Gas concentration measuring device and manufacturing method thereof

Abstract

The application provides a gas concentration measuring device and a manufacturing method thereof. The manufacturing method comprises the following steps: at least one periodic alternation and lamination of at least two material layers with different compositions is used to manufacture a phononic crystal layer; from the inside to the outside of a cavity structure, the phononic crystal layer and a transducer transmitter are sequentially and laminatedly arranged at an opening end of the cavity structure; the phononic crystal layer and a transducer receiver are sequentially and laminatedly arranged at another opening end of the cavity structure; a relationship model among a band gap center frequency f of the established phononic crystal layer, thicknesses of the material layers and a sound wave propagation speed c in the material layers is established; and based on the relationship model, the thicknesses of the material layers at the maximum transmission efficiency η max The thicknesses of the material layers can avoid pollution of the transducer by sensitive or corrosive gases to be measured, and can also maximize the transmission effect of the phononic crystal layer on the sound wave, thereby improving the detection quality of the gas.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, and more specifically, to a gas concentration measuring device and its manufacturing method. Background Technology

[0002] In semiconductor manufacturing processes using equipment such as MOCVD, detecting the concentration of precursor gases is crucial for process control and product quality. Currently, gas concentration measurement methods based on ultrasonic time-of-flight (TOF) are widely used. The basic principle is to utilize the difference in the propagation speed of ultrasound in different gas media. By measuring the time (TOF) from emission to reception of the ultrasound, the molar mass of the gas can be calculated, and thus the concentration of the target gas can be determined.

[0003] However, current gas concentration detection methods mostly rely on the difference in TOF values ​​of ultrasound at different gas concentrations to estimate the actual molar mass of the mixed gas, and then convert this value to obtain the target gas concentration. This method of measurement has the following problems:

[0004] The installation location of the transducer directly affects the ultrasonic wave propagation distance. To improve signal strength, traditional solutions often place the transducer directly inside the measurement cavity. This not only may cause the transducer material to be contaminated by high-purity process gases (such as MO sources), affecting the quality of semiconductor thin film growth, but may also affect its lifespan and performance due to contact with corrosive, high-temperature, and other harsh fluid environments. Furthermore, it can easily increase sealing difficulties and reduce system reliability because the signal leads penetrate the cavity wall.

[0005] Therefore, there is an urgent need for a gas concentration measurement device that can accurately monitor gas concentration in high-end fields such as semiconductor manufacturing. Summary of the Invention

[0006] To achieve the above objectives, this application provides a gas concentration measuring device and its manufacturing method, which can reduce the dependence on transducer installation and avoid the disadvantage of providing high-precision gas concentration measurement due to gas contamination of the transducer.

[0007] To achieve the above and other related objectives, the present invention provides a method for manufacturing a gas concentration measuring device, comprising:

[0008] S0: Provides a cavity structure with openings at both ends, provides a transducer transmitter, a transducer receiver, and at least two layers of materials with different compositions;

[0009] S1: A phononic crystal layer is fabricated by at least one periodic alternating layering of each of the aforementioned material layers;

[0010] S2: From the inside to the outside of the cavity structure, the phonon crystal layer and the transducer transmitter are stacked sequentially at one opening end of the cavity structure, and the phonon crystal layer and the transducer receiver are stacked sequentially at the other opening end of the cavity structure to achieve the sealing of the cavity structure;

[0011] In step S1, the step of fabricating the phonon crystal layer includes:

[0012] S11: Establish a model relating the bandgap center frequency f of the phononic crystal layer to the thickness of each material layer and the propagation speed c of the sound wave within each material layer;

[0013] S12: Based on the relationship model, calculate the distribution of the transmission efficiency η of the sound wave emitted by the transducer at the working frequency f0 of the phononic crystal layer under different thicknesses of each of the material layers.

[0014] S13: Based on the aforementioned distribution diagram, determine the maximum transmission efficiency η max The thickness of each of the material layers described below.

[0015] Optionally, step S11 further includes: setting the constraint conditions of the relation model: the bandgap center frequency f and the operating frequency f0 satisfy: f≤0.8f0 or f≥1.2f0.

[0016] Optionally, the at least two material layers include at least a first material layer A and a second material layer B, which have different compositions;

[0017] In step S1: the phonon crystal layer is fabricated by alternately stacking the first material layer A and the second material layer B, wherein the number of periods of the stacked structure formed by stacking the first material layer A and the second material layer B is n;

[0018] In step S1, the step of preparing the phonon crystal layer includes:

[0019] S11: Establish the bandgap center frequency f of the phononic crystal layer and the thickness d of the first material layer A. A The thickness d of the second material layer B B and the propagation speed c of sound waves within the first material layer A A The speed of sound wave propagation within the second material layer B is c B Relationship model;

[0020] S12: Thickness d of the first material layer A A Within the range of values, based on the relational model, different thicknesses d of the first material layer A are obtained. A Below, at the operating frequency f0, the transmission efficiency η of the sound wave emitted by the transducer transmitter in the phononic crystal layer is related to the thickness d of the second material layer B.B Distribution map;

[0021] S13: Based on the distribution diagram, determine the maximum transmission efficiency η max Within the region, the design thickness of the first material layer A, the design thickness range of the second material layer B, and the number of cycles n.

[0022] Optionally, the first material layer A is reactively inert to the gas to be tested compared to the second material layer B. In step S2, in the same stacked structure, the first material layer A is disposed on the side closer to the cavity structure compared to the second material layer B.

[0023] Optionally, the second material layer B is reactively inert to the gas to be tested, both the transducer transmitter and the transducer receiver include transducer elements, both the first material layer A and the second material layer B are reactively inert to the gas to be tested, and the acoustic impedance of the first material layer A is Z. A The acoustic impedance of the second material layer B is Z. B The acoustic impedance of the transducer is Z0; if and middle, Closer to step 1, in step S2, in the same stacked structure, the first material layer A is disposed on the side closer to the cavity structure than the second material layer B.

[0024] Optionally, the bandgap center frequency f of the phononic crystal layer is related to the thickness d of the first material layer A. A The thickness d of the second material layer B B and the propagation speed c of sound waves within the first material layer A A The speed of sound wave propagation within the second material layer B, c B The relational model is as follows: .

