Gas chromatography device for analyzing impurities in F2 / N2 mixed gas

Abstract

The gas chromatography device for impurity analysis in F2 / N2 mixed gas provided by the invention has the characteristics of high corrosion resistance, high sensitivity, high integration level and simplicity and convenience in operation, and a hastelloy injection valve and a pipeline are combined with a plasma emission detector and a helium carrier gas system; f2 corrosion is effectively prevented, the detection sensitivity is remarkably improved to 10 ppb or below by utilizing the advantages of plasma selective emission spectrum, meanwhile, the separation process is optimized through a multi-chromatographic-column path, a reverse blowing valve and a center cutting technology, synchronous detection of multiple impurities such as CF4, O2 and N2 is achieved, total analysis can be completed through one set of equipment, extra dangerous sources or complex maintenance is not needed, and the cost is low. The cost and the operation difficulty are remarkably reduced, and the method is particularly suitable for the accurate analysis requirements of high-end fields such as semiconductor photoetching and superconducting scientific research on trace impurities.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and in particular to a gas chromatography apparatus for the analysis of impurities in an F2 / N2 mixture. Background Technology

[0002] High-purity F2 / N2 mixtures are critical process gases with wide applications in semiconductor lithography, superconductivity and quantum research, specialty gases, and aerospace propulsion systems. These applications have extremely stringent requirements for the content of impurities (such as O2, CF4, CO, CO2, and CH4) in the mixture, as even trace amounts of impurities can lead to process defects, equipment corrosion, or system failures. Currently, gas chromatography is a commonly used technique for analyzing impurities in F2 / N2 mixtures. Existing methods typically employ corrosion-resistant materials to construct the injection system, such as using a nickel-based alloy six-way valve equipped with a polychlorotrifluoroethylene (PTFE) sealing ring to resist the chemical corrosion of F2. For column selection, a combination of a Porapak QS pre-column and a Molsieve 5A main column is often used to separate fluorine-containing impurities such as O2 and CF4, or a composite PLOT Al2O3 capillary column is used to separate components such as CO, CO2, and CH4. Detectors rely on thermal conductivity detectors for general gas detection, or are supplemented with electron capture detectors for the analysis of trace fluorine-containing organic compounds.

[0003] However, existing technical solutions have significant problems and drawbacks. First, F2 is extremely corrosive and reactive. Even with nickel-based alloys and partially inert materials, non-completely inert components (such as seals and connections) can still be slowly corroded, leading to decreased system sealing, shortened lifespan, and the need for frequent maintenance and component replacement, increasing operating costs and downtime risks. Second, the detection sensitivity is insufficient. Thermal conductivity detectors have high background noise in trace analysis, while electron capture detectors are susceptible to interference from high concentrations of F2, resulting in low signal-to-noise ratios and difficulty in achieving ppb-level detection limits, failing to meet the precise monitoring requirements of high-end applications for trace impurities. Furthermore, existing chromatographic column combinations are complex, often requiring multiple column switching or injections to cover full component analysis. This results in low system integration, cumbersome operation procedures, reliance on professional personnel, low efficiency, and the potential for cross-contamination or errors due to multiple sample processing steps.

[0004] Therefore, there is an urgent need in this field to develop a novel gas chromatography method that can fundamentally solve the F2 corrosion problem, significantly improve detection sensitivity, and achieve high integration and ease of operation, so as to meet the needs of high-end fields such as semiconductors and aerospace for rapid, accurate and reliable analysis of impurities in F2 / N2 mixed gas. Summary of the Invention

[0005] The purpose of this invention is to provide a gas chromatography apparatus for analyzing impurities in an F2 / N2 mixture, thereby solving the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a gas chromatography apparatus for analyzing impurities in an F2 / N2 mixture, comprising: A pretreatment system, comprising an adsorption tank connected to a first vacuum pump group and a second vacuum pump group, for pretreating samples; A carrier gas system that provides helium as a carrier gas; The sample injection system includes a first sample injection valve, a second sample injection valve, a third sample injection valve, a first cutting valve, and a second cutting valve. The first sample injection valve, the second sample injection valve, and the third sample injection valve are all equipped with a metering ring. The first sample injection valve, the second sample injection valve, the third sample injection valve, the first cutting valve, and the second cutting valve are all equipped with corrosion-resistant sealing rings. A chromatographic separation system comprising a first chromatographic column, a second chromatographic column, a third chromatographic column, a fourth chromatographic column, a fifth chromatographic column, a sixth chromatographic column, a seventh chromatographic column, and an eighth chromatographic column. The first chromatographic column is connected to a first injection valve; the second chromatographic column is connected to the first chromatographic column and a first cutting valve; the third chromatographic column is connected to the first cutting valve; the fourth chromatographic column is connected to the second injection valve; the fifth chromatographic column is connected to the fourth chromatographic column and the second cutting valve; the sixth chromatographic column is connected to the second cutting valve; the seventh chromatographic column is connected to the third injection valve; and the eighth chromatographic column is connected to the seventh chromatographic column. The detection system includes a plasma emission detector and a thermal conductivity detector.

