A method for pretreatment of a triethyl borate sample and a method for detecting trace metal impurities in triethyl borate

Abstract

This application relates to the field of chemical analysis technology, and discloses a pretreatment method for triethyl borate samples and a method for detecting trace metal impurities in triethyl borate. The pretreatment method provided in this application accelerates the drying process of triethyl borate samples by combining heating and evaporation with protective gas-assisted evaporation, reducing sample preparation time and lowering the risk of hydrolysis due to prolonged evaporation. This avoids introducing exogenous contamination from hydrolysis. The subsequent acid digestion step ensures the complete dissolution of trace metal impurities, thereby eliminating mass spectrometry interference and improving the accuracy and efficiency of detection.

Description

Technical Field

[0001] This application relates to the field of chemical analysis technology, specifically to a pretreatment method for electronic-grade triethyl borate samples and a method for detecting trace metal impurities in electronic-grade triethyl borate. Background Technology

[0002] Electronic-grade triethyl borate (TEB) plays a crucial role in semiconductor manufacturing, primarily serving as a boron source to form borosilicate glass (BPSG) films on wafer surfaces via chemical vapor deposition. BPSG, acting as an insulating layer, is essential for chip performance and stability. TEB can also be used as a doping source to alter the electrical properties of semiconductors, enabling the fabrication of structures such as PN junctions. TEB has extremely stringent requirements regarding metal ions, typically needing to be controlled at the ppb (parts per billion) level. This is because, in semiconductor manufacturing, these trace amounts of metal impurities can act like "electronic poison," fatally damaging chip performance, reliability, and yield.

[0003] The requirements for metal ion indicators vary depending on the process and application of electronic specialty gases and precursors. Therefore, the pretreatment methods for metal ion detection will also differ based on the characteristics of the electronic specialty gases and precursors. Currently, the core objective of pretreatment for metal ion testing of electronic specialty gases and precursor materials is consistent: to completely and cleanly separate the analyte metal element from the complex and high-purity matrix without introducing new contamination, in order to meet the detection requirements of instruments such as ICP-MS at the ppt or even sub-ppt level. Based on the physical morphology and chemical properties of the sample, pretreatment methods can be mainly divided into: ① Matrix separation / elimination method: selectively removing the main matrix through chemical reactions or physical processes, enriching the metal impurities. This method is suitable for samples where the matrix is ​​volatile or can be converted into volatile / insoluble products; ② Acid digestion method: using strong inorganic acids to destroy the sample matrix under heating or pressure, allowing the metal to enter the solution in ionic form. This method is suitable for non-volatile liquid or solid precursors, or residues after other treatment methods. ③ Volatilization method: Separation is achieved by utilizing the significant difference in volatility between metallic impurities and the main gas. Suitable for liquefied electronic specialty gases (such as HCl, Cl2, NH3, WF6, etc.).

[0004] Currently, none of the above pretreatment methods can handle electronic-grade triethyl borate samples with excessively high substrate concentrations and easy hydrolysis. In addition, the pretreatment time is relatively long, which is not conducive to improving sample testing efficiency. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a pretreatment method for triethyl borate samples, which can shorten the sample pretreatment time, prevent the hydrolysis of electronic grade triethyl borate and the introduction of exogenous contamination, and improve sample preparation efficiency.

[0006] Another objective of this application is to provide a method for detecting trace metal impurities in triethyl borate based on the above-described pretreatment method.

[0007] To solve the aforementioned technical problems, or at least partially solve them, this application provides a method for solving the aforementioned technical problems, or at least partially solves them. As a first aspect of this application, a pretreatment method for a triethyl borate sample is provided, comprising:

[0008] The triethyl borate sample was added to a digestion container equipped with a gas inlet and outlet. The digestion container was heated while a trace amount of protective gas was continuously introduced through the gas inlet and outlet to assist in evaporation.

[0009] After the liquid in the digestion container is no longer obvious, the liquid is evaporated and acid is added for further digestion to complete the triethyl borate sample.

