A method for detecting the content of hydrofluoric acid or fluoride ion or fluoride or sulfuric acid in mixed acid

Abstract

The present application relates to a kind of detection methods of the content of hydrofluoric acid or fluoride ion or fluoride or sulfuric acid in mixed acid.The fluoride standard solution of different concentration gradient is first prepared, then the potential of fluoride standard solution is tested, and the standard curve reflecting the relationship between potential and fluoride ion concentration is drawn;Then, the etching liquid sample to be measured is weighed, hydrolysis treatment is carried out, potential test is carried out, and the content of hydrofluoric acid or fluoride ion or fluoride concentration in the sample to be measured is calculated by the standard curve described above using potential value test, the content of sulfuric acid in the sample to be measured is tested by using the hydrolysis solution after hydrolysis with automatic titrator.The present application effectively avoids the deviation of detection value caused by temperature change, fluoride ion electrode wear, ion masking effect, fluoride ion reaction and the like in the testing process, greatly improves the detection accuracy of fluorine-containing product and the detection accuracy of sulfuric acid content in mixed acid, solves the interference of instrument, environment, product characteristics and human factors, and saves detection cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the detection of electronic chemicals and semiconductor wet etching field, and particularly relates to a detection method of hydrofluoric acid or fluoride ion or fluoride or sulfuric acid content in mixed acid, which can accurately detect the content of fluoride ion component and sulfuric acid component, and avoid the interference of product characteristics, operation errors, environment and instruments. BACKGROUND

[0002] Wet etching is one of the mainstream etching technologies in the semiconductor. The etching liquid used in wet etching is usually mainly acid and contains fluorine because fluorine element is easy to react with silicon element. Fluoride ion is crucial in the etching process, and its content has a great influence on the etching rate and surface morphology of semiconductor wafer or chip. Therefore, the content of fluoride ion has a great influence on the performance of silicon etching liquid product. Fluorine element has high first ionization energy, so ICP-MS and other trace analysis instruments requiring atomic ionization cannot detect it; the alizarin ketone colorimetric method is complex and has a large error. It is also difficult for ion chromatography to detect anions in mixed acid with complex components. In the long-term exploration, the fluoride ion electrode detection method has become the mainstream method for detecting fluorine element. According to the Nernst equation, the potential is proportional to the negative logarithm of the ion activity, and the fluoride ion activity in a dilute solution is approximately equal to its concentration. However, the coefficient affecting the corresponding relationship between potential and concentration is affected by temperature, ion strength, etc. Therefore, when detecting fluoride ion, temperature and other conditions will affect the detection accuracy. Fluoride ion meter uses a special lanthanum fluoride electrode to combine with free fluoride ions to indicate the potential. Lanthanum fluoride is easy to react with alkali to generate lanthanum hydroxide, resulting in electrode damage; when the acidity is strong, fluoride ions will combine with hydrogen ions to generate hydrogen fluoride or hydrogen difluoride, reducing the free fluoride ions; when the free water is very little, hydrofluoric acid shows super acidity, and will further consume free fluoride ions by replacing the reaction with hydroxyl-containing acids. In summary, the accurate detection of fluoride ions in acid-containing etching liquid is more difficult than the detection of fluoride ions in neutral or alkaline samples. In addition, the masking effect of other ions in the sample, mechanical wear of the electrode, human operation errors or errors will have a certain influence on the detection of fluoride ions. Therefore, the detection deviation of fluoride ions is often more than 10%, and it is a difficult problem for the entire chemical industry and semiconductor etching liquid to extremely accurately detect the content of hydrofluoric acid or fluoride ion in the sample, especially the content of hydrofluoric acid or fluoride ion in the acid etching liquid. Therefore, it also makes it more difficult to test the content of the sulfuric acid component.

[0003] The existing detection method is to configure the quality control sample and the standard calibration sample according to the components of the sample, and even the standard curve is also configured according to the sample, only the content of fluoride and water is different, which is more troublesome. The data detected by the method is very different from the actual configuration value, and the final value is close to the configuration value only after the calibration sample is calibrated, and the concentration of the calibration sample has a great influence. Summary of the Invention

[0004] In response to the problems of the prior art, the present invention provides a method for detecting the content of hydrofluoric acid, fluoride ions, fluoride, or sulfuric acid in mixed acids. By using a hydrolysis process to release nearly all fluoride ions, the method significantly improves detection accuracy. This also enhances the accuracy of sulfuric acid detection. Furthermore, a standard control sample can be used simultaneously to further correct the results to account for deviations and errors caused by masking effects, mechanical wear of electrodes, human manipulation, and environmental influences such as temperature. This method significantly improves experimental conditions and enhances detection precision and accuracy.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A method for detecting the content of hydrofluoric acid, fluoride ions, fluoride, or sulfuric acid in a mixed acid comprises pre-treating the sample, adding water to the sample for heating and hydrolysis, and then performing a subsequent detection process.