[0025] Optionally, in step S12: the thickness d of the first material layer A A Within the range of values, based on the relationship model, different thicknesses d of the first material layer A are obtained. A Below, at the operating frequency f0, the transmission efficiency η of the sound wave emitted by the transducer at the phonon crystal layer is related to the thickness d of the second material layer B. B The steps for creating a distribution map include:

[0026] S121: Determine the thickness d of the first material layer A. A The range of values ​​for;

[0027] S122: Based on the aforementioned relationship model, obtain the thickness d AFor any value within the range of values, the thickness d B The relationship between the bandgap center frequency f and the change of the bandgap center frequency;

[0028] S123: Based on the propagation speed c A The propagation speed c B The acoustic impedance Z of the first material layer A A The acoustic impedance Z of the second material layer B B And the thickness d in step S122 A The value and the thickness d B The relationship between the bandgap center frequency f and the transmission matrix is ​​used to perform transmission matrix operations under different period numbers n to obtain the thickness d at different times. B The corresponding thermodynamic distribution diagram of transmission efficiency η;

[0029] S124: Select the thickness d A For another value within the range of d, repeat steps S122 to S123 until different thicknesses d are obtained. A Thickness d under different values ​​of n and different number of periods B The corresponding thermodynamic distribution diagram of the transmission efficiency η.

[0030] Optionally, in step S13: based on the distribution map, determine the maximum transmission efficiency η max Within the region, the steps for determining the design thickness of the first material layer A, the design thickness range of the second material layer B, and the number of cycles n of the alternating stacking of the first material layer A and the second material layer B include:

[0031] S131: Obtain different thicknesses d A The maximum transmission efficiency η in the thermodynamic distribution map obtained under different values max Location;

[0032] S132: Compare the maximum transmission efficiency η of each. max The area of ​​the region, and the thickness d corresponding to the region with the largest area. A The design thickness of the first material layer A is selected as the maximum transmission efficiency η. max The thickness d corresponding to the largest area in the region B The range is defined as the design thickness range of the second material layer B, and the maximum transmission efficiency η is... max The period number n corresponding to the largest area in the region is taken as the period number of the alternating layer number.

[0033] Optionally, in step S123, the transmission matrix model M total It is obtained from the single-period transmission matrix M and the number of periods n;

[0034] The single-period transmission matrix M is: ;

[0035] in: , , , , , ;

[0036] The transmission matrix model M total for: ;

[0037] Wherein, An, Bn, Cn, and Dn are the corresponding matrix elements obtained by multiplying the single-cycle transmission matrix M by itself n times;

[0038] The formula for calculating the transmission efficiency η is:

[0039] ;

[0040] Among them, Z A Z is the acoustic impedance of the first material layer A. B Let be the acoustic impedance of the second material layer B.

[0041] Optionally, step S132 includes:

[0042] Select the maximum transmission efficiency η max The thickness d corresponding to the geometric center of the largest area in the region. B This serves as the design thickness of the second material layer B.

[0043] Optionally, the cavity structure further includes a sidewall, and step S0 further includes providing an air inlet and an air outlet opposite to each other on the sidewall for the gas to be tested to enter and exit.

[0044] The line connecting the acoustic center of the acoustic transducer transmitter and the acoustic center of the acoustic transducer receiver is defined as the first axis, and the line connecting the air inlet and the air outlet is defined as the second axis, wherein the first axis and the second axis are orthogonal.

[0045] Optionally, step S0 further includes: the structure enclosed by the inner wall of the cavity structure is part of an ellipsoidal geometry and is an axisymmetric structure, wherein the ellipsoidal geometry is a structure formed by rotating an ellipse around its major axis.

[0046] Step S2 further includes: placing the transducer transmitter and the transducer receiver on the phonon crystal layers at both ends of the cavity structure, and positioning the geometric center of the transducer transmitter and the geometric center of the transducer receiver at the foci of the ellipse.

[0047] This application also provides a gas concentration measuring device, comprising:

[0048] A cavity structure with openings at both ends, including a first opening end and a second opening end;

[0049] Two phonon crystal layers are respectively disposed at the first opening end and the second opening end to seal the cavity structure;

[0050] The transducer transmitter and transducer receiver are respectively located on the side of the two phonon crystal layers away from the interior of the cavity structure.

[0051] Optionally, it also includes an air inlet and an air outlet respectively disposed opposite to each other on the sidewall of the cavity structure; the acoustic center of the transducer and the acoustic center of the transducer form a first axis, the line connecting the air inlet and the air outlet forms a second axis, and the first axis and the second axis are orthogonal.

[0052] Optionally, the structure enclosed by the inner wall of the cavity structure is part of an ellipsoidal geometry and is an axisymmetric structure. The ellipsoidal geometry is a structure formed by rotating an ellipse around its major axis, and the geometric center of the transducer and the geometric center of the transducer are located at the foci of the ellipse.

[0053] Optionally, both the transducer transmitter and the transducer receiver include a transducer element, and the acoustic impedance of the first material layer A is Z. A The phonon crystal layer is composed of a first material layer A and a second material layer B, which are periodically stacked alternately, wherein the acoustic impedance of the second material layer B is Z. B The transducer has an acoustic impedance of Z0, and the stacked structure formed by the first material layer A and the second material layer B has a period number of n, satisfying one of the following conditions: in the same stacked structure, the first material layer A is disposed closer to the cavity structure than the second material layer B.

[0054] (1) The first material layer A is reactively inert to the gas to be tested compared to the second material layer B;

[0055] (2) Both the first material layer A and the second material layer B are reactively inert to the gas to be tested, and and middle, Closer to 1.

[0056] Optionally, the first material layer A is a rigid material layer, and the second material layer B is an elastic material layer.

[0057] Optionally, the first material layer A is a glass layer, a sapphire layer, or a polytetrafluoroethylene layer, and the second material layer B is a polyethylene layer or a silicone layer.

[0058] As described above, the gas concentration measuring device and its manufacturing method provided by the present invention have at least the following beneficial technical effects:

[0059] Phononic crystal layers are fabricated using at least one periodic alternating layering of at least two different material layers. From the inside to the outside of the cavity structure, the phononic crystal layer and the transducer emitter are sequentially stacked at one opening of the cavity structure, and the phononic crystal layer and the transducer receiver are sequentially stacked at the other opening. This ensures that the transducer emitter and transducer receiver do not directly contact the gas medium within the cavity structure, avoiding contamination of the transducer by sensitive or corrosive gases being tested, and preventing potential contamination of the gases being tested within the cavity, especially process gases, by the transducer. Furthermore, in the step of fabricating the phononic crystal layer, the relationship between the established bandgap center frequency f of the phononic crystal layer and the thickness of each material layer, as well as the propagation speed c of the sound wave within each material layer, is determined through steps S12 and S13 to achieve the maximum transmission efficiency η. max The thickness of each material layer allows the phonon crystal layer to maximize the transmission of sound waves, thereby improving the quality of gas detection. Attached Figure Description

[0060] Figure 1 The flowchart shown is a method for manufacturing a phononic crystal layer provided in Example 1.