[0010] Optionally, both the gas inlet and outlet are located at the top of the digestion container; the gas inlet and outlet are respectively located on different sides of the digestion container. More optionally, the gas inlet and outlet are respectively located on two opposite sides of the digestion container.

[0011] Optionally, the protective gas includes nitrogen and / or an inert gas.

[0012] Optionally, the flow rate of the protective gas is 0.1-1 L / min, and the pressure is 1-10 kPa.

[0013] Optionally, the heating temperature is 118-200℃.

[0014] Optionally, the acid includes nitric acid.

[0015] As a second aspect of this application, a method for detecting trace metal impurities in triethyl borate is provided, comprising:

[0016] The blank sample and the spiked sample of triethyl borate were pretreated according to the pretreatment method described in this application. The spiked sample was tested to obtain a standard curve. The signal value of the blank sample was substituted into the standard curve to obtain the trace metal impurity content in triethyl borate.

[0017] Optionally, the dilution factor of the blank sample and the spiked sample before detection is 2-5 times.

[0018] Optionally, the metallic impurities include one or more of Li, Na, Mg, Al, Fe, Cu, Zr, Mo, Ag, Sn, and W.

[0019] The pretreatment method provided in this application accelerates the drying process of triethyl borate samples by combining heating and evaporation with protective gas-assisted evaporation, reduces sample preparation time, and lowers the risk of hydrolysis due to prolonged evaporation, thereby avoiding the introduction of exogenous contamination caused by hydrolysis. The subsequent acid digestion step ensures the complete dissolution of trace metal impurities, thereby eliminating mass spectrometry interference and improving the accuracy and efficiency of detection. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0021] Figure 1 The diagram shows two gas inlet / outlet settings for the digestion container; A: Top inlet / outlet; B: Relative side inlets / outlets. Detailed Implementation

[0022] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be used in this application. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0024] For ease of understanding, the following explains some key terms used in this application:

[0025] Triethyl borate sample: refers to electronic-grade triethyl borate to be tested for trace metal impurities, which has a high matrix concentration and is easily hydrolyzed by moisture.

[0026] Digestion container: refers to a closed or semi-closed container used to hold triethyl borate samples and to heat them to evaporate and digest them with acid. It has internal channels for gas to enter and exit.

[0027] Gas inlet and outlet: refers to the channels set on the digestion container for introducing and discharging gas, through which the gas inside the container can circulate and be replaced.

[0028] Protective gas: refers to the gas continuously introduced into the digestion container during the evaporation process. Its main function is to isolate the sample from moisture and oxygen in the external air, prevent sample hydrolysis, and assist in the volatilization of the sample matrix.

[0029] Volatilization: This refers to the process of gradually volatilizing the organic matrix in a triethyl borate sample through heating and the assistance of a protective gas, thereby reducing the matrix concentration and creating conditions for subsequent digestion and detection.

[0030] Digestion: After evaporation, acid is added to the digestion container. The acid converts the residual metal impurities in the sample into soluble ionic forms, which are then easier for subsequent instrument detection.

[0031] Traditional pretreatment methods for electronic-grade triethyl borate samples face numerous challenges in detecting trace metal impurities. Because the concentration of electronic-grade triethyl borate substrates is typically high (exceeding 1000 ppm), conventional instruments such as ICP-MS cannot directly measure it. Furthermore, high-concentration organic substrates can interfere with mass spectrometry analysis; for example, decomposition products of organic substrates (such as C, H, and O) may form polyatomic ion clusters, directly interfering with the mass spectrometric peaks of certain key metal elements. Therefore, pretreatment of triethyl borate is necessary. However, triethyl borate itself is easily hydrolyzed and cannot be diluted before detection. Existing methods typically involve heating and evaporation, but this process is time-consuming. Even with inert gas protection, prolonged evaporation increases the risk of hydrolysis, leading to the introduction of exogenous metal contamination and the formation of boric acid particles, affecting subsequent detection. Therefore, existing pretreatment methods are generally time-consuming and inefficient, failing to meet the stringent requirements of semiconductor manufacturing for high-purity materials.

