A method and system for in-situ preparation of cmp ceria precursor in an integrated reactor

Abstract

The application discloses a kind of integrated reaction kettle in-situ preparation CMP cerium oxide precursor method and system.The system uses integrated reaction kettle with three independent PID temperature control jacket, atomization spraying device and three layers gradient stirring mechanism.The method includes: with ammonium bicarbonate-ammonia as composite precipitant, with cerium salt base solution Synchronization atomization is added into reaction kettle, steady-state precipitation is carried out under pH 7.5-8.0, then gradient ripening and in-situ closed hydrothermal crystallization are carried out, and the whole process is completed in a single kettle closed.Aiming at the problem that the existing ammonium bicarbonate precipitation method pH drift leads to uneven particle size, and the pre-mixed composite precipitant is easy to decompose and fail, the obtained precursor has high purity, narrow particle size distribution and good batch consistency, and is suitable for the preparation of CMP polishing abrasive.

Description

Technical Field

[0002] This invention belongs to the field of semiconductor precision polishing material preparation technology, specifically relating to a method and system for in-situ preparation of high-purity nano-cerium oxide precursors for CMP (chemical mechanical polishing) in an integrated reaction vessel. Background Technology

[0004] Semiconductor chemical mechanical polishing (CMP) is a key process for achieving global wafer planarization in integrated circuit manufacturing. As integrated circuit manufacturing processes continue to evolve towards 7nm and below nodes, CMP processes place higher demands on polishing abrasives—high purity (total metal impurities ≤1ppm), high sphericity (sphericity ≥0.95), narrow particle size distribution (dispersion index PDI ≤0.15), and excellent batch consistency. Cerium oxide (CeO2), due to its extremely high polishing selectivity for silicon oxide media, has become the core abrasive choice for polishing STI (shallow trench isolation) layers in advanced processes at 7nm and below.

[0005] Liquid-phase precipitation is the mainstream process for preparing nano-cerium oxide precursors. The selection of precipitant and system design directly determine the purity, morphology, particle size distribution of the precursor and the final performance of the subsequent products.

[0006] Using ammonium bicarbonate as a precipitant to prepare cerium oxide is a known technical route in the field. Chinese patent CN102502758A discloses a method for preparing large-particle cerium oxide, using cerium chloride solution as a raw material and ammonium bicarbonate as a precipitant to prepare cerium oxycarbonate, followed by washing, filtration, and calcination to obtain a cerium oxide product with a central particle size of 35–45 μm. However, the cerium oxide particles prepared by this method are in the micrometer range (35–45 μm), much larger than the nanoscale abrasives required for CMP polishing (typically requiring D50 ≤ 100 nm). Furthermore, the precipitation process is carried out at a high temperature of 85–95 °C, resulting in high energy consumption and a narrow process window. In addition, the pH during the precipitation process is difficult to control precisely, leading to a widened particle size distribution.

[0007] Existing technologies also include methods for preparing cerium oxide using a mixed precipitant of ammonium bicarbonate and ammonia. Chinese patent CN104891550A discloses a method for preparing cerium dioxide using a mixed precipitant, employing a mixed solution of ammonium bicarbonate and ammonia as the precipitant to precipitate cerium ions in a cerium chloride solution into a mixture primarily composed of basic cerium carbonate, which is then further calcined to prepare cerium dioxide. This method involves adding the pre-prepared mixed precipitant solution. Because ammonium bicarbonate is easily decomposed in an alkaline environment, the actual ratio is difficult to control precisely. The precipitation process only controls the pH at the reaction endpoint (6.6–8.2), failing to achieve closed-loop pH control throughout the entire process, resulting in large fluctuations in the precipitation environment. Furthermore, this method requires operation at 50–70°C and a feeding time of 4–10 hours, leading to high energy consumption and low efficiency. Additionally, the addition of 10%–20% seed crystals increases the process complexity. Furthermore, this method employs a separate process route of reaction tank → vacuum filtration → muffle furnace, which involves multiple material transfers and easily introduces metallic impurities, making it difficult to meet the requirements of semiconductor CMP for high purity and high batch consistency of cerium oxide abrasives.

[0008] Furthermore, Chinese patent CN121872427A discloses a method for preparing an alumina@cerium oxide composite material. This method employs a stepwise precipitation process to first prepare an alumina hydroxide precursor, then deposits cerium hydroxide in situ on its surface, and finally calcines to form an Al2O3@CeO2 core-shell structure. However, this method prepares a core-shell composite material rather than a single cerium oxide abrasive; moreover, it relies on the synergistic effect of multiple additives such as complexing agents, steric hindrance agents, and dispersants, resulting in a complex and costly process. Additionally, it still requires multiple post-processing steps, including filtration, washing, drying, and calcination, involving multiple material transfers and posing a risk of impurity introduction.

[0009] In summary, the existing technical routes for preparing cerium oxide using the ammonium bicarbonate precipitation method share the following common problems:

[0010] (1) The pH of the precipitation process is difficult to control precisely, resulting in a widening of the particle size distribution. Ammonium bicarbonate has limited buffering capacity when used alone as a precipitant; the actual ratio of the pre-mixed ammonium bicarbonate-ammonia water composite system deviates from the preset value due to the decomposition of ammonium bicarbonate. Cerium ions nucleate and grow at different rates in different pH ranges, resulting in uneven grain size and a widening of the particle size distribution.

[0011] (2) The precursor exhibits obvious colloidal characteristics, poor filtration performance, and severe impurity encapsulation. The cerium carbonate precursor prepared using ammonium bicarbonate as a precipitant is a colloidal precipitate, which needs to be aged at high temperature for a sufficiently long time to obtain a product with good dispersibility; otherwise, large agglomerates will form. The colloidal precipitate has a strong encapsulation effect on free impurities in the reaction system, resulting in high residual metal impurities in the product, making it difficult to meet the stringent requirements of semiconductor CMP for abrasive purity.

[0012] (3) The split-process leads to the introduction of metal impurities. Existing cerium oxide precursor preparation processes generally use split-process equipment—the precipitation reaction is completed in a stirred precipitation vessel, and the material is transferred to a hydrothermal reactor or calcination furnace for subsequent processing after discharge. The material transfer process not only increases the number of operating procedures and human error, but also introduces metal impurities such as Fe, Cr, and Ni due to equipment wear and air dust, which seriously affects the purity of the product. At the same time, the split-process makes it difficult to achieve continuous and automated control of processes such as precipitation, ripening, and hydrothermal crystallization, resulting in large batch-to-batch fluctuations.

