KR100823666B1 - Device and method for recycling silicon sludge - Google Patents

Abstract

A system and a method for recycling waste silicon sludge are provided to effectively cope with shortage and sharp price rise of a silicon raw material and increase national industrial competitiveness of related industries in the long term basis by regenerating silicon from waste silicon sludge. A system and a method for recycling waste silicon sludge comprises: a mixing part(20) for mixing a diluent with waste silicon sludge; a magnetic cleaning part(30) for separating and removing magnetic impurities from the waste silicon sludge mixed with the diluent using a magnet formed longitudinally along the direction perpendicular to a flow direction of the waste silicon sludge mixed with the diluent while flowing the waste silicon sludge that has been mixed with the diluent in the mixing part; a chemical cleaning part(40) adding a chemical sealing agent to the waste silicon sludge that has been magnetically cleaned in the magnetic cleaning part to clean the waste silicon sludge; and a solid-liquid separating part(50) for performing a solid-liquid separation process of the waste silicon sludge that has been chemically cleaned in the chemical cleaning part to separately extract a solid component from the waste silicon sludge, wherein the diluent is deionized water, the chemical cleaning agent comprises an acid, and a decanter, a disk type centrifuge or a filter pres is used as the solid-liquid separating part.

Description

Waste silicon sludge recycling apparatus and method {DEVICE AND METHOD FOR RECYCLING SILICON SLUDGE}

The present invention relates to a waste silicon sludge recycling apparatus and method, and more particularly, to a waste silicon sludge recycling apparatus and method capable of recycling high purity silicon with excellent efficiency.

Polycrystalline silicon (polysilicon) is made by refining quartz or sand. Polysilicon having a purity of 6N (99.9999%) or more is used as a raw material (SoG-Si) of a solar cell substrate, and polysilicon having a purity of 11N or more is used as a single crystal raw material (EG-Si) for semiconductor wafer manufacturing. Polysilicon manufacturing industry is directly related to industries such as fine chemicals / materials, optical communication, and organosilicon in addition to semiconductor and solar power generation.

At present, the supply shortage of silicon raw materials is seriously increasing, resulting in a surge in the price of silicon raw materials. Therefore, efforts to secure smooth supply and demand of silicon raw materials have emerged as an issue in related industries.

On the other hand, in recent years, the interest of renewable energy is increasing due to high oil prices and increasing interest in environmental protection. By 2050, about half of the world's energy consumption will be generated by renewables, with 50% of that being generated by solar power. Therefore, for the stable supply and demand of energy in the future, continuous research and development of solar power is required.

As of 2005, the solar cell market is about 37% of the total silicon. As of 2005, polysilicon production is 29,100 tons annually, of which about 29% is solar cell, producing 8,500 tons. In 2005, the total demand for polysilicon for solar cells was 16,500 tons, with the remainder being filled with by-products such as inventory and scrap from semiconductor silicon manufacturing. The share of solar cells in polysilicon production is expected to rise from 29% in 2005 to 40% in 2007 and 69% in 2010.

Due to the rapid development of the photovoltaic industry, the shortage of polysilicon is intensifying around the world, and price spikes and shortages are expected to continue for a long time after 2010.

However, waste silicon sludge from various sources generated in semiconductor manufacturing processes, etc., is mostly collected and reclaimed on a large scale, synthesized from waste silicon sludge into silicon compounds, or recycled to other uses such as construction raw materials. .

Therefore, various research efforts have been made to recover waste silicon sludge from various sources generated in a semiconductor manufacturing process and the like with high purity silicon.

The present invention has been submitted in order to solve the above problems, and an object of the present invention is to recover silicon from waste silicon sludge to effectively cope with the shortage of silicon raw material and the price increase, and in the long term, the national industrial competitiveness of related industries. The purpose is to increase.

It is another object of the present invention to provide a regeneration apparatus and method capable of regenerating high purity and high efficiency in regenerating silicon from waste silicon sludge.

