Method and device for purifying and preparing electronic-grade phosphoric acid by using microwave temperature control technology

Abstract

The present application relates to the technical field of phosphoric acid production, and particularly relates to a method and device for purifying and preparing electronic-grade phosphoric acid by using microwave temperature control technology. The method comprises the following steps: S1, using a composite impurity removal agent to perform chemical precipitation pretreatment on industrial-grade wet-process phosphoric acid, and adjusting the concentration after solid-liquid separation; S2, performing microwave temperature control concentration on the pretreated liquid at a vacuum degree of 0.085-0.095 MPa and a temperature of 160-220 DEG C to obtain a concentrated liquid with P2O5 of 85% or more; S3, performing crystallization, sweating and chelating resin ion exchange deep impurity removal on the concentrated liquid; and S4, performing decolorization, super-clean filtration and dilution and filling to obtain electronic-grade phosphoric acid finished products. The present application also provides a special device. The present application is coupled by microwave concentration and multi-stage deep impurity removal, the concentration efficiency is improved by 30%-50%, the energy consumption is reduced by more than 30%, the finished product metal impurity is less than or equal to 10 ppb, and the finished product meets the GB / T1282-2011 standard; the device adopts high-purity PTFE anticorrosion lining to avoid secondary pollution and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of phosphoric acid production technology, specifically to a method and apparatus for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology. Background Technology

[0002] Electronic-grade phosphoric acid is a crucial high-purity acidic wet electronic chemical reagent in semiconductor manufacturing. Classified by purity from G1 to G5, it is widely used in key processes such as etching, cleaning, doping, and polishing in wafer fabrication and advanced packaging. Its applications include various scenarios within semiconductor manufacturing processes. 1. Wet etching (important application area) As a selective etchant for silicon-based / compound semiconductors, it can be used alone or mixed with HF, H2O2, acetic acid, etc. to etch SiO2 and Si3N4 thin films on silicon wafers to achieve fine patterning (adapted to front-end wafer fabrication processes), to etch substrates or epitaxial layers of compound semiconductors such as GaAs and GaN (used in the manufacture of radio frequency and optoelectronic devices), and to etch the dielectric layers of wafer bumps and redistribution layers in advanced packaging to achieve micro and nano structure formation. 2. Wet cleaning of wafers Incorporated into the RCA cleaning system (often in combination with H2O2), it is used to remove metallic impurities (such as Fe, Cu, Ni), particulate contaminants, and organic residues from the wafer surface. In an acidic environment, it complexes metal ions, which, combined with the oxidizing effect of H2O2, achieves efficient stripping of metallic impurities; simultaneously, it cleans surface residues from photolithography and etching, ensuring the cleanliness requirements of subsequent processes. 3. Ion implantation doping High-purity electronic-grade phosphoric acid is an important precursor for phosphorus doping in semiconductors. Phosphorus is incorporated into silicon substrates via ion implantation to adjust the semiconductor's conductivity type (N-type) and carrier concentration, adapting it to the doping processes of the chip's active region and gate. Its purity directly determines the doping uniformity and the device's electrical performance. 4. Chemical Mechanical Polishing (CMP) As an acidity regulator / polishing aid in CMP polishing slurries, it is used in the polishing processes of silicon wafers, metal layers (W, Cu), and dielectric layers. Its main functions include stabilizing the pH value of the polishing slurry, controlling the dispersion of abrasives (such as SiO2, Al2O3), slightly corroding the polished surface, assisting the abrasives in achieving uniform material removal, and improving polishing smoothness (overall smoothness <0.5nm). 5. Advanced packaging technology Used for bump fabrication, TSV (through silicon via) etching and cleaning in the packaging process, as well as surface passivation cleaning after chip packaging, to remove residual contaminants in micro and nano structures and ensure the reliability of package interconnects.

[0003] Semiconductor-grade electronic phosphate is classified according to its metal impurity content, particle size, and resistivity to suit different process nodes. More advanced processes (e.g., 7nm and below) require higher purity: Low purity (G1~G2): used for photovoltaic silicon wafers and discrete device manufacturing, with a metal impurity content of ≈10~100ppb; High purity (G3~G4): used for mid-to-low process chips (28nm and above) and packaging, with a metal impurity content of ≈1~10ppb and particle size (≥0.5μm) <10 particles / mL; Ultra-high purity (G5): used for advanced wafer processes of 7nm and below, with a metal impurity content <0.1ppb, particle size (≥0.2μm) <1 particle / mL, and resistivity ≥10MΩcm. The technical specifications for each grade of electronic phosphate according to SEMI C27-0701 are shown in Table 1 below.

