Grinding and cutting fluid wastewater recycling device in semiconductor chip production and manufacturing

Abstract

The utility model relates to a grinding and cutting fluid wastewater recycling device in semiconductor chip production and manufacturing, in particular to a device for recycling silicon powder and ionized water from grinding and cutting fluid wastewater, and belongs to the technical field of water treatment. Comprising a pH adjusting tank used for adjusting the pH of wastewater, and further comprises an acid liquor tank used for adding acid liquor into the pH adjusting tank; the ceramic membrane is used for filtering the wastewater in the pH adjusting tank; the plate-and-frame filter press is connected to the interception side of the ceramic membrane and is used for carrying out solid-liquid separation on the concentrated slurry obtained in the ceramic membrane to obtain silicon powder waste; the first-stage reverse osmosis membrane is connected to the osmosis side of the ceramic membrane and is used for filtering the penetrating fluid of the ceramic membrane; and the second-stage reverse osmosis membrane is connected to the osmosis side of the first-stage reverse osmosis membrane and is used for filtering the penetrating fluid of the first-stage reverse osmosis membrane to obtain deionized water.

Description

Technical Field

[0001] This utility model relates to a device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing, specifically a device for recovering silicon powder and deionized water from grinding and cutting fluid wastewater, belonging to the field of water treatment technology. Background Technology

[0002] Silicon wafer processing technology refers to the process of cutting and grinding semiconductor wafers using physical or chemical methods to obtain semiconductor wafers or other silicon-based materials that meet the requirements. In this process, wafer cutting and grinding slurry is an important auxiliary material, which not only improves cutting and grinding efficiency but also effectively reduces mechanical and thermal damage during the cutting process, thus increasing the yield. However, a large amount of silicon wafer cutting and grinding slurry waste is generated during wafer cutting and grinding. This waste contains a large amount of metal ions, organic matter, silicon powder, and other impurities, which will pollute the environment if not treated. Waste resource utilization technology refers to the process of reducing, rendering harmless, and recycling waste through collection, treatment, transformation, and reuse. This technology can not only reduce waste emissions but also transform waste into useful resources, thereby achieving sustainable resource utilization. Chemical engineering technology refers to the technology of processing, transforming, and utilizing substances using chemical principles and engineering methods. It mainly includes chemical processes, chemical equipment, chemical reaction engineering, and chemical thermodynamics. 3) Existing technology problems: However, existing technologies in this field have some problems or shortcomings. First, existing technologies typically only recover a portion of the useful components from wafer dicing and polishing slurries, not all of them, leading to resource waste. Second, current technologies often require significant amounts of energy and chemicals to process wafer dicing and polishing slurry waste, increasing processing costs and causing secondary pollution. Finally, existing technologies for recycling silicon wafer dicing slurries often require complex processes and equipment, increasing investment costs, extending processing cycles, and reducing production efficiency. Therefore, production workshops recycle silicon wafer dicing slurries.

[0003] Existing technological solutions: Current technologies typically employ physical or chemical methods to treat silicon wafer cutting fluid to recover useful components and reduce environmental pollution. For example, methods such as precipitation, filtration, adsorption, ion exchange, and reverse osmosis can be used to treat the fluid and recover metal ions, organic matter, and other impurities. Cutting and grinding wastewater is collected, its pH adjusted, PAC added, and after thorough mixing, discharged into a flocculation tank. Flocculants are added, and the wastewater enters a sedimentation tank. The treated clarified wastewater then enters an acid / alkali wastewater treatment system for re-neutralization. The resulting sludge is concentrated, dewatered, and transported off-site, thus creating a recycling system.

