JP2013244547A - Recovery processing method and device for waste generated by cutting and polishing silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery processing method and device for waste generated by cutting and polishing a silicon wafer, the method and device being capable of effectively solving an environmental pollution problem while increasing an additional value of product.SOLUTION: A recovery processing device for waste generated by cutting and polishing a silicon wafer includes a processing tank 200, a gas storage tank 400, a filter tank 500, a solid-liquid separation unit 600, and a reverse osmosis processing unit 700. The processing tank 200 is a closed type container, stores a hydraulic fluid obtained by mixing a waste filter cake with an aqueous liquid, and includes a material supply port 210 provided at a position higher than a liquid level, an exhaust port 230 for sucking hydrogen, and a pumping hole placed adjacent to a bottom. The gas storage tank 400 is used to recover hydrogen generated in the processing tank 200. The filter tank 500 includes an expansion pipe 510. The expansion pipe 510 is extended into the processing tank 200 from the outside.

Description

  The present invention relates to a silicon wafer waste processing method and apparatus, and more particularly to a method for recovering waste generated by cutting and polishing a silicon wafer, which increases the added value of products and effectively solves environmental pollution problems. And an apparatus for the same.

  In the semiconductor chip and solar panel industry, the technology of cutting silicon ingots into silicon wafers (chips) of uniform thickness is one of the standard processes, and a special metal wire saw is used as a cutting tool. Hardened silicon carbide (SiC: carborundum) is used as an abrasive material, and mineral oils such as polyethylene glycol (PEG), diethylene glycol (DEG), and propylene glycol (PG) are used as cutting coolants. When reciprocating at high speed, silicon carbide is used as a medium to cut the silicon tip by increasing the cutting ability of the wire saw, and at the same time as cutting, a cutting fluid mainly composed of polyethylene glycol is sprayed to the cut site, thereby cooling applications In addition to being used for lubrication, By taking out the silicon debris and impurities resulting from the cutting grooves, performs wafer cutting process smoothly and stably, to allow conveniently the subsequent step.

  In the process of cutting / polishing silicon wafers, the cutting fluid sprayed and used on the cutting area takes out silicon waste, impurities and worn silicon carbide generated during cutting and continuously discharges them to the outside of the cutting area. Thus, a waste oil slurry having a very high particle concentration and turbidity is formed. Traditionally, many silicon wafer cutting factories in Taiwan treated these waste oils as waste or incinerated them with heavy oil and buried them. However, in either case, if a waste disposal contractor is requested to process at a high cost and the waste oil slurry is incinerated, a large amount of carbon dioxide is generated, which may adversely affect the environment. . Therefore, a treatment method that incinerates or fills the waste oil slurry generated after the wafer is cut and polished is not ideal.

  Traditionally, manufacturers outside of Taiwan collect cutting oil in waste oil slurry with a filtration device and usually perform solid-liquid separation with thin film technology, but this method can obtain some liquid recycled oil, silicon It can be recovered and reused when the wafer is cut and polished. However, this method generates a large amount of sludge (filter cake), but these sludges still contain reusable silicon carbide, silicon particles and polyethylene glycol, but they are not recovered and waste Therefore, serious environmental pollution problems may still occur. Therefore, when recovering reclaimed oil only by solid-liquid separation method, the economic profit is not ideal, and when filtering the waste oil slurry with a membrane, if the pretreatment is not good, the membrane pores are likely to be clogged, There is a possibility that the service life of the membrane is shortened and the cost is increased.

  In recent years, due to the rapid development of the solar energy industry, the supply and demand of silicon carbide has increased, resulting in a shortage of products, and the amount of polyethylene glycol used for lubrication and cooling has increased significantly and the cost has increased. Therefore, the manufacturer considers the impact on the cost and the environment, and in addition to recovering recycled oil from waste oil slurry, the manufacturer can generate and reduce waste by separating and recovering valuable silicon carbide and silicon particles from the filter cake. The total amount can be reduced and the cost of environmental pollution and treatment can be reduced.