[0004] Currently, the industrial production of electronic-grade phosphoric acid primarily uses industrial-grade wet-process or thermal-process phosphoric acid as raw materials. Purification technologies employed include crystallization, ion exchange, membrane separation, and vacuum concentration. Vacuum concentration is a key unit operation for increasing phosphoric acid concentration; however, traditional processes often employ jacket heating, which suffers from uneven temperature distribution, localized overheating, easy decomposition of phosphoric acid upon heating, and low concentration efficiency. While crystallization or ion exchange methods can remove some metal ions, their integration with existing concentration processes often faces limitations such as lengthy processes, high energy consumption, and insufficient impurity removal depth, making it difficult to consistently meet ppb-level metal impurity and particle control requirements.

[0005] Existing technologies have attempted to apply microwave heating to phosphoric acid concentration. For example, CN102730647B discloses a method for preparing polyphosphoric acid and crystalline orthophosphoric acid using microwave heating. However, this method has the following technical drawbacks: First, the temperature control accuracy is low, mainly targeting industrial or food-grade phosphoric acid processing, and cannot achieve the high purity required for electronic-grade products. Second, this process is not effectively coupled with deep impurity removal technology, making it difficult to meet the control requirements for ppb-level metal impurities. Third, existing microwave phosphoric acid processing devices generally lack precise temperature control and corrosion-resistant designs specifically for high-purity phosphoric acid systems, which can easily lead to problems such as scaling inside the microwave cavity, leaching of metal components, and the introduction of secondary pollution. Therefore, a technical solution suitable for the stable industrial production of electronic-grade phosphoric acid has not yet been developed.

[0006] To address the technical problems of insufficient temperature control accuracy, incomplete impurity removal, and poor device adaptability in the existing technologies, there is an urgent need to develop a method for preparing electronic-grade phosphoric acid that couples microwave precision temperature control technology with a multi-stage deep impurity removal process. This method would achieve low-temperature high-efficiency concentration and synergistic removal of ppb-level impurities, and incorporate a dedicated device design to improve temperature control accuracy and corrosion resistance, thereby meeting the increasingly stringent purity and stability requirements of advanced processes for electronic-grade phosphoric acid. Summary of the Invention

[0007] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology. This method achieves low-temperature and high-efficiency concentration through precise microwave temperature control, and combines crystallization-ion exchange coupling to remove impurities, which greatly improves the impurity removal efficiency, reduces the metal impurity content to the ppb level, and has low energy consumption and short process, making it suitable for industrial production. At the same time, this invention also provides a dedicated device for implementing this method. This device is specifically designed with a microwave constant temperature control system and a corrosion-resistant structure to avoid secondary pollution and ensure stable implementation of the process.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology, comprising the following steps: S1. Raw material pretreatment: Add CaO and Al2O3 composite impurity removal agent to industrial-grade wet-process phosphoric acid (mass fraction 50%-60%, metal impurity content 1-10ppm), with a CaO to Al2O3 mass ratio of 1:(0.8-1.2), and the amount added is 0.5%-1.0% of the raw phosphoric acid mass. Stir and react at 40-60℃ for 30-60min to precipitate fluorine and arsenic impurities. Filter through a 1-5μm precision filter to remove residue, and adjust the phosphoric acid concentration of the filtrate to 75%-85% to obtain the pretreated solution. S2. Microwave vacuum temperature-controlled concentration: The pretreated liquid obtained in step S1 is sent into a microwave vacuum reactor. The vacuum system is started to make the vacuum degree in the reactor reach 0.085-0.095MPa. The microwave emission module and intelligent temperature control system are started to maintain the temperature at 160-220℃ and the stirring rate at 80-120rpm. The mixture is kept at this temperature for 1-2 hours to obtain a concentrated phosphoric acid solution with a P2O5 content ≥85%. During the concentration process, trace impurities that have volatilized are recovered through a reflux condenser. S3. Deep Coupling Impurity Removal: The concentrated phosphoric acid solution obtained in step S2 is sent to a crystallization kettle, cooled to 8-14℃, and 0.1%-0.3% of phosphoric acid seed crystals are added. The mixture is stirred at low speed and suspended for crystallization for 0.5-2 hours. The solution is then filtered to obtain phosphoric acid crystals. The phosphoric acid crystals are sent to a sweating tank and heated to 30-40℃ for sweating purification for 0.5-2 hours to remove the impurities adsorbed on the crystal surface. The sweated solution is then passed through a chelating resin ion exchange column to adsorb residual metal ions, resulting in a purified solution. S4. Refining and post-treatment: Add 0.05%-0.1% of 30% H2O2 to the impurity removal solution obtained in step S3, keep it at 60-80℃ for 20-50 minutes for decolorization, filter through a 0.1μm PTFE ultra-clean filter to remove microparticles, and finally dilute with ultrapure water to a mass fraction of 85%. Fill the solution in a Class 100 clean environment to obtain electronic grade phosphoric acid product.

