed slurry is dried to produce a binder-coated granule. The method of drying the mixed slurry is not particularly limited, and for example, it can be put into a spray dryer (spray dryer) to produce granules of the second raw material powder having a binder coated on the surface. This spray dryer has a cylindrical hopper-type chamber, an apparatus (atomizer) for spraying the granule preparation mixed slurry installed at the upper part of the chamber, a hot air supply duct installed at the side of the chamber, and the lower part of the chamber It consists of a granule collection port installed in the. 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 produced in this way are aggregates of second raw material powders whose surfaces are coated with a binder, and can be set to a predetermined average particle size in the range of 5 to 500 μm.

  The first raw material powder and the second raw material powder are produced as described above. In the present invention, Al element is added to at least one of the first raw material powder, the second raw material powder, and a mixed slurry obtained by mixing the first raw material powder, the second raw material powder, and water, which will be described later (doping). ) As a result, the porous silica substrate 151 can contain Al element. Accordingly, as described above, movement and diffusion of alkali metal elements such as Li, Na, and K and transition metal elements such as Ti, Cr, Fe, Ni, Cu, Zn, Mo, and Au in the porous silica substrate 151 are performed. Can be prevented, and the heat-resistant deformation property of the square silica container 10 can be improved.

  In order to add Al element to at least one of the first raw material powder and the second raw material powder, the raw material powder is immersed and impregnated in an Al compound solution soluble in water or alcohol, and then pulled up at a constant rate. A method such as drying can be used. The amount of Al to be added is such that the Al concentration in the porous silica substrate 151 of the square silica container 10 after manufacture is 5 to 500 wt. ppm, and 10 to 100 wt. It is preferable to make it ppm.

  Next, as shown to (a-2) of FIG. 2, the mixed slurry 131 containing 1st raw material powder, 2nd raw material powder, and water is produced. The second raw material powder can be mixed in the state of granules as described above to form a mixed slurry 131.

  Specifically, the mixed slurry 131 is prepared as follows: (1) mixing of the first raw material powder and second raw material powder, (2) preparation of the mixed slurry, (3) homogeneous mixing of the slurry, (4) Although it can be performed through each sub-step such as vacuum degassing of the slurry, it is not limited to this.

(1) Mixing of first raw material powder and second raw material powder First, the first raw material powder is used as a main raw material, and the second raw material powder is preferably 5 wt. % To 50 wt. %, More preferably 10-30 wt. Mix evenly in the% range. The mixing ratio of the raw material powder here determines the mixing ratio of the first raw material powder and the second raw material powder when the mixed slurry 131 is produced. In order to reduce the manufacturing cost, it is necessary to increase the ratio of the first raw material powder to the second raw material powder as much as possible. The mixing ratio of the second raw material powder is 5 wt. If it is% or more, the voids of the porous silica substrate 151 after molding and firing are reduced, and the density is sufficiently high. As a result, the dimensional system and heat resistance of the porous silica substrate 151 can be improved. The mixing ratio of the second raw material powder is 50 wt. If it is% or less, sufficient voids in the porous silica substrate 151 after molding and firing can be secured, and the releasability can be further improved. As a mixing method, when the amount is relatively small, a V-type mixer can be used, but it is not limited to this method.

(2) Preparation of slurry (mixed aqueous solution) The mixed powder of the first raw material powder and the second raw material powder prepared above was used as a main raw material at 95 to 80 wt. %, Pure water 5-20 wt. % Is used as the mixed slurry 131. Care must be taken for impurity contamination during the production of the square silica container 10, and the concentration of Li, Na, and K in the porous silica substrate 151 is 5 wt. It is preferable to prepare the mixed slurry 131 so as to be equal to or lower than ppm. More preferably, it is at most ppm.

  In the present invention, Al element is added to at least one of the first raw material powder, the second raw material powder, and the mixed slurry 131 as described above. In order to contain the Al element in the mixed slurry 131, by dissolving and mixing an Al compound soluble in water or alcohol, for example, any one of a small amount of aluminum nitrate, aluminum carbonate, and aluminum chloride in pure water or alcohol. It can be carried out. The amount of Al to be added is such that the Al concentration in the porous silica substrate 151 of the square silica container 10 after manufacture is 5 to 500 wt. ppm, and 10 to 100 wt. It is preferable to make it ppm.