  As a result, there is still no processing method that balances recovery costs and environmental conservation, is efficient, and is consistent with operating costs. In addition, by improving pollution prevention technology, it has been demanded to combine the economy and environmental protection and enhance industrial competitiveness.

The object of the present invention is to effectively prevent environmental pollution by reducing the generation of waste and reducing the recovery cost, and also separates by-products such as recycled oil and silicon carbide that can be recovered from the waste. Another object of the present invention is to provide a method for recovering waste generated by cutting and polishing a silicon wafer to be recovered.
Another object of the present invention is to provide an apparatus for recovering and treating waste generated by cutting and polishing a silicon wafer to improve the efficiency of the recovery process by preventing clogging of the film and extending the life of the film.

In order to solve the above-mentioned problem, a method for recovering waste generated by cutting and polishing a silicon wafer, firstly, a waste oil slurry generated by cutting and polishing the wafer is produced by squeezing and filtering silicon ( A step (A) of dehydrating a filter cake containing Si), silicon carbide (SiC), and residual cutting fluid mainly composed of polyethylene glycol (PEG) into the processing tank; and the processing tank A reaction agent is put into the mixture and mixed with the filter cake to produce a working fluid. The silicon and the reactant in the working fluid are catalyzed to react with solid silicon dioxide (SiO ₂ ) and gaseous hydrogen. (H) generating step (B), guiding the hydrogen in the processing tank to a compression storage device in a gas storage tank (C), utilizing a specific gravity separation method, (D) separating and recovering the silicon and silicon carbide from the working fluid diluted in mud concentration; and screening the working fluid of the silicon and silicon carbide; Separating the working fluid into solid silicon dioxide, liquid water, and polyethylene glycol (E), and the liquid water and polyethylene glycol can be reused after reverse osmosis treatment. And a step (F) of obtaining a recovered cutting fluid containing polyethylene glycol as a main component, and a method for recovering waste generated by cutting and polishing a silicon wafer is provided. .

  In the step (B), the reactant is preferably water.

  In the step (E), the solid-liquid separation is preferably performed by a circular plate-shaped UF membrane.

  In the step (F), the water recovered by reverse osmosis is preferably guided into the treatment tank and used as a catalyst agent in the step (B).

  After performing the step (F), it is preferable to remove residual water and waste oil from the liquid polyethylene glycol by a distillation method to obtain a reusable reclaimed oil.

  In the step (F), it is preferable to perform reverse osmosis treatment with an RO or NF membrane.

  In the step (B), it is preferable that pressurized gas is added and mixed in the processing tank to generate a working fluid.

  After performing the step (D), it is preferable to dry the sorted silicon and silicon carbide, and perform packaging and recovery.

  In the step (E), it is preferable to suck water and polyethylene glycol in the working fluid by a negative pressure suction force.

  A device for recovering waste generated by cutting / polishing silicon wafers, comprising a processing tank, a gas storage tank, a filtration tank, a solid-liquid separation unit, and a reverse osmosis processing unit, wherein the processing tank is a sealed container Contains the working fluid obtained by mixing the waste filter cake and aqueous liquid, and feeds the raw material supply port provided above the liquid level, the exhaust port for sucking hydrogen, and the pumping adjacent to the bottom. The gas storage tank is used for recovering hydrogen generated in the processing tank, the filtration tank has a telescopic tube, and the telescopic tube is external to the processing tank. And a movable suction port used to guide water, silicon dioxide, and polyethylene glycol liquid in the working fluid to the filtration tank is provided at the bottom end, and the solid-liquid separation unit is provided. Is composed of a circular plate-shaped UF membrane and is arranged in the filtration tank, a plurality of UF membranes, a liquid recovery pipe arranged in series and pivotally connected in series to the UF membrane, and the filtration A motor that is disposed outside the tank and that rotates the UF membrane around the liquid recovery pipe; and an oil pump that is used to suck the liquid in the liquid recovery pipe through the UF membrane, The reverse osmosis treatment unit is connected to a water discharge end of the oil pump, and separates and collects water and concentrated polyethylene glycol to obtain water that can be recovered and reused, and reclaimed oil mainly composed of polyethylene glycol. The reverse osmosis filtration device has a return water pipe, and the collected water is sucked into the treatment tank through the return water pipe, and waste generated by cutting and polishing silicon wafers is characterized in that Yield processing apparatus is provided.

