A gas chromatography valve system with oxygen-free adsorption for high-purity nitrogen trifluoride analysis and its use method

Abstract

The invention discloses a gas chromatography valve system with oxygen-free adsorption for high-purity nitrogen trifluoride analysis and a use method thereof. The valve system adopts a four-valve four-column valve system, including two four-way valves, two ten-way valves, two quantitative loops, four chromatographic columns, 11 pressure balance regulating valves and a discharge ionization detector. The system carrier gas is high-purity helium of more than 99.9999%. The system is simple, easy to operate and accurate in analysis.

Description

Technical Field

[0001] The invention relates to an analysis device and an analysis method for nitrogen trifluoride. Background Art

[0002] Nitrogen trifluoride (NF3) is widely used in integrated circuits, photovoltaics, and displays (TFT-LCD) due to its advantages of fast etching rate, high selectivity, and no residual substances left on the surface of the etched material. Since its purity has a great influence on the material etching effect, it is particularly important to accurately analyze the content of the main gas phase impurities O2, N2, CO, CO2, N2O and SF6 in NF3.

[0003] CN102636598A discloses a gas chromatography valve circuit system for analyzing a variety of high-purity fluorine-containing electronic gases and a method of using the same. The system uses five valves and four columns, and can complete the determination of gas phase impurities of a variety of high-purity fluorine-containing electronic special gases including NF3 in one injection. However, the system is complex, and since the pre-separation column will adsorb trace oxygen, it will inevitably affect the accuracy of the analysis and determination of trace oxygen components in high-purity NF3. Summary of the invention

[0004] The first technical problem to be solved by the present invention is to provide a gas chromatography valve system with oxygen-free adsorption for high-purity nitrogen trifluoride analysis, which is simple, easy to operate and accurate in analysis.

[0005] The second technical problem to be solved by the present invention is to provide a method for using the system.

[0006] To solve the first problem mentioned above, the present invention adopts a four-valve four-column valve system, including two four-way valves, two ten-way valves, two quantitative loops, four chromatographic columns, 11 pressure balance regulating valves and one discharge ionization detector, and the system carrier gas is high-purity helium of more than 99.9999%;

[0007] The first interface of the first four-way valve 1 is connected to the pressure regulating valve 10 and then to the helium source, the second interface is connected to the pressure balance regulating valve 19 and then to the gas outlet, the third interface is connected to the second interface of the twentieth-way valve 3, and the fourth interface is connected to the second analytical chromatographic column 8 and then to the fourth interface of the second four-way valve 4;

[0008] The first interface of the first ten-way valve 2 is connected to the helium source through the pressure regulating valve 11, the second interface is connected to the first analysis chromatographic column 6 and then connected to the second interface of the second four-way valve 4, the first pre-separation chromatographic column 5 is connected between the third interface and the ninth interface, the fourth interface is connected to the helium source through the pressure regulating valve 12, the first quantitative loop 20 is connected between the fifth interface and the eighth interface, the sixth interface is connected to the sixth interface of the twentieth-way valve 3, the seventh interface is connected to the sample inlet, and the tenth interface is connected to the pressure balance regulating valve 18 and then connected to the gas outlet;

[0009] The first interface of the twentieth-way valve 3 is connected to the helium source through the pressure regulating valve 13, the second pre-separation chromatographic column 7 is connected between the third interface and the ninth interface, the fourth interface is connected to the helium source through the pressure regulating valve 14, the second quantitative loop 21 is connected between the fifth interface and the eighth interface, the seventh interface is connected to the sample outlet, and the tenth interface is connected to the pressure balance regulating valve 17 and then connected to the gas outlet;

[0010] The first interface of the second four-way valve 4 is connected to the discharge ionization detector 22 , and the third interface is connected to the pressure balance regulating valve 16 and then to the gas outlet.

[0011] The first pre-separation chromatographic column 5 is preferably a carbon molecular sieve (CST) chromatographic column.

[0012] The first analytical chromatographic column 6 is preferably a 13X chromatographic column.

[0013] The second pre-separation chromatographic column 7 is preferably a Hayesep D chromatographic column.

[0014] The second analytical chromatographic column 8 is preferably a Hayesep DB chromatographic column.

[0015] This valve circuit system consists of three parts: carrier gas regulation system, component separation system and detector.

[0016] 1. The carrier gas regulation system includes 11 pressure balance regulating valves and connecting pipelines. High-purity helium is introduced into the valve system through the pressure balance regulating valve 9. The pressure balance regulating valves 10 to 14 respectively control the pressure and flow rate of the carrier gas entering the first four-way valve 1, the first ten-way valve 2, the twentieth-way valve 3 and the second four-way valve 4; the pressure balance regulating valve 15 controls the pressure and flow rate of the carrier gas entering the discharge ionization detector 22 to be stable; the pressure balance regulating valves 16 to 19 respectively control the pressure and flow rate of the gas outlets of the first four-way valve 1, the first ten-way valve 2, the twentieth-way valve 3 and the second four-way valve 4.

