Device and method for analyzing impurities in high-purity fluorine gas

Abstract

The invention belongs to the technical field of chemical engineering, and particularly relates to a device for analyzing impurities in high-purity fluorine gas, which comprises a gas mixing tank, a gas inlet of the gas mixing tank is connected with a fluorine gas inlet pipeline and a diluent gas inlet pipeline, a fluorine gas inlet valve is arranged on the fluorine gas inlet pipeline, and a diluent gas inlet valve is arranged on the diluent gas inlet pipeline. A diluted gas inlet valve is arranged on the diluted gas inlet pipeline; a gas outlet of the gas mixing tank is connected with a vacuum pipeline and a mixed gas outlet pipeline, a vacuum valve is arranged on the vacuum pipeline, and a mixed gas outlet valve is arranged on the mixed gas outlet pipeline; a high-precision pressure gauge is also arranged on the gas mixing tank; the invention also relates to an analysis method, the pure high-purity fluorine gas is mixed with the diluent gas through the analysis device before entering the chromatography to generate the mixed gas of the fluorine gas and the diluent gas with the fluorine gas volume content of less than 30%, and then the mixed gas is purged by the carrier gas to enter the chromatography for analysis, so that the component impurities can be analyzed more accurately; the index requirements of high-purity fluorine gas on impurity analysis can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and particularly relates to an analysis device and method for impurities in high-purity fluorine gas. Background Art

[0002] High-purity fluorine gas (F2) is a very active gas with strong oxidizing properties. Due to its reaction characteristics, it is used as an etching gas or cleaning gas in the semiconductor industry to manufacture TFTs (thin film transistors) for photovoltaic cells and liquid crystal displays. At the same time, as a gas for excimer lasers, fluorine lasers are also widely used in the semiconductor industry. At the same time, F2 is used as a cleaning agent for chemical vapor deposition (CVD) reaction chambers. Compared with NF3, F2 has stronger reactivity and does not cause a greenhouse effect. With the vigorous development of the domestic semiconductor industry, the demand for fluorine gas used for this purpose is also increasing significantly. In order to meet the requirements of the electronics and photovoltaic industries, high-purity fluorine gas with a purity of more than 99.9% or even 99.99% is required. Among them, the requirements for impurities such as oxygen and nitrogen are very high, and most of the impurity contents are less than 100ppm, so higher requirements are also placed on the analysis of impurities in fluorine gas.

[0003] The method described in US6955801B2 is a method for producing a high-purity fluorine gas and analyzing impurities therein, comprising filling a fluorinated nickel compound into a container comprising a metal material or a metal material having a nickel film, the container having a fluorinated layer formed on the surface of the metal material or the nickel film; performing a step of heating the fluorinated nickel compound to 250°C to 600°C and reducing the pressure in the container to 0.01 MPa (absolute pressure) or less, and a step of allowing the fluorine gas whose hydrogen fluoride content is reduced to 500 volppm or less to be sealed in the fluorinated nickel compound after the first step at least once respectively and further performing the first step; then bringing a fluorine gas containing impurities into contact with the fluorinated nickel compound at 200°C to 350°C to fix and remove the fluorine gas; and analyzing the impurities by GC or IR. Using this method, the post-processing treatment and the required conditions are very complicated and expensive, and are not suitable for conventional analysis.

[0004] The commonly used pure fluorine gas analysis method, as described in the national standard GB / T20256-2010, requires that the fluorine gas first pass through a potassium chloride reaction column to react with potassium chloride to generate chlorine gas, and then enter the chromatographic analysis of gas components and impurities to complete the quantitative analysis of components in pure fluorine gas. However, this method has a major problem, that is, the reaction rate of fluorine gas and potassium chloride is only 70% to 80%, that is, in the case of pure fluorine gas, at least 20% of the fluorine gas will enter the chromatographic system. Fluorine gas is a strong oxidizing substance that will react with the filler in the chromatographic column to produce impurities that affect the component analysis of pure fluorine gas, resulting in a large deviation in the impurity analysis of fluorine gas, and it is impossible to perform accurate analysis. Summary of the invention

[0005] The purpose of the present invention is to provide an analysis device and method for impurities in high-purity fluorine gas, which can reduce the volume concentration of fluorine gas to below 30% without affecting the component impurities, thereby reducing the fluorine gas entering the chromatographic system, avoiding the reaction of fluorine gas with substances in the chromatogram, and accurately analyzing the component impurities.

