Multi-component gas concentration detector based on fabry-perot resonator

Abstract

The application discloses a multi-element gas concentration detector based on a Fabry-Perot resonant cavity and relates to the field of gas measuring equipment, which comprises oppositely arranged first and second reflection structures, a pyroelectric unit with a sensing area in an optical path, the pyroelectric unit being located behind the optical path of the Fabry-Perot resonant cavity and used for receiving selected light of the Fabry-Perot resonant cavity and generating an electric signal, and a driving member connected with the first or second reflection structure and used for driving the movement of the first or second reflection structure to change the cavity length, wherein the driving member has a first driving mode and a second driving mode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas measuring equipment, in particular to a multi-component gas concentration detector based on a Fabry-Perot resonant cavity. BACKGROUND

[0002] In modern large-scale integrated circuit manufacturing, plasma enhanced chemical vapor deposition and etching processes leave complex byproduct deposits on the inner walls of the reaction chamber. In order to ensure the consistency of wafer processing and prevent particle contamination, it is necessary to introduce cleaning gas for in-situ cleaning on a regular basis. As the process node moves towards finer directions, gas endpoint detection for chamber cleaning has become a key to improving the overall efficiency of the equipment. Accurate capture of the instant state of cleaning completion not only reduces the waste of expensive cleaning gas, but also effectively avoids corrosion damage to sensitive components of the chamber due to excessive cleaning.

[0003] The existing endpoint detection scheme mainly relies on optical emission spectroscopy or non-dispersive infrared sensing technology. However, in a complex cleaning process, the types and concentrations of reaction byproducts and cleaning gases will change flexibly with process steps. Current multi-component gas detection usually uses a parallel multi-channel structure, that is, an independent narrow-band optical filter, sensor and its supporting optical mechanical structure are configured for each type of gas component to be detected. This "one component, one channel" stacking mode directly leads to bulky detection modules, low system integration, and increased complexity of hardware assembly and maintenance.

[0004] The current industry is faced with the problem of how to achieve high-sensitivity detection of dynamically changing multiple gases and their concentrations without increasing physical channels. Due to the overlapping of the infrared absorption characteristic peaks or characteristic spectral lines of different gases, the existing fixed channel structure lacks flexibility in spectral tuning. Once the cleaning process recipe changes, the physical sensor hardware often needs to be redesigned or replaced. Developing a "single-channel multi-component" detection mechanism that can be compatible with multiple gas characteristic spectra and has compact structure and detection flexibility has become a key technical challenge to break through the bottleneck of semiconductor process monitoring. SUMMARY

[0005] The present application relates to the technical field of gas measuring equipment, in particular to a multi-component gas concentration detector based on a Fabry-Perot resonant cavity.

[0006] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0007] The multi-component gas concentration detector based on a Fabry-Perot resonant cavity comprises:

[0008] A Fabry-Perot resonant cavity is formed by oppositely arranged first and second reflective structures, a working cavity is formed between the first and second reflective structures, and a cavity length of the working cavity is adjustable.

[0009] A pyroelectric unit has a sensing region in an optical path, the pyroelectric unit is located behind the Fabry-Perot resonant cavity in the optical path, and is used to receive light selected by the Fabry-Perot resonant cavity and generate an electrical signal.

[0010] A driving member is connected to the first or second reflective structure, and is used to drive movement of the first or second reflective structure to change the cavity length, the driving member has a first driving mode and a second driving mode.

[0011] The first driving mode is used to adjust the cavity length to a resonant length corresponding to a characteristic absorption wavelength band of a target gas component, and the second driving mode drives the first or second reflective structure to perform periodic micro-displacement on the basis of the resonant length set by the first driving mode, so as to modulate the intensity of incident light.

[0012] Further, the Fabry-Perot resonant cavity further comprises:

[0013] A movable structure layer, the first reflective structure is fixedly connected to a lower surface of the movable structure layer, and the second reflective structure is located between the first reflective structure and the pyroelectric unit.

[0014] The driving member is connected to the movable structure layer, and is used to drive the movable structure layer to displace in a direction perpendicular to the second reflective structure, so as to change the cavity length of the Fabry-Perot resonant cavity.

[0015] Further, the movable structure layer comprises an electrical functional layer and a mechanical support layer, the mechanical support layer is arranged at the bottom of the electrical functional layer, and is used to provide elastic force and support the electrical functional layer, and the movable structure layer is a light-transmitting layer.

[0016] Further, the Fabry-Perot resonant cavity further comprises:

[0017] A sealed cavity is arranged in the light incidence direction of the Fabry-Perot resonant cavity, and is used to provide a vacuum-sealed space for movement of the movable structure layer.

