A system and method for detecting ultra-high purity helium for the electronics industry

Abstract

This invention discloses a system and method for detecting ultra-high purity helium for the electronics industry. The sample introduction and current limiting unit includes a series-connected primary pressure reducing unit and a secondary micro-diameter current limiting structure, used to introduce the helium to be tested into the ionization chamber and control the gas entering the ionization chamber to maintain a constant molecular flow. A multi-dimensional spatial orbit separation unit is used to guide target impurity ions in the characteristic ion cluster along a preset compensated voltage orbit using an asymmetric electric field. A collaborative quantitative detection unit is used to receive the trigger pulse and simultaneously open the ion gate of the segmented differential pressure mass spectrometry unit to perform mass dimension detection on the target impurity ions. This invention eliminates the limitation of the detection limit by substrate interference at the physical source, significantly improves the long-term reliability of online detection, achieves efficient protection of the back-end precision mass spectrometry unit, and extends the equipment maintenance cycle.

Description

Technical Field

[0001] This invention relates to the field of gas analysis and detection technology, and more particularly to a system and method for detecting ultra-high purity helium for the electronics industry. Background Technology

[0002] With the rapid development of the electronics industry, including semiconductor, integrated circuit, and fiber optic manufacturing, ultra-high purity helium, as a key process gas, carrier gas, and protective gas, directly affects the yield and performance stability of electronic devices. In electronics production, even trace impurities at the ppt level can cause diffusion defects or electrical performance deviations in semiconductor wafers. Therefore, achieving extremely high sensitivity detection of trace impurities in ultra-high purity helium has become a core requirement. Currently, existing ultra-high purity gas detection technologies mainly include gas chromatography, ion mobility spectrometry, and traditional mass spectrometry. However, in practical applications of ultra-high purity helium detection, these technologies still have the following shortcomings:

[0003] First, helium has extremely high ionization energy. Traditional discharge or high-energy electron bombardment ionization methods, while ionizing trace impurities, easily cause large-scale ionization of the helium substrate, generating a strong substrate interference effect, which significantly weakens the ability to capture signals from extremely low concentration impurities. Second, although traditional ion mobility spectrometry has high sensitivity, in continuous sampling mode, metastable helium atoms generated by the ionization source and strong photon radiation generated during discharge will enter the detector with the gas flow, forming continuous background current noise and photon interference, making it difficult to further improve the signal-to-noise ratio. Third, existing sample introduction systems usually use simple regulating valves for flow restriction. When handling the conversion from high-pressure helium to a vacuum system, a severe adiabatic expansion and cooling effect is easily generated, leading to drastic fluctuations in the flow field temperature, which in turn causes changes in the gas mean free path. This instability of the flow field will cause baseline drift of the detection signal, which cannot meet the long-term stability requirements of online detection in the electronics industry.

[0004] Therefore, those skilled in the art are dedicated to providing a system and method for detecting ultra-high purity helium for the electronics industry that can effectively solve the above-mentioned technical problems. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides a system for detecting ultra-high purity helium gas for the electronics industry, the system comprising:

[0006] The sample introduction flow limiting unit includes a series-connected primary pressure reducing unit and a secondary micro-diameter flow limiting structure, which is used to introduce the helium gas to be measured into the ionization chamber and control the gas entering the ionization chamber to be in a constant molecular flow state.

[0007] An adaptive selective excitation unit is used to generate low-temperature plasma using microwave induction. Combined with a spectral monitoring feedback loop, the microwave power is dynamically compensated based on the intensity shift of the helium atom characteristic spectral lines monitored in real time, so that the electron energy is precisely locked within the target energy range, and trace impurity molecules are selectively ionized to form characteristic ion clusters.

[0008] A multi-dimensional spatial orbit separation unit is used to guide target impurity ions in the characteristic ion cluster along a preset compensated voltage orbit using an asymmetric electric field;

[0009] The time-domain locking and sampling control unit is used to acquire ion current peaks in real time and generate trigger pulses based on the ion flight characteristic curve;

[0010] The collaborative quantitative detection unit is used to receive the trigger pulse and synchronously open the ion gate of the segmented differential pressure mass spectrometry unit to perform mass dimension detection on the target impurity ions.