In order to achieve the above object, the present invention, the mixing portion for mixing the diluent to the waste silicon sludge; A magnetic cleaning unit for separating and removing magnetic impurities by applying a magnetic force to the waste silicon sludge mixed with the diluent in the mixing unit; A chemical cleaner for cleaning by adding a chemical cleaner to the waste silicon sludge that has been self-cleaned by the magnetic cleaner; And a solid-liquid separator separating and extracting solid phase by solid-liquid separation of the waste silicon sludge chemically washed in the chemical cleaning unit.

 Preferably, further comprising a collecting unit for collecting the solid phase from the waste silicon sludge, wherein the mixing unit mixes the diluent to the waste silicon sludge collected in the collecting unit.

Preferably, the method further includes a melting part for heating and removing impurities by melting waste silicon sludge separated and extracted in the solid-liquid separation part.

Preferably, it further comprises a drying unit for drying the waste silicon sludge between the solid-liquid separator and the molten portion.

In addition, the present invention, the mixing step of mixing the diluent to the waste silicon sludge; A magnetic cleaning step of separating and removing magnetic impurities by applying a magnetic force to the waste silicon sludge which has passed through the mixing step; A chemical cleaning step of adding and cleaning a chemical cleaner to the waste silicon sludge which has undergone the self-cleaning step; And solid-liquid separation step of separating and extracting solid phase by solid-liquid separation of the waste silicon sludge, which has undergone the chemical cleaning step, to provide waste silicon sludge regeneration method.

According to the above configuration, the present invention can effectively cope with the shortage of silicon raw material and the price increase by regenerating silicon from waste silicon sludge, and in the long run, it is possible to increase the national industrial competitiveness of related industries.

In another aspect, the present invention can provide a regeneration apparatus and method that can be regenerated in high purity and high efficiency in the regeneration of silicon from the waste silicon sludge.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a result of comparing and analyzing the generation rate of waste silicon sludge generated during semiconductor wafer manufacturing.

The 12-inch wafer thickness was estimated at 837 microns and the 8-inch wafer was 725 microns or 800 microns.

69% of the ingot body is obtained from the original polysilicon and the remaining 31% is removed with waste silicon sludge.

This 31% contains 3% of silicon lost due to outer grinding.

In addition, in order to divide the pulled up ingot into a size that can be processed in the next step, cutting is performed, and the length is roughly 30 cm to 50 cm in circumference (cylindrical). At this time, the top and tail generated when pulling up are cut and removed, where 5% and 13% of silicon is lost, respectively.

In addition, after growing the ingot, silicon crystals are present in the crucible, which causes 10% silicon loss. If they are removed from the crucible wall or floor, they may remain and the impurities may be contaminated.

Next, 17.2% of silicon is lost in the sawing process. In the sawing process, it was estimated to be 200 microns considering the saw thickness of 160 microns and the vibration fraction 40 microns.

Next, 5.2% of silicon is lost in the chemical and mechanical polishing CMP process. Waste sludge in the CMP process was assumed to be 10% loss in the wafer.

Next, a backgrinding process of the silicon wafer is performed. The backgrinding process is a process of removing unnecessary film on the back side of the wafer and cutting off the thick back side more than necessary to reduce the resistance and improve the thermal conductivity. In the backgrinding process, 30.0% silicon is lost. The thickness of the wafer after the backgrinding process was assumed to be 250 microns.

Therefore, since silicon amounting to 30% of the total input amount from the polysilicon loading to the wafer dicing process is generated as waste silicon sludge in the backgrinding, it may be fully recognized that the waste silicon sludge needs to be recycled.

The thickness of the wafer mainly used in the semiconductor device and photovoltaic industry is based on 800㎛ / 300㎛, and the package uses about 275㎛ for wafer and 125㎛ for flash memory card, credit card, etc. As a result, more waste silicon sludge is expected.

2 is a view schematically showing the overall configuration of the waste sludge recycling apparatus according to the first embodiment of the present invention, Figure 3 is a schematic view of the overall configuration of a waste sludge recycling apparatus according to a second embodiment of the present invention more preferred Figure showing.