[0061] Figure 2 The device shown is a gas concentration measuring device provided in this application.

[0062] Figure 3 This is a schematic diagram showing the relationship between the bandgap center frequency f of the phononic crystal layer provided in Example 1 and the thickness of the first material layer A and the thickness of the second material layer B.

[0063] Figure 4 This is shown as the relationship between the thickness of the second material layer B and the bandgap center frequency f when the thickness of the first material layer A is 1 mm.

[0064] Figure 5 Displayed as according to Figure 4 The corresponding relationship shown is the distribution of the changes in the thickness of the second material layer B, the number of cycles n, and the transmission efficiency when the thickness of the first material layer A is 1 mm and the operating frequency is 1 MHz.

[0065] Figure 6 The diagram shows the relationship between the thickness of the second material layer B and the bandgap center frequency f when the thickness of the first material layer A is 2 mm.

[0066] Figure 7 Displayed as according to Figure 6 The corresponding relationship shown is the distribution of the thickness of the second material layer B, the number of cycles n, and the transmission efficiency when the thickness of the first material layer A is 2 mm and the operating frequency is 1 MHz.

[0067] Figure 8 The diagram shows the relationship between the thickness of the second material layer B and the bandgap center frequency f when the thickness of the first material layer A is 3 mm.

[0068] Figure 9 Displayed as according to Figure 8 The corresponding relationship shown is the distribution of the thickness of the second material layer B, the number of cycles n, and the transmission efficiency when the thickness of the first material layer A is 3 mm and the operating frequency is 1 MHz.

[0069] Figure 10 The diagram shows the relationship between the thickness of the second material layer B and the bandgap center frequency f when the thickness of the first material layer A is 4 mm.

[0070] Figure 11 Displayed as according to Figure 10 The corresponding relationship shown is the distribution of the thickness of the second material layer B, the number of cycles n, and the transmission efficiency when the thickness of the first material layer A is 4 mm and the operating frequency is 1 MHz.

[0071] Figure 12 The diagram shows the relationship between the thickness of the second material layer B and the bandgap center frequency f when the thickness of the first material layer A is 5 mm.

[0072] Figure 13 Displayed as according to Figure 12 The corresponding relationship shown is the distribution of the changes in the thickness of the second material layer B, the number of cycles n, and the transmission efficiency when the thickness of the first material layer A is 5 mm and the operating frequency is 1 MHz.

[0073] Figure 14 The diagram shows the relationship between the thickness of the second material layer B and the bandgap center frequency f when the thickness of the first material layer A is 6 mm.

[0074] Figure 15 Displayed as according to Figure 14 The corresponding relationship shown is the distribution of the changes in the thickness of the second material layer B, the number of cycles n, and the transmission efficiency when the thickness of the first material layer A is 6 mm and the operating frequency is 1 MHz.

[0075] Figure 16 The diagram shown illustrates the ultrasonic wave propagation path in the gas concentration measuring device provided in Example 2.

[0076] Reference numerals: 10, cavity structure; 12, side wall; 121, air inlet; 122, air outlet; 131, transducer transmitter; 132, transducer receiver; 14, phonon crystal layer. Detailed Implementation

[0077] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0078] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components, the shape, quantity, positional relationship and proportion of each component can be arbitrarily changed under the premise of realizing the technical solution of this invention, and the layout of the components may also be more complex.

[0079] Example 1

[0080] This embodiment provides a method for manufacturing a gas concentration measuring device, including:

[0081] S0: Provides a cavity structure with openings at both ends, provides a transducer transmitter, a transducer receiver, and at least two layers of materials with different compositions;

[0082] S1: A phononic crystal layer is fabricated by periodically alternating layers of each material layer at least once;

[0083] S2: From the inside to the outside of the cavity structure, a phononic crystal layer and a transducer transmitter are stacked sequentially at one opening end of the cavity structure, and a phononic crystal layer and a transducer receiver are stacked sequentially at the other opening end of the cavity structure to achieve cavity structure sealing.

[0084] Among them, reference Figure 1 In step S1, the steps for fabricating the phonon crystal layer include:

[0085] S11: Establish a model relating the bandgap center frequency f of the phononic crystal layer to the thickness of each material layer and the propagation speed c of the sound wave within each material layer;

[0086] S12: Based on the relational model, calculate the distribution of the transmission efficiency η of the acoustic wave emitted by the transducer at the working frequency f0 of the phononic crystal layer under different thicknesses of each material layer.

[0087] S13: Based on the distribution diagram, determine the maximum transmission efficiency η maxThe thickness of each material layer.

[0088] Specifically, step S0: providing a cavity structure with openings at both ends, the cavity structure including sidewalls; an air inlet 121 and an air outlet 122 are also disposed opposite to each other on the sidewalls; such as Figure 2 As shown, this is the gas concentration measuring device provided in this embodiment.

[0089] Please see Figure 2 and Figure 16 The inner wall of the cavity structure 10 is a partially ellipsoidal geometry, and it is an axisymmetric structure. The ellipsoidal geometry is formed by rotating an ellipse around its major axis. The cavity structure 10 is composed of an ellipsoidal geometry truncated by two parallel planes. An air inlet 121 and an air outlet 122 are provided opposite to each other on the side wall 12 of the cavity structure 10 to allow the gas to be measured to enter and exit.

[0090] Specifically, in step S3, from the inside to the outside of the cavity structure, a phonon crystal layer and a transducer are stacked sequentially at one opening end of the cavity structure; a phonon crystal layer and a transducer receiver are stacked sequentially at the other opening end of the cavity structure; the phonon crystal layer seals the cavity structure. Specifically, a transducer 131 and a transducer receiver 132 are respectively arranged on the inner side of the cavity structure, away from both ends. Specifically, the acoustic centers of the transducer 131 and the transducer receiver 132 are located at the two geometric foci corresponding to the ellipsoidal geometry. This arrangement ensures that sound waves emitted from one focal point, after reflection by the ellipsoidal surface, will converge to the other focal point. Therefore, the ultrasonic waves emitted from the transmitter, in addition to the straight propagation path, will also generate a converging path reflected by the inner wall of the cavity, achieving high precision and interference-resistant time-of-flight (TOF)... D Measurement provides the physical basis.