[0011] Furthermore, the constant molecular flow state is achieved by controlling the Knudsen number of the incoming gas. >10 maintained; the Knudsen number The expression is ;

[0012] In the formula The mean free path of gas molecules,

[0013] This represents the characteristic length of the secondary micro-diameter flow-limiting structure;

[0014] The secondary micro-diameter flow-limiting structure consists of multiple parallel capillary arrays, the capillary arrays having the specified axial length. and equivalent aperture And satisfy the ratio relationship >10;

[0015] The system further includes a thermal compensation component and a semiconductor cooling chip, wherein the thermal compensation component is used to maintain a constant airflow temperature before flow restriction to lock the mean free path. The semiconductor cooling chip is used to control the indoor temperature fluctuation of the ionization chamber within ±0.005℃; and the frequency phase locking unit is used to phase lock the modulation frequency of the microwave-induced low-temperature plasma with the voltage scanning period of the multi-dimensional space orbit separation unit.

[0016] A detection method for detecting ultra-high purity helium for the electronics industry includes the following steps:

[0017] The ultra-high purity helium gas to be tested is introduced into the low-temperature plasma enhanced ionization chamber through the sample introduction flow limiting unit, and the gas entering the low-temperature plasma enhanced ionization chamber is controlled to be in a constant molecular flow state.

[0018] In the low-temperature plasma enhanced ionization chamber, low-temperature plasma with controlled energy is generated by microwave induction to selectively excite the ultra-high purity helium gas under constant molecular flow state, causing trace impurity molecules in it to ionize and form characteristic ion clusters.

[0019] The characteristic ion clusters are extracted from the outlet of the low-temperature plasma enhanced ionization chamber and introduced into the adjacent multi-dimensional space orbital separation unit. The characteristic ion clusters are separated in the first stage of spatial dimension using an asymmetric electric field to screen out the target impurity ions.

[0020] The target impurity ions screened by the multidimensional spatial orbital separation unit generate trigger pulses, which simultaneously open the ion gate of the segmented differential pressure mass spectrometry unit to perform second-level mass dimension detection on the target impurity ions, thereby realizing the synergistic quantitative analysis of trace impurities.

[0021] Furthermore, the constant molecular flow state is achieved by controlling the Knudsen number of the incoming gas. >10 maintained; the Knudsen number The expression is as follows:

[0022]

[0023] In the formula, The mean free path of gas molecules,

[0024] This represents the characteristic length of the secondary micro-diameter flow-limiting structure in the sample injection flow-limiting unit;

[0025] The sample injection flow limiting unit includes a first-stage pressure reducing unit and a second-stage micro-diameter flow limiting structure connected in series. The second-stage micro-diameter flow limiting structure is used to further expand the gas in the transition flow range to a free molecular flow state, and simultaneously suppress the adiabatic expansion and cooling effect of the gas during the flow limiting process.

[0026] The secondary micro-diameter flow-limiting structure consists of multiple parallel capillary arrays, each capillary array having an axial length. and equivalent aperture And the axial length With the equivalent aperture Satisfy the ratio relationship >10; Before the gas enters the secondary micro-diameter flow-limiting structure,

[0027] The heat loss caused by adiabatic expansion is compensated by the thermal compensation component, maintaining a constant airflow temperature and thus locking the mean free path. And stabilize the Knudsen number in the spatial dimension. .

[0028] Furthermore, the selective excitation includes: real-time monitoring of the intensity of helium atom characteristic spectral lines in the low-temperature plasma enhanced ionization chamber, and dynamic compensation of microwave power based on the offset of the intensity of the characteristic spectral lines, so that the electron energy is always within the energy range that is higher than the ionization energy of trace impurities and lower than the ionization energy of helium, so that the helium matrix remains as uncharged metastable atoms.

[0029] The dynamic compensation includes: establishing a negative feedback decoupling model between the microwave power and the helium base effect ionization current; when the intensity of the characteristic spectral line is detected to exceed a preset safety threshold, the coupling coefficient of the microwave source is automatically reduced, and the narrow-band characteristics of the electron energy distribution function in the plasma region are maintained by suppressing the avalanche ionization effect of helium atoms, thereby increasing the purity of the ion clusters generated by the ionization of trace impurities to more than 95%.