[0006] The technical solution of the present invention:

[0007] A device for analyzing impurities in high-purity fluorine gas comprises a gas mixing tank, wherein the lower end of the gas mixing tank is provided with an air inlet, and the upper end is provided with an air outlet; the air inlet of the gas mixing tank is connected to a fluorine gas inlet pipeline and a dilution gas inlet pipeline, the fluorine gas inlet pipeline is provided with a fluorine gas inlet valve, and the dilution gas inlet pipeline is provided with a dilution gas inlet valve; the air outlet of the gas mixing tank is connected to a vacuum pipeline and a mixed gas outlet pipeline, the vacuum pipeline is provided with a vacuum valve, and the mixed gas outlet pipeline is provided with a mixed gas outlet valve; the gas mixing tank is also provided with a high-precision pressure gauge.

[0008] Preferably, the mixing tank, fluorine gas inlet pipeline, dilution gas inlet pipeline, vacuum pipeline and mixed gas outlet pipeline are made of stainless steel or monel HF corrosion-resistant material;

[0009] The volume of the mixing tank is between 2 and 30 L;

[0010] The accuracy of the high-precision pressure gauge reaches 0.001MPa.

[0011] Furthermore, a method for analyzing impurities in high-purity fluorine gas comprises the following steps:

[0012] S1. Before the high-purity fluorine gas enters the fluorine gas inlet pipeline, use high-purity nitrogen to vacuum the mixing tank for replacement at least 5 times, perform chromatographic analysis on the last replacement gas, vacuum the mixing tank, and close the vacuum valve after reaching the pressure;

[0013] S2. Open the fluorine gas inlet valve to allow high-purity fluorine gas to enter the mixing tank. After the pressure reaches 0 MPa, close the fluorine gas inlet valve. Open the dilution gas inlet valve to allow the dilution gas to enter the mixing tank. Control the pressure of the entire mixing tank and the volume content of high-purity fluorine gas at the same time. Then close the dilution gas inlet valve, let it stand and mix well, and then enter the chromatogram for analysis.

[0014] Preferably, the last time of the vacuum replacement operation in S1 is subjected to chromatographic analysis, and the product is deemed qualified when the oxygen index is less than 1 ppm; the purity of the high-purity nitrogen is 99.9999%.

[0015] In S1, the mixing tank is evacuated until the pressure is less than -0.099 MPa and then the vacuum valve is closed.

[0016] Preferably, the dilution gas is nitrogen or an inert gas, and the purity of the dilution gas is 99.9999%.

[0017] Preferably, the inert gas includes helium and argon.

[0018] Preferably, after the dilution gas enters the mixing tank, the pressure is controlled between 0.25 and 2 MPa, and the volume content of the high-purity fluorine gas is less than 30%. When the volume content is greater than 5%, the dilution gas inlet valve is closed.

[0019] Preferably, the mixing time is 0.5 to 2 hours.

[0020] Preferably, the specific steps of S1 are: open the vacuum system valve to perform vacuum treatment, after the mixing tank is vacuumed, close the vacuum valve, open the nitrogen inlet valve to replace the system, repeat the above process 5 to 10 times, perform chromatographic analysis on the gas in the mixing tank, and after the oxygen content is less than 1ppm, vacuum the system and close all valves for standby use.