[0018] Further, the Fabry-Perot resonant cavity has a plurality of Fabry-Perot resonant cavities, and the plurality of Fabry-Perot resonant cavities are respectively used to allow light in different wavelength ranges to transmit through.

[0019] Further, the driving member comprises a first driving electrode and a second driving electrode, the first driving electrode is arranged on the electrically functional layer, and the second driving electrode is arranged on the pyroelectric unit, and the first driving electrode and the second driving electrode are electrically connected to drive the movable structure layer to linearly displace.

[0020] Further, the driving member further comprises a plurality of first calibration electrodes and a plurality of second calibration electrodes, the plurality of first calibration electrodes are uniformly arranged on the first reflecting structure, the plurality of second calibration electrodes are uniformly arranged on the second reflecting structure, and the plurality of first calibration electrodes and the plurality of second calibration electrodes are arranged in one-to-one correspondence and are electrically connected.

[0021] Further, an attractive force can be generated between each of the first calibration electrodes and the second calibration electrodes, and the attractive force is independently adjustable.

[0022] Further, the mechanical support layer comprises a cantilever film and a cantilever elastic beam, the first driving electrode can drive the cantilever film to periodically vibrate, the cantilever elastic beam is arranged in a direction perpendicular to the cantilever film, and the cantilever elastic beam is used to provide an elastic support force for the cantilever film.

[0023] Further, the pyroelectric unit comprises a pyroelectric layer, a micro-bridge and a support substrate layer which are distributed along the light incident direction, and the micro-bridge is used to thermally isolate the pyroelectric layer from the support substrate layer.

[0024] The multi-component gas concentration detector based on the Fabry-Perot resonant cavity provided by the present application has the following beneficial effects: by introducing the Fabry-Perot resonant cavity with adjustable cavity length and cooperating with the driving member with the double driving mode, the selective scanning and high-sensitivity detection of the characteristic absorption waveband of multiple gas components are realized under the structure of single optical path and single pyroelectric detection unit, and the problems of bulky structure and insufficient flexibility caused by the parallel connection of multiple physical channels in the prior art are fundamentally solved. Specifically, by the first driving mode, the cavity length of the Fabry-Perot resonant cavity is accurately adjusted to the resonant length matched with the characteristic absorption waveband of the target gas component, so that the resonant cavity plays a role of narrow-band adjustable filtering in the spectral dimension, thereby realizing the spectral selection of different gas components without replacing the optical filter or increasing the detection channels; on this basis, by the second driving mode, the periodic micro-displacement is applied to the reflecting structure, so that the cavity length generates a slight change around the resonant length, thereby modulating the transmitted light intensity, and in combination with the characteristic that the pyroelectric unit is highly sensitive to the modulated light signal, the background radiation and low-frequency noise interference are effectively suppressed, and the signal-to-noise ratio and detection sensitivity of the weak absorption signal are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1Fig. 1 is a schematic diagram of an overall structure of a multi-component gas concentration detector based on a Fabry-Perot resonant cavity according to an embodiment of the present application;

[0026] Figure 2 Fig. 2 is a schematic diagram of a stacked structure of a multi-component gas concentration detector based on a Fabry-Perot resonant cavity according to an embodiment of the present application;

[0027] Figure 3 Fig. 3 is a schematic diagram of a Fabry-Perot resonant cavity according to an embodiment of the present application;

[0028] Figure 4 Fig. 4 is a schematic diagram of a third calibration electrode according to an embodiment of the present application.

[0029] Fig. 1 is a schematic diagram of an overall structure of a multi-component gas concentration detector based on a Fabry-Perot resonant cavity according to an embodiment of the present application; DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application. Unless otherwise defined, the technical terms or scientific terms used herein should be interpreted as their common meanings understood by those of ordinary skill in the art to which the present application belongs. The words such as “comprise” and the like used herein mean that the elements or objects before the words encompass the elements or objects listed after the words and their equivalents, and do not exclude other elements or objects.

[0031] The above-mentioned and other objects, features and advantages of the present application will be better understood from the following Figure 1 Fig. 1 is a schematic diagram of an overall structure of a multi-component gas concentration detector based on a Fabry-Perot resonant cavity according to an embodiment of the present application; Figure 4 The specific embodiments of the present application are further described in detail.