[0030] Furthermore, the first-level spatial dimension separation includes: applying an asymmetric high-frequency pulse voltage to the electrodes of the multi-dimensional spatial orbit separation unit, causing the target impurity ions to pass along a preset compensation voltage orbit, and repelling the metastable atoms outside the compensation voltage orbit.

[0031] Furthermore, the collaborative quantitative analysis includes: real-time acquisition of ion current peaks generated by the compensation voltage scan within the multidimensional spatial orbit separation unit; and when the intensity of the ion current peak reaches a preset threshold, setting the delay time of the trigger pulse relative to the excitation time of the cryogenic plasma in conjunction with a preset ion flight characteristic curve; precisely controlling the opening time of the ion gate through the delay time, so that the opening time window of the ion gate coincides with the time window of the target impurity ion arriving at the mass spectrometry unit, and ensuring that the opening time of the ion gate avoids the initial instantaneous moment of the cryogenic plasma excitation, thereby synchronously filtering out the instantaneous background radiation noise and photon interference generated by the cryogenic plasma enhanced ionization chamber.

[0032] Furthermore, the method further includes: phase-locking the modulation frequency of the microwave-induced low-temperature plasma with the voltage scanning period of the multidimensional space orbit separation unit, and setting the delay time of the trigger pulse relative to the excitation time of the low-temperature plasma according to the equivalent mobility of the characteristic ion cluster during the drift process, and physically stripping the target impurity ions from the non-ionized metastable helium atom flow in the time domain through the delay time.

[0033] Furthermore, the method further includes: at the inlet of the segmented differential pressure mass spectrometry unit, using a three-stage flow splitter structure, utilizing the mass inertia difference between the metastable atoms and the target impurity ions, guiding more than 99% of the metastable atoms to the auxiliary pumping system.

[0034] Furthermore, the method also includes:

[0035] By utilizing the semiconductor cooling chip installed on the outer wall of the low-temperature plasma enhanced ionization chamber, the indoor temperature fluctuation is controlled within ±0.005℃.

[0036] Before the gas enters, a nanoporous graphene membrane is used to trap micron-sized particles in the ultra-high purity helium being tested, to ensure that gaseous impurity molecules are not intercepted.

[0037] The present invention has the following beneficial effects:

[0038] 1. This invention employs an adaptive selective excitation unit, which monitors the intensity of helium atom characteristic spectral lines in the ionization chamber in real time and establishes a negative feedback decoupling model between microwave power and helium floor effect ionization current, thereby dynamically compensating the microwave source. It can precisely lock the electron energy distribution within an extremely narrow window that is higher than the impurity ionization energy and lower than the helium ionization energy, effectively suppressing the avalanche ionization effect of helium atoms, increasing the purity of ion clusters formed by trace impurities to over 95%, and eliminating the limitation of the detection limit by floor interference from the physical source.

[0039] 2. This invention utilizes a time-domain locking and sampling control unit to phase-lock the microwave excitation frequency with the voltage scan period, and sets a precise delay time based on the ion flight characteristic curve. Combined with a three-stage shunt cone structure at the inlet of the segmented differential pressure mass spectrometry unit, it achieves dual separation of target impurity ions and interference signals in both the time and spatial dimensions. By delaying the opening of the ion gate, the sampling window perfectly avoids the strong photon radiation and background radiation noise generated during plasma excitation, resulting in a geometric increase in the signal-to-noise ratio. This successfully meets the quantitative analysis needs of the electronics industry for ppt-level trace impurities.

[0040] 3. This invention employs a primary pressure reduction unit and a secondary micro-diameter flow limiting structure in the sample injection flow limiting unit for gradient pressure reduction, and simultaneously couples a thermal compensation component and a semiconductor cooling chip; through the synergistic effect of gradient flow limiting and high-precision temperature control, the heat loss caused by gas expansion is offset, effectively maintaining the stability of the mean free path of gas molecules, eliminating signal drift caused by environmental fluctuations, and significantly improving the long-term reliability of online detection.