[0021] Preferably, the purity of the high-purity fluorine gas reaches above 99.9%.

[0022] Beneficial effects of the present invention:

[0023] The purpose of the present invention is to provide an analysis device for impurities in high-purity fluorine gas on the basis of the existing fluorine gas analysis chromatography, so that the pure fluorine gas is mixed with nitrogen or inert gas before entering the chromatograph through the device. The device reduces the volume concentration of fluorine gas to below 30% without affecting the component impurities, thereby reducing the fluorine gas entering the chromatographic system and avoiding the reaction of fluorine gas with substances in the chromatogram. The component impurities can be analyzed more accurately to ensure that the impurities in pure fluorine gas can meet the 99.9% high-purity fluorine gas analysis standard requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the device of the present invention;

[0025] 1. Fluorine gas inlet valve; 2. Dilution gas inlet valve; 3. Mixing tank; 4. Vacuum valve; 5. Mixed gas outlet valve; 6. High-precision pressure gauge. DETAILED DESCRIPTION

[0026] The following is combined with Figure 1 The device of the present invention is further described in detail with reference to the accompanying drawings and embodiments.

[0027] Device Embodiment

[0028] like Figure 1 As shown, an analysis device for impurities in high-purity fluorine gas comprises a 2-30L gas mixing tank 3, wherein the lower end of the gas mixing tank 3 is provided with an air inlet, and the upper end is provided with an air outlet; the air inlet of the gas mixing tank 3 is connected to a fluorine gas inlet pipeline and a dilution gas inlet pipeline, a fluorine gas inlet valve 1 is provided on the fluorine gas inlet pipeline, and a dilution gas inlet valve 2 is provided on the dilution gas inlet pipeline; the air outlet of the gas mixing tank 3 is connected to a vacuum pipeline and a mixed gas outlet pipeline, a vacuum valve 4 is provided on the vacuum pipeline, and a mixed gas outlet valve 5 is provided on the mixed gas outlet pipeline; the gas mixing tank 3 is also provided with a high-precision pressure gauge, and the model used is a Sichuan Instrument PDS873 series remote pressure gauge 6. The mixing tank 3, the fluorine gas inlet pipeline, the dilution gas inlet pipeline, the vacuum pipeline and the mixed gas outlet pipeline are made of stainless steel or monel HF corrosion-resistant material.

[0029] Method Embodiment

[0030] Examples 1-3 and Comparative Examples 1-6 all use the device of the device example.

[0031] Before each analysis, first open the vacuum valve 4 to evacuate the system. After the vacuum is evacuated, close the vacuum valve 4 and open the dilution gas inlet valve 2 to replace the system. After repeating the above process 5 to 10 times, perform chromatographic analysis on the gas in the mixing tank 3. After the oxygen content is lower than 1ppm, the system is evacuated. After the pressure is less than -0.099MPa, close the vacuum valve and close all valves for standby use.

[0032] Open the fluorine gas inlet valve 1 to allow high-purity fluorine gas to enter the mixing tank 3. After the pressure reaches 0 MPa, close the fluorine gas inlet valve 1; open the dilution gas inlet valve 2 to allow nitrogen to enter the mixing tank. The pressure is controlled between 0.25 and 2 MPa. Let it stand for 0.5 to 2 hours. After the gas is fully mixed, open the mixing tank outlet valve 5 to allow the gas to enter the subsequent chromatographic analysis system for impurity analysis.

[0033] The chromatographic instrument used was Fanwei GC-6600 helium ion chromatograph for analysis.

[0034] Example 1

[0035] A method for analyzing impurities in high-purity fluorine gas comprises the following steps:

[0036] Step 1, assembling the system, wherein the mixing tank has a volume of 2 liters;

[0037] Step 2, open the vacuum valve 4 to evacuate the system. After the vacuum is evacuated, close the vacuum valve 4 and open the nitrogen inlet valve 2 to replace the system. After repeating the above process 5 times, perform chromatographic analysis on the gas in the mixing tank. The oxygen content is 0.8ppm. The system is evacuated. After the pressure is -0.10MPa, close the vacuum valve 4 and close all valves for standby use.