  In the method and apparatus for recovering waste generated by cutting and polishing a silicon wafer according to the present invention, first, a catalyst agent mainly composed of water is mixed with a filter cake, and the filter cake is diluted to obtain a working fluid. After producing silicon dioxide and hydrogen by catalytic reaction with silicon powder, the hydrogen is sucked and collected, and then the specific gravity separation is performed with water to separate silicon carbide and the remaining silicon particles. Then, solid-liquid separation is performed, and the working fluid is separated into solid silicon dioxide, liquid water, and polyethylene glycol, and finally water and polyethylene glycol are separated. As a result, useful silicon particles, silicon carbide, silicon dioxide, and polyethylene glycol are recovered again from the sludge that was originally generated in the recovery process, reducing the amount of waste generated and solving problems when filling the waste. It generates industrial value hydrogen and enhances the added value of its use, reduces energy consumption and carbon dioxide emissions, and does not pollute the environment.

It is a flowchart which shows the collection | recovery processing method of the waste generated by the cutting | disconnection and grinding | polishing of the silicon wafer concerning one Embodiment of this invention. It is a schematic diagram which shows the collection | recovery system of the filter cake which concerns on one Embodiment of this invention. It is sectional drawing which shows the internal structure of the filtration tank which concerns on one Embodiment of this invention. It is sectional drawing which shows the circular plate-shaped UF membrane which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited thereby.

(First embodiment)
Please refer to FIG. As shown in FIGS. 1 to 3, the method for recovering waste generated by cutting and polishing a silicon wafer according to the first embodiment of the present invention includes the following steps (A) to (E).

  Step (A): First, the filter cake 100 that has been subjected to the compression dehydration process is put into the processing tank 200 from the raw material supply port 210. The processing tank 200 is in a hermetically sealed state, and the filter cake 100 is a wafer cutting waste produced by cutting and polishing the wafer, which is generated after initial squeezing filtration and is made of silicon (Si ), Silicon carbide (SiC), and residual cutting fluid mainly composed of polyethylene glycol (PEG).

  The wafer cutting waste of this embodiment is dehydrated by a plate-frame filter press, and the filter plate of the filter press machine is used to filter most of the solids in the wafer cutting waste. Then, after secondarily compressing with high-pressure air, a sludge-like filter cake is formed. This type of filter cake contains silicon powder (Si), silicon carbide (SiC) and impurities, and a small amount of cutting oil mainly composed of polyethylene glycol (PEG) remains. These compositions are reprocessed and collected and packaged.

Step (B): The reactant is put into the processing tank 200 by a pump. The reactant in the present embodiment is preferably a liquid containing moisture. Furthermore, since this liquid contains a small amount of fine bubbles, after the filter cake 100 that was originally sludge is diluted, a working fluid 300 containing bubbles and solids is generated, and the aforementioned fine bubbles are generated. Uses the Venturi effect to preliminarily mix the liquid and gas and then pump it into the processing tank 200 to accelerate the chemical reaction generated by the stirring of the liquid and the filter cake 100, and the weight in the filter cake 100 The remaining light oil and impurities, such as polyethylene glycol, are floated to the upper surface of the liquid surface by the buoyancy of the bubbles so that subsequent separation can be performed conveniently. Therefore, after a predetermined time has passed, the reactant in the hydraulic fluid 300 is catalytically reacted with the silicon powder to gradually produce solid silicon dioxide (SiO ₂ ) and gaseous hydrogen (H), and the chemical reaction formula is It can be represented by chemical formula (I).