[0041] 4. In this invention, the ultra-high purity helium gas to be measured is pretreated by a nanoporous graphene membrane before the gas enters the flow-limiting structure. By utilizing the ultra-fine micropore characteristics of the graphene membrane, this physical barrier achieves efficient protection of the back-end precision mass spectrometry unit without affecting the molecular flow state of the gas flow, thus extending the equipment maintenance cycle. Attached Figure Description

[0042] Figure 1 This is a schematic block diagram of the system for detecting ultra-high purity helium gas for the electronics industry in this invention.

[0043] Figure 2 This is a schematic block diagram of the detection method for ultra-high purity helium used in the electronics industry in this invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0045] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," 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. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0046] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "setting," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] like Figures 1 to 2 As shown, a system for detecting ultra-high purity helium for the electronics industry is provided, the system comprising:

[0048] The sample introduction flow limiting unit includes a series-connected primary pressure reducing unit and a secondary micro-diameter flow limiting structure, which is used to introduce the helium gas to be measured into the ionization chamber and control the gas entering the ionization chamber to be in a constant molecular flow state.

[0049] An adaptive selective excitation unit is used to generate low-temperature plasma using microwave induction. Combined with a spectral monitoring feedback loop, the microwave power is dynamically compensated based on the intensity shift of the helium atom characteristic spectral lines monitored in real time, so that the electron energy is precisely locked within the target energy range, and trace impurity molecules are selectively ionized to form characteristic ion clusters.

[0050] A multi-dimensional spatial orbit separation unit is used to guide target impurity ions in the characteristic ion cluster along a preset compensated voltage orbit using an asymmetric electric field;

[0051] The time-domain locking and sampling control unit is used to acquire ion current peaks in real time and generate trigger pulses based on the ion flight characteristic curve;

[0052] The collaborative quantitative detection unit is used to receive the trigger pulse and synchronously open the ion gate of the segmented differential pressure mass spectrometry unit to perform mass dimension detection on the target impurity ions.

[0053] The constant molecular flow state is achieved by controlling the Knudsen number of the incoming gas. >10 maintained; the Knudsen number The expression is ;

[0054] In the formula The mean free path of gas molecules,

[0055] This represents the characteristic length of the secondary micro-diameter flow-limiting structure;

[0056] The secondary micro-diameter flow-limiting structure consists of multiple parallel capillary arrays, the capillary arrays having the specified axial length. and equivalent aperture And satisfy the ratio relationship >10;

[0057] The system further includes a thermal compensation component and a semiconductor cooling chip, wherein the thermal compensation component is used to maintain a constant airflow temperature before flow restriction to lock the mean free path. The semiconductor cooling chip is used to control the indoor temperature fluctuation of the ionization chamber within ±0.005℃; and the frequency phase locking unit is used to phase lock the modulation frequency of the microwave-induced low-temperature plasma with the voltage scanning period of the multi-dimensional space orbit separation unit.

[0058] A detection method for detecting ultra-high purity helium for the electronics industry includes the following steps:

[0059] The ultra-high purity helium gas to be tested is introduced into the low-temperature plasma enhanced ionization chamber through the sample introduction flow limiting unit, and the gas entering the low-temperature plasma enhanced ionization chamber is controlled to be in a constant molecular flow state.

[0060] In the low-temperature plasma enhanced ionization chamber, low-temperature plasma with controlled energy is generated by microwave induction to selectively excite the ultra-high purity helium gas under constant molecular flow state, causing trace impurity molecules in it to ionize and form characteristic ion clusters.

[0061] The characteristic ion clusters are extracted from the outlet of the low-temperature plasma enhanced ionization chamber and introduced into the adjacent multi-dimensional space orbital separation unit. The characteristic ion clusters are separated in the first stage of spatial dimension using an asymmetric electric field to screen out the target impurity ions.

[0062] The target impurity ions screened by the multidimensional spatial orbital separation unit generate trigger pulses, which simultaneously open the ion gate of the segmented differential pressure mass spectrometry unit to perform second-level mass dimension detection on the target impurity ions, thereby realizing the synergistic quantitative analysis of trace impurities.

