JP2011121049A - Silicon recycling system and silicon recycling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon recycling system capable of recycling waste silicon with high efficiency, economy and safety under a simple processing process. <P>SOLUTION: The silicon recycling system 10 includes a silicon ingot processing apparatus 17, a solid-liquid separator 18, a heat and baking treatment apparatus 19, a heat and melting means 20, and a one-way coagulation means 21. The heat and burning treatment apparatus 19 burns a silicon solid contents at heating temperatures between room temperature and 300°C, 300°C and 850°C, and 850°C and 1,200°C in the presence of inert gas or oxygen gas or under a vacuum condition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention regenerates silicon powder or silicon particles generated in large quantities when a silicon ingot is sliced using a multi-wire saw when manufacturing a silicon wafer for a solar cell or a semiconductor device. The present invention relates to a system and method for reusing it as a raw material for silicon wafers for batteries or semiconductor devices.

When manufacturing silicon wafers for solar cells or semiconductor devices, it is necessary to use extremely high-purity silicon ingots, but in addition to the cost of raw materials for silicon, environmental problems in recent years As a countermeasure against this, solar power generation is in the spotlight, and further supported by the Japanese government's policies, the demand for solar cells has soared.
As a result, the supply of high-purity silicon is tightened and the raw material price of the silicon tends to rise further.
Therefore, there is an increasing need to increase the production of high-purity silicon and stabilize the manufacturing price of solar cells.

  On the other hand, when silicon ingots are conventionally ground to produce silicon wafers for solar cells or semiconductor devices, a large amount of silicon cutting waste is generated, but such cutting waste is used during cutting. It contains impurities such as organic materials generated from organic solvents, various metals generated from cutting members and silicon carbide (SiC), and the separation operation is complicated and costly. In fact, silicon slurries etc. are disposed of.

  Under such circumstances, technology development has been conducted so far to treat the silicon cutting waste to extract high-purity silicon and recycle it as a raw material for solar cells or semiconductor devices. However, there are few things that are linked to actual production due to various problems and limitations.

  For example, in order to manufacture silicon wafers for solar cells or semiconductor devices, a silicon ingot conventionally formed of high-purity silicon is sliced using a multi-wire saw, and a plurality of silicon wafers are produced. A method of forming the two at the same time is generally used as disclosed in, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-159642) or Non-Patent Document 1 described later.

  Such a conventional silicon ingot slicing technique generally has a configuration as shown in FIG. 2, and specifically, as shown in FIG. 2, the silicon block 1 descends and contacts the wire saw 4. The slice processing is executed.

  If the said structure is demonstrated in detail, the wire saw 4 will move in the groove | channel provided in the several guide roller 5 to one direction or both directions. A silicon block 1 which is a silicon ingot to be sliced is fixed to a beam 2 made of a carbon-based material having an appropriate strength by an adhesive 3.

  In such a configuration, the position of the rotating guide roller 5 is fixed, the silicon block 1 is lowered while flowing the lubricating and cooling coolant made of an appropriate organic solvent, and is brought into contact with the wire saw 4 to start the slicing process. . In the final stage of the slicing process, the wire saw 4 passes through the adhesive material part 3 and slices the lower part of the beam 2.

  In the conventional silicon ingot slicing technique, silicon carbide SiC abrasive grains are used as abrasive grains. In this multi-wire saw, a long steel wire is moved on the surface of the silicon block to perform a cutting process. At this time, an appropriate adhesive is applied to the surface of the wire saw 4 using the silicon carbide SiC abrasive grains as a cutting material. The cutting operation is performed while continuously supplying a coolant in which silicon carbide (SiC) abrasive powder is dispersed in the above-described appropriate solvent to the cutting portion.

  However, the silicon carbide (SiC) abrasive powder dropped from the multi-wire saw 4 or the mixed slurry or sludge of the granular silicon generated in the process of grinding the silicon ingot and the coolant A large amount of the silicon carbide (SiC) abrasive powder mixed in the coolant is contained.

  However, it is not easy to separate the silicon carbide (SiC) abrasive powder from the slurry or sludge. For example, the filter means and the oxidation treatment as disclosed in JP-A-5-270814 (Patent Document 2) Or a mechanical separation method using magnetic separation means as disclosed in Japanese Patent Application Laid-Open No. 9-165212 (Patent Document 3), and further, Japanese Patent Application Laid-Open No. 2004-223321 (Patent Document). As shown in 4), a method of separating by using a collector and a foaming agent in combination has been proposed, but the process is complicated and takes a long time, thus increasing the cost. The fact is that collecting silicon from silicon sludge or silicon slurry and reusing it as a raw material for producing silicon wafers has not been commercialized as an actual production process.

  In addition, when slicing the silicon ingot using the multi-wire saw 4, when the silicon ingot is fixed to a processing device, the silicon ingot has an appropriate strength and hardness so that the silicon ingot is not deformed by the gripping device. Conventionally, the beam material 2 is used, but conventionally, a carbon-based material is mainly used. Therefore, the beam material 2 is ground at the final stage of the slicing process of the silicon ingot, and a large amount of carbon is applied. It was mixed in the slurry or sludge, and it took time and cost to remove the carbon.