[0032] Therefore, in the first aspect of this application, a pretreatment method for a triethyl borate sample is proposed, comprising: adding the triethyl borate sample into a digestion container equipped with a gas inlet and outlet; heating the digestion container while continuously introducing a trace amount of protective gas through the gas inlet and outlet to assist in evaporation; completing evaporation after there is no obvious liquid in the digestion container; adding acid for digestion to complete the triethyl borate sample preparation.

[0033] In this application, a triethyl borate sample is added to a digestion container equipped with a gas inlet and outlet. This digestion container can be a closed digestion bottle with a gas inlet and outlet, and the material of the digestion bottle mainly includes fluoroplastics (such as PTFE, TFM, PFA) and quartz. Generally, PFA is chosen for containers that directly contact the material; the cap of the digestion bottle used for pretreatment is made of PTFE, while the body of the bottle in contact with the material is made of PFA, which has a smaller impact on metal ion precipitation compared to PTFE. The digestion bottle can have openings on its top or side wall to serve as a gas inlet and outlet. For example, both the gas inlet and outlet can be located on the top of the container; or one of the gas inlet and outlet can be located on the top of the container, and the other on the side wall; or both the gas inlet and outlet can be located on the side wall of the container.

[0034] Subsequently, the digestion container is heated. Heating can be achieved in various ways, such as placing the digestion container on a hot plate for external heating, or wrapping the container with a heating jacket for heating. The heating temperature can be selected according to the volatility characteristics of the sample. Simultaneously with heating, a trace amount of protective gas is continuously introduced through the gas inlet and outlet to assist in evaporation. The protective gas can be nitrogen or a known inert gas. The flow rate of this gas can be set to a low value to maintain a trace amount; by continuously introducing the gas, the volatilized organic vapors can be effectively removed, accelerating the evaporation process and preventing moisture from the outside air from entering the container.

[0035] The evaporation process is complete once no obvious liquid remains in the container. This can be determined visually; evaporation is considered complete when no liquid remains at the bottom of the container. Alternatively, it can be done by weighing the container; evaporation is considered complete when the container's weight no longer changes significantly.

[0036] After evaporation, acid is added to the digestion vessel for digestion. The added acid can be an inorganic acid such as nitric acid, sulfuric acid, or hydrochloric acid. By adding acid and performing appropriate sonication (if necessary), trace metal impurities remaining in the sample can be converted into ionic states, dissolving them in the acid solution, thus facilitating subsequent detection. For example, in actual use in this application, approximately 5% nitric acid can be selected for digestion, or the same concentration of nitric acid as the standard solution used in subsequent detection can be selected to eliminate the potential influence of differences in acid concentration.

[0037] The above steps complete the pretreatment of electronic-grade triethyl borate samples. This method aims to effectively pretreat samples with high concentrations of organic substrates and easy hydrolysis, shortening sample preparation time, avoiding hydrolysis, and converting trace metal impurities into detectable forms.

[0038] In some embodiments of this application, in order to optimize the gas distribution during the evaporation process, both the gas inlet and outlet are located at the top of the digestion container; or the gas inlet and outlet are located on different sides of the digestion container.

[0039] When both the gas inlet and outlet are located at the top of the digestion container, this configuration positions both the protective gas inlet and the volatile matter outlet at the upper part of the digestion container. For example, the gas inlet and outlet can be arranged side by side at the top of the digestion container, guiding the protective gas to form a stable and uniform downward flow inside the container, thereby efficiently carrying volatile substances away from the sample surface. This arrangement aims to ensure that the protective gas can uniformly cover the sample surface, avoiding local airflow stagnation, thereby accelerating the evaporation process and effectively reducing the opportunity for the sample to come into contact with the outside air.

[0040] When the gas inlet and outlet are respectively located on different sides of the digestion container, this configuration aims to enhance the gas circulation efficiency inside the container by establishing a convection or lateral flow airflow pattern inside the digestion container, eliminating possible dead zones, and ensuring that the protective gas completely isolates the sample, thereby effectively preventing external contamination.