[0013] (4) Difficulty in controlling particle morphology. The morphology of cerium oxide precursors prepared by existing methods is mostly irregular polyhedral or plate-like with poor sphericity. Existing processes lack systematic control over the entire process of precipitation, ripening, and hydrothermal crystallization within the same system, resulting in limited morphology control capabilities.

[0014] In terms of equipment, existing cerium oxide precursor preparation processes generally lack integrated design for the entire process of precipitation, aging, and hydrothermal crystallization. Precipitation, aging, and hydrothermal crystallization are completed in different equipment, and materials are transferred multiple times. This not only increases the risk of introducing metal impurities, but also makes it difficult to accurately control the parameter transfer and matching between processes, seriously affecting the batch consistency of products.

[0015] In summary, among the existing technical routes for preparing cerium oxide using ammonium bicarbonate precipitation, there is still a lack of a complete process scheme that can simultaneously achieve precise pH control during the precipitation process, a completely sealed and transfer-free process, and products with high sphericity and narrow particle size distribution. This makes it difficult to meet the comprehensive requirements of semiconductor CMP polishing for cerium oxide abrasives, which require high purity, high sphericity, narrow particle size distribution, low metal impurity residue, and high batch consistency. Summary of the Invention

[0017] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and solve the technical problems of unstable precipitation environment caused by fluctuation in the ratio of ammonium bicarbonate-ammonia water composite precipitant in the preparation of existing cerium oxide precursors, introduction of metal impurities by material transfer in the split process, and poor uniformity of grain morphology. The present invention provides a method and system for in-situ preparation of CMP cerium oxide precursors in an integrated reactor.

[0018] To address the aforementioned technical problems, this invention provides a method for in-situ preparation of CMP cerium oxide precursor using an integrated reactor. The integrated reactor is equipped with a three-section independent PID temperature control jacket, a metering pump system, an atomizing spray device, a three-layer gradient stirring mechanism, and an integrated sealing interface for the reactor lid. The method includes the following steps:

[0019] The reactor cavity was purged and replaced with high-purity nitrogen to maintain an oxygen-free environment;

[0020] An ammonium bicarbonate-ammonia water composite precipitant is injected into the reactor, wherein the molar ratio of ammonium bicarbonate to ammonia water in the composite precipitant is 1:0.8 to 1.2;

[0021] Electronic-grade cerium salt base liquid is injected into the reactor, and the ratio of composite precipitant to cerium salt is controlled. The cerium salt base liquid is added to the composite precipitation system through the atomizing spray device. The precipitation temperature is controlled at 35-45℃ and the stirring speed is controlled at 60-250 r / min. The system is precipitated at pH 7.5-8.0 to generate cerium oxide precursor precipitate.

[0022] After precipitation, gradient aging is carried out in the same reactor at a temperature of 40–60°C.

[0023] After the ripening process is completed, the reactor is sealed, the temperature is raised to 120-150°C, and the pressure is raised to 0.5-1.5 MPa for in-situ hydrothermal crystallization.

[0024] After crystallization, the material is cooled gradually, depressurized, and discharged.

[0025] The Ce³⁺ concentration in the cerium salt base solution is 0.1–0.8 mol / L; the electronic-grade cerium salt is cerium nitrate.

[0026] The ammonium bicarbonate-ammonia water composite precipitant is prepared by using an ammonium bicarbonate solution with a concentration of 0.5–2.0 mol / L and an ammonia water buffer solution with a concentration of 1.0–5.0 mol / L.

[0027] The gradient maturation method is as follows: first, stir and mature at low speed for 0.5 to 1 hour, then let it stand and mature for 1 to 3 hours.

[0028] In the hydrothermal crystallization process, the heating rate is 1–3 °C / min, and the isothermal crystallization time is 3–5 h.

[0029] The sealing and pressurization method of the reactor is as follows: all feed valves and exhaust valves are closed, and the system's own pressure is used in conjunction with external high-purity nitrogen to pressurize to the target pressure, with a pressure stabilization accuracy of ±0.1MPa.

[0030] The three-layer gradient stirring mechanism includes an upper dispersing impeller, a middle shearing impeller, and a bottom anti-settling impeller; a stirring speed of 100-250 r / min is used in the sedimentation step, a stirring speed of 30-80 r / min is used in the maturation step, and a stirring speed of 50-150 r / min is used in the hydrothermal crystallization step.

[0031] The gradient cooling is a segmented cooling process: first, the temperature is reduced to 80°C at a rate of 1–2°C / min, then reduced to 40°C at a rate of 0.5–1°C / min, and finally cooled naturally to room temperature.

[0032] The present invention further provides an integrated reactor system for implementing the above method, comprising:

[0033] The vessel body is equipped with three independent PID temperature control jackets; the vessel body is equipped with a three-layer gradient stirring mechanism;

[0034] The vessel lid integrates a feed inlet, a metering pump inlet, an atomizing spray inlet, an air replenishment inlet, a sensor inlet, and a discharge inlet.

[0035] The system includes a PLC automatic control system, which is electrically connected to the three independent PID temperature control jackets, the metering pumping system, the atomizing spray device, the three-layer gradient stirring mechanism, and each sensor.

[0036] The reactor body is also equipped with a baffle plate; in the three-layer gradient stirring mechanism, the upper layer dispersion blade is a propeller blade, the middle layer shear blade is a straight-bladed turbine blade, and the bottom layer anti-sinking blade is an anchor blade; the feed port, metering pump port, atomizing spray port, gas supply port, sensor port, and discharge port integrated on the reactor cover are all sealed ports; the sensor port is equipped with an online pH sensor, temperature sensor, and turbidity sensor; the inner walls of the reactor body and the parts in contact with the material at the discharge port are provided with an anti-corrosion lining layer, and the material of the anti-corrosion lining layer is polytetrafluoroethylene; the connection between the reactor cover and the stirring shaft adopts a mechanical seal structure, and the sealing surface material is ceramic; the integrated reactor is also equipped with a one-way pressure reducing valve.

[0037] The beneficial effects achieved by this invention are as follows:

[0038] (i) Stable precipitation environment and narrow particle size distribution. Ammonium bicarbonate-ammonia water composite precipitant is used. It is independently and accurately proportioned and mixed online by dual metering pumps. Combined with uniform addition by atomized spray and pH closed-loop feedback control, the precipitation process is carried out in a stable environment of pH 7.5 to 8.0. Cerium ions nucleate and grow synchronously throughout the entire range. The batch-to-batch CV value of the product particle size is ≤0.4%.