[0017] 2. The component separation system includes 2 four-way valves, 2 ten-way valves, 2 pre-separation chromatographic columns and 2 analytical chromatographic columns;

[0018] 3. The detector is a discharge ionization detector 22;

[0019] The system of the present invention has the following characteristics:

[0020] 1. The system includes two groups of sample collection-pre-separation-separation systems, the first group is composed of the first ten-way valve 2, the first quantitative loop 20, the first pre-separation chromatographic column 5 and the first analytical chromatographic column 6; the second group is composed of the twentieth-way valve 3, the second quantitative loop 21, the second pre-separation chromatographic column 7 and the second analytical chromatographic column 8. After one injection, the samples collected in the two quantitative loops can enter their respective pre-separation chromatographic columns and analytical chromatographic columns.

[0021] 2. The system has backflush and heart-cut functions. The sample pre-separated by the first pre-separation chromatographic column 5 is back-flushed to remove the base NF3 by switching the first ten-way valve 2; the sample pre-separated by the second pre-separation chromatographic column 7 is heart-cut by the first four-way valve 1, eliminating the influence of the base component on the analysis of the trace impurity content and avoiding contamination and damage to the detector.

[0022] 3. Using carbon molecular sieve (CST) chromatographic column as the pre-separation chromatographic column avoids oxygen adsorption, improves the accuracy of oxygen analysis, and reduces system errors. It can achieve accurate quantification of all impurity components including oxygen.

[0023] As attached Figure 1 The system state shown, the method of using the device of the present invention includes:

[0024] 1. Each valve in the figure is in the "open" state. After the valve is moved once, it is in the "closed" state, and after the valve is moved again, it is in the "open" state;

[0025] 2. Open the first ten-way valve 2 to collect the sample to be measured in the first quantitative ring 20; open the twentieth-way valve 3 to collect the sample to be measured in the second quantitative ring 21;

[0026] 3. Close the first ten-way valve 2 and the second four-way valve 4, and blow the sample collected by the first quantitative loop 20 into the first pre-separation chromatographic column 5 through the carrier gas of the pressure balance regulating valve 12;

[0027] 4. After pre-separation by the first pre-separation chromatographic column 5, the pre-separated components O2, N2, and CO enter the first analytical chromatographic column 6; the first ten-way valve 2 is opened, and the other components are back-blown and vented;

[0028] 5. The O2, N2, and CO components separated by the first analytical chromatographic column 6 are transmitted from the second four-way valve 4 to the detector 22 to realize the detection of the components to be measured;

[0029] 6. Close the 20th-way valve 3, open the first four-way valve 1, and use the carrier gas at the outlet of the pressure balance regulating valve 14 to blow the sample collected in the second quantitative loop 21 into the second pre-separation chromatographic column 7;

[0030] 7. After pre-separation by the second pre-separation chromatographic column 7, the pre-separated components N2, O2, and CO are discharged through the 20th-way valve 3 to the first four-way valve 1;

[0031] 8. Close the first four-way valve 1, open the second four-way valve 4, and the pre-separated components CF4 and a small amount of NF3 are pre-separated by the second pre-separation chromatographic column 7 and enter the second analysis chromatographic column 8 through the first four-way valve 1. After separation by the second analysis chromatographic column 8, the components are detected by the second four-way valve 4 to the detector 22;

[0032] 9. Open the first four-way valve 1, and discharge a large amount of main component NF3 pre-separated by the second pre-separation chromatographic column 7 through the first four-way valve 1;

[0033] 10. Close the first four-way valve 1, and the CO2, N2O, SF6 and a small amount of NF3 pre-separated by the second pre-separation chromatographic column 7 enter the second analysis chromatographic column 8 through the first four-way valve 1. After separation by the second analysis chromatographic column 8, the components are detected by the second four-way valve 4 to the detector 22.

[0034] Compared with the prior art, the method of the present invention has the following advantages:

[0035] 1. The first pre-separation chromatographic column 5 is used to pre-separate the impurity components of O2, N2, and CO from the substrate NF3. O2, N2, and CO enter the first analytical chromatographic column 6 for separation. The substrate NF3 and other impurities are back-blown and vented by switching the first ten-way valve 2, and the analysis of O2, N2, and CO impurities is more accurate.

[0036] 2. The second pre-separation chromatographic column 7 is used to pre-separate the impurity components from the substrate NF3, and the cutting and venting of the substrate components is achieved by switching the first four-way valve 1, thereby avoiding the influence of the substrate components on the analysis of the impurity components and the pollution and damage to the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the chromatography valve system of the present invention.

