JP2009292656A - Method for manufacturing silicon ingot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a silicon ingot by which a high-purity silicon ingot can be manufactured from a powdery silicon material at a relatively low temperature. <P>SOLUTION: The method for manufacturing the silicon ingot includes: a step of forming molten silicon by melting a powdery silicon material in the presence of a melting aid; a step of forming a silicon ingot by solidifying the molten silicon; and a step of removing the impurities in the molten silicon before solidifying the molten silicon. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a silicon mass for obtaining a silicon mass from a powdered silicon material.

  In the manufacturing process of a thin plate made of silicon single crystal or polycrystal (hereinafter referred to as “silicon wafer”) widely used for IC chips and solar cells, about 60% of the raw material silicon is drained by cutting, chamfering or polishing. The cost to the product and the environmental impact associated with disposal (this waste liquid is generally disposed of in landfill after concentrating and collecting some materials) is a major problem. It has become.

In particular, in recent years, the production of solar cells has been steadily increasing, and the demand for raw material silicon has been increasing rapidly. For this reason, a shortage of silicon for solar cells has become apparent.
Therefore, conventionally, a method for recovering silicon from waste liquid generated during the production of a silicon wafer such as cutting or polishing has been proposed.

For example, in Patent Document 1, solid content is recovered from waste slurry discharged from a process of cutting or polishing a silicon single crystal or polycrystalline ingot using a slurry in which abrasive grains are dispersed in a coolant, and the recovered solid content In contrast, organic solvent cleaning to remove coolant, water cleaning to wash away organic solvent, metals (iron, copper, etc.) contained in waste slurry are dissolved in acid aqueous solution (hydrofluoric acid aqueous solution, etc.) Acid cleaning for removing the water and water cleaning for washing away the acid aqueous solution are performed.
Patent Document 2 describes a method for recovering silicon powder generated when silicon is processed and reusing it as a silicon raw material.
Patent Document 3 describes a method of removing impurities by pulverizing silicon to a maximum particle size of 1 to 5 mm and then washing with an acid such as hydrofluoric acid and nitric acid and reusing it as a silicon raw material. Yes.
In addition, as a problem when reusing powdered silicon, if melting proceeds while adding powdered silicon to molten silicon, silicon has a lower solid density than the melt. It is known that it floats on the surface and hardly melts (for example, Patent Document 4).
JP 2001-278612 A JP 2002-176016 PR JP 10-324514 A JP 2001-48697 A

In the powdered silicon having a fine average particle size as obtained from the solid content recovered from the waste slurry, the present inventors do not completely melt unless the temperature is significantly higher than the melting point of silicon (1412 ° C.). I found a problem. For example, in order to quickly melt powdered silicon having an average particle diameter of 1 μm, it was necessary to heat to a temperature of 1800 ° C. or higher.
When the silicon material is heated to such a high temperature, there arises a problem that a power consumption for melting increases, and a problem that yield decreases because evaporation of molten silicon is accelerated.

This invention is made | formed in view of such a situation, and provides the manufacturing method of the silicon lump which can manufacture a high purity silicon lump from a powdery silicon material at comparatively low temperature.
In addition, the present invention provides a method for producing a silicon lump that can obtain a better melting speed than before when the melting is advanced while adding a powdered silicon material to the molten silicon.

  The present invention includes a step of melting a powdered silicon material in the presence of a melting aid to form a molten metal, a step of solidifying the molten metal to form a silicon lump, and removing impurities before solidifying the molten metal A process for producing a silicon lump.

The melting aid may comprise an alkali metal or alkaline earth metal salt or oxide anhydride or hydrate or a mixture thereof.
The melting aid may include an alkali metal or alkaline earth metal salt or oxide hydrate.
The melting aid may comprise a carbonate anhydride or hydrate or a mixture thereof.
The mixing ratio of the melting aid to the powdered silicon material may be 20 wt% or more and 30 wt% or less.
The temperature at which the powdered silicon material is melted may be 1410 ° C. or higher and 1600 ° C. or lower.
The removal is performed by physically removing the impurities from the molten metal, tilting a crucible containing the molten metal to discharge molten silicon in the molten metal, and installed on a side surface or a lower surface of the crucible. It may be performed by one or more of discharging molten silicon in the molten metal by opening a hole that can be opened and closed.
The powdery silicon material may be obtained from a pulverized metal silicon lump.
The powdery silicon material may be obtained from a waste liquid containing silicon powder generated during silicon processing.
The powdered silicon material is obtained by solid-liquid separation of a waste slurry in which silicon powder is mixed in the slurry by cutting or polishing a silicon lump or a silicon wafer using a slurry containing abrasive grains and a coolant, or a concentrated portion thereof. Also good.
The powdered silicon material is obtained by solid-liquid separation of a silicon slurry using a slurry containing abrasive grains and coolant or waste slurry in which silicon powder is mixed into the slurry or by concentrating the slurry by cutting or polishing the silicon wafer. A solid-liquid separation step of obtaining a solid content for silicon recovery containing, a cleaning step of washing the solid content for silicon recovery using an organic solvent, and a classification for the solid content for silicon recovery from the cleaning step May be obtained by a method including a classification step of reducing the content of abrasive grains and increasing the content of silicon than before classification.
The powdery silicon material may have an average particle size of 0.1 μm to 1 mm.
The various embodiments illustrated here can be combined with each other.

  According to the present invention, even a powdery silicon material can be melted at a relatively low temperature. Furthermore, in the present invention, by removing glassy impurities generated by the reaction between the melting aid used and silicon oxide formed on the surface of the powdered silicon material, it is more effective than the raw material powdered silicon material. A high-purity silicon lump can be obtained.

The method for producing a silicon lump of the present invention includes a step of melting a powdered silicon material in the presence of a melting aid to form a molten metal, a step of solidifying the molten metal to form a silicon lump, and a solidifying of the molten metal. And a step of removing impurities before the step.
First, the relationship between the silicon particle size and the molten state, which has been found by the present inventors, will be described.
When silicon is placed in an atmosphere containing oxygen, such as in the air, the surface is oxidized to form a film-like silicon oxide.
Silicon oxide is fluid when it reaches a softening point (900 ° C. to 1000 ° C.) or higher, but is known to have a high viscosity even at a temperature higher than the melting point of silicon. However, in a silicon material of a size normally used for manufacturing a silicon wafer (for example, a lump having a particle size of 5 to 20 cm), the influence of such (film-like) silicon oxide on the melting of the silicon material is negligible. Can be melted well near the melting point of silicon.

