WO2008152742A1

WO2008152742A1 - Method and apparatus for recycling semiconductor material, and method and apparatus for manufacturing solar battery

Info

Publication number: WO2008152742A1
Application number: PCT/JP2007/062467
Authority: WO
Inventors: Mineo Ikematsu; Kazuhiro Kaneda; Daizo Takaoka
Original assignee: Sanyo Electric Co., Ltd.
Priority date: 2007-06-12
Filing date: 2007-06-12
Publication date: 2008-12-18

Abstract

This invention provides a method for recycling a semiconductor material, which can recycle semiconductor materials at low cost. The method comprises the step (S11) of collecting used silicon debris (a semiconductor silicon material), the step (S12) of conducting gettering to remove phosphorus from the collected silicon debris, the step (S13) of inactivating boron contained in the silicon debris, and the step (S14) of recycling the silicon debris, with the impurities having been removed or inactivated, as a solar battery or the like. According to the above constitution, the recycling of silicon debris and the manufacture of solar batteries and the like can be realized at lower cost.

Description

Specification

Semiconductor material recycling method and recycling apparatus, solar cell manufacturing method and manufacturing apparatus

The present invention relates to a semiconductor material recycling method and a recycling apparatus, and more particularly to a semiconductor material that can be reused by removing or inactivating boron or phosphorus light elements from the semiconductor material. The present invention further relates to a solar cell manufacturing method and a manufacturing apparatus for manufacturing a solar cell by removing these light metals from a semiconductor material. Background art

According to Japanese Patent Laid-Open No. 10-324 5 14, solar cells made of semiconductor materials such as silicon are currently out of the standard that are generated by the semiconductor industry that manufactures LSI (Large Scale Integration). Manufactured using silicon wafers as raw materials. However, the power generation method using solar cells is superior to other power generation methods such as thermal power generation from the viewpoint of environmental protection, so the demand for solar cells increases at a rate of several tens of percent or more per year. ing. Therefore, the above-mentioned method using non-standard products generated from the semiconductor industry has a limit on the amount of non-standard products generated, so it is difficult to meet the increasing demand for solar cells.

As a method of solving this problem, there is a method of manufacturing a solar cell using semiconductor silicon which is a material such as LSI. However, the purity required for silicon as a material for solar cells is significantly lower than that for silicon for semiconductors. Specifically, the purity required for silicon for solar cells is 7 N (9 9. 9 9 9 9 9%), and the purity required for silicon for semiconductors is 1 1 N (9 9. 9 9 9 9 9 9 9 9 9%) (common name: Eleven Nine). And the energy consumed to purify 1 N silicon is greater than the energy consumed to purify 7 N silicon. For this reason, manufacturing solar cells from silicon for semiconductors with higher purity than necessary is problematic from the viewpoint of environmental protection because of the large energy loss.

In addition, as a method for refining silicon for solar cells, there is a method using silicon waste generated from a dicing process of a semiconductor manufacturing process. In this method, impurities contained in silicon waste Things need to be removed. As a method of removing impurities contained in silicon scrap, there is a method of removing phosphorus contained in a silicon melting process by a beam and removing boron in a plasma melting process. According to this method, phosphorus and boron contained in silicon waste can be removed, and a silicon material for solar cells having a purity usable for solar cells can be obtained. Disclosure of the invention

However, the above-described method for refining silicon for solar cells has a problem in that the cost required for removing phosphorus and the like is high. Specifically, in the above-mentioned method of performing beam irradiation and plasma melting, a cost of about 2300 yen Z kg is required to obtain silicon for solar cells having a purity that can be regenerated as a solar cell. . On the other hand, as of FY 2005, the price of commercially available silicon materials (pigment materials) is 4 0 0 0-6 0 0 0 yen Z kg. Therefore, as of 2005, the solar cell silicon regenerated by the above-described method is superior in terms of cost for the virgin material. However, since the price of the purgin material fluctuates depending on the balance between supply and demand, the price of the purgin material is cheaper than the cost of generating silicon for semiconductors (2300 yen / kg). There is. For example, as of 2000, the price of the pearline material was about 200,000 yen kg, so in this case, the method for producing silicon for solar cells described above is disadvantageous in terms of cost.

Furthermore, particulate semiconductor waste is discharged from the process of manufacturing a semiconductor device such as L S I. However, it is not easy to transport the semiconductor waste as it is in order to regenerate the semiconductor waste. Furthermore, there is a possibility that the particulate semiconductor waste may be scattered during the semiconductor regeneration process. Accordingly, an object of the present invention is to provide a semiconductor material recycling method, a semiconductor material recycling device, a solar cell manufacturing method, and a solar cell manufacturing device that can be realized at a lower cost. The method for regenerating a semiconductor material according to the present invention is a method for regenerating a semiconductor material in which phosphorus is removed from the collected semiconductor material, and the phosphorus is moved to the surface of the semiconductor material by heating the semiconductor material. A heating step; and a separation step of separating the phosphorus located on the surface of the semiconductor material from the semiconductor material.

The method for regenerating a semiconductor material according to the present invention is a method for regenerating a semiconductor material in which boron contained in the recovered semiconductor material is deactivated. A deactivation step of deactivating the boron.

The method for producing a solar cell according to the present invention is a method for producing a solar cell in which a collected semiconductor material is reused as a solar cell, and the phosphorus moved to the surface of the semiconductor material by heat treatment is extracted from the semiconductor material. It is characterized by comprising a removing step of separating or an inactivating step of inactivating boron contained in the semiconductor material.

The semiconductor material recycling apparatus of the present invention is a semiconductor material recycling apparatus that removes phosphorus from the recovered semiconductor material, and moves the phosphorus to the surface of the semiconductor material by heating the semiconductor material. A heating device; and a separation device for separating the phosphorus located on the surface of the semiconductor material from the semiconductor material.

The semiconductor material regeneration device of the present invention is a semiconductor material regeneration device that inactivates boron contained in a semiconductor material, wherein the semiconductor material is heated and the poron is deactivated by a thermal donor. It is characterized by comprising an inactivating device.

The solar cell manufacturing apparatus of the present invention is a solar cell manufacturing apparatus that reuses the collected semiconductor material as a solar cell. The phosphorus that has moved to the surface of the semiconductor material by heat treatment is extracted from the semiconductor material. It is characterized by comprising a removing device for separating or an inactivating device for inactivating boron contained in the semiconductor material.

The method for regenerating a semiconductor material according to the present invention is a method for regenerating a semiconductor material by removing impurities from the collected semiconductor material and reusing the collected semiconductor material, and an assembly process for collecting the semiconductor material to form an aggregate; An impurity removing step of removing the impurities contained in the material in an aggregated state.

A semiconductor material recycling apparatus according to the present invention is a semiconductor material recycling apparatus that removes impurities from a collected semiconductor material and reuses the semiconductor material, and collects the semiconductor materials to form an aggregate; And an impurity removing device for removing the impurities contained in the semiconductor material in an aggregated state.

The method for producing a solar cell of the present invention is a method for producing a solar cell in which a collected semiconductor material is reused as a solar cell, and an assembly step of assembling the semiconductor material to form an assembly, An impurity removing step of removing the impurities contained in the material in a body state. The solar cell manufacturing apparatus of the present invention is a solar cell manufacturing apparatus that reuses the collected semiconductor material as a solar cell, and an assembly device that aggregates the semiconductor materials to form an aggregate; And an impurity removing device for removing the impurities contained in the semiconductor material in a body state. Brief Description of Drawings

FIG. 1 is a diagram showing a method for regenerating a semiconductor silicon material according to the present invention. (A) — (C) is a flow chart, and FIG. 2 is a method for regenerating a semiconductor silicon material according to the present invention. (A) is a conceptual diagram showing gettering, (B) is a conceptual diagram showing a thermal donor, and FIG. 3 is a diagram of a solar to which the method for regenerating a semiconductor silicon material of the present invention is applied. FIG. 4 is a flowchart showing a method for manufacturing a solar cell to which the method for regenerating semiconductor silicon material of the present invention is applied. FIG. 5 is a flowchart showing the method for manufacturing the battery. FIG. 6 is a diagram showing a semiconductor material recycling apparatus, (A) — (C) is a block diagram, FIG. 6 is a diagram showing a semiconductor material recycling apparatus of the present invention, and (A) is a block diagram. , (B) is a sectional view, (C) is a schematic diagram, and FIG. FIG. 8 is a sectional view showing a thermal donor device included in a material recycling apparatus, FIG. 8 is a sectional view showing a plasma removing apparatus included in a semiconductor material recycling apparatus of the present invention, and FIG. FIG. 10 is a cross-sectional view showing a heated phosphorus removing device included in a semiconductor material recycling apparatus. FIG. 10 (A) is a flowchart showing a semiconductor material recycling method of the present invention, and FIG. FIG. 11 is a block diagram showing a configuration of a silicon scrap collecting device included in the semiconductor material recycling apparatus of the present invention. FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of a separation device included in a semiconductor material regeneration device of the present invention, and FIG. BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIG. 1, in this embodiment, an outline of a method for regenerating a semiconductor material (a semiconductor silicon material as an example) will be described. Each figure in FIG. 1 is a flowchart showing a first method, a second method, and a third method for regenerating semiconductor silicon materials. In each method, contained in semiconductor scrap The combination of methods for treating phosphorous and boron is different.

