Preparation method of electronic-grade ammonium fluoride solution

Abstract

The invention belongs to the field of chemical engineering, and particularly relates to a preparation method of an electronic-grade ammonium fluoride solution. The method comprises the following steps: taking a solid-state ammonia source and hydrogen fluoride as a solid-phase raw material and a gas-phase raw material respectively, putting the solid-state ammonia source into a reaction container, taking inert gas as carrier gas, mixing the carrier gas with hydrogen fluoride gas to form reaction gas, and heating the reaction gas; introducing the reaction gas into the reaction container to be in contact with a solid ammonia source to carry out temperature-controlled solid-gas contact reaction; in the reaction process, the temperature of the reaction container is monitored, introduction of hydrogen fluoride is stopped and the carrier gas is continuously introduced after the reaction container starts to be cooled, and after continuous cooling, the reaction container is stopped and a solid-phase product is recovered; and preparing the recovered solid-phase product into an electronic-grade ammonium fluoride solution with a target concentration according to requirements. The novel solid-gas contact thermal reaction method is adopted, the preparation difficulty and equipment requirements of the electronic-grade ammonium fluoride solution are effectively reduced, operation is convenient, meanwhile, the safety of the preparation process is higher, and the utilization rate of raw materials is higher.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, and in particular relates to a method for preparing electronic-grade ammonium fluoride solution. Background Technology

[0002] Ammonium fluoride (NH4F) is a common and widely used chemical raw material, which is widely used in various fields such as mineral processing, electroplating, glassmaking, steel industry, organic synthesis and agriculture, and has a very wide range of applications.

[0003] In the electronics industry, ammonium fluoride used in semiconductor manufacturing requires extremely high purity, typically meeting electronic-grade standards. Its impurity content, particularly metal ions and particulate impurities, must be strictly controlled to very low levels. Similarly, electronic-grade ammonium fluoride solutions also have very stringent requirements regarding the content of metal ions and particulate impurities; for example, the requirement for metal ion impurities is usually at the ppm level.

[0004] Currently, there are two main processes for preparing ammonium fluoride or ammonium fluoride solutions: gas-phase and liquid-phase methods. The gas-phase method offers advantages such as fast reaction rates and high product purity, meeting electronic-grade standards. However, it requires stringent reaction conditions and highly sophisticated equipment, including precise temperature and pressure control. Furthermore, high-purity hydrogen fluoride gas is costly and has poor safety. While the liquid-phase method is simple, economical, and safe, its purity is lower, requiring multiple impurity treatment steps, and it typically struggles to meet electronic-grade standards. In addition, both the gas-phase and liquid-phase methods suffer from a significant disadvantage: low raw material utilization. Recovered raw materials are difficult to reuse (purity declines, failing to meet raw material standards), and excess raw materials can easily form difficult-to-remove impurities. Other common processes, such as the fluorosilicic acid method and the ammonium chloride / sodium fluoride heating sublimation method, also have their own disadvantages to varying degrees.

[0005] Therefore, it is very important to develop a greener, more environmentally friendly, and simpler synthetic route. Summary of the Invention

[0006] To address the problems of fixed existing ammonium fluoride and ammonium fluoride solution synthesis processes, which often make it difficult to prepare electronic-grade ammonium fluoride solution products, or result in high preparation difficulty, poor safety, and low raw material utilization, this invention provides a method for preparing electronic-grade ammonium fluoride solution.