[0032] Reference will now be made to the drawings, in which Figures 1-4 In some embodiments of the present application, a multi-component gas concentration detector based on a Fabry-Perot resonant cavity is provided, which is used for selectively and spectrally detecting a plurality of dynamically changing gas components in a cleaning process. The above-mentioned detector device has a Fabry-Perot resonant cavity 1 as a core spectral selection unit in structure, and a pyroelectric unit 2 is arranged downstream of the cavity for signal receiving. A driving member 3 is used to adjust and modulate the cavity length of the resonant cavity, so as to realize high-sensitivity detection of multi-component gases under a single light path condition.

[0033] In some embodiments of the present application, the Fabry-Perot resonant cavity 1 is composed of a first reflective structure 11 and a second reflective structure 12 arranged oppositely, and a working cavity is defined between the first reflective structure 11 and the second reflective structure 12. The cavity length of the working cavity is an adjustable structure. After the incident light enters the Fabry-Perot resonant cavity 1 along a predetermined light path, resonance transmission can only occur when the wavelength of the incident light meets the corresponding cavity length condition, so that the Fabry-Perot resonant cavity 1 plays a role of narrow-band selection in the spectral dimension. By adjusting the cavity length of the working cavity, the center wavelength of the resonance transmission can be changed to match the characteristic absorption wavelength band of different target gas components.

[0034] In some embodiments of the present application, on the basis of the above structure, the pyroelectric unit 2 is arranged behind the Fabry-Perot resonant cavity 1 in the light path, and has a sensing region in the light path for receiving the transmitted light selected by the Fabry-Perot resonant cavity 1 and converting the optical signal into an electrical signal output. By concentrating the spectral selection function in the Fabry-Perot resonant cavity 1 and concentrating the signal detection function in the pyroelectric unit 2, the entire detector device can complete the detection task of multi-band and multi-component gas under the condition of a single detection unit.

[0035] In some embodiments of the present application, the Fabry-Perot resonant cavity 1 further comprises a movable structure layer 13, the first reflective structure 11 is fixedly connected and arranged on the lower surface of the movable structure layer 13, and the second reflective structure 12 is located between the first reflective structure 11 and the pyroelectric unit 2. The driving member 3 is connected with the movable structure layer 13 for driving the movable structure layer 13 to displace in a direction perpendicular to the second reflective structure 12, so as to change the distance between the first reflective structure 11 and the second reflective structure 12, and realize continuous adjustment of the working cavity length. Specifically, the first reflective structure 11 and the second reflective structure 12 are core optical surfaces, the first reflective structure 11 and the second reflective structure 12 are used for high reflection of light of a target wavelength band, and most of the light is reflected between the first reflective structure 11 and the second reflective structure 12 and interferes.

[0036] In some embodiments of the present application, the first reflective structure 11 and the second reflective structure 12 are both distributed Bragg reflector structures, to form a high-reflectivity Fabry-Perot resonator 1. The reflectivity design of the reflective structures is not only used to establish the resonance condition, but also directly related to the required gas concentration detection range and detection accuracy of the present application. Specifically, the detector device of the present application is used to achieve a measurement requirement of a gas concentration range of 0-1000 ppm and a detection accuracy of 5 ppm. The relative resolution corresponding to the above detection accuracy is the ratio of the detection accuracy to the full scale, i.e. 5 ppm / 1000 ppm, about 0.5%. This means that the detection system must be able to stably distinguish about 0.5% change in transmitted light intensity caused by gas absorption. Since the spectral resolution capability of the Fabry-Perot resonator 1 is mainly determined by its fineness, in order to reliably distinguish the light intensity change of the above order of magnitude, the Fabry-Perot resonator 1 needs to have a high enough fineness. In the existing optical theory, there is a clear correspondence between the fineness of the Fabry-Perot resonator 1 and the reflectivity of the reflective structure, and the approximate relationship can be expressed as a function of the fineness and the reflectivity. In order to make the resonator fineness reach the level required to stably distinguish 0.5% light intensity change, the theoretical calculation value of the reflectivity of the first reflective structure and the second reflective structure needs to exceed 99.5%. When the reflectivity is lower than this level, the resonance peak width increases, and the response capability of the in-cavity transmission spectrum to small absorption changes decreases significantly, making it difficult to meet the detection accuracy requirement.

[0037] Therefore, in the present embodiment, by using the distributed Bragg reflector structure formed by the multi-layer alternative stacking, the theoretical reflectivity of the first reflective structure 11 and the second reflective structure 12 exceeds 99.5%, thereby significantly improving the fineness of the Fabry-Perot resonator 1. The high-fineness resonator can form a steep and stable transmission spectrum near the target gas characteristic absorption band, so that the small absorption difference caused by the change in gas concentration is converted into a modulated signal that can be reliably detected by the pyroelectric unit 2, thereby ensuring that the detection accuracy of 5 ppm level is achieved in the detection range of 0-1000 ppm.