Referring to FIG. 1 (A), the first method for regenerating semiconductor silicon material is to collect silicon waste (used semiconductor silicon material) S 1 1 and from the recovered silicon waste. Step S 1 2 to perform gettering to remove phosphorus, Step S 1 3 to inactivate boron contained in silicon waste, and silicon waste from which impurities are removed or inactivated Etc., and step S 14 is reused. Details of each of these steps are described in detail below.

In step S 11, silicon waste generated from the semiconductor manufacturing process is collected. For silicon scrap, for example, the process of cutting off both ends of the silicon ingot, the process of grinding the periphery so that the silicon ingot has a predetermined diameter, the process of slicing the silicon ingot to obtain a silicon wafer, and the silicon wafer thinning Therefore, it occurs in the process of pack grinding the back side.

Furthermore, in the process of machining the silicon ingot described above, the machining is performed while spraying water such as cooling water onto the silicon ingot. Therefore, silicon waste is included in the wastewater generated from these processes. In order to collect silicon waste, after separating the silicon waste from the wastewater using a filtration device, etc., the silicon waste is dehydrated using a filter press, and further silicon waste is removed using a drying furnace or the like. It is dried.

In each of the above steps, basically only silicon is machined, so for example, silicon scrap having a relatively high purity of about 90% or more can be obtained. However, this purity is not sufficient for solar cell silicon that requires a purity of 99.999.99% (7N). Furthermore, silicon wafers include P-type substrates into which boron (B) is introduced and N-type substrates into which phosphorus (P) is introduced. The above-mentioned silicon waste is P-type silicon waste. And N-type silicon waste are mixed. For these reasons, it is necessary to remove impurities mixed in silicon scrap in order to reuse silicon scrap.

In this embodiment, the phosphorus contained in the silicon waste is removed and the boron is inactivated in the following steps S12 and S13. Silicon scrap also contains heavy metals such as aluminum (A l), iron (F e :), and calcium (C a) in addition to light elements such as phosphorus and pollon. In this embodiment, these heavy metals have a small solid-liquid distribution coefficient of heavy metals. Is removed by unidirectional coagulation purification. This unidirectional solidification purification is a relatively inexpensive and simple process.

In step S 12, phosphorus contained in the silicon scrap is removed by gettering. Specifically, the silicon waste is heated to about 100 ° C. or more to move phosphorus to the surface of the silicon waste, and then the phosphorus is removed from the silicon waste. Details of this step will be described later with reference to FIG. 2 (A).

In step S 1 3, silicon scrap is heated at a constant temperature to generate a thermal donor and inactivate boron contained in the silicon scrap. A thermal donor is a phenomenon in which a plurality of oxygen atoms contained in silicon gather to emit electrons and become a donor, and is sometimes referred to as an oxygen donor. In a general semiconductor process, when a thermal donor is generated, the resistivity of the semiconductor changes from a desired value, so it is understood that the thermal donor is an undesirable phenomenon. In the present invention, this thermal donor is actively used to inactivate boron contained in the silicon waste and remove it in a pseudo manner. Details of the thermal donor will be described later with reference to Fig. 2 (B).

In addition, the thermal donor in this step needs to be performed after step S 1 2 in which gettering for removing phosphorus is performed. The reason for this is that if the silicon waste is heated to about 100 ° C after gettering, then boron in the silicon waste deactivated by the thermal donor will be This is because it is activated again by heating. In step S14, the silicon waste from which phosphorus has been removed and boron has been inactivated by the above steps is reused. In this step, silicon scraps can be used as solar cells. Furthermore, if the purity of silicon waste is further increased, it can be used as a semiconductor silicon that is a material such as LSI. Also, silicon scrap can be used as a deoxidizer that is put into the furnace together with iron ore when steel is refined.

Further, any one of the above-described steps S12 and S13 may be deleted from the above-described method for regenerating the semiconductor silicon material. In other words, boron is deactivated only in step S 1 3 in which thermal donor is performed without performing step S 12 in which gettering for removing phosphorus is performed, and N-type silicon waste containing phosphorus is removed. You may get. In addition, the step S 1 2 for removing phosphorus by gettering is performed, and the step S 1 3 for inactivating boron is not performed. P-type silicon scraps containing may be obtained.

With reference to FIG. 1 (B), a second method for regenerating semiconductor silicon material will be described. In the second method, the same parts as those in the first method described above are denoted by the same reference numerals, and the description thereof is omitted. The second method shown in this figure includes a step S 1 1 for collecting silicon waste, a step S 1 2 for removing phosphorus contained in silicon waste by gettering, and boron contained in silicon waste by an oxidation process. Step S 15 is removed, and Step S 14 is used to reuse silicon scrap. That is, in the first method described above, boron is inactivated by the step S 1 3 in which thermal donor is performed. In the second method, however, the oxidation step is performed instead of step S 1 3. The boron is substantially removed. The other steps of the second method are the same as the first method described above.

In step S 15, the silicon scrap from which phosphorus has been removed in step S 12 is melted to form molten silicon. Then, water vapor is sprayed on the surface of the molten silicon to combine boron and oxygen to form boron oxide, and then the boron oxide is removed. In this process, carbon contained in silicon scrap is also removed in the form of carbon dioxide.

In this second method, boron contained in the silicon scrap is removed rather than inactivated, so the order of steps S 12 and S 15 may be reversed. In addition, according to this method, it is possible to obtain a silicon material for a semiconductor made of an intrinsic semiconductor from which both phosphorus and boron are removed.

With reference to FIG. 1 (C), a third method for reclaiming a semiconductor silicon material will be described. Also in this third method, the same parts as those in the first method described above are denoted by the same reference numerals, and description thereof is omitted. The third method shown in this figure consists of step S 1 1 for recovering silicon waste, step S 16 for removing phosphorus contained in silicon waste by the evaporation process, and silicon waste due to thermal donors. Step S 1 3 for inactivating boron and Step S 14 for reusing silicon waste are provided. That is, in the first method described above, phosphorus is removed in step S12 for performing gettering, but in this third method, step S16 for performing an evaporation step instead of step S12 is provided. is doing. The other steps of the third method are the same as the first method described above.

In step S 1 6, first, the silicon scrap collected in step S 11 is dried. So After that, the silicon scrap is kept in a reduced pressure atmosphere or vacuum atmosphere of about 10 Pa to 0.001 Pa in an inert gas atmosphere such as argon. Then, the phosphorus contained in the silicon waste is removed by evaporation. Phosphorus is an easily-evaporable component that easily evaporates as compared with other impurities, and is thus removed by evaporation in this step. After phosphorus is removed from the silicon waste, after performing step S 1 3 to perform thermal donors that deactivate boron contained in the silicon waste, silicon waste is removed from the solar cells, etc. in step S 1 4 As reused.

According to the third method, a pseudo intrinsic semiconductor in which phosphorus is removed and boron is inactivated can be obtained. That is, the silicon material for semiconductors obtained as a result of the treatment is the same as in the first method described above.

In the above-described embodiment, silicon scrap is used as an example of the semiconductor material. However, this embodiment can also be applied to the regeneration of other semiconductor materials (for example, germanium (G e)). The same applies to other embodiments described later.

With reference to FIG. 2, in the present embodiment, details of gettering and thermal donor performed in steps S 12 and S 13 described above will be described. FIG. 2 (A) is a conceptual diagram for explaining the details of gettering for removing phosphorus, and FIG. 2 (B) is a conceptual diagram for explaining the details of a thermal donor for inactivating boron.

With reference to FIG. 2 (A), the process of gettering (gettering) for removing phosphorus 12 from the silicon waste 10 will be described. Here, the gettering is a process in which phosphorus 12 contained in the silicon scrap 10 is moved to the surface and trapped in the oxide film layer by heat treatment. Further, the phosphorus 12 moved to the surface of the silicon waste 10 is removed from the silicon waste 10 together with the oxide film by chemical or physical treatment. In this figure, phosphorus 12 is indicated by a black circle.

In this step, first, when the particle size of the silicon waste 10 is large, pulverization is performed to reduce the particle size of the silicon waste 10. Here, the phosphorus 12 contained in the silicon waste 10 is moved to the surface by heat treatment, and therefore, the treatment becomes easier when the particle size of the silicon waste 10 is smaller. For example, if the particle size of silicon waste 10 ··· is as large as several millimeters, the particle size is reduced by dusting treatment. In addition, when the particle size of silicon scrap 10 is about several hundred μ πι or less The pulverization process is unnecessary.

As an example of the particle size of silicon scrap 10, for example, if the average value (average particle diameter: arithmetic average diameter) of silicon scrap 10 is about 1.2 μm, the above gettering is preferably used. It can be carried out. Furthermore, with this average particle size, formation of an aggregate by a cold press described later can be suitably performed.