[0007] The main objective of this invention is: First, it can effectively reduce the difficulty and equipment requirements for preparing electronic-grade ammonium fluoride solutions; II. Improve the safety of the preparation process; Third, significantly reduce the requirements for some raw materials and improve the utilization rate of raw materials.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A method for preparing electronic-grade ammonium fluoride solution. The method includes: Solid ammonia source and hydrogen fluoride are used as solid-phase raw materials and gas-phase raw materials, respectively. The solid ammonia source is placed in the reaction vessel, and an inert gas is used as the carrier gas. The carrier gas is mixed with hydrogen fluoride gas to form a reaction gas, which is then heated. The reaction gas is then introduced into the reaction vessel to contact the solid ammonia source for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the reaction vessel begins to cool down, the flow of hydrogen fluoride is stopped and the carrier gas is continued. The flow is stopped and the solid product is recovered when the temperature of the reaction vessel drops to only 2-3 °C above the temperature of the reaction gas. The recovered solid product is prepared into an electronic-grade ammonium fluoride solution of the target concentration as required.

[0010] As a preferred option The solid ammonia source is ammonium carbamate.

[0011] As a preferred option The hydrogen fluoride gas is prepared by evaporation of industrial hydrofluoric acid.

[0012] As a preferred option The inert gas is nitrogen and / or argon.

[0013] As a preferred option The reaction gas is heated to 36–38 °C.

[0014] As a preferred option The carrier gas and hydrogen fluoride gas are mixed in a volume ratio of (6-10):1 to form a reaction gas.

[0015] As a preferred option The flow rate of hydrogen fluoride gas in the reaction gas is controlled at 0.02–0.05 mol·min. -1 ·mol -1 Solid ammonia source.

[0016] The technical solution of this invention is actually a very simple and clear solid-gas contact reaction. However, what makes this invention different is its significant uniqueness in the selection of raw materials. Specifically, the solid ammonia source is ammonium carbamate, a special component. Ammonium carbamate (NH2COONH4) is a common industrial product, frequently used in the urea production industry, and is an intermediate product in the urea synthesis process. The development of this invention also began with a chance urea synthesis experiment. Experiments revealed that the low-temperature decomposition-recombination process of ammonium carbamate at 35–59 °C makes it an excellent ammonia source for the synthesis of ammonium fluoride. Due to this unique property, when heated hydrogen fluoride gas is released from it, ammonium carbamate decomposes and reacts with ammonia and hydrogen fluoride at an extremely rapid rate to produce ammonium fluoride powder. In this process, since nitrogen is used as the carrier gas for purging, it also plays a certain role in separation. However, when the carrier gas (reaction gas) flow rate is approximately 0.5 m / s, it can cause a short-range displacement of ammonia and hydrogen fluoride gas, and similar short-range displacement occurs after the formation of ammonium fluoride powder. During the experimental development process, the reaction gas with a transverse flow rate of 0.5 m / s ensured that the minimum distance between the solid product ammonium fluoride pile and the raw material ammonium carbamate pile was 4–5 mm. The 1 cm stacking interval makes it easy to distinguish between the raw material stack and the product stack (solid product stack) during recycling. In industrial production, this interval may be further increased through flow channel optimization or other methods, thereby further reducing recycling costs and difficulties, and helping to control the purity of the directly obtained solid product.

[0017] In a laboratory environment, after being heated under vacuum at 50 °C for 5 minutes, the product pile showed a mass loss rate of <1%, indicating that the raw material pile was essentially not entrained into the product pile by the reactant gas. This is mainly attributed to the low-cost approach adopted in the early stages of the experiment. Industrial hydrofluoric acid was used to obtain hydrogen fluoride gas via a low-temperature, low-pressure evaporation process. This gas actually contains water, and since both ammonium fluoride and ammonium carbamate are hygroscopic, the two piles absorbed moisture and formed clumps. While this reduced the purity of the solid product, ammonium fluoride, it had almost no impact on its use in preparing electronic-grade ammonium fluoride solutions. Similarly, ammonium carbamate, after absorbing moisture, did not affect the reaction or significantly increase the decomposition temperature, having virtually no impact on the reaction process. The macroscopic phenomenon observed was that the raw material was powdered ammonium carbamate, while after the reaction terminated, both the raw material pile and the product pile consisted of particles of a certain size, with some experimental groups even showing larger agglomerated products or remaining raw materials.