  However, according to the study by the present inventors, when the particle size of the silicon material is reduced, the influence of silicon oxide becomes a level that cannot be ignored, and a temperature significantly higher than the silicon melting point is necessary to obtain a practical melting rate. I found out that

  For example, after pulverizing a silicon material and sieving the particle size as shown in Table 1, it is heated and melted to 1800 ° C. in a vacuum furnace to determine whether or not a viscous fluid composed of silicon oxide is formed on the molten metal. Confirmed. As shown in Table 1, when the silicon material finely pulverized to 1 mm or less was melted, a viscous fluid composed of silicon oxide was confirmed, and it was found that the influence of silicon oxide cannot be ignored.

  And based on this knowledge, the present inventors can melt the powdered silicon material in the presence of a melting aid to form a molten metal, so that the powdered silicon material can be melted at a relatively low temperature. The inventors found that a silicon mass can be produced from a powdered silicon material at a low temperature, and the present invention has been completed.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

1. Silicon Mass Manufacturing Method A silicon mass manufacturing method according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a conceptual diagram of an apparatus that can be used for carrying out the silicon lump manufacturing method of the present embodiment. FIG. 2 is a conceptual diagram showing a process until a silicon lump is obtained from a powdered silicon material in the silicon lump manufacturing method of the present embodiment.

The silicon lump manufacturing method of the present embodiment includes a step of melting the powdered silicon material 3 in the presence of the melting aid 4 to form the molten metal 2, and a step of solidifying the molten metal 2 to form the silicon lump 10. And a step of removing the impurities 11 before the molten metal 2 is solidified.
In the present embodiment, the molten metal 2 is formed in the crucible 1.
Hereinafter, each component will be described.

1-1. Crucible The crucible 1 is installed in any one of an open-air furnace, a furnace in an inert gas atmosphere such as nitrogen or argon, or a vacuum atmosphere furnace. Is desirable.

  As the material of the crucible 1, carbon, mullite, alumina, magnesia, or the like can be applied. However, when an atmosphere open furnace is used, mullite and alumina are preferable because carbon is highly oxidized.

1-2. Powdered silicon material The powdered silicon material 3 is a powdery material containing silicon (preferably having a main component). In one example, as shown in FIG. A silicon oxide film 6 covering the grains 5 and impurities 7 are included. The silicon content in the powdery silicon material 3 is, for example, 80 to 99.99 wt%, specifically, for example, 80, 85, 90, 95, 99, 99.9, 99.99 wt%. The silicon content may be within a range between any two of the numerical values exemplified herein.

The average particle diameter of the powdered silicon material 3 is, for example, about 0.1 μm to 1 mm, and the ratio of the surface area is larger than the volume, and the influence of the surface oxide film cannot be ignored. In the present invention, the “average particle size” means a Coulter counter type particle size distribution meter, in which the powdered silicon material 3 is dispersed in water or alcohol, and if necessary, a dispersion medium such as sodium hexametaphosphate is used. The particle size D50 (particle size in which 50% is present from the larger or smaller particle size distribution) is measured. According to this definition, for example, in the case of a powdered silicon material in which a large number of particles having a diameter of 0.1 μm are aggregated to form a lump having a size of 10 mm, the average particle diameter is about 0.1 μm.
Specifically, the average particle diameter of the powdered silicon material 3 is, for example, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 500 μm, and 1 mm. This average particle diameter may be within a range between any two of the numerical values exemplified here.

  The method for obtaining the powdered silicon material 3 is not particularly limited, but the powdered silicon material 3 can be obtained, for example, by the following method.

(1) When obtaining a powdery silicon material from a pulverized product of a metal silicon lump The powdered silicon material 3 can be obtained from a pulverized product of a metal silicon lump. A metal silicon lump means a silicon lump prior to purification obtained by reducing a silicon oxide raw material such as silica stone or quartz sand. The silicon content in the metal silicon mass is not particularly limited, but is generally about 98 to 99 wt%. The method of pulverizing the metal silicon lump is not particularly limited. In one example, the pulverized metal silicon lump is obtained by coarsely crushing the metal silicon lump with a jaw crusher and then finely crushing with a hammer mill, jet mill, or the like. It is done. The pulverized product of the metal silicon lump may be used as it is as the powdered silicon material 3, or the pulverized product of the metal silicon lump may be subjected to another treatment (eg, washing with acid or alkali) as the powdered silicon material 3. Good.

(2) When obtaining powdered silicon material from waste liquid generated during silicon processing The powdered silicon material 3 is processed by silicon processing (for example, silicon cylindrical grinding, silicon cutting, back surface polishing, wafer slicing, that is, silicon lump or silicon wafer) It can be obtained from a waste liquid containing silicon powder generated at the time of cutting or polishing. The waste liquid contains silicon powder and a lubricant, and may further contain abrasive grains. The lubricant is, for example, water or a water-soluble oil. Therefore, the powdered silicon material 3 is obtained by removing the lubricant from the waste liquid and further removing the abrasive grains as necessary.

  When the lubricant consists of water, recover the waste liquid containing silicon powder and water, apply a filter press to recover the cake containing a lot of silicon powder, and then heat it with a dryer to remove moisture. Lubricant can be removed.

  When the lubricant is composed of a water-soluble oil, for example, a water-soluble oil mainly composed of propylene glycol and water, a waste liquid containing silicon powder and water-soluble oil is recovered, and the temperature is equal to or higher than the boiling point (187 ° C.) of propylene glycol. Distill in vacuo. The degree of vacuum is preferably 10 Torr or less. By vacuum distillation, the liquid and solid components are separated and the solid component is recovered. The solid content contains a large amount of silicon, but the oil content remains on the order of several percent. In order to remove this, for example, it is washed with an organic solvent such as methanol, ethanol, isopropyl alcohol as disclosed in JP2007-246366. I do. Thereby, the lubricant composed of water-soluble oil is removed.

  Further, when the waste liquid contains abrasive grains, the abrasive grains are separated and separated by classification using the difference in particle size between the silicon powder and the abrasive grains. For classification, for example, a micron separator manufactured by Hosokawa Micron Corporation can be used.