[0041] In other embodiments of this application, the gas inlet and outlet are respectively located on opposite sides of the digestion container. Specifically, "the gas inlet and outlet are respectively located on opposite sides of the digestion container" means that the gas inlet and outlet are geometrically opposite or furthest apart from each other in the digestion container. For example, the gas inlet can be located on one side wall of the digestion container, while the gas outlet is located on the opposite side wall. This arrangement aims to ensure that the protective gas can traverse the internal space of the digestion container, forming a relatively uniform flow field.

[0042] In one embodiment of this application, the gas inlet can be located at a lower position on one side of the digestion container, while the gas outlet is located at a higher position on the opposite side, forming an oblique convection that allows the protective gas to fully sweep across the sample surface and effectively remove volatiles. Alternatively, the gas inlet can be located at a higher position on one side of the digestion container, while the gas outlet is located at a lower position on the opposite side, forming a top-down and bottom-up circulation flow to ensure sufficient gas exchange within the container. Alternatively, the gas inlet and outlet can be located at the same height on opposite sides of the digestion container, guiding the gas to form a horizontal circulation flow within the container. Compared to the oblique circulation of "top in, bottom out" and "bottom in, top out," this horizontal convection path is shorter and has less resistance, allowing the protective gas to quickly reach the central area of ​​the container and promoting more thorough contact and exchange between the gas and triethyl borate, reducing dead zones. As a further arrangement, the projection of the gas inlet onto its opposite sidewall coincides with the gas outlet; for example, both the gas inlet and outlet are located at the top center of two opposite sidewalls.

[0043] The opposing gas inlet and outlet layout of this application allows the protective gas to enter stably from one side and exit uniformly from the other, thus creating a continuous and uniform convection field inside the digestion container. This uniform airflow distribution ensures that the protective gas fully covers the surface of the triethyl borate sample, avoiding localized gas stagnation or insufficient coverage. Given the easily hydrolyzed nature of triethyl borate samples, the uniform airflow can more efficiently remove volatiles and any present moisture, significantly improving the uniformity and efficiency of evaporation and effectively reducing the risk of hydrolysis due to localized moisture accumulation during evaporation. Simultaneously, the uniform airflow also reduces the possibility of external contaminants entering the container through irregular airflow and depositing on the sample, further enhancing sample protection. Therefore, this technical solution not only optimizes the evaporation process and shortens the pretreatment time but also significantly improves the stability and reliability of triethyl borate sample pretreatment, laying the foundation for the accurate detection of trace metal impurities.

[0044] In some embodiments of this application, the protective gas includes nitrogen and / or an inert gas. During the pretreatment of triethyl borate samples, the main function of the protective gas is to provide an inert environment to isolate the sample from reactive components in the outside air, particularly water vapor and oxygen, thereby preventing undesirable chemical reactions such as hydrolysis and avoiding the introduction of external contaminants. This can be achieved by supplying high-purity gas through a high-pressure gas cylinder and using a precision flow controller and pressure regulating valve to stably introduce it into the digestion container; alternatively, the required gas can be prepared and purified on-site using a gas generator or purification device to ensure its purity and stability. Nitrogen, as a common and economical inert gas, is chemically stable and does not readily react with most substances at room temperature. Using nitrogen during the evaporation process effectively displaces the air in the digestion container, forming an inert atmosphere that isolates moisture from the air, prevents the hydrolysis of triethyl borate, and reduces the potential oxidation of the sample by oxygen. Inert gases, specifically rare gases such as argon and helium, are chemically extremely inert and react almost no with any substance. Using inert gases in the evaporation process provides a superior chemically inert environment compared to nitrogen, but is typically more expensive. They minimize the possibility of any reaction between the protective gas and the triethyl borate sample, or the introduction of any trace impurities, which is crucial for the accurate detection of trace metal impurities.