[0018] As can be seen from the above, hydrogen fluoride in the reaction gas of this invention actually participates in the reaction as a gaseous raw material, while the carrier gas, as another core component of the reaction gas, actually plays the role of temperature control and separation of raw materials and products. Generally speaking, according to the search data, 0.5 m / s powder can only be blown up by ultrafine powder with D95 < 20 μm. However, in actual experiments or industrial production, the maximum possible wind speed can be selected based on the minimum wind speed that can be blown up according to the search data for the raw material particle size to achieve separation of the raw material pile and the product pile. Of course, separation is not necessary. It is only necessary to perform a certain degree of low-temperature vacuum heating on the mixed pile after the reaction to decompose and remove the unreacted raw materials. Of course, this will lead to an increase in the impurity content of the product, because the separation of the product pile and the raw material pile can also separate some impurities in the raw materials. These impurities and the remaining raw materials are agglomerated and fixed in the raw material pile, which can further improve the purity of the product pile.

[0019] Having discussed the combination and reaction of solid ammonia source, hydrogen fluoride gas, and carrier gas, it is crucial to emphasize the control of three key factors: reaction gas temperature, the volume ratio of carrier gas to hydrogen fluoride gas, and hydrogen fluoride flow rate. As mentioned earlier, the combination of solid ammonia source, hydrogen fluoride gas, and carrier gas completes the reaction and facilitates the separation of products and raw materials through gas flow. The reaction gas temperature, the volume ratio of carrier gas to hydrogen fluoride gas, and the hydrogen fluoride flow rate are the three key factors for controlling the temperature during the reaction process.

[0020] Firstly, the temperature control of the reactant gas. The reactant gas should initially be slightly higher than the initial decomposition temperature (35 °C) of the solid ammonia source, ammonium carbamate, to initiate the reaction. Only before and during the initiation of the reaction does the reactant gas serve to raise the temperature. Once the reaction begins, the reactant gas then serves to cool and control the temperature, preventing excessive temperature drops that could lead to the formation of the byproduct ammonium difluoride. This cooling and temperature control function is necessary because the reaction between ammonia and hydrogen fluoride is highly exothermic, causing the system to heat up. This intensifies the decomposition of ammonium carbamate, producing more ammonia, which further amplifies the exothermic reaction, resulting in an uncontrollable and continuous rise in system temperature. At this point, the carrier gas in the reactant gas, which does not participate in the reaction, acts as a temperature controller, carrying away excess heat and preventing the ammonium carbamate decomposition process from becoming too rapid, causing rapid pulverization of the raw materials and potentially introducing impurities into the product pile. It also prevents other side reactions that might occur under high-temperature conditions.

[0021] Temperature control is primarily achieved through the temperature of the reaction gases, especially the carrier gas. Since the carrier gas itself does not participate in the reaction, it acts as a temperature buffer. Therefore, the relative volume ratio of the carrier gas to hydrogen chloride gas is crucial, decisively affecting the temperature control of the reaction system. Insufficient carrier gas will cause the reaction temperature to rise uncontrollably, while excessive carrier gas will severely limit reaction efficiency. Hydrogen fluoride, as one of the reaction raw materials, is an exothermic process, and its dosage relative to the solid ammonia source ammonium carbamate needs to be carefully controlled per minute. Thus, the three factors work together to achieve temperature control.

[0022] In summary, the technical solution of this invention appears simple, but each parameter requires relatively precise control to achieve fine control of the reaction process. However, unlike conventional gas-phase methods, the technical solution of this invention is simpler to control, has relatively lower equipment requirements, and is easier to implement, which essentially greatly reduces the preparation difficulty.