  Instead of adding the Al element in the mixed slurry state, the Al element may be added to the mixed slurry 131 by adding the Al element to the water before mixing before preparing the mixed slurry 131. Good.

  Further, the mixed slurry 131 may further include a dispersant (for example, polyacrylate), an antifoaming agent (for example, polyethylene glycol), a lubricant (for example, stearic acid, wax), a binder (for example, polyethylene, A suitable amount of polypropylene, a polystyrene acrylic resin, a paraffin wax, an epoxy resin, methyl cellulose, ethyl cellulose, or the like can be mixed.

(3) Homogenous mixing of slurry The mixed slurry 131 is put into a ball mill composed of a cylindrical silica glass container and silica glass balls, and mixed for 1 to 2 hours. The density (specific gravity) of the prepared mixed slurry 131 is 1.6 to 2.1 g / cm ^3, preferably 1.7 to 2.0 g / cm ³ , and the viscosity is 300 to 300 at a shear rate of 1 to 10 / sec. It is preferable to set it as 3000 mPa * sec.

(4) Vacuum degassing of slurry The mixed slurry 131 is placed in a silica glass chamber, and vacuum degassing is performed at room temperature at a vacuum degree of 10 ⁴ Pa or less for 5 to 30 minutes. However, this treatment may not be performed depending on the use of the manufactured square silica container.

  After preparing the mixed slurry 131 in this way, the mixed slurry 131 is introduced into a rectangular mold having a rectangular shape, as shown in FIG.

  Next, as shown in (a-4) of FIG. 2, the mixed slurry is dehydrated and dried in a square mold to produce a porous silica substrate temporary molded body 141 (temporary molding step). Specifically, the mixed slurry 131 contained in the square mold is put in a clean oven, heated from room temperature to 5 to 20 ° C./hour, and then held at 50 to 200 ° C. for 10 to 100 hours to obtain moisture. Is evaporated to dryness.

  In this way, after the porous silica substrate temporary molded body 141 is produced, it is fired to form the porous silica substrate 151 (firing step). In the present invention, the inner surface portion of the porous silica substrate 151 is formed. A release accelerator that promotes release of the polycrystalline silicon ingot is included in at least a part. The release accelerator is contained in at least one of the inner surface portions of the temporary molded body 141 by applying the mold release accelerator to at least a part of the inner surface of the temporary molded body 141 and drying it after the temporary molding step. It can also be performed by adding a mold release accelerator to the part, or, as will be described later, by applying a mold release accelerator to at least a part of the inner surface of the porous silica substrate 151 after the firing step. You can also. A specific method of containing the mold release accelerator will be described later.

After the temporary molding step, as shown in FIG. 2 (a-5), the porous silica substrate temporary molded body 141 is fired to form a porous silica substrate 151 (firing step). The firing conditions of this firing step are performed at a temperature of 1200 to 1500 ° C. in an atmosphere containing an inert gas as a main component and O ₂ gas.

Specifically, the temporary molded body 141 removed from the rectangular mold is placed in an electric resistance heating furnace using, for example, a high-purity alumina board as a heat insulating material and molybdenum disilicide as a heater. Next, in an atmosphere containing O ₂ (oxygen) gas containing an inert gas such as N ₂ (nitrogen) gas, He (helium) gas, or Ar (argon) gas as a main component, 50 ° C. from room temperature to 1000 ° C. The temperature is raised at / hour to 500 ° C./hour to oxidize, burn, and remove organic substances such as a binder contained in the temporary molded body 141. Subsequently, the temperature is increased from 1000 ° C. to 1200 to 1500 ° C. at 20 ° C./hour to 200 ° C./hour, and subsequently at a predetermined temperature in the range of 1200 to 1500 ° C., preferably 1250 to 1350 ° C., for 1 to 10 hours. The first raw material powder in the temporary molded body 141 and the second raw material powder are sintered.