[0039] (ii) High purity. The entire process of precipitation, ripening, hydrothermal crystallization and discharge is completed sequentially in an integrated reactor. The material does not need to be transferred and the reactor lid does not need to be opened. The total content of metal impurities in the product is ≤3ppm and the surface roughness Ra of the polished surface is ≤0.4nm.

[0040] (iii) Good sphericity and no hard agglomeration. A two-stage gradient ripening process is adopted: first, low-speed stirring is used to make the temperature and concentration fields uniform, and then the Oswald ripening effect is utilized to make the grains grow naturally in orientation. Combined with in-situ hydrothermal crystallization, the product has round and spherical grains with a particle size of 60-100nm and no agglomeration.

[0041] (iv) The morphology is controllable and adjustable. The morphology of the precursor particles can be controlled by adjusting the precipitation pH (7.5-8.0) and maturation time (2-4h), and the spherical product with the best sphericity can be obtained.

[0042] (V) Simplified process, low pressure and energy saving, reliable scale-up. The dual-channel metering pump system enables precise proportioning and stable delivery of the composite precipitant, and the process parameters are easy to solidify; the hydrothermal crystallization pressure is only 0.5 to 1.5 MPa, which is significantly lower than the traditional process, thus significantly reducing equipment costs and operating energy consumption; after scale-up verification from 50L to 300L, the key indicators of the product are highly consistent, and it can be scaled up to the industrial scale of 300 to 5000L.

[0043] (vi) The precursor has excellent quality and can be used to obtain advanced process-grade CMP polishing powder after conventional post-processing. It can be applied to low-damage precision polishing of 7-28nm process CMP. Attached Figure Description

[0045] Figure 1 A flowchart illustrating a method for preparing cerium oxide precursor, which is an exemplary embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the elevation structure of an integrated reactor in an exemplary embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the top structure of an integrated reactor in an exemplary embodiment of the present invention;

[0048] Figure 4 TEM images of the products of exemplary embodiments of the present invention;

[0049] Figure 5 Scanning electron microscope images of the products of exemplary embodiments of the present invention. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0052] like Figure 1 The general step flow of the exemplary embodiment of the present invention shown is as follows:

[0053] (1) Cavity cleaning pretreatment

[0054] Purge the reactor with high-purity nitrogen (≥99.999%) to replace the air inside. The nitrogen flow rate should be 0.5–2 L / min, and the purging time should be 10–30 min to maintain an oxygen-free environment with an oxygen content ≤10 ppm, thus preventing impurity adsorption and oxidation interference. After purging, close the exhaust valve and maintain a slight positive pressure of 0.01–0.05 MPa inside the reactor for later use.

[0055] (2) Preparation and injection of base liquid and composite precipitant

[0056] Preparation of cerium salt base solution: Electronic-grade cerium nitrate was used as the cerium source. The molecular formula of electronic-grade cerium nitrate is Ce(NO3)3·6H2O, and its purity is ≥99.99%. Electronic-grade cerium nitrate was dissolved in ultrapure water with a resistivity ≥18 MΩ·cm to prepare a base solution with a Ce³⁺ concentration of 0.1–0.8 mol / L. The pH of the base solution was adjusted to 2.5–3.5 using dilute nitric acid or dilute ammonia, and the temperature was stabilized to the target precipitation temperature of 35–45℃.

[0057] After the base solution is prepared, it is filtered through a precision filter to remove insoluble impurities and large external particles. The precision filter has a filtration accuracy of 0.05–0.45 μm, resulting in a high-purity, transparent cerium salt base solution. The base solution is then injected into the reactor via a metering pump system and an atomizing spray device.

[0058] Preparation of ammonium bicarbonate-ammonia water composite precipitant: Electronic grade ammonium bicarbonate (NH4HCO3, purity ≥99.5%) and electronic grade ammonia water (NH3·H2O, purity ≥99.99%) are selected as composite precipitant raw materials. Ammonium bicarbonate is dissolved in ultrapure water to prepare an ammonium bicarbonate solution with a concentration of 0.5–2.0 mol / L; electronic grade ammonia water is diluted with ultrapure water to prepare an ammonia water buffer solution with a concentration of 1.0–5.0 mol / L. The ammonium bicarbonate solution and ammonia water buffer solution are independently delivered and mixed online using a dual-channel metering pump system at a molar ratio of ammonium bicarbonate to ammonia water of 1:0.8–1.2 before being injected into the reactor. After preparation, the mixture is filtered through a precision filter to remove impurities before use.

[0059] The independent delivery mode of the dual-metering pump system ensures that ammonium bicarbonate and ammonia water maintain a precise ratio during the precipitation process, avoiding the decomposition and failure of ammonium bicarbonate caused by pre-mixing.

[0060] (3) Temperature-controlled steady-state precipitation

[0061] The dual-metering pump system is activated to independently deliver and online mix the ammonium bicarbonate solution and ammonia buffer solution at a preset molar ratio. These solutions are then simultaneously added to the reactor as atomized droplets via a spraying device, along with the cerium salt base solution. Ammonium bicarbonate provides the carbonate ions required for precipitation, while ammonia adjusts the pH and provides a buffer environment. Their synergistic effect allows cerium ions to nucleate and grow uniformly in a stable, weakly alkaline environment.

[0062] The precipitation temperature is controlled between 35 and 45°C. Within this temperature range, the decomposition rate of ammonium bicarbonate is low, the amount of ammonia volatilization is small, and the precipitation reaction rate is gradual and controllable.

[0063] The stirring speed is controlled between 100 and 250 r / min. At this speed, the three-layer gradient stirring mechanism can make the temperature field and concentration field uniform throughout the entire reactor, ensuring that cerium ions nucleate and grow isotropically in the system simultaneously.

[0064] The system was precipitated in a weakly alkaline environment with a pH of 7.5–8.0. A pH sensor provided real-time feedback to the PLC system, which achieved closed-loop pH control by adjusting the delivery rate of the ammonia buffer solution, with a stability accuracy of ±0.1%. The dropping rate of the cerium salt base solution was controlled at 1–3 mL / min (at a 5m... 3 Based on the large-scale reactor, the speed can be adjusted proportionally in actual production, and the entire process is uniform and controllable.

[0065] The precipitation endpoint was determined using an online turbidity sensor: precipitation was considered complete when the turbidity change rate was ≤0.5% / min for 10 consecutive minutes and the pH value remained stable within the set range for ≥5 minutes. The PLC system then automatically stopped the titration.