[0091] Specifically, the line connecting the transducer transmitter 131 and the transducer receiver 132 forms the first axis, and the line connecting the air inlet 121 and the air outlet 122 forms the second axis. The first and second axes are orthogonal. This orthogonal design ensures that the main direction of gas flow (along the second axis) is perpendicular to the main direction of ultrasonic wave propagation (along the first axis), theoretically making the projection of the airflow velocity vector onto the ultrasonic wave propagation direction zero, thus significantly reducing the direct impact of airflow velocity on the ultrasonic wave's time of flight. Specifically, the air inlet 121 and air outlet 122 of the ellipsoidal cavity are located at the middle of the side wall 12. Due to geometric symmetry, the airflow field is distributed in an approximately symmetrical shape about the first axis. The airflow environment experienced by the first and second halves of the ultrasonic wave propagation path (along the first axis) is statistically symmetrical and complementary. Therefore, even if there are localized, non-ideal airflow disturbances, their phase advance or delay effects on the ultrasonic signal will accumulate and cancel each other out along the entire propagation path, ultimately ensuring that the measured time-of-flight signal is not disturbed by the macroscopic flow of air.

[0092] Specifically, the transducer transmitter 131 and the transducer receiver 132 are disposed on the side of the phonon crystal layer 14 away from the inside of the cavity, that is, the transducer transmitter 131 and the transducer receiver 132 are disposed outside the cavity to avoid the transducer contaminating the gas to be measured inside the cavity, or the gas to be measured contaminating the transducer. At the same time, the sealing structure is simplified and the reliability of the device is improved.

[0093] Specifically, S1: A phonon crystal layer 14 is fabricated by periodically alternating layers of various materials at least once. In order to enable the transducer to emit signals from outside the cavity and receive signals through the transducer receiver, and to maximize the transmission of sound wave signals, a phonon crystal layer is designed and embedded between the transducer and the cavity wall. The phonon crystal layer achieves maximum transmission of ultrasonic waves, thereby reducing the difficulty of transducer installation, avoiding pollution problems, and still maintaining a high ultrasonic signal strength.

[0094] In some embodiments, the transducer transmitter is an ultrasonic transducer transmitter, and the transducer receiver is an ultrasonic transducer receiver.

[0095] like Figure 2 As shown, the phonon crystal layer 14 provided in this embodiment includes a one-dimensional phonon crystal layer formed by alternating stacking of two or more different materials along a certain direction. The phonon crystal layer has a bandgap center frequency f, which means that electromagnetic waves or elastic waves cannot propagate within a specific frequency range. Therefore, it is necessary to select appropriate materials, the number of layers of different materials stacked alternately, and the thickness of the materials so that the phonon crystal layer can achieve maximum transmission of sound waves at the operating frequency and maintain good signal strength.

[0096] Specifically, such as Figure 1As shown: Step S1, the steps for fabricating the phononic crystal layer include: S11: Establishing a relationship model between the bandgap center frequency f of the phononic crystal layer and the thickness of each material layer and the propagation speed c of the sound wave within each material layer; S12: Based on the relationship model, calculating the distribution of the transmission efficiency η of the sound wave emitted by the transducer at the operating frequency f0 of the phononic crystal layer under different thicknesses of each material layer; S13: Determining the maximum transmission efficiency η based on the distribution map. max The thickness of each material layer.

[0097] Specifically, the multiple material layers include at least two layers, and the selection of material layers includes materials with good acoustic properties, chemical stability, and processability, such as quartz glass, polyethylene, and epoxy resin. In this embodiment, the first material layer A is closer to the cavity and directly contacts the gas medium inside the cavity than the second material layer B. Therefore, generally, when the first material layer A is chemically inert to the gas to be tested compared to the second material layer B, in the same stacked structure composed of the first material layer A and the second material layer B, the first material layer A is closer to the cavity structure than the second material layer B.

[0098] In some embodiments, both the transducer transmitter and the transducer receiver include a transducer with an acoustic impedance of Z0, and both the first material layer A and the second material layer B are reactively inert to the gas to be measured. The acoustic impedance of the first material layer A is Z0. A The acoustic impedance of the second material layer B is Z. B ,like and middle, Closer to step 1, in step S2, in the same stacked structure, the first material layer A is disposed on the side closer to the cavity structure than the second material layer B.

[0099] In an optional embodiment, the first material layer A is a rigid material layer, and the second material layer B is an elastic material layer. In this case, adjacent first material layers A and second material layers B, as well as adjacent transducers and second material layers B, can fit together better, improving sound wave transmission efficiency. If gaps exist, the gas within the gaps, such as air, will affect sound wave transmission.

[0100] Specifically, the first material layer A is a glass layer, a sapphire layer, or a polytetrafluoroethylene layer, and the second material layer B is a polyethylene layer or a silicone layer. In this embodiment, the first material layer A and the second material layer B are selected. Specifically, the first material layer A is a quartz glass layer, and the second material layer is a polyethylene (PE) layer.

[0101] Specifically, S11: Establish the bandgap center frequency f of the phononic crystal layer and the thickness d of the first material layer A. A The thickness d of the second material layer B Band the propagation speed c of sound waves within the first material layer A A The speed of sound wave propagation within the second material layer B is c B The relationship model is as follows: .

[0102] The goal of step S12 is to make the bandgap center frequency f of the phononic crystal layer far away from the transducer's operating frequency f0, ensuring that f0 is within the passband of the phononic crystal layer and that the sound wave has good transmission properties.

[0103] The bandgap center frequency f and the operating frequency f0 are kept at an interval: Δf is set based on the bandgap radius or an empirical value. For example, in this case, with f0 = 1 MHz, Δf = 0.2 MHz, meaning the design constraint is set as: f ≤ 0.8 f0 or f ≥ 1.2 f0. Further, with Δf = 0.3 MHz, the design constraint is set as: f ≤ 0.7 f0 or f ≥ 1.3 f0. Step S12 initially selects d values ​​that meet the bandgap position requirements. A and d B The range of combinations.

[0104] like Figure 3 The diagram shown illustrates the relationship between the bandgap center frequency f of the phononic crystal layer provided in this embodiment and the thicknesses of the first material layer A (glass layer) and the second material layer B (polyethylene layer). Figure 3 As shown, the horizontal axis represents the thickness d of the first material layer A. A The vertical axis represents the thickness d of the second material layer B. B In the figure, each line represents the bandgap center frequency f of the phononic crystal layer under a specific combination of thicknesses. The red line in the figure indicates the bandgap position with a center frequency of 1 MHz, meaning that d on this curve... A and d B The thickness combination will prevent 1 MHz sound waves from propagating, and the phononic crystal layer formed by the thickness combination of the first material layer A and the second material layer B near this line also has low efficiency in propagating 1 MHz sound waves.

