TWI775612B - Reclamation of silicon carbide from abrasive slurry - Google Patents

Abstract

A method is provided for recycling silicon carbide. The method uses purification. A sustainable resource of silicon carbide is built by purifying and extracting wafer-cut material with the material life cycle increased. Firstly, silicon particles and magnetic materials scattered in slurry are removed by physical and chemical methods. Then, silicon carbide is extracted by purification. Thus, the used silicon carbide is effectively recycled and reused, instead of being disposed as waste. An powder of the purified silicon carbide material is subjected to X-ray diffraction analysis. The data shows that the purified silicon carbide powder has a 3C and 6H-SiC structure, and there is only silicon carbide in the powder without residual silicon and other component. The present invention successfully purifies and extracts silicon carbide powder, which can be used to develop drying, dehumidifying, cleaning, and energy-saving devices, equipment, and systems for solving environmental protection issue and improving energy efficiency.

Description

Method for purifying and recycling silicon carbide materials

The present invention relates to a method for purifying and recycling silicon carbide materials, in particular to a method for effectively and successfully purifying and extracting silicon carbide from waste wafer cutting materials by using physical and chemical separation processes, especially the purified silicon carbide powder is 3C and 6H-SiC structure and only contain silicon carbide without residual silicon and other components.

With the vigorous development of the optoelectronic semiconductor industry, various fields such as 5G, Internet of things (IOT), automotive, artificial intelligence (AI) chip applications are increasing day by day and the third-generation silicon carbide wafer semiconductor material application The rise has increased the basic demand for wafers. With the substantial increase in the supply of wafers, the waste of cutting materials after wafer cutting will also increase, causing industrial safety and environmental hazards. Silicon carbide is a common ceramic material with excellent wear resistance. It is widely used in the cutting, grinding and polishing processes of the semiconductor industry and the solar photovoltaic industry. In the process of cutting silicon ingots, silicon carbide is usually uniformly mixed in the cutting fluid and the additive is added simultaneously when the metal saw wire moves rapidly to cut silicon ingots. Wafer cutting material is a solid-liquid mixture obtained in the cutting process of converting silicon ingots into single wafers, wherein the liquid phase contains polyethylene glycol, polyethylene glycol (PEG) or diethylene glycol ( Diethylene glycol, DEG) and other organic solutions; the solid phase contains silicon carbide, silicon and a small amount of magnetic metals such as iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), nickel (Ni).

In Taiwan, wafer cutting materials from the optoelectronic semiconductor industry are classified as waste, and A series of treatment processes (eg: separation of solid and liquid) must be carried out prior to burial disposal; as the cost of burial treatment increases and the space available for burial treatment sites in Taiwan decreases, for the disposal of wafer cutting materials , burying is not the best way. Moreover, improper disposal methods will cause secondary pollution and have a huge impact on the environment. Therefore, the establishment of a recycling method for waste wafer cutting materials in the optoelectronic semiconductor industry is very important for the sustainable development of the industry and social responsibility. Minerals are limited resources and can also increase the material life cycle. According to previous studies, silicon, silicon carbide and ethylene glycol can be obtained from wafer cutting materials produced in the optoelectronic semiconductor industry through comparable regeneration techniques. Although magnetic sorting and flotation purification methods have been published in literature, the main By refining silicon wafers, only the silicon part is purified, so the resulting silicon content is very small. For this reason, considering that high-efficiency wafer cutting material recycling technology is still necessary in the optoelectronic semiconductor industry in China, if a large amount of silicon carbide can be recovered in the easiest way and the recovery rate can be increased, it will be possible to solve the problem of optoelectronics. The disposal of waste cutting materials in the semiconductor industry. Therefore, it is necessary to develop a set of inventions that can solve the related environmental problems and the technical shortcomings of the previous case.

The main purpose of the present invention is to overcome the above-mentioned problems encountered in the prior art and to provide a method that can effectively and successfully purify and extract silicon carbide powder from waste wafer cutting materials by using a physical and chemical separation process, and at the same time solve the problem of waste in the optoelectronic semiconductor industry. A method for the purification and recycling of silicon carbide materials for the disposal of wafer cutting materials.