[0007] Preferably, the carrier gas system includes a high-purity helium source and a helium purifier for providing and maintaining the purity of the carrier gas.

[0008] Preferably, the first injection valve, the second injection valve, and the third injection valve are all ten-way valves and are made of Hastelloy alloy.

[0009] Preferably, the first, seventh, and eighth chromatographic columns are all AL2O3 columns, the second and third chromatographic columns are shincarbon columns, the fourth chromatographic column is an MXT-1 column, and the fifth and sixth chromatographic columns are MXT-5A columns.

[0010] Preferably, the first chromatographic column has a length of 2m, the second chromatographic column has a length of 2ft, and the third chromatographic column has a length of 3ft.

[0011] Preferably, the fourth, fifth, and sixth chromatographic columns are all 30m in length.

[0012] Preferably, the seventh and eighth chromatographic columns are both 4m in length.

[0013] Preferably, the plasma emission detector includes a quartz flow cell, an electrode assembly, a spectrometer, and a photodetector; the electrode assembly is arranged in parallel on the upper and lower sides of the quartz flow cell to apply a high-frequency, high-voltage alternating electric field to form plasma.

[0014] Preferably, the plasma emission detector operates at a frequency of 10-50 kHz and a voltage of 1-20 kV; the spectrometer includes a feature filter for selectively transmitting the feature light signal of the impurity gas.

[0015] Preferably, it also includes a signal processing unit for receiving detection signals and performing data analysis and concentration calculation to achieve quantitative detection of impurity concentration.

[0016] The present invention achieves the following beneficial technical effects compared to the prior art: This invention provides a gas chromatography device for the analysis of impurities in F2 / N2 mixed gases. It features high corrosion resistance, high sensitivity, high integration, and ease of operation. The device employs a Hastelloy injection valve and tubing combined with a plasma emission detector and a helium carrier gas system, effectively preventing F2 corrosion and significantly improving detection sensitivity to below 10 ppb by utilizing the advantages of plasma selective emission spectroscopy. Simultaneously, the separation process is optimized through multiple column paths, backflush valves, and center-cutting technology, enabling simultaneous detection of multiple impurities such as CF4, O2, and N2. A single device can complete the entire analysis without additional hazards or complex maintenance, significantly reducing costs and operational complexity. It is particularly suitable for the precise analysis needs of trace impurities in high-end fields such as semiconductor lithography and superconducting research. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of CF4 testing in a gas chromatograph for analyzing impurities in an F2 / N2 mixture, provided by the present invention; Figure 2 A schematic diagram of O2 testing in a gas chromatograph for analyzing impurities in an F2 / N2 mixture, provided by the present invention; Figure 3 A schematic diagram of N2 testing in a gas chromatography apparatus for analyzing impurities in an F2 / N2 mixture provided by the present invention. Detailed Implementation

[0019] The serial numbers assigned to components in this document, such as "first," "second," etc., are merely used to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages). In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0020] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The purpose of this invention is to provide a gas chromatography apparatus for the analysis of impurities in F2 / N2 mixtures, addressing the problems of insufficient system corrosion resistance, low detection sensitivity, complex operation, and low integration in existing technologies. This apparatus effectively prevents F2 corrosion by employing an all-Hastelloy flow path combined with a plasma emission detector and a helium carrier gas system. Simultaneously, it optimizes the separation process through multiple column paths, backflush valves, and center-cutting technology, achieving efficient separation and high-sensitivity detection of multiple impurities such as CF4, O2, and N2 at the ppb level. The entire apparatus features high corrosion resistance, high integration, ease of operation, and low maintenance costs, making it particularly suitable for fields with stringent requirements for the detection of trace impurities in F2 / N2 mixtures, such as semiconductor lithography, superconducting research, and aerospace propulsion.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1: like Figures 1 to 3 As shown, this invention provides a gas chromatography apparatus for impurity analysis in an F2 / N2 mixture, mainly comprising a pretreatment system, a carrier gas system, an injection system, a chromatographic separation system, a detection system, and a signal processing unit. These systems are connected via Hastelloy tubing, and all connections use Swagelok or similar corrosion-resistant fittings to ensure airtightness and resistance to F2 corrosion, reducing sample adsorption and contamination. The gas path design employs a low dead volume structure to minimize peak broadening and memory effects.