[0063] The constant molecular flow state is achieved by controlling the Knudsen number of the incoming gas. >10 maintained; the Knudsen number The expression is as follows:

[0064]

[0065] In the formula, The mean free path of gas molecules,

[0066] This represents the characteristic length of the secondary micro-diameter flow-limiting structure in the sample injection flow-limiting unit;

[0067] The sample injection flow limiting unit includes a first-stage pressure reducing unit and a second-stage micro-diameter flow limiting structure connected in series. The second-stage micro-diameter flow limiting structure is used to further expand the gas in the transition flow range to a free molecular flow state, and simultaneously suppress the adiabatic expansion and cooling effect of the gas during the flow limiting process.

[0068] The secondary micro-diameter flow-limiting structure consists of multiple parallel capillary arrays, each capillary array having an axial length. and equivalent aperture And the axial length With the equivalent aperture Satisfy the ratio relationship >10; Before the gas enters the secondary micro-diameter flow-limiting structure,

[0069] The heat loss caused by adiabatic expansion is compensated by the thermal compensation component, maintaining a constant airflow temperature and thus locking the mean free path. And stabilize the Knudsen number in the spatial dimension. .

[0070] The selective excitation includes: real-time monitoring of the intensity of the characteristic spectral lines of helium atoms in the low-temperature plasma enhanced ionization chamber, and dynamic compensation of the microwave power according to the offset of the intensity of the characteristic spectral lines, so that the electron energy is always in the energy range that is higher than the ionization energy of trace impurities and lower than the ionization energy of helium, so that the helium matrix remains as uncharged metastable atoms.

[0071] The dynamic compensation includes: establishing a negative feedback decoupling model between the microwave power and the helium base effect ionization current; when the intensity of the characteristic spectral line is detected to exceed a preset safety threshold, the coupling coefficient of the microwave source is automatically reduced, and the narrow-band characteristics of the electron energy distribution function in the plasma region are maintained by suppressing the avalanche ionization effect of helium atoms, thereby increasing the purity of the ion clusters generated by the ionization of trace impurities to more than 95%.

[0072] The first-level spatial dimension separation includes: applying an asymmetric high-frequency pulse voltage to the electrodes of the multi-dimensional spatial orbit separation unit, causing the target impurity ions to pass along a preset compensation voltage orbit, and repelling the metastable atoms outside the compensation voltage orbit.

[0073] The collaborative quantitative analysis includes: real-time acquisition of ion current peaks generated by the compensation voltage scan within the multidimensional spatial orbit separation unit; and setting the delay time of the trigger pulse relative to the excitation time of the cryogenic plasma when the intensity of the ion current peak reaches a preset threshold, in conjunction with a preset ion flight characteristic curve; precisely controlling the opening time of the ion gate through the delay time, so that the opening time window of the ion gate coincides with the time window of the target impurity ion arriving at the mass spectrometry unit, and that the opening time of the ion gate avoids the initial instantaneous moment of the cryogenic plasma excitation, thereby simultaneously filtering out the instantaneous background radiation noise and photon interference generated by the cryogenic plasma enhanced ionization chamber.

[0074] The method further includes: phase-locking the modulation frequency of the microwave-induced low-temperature plasma with the voltage scanning period of the multidimensional space orbit separation unit, and setting the delay time of the trigger pulse relative to the excitation time of the low-temperature plasma according to the equivalent mobility of the characteristic ion cluster during the drift process, and physically stripping the target impurity ions from the non-ionized metastable helium atom flow in the time domain through the delay time.

[0075] The method further includes: at the inlet of the segmented differential pressure mass spectrometry unit, using a three-stage flow splitter structure, utilizing the difference in mass inertia between the metastable atoms and the target impurity ions, guiding more than 99% of the metastable atoms to the auxiliary pumping system.

[0076] The method further includes: using a semiconductor cooling chip disposed on the outer wall of the low-temperature plasma enhanced ionization chamber to control the indoor temperature fluctuation within ±0.005℃;

[0077] Before the gas enters, a nanoporous graphene membrane is used to trap micron-sized particles in the ultra-high purity helium being tested, to ensure that gaseous impurity molecules are not intercepted.