[0023] The beneficial effects of this invention are: This invention employs a novel solid-gas contact thermal reaction method, which effectively reduces the difficulty and equipment requirements for preparing electronic-grade ammonium fluoride solution, simplifies operation, enhances safety during the preparation process, and increases the utilization rate of raw materials. Detailed Implementation

[0024] The present invention will be further described clearly and in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0025] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0026] Example 1: A method for preparing an electronic-grade ammonium fluoride solution, the method comprising: Industrial-grade refined ammonium carbamate was placed in a reaction vessel. Nitrogen was used as the carrier gas. A small amount of potassium permanganate was added to industrial hydrofluoric acid until it began to turn purple. The mixture was then evaporated at 23±1 °C and 0.75 atm to form hydrogen fluoride gas (the hydrogen fluoride content in the hydrogen fluoride gas was calculated based on a 70% concentration). The carrier gas and hydrogen fluoride gas were mixed at a volume ratio of 8:1 to form a reaction gas and heated to 36 °C. The reaction gas was then introduced at a flow rate of 0.5 m / s, and the flow rate of hydrogen fluoride gas in the reaction gas was 0.05 mol of hydrogen fluoride per minute per mole of ammonium carbamate raw material. The reaction gas was then introduced into the reaction vessel to contact the ammonium carbamate for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the temperature of the reaction vessel begins to drop and falls below 5°C below the highest temperature of the reaction vessel during the reaction, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. For example, in this case, the reaction vessel temperature rises to a maximum of 52°C. When the temperature drops to 47°C, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. Once the temperature of the reaction vessel drops to 39°C, all gas flow is stopped. After natural cooling to room temperature, the container is opened and the two material piles are observed. The material pile on the side furthest from the gas inlet and closest to the gas outlet is the solid product material pile. The solid product material pile is vacuum heated at 50°C for 5 minutes and then naturally cooled to room temperature to recover the solid product. The recovered solid product was dissolved in ultrapure water at a ratio of 60 g: 100 mL. After the initial concentration was measured, the solid product was slowly added to prepare an electronic grade ammonium fluoride solution of 40 ± 1 wt% as required.

[0027] The electronic-grade ammonium fluoride solution was characterized and tested, and the results are shown in the table below.

[0028]

[0029] In the table: chloride concentration is expressed as Cl, nitrate concentration as NO3, phosphate concentration as PO4, and sulfate concentration as SO4.

[0030] The characterization results in the table above show that the electronic-grade ammonium fluoride solution sample prepared in this example meets the standards of commercially available electronic-grade UP-grade ammonium fluoride solutions, and in terms of chloride, nitrate, and phosphate, it is close to meeting the UP-S grade standards. Furthermore, the purification steps in the preparation process of this invention are almost directly used to synthesize the target product, demonstrating significant efficiency.

[0031] Furthermore, the effective utilization rates of ammonium carbamate and hydrogen fluoride were calculated based on the product yield, the amount of ammonium carbamate used (original amount - residual amount = consumption amount, i.e., usage amount), and the amount of hydrogen fluoride used (input amount - recovery amount - residual amount = consumption amount, i.e., usage amount, recovery is carried out by condensation recovery at 8 ℃). The effective utilization rate of ammonium carbamate was approximately 98.2%, and the effective utilization rate of hydrogen fluoride was approximately 95.1%, both achieving high efficiency utilization of over 95%.