Next, the silicon waste 10 is heated at a high temperature of about 100 ° C. or more for several tens of minutes, so that the phosphorus 1 2 contained in the silicon waste 10 is Move to the surface. Lin 1 2 is a substance with higher mobility than boron. Therefore, when the silicon waste 10 is heated to a high temperature, the contained phosphorus moves to the surface (grain boundary) of the silicon waste 10. In addition, since the surface of the silicon scrap 10 is oxidized by oxygen in the atmosphere by the heat treatment, it is covered with the oxide film (Sio ₂ ) 11. Accordingly, the phosphorus 12 contained in the silicon scrap 10 moves to the inside of the oxide film 11. Alternatively, phosphorus 12 is located at the interface between silicon scrap 10 and oxide film 11 (or near the surface of silicon scrap 10). On the other hand, boron contained in silicon scrap 10 has a low diffusion coefficient, and therefore hardly moves by heating in this step. Note that this heating process is not heated until the silicon scrap 10 is melted. Therefore, in comparison with a well-known impurity removing method that melts the silicon scrap 10 to remove impurities such as phosphorus, The thermal energy required for removal can be reduced. The same applies to the removal of boron from the silicon scrap 10.

Next, the oxide film 11 and phosphorus 12 are removed from the silicon scrap 10. By the heat treatment described above, phosphorus 12 is located inside oxide film 11 1 or at the interface between oxide film 11 1 and silicon scrap 10, so that oxide film 11 1 is removed from silicon scrap 10. So phosphorus 1 and 2 are also removed. As a method for removing the oxide film 11 and phosphorus 12, there are a chemical method using etching and a machining process by grinding.

In the case of etching, the silicon scrap 10 that has undergone the above heating process is immersed in an aqueous solution of hydrofluoric acid (HF), and the surrounding oxide film 11 is removed together with the phosphorus 12. The oxide film 11 is melted by hydrofluoric acid, but the silicon scrap 10 basically does not react with hydrofluoric acid. Therefore, silicon scrap 10 from which phosphorus 12 has been removed is obtained by the etching process. In addition, after processing silicon waste 10 by etching, silicon waste 10 is washed, solid-liquid separation treatment, dehydration treatment, A drying process etc. may be required.

In the case of grinding, phosphorus 12 is removed together with the oxide film 1 1 by grinding the oxide film 11 covering the silicon scrap 10 entirely.

The cost for removing phosphorus by the gettering is about 3500 yen Z kg, which is lower than the cost for the background technology using the laser (5500 yen / kg). Therefore, the phosphorus removal method based on the gettering of this embodiment is cost-effective.

Next, referring to FIG. 2 (B), a thermal donor process for inactivating boron 13 contained in silicon scrap 10 will be described. The thermal donor is performed on the silicon waste 10 from which the phosphorus has been removed by the gettering described above.

Here, thermal donors are generated by heating silicon scraps 10 continuously for about 1 hour, for example, in a temperature range of 300 ° C. to 500 ° C. (especially 45 ° C.). In this way, boron 13 contained in the silicon waste 10 is inactivated.

The details of the thermal donor are as follows. In silicon waste 10, oxygen atoms of l O is Z cm ³ are present as impurities. This oxygen atom normally does not supply a carrier such as an electron or a hole alone, but when subjected to a heat treatment within the above temperature range, a plurality of oxygen atoms gather and emit electrons to form a donor. . Specifically, by the heat ^{_{treatment, 1 0 1 6 / c m}} 3 extent of oxygen donors are generated. This oxygen donor inactivates the boron 13 inside the silicon waste 10, increases the resistivity of the silicon waste 10, and simulates the state in which the boron 13 is removed. Has been produced.

As mentioned above, it is understood that thermal donors are an undesirable phenomenon in normal semiconductor manufacturing processes. The reason is that when a thermal donor occurs, the resistance value of the semiconductor converted to P-type or N-type changes. In this embodiment, this thermal donor is actively used to inactivate boron, which is difficult to remove by a physical method or a chemical method, and is pseudo-removed from the silicon waste 10.

In addition, if silicon waste 10 is exposed to a temperature of about 600 ° C. or higher after performing the thermal donor, the oxygen donor is erased and the deactivated boron is reactivated. End up. Therefore, after performing the above thermal donor, it is necessary to avoid exposing the silicon waste 10 to a high temperature of 600 ° C. or higher in order to prevent the oxygen donor from being erased. for that reason 1 0 0 0. The gettering process for heating the silicon scrap 10 to about C must be performed before the thermal donor process. Also, the process of melting the silicon waste 10 for reuse needs to be performed before the thermal donor process. Furthermore, in order to prevent the oxygen donor from being erased, it is better to avoid a rapid temperature change of the silicon scrap 10.

In the present embodiment, a solar cell manufacturing method will be described as an application example of the above-described silicon waste recycling method. That is, in this embodiment, solar cells are manufactured after removing silicon, inactivating boron, or both from silicon waste generated in the semiconductor manufacturing process. The solar cell manufacturing method of this embodiment includes a first manufacturing method for manufacturing a solar cell after manufacturing a P-type semiconductor substrate, and a second manufacturing method for manufacturing a solar cell after manufacturing an N-type semiconductor substrate. There is a manufacturing method. The first manufacturing method will be described with reference to FIG. 3, and the second manufacturing method will be described with reference to FIG.

The first manufacturing method will be described with reference to FIG. Here, by removing phosphorus by the above-described gettering, a P-type semiconductor substrate in which boron remains is manufactured, and a solar cell is manufactured from this P-type semiconductor substrate. In this embodiment, the manufacturing process of the polycrystalline solar cell is described below. However, it is also possible to manufacture a single crystal solar cell and an amorphous (amorphous silicon) solar cell from silicon waste.

The flowchart shown in FIG. 3 can be broadly divided into a process for removing impurities such as phosphorus (step S 3 1 and step S 3 2) contained in the recovered silicon waste, and melting the silicon material. It consists of a process (Step S 3 3) and a process for manufacturing a solar cell (Step S 3 4 to Step S 4 2). Each of these steps is described in detail below.

In step S 30, silicon waste generated from the process of manufacturing a semiconductor such as L S I is collected. The details are the same as step S 1 1 described with reference to FIG. The recovered silicon waste contains silicon waste introduced with boron and silicon waste introduced with phosphorus.

In step S 3 1, heavy metals such as copper contained in the silicon waste are removed by performing unidirectional solidification.

In step S 3 2, phosphorus contained in the silicon waste is removed. As a way to remove phosphorus Thus, the gettering described in detail with reference to FIG. 2 (A) and the evaporation process described with reference to FIG. 1 (C) can be employed. In particular, gettering can remove phosphorus contained in silicon scrap at low cost. In addition, when phosphorus is removed by gettering, a step of fragmenting silicon scraps may be performed before performing step S 3 2. Thus, the effect of removing phosphorus by gettering can be improved.

Here, when the semiconductor material recycling method using an assembly described later is applied to a method for manufacturing a solar cell, a large amount of silicon waste is generated by pressing without performing the directional solidification step S 3 1. Aggregated aggregates may be formed. In other words, the silicon scrap is not melted, but undergoes the process of step S 3 2 for removing phosphorus in an aggregated state.

In the silicon scraps that have undergone this process, phosphorus has been removed but boron has not been removed. Therefore, the silicon scrap that has undergone this process is a P-type semiconductor silicon material containing boron. In step S 33, the silicon scrap is melted to produce a silicon ingot of a predetermined size. In this method of manufacturing a polycrystalline solar cell, silicon scraps are melted at a temperature of 100 ° C. and fabricated in a vertical shape. When a single crystal solar cell is manufactured, the silicon crystal is melted in a melting furnace at a temperature of about 150 ° C., and then the single crystal is pulled. Furthermore, when manufacturing an amorphous solar cell, a solar cell film having a thickness of about 500 nm is obtained by a chemical method using silane gas at a temperature of about 300 ° C. It is formed on the main surface of a substrate made of glass.

In step S 3 4, the silicon ingot is sliced to obtain a semiconductor wafer 20. As a method of slicing a silicon ingot, there is a cutting method using a multi-wire saw. The wafer 20 obtained in this step is a P-type semiconductor wafer containing boron, and its thickness is, for example, about 200 / m.

In step S 35, the surface of the wafer 20 is chemically etched to form unevenness (texture). This texture is formed by utilizing the difference in etching rate depending on the crystal orientation of silicon. By forming the texture on the surface of the wafer 20 in this way, the effect of confining light on the wafer surface can be obtained.

In step S 36, a PN junction is formed on wafer 20. As described above, since wafer 20 is a P-type semiconductor containing boron, phosphorus is used to form a PN junction. Introduce to 20. In this step, the wafer 20 is heated at a temperature of about 85 ° C. for about 30 minutes. Further, the periphery of the wafer 20 is converted into N type or N + type into which phosphorus is introduced.

In step S 37, the protective film 21 is formed on the surface of the wafer 20. The protective layer 2 1 is made of T i 0 _2, it is formed by atmospheric CVD. The protective film 21 also functions as an antireflection film.

In step S 3 8, the back surface of wafer 20 is etched. Specifically, the N layer other than the light-receiving surface is removed by chemical etching using KOH aqueous solution.

In Step S 39, the back electrode 22 is formed on the back surface of the wafer 20. Specifically, the back electrode 22 is formed by screen-printing and baking Ag paste and A 1 paste on the back surface of the wafer 20. When screen printing is performed, the wafer 20 is heated at about 200 ° C. for about 1 minute. Further, when baking is performed, the wafer 20 is heated at about 75 ° C. for about 1 minute.