[0078] To fully demonstrate the technical feasibility of the present invention under different process requirements, different impurity concentration levels, and various extreme operating conditions, two representative preferred embodiments are given below.

[0079] Example 1

[0080] This embodiment takes the detection of 6N-grade ultra-high purity helium, commonly used in electronic industrial production, as an example. It describes the basic operating flow and collaborative control effect of the system under conventional high-sensitivity requirements:

[0081] 1. Sample Introduction and Flow Limiting Pretreatment: The ultra-high purity helium gas to be tested is pretreated using a nanoporous graphene membrane to trap micron-sized particles. Subsequently, the gas is introduced through the sample introduction and flow limiting unit. The first-stage pressure reduction unit reduces the gas source pressure to the transition flow range. The second-stage micro-diameter flow limiting structure consists of multiple parallel capillary arrays, with their axial length set. The equivalent aperture is 120mm. It is 8mm in diameter and has a length-to-diameter ratio of 1.5mm. The value is 15 (meeting the requirement of being greater than 10); the Knudsen number of the gas entering the ionization chamber is controlled through real-time adjustment. Maintaining the temperature at around 15°C ensures a stable, constant molecular flow. During this process, the semiconductor cooling chip strictly controls indoor temperature fluctuations within ±0.003°C, while the thermal compensation component locks in the gas's mean free path. .

[0082] 2. Selective excitation and ionization: In a low-temperature plasma enhanced ionization chamber, energy-controlled plasma is generated by microwave induction; the spectral monitoring feedback loop collects the intensity of helium atom characteristic spectral lines in real time and establishes a negative feedback decoupling model to dynamically compensate for microwave power; in this embodiment, the electron energy is precisely locked, so that the purity of the characteristic ion clusters formed by the ionization of trace impurities reaches 96.5%.

[0083] 3. Multidimensional Separation and Quantitative Detection: Ion clusters enter the multidimensional spatial orbital separation unit. Under the asymmetric high-frequency pulse applied by the electrode, the target impurity ions pass through the preset orbit, while metastable helium atoms are repelled. The system sets the delay time of the trigger pulse according to the equivalent mobility of the characteristic ion clusters. When the ion current peak reaches the preset threshold, the ion gate of the mass spectrometry unit is opened simultaneously for sampling. Finally, the interference of residual metastable atoms is eliminated through the three-stage split cone structure, realizing the quantitative analysis of trace impurities. Its signal-to-noise ratio is improved by about 3 times compared with traditional methods.

[0084] Example 2

[0085] This embodiment addresses the extreme detection requirements for 7N-level helium in VLSI manufacturing, showcasing its performance under deeper molecular flow conditions and higher sensitivity settings:

[0086] 1. Extreme Molecular Flow Control: To obtain a purer molecular flow trajectory, the capillary array of the secondary micro-diameter flow-limiting structure in this embodiment adopts a more slender design, with an axial length of... 200mm equivalent aperture It is 8mm in diameter and has a length-to-diameter ratio of 1.5mm. Reaching 25; through this extreme structural setting, the Knudsen number of the gas entering the ionization chamber is increased. The temperature is increased and maintained at around 25, which greatly reduces the probability of collisions between molecules; the semiconductor cooling chip further compresses the indoor temperature fluctuation to within ±0.001℃, providing extremely high physical environmental stability for the ionization of extremely low concentrations of impurities.

[0087] 2. Deep suppression of avalanche effect: During the selective excitation stage, the system automatically executes a more stringent feedback algorithm to reduce the coupling coefficient of the microwave source to an extremely narrow bandwidth mode; through real-time monitoring, the helium matrix is ​​kept basically as uncharged metastable atoms, and the purity of the ionized ion clusters is further improved to over 98%.

[0088] 3. Enhanced Temporal and Inertial Separation: In this embodiment, the system performs deep phase locking between the microwave modulation frequency and the FAIMS scan cycle; a more precise delay time is set to achieve a more thorough physical separation of target ions and metastable currents in the temporal domain; subsequently, using a precisely designed three-stage shunt cone at the inlet of the segmented differential pressure mass spectrometry unit, more than 99.5% of the metastable atoms are guided to the auxiliary pumping system by the difference in mass inertia; after testing, this implementation method effectively filters out background radiation noise and significantly optimizes the detection limit when detecting extremely trace impurities, perfectly meeting the monitoring requirements of high-end semiconductor processes.