[0032] Example 2: A method for preparing an electronic-grade ammonium fluoride solution, the method comprising: Industrial-grade refined ammonium carbamate was placed in a reaction vessel. Nitrogen was used as the carrier gas. A small amount of potassium permanganate was added to industrial hydrofluoric acid until it began to turn purple. The mixture was then evaporated at 23±1 °C and 0.75 atm to form hydrogen fluoride gas (the hydrogen fluoride content in the hydrogen fluoride gas was calculated based on a 70% concentration). The carrier gas and hydrogen fluoride gas were mixed at a volume ratio of 8:1 to form a reaction gas and heated to 38 °C. The reaction gas was then introduced at a flow rate of 0.5 m / s, and the flow rate of hydrogen fluoride gas in the reaction gas was 0.05 mol of hydrogen fluoride per minute per mole of ammonium carbamate raw material. The reaction gas was then introduced into the reaction vessel to contact the ammonium carbamate for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the temperature of the reaction vessel begins to drop and drops to 5°C below the highest temperature of the reaction vessel during the reaction, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. For example, in this case, the highest temperature of the reaction vessel during the preparation process is 54°C. When the temperature drops to 49°C, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. Once the temperature of the reaction vessel drops to 40°C, all gas flow is stopped. After natural cooling to room temperature, the container is opened and the two material piles are observed. The material pile on the side away from the gas inlet and close to the gas outlet is the solid product material pile. The solid product material pile is vacuum heated at 50°C for 5 minutes and then naturally cooled to room temperature to recover the solid product. The recovered solid product was dissolved in ultrapure water at a ratio of 60 g: 100 mL. After the initial concentration was measured, the solid product was slowly added to prepare an electronic grade ammonium fluoride solution of 40 ± 1 wt% as required.

[0033] The electronic-grade ammonium fluoride solution was characterized and tested in the same manner as in Example 1, and the utilization rates of ammonium carbamate and hydrogen fluoride were calculated in the same way. The characterization results showed that the sample in this example also met the standard for UP-grade electronic-grade ammonium fluoride solution, but the utilization rate of ammonium carbamate decreased to 97.6%, while the utilization rate of hydrogen fluoride remained basically unchanged at 94.9%.

[0034] Comparative Example 1: A method for preparing an electronic-grade ammonium fluoride solution, the method comprising: Industrial-grade refined ammonium carbamate was placed in a reaction vessel. Nitrogen was used as the carrier gas. A small amount of potassium permanganate was added to industrial hydrofluoric acid until it began to turn purple. The mixture was then evaporated at 23±1 °C and 0.75 atm to form hydrogen fluoride gas (the hydrogen fluoride content in the hydrogen fluoride gas was calculated based on a 70% concentration). The carrier gas and hydrogen fluoride gas were mixed at a volume ratio of 8:1 to form a reaction gas and heated to 40 °C. The reaction gas was then introduced at a flow rate of 0.5 m / s, and the flow rate of hydrogen fluoride gas in the reaction gas was 0.05 mol of hydrogen fluoride per minute per mole of ammonium carbamate raw material. The reaction gas was then introduced into the reaction vessel to contact the ammonium carbamate for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the temperature of the reaction vessel begins to drop and falls below 5°C below the highest temperature of the reaction vessel during the reaction, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. For example, in this case, the temperature of the reaction vessel rises to a maximum of 63°C. When the temperature drops to 58°C, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. Once the temperature of the reaction vessel drops to 43°C, all gas flow is stopped. After natural cooling to room temperature, the container is opened and the two material piles are observed. The material pile on the side furthest from the gas inlet and closest to the gas outlet is the solid product pile. The solid product pile is vacuum heated at 50°C for 5 minutes and then naturally cooled to room temperature to recover the solid product. The recovered solid product was dissolved in ultrapure water at a ratio of 60 g: 100 mL. After the initial concentration was measured, the solid product was slowly added to prepare an electronic grade ammonium fluoride solution of 40 ± 1 wt% as required.

[0035] The electronic-grade ammonium fluoride solution was characterized and tested in the same way as in Example 1, and the utilization rates of ammonium carbamate and hydrogen fluoride were calculated. The characterization results showed that this sample no longer met the characterization requirements for UP-grade electronic-grade ammonium fluoride solution, particularly with significant exceedances in sulfate and metal ion levels. Furthermore, compared to Examples 1 and 2, the crystallization degree of the raw material pile was lower, and the residual amount was extremely low, almost completely absent, indicating severe pulverization of raw material impurities, which entered the solid product pile with the carrier gas, leading to a decrease in purity. The utilization rate also differed significantly from Examples 1 and 2, with ammonium carbamate utilization at only 78.2%, while hydrogen fluoride utilization was higher at 95.2%. This indicates that the excessively high reaction temperature caused severe decomposition of ammonium carbamate, making it impossible to fix trace impurities through hygroscopic crystallization. This was also evident in the partial recovery of ammonium fluoride particles outside the reaction vessel and in the recovery gas. The excessively high temperature caused a large amount of ammonium carbamate to decompose excessively and flow out of the reactor outlet with the carrier gas, resulting in a significant decrease in utilization.