[0045] In some embodiments of this application, a trace amount of protective gas can be continuously introduced to assist in evaporation. Excessive nitrogen flow rate and pressure will inhibit the evaporation process, while insufficient flow rate will result in ineffective evaporation. Therefore, the flow rate of the protective gas described in this application can be selected as 0.1-1 L / min, such as 0.1 L / min, 0.2 L / min, 0.3 L / min, 0.4 L / min, 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min, 1.0 L / min, or any value between these two ranges; the pressure is 1-10 kPa, such as 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, 10 kPa, or any value between these two ranges. Within this range, the amount of protective gas can be controlled appropriately to maximize the efficiency of assisted evaporation.

[0046] The flow rate of the protective gas refers to the volume of gas passing through the digestion container per unit time. In the pretreatment of triethyl borate samples, it directly affects the protective gas's coverage of the sample surface, the efficiency of removing volatile products, and its ability to inhibit sample hydrolysis and external contamination. This flow rate can be precisely controlled in several ways. For example, a mass flow controller (MFC) can be used to monitor and adjust the gas flow rate in real time, ensuring it remains stable within a preset range of 0.1-1 L / min. Alternatively, a precision pressure reducing valve equipped with a flow meter can be used in conjunction with a needle valve for manual or automatic adjustment to achieve the desired flow rate. Furthermore, effective flow control can also be achieved by adjusting the output rate of the gas source or by using a flow restrictor with a specific orifice size.

[0047] Meanwhile, the pressure of the protective gas refers to the force exerted per unit area. During the evaporation process, it significantly affects the uniformity of gas distribution within the digestion container, the force exerted on the sample surface, and the effect of assisting evaporation. This pressure can be maintained and adjusted through various technical means. For example, a precision pressure reducing valve can be used to stabilize the pressure of the high-pressure gas source within the range of 1-10 kPa, ensuring the stability of the gas supply. Alternatively, a vacuum pump and pressure controller can work together to create a slightly negative pressure or precisely controlled slightly positive pressure environment inside the digestion container to maintain the required pressure conditions. Furthermore, by rationally designing the resistance at the gas inlet or the back pressure at the outlet, effective control of the pressure within the digestion container can also be indirectly achieved.

[0048] Limiting the flow rate of the protective gas to 0.1-1 L / min ensures that the gas fully covers the surface of the triethyl borate sample, forming a stable protective barrier that effectively isolates moisture and potential contaminants from the air, thus significantly reducing the risk of sample hydrolysis and exogenous contamination. Simultaneously, this flow rate range avoids waste caused by excessive gas flow, improving resource utilization efficiency. Controlling the pressure of the protective gas to 1-10 kPa ensures stable and uniform gas flow within the digestion vessel, efficiently carrying volatilized products away from the sample surface, thereby improving evaporation efficiency and shortening pretreatment time. This precise flow and pressure control, combined with the technical feature of continuously introducing trace amounts of protective gas to assist evaporation, especially when the protective gas is nitrogen and / or an inert gas, maximizes its inert protective effect, ensuring effective protection of the triethyl borate sample matrix during heating and evaporation. This avoids problems such as low evaporation efficiency, gas waste, and increased contamination risk caused by improper flow or pressure, providing a foundation for accurate detection of trace metal impurities.

[0049] In some embodiments of this application, the heating temperature is 118-200°C, for example, 118°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or any value between the two. Triethyl borate has a boiling point of 118°C; the heating temperature should be equal to or higher than the boiling point, but not too high to avoid pyrolysis. The heating temperature range applied during the assisted evaporation of the triethyl borate sample serves to ensure the efficiency of the evaporation process and the integrity of the sample. This temperature control can be achieved, but is not limited to: using a heating plate or heating jacket with precise temperature control function, and monitoring the temperature of the digestion container in real time through a built-in temperature sensor.