  The waste liquid is, for example, a waste slurry in which silicon powder is mixed into the slurry by cutting or polishing a silicon lump or a silicon wafer using a slurry containing abrasive grains and coolant, or a concentrated portion thereof, and the waste slurry or the concentrated content thereof. The method for obtaining the powdered silicon material 3 from the minute will be described in detail later.

1-3. Melting aid The melting aid 4 has a function of lowering the softening point of silicon oxide, for example, an alkali metal or alkaline earth metal salt, an oxide anhydride or hydrate, or a mixture thereof. Become. By melting the silicon material 3 in the presence of the melting aid 4, the silicon mass 10 can be produced from the silicon material 3 at a relatively low temperature.

  The alkali metal is, for example, lithium, sodium, or potassium. Alkaline earth metals are, for example, magnesium and calcium. The salt is, for example, carbonate. The hydrate is, for example, a monohydrate. The alkali metal or alkaline earth metal oxide is, for example, sodium oxide or magnesium oxide, and the alkali metal or alkaline earth metal salt is, for example, lithium carbonate, sodium carbonate, magnesium carbonate, potassium carbonate, or calcium carbonate. is there.

  In view of the price, the amount of impurities, and the availability, the melting aid 4 is preferably composed of an anhydride or hydrate of carbonate (preferably sodium carbonate) or a mixture thereof.

  The melting aid 4 may consist of an anhydride alone, a hydrate alone, or a mixture of an anhydride and a hydrate. As will be described later, the hydrate efficiently removes impurities by reducing the viscosity of the glassy impurities 8 generated by the reaction between the melting aid 4 and the silicon material 3, and improves the silicon recovery rate. It has the function. Therefore, when the particle size of the powdered silicon material 3 is small or when the mixing ratio of impurities in the powdered silicon material 3 is high, the melt auxiliary agent 4 consisting of hydrate or containing hydrate is used. It is preferable. Note that anhydrides have the advantage of being relatively inexpensive. In one example, the general price of sodium carbonate monohydrate is about 5 times that of sodium carbonate (sodium carbonate is 50-100 yen / kg, sodium carbonate monohydrate is 300-400 yen / kg).

  The mixing ratio of the melting aid 4 to the silicon material 3 ((weight of the melting aid 4) / weight of the silicon material) is not particularly limited, but is preferably 20 wt% or more and 30 wt% or less. This is because a larger mixing ratio of the melting aid 4 has an advantage of promoting the melting of the silicon material 3, but there is also a problem that a generation amount of glassy impurities (eg, sodium glass) described later is increased. . Specifically, the mixing ratio is, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 wt%. This mixing ratio may be within a range between any two of the numerical values exemplified here.

1-4. Method for Melting Powdered Silicon As a method for melting powdered silicon material 3, a method of producing molten metal 2 by charging powdered silicon material 3 and melting aid 4 into crucible 1 and then heating (method A) ).
In addition, there is a melting method (Method B) in which an initial molten metal 2 is made inside the crucible 1 and the crucible 1 is filled by adding the powdered silicon material 3 and the melting auxiliary agent 4 into the initial molten metal 2. preferable. In this case, the silicon material 3 and the melting aid 4 can be quickly heated by heat transfer from the molten metal.

Although the manufacturing method of the initial molten metal 2 is not particularly limited, in one example, the silicon melt is introduced into the crucible 1 and then heated from room temperature. The heating rate is preferably a low rate, for example, 300 ° C./hour to 450 ° C./hour, in order to prevent thermal shock to the crucible 1. When the temperature of silicon in the crucible 1 reaches 1410 ° C., control is performed so that the temperature is 1410 ° C. or higher and 1600 ° C. or lower, preferably 1550 ° C. or higher and 1600 ° C. or lower. After the initial molten metal 2 is formed, the crucible 1 is filled with the powdered silicon material 3 and the melting aid 4 in the crucible 1.
Specifically, the temperature of the molten metal 2 is, for example, 1410, 1420, 1430, 1440, 1450, 1460, 1470, 1480, 1490, 1500, 1510, 1520, 1530, 1540, 1550, 1560, 1570, 1580, 1590, 1600 ° C. The temperature of the molten metal 2 may be within a range between any two of the numerical values exemplified here.

  In the above method A and method B, the silicon material 3 and the melting aid 4 may be mixed in advance and then charged into the crucible 1, or both may be charged independently and simultaneously. Moreover, it is possible to repeat one or more times that either one is input first and the other is input later.

1-5. Description of mechanism for obtaining high-purity silicon mass at relatively low temperature Purity at relatively low temperature by heating silicon material 3 in the presence of melting aid 4 using FIGS. 2 (a) to 2 (d) A mechanism for obtaining a high silicon mass 10 will be described.
Hereinafter, the description will be given by taking as an example the case where the melting aid 4 is made of sodium carbonate or sodium carbonate monohydrate, but the same is basically true when the melting aid 4 has a composition other than this.

The silicon oxide film 6 (see FIG. 2A) covering the silicon grains 5 in the powdered silicon material 3 reacts with the melting aid 4 to generate glassy impurities 8 (see FIG. 2B). ). The main component of the glassy impurity 8 is sodium glass when the melting aid 4 is sodium carbonate.
Formation of sodium glass is represented by the following reaction formula.
SiO ₂ + Na ₂ CO ₃ → Na ₂ SiO ₃ + CO ₂
Thereby, the softening point of the silicon oxide film 6 is lowered. The softening point varies depending on the charging ratio of the powdered silicon material 3 and the melting aid 4 and the like, but decreases to around 1000 ° C. depending on the case.
At this time, since the glassy impurities 8 have a lower viscosity than silicon oxide, the glassy impurities 8 are fixed and floated with each other. The inside 5 of the powdery silicon material 3 is high-purity silicon that does not contain SiO 2 or the like, and when heated to a temperature equal to or higher than the melting point of silicon, it becomes liquid and a molten silicon 9 is obtained. (See FIG. 2 (c)).
Properties of each component in FIGS. 2A to 2C are as shown in Table 2.

