Method for purifying regenerated phosphoric acid from waste phosphoric acid etching solution and regenerated phosphoric acid

Abstract

The invention belongs to the technical field of waste etching liquid recycling and reusing, and discloses a method for purifying and regenerating phosphoric acid from waste phosphoric acid etching liquid and regenerated phosphoric acid, and the method comprises the following steps: adding water into the waste phosphoric acid etching liquid for dilution; filtering the diluted waste phosphoric acid etching solution, adding a fluorine-containing inorganic compound as an additive into the filtered waste phosphoric acid etching solution, and carrying out a stirring reaction to obtain silicon tetrafluoride gas and a reacted phosphoric acid aqueous solution; and evaporating and concentrating the phosphoric acid aqueous solution to obtain electronic-grade regenerated phosphoric acid and industrial-grade regenerated phosphoric acid. According to the method for regenerating and purifying phosphoric acid, silicon-containing compound impurities in the waste phosphoric acid etching liquid can be removed by using the fluorine-containing inorganic compound, so that electronic-grade and industrial-grade regenerated phosphoric acid products are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling and reusing waste etching liquid, and particularly relates to a method for purifying and regenerating phosphoric acid from waste phosphoric acid etching liquid and the regenerated phosphoric acid. Background Art

[0002] Due to the different properties of silicon nitride and silicon substrate, silicon nitride is widely used in local oxidation (local oxidation) and shallow trench isolation (STI) technology in the semiconductor industry integrated circuit process. In the local oxidation process, the oxidation rate of silicon nitride film is very slow compared with that of silicon substrate, so it acts as an isolation layer during the oxidation of silicon substrate and plays the role of isolating devices. After the device isolation is formed, the remaining silicon nitride film needs to be completely removed. Hot phosphoric acid wet etching is widely used in the semiconductor integrated circuit process because of its good uniformity and high selectivity. The commonly used hot phosphoric acid etching solution is composed of 85% phosphoric acid and 15% deionized water in volume percentage. The specific process is: put the wafer into the wet etching tank and keep the temperature at 140-160°C, so that the silicon nitride layer reacts chemically with the hot phosphoric acid etching solution and is etched away. As the etching process proceeds, more and more silicon compounds are contained in the etching solution. For example, Chinese invention patent CN116837466A uses the different solubility of silicon compounds at different temperatures to invent a method for recycling and etching etching liquid, which can increase the service life of phosphoric acid, reduce process costs and waste acid emissions. However, this method cannot achieve infinite circulation and zero emissions of phosphoric acid etching liquid. As the service life increases, the concentration of silicon compounds in the waste phosphoric acid etching liquid discharged after use will also be higher. Usually, the waste phosphoric acid etching liquid discharged after use will be transferred to hazardous waste collection and storage disposal enterprises as hazardous waste (hazardous waste code HW-398-007-34). The current more conventional disposal and reuse methods are to add lime for neutralization or prepare phosphates. However, since the impurities are not removed, the silicon impurities therein will be brought into the subsequent phosphate products, resulting in quality risks and safety issues in the phosphate products. For example, Chinese invention patent CN 115159482 A discloses a method for obtaining electronic grade phosphoric acid by using waste phosphoric acid etching liquid generated by the semiconductor chip industry as a raw material through metal removal, decolorization, extraction, backwashing, and concentration processes. The method purifies and regenerates the waste phosphoric acid etching solution composed of a mixture of phosphoric acid, nitric acid and acetic acid through the above steps to obtain electronic grade phosphoric acid. Since the phosphoric acid etching solution is used to remove the metal layer, the regeneration treatment of this type of waste phosphoric acid etching solution mainly considers the removal of acetic acid, nitric acid and metal specific impurities, resulting in low added value of the obtained product, quality safety and complex process routes. Summary of the invention

[0003] The object of the present invention is to provide a method for purifying waste phosphoric acid etching solution to regenerate phosphoric acid and regenerate phosphoric acid, so as to solve the problems of low added value of products in the prior art, quality safety and complex process routes.