  Similarly, an organic adhesive is used to bond the beam material 2 to the silicon ingot 1, but the adhesive is also ground at the final stage of the slicing process of the silicon ingot. Since a large amount of particulate matter made of a system material is mixed in the slurry or sludge, the amount of carbon or oxygen to be removed from the slurry or sludge increases, so that the treatment is performed in the same manner as described above. It has the problem of increasing time and processing costs.

  As a method for solving such a problem, Patent Document 1 described above proposes to use a beam material made of a silicon-based material having the same characteristics as a silicon ingot as the beam material. Since the adhesive is still used, the direction of increasing the generation amount of carbon or oxygen has not been improved.

  On the other hand, the silicon slurry or silicon sludge generated in the slicing process of the silicon ingot is often mixed mainly with metal components such as iron, aluminum, and titanium separated from the wire saw as impurities. Silicon ingots obtained from doped silicon or silicon ingots obtained from defective semiconductor wafers include metals such as boron, phosphorus, arsenic, antimony, gold, silver, copper, nickel, and calcium. Impurities are often mixed, and depending on the starting material, for example, as disclosed in Japanese Patent Application Laid-Open No. 2008-115040 (Patent Document 5), a method for removing such metal impurities is also used in combination. Therefore, in addition to further increase in processing steps and complexity, the processing efficiency is reduced and only the cost is reduced. Because of the situation to say that large to, in the past, have no facts were actually industrialize the recycling method of the silicon sludge or silicon slurry that had been discarded is the actual situation.

  The inventors of the present application have taken into consideration the above-mentioned many problems, and from a silicon sludge or silicon slurry that has been conventionally discarded, a high-quality silicon ingot can be efficiently and quickly processed in a simple processing step. Therefore, intensive studies have been conducted on methods for manufacturing at low cost.

  As a result, conventionally, silicon carbide (SiC), which has been conventionally used, is used as abrasive grains as one of the measures for preventing the generation of silicon carbide (SiC) that has many problems in its removal. Instead, technological development has been continued on the premise of adopting a method of using a diamond wire saw in which diamond abrasive grains are bonded and solidified using nickel on the metallic wire.

By the way, the method of using the said diamond wire saw and the method of spraying the coolant containing a diamond abrasive grain on the said wire saw, for example, patent 3078020 gazette (patent document) other than the above (patent document 1) 6), Japanese Patent Application Laid-Open No. 2008-126341 (Patent Document 7), or Non-Patent Document 1 shown below, carbon emitted from the diamond, the carbon-based beam material, the organic adhesive, and the organic coolant. Since the amount of carbon is extremely large, carbon removal treatment becomes a problem, and further, silicon oxide SiO ₂ is formed during and after silicon sludge treatment during slicing, and oxygen removal treatment is necessary. In addition, the processing process becomes complicated and complicated, which causes problems such as reduced processing efficiency, increased processing time, and processing cost. It was.

For this reason, the inventors of the present application are not limited to the large amount of carbon generated from the diamond and organic coolant in addition to the carbon generated from the organic solvent constituting the coolant contained in the silicon slurry or silicon sludge. In addition, the present inventors have studied whether to efficiently remove the oxide in a short time, and at the same time, have been studying a treatment method that can effectively suppress the generation of oxides of SiO ₂ and effectively remove oxygen of the oxides .

Japanese Patent Laid-Open No. 5-270814 JP-A-9-165212 JP 2004-223321 A JP 2008-1105040 A Japanese Patent No. 3078020 JP 2008-126341 A

“Characterization of Multicrystalline Line Silicon Wafers for Solar Cell Applications sliced with a Fixed Absive Wire,” Y. Kondo et. al. , Presented at 23rd European Photovoltaic Solar Energy Conference 2008

  The present invention improves the above-described conventional problems, and enables silicon recycling to be performed efficiently and economically and with a high level of safety under simple processing steps. A use system and a method thereof are provided.

  In order to achieve the above object, the present invention basically adopts the following technical configuration. That is, as a first aspect according to the present invention, when manufacturing a silicon wafer for a solar cell or a semiconductor device, silicon is extracted from silicon waste material generated during cutting and grinding of the silicon ingot, or for the solar cell or A silicon recycling system that is reused for the manufacture of silicon wafers for semiconductor devices, the silicon recycling system,