The O ₂ gas content in the firing step is 1 to 30 vol. For the purpose of oxidizing and removing various organic binders. % Is preferred. O ₂ gas content is 1 vol. If it is% or more, the organic binder can be removed more effectively. The O ₂ gas content is 30 vol. If it is% or less, it is sufficient for removing the organic binder, and the consumption of the heater material can be reduced, and the cost of gas for firing can be suppressed, which is industrially preferable.

  As described above, the porous silica substrate 151 is manufactured. As described above, in the present invention, the release of the polycrystalline silicon ingot is applied to at least a part of the inner surface portion of the porous silica substrate 151. Include a release accelerator to promote.

  As a specific method for containing the mold release accelerator, first, after the temporary molding step, at least a part of the inner surface of the temporary molded body 141 is applied and dried, and at least the inner surface part of the temporary molded body 141 is dried. A specific method of adding a mold release accelerator by adding a mold release accelerator to a part will be described as an example.

For example, in the case of alkaline earth metal elements such as recrystallized type Ca, Sr, Ba, etc., chlorides, nitrates, carbonates, acetates, etc., which are these elemental compounds dissolved in water or alcohol, are selected, and a temporary molded body 141 Addition treatment is performed by applying and drying from the inner surface by spraying, airbrushing, rollering, or brushing. The temporary molded body 141 to which the release accelerator has been added is fired at 1200 to 1500 ° C. in an O ₂ gas-containing atmosphere containing an inert gas as a main component in a firing step described later. These mold release accelerators are contained in at least 2 mm thickness of the inner surface of the container by the firing step. The content concentration is 50 to 5000 wt. As the total value of alkaline earth metal elements of Ca, Sr, and Ba. ppm, preferably 100 to 1000 wt. More preferably, it is ppm.

  As another specific method for containing a mold release accelerator, a method of applying a mold release accelerator to at least a part of the inner surface of the porous silica substrate 151 after the firing step will be described.

Instead of, or in addition to, the method of adding the release accelerator by application after the temporary forming step, the release accelerator is applied to at least a part of the inner surface of the porous silica substrate 151 after the firing step. A mold release accelerator can be incorporated by coating. By applying and drying at least one compound mixed solution of alkaline earth metal elements such as Ca, Sr, Ba on the inner surface of the fired porous silica substrate 151 by a spray method, an air brush method, and the like, A coating process is performed. The coating concentration, Ca, Sr, it is preferable that the 50~5000μg / cm ² as an alkaline earth metal element sum of such Ba, and even more preferably from 100-1000 / cm ^2.

  The OH group concentration is adjusted by selecting the type of the first raw material powder and changing the atmosphere, temperature, and time conditions of the drying process and the sintering process, so that the porous silica substrate 151 has 5 to 500 wt. Set to ppm. Furthermore, 30 to 300 wt. A range of ppm is preferred.

(II) 2nd aspect The outline of another example (2nd aspect, a dry process) of the manufacturing method of the square silica container 10 which concerns on this invention was shown in FIG.

  First, as shown to (b-1) of FIG. 3, raw material powder is produced. Specifically, silica powder having a particle size of 0.03 to 3.0 mm and silica powder having a particle size of 0.1 to 10 μm are prepared as the first raw material powder. These raw material powders can be produced in the same manner as in the first embodiment.

  After producing the second raw material powder, before producing the mixed powder to be described later, it is possible to produce a granule having a particle size of 5 to 500 μm in which the second raw material powder is aggregated from the second raw material powder. What can be done is the same as in the first embodiment. Thus, it is preferable to use the second raw material powder as a granule because the second raw material powder can be handled easily.

  In this embodiment (second aspect), the first raw material powder, the second raw material powder, and the mixed powder 231 obtained by mixing the first raw material powder, the second raw material powder, and the organic binder described later are used. Al element is added (doping) to at least one. As a result, the porous silica substrate 151 can contain Al element. Accordingly, as described above, movement and diffusion of alkali metal elements such as Li, Na, and K and transition metal elements such as Ti, Cr, Fe, Ni, Cu, Zn, Mo, and Au in the porous silica substrate 151 are performed. Can be prevented, and the heat-resistant deformation property of the square silica container 10 can be improved.