[0004] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for purifying and regenerating phosphoric acid from a waste phosphoric acid etching solution, comprising: Add water to dilute the waste phosphoric acid etching solution; The diluted waste phosphoric acid etching solution is filtered, and a fluorine-containing inorganic compound is added to the filtered waste acid etching solution as an additive, and stirred for reaction to obtain silicon tetrafluoride gas and a phosphoric acid aqueous solution after the reaction; The phosphoric acid aqueous solution is evaporated and concentrated to obtain electronic grade regenerated phosphoric acid or industrial grade regenerated phosphoric acid.

[0005] Furthermore, during dilution, the waste phosphoric acid etching solution is diluted according to a weight ratio of waste phosphoric acid etching solution: water = 1:1 to 1:5.

[0006] Furthermore, during filtration, filtration is performed through a filter medium with a pore size of 0.2 μm-1 μm.

[0007] Furthermore, the fluorine-containing inorganic compound is hydrofluoric acid, sodium fluoride, potassium fluoride or ammonium fluoride.

[0008] Furthermore, the concentration range of the fluorine-containing inorganic compound is 1000 ppm -8000 ppm.

[0009] Furthermore, when hydrofluoric acid or ammonium fluoride is selected as the additive, electronic grade phosphoric acid is obtained after the reaction; when sodium fluoride or potassium fluoride is selected as the additive, industrial grade phosphoric acid is obtained after the reaction.

[0010] Furthermore, the evaporation conditions are: under vacuum conditions, evaporation concentration is carried out in a vacuum device with a pressure in the range of 70KPa-100KPa, the evaporation temperature is 80°C-120°C, and the evaporation concentration time is 2-6 hours.

[0011] Furthermore, the outlet of the vacuum device uses a strong alkaline solution to absorb the silicon tetrafluoride gas generated by the evaporation and concentration treatment.

[0012] In a second aspect, the present invention provides a regenerated phosphoric acid, and electronic grade regenerated phosphoric acid or industrial grade regenerated phosphoric acid is prepared based on the method for purifying regenerated phosphoric acid from waste phosphoric acid etching solution.

[0013] The "electronic grade regenerated phosphoric acid" described in the present invention refers to phosphoric acid that meets the requirements of the electronic device manufacturing process, and the national standard is GB / T 28159-2011 "Electronic Grade Phosphoric Acid"; The "industrial grade regenerated phosphoric acid" described in the present invention refers to phosphoric acid used in electroplating, medicine, phosphate industry, metallurgical industry and fertilizer production in agriculture, and the national standard is GB / T 2091-2003 "Industrial Phosphoric Acid".

[0014] Compared with the prior art, the present invention has the following technical effects: According to the method for regenerating and purifying phosphoric acid of the present invention, by using fluorine-containing inorganic compounds, silicon-containing compound impurities in waste phosphoric acid etching liquid can be removed, thereby obtaining electronic-grade and industrial-grade regenerated phosphoric acid products. By adopting a combination of dilution and adding additives, silicon impurities in waste phosphoric acid etching liquid can be completely removed, thereby obtaining a pure phosphoric acid product, which is divided into electronic-grade phosphoric acid and industrial phosphoric acid, both of which can meet electronic-grade and industrial-grade standards. There is no quality safety problem in preparing phosphates using the phosphoric acid product obtained after treatment with the invention technology.

[0015] Compared with the process of obtaining electronic grade phosphoric acid through metal removal, decolorization, extraction, backwashing and concentration in patent CN 115159482 A, the present invention can obtain electronic grade or industrial grade phosphoric acid products only through a combined process of dilution, filtration, reaction and concentration. The process is short, the operation is simple, and it is easier to industrialize production.

[0016] The present invention adopts a preferential dilution process, which can reduce the solubility of silicon dioxide in phosphoric acid and remove most impurities by filtering. On the other hand, it overcomes the problem that concentrated phosphoric acid is difficult to filter due to its high viscosity and large amount of impurities.