[0004] However, existing technologies in this field have some problems or drawbacks. First, each cycle of the process treats 2000-3000 cubic meters of wastewater, requiring the addition of large amounts of flocculants and PAC. The treated water has a high chemical oxygen demand (COD) and cannot be reused, resulting in significant waste of water resources. Furthermore, the solid waste generated by the plate and frame filter after flocculation requires costly treatment, increasing production and operating costs. Existing technologies typically only recover a portion of the useful components from silicon wafer cutting fluid, not all of them, leading to further resource waste. Second, existing technologies often require large amounts of energy and chemicals to treat silicon wafer cutting fluid waste, increasing treatment costs and causing secondary pollution. Finally, existing technologies often require complex processes and equipment for recovering wafer cutting and polishing fluids, increasing investment costs, extending processing cycles, and reducing production efficiency. Summary of the Invention

[0005] This invention provides a device for recovering silicon powder and deionized water from grinding and cutting slurry wastewater in semiconductor chip manufacturing, mainly applied to wafer cutting and grinding slurry recovery. The technical problem this invention aims to solve is overcoming the difficulty in recovering and reusing pure water and silicon powder after coagulation and sedimentation of the cutting and grinding slurry.

[0006] A device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing includes:

[0007] pH adjustment tank, used to adjust the pH of wastewater, and also includes an acid tank for adding acid to the pH adjustment tank;

[0008] Ceramic membranes are used to filter wastewater in pH adjustment tanks.

[0009] A plate and frame filter press, connected to the retrieval side of a ceramic membrane, is used to separate the concentrated slurry obtained from the ceramic membrane into solid and liquid materials to obtain silicon powder waste.

[0010] The first-stage reverse osmosis membrane is connected to the permeate side of the ceramic membrane and is used to filter the permeate from the ceramic membrane.

[0011] The second-stage reverse osmosis membrane is connected to the permeate side of the first-stage reverse osmosis membrane and is used to filter the permeate from the first-stage reverse osmosis membrane to obtain deionized water.

[0012] It also includes a deionized water collection window, which is connected to the permeate side of the second-stage reverse osmosis membrane.

[0013] It also includes a security filter, which is connected to the inlet of the ceramic membrane and is used to filter the wastewater entering the ceramic membrane.

[0014] Security filters are pleated filter cartridges, meltblown filter cartridges, bag filters, or ultrafiltration membranes.

[0015] The ultrafiltration membrane is configured as a hollow fiber membrane, a flat sheet membrane, or a tubular membrane.

[0016] The pore size range of the ceramic membrane is 50nm-200nm.

[0017] The ceramic membrane is configured as a multi-channel or flat sheet.

[0018] The molecular weight cutoff range of the first-stage reverse osmosis membrane and / or the second-stage reverse osmosis membrane is 50-200 Da. Beneficial effects

[0019] This invention effectively recovers solid powder from wafer dicing and grinding fluid, while simultaneously using a reverse osmosis membrane to remove organic matter and metal ions from the dicing fluid. Furthermore, the filtration process using a reverse osmosis organic membrane and a high-packed ceramic membrane requires no added chemicals, resulting in stable effluent quality. The high-packed ceramic membrane offers advantages such as small footprint, high membrane flux, long membrane stability, and low investment cost. The clarified liquid after plate and frame filtration can be reused as feed liquid for the high-packed ceramic membrane, while the concentrate from the first stage of the organic membrane is sent to the biochemical treatment system. The concentrate from the second stage of the organic membrane can be used as feed liquid for the first stage of the organic membrane, significantly improving the pure water recovery rate without increasing system operating costs. The amount of filtrate is controlled to an acceptable level for dicing operations, allowing the mixed permeate to be suitable for further dicing. Attached Figure Description

[0020] Figure 1 This is a flowchart of the patent;

[0021] Figure 2 This is a diagram of the device in this patent.

[0022] The components include: 1. pH adjustment tank; 2. acid tank; 3. ceramic membrane; 4. plate and frame filter press; 5. first-stage reverse osmosis membrane; 6. second-stage reverse osmosis membrane; and 7. deionized water collection container. Detailed Implementation

[0023] Unless otherwise specified, all percentages mentioned in this invention refer to mass percentages.