As shown, the waste sludge recycling apparatus according to the first embodiment of the present invention includes a mixing section 20, a self-cleaning section 30, a chemical cleaning section 40 and a solid-liquid separator 50.

In addition, the waste sludge recycling apparatus according to the second embodiment of the present invention, which is a more preferred embodiment, further includes a collecting unit 10, a drying unit 60, and a melting unit 70.

The collecting part 10 collects a solid phase from waste silicon sludge. For example, a decanter as shown in FIG. 4 may be used as the collecting unit 10. Since the structure and operation of the decanter is known in the art, a detailed description thereof will be omitted.

The waste silicon sludge supplied to the collecting unit 10, that is, the waste silicon sludge to be recycled in the present invention may correspond to various sources of sludge, but typically, the waste silicon sludge or the backgrinding process generated in the growth process described above. This corresponds to waste silicon sludge generated in, more typically waste silicon sludge generated in the backgrinding process.

As a process for manufacturing a silicon wafer, polishing or cutting is performed, in which a large amount of coolant such as Di Water (De Water) is used to prevent heat generation. Therefore, the waste silicon sludge occurs in a state in which silicon powder is mixed in the cooling liquid.

The collecting unit 10 separates solid suspended solids that are not dissolved in the cooling liquid by using centrifugal force, gravity, a filter, or the like.

In the collecting unit 10, a flocculant is used to increase the collecting efficiency. Prior to the collection, a flocculant is added to agglomerate the fine silicon powder so that it can be collected in the form of a solid silicon powder without being lost by being mixed with the liquid powder.

The collecting unit 10 adds a flocculant to the waste silicon sludge so that the hydrogen ion concentration PH is 5-6. In order to control the concentration of hydrogen ions, acid series such as nitric acid, sulfuric acid and hydrochloric acid are used. As a result of the cohesive test, hydrochloric acid showed good cohesiveness.

The mixing unit 20 mixes the diluent to waste silicon sludge collected in the form of silicon powder by the collecting unit 10. As the diluent, preferably DI water is used. In addition, alcohols, acids, alkaline liquids, and the like can be used.

The mixing concentration is mixed so that the mixing weight ratio of the waste silicon sludge to the diluent is 1: 0.1 to 0.15.

For example, 500 liters of the diluent is filled in the mixing tank while sensing with a load cell, and 50 kg of the silicon powder collected in the collecting unit 10 is mixed. Then, 500 liters of the diluent is filled while sensing with a load cell, and 50 to 100 kg of silicon powder collected from the collecting unit 10 is put therein. The silicon powder is stirred and circulated to ensure uniform mixing.

The magnetic cleaning unit 30 applies magnetic force to the waste silicon sludge mixed with the diluent in the mixing unit 20 to remove and remove magnetic impurities.

The self-cleaning unit 30 removes impurities mixed in the waste silicon sludge mixed with the dilution liquid by using a magnetic force. As compared with removing impurities from the solid waste silicon sludge, that is, silicon powder, the impurities can be greatly removed by mixing the diluents and then removing the impurities. As a result of removing impurities by the self-cleaning portion 30 of the present invention, magnetic, Fe, Cr, Co, and the like having strong magnetic properties can be reliably removed.

After pulverizing the silicon powder, when the impurities are removed with a magnet without mixing the mixed solution, the impurities were contaminated again without being removed, and it was confirmed that the optimal condition was to remove the impurities from the liquid phase.

In addition, the magnetic cleaning unit 30 removes the magnetic impurities using a magnet in a state in which the waste silicon sludge mixed with the diluent is flowed at a predetermined flow rate without removing impurities from the stationary waste silicon sludge, thereby removing impurities. Can be further increased.

In addition, the magnet is provided to be formed long along the direction perpendicular to the flow direction. That is, by disposing the magnet so that the flow direction and the longitudinal direction of the magnet is perpendicular to each other, it is possible to maximize the removal efficiency of impurities. As a result of experimenting with the magnet installed in the same direction as the flow direction, it was confirmed that the impurity removal efficiency was lowered.