[0089] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A system for detecting ultra-high purity helium gas used in the electronics industry, characterized in that, The system includes: The sample introduction flow limiting unit includes a series-connected primary pressure reducing unit and a secondary micro-diameter flow limiting structure, which is used to introduce the helium gas to be measured into the ionization chamber and control the gas entering the ionization chamber to be in a constant molecular flow state. An adaptive selective excitation unit is used to generate low-temperature plasma using microwave induction. Combined with a spectral monitoring feedback loop, the microwave power is dynamically compensated based on the intensity shift of the helium atom characteristic spectral lines monitored in real time, so that the electron energy is precisely locked within the target energy range, and trace impurity molecules are selectively ionized to form characteristic ion clusters. A multi-dimensional spatial orbit separation unit is used to guide target impurity ions in the characteristic ion cluster along a preset compensated voltage orbit using an asymmetric electric field; The time-domain locking and sampling control unit is used to acquire ion current peaks in real time and generate trigger pulses based on the ion flight characteristic curve; The collaborative quantitative detection unit is used to receive the trigger pulse and synchronously open the ion gate of the segmented differential pressure mass spectrometry unit to perform mass dimension detection on the target impurity ions.

2. The detection system for detecting ultra-high purity helium for the electronics industry according to claim 1, characterized in that: The constant molecular flow state is achieved by controlling the Knudsen number of the incoming gas. >10 maintained; the Knudsen number The expression is ; In the formula The mean free path of gas molecules, This represents the characteristic length of the secondary micro-diameter flow-limiting structure; The secondary micro-diameter flow-limiting structure consists of multiple parallel capillary arrays, the capillary arrays having the specified axial length. and equivalent aperture And satisfy the ratio relationship >10; The system further includes a thermal compensation component and a semiconductor cooling chip, wherein the thermal compensation component is used to maintain a constant airflow temperature before flow restriction to lock the mean free path. The semiconductor cooling chip is used to control the indoor temperature fluctuation of the ionization chamber within ±0.005℃; and the frequency phase locking unit is used to phase lock the modulation frequency of the microwave-induced low-temperature plasma with the voltage scanning period of the multi-dimensional space orbit separation unit.

3. A detection method for detecting ultra-high purity helium gas used in the electronics industry, characterized in that, Includes the following steps: The ultra-high purity helium gas to be tested is introduced into the low-temperature plasma enhanced ionization chamber through the sample introduction flow limiting unit, and the gas entering the low-temperature plasma enhanced ionization chamber is controlled to be in a constant molecular flow state. In the low-temperature plasma enhanced ionization chamber, low-temperature plasma with controlled energy is generated by microwave induction to selectively excite the ultra-high purity helium gas under constant molecular flow state, causing trace impurity molecules in it to ionize and form characteristic ion clusters. The characteristic ion clusters are extracted from the outlet of the low-temperature plasma enhanced ionization chamber and introduced into the adjacent multi-dimensional space orbital separation unit. The characteristic ion clusters are separated in the first stage of spatial dimension using an asymmetric electric field to screen out the target impurity ions. The target impurity ions screened by the multidimensional spatial orbital separation unit generate trigger pulses, which simultaneously open the ion gate of the segmented differential pressure mass spectrometry unit to perform second-level mass dimension detection on the target impurity ions, thereby realizing the synergistic quantitative analysis of trace impurities.