In step S 40, the light receiving surface electrode 23 is formed on the light receiving surface which is the surface of the wafer 20. The formation method of the light receiving surface electrode 23 is the same as that of the back electrode 22 described above. In this step, the protective film 21 is partially removed to form an opening, and then the light-receiving surface electrode 23 is formed in the opening.

In step S41, the characteristics of the solar cell formed by the above process are measured and inspected using a solar simulator or the like. Only those that pass the inspection are transported to the module assembly process, and the solar cell is completed through the assembly process (step S42).

In this embodiment, in order to partially inactivate boron contained in the wafer 20 and reduce the concentration of the pores in a pseudo manner, step S 46 for performing a thermal donor may be added. Recovered silicon waste sometimes contains higher concentrations of boron than necessary. Therefore, the characteristics of the manufactured solar cell can be improved by partially inactivating boron with a thermal donor. Partial thermal donors are achieved by adjusting the heating temperature, heating time, or both heating time and heating temperature. This adjustment may be, for example, lowering the heating temperature or shortening the heating time than the thermal donor described with reference to FIG. 2 (B).

Steps S 4 6 to perform a partial thermal donor, steps S 34 to S 40 Can be inserted between each step. That is, step S 46 only partially deactivates the polone, so this does not adversely affect the PN junction formed in step S 36. Therefore, step S 46 for performing a partial thermal donor may be performed before step S 36 6 for forming a PN junction, or may be performed after step S 36.

Next, referring to FIG. 4, a method for manufacturing a solar cell using an N-type wafer from which boron contained in silicon waste is inactivated and pseudo boron is removed will be described. Further, in FIG. 4, the same parts as those in the manufacturing process of FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. In Step S 30 and Step S 31, after collecting the silicon waste, heavy metals such as copper are removed from the silicon waste by unidirectional solidification. In addition, as described above, an aggregate in which a large number of silicon scraps are aggregated by press working may be formed without performing the directional solidification S31. Then, phosphorus removal in step S43 may be performed on this aggregate. In step S 4 3, the phosphorus is partially removed from the silicon waste. In the manufacturing method shown in Fig. 3, all or most of the phosphorus contained in the silicon waste was removed by gettering in step S32, but all phosphorus was removed in this step. It is removed only partially. As a result, when the concentration of phosphorus contained in silicon scrap is too high, the concentration can be lowered to a predetermined value. This step is performed by adjusting the time, temperature, or both time and temperature during gettering. This adjustment means, for example, that the gettering process described with reference to FIG. 2 (A) also lowers the heating temperature during gettering or shortens the heating time.

In step S 3 3, step S 3 4, and step S 3 5, after the ingot is fabricated, the ingot is sliced to produce wafer 20, and unevenness (texture) is formed on the surface of wafer 20. Form. Both phosphorous and boron are present in the wafer 20 obtained in step S 3 4.

In this manufacturing method, Step S 4 4 for performing a thermal donor is performed between Step S 3 4 for processing a wafer and Step S 45 for forming an NP junction. In other words, here, it is necessary to perform a thermal donor before step S 45 in which boron is diffused into wafer 20 to form an NP junction. The reason for this is that after boron is implanted to form the NP junction, This is because if the thermal donor that inactivates most of the boron contained is performed, the entire wafer 20 becomes N-type, and the wafer 20 is no longer a solar cell. The details of the thermal donor are the same as those in Fig. 2 (B).

Furthermore, the step S 4 4 for carrying out the thermal donor needs to be carried out after the step S 3 3 for producing the ingot. This is because, in step S 33, silicon waste is heated and melted at a high temperature of, for example, 100 ° C. or higher. That is, if the thermal donor of step S44 is performed prior to step S33, the opening deactivated by the thermal donor is reactivated by the heating of step S33.

The wafer 20 that has undergone the thermal donor step S 44 is in an N-type containing phosphorus, in which boron contained therein is inactivated and pseudo-removed.

In step S 45, an N P junction is formed on the wafer by diffusing boron into the wafer 20. In step S36 shown in Fig. 3, phosphorus was introduced, but here boron is introduced. Therefore, in the solar cell manufactured by this manufacturing method, both deactivated boron and active boron that has not been deactivated are mixed.

Subsequently, a protective film 21 is formed in step S 37, and the back surface of the wafer 20 is etched in step S 38 to remove the P-type region except for the light receiving surface. Further, the back electrode 2 2 is formed in step S 39, the light receiving surface electrode 2 3 is formed in step S 40, the characteristic inspection in step S 4 1 is performed, and in step S 4 2 A solar cell is completed.

In the manufacturing method described above, care must be taken so that the deactivated boron is not activated again after step S44 of performing thermal donor is performed. For example, if the wafer 20 is exposed to a high temperature of 600 ° C. or more for about 30 minutes to 1 hour or more, the deactivated boron may be activated again. Since the above-mentioned steps after step S45 are not accompanied by such conditions, the possibility that boron is activated again is eliminated. Furthermore, in the solar cell manufacturing method described above, either phosphorus or boron was removed from silicon scrap to produce a P-type or N-type wafer. For example, the method shown in FIG. When used, a wafer made of an intrinsic semiconductor from which both phosphorus and boron have been removed is produced. It is also possible to manufacture solar cells using a wafer made of this intrinsic semiconductor. Furthermore, this wafer can be used as a material for other semiconductor devices such as LSI. Fourth Embodiment: Configuration of Semiconductor Material Recycling Device>

In the present embodiment, a configuration of a semiconductor material recycling apparatus applied to the above-described semiconductor material recycling method will be described with reference to FIGS. Each figure in FIG. 5 is a diagram showing an outline of each playback device, and FIGS. 6 to 9 are diagrams showing details of each device included in the playback device. Moreover, in the following description, in addition to the semiconductor material recycling apparatus, reference is also made to a solar cell manufacturing apparatus. Referring to FIG. 5 (A), this figure shows a silicon scrap collecting device 32, a regenerating device 30A, and a solar cell manufacturing device 42. Further, the regenerator 3 O A includes a phosphorus removal device 3 4 and a thermal donor device 40 (deactivation device). Then, by using silicon scraps in order from the device located on the upper side on the paper surface, the silicon scraps are regenerated and solar cells are manufactured.

The silicon scrap collecting device 32 is a device for realizing the method described with reference to the silicon collecting step S 30 in FIG. For example, a filtration device for concentrating waste water containing silicon waste, a filter press for dewatering this waste water, or the like can be used as the silicon waste recovery device 32. As described above, the silicon scrap recovered by this equipment is a mixture of N-type silicon scrap with phosphorus introduced and P-type silicon scrap with boron introduced.

The regenerator 30 A is a device for removing or inactivating impurities contained in the collected silicon waste, and comprises a phosphorus removing device 34 and a thermal donor device 40.

The phosphorus removing device 3 4 is a device for removing phosphorus contained in silicon waste, and includes a gettering device 3 6 and a separating device 3 8. The gettering device 36 is a device that performs a gettering process in which phosphorus contained in silicon scrap is moved to the surface of silicon scrap almost uniformly by heating silicon scrap. The separation device 38 is a grinding device or an etching device, and separates the moved phosphorus from the silicon exhibition.

The thermal donor device 40 is a device that inactivates boron contained in silicon scraps by heating silicon scraps at a predetermined temperature and time, and removes boron in a pseudo manner. The silicon waste regenerated by the regenerator 30 A is in a state in which the phosphorus is removed and boron is inactivated, and it has a pseudo-intrinsic physical property. Here, for example, if the silicon scrap to be collected is either N-type or P-type silicon scrap, the regenerator 30A is configured by only the gettering device 36 or the thermal donor device 40. It is also possible Noh.

The solar cell manufacturing apparatus 42 is an apparatus that manufactures solar cells using the semiconductor material regenerated by the regenerating apparatus 30A. For example, the solar cell manufacturing apparatus 4 2 is configured by an apparatus for realizing the steps after step S 3 4 with reference to FIG. That is, an apparatus that cuts out the wafer 20 from the ingot (step S 3 4), an apparatus that forms a texture on the main surface of the wafer 20 (step S 3 5), and phosphorus that is formed on the wafer 20 to form a PN junction. Device to be introduced (Step S 3 6) Device for forming the protective film 21 on the upper surface of the wafer 20 (Step S 3 7), Device for etching the back surface of the wafer (Step S 3 8), Back surface of the wafer 20 A device for forming the back electrode 2 2 on the substrate (Step S 39), a device for forming the electrode on the light receiving surface of the wafer 20 (Step S 40), and the characteristics of the solar cell formed by using these devices The solar cell manufacturing apparatus 4 2 is formed from the apparatus (step S 4 1) for inspecting

Referring to Fig. 5 (A), further, here, a combination of two or more of silicon waste recovery device 3 2, recycling device 3 OA and solar cell manufacturing device 4 2 is regarded as a solar cell manufacturing device. May be. With reference to FIG. 5 (B), the configuration of another embodiment of the playback device 30 B will be described. The configuration of the playback device 30B shown in this figure is basically the same as that of the playback device 30A described above. The difference between the regenerator 30B and the regenerator 30A is that, in the regenerator 30A, the boron contained in the silicon debris was removed by the thermal donor device 40, whereas the regenerator 30 In 3 0 B, boron is removed by the plasma removal device 4 4. Other configurations of the playback device 30B are the same as those of the playback device 30A.