  In order to add Al element to at least one of the first raw material powder and the second raw material powder, the raw material powder is immersed and impregnated in an Al compound solution soluble in water or alcohol, and then pulled up at a constant rate. A method such as drying can be used. The amount of Al to be added is such that the Al concentration in the porous silica substrate 151 of the square silica container 10 after manufacture is 5 to 500 wt. ppm, and 10 to 100 wt. It is preferable to make it ppm.

  Next, as shown to (b-2) of FIG. 3, 1st raw material powder, 2nd raw material powder, and an organic binder are mixed, and the mixed powder 231 is produced. The second raw material powder may be mixed in the state of granules as described above to obtain a mixed powder 231.

  In this mixing, the first raw material powder is the main raw material and the second raw material powder is preferably 5 wt. % Or more and 50 wt. %, More preferably 10-30 wt. Mix evenly in the% range. The ratio of the organic binder in the mixed powder 231 is 1 to 10 wt. % Is preferable.

  In order to reduce the manufacturing cost, it is necessary to increase the ratio of the first raw material powder to the second raw material powder as much as possible. The mixing ratio of the second raw material powder is 5 wt. If it is%, the voids of the porous silica substrate 151 after molding and firing are reduced, and the density is sufficiently high. As a result, the dimensional system and heat resistance of the porous silica substrate 151 can be improved. The mixing ratio of the second raw material powder is 50 wt. If it is% or less, sufficient voids in the porous silica substrate 151 after molding and firing can be secured, and the releasability can be further improved. As a mixing method, when the amount is relatively small, a V-type mixer can be used, but it is not limited to this method.

  As described above, an Al element may be added to the mixed powder 231 instead of or in addition to adding the Al element to at least one of the first raw material powder and the second raw material powder. In this case, it is possible to use a method in which the mixed powder 231 is immersed and impregnated in an Al compound solution soluble in water or alcohol, and then pulled up at a constant speed and dried. The amount of Al to be added is such that the Al concentration in the porous silica substrate 151 of the square silica container 10 after manufacture is 5 to 500 wt. ppm, and 10 to 100 wt. It is preferable to make it ppm.

  Next, as shown in (b-3) and (b-4) of FIG. 3, the mixed powder 231 is introduced into the square formwork, and heated to 50 to 200 ° C. to melt the organic binder. A porous silica-based temporary molded body 241 is prepared.

  Specifically, first, the mixed powder 231 is introduced into a rectangular mold and formed into a predetermined shape in accordance with the shape of the inner wall portion. Next, the mixed powder 231 in the square formwork is pressurized and adjusted to a predetermined pressure of 0.1 to 1 MPa, and the temperature of the mixed powder 231 is increased to a predetermined temperature of 50 to 200 ° C. Consolidate and hold until binder is welded. Next, it is allowed to cool to room temperature to obtain a raw material porous silica base temporary molding 241.

  In this way, the porous silica substrate temporary molded body 241 is prepared and then fired to form the porous silica substrate 151 (firing step). In the present invention, the inner surface portion of the porous silica substrate 151 is formed. A release accelerator that promotes release of the polycrystalline silicon ingot is included in at least a part. In this embodiment, the release accelerator is contained in at least a part of the inner surface of the temporary molded body 241 after the temporary molding step and dried, as in the first aspect. It can also be carried out by adding a mold release accelerator to at least a part of the inner surface portion of the molded body 241. As will be described later, the mold release accelerator is applied to the inner surface of the porous silica substrate 151 after the firing step. It can also be carried out by applying to at least a part of.

Next, as shown in FIG. 3 (b-5), the porous silica-based temporary molded body is 1200 to 1500 ° C. in an atmosphere containing an inert gas as a main component and O ₂ gas. Firing at temperature to form a porous silica substrate (firing step).
This step can be performed in the same manner as the firing step of the first aspect described above.

  As described above, the porous silica substrate 151 is manufactured. As in the first embodiment, the release accelerator is contained in the porous silica substrate 151 after the firing step. It can also be performed by applying to at least a part of the inner surface.

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
In accordance with the method for producing a rectangular silica container of the present invention shown in FIG. 2 (first embodiment), a rectangular silica container was produced as follows.

First, the first raw material powder was produced as follows.
50 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 0.03 to 3.0 mm and a silica (SiO ₂ ) purity of 99.99 wt. % And a total weight of 40 kg of silica powder (natural silica powder).