(Chemical formula 1)
Si + 2H ₂ O = SiO ₂ (solid) + 2H ₂ (gas) (I)

  The reactant of the present embodiment is pumped from the diffuser hole 220 provided near the bottom of the processing tank 200, and the ratio of the liquid to the bubbles contained in the reactant is 3: 1. It is optimal and the liquid level of the working fluid 300 is preferably slightly lower than the raw material supply port 210 so that hydrogen can be temporarily stored.

  Step (C): After a predetermined time has passed, the hydrogen in the upper layer of the processing tank 200 is stored in a compressed state by being pumped into the gas storage tank 400 from the exhaust port 230, and the generated hydrogen is separately stored. It may be packaged and sold and the heat source may be reused.

  Step (D): Since the specific gravity of silicon particles and silicon carbide is higher than that of water (the specific gravity of silicon is 2.3 and the specific gravity of silicon carbide is 3.2), hydrogen (H) is contained in the treatment tank 200. When discharged from the working fluid 300, the silicon particles and silicon carbide remaining in the working fluid 300 can be further separated using a specific gravity separation method. In this embodiment, solid silicon carbide and silicon particles are sequentially precipitated at the bottom of the processing tank 200, and then discharged from the bottom raw material outlet 240 into the raw material sieve tank 250, dried, and sorted. Collected.

  Step (E): The silicon particle and silicon carbide working fluid 300 is selected and guided into the filtration tank 500 for solid-liquid separation. The filtration tank 500 of the present embodiment has a telescopic tube 510. The telescopic tube 510 is extended from the outside into the processing tank 200, and a conical suction port 520 is connected to the bottom end. The suction port 520 moves up and down according to the water level of the hydraulic fluid 300, and a fine screen (not shown) is provided at the opening at the bottom end. This fine screen is used to put liquids such as water, silicon dioxide and polyethylene glycol in the working fluid 300 into the filtration tank 500.

  A semi-submerged solid-liquid separation unit 600 is provided in the filtration tank 500. The solid-liquid separation unit 600 is preferably a circular plate-shaped UF membrane. Please refer to FIG. As shown in FIG. 4, the overall structure is such that a plurality of UF membranes 610 are connected in series to be horizontal and pivotally mounted on the liquid recovery pipe 620, and the liquid recovery pipe 620 is externally attached to the filtration tank 500 by a motor 630. The UF membrane 610 is driven around the center, and the other side uses the oil pump 640 to collect the liquid in the liquid recovery pipe 620 via the UF membrane 610, thereby the negative pressure suction force of the motor 630 The cutting fluid such as water and polyethylene glycol which are liquid in the working fluid 300 is filtered through the UF membrane 610 and sent out to the outside of the filtration tank 500. Solid matter such as fine impurities such as silicon dioxide that is solid remains in the filtration tank 500, and as the particle concentration of the solid matter in the filtration tank 500 continuously increases, the silicon dioxide and impurities are evaporated and dried. And can be reused as secondary building materials (for example, bricks, partition building materials, sidewalk blocks). As a result, the original working fluid 300 is separated into silicon dioxide that is solid and cutting fluid such as water and polyethylene glycol that are liquid.

  In this step, a scraping member 650 is hooked between the UF membranes 610 in order to extend the service life of the UF membranes. When the UF membrane 610 rotates, the scraping member 650 automatically scrapes off the sludge on the membrane surface, preventing dirt from accumulating on the membrane surface and closing the pores, thereby reducing the filtration rate of the aqueous liquid.

  Step (F): Liquid water and polyethylene glycol are subjected to reverse osmosis treatment by the reverse osmosis treatment unit 700. The reverse osmosis processing unit 700 may use an NF (Nano Filtration) membrane or an RO (Reverse Osmosis) membrane. In this embodiment, an RO membrane is used, and only water molecules are dialyzed through the pores of the membrane by using the RO membrane. Further, water and polyethylene glycol that have been separated from water and collected can be recovered and reused. An oily liquid with the main component is obtained. Here, the recovered water is sent into the processing tank 200 in step (B) via the return water pipe 710 and used as a catalytic agent for silicon powder, and the amount of water required for the processing tank 200 is reduced.