Here, the viscosity of the molten silicon 9 is 0.6 mPa · s, but the viscosity of the glassy impurity 8 is, for example, about 10 ⁴ to 10 ⁶ mPa · s, which is lower than the viscosity of silicon oxide, but compared to the molten silicon 9. Very big. Further, since the density of the glassy impurities 8 is smaller than that of liquid silicon, the glassy impurities 8 emerge with the passage of time.
At this point, impurities (eg diamond, silicon dioxide, aluminum oxide, silicon carbide, silicon nitride, or Sc, Ti, V, Cr, Fe, etc. contained in the powder silicon material 3 from the beginning. (Co, Ni, Y, Zr, Nb, Mo, Ru, Rh, Pd, In, Ta, W, Re, Os, Ir, Pt) 7 is generally a solid or a liquid having a high viscosity. The impurity 8 is taken in.
Furthermore, the impurities 7 shown here are, for example, those used as abrasive grains (silicon carbide, silicon nitride, alumina, zirconia, diamond, etc.), and those contained in wires and cutting blades (Fe and Metal impurities such as Ni) and those contained in metal silicon (metal impurities such as Fe and Ni). Thus, glassy impurities 8 generated by the reaction of the silicon oxide film 6 and the melting aid 4 are contained. However, since various impurities 7 are taken in and float on the molten silicon 9 due to the density difference from the molten silicon 9, the molten silicon 9 is refined as compared with the powdered silicon material 3.

  As a specific purification method, the impurity 11 composed of the impurity 7 and the glassy impurity 8 may be removed. The removal of the impurities 11 is performed by removing the impurities 11 before the molten metal 2 is solidified. The removal of the impurity 11 and the molten silicon 9 is performed by (1) physically removing the surfaced impurity 11 (for example, scraping out the impurity 11 using a rod made of a material having high heat resistance such as a carbon rod). (2) The crucible 2 may be tilted and the molten silicon 9 in the molten metal 2 may be discharged, for example, into a mold, and (3) an openable / closable hole is provided on the side surface or the lower surface of the crucible 2. Alternatively, the molten silicon 9 in the molten metal 2 may be discharged into a mold, for example, by opening the hole. You may carry out by the method of combining two or more of these. After separating the impurity 11 and the molten silicon 9, the molten silicon 9 can be solidified to obtain the silicon lump 10 (see FIG. 2 (d)).

  Further, when sodium carbonate monohydrate is used as the melting auxiliary agent 4 instead of sodium carbonate, the viscosity of the glassy impurity 8 can be further reduced, whereby silicon is taken into the glassy impurity 8. Thus, the silicon recovery rate can be improved. The action of reducing the viscosity of the glassy impurity 8 is not necessarily clear, but it is assumed that it is caused by the evaporation of water in the hydrate to generate water vapor.

  The description in the section “1-5” is about the method A, but it is obvious that the same reaction and melting proceed on the surface of the initial molten metal 2 in the method B as well.

  Further, in the above method B, there is a problem that the powdered silicon material floats on the molten silicon when the powdered silicon material is put on the molten silicon, but it is difficult to melt. Since the material is rapidly melted, the occurrence of such a problem is suppressed.

2. Method for Obtaining Powdered Silicon Material from Waste Slurry or Concentrated Content Here, a method for obtaining powdered silicon material 3 from waste slurry or the concentrated content thereof (hereinafter referred to as “silicon material obtaining method”) will be described in detail.

  In this silicon material acquisition method, a silicon lump using a slurry containing abrasive grains and a coolant or a silicon slurry is cut or polished, and the waste slurry in which silicon powder is mixed into the slurry or its concentrated component is solid-liquid separated to obtain a silicon powder. A solid-liquid separation step of obtaining a solid content for silicon recovery containing, a cleaning step of washing the solid content for silicon recovery using an organic solvent, and a classification for the solid content for silicon recovery from the cleaning step And a classification step of reducing the content of abrasive grains and increasing the content of silicon than before classification.

In addition, as shown in FIG. 3, the silicon material acquisition method includes a waste slurry in which silicon powder is mixed into the slurry by cutting or polishing a silicon lump or a silicon wafer using a slurry containing abrasive grains and coolant, or concentration thereof. From the solid-liquid separation part 12 which solid-liquid-separates a part and acquires the solid content for silicon | silicone collection containing a silicon powder, the washing | cleaning part 13 which wash | cleans the said solid part for silicon | silicone collection | recovery using an organic solvent, Classifying the solid content for recovering silicon, and using a silicon material acquisition device including a classification unit 14 that reduces the content of abrasive grains and increases the content of silicon than before classification. it can.
This silicon material acquisition device includes one or more of a drying and pulverizing unit 15, a metal scrap removing unit 17, and a forming unit 18 as necessary.
Hereinafter, each component will be described.

2-1. Solid-Liquid Separation Unit The solid-liquid separation unit 12 performs solid-liquid separation on the waste slurry or its concentrated component to obtain a solid content for silicon recovery.

(1) Waste slurry, concentration of waste slurry First, the waste slurry will be described.
The waste slurry is a slurry in which silicon powder is mixed by cutting or polishing a silicon lump or a silicon wafer using a slurry containing abrasive grains and coolant. The concentrated portion of the waste slurry is a concentrate of the waste slurry.
The silicon material acquisition device is for recovering silicon powder mixed in the waste slurry to obtain the silicon material 3. The silicon lump is a lump of silicon, for example, a silicon ingot. The shape of the silicon lump is not particularly limited, but in an example, it is a columnar shape or a quadrangular prism shape.

The silicon lump or the silicon wafer is cut or polished using a cutting device or a polishing device, and the used slurry discharged from the cutting device or the polishing device is a waste slurry.
An example of the cutting device is a multi-wire saw device (hereinafter referred to as “MWS”) that is widely used as a silicon ingot cutting device. In general, MWS is a cutting device that wraps and winds a wire between a plurality of rollers, runs slurry while supplying slurry containing abrasive grains and coolant, and presses an object to be cut against the wire for cutting. . When a silicon ingot is cut using such MWS, silicon scraps, crushed abrasive grains and non-crushed abrasive grains, and metal scraps that are wear pieces of wires are mixed in the slurry. Become.

  In MWS, a slurry is usually used repeatedly, but the proportion of silicon or the like contained in the slurry increases with use. When these ratios become high (for example, when the silicon ratio in the slurry becomes 5 wt% or more), defects such as thickness unevenness (often expressed as TTV) and warpage occur in the silicon wafer, and wire breakage occurs. It is known that various problems occur. For this reason, part or all of the slurry is appropriately discharged out of the MWS as a waste slurry, and a new slurry is supplied to the MWS. The waste slurry discharged out of the MWS is processed by the silicon material acquisition device.