4. The detection method for detecting ultra-high purity helium for the electronics industry according to claim 3, characterized in that: The constant molecular flow state is achieved by controlling the Knudsen number of the incoming gas. >10 maintained; the Knudsen number The expression is as follows: In the formula, The mean free path of gas molecules, This represents the characteristic length of the secondary micro-diameter flow-limiting structure in the sample injection flow-limiting unit; The sample injection flow limiting unit includes a first-stage pressure reducing unit and a second-stage micro-diameter flow limiting structure connected in series. The second-stage micro-diameter flow limiting structure is used to further expand the gas in the transition flow range to a free molecular flow state, and simultaneously suppress the adiabatic expansion and cooling effect of the gas during the flow limiting process. The secondary micro-diameter flow-limiting structure consists of multiple parallel capillary arrays, each capillary array having an axial length. and equivalent aperture And the axial length With the equivalent aperture Satisfy the ratio relationship >10; Before the gas enters the secondary micro-diameter flow-limiting structure, The heat loss caused by adiabatic expansion is compensated by the thermal compensation component, maintaining a constant airflow temperature and thus locking the mean free path. And stabilize the Knudsen number in the spatial dimension. .

5. The detection method for detecting ultra-high purity helium for the electronics industry according to claim 4, characterized in that, The selective excitation includes: real-time monitoring of the intensity of the characteristic spectral lines of helium atoms in the low-temperature plasma enhanced ionization chamber, and dynamic compensation of the microwave power according to the offset of the intensity of the characteristic spectral lines, so that the electron energy is always in the energy range that is higher than the ionization energy of trace impurities and lower than the ionization energy of helium, so that the helium matrix remains as uncharged metastable atoms. The dynamic compensation includes: establishing a negative feedback decoupling model between the microwave power and the helium base effect ionization current; when the intensity of the characteristic spectral line is detected to exceed a preset safety threshold, the coupling coefficient of the microwave source is automatically reduced, and the narrow-band characteristics of the electron energy distribution function in the plasma region are maintained by suppressing the avalanche ionization effect of helium atoms, thereby increasing the purity of the ion clusters generated by the ionization of trace impurities to more than 95%.

6. The detection method for detecting ultra-high purity helium for the electronics industry according to claim 5, characterized in that, The first-level spatial dimension separation includes: applying an asymmetric high-frequency pulse voltage to the electrodes of the multi-dimensional spatial orbit separation unit, causing the target impurity ions to pass along a preset compensation voltage orbit, and repelling the metastable atoms outside the compensation voltage orbit.

7. The detection method for detecting ultra-high purity helium for the electronics industry according to claim 3, characterized in that, The collaborative quantitative analysis includes: real-time acquisition of ion current peaks generated by the compensation voltage scan within the multidimensional spatial orbit separation unit; and setting the delay time of the trigger pulse relative to the excitation time of the cryogenic plasma when the intensity of the ion current peak reaches a preset threshold, in conjunction with a preset ion flight characteristic curve; precisely controlling the opening time of the ion gate through the delay time, so that the opening time window of the ion gate coincides with the time window of the target impurity ion arriving at the mass spectrometry unit, and that the opening time of the ion gate avoids the initial instantaneous moment of the cryogenic plasma excitation, thereby simultaneously filtering out the instantaneous background radiation noise and photon interference generated by the cryogenic plasma enhanced ionization chamber.

8. The detection method for detecting ultra-high purity helium for the electronics industry according to claim 6, characterized in that: The method further includes: phase-locking the modulation frequency of the microwave-induced low-temperature plasma with the voltage scanning period of the multidimensional space orbit separation unit, and setting the delay time of the trigger pulse relative to the excitation time of the low-temperature plasma according to the equivalent mobility of the characteristic ion cluster during the drift process, and physically stripping the target impurity ions from the non-ionized metastable helium atom flow in the time domain through the delay time.

9. The detection method for detecting ultra-high purity helium for the electronics industry according to claim 8, characterized in that: The method further includes: at the inlet of the segmented differential pressure mass spectrometry unit, using a three-stage flow splitter structure, utilizing the difference in mass inertia between the metastable atoms and the target impurity ions, guiding more than 99% of the metastable atoms to the auxiliary pumping system.

10. The detection method for detecting ultra-high purity helium for the electronics industry according to claim 9, characterized in that: The method further includes: By using a semiconductor cooling chip installed on the outer wall of the low-temperature plasma enhanced ionization chamber, the indoor temperature fluctuation is controlled within ±0.005℃; before the gas enters, a nanoporous graphene membrane is used to trap micron-sized particles in the ultra-high purity helium gas being tested, to ensure that gaseous impurity molecules are not intercepted.

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