Another object of the present invention is to provide a purified silicon carbide powder with a 3C and 6H-SiC structure and only containing silicon carbide without residual silicon and other components; its d ₅₀ particle size is 9.8 μm, which can be repeatedly applied to optoelectronics A method for purifying and recycling silicon carbide materials in the semiconductor field.

Another object of the present invention is to provide a method for purifying and recycling silicon carbide materials whose quality has a considerable potential to be sold as a commercial product in the market.

In order to achieve the above purpose, the present invention relates to a method for purifying and recycling silicon carbide materials, which at least comprises the following steps: a physical separation step: a solid-liquid mixture of a waste wafer cutting material is subjected to solid-liquid separation to obtain a solid-liquid mixture. Phase filter cake, the solid phase filter cake is dried to form granular waste wafer cutting materials with various particle sizes, and the solid phase particle size distribution of these granular waste wafer cutting materials is analyzed by sieving method ; and chemical separation step: mix the waste wafer cutting material after sieving and sorting with sodium hydroxide aqueous solution uniformly to form an alkaline solution and continue stirring at room temperature with a magnetic stirring device, so that the silicon dioxide in the alkaline solution After reacting with sodium hydroxide, sodium silicate (Na ₂ SiO ₃ ) is generated, and the magnetic material and silicon particles scattered in the waste wafer cutting material are removed, and then silicon carbide (SiC) is extracted from the reacted solution through purification. , to obtain purified silicon carbide powder.

In the above embodiments of the present invention, the solid-liquid separation method in the physical separation step is at least one of centrifugation, pressure filtration or filtration.

In the above-mentioned embodiment of the present invention, in the physical separation step, the sieving method is used to sample the unpurified solid-phase particle size distribution of the waste wafer cutting material in the range of 840-149 micrometers (μm), among which 68 ~72% of the waste wafer cutting material had solid particle size larger than 149 μm.

In the above-mentioned embodiment of the present invention, in the chemical separation step, the waste wafer cutting material after sieving and sorting is put into a glass reaction vessel, and the sodium hydroxide aqueous solution is gradually added to the glass reaction vessel at a rate of 20ml/min. The alkaline concentration was adjusted to 2M in a glass reaction vessel to form the alkaline solution.

In the above embodiments of the present invention, the magnetic stirring device in the chemical separation step is a magnet or a magnet.

In the above-mentioned embodiment of the present invention, in the chemical separation step, the magnetic stirring device removes the magnetic material dispersed in the waste wafer cutting material at a rate of 100 ml/min.

In the above embodiments of the present invention, the purification method in the chemical separation step is at least one of centrifugation, filtration or drying.

In the above-mentioned embodiment of the present invention, the silicon carbide powder has a 3C and 6H-SiC structure, and the powder only contains silicon carbide without residual silicon and other components.

In the above embodiments of the present invention, the d ₅₀ particle size of the silicon carbide powder is 9.8 μm.

s1: Physical separation step

s11~s13: Substeps

s2: chemical separation step

s21~s25: Substeps

FIG. 1 is a schematic diagram of the process of purifying and extracting silicon carbide from waste wafer cutting materials according to the present invention.

Fig. 2 is a particle size distribution diagram of the three-repeat analysis of the solid phase particles of the waste wafer cutting material of the present invention.

Fig. 3 is a photograph of the experimental flow of the present invention for purifying silicon carbide.

Fig. 4 is a graph showing the particle size distribution of the purified silicon carbide powder of the present invention.

Fig. 5 is an X-ray diffraction analysis diagram of the purified silicon carbide powder of the present invention.

Please refer to Figures 1 to 5, which are a schematic diagram of the process of purifying and extracting silicon carbide from the waste wafer cutting material of the present invention, and the particle size distribution diagram of the three-repeat analysis of solid phase particles of the waste wafer cutting material of the present invention. , the photo of the experimental process of the purified silicon carbide of the present invention, the particle size distribution curve of the purified silicon carbide powder of the present invention, and the X-ray diffraction analysis diagram of the purified silicon carbide powder of the present invention. As shown in the figure: The present invention is a method for purifying and recycling silicon carbide materials. It uses physical (sieving) and chemical (adding alkaline solution) separation processes to remove magnetic materials and silicon carbide scattered in waste wafer cutting materials. particles.