  Here, the composition and composition of the slurry will be described. The slurry consists of abrasive grains and coolant that disperses them. The type of abrasive grains is not limited, and is made of, for example, SiC, diamond, CBN, alumina, or the like. The type of the coolant is not limited. For example, an oil-based coolant (oil based on mineral oil), an aqueous coolant (a glycol solvent based on water (for example, ethylene glycol, propylene glycol or polyethylene glycol), surfactant) Or an organic acid added thereto). The coolant is mainly composed of an organic solvent (water-soluble organic solvent) such as ethylene glycol, propylene glycol or polyethylene glycol, and an additive such as organic acid or bentonite is added thereto at 10 wt% or less (preferably 3 wt% or less). It may be. Note that the phrase “having the organic solvent as a main component” here means that, for example, the coolant may contain 20 wt% or less (preferably 15 wt% or less) of water.

(2) Configuration of Solid-Liquid Separation Unit and Solid-Liquid Separation Method by Solid-Liquid Separation Unit Next, the configuration of the solid-liquid separation unit 12 and the solid-liquid separation method by the solid-liquid separation unit 12 will be described.
The configuration of the solid-liquid separation unit 12 is not particularly limited as long as it is a configuration capable of solid-liquid separation of the waste slurry or its concentrated component to obtain a solid content for silicon recovery. The solid-liquid separation device such as a centrifuge, a filtration device or a distillation device is used alone or in combination of two or more thereof in series. Specific examples of the combination are (1) a centrifuge and a distillation device, (2) a centrifuge and a filtration device, or (3) a filtration device and a distillation device. In (1) to (3), two or more centrifuges, filtration devices, or distillation devices may be included. Each solid-liquid separation unit may send either the separated liquid or solid content to the next solid-liquid separation device, and a part of the liquid and a mixture of solids or a part of the solids and liquid. The mixture may be sent to the next solid-liquid separator.

  Here, the structural example of the solid-liquid separation part 12 is demonstrated using FIG.4 and FIG.5. 4 and 5 are block diagrams showing the configuration of the solid-liquid separation unit 12, respectively.

(A) First Configuration Example A first configuration example of the solid-liquid separation unit 12 will be described with reference to FIG. The solid-liquid separation unit 12 of this configuration example includes a primary centrifuge 19, a secondary centrifuge 21, and a distillation device 23.

  The primary centrifuge 19 separates the waste slurry or its concentrated component into a primary liquid component and a primary solid component by primary centrifugation. The primary centrifugation is performed at a relatively low speed, for example, 100 G or more and 1000 G or less. Since the primary solid content is mainly composed of abrasive grains, it can be reused as recycled abrasive grains in MWS or the like after washing, drying and the like. The primary liquid is sent to the secondary centrifuge 21. The primary liquid may be sent directly to the distillation apparatus 23 instead of being sent to the secondary centrifuge 21. In this case, the secondary centrifuge 21 can be omitted.

  The secondary centrifuge 21 separates the primary liquid component into a secondary liquid component and a secondary solid content by secondary centrifugation. The secondary centrifugation is performed at a relatively high speed, for example, 2000 G or more and 5000 G or less. Secondary solids mainly contain silicon and also contain abrasive grains that could not be separated by primary centrifugation. The secondary solid content may be discarded, or a part or all of the secondary solid content may be used for silicon regeneration as in a second configuration example described later. Since the secondary liquid contains a large amount of silicon, a solid content for silicon recovery containing a large amount of silicon can be obtained by distilling the secondary liquid. The secondary liquid is sent to the distillation device 23. In addition, you may send a secondary solid content to the distillation apparatus 23 instead of a secondary liquid component. Moreover, you may send to the distillation apparatus 23 what mixed a part of secondary liquid part and secondary solid content, and what mixed a part of secondary solid part and secondary liquid part.

  The distillation apparatus 23 separates the secondary liquid component into a distillate liquid component and a distilled solid content by distillation. The distillation is preferably performed under reduced pressure (for example, 5 Torr to 20 Torr). This is because distillation at a relatively low temperature and / or high speed becomes possible because the boiling point of the liquid is lowered by the reduced pressure. The distillate can be reused as it is (distilled coolant) or separately as a regenerated coolant by MWS or the like. The distilled solid content is sent to the cleaning unit 13 as a solid content for silicon recovery.

(B) Second Configuration Example A second configuration example of the solid-liquid separation unit 12 will be described with reference to FIG. The solid-liquid separator 12 of this configuration example includes a primary centrifuge 19, a secondary centrifuge 21, a first distillation device 23a, and a second distillation device 23b.

  Regarding the primary centrifuge 19, the description in the first configuration example applies as it is.

  The secondary centrifuge 21 is also similar to the first configuration example, but in this configuration example, a part or all of the secondary solids, together with the distilled solid content from the first distillation apparatus 23a described later, The point which is sent to the 2nd distillation apparatus 23b differs.

  The first distillation apparatus 23a is similar to the distillation apparatus 23 of the first configuration example, but instead of taking the distilled solid content from the first distillation apparatus 23a as the solid content for silicon recovery, the second distillation apparatus 23b is used. Sent to. Part or all of the secondary solids and the distilled solids from the first distillation apparatus 23a are mixed and then sent to the second distillation apparatus 23b or mixed in the second distillation apparatus 23b.

  The second distillation apparatus 23b is the same as the distillation apparatus 23 of the first configuration example except that the subject of distillation is different. In addition, although the example which distills twice using two distillation apparatuses was shown here, you may distill twice using one distilling apparatus. In this case, the second distillation apparatus 23b is omitted, and a part or all of the secondary solid content and the distilled solid content from the first distillation apparatus 23a are sent again to the first distillation apparatus 23a and distilled again. .

2-2. Next, the cleaning unit 13 will be described. The cleaning unit 13 cleans the solid content for silicon recovery using an organic solvent. The solid content for silicon recovery usually contains about 5 wt% to 20 wt% of residual organic substances derived from coolant (hereinafter referred to as “residual coolant”) such as glycol solvents and additives. This causes a decrease in the purity of the material 3. Further, the residual organic matter forms SiC when the silicon material 3 is melted, and causes unnecessary SiC to be generated in the silicon ingot formed by solidifying the molten silicon. Therefore, in order to reduce the residual coolant concentration, the silicon recovery solids are washed.
The organic solvent used is preferably compatible with the coolant. In this case, the residual coolant is easily extracted into the organic solvent. The organic solvent is, for example, an alcohol having 1 to 6 carbon atoms (preferably, a range between any two of 1, 2, 3, 4, 5, and 6) or 1 to 3 carbon atoms (preferably 3 , 4, 5, and 6). Specific examples of such alcohol include methanol, ethanol, isopropyl alcohol, butyl alcohol and the like. Specific examples of such ketones include acetone and methyl ethyl ketone. The organic solvent may be a mixture of a plurality of types of organic solvents. Further, the organic solvent preferably has a lower boiling point than the coolant. Specifically, the organic solvent preferably has a boiling point lower by 50 ° C. or more (preferably 60 ° C., 70 ° C., 80 ° C., 90 ° C. or 100 ° C. or more) than the coolant. This is because the organic solvent is usually removed by evaporation in a later step, but if it has a low boiling point, it is easily evaporated.