[0038] In some embodiments of the present application, the movable structure layer 13 includes an electrical functional layer and a mechanical support layer, wherein the mechanical support layer is arranged at the bottom of the electrical functional layer, and is used to provide elastic support force for the electrical functional layer, so that the electrical functional layer can be controlled to displace under the action of the driving member 3 and restore to the initial position after the driving force is removed. In this embodiment, the movable structure layer 13 as a whole is a light-transmitting layer structure, to ensure that the incident light can pass through the movable structure layer 13 and enter the Fabry-Perot resonator 1, thereby not affecting the integrity of the optical path. Specifically, the electrical functional layer is a semi-transparent or patterned metal, for allowing most of the detection light to pass through.

[0039] In some other embodiments of the present invention, the detection device further includes a sealed cavity 4, which is disposed in the light incident direction of the Fabry-Perot resonator 1 to provide a vacuum-sealed space for the movement of the movable structural layer 13. By providing the sealed cavity 4, the influence of air damping and ambient air pressure fluctuations on the movement state of the movable structural layer 13 can be effectively reduced, improving the stability and repeatability of cavity length adjustment and micro-displacement modulation processes, thereby enhancing the spectral selection accuracy.

[0040] In a further embodiment, the driving element 3 has a first driving mode and a second driving mode. In the first driving mode, the driving element 3 drives the movable structural layer 13 to generate a quasi-static displacement, adjusting the cavity length of the working cavity to a resonant length corresponding to the characteristic absorption band of the target gas component, thereby maximizing the transmission capability of the Fabry-Perot resonator 1 for the target wavelength. In this mode, the Fabry-Perot resonator 1 is used to perform spectral selection of the gas component.

[0041] In the second driving mode, the driving component 3 drives the movable structural layer 13 to perform periodic micro-displacements based on the resonant length set in the first driving mode, causing the cavity length of the working cavity to oscillate slightly around the resonant length, thereby periodically modulating the transmitted light intensity. This modulated light signal is detected by the pyroelectric unit 2. Because the pyroelectric unit 2 has high response sensitivity to the modulated light signal, it can effectively suppress ambient background radiation and low-frequency noise interference, significantly improving the detection signal-to-noise ratio of the weakly absorbed gas signal.

[0042] In some embodiments of the present invention, the mechanical support layer includes a cantilever membrane and a cantilever elastic beam. The combined structure of the cantilever membrane and cantilever elastic beam has been widely used in devices such as micromirrors, micro-oscillators, and micro-tuners in the field of microelectromechanical systems (MEMS). The basic working principle is as follows: by combining a thin-film structure with one or more ends fixed and the rest suspended with a beam structure having elastic recovery capability, the suspended structure undergoes controllable displacement under external force and recovers to its initial state through elastic force after the external force is removed.

[0043] Specifically, in this embodiment, the cantilever membrane, as part of the movable structural layer 13, has a first driving electrode integrated thereon, and is connected to a second driving electrode disposed on the pyroelectric unit 2 via a wire (i.e., Figure 1 When a driving voltage is applied (as shown in Figure 3), an electrostatic force is generated between the two. This electrostatic force acts on the cantilever membrane in a direction perpendicular to the plane of the cantilever membrane, causing the cantilever membrane to displace or vibrate in that direction, thereby driving the first reflective structure 11, which is fixedly connected to it, to move synchronously and realize the modulation of the cavity length of the Fabry-Perot resonant cavity 1.

[0044] The cantilever elastic beam is arranged in a direction perpendicular to the cantilever film, one end of the cantilever elastic beam is connected with the cantilever film, and the other end of the cantilever elastic beam is fixed to the support structure, and the cantilever elastic beam is used to provide an elastic supporting force for the cantilever film. Under the action of an electrostatic force, the cantilever elastic beam is elastically deformed to allow the cantilever film to displace; when the driving voltage is reduced or removed, the cantilever elastic beam pushes the cantilever film back to the initial equilibrium position by relying on the elastic restoring force of the cantilever elastic beam. By reasonably designing the geometric size and material parameters of the cantilever elastic beam, the cantilever film can have a high response speed and good displacement linearity while ensuring the mechanical stability of the structure. Since the cantilever film and the cantilever elastic beam both belong to typical microstructure forms, they can be realized through mature thin film deposition, photolithography and etching processes, and have been widely verified to have good reliability and repeatability in existing micro-electro-mechanical devices. Therefore, the cantilever film and the cantilever elastic beam are introduced into the Fabry-Perot resonant cavity 1 driving structure of the application, which not only can realize the quasi-static cavity length adjustment in the first driving mode, but also can realize the high-frequency and small-amplitude periodic micro-displacement modulation in the second driving mode, thereby ensuring the implementability of the driving mode of the application from the structure and process levels.