The proposed method contains at least the following steps:

Physical separation step s1: solid-liquid separation is performed on the solid-liquid mixture of a waste wafer cutting material, and a solid-phase filter cake is obtained by at least one solid-liquid separation method among centrifugation, pressure filtration or filtration. The solid phase filter cake is dried to form granular waste wafer cutting materials with various particle sizes. In sub-step s12, the solid phase particle size distribution of the granular waste wafer cutting materials is analyzed by sieving method. , as in sub-step s13.

Chemical separation step s2: Mix the waste wafer cutting material after the sieving and sorting is completed with the sodium hydroxide aqueous solution to form an alkaline solution, such as sub-steps s21 and s22, use a magnetic stirring device with an ultrasonic oscillator at room temperature. Stirring continuously in the alkaline solution makes the silicon in the alkaline solution react with sodium hydroxide to generate sodium silicate (Na ₂ SiO ₃ ), and remove the magnetic material and silicon particles scattered in the waste wafer cutting material, such as sub-steps s23, and then extract silicon carbide (SiC) from the reacted solution through at least one purification method of centrifugation, filtration or drying to obtain purified silicon carbide powder, as shown in sub-steps s24 and s25; wherein, the magnetic stirring device is Magnet or magnet. In this case, a new method for purifying and recycling silicon carbide materials is formed by the above disclosed process.

The following examples are only examples for understanding the details and connotations of the present invention, but are not intended to limit the scope of the patent application of the present invention.

When used, in a specific implementation, the solid-liquid mixture of the waste wafer cutting material of the optoelectronic semiconductor industry used in this embodiment is obtained from an environmental protection company. The original wafer cutting waste mud is in the form of a black solution. The solid content is 40~50wt%; in this experiment, a plate-and-frame filter press was used for solid-liquid separation, the liquid filtrate was cutting oil, and the solid-phase filter cake was black fine sand after drying. After the solid-liquid separation, the solid-phase filter cake of the waste wafer cutting material is dried in a rotary container, and after completion, there are granular waste wafer cutting materials of various particle sizes.

The sieving rule is used to analyze the solid phase particle size distribution of granular waste wafer cutting materials. As shown in Figure 2, the black bar is the first sieving particle size analysis, and the red bar is the second The second sieving particle size analysis, the blue bar is the third sieving particle size analysis. As shown in the figure, the particle size distribution range of the unpurified samples was 840~149 microns (μm), and 68~72% of the samples had a particle size larger than 149 μm. The moisture content of the sample was measured by infrared moisture meter. 5 grams of the sample was placed in the machine, and dried at 110 °C until there was no weight change at a constant weight. The measured moisture content was 8.52%.

The present invention establishes a key technology for purifying and extracting silicon carbide from waste wafer cutting materials. The experimental steps for purifying silicon carbide are shown in Figure 1. After the waste wafer cutting materials are screened and sorted, the waste wafers with a particle size of less than 149 μm are cut. The material was put into a glass conical flask for experiment, and the sodium hydroxide aqueous solution was gradually added to the glass reaction vessel at a rate of 20ml/min to adjust the alkaline concentration to 2M to form an alkaline solution, and the optimal stirring speed was 300rpm. The alkaline solution is passed through a magnetic stirring device to remove the magnetic material scattered in the waste wafer cutting material at a rate of 100ml/min. At the same time, the silicon in the alkaline solution will react with sodium hydroxide to form sodium metasilicate ( Equation 1), the silicon particles are removed from the waste wafer cutting material. Silicon carbide can then be obtained by centrifuging, filtering or drying the liquid.

Si+H ₂ O+2NaOH→Na ₂ SiO ₃ +2H ₂ (Formula 1)

Carry out property analysis of waste wafer cutting materials and silicon carbide materials: the present invention first uses an infrared moisture meter (AD-4715, A&D Co., Ltd., Japan) to test the moisture content of waste wafer cutting materials; The samples after solid-liquid separation of silicon carbide were extracted, and the crystal phase was identified by X-ray powder diffractometer (D8 ADVANCE, Bruker, USA), in order to confirm whether the content of single crystal silicon changed before and after alkali washing; in addition, after sieving And the samples after alkali washing solid-liquid separation were also quantitatively analyzed by X-ray fluorescence analyzer (S2 Ranger, Bruker, USA).