[0050] Precisely controlling the heating temperature within the range of 118-200℃ during the pretreatment of triethyl borate samples effectively solves problems caused by improper temperature control. Specifically, setting the heating temperature to 118-200℃ ensures sufficient energy input, allowing the triethyl borate sample to volatilize efficiently and completely, significantly shortening the time required for evaporation and thus improving the overall efficiency of pretreatment. This avoids problems such as incomplete evaporation or excessively long evaporation times caused by excessively low temperatures. On the other hand, setting the upper limit of the heating temperature to 200℃ effectively avoids pyrolysis of the triethyl borate sample caused by excessively high temperatures, thereby maximizing the chemical stability of the sample matrix, preventing the introduction of exogenous contamination, and ensuring the accuracy and reliability of subsequent trace metal impurity detection results. This precise temperature control, while ensuring evaporation efficiency, also maintains the purity of the sample matrix, providing high-quality samples for subsequent high-sensitivity instruments such as ICP-MS.

[0051] In some embodiments of this application, the acid includes nitric acid. Nitric acid, as a strong oxidizing inorganic acid, plays a crucial role in the digestion of triethyl borate samples. Its main function is to convert trace metal elements into soluble ionic forms for subsequent detection. In practical applications, to meet the extremely high purity requirements for trace metal detection, high-purity nitric acid, such as electronic-grade nitric acid or ultrapure nitric acid, is typically selected to minimize the possibility of introducing exogenous impurities. Furthermore, the concentration of nitric acid can be adjusted according to specific digestion conditions and sample characteristics. For example, different concentrations of nitric acid solutions, such as 5% (G3) nitric acid or 6.9% (G6) nitric acid, can be used to adapt to different digestion intensity requirements.

[0052] Compared to other acids, nitric acid possesses excellent purity, significantly reducing the risk of introducing additional metal impurities during digestion. Furthermore, metal nitrates typically exhibit excellent water solubility and stability, effectively preventing metal ions from hydrolyzing and precipitating or adsorbing onto the container walls under acidic conditions, thus ensuring the recovery rate and accuracy of trace metal detection. In addition, the nitric acid matrix demonstrates good compatibility with subsequent trace metal detection techniques such as inductively coupled plasma mass spectrometry (ICP-MS), generating far less spectral and mass spectrometric interference than other commonly used acids like hydrochloric acid, sulfuric acid, or phosphoric acid, further guaranteeing the reliability of the detection results. Therefore, using nitric acid for digestion not only avoids sample hydrolysis and exogenous contamination but also lays a solid foundation for the accurate detection of subsequent trace metals.

[0053] In a second aspect of this application, a method for detecting trace metal impurities in triethyl borate is proposed. The method includes: pretreating a blank sample and a spiked sample of triethyl borate according to the aforementioned pretreatment method of this application; detecting the spiked sample to obtain a standard curve; substituting the signal value of the detected blank sample into the standard curve; thereby obtaining the content of trace metal impurities in triethyl borate.

[0054] In practice, a blank sample of triethyl borate is added to a digestion vessel equipped with a gas inlet and outlet. The digestion vessel is heated while a trace amount of protective gas is continuously introduced through the gas inlet and outlet. Nitrogen is preferred as the protective gas, with a flow rate controlled at 0.5 L / min to isolate the sample from external air and prevent hydrolysis. The heating temperature is set at 150°C to promote the volatilization of the organic matrix. Heating is stopped when no significant liquid residue remains in the digestion vessel, completing the evaporation step. Subsequently, nitric acid is added to the vessel for digestion, converting trace metal impurities into soluble ions.

[0055] For spiked samples, a standard curve is established after detection by adding a metal standard solution of known concentration, reflecting the linear relationship between signal intensity and metal concentration. Blank samples are detected after the same pretreatment. The obtained signal value is substituted into the standard curve, and background interference is subtracted to accurately calculate the true content of trace metal impurities in the sample.

[0056] This application effectively solves key problems in the detection of triethyl borate samples. Continuous introduction of protective gas ensures that the evaporation process is carried out in an anhydrous environment, avoiding the formation of hydrolysis products and exogenous contamination; complete removal of the organic matrix eliminates mass spectrometry interference caused by high matrix; and the standard curve and signal substitution mechanism provide a reliable quantitative benchmark, significantly improving detection efficiency and accuracy, and meeting the stringent requirements of semiconductor manufacturing for high-purity materials.