[0024] This utility model relates to a device for the resource utilization of silicon wafer cutting fluid. It includes: a pH adjustment tank for adjusting the pH of the silicon wafer cutting fluid to neutral; a high-packing ceramic membrane connected to the pH adjustment tank for clarifying and removing impurities from the pH-adjusted silicon wafer cutting fluid; a plate and frame filter press connected to the concentration side of the high-packing ceramic membrane for press filtration of the concentrated solution from the ultrafiltration membrane, with the concentrated liquid (filter cake) recycled and reused on the concentrated side, and the clarified liquid sent to the pH adjustment tank to increase the deionized water recovery rate; an organic membrane connected to the permeate side of the high-packing ceramic membrane for removing organic impurities and metal ions from the permeate; and a diamond wire cutting device connected to the permeate side of the organic membrane for using the filtrate obtained from the organic membrane as a cutting fluid for cutting and grinding semiconductor wafers. It effectively recovers solid powder generated during semiconductor cutting and grinding, and at the same time uses a reverse osmosis membrane to remove metal ions and organic matter from the cutting fluid to meet the reuse standards of deionized water. It can be used to clean impurities such as silicon powder on the wafer surface after semiconductor wafer cutting and grinding, or after adjustment, the amount of filtrate can be controlled to an acceptable level for cutting and grinding operations, so that the mixed permeate can be used for further cutting processing.

[0025] The silicon wafer diamond wire cutting fluid to be treated in this invention originates from the cutting of silicon rods and the grinding of wafers. The wastewater mainly contains silicon powder, dispersant, and water. The wastewater volume is large, and the silicon powder has high value. In one embodiment, the COD content of the cutting and grinding fluid is between 20-100 mg / L, the conductivity is between 5-20 μS / cm, the pH is between 6-6.5, and the SS is 500-2000 mg / L. The device of this invention is mainly based on the following technology: the waste cutting fluid enters a mixing tank, where the pH is adjusted to weakly acidic. Then, it is pumped into a high-packed ceramic membrane system to achieve solid-liquid separation. The clarified liquid from the high-packed ceramic membrane enters an organic membrane stage to remove metal ions and organic matter. The membrane concentrate is dehydrated using a filter press, and the sludge cake is transported off-site. The clarified liquid from the filter press is filtered through a security filter and then enters the high-packed ceramic membrane system for further solid-liquid separation to improve the recovery rate. After filtration through the first stage of the organic membrane, the clarified liquid enters the second stage of the organic membrane for further removal of metal ions and organic matter. The concentrated liquid enters the biochemical treatment system for COD degradation and is then discharged. The pure water after filtration through the second stage of the organic membrane has a conductivity of less than 1 μS / cm and a silicon content of less than 0.02 mg / L. When the cutting fluid fails to meet the standards or when a membrane system is being cleaned or repaired, some of the cutting fluid bypasses the ceramic membrane and directly enters the filter press and other subsequent treatment stages.

[0026] More specifically, the implementation process of this patent is as follows:

[0027] Step 1: Homogenization treatment of semiconductor cutting and grinding wastewater. The purpose of this step is to make the water quality of the cutting and grinding wastewater more consistent. Semiconductor cutting and grinding fluid mainly refers to the liquid containing coolant, dispersant, and silicon powder sprayed during the diamond wire cutting of silicon ingots to protect the diamond wire. The silicon powder content of the cutting fluid is between 500-2000 mg / L, COD is between 10-100 mg / L, pH is between 6-8, and conductivity is between 3-30 uS / cm.

[0028] Step 2: Adjust the pH of the cutting fluid treated in Step 1 to a slightly acidic state. Since alkali treatment is required during the cutting and grinding process, in order to avoid the polymer membrane in the subsequent membrane separation process being affected by the alkali solution, this step requires adding acid to control the pH of the cutting fluid to a slightly acidic state. The pH of the cutting fluid needs to be adjusted to around 7. The added acids include, but are not limited to, citric acid, oxalic acid, and sulfuric acid. The adjustment tank contains a pH meter, a stirring device, a liquid level control device, a flow control device, and a dosing device.