[0038] Step 3, open the fluorine gas inlet valve 1 to allow high-purity fluorine gas to enter the mixing tank. After the pressure reaches 0 MPa, close the fluorine gas inlet valve 1; open the dilution gas inlet valve 2 to allow nitrogen to enter the mixing tank 3, control the pressure at 1.8 MPa, and let it stand for 0.5 hours. After the gas is fully mixed, open the mixing tank outlet valve 5 to allow the gas to enter the subsequent chromatographic analysis system for impurity analysis.

[0039] The analysis results show that the oxygen impurity content in the mixed gas is 4.5ppm, and the carbon dioxide is 1.1ppm, which is basically consistent with the oxygen and carbon dioxide content in the standard fluorine gas provided by Shanghai Fanwei. See Table 1 for specific data:

[0040] Table 1

[0041]

[0042]

[0043] Example 2

[0044] A method for analyzing impurities in high-purity fluorine gas comprises the following steps:

[0045] Step 1, assembling the system, wherein the mixing tank has a volume of 30 liters;

[0046] Step 2, open the vacuum valve 4 to evacuate the system. After the vacuum is evacuated, close the vacuum valve 4 and open the dilution gas inlet valve 2 to replace the system. After repeating the above process 8 times, perform chromatographic analysis on the gas in the mixing tank. The oxygen content is 0.5ppm. The system is evacuated. After the pressure reaches -0.10MPa, close the vacuum valve 4 and close all valves for standby use.

[0047] Step 3, open the fluorine gas inlet valve 1 to allow high-purity fluorine gas to enter the mixing tank. After the pressure reaches 0 MPa, close the fluorine gas inlet valve 1; open the dilution gas inlet valve 2 to allow helium to enter the mixing tank 3, control the pressure to 0.25 MPa, let it stand for 1 hour, and after the gas is fully mixed, open the mixing tank outlet valve 5 to allow the gas to enter the subsequent chromatographic analysis system for impurity analysis.

[0048] The analysis results show that the oxygen impurity content in the mixed gas is 23ppm, and the carbon dioxide is 5.4ppm, which are basically consistent with the oxygen and carbon dioxide contents in the standard fluorine gas provided by Shanghai Fanwei.

[0049] See Table 2 for specific data:

[0050] Table 2

[0051] project Oxygen (ppm) Carbon dioxide (ppm) Experimental gas (28.6% fluorine gas) 23 5.4 Fluorine gas standard gas 85 20.9

[0052] Example 3

[0053] A method for analyzing impurities in high-purity fluorine gas comprises the following steps:

[0054] Step 1, assembling the system, wherein the mixing tank has a volume of 15 liters;

[0055] Step 2, open the vacuum system valve 4 to evacuate the system. After the vacuum is evacuated, close the vacuum system valve 4 and open the dilution gas inlet valve 2 to replace the system. After repeating the above process 10 times, perform chromatographic analysis on the gas in the mixing tank. The oxygen content is 0.4ppm. The system is evacuated. After the pressure reaches -0.10MPa, close the vacuum valve 4 and close all valves for standby use.

[0056] Step 3, open the fluorine gas inlet valve 1 to allow fluorine gas to enter the mixing tank. After the pressure reaches 0 MPa, close the fluorine gas inlet valve 1; open the dilution gas inlet valve 2 to allow argon gas to enter the mixing tank 3, control the pressure to 1 MPa, and let it stand for 2 hours. After the gas is fully mixed, open the mixing tank outlet valve 5 to allow the gas to enter the subsequent chromatographic analysis system for impurity analysis.