[0066] (4) Gradient ripening

[0067] After sedimentation, the process proceeds to a gradient ripening step. In this invention, "gradient ripening" refers to a two-stage ripening treatment performed sequentially under different stirring conditions within the same reactor at a medium temperature of 40–60°C.

[0068] The first stage – low-speed stirring and ripening: stirring at a speed of 30–80 r / min for 0.5–1 h. The purpose of this stage is to rapidly homogenize the temperature and concentration fields within the reactor, avoiding abnormal grain growth caused by local temperature or concentration differences, while simultaneously promoting the initial dissolution of extremely small grains within the system, providing a material basis for subsequent Oswald ripening.

[0069] The second stage – static ripening: stop stirring and let stand for 1–3 hours. Under conditions without external shear force, the system proceeds naturally by relying on the Oswald ripening effect – small-sized grains continue to dissolve, and the dissolved substances are deposited and grown on the surface of large-sized grains, making the grain size more uniform, the morphology more regular, and the micro-edges blunted, ultimately obtaining precursor particles with narrow particle size distribution and high sphericity.

[0070] The total curing time for the two stages is 2–3.5 hours (preferably 3 hours). The curing temperature is controlled at 40–60°C (preferably 50°C).

[0071] The criteria for determining the maturation endpoint are: the turbidity value monitored by the online turbidity sensor is stable, with fluctuations ≤ ±2% for 30 minutes, and the temperature sensor shows that the temperature in each temperature zone inside the vessel is uniform, with a temperature difference ≤ ±1℃.

[0072] (5) In-situ closed hydrothermal crystallization

[0073] After maturation, close all feed valves and exhaust valves, and the reactor enters a fully sealed state. Start the lower jacket for main heating, and the middle jacket for auxiliary heat preservation, raising the temperature to 120-150℃ at a heating rate of 1-3℃ / min.

[0074] The pressure required for hydrothermal crystallization consists of two parts: the self-generated pressure of the hydrothermal reaction system at high temperature, and the pressure replenishment from externally supplied high-purity nitrogen through the inlet pressure regulator. The self-generated pressure originates from water vapor and gaseous products. A pressure sensor monitors the pressure inside the reactor in real time. When the pressure is lower than the set value, the PLC automatically opens the inlet pressure regulator valve to replenish nitrogen; when the pressure is higher than the set value, the exhaust valve opens to release excess pressure through the back pressure regulating valve. The pressure regulation accuracy is controlled within ±0.1 MPa. The hydrothermal crystallization pressure is controlled between 0.5 and 1.5 MPa.

[0075] The matching relationship between hydrothermal crystallization temperature and pressure follows the saturated vapor pressure curve of water: 120℃ corresponds to an autogenous pressure of approximately 0.20 MPa, 135℃ to approximately 0.32 MPa, and 150℃ to approximately 0.48 MPa. Nitrogen gas is added to pressurize to the target pressure of 0.5–1.5 MPa to ensure the liquid phase system remains liquid at high temperatures, preventing boiling and guaranteeing homogeneous conditions for the hydrothermal reaction.

[0076] The isothermal crystallization time is 3-5 hours (preferably 4 hours). During hydrothermal crystallization, the stirring speed is controlled at 50-150 r / min (preferably 80-120 r / min).

[0077] Determining the endpoint of hydrothermal crystallization: After the hydrothermal time reaches the set value, the PLC system automatically starts the cooling program. A trace amount of slurry can be collected online via the sampling port for rapid XRD detection, or offline detection can be performed to confirm the completion of the crystal phase transformation—the cerium oxide precursor transforms into a CeO2 fluorite structure crystal phase.

[0078] (6) Gradient cooling and discharge

[0079] After crystallization, segmented gradient cooling is performed:

[0080] The first stage of cooling: cooling from 120-150℃ to 80℃ at a rate of 1-2℃ / min, with medium-temperature heat transfer oil or circulating hot water introduced into the jacket. The temperature of the medium-temperature heat transfer oil is 60-80℃.

[0081] The second stage of cooling: the temperature is reduced from 80℃ to 40℃ at a rate of 0.5 to 1℃ / min. The jacket is switched to circulating cooling water with a temperature of 5 to 25℃.

[0082] The third stage of cooling: cooling from 40℃ to room temperature, either through natural cooling or by introducing low-temperature cooling water at a temperature of 5-10℃.

[0083] Total cooling time: 1-3 hours.

[0084] After the temperature drops to ≤60℃, open the exhaust valve and slowly release the pressure to atmospheric pressure through the acid mist absorption device at a rate ≤0.1MPa / min. Open the bottom discharge valve, and the slurry is discharged through a precision filter with a filtration accuracy of 0.45~5μm and a filtration pressure of 0.2~0.5MPa. Nitrogen gas is used for pressurization, and the filtration time is 10~30min.

[0085] After discharge, the precursor filter cake is transferred to a nitrogen-protected transfer tank. The oxygen content in the nitrogen-protected transfer tank is ≤10ppm and the humidity is ≤10%RH. It is then sealed and stored or directly transferred to the calcination process.

[0086] like Figure 2 The integrated reactor system for implementing the present invention is shown below:

[0087] The integrated reactor system used in implementing the method of the present invention includes a reactor body 21, a reactor cover 22, a baffle plate 19 disposed in the reactor body, a three-layer gradient stirring mechanism, and a PLC automatic control system.

[0088] The vessel body is equipped with three independent PID temperature control jackets 23 (proportional-integral-derivative) distributed along the axial direction of the vessel body – upper jacket, middle jacket and lower jacket. Each jacket can be independently set in temperature and controlled in a closed loop. They are connected to the hot oil circulation system or the cooling water circulation system respectively to achieve segmented precise temperature control.

[0089] like Figure 3As shown, the reactor lid integrates a feed inlet 20, a metering pump inlet, an atomizing spray inlet, a gas supply inlet, a sensor inlet, and a discharge inlet. All inlets feature a sealed design, ensuring the reactor remains airtight throughout the entire precipitation, ripening, and hydrothermal crystallization process. Feeding, titration, gas supply, sensor monitoring, and discharge operations can be completed without opening the lid. The sensor inlet is used to install an online pH sensor 27, a temperature sensor 28, and a turbidity sensor, enabling real-time monitoring of the reaction process.

[0090] A three-layer gradient stirring mechanism is installed inside the reactor, comprising an upper dispersing impeller 24, a middle shearing impeller 25, and a bottom anti-settling impeller 26. The three impellers are arranged from top to bottom along the stirring shaft. The upper dispersing impeller disperses and mixes materials near the liquid surface; the middle shearing impeller provides medium to high shear force to break up soft agglomerates that may form during the reaction; and the bottom anti-settling impeller prevents particle deposition at the bottom. The rotational speeds of the three impellers can be independently or in conjunction with a PLC system to meet the varying requirements for stirring intensity and shear force at different process stages.