[0029] Step 3 involves feeding the cutting fluid treated in Step 2 into a high-packed ceramic membrane filtration system using a feed pump. The membrane concentrate then enters a pressure filtration system, while the membrane clear liquid enters a clear liquid preparation system. The purpose of this step is to remove suspended solids such as silica powder, silicic acid, bacteria, and algae from the cutting fluid through filtration using a high-packed ceramic membrane. The high-packed ceramic membrane system operates at a pressure between 0.1 and 2 bar and a temperature between 5°C and 80°C. The high-packed ceramic membrane system concentrate has a solid content of 0.5% to 1.5%, a membrane permeate turbidity ≤ 0.2 NTU, and an ultrafiltration membrane system recovery rate between 85% and 95%.

[0030] Step 4 involves dewatering the concentrate from the membrane in Step 3 using a filter press. The resulting cake, primarily composed of silica powder, can be sold or recycled. The clarified liquid is returned to the high-packed ceramic membrane for further filtration. The cake moisture content is between 30% and 50%.

[0031] Step 5: After treating the permeate from the plate and frame filter press in step 4 with a security filter, it enters the organic membrane system; the security filter can be a high-flow pleated filter cartridge, meltblown filter cartridge, bag filter, or ultrafiltration membrane. Ultrafiltration membranes include, but are not limited to, hollow fiber membranes, flat sheet membranes, and tubular membranes.

[0032] Step 6: The cutting and grinding fluid, after being treated by the security filter in Step 5, is treated using a spiral wound organic membrane. The clarified liquid from the first stage of the organic membrane enters the second stage, while the concentrated liquid is sent to the biochemical treatment system. The clarified liquid from the second stage enters the deionized water collection tank, while the concentrated liquid from the second stage enters the first stage for recirculation filtration to improve the recovery rate. The conductivity of the concentrated liquid from the first stage organic membrane is between 30-300 μs / cm, and the COD content is between 100 mg / L and 1000 mg / L. The conductivity of the concentrated liquid from the second stage organic membrane is between 10-30 μs / cm, and the COD is between 10-100 mg / L. The organic membrane is a spiral wound membrane with a filtration accuracy of 100 Da, an operating pressure between 10 bar and 30 bar, and a temperature between 5°C and 45°C. The conductivity of the permeate from the organic membrane is below 0.1 μs / cm, and the recovery rate is between 85% and 95%.

[0033] Step 7: When cleaning or repairing unqualified cutting fluid or membrane equipment, the cutting and grinding fluid, after being treated in step 2, directly bypasses the high-filling ceramic membrane system and enters the pressure filtration and subsequent systems.

[0034] Based on the above technical approach, the adopted device structure includes:

[0035] pH adjustment tank: used to adjust the pH of silicon wafer cutting fluid;

[0036] High-fill ceramic membrane: connected to the pH adjustment tank, used for ultrafiltration of wafer cutting and grinding fluid after pH adjustment;

[0037] Plate and frame filter press: Connected to the concentrate side of a high-packed ceramic membrane, it is used for pressure filtration of the concentrate from the high-packed ceramic membrane.

[0038] Organic membrane section: Connected to the permeate side of the high-packed ceramic membrane, used to filter out organic impurities from the permeate of the high-packed ceramic membrane;

[0039] Organic membrane stage 2: Connects to the permeate side of organic membrane stage 1, and is used to further filter out organic impurities from the permeate of organic membrane stage 1;

[0040] Deionized water collection tank: Connected to the permeate side of the second stage of the organic membrane, it is used to collect the filtrate obtained from the second stage of the organic membrane as wafer washing water or as a slurry for silicon wafer cutting. Example 1