[0007] Preferably, the sample is added to water and then heated before testing.

[0008] Preferably, the heating temperature is 20-100° C. and the heating time is 20-100 min.

[0009] Preferably, when heating and hydrolyzing, the bottle cap needs to be tightly closed to prevent the components from volatilizing.

[0010] A method for detecting the content of hydrofluoric acid, fluoride ions, or fluoride in a mixed acid comprises the following steps:

[0011] S1. Prepare fluoride solutions with different concentration gradients as standard solutions, draw a standard curve using a fluoride ion meter, and fit the corresponding relationship between fluoride ion or hydrofluoric acid content and potential;

[0012] S2. Take a sample of the etching solution to be tested, add water and the sample to the container in sequence, dilute with water, shake well, quickly cap the bottle, and heat to hydrolyze; after hydrolysis, adjust the volume to volume, add the hydrolysis solution, adjust the pH value and total ionic strength according to GB / T 21057-2007 "General method for determination of fluorine content in inorganic chemical products - Ion-selective electrode method", adjust the volume to volume, shake well, and measure the potential value; calculate the content of hydrofluoric acid, fluoride ion, or fluoride in the corresponding sample using the curve equation obtained in S1; GB / T 21057-2007 "General method for determination of fluorine content in inorganic chemical products - Ion-selective electrode method" may also be other national or industry standards.

[0013] Preferably, the standard used in step S1 to draw the standard curve is fluoride, which can be one or more of ammonium fluoride, sodium fluoride, potassium fluoride, etc. capable of ionizing fluoride ions, and does not have to be the same as the fluoride in the sample to be tested; or a gradient standard solution can be prepared using hydrofluoric acid, but the volatilization during operation, the test temperature and the test time must be controlled. This is a major innovation of the method in the application of mixed acid testing. It is not necessary to draw a standard curve by preparing a series of solutions with different gradient concentrations of the component to be tested in a sample similar to the sample to be tested. The reagents obtained by drawing the standard curve in the method have more selectivity and are easier to obtain. The process of preparing the standard solution for drawing the curve is very simple and easy to operate. Moreover, the linear coefficient of the curve can easily meet the requirements.

[0014] Preferably, the standard curve drawn in step S1 reflects a linear relationship between the potential value and the concentration of hydrofluoric acid or fluoride ions. The R value in the linear regression of the standard curve 2 must be greater than or equal to 0.99; and the potential value range of the curve must cover the potential value of the solution to be tested. When using an ionic compound such as sodium fluoride to draw the curve, the R 2 value can easily reach more than 0.999; and the operation is very simple and fast.

[0015] Preferably, the sample pretreatment in step 2 is hydrolysis by heating. The amount of sample taken and the total amount of water sample correspond to a dilution factor of more than 5 times.

[0016] Preferably, the sample pretreatment in step S2 is hydrolysis by heating. The heating temperature and time are determined by the components of the system. When the concentration of sulfuric acid, phosphoric acid or other substances prone to dehydration and condensation is high, the required heating temperature is high and the heating time is long, and vice versa. Other methods that can promote the hydrolysis of different forms of fluorine can also be used. When hydrolysis by heating, the bottle cap needs to be tightly covered to prevent the components from volatilizing.

[0017] Preferably, when the sample is weighed in step S2, a small amount of water is added to the container in advance in order to further reduce the impact of the volatility of the sample during the process. Secondly, when hydrolysis by heating, the bottle cap needs to be tightly covered to prevent the components from volatilizing and affecting the accuracy of the test results. In general, attention should be paid to minimizing the impact of the volatility of the sample.