[0091] The upper dispersing impeller is preferably a propeller blade, used to generate axial circulating flow and push the material near the liquid surface downward to achieve overall mixing and dispersion; the middle shear impeller is preferably a straight-bladed turbine blade, used to generate high-shear radial flow to break up soft agglomerates that may be formed during the reaction; the bottom anti-settling impeller is preferably an anchor blade, used to fit the bottom of the vessel and rotate at low speed to loosen the bottom sediment and prevent particle settling.

[0092] The PLC automatic control system is electrically connected to three independent PID temperature control jackets, a metering pump system, an atomizing spray device, a three-layer gradient stirring mechanism, and various sensors. These sensors include a pH sensor, a temperature sensor, a turbidity sensor, and a pressure sensor. The PLC system can automatically complete the entire process, including chamber purging, base liquid injection, precipitant titration, temperature switching, speed adjustment, pressure control, and endpoint determination, according to a preset program.

[0093] In this invention, the "integrated reactor" refers to a reactor in which the entire process of precipitation, ripening, and hydrothermal crystallization is completed sequentially within the same reactor body without the need for material transfer. The "in-situ preparation" refers to the entire process from precipitation to hydrothermal crystallization being completed within the same reactor body without material transfer or opening the reactor lid.

[0094] In this invention, the PLC automatic control system uses a programmable logic controller (PLC) as the core control unit, and achieves closed-loop temperature control through a PID calculation module built into the controller. Its basic control logic is as follows: a temperature sensor installed inside the reactor collects the internal temperature signal in real time and feeds it back to the PLC. The PLC compares the measured temperature with a preset target temperature, performs PID calculations, and outputs a control signal to adjust the opening of the regulating valves in the heat transfer oil or cooling water circulation loops connected to each jacket section, thereby achieving independent and precise temperature control of each temperature zone of the reactor. The PLC control system also automatically executes the entire process of cavity purging, base liquid injection, precipitant titration, speed adjustment, pressure control, and endpoint determination through a preset timing program.

[0095] More preferably:

[0096] In this invention, the inner walls of the reactor body and the discharge port, and other components in contact with the material, are all provided with an anti-corrosion lining layer. The material of the anti-corrosion lining layer is polytetrafluoroethylene (PTFE), and the lining thickness is 3 mm. PTFE material is chemically inert throughout the pH range of 0 to 14, exhibits excellent resistance to corrosive media such as acids and alkalis, and does not release metal ions, effectively preventing corrosion of the reactor body by the reaction medium and the introduction of metal impurities.

[0097] In this invention, three baffles are uniformly arranged circumferentially on the inner wall of the reactor, with an included angle of 120° between adjacent baffles. The baffles are 200mm wide, 1500mm high, and 10mm thick. The function of the baffles is to disrupt the swirling flow, increase the degree of turbulence, improve the mixing efficiency, and ensure the uniformity of the temperature and concentration fields of the reaction system.

[0098] In this invention, the three-layer gradient stirring mechanism comprises an upper dispersion impeller with four propeller blades rotating horizontally at 45° to the right to generate axial circulating flow, pushing materials near the liquid surface downwards for overall mixing and dispersion; a middle shear impeller with straight-bladed turbine blades to generate high-shear radial flow, breaking up soft agglomerates that may form during the reaction; and a bottom anti-settling impeller with anchor blades that rotates at low speed against the bottom of the vessel, loosening bottom sediments and preventing particle settling. The stirring shaft is made of 89mm × 6mm seamless steel pipe, and the impeller blades are made of 12mm thick Q235A steel plate. The connection between the impeller blades and the shaft is reinforced after strength calculations, and the outer layer is coated with an ethylene-tetrafluoroethylene copolymer (ETFE) anti-corrosion coating. The material and structural design of the above stirring mechanism ensure mechanical strength and corrosion resistance at each stage of sedimentation, maturation, and hydrothermal crystallization.

[0099] In this invention, the connection between the vessel lid and the stirring shaft employs a mechanical seal structure, with the sealing surface material being ceramic. The ceramic sealing surface possesses excellent wear resistance and corrosion resistance; even if slight wear occurs during long-term operation, the sealing effect can be maintained through regular cleaning.

[0100] In this invention, the integrated reactor is also equipped with a one-way pressure reducing valve, which is used to automatically release pressure when the reactor pressure exceeds a preset safety value, thereby ensuring the safe operation of the equipment.

[0101] In this invention, the outer wall of the vessel is provided with a heat-insulating outer protective layer, and the material of the heat-insulating outer protective layer is a stainless steel wire plate with a thickness of 1mm.

[0102] In this invention, all butt welds in the reactor adopt a full penetration structure, with smooth transitions on the weld surface and no welding defects such as cracks, incomplete penetration, lack of fusion, porosity, slag inclusion, or undercut, to ensure the structural integrity and sealing reliability of the reactor body under high temperature and high pressure conditions.

[0103] More specific production practice examples

[0104] Example 1

[0105] This embodiment describes the in-situ synthesis of high-purity cerium oxide precursors for CMP, using a 50L integrated reactor system equipped with a three-stage independent PID temperature control jacket, dual-channel metering pumps, atomizing spray heads, a three-layer gradient stirring mechanism, and online pH, temperature, and turbidity sensors.

[0106] Cavity cleaning pretreatment. Turn on high-purity nitrogen to purge and replace the air inside the vessel. The purity of the high-purity nitrogen is ≥99.999%, the nitrogen flow rate is 1L / min, the purging time is 10min, and a slight positive pressure of 0.02MPa is maintained.

[0107] Preparation and injection of the base solution and composite precipitant. Prepare an electronic-grade cerium nitrate base solution with a Ce³⁺ concentration of 0.3 mol / L and pH=3.0. Inject the solution into the reactor and activate the gradient stirring mechanism for low-speed homogenization at 50 r / min for 5 min. Prepare an ammonium bicarbonate solution (1.0 mol / L) and an ammonia buffer solution (2.0 mol / L). Mix these solutions online using a dual-metering pump system at a molar ratio of 1:1.0 before injecting them into the reactor.