[0017] The present invention selects fluorine-containing inorganic compounds as additives, and can completely remove impurities in the waste phosphoric acid etching solution through chemical reactions. The products are silicon tetrafluoride gas and water. The whole process does not generate or introduce any new impurities, thereby ensuring the high quality of the regenerated phosphoric acid.

[0018] The subsequent evaporation and concentration process of the present invention can evaporate and remove excess additives.

[0019] The above additive selection and process combination can ensure that the waste phosphoric acid etching solution is purified and regenerated to the required electronic grade or industrial product quality.

[0020] The present invention can remove impurities in the phosphoric acid through the above dilution, filtration, reaction and concentration process sequence, and the added substances and newly generated substances in the reaction can be effectively removed in the subsequent process stage, thereby ensuring the high quality of phosphoric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a process flow chart for the purification and regeneration of waste phosphoric acid etching solution; DETAILED DESCRIPTION The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0023] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0024] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0025] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0026] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0027] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0028] The present invention provides a method for purifying and regenerating phosphoric acid from a waste phosphoric acid etching solution, comprising: Add water to dilute the waste phosphoric acid etching solution; The diluted waste phosphoric acid etching solution is filtered, and a fluorine-containing inorganic compound is added to the filtered waste acid etching solution as an additive, and stirred for reaction to obtain silicon tetrafluoride gas and a phosphoric acid aqueous solution after the reaction; The phosphoric acid aqueous solution is evaporated and concentrated to obtain electronic grade regenerated phosphoric acid or industrial grade regenerated phosphoric acid.

[0029] The present invention introduces fluorine-containing inorganic compounds as additives, aiming to deeply purify waste phosphoric acid etching solution, efficiently remove stubborn silicon-containing compound impurities, and ultimately produce regenerated phosphoric acid products that meet electronic and industrial standards. This breakthrough technology not only solves the problem of the difficulty in completely removing silicon-containing impurities in traditional treatment methods, but also significantly improves the purity and quality of regenerated phosphoric acid, providing a stable and reliable source of raw materials for multiple fields such as the electronics industry and chemical manufacturing.

[0030] In the specific implementation process, the present invention adopts a unique priority dilution process strategy. First, by accurately controlling the dilution ratio, the solubility of silicon dioxide in the phosphoric acid solution is effectively reduced. This step creates favorable conditions for subsequent physical filtration, so that most large-sized silicon-based impurities can be effectively intercepted and removed through simple filtration operations. Secondly, the dilution process also cleverly overcomes the problem of low filtration efficiency caused by concentrated phosphoric acid due to its high viscosity characteristics and the large amount of impurities it contains, significantly improving the smoothness and efficiency of the overall processing flow.

[0031] The present invention selects and applies specific fluorine-containing inorganic compounds as additives. These additives react chemically with silicon-containing impurities in waste phosphoric acid etching solution under specific conditions to generate two harmless products, silicon tetrafluoride gas and water. Among them, silicon tetrafluoride gas is easily discharged from the system through gas separation technology, and no new impurities are introduced in the whole process, ensuring the absolute purity of the regenerated phosphoric acid product. This chemical decontamination method not only achieves deep removal of impurities, but also ensures the stability of the chemical composition of the regenerated phosphoric acid, meeting the stringent requirements of electronic grade phosphoric acid for high purity and low metal ion content.

[0032] In summary, the method for regenerating and purifying phosphoric acid of the present invention, by virtue of its innovative process design, efficient impurity removal capability and strict control of product quality, has opened up a new way for the resource utilization of waste phosphoric acid etching solution, and has significant environmental, economic and social benefits.

[0033] Embodiment 1, the present invention provides a method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution, specifically comprising: Take 500g of semiconductor waste phosphoric acid etching liquid in the 1# reactor, add 1500g of deionized water to the 1# reactor, stir and react for 60min, filter it through a filter medium with a pore size of 0.3μm, and transfer 1900g of phosphoric acid obtained after filtration into the 2# reactor, add 1.5g of hydrofluoric acid with a mass concentration of 10%, and stir and react for 30min to obtain the waste phosphoric acid etching liquid pretreatment liquid. The pretreatment liquid is evaporated and concentrated in a vacuum device with a pressure of 80KPa, the evaporation temperature is 90℃, the evaporation concentration time is 3 hours, and the vacuum pump outlet is treated with silicon tetrafluoride gas absorption using sodium hydroxide solution.