[0018] Preferably, in the method, two standard control samples with known concentrations of hydrofluoric acid or fluoride ions or fluoride can also be prepared for reference. The components and proportions of the solutions are the same as those of the sample to be tested. The sample pretreatment step is performed as in step S2, and the same test step is performed under the same conditions. The test potential value can be directly calculated by the curve equation obtained in step S1 to calculate the content of hydrofluoric acid or fluoride ions or fluoride in the corresponding sample.

[0019] The prepared standard control sample with known concentration of hydrofluoric acid or fluoride ion or fluoride is used as a reference. One sample is used as a calibration sample to correct the result of the test sample. Another sample is used as a quality control sample to monitor whether there is an abnormal situation in the detection process. If the detection value is consistent with the configuration value, it indicates that there is no problem in the detection process, including personnel operation, equipment and electrode state, signal value drift, reagent, curve, environment, etc. The standard control sample is processed and detected under the same conditions as the sample to be tested. That is, the calibration sample and the quality control sample need to be hydrolyzed.

[0020] The standard control sample can be configured or not configured. Because the content of hydrofluoric acid or fluoride ion or fluoride in the sample measured by the hydrolysis method is very close to the actual level, the relative deviation is very small. It can well feedback whether there is an abnormal situation in the detection process. Therefore, calibration and quality control samples can be used to judge whether there is an abnormality. Because the test value of the sample itself is very close to the true value, which is another big innovation point in the method. The solution is simple and efficient.

[0021] Further preferably, the prepared standard control sample with known concentration of hydrofluoric acid is used as a reference. One sample is used as a calibration sample and one sample is used as a quality control sample. The ratio of the fluoride concentration of the standard control sample to the fluoride concentration of the sample to be tested is between 0.7 and 1.4 times.

[0022] Preferably, the method can be used to detect the content of fluoride in a single-component etching solution, or to detect the content of fluoride in a mixed acid and a mixed acid system with additives, or the content of hydrofluoric acid, or the content of fluoride-containing substances.

[0023] Further preferably, the mixed acid is one or more of phosphoric acid, sulfuric acid, acetic acid, nitric acid, boric acid, fluoroboric acid, hydrochloric acid, etc. or even an etching solution sample of a mixed acid system with other additives.

[0024] The present application fully releases the fluoride ion in the sample containing hydrofluoric acid or fluoride by hydrolysis, calculates the result by using the standard curve, and further corrects the deviation caused by the masking effect, mechanical wear of the electrode and temperature and other environmental influences by processing the standard control solution with similar background as the test solution under the same conditions. The present application simplifies the operation steps and reduces the difficulty. By simply preparing a standard curve and hydrolysis processing, even without standard sample correction, the obtained data is very close to the actual content level. Especially for production control, it is very advantageous.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] First, different standard solutions of different gradients can be prepared by using simple single fluoride to draw a standard curve. The standard used is fluoride, which can be one of ammonium fluoride, sodium fluoride, potassium fluoride, hydrofluoric acid and other compounds that can ionize fluoride. Of course, it can also be multiple, not necessarily consistent with all components in the sample to be tested. This way, the selection is selective, and single-component fluoride that is easy to obtain can be used to draw a standard curve, greatly simplifying the operation, and the obtained curve is linear.

[0027] Second, it directly solves the problem of inaccurate detection caused by the consumption of fluoride ions and other components due to substitution reaction, etc. The above hydrolysis method is particularly advantageous for etching liquid containing two or more mixed hydrofluoric acid, phosphoric acid, sulfuric acid, boric acid, etc. The hydrolysis method is simple, efficient, and the results are accurate and reliable.

[0028] Third, the pretreatment step is simple and effective. The present application only needs to heat and hydrolyze the acid etching liquid sample, and the result of detecting hydrofluoric acid is very close to the true value. At any time, without the help of quality control samples, the true level of hydrofluoric acid or fluoride ions in the sample can be quickly judged, helping production to quickly and accurately clarify the mixing effect of the sample, whether there is an abnormal situation in production, and whether the result is reliable. Without correction, a better result can be obtained. And the detection result is not affected by the standard comparison sample used for correction at any time; compared with production control monitoring, the original method may not be able to handle special concentrations well and quickly, and a sample with the same level needs to be configured for calibration to obtain the true level data of the sample in the process, especially when the sample is abnormal. However, by using the hydrolysis method in the present application, the true concentration level of hydrofluoric acid or fluoride in the sample taken at the time can be quickly and accurately obtained by only processing the sample itself. This has a profound significance in the actual work of daily production monitoring and guiding production control.