[0108] Constant-temperature controlled steady-state precipitation. A dual-metering pump system is activated to independently deliver and online mix ammonium bicarbonate solution and ammonia buffer solution at a preset molar ratio. These solutions are then simultaneously added to the reactor via an atomizing spray device along with the cerium salt base solution. The reaction temperature is controlled at 40℃, with 25℃ cooling water circulated through the upper jacket, and temperature is controlled by PID control. The system pH is stabilized at 7.8±0.1, with a pH sensor providing real-time feedback to the PLC system. The PLC achieves closed-loop pH control by adjusting the delivery rate of the ammonia buffer solution. The cerium salt base solution droplet acceleration rate is 1.8 mL / min, and uniform titration is completed in 2 hours. During the process, the stirring speed is 200 r / min, with the upper dispersion impeller, middle shear impeller, and bottom anti-settling impeller working in tandem. The precipitation endpoint is determined when the turbidity change rate monitored by the online turbidity sensor is ≤0.5% / min for 10 consecutive minutes, and the pH value remains stable within the set range for ≥5 minutes; at this point, the PLC system automatically stops the titration.

[0109] Gradient maturation. After sedimentation, the stirring speed was reduced to 60 r / min, and the maturation temperature was 50℃, with uniform temperature control across all three jacket sections. The first stage was low-speed stirring and maturation for 1 hour; the second stage involved stopping stirring and allowing the mixture to stand for 2 hours, for a total of 3 hours. The maturation endpoint was determined by: stable turbidity values ​​monitored by the online turbidity sensor, with fluctuations ≤ ±2% for 30 minutes, and uniform temperature across all jacket sections within the vessel, with a temperature difference ≤ ±1℃.

[0110] In-situ closed-loop hydrothermal crystallization. After maturation, all feed and exhaust valves are closed, and the reactor is completely sealed. The lower jacket is started for main heating, while the middle jacket provides auxiliary insulation, raising the temperature to 135°C at a rate of 2°C / min. Simultaneously, high-purity nitrogen is supplied through the pressure inlet to a pressure of 0.6 MPa, with a pressure stabilization accuracy of ±0.1 MPa. Crystallization is carried out at a constant temperature for 4 hours, with a stirring speed of 100 r / min.

[0111] Gradient cooling and discharge. After crystallization, the temperature is reduced to 80℃ at a rate of 1.5℃ / min, and then further reduced to 40℃ at a rate of 0.8℃ / min. The pressure is then released to atmospheric pressure at a rate of 0.05MPa / min. The material is discharged through a bottom precision filter with a filtration accuracy of 1μm, pressurized with nitrogen at 0.3MPa, and the filtration time is 15min.

[0112] Washing. Wash the vessel three times with ultrapure water, each time adding 20L of ultrapure water, stirring and washing for 15min, then filter out the washing solution until the conductivity of the washing solution is ≤5μS / cm.

[0113] The cerium oxide precursor obtained in this embodiment was determined by XRD to be a pure CeO2 fluorite crystalline phase. SEM showed that the grains were rounded, nearly spherical, with a particle size of 60–100 nm, and without agglomeration. ICP-MS analysis showed that the total content of metallic impurities was ≤3 ppm. The batch CV value was ≤0.4%.

[0114] Figure 4This is a scanning electron microscope (SEM) image of the cerium oxide precursor obtained in this embodiment. Figure 5 Here is its transmission electron microscope (TEM) image. (By...) Figure 4 As can be seen, the precursor grains are nearly spherical, with smooth, rounded surfaces, no obvious sharp edges, and are well dispersed without agglomeration. Figure 5 As can be seen, the internal structure of the grains is dense, without structural defects such as pores or cracks, and the particle size distribution ranges from 60 to 100 nm, which is consistent with the test results of the laser particle size analyzer.

[0115] Example 2: Morphology regulation of cerium oxide precursor

[0116] Using the process route of Example 1, with other parameters kept constant, the precipitation pH was set to 7.5, 7.8, and 8.2, and the aging time was set to 2 h, 3 h, and 4 h, respectively, to investigate the effect on the morphology of the cerium oxide precursor.

[0117] 7.5 2h The particles are irregular polyhedrons with distinct edges and corners. Poor 7.8 3h The particles are spherical with a smooth surface. optimal 8.2 4h The particles tend to be spherical, but a small amount of secondary aggregation occurs. generally

[0118] The results show that pH=7.8 and aging for 3 hours is the optimal process window for cerium oxide precursor, which can yield products with the best sphericity and dispersibility.

[0119] Example 3: Batch Repeatability Validation

[0120] Using the optimized process parameters from Example 1, 10 batches were continuously run. Each batch underwent particle size analysis, purity analysis, and phase analysis using laser particle size analyzer, ICP-MS, and XRD, respectively. The results are as follows:

[0121] Average of 1-10 batches 80±10 ≥99.999% <![CDATA[pure CeO2 fluorite structure]]> inter-batch CV value ≤0.4% — —

[0122] The superimposed comparison of XRD diffraction patterns from 10 batches showed that the characteristic peak positions and peak intensities were consistent, the relative standard deviation was ≤2%, and the particle size distribution curves almost overlapped, verifying the excellent repeatability of the equipment and process of this invention.

[0123] Example 4: Comparative Experiment with Split Process

[0124] A control experiment was set up: traditional split process (stirred sedimentation tank → discharge → hydrothermal tank) vs. the single-tank in-situ process of the present invention (parameters of Example 1):

[0125] Product purity (ICP-MS) 99.95～99.98% ≥99.999% Particle morphology (SEM rating) Irregular, serious family reunions Spherical shape, well dispersed Batch CV value ≥1.0% ≤0.4% Polished surface roughness Ra 0.6~1.0nm ≤0.4nm

[0126] ICP-MS analysis of the split-process products showed significant metallic impurities such as Fe, Cr, and Ni, originating from equipment wear and airborne dust during material transfer. The single-reactor in-situ process of this invention, due to its completely closed system and lack of material transfer, significantly reduces the content of metallic impurities.

[0127] Example 5: Scale-up Production Verification

[0128] The 50L pilot-scale process of Example 1 was directly scaled up to a 300L pilot-scale. The equipment structure was scaled up proportionally, the PTFE lining thickness was increased from 4mm to 6mm, the jacket heat exchange area was scaled up proportionally, and the agitator diameter was scaled up proportionally to the inner diameter of the reactor. Three batches were run continuously, and the results are shown in the table below:

[0129] 50L (trial run) 80±10 ≥99.999% ≤0.4% <![CDATA[pure CeO₂ with fluorite structure]]> 300L (pilot test) 82±12 ≥99.999% ≤0.42% <![CDATA[Pure CeO₂ with fluorite structure]]>

[0130] The key indicators of the 300L pilot-scale product, such as particle size, purity, phase composition, and CV value, were highly consistent with the small-scale test results, showing no significant scale-up effect. Stepwise scale-up verification from 50L to 300L demonstrated that, while maintaining geometric similarity and key process parameters, the scale-up law of this process is clear and reproducible. Based on the principles of chemical process scale-up, the transfer characteristics and mixing behavior verified in the 300L pilot-scale test can be reasonably extrapolated to the 300–5000L industrial scale, providing a technical foundation for large-scale industrial application.