[0025] Specifically, the pretreatment system includes an adsorption tank 16, which is connected to a first vacuum pump group 17 and a second vacuum pump group 18 for pretreatment of the sample.

[0026] Furthermore, the carrier gas system provides high-purity helium as the carrier gas, with a purity of not less than 99.999%. The carrier gas system includes a high-purity helium source and a helium purifier. The helium purifier employs highly efficient adsorbents or cryogenic trapping technology to remove any trace amounts of moisture, oxygen, hydrocarbons, and other impurities that may remain in the carrier gas, ensuring minimal background interference. The carrier gas flow rate is typically controlled within the range of 10-50 mL / min and can be precisely adjusted according to analytical requirements, with flow rate stability better than ±1%. By using helium as the carrier gas, this device avoids the safety risks associated with using hydrogen and provides a stable carrier gas environment.

[0027] Furthermore, the injection system includes a first injection valve 1, a second injection valve 2, a third injection valve 3, a first cut valve 4, and a second cut valve 5. All injection valves are ten-way valves made of Hastelloy alloy. Both the injection and cut valves are equipped with F2 corrosion-resistant sealing rings, which can be made of perfluoroether rubber or modified polychlorotrifluoroethylene. The first injection valve 1, second injection valve 2, and third injection valve 3 are each equipped with a metering loop with a volume of 0.5-1 mL, preferably 0.5 mL, to ensure the accuracy and repeatability of the injection while avoiding damage to the chromatographic column from high concentrations of F2. The sample enters the injection valve through the sample inlet, filling the metering loop with sample gas. Subsequently, by switching the valves, the sample gas, driven by the carrier gas, is injected into the chromatographic separation system from the metering loop. The multi-way valve design supports both backflushing and pre-flushing operations, such as... Figure 1 As shown, during CF4 detection, most of the F2 is evacuated by backflushing, leaving only CF4 for separation from other impurities; as Figure 2 As shown, when detecting O2, F2 is further removed using a center-cutting technique; as Figure 3As shown, when detecting N2, the main components are separated by backflushing.

[0028] Furthermore, the chromatographic separation system includes a first chromatographic column 6, a second chromatographic column 7, a third chromatographic column 8, a fourth chromatographic column 9, a fifth chromatographic column 10, a sixth chromatographic column 11, a seventh chromatographic column 12, and an eighth chromatographic column 13. The first chromatographic column 6 is connected to the first injection valve 1; the second chromatographic column 7 is connected to the first chromatographic column 6 and the first cut valve 4; and the third chromatographic column 8 is connected to the first cut valve 4, thus forming the CF4 detection path. The fourth chromatographic column 9 is connected to the second injection valve 2; the fifth chromatographic column 10 is connected to the fourth chromatographic column 9 and the second cut valve 5; and the sixth chromatographic column 11 is connected to the second cut valve 5, thus forming the O2 detection path. The seventh chromatographic column 12 is connected to the third injection valve 3; and the eighth chromatographic column 13 is connected to the seventh chromatographic column 12, thus forming the N2 detection path.

[0029] Specifically, the first column 6, the seventh column 12, and the eighth column 13 are all Al₂O₃ columns, with the first column 6 being 2m long and the seventh and eighth columns 12 and 13 both being 4m long. The second column 7 and the third column 8 are shincarbon columns, with lengths of 2ft and 3ft, respectively. The fourth column 9 is an MXT-1 column, and the fifth column 10 and the sixth column 11 are MXT-5A columns, each 30m long. The columns are made of stainless steel or inert material, with passivated inner walls. The column temperature is controlled between 45℃ and 80℃, and a constant temperature mode can be used according to separation requirements, with temperature stability better than ±0.5℃. The columns are connected by multi-port valves to achieve flow path switching and center-cutting technology, effectively separating different impurity components. At the same time, backflushing removes most of the F₂ from the system in advance, reducing its interference with the detector and subsequent columns.