[Experimental Results]

Appearance of silicon carbide: First of all, in order to identify the purification result of silicon carbide, the color of the experimental sample must be visually inspected. The experimental process of purifying silicon carbide is shown in Figure 3. Take 100 grams of the sieved and sorted solid phase sample and mix it with an aqueous sodium hydroxide solution to form an alkaline solution and continue stirring at room temperature with a magnet. Before stirring, the sample settles on the bottom of the bottle. As shown in Figure 3 (1), the color of the alkaline solution in the glass conical flask is dark black at first, and the reaction starts when the stirring time is about 20 minutes, and there is bubbling. Heat is generated and released. At this time, the temperature in the bottle is about 60~70°C, as shown in Figure 3 (2) and (3); after continuing to stir for about 10 minutes, the temperature begins to drop, and the bubbling tends to stop. , as shown in Figure 3 (4), the alkaline solution turns green, the silicon in the alkaline solution reacts with sodium hydroxide to generate sodium silicate, and the fine silicon carbide powder can be purified.

It is inferred from the above that the overall experimental time is about half an hour. The pH value of the alkaline solution was measured before and after the reaction. When comparing the pH value before and after the reaction, it was found that the pH value decreased slightly after the reaction; The radical ions react with the silicon to produce metasilicate ions, so a decrease in the concentration of hydroxide ions in the solution results in a drop in pH. In order to maintain the good dispersibility of the solution for efficient experiments, the whole cup of the solution was placed in an ultrasonic shaker in subsequent experiments, and the particles in the solution were suspended without precipitating at the bottom by continuous shaking. After the experiment is over, a centrifuge is used for solid-liquid separation, and the bottom precipitated solid is obtained as the purified silicon carbide powder. The regeneration efficiency of silicon carbide produced by this purification technology depends on the amount of waste wafer cutting material and silicon carbide collected in the reaction vessel. After this experiment, the yield of silicon carbide is about 90.2%. On the wall of the reaction vessel, its proportion is about 9.8%.

Particle size distribution of silicon carbide: Figure 4 shows the particle size distribution curve of purified silicon carbide powder. The volume distribution is within a certain particle size range, and the proportion of each particle size volume of the sample in the total volume is expressed as a percentage (left vertical axis); while the cumulative volume curve is the sum of the particle volume percentages in all size ranges, and the curve trend will gradually approach 100% as the particle size increases (right vertical axis). As shown in Figure 4, the d ₁₀ , d ₅₀ and d ₉₀ values can be marked on the X-axis (particle size) where the X-axis and the right Y-axis intersect at the cumulative volume curve values of 10%, 50% and 90%, so 10%, 50% and 90% of the size of the purified silicon carbide particles are about 5.7 μm, 9.8 μm and 15.2 μm, respectively. In view of the particle size of silicon carbide abrasives, the application range of the optoelectronic semiconductor industry is between 5 and 25 μm, and the average diameter is 15 μm. It can be seen that, by the regeneration technology established by the present invention, the purified silicon carbide powder can be converted into a grinding material with a particle size equivalent to the original material and can be reused.

X-ray diffraction analysis of purified silicon carbide: The crystal relative chemical composition of the purified silicon carbide powder can be obtained by XRD. Figure 5 shows the X-ray diffraction pattern of the purified silicon carbide powder. This X-ray diffraction analysis image shows that the purified silicon carbide powder is of 3C and 6H-SiC structure, and the powder only contains silicon carbide without residual silicon and other components.

It can be seen from the above experimental method that the present invention can effectively and successfully purify and extract silicon carbide powder by utilizing the physical and chemical separation process. It is 3C and 6H-SiC structure and only contains silicon carbide without residual silicon and other components; its d ₅₀ particle size is 9.8μm, which can be repeatedly used in the field of optoelectronic semiconductors. The quality of the silicon carbide produced by the purification method of the present invention has considerable potential and can be sold on the market as a commercial product. The present invention establishes the regeneration technology for high-efficiency purification of silicon carbide from effective wafer cutting materials, can recover a large amount of silicon carbide by the simplest method, and improves the recovery ratio, which is very useful for the extraction of silicon carbide from waste wafer cutting materials in the optoelectronic semiconductor industry. It can help solve the environmental problems of waste wafer cutting materials in the optoelectronic semiconductor industry, increase the life cycle of secondary resources, reduce the demand for imported primary resources, avoid the development of natural resources, reduce carbon dioxide emissions, and reduce the energy consumption of industrial waste. Dispose of properly and efficiently. The silicon carbide extracted by the purification technology of the present invention can be used for the research and development of drying, dehumidifying, clean and energy-saving components, equipment and systems, so as to solve the environmental protection problems to be solved by the country and the industry and improve the efficiency of energy use.