[0105] To ensure that ultrasound at the operating frequency f can pass through smoothly, a thickness parameter combination far from the red curve needs to be selected. Specifically, in this embodiment, the design constraint is set to ensure that f0 is within the passband of the phonon crystal layer: f ≤ 0.8 f0 or f ≥ 1.2 f0.

[0106] Specifically, S12 includes:

[0107] S121: Determine the thickness d of the first material layer A A The range of values ​​for;

[0108] S122: Based on the relational model, obtain the thickness d A For any value within the range of values, the thickness d B Relationship with the change of the bandgap center frequency f;

[0109] S123: Based on propagation speed c A Propagation speed c B The acoustic impedance Z of the first material layer A A The acoustic impedance Z of the second material layer B B And the thickness d in step S122 A Values ​​and thickness d B The relationship between the bandgap center frequency f and the transmission matrix is ​​used to perform transmission matrix operations under different period numbers n to obtain the thickness d at different times. B The corresponding thermodynamic distribution diagram of transmission efficiency η;

[0110] S124: Select thickness d A Take another value within the range of values, and repeat steps S122 to S123 until the thickness d is obtained. A Thickness d under different values ​​of n and different number of periods B The corresponding thermodynamic distribution diagram of the transmission efficiency η.

[0111] Specifically, step S121: Based on the processing conditions of the first material layer A, determine d A The value range of . In this embodiment, the first material layer A is quartz glass, and the thickness d of the quartz glass is . A If it's too thin, it's fragile and difficult to process; if it's too thick, it needs to meet the requirement of good sound wave transmission, resulting in a d... B The range of options narrows, reducing design freedom. Therefore, in some specific embodiments, based on process experience, d A The suitable range is limited to 1 mm-6 mm.

[0112] Specifically, step S122: Based on the relational model, obtain the value in d. A For any value within the range of values, the thickness d B Relationship with the center frequency f of the bandgap.

[0113] Specifically, according to the relational model Select a d A By substituting the value of into the formula, the thickness d of the second material layer B can be calculated and plotted. B The curve showing the correspondence between the bandgap center frequency f of the phononic crystal layer and the design constraint boundary f ≤ 0.8 f0 or f ≥ 1.2 f0 is then plotted on the curve, thus clarifying the current d A Under the given value, d satisfies the design constraints. B Range of values.

[0114] Specifically, in step S123, the total transfer matrix M of the model total The result is obtained from the single-cycle transmission matrix M and the number of cycles n:

[0115] The formula for the single-period transmission matrix M is: ;in, ; ; ; ; ; ; n is the number of cycles for material A and material B, Z A Z is the acoustic impedance of material A. B The acoustic impedance of material B, C A C is the speed at which sound waves propagate in the first material. B The velocity of sound waves in the second material is denoted as .

[0116] Transmission Matrix Model M total for: Where An, Bn, Cn, and Dn are the corresponding matrix elements obtained by multiplying the single-cycle transmission matrix M by itself n times.

[0117] The transmission efficiency η of ultrasound through the phonon crystal layer at the operating frequency f0: ;

[0118] Specifically, in d B A series of values ​​were selected within the range, and a thermogram of the transmission efficiency η of the phonon crystal layer as a function of the operating frequency f0 and the number of periods n was calculated and plotted using the transfer matrix method. In this thermogram, the horizontal axis represents the number of periods n, and the vertical axis represents the thickness d of the second material layer B (PE). B The shade of color indicates the specific (n, d) B In coordinate system, with a fixed d A The transmission efficiency η at f0 is given by the color, where redder indicates higher transmission efficiency and bluer indicates lower transmission efficiency.

[0119] like Figures 4 to 15 As shown, this is illustrated by the relationship model and the transfer matrix model, for different thicknesses (d) of the first material (glass). A The systematic analysis results of the design space and transmission performance of the phonon crystal layer are as follows. Specifically: Figure 4 , 6 8, 10, 12, and 14 represent the thickness d of the first material layer A. A When the thickness d of the second material layer B (PE) is 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm, the thickness d is determined according to the relational model. BThe correspondence between the bandgap center frequency f and the design constraint boundary f ≤ 0.8 f0 or f ≥ 1.2 f0 is indicated in the figure. In this example, f0 = 1 MHz is taken as an example. Figure 5 , 7 1, 2, 3, 4, 5 show the thickness d of the first material layer A. A For ultrasonic waves with thicknesses of 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm, the transmission efficiency η of the corresponding phonon crystal layer varies with the ultrasonic operating frequency f, the number of cycles n, and the thickness d. B Heat map showing the changing distribution.

[0120] Specifically, S13: Based on the distribution diagram, determine the maximum transmission efficiency η max Within the region, the design thickness of the first material layer A, the range of the design thickness of the second material layer B, and the number of cycles n of the alternating stacking of the first material layer A and the second material layer B.

[0121] Specifically, S131: Obtain the thickness d A The maximum transmission efficiency η in the thermodynamic distribution diagram obtained under different values max Location;

[0122] S132: Compare the maximum transmission efficiency η for each thickness max The area of ​​the region, and the thickness d corresponding to the largest area. A The design thickness of the first material layer A is chosen to maximize the transmission efficiency η. max The thickness d corresponding to the largest area in the region B The range is defined as the design thickness range of the second material layer B, with a maximum transmission efficiency η. max The period number n corresponding to the largest area in the region is taken as the period number of the alternating layer number.

[0123] In some specific embodiments, the maximum transmission efficiency η is selected. max The thickness d corresponding to the geometric center of the largest area in the region. B The design thickness of the second material layer B.

[0124] like Figure 4 and Figure 5 As shown, d A When it is 1 mm, Figure 5 The transmission efficiency represented by the red areas within the yellow dashed boxes shown is higher than that represented by other red areas. Therefore, the period number n is determined to be 13. Based on the d values ​​corresponding to the red areas within the yellow dashed boxes... B A range can be used as a range of values, for example, d. BThe thickness can be 1 mm, 2 mm, or 3 mm. The specific thickness can be flexibly selected based on the specific material selection of the second material layer B, the bonding strength of the first material layer A and the second material layer B, etc.

[0125] like Figure 6 and Figure 7 As shown, d A When it is 2 mm, Figure 7 The transmission efficiency represented by the red areas within the yellow dashed boxes shown is higher than that represented by other red areas. Therefore, the period number n is determined to be 13. Based on the d values ​​corresponding to the red areas within the yellow dashed boxes... B A range can be used as a range of values, for example, d. B The thickness can be 1 mm, 2 mm, or 3 mm. The specific thickness can be flexibly selected based on the specific material selection of the second material layer B, the bonding strength of the first material layer A and the second material layer B, etc.