  Moreover, the 2nd raw material powder was produced as follows and this was made into the state of a granule.

  As the second raw material powder, spherical amorphous silica powder was produced by a melting method. The particle size was 0.2-5 μm and the weight was 10 kg.

  The second raw material powder produced in this way was used as a binder-coated granule as follows. 50 g of paraffinic binder (melting point 55 ° C.), 50 g of stearic acid binder (melting point 100 ° C.) and 2.5 kg of pure water are mixed with 10 kg of the second raw material powder to produce a mixed slurry for forming granules. did. This mixed slurry was dried by a spray dryer to prepare a binder-coated granule. The granule diameter of the second raw material powder coated with the binder was 10 to 100 μm, and the average was 50 μm.

  Next, using a V-type mixer, 80 wt. % Of the second raw material powder in a granular form with respect to 20% by weight. % Were uniformly dry mixed.

To 90 parts by weight of the mixed powder of the first raw material powder and the granular second raw material powder, 10 parts by weight of pure water, and a small amount of aluminum chloride AlCl ₃ and a dispersing agent (ammonium polyacrylate) were mixed. A slurry was formed. Next, the slurry was uniformly mixed for 1 hour in a ball mill composed of a cylindrical silica glass container and silica glass balls. An appropriate amount of pure water was added to the uniformly mixed slurry so that the density was 1.8 to 1.9 g / cm ³ and the viscosity was about 500 to 1000 mPa · sec at a shear rate of 1 to 10 / sec. . Next, this slurry was put in a container, placed in a silica glass chamber, and vacuum degassed for 3 minutes at a vacuum of 10 ⁴ Pa at room temperature. Thus, a mixed slurry 131 was obtained.

  Next, the mixed slurry 131 was introduced into the square formwork.

  Next, the mixed slurry 131 introduced into the rectangular formwork was kept in a clean oven at 100 ° C. for 10 hours, and then cooled to room temperature to prepare a porous silica substrate temporary molded body 141.

  Next, a barium chloride solution was applied to the entire inner surface portion of the porous silica-based temporary molded body 141 by a spray method.

  Next, a temporary molded body 141 made of a porous silica substrate was placed in an electric resistance heating furnace made of a heat-resistant material of a high-purity alumina board having an in-furnace size of 1 m × 1 m × 1 m and equipped with a molybdenum disilicide heater. And oxygen 20 vol. %, Nitrogen 80 vol. In an atmosphere, the temperature was raised from room temperature to 1000 ° C. at a rate of 200 ° C./hour over about 5 hours, raised to 1350 ° C. at a rate of 100 ° C./hour, and then at 1350 ° Hold for 1 hour. In this way, the porous silica-based temporary molded body 141 was fired to produce the square silica container 10.

  The dimensions of the porous silica substrate 151 were such that the inner dimension was 400 mm wide × 400 mm deep × 400 mm high and the thickness was 15 mm.

(Example 2)
As in Example 1, except that the Al element concentration and the OH group concentration contained in the porous silica substrate 151 are about 3 to 10 times and applied to the entire inner surface portion of the temporary molded body 141 of the porous silica substrate. The square silica container 10 was manufactured at a barium chloride concentration of about 10 times. Further, when the temporary molded body 141 is fired, the temperature is raised to 1350 ° C. and held instead of being raised to 1350 ° C.

(Example 3)
According to the method for producing a rectangular silica container of the present invention shown in FIG. 3 (second embodiment), a rectangular silica container was produced as follows.

  First, the first raw material powder and the second raw material powder were produced in the same manner as in Example 1. The second raw material powder was made into granules in the same manner as in Example 1.

  Next, using a V-type mixer, 80 wt. % Of the second raw material powder in a granular form with respect to 20% by weight. % Were uniformly dry mixed.

A small amount of aluminum chloride AlCl ₃ and an organic binder were mixed in the mixed powder 90 of the first raw material powder and the granular second raw material powder to obtain a mixed powder 231.

  Next, the mixed powder 231 was introduced into the square formwork.

  Next, the mixed powder 231 introduced into the rectangular formwork was kept in a clean oven at 100 ° C. for 10 hours, and then cooled to room temperature to prepare a porous silica-based temporary molded body 241.