Specifically, FIG. 5 (B) shows a silicon waste collecting device 3 2, a regenerator 30 B, and a solar cell manufacturing device 4 2. The reproduction apparatus 30B includes a line removal apparatus 3 4 and a plasma removal apparatus 44. The phosphorus removal device 34 includes a gettering device 36 and a separation device 38.

The above-described plasma removing apparatus 44 is an apparatus that removes boron contained in silicon by irradiating the molten silicon with plasma. In the regenerator 30 A, boron was artificially removed by the thermal donor device 40, but in the regenerator 30B, boron was substantially removed from the silicon waste. Therefore, since the semiconductor silicon material regenerated by the regenerator 30 B having the above-described configuration has both phosphorus and boron removed, the regenerator 3 OA The purity is higher than the regenerated semiconductor silicon material.

With reference to FIG. 5 (C), the structure of another embodiment of the playback device 30 C will be described. The basic configuration of the playback device 30 C is the same as that of the playback device 3 O A described above. The difference between the regenerator 30 A and the regenerator 30 C is that the regenerator 30 A was equipped with the phosphorus removal device 34, whereas the regenerative device 30 C was a hot phosphorus removal device 4. It is in that it has six. That is, in the reproduction apparatus 30 C, phosphorus contained in the silicon scrap is removed by irradiating the melted silicon scrap with a beam with an electron gun.

Specifically, the regenerator 30 C shown in this figure includes a heated phosphorus removing device 46 and a thermal donor device 40. The heated phosphorus removal device 46 removes phosphorus from silicon by irradiating a silicon melted under high vacuum with a beam using an electron gun. Further, in the thermal donor device 40, as described above, boron is pseudo-removed by inactivating (thermal donor) boron contained in the silicon waste.

The semiconductor material regenerated by the regenerating apparatus 30 C is in a state where phosphorus is removed and boron is inactivated and pseudo-removed.

Comparing the three regenerators 30 A, 30 B, and 30 C described above, the regenerator 30 A can regenerate semiconductor waste at the lowest cost. The reason is that, in the regenerators 30 B and 30 C, the silicon scrap is melted in the regenerator 3 O A, but the silicon scrap is heated but not melted. In the regenerator 3 O A, it is not necessary to raise the temperature of the apparatus as the silicon melts, so that less heat energy is required and the silicon can be regenerated at a low cost.

Next, with reference to FIGS. 6 to 9, the configuration of each device included in the playback device 30 A and the like will be specifically described.

Referring to FIG. 6, the configuration of phosphorus removal device 3 4 included in regenerator 30 A shown in FIG. 5 (A) or regenerator 30 B shown in FIG. 5 (B) is shown. explain. FIG. 6 (A) is a schematic view of the phosphorus removing device 34, FIG. 6 (B) is a sectional view showing the structure of the gettering device 36, and FIG. 6 (C) is a separation device 3 8. It is a conceptual diagram which shows the structure of.

Referring to FIG. 6 (A), the phosphorus removing device 3 4 for removing phosphorus from the silicon waste is a gettering device 3 6 for moving the phosphorus contained in the silicon waste toward the surface. When, And a separation device 38 for separating phosphorus that has moved to the surface of the silicon scrap from the silicon scrap. More specifically, the surface of silicon waste is covered with silicon oxide (silicon compound) in the gettering device 36, and the silicon oxide is removed from the silicon waste together with phosphorus in the separation device 38. . This silicon oxide may be generated in the heating process, or may be formed by the reaction of oxygen in the air and silicon waste before heating.

The structure of the gettering device 36 will be described with reference to FIG. 6 (B). Gettering equipment

36 mainly includes a quartz tube 48, an introduction part 52, a discharge part 54, and a heater 50. The quartz tube 48 is a housing made of quartz having excellent heat resistance, and a space for heating the silicon waste 62 is secured inside. The introduction part 52 is provided on the right side wall of the quartz tube 48 and allows the inside and outside of the quartz tube 48 to communicate with each other. The introduction part 52 is attached to the left side wall of the quartz tube 48 and allows the inside and outside of the quartz tube 48 to communicate with each other. Gas 5 6 required for gettering is introduced from introduction section 52, and quartz tube is introduced from discharge section 54.

Gas 5 8 via 4 8 is discharged to the outside.

The heater 50 is provided in the quartz tube 48, and heats the atmosphere inside the quartz tube 48 to a predetermined temperature. As the heater 50, a resistance heater can be used.

The quartz port 60 is a container for containing silicon waste 62 made of quartz. Inside the quartz tube 48, for example, a temperature monitor 92 made of a thermocouple is installed. Here, instead of the quartz boat 60, a storage container made of alumina may be employed.

A method for gettering silicon scrap 62 using the gettering device 36 having the above configuration will be described below.

First, after the silicon scrap 62 is placed and stored in the quartz boat 60, the quartz boat 60 is transported into the quartz tube 48. Here, an aggregate in which a large number of particulate silicon scraps 62 are gathered by pressing is placed on and stored in a quartz boat 60.

Next, while the gas 56 is introduced into the quartz tube 48 from the introduction part 52, the heater 50 is energized to heat the atmosphere inside the quartz tube 48. As the gas 56, argon or nitrogen gas is adopted, and the gas is introduced at a pressure of 0.01 Torr or more and 7660 Torr or less. Here, while monitoring the temperature of the atmosphere near the silicon scrap 62 with the temperature monitor 92, the quartz tube Maintain the internal temperature of 4 8 at 90 ° C or higher and 1 200 ° C or lower. If this temperature is less than 900 ° C, the effect of gettering will be reduced, and if this temperature is 1 2 0 0 or more, the internal temperature will exceed the upper limit of the heat resistant temperature of the quartz tube 48, and the quartz tube will 4 8 may be destroyed. Then, heating at this temperature is continuously performed for 0.5 hour or more and 2 hours or less. If this time is less than 0.5 hours, gettering is insufficient and phosphorus may remain inside the silicon waste 62. On the other hand, if this time is longer than 2 hours, the time required for gettering becomes longer than necessary, which may reduce the efficiency of the regeneration work.

Next, after the heating by the heater 50 is stopped, the quartz tube 48 is left until the internal atmosphere of the quartz tube 48 becomes about the room temperature, and the silicon scrap 62 is taken out together with the quartz boat 60. Each of the silicon scraps 62 that have undergone the above process is in a state in which the contained phosphorus has been moved to the surface of the silicon scraps 62.

Next, with reference to FIG. 6 (C), the structure of the separation device 38 for separating phosphorus that has moved to the surface of the silicon scrap 62 from the silicon scrap will be described.

Separator 3 8 includes mesh basket 6 6 that is a container for storing silicon waste 62 that has undergone gettering treatment, tank 6 8 that stores hydrofluoric acid 70, and water that is pure water 7 4 Is mainly equipped with a tank 72. The mesh basket 66 is suspended on the conveyor 64, so that it can move in the vertical direction and the horizontal direction. The tank 68 is made of, for example, Teflon or the like, and hydrofluoric acid 70 (hydrofluoric acid) is stored in the tank 68. Since hydrofluoric acid 70 is a highly corrosive chemical, tank 68 needs to be made of a material such as Teflon having excellent corrosion resistance. Here, the concentration of hydrofluoric acid is, for example, 5%.

The tank 7 2 is made of, for example, Teflon, and water 7 4, which is pure water, is stored therein. In addition, the tank 7 2 is arranged at a later stage than the tank 6 8 in the path through which the conveyor 6 4 transports the mesh basket 6 6. The water 74 stored in the tank 72 is used to perform a rinsing process for removing the hydrofluoric acid 70 impregnated in the silicon waste 62. A plurality of tanks 72 may be arranged in the transport path of the conveyor 64. A method for separating phosphorus from the surface of the silicon scrap 62 using the separating device 38 having the above-described configuration is as follows. First, the silicon scraps 62 that have undergone the gettering process described above are accommodated in the mesh cage 66. Here, the silicon scrap 62 is pressed, and for example, the shape thereof is a tablet shape having a diameter of several centimeters and a thickness of several centimeters. Accordingly, the conveyance of the silicon waste 62 is easy, and the mesh basket 66 may have a coarse stitch. In the figure, the mesh basket 6 6 exemplifies the silicon scrap 62 in the state of only one aggregate, but a large number of hundreds of silicon scraps 6 2 are accommodated in the mesh basket 6 6. May be. The mesh basket 6 6 is suspended from the conveyor 64 via a metal cable or the like.

Next, the mesh basket 66 containing the silicon scrap 62 is moved by the conveyor 64 and immersed in hydrofluoric acid 70 stored in the tank 68 for a certain period of time. As a result, wet etching is performed to separate the phosphorus existing on the surface of the silicon waste 62 from the silicon waste 62. If a silicon compound is present on the surface of the silicon waste 62, this compound is also separated and removed together with the phosphorus. The time for which silicon waste 62 is immersed in hydrofluoric acid 70 is, for example, not less than 0.5 minutes and not more than 10 minutes. If this time is less than 0.5 minutes, the etching process of the silicon waste 62 is insufficient, and there is a possibility that the phosphorus remains in the silicon waste 62. Further, if the time is longer than 10 minutes, the efficiency of this process may be deteriorated. When this process is completed, the conveyor 64 is driven to move the mesh basket 66 from the tank 68 to the tank 72.