[0126] like Figure 8 and Figure 9 As shown, d A When it is 3 mm, Figure 9 The transmission efficiency represented by the red areas within the yellow dashed boxes shown is higher than that represented by other red areas. Therefore, the period number n is set to 10. Based on the d values ​​corresponding to the red areas within the yellow dashed boxes... B A range can be used as a range of values, for example, d. B The thickness can be 0.2-0.5 mm, 1.0-1.3 mm, or 2.0-2.3 mm. The specific thickness can be flexibly selected based on the specific material selection of the second material layer B, the bonding strength of the first material layer A and the second material layer B, etc.

[0127] like Figure 10 and Figure 11 As shown, d A When it is 4 mm, Figure 11 The transmission efficiency represented by the red areas within the yellow dashed boxes shown is higher than that represented by other red areas. Therefore, the period number n is determined to be 13. Based on the d values ​​corresponding to the red areas within the yellow dashed boxes... B A range can be used as a range of values, for example, d. B The thickness can be 1 mm, 2 mm, or 3 mm. The specific thickness can be flexibly selected based on the specific material selection of the second material layer B, the bonding strength of the first material layer A and the second material layer B, etc.

[0128] like Figure 12 and Figure 13 As shown, d A When it is 5 mm, Figure 13The transmission efficiency represented by the red areas within the yellow dashed boxes shown is higher than that represented by other red areas. Therefore, the period number n is determined to be 13. Based on the d values ​​corresponding to the red areas within the yellow dashed boxes... B A range can be used as a range of values, for example, d. B The thickness can be 0.5-1.0 mm, 1.5-2.0 mm, or 2.5-3.0 mm. The specific thickness can be flexibly selected based on the specific material selection of the second material layer B, the bonding strength between the first material layer A and the second material layer B, etc.

[0129] like Figure 14 and Figure 15 As shown, d A When it is 6 mm, Figure 13 The transmission efficiency represented by the red areas within the yellow dashed boxes shown is higher than that represented by other red areas. Therefore, the period number n is determined to be 13. Based on the d values ​​corresponding to the red areas within the yellow dashed boxes... B A range can be used as a range of values, for example, d. B The thickness can be 1 mm, 2 mm, or 3 mm. The specific thickness can be flexibly selected based on the specific material selection of the second material layer B, the bonding strength of the first material layer A and the second material layer B, etc.

[0130] Then Figure 5 , 7 The regions with the highest transmission efficiency η and the widest thickness range selected from 9, 11, 13, and 15 are compared to obtain the region with the highest transmission efficiency η and the widest thickness range (i.e., the region with the highest transmission efficiency η and the widest thickness range). Figure 9 (The red area within the yellow box in the image), from which the corresponding period number n=10, d can be determined. B The acceptable thicknesses are 0.2-0.5 mm, 1.0-1.3 mm, and 2.0-2.3 mm. Specifically, d B The thickness can be 0.2 mm, 1.2 mm, etc. The data provided in this embodiment are for illustrative purposes only, and the method provided in this application cannot be used to limit the scope of protection of this application.

[0131] In this embodiment, the phononic crystal layer not only serves as a highly efficient sound wave transmission structure but also functions as a sealed cavity and an isolation mechanism between the transducer and the gas to be measured. The stacking order of the material layers is prioritized based on the chemical inertness criterion: materials in contact with the gas to be measured are given priority to ensure that they do not chemically react or physically adsorb, thus avoiding gas contamination or self-degradation. If all material layers are chemically inert, the acoustic impedance matching criterion is applied.

[0132] If, among the various materials constituting the phonon crystal layer, only one material is verified to be reactively inert with the test gas, then regardless of its acoustic properties, this material layer must be placed on the innermost side in each stacking cycle. That is, it must be closer to the cavity space than the other material layer in the same stacking cycle. The material layer closest to the cavity is the first material layer A and the second material layer B, which directly contact the gas inside the cavity. Specifically, in this embodiment, if the first material layer A is reactively inert with the test gas, in step S2, the first material layer A is placed on the side close to the cavity structure and away from the second material layer B.

[0133] Taking the measurement of MO sources commonly used in semiconductor processes (such as trimethylgallium, with hydrogen as the carrier gas) as an example. The first material layer A is made of quartz glass, and the second material layer B is made of polyethylene. It is known that quartz glass has excellent chemical inertness to most MO sources and H2 and N2 carrier gases, and will not react or release contaminants. Although polyethylene has good chemical stability, it may have a slight risk of adsorption or swelling when in contact with certain organometallic compounds for a long time. Therefore, according to the chemical inertness criterion, the quartz glass layer (first material layer A) should be set to the side closer to the cavity gas in each cycle.

[0134] Example 2

[0135] This embodiment provides a gas concentration measuring device, such as... Figure 2 The image shows the gas concentration measuring device of this embodiment. The gas concentration measuring device provided in this embodiment is manufactured using the gas concentration measuring device manufacturing method in Embodiment 1. The gas concentration measuring device includes: a cavity structure 10, which is part of an ellipsoidal geometry. The ellipsoidal geometry is a cavity formed by rotating an ellipse around its major axis. The cavity structure 10 includes a sidewall 12, and an inlet 121 and an outlet 122 disposed on the sidewall 12 and arranged opposite to each other. A transducer 131 and a transducer 132 are disposed on the side of the sidewall 12 away from the interior of the cavity. A phonon crystal layer 14 is located at the first opening end and the second opening end, respectively, to seal the cavity structure. Specifically, both the transducer 131 and the transducer 132 include transducer plates, and the acoustic centers of the two transducer plates are located at the two geometric foci corresponding to the ellipsoidal geometry. The line connecting the acoustic center of the transducer 131 and the acoustic center of the transducer 132 forms a first axis, and the line connecting the inlet 121 and the outlet 122 forms a second axis. The first axis and the second axis are orthogonal. Specifically, the air inlet 121 and the air outlet 122 are located at the middle position of the side wall 12 along the first axis.

[0136] In some embodiments, both the transducer transmitter and the transducer receiver include a transducer with an acoustic impedance of Z0, and both the first material layer A and the second material layer B are reactively inert to the gas to be measured. The acoustic impedance of the first material layer A is Z0. AThe acoustic impedance of the second material layer B is Z. B ,like and middle, Closer to step 1, in step S2, in the same stacked structure, the first material layer A is disposed on the side closer to the cavity structure than the second material layer B.

[0137] Optionally, the first material layer A is a rigid material layer, and the second material layer B is an elastic material layer. In this embodiment, the first material layer A is a glass layer, a sapphire layer, or a polytetrafluoroethylene layer, and the second material layer B is a polyethylene layer or a silicone layer.