  Next, a barium chloride solution was applied to the entire inner surface portion of the porous silica-based temporary molded body 241 by a spray method.

  Next, a temporary molded body 241 of a porous silica substrate was installed in an electric resistance heating furnace made of a heat-resistant material of a high-purity alumina board having an in-furnace size of 1 m × 1 m × 1 m and equipped with a molybdenum disilicide heater. And oxygen 20 vol. %, Nitrogen 80 vol. In an atmosphere, the temperature was raised from room temperature to 1000 ° C. at a rate of 200 ° C./hour over about 5 hours, raised to 1350 ° C. at a rate of 100 ° C./hour, and then at 1350 ° Hold for 1 hour. In this way, the porous silica-based temporary molded body 241 was fired to produce the square silica container 10.

Example 4
Similar to Example 3, except that the Al element concentration and the OH group concentration contained in the porous silica substrate 151 are about 2 to 10 times and applied to the entire inner surface portion of the temporary molded body 241 of the porous silica substrate. The square silica container 10 was manufactured at a barium chloride concentration of about 10 times. Further, when the temporary molded body 141 is fired, the temperature is raised to 1350 ° C. and held instead of being raised to 1350 ° C.

(Example 5)
The square silica container 10 was manufactured by changing the conditions from Example 3 as follows. First, the mixing ratio of the first raw material powder and the granular second raw material powder was 90:10. Further, the Al element concentration contained in the porous silica substrate 151 was set to about 5 times. The concentration of barium chloride applied to the entire inner surface portion of the porous silica-based temporary molded body 241 was also set to about 10 times.

(Example 6)
As in Example 5, except that the mixing ratio of the first raw material powder and the granular second raw material powder is 95: 5, and the temperature during firing of the temporary molded body 141 is up to 1370 ° C. The square silica container 10 was manufactured by raising and holding the temperature.

(Comparative Example 1)
A square silica container was produced in the same manner as in Example 2, except that Al was not added and a release accelerator was not contained in the inner surface portion of the porous silica substrate.

(Comparative Example 2)
A square silica container was produced in the same manner as in Example 4 except that Al was not added and a release accelerator was not contained in the inner surface portion of the porous silica substrate.

(Comparative Example 3)
As in Comparative Example 1, except that silica (SiO ₂ ) purity 99.9999 wt. % High-purity product, the mixing ratio of the first raw material powder and the granular second raw material powder is 60:40, Al element is contained in the porous silica substrate, Manufactured.

(Comparative Example 4)
Similar to Comparative Example 2, except that silica (SiO ₂ ) purity 99.9999 wt. % High-purity product, the mixing ratio of the first raw material powder and the granular second raw material powder is 60:40, Al element is contained in the porous silica substrate, Manufactured.

[Evaluation Methods in Examples and Comparative Examples]
The physical properties and characteristics of the raw material powder used in each example and comparative example and the manufactured square silica container were evaluated as follows.
Bulk density measurement method:
A plate-like sample of 50 mm × 50 mm × 15 mm was cut out from the square silica container, and the weight (g) of the sample was measured.
Next, the volume of the sample (cm ³ ) was determined by immersing the sample in a water tank containing pure water and measuring the weight loss of the sample. The bulk density (g / cm ³ ) was calculated from these two values.

Particle size measurement method for each raw material powder:
Two-dimensional shape observation and area measurement of each raw material powder were performed with an optical microscope or an electron microscope. Next, assuming that the shape of the particle is a perfect circle, the diameter was calculated from the area value. This method was repeated statistically to obtain a value within the range of the particle size (in this range, 99 wt.% Or more of the raw material powder was included).

Metal element concentration analysis:
A sample sample was prepared by cutting a silica sample piece from a predetermined position and dissolving it with a hydrofluoric acid aqueous solution. In particular, in the concentration analysis of the mold release accelerator, a plurality of 20 mm × 20 mm × 2 mm samples were cut out from the inner surface layer portion of the square silica container to obtain a silica sample piece for analysis. When the concentration of the contained metal element is relatively low, plasma emission spectrometry (ICP-AES, Inductively Coupled Plasma-Atomic Emission Spectroscopy) or plasma mass spectrometry (ICP-MS, Inductively Coupled Plasma, When the element concentration was relatively high, it was performed by atomic absorption spectrophotometry (AAS, Atomic Absorption Spectroscopy).