[0057] The analysis results show that the oxygen impurity content in the pure mixed gas is 7.7ppm, and the carbon dioxide is 1.8ppm, which is basically consistent with the oxygen and carbon dioxide content in the standard fluorine gas provided by Shanghai Fanwei. See Table 3 for specific data:

[0058] Table 3

[0059] project Oxygen (ppm) Carbon dioxide (ppm) Experimental gas (9.1% fluorine gas) 7.7 1.8 Fluorine gas standard gas 85 20.9

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that in this comparative example, the system is replaced, and after repeating the above process once, the gas in the mixing tank is subjected to chromatographic analysis, and the oxygen content is 1.8 ppm, and other places are the same;

[0062] The analysis results are shown in Table 4:

[0063] Table 4

[0064] project Oxygen (ppm) Carbon dioxide (ppm) Experimental gas (5.3% fluorine gas) 6.2 1.8 Fluorine gas standard gas 85 20.9

[0065] The analysis results show that under the condition of insufficient substitution, the analysis will lead to deviation in the experimental data.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 1 is that the fluorine gas inlet valve 1 is opened to allow the fluorine gas to enter the mixing tank. After the pressure reaches 0.7 MPa (the fluorine gas content is 42.1% under this condition), the fluorine gas inlet valve 1 is closed, and other places are the same;

[0068] The analysis results are shown in Table 5:

[0069] Table 5

[0070]

[0071]

[0072] The analysis results show that after exceeding the right range, the impurity index caused by analysis is much greater than the standard gas.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 1 is that the fluorine gas inlet valve 1 is opened to allow the fluorine gas to enter the mixing tank, and after the pressure reaches -0.5MPa (the fluorine gas content is 2.6% under this condition), the fluorine gas inlet valve 1 is closed, and other places are the same;

[0075] The analysis results are shown in Table 6:

[0076] Table 6

[0077] project Oxygen (ppm) Carbon dioxide (ppm) Experimental gas (2.6% fluorine gas) cover Not detected Fluorine gas standard gas 85 20.9

[0078] The analysis results showed that the fluorine content was too low, causing the oxygen peak to be masked and unable to be accurately analyzed.

[0079] Comparative Example 4

[0080] The difference between this comparative example and Example 1 is that the pressure of the dilution gas after entering the mixing tank is controlled to be 0.1MPa (the fluorine content is 50% under this condition), and other places are the same;

[0081] The analysis results are shown in Table 7:

[0082] Table 7

[0083] project Oxygen (ppm) Carbon dioxide (ppm) Experimental gas (50% fluorine) 6.5 286.7 Fluorine gas standard gas 85 20.9

[0084] The analysis results show that when the fluorine gas content is within the authorized range, the content of impurities such as oxygen in the fluorine gas can be analyzed more accurately.

[0085] Comparative Example 5

[0086] The difference between this comparative example and Example 1 is that the pressure of the dilution gas after entering the mixing tank is controlled to be 3.0 MPa (the fluorine content is 3.2% under this condition), and other places are the same;

[0087] The analysis results are shown in Table 8:

[0088] Table 8

[0089]

[0090]

[0091] The analysis results show that the fluorine content is lower than the authorized range. Although the content of impurities such as oxygen in fluorine can be analyzed, the accuracy is very poor.

[0092] Comparative Example 6

[0093] The difference between this comparative example and Example 1 is that the time of standing and mixing is 0.1h, and other places are the same;

[0094] The analysis results are shown in Table 9:

[0095] Table 9

[0096] project Oxygen (ppm) Carbon dioxide (ppm) Experimental gas (5.3% fluorine gas) 0.8 1.2 Fluorine gas standard gas 85 20.9

[0097] The analysis results show that under the condition of insufficient mixing, the analysis results deviate significantly due to different gas densities.