[0030] Furthermore, the detection system includes a plasma emission detector 14 and a thermal conductivity detector 15. The plasma emission detector 14 is used to detect trace amounts of fluorine-containing impurities (such as CF4) and other trace components. Its core components include a quartz flow cell, an electrode assembly, a spectrometer, and a photodetector. The quartz flow cell is cylindrical, internally polished to reduce light scattering, and has a volume of approximately 300-400 μL. The electrode assembly, made of platinum or other inert metals, is arranged parallel to the upper and lower sides of the quartz flow cell. An alternating electric field is applied by an external high-frequency power supply, with an operating frequency of 10-50 kHz and a voltage of 1-20 kV, to form a stable plasma within the flow cell. When the separated gas components enter the flow cell, they are excited and emit characteristic spectra under the influence of the electric field. The spectrometer includes a characteristic filter with a center wavelength targeting the characteristic spectra of impurities such as CF4 and O2 (e.g., the characteristic wavelength of O2 is approximately 7.8 μm), and a half-width of less than 10 nm, to selectively transmit the characteristic light signals of the impurity gases and avoid spectral interference from other gas components. The photodetector is a photomultiplier tube or semiconductor photodetector with a response wavelength range covering 2-10 μm. It converts light signals into electrical signals and has a detection sensitivity better than 0.1 pA. The thermal conductivity detector 15 is used to detect main components such as N2. Its cell temperature is 100℃, and baseline drift is reduced through constant temperature control to ensure the accuracy of percentage content measurement.

[0031] Furthermore, the signal processing unit receives the output signals from the plasma emission detector 14 and the thermal conductivity detector 15, amplifies, filters, and performs analog-to-digital conversion, and then calculates the concentration of each impurity using built-in algorithms (such as integration, peak identification, and calibration curve fitting). The signal processing unit may also include data display, storage, and communication functions, supporting real-time monitoring and remote operation. The calibration method employs the external standard method, using NIST traceable standard gases (PED concentration range 0.1-10 ppm, TCD concentration range 0%~100%) for single-point calibration.

[0032] The working process of this invention is as follows: First, turn on the carrier gas system, adjust the carrier gas flow rate to the set value (e.g., 30 mL / min), and preheat the chromatographic column and detector. After the system stabilizes (usually 30-60 minutes), introduce the F2 / N2 mixed gas sample into the injection system through the sample inlet. After the sample fills the quantitative loop, switch the multi-port valve, and the carrier gas carries the sample in the quantitative loop into the chromatographic separation system. For CF4 detection, the sample first passes through the first chromatographic column, where most of the F2 is purged through the ten-port backflush valve, and then passes through the center cut to enter the second and third chromatographic columns for separation. Finally, the CF4 component is carried by the carrier gas into the plasma emission detector. For O2 detection, the sample passes through the fourth chromatographic column, where most of the F2 is removed through the backflush valve, and then passes through the center cut to enter the fifth and sixth chromatographic columns for separation. The separated O2 enters the plasma emission detector. For N2 detection, the sample passes through the seventh chromatographic column, where most of the F2 is removed through the backflush valve, and then enters the eighth chromatographic column for further separation. Finally, the N2 main component is detected by the thermal conductivity detector. Inside the detector, impurity gases are excited in the plasma and emit characteristic spectra, which are then detected by a photodetector after passing through a characteristic filter; or by a thermal conductivity detector to measure changes in thermal conductivity. The signal processing unit records the signal intensity and calculates the concentration based on a pre-established calibration curve. The detection limit of the plasma emission detector can reach the ppb level, and the linear dynamic range covers 0.1-10 ppmv.

[0033] In this embodiment, the column temperature was set to 50°C, the carrier gas flow rate to 30 mL / min, the plasma emission detector operating frequency to 30 kHz, and the voltage to 5 kV. Under these conditions, an F2 / N2 mixture containing 10 ppm CF4 and 10 ppm O2 was analyzed. The repeatability relative standard deviation was less than 3%, and the theoretically calculated detection limit for CF4 was 10 ppb, and the detection limit for O2 was also 10 ppb. Furthermore, thanks to the design of the Hastelloy flow path and corrosion-resistant sealing ring, the system showed no significant corrosion or performance degradation after 200 hours of continuous operation, significantly outperforming traditional nickel-based alloy systems. The entire device requires no additional hazards or complex safety measures, reducing operational risks and maintenance costs.