  The configuration of the apparatus used for the cleaning unit 13 is not limited as long as the residual coolant in the solid content for silicon recovery can be extracted and removed into an organic solvent. For example, the solid content for silicon recovery and the organic solvent can be removed. A device having a function of mixing, extracting at least a part of the residual organic matter in the solid content for silicon recovery into an organic solvent by vibration, rotation or stirring and removing the organic solvent can be employed. The removal of the organic solvent can be performed, for example, by centrifugation or filtration. Accordingly, the cleaning unit 13 includes, for example, a stirrer having a stirring blade that stirs a mixture of the solids for collecting silicon and the organic solvent charged in the container, and a centrifuge that removes the organic solvent from the stirred mixture. Or it is comprised with a filtration apparatus.

2-3. Next, the drying and pulverizing unit 15 will be described. The drying and pulverizing unit 15 has a function of removing the organic solvent remaining in the silicon recovery solid content after washing and pulverizing the silicon recovery solid content. Drying and pulverization may be performed at the same time, pulverization may be performed after drying, or vice versa. The silicon recovery solid content can be dried by, for example, heating the silicon recovery solid content or reducing the ambient atmosphere of the silicon recovery solid content. The pulverization of the solid content for silicon recovery can be performed using a known device such as a pulverizer using a pulverizing blade, a ball mill, a jet mill, or a vibration vacuum dryer.

  The solid content for silicon recovery may be naturally dried, or may be dried at the time of classification by a classifier described later, so that drying of the solid content for silicon recovery can be omitted. Further, since the solid content for silicon recovery may be pulverized during classification by a classification device such as a cyclone device, the pulverization of the solid content for silicon recovery can be omitted. Accordingly, the drying and pulverizing unit 15 may be a drying unit, a pulverizing unit, or may be omitted.

2-4. Next, the classifying unit 14 will be described. The classifying unit 14 classifies the solid content for silicon recovery after washing. One of the purposes of classification is to reduce the content of abrasive grains and increase the content of silicon than before classification. Classification is a method of classifying particles based on particle parameters such as particle size and density. The classifying unit 14 can be configured by a sieve, an inertia classifier, a centrifugal classifier, or the like.

When classification is performed on the solid content for silicon recovery, the contents of silicon, abrasive grains, and metal change depending on the value of the particle parameter.
For example, when the particle parameter is the particle size, the silicon content varies depending on the particle size (in one example, the silicon content increases as the particle size increases up to a particle size of 5 μm, and the particle size The silicon content becomes maximum at 5 μm, and thereafter, the silicon content decreases as the particle size increases.) The silicon content of a group of particles having a particle size within a certain range (for example, 1 μm or more and less than 10 μm) is higher than the group of particles having a particle size other than this (for example, less than 1 μm or 10 μm or more), and It becomes higher than the solid content for silicon recovery before classification. In this case, in the former group, the abrasive grain content is usually lower than in the latter group, and lower than the solid content for silicon recovery before classification. Therefore, by removing the former group from the classification unit 14, it is possible to reduce the content of abrasive grains and increase the content of silicon compared to before classification.

  In addition, the metal content of a group of particles having a particle size within a predetermined range (for example, less than 1 μm, or 0.1 μm or more and less than 1 μm) is a group of particles having a particle size other than this (for example, 1 μm or more). Higher than the solid content for silicon recovery before classification. Therefore, by removing the group having a high metal content, the metal content of the solids for silicon recovery can be made lower than that before classification.

In the description of classification, “particle size” means that measured by a method in accordance with JIS R1629. The “powder having a particle size of less than X μm” means a powder having a particle size of 98% of particles in the powder of less than X μm. The “powder having a particle size of Y μm or more and less than Z μm” means a powder remaining after removing “a powder having a particle size of less than Y μm” from the “powder of a particle size of less than Z μm”.
Even if the particle parameter is other than the particle size, the above description is similarly applied, and by classification, the content of abrasive grains can be reduced and the content of silicon can be increased as compared to before classification.

  The solid content for silicon recovery after classification may be recovered as it is as the powdered silicon material 3 or may be sent to the molding unit 18 for granulation.

Here, a specific example of classification will be described.
(1) Separation into two types of powders In this example, the solid content for silicon recovery is a first powder having a first particle size range and silicon as a main component, and a first powder having a second particle size range. It isolate | separates into the 2nd powder whose content rate of an abrasive grain is higher than a body.
For example, when SiC having a particle size of 10 μm or more and 30 μm or less is used as the abrasive grain, the first powder having a particle size range of 0.1 μm or more and less than 10 μm obtained by classification is mainly composed of silicon and has a particle size of 10 μm or more and 30 μm or less. It can be seen that the second powder having a particle size range has a higher abrasive content than the first powder. The second powder can be used for regeneration of abrasive grains.

(2) Separation into three types of powders In this example, the solid content for silicon recovery is a third powder having a third particle size range and containing silicon as a main component, and a fourth particle size range having a fourth particle size range. The powder is separated into a fourth powder having a higher abrasive content than the third powder and a fifth powder having a fifth particle size range and a higher metal content than the third powder.
Many metal scraps (including iron as a main component) derived from wires have a particle size smaller than 1 μm. Therefore, for example, the third powder having a particle size range of 1 μm or more and less than 10 μm obtained by classification is composed mainly of silicon, and the fourth powder having a particle size range of 10 μm or more and less than 30 μm is more than the third powder. It turns out that the content rate of an abrasive grain becomes high and the content rate of a metal is higher than the 3rd powder in the 5th powder with a particle size of 0.1 micrometer or more and less than 1 micrometer. The fourth powder can be used for regenerating abrasive grains.