  Step (G): The above-mentioned liquid polyethylene glycol removes residual water and waste oil by a distillation method, and the concentrated polyethylene glycol is recovered after being measured by a turbidimeter to obtain a reusable reusable oil. To the oil storage tank 800. The recycled oil is packaged separately and then used in the wafer cutting / polishing process.

  Therefore, in the present invention, a catalyst agent mainly composed of water is mixed with the filter cake 100 (sludge) subjected to the pressure dewatering treatment, and the filter cake 100 is diluted to obtain a hydraulic fluid 300 having a low sludge concentration, and silicon. After generating powder and catalytic action to produce solid silicon dioxide and gaseous oxygen, the hydrogen is sucked and recovered. Subsequently, specific gravity separation is performed with water, and silicon carbide and residual silicon particles in the working fluid 300 are selected. Then, solid-liquid separation is performed with the UF membrane 610, and the working fluid 300 is separated to obtain solid dioxide. After separating into silicon and liquid water and polyethylene glycol, finally, it is separated into water and polyethylene glycol by the RO membrane. Thus, useful silicon particles, silicon carbide, silicon dioxide and polyethylene glycol can be recovered again from the sludge generated in the original recovery process. Therefore, it is not necessary to reduce the total amount of waste, landfill and dispose of waste, and obtain hydrogen having commercial value. Therefore, the present invention has high added value for use, energy consumption and carbon dioxide emission. The amount is small and does not pollute the environment.

As can be seen from the above, the method and apparatus for recovering waste generated by cutting and polishing a silicon wafer according to the present invention have the following advantages (1) to (3), unlike the prior art.
(1) The filter cake (sludge) that could not be reprocessed originally was first catalyzed by hydration to produce hydrogen, and the silicon carbide and silicon particles were separated by specific gravity separation, and the UF membrane and RO membrane were used. By separating the silicon dioxide, water and polyethylene glycol in the working fluid, and finally producing hydrogen, silicon particles, silicon carbide, silicon dioxide, water and polyethylene glycol that can be recovered and used, Increases the added value of collection and use, and the amount of waste such as waste left after processing is very small, so it consumes less energy and emits less carbon dioxide and does not pollute the environment.
(2) Before performing the solid-liquid separation step, the solid silicon carbide and silicon particles are separated by a specific gravity separation method to reduce the ratio of solids in the working fluid, and when performing the solid-liquid separation performed in the subsequent step, UF Delays clogging of dirt accumulated in the membrane, prevents the concentration of hydraulic fluid from increasing, prolongs the useful life of the membrane and reduces costs.
(3) A circular plate-shaped UF membrane used for solid-liquid separation can prevent a filter cake from being generated on the membrane surface by scraping when the membrane rotates. As described above, since the entire recovery processing efficiency can be increased and the life of the membrane can be extended, it is preferable in terms of recovery efficiency and cost.

  While the preferred embodiments of the present invention have been disclosed above, as may be appreciated by those skilled in the art, they are not intended to limit the invention in any way. Various changes and modifications can be made without departing from the spirit and scope of the present invention. Accordingly, the scope of the claims of the present invention should be construed broadly including such changes and modifications.

DESCRIPTION OF SYMBOLS 100 Filtration cake 200 Processing tank 210 Raw material supply port 220 Aeration hole 230 Exhaust port 240 Raw material discharge port 250 Raw material sieve tank 300 Working fluid 400 Gas storage tank 500 Filtration tank 510 Telescopic tube 520 Suction port 600 Solid-liquid separation unit 610 UF membrane 620 Liquid Recovery pipe 630 Motor 640 Oil pump 650 Scraping member 700 Reverse osmosis processing unit 710 Return water pipe 800 Oil storage tank

Claims (8)