[0036] Example 3: A method for preparing an electronic-grade ammonium fluoride solution, the method comprising: Industrial-grade refined ammonium carbamate was placed in a reaction vessel. Nitrogen was used as the carrier gas. A small amount of potassium permanganate was added to industrial hydrofluoric acid until it began to turn purple. The mixture was then evaporated at 23±1 °C and 0.75 atm to form hydrogen fluoride gas (the hydrogen fluoride content in the hydrogen fluoride gas was calculated based on a 70% concentration). The carrier gas and hydrogen fluoride gas were mixed at a volume ratio of 6:1 to form a reaction gas and heated to 36 °C. The reaction gas was then introduced at a flow rate of 0.5 m / s, and the flow rate of hydrogen fluoride gas in the reaction gas was 0.02 mol of hydrogen fluoride per minute per mole of ammonium carbamate raw material. The reaction gas was then introduced into the reaction vessel to contact the ammonium carbamate for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the temperature of the reaction vessel begins to drop and falls below 5°C below the highest temperature of the reaction vessel during the reaction, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. For example, in this case, the temperature of the reaction vessel rises to a maximum of 51°C. When the temperature drops to 46°C, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. Once the temperature of the reaction vessel drops to 39°C, all gas flow is stopped. After natural cooling to room temperature, the container is opened and the two material piles are observed. The material pile on the side furthest from the gas inlet and closest to the gas outlet is the solid product material pile. The solid product material pile is vacuum heated at 50°C for 5 minutes and then naturally cooled to room temperature to recover the solid product. The recovered solid product was dissolved in ultrapure water at a ratio of 60 g: 100 mL. After the initial concentration was measured, the solid product was slowly added to prepare an electronic grade ammonium fluoride solution of 40 ± 1 wt% as required.

[0037] The electronic-grade ammonium fluoride solution was characterized and tested in the same manner as in Example 1, and the utilization rates of ammonium carbamate and hydrogen fluoride were calculated in the same way. The characterization results showed that the sample in this example also met the standard for UP-grade electronic-grade ammonium fluoride solution, with an ammonium carbamate utilization rate of 97.9% and a hydrogen fluoride utilization rate of 95.5%.

[0038] Example 4: A method for preparing an electronic-grade ammonium fluoride solution, the method comprising: Industrial-grade refined ammonium carbamate was placed in a reaction vessel. Nitrogen was used as the carrier gas. A small amount of potassium permanganate was added to industrial hydrofluoric acid until it began to turn purple. The mixture was then evaporated at 23±1 °C and 0.75 atm to form hydrogen fluoride gas (the hydrogen fluoride content in the hydrogen fluoride gas was calculated based on a 70% concentration). The carrier gas and hydrogen fluoride gas were mixed at a volume ratio of 10:1 to form a reaction gas and heated to 36 °C. The reaction gas was then introduced at a flow rate of 0.5 m / s, and the flow rate of hydrogen fluoride gas in the reaction gas was 0.02 mol of hydrogen fluoride per minute per mole of ammonium carbamate raw material. The reaction gas was then introduced into the reaction vessel to contact the ammonium carbamate for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the temperature of the reaction vessel begins to drop and drops to 5°C below the highest temperature of the reaction vessel during the reaction, the flow of hydrogen fluoride gas is stopped, while the flow of carrier gas continues. For example, in this preparation process, the temperature of the reaction vessel rises to a maximum of 50°C. When it drops to 45°C, the flow of hydrogen fluoride gas is stopped, while the flow of carrier gas continues. Once the temperature of the reaction vessel drops to 39°C, all gas flow is stopped. After natural cooling to room temperature, the container is opened and the two material piles are observed. The material pile on the side furthest from the gas inlet and closest to the gas outlet is the solid product material pile. The solid product material pile is vacuum heated at 50°C for 5 minutes and then naturally cooled to room temperature to recover the solid product. The recovered solid product was dissolved in ultrapure water at a ratio of 60 g: 100 mL. After the initial concentration was measured, the solid product was slowly added to prepare an electronic grade ammonium fluoride solution of 40 ± 1 wt% as required.