  In this way, by classifying into three or more types of powder and removing the powder having a high metal content (the fifth powder in the above example), an acid aqueous solution such as sulfuric acid or nitric acid is used as in the past. Thus, it is possible to obtain the silicon material 3 in which mixing of the metal derived from the wire is suppressed without removing the metal.

2-5. Metal Waste Removal Part Next, the metal waste removal part 17 will be described. The metal debris removal unit 17 uses a magnetic field to remove ferromagnetic metal (for example, iron) debris mixed in waste slurry (for example, derived from a silicon cutting wire) when cutting or polishing a silicon lump or silicon wafer. Has the function of removing. Metal debris may be removed with silicon or SiC attached. The metal waste removing unit 17 is configured by, for example, a magnet.

  The removal of metal debris is performed by pulverizing silicon recovery solids dispersed in a cleaning organic solvent, or powdered silicon recovery solids (for example, silicon recovery solids after cleaning by a cleaning unit). The solid content for silicon recovery), the powder conveyed by the air flow during classification, and the solid content for silicon recovery after classification can be applied to any one or two or more. Therefore, the metal scrap removing unit 17 can be provided in any one or more of the cleaning unit 13, the drying and pulverizing unit 15, and the classifying unit 14, for example. The metal concentration in the silicon material 3 can be reduced by removing the metal scrap from the solid content for silicon recovery. Moreover, the wire used for MWS often contains phosphorus, and in this case, the metal waste mixed in the waste slurry also contains phosphorus. Phosphorus is a component unnecessary for the production of a P-type solar cell, and therefore it is preferable to remove it before melting. However, by providing the metal waste removal unit 17, phosphorus can be removed together with removal of metal waste.

2-6. Molding Part Next, the molding part 18 will be described. If the shaping | molding part 18 is an apparatus which pressurizes solid content for silicon | silicone collection | recovery and granulates in plate shape, block shape, pellet shape etc., the structure will not be specifically limited. For the molding unit 18, for example, a press-press type granulator or a roller press-type granulator can be used. The molding conditions can be performed, for example, at room temperature and a pressure of 3 to 60 ton / cm ² . Moreover, you may heat at the time of pressurization. The solid content for silicon recovery is easily handled by granulation, and heat conduction becomes smooth and is easily melted.

  The solid content for silicon recovery granulated by the molding unit 18 can be recovered as the powdered silicon material 3.

  The description so far has been made by taking the silicon material acquisition apparatus as an example, but the description of the silicon material acquisition apparatus basically applies to the silicon material acquisition method.

3. Effect verification test The effect verification experiment of the present invention was performed according to the following method.

3-1. Example 1
In Example 1, initial molten metal preparation, material charging, impurity removal, and tilting hot water were performed according to the following method.

3-1-1. Initial molten metal production process The initial molten metal was produced in the crucible by the following method.
First, an alumina crucible was set inside the tiltable open-air induction heating furnace. A crucible having a diameter of 500 mm, a height of 700 mm, and a wall thickness of 40 mm was used. 50 kg of granular metal silicon having a purity of 7N was introduced therein.
As the granular metal silicon, for example, metal silicon was roughly pulverized with a jaw crusher and then pulverized with a cutter mill to have an average particle diameter of 2 mm. As described above, by setting the particle size to about 2 mm, melting is accelerated.
Next, by inserting a carbon rod with high conductivity into the crucible center and heating the carbon rod to transmit heat from the carbon rod, the metal silicon was melted. This is because the electrical conductivity is low in the solid state and is not affected by the heating by induction heating).

The output of induction heating was set to 20 kW at the initial stage of heating, then increased by 1 kW / min, and held at 140 kW. As described above, the output was slowly increased to prevent an excessive thermal shock from being applied to the alumina crucible. The induction heating frequency was 1 kHz.
When the melting of metallic silicon began, the carbon rod was taken out, and the output of induction heating was controlled in the range of 60 to 90 kW so that the molten metal temperature was 1450 ° C., and the metallic silicon was completely melted to prepare the initial molten metal. . The carbon rod was taken out because the molten silicon has a high electrical conductivity and is significantly affected by the heating by induction heating, so that the carbon rod is no longer necessary.

3-1-2. Material charging step Next, a melting aid comprising a powdered silicon material obtained by the method described in the section of “2. Method for obtaining powdered silicon material from waste slurry or concentrated content thereof” and sodium carbonate monohydrate Was put into the molten metal. In a single charge, 10 kg of powdered silicon material and 2.5 kg of melting aid were mixed and charged (in this case, the mixing ratio of the melting aid to the powdered silicon material was 25 wt%). The charging was performed in 10 to 20 minutes.
After completion of the charging, the mixture was held for 10 to 30 minutes, and after confirming the melting of the powdered silicon material, the powdered silicon material and the melting aid were added at the same mixing ratio and melted.
The output of induction heating was adjusted so that the molten metal temperature was 1600 ° C.

3-1-3. Impurity removing step If the above-mentioned replenishment is carried out 3 to 5 times, a slag containing a large amount of silicon oxide has been surfaced. After the crucible was tilted at an appropriate angle (50 to 70 degrees), impurities in the molten metal were removed by discharging the slag using a carbon spatula-shaped one. The slag was higher in viscosity than molten silicon and could be distinguished by touch.

3-1-4. Tilted hot water step After that, the charging of the powdered silicon material and the melting auxiliary agent and the removal of impurities are repeated, and after the molten metal has accumulated up to the eighth minute in the crucible, the molten silicon is subjected to the tilted hot water, and this molten silicon Was solidified to obtain a silicon lump. The angle of the tilted hot water was about 70 to 80 degrees, and the molten metal was left in the crucible about 30 to 50 kg.
Thereafter, the above-described “3-1-2. Material charging step” to “3-1-4. Tilt hot water step” were repeated until a necessary amount of silicon lump was obtained.

  In addition, when it is the last tilting hot water process in the production plan, when significant accumulation of slag is observed in the crucible, or when cracks occur in the crucible and it is difficult to continue, the tilt angle is set to 90 degrees or more. After all the molten silicon present in the crucible was discharged, the output to induction heating was stopped.

3-2. Example 2
In Example 2, 10 kg of powdered silicon material and 5 kg of a melting auxiliary agent were mixed and added in a single charge. In this case, the mixing ratio of the melting aid to the powdered silicon material is 50 wt%). About the point other than this, it was set as the same conditions as Example 1. FIG.