Next, the silicon waste 6 2 accommodated in the mesh basket 6 6 is immersed in the water 7 4 stored in the tank 7 2. By this step, the hydrofluoric acid 70 impregnated in the silicon waste 62 in the solid state is removed, and phosphorus and compounds remaining on the surface of the silicon waste 62 are also separated. This process is generally called a rinse process. The number of times of this rinsing process is 3 times or more and 10 times or less, and the number of tanks 72 corresponding to this number of times may be prepared with water 74 stored. Furthermore, water 74 may be caused to flow inside the tank 72 in order to suitably perform the separation in this step.

Next, the structure of the thermal donor device 40 and the inactivation using this device will be described with reference to FIG. The schematic configuration of the thermal donor device 40 illustrated in this figure is the same as that of the gettering device 36 shown in FIG. 6 (B).

Specifically, the thermal donor device 40 includes a quartz tube 76 and a heating heater for heating the quartz tube 76. The gas inlet 8 0 through which the gas 9 8 is introduced from the outside by communicating the inside of the quartz tube 7 6 with the inside and outside of the quartz tube 7 6, and the gas 8 4 It is composed of a discharge part 8 2 and Further, the silicon scrap 86 from which phosphorus has been removed through the previous process is stored in the quartz tube 76 while being placed on the quartz boat 88.

A method of using a thermal donor apparatus 40 to thermally treat silicon waste 86 is as follows. First, the silicon scrap 86 in an aggregated state is placed on top of the quartz port 88 and accommodated in the internal space of the quartz tube 76. Next, a gas 78 containing argon or nitrogen gas is introduced from the introduction unit 80 into the quartz tube 76 from the introduction unit 80. The pressure of the introduced gas 78 is, for example, not less than 0.01 Torr and not more than 760 Torr. As a result, the inside of the quartz tube 76 is filled with the gas 78. The introduced gas 7 8 is finally discharged to the outside from the discharge section 8 2.

In synchronization with the introduction of the gas 78, the quartz tube 6 is heated by the heater 90. The temperature inside the quartz tube 76 is monitored by a temperature monitor 94, and the heater 90 is controlled based on the output from the temperature monitor 94. In this process, the temperature of the internal atmosphere of the quartz tube 76 (that is, the temperature at which the silicon scrap 86 is heated) is preferably from 300 ° C. to 500 ° C., for example, as a set value Is 45 ° C. By making the internal temperature of the quartz tube 76 in this process within this range, boron contained in the silicon waste 8 6 is inactivated and pseudo boron is removed from the silicon waste 8 6. be able to. On the other hand, when the internal temperature of the quartz tube 76 is less than 300 ° C., thermal donors are not generated and boron is not removed in a pseudo manner. If this temperature is higher than 500 ° C., the generated thermal donor is lost, and boron is not pseudo-removed.

With reference to FIG. 8, the configuration of a plasma removing apparatus 44 for substantially removing boron from silicon scraps 106 and a method for removing boron using this apparatus will be described.

The plasma removal apparatus 44 shown in this figure includes a quartz tube 9 6 having a space formed therein, an introduction part 10 0 for communicating the internal space of the stone tube 9 6 and the outside, and a quartz tube 9 6 Temperature monitor that measures the temperature of the exhaust section 1 0 2 that connects the interior space of the interior and the outside, the quartz boat 1 0 8 that contains the silicon waste 1 0 6 and the eaves of the stone tube 9 6 1 1 0 And a plasma torch 1 1 2 for generating plasma and a nozzle 1 1 4 for generating water vapor. The configuration of the quartz tube 96, the introduction unit 100, and the discharge unit 1002 may be the same as the quartz tube 48, the introduction unit 52, and the discharge unit 54 described with reference to FIG. 6 (B). .

The quartz bottle 10 8 is a container made of a material having high heat resistance such as quartz, and contains silicon waste 10 6 in an aggregated state or a particle state. Further, since the silicon waste 10 6 is melted, the shape of the quartz port 10 8 is preferably a tank shape in which the molten liquid silicon waste 10 6 does not flow out to the outside.

The temperature monitor 110 is installed at or near the quartz boat 108 and is used to measure the temperature at this location.

A method of substantially removing boron contained in the silicon scrap 106 using the plasma removing apparatus 44 having such a configuration is as follows. First, the quartz boat 10 8 in which the silicon waste 106 is stored is stored in the quartz tube 96.

Next, the quartz tube 96 is heated by a ripening heater (not shown) to melt the silicon scraps 106. In order to melt the silicon scrap 10 6, it is necessary to heat the temperature inside the quartz tube 96 to 1550 ° C. or higher. In other words, the plasma removal device 44 that melts the silicon waste 106 and removes boron consumes a larger amount of thermal energy than the thermal donor device 40 that deactivates boron. Further, in synchronism with this heat treatment, argon gas or nitrogen gas (gas 9 8) is introduced into the quartz tube 96 from the introduction part 100. Then, the gas filled in the quartz tube 96 is finally discharged to the outside as the gas 10 4 from the discharge unit 10 2. When the silicon scraps 10 6 are melted, boron is removed from the liquid silicon scraps 10 6 using the plasma torch 1 1 2 and the nozzle 1 1 4. Specifically, a plasma gas, which is a gas containing plasma, is blown from the plasma torch 1 1 2 to the silicon scraps 1 0 6. At the same time, water vapor is blown to the silicon scraps 1 0 6 through the nozzles 1 1 4. The plasma gas ejected from the plasma torch 1 1 2 and the water vapor ejected from the nozzle 1 1 4 reach the same location on the liquid surface of the molten silicon scrap 1 0 6. Here, hydrogen gas may be sprayed on the silicon scraps 10 6 simultaneously with the water vapor. As a result, boron contained in the silicon waste 106 is removed in the form of boron oxide.

When boron is removed from the silicon scrap 10 6 by the above method, the inside of the quartz tube 96 is cooled, and then the silicon scrap 10 6 is taken out from the quartz tube 96. Silicon waste after this treatment 1 0 6 is in a state where boron is removed.

With reference to FIG. 9, the structure of a heated phosphorus removing device 46 that substantially removes phosphorus from silicon scrap 120 and a method of removing phosphorus using this will be described. The heated phosphorus removal device 46 includes a pump 1 1 8, a discharge unit 1 24 drawn from the champ 1 1 8, and a pump connected to the internal space of the champ 1 1 8 via the discharge unit 1 24. 1 2 6 and an electron gun 1 1 6 for applying a beam to silicon scrap 1 20. The silicon waste 1 2 0 stored in the quartz port 1 2 2 which is a storage container is stored inside the chamber 1 1 8.

The Champa 1 1 8 is a storage container made of metal such as SUS (Stainless Used Steel) so that it does not deform even when the inside is in a high vacuum state. Molded. The pump 1 2 6 is, for example, a rotary pump and is connected to the champ 1 1 1 8 via the discharge section 1 24 and is used to reduce the internal space of the champ 1 1 8. The Furthermore, the electron gun 1 1 6 has a function of converting electric energy supplied from a power source located outside the chamber 1 1 8 and generating an electron beam inside the chamber 1 1 8.

The method of removing the phosphorus using the heated phosphorus removing device 46 having such a configuration is as follows. First, the silicon waste 1 2 0 stored in the quartz boat 1 2 2 is stored in the internal space of the chamber 1 1 8.

Next, the pump 1 2 6 is operated and the air located in the internal space of the champ 1 1 1 8 is sucked to make the inside of the champ 1 1 1 8 into a low pressure state. For example, the air pressure in the internal space of the champ 1 1 8 is set to l O Pa or less 0. O l Pa or more.

Next, or simultaneously with the previous step, the silicon waste 120 is heated and melted. For example, silicon waste 120 is heated to about 1500 ° C. and melted.

Further, the electron gun 1 1 6 is operated to irradiate the molten silicon scrap 1 20 with an electron beam. By performing this operation, phosphorus contained in the silicon waste 1 2 0 is removed by evaporation.

In the present embodiment, a method and an apparatus for regenerating a semiconductor material composed of particulate silicon scrap will be described with reference to FIGS. In the present embodiment, description of parts having names or reference numerals common to the above-described embodiments is omitted. Characteristic of this embodiment The important point is that impurities such as phosphorus and boron contained in the silicon waste are removed after the silicon waste in the particle state is pressed into an aggregated state.

First, with reference to FIG. 10, the playback method and playback apparatus of the present embodiment will be described. FIG. 10 (A) is a flowchart showing the reproducing method, and FIG. 10 (B) is a block diagram showing the reproducing apparatus.

With reference to FIG. 10A, a method for regenerating a semiconductor material of the present embodiment will be described. The recycling method of the present embodiment includes a step S 51 for collecting silicon waste, a step S 52 for forming an aggregate, a step S 53 for removing impurities, and a step for reusing silicon waste. S 5 4. Here, all of these steps can be regarded as a regeneration process, or only the step S 52 for forming an aggregate and the step S 53 for removing impurities can be regarded as a regeneration process.