[0038] Wherein: 1. First four-way valve; 2. First ten-way valve; 3. Twentieth-way valve; 4. Second four-way valve; 5. First pre-separation chromatographic column; 6. First analytical chromatographic column; 7. Second pre-separation chromatographic column; 8. Second analytical chromatographic column; 9-19. Pressure balance regulating valve DETAILED DESCRIPTION

[0039] To introduce the technical solution provided by the present invention in more detail, it is described below in conjunction with embodiments.

[0040] Example 1

[0041] As attached Figure 1 The gas chromatography valve system shown is used for separation and detection of trace impurities in nitrogen trifluoride.

[0042] Trace impurities in nitrogen trifluoride with a purity of more than 99.99% mainly include: oxygen (O2), nitrogen (N2), carbon monoxide (CO), carbon tetrafluoride (CF4), carbon dioxide (CO2), nitrous oxide (N2O) and sulfur hexafluoride (SF6).

[0043] The first pre-separation chromatographic column 5 is a carbon molecular sieve (CST) chromatographic column with a length of 2 m.

[0044] The first analytical chromatographic column 6 is a 13X molecular sieve chromatographic column with a length of 3 m.

[0045] The second pre-separation chromatographic column 7 is a 5 m long Hayesep D chromatographic column.

[0046] The second analytical chromatographic column 8 is a 5 m long Hayesep DB chromatographic column.

[0047] 1. As attached Figure 1 As shown, each valve is in the "open" state;

[0048] 2. Open the first ten-way valve 2 and the second ten-way valve 3, and the sample enters the first quantitative ring 20 and the second quantitative ring 21 along the pipeline, so as to collect the sample to be measured in the two quantitative rings;

[0049] 3. Close the first ten-way valve 2 and the second four-way valve 4, and pass the carrier gas of the pressure balance regulating valve 12 through the fourth interface of the first ten-way valve 2 → the fifth interface → the first quantitative ring 20 → the eighth interface → the ninth interface → the first pre-separation chromatographic column 5 to achieve pre-separation of the impurity components O2, N2, CO and other components;

[0050] 4. After pre-separation by the first pre-separation chromatographic column 5, the pre-separated components O2, N2, and CO are passed through the third interface of the first ten-way valve 2 → the second interface → the first analytical chromatographic column 6; the first ten-way valve 2 is opened, and the CF4, CO2, N2O, SF6 and the main component NF3 pre-separated by the first pre-separation chromatographic column 5 are passed through the ninth interface of the first ten-way valve 2 → the tenth interface, and are back-blown and vented;

[0051] 5. The O2, N2, and CO components separated by the first analytical chromatographic column 6 are detected by the second interface of the second four-way valve 4 → the first interface → the detector 22, and the peak order is O2, N2, and CO;

[0052] 6. Close the 20th-way valve 3, open the second four-way valve 4, and blow the carrier gas at the outlet of the pressure balance regulating valve 14 through the 4th interface of the 20th-way valve 3 → the 5th interface → the second quantitative ring 21 → the 8th interface → the 9th interface to blow the sample into the second pre-separation chromatographic column 7;

[0053] 7. After pre-separation by the second pre-separation chromatographic column 7, the pre-separated components N2, O2, and CO are discharged through the third interface of the twentieth-way valve 3 → the second interface → the third interface of the first four-way valve 1 → the second interface → the pressure balance valve 19;

[0054] 8. Close the first four-way valve 1, open the second four-way valve 4, pre-separate the components CF4 and a small amount of NF3 through the second pre-separation chromatographic column 7, pass through the third interface of the first four-way valve 1 → the fourth interface → the second analytical chromatographic column 8, and after separation through the second analytical chromatographic column 8, pass through the fourth interface of the second four-way valve 4 → the first interface → the detector 22 to achieve detection of the components to be measured;

[0055] 9. Open the first four-way valve 1, and discharge a large amount of main component NF3 separated by the second pre-separation chromatographic column 7 through the third interface of the first four-way valve 1 → the second interface → the pressure balance valve 19;

[0056] 10. Close the first four-way valve 1, and the CO2, N2O, SF6 and a small amount of NF3 pre-separated by the second pre-separation chromatographic column 7 are passed through the 3rd interface of the first four-way valve 1 → the 4th interface → the second analysis chromatographic column 8. After separation by the second analysis chromatographic column 8, the components are detected through the 4th interface of the second four-way valve 4 → the 1st interface → the detector 22, and the peak order is CO2, N2O, and SF6.