[0009] An apparatus for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology, employing the aforementioned method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology, includes a pretreatment unit, a microwave vacuum concentration unit, a deep impurity removal unit, and a purification unit connected in sequence. The microwave vacuum concentration unit is the core, comprising a microwave reactor body, a vacuum system, an intelligent temperature control system, and a stirring system. The reactor body is lined with high-purity PTFE material, with a microwave emission power of 5-20kW and a temperature control accuracy of ±0.5℃ for the intelligent temperature control system. The pretreatment unit includes a mixing reactor and a 1-5μm precision filter. The deep impurity removal unit includes a crystallization vessel, a sweating tank, and a chelating resin ion exchange column. The purification unit includes a decolorization vessel, a 0.1μm PTFE ultra-clean filter, and a clean filling machine.

[0010] Compared with the prior art, the technical solution of this application has the following beneficial effects: 1. High-efficiency concentration and precise temperature control: Utilizing microwave vacuum temperature-controlled concentration technology, the intelligent temperature control system achieves high-precision temperature control within ±0.5℃, ensuring a uniform temperature distribution within the reactor and effectively avoiding the phosphoric acid decomposition problem caused by localized overheating in traditional jacketed heating methods. Microwave heating enables low-temperature, high-efficiency concentration, increasing concentration efficiency by 30%-50% compared to traditional vacuum concentration processes, while reducing energy consumption by over 30%, significantly improving production economics. 2. Deep Impurity Removal and High-Purity Product: A coupled "crystallization-perspiration-ion exchange" impurity removal process is employed. First, low-temperature crystallization removes most metal impurities. Then, perspiration purification removes mother liquor impurities adsorbed on the crystal surface. Finally, deep purification is achieved using a chelating resin ion exchange column, resulting in a total metal impurity removal rate of over 99.9%. The resulting phosphoric acid contains ≤10 ppb of metal impurities, and both anion and particulate indicators meet the requirements of GB / T 1282-2011 "Electronic Grade Phosphoric Acid" standard, making it suitable for advanced processes requiring ultra-high purity chemical reagents. 3. Raw material adaptability and pretreatment optimization: For volatile impurities such as fluorine and arsenic in industrial-grade wet-process phosphoric acid, a chemical precipitation pretreatment is carried out using a composite impurity removal agent of CaO and Al2O3. This efficiently removes fluorine and arsenic impurities before concentration, preventing them from volatilizing during subsequent vacuum concentration, which could cause equipment corrosion and secondary pollution, extend equipment service life, and ensure the stability and safety of the production process. 4. Specialized anti-corrosion design: In response to the highly corrosive nature of phosphoric acid, the microwave reactor body is lined with high-purity PTFE material, which effectively isolates phosphoric acid from contact with the metal cavity and avoids secondary pollution of the product caused by metal leaching from the equipment; at the same time, a condensation reflux device is equipped to recover trace impurities volatilized during the concentration process, realizing resource recovery and green and clean production. 5. Compact Process Flow and Industrial Adaptability: Seamless coupling of each unit operation forms a complete continuous or batch production process, effectively shortening the production cycle and improving raw material utilization. The entire unit is rationally designed and easy to operate, suitable for large-scale industrial production using industrial-grade wet-process phosphoric acid as raw material, and has good industrial promotion value. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the apparatus for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology in a preferred embodiment of the present invention.