In step S 51, particulate silicon waste generated from the semiconductor manufacturing process is collected. The details of this process are the same as the recovery step described above (for example, step S 30 shown in FIG. 4), and the silicon waste is removed by performing concentration treatment or dehydration treatment of waste water containing silicon waste. Collected.

In step S 52, the silicon scrap collected in step S 51 is assembled to form an aggregate. Specifically, silicon waste is subdivided into a predetermined amount, and the divided silicon waste is pressed to form an aggregate. By this processing, for example, a cylindrical aggregate is formed. In this step, basically, by applying pressure to the particulate silicon waste, the silicon waste gathers to form a solid body. In other words, binders made from resin materials are not used. Therefore, a fine space is formed between the silicon scraps constituting the aggregate.

Furthermore, in this step, pressing is performed at normal temperature without applying thermal energy to the silicon waste, and this processing method is called a cold press. Furthermore, the above-mentioned aggregate composed of silicon waste can also be called a pressure-molded body or a solid body. Further, the formation of the aggregate may be performed by dividing the silicon waste into small parts and temporarily forming the shape of the aggregate, and by pressing the temporary molded aggregate. good. The steps after this step are performed on the silicon scrap in the aggregated state. In step S 53, a process for removing impurities (phosphorus and boron) contained in the silicon scrap is performed on the silicon scrap in the aggregated state. As this process, referring to each figure in FIG. 1, gettering, thermal donor, oxidation process, evaporation process, or a combination thereof may be considered. To be precise, the gettering includes a gettering process in which phosphorus contained in silicon waste is moved to the surface by heat treatment, and a separation process in which phosphorus moved to the surface is separated from the silicon waste. The thermal donor is a process of removing boron in a pseudo manner by inactivating boron contained in the silicon waste by heating the silicon waste at a predetermined temperature for a predetermined time. The oxidation process is a process of substantially removing boron contained in the silicon scrap by spraying plasma gas and water vapor to the molten silicon scrap. The evaporation step is a step of substantially removing the phosphorus contained in the silicon waste by irradiating the molten silicon waste with an electron beam.

Details of each step of removing impurities from silicon scrap are described in the other embodiments described above.

In the present embodiment, after the fine granular silicon waste is aggregated, the above-described impurities are removed from the silicon scrap in the aggregated state. Therefore, handling of silicon waste is improved and scattering of silicon waste is prevented.

As step S54, it is also possible to employ the solar cell manufacturing method described above. Applying step S 52 to form the assembly to the solar cell manufacturing method facilitates the transport of silicon waste and consequently reduces the cost required for solar cell manufacturing. Can do.

Referring to FIG. 10 (B), this figure shows a silicon scrap collecting device 1 2 8, a regenerating device 1 3 2, and a solar cell manufacturing device 1 4 2. Here, all of these devices may be regarded as playback devices. Furthermore, the playback device 1 3 2 may be regarded as a part of a device for manufacturing a solar cell.

Further, the regenerator 1 3 2 includes a silicon scrap collecting device 1 3 0, a phosphorus removing device 1 3 4, and a thermal donor device 1 4 0. Further, the phosphorus removing device 1 3 4 includes a gettering device 1 3 6 and a separating device 1 3 8. Here, impurities contained in silicon waste are mainly phosphorus or boron. Therefore, the phosphorus removal device to remove phosphorus 1 3 4 and poron The thermal donor device 1 4 0 that is inactivated and removed in a pseudo manner is an example of the impurity removal device 1 4 4.

Here, the configuration of the playback device 1 3 2 may be changed. That is, instead of the phosphorus removing device 1 34 shown in FIG. 10 (B), the heated phosphorus removing device 46 shown in FIG. 5 (C) may be adopted. Further, instead of the thermal donor device 140 shown in FIG. 10 (B), the plasma removing device 44 shown in FIG. 5 (B) may be adopted. As a result, it is possible to remove silicon and boron from the silicon scrap and regenerate the silicon scrap to obtain an intrinsic semiconductor.

The details of the silicon waste collecting device 1 30 will be described with reference to FIG. Silicon scrap collecting device 1 3 0 consists of punch 1 4 6, die 1 5 0, punch 1 4 8, pressurizing part 1 5 4, pressure gauge 1 5 6 and press rod 1 5 9 And the main.

The die 150 is made of a metal material such as iron and has a cylindrical space inside, and the size of this space corresponds to the shape of the formed aggregate.

The punch 1 46 is a steel rod having a size that can be inserted into the inner space of the die 1 5 0 without a gap, and is inserted into the internal space of the die 1 5 0 from above.

The punch 1 46 has the same shape as the punch 1 46 and is inserted into the internal space of the die 1 50 from below.

The pressurizing unit 1 5 4 is a part that pressurizes the table on which the punch 1 4 8 is placed from below to above, and employs driving means such as hydraulic pressure or a motor.

The pressure gauge 1 5 6 is a part indicating the pressure generated by the pressurizing unit, and an analog display method or a digital display method is adopted.

The pressure rod 1 5 9 is a portion that applies a driving force to the pressure portion 1 5 4.

A method for collecting silicon scraps 1 5 2 using the silicon scrap collecting apparatus 1 3 0 is as follows. First, after the die 1 5 0 is placed above the punch 1 4 8, the silicon scrap 1 5 2 is stored in the inner space of the die 1 5 0. The silicon scrap 15 2 may be granular or may be preliminarily molded into a solid state. Next, the punch 1 46 is inserted into the internal space of the die 1 5 0 from above. Further, the press rod 1 5 9 is operated to give a predetermined shrunk from the press unit 1 5 4 to the silicon waste 1 5 2 via the punch 1 4 8.

At this time, the pressure applied from the pressurizing unit 1 5 4 to the silicon scrap 1 5 2 is, for example, 2 OM P a or more and 3 0 OMP a or less. By setting the pressure within this range, a large number of silicon scraps 15 2 are integrated, and an aggregate having a fine space inside is formed. If the pressure is less than 20 MPa, it is difficult to integrate the silicon scraps 1 5 2 as an aggregate. On the other hand, if the pressure is greater than 300 MPa, the required fine space may not be formed inside the silicon waste 15 2.

With reference to FIG. 12, a separation device 1 38 and a separation method for separating the phosphorus located on the surface of the silicon waste (aggregate 15 8) will be described. FIG. 12 (A) is a view showing the separation device 1 38, and FIG. 12 (B) is a view showing a state in which hydrofluoric acid 70 has infiltrated into the aggregate 15 8. Referring to FIG. 12 (A), the separating device 1 3 8 has a mesh basket 6 6 that accommodates the assembly 1 5 8 and a mesh basket 6 6 vertically via a locking means such as a wire. And a tank 6 2 for storing hydrofluoric acid 70 (etchant), and a tank 7 2 for storing water 74 (pure water). It has become.

The aggregate 1558 molded by the silicon scrap collecting apparatus 130 shown in FIG. 11 is housed in the mesh skirt 66 and then immersed in hydrofluoric acid 70 for a certain period of time. For example, the aggregate 15 8 made of silicon waste is immersed in hydrofluoric acid 70 for 0.5 to 10 minutes. As a result, the phosphorus located on the surface of the particulate silicon debris constituting the aggregate 1 5 8 is wet-etched by hydrofluoric acid 70 and the silicon debris (aggregate 1 5 8) force, 'Is removed together with the oxide film. After this separation is completed, the aggregate 1 5 8 stored in the mesh basket 66 is conveyed to the tank 7 2 by the conveyor 6 4.

Next, the aggregate 1 5 8 is immersed in water 74 stored in the tank 7 2 and rinsed. That is, the phosphorous acid 70 remaining on the surface of each silicon scrap constituting the aggregate 1558 is removed from the surface of the silicon scrap. This rinse process is, for example, not less than 0.5 minutes and not more than 2.0 minutes. Further, the number of times this rinse process is performed is not less than 3 times and not more than 10 times. Even in this rinsing process, fine gaps are formed between the silicon scraps constituting the aggregate 1 5 8, so that the water 7 4 passes through these gaps. Enter inside 8. Therefore, the silicon waste located inside the aggregate 1 5 8 is sufficiently rinsed.

Referring to FIG. 12 (B), the silicon scrap 6 2 constituting the aggregate 1 5 8 is etched. Explain the situation. This figure is an enlarged view of a cross-section in which a part of the aggregate 1 5 8 is cut, and the aggregate 1 5 8 is configured by a large number of silicon scraps 6 2 being assembled and integrated. The particle size of the silicon waste 62 is, for example, about 1 m, and the same gap is formed between the silicon wastes 62. Further, in the present embodiment, the aggregate 15 8 is formed by a so-called cold press in which the silicon waste 62 is pressure-molded at room temperature without being heated. Therefore, the adjacent silicon scraps 62 are joined to each other by a point rather than a surface, and the gap formed between the silicon scraps 62 is continuous up to the ridge of the assembly 15 8. . Therefore, hydrofluoric acid 70, which is an etchant used for wet etching, passes through the gap between the silicon scraps 62 and the silicon located inside the assembly 1558. Reach up to 6 2. The arrived hydrofluoric acid 70 removes impurities and the like attached to the surface of the silicon scrap 62 existing inside the aggregate 1558.