[0039] The electronic-grade ammonium fluoride solution was characterized and tested in the same manner as in Example 1, and the utilization rates of ammonium carbamate and hydrogen fluoride were calculated in the same way. The characterization results showed that the sample in this example also met the standard for UP-grade electronic-grade ammonium fluoride solution, with an ammonium carbamate utilization rate of 98.0% and a hydrogen fluoride utilization rate of 94.3%.

[0040] Comparative Example 2: A method for preparing an electronic-grade ammonium fluoride solution, the method comprising: Industrial-grade refined ammonium carbamate was placed in a reaction vessel. Nitrogen was used as the carrier gas. A small amount of potassium permanganate was added to industrial hydrofluoric acid until it began to turn purple. The mixture was then evaporated at 23±1 °C and 0.75 atm to form hydrogen fluoride gas (the hydrogen fluoride content in the hydrogen fluoride gas was calculated based on a 70% concentration). The carrier gas and hydrogen fluoride gas were mixed at a volume ratio of 4:1 to form a reaction gas and heated to 36 °C. The reaction gas was then introduced at a flow rate of 0.5 m / s, and the flow rate of hydrogen fluoride gas in the reaction gas was 0.05 mol of hydrogen fluoride per minute per mole of ammonium carbamate raw material. The reaction gas was then introduced into the reaction vessel to contact the ammonium carbamate for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the temperature of the reaction vessel begins to drop and drops to 5°C below the highest temperature of the reaction vessel during the reaction, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. For example, in this case, the reaction vessel temperature rises to a maximum of 57°C. When the temperature drops to 52°C, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. Once the temperature of the reaction vessel drops to 39°C, all gas flow is stopped. After natural cooling to room temperature, the container is opened and the two material piles are observed. The material pile on the side furthest from the gas inlet and closest to the gas outlet is the solid product material pile. The solid product material pile is vacuum heated at 50°C for 5 minutes and then naturally cooled to room temperature to recover the solid product. The recovered solid product was dissolved in ultrapure water at a ratio of 60 g: 100 mL. After the initial concentration was measured, the solid product was slowly added to prepare an electronic grade ammonium fluoride solution of 40 ± 1 wt% as required.

[0041] The electronic-grade ammonium fluoride solution was characterized and tested in the same manner as in Example 1, and the utilization rates of ammonium carbamate and hydrogen fluoride were calculated similarly. The characterization results showed that the sulfate content of this sample did not meet the standard for UP-grade electronic-grade ammonium fluoride solution, with an ammonium carbamate utilization rate of 93.6% and a hydrogen fluoride utilization rate of 95.3%.