[0138] like Figure 16 The diagram shows the ultrasonic wave propagation path in the gas concentration measuring device provided in this embodiment. For ease of illustration, this application uses two propagation paths as examples: Path 1: The ultrasonic wave propagates in a straight line from the transducer transmitter 131 located at focus F1 to the transducer receiver 132 located at focus F2, with a distance of 2C between F1 and F2; Path 2: Starting from focus F1, the ultrasonic wave is reflected by point D on the side wall 12 and converges to F2. According to the geometric properties of the ellipsoid, the total length of path F1-D-F2 is always 2a (where a is the semi-major axis of the ellipse). Therefore, the difference in physical length between path 1 and path 2 is: .

[0139] The following is a method for calculating the time difference of flight (TOF) of ultrasonic waves. D The gas concentration is obtained by using the physical relationship between the fixed acoustic path difference and sound velocity generated by the ellipsoidal cavity and the gas composition. The specific steps are as follows:

[0140] 1. Determine the difference between the cavity's geometric parameters and its physical length, ΔL. The physical length difference ΔL is: .

[0141] 2. Measurement of ultrasonic time difference of flight (TOF) D Specifically, ultrasonic waves are emitted from focal point F1, and the arrival times at F2 are recorded for two separate paths. Path 1 (F1-F2) takes time T1; Path 2 (F1-F2) takes time T2. The time difference is calculated using Time of Flight (TOF). D =T2-T1.

[0142] 3. Calculate the speed of sound C in the gas mixture. Specifically, the physical length difference ΔL and the time difference of flight of the ultrasonic waves (TOF) are related. D ), calculate the speed of sound: Note: This sound speed is the actual propagation speed of the gas mixture at the measurement temperature.

[0143] 4. Establish a model relating the speed of sound to the gas composition. Specifically, for an ideal gas mixture, the speed of sound C is: ;in: R is the specific heat capacity ratio (adiabatic index) of the gas mixture, R is the universal gas constant (approximately 8.314 J / (mol·K)), and T is the absolute temperature of the gas (measured by a temperature sensor, unit: K). The average molar mass of the gas mixture (unit: kg / mol).

[0144] 5. Establish expressions for the average molar mass M and specific heat ratio K of the mixed gas. Specifically, let the molar fraction of the MO source reactant gas be x (concentration to be determined), and the molar fraction of the carrier gas be 1-x. Then the average heat ratio... : Average molar mass for: , where Ka and Ma are the molar mass and specific heat ratio of the carrier gas, and Kb and Mb are the molar mass and specific heat ratio of the MO source.

[0145] 6. Solve the equations simultaneously to find the gas concentration x of the MO source. Substitute equations (3) and (4) into equation (2) to calculate the gas concentration x of the MO source.

[0146] This application converts concentration measurement into time-of-flight (TOF) measurement by fixing the geometric path difference ΔL. D The high-precision measurement effectively eliminates common-mode errors such as system delay and circuit drift. Ultimately, only the Time-of-Flight (TOF) measurement is required. D The gas concentration can be directly calculated using the temperature T. The system is simple, highly accurate, and has strong anti-interference capabilities.

[0147] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for manufacturing a gas concentration measuring device, characterized in that, Includes the following steps: S0: Provides a cavity structure with openings at both ends, provides a transducer transmitter, a transducer receiver, and at least two layers of materials with different compositions; S1: A phononic crystal layer is fabricated by at least one periodic alternating layering of each of the aforementioned material layers; S2: From the inside to the outside of the cavity structure, the phonon crystal layer and the transducer transmitter are stacked sequentially at one opening end of the cavity structure, and the phonon crystal layer and the transducer receiver are stacked sequentially at the other opening end of the cavity structure to achieve the sealing of the cavity structure; In step S1, the step of fabricating the phonon crystal layer includes: S11: Establish a model relating the bandgap center frequency f of the phononic crystal layer to the thickness of each material layer and the propagation speed c of the sound wave within each material layer; S12: Based on the relationship model, calculate the distribution of the transmission efficiency η of the sound wave emitted by the transducer at the working frequency f0 of the phononic crystal layer under different thicknesses of each material layer. S13: Based on the aforementioned distribution diagram, determine the maximum transmission efficiency η max The thickness of each of the material layers described below.

2. The method for manufacturing the gas concentration measuring device according to claim 1, characterized in that, Step S11 further includes: setting the constraint conditions of the relation model: the bandgap center frequency f and the operating frequency f0 satisfy: f≤0.8f0 or f≥1.2f0.

3. The method for manufacturing the gas concentration measuring device according to claim 1, characterized in that, The at least two material layers include a first material layer A and a second material layer B; In step S1, the phonon crystal layer is fabricated by alternately stacking the first material layer A and the second material layer B, wherein the number of periods of the stacked structure formed by stacking the first material layer A and the second material layer B is n; The step of fabricating the phonon crystal layer in step S1 includes: S11: Establish the bandgap center frequency f of the phononic crystal layer and the thickness d of the first material layer A. A The thickness d of the second material layer B B and the propagation speed c of sound waves within the first material layer A A The speed of sound wave propagation within the second material layer B, c B Relationship model; S12: At the thickness d of the first material layer A A Within the range of values, based on the relationship model, different thicknesses d of the first material layer A are obtained. A Below, at the operating frequency f0, the transmission efficiency η of the sound wave emitted by the transducer at the phonon crystal layer is related to the thickness d of the second material layer B. B Distribution map; S13: Based on the aforementioned distribution diagram, determine the maximum transmission efficiency η max Within the region, the design thickness of the first material layer A, the design thickness range of the second material layer B, and the number of cycles n.

4. The method for manufacturing the gas concentration measuring device according to claim 3, characterized in that, The first material layer A is reactively inert to the gas to be tested compared to the second material layer B. In step S2, in the same stacked structure, the first material layer A is disposed on the side closer to the cavity structure compared to the second material layer B.

5. The method for manufacturing the gas concentration measuring device according to claim 3, characterized in that, Both the transducer transmitter and the transducer receiver include transducer elements. The first material layer A and the second material layer B are both reactively inert to the gas being measured. The acoustic impedance of the first material layer A is Z. A The acoustic impedance of the second material layer B is Z. B The acoustic impedance of the transducer is Z0; if and middle, Closer to step 1, in step S2, in the same stacked structure, the first material layer A is disposed on the side closer to the cavity structure than the second material layer B.