[0034] This invention effectively overcomes the problems of F2 corrosion, insufficient sensitivity, and complex operation in existing technologies by optimizing the chromatographic column combination, adopting an all-Hastelloy flow path, and using a plasma emission detector. It achieves safe, efficient, and highly sensitive direct detection of multiple impurities in F2 / N2 mixed gas, providing a reliable solution for fields such as semiconductors, superconductors, and aerospace.

[0035] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0036] It should be noted that the components mentioned in the above embodiments are all general standard parts or components known to those skilled in the art. Their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0037] This invention has used specific examples to illustrate its principles and implementation methods. The above descriptions of the embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A gas chromatographic apparatus for analyzing impurities in an F2 / N2 mixture, characterized in that, include: A pretreatment system, comprising an adsorption tank connected to a first vacuum pump group and a second vacuum pump group, for pretreating samples; A carrier gas system that provides helium as a carrier gas; The sample injection system includes a first sample injection valve, a second sample injection valve, a third sample injection valve, a first cutting valve, and a second cutting valve. The first sample injection valve, the second sample injection valve, and the third sample injection valve are all equipped with a metering ring. The first sample injection valve, the second sample injection valve, the third sample injection valve, the first cutting valve, and the second cutting valve are all equipped with corrosion-resistant sealing rings. A chromatographic separation system comprising a first chromatographic column, a second chromatographic column, a third chromatographic column, a fourth chromatographic column, a fifth chromatographic column, a sixth chromatographic column, a seventh chromatographic column, and an eighth chromatographic column. The first chromatographic column is connected to a first injection valve; the second chromatographic column is connected to the first chromatographic column and a first cutting valve; the third chromatographic column is connected to the first cutting valve; the fourth chromatographic column is connected to the second injection valve; the fifth chromatographic column is connected to the fourth chromatographic column and the second cutting valve; the sixth chromatographic column is connected to the second cutting valve; the seventh chromatographic column is connected to the third injection valve; and the eighth chromatographic column is connected to the seventh chromatographic column. The detection system includes a plasma emission detector and a thermal conductivity detector.

2. The gas chromatographic apparatus for impurity analysis in F2 / N2 mixtures according to claim 1, characterized in that, The carrier gas system includes a high-purity helium source and a helium purifier, used to provide and maintain the purity of the carrier gas.

3. The gas chromatographic apparatus for impurity analysis in F2 / N2 mixtures according to claim 1, characterized in that, The first, second, and third injection valves are all ten-way valves made of Hastelloy alloy.

4. The gas chromatographic apparatus for impurity analysis in F2 / N2 mixtures according to claim 1, characterized in that, The first, seventh, and eighth chromatographic columns are all AL2O3 columns, the second and third chromatographic columns are shincarbon columns, the fourth chromatographic column is an MXT-1 column, and the fifth and sixth chromatographic columns are MXT-5A columns.

5. The gas chromatographic apparatus for impurity analysis in F2 / N2 mixtures according to claim 4, characterized in that, The first chromatographic column is 2m long, the second chromatographic column is 2ft long, and the third chromatographic column is 3ft long.

6. The gas chromatographic apparatus for impurity analysis in F2 / N2 mixtures according to claim 4, characterized in that, The fourth, fifth, and sixth chromatographic columns are all 30m in length.

7. The gas chromatographic apparatus for impurity analysis in F2 / N2 mixtures according to claim 4, characterized in that, The seventh and eighth chromatographic columns are both 4m in length.

8. The gas chromatographic apparatus for impurity analysis in F2 / N2 mixtures according to claim 1, characterized in that, The plasma emission detector includes a quartz flow cell, an electrode assembly, a spectrometer, and a photodetector; the electrode assembly is arranged in parallel on the upper and lower sides of the quartz flow cell to apply a high-frequency, high-voltage alternating electric field to form plasma.

9. The gas chromatographic apparatus for impurity analysis in an F2 / N2 mixture according to claim 8, characterized in that, The plasma emission detector operates at a frequency of 10-50 kHz and a voltage of 1-20 kV; the spectrometer includes a feature filter for selectively transmitting the feature light signal of the impurity gas.

10. The gas chromatographic apparatus for analyzing impurities in an F2 / N2 mixture according to any one of claims 1-9, characterized in that, It also includes a signal processing unit, which receives detection signals and performs data analysis and concentration calculation to achieve quantitative detection of impurity concentration.

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