[0034] Embodiment 2, the present invention provides a method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution, specifically comprising: Take 500g of semiconductor waste phosphoric acid etching liquid in the 1# reactor, add 2500g of deionized water to the reactor, stir and react for 20min, filter it through a filter medium with a pore size of 0.2μm, and transfer 2900g of phosphoric acid obtained after filtration into the 2# reactor, add 0.2g of hydrofluoric acid with a mass concentration of 49%, and stir and react for 60min to obtain the waste phosphoric acid etching liquid pretreatment liquid. The pretreatment liquid is evaporated and concentrated in a vacuum device with a pressure of 90KPa, the evaporation temperature is 100℃, the evaporation concentration time is 6 hours, and the vacuum pump outlet is treated with silicon tetrafluoride gas absorption using potassium hydroxide solution.

[0035] Embodiment 3, the present invention provides a method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution, specifically comprising: Take 500g of semiconductor waste phosphoric acid etching liquid in the 1# reactor, add 500g of deionized water to the reactor, stir and react for 40min, filter it through a filter medium with a pore size of 1.0μm, and transfer 900g of phosphoric acid obtained after filtration into the 2# reactor, add 1.5g of hydrofluoric acid with a mass concentration of 30%, and stir and react for 60min to obtain the waste phosphoric acid etching liquid pretreatment liquid. The pretreatment liquid is evaporated and concentrated in a vacuum device with a pressure of 100KPa, the evaporation temperature is 120℃, the evaporation concentration time is 3 hours, and the vacuum pump outlet is treated with silicon tetrafluoride gas absorption using sodium carbonate + sodium hydroxide solution.

[0036] Embodiment 4, the present invention provides a method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution, specifically comprising: Take 500g of semiconductor waste phosphoric acid etching liquid in the 1# reactor, add 500g of deionized water to the reactor, stir and react for 40min, filter it through a filter medium with a pore size of 1.0μm, and transfer 900g of phosphoric acid obtained after filtration into the 2# reactor, add 3.0g of sodium fluoride with a mass concentration of 30%, and stir and react for 60min to obtain the waste phosphoric acid etching liquid pretreatment liquid. The pretreatment liquid is evaporated and concentrated in a vacuum device with a pressure of 70KPa, the evaporation temperature is 100℃, the evaporation concentration time is 4 hours, and the vacuum pump outlet is treated with potassium hydroxide + sodium carbonate solution for silicon tetrafluoride gas absorption.

[0037] Embodiment 5, the present invention provides a method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution, specifically comprising: Take 500g of semiconductor waste phosphoric acid etching liquid in the 1# reactor, add 1500g of deionized water to the reactor, stir and react for 60min, filter it through a filter medium with a pore size of 0.3μm, and transfer 1900g of phosphoric acid obtained after filtration into the 2# reactor, add 5.0g of potassium fluoride with a mass concentration of 30%, and stir and react for 30min to obtain the waste phosphoric acid etching liquid pretreatment liquid. The pretreatment liquid is evaporated and concentrated in a vacuum device with a pressure of 90KPa, the evaporation temperature is 90℃, the evaporation concentration time is 2 hours, and the vacuum pump outlet is treated with potassium hydroxide + potassium carbonate solution for silicon tetrafluoride gas absorption.

[0038] Table 1 Electronic Phosphoric Acid Examples

[0039] Table 2 Industrial phosphoric acid examples

[0040] Tables 1 and 2 characterize the quality of the regenerated electronic phosphoric acid and industrial phosphoric acid, respectively. Compared with the national standard for electronic phosphoric acid GBT 28159-2011 "Electronic phosphoric acid" and the national standard for industrial phosphoric acid GB / T 2091-2003 "Industrial phosphoric acid", the indicators of the regenerated product meet the relevant requirements.