(1) a silicon ingot fixing device for fixing a silicon ingot via a beam material made of a silicon-based material;
Cutting the silicon ingot fixed to the fixing means with a diamond wire saw, cutting with a grinding member, grinding, a grinding apparatus,
A coolant supply device for supplying water or an organic material containing water to the cutting, cutting of the grinding means, and a grinding portion;
A silicon ingot processing means comprising:
(2) solid-liquid separation means for separating silicon solids from silicon slurry or silicon sludge containing desorbed diamond particles obtained by the silicon ingot processing means;
(3) a heating and baking treatment means for heating and baking silicon solids containing the residual organic substance and diamond particles obtained from the solid-liquid separation means;
(4) heating and melting means for melting the silicon fired product obtained from the heat treatment means at a temperature equal to or higher than the melting point of the silicon;
(5) Unidirectional solidification means for unidirectionally solidifying the molten silicon to form a silicon ingot;
A silicon recycling system comprising:

  The heating and baking treatment means in the system includes a gas supply control means for supplying an inert gas, hydrogen gas or oxygen gas to a region where silicon solids containing residual organic substances and diamond particles are burned, or A vacuum generating means for making the firing region in a vacuum state, and a temperature of the region for firing the silicon solid content, a first temperature region range from room temperature to 300 ° C., a second temperature region range from 300 ° C. to 850 ° C., And a first temperature control means for sequentially controlling in a third temperature range of 850 ° C. to 1200 ° C.,

  The heating and melting means includes a gas supply means for supplying an inert gas, oxygen gas, or hydrogen gas, and a maximum temperature of 1500 ° C. or higher in order to melt the silicon solid content after the heating and baking. The silicon recycling system is characterized in that second temperature control means for controlling the temperature in the heating / melting region in the heating / melting means is provided in accordance with a predetermined specific temperature profile.

In the present invention, in particular, the first temperature control means executes a firing treatment in the first temperature region range in the presence of at least an inert gas, and at least the presence of the inert gas and oxygen. Under the control, the firing process is executed in the second temperature range, and the firing process is executed in the third temperature range at least in the presence of an inert gas and hydrogen. Something is desirable.
In addition, as a second aspect of the present invention, when manufacturing a silicon wafer for a solar cell or a semiconductor device, silicon is extracted from silicon waste material generated during cutting and grinding of the silicon ingot, or for the solar cell or A silicon recycling method that is reused in the manufacture of silicon wafers for semiconductor devices, the silicon recycling method,

(1) a silicon ingot fixing device for fixing a silicon ingot via a beam material made of a silicon-based material;
Cutting the silicon ingot fixed to the fixing means with a diamond wire saw, cutting with a grinding member, grinding, a grinding apparatus,
A coolant supply device for supplying water or an organic material containing water to the cutting, cutting of the grinding means, and a grinding portion;
A silicon ingot processing means comprising:
(2) solid-liquid separation means for separating silicon solids from silicon slurry or silicon sludge containing desorbed diamond particles obtained by the silicon ingot processing means;
(3) a heating and baking treatment means for heating and baking silicon solids containing residual organic substances and diamond particles obtained from the solid-liquid separation means;
(4) heating and melting means for melting the silicon fired product obtained from the heat treatment means at a temperature equal to or higher than the melting point of the silicon;
(5) Unidirectional solidification means for unidirectionally solidifying the molten silicon to form a silicon ingot;
In a silicon recycling system, including

  In the heating and baking treatment means, a silicon solid content containing residual organic substances and diamond particles is converted into a first temperature of room temperature to 300 ° C. in the presence of an inert gas, hydrogen gas or oxygen gas, or in a vacuum state. In the heating and melting means, firing is performed under temperature conditions sequentially controlled in a temperature region range, a second temperature region range of 300 ° C. to 850 ° C., and a third temperature region range of 850 ° C. to 1200 ° C. The silicon recycling method is characterized by heat-melting the silicon solid content after the firing in accordance with a predetermined specific temperature profile indicating a maximum temperature of 1500 ° C. or higher and then performing a unidirectional solidification treatment.

  As a result of adopting the above-described technical configuration, the present invention is an efficient, economical and yet highly safe state under a simple processing process as compared with the conventional recycling method of waste silicon. Thus, a silicon recycling system and a silicon recycling method capable of recycling waste silicon are provided.

FIG. 1A is a block diagram illustrating a configuration of a silicon recycling system according to the present invention, and FIG. 1B is a diagram illustrating a configuration of a specific example of a heating and baking apparatus according to the present invention. is there. FIG. 2 is a diagram illustrating a state in which a silicon block is sliced using a wire saw. FIG. 3 is a graph showing the relationship between the firing temperature and the change in weight of the silicon solids when the silicon solids after the silicon sludge is solid-liquid separated are fired. FIG. 4 is a diagram showing an example of an arrangement shape of each means or each device in the present invention. FIG. 5 shows an example of a heating temperature profile used when the silicon fired body in the present invention is heated and melted. FIG. 6 is a graph showing the degree to which organic substances are removed when baking silicon sludge.