[0131] Definitions and parameter references for key terms in this case

[0132] The proportioning basis of ammonium bicarbonate-ammonia water composite precipitant

[0133] The determination of the ammonium bicarbonate to ammonia molar ratio of 1:0.8 to 1.2 is based on the following: ammonium bicarbonate provides the carbonate ions required for precipitation, forming the cerium carbonate precursor precipitate with Ce³⁺; ammonia adjusts the pH of the system and provides a buffer environment, maintaining precipitation under stable, weakly alkaline conditions. When the molar ratio is lower than 1:0.8, the proportion of ammonia is too low, making it difficult to stabilize the system pH within the target range of 7.5 to 8.0; when the molar ratio is higher than 1:1.2, the proportion of ammonia is too high, resulting in excessively alkaline system conditions, which may lead to the formation of cerium hydroxide byproducts and affect the purity of the precursor.

[0134] Basis for determining the pH range of 7.5–8.0 for precipitation

[0135] The lower pH limit of 7.5 is determined as follows: cerium carbonate precursors precipitate stably under weakly alkaline conditions. When the pH is below 7.5, precipitation is incomplete, leaving residual cerium ions in the supernatant. The upper pH limit of 8.0 is determined as follows: above 8.0, the alkalinity of the system increases, and some cerium ions may precipitate as cerium hydroxide rather than as cerium carbonate precursors, affecting the morphology and purity of subsequent hydrothermal crystallization products.

[0136] Basis for determining the hydrothermal crystallization temperature range of 120–150℃

[0137] When the hydrothermal temperature is below 120℃, the precursor crystallization is incomplete, resulting in low crystallinity of the CeO2 fluorite structure; when the temperature is above 150℃, the grain growth is too rapid, leading to increased grain size and wider distribution. A temperature of 135℃ is preferred to obtain a CeO2 precursor with complete crystallization and uniform grain size.

[0138] Segmented temperature control logic of a three-segment independent PID temperature control jacket

[0139] The three temperature zones are distributed along the axial direction of the vessel body, divided into upper, middle, and lower sections, each serving a different function at different stages of the process:

[0140] Precipitation (35-45℃) Temperature control via cooling water Temperature control via cooling water Temperature control via cooling water Whole vessel temperature uniformity Mature (40-60℃) Temperature control via heat transfer oil Temperature control via heat transfer oil Temperature control via heat transfer oil Whole vessel temperature uniformity Hydrothermal (120-150℃) Insulate with heat transfer oil or shut off Heat transfer oil auxiliary heating Main heating with heat transfer oil Lower section for main heating, upper section for insulation.

[0141] The hydrothermal crystallization stage adopts a temperature field design with a lower section for main heating and an upper section for heat preservation, which can promote natural convection circulation inside the reactor and assist the stirring mechanism to achieve uniform temperature.

[0142] The rotation speed setting logic of the three-layer gradient stirring mechanism at each stage

[0143] The underlying mechanisms for setting the rotational speed at each stage are as follows:

[0144] During the sedimentation stage, the stirring speed is 100-250 r / min: a high stirring speed is required to ensure rapid mixing and dispersion of the cerium salt solution and the composite precipitant, avoid local oversaturation, and at the same time use the shearing force of the middle layer shear impeller to break up any soft agglomerates that may be formed.

[0145] During the maturation stage, the stirring speed is 30–80 r / min: a low stirring speed is required to avoid high shear forces damaging the growing grains. The low-speed stirring in the first stage is only to ensure uniformity of the temperature and concentration fields, and the second stage is complete settling.

[0146] Stirring speed of 50-150 r / min during hydrothermal stage: A medium stirring speed is required to ensure uniform heat transfer under high temperature and high pressure, while avoiding mechanical damage to the grains caused by excessive speed.

[0147] Compared with the prior art, the present invention has the following beneficial effects:

[0148] (i) The sedimentation environment is stable and the particle size distribution is narrow.

[0149] This invention employs an ammonium bicarbonate-ammonia composite precipitant, utilizing a dual-metering pump system to achieve independent and precise proportioning and online mixing of ammonium bicarbonate and ammonia, thus avoiding the decomposition and failure of ammonium bicarbonate caused by pre-mixing. Combined with uniform addition via atomized spraying and closed-loop pH feedback control (pressure stabilization accuracy ±0.1), the entire precipitation process takes place in a stable environment of pH 7.5–8.0, enabling simultaneous nucleation and growth of cerium ions throughout the entire precipitation process. Verification through ten batches of continuous operation in Example 3 showed that the batch-to-batch particle size CV value was ≤0.4%, and the relative standard deviation of XRD characteristic peaks was ≤2%, demonstrating excellent batch consistency.

[0150] (ii) High purity.

[0151] This invention completes the entire process of precipitation, ripening, hydrothermal crystallization, and discharge sequentially within an integrated reactor. No material transfer is required, the reactor lid does not need to be opened, and the entire operation is completely sealed. Combined with high-purity raw materials and an oxygen-free environment, it eliminates the introduction of metallic impurities such as Fe, Cr, and Ni due to equipment wear and airborne dust, which is present in traditional separate processes. Examples 1 and 4 verify that the product purity is ≥99.999%, the total content of metallic impurities is ≤3ppm, and the polished surface roughness Ra is ≤0.4nm.

[0152] (iii) Good sphericity and no hard agglomeration.

[0153] After precipitation, a two-stage gradient ripening process is adopted—first, low-speed stirring is used to homogenize the temperature and concentration fields, and then the grains are allowed to stand to utilize the Oswald ripening effect to allow the grains to grow naturally in orientation, and the microscopic edges are blunted. Combined with in-situ hydrothermal crystallization, the product of Example 1 has rounded, spherical grains with a particle size of 60-100 nm and no agglomeration, which meets the requirements of CMP low-damage polishing for abrasive morphology.

[0154] (iv) The appearance is controllable and adjustable.