3-3. Comparative Example 1
In Comparative Example 1, only 10 kg of powdered silicon material was charged in a single charge. About the point other than this, it was set as the same conditions as Example 1. FIG.
When the same steps as in Example 1 were performed under the above conditions, in Comparative Example 1, the melting rate of the charged material was slow, the viscosity of the powdered silicon material was extremely high, and the slag discharge operation was difficult. The crucible was covered with unmelted powdered silicon.

3-4. Comparative Example 2
In Comparative Example 2, the output of induction heating was adjusted so that the molten metal temperature was 1650 ° C. About the point other than this, it was set as the same conditions as the comparative example 1. FIG.
When the same process as Example 1 was implemented on the above conditions, since the crack of the crucible was confirmed during melting | fusing of the thrown-in material, melting | fusing was stopped on the way.

3-5. Summary Table 3 shows the amount of powdered silicon material input in Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the amount of melting auxiliary agent, the amount of silicon recovered by tilting hot water, the amount of slag discharged, all the steps. The amount of silicon, slag, etc. remaining in the crucible after completion of the process, and the recovery rate (= the amount of silicon recovered by tilting hot water ÷ the amount of powdered silicon material charged) are shown. The higher the recovery rate, the better. The sum of the recovered amount, the discharged amount, and the residual amount is smaller than the input amount, but the difference between the two is considered to be caused by an amount that is difficult to measure such as evaporation or scattering.

  Referring to Table 3, in the example, the recovery rate was much larger than that of the comparative example, and it was demonstrated that the silicon recovery rate was improved by adding a melting aid, and the effect of the present invention was verified. In Example 1, the silicon recovery rate was 48% instead of 100% because silicon was oxidized due to contact between silicon and air by using an open-air melting furnace, and silicon It is considered that the main cause is that silicon was oxidized by contact between the slag and a melting aid (sodium carbonate monohydrate).

  The reason why the recovery rate of Example 2 is smaller than that of Example 1 is considered to be that in the example, the mixing ratio of the melting aid was large and the oxidation of silicon due to the reaction between silicon and the melting aid was remarkable. This result shows that when the mixing ratio of the melting aid is too high, the silicon recovery rate is decreased. Further, it is clear from the results of Comparative Example 1 that when the mixing ratio of the melting aid is too low, the viscosity of silicon oxide is not sufficiently lowered and the silicon recovery rate is lowered. Therefore, it can be seen that the mixing ratio of the melting aid is preferably about 20 to 30 wt%.

Moreover, in Example 1, the impurity content rate of the powdery silicon material thrown in in a crucible was 5.0 wt%. On the other hand, the impurity content of the silicon lump prepared from the molten silicon discharged from the crucible was 1.0 wt% or less. Therefore, according to the present invention, it has been demonstrated that the impurity content can be significantly reduced.

It is a conceptual diagram of the apparatus which can be utilized for implementation of the manufacturing method of the silicon lump of one Embodiment of this invention. FIGS. 2A to 2D are conceptual diagrams showing a process until a silicon lump is obtained from a powdered silicon material in the method for manufacturing a silicon lump according to an embodiment of the present invention. It is a block diagram which shows the structure of the silicon material acquisition apparatus which can acquire the powdery silicon material used for the manufacturing method of the silicon lump of this invention. It is a block diagram which shows the 1st structural example of the solid-liquid separation part of FIG. It is a block diagram which shows the 2nd structural example of the solid-liquid separation part of FIG.

Explanation of symbols

1: Crucible 2: Molten metal 3: Powdered silicon material 4: Melting aid 5: Silicon grain 6: Silicon oxide film 7: Impurity 8: Glassy impurity 9: Molten silicon 10: Silicon mass 11: Impurity 12: Solid-liquid separation Part 13: Washing part 14: Classifying part 15: Drying and grinding part 17: Metal scrap removing part 18: Molding part 19: Primary centrifuge 21: Secondary centrifuge 23: Distillation apparatus 23a: First distillation apparatus 23b: Second distillation device

Claims (12)

Melting a powdered silicon material in the presence of a melting aid to form a molten metal; solidifying the molten metal to form a silicon lump; and removing impurities before solidifying the molten metal. The manufacturing method of the silicon lump provided. The method according to claim 1, wherein the melting aid comprises an alkali metal or alkaline earth metal salt or oxide anhydride or hydrate or a mixture thereof. The method according to claim 2, wherein the melting aid comprises a hydrate of an alkali metal or alkaline earth metal salt or oxide. The method according to claim 2 or 3, wherein the melting aid comprises an anhydride or hydrate of carbonate or a mixture thereof. The method according to claim 1, wherein a mixing ratio of the melting aid to the powdered silicon material is 20 wt% or more and 30 wt% or less. The method according to any one of claims 1 to 5, wherein a temperature at which the powdered silicon material is melted is 1410 ° C or higher and 1600 ° C or lower. The removal is performed by physically removing the impurities from the molten metal, tilting a crucible containing the molten metal to discharge molten silicon in the molten metal, and installed on a side surface or a lower surface of the crucible. The method according to any one of claims 1 to 6, wherein the method is performed by one or more of discharging molten silicon in the molten metal by opening an openable / closable hole. The method according to any one of claims 1 to 7, wherein the powdery silicon material is obtained from a pulverized metal silicon lump. The method according to claim 1, wherein the powdered silicon material is obtained from a waste liquid containing silicon powder generated during silicon processing. The powdered silicon material was obtained by solid-liquid separation of a waste slurry in which silicon powder was mixed in the slurry by cutting or polishing a silicon lump or silicon wafer using a slurry containing abrasive grains and a coolant, or a concentrated portion thereof. The method according to claim 1, which is a powdered silicon material. The powdered silicon material is obtained by solid-liquid separation of a silicon slurry using a slurry containing abrasive grains and coolant or waste slurry in which silicon powder is mixed into the slurry or by concentrating the slurry by cutting or polishing the silicon wafer. A solid-liquid separation step of obtaining a solid content for silicon recovery containing, a cleaning step of washing the solid content for silicon recovery using an organic solvent, and a classification for the solid content for silicon recovery from the cleaning step A method according to any one of claims 1 to 7, which is obtained by a method comprising: performing a classification step of reducing the content of abrasive grains and increasing the content of silicon more than before classification. The method according to any one of claims 1 to 11, wherein an average particle size of the powdery silicon material is 0.1 µm or more and 1 mm or less.

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