A specific example of the silicon recycling system according to the present invention will be described below with reference to the drawings.
1 is a block diagram showing the configuration of a specific example of a silicon recycling system according to the present invention. In the figure, when manufacturing a silicon wafer for a solar cell or a semiconductor device, the silicon ingot is cut and ground. A silicon recycling system 10 that extracts silicon from silicon waste material generated during processing and reuses it in the production of silicon wafers for solar cells and / or semiconductor devices. The silicon recycling system 10 includes a silicon ingot 11. A silicon ingot fixing device 14 having a function of fixing and holding the material through a beam material 12 made of a silicon-based material, and a silicon ingot 11 fixed to the silicon ingot fixing means 14 is cut and ground by a diamond wire saw 4. Cutting, grinding by cutting, grinding Silicon ingot processing comprising a construction device 15 and a coolant supply device 16 for supplying water or an organic material containing water to the cutting, cutting of the grinding means, and supplying to the grinding portion Means 17, solid-liquid separation means 18 for separating silicon solids from silicon slurry or silicon sludge containing diamond particles obtained by the silicon ingot processing means 17, and the residue obtained from the solid-liquid separation means 18 Heat-firing treatment means 19 for heat-firing treatment of silicon solids containing organic substances and residual diamond particles, and heat-melting for melting the silicon fired product obtained from the heat-treatment means 19 at a temperature equal to or higher than the melting point of the silicon. The means 20 and the molten silicon are unidirectionally solidified to form a silicon ingot. And a unidirectional solidification means 21, wherein the heating and firing treatment means 19 in the system 10 fires silicon solids containing residual organic substances and residual diamond particles. The gas supply control means 22 for supplying an inert gas, hydrogen gas or oxygen gas to the area or the vacuum generating means 23 for making the firing area in a vacuum state, and the temperature of the area where the silicon solid content is fired First temperature control for sequentially controlling in a first temperature region range from room temperature to 300 ° C., a second temperature region range from 300 ° C. to 850 ° C., and a third temperature region range from 850 ° C. to 1200 ° C. Means 24, and the heating and melting means 20 has a predetermined maximum temperature of 1500 ° C. or higher in order to melt the silicon solid content after the heating and firing. A silicon recycling system 10 is shown in which a second temperature control means 25 is provided for controlling the temperature in the heating / melting region in the heating / melting means 20 according to the specific temperature profile.

  In the specific example of the present invention, the organic component of the coolant is removed between the solid-liquid separation means 18 and the heating and firing treatment means 19 or a predetermined metal is removed. The 1st washing means 28 for doing may be arranged.

  Furthermore, in the specific example of the present invention, an acid treatment is performed between the heat-firing treatment means 19 and the heat-melting means 20 for removing the metal component contained in the silicon solid content. The second cleaning device 29 and / or the molding means 50 for deforming the solid silicon content after heating and baking into a plurality of solid materials having an appropriate size is disposed prior to the melting treatment. There may be.

As described above, the basic technical idea of the recycled silicon utilization method and the recycled silicon utilization system of the present invention is that a wire saw using conventional SiC-based abrasive grains is used so as not to substantially generate SiC. Instead of using diamond saws, how much carbon is generated in response to the generation of a large amount of carbon, and at the same time, carbon such as diamond is burned at a low temperature and at the same time the generation of oxides such as SiO ₂ is as much as possible. In consideration of the control, the opportunity to generate oxygen is avoided as much as possible.

  In the present invention, when fixing the silicon ingot 11 to the beam member 12 made of a silicon-based material, a known organic adhesive can be used, but impurities are hardly mixed as much as possible. It is preferable to use an adhesive.

  In addition, water can be used as the coolant used in the present invention, but it is desirable to use a water-soluble organic coolant, such as diethylene glycol, polyethylene glycol, or polypropylene glycol. It is desirable to be done.

On the other hand, the configuration of the solid-liquid separation means 18 in the present invention is not particularly limited, and a conventionally known solid-liquid separation method can be adopted.
Next, in the present invention, the first cleaning means 28 provided as necessary between the solid-liquid separation means 18 and the heating and baking treatment means 19 also removes organic components, or Any known cleaning means conventionally used for removing a predetermined metal can be used.

  Furthermore, the heat-firing treatment means 19 in the present invention remains in the silicon solid content by heat-firing the silicon solid content containing the diamond particles obtained from the solid-liquid separation means 18. The organic substance is removed by evaporation, and a large amount of carbon generated from the residual organic substance and diamond is removed by combustion.

  Then, as shown in FIG. 1 (B), the heating and baking treatment means 19 has an inert gas or oxygen in a baking region for baking silicon solids containing the organic substance and diamond particles, for example, a baking furnace 30. A gas supply pipe 32 connected to a gas supply source 31 for supplying gas or hydrogen gas, appropriate switch means 33 provided in the inert gas supply pipe 32, and control means for controlling the switch means 33 34 and / or a vacuum generating means 36 (23) for bringing the firing region 30 into a vacuum state, a pressure reducing pipe 37 connected to the vacuum generating means 36, and the pressure reducing pipe 37 Are provided with appropriate switch means 38 and control means 34 for controlling the switch means 38.