[0155] The precursor particle morphology can be controlled by adjusting the precipitation pH (7.5–8.0) and aging time (2–4 h). Example 2 verified that pH=7.8 and aging for 3 h are the preferred process windows, which can obtain spherical products with the best sphericity and dispersibility, meeting the differentiated requirements of abrasive morphology in different CMP polishing scenarios.

[0156] (v) Simplified process, low voltage energy saving, and reliable amplification.

[0157] The dual-metering pump system enables precise proportioning and stable delivery of the composite precipitant, with easily solidified process parameters and strong anti-interference capabilities. The hydrothermal crystallization pressure is only 0.5–1.5 MPa, significantly lower than traditional processes, substantially reducing equipment pressure rating requirements and manufacturing costs, improving operational safety, reducing the amount of high-purity nitrogen used for pressurization, and significantly lowering operating costs. Scale-up verification from 50L to 300L in Example 5 showed highly consistent key product indicators with no significant scale-up effect. Based on the principles of chemical process scale-up, it can be further scaled up to an industrial scale of 300–5000L, possessing the technological foundation for direct industrial transformation.

[0158] (vi) The precursor has excellent quality and can be used to obtain advanced process-grade CMP polishing powder through conventional post-processing.

[0159] Cerium oxide is a core abrasive choice for polishing STI (shallow trench isolation) layers in advanced processes of 7nm and below, exhibiting extremely high polishing selectivity for silicon oxide media. The cerium oxide precursor prepared in this invention possesses high purity (≥99.999%), narrow distribution, and excellent sphericity. After gradient calcination and airflow classification treatment, it is expected to yield high-performance CeO2 polishing powder with D50=30~80nm, PDI≤0.12, and sphericity≥0.98, which can be applied to low-damage precision polishing in CMP processes of 7-28nm.

[0160] This invention may have many other embodiments. The embodiments described above are merely specific implementations of this invention, used to exemplify the technical solutions of this invention, and not to limit it. The scope of protection of this invention should cover any modifications, equivalent substitutions, and functional extensions made by those skilled in the art based on the core technical concept and principles of this invention. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, all of which should be included within the scope of protection defined by the claims of this invention.

Claims

1. A method for in-situ preparation of CMP cerium oxide precursor in an integrated reactor, wherein the integrated reactor is equipped with a three-section independent PID temperature control jacket, a metering pump system, an atomizing spray device, a three-layer gradient stirring mechanism, and an integrated sealing interface for the reactor lid, characterized in that, Includes the following steps: The reactor cavity was purged and replaced with high-purity nitrogen to maintain an oxygen-free environment; An ammonium bicarbonate-ammonia water composite precipitant is injected into the reactor, wherein the molar ratio of ammonium bicarbonate to ammonia water in the composite precipitant is 1:0.8 to 1.2; Electronic-grade cerium salt base liquid is injected into the reactor, and the ratio of composite precipitant to cerium salt is controlled. The cerium salt base liquid is added to the composite precipitation system through the atomizing spray device. The precipitation temperature is controlled at 35-45℃ and the stirring speed is controlled at 60-250 r / min. The system is precipitated at pH 7.5-8.0 to generate cerium oxide precursor precipitate. After precipitation, gradient aging is carried out in the same reactor at a temperature of 40–60°C. After the ripening process is completed, the reactor is sealed, the temperature is raised to 120-150°C, and the pressure is raised to 0.5-1.5 MPa for in-situ hydrothermal crystallization. After crystallization, the material is cooled gradually, depressurized, and discharged.

2. The method according to claim 1, characterized in that, The Ce³⁺ concentration in the cerium salt base solution is 0.1–0.8 mol / L; the electronic-grade cerium salt is cerium nitrate.

3. The method according to claim 1, characterized in that, The ammonium bicarbonate-ammonia water composite precipitant is prepared by using an ammonium bicarbonate solution with a concentration of 0.5–2.0 mol / L and an ammonia water buffer solution with a concentration of 1.0–5.0 mol / L.

4. The method according to claim 1, characterized in that, The gradient maturation method is as follows: first, stir and mature at low speed for 0.5 to 1 hour, then let it stand and mature for 1 to 3 hours.

5. The method according to claim 1, characterized in that, In the hydrothermal crystallization process, the heating rate is 1–3 °C / min, and the isothermal crystallization time is 3–5 h.

6. The method according to claim 1, characterized in that, The sealing and pressurization method of the reactor is as follows: all feed valves and exhaust valves are closed, and the system's own pressure is used in conjunction with external high-purity nitrogen to pressurize to the target pressure, with a pressure stabilization accuracy of ±0.1MPa.

7. The method according to claim 1, characterized in that, The three-layer gradient stirring mechanism includes an upper dispersing impeller, a middle shearing impeller, and a bottom anti-settling impeller; a stirring speed of 100-250 r / min is used in the sedimentation step, a stirring speed of 30-80 r / min is used in the maturation step, and a stirring speed of 50-150 r / min is used in the hydrothermal crystallization step.

8. The method according to claim 1, characterized in that, The gradient cooling is a segmented cooling process: first, the temperature is reduced to 80°C at a rate of 1–2°C / min, then reduced to 40°C at a rate of 0.5–1°C / min, and finally cooled naturally to room temperature.

9. An integrated reactor system for implementing the method according to any one of claims 1 to 8, characterized in that, include: The vessel body is equipped with three independent PID temperature control jackets; the vessel body is equipped with a three-layer gradient stirring mechanism; The vessel lid integrates a feed inlet, a metering pump inlet, an atomizing spray inlet, an air replenishment inlet, a sensor inlet, and a discharge inlet. The system includes a PLC automatic control system, which is electrically connected to the three independent PID temperature control jackets, the metering pumping system, the atomizing spray device, the three-layer gradient stirring mechanism, and each sensor.

10. The integrated reactor system according to claim 9, characterized in that, The reactor body is also equipped with a baffle plate; in the three-layer gradient stirring mechanism, the upper layer dispersion blade is a propeller blade, the middle layer shear blade is a straight-bladed turbine blade, and the bottom layer anti-sinking blade is an anchor blade; the feed port, metering pump port, atomizing spray port, gas supply port, sensor port, and discharge port integrated on the reactor cover are all sealed ports; the sensor port is equipped with an online pH sensor, temperature sensor, and turbidity sensor; the inner walls of the reactor body and the parts in contact with the material at the discharge port are provided with an anti-corrosion lining layer, and the material of the anti-corrosion lining layer is polytetrafluoroethylene; the connection between the reactor cover and the stirring shaft adopts a mechanical seal structure, and the sealing surface material is ceramic; the integrated reactor is also equipped with a one-way pressure reducing valve.

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