A method for collecting and processing waste generated by cutting and polishing a silicon wafer,
First, a waste oil slurry generated by cutting and polishing the wafer is generated by squeezing and filtering, and a residual cutting fluid mainly composed of silicon (Si), silicon carbide (SiC), and polyethylene glycol (PEG), A step (A) of dehydrating the filter cake containing the solution into a processing tank;
Reactant is placed in the processing tank, mixed with the filter cake to produce a working fluid, the silicon in the working fluid and the reactant are catalyzed, and solid silicon dioxide (SiO ₂ ), Generating gaseous hydrogen (H) (B);
Guiding the hydrogen in the processing tank to a compression storage device in a gas storage tank (C);
(D) separating and collecting the silicon and the silicon carbide from the working fluid diluted in sludge concentration using a specific gravity separation method;
The step of separating the working fluid of the silicon and the silicon carbide, followed by solid-liquid separation by filtration through a membrane, and separating the working fluid into solid silicon dioxide, liquid water, and polyethylene glycol (E )When,
A silicon wafer comprising: a step (F) of obtaining water that can be reused after reverse osmosis treatment of the liquid water and polyethylene glycol, and a recovered cutting fluid mainly composed of polyethylene glycol. For recovering waste generated by cutting and polishing.   2. The method for recovering waste generated by cutting and polishing a silicon wafer according to claim 1, wherein in the step (B), the reactant is water.   The silicon wafer cut according to claim 1, wherein water recovered by reverse osmosis in the step (F) is guided into the processing tank and used as a catalyst agent in the step (B). -A method for recovering waste generated by polishing.   2. The silicon wafer according to claim 1, wherein after the step (F) is performed, residual water and waste oil are removed from the liquid polyethylene glycol by a distillation method to obtain a reusable reclaimed oil. A method for recovering waste generated by cutting and polishing.   2. The recovery of waste generated by cutting and polishing a silicon wafer according to claim 1, wherein in the step (B), a pressurized gas is added and mixed in the processing tank to generate a working fluid. Processing method.   2. The disposal generated by cutting and polishing the silicon wafer according to claim 1, wherein after the step (D) is performed, the sorted silicon and the silicon carbide are dried, packaged and collected. Collection processing method.   The method for recovering waste generated by cutting and polishing a silicon wafer according to claim 1, wherein in the step (E), water and polyethylene glycol in the working fluid are sucked by a negative pressure suction force. . A device for recovering and treating waste generated by cutting and polishing a silicon wafer comprising a processing tank, a gas storage tank, a filtration tank, a solid-liquid separation unit and a reverse osmosis processing unit,
The processing tank is a hermetically sealed container that stores a working liquid obtained by mixing a waste filter cake and an aqueous liquid, and a raw material supply port provided at a position higher than the liquid level, and an exhaust for sucking in hydrogen. Having a mouth and a pumping hole adjacent to the bottom;
The gas storage tank is used to recover hydrogen generated in the processing tank,
The filtration tank has an expansion / contraction tube, and the expansion / contraction tube is extended from the outside into the treatment tank and used to guide water, silicon dioxide, and polyethylene glycol liquid in the working fluid to the filtration tank. A movable suction port is provided at the bottom end,
The solid-liquid separation unit is configured by a circular plate-shaped UF membrane and disposed in the filtration tank, and a plurality of UF membranes and a series of the UF membranes connected in series and horizontally arranged to be pivotally attached. A pipe, a motor that is arranged outside the filtration tank and rotates the UF membrane around the liquid recovery tube, and an oil pump used for sucking the liquid in the liquid recovery tube through the UF membrane, Have
The reverse osmosis treatment unit is connected to a water discharge end of the oil pump, separates water and concentrated polyethylene glycol, collects and recycles water, and recycled oil mainly composed of polyethylene glycol. The reverse osmosis filtration device has a return water pipe, and the collected water is sucked into the processing tank through the return water pipe, and waste generated by cutting and polishing of a silicon wafer, Recovery processing equipment.

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