  Further, the heating and baking treatment means 19 includes a heating means 40 for heating the temperature in the baking area 30 and an energy supply source for supplying heating energy to the heating means 40, such as a power source 41 and the baking area 30. The heating temperature adjusting means 42 is provided for adjusting the temperature of the heating region. The heating temperature adjusting means 42 adjusts the temperature in the firing region 30 in response to the control of the control means 34 described above.

The control means 34 in the present invention can control and operate the switch means 33 and 38 and the heating temperature adjusting means 42 based on a command of a predetermined program.
Regarding the firing temperature of the firing region of the heating and firing treatment means 19 in the present invention, the inventors of the present application have studied based on various experiments, and as a result, the residual organic matter and the carbonaceous material of diamond are generated when burned. As a result of examining the amount of CO ₂ generated in relation to the combustion temperature, in particular, as shown in FIG. 6, for example, when organic matter is burned in the presence of an inert gas such as argon gas. It is found that between 100 ° C. and 200 ° C., the combustion of carbon is promoted, and, for example, in the presence of an inert gas and oxygen gas such as argon gas, the temperature is between 300 ° C. and 850 ° C. Thus, it is determined that CO ₂ is sufficiently burned (oxidation reaction) in the above temperature condition region.

That is, the inventors of the present application examined the relationship between the combustion temperature and the generation amount of SiO ₂ under the temperature condition and the atmospheric condition when the silicon solid content separated into solid and liquid was burned. As shown in FIG. 3, it was found that when the combustion temperature exceeds 850 ° C., the generation amount of the SiO ₂ rapidly increases.
As a result, in the present invention, oxygen gas and inert gas are supplied in the temperature range of 300 ° C. to 850 ° C. in the baking region 30 of the heat baking processing means 19 to burn the residual carbon-based material. The knowledge that it is desirable to perform is obtained.

On the other hand, the state of oxide generation was analyzed while increasing the temperature from 850 ° C. to 1200 ° C. while supplying hydrogen gas in the presence of an inert gas to the silicon solid content baked by the above baking treatment step. It has been found that oxygen is absorbed by hydrogen gas and the generation of oxides is reduced.
Specifically, the temperature in the baking region of the heating and baking processing means 19 is gradually increased from room temperature to 1200 ° C. along a predetermined profile while changing the atmospheric conditions. Between room temperature and 300 ° C., residual organic substances are mainly removed, and the residual carbon-based material containing diamond is in a state of burning at a temperature higher than that.

  As is apparent from the above, in the heating and baking treatment step in the present invention, the baking treatment in the first temperature range is performed at least in the presence of an inert gas, and at least the inert gas and oxygen are added. It is desirable that the firing process in the second temperature region range be performed in the presence, and the firing process in the third temperature region range be performed in the presence of at least an inert gas and hydrogen.

  In the present invention, the second cleaning device 29 performs an acid treatment for removing the metal component contained in the silicon solid content between the heating and baking means 19 and the heating and melting means 20. And / or prior to melting the silicon solid content after the heating and firing, a molding means 50 is arranged for transforming into a plurality of solids of an appropriate size. In any case, a conventionally known apparatus and method can be used.

Further, the heat treatment means 19 removes oxygen from the silicon oxide SiO ₂ contained in the silicon solid content by treating the silicon solid content between 1000 ° C. and 1100 ° C. with a mixed gas of argon and hydrogen. Is possible.
In the present invention, the molding means 50 has as much silicon solid content as possible when the baked silicon solid content is loaded into, for example, a quartz crucible provided in the heating and melting means 20. In order to fill the liquid, it is desirable to make the solid material of an appropriate size.

In the molding process according to the present invention, it is desirable to process in a pressurized state.
Next, in the present invention, a plurality of silicon solids filled in the crucible are heated and melted by the heating and melting means 20. In this process, the silicon oxide SiO can be evaporated to remove oxygen. In the unidirectional solidification means 21, the molten silicon is unidirectionally solidified to form a silicon ingot.

  In the present invention, both the heating and melting means 20 and the unidirectional solidification means 21 can use conventional methods and apparatuses. However, in the heating and melting means 20, after the heating and baking, A second temperature for controlling the temperature in the heating and melting region in the heating and melting means 20 in accordance with a predetermined specific temperature profile in which the maximum temperature is 1600 ° C. or higher. It is desirable that a control means 25 is provided. The unidirectional solidification means 21 can remove metal impurities by segregation by a temperature profile as shown in FIG.

Further, it is desirable that the heating and melting means 20 is provided with a gas supply control means for supplying argon and hydrogen gas. Thus, the hydrogen reduction reaction at the time of heating temperature increase, it is possible to remove the oxygen of the silicon oxide SiO _2.
In the present invention, the heating and melting means 20 and the unidirectional solidification means 21 can use the same apparatus.

  That is, when the silicon solid content is melted in the heating and melting means 20 in the present invention, the present inventors have intensively studied. As a result, the heating temperature is gradually increased in the initial stage of the melting and heating operation. It was found that it is desirable to melt and solidify it according to a temperature profile that causes the peak temperature to reach at least around 1600 ° C. and then gradually lowers the heating temperature.