[0098] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An analysis device for impurities in high-purity fluorine gas, characterized in that: The invention comprises a gas mixing tank (3), wherein the lower end of the gas mixing tank (3) is provided with an air inlet, and the upper end is provided with an air outlet; the air inlet of the gas mixing tank (3) is connected to a fluorine gas inlet pipeline and a dilution gas inlet pipeline, the fluorine gas inlet pipeline is provided with a fluorine gas inlet valve (1), and the dilution gas inlet pipeline is provided with a dilution gas inlet valve (2); the air outlet of the gas mixing tank (3) is connected to a vacuum pipeline and a mixed gas outlet pipeline, the vacuum pipeline is provided with a vacuum valve (4), and the mixed gas outlet pipeline is provided with a mixed gas outlet valve (5); the gas mixing tank (3) is also provided with a high-precision pressure gauge (6).

2. The device for analyzing impurities in high-purity fluorine gas according to claim 1, characterized in that: The mixing tank (3), the fluorine gas inlet pipeline, the dilution gas inlet pipeline, the vacuum pipeline and the mixed gas outlet pipeline are made of stainless steel or monel HF corrosion-resistant material; The volume of the mixing tank (3) is between 2 and 30 L; The accuracy of the high-precision pressure gauge (6) reaches 0.001 MPa.

3. A method for analyzing impurities in high-purity fluorine gas, using the device for analyzing impurities in high-purity fluorine gas according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Before the high-purity fluorine gas enters the fluorine gas inlet pipeline, the mixing tank (3) is evacuated and replaced with high-purity nitrogen gas at least five times. The last replacement gas is subjected to chromatographic analysis. The mixing tank (3) is evacuated and the vacuum valve (4) is closed after the pressure is reached. S2. Open the fluorine gas inlet valve (1) to allow high-purity fluorine gas to enter the mixing tank (3). After the pressure reaches 0 MPa, close the fluorine gas inlet valve (1). Open the dilution gas inlet valve (2) to allow the dilution gas to enter the mixing tank (3). Control the pressure of the entire mixing tank (3) and the volume content of high-purity fluorine gas at the same time. Then close the dilution gas inlet valve (2), let it stand and mix well, and enter the chromatogram for analysis.

4. The method for analyzing impurities in high-purity fluorine gas according to claim 3, characterized in that: The last time of vacuum replacement operation in S1 is to conduct chromatographic analysis, and the oxygen index is less than 1ppm to determine the pass; the purity of high-purity nitrogen is 99.9999%; In S1, the mixing tank (3) is evacuated until the pressure is less than -0.099 MPa and then the vacuum valve (4) is closed.

5. The method for analyzing impurities in high-purity fluorine gas according to claim 3, characterized in that: The diluent gas is nitrogen or inert gas, and the purity of the diluent gas is 99.9999%.

6. The method for analyzing impurities in high-purity fluorine gas according to claim 5, characterized in that: The inert gas includes helium and argon.

7. The method for analyzing impurities in high-purity fluorine gas according to claim 3, characterized in that: After the dilution gas enters the mixing tank (3), the pressure is controlled between 0.25 and 2 MPa, and the volume content of the high-purity fluorine gas is less than 30%. When the volume content is greater than 5%, the dilution gas inlet valve (2) is closed.

8. The method for analyzing impurities in high-purity fluorine gas according to claim 3, characterized in that: The mixing time is 0.5 to 2 hours.

9. The method for analyzing impurities in high-purity fluorine gas according to claim 3, characterized in that: The specific steps of S1 are: open the vacuum system valve (4) to carry out vacuum treatment, after the mixing tank (3) is completely vacuumed, close the vacuum valve (4), open the nitrogen inlet valve (2) to replace the system, repeat the above process 5 to 10 times, perform chromatographic analysis on the gas in the mixing tank (3), and after the oxygen content is less than 1 ppm, vacuum the system and close all valves for standby use.

10. The method for analyzing impurities in high-purity fluorine gas according to claim 3, characterized in that: The purity of high-purity fluorine gas reaches over 99.9%.

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