[0057] After injection, the final peak order of impurities in nitrogen trifluoride is: O2, N2, CO, CF4, CO2, N2O, SF6. The peak times are: 2.45min, 3.03min, 4.81min, 8.01min, 15.44min, 17.91min, 21.83min respectively.

Claims

1. A gas chromatography valve system for oxygen-free adsorption for high-purity nitrogen trifluoride analysis, using a four-valve four-column valve system, including 2 four-way valves, 2 ten-way valves, 2 quantitative loops, 4 chromatographic columns, 11 pressure balance regulating valves and 1 discharge ionization detector, the system carrier gas is 99.9999% or more high-purity helium; The first interface of the first four-way valve (1) is connected to the pressure balance regulating valve (10) and then connected to the helium source, the second interface is connected to the pressure balance regulating valve (19) and then connected to the gas outlet, the third interface is connected to the second interface of the twentieth-way valve (3), and the fourth interface is connected to the second analytical chromatographic column (8) and then connected to the fourth interface of the second four-way valve (4); The first interface of the first ten-way valve (2) is connected to the helium source through a pressure balance regulating valve (11), the second interface is connected to the first analytical chromatographic column (6) and then connected to the second interface of the second four-way valve (4), the third interface and the ninth interface are connected to the first pre-separation chromatographic column (5), the fourth interface is connected to the helium source through a pressure balance regulating valve (12), the fifth interface and the eighth interface are connected to the first quantitative loop (20), the sixth interface is connected to the sixth interface of the twentieth-way valve (3), the seventh interface is connected to the sample inlet, and the tenth interface is connected to the pressure balance regulating valve (18) and then connected to the gas outlet; the first pre-separation chromatographic column (5) is a carbon molecular sieve chromatographic column; The first interface of the twentieth-way valve (3) is connected to a helium source via a pressure balance regulating valve (13), the third interface and the ninth interface are connected to a second pre-separation chromatographic column (7), the fourth interface is connected to a helium source via a pressure balance regulating valve (14), the fifth interface and the eighth interface are connected to a second quantitative loop (21), the seventh interface is connected to a sample outlet, and the tenth interface is connected to a pressure balance regulating valve (17) and then to a gas outlet; The first interface of the second four-way valve (4) is connected to the discharge ionization detector (22), and the third interface is connected to the pressure balance regulating valve (16) and then to the gas outlet.

2. The gas chromatography valve circuit system according to claim 1, characterized in that: The first analytical chromatographic column (6) is a 13X chromatographic column; the second pre-separation chromatographic column (7) is a Hayesep D chromatographic column; and the second analytical chromatographic column (8) is a Hayesep DB chromatographic column.

3. A method for using the gas chromatography valve path system according to claim 1 or 2, comprising: (1) In the initial state of use, all valves are in the "open" state, after the valve is moved once, they are in the "closed" state, and after the valve is moved again, they are in the "open" state; (2) Open the first ten-way valve (2) to collect the sample to be measured in the first quantitative loop (20); open the twentieth-way valve (3) to collect the sample to be measured in the second quantitative loop (21); (3) Close the first ten-way valve (2) and the second four-way valve (4), and blow the sample collected by the first quantitative loop (20) into the first pre-separation chromatographic column (5) through the carrier gas of the pressure balance regulating valve (12); (4) After pre-separation by the first pre-separation chromatographic column (5), the pre-separated components O2, N2, and CO enter the first analytical chromatographic column (6); open the first ten-way valve (2), and the other components are back-blown and vented; (5) The O2, N2, and CO components separated by the first analytical column (6) are detected by the second four-way valve (4) to the detector (22); (6) Close the twentieth-way valve (3), open the first four-way valve (1), and blow the sample collected in the second quantitative loop (21) into the second pre-separation chromatographic column (7) through the outlet carrier gas of the pressure balance regulating valve (14); (7) After pre-separation by the second pre-separation chromatographic column (7), the pre-separated components N2, O2, and CO are vented through the twentieth-way valve (3) to the first four-way valve (1); (8) Close the first four-way valve (1), open the second four-way valve (4), and the pre-separated components CF4 and a small amount of NF3 are pre-separated by the second pre-separation chromatographic column (7) and enter the second analytical chromatographic column (8) through the first four-way valve (1). After separation by the second analytical chromatographic column (8), the components are detected by the second four-way valve (4) to the detector (22); (9) Open the first four-way valve (1), and the large amount of main component NF3 pre-separated by the second pre-separation column (7) is vented through the first four-way valve (1); (10). The first four-way valve (1) is closed, and the CO2, N2O, SF6 and a small amount of NF3 pre-separated by the second pre-separation chromatographic column (7) enter the second analytical chromatographic column (8). After separation by the second analytical chromatographic column (8), the components to be measured are detected through the second four-way valve (4) to the detector (22).

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