[0012] Figure labels: 1. Reactor; 2. Precision filter; 3. Microwave vacuum concentration unit; 4. Crystallization vessel; 5. Sweating tank; 6. Chelating resin ion exchange column; 7. Decolorization vessel; 8. Ultra-clean filter; 9. Clean filling machine. Detailed Implementation

[0013] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0014] Reference Figure 1 As shown in the preferred embodiment of the present invention, the apparatus for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology employs the following method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology, comprising a pretreatment unit, a microwave vacuum concentration unit 3, a deep impurity removal unit, and a purification unit connected in sequence; wherein the microwave vacuum concentration unit 3 is the core, including a microwave reactor body, a vacuum system, an intelligent temperature control system, and a stirring system, the reactor body is lined with high-purity PTFE material, the microwave emission power is 5-20kW, and the intelligent temperature control system has a temperature control accuracy of ±0.5℃; the pretreatment unit includes a mixing reactor 1 and a 1-5μm precision filter 2; the deep impurity removal unit includes a crystallization vessel 4, a sweating tank 5, and a chelating resin ion exchange column 6; the purification unit includes a decolorization vessel 7, a 0.1μm PTFE ultra-clean filter 8, and a clean filling machine 9.

[0015] Example 1 The method for preparing electronic-grade phosphoric acid using the above-described apparatus includes the following steps: S1. Raw material pretreatment: Take 100L of industrial-grade wet-process phosphoric acid (mass fraction 55%, total content of metal impurities such as Fe / Al / Ca / Mg 5ppm), add 0.75kg of composite impurity removal agent (CaO:Al2O3=1:1), stir and react at 50℃ for 45min, filter through a 3μm precision filter, adjust the concentration of the filtrate to 80%, and obtain the pretreated solution. S2. Microwave vacuum concentration: The pretreated liquid is fed into a microwave vacuum reactor, the vacuum degree is controlled at 0.09MPa, the microwave power is 10kW, the temperature is controlled at 190℃, the stirring speed is 100rpm, and the liquid is kept at the temperature for 1.5h to obtain a concentrated phosphoric acid solution with a P2O5 content of 86%. S3. Deep coupling impurity removal: The concentrate is cooled to 10℃, 0.2% phosphate seed crystals are added, and the solution is suspended and crystallized for 1 hour. After filtration, the crystals are evaporated at 35℃ for 1 hour, and then passed through a chelating resin ion exchange column to obtain the impurity-removed solution. S4. Refining and post-processing: Add 0.08% of 30% H2O2, microwave decolorize at 70℃ for 30 minutes, filter through a 0.1μm PTFE membrane, dilute with ultrapure water to 85% concentration, and fill in a clean environment. Test results: The total content of metal impurities in the finished phosphate product is ≤5ppb, the fluorine content is ≤1ppb, the arsenic content is ≤0.5ppb, and the particulate matter (≥0.5μm) is ≤10 particles / mL, all of which meet the GB / T 1282-2011 standard for superior grade electronic phosphate.

[0016] Example 2 The difference between this embodiment and Embodiment 1 lies in the following parameters: S1. Raw material pretreatment: Take 100L of industrial-grade wet-process phosphoric acid (mass fraction 50%, total metal impurity content 10ppm), add 0.5kg of composite impurity removal agent (CaO:Al2O3=1:0.8), stir and react at 40℃ for 60min, filter with 1μm, adjust the concentration to 75%, and obtain the pretreated solution. S2. Microwave vacuum concentration: vacuum degree 0.085MPa, microwave power 5kW, constant temperature control 160℃, stirring 80rpm, concentration for 2h, P2O5 content 85%; S3, Deep Coupling Purification: Crystallize at 8℃ for 2 hours, seed crystals 0.1%, sweat at 30℃ for 2 hours, then pass through an ion exchange column; S4. Refining and post-treatment: 0.05% H2O2, decolorize at 60℃ for 50 min, filter at 0.1μm, and dilute to 85%; Test results: Total metal impurities ≤8ppb, fluorine ≤2ppb, arsenic ≤1ppb, meeting the standards for electronic-grade phosphoric acid.

[0017] Example 3 The difference between this embodiment and Embodiment 1 lies in the following parameters: S1. Raw material pretreatment: Take 100L of industrial-grade wet-process phosphoric acid (mass fraction 60%, total metal impurity content 1ppm), add 1.0kg of composite impurity removal agent (CaO:Al2O3=1:1.2), stir and react at 60℃ for 30min, filter at 5μm, adjust the concentration to 85%, and obtain the pretreated solution. S2. Microwave vacuum concentration: vacuum degree 0.095MPa, microwave power 20kW, constant temperature control 220℃, stirring 120rpm, concentration for 1h, P2O5 content 87%; S3, Deep Coupling Purification: Crystallize at 14℃ for 0.5h, seed crystals 0.3%, sweat at 40℃ for 0.5h, then pass through an ion exchange column; S4. Refining and post-treatment: 0.1% H2O2, decolorize at 80℃ for 20 min, filter at 0.1μm, and dilute to 85%; Test results: Total metal impurities ≤3ppb, fluorine ≤0.5ppb, arsenic ≤0.3ppb, which is better than the standard for electronic grade phosphoric acid.