[0041] The regeneration and purification of phosphoric acid process of the present invention, after completing a series of key steps of dilution, filtration and chemical reaction, immediately enters the evaporation and concentration process stage. The main purpose of this stage is to further purify the phosphoric acid solution, and by precisely controlling the temperature and pressure conditions, the excess additives that may remain in the previous treatment process and the by-products generated by the reaction (such as trace amounts of water vapor or other volatile substances) are thoroughly evaporated and effectively removed. This step not only improves the purity of the phosphoric acid solution, but also ensures that the final concentration of the regenerated phosphoric acid meets the requirements of specific application fields, whether it is the high-precision requirements of the electronic grade or the wide application of the industrial grade.

[0042] In the selection of additives, the present invention ensures that the selected substances can not only effectively remove impurities in the waste phosphoric acid etching solution, but also will not introduce new pollutants in the subsequent treatment process. After the additives react chemically with the impurities in the phosphoric acid solution, the generated products, such as silicon tetrafluoride gas, can be easily separated from the system during the evaporation and concentration stage, thereby avoiding any factors that may affect the quality of phosphoric acid.

[0043] The combination and optimization of the process is the key to the efficient purification of the present invention. From the initial dilution to reduce the solubility of impurities, to filtering to remove large impurities, to chemical reaction deep purification, to the final evaporation and concentration to improve the concentration and purity, each step is closely connected and complements each other. This systematic processing flow not only improves the overall processing efficiency, but also greatly enhances the removal effect of impurities, ensuring that the regenerated phosphoric acid can stably meet the strict quality standards of electronic or industrial grade products.

[0044] In summary, the present invention successfully achieves efficient purification and regeneration of waste phosphoric acid etching solution through the scientific and reasonable process sequence of dilution, filtration, reaction, and concentration. In the entire treatment process, the added substances and the newly generated substances in the reaction can be effectively removed in the subsequent process stages, thereby ensuring the high quality and purity of the regenerated phosphoric acid, and providing strong support for the sustainable development of related industries.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution, characterized in that: include: Add water to dilute the waste phosphoric acid etching solution; The diluted waste phosphoric acid etching solution is filtered, and a fluorine-containing inorganic compound is added to the filtered waste acid etching solution as an additive, and stirred for reaction to obtain silicon tetrafluoride gas and a phosphoric acid aqueous solution after the reaction; The phosphoric acid aqueous solution is evaporated and concentrated to obtain electronic grade regenerated phosphoric acid or industrial grade regenerated phosphoric acid.

2. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 1, characterized in that: When diluting, dilute according to the mass ratio of waste phosphoric acid etching solution: water = 1:1~1:

5.

3. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 1, characterized in that: When filtering, a filter medium with a pore size of 0.2 μm-1 μm is used for filtering.

4. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 1, characterized in that: The fluorine-containing inorganic compound is hydrofluoric acid, sodium fluoride, potassium fluoride or ammonium fluoride.

5. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 4, characterized in that: The concentration range of fluorine-containing inorganic compounds is 1000ppm-8000ppm.

6. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 4, characterized in that: When hydrofluoric acid or ammonium fluoride is selected as the additive, electronic grade phosphoric acid is obtained after the reaction.

7. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 4, characterized in that: When sodium fluoride or potassium fluoride is selected as the additive, industrial grade phosphoric acid is obtained after the reaction.

8. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 1, characterized in that: The evaporation conditions are: under vacuum conditions, evaporation concentration treatment is carried out at a pressure range of 70KPa-100KPa, the evaporation temperature is 80°C-120°C, and the evaporation concentration time is 2-6 hours.

9. The method for purifying and regenerating phosphoric acid from waste phosphoric acid etching solution according to claim 8, characterized in that: The silicon tetrafluoride gas produced by the evaporation and concentration treatment is absorbed by a strong alkaline solution.

10. A regenerated phosphoric acid, characterized in that Electronic grade regenerated phosphoric acid or industrial grade regenerated phosphoric acid is prepared by the method for purifying regenerated phosphoric acid from waste phosphoric acid etching solution according to any one of claims 1 to 9.

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