As the peak temperature value, a temperature between 1500 ° C. and 1850 ° C. can be used.
On the other hand, in the present invention, it is desired to treat the waste silicon in a state in which the generation of oxygen is reduced as much as possible. Therefore, each means in the present invention described above, and each step in each stage. It is desirable that this processing operation be performed in an inert gas atmosphere or in a vacuum state.
As the inert gas, nitrogen, argon or the like is desirable.

Furthermore, in the present invention, in order to ensure the above processing operation, as shown in FIG. 4, at least one of the above-described means and devices of the present invention is disposed in a completely sealed space. The completely sealed space is preferably sealed with a closed side wall portion that is intimately joined to a floor surface made of an appropriate material having no air permeability and a ceiling portion of the closed side wall portion. It is comprised by the closing body 51 which consists of an upper cover part covered.
Therefore, each of the closed bodies 51 is provided with an inert gas supply means or a vacuum state generation means.

Further, in the present invention, all the means, devices, etc. in the present invention described above may be provided in one closing body 52.
As another aspect of the present invention, when manufacturing silicon wafers for solar cells or semiconductor devices, silicon is extracted from silicon waste material generated during cutting and grinding of silicon ingots, and for the solar cells or semiconductor devices. A silicon recycling method that is reused for manufacturing a silicon wafer, the silicon recycling method including a silicon ingot fixing device that fixes a silicon ingot via a beam material made of a silicon-based material, and a fixing means. Cutting a fixed silicon ingot made of a diamond wire saw, cutting using a grinding member, grinding, a grinding processing device, and water or a coolant composed of an organic material containing water, cutting the grinding processing means , Coolant supply device for supplying to the grinding part, Silicon ingot processing means constituted, solid-liquid separation means for separating silicon solids from silicon slurry or silicon sludge containing desorbed diamond particles obtained by the silicon ingot processing means, and the solid-liquid separation means A heating and baking treatment means for heating and baking silicon solids containing the residual organic substance and diamond particles obtained from the above, and the fired silicon product obtained from the heating treatment means is melted at a temperature equal to or higher than the melting point of the silicon. In a silicon recycling method, comprising: a heat-melting means; and a unidirectional solidification means for forming a silicon ingot by unidirectionally solidifying the melted silicon. Silicon solids containing organic substances and diamond particles are converted into inert gas, hydrogen gas or oxygen gas. In the heating or melting means, firing is carried out in the presence or in a vacuum state under controlled temperature conditions in the range of room temperature to 300 ° C, in the range of 300 ° C to 850 ° C, and in the range of 850 ° C to 1200 ° C. Is a silicon recycling method characterized by heat-melting the silicon solid content after firing in accordance with a predetermined temperature profile in which the maximum temperature is 1500 ° C. or higher and then subjecting it to unidirectional solidification. .
Hereinafter, in order to examine preferable specific conditions of the heating temperature condition in the present invention, the following experiment was conducted.

(Experimental example 1)
After fixing the polycrystalline silicon ingot for solar cells to an appropriate fixing means using a silicon-based adhesive, the silicon ingot is used in FIG. 2 using a coolant mainly composed of diethylene glycol (DEG). The silicon sludge containing diamond particles obtained by slicing with diamond wire saw 4 (EDSW EW-160 manufactured by Japan Fine Steel Co., Ltd.) using an ingot processing means as shown in FIG. Separation was performed to recover silicon solids.

A 10 kg sample was taken out of the solid content, washed twice by an aqueous cleaning method, and dried at 50 ° C. for 24 hours with a heat dryer to prepare a dry powder.
In such a process, it is possible to use an organic solvent as a cleaning agent, and the sample to be taken out may be about 1 kg depending on the case. Furthermore, the temperature of the heating dryer is set to 80 ° C. It may be a thing.

Next, 50 g is taken out of the dry powder, filled into a square quartz container, and this container is inserted into a quartz tube heating electric furnace (KRB-23HH manufactured by Isuzu Seisakusho), and heated while flowing argon gas. A baking treatment was performed. The heating and baking treatment was performed by heating from room temperature to 300 ° C. at a rate of 15 ° C./min and holding at 300 ° C. for 30 minutes to remove liquid residues (water, organic matter).
Next, it heated up to 1540 degreeC with the temperature increase rate of 15 degree-C / min, and heat-melted for 30 minutes. During the heating and melting, when the heating temperature was 1200 ° C. or higher, it was confirmed that the reaction product from the residue was deposited and adhered to the inner surface of the quartz tube.

Thereafter, cooling was performed at a rate of temperature decrease of 5 ° C./min.
From the above experiment, it was confirmed that silicon solid was formed in the quartz container and silicon could be recovered.
It was confirmed by thermogravimetric analysis that about 10% of the liquid residue was contained in a part of the dry powder obtained by the drying treatment in the examples.
This was a phenomenon observed when water was used as a cleaning agent in the cleaning process.