[0029] Fourth, calibration can be done at the same time, and many times it can also be done without calibration. Calibration can further slightly improve the test accuracy of hydrofluoric acid or fluoride ions. It can be decided according to the actual situation. Standard comparison samples with known hydrofluoric acid or fluoride ion concentration can be prepared to further correct the deviation caused by environmental factors such as masking effect, mechanical wear of electrode and temperature. Further reduce the fluctuation of detection. The results of the sample to be tested can be calibrated by using the standard comparison sample or not. In short, this detection method can greatly improve the detection accuracy and stability of fluoride ion products. Most importantly, the true level of hydrofluoric acid or fluoride concentration in the sample can be obtained by testing the sample itself at any time, because the test value is very close to the true level. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Fluorine content standard curve. DETAILED DESCRIPTION

[0031] In order to better understand the present application, the following further illustrates the content of the present application in combination with examples and drawings, but in order to make those skilled in the art fully understand the technical solutions and beneficial effects of the present application, the following further illustrates in combination with specific examples, the examples are only simple examples of the present application, and do not represent or limit the protection scope of the present application, and the protection scope of the present application is subject to the claims.

[0032] Figure 1 The standard curve is made by using a standard dilution sample prepared by changing only the concentration of hydrofluoric acid and water without needing to configure and the components of the sample to be tested are the same; but a standard curve is simply made by using a fluorine-containing solution. The pre-treatment operation steps are greatly simplified, simple and efficient, and high in accuracy.

[0033] Standard curve method: first, a fluorine-containing aqueous solution with a larger concentration is prepared as a mother liquor of a fluorine-containing standard solution. Then, different volumes of the above mother liquor are taken and added to 100 mL of a plastic volumetric flask, at room temperature, according to the operation of GB / T 21057-2007 “General method for determination of fluorine content in inorganic chemical products-ion selective electrode method”, the sample pH value is first adjusted, the ion adjusting buffer is added, and finally the corresponding potential value is tested by using a fluorine ion selective electrode, and a standard curve of the fluorine ion concentration and the potential is drawn.

[0034] First, there is no need for a standard control sample to judge whether the detection is abnormal or not. Also, there is no need to use a standard control sample with a relatively close hydrofluoric acid content to the sample to be tested to further correct the results. It can well guide the production to solve problems. Of course, the results after correction are closer to the theoretical value. Second, the reagent obtained by drawing the standard curve can be more selective and more easily obtained, and the process of configuring the standard solution for drawing the curve is very simple and easy to operate. And the linear coefficient of the curve can easily meet the requirements.

[0035] The following examples and comparative examples can be drawn in the same way. Figure 1 The standard curve is made by using a sodium fluoride solution. As shown below:

[0036] Comparative Example 1

[0037] This comparative example tests the test concentration value of fluorine ions in a certain mixed acid A (containing phosphoric acid, sulfuric acid, hydrofluoric acid, nitric acid) at room temperature according to the traditional method for testing the content of fluorine ions, and compares it with the theoretical preparation concentration value to calculate the deviation rate (the ratio of the difference between the test concentration and the preparation concentration in the preparation concentration). The specific is as follows:

[0038] First, a standard dilution sample with a known fluoride ion concentration is prepared. The added components are similar to those of the sample to be tested or the production sample, and the content of the components other than fluoride and water is also similar to that of the production sample. This sample is used as a quality control sample.

[0039] A mixed acid etching solution A sample with a formula of 3.208% fluoride ion concentration is prepared by adding 0.2697 g to a 100 mL plastic volumetric flask. At room temperature, the pH and ionic strength are adjusted according to the national standard GB / T 21057-2007, and the corresponding potential value is tested. At the same time, two standard reference samples with a configuration value are selected, one for calibration and one for quality control. For example, a mixed acid etching solution standard reference sample with a formula of 3.204% fluoride ion concentration is selected as a calibration sample, and a quality control sample with a theoretical value of 3.304% is also prepared and processed in the same way. The fluoride ion concentration of the test sample and the quality control sample is calculated according to the above standard curve. The concentration of hydrofluoric acid is converted. The concentration of hydrofluoric acid obtained by curve calculation of the sample is 2.43%, the calibration sample is 2.44, and the quality control sample is 2.47%. After the test values of the calibration sample and the corresponding configuration value concentration are used to correct the test sample and the quality control sample processed at the same time, the final content of hydrofluoric acid in the sample is 3.20%. The corrected quality control sample is also 3.24%. If corrected to 3.304%, the content of hydrofluoric acid in the sample is 3.25%. The corrected quality control sample (3.204%) is also 3.26%.