6. The method for manufacturing the gas concentration measuring device according to claim 3, characterized in that, The bandgap center frequency f of the phononic crystal layer is related to the thickness d of the first material layer A. A The thickness d of the second material layer B B and the propagation speed c of sound waves within the first material layer A A The speed of sound wave propagation within the second material layer B, c B The relational model is as follows: .

7. The method for manufacturing the gas concentration measuring device according to claim 3, characterized in that, In step S12: at the thickness d of the first material layer A A Within the range of values, based on the relationship model, different thicknesses d of the first material layer A are obtained. A Below, at the operating frequency f0, the transmission efficiency η of the sound wave emitted by the transducer at the phonon crystal layer is related to the thickness d of the second material layer B. B The steps for creating a distribution map include: S121: Determine the thickness d of the first material layer A. A The range of values ​​for; S122: Based on the aforementioned relationship model, obtain the value at the thickness d. A For any value within the range of values, the thickness d B The relationship between the bandgap center frequency f and the change of the bandgap center frequency; S123: Based on the propagation speed c A The propagation speed c B The acoustic impedance Z of the first material layer A A The acoustic impedance Z of the second material layer B B And the thickness d in step S122 A The value and the thickness d B The relationship between the bandgap center frequency f and the transmission matrix is ​​used to perform transmission matrix operations under different period numbers n to obtain the thickness d at different times. B The corresponding thermodynamic distribution diagram of transmission efficiency η; S124: Select the thickness d A Take another value within the range of values, and repeat steps S122 to S123 until the thickness d is obtained. A Thickness d under different values ​​of n and different number of periods B The corresponding thermodynamic distribution diagram of the transmission efficiency η.

8. The method for manufacturing the gas concentration measuring device according to claim 7, characterized in that, In step S13: Based on the distribution map, determine the maximum transmission efficiency η. max Within the region, the steps for determining the design thickness of the first material layer A, the design thickness range of the second material layer B, and the number of cycles n of the alternating stacking of the first material layer A and the second material layer B include: S131: Obtain the thickness d A The maximum transmission efficiency η in the thermodynamic distribution map obtained under different values max Location; S132: Compare the maximum transmission efficiency η of each. max The area of ​​the region, and the thickness d corresponding to the region with the largest area. A The design thickness of the first material layer A is selected as the maximum transmission efficiency η. max The thickness d corresponding to the largest area in the region B The range is defined as the design thickness range of the second material layer B, and the maximum transmission efficiency η is... max The period number n corresponding to the largest area in the region is taken as the period number of the alternating layer number.

9. The method for manufacturing the gas concentration measuring device according to claim 7, characterized in that, In step S123, the transmission matrix model M total It is obtained from the single-period transmission matrix M and the number of periods n; The single-period transmission matrix M is: ; in: , , , , , ; The transmission matrix model M total for: ; Wherein, An, Bn, Cn, and Dn are the corresponding matrix elements obtained by multiplying the single-cycle transmission matrix M by itself n times; The formula for calculating the transmission efficiency η is: ； Among them, Z A Z is the acoustic impedance of the first material layer A. B Let be the acoustic impedance of the second material layer B.

10. The method for manufacturing the gas concentration measuring device according to claim 8, characterized in that, Step S132 includes: Select the maximum transmission efficiency η max The thickness d corresponding to the geometric center of the largest area in the region. B This serves as the design thickness of the second material layer B.

11. The method for manufacturing the gas concentration measuring device according to claim 1, characterized in that, The cavity structure also includes a side wall, and step S0 further includes providing an air inlet and an air outlet opposite to each other on the side wall for the gas to be tested to enter and exit. The line connecting the acoustic center of the acoustic transducer transmitter and the acoustic center of the acoustic transducer receiver is defined as the first axis, and the line connecting the air inlet and the air outlet is defined as the second axis, wherein the first axis and the second axis are orthogonal.

12. The method for manufacturing the gas concentration measuring device according to claim 1, characterized in that, Step S0 further includes: the structure enclosed by the inner wall of the cavity structure is part of an ellipsoid geometry and is an axisymmetric structure, wherein the ellipsoid geometry is a structure formed by rotating an ellipse around its major axis. Step S2 further includes: placing the transducer transmitter and the transducer receiver on the phonon crystal layers at both ends of the cavity structure, and positioning the geometric center of the transducer transmitter and the geometric center of the transducer receiver at the foci of the ellipse.

13. A gas concentration measuring device, characterized in that, The gas concentration measuring device is manufactured using the manufacturing method of any one of claims 1 to 12, wherein the gas concentration measuring device comprises: A cavity structure with openings at both ends, including a first opening end and a second opening end; Two phonon crystal layers are respectively disposed at the first opening end and the second opening end to seal the cavity structure; The transducer transmitter and transducer receiver are located on the side of the two phonon crystal layers away from the interior of the cavity structure, respectively.

14. The gas concentration measuring device according to claim 13, characterized in that, It also includes an air inlet and an air outlet respectively disposed opposite to each other on the side wall of the cavity structure; the acoustic center of the transducer transmitter and the acoustic center of the transducer receiver form a first axis, and the line connecting the air inlet and the air outlet forms a second axis, the first axis and the second axis being orthogonal.

15. The gas concentration measuring device according to claim 13, characterized in that, The structure enclosed by the inner wall of the cavity is part of an ellipsoidal geometry and is an axisymmetric structure. The ellipsoidal geometry is a structure formed by rotating an ellipse around its major axis, and the geometric center of the transducer transmitter and the geometric center of the transducer receiver are located at the foci of the ellipse.

16. The gas concentration measuring device according to claim 13, characterized in that, Both the transducer transmitter and the transducer receiver include a transducer element. The phononic crystal layer is composed of a first material layer A and a second material layer B, which are periodically stacked alternately. The acoustic impedance of the first material layer A is Z. A The acoustic impedance of the second material layer B is Z. B The transducer has an acoustic impedance of Z0, and the stacked structure formed by the first material layer A and the second material layer B has a period number of n, satisfying one of the following conditions: in the same stacked structure, the first material layer A is disposed closer to the cavity structure than the second material layer B. (1) The first material layer A is reactively inert to the gas to be tested compared to the second material layer B; (2) Both the first material layer A and the second material layer B are reactively inert to the gas to be tested, and and middle, Closer to 1.

17. The gas concentration measuring device according to claim 16, characterized in that, The first material layer A is a rigid material layer, and the second material layer B is an elastic material layer.

18. The gas concentration measuring device according to claim 17, characterized in that, The first material layer A is a glass layer, a sapphire layer, or a polytetrafluoroethylene layer, and the second material layer B is a polyethylene layer or a silicone layer.

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