(Experimental example 2)
In the experimental example 1, a low temperature combustion experiment for removing carbon-containing residues including diamond was performed using silicon solid content obtained by solid-liquid separation. In this experiment, a quartz tube heating electric furnace was used.
20 g of silicon solid content obtained as described above was filled in a quartz container, and this container was inserted into a quartz tube type heating electric furnace (EKRO-13K manufactured by Isuzu Seisakusho) and subjected to heat treatment in an air atmosphere.

First, the temperature was increased from room temperature to 800 ° C. at a rate of temperature increase of 10 ° C./min, and changes in the silicon solid content were observed.
As a result, smoke-like organic precipitates are observed in the temperature range of about 170 ° C. to 300 ° C., red combustion is observed in the temperature range of about 550 ° C. to 800 ° C., and the generation of CO ₂ occurs. Admitted.

The precipitate in the temperature range of about 170 ° C. to 300 ° C. is considered as a residual solvent (mainly a coolant component), and the combustion phenomenon or the generation of CO _{2 in} the temperature range of about 550 ° C. to 800 ° C. It is thought to be due to the combustion of (diamond abrasive grains and residual carbon).

  This result shows that when the combustion treatment is performed at a temperature of 550 ° C. or higher, the carbon generated from the carbon-based residue including the diamond abrasive grains is burned very efficiently (oxidation reaction). By avoiding the temperature of 900 ° C. or higher, which is the temperature at which silicon oxide is likely to be generated, and performing combustion treatment at a temperature of 900 ° C. or lower, carbon is efficiently generated while suppressing generation of silicon oxide efficiently. In this way, it is not necessary to carry out a separate process for removing carbon and oxygen in the subsequent process, and the diamond abrasive grains can be efficiently and easily manufactured at a low cost in a short time. It is shown that it is possible to remove carbon impurities from the above.

(Experimental example 3)
Using the silicon solid content obtained by the individual liquid separation in Experimental Example 1, an organic residue and silicon oxide were reduced and removed, and an experiment for forming a silicon solid was performed.
The organic residue was removed at 800 ° C. under an argon gas atmosphere for 1 hour using a rotary tubular furnace (Flutech, FT-1100-100). This treatment confirmed the removal of the organic coolant. The obtained silicon solid content was heated up to 1600 ° C. at a rate of 10 ° C./min while flowing a mixed gas of argon and hydrogen using a high-temperature electric furnace (Flutech, FVT-1600P). After holding for a period of time, it was allowed to cool naturally. From this experiment, it was confirmed that a silicon solid body could be formed.

  The present invention is to extract high-purity silicon with less impurities from silicon scrap generated in the process of cutting a silicon ingot, and reuse it as a raw material for manufacturing a wafer for a solar cell or a semiconductor device. It can be used to make up for the shortage of silicon raw materials and suppress the rise in silicon raw material costs.

1: Si block 2: Beam material 3: Adhesive 4: Diamond wire 5: Guide roller 10: Silicon recycling system 11: Silicon ingot 12: Beam material 14: Silicon ingot fixing device 15: Cutting and grinding device 16: Coolant Supply device 17: Silicon ingot processing means 18: Solid-liquid separation means 19: Heat-firing treatment means 20: Heat-melting means 21: Unidirectional solidification means 22: Inert gas supply control means 23: Vacuum generation means 24: First temperature Control means 25: Second temperature control means 28: First cleaning means 29: Second cleaning device 30: Firing region 31: Gas supply source 32: Gas supply pipe 33: Switch means 34: Control means 36: Vacuum generation Means 37: Pressure reducing pipe 38: Switch means 40: Heating means 41: Energy supply source 42: Heating temperature Adjustment means 50: molding means 51: closing member 52: the closing body

Claims (15)