In the chemical cleaning unit 40, a chemical cleaner, that is, a chemical agent, is added to the waste silicon sludge that is self-cleaned by the magnetic cleaner 30.

As a chemical cleaning agent, impurities are removed using acid, acid + ethanol, etc. in consideration of chemical properties of impurities. Since the acid is used as the cleaning agent in the chemical cleaning unit 40, the magnetic cleaning unit 30 must be installed at the front end of the chemical cleaning unit 40. This is because the stainless steel material surrounding the magnet does not have complete chemical resistance to hydrochloric acid or hydrofluoric acid.

The self-cleaning unit 30 primarily removes chromium, iron, cobalt, and the like to reduce the load of impurities, and then removes the impurities by a chemical method, so that the efficiency is excellent.

A baffle is preferably provided inside the cleaning tank so that the chemical cleaner and the waste silicon sludge are uniformly mixed. It is also equipped with concentration measuring equipment for uniform mixing. When using the level sensor, when mixed with the silicon powder, the sight glass (sight glass) is not visible, it is possible to prevent the clogging phenomenon by the deposition of the silicon powder.

Since the silicon powder in the dead zone is not cleaned and affects the concentration of impurities, it is necessary to design a drain line under the cleaning tank to minimize the dead zone. have.

The solid-liquid separation unit 50 performs solid-liquid separation of waste silicon sludge that has been chemically cleaned in the chemical cleaning unit 40, and extracts and extracts the solid phase.

As the solid-liquid separator 50, a decanter as shown in FIG. 4, a disc type centrifuge as shown in FIG. 5, and a filter press as shown in FIG. 6 may be used.

The drying unit 60 is a waste silicon sludge is dried using far infrared rays, etc. to completely remove the moisture present in the inside and outside of the silicon powder.

The molten portion 70 melts the waste silicon sludge, thereby heating and removing impurities using oxidation, evaporation, or the like. Low melting point impurities can be removed by evaporation, and carbon and oxygen can be removed by oxidation. In addition, a separate removal method may be prepared for each element in consideration of chemical and physical properties.

The melting part 70 melts the waste silicon sludge in an atmosphere of inert gas such as argon.

After melting, impurities are removed by one-way solidification.

4 is a view showing a decanter as an embodiment of the collecting unit 10 or the solid-liquid separator 50 of FIGS. 2 and 3.

The decanter applies centrifugal force to the waste silicon sludge introduced into the rotating cylinder (bowl, bowl) at high speed to rapidly settle the solid phase by using the specific gravity difference between the liquid and solid phase, and rotates while maintaining a constant speed difference with the rotating cylinder. The solids settled on the inner surface of the rotating cylinder by screw conveyor are transferred to the solids outlet and dehydrated and discharged from the conical inclined portion. The liquids are discharged to the liquids outlet through the spiral channel of the screw conveyor.

FIG. 5 is a diagram showing a disc type centrifuge as an example of the collecting portion 10 or the solid-liquid separator 50 of FIGS. 2 and 3.

Similar to the gravity sedimentation caused by the specific gravity difference of the material in the natural stationary state, the centrifugal sedimentation principle is applied even in the centrifugal gravity state to apply the ultracentrifugal force of 13,000 times the gravity to separate the sediment in 1 / 13,000 short time. Do it.

6 is a view showing a filter press as another embodiment of the collector 10 or the solid-liquid separator 50 of FIGS. 2 and 3.

The filter press performs pressurized dewatering filtration. The filter cloth acts as a filter so that the filtrate goes out through the unevenness of the filter plate. The filter plate and the filter cloth can be made of P.P., which has the advantage of no corrosion by acid.

1 is a result of comparing and analyzing the generation rate of waste silicon sludge generated during semiconductor wafer manufacturing.

2 is a view schematically showing the overall configuration of the waste sludge recycling apparatus according to the first embodiment of the present invention.

3 is a view schematically showing the overall configuration of a waste sludge recycling apparatus according to a second embodiment of the present invention.

4 is a view showing a decanter as an embodiment of the collecting portion or the solid-liquid separator of FIGS. 2 and 3.

5 is a view showing a disc type centrifuge which is an embodiment of the collecting portion or the solid-liquid separator of FIGS. 2 and 3.

6 is a view showing a filter press that is an embodiment of the collecting portion or the solid-liquid separator of FIGS. 2 and 3.

Claims (22)

Mixing unit for mixing the diluent to waste silicon sludge; A magnetic cleaning unit for separating and removing magnetic impurities from the waste silicon sludge mixed with the diluent by using a magnet which is formed to extend along the direction perpendicular to the flow direction while flowing the waste silicon sludge mixed with the diluent in the mixing unit; A chemical cleaner for cleaning by adding a chemical cleaner to the waste silicon sludge that has been self-cleaned by the magnetic cleaner; And And a solid-liquid separator for separating and extracting solid phase by solid-liquid separation of the waste silicon sludge chemically cleaned in the chemical cleaning unit. The diluent is DI water, the chemical cleaner comprises an acid, The decanter, disc type centrifuge or filter press is used as the solid-liquid separator, waste silicon sludge recycling apparatus. The method of claim 1, Further comprising a collecting unit for collecting the solid phase from the waste silicon sludge, the decanter is used as the collecting unit, The mixing unit waste silicon sludge regeneration apparatus, characterized in that for mixing the diluent to the waste silicon sludge collected in the collecting unit. delete The method of claim 2, The collecting unit adds a flocculant to the waste silicon sludge, and then collects a solid phase, Waste floc sludge regeneration apparatus, characterized in that the flocculant is hydrochloric acid. The method of claim 4, wherein The collection unit is a waste silicon sludge regeneration apparatus, characterized in that for adding the flocculant to the waste silicon sludge so that the hydrogen ion concentration is pH 5 ~ 6. delete delete The method of claim 1, Mixing weight ratio of the waste silicon sludge to the diluent is 1: 0.1 ~ 0.15 waste silicon sludge recycling apparatus, characterized in that. delete delete delete The method of claim 1, Waste silicon sludge regeneration apparatus characterized in that it further comprises a melting portion for heating the impurities to remove by using at least one of oxidation and evaporation by melting the waste silicon sludge separated and extracted in the solid-liquid separation unit under an atmosphere of inert gas. The method of claim 1, And a molten portion for melting the waste silicon sludge separated and extracted from the solid-liquid separator under an inert gas atmosphere to heat the impurities to react carbon and oxygen as impurities to remove the waste silicon sludge. delete delete delete delete The method of claim 1, Waste silicon regeneration apparatus characterized in that for recycling the waste silicon generated in the back grinding process of the silicon wafer. Mixing the diluent to waste silicon sludge; A self-cleaning step of separating and removing magnetic impurities from the waste silicon sludge passed through the mixing step by using a magnet which is formed to extend in a direction perpendicular to the flow direction while flowing the waste silicon sludge passed through the mixing step; A chemical cleaning step of adding and cleaning a chemical cleaner to the waste silicon sludge which has undergone the self-cleaning step; And It comprises a solid-liquid separation step of separating and extracting the solid phase by solid-liquid separation of the waste silicon sludge passed through the chemical cleaning step, The diluent is DI water, the chemical cleaner comprises an acid, The solid-liquid separation step of the waste silicon sludge recycling method characterized in that the solid phase is separated and extracted using a decanter, a disk type centrifuge or a filter press. The method of claim 19, A decanter, further comprising a collecting step of collecting solid phase from the waste silicon sludge, The mixing step is a waste silicon sludge regeneration method, characterized in that for mixing the diluent to the waste silicon sludge collected in the collecting step. delete The method of claim 19, And melting the waste silicon sludge that has undergone the solid-liquid separation in an atmosphere of an inert gas, thereby further heating the impurities to remove them using at least one of oxidation and evaporation.

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