[0040] The above standard curve is shown in Figure 1 It can be seen that the correlation coefficient is close to 1, indicating that the method has good quantitative detection ability for free fluoride. However, the incomplete dissociation of fluoride in the actual sample will cause deviation in the test results. In Comparative Example 1, the test sample was directly detected as 2.43%, while the actual configuration value was 3.208%, showing a significant deviation. The deviation can only be corrected by adding a quality control sample to correct the deviation caused by temperature changes, fluoride ion electrode wear, ion masking effect, etc. during the test process. After correction, the deviation is greatly reduced, and the accuracy is improved. The corrected result is 3.20% when corrected with 3.204%, and 3.25% when corrected with 3.304%. From this point, it can be seen that the closer the standard reference sample used for correction to the component concentration of the test sample, the smaller the deviation.

[0041] Table 1 is a summary of the test results of the various comparative examples and examples.

[0042] Example 1

[0043] In this example, the concentration of fluoride ions in the hydrolysis solution is directly measured by a relatively simple hydrolysis operation, and a result close to the true level can be obtained. It can quickly guide the next step of production. The specific process is as follows:

[0044] Firstly, the test sample and quality control sample in Comparative Example 1 are hydrolyzed. That is, 5 g of sample of mixed acid etching liquid A with a formula of 3.208% fluoride ion concentration is added to a 50 mL plastic bottle with pre-added part of pure water, and then water is added, and the total amount of water is about 45 g of distilled water. Mix well, tightly cover the bottle cap, and place the plastic bottle in a water bath at 75°C for 45 min. After cooling to room temperature, 2.5-3.0 g of the treated hydrolysis liquid is weighed, the pH and ionic strength are adjusted according to the national standard GB / T 21057-2007, and the potential is measured. The fluoride ion concentration in the test solution is calculated according to the above standard curve, and the final hydrofluoric acid concentration value is converted to 3.30% considering the dilution factor.

[0045] The above only tests the sample itself, which can reflect the concentration level of hydrofluoric acid in the sample itself, and is very close to the configuration value, and the difference between the test value and the theoretical value is within the acceptable range of 0.1%. This is very meaningful for production guidance. Of course, we can also process the standard control sample with similar concentration at the same time to correct it, or not. The test value of the above-mentioned correction sample (hydrofluoric acid concentration of 3.15%, other components are the same as the test sample A) is 3.18%, and the corrected result of the above-mentioned test sample A is 3.27% after correction. Using a standard control sample for correction can further reduce the deviation. Without correction, the absolute deviation is also within the acceptable range. It can be determined according to the actual situation. The greatest significance is that during the production process, the real hydrofluoric acid level of the etching liquid can be quickly and efficiently reflected, which is simple, efficient and accurate. When checking the sample, it is particularly simple, and there is no need to check the quality control sample and the correction sample as in Comparative Example 1.

[0046] Comparative Example 2

[0047] This comparative example tests the test concentration value of hydrofluoric acid or fluoride ion in mixed acid etching liquid B sample (containing sulfuric acid, hydrofluoric acid, nitric acid) at room temperature according to the traditional method of testing fluoride ion content, and compares it with the theoretical preparation concentration value to calculate the deviation rate (the difference between the test concentration and the preparation concentration in the proportion of the preparation concentration). The specific is as follows:

[0048] First, a standard dilution sample with a known fluoride ion concentration is prepared, and the components added are similar to the test sample or production sample, and the content of the remaining components except fluoride and water is also similar to the production sample. This sample is used as a quality control sample.