OH group concentration measurement:
A powdery sample having a particle size of 10 to 100 μm was prepared from a porous silica substrate, and was subjected to infrared diffuse reflection spectrophotometry. Conversion to the OH group concentration follows the literature below.
Dodd, D.D. M.M. and Fraser, D.A. B. (1966) Optical determination of OH in fused silica. Journal of Applied Physics, vol. 37, P.I. 3911.

Anti-diffusion effect from rectangular silica container to polycrystalline silicon ingot:
Si purity 99.99999999 wt. % High-purity silicon melt was charged and cooled to room temperature to prepare a polycrystalline silicon ingot having dimensions of 400 mm × 400 mm × 300 mm. Next, a silicon piece was sampled at a position 5 mm deep from the surface of the ingot, and this was treated with an acidic solution to obtain a solution sample, and then Na concentration analysis was performed by ICP-MS. The effect of preventing impurity diffusion from the rectangular silica container to the polycrystalline silicon ingot was evaluated by the Na concentration value.
High impurity diffusion prevention effect ○ (Na concentration is less than 10wt.ppb)
During impurity diffusion prevention effect Δ (Na concentration is 10 wt. Ppb or more and less than 100 wt. Ppb)
Small impurity diffusion prevention effect × (Na concentration is 100wt.ppb or more)

Release property evaluation:
A polycrystalline silicon ingot was prepared in the same manner as described above, and then the four corners of the square silica container were cut with a cutter, and the four side walls and bottom plate of the square silica container were peeled off from the ingot. The releasability was evaluated by measuring the depth of unevenness and cracks remaining on the surface of the ingot from the position in contact with the inner surface of the square silica container to the inner direction with a scale.
Good releasability ○ (depth less than 2mm)
Moderate releasability △ (depth 2mm or more and less than 5mm)
Good releasability × (depth 5mm or more)

Manufacturing cost (relative) evaluation:
The manufacturing cost of the square silica container was examined.
The reference was set as Comparative Examples 3 and 4, and the total values of the silica raw material powder cost, the powder molding cost, the fired cost of the molded body and the like were relatively evaluated. In Comparative Examples 3 and 4, the first raw material powder has a silica purity of 99.9999 wt. %, And the second raw material powder was made of high-purity synthetic spherical silica glass and the mixing ratio was high, resulting in an increase in the total cost.
Low cost ○ (50% or less)
Medium cost △ (about 50-90%)
Cost is high × (Comparative Examples 3 and 4 are 100%)

  The production conditions, measured physical property values, and evaluation results of the respective square silica containers produced in Examples 1 to 6 and Comparative Examples 1 to 4 are summarized and shown in Tables 1 to 5 below.

  As can be seen from Tables 1 to 5, in Examples 1 to 6 according to the method for producing a silica container according to the present invention, a rectangular silica container for producing a polycrystalline silicon ingot excellent in releasability is produced at low cost. I was able to.

  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.

10 ... Square silica container for producing a polycrystalline silicon ingot of the present invention,
11 ... Side wall portion of porous silica substrate, 12 ... Inner surface of side wall portion of porous silica substrate,
21 ... Bottom of the porous silica substrate, 22 ... Inner surface of the bottom of the porous silica substrate,
131 ... Mixed slurry, 141 ... Temporary molded article, 151 ... Porous silica substrate,
231 ... Mixed powder, 241 ... Temporary molding.