When manufacturing silicon wafers for solar cells or semiconductor devices, silicon is extracted from silicon waste material generated during cutting and grinding of silicon ingots and reused for manufacturing silicon wafers for solar cells or semiconductor devices A silicon recycling system,
(1) a silicon ingot fixing device for fixing a silicon ingot via a beam material made of a silicon-based material;
Cutting the silicon ingot fixed to the fixing means with a diamond wire saw, cutting with a grinding member, grinding, a grinding apparatus,
A coolant supply device for supplying water or an organic material containing water to the cutting, cutting of the grinding means, and a grinding portion;
A silicon ingot processing means comprising:
(2) solid-liquid separation means for separating silicon solids from silicon slurry or silicon sludge containing diamond particles obtained by the silicon ingot processing means;
(3) a heating and baking treatment means for heating and baking silicon solids containing the residual organic substance and diamond particles obtained from the solid-liquid separation means;
(4) heating and melting means for melting the silicon fired product obtained from the heat treatment means at a temperature equal to or higher than the melting point of the silicon;
(5) Unidirectional solidification means for unidirectionally solidifying the molten silicon to form a silicon ingot;
A silicon recycling system comprising:
The heating and baking treatment means in the system includes a gas supply control for supplying an inert gas, a hydrogen gas, or an oxygen gas to a region for baking silicon solids containing residual organic substances and diamond particles. Means for generating a vacuum in the firing region, and the temperature of the region in which the silicon solid content is fired, the first temperature region range from room temperature to 300 ° C., and the second temperature region range from 300 ° C. to 850 ° C. , And a first temperature control means for sequentially controlling in a third temperature region range from 850 ° C. to 1200 ° C.,
In addition, the heating and melting means includes a heating and melting region in the heating and melting means according to a predetermined specific temperature profile in which the maximum temperature is 1500 ° C. or higher in order to melt the silicon solid content after the heating and baking. A silicon recycling system characterized in that second temperature control means for controlling the temperature inside is provided.   The first temperature control means executes a firing process in the first temperature region range at least in the presence of an inert gas, and the second temperature region in the presence of at least an inert gas and oxygen. 2. The silicon regeneration according to claim 1, wherein the baking treatment is performed in a range, and the baking treatment is performed in the third temperature region range at least in the presence of an inert gas and hydrogen. Usage system.   2. A cleaning device for removing an organic substance component of the coolant or a metal contained in the silicon solid content is disposed between the solid-liquid separation unit and the heating and baking unit. The silicon recycling system described in 1.   The firing temperature set in the heating and firing treatment means is selected from a temperature region in which the diamond burns and a temperature region in which silicon in the silicon solid content is not oxidized overlaps. The silicon recycling system according to claim 1, wherein the system is used.   Between the heat-firing treatment means and the heat-melting means, there is provided a molding means for transforming the solid silicon content after the heat-firing into a plurality of solids having an appropriate size. The silicon recycling system according to any one of claims 1 to 4, wherein the silicon recycling system is provided.   6. The silicon recycling system according to claim 5, wherein said molding means is further provided with a pressurizing means for applying pressure to the silicon solid content after the heating and firing.   Each means in the silicon recycling system is such that each process is performed under conditions such that no oxide is generated in the silicon solid content or oxide is not generated from the silicon solid content. The silicon recycling system according to any one of claims 1 to 6, characterized in that:   At least one of the means in the silicon recycling system is characterized in that a predetermined process is performed in an inert gas atmosphere or in a vacuum state. The silicon recycling system according to claim 7.   9. The silicon recycling system according to claim 8, wherein at least one of the means in the silicon recycling system is disposed in a sealed space. When manufacturing silicon wafers for solar cells or semiconductor devices, silicon is extracted from silicon waste material generated during cutting and grinding of silicon ingots and reused for manufacturing silicon wafers for solar cells or semiconductor devices The method of using the silicon recycling method is as follows:
(1) a silicon ingot fixing device for fixing a silicon ingot via a beam material made of a silicon-based material;
Cutting the silicon ingot fixed to the fixing means with a diamond wire saw, cutting with a grinding member, grinding, a grinding apparatus,
A coolant supply device for supplying the coolant made of an organic material to the cutting, cutting of the grinding means, and the grinding portion;
A silicon ingot processing means comprising:
(2) solid-liquid separation means for separating silicon solids containing diamond particles from silicon slurry or silicon sludge containing diamond particles obtained by the silicon ingot processing means;
(3) a heating and baking treatment means for heating and baking silicon solids containing the diamond particles obtained from the solid-liquid separation means;
(4) heating and melting means for melting the silicon fired product obtained from the heat treatment means at a temperature equal to or higher than the melting point of the silicon;
(5) Unidirectional solidification means for unidirectionally solidifying the molten silicon to form a silicon ingot;
In the silicon recycling method, including
In the heating and baking treatment means, the silicon solid content containing the diamond particles is converted into a first temperature of room temperature to 300 ° C. in the presence of an inert gas, hydrogen gas, oxygen gas, or vacuum. In the heating and melting means, the maximum temperature is 1500, while firing under the temperature conditions of the region range, the second temperature region range of 300 ° C to 850 ° C, and the third temperature region range of 850 ° C to 1200 ° C. A silicon recycling method characterized by heat-melting the silicon solid content after firing in accordance with a predetermined temperature profile indicating a temperature equal to or higher than ° C., followed by unidirectional solidification.   Before the heat-firing treatment means and the heat-melting means, the silicon solid content after the heat-firing is subjected to a process of transforming into a plurality of solids of an appropriate size prior to the melting treatment. The silicon recycling method according to claim 10.   The silicon recycling method according to claim 11, wherein in the molding process, pressure is applied to the silicon solid content after the heating and baking.   Each means in the silicon recycling method is characterized in that each process is executed under conditions such that no oxide is generated in the silicon solid content or oxide is not generated from the silicon solid content. The silicon recycling method according to any one of claims 10 to 12.   14. The silicon recycling method, wherein at least one means described in claim 13 is disposed in a sealed space region.   In at least one of the processes in the silicon recycling method, a predetermined process is performed in an atmosphere of an inert gas or an oxygen gas, or in a vacuum state. The silicon recycling method according to claim 13, wherein:

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