[0042] Comparative Example 3: A method for preparing an electronic-grade ammonium fluoride solution, the method comprising: Industrial-grade refined ammonium carbamate was placed in a reaction vessel. Nitrogen was used as the carrier gas. A small amount of potassium permanganate was added to industrial hydrofluoric acid until it began to turn purple. The mixture was then evaporated at 23±1 °C and 0.75 atm to form hydrogen fluoride gas (the hydrogen fluoride content in the hydrogen fluoride gas was calculated based on a 70% concentration). The carrier gas and hydrogen fluoride gas were mixed at a volume ratio of 12:1 to form a reaction gas and heated to 36 °C. The reaction gas was then introduced at a flow rate of 0.5 m / s, and the flow rate of hydrogen fluoride gas in the reaction gas was 0.05 mol of hydrogen fluoride per minute per mole of ammonium carbamate raw material. The reaction gas was then introduced into the reaction vessel to contact the ammonium carbamate for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the temperature of the reaction vessel begins to drop and drops to 5°C below the highest temperature of the reaction vessel during the reaction, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. For example, in this preparation process, the temperature of the reaction vessel rises to a maximum of 46°C. When it drops to 41°C, the flow of hydrogen fluoride gas is stopped while the flow of carrier gas continues. Once the temperature of the reaction vessel drops to 39°C, all gas flow is stopped. After natural cooling to room temperature, the container is opened and the two material piles are observed. The material pile on the side furthest from the gas inlet and closest to the gas outlet is the solid product material pile. The solid product material pile is vacuum heated at 50°C for 5 minutes and then naturally cooled to room temperature to recover the solid product. The recovered solid product was dissolved in ultrapure water at a ratio of 60 g: 100 mL. After the initial concentration was measured, the solid product was slowly added to prepare an electronic grade ammonium fluoride solution of 40 ± 1 wt% as required.

[0043] The electronic-grade ammonium fluoride solution was characterized and tested in the same manner as in Example 1, and the utilization rates of ammonium carbamate and hydrogen fluoride were calculated similarly. The characterization results showed that this sample also met the UP-grade electronic-grade ammonium fluoride solution standard, with an ammonium carbamate utilization rate of 98.3% and a significant decrease in hydrogen fluoride utilization rate to 86.2%.

[0044] A comparison of Examples 3-4 and Comparative Examples 2-3 clearly shows that the relative amount of carrier gas and the flow rate of hydrogen fluoride in the reaction gas have a significant impact on the reaction temperature. The reaction temperature, in turn, affects the decomposition process of ammonium carbamate, thus significantly influencing product purity and raw material utilization.

Claims

1. A method for preparing an electronic-grade ammonium fluoride solution, characterized in that, The method includes: Solid ammonia source and hydrogen fluoride are used as solid-phase raw materials and gas-phase raw materials, respectively. The solid ammonia source is placed in the reaction vessel, and an inert gas is used as the carrier gas. The carrier gas is mixed with hydrogen fluoride gas to form a reaction gas, which is then heated. The reaction gas is then introduced into the reaction vessel to contact the solid ammonia source for a temperature-controlled solid-gas contact reaction. During the reaction, the temperature of the reaction vessel is monitored. Once the reaction vessel begins to cool down, the flow of hydrogen fluoride is stopped and the carrier gas is continued. The flow is stopped and the solid product is recovered when the temperature of the reaction vessel drops to only 2-3 °C above the temperature of the reaction gas. The recovered solid product is prepared into an electronic-grade ammonium fluoride solution of the target concentration as required.

2. The method for preparing an electronic-grade ammonium fluoride solution according to claim 1, characterized in that, The solid ammonia source is ammonium carbamate.

3. The method for preparing an electronic-grade ammonium fluoride solution according to claim 1, characterized in that, The hydrogen fluoride gas is prepared by evaporation of industrial hydrofluoric acid.

4. A method for preparing an electronic-grade ammonium fluoride solution according to claim 1, 2, or 3, characterized in that, The inert gas is nitrogen and / or argon.

5. The method for preparing an electronic-grade ammonium fluoride solution according to claim 4, characterized in that, The reaction gas is heated to 36–38 °C.

6. The method for preparing an electronic-grade ammonium fluoride solution according to claim 1, characterized in that, The carrier gas and hydrogen fluoride gas are mixed in a volume ratio of (6-10):1 to form a reaction gas.

7. The method for preparing electronic-grade ammonium fluoride solution according to claim 1 or 6, characterized in that, The flow rate of hydrogen fluoride gas in the reaction gas is controlled to be 0.02–0.05 mol·min⁻¹·mol⁻¹ solid ammonia source.

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