Claims (10)

A rectangular silica container for producing a polycrystalline silicon ingot by solidifying after containing a silicon melt,
The rectangular silica container is composed of at least a porous silica substrate,
The porous silica substrate has a bulk density of 1.80 to 2.10 g / cm ³ and an Al concentration of 5 to 500 wt. ppm, and the OH group concentration is 5 to 500 wt. ppm,
Polygonal silicon ingot-producing square, characterized in that at least a part of the inner surface portion of the porous silica substrate contains a mold release accelerator for promoting mold release of the polycrystalline silicon ingot. Silica container.   One or more of Ca, Sr, and Ba as the mold release accelerator may be added to at least a part of the inner surface portion of the porous silica substrate at a depth of 2 mm from the inner surface as a total value of each element from 50 to 50. 5000 wt. The rectangular silica container for producing a polycrystalline silicon ingot according to claim 1, which is added at a concentration of ppm. One or more of Ca, Sr, and Ba as the release accelerator is applied to at least a part of the inner surface portion of the porous silica substrate at a concentration of 50 to 5000 μg / cm ² as a total value of each element. The rectangular silica container for producing a polycrystalline silicon ingot according to claim 1 or 2, wherein the container is a rectangular silica container.   The concentration of each of Li, Na, and K contained in the porous silica substrate is 5 wt. The rectangular silica container for producing a polycrystalline silicon ingot according to any one of claims 1 to 3, wherein the square silica container is at most ppm. A method for producing a rectangular silica container for producing a polycrystalline silicon ingot by solidifying after containing a silicon melt, comprising at least:
A step of producing silica powder having a particle size of 0.03 to 3.0 mm as the first raw material powder,
Producing silica powder having a particle size of 0.1 to 10 μm as the second raw material powder;
Producing a mixed slurry containing the first raw material powder, the second raw material powder, and water;
The mixed slurry is dehydrated and dried in a square mold, and a temporary molding step for producing a temporary molded body of a porous silica substrate;
A calcining step in which the porous silica substrate temporary molded body is calcined at a temperature of 1200 to 1500 ° C. in an atmosphere containing an inert gas as a main component and an O ₂ gas to obtain a porous silica substrate. ,
By adding Al element to at least one of the first raw material powder, the second raw material powder, and the mixed slurry, the porous silica substrate contains Al element,
A method for producing a rectangular silica container for producing a polycrystalline silicon ingot, characterized in that a release accelerator that promotes the release of the polycrystalline silicon ingot is contained in at least a part of the inner surface portion of the porous silica substrate. . A method for producing a rectangular silica container for producing a polycrystalline silicon ingot by solidifying after containing a silicon melt,
A step of producing silica powder having a particle size of 0.03 to 3.0 mm as the first raw material powder,
Producing silica powder having a particle size of 0.1 to 10 μm as the second raw material powder;
Mixing the first raw material powder, the second raw material powder and an organic binder to produce a mixed powder;
Introducing the mixed powder into a square mold, heating to 50 to 200 ° C., and melting the organic binder to produce a porous silica substrate temporary molded body; and
A calcining step in which the porous silica substrate temporary molded body is calcined at a temperature of 1200 to 1500 ° C. in an atmosphere containing an inert gas as a main component and an O ₂ gas to obtain a porous silica substrate. ,
By adding Al element to at least one of the first raw material powder, the second raw material powder, and the mixed powder, the porous silica substrate is caused to contain Al element,
A method for producing a rectangular silica container for producing a polycrystalline silicon ingot, characterized in that a release accelerator that promotes the release of the polycrystalline silicon ingot is contained in at least a part of the inner surface portion of the porous silica substrate. .   After the temporary molding step, the release accelerator is applied to at least a part of the inner surface of the temporary molded body and dried, so that the release agent is applied to at least a part of the inner surface part of the temporary molded body. It is performed by adding a mold accelerator and / or by applying the mold release accelerator to at least a part of the inner surface of the porous silica substrate after the firing step. The manufacturing method of the square silica container for polycrystal silicon ingot manufacture of Claim 5 or Claim 6.   The method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to any one of claims 5 to 7, wherein the mold release accelerator is one or more of Ca, Sr, and Ba.   Before producing the mixed slurry or the mixed powder, a granule having a particle diameter of 5 to 500 μm formed by collecting the second raw material powder is produced from the second raw material powder, and the second raw material powder The method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to any one of claims 5 to 8, wherein the mixed slurry or the mixed powder is prepared by using a granule. In the firing step, the inert gas is at least one of N ₂ gas, He gas, and Ar gas, and the content of O ₂ gas is 1 to 30 vol. The method for producing a rectangular silica container for producing a polycrystalline silicon ingot according to any one of claims 5 to 9, wherein the percentage is%.

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