[0057] In some embodiments of this application, the dilution factor for blank and spiked samples before detection is 2-5 times, for example, 2, 3, 4, 5 times, or any value between the two. The dilution factor refers to the ratio of the final volume of the sample after dilution to the volume of the original sample before detection. For example, a dilution factor of 2 means that the sample is diluted to twice its original volume. This dilution operation is typically performed by adding an appropriate amount of diluent (e.g., high-purity water, dilute nitric acid, or other matrix-compatible solution) to the digested sample. Limiting the dilution factor to the range of 2-5 times allows for appropriate dilution, which helps reduce the acid concentration in the digested sample, thereby effectively protecting the sample introduction system and torch of instruments such as ICP-MS and extending the instrument's lifespan. Furthermore, by diluting the sample to 2-5 times, the concentration of the analyte metal element falls within the linear dynamic detection range of the ICP-MS instrument, enabling accurate quantitative analysis using a pre-established standard curve.

[0058] In certain embodiments of this application, the types of metal impurities to be detected are further specified. Specifically, the metal impurities include one or more of Li, Na, Mg, Al, Fe, Cu, Zr, Mo, Ag, Sn, and W. These metal elements, namely Li, Na, Mg, Al, Fe, Cu, Zr, Mo, Ag, Sn, and W, are widely considered critical "electronic poisons" in the semiconductor manufacturing field. Even in trace amounts, they can severely damage the electrical performance, reliability, and yield of semiconductor devices. Therefore, accurate detection and control of these specific metal impurities are crucial to ensuring the purity of electronic-grade triethyl borate. The method described in this application can selectively detect one or more metal elements based on the actual production process, potential contamination source analysis, or the sensitivity of the final product to specific metal impurities. For example, in some applications, only the content of sodium and iron may need to be considered; while in other applications, a comprehensive screening of all listed metal elements may be necessary. This selective or combined detection approach allows the detection scheme to more accurately respond to different quality control requirements.

[0059] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all purchased from commercial channels. In the specific embodiments of this application, unless otherwise specified, the experimental environment and parameter conditions of each group in the tests are consistent.

[0060] The following provides a further explanation of the pretreatment method for triethyl borate samples and the method for detecting trace metal impurities in triethyl borate provided in this application.

[0061] Example 1:

[0062] 1. Experimental reagents and instruments

[0063] Samples of electronic-grade triethyl borate (TEB), 6.9% nitric acid (G6), 5% nitric acid (G3), ultrapure water, and digestion flasks. Figure 1 (Two specifications shown), PFA bottle, cold trap, analytical balance, ICP-MS (standard solution 100 ppb)

[0064] 2. Experimental Procedure

[0065] 2.1 Sample Pretreatment and Preparation Stage

[0066] 2.1.1 Sample Pretreatment

[0067] First, the digestion flask and PFA flask were repeatedly cleaned with ultrapure water and 5% nitric acid (G3), at least three times each. After cleaning, online ICP-MS detection was performed, and the concentration of each metal ion was basically 0 ppb, which was sufficient for sample preparation.

[0068] 2.1.2 Sample preparation (three sets of samples were prepared in parallel)

[0069] ①: Blank sample: Use a pipette to take 15g of sample into a clean digestion bottle.

[0070] ②: Spiked Samples: First, use a pipette to take 15g of sample into a digestion bottle, and then add different masses of standard solution with a concentration of 100 ppb, so that the final standard solution concentrations reach 0.2ppb, 0.5ppb and 1ppb respectively, in preparation for subsequent instrument testing.

[0071] 2.2 Nitrogen-assisted volatilization stage

[0072] Nitrogen inlet and outlet are provided on the digestion flask cap. Nitrogen is continuously introduced during the evaporation process, with the nitrogen flow rate controlled at 0.5 L / min and the pressure at 5 kPa. The digestion flask is heated by a heating mantle at a temperature of 150°C.

[0073] 2.3 Dilute acid digestion and dilution to volume stage

[0074] The absence of visible liquid at the bottom of the digestion flask indicates that evaporation is complete. After evaporation, turn off the nitrogen gas supply and the hot plate. Once the digestion flask has returned to room temperature, add 30g of 6.9% (G6) nitric acid and sonicate for 30 minutes, ensuring thorough mixing. Finally, transfer the digestion solution to a clean PFA bottle. At this point, both the sample and standard solution used for ICP-MS testing have been diluted by two times.

[0075] 2.4 On-machine testing phase

[0076] The samples that have been brought to a constant volume are transferred to the instrument room for testing. The specific testing process is carried out according to the different ICP-MS procedures.

[0077] 3. Results and Conclusions

[0078] 3.1 Results

[0079] 3.1.1 The test results of metal ions of each element in the 6 parallel experiments are shown in Table 1 below:

[0080] Table 1

[0081]

[0082] 3.1.2 The required evaporation time for the two types of digestion flasks in the sample evaporation experiment is shown in Table 2 below:

[0083] Table 2

[0084]

[0085] 3.2 Conclusion

[0086] The metal ion test of the product was carried out according to the above pretreatment experimental plan. The values ​​were basically close to the product COA (standard value recorded in the instruction manual), which further verified the feasibility of the method. At the same time, the use of the top inlet and outlet and the left and right inlet and outlet of the digestion bottle had little impact on the final sample test results, but the latter had a shorter drying time and higher efficiency.

[0087] In addition, the conventional method of heating and drying with a nitrogen-protected heating plate (without continuous nitrogen flow) resulted in the longest drying time and slight hydrolysis (white powder on the cup wall). Hydrolysis easily introduces external contamination, especially easily contaminated elements such as Na, Mg, and Al. Table 1 shows a significant increase in the concentrations of these elements in the test results. However, because this experiment was conducted in a clean room, the content of these easily contaminated elements did not seriously exceed the standard. Although the test concentrations were relatively accurate, the results were still worse than the nitrogen-assisted drying method used in this application, and the time was longer.

[0088] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

[0089] The present application and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present application. Actual applications are not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present application, such designs should fall within the protection scope of this application.

Claims

1. A pretreatment method for triethyl borate samples, characterized in that, include: The triethyl borate sample was added to a digestion container equipped with a gas inlet and outlet. The digestion container was heated while a trace amount of protective gas was continuously introduced through the gas inlet and outlet to assist in evaporation. After the liquid in the digestion container is no longer obvious, the liquid is evaporated and acid is added for further digestion to complete the triethyl borate sample.

2. The pretreatment method according to claim 1, characterized in that, The gas inlet and outlet are both located at the top of the digestion container; the gas inlet and outlet are respectively located on different sides of the digestion container.

3. The pretreatment method according to claim 2, characterized in that, The gas inlet and outlet are respectively located on two opposite sides of the digestion container.

4. The pretreatment method according to claim 1, characterized in that, The protective gas includes nitrogen and / or an inert gas.

5. The pretreatment method according to claim 1 or 4, characterized in that, The flow rate of the protective gas is 0.1-1 L / min, and the pressure is 1-10 kPa.

6. The pretreatment method according to claim 1, characterized in that, The heating temperature is 118-200℃.

7. The pretreatment method according to claim 1, characterized in that, The acid includes nitric acid.

8. A method for detecting trace metallic impurities in triethyl borate, characterized in that, include: The blank sample and the spiked sample of triethyl borate were pretreated according to any one of claims 1-7. The spiked sample was tested to obtain a standard curve. The signal value of the blank sample was substituted into the standard curve to obtain the content of trace metal impurities in triethyl borate.

9. The method according to claim 8, characterized in that, The dilution factor of the blank sample and the spiked sample before testing was 2-5 times.

10. The method according to claim 8, characterized in that, The metallic impurities include one or more of the following: Li, Na, Mg, Al, Fe, Cu, Zr, Mo, Ag, Sn, and W.

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