[0049] The test formula is a mixed acid etching solution B sample with a fluorine ion concentration of 2.90%. 0.5100 g of the sample is weighed into a 100 mL plastic volumetric flask. At room temperature, the pH and ionic strength are adjusted according to the national standard GB / T 21057-2007, and the corresponding potential value is tested. At the same time, two quality control samples with configured values are selected, one for calibration and one for quality control. For example, a mixed acid etching solution standard reference sample with the same components and a fluorine ion concentration of 2.894% is weighed as a calibration sample, and a quality control sample with a theoretical value of 3.008% is also processed in the same way. The fluorine ion concentration of the test sample and the quality control sample is calculated according to the above standard curve. The concentration of hydrofluoric acid is converted. The concentration of hydrofluoric acid obtained by curve calculation of the sample is 1.37%, the calibration sample is 1.40, and the quality control sample is 1.42%. After calibration of the test sample and the quality control sample by using the test value and the corresponding configured value concentration of the calibration sample, the final content of hydrofluoric acid in the sample is 2.83%. The quality control sample (3.008%) is also calibrated to 2.93%. If calibrated at 3.008%, the sample hydrofluoric acid content is 2.90%. The quality control sample (2.894%) is also calibrated to 2.96%. After calibration, the sample has a significantly reduced deviation and improved accuracy.

[0050] Table 1 is a summary of the test results of the various comparative examples and examples, shown at the end of the text.

[0051] Example 2

[0052] This example uses a relatively simple hydrolysis operation to directly measure the concentration of fluorine ions in the hydrolysis solution, which can obtain results comparable to the true level. It can quickly guide the next step of production. The specific process is as follows:

[0053] The test formula is a mixed acid etching solution B sample with a hydrofluoric acid concentration of 2.90% (containing sulfuric acid, hydrofluoric acid, nitric acid). 3 g of the sample is weighed into a 50 mL plastic bottle pre-added with part of pure water. Then, pure water is added, and the total water volume is about 147 g of pure water. Mix well, tightly cap the bottle, and place the plastic bottle in a 90°C water bath for 60 min. After cooling to room temperature, about 5 g of the treated hydrolysis solution is weighed. The pH and ionic strength are adjusted according to the national standard GB / T 21057-2007, and the potential is measured to be 156.4 mV. The fluorine ion concentration in the test solution is calculated according to the above standard curve, and the final hydrofluoric acid concentration value is converted to be 2.88% considering the dilution factor. The difference from the configured value of 2.90% is small. The calibration sample has a hydrofluoric acid concentration of 3.00%, and the test value is 2.98%. After calibration, the test sample B has a result of 2.90%. The detection accuracy is further improved.

[0054] Example 3

[0055] The embodiment tests the test concentration of fluorine ions in another mixed acid C (containing phosphoric acid, nitric acid, acetic acid and fluoroboric acid) according to the conventional method for testing the content of fluorine ions, and then converts the test concentration into the concentration of fluoroboric acid, and compares the converted concentration with the theoretical preparation concentration value to calculate the absolute deviation value (the difference between the test concentration and the preparation concentration). The specific process is as follows.

[0056] The test formula is a sample of acid-containing etching liquid C with a fluoroboric acid concentration of 1.06%. 3g of the sample is added to a sample bottle to which a part of pure water is added, and then diluted to a certain concentration. The bottle cap is tightly covered, and then hydrolysis is carried out in a 90°C water bath for 60 minutes. After cooling to room temperature, 2.5-3.0g of the treated hydrolysis liquid is weighed, the pH and ionic strength are adjusted according to the national standard GB / T 21057-2007, and the potential is measured. The fluorine ion concentration in the test solution is calculated according to the above standard curve, and the final hydrofluoric acid concentration is converted to 4.15% considering the dilution multiple, and the fluoroboric acid concentration is calculated to be 1.04%. The difference between the calculated value 1.04% and the preparation value 1.06% is only 0.02%, which is very close.

[0057] Table 1

[0058]

[0059]

[0060] Example 4

[0061] The embodiment tests the test concentration of sulfuric acid in a mixed acid D (containing sulfuric acid, nitric acid, acetic acid and hydrofluoric acid), and compares the test concentration with the theoretical preparation concentration value to calculate the absolute deviation value (the difference between the test concentration and the preparation concentration). The specific process is as follows.

[0062] The test formula is a sample of acid-containing etching liquid D with a sulfuric acid concentration of 73.90%. 3g of the sample is added to a sample bottle to which a part of pure water is added, and then diluted to a certain concentration. The bottle cap is tightly covered, and then hydrolysis is carried out in a 90°C water bath for 60 minutes. After cooling to room temperature, 30g of the treated hydrolysis liquid is weighed in a titration cup, 40mL of water is added, the titration cup is placed on an automatic titrator, and the corresponding method is selected. The titration is carried out by using a 1mol / L sodium hydroxide standard titration solution. The inflection point identified by the titration curve is used as the titration end point. According to the concentration of other acids and the titration data, the concentration value of sulfuric acid is calculated to be 74.17%. The difference between the calculated value 74.17% and the preparation value 73.9% is only 0.27%, which is very close.