[0041] This embodiment provides a device for the resource utilization of silicon wafer cutting fluid, including the following steps: Step 1: pH adjustment of silicon wafer cutting fluid. The silicon wafer cutting fluid is poured into a pH adjustment tank, and the pH value is adjusted to neutral by adding an appropriate amount of acid or alkali. Specifically, an appropriate amount of hydrochloric acid or sodium hydroxide can be added according to the initial pH value of the silicon wafer cutting fluid to make the pH value between 6.5 and 7.5. Step 2: Clarification and impurity removal of silicon wafer cutting fluid. The pH-adjusted silicon wafer cutting fluid is filtered through a high-packing ceramic membrane to remove solid and organic impurities. Specifically, the pore size of the high-packing ceramic membrane can be set between 50nm and 200nm, and the pressure can be set between 0.05 and 0.15MPa to effectively remove impurities from the silicon wafer cutting fluid. Step 3: Concentration treatment of silicon wafer cutting fluid. The liquid on the concentrated side of the high-packing ceramic membrane is filtered through a plate and frame filter press to obtain a filter cake-like concentrated liquid and a clear liquid. Specifically, the pressure of the plate and frame filter press can be set to 0.5-5.0 MPa to effectively separate solid impurities from the concentrate. Step 4: Treatment of organic impurities and metal ions in the silicon wafer cutting fluid. The liquid on the permeate side of the high-packed ceramic membrane is filtered through an organic membrane to remove organic impurities and metal ions. Specifically, the organic membrane is a 150 Da RO reverse osmosis organic membrane, and a two-stage reverse osmosis process is used to effectively remove organic impurities and metal ions from the silicon wafer cutting fluid. Step 5: Cutting and grinding operations of the silicon wafer cutting fluid. The liquid on the permeate side of the organic membrane is filtered through a diamond wire cutting device to obtain a filtrate suitable for cutting and grinding operations. Specifically, the cutting speed of the diamond wire cutting device can be set to 1-100 mm / s to effectively perform semiconductor wafer cutting and grinding operations. The above steps are performed at room temperature, and the pressure and time can be adjusted according to actual needs. Through the above steps, solid powder generated during semiconductor cutting and grinding can be effectively recovered, and metal ions and organic matter in the cutting fluid can be removed using a reverse osmosis membrane to meet the reuse standards of deionized water, thus achieving efficient recycling of silicon wafer cutting fluid.

Claims

1. A device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing, characterized in that, include: pH adjustment tank (1) is used to adjust the pH of wastewater, and also includes an acid tank (2) for adding acid to the pH adjustment tank; Ceramic membrane (3) is used to filter wastewater in pH adjustment tank; Plate and frame filter press (4) is connected to the truncation side of ceramic membrane (3) and is used to separate the concentrated slurry obtained from ceramic membrane (3) into solid and liquid materials to obtain silicon powder waste. The first-stage reverse osmosis membrane (5) is connected to the permeate side of the ceramic membrane (3) and is used to filter the permeate of the ceramic membrane (3). The second-stage reverse osmosis membrane (6) is connected to the permeate side of the first-stage reverse osmosis membrane (5) and is used to filter the permeate of the first-stage reverse osmosis membrane (5) to obtain deionized water.

2. The device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing according to claim 1, characterized in that, It also includes a deionized water collection window (7) connected to the permeate side of the second-stage reverse osmosis membrane (6).

3. The device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing according to claim 1, characterized in that, It also includes a security filter, which is connected to the inlet of the ceramic membrane (3) and is used to filter the wastewater entering the ceramic membrane (3).

4. The device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing according to claim 1, characterized in that, Security filters are pleated filter cartridges, meltblown filter cartridges, bag filters, or ultrafiltration membranes.

5. The device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing according to claim 4, characterized in that, The ultrafiltration membrane is configured as a hollow fiber membrane, a flat sheet membrane, or a tubular membrane.

6. The device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing according to claim 1, characterized in that, The pore size range of the ceramic membrane (3) is 50nm-200nm.

7. The device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing according to claim 1, characterized in that, The ceramic membrane (3) is configured as a multi-channel or flat plate.

8. The device for reusing grinding and cutting fluid wastewater in semiconductor chip manufacturing according to claim 1, characterized in that, The molecular weight cutoff range of the first-stage reverse osmosis membrane (5) and / or the second-stage reverse osmosis membrane (6) is 50-200 Da.

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