[0018] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0019] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology, characterized in that, Includes the following steps: S1. Raw material pretreatment: Industrial-grade wet-process phosphoric acid is chemically precipitated to remove impurities. After solid-liquid separation, the phosphoric acid concentration is adjusted to obtain a pretreated solution. S2. Microwave vacuum temperature-controlled concentration: The pretreated liquid obtained in step S1 is placed under vacuum and microwave heated for concentration, and the concentration temperature is controlled to obtain a concentrated phosphoric acid solution with a P2O5 content ≥85%. S3, Deep coupling impurity removal: The concentrated phosphoric acid solution obtained in step S2 is subjected to crystallization, sweating and ion exchange treatment in sequence to obtain the impurity removal solution; S4. Refining and post-processing: The impurity removal solution obtained in step S3 is decolorized, ultra-clean filtered, diluted and filled to obtain electronic grade phosphoric acid product.

2. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 1, characterized in that: In step S1, the industrial-grade wet-process phosphoric acid has a mass fraction of 50%-60% and a metal impurity content of 1-10 ppm. Chemical precipitation is performed using a composite impurity remover, which is a mixture of CaO and Al2O3 with a mass ratio of 1:(0.8-1.2).

3. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 2, characterized in that: The amount of the composite impurity remover added is 0.5%-1.0% of the mass of industrial-grade wet-process phosphoric acid; the reaction temperature for precipitation and impurity removal is 40-60℃, and the reaction time is 30-60min; solid-liquid separation is performed using a precision filter with a pore size of 1-5μm.

4. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 1, characterized in that: In step S2, the vacuum degree is controlled at 0.085-0.095MPa; the concentration temperature is constantly controlled at 160-220℃ by an intelligent temperature control system; stirring is carried out during the concentration process at a stirring rate of 80-120rpm, and the heat preservation and concentration time is 1-2h; and the volatile trace impurities are recovered by a condensation reflux device; the microwave emission power of the microwave heating is 5-20kW.

5. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 1, characterized in that: The crystallization process in step S3 specifically involves: cooling the concentrated phosphoric acid solution to 8-14°C, adding phosphoric acid seed crystals, suspending and crystallizing under low-speed stirring for 0.5-2 hours, and then filtering to obtain phosphoric acid crystals.

6. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 5, characterized in that: The amount of phosphate seed crystals added is 0.1%-0.3% of the mass of the concentrated phosphate solution.

7. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 1, characterized in that: The sweating treatment in step S3 specifically involves purifying the phosphate crystals obtained from crystallization by sweating at 30-40℃ for 0.5-2 hours to remove the impurities and mother liquor adsorbed on the crystal surface.

8. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 1, characterized in that: The ion exchange treatment in step S3 specifically involves passing the sweated liquid through a chelating resin ion exchange column to adsorb residual metal ions.

9. The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology according to claim 1, characterized in that: In step S4, 30% H2O2 by mass is used as a decolorizing agent, and its addition amount is 0.05%-0.1% of the mass of the impurity removal solution; the decolorization temperature is 60-80℃, and the decolorization time is 20-50min; after decolorization, it is filtered through a 0.1μm PTFE ultra-clean filter; finally, it is diluted with ultrapure water to a mass fraction of 85%, and filled in a Class 100 clean environment.

10. An apparatus for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology, characterized in that: The method for purifying and preparing electronic-grade phosphoric acid using microwave constant temperature control technology as described in any one of claims 1-9 includes a pretreatment unit, a microwave vacuum concentration unit, a deep impurity removal unit, and a purification unit connected in sequence. The pretreatment unit includes a mixing reactor and a 1-5μm precision filter; The microwave vacuum concentration unit includes a microwave reactor body, a vacuum system connected to the reactor body, an intelligent temperature control system, and a stirring system; the inner lining of the reactor body is made of high-purity PTFE material. The deep impurity removal unit includes a crystallization kettle, a sweating tank, and a chelating resin ion exchange column; The refining unit includes a decolorizing kettle, an ultra-clean filter, and a clean filling machine.

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