[0063] As can be seen from the above examples, the present application can well solve the problem of real production monitoring. From the simple and easy-to-operate curve preparation to the subsequent detection, only the sample itself can quickly know the approximate concentration level of the sample itself, which can better guide the production and is simpler and more efficient. Moreover, the method can detect fluorine or other fluorine-containing substances by hydrolysis.

[0064] The above embodiments are merely preferred technical solutions of the present application and should not be regarded as limitations of the present application. The embodiments in the present application and the features in the embodiments can be combined with each other as long as there is no conflict. The protection scope of the present application should be based on the technical solutions recorded in the claims and include equivalent replacement solutions of the technical features recorded in the claims. That is, equivalent replacement improvements within this range are also within the protection scope of the present application.

Claims

1. A method for detecting hydrofluoric acid or fluoride ions in a mixed acid, characterized in that: The method comprises pre-treating the sample, adding water to the sample for heating and hydrolysis, and then performing a subsequent detection process. The heating temperature is 20-100° C., the heating time is 20-100 minutes, and the bottle cap needs to be tightly closed during the heating and hydrolysis. The method comprises the following steps: S1. Prepare fluoride solutions with different concentration gradients as standard solutions, draw a standard curve using a fluoride ion meter, and fit the corresponding relationship between fluoride ion or hydrofluoric acid content and potential; S2. Take the etching solution sample to be tested, add water and sample to the container in sequence, dilute with water, shake well, quickly cover the bottle cap, and heat to hydrolyze; after hydrolysis, adjust the volume; After shaking, weigh a certain amount of hydrolyzate, adjust the pH value and total ionic strength according to GB / T 21057-2007 "General method for determination of fluorine content in inorganic chemical products - Ion-selective electrode method", make the volume constant and shake well, and test the potential value; calculate the content of hydrofluoric acid or fluoride ion in the corresponding sample using the curve equation obtained in S1.

2. The method for detecting hydrofluoric acid or fluoride ions in mixed acid according to claim 1, wherein: The standard substance used for drawing the standard curve in step S1 is fluoride, which is one or more of ammonium fluoride, sodium fluoride, and potassium fluoride; or a gradient standard solution is prepared using hydrofluoric acid, but the volatilization during the operation and the test temperature conditions must be controlled to be consistent with those during the sample measurement; The standard curve drawn in step S1 reflects the linear relationship between the potential value and the hydrofluoric acid concentration or the fluoride ion concentration. The R2 value in the linear regression of the standard curve must be greater than or equal to 0.99; and the potential value range of the curve must cover the potential value of the solution to be tested. Sample pretreatment in step 2: heating and hydrolysis, the sample amount weighed and the corresponding total water sample, the dilution multiple is more than 5 times; Sample pretreatment in step S2: heating and hydrolysis; the heating temperature and heating time are determined by the system components. When the concentration of sulfuric acid and phosphoric acid is high, the required heating temperature is higher and the heating time is longer, and vice versa; When heating and hydrolyzing, the bottle cap needs to be tightly closed to prevent the components from volatilizing.

3. The method for detecting hydrofluoric acid or fluoride ions in mixed acid according to claim 1, wherein: In the method, two standard control samples with known hydrofluoric acid or fluoride ion concentrations are prepared for use as reference. The components and proportions of the solutions are the same as those of the test sample. The samples are pretreated according to the sample pretreatment steps in step S2, and the same test steps and conditions are used to test the potential values. The hydrofluoric acid or fluoride ion content in the corresponding samples is directly calculated using the curve equation obtained in S1. A standard control sample with a known hydrofluoric acid or fluoride ion concentration is prepared for use as a reference, one sample being used as a calibration sample and the other being used as a quality control sample. The ratio of the fluoride concentration of the standard control sample to the fluoride concentration of the sample to be tested is between 0.7 and 1.4 times.

4. The method for detecting hydrofluoric acid or fluoride ions in a mixed acid according to any one of claims 1 to 3, wherein: The method is used to measure the fluorine content in a single-component etching solution, or to detect the fluorine content in an etching solution of a mixed acid system or a mixed acid system with additives.

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