To sum up, the present invention is a method for purifying and recycling silicon carbide material, which can effectively improve various shortcomings of conventional methods, and can effectively and successfully purify and extract silicon carbide powder by using the physical and chemical separation process, while solving the waste wafer in the optoelectronic semiconductor industry. There is a problem with the disposal of cutting materials, and the purified silicon carbide powder has 3C and 6H-SiC structures, and only contains silicon carbide without residual silicon and other components; its d ₅₀ particle size is 9.8μm, which can be repeatedly used in the field of optoelectronic semiconductors. The quality of the silicon carbide produced by the purification method has considerable potential and can be sold in the market as a commercial product, so that the production of the present invention can be more advanced, more practical, and more in line with the needs of users, which has indeed met the requirements of the invention patent application. The requirements are to file a patent application in accordance with the law.

However, the above are only preferred embodiments of the present invention, and should not limit the scope of implementation of the present invention; therefore, any simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the description of the invention , shall still fall within the scope covered by the patent of the present invention.

s1: Physical separation step

s11~s13: Substeps

s2: chemical separation step

s21~s25: Substeps

Claims (7)

A method for purifying and recycling silicon carbide materials, which at least comprises the following steps: a physical separation step: performing solid-liquid separation on a solid-liquid mixture of a waste wafer cutting material to obtain a solid-phase filter cake; After the cake is dried, granular waste wafer cutting materials with various particle sizes are formed, and the solid-phase particle size distribution of these granular waste wafer cutting materials is analyzed by a sieving method. The solid-phase particle size distribution range of the purified waste wafer cutting material is 840-149 micrometers (μm), and 68-72% of the solid-phase particle size of the waste wafer cutting material is larger than 149 μm; and Chemical separation step: After sieving and sorting, the waste wafer cutting material with a particle size of less than 149 μm is evenly mixed with an aqueous sodium hydroxide solution to form an alkaline solution, which is continuously stirred at room temperature with a magnetic stirring device to make the alkaline solution. The silicon and sodium hydroxide reacted to generate sodium silicate (Na ₂ SiO ₃ ), the magnetic material and silicon particles scattered in the waste wafer cutting material were removed, and then silicon carbide was extracted from the reacted solution by means of purification (SiC), obtain purified silicon carbide powder, the silicon carbide powder is 3C and 6H-SiC structure, the powder only contains silicon carbide and has no residual silicon and other components. According to the method for purifying, recycling and reusing silicon carbide materials as described in item 1 of the scope of the patent application, the solid-liquid separation method in the physical separation step is at least one of centrifugation, pressure filtration or filtration. According to the method for purifying, recycling and reusing silicon carbide materials as described in item 1 of the scope of the patent application, wherein, in the chemical separation step, the waste wafer cutting materials after the sieving and sorting are put into a glass reaction vessel, The aqueous sodium hydroxide solution was gradually added to the glass reaction vessel at a rate of 20 ml/min to adjust the alkaline concentration to 2M to form the alkaline solution. Purification and recycling of silicon carbide materials according to item 1 of the scope of the patent application The method, wherein in the chemical separation step, the magnetic stirring device is a magnet or a magnet. According to the method for purifying and recycling silicon carbide material as described in item 1 of the scope of the application, wherein in the chemical separation step, the magnetic stirring device removes the disperse in the waste wafer cutting material at a rate of 100ml/min. Magnetic material. According to the method for purifying and recycling silicon carbide material as described in item 1 of the claimed scope, wherein, the purification method in the chemical separation step is at least one of centrifugation, filtration or drying. According to the method for purifying and recycling silicon carbide material as described in item 1 of the claimed scope, the d50 particle size of the silicon carbide powder is 9.8 μm.

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