According to the present invention, the cost required for silicon regeneration can be reduced. Specifically, the cost required to regenerate silicon for solar cells can be reduced to 100 yen / kg or less, and the cost can be reduced to less than half that of the background art.

More specifically, in the present invention, the recovered semiconductor material is heated to remove the contained phosphorus after moving it to the surface of the semiconductor material. That is, in order to recycle the semiconductor waste as a semiconductor material, the semiconductor waste is not melted. Therefore, the cost associated with phosphorus removal can be reduced as compared with the background technology in which semiconductor waste is melted and beam irradiation is performed. Furthermore, in the present invention, the thermal donor is actively used to inactivate boron contained in the semiconductor material, thereby creating a situation in which boron is pseudo-removed. Therefore, the cost can be reduced compared with the background art in which boron is removed by applying plasma to the molten semiconductor.

Furthermore, according to the method and apparatus for manufacturing a solar cell of the present invention, a solar cell can be manufactured at a low cost by using the above-described method for removing phosphorus and boron. Therefore, the price of the solar cell can be greatly reduced, and the use of the solar cell can be promoted.

Furthermore, according to the method for regenerating a semiconductor material of the present invention, the semiconductor materials are aggregated to form an aggregate, and then impurities contained in the semiconductor material are removed. Therefore, the cost of transporting semiconductor materials In addition to reducing the strikes, it is possible to suppress the scattering of semiconductor material collected in the form of particles or powder.

Furthermore, according to the present invention, the temperature at which the semiconductor material is heated in the gettering step of moving phosphorus to the surface of the semiconductor material is set to 90 ° C. or higher and 1200 ° C. or lower. By heating the semiconductor material in such a temperature range, it is possible to remove the phosphorus without melting the semiconductor material in a solid state. Therefore, compared with the conventional technology that melts the semiconductor material and removes the phosphorus, less heat energy is input. This reduces the cost of removing phosphorus.

Claims

The scope of the claims

1. In a method of reclaiming semiconductor material that removes phosphorus from recovered semiconductor material,

Heating the semiconductor material to move the phosphorus to the surface of the semiconductor material; and

A separation step of separating the phosphorus located on the surface of the semiconductor material from the semiconductor material.

2. The method for regenerating a semiconductor material according to claim 1, wherein, in the separation step, the phosphorus is separated from the semiconductor material together with an oxide covering the semiconductor material.

3. The method for regenerating a semiconductor material according to claim 1, wherein, in the separation step, the line is separated from the semiconductor material by etching or grinding.

4. Further, an oxidation process for removing boron contained in the semiconductor material by an oxidation treatment, or

2. The method for regenerating a semiconductor material according to claim 1, further comprising an inactivation step of inactivating the boron with a thermal donor.

5. In the heating step, the temperature at which the semiconductor material is heated is not less than 90 ° C. and not more than 120 ° C. The semiconductor material according to claim 1, Playback method.

6. In a method of reclaiming semiconductor material that inactivates boron contained in recovered semiconductor material,

A method for regenerating a semiconductor material, comprising a deactivation step of heating the semiconductor material and deactivating the boron by a thermal donor.

7. The semiconductor material according to claim 6, wherein, in the deactivation step, a temperature at which the semiconductor material is heated is not less than 300 ° C and not more than 500 ° C. How to play.

8. Further, an evaporation step of evaporating and removing phosphorus contained in the semiconductor material, or

7. The method for regenerating a semiconductor material according to claim 6, further comprising a separation step of separating the phosphorus that has moved to the surface of the semiconductor material by heat treatment from the semiconductor material.

9. A method of manufacturing a solar cell in which the collected semiconductor material is reused as a solar cell, wherein the phosphorus that has moved to the surface of the semiconductor material by heat treatment is separated from the semiconductor material. Or a deactivation step of deactivating poron contained in the semiconductor material. A method for manufacturing a solar cell, comprising:

10. The method for manufacturing a solar cell according to claim 9, wherein the semiconductor material is particulate silicon.

11. The method for manufacturing a solar cell according to claim 9, comprising both the removal step and the deactivation step.

1 2. In a semiconductor material recycling apparatus that removes phosphorus from recovered semiconductor material, by heating the semiconductor material, the heating apparatus moves the phosphorus to the surface of the semiconductor material;

A separation apparatus for separating the phosphorus located on the surface of the semiconductor material from the semiconductor material, and a semiconductor material recycling apparatus.

1 3. In the heating device, an oxide is formed on the surface of the semiconductor material,

13. The semiconductor material regeneration device according to claim 12, wherein the phosphorus is separated from the semiconductor material together with the oxide in the separation device.

14. The semiconductor material regeneration device according to claim 12, wherein the separation device separates the phosphorus from the semiconductor material by etching or grinding.

15. An oxidation apparatus for removing boron contained in the semiconductor material by an oxidation treatment, or an inactivation apparatus for inactivating the boron by a thermal donor. 12. A semiconductor material recycling apparatus according to item 12.

16. The temperature of the semiconductor material according to claim 12, wherein the temperature at which the heating device heats the semiconductor material is not less than 90 ° C. and not more than 12 00 ^. Playback device.

17. A semiconductor material regeneration device for inactivating boron contained in a semiconductor material, comprising: an inactivation device for heating the semiconductor material to inactivate the boron by a thermal donor. A semiconductor material recycling apparatus.

18. In the deactivation apparatus, the temperature at which the semiconductor material is heated is 30 ° C. or higher and 50 ° C. or lower. Semiconductor material recycling equipment.

1 9. Further, an evaporation apparatus for evaporating and removing phosphorus contained in the semiconductor material, or 18. The semiconductor material regeneration device according to claim 17, further comprising a separation device for separating the phosphorus that has moved to the surface of the semiconductor material by heat treatment from the semiconductor material.

2 0. A solar cell manufacturing apparatus for reusing a collected semiconductor material as a solar cell, wherein the phosphorus moved to the surface of the semiconductor material by heat treatment is separated from the semiconductor material, or An apparatus for producing a solar cell, comprising: an inactivation device for inactivating boron contained in a semiconductor material.

21. The apparatus for manufacturing a solar cell according to claim 20, wherein the semiconductor material is particulate silicon.

2. The solar cell manufacturing apparatus according to claim 2, further comprising both the removing device and the deactivating device.

2 3. A method for reclaiming semiconductor material by removing impurities from the collected semiconductor material and reusing it.

An assembling step of assembling the semiconductor materials to form an aggregate;

An impurity removal step of removing the impurities contained in the material in the aggregate state. A method for regenerating a semiconductor material, comprising:

24. The method of reclaiming a semiconductor material according to claim 23, wherein, in the assembly step, a large number of the semiconductor materials are formed into the aggregate by pressure molding.

25. The method for regenerating a semiconductor material according to claim 23, wherein in the assembly step, a large number of the semiconductor materials are used as the aggregate without using a binder.

26. The method for reclaiming a semiconductor material according to claim 23, wherein, in the assembly step, the aggregate including voids is formed therein.

27. The impurity removal step includes a step of etching the semiconductor material using a liquid,

The method for regenerating a semiconductor material according to claim 23, wherein the semiconductor material is immersed in the liquid in the state of the aggregate.

2 8. The impurity removal step comprises:

By heating the semiconductor material, the impurities contained in the semiconductor material are converted into the semiconductor. A heating step to move to the surface of the body material;

A step of immersing the semiconductor material in an aggregate state in a liquid to remove the impurities present on the surface of the semiconductor material, and

In the separation step, the liquid infiltrates into the aggregate through a gap formed in the aggregate, and the impurities present on the surface of the particulate semiconductor material constituting the aggregate are The method for regenerating a semiconductor material according to claim 23, wherein the method is removed.

2 9. The impurity removal step comprises:

The method for regenerating a semiconductor material according to claim 23, comprising a separation step of separating the phosphorus located on the surface of the semiconductor material from the semiconductor material.

3 0. The impurity removal step includes:

The method for regenerating a semiconductor material according to claim 23, further comprising an inactivation step of heating the semiconductor material and inactivating the boron by a thermal donor.

3 1. The impurity removal step includes:

The semiconductor material according to claim 23, comprising: a removing step of removing phosphorus from the semiconductor material; and an inactivating step of inactivating a polone contained in the semiconductor material. How to play.

3. The method for regenerating a semiconductor material according to claim 2, wherein the semiconductor material is particulate silicon.

3 3. A semiconductor material recycling device that removes impurities from the collected semiconductor material and reuses it.

An assembly device that aggregates the semiconductor materials to form an aggregate;

An impurity removal apparatus for removing the impurities contained in the semiconductor material in the aggregated state, and a semiconductor material recycling apparatus. '

3 4. A method of manufacturing a solar cell in which the recovered semiconductor material is reused as a solar cell, the assembly step of assembling the semiconductor material to form an aggregate;

An impurity removal step of removing the impurities contained in the material in the aggregate state. A method for manufacturing a solar cell, characterized by comprising:

35. A solar cell manufacturing apparatus that reuses the collected semiconductor material as a solar cell, and an assembly device that aggregates the semiconductor materials to form an aggregate;

An impurity removing device for removing the impurities contained in the semiconductor material in the aggregated state, and a solar cell manufacturing apparatus comprising: