WO2014126284A1

WO2014126284A1 - Silicon plate impurity removing method using water jet

Info

Publication number: WO2014126284A1
Application number: PCT/KR2013/001273
Authority: WO
Inventors: 한성욱
Original assignee: 주식회사 클린솔루션
Priority date: 2013-02-18
Filing date: 2013-02-18
Publication date: 2014-08-21

Abstract

In the context of the production of silicon ingots for solar cell, the present invention relates to technology for removing and reusing impurities from a silicon dissolution process by using a water jet in a site comprising the impurities. To this end, the silicon plate impurity removing method of the present invention entails immersion in water up to the upper surface of a silicon plate comprising impurities constituted by portions cut from a polycrystalline silicon block, and, in this state, removing the impurities by using a water jet; the water sprayed from the water jet comprising an abrasive.

Description

Impurity Removal Method of Silicon Plate Using Waterjet

The present invention relates to a method of cutting a silicon plate using a waterjet, and more particularly, to a method of removing a region containing impurities in a polycrystalline silicon plate by a waterjet.

High-purity silicon of 99.9999% (6N) or more is used for the manufacture of silicon wafers. The use of high-purity and expensive raw materials leads to an increase in the cost of solar power generation. This is a cause of weakening the competitiveness of photovoltaic power generation compared to the power generation method using fossil fuel. In order to reduce the cost of raw materials, photovoltaic wafer manufacturers are adopting a method of recovering and re-melting silicon scrap from the wafer fabrication process.

Silicon wafer melts silicon and grows crystal in a certain direction for a long time to process a round column-shaped ingot into a wafer, and inside the single crystal wafer and furnace (furnace) simply dissolve and solidify the silicon in various directions It can be classified into a polycrystalline wafer which is manufactured by processing a silicon block having a grain boundary. In particular, the silicon dissolved and solidified in the furnace for the manufacture of the polycrystalline wafer is distributed most of the impurities to the upper layer of the silicon block due to the thermal buoyancy due to the high temperature (about 1400 degrees) during melting. Therefore, the silicon ingot used to make the silicon wafer is cut off and removed about 2 to 3 cm of the upper part of the solidified silicon block, and the center silicon is used.

The furnace consists of a tower for supporting a silicon wafer, a pedestal supporting the wafer, a liner which is a case surrounding the tower and the pedestal, a gas supply pipe for transporting various gases, and a heater for maintaining a high temperature. In general, the furnace is of the form of a tube and a box. The heat treatment through the furnace can remove unwanted impurities or organic matter, and the material can be formed with a new phase through mutual diffusion between raw material samples.

1 illustrates a silicon block 100. 1 illustrates a shape in which a silicon block is cut on top of a silicon block using a diamond wire saw. Since the upper silicon plate 110 cut as described above contains a large amount of impurities, it cannot be recycled as it is, and thus the impurities remaining in the silicon surface and the deep portion should be removed.

In the conventional method of removing impurities of the cut silicon plate 110, compressed air, which is injected at a high pressure with contaminated impurities on a surface, carries an abrasive (Sic or zirconium) and sprays it on a contaminated portion to remove contaminants or to reduce the hardness of the abrasive. Grinding method is used to grind contaminated parts of silicon blocks by rotating grinding wheels containing high materials. Since the kinetic energy of the compressed air and the abrasive is relatively small, the above-described method increases time and cost in order to penetrate deeply into the silicon (about 3 cm thick) and remove impurities, making it impossible to use commercially.

The problem to be solved by the present invention is to propose a method for effectively removing the impurities present on the upper portion of the silicon plate.

Another problem to be solved by the present invention is to propose a method for preventing dust from scattering in the process of removing impurities.

To this end, the impurity removal method of the silicon plate of the present invention removes the impurity using a waterjet in the state submerged in the water to the upper surface of the silicon plate containing the impurity which is a part cut from the polycrystalline silicon block, and sprayed from the waterjet Water includes an abrasive.

In the above-described impurity removal method, the impurity removal method includes removing a surface of the silicon plate by using a waterjet in which a nozzle injection angle is set to a first injection angle, and a portion where impurities are aggregated in the silicon plate from which the surface is removed. And cutting using the waterjet in which the spray angle of the nozzle is set to the second spray angle.

The impurity removal method described above includes removing the surface of the silicon plate using a set spray angle, and removing a portion of the silicon plate from which the surface is removed by applying a physical impact.

The present invention effectively removes impurities present in the silicon plate, which is a part cut from the silicon block, according to the water jet. In addition, the present invention can be used commercially by reducing the time and cost by removing impurities contained in the silicon plate using a waterjet method.

In addition, by including an abrasive in the water sprayed from the waterjet and spraying has the advantage that the kinetic energy can be increased to cleanly etch the desired portion.

In addition, by filling the water to the extent that the silicon plate is immersed, by etching the silicon plate using a water jet, it is possible to prevent the dust generated during etching to scatter.

1 shows a polycrystalline silicon ingot,

2 illustrates a silicon plate obtained by cutting a polycrystalline silicon ingot by a diamond wire saw method according to an embodiment of the present invention.

3 is a flowchart illustrating a process of removing a region including impurities according to an embodiment of the present invention.

4 is a view illustrating a difference in injection angles injected from a nozzle of a waterjet according to an embodiment of the present invention.

5 illustrates a silicon plate from which regions containing impurities are removed according to an embodiment of the present invention.

The foregoing and further aspects of the present invention will become more apparent through the preferred embodiments described with reference to the accompanying drawings. Hereinafter will be described in detail to enable those skilled in the art to easily understand and reproduce through this embodiment of the present invention.

FIG. 2 illustrates a silicon plate cut from a silicon block including impurities according to an embodiment of the present invention. As described above, the silicon melted and solidified in the furnace for the manufacture of the polycrystalline wafer is distributed by dispersing impurities in the upper part of the silicon block due to thermal buoyancy due to the temperature at the time of melting. In addition, impurities are widely distributed in the upper surface layer of the silicon block, but as they move downward from the upper surface layer, the impurities are distributed only in specific portions. Therefore, when the upper surface layer of the cut silicon block is removed by about 2 mm, it is possible to identify a part where the impurities are aggregated. The present invention relates to a method for efficiently cutting a portion in which impurities are aggregated as described above by using a waterjet. Hereinafter, the upper portion of the silicon block having a relatively large amount of impurities in the silicon block will be described, but is not limited thereto. In other words, the lower part or the side of the silicon block in which the impurities are aggregated may be equally applied.

Waterjet is a technology that precisely cuts the material using water. Compresses the water pressure to ultra high pressure (3500 bar to 4000 bar) and converts the stop energy of the water into kinetic energy. It is a technology to precisely cut the material by intensive spraying. In general, water is compressed and sprayed to ultra high pressure in order to increase the cutting ability, and the abrasive is mixed and sprayed.

Waterjet is characterized by high energy and ultra high pressure processing, so it is high energy and ultra high pressure processing.Therefore, there is no deformation, residual stress, microcracking, or chemical deformation of the base material. It is suitable for cutting of materials or hard materials, non-ferrous materials, glass, resin, stone, etc., and excellent quality can be obtained.

In addition, the waterjet can be freely designed because it is not affected by the shape, and it is suitable for cutting complex products, and the post-processing time is significantly shortened by the excellent roughness and quality of the cut surface.

In addition, the waterjet is water-cutting, so it is suitable for cutting products with explosive, oxidizing and volatile properties. It is an environmentally friendly technology that does not generate dust or harmful gas during operation, and complements the disadvantages of conventional equipment. Safety can be secured.

Water jets are divided into pure water cutting and abrasive mixed cutting depending on the type of application. Pure water cutting is cut under the pressure of pure water and is easy to cut paper, wood, rubber, fiber, synthetic resin, etc. Abrasive mixed cutting is a method of cutting water and abrasives at a very high pressure, and is easy to cut tiles, marble, metals and nonmetals.

3 is a flowchart illustrating a method of removing impurities distributed in a silicon plate according to an embodiment of the present invention. Hereinafter, a method of removing impurities distributed in a silicon plate according to an embodiment of the present invention will be described in detail with reference to FIG. 3.

In operation S300, at least one surface of the top, bottom, and sides of the polycrystalline silicon block is cut to have a predetermined thickness by using a diamond wire saw method. Depending on the thickness of the impurities, the thickness cut by the diamond wire saw method may also vary.

As described above, the silicon block is generally cut to have a thickness of about 2 to 3 cm. However, the thickness to be cut may vary depending on the form or amount of impurities. For example, the cutting thickness of the upper part where impurities are concentrated by thermal stress is larger than the cutting thickness of the lower part or the side part. Hereinafter, the part cut from the silicon block is called a silicon plate. As described above, the central portion of the silicon block from which the top, bottom, and sides are removed does not contain impurities.

In step S302, the silicon plate is filled with enough water to immerse. That is, water is filled to the extent that the silicon plate is immersed in a container that performs a process of removing impurities distributed in the silicon plate. In this manner, dust generated when the silicon plate is etched using the waterjet can be prevented from scattering. To this end, a container that performs a process of removing impurities distributed in the silicon plate forms holes at a predetermined height to discharge water generated when etching the silicon plate using a waterjet.

In operation S304, the upper surface of the silicon plate is removed using a waterjet. As described above, impurities are unevenly distributed in the upper portion of the silicon plate, while the lower portion is aggregated. Thus, the waterjet is used to remove the top surface of the silicon plate. The waterjet widens the spray angle of the water sprayed from the nozzle to remove only the top surface. In other words, when the spray angle of the water sprayed from the nozzle is wide, the hydraulic pressure is relatively weak so that only the surface is removed (etched) without the silicon plate being cut. On the other hand, when the spray angle of water sprayed from the nozzle is narrow, the hydraulic pressure is relatively high to cut the silicon plate. In step S302, only the surface of the silicon plate has to be removed, thereby widening the spray angle of the water sprayed from the nozzle.

4 illustrates an injection angle of water injected from a nozzle according to an embodiment of the present invention. 4 illustrates a case where the spray angles of the water sprayed from the nozzles are wide (a) and narrow (b).

In step S306, the portion of the silicon plate from which the top surface is removed is cut by using a waterjet. As described above, when the surface of the silicon plate is removed by a predetermined thickness, the parts where the impurities are aggregated can be known. Therefore, the injection angle of the water sprayed from the nozzle is narrowed to cut off the portion where the impurities are aggregated. Of course, if the part where the impurities are aggregated in the silicon plate is not confirmed, the step S304 is performed again.

As described above, the present invention proposes a method of removing or cutting the surface of the silicon plate by adjusting the spray angle of water sprayed from the nozzle of the waterjet.

Of course, it can be removed by applying pressure to a part where the impurities are agglomerated in the silicon plate in step S304. For example, a portion of the silicon plate in which impurities are aggregated may be removed by applying an impact using a hammer or the like. The portion where the impurities are aggregated can be separated from the portion composed of silicon even with a small impact.

5 illustrates before and after removing a portion containing impurities using a waterjet according to an embodiment of the present invention.

FIG. 5 illustrates a part containing impurities on one side of the silicon plate, and FIG. 5 illustrates a process in which the part containing impurities is removed using a waterjet. have. As described above, it can be seen that the cutting surface is clean and the cutting time is shortened by removing the portion containing impurities using the waterjet.

In addition, the present invention can sense an area containing impurities using a sensor, and automatically cut an area containing impurities using the sensed information. For this purpose, the sensor should be able to distinguish between the region containing impurities and the region containing no impurities, and generally distinguishes the color difference between the region containing impurities and the region containing no impurities.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. .

(Explanation of the sign)

100: silicon block, 110: silicon plate

Claims

The silicon is characterized in that the impurities are removed using a waterjet in a state submerged to the upper surface of the silicon plate containing impurities, which are parts cut from the polycrystalline silicon block, and the water sprayed from the waterjet contains an abrasive. How to remove impurities from the plate.
The method of claim 1, wherein the impurity removal method,

Removing the surface of the silicon plate using a waterjet in which the nozzle spray angle is set to the first spray angle;

And cutting the portion in which the surface of the silicon plate from which impurities have been aggregated by using a waterjet in which a nozzle spray angle is set to a second spray angle.
The method of claim 2, wherein the first injection angle is set relatively wider than the second injection angle.
4. The method of claim 3, wherein the thickness of the silicon plate removed at the first injection angle is 2 mm or more.
The method of claim 1, wherein the impurity removal method,

Removing the surface of the silicon plate using a set spray angle;

And removing a portion of the silicon plate from which the surface is removed by applying a physical impact to the portion where the impurities are agglomerated.