[0045] Reference Figure 3 In further embodiments of the application, the first reflective structure 11 and the second reflective structure 12 preferably adopt a form of a multilayer reflective structure with high reflectivity. Since the Fabry-Perot resonant cavity 1 has a high reflectivity requirement, in order to obtain the required reflection characteristics, the first reflective structure 11 and the second reflective structure 12 usually need to be formed by a multilayer material stack. In the actual preparation process, the multilayer stack structure is prone to cause small undulations or warping on the surface of the reflective structure due to uneven film stress or process fluctuations, thereby reducing the relative parallelism between the first reflective structure 11 and the second reflective structure 12, and further causing local cavity length inconsistency of the working cavity, thereby affecting the stability of the resonance condition and the effective reflectivity of the Fabry-Perot resonant cavity 1.

[0046] To solve the above problems, in some specific embodiments of the application, the driving member 3 further includes a plurality of first calibration electrodes 31 and a plurality of second calibration electrodes 32, the plurality of first calibration electrodes 31 are uniformly arranged on the first reflective structure 11, the plurality of second calibration electrodes 32 are uniformly arranged on the second reflective structure 12, and the plurality of first calibration electrodes 31 and the plurality of second calibration electrodes 32 correspond to each other and are electrically connected. By applying voltages to different corresponding electrode pairs, an independently adjustable attractive force is generated between each pair of first calibration electrodes 31 and second calibration electrodes 32, thereby finely adjusting the local spacing between the first reflective structure 11 and the second reflective structure 12, and realizing calibration of the overall parallelism of the reflective structure.

[0047] With the above structural configuration, surface unevenness introduced by multi-layer stacking can be actively compensated without changing the reflective structure material and number of layers. This ensures that the first reflective structure 11 and the second reflective structure 12 maintain a good parallel relationship within the effective light spot range, thereby improving the resonance consistency of the Fabry-Perot resonator 1 and reducing resonance peak broadening and position drift. Simultaneously, since the reflective structure can maintain the designed reflectivity conditions under operating conditions, the spectral resolution and transmission stability of the Fabry-Perot resonator 1 are further enhanced, which is beneficial for improving the measurement accuracy and repeatability in the multi-element gas concentration detection process.

[0048] In some specific embodiments of the present invention, there are multiple Fabry-Perot resonators 1, each of which is used to allow light transmission through different wavelength ranges. Specifically, the multi-gas concentration detection device based on Fabry-Perot resonators 1 includes two Fabry-Perot resonators 1 arranged in parallel, each corresponding to a different infrared spectral band, used to cover the characteristic absorption ranges of different gas components during the cleaning process, thereby achieving group detection of multiple gases within a single device.

[0049] Based on the above embodiments, the present invention further utilizes the independent driving characteristics of the first calibration electrode 31 and the second calibration electrode 32 to enable the Fabry-Perot resonator 1 to have controllable cavity length adjustment capability in different operating modes. When multiple Fabry-Perot resonators 1 are arranged in parallel and their corresponding transmission wavelength ranges are close or overlap, a preset voltage can be applied to the first calibration electrode 31 and the second calibration electrode 32 corresponding to at least one resonator to make the cavity length of the resonator deviate from its target resonance condition, so that the corresponding Fabry-Perot resonator 1 operates in a non-target detection state, thereby suppressing the effective photoelectric response output of the channel. In this way, without adding additional detection channels or electrical isolation structures, the electrical coupling and signal crosstalk between different detection channels can be reduced under the condition of multiple resonators operating in parallel, thereby improving the stability of multi-band gas concentration detection results.

[0050] Reference Figure 4 In some embodiments, an active calibration mechanism based on lateral stress compensation is introduced to address the in-plane deformation of the first reflective structure 11 and the second reflective structure 12 that may occur due to variations in the stacking process. Multiple third calibration electrodes 33 are disposed on the first reflective structure 11, and corresponding fourth calibration electrodes are disposed on the second reflective structure 12. Figure 4The local control logic of the third calibration electrode 33 is taken as an example: a plurality of third calibration electrodes 33 constitute a group control unit in pairs, and a control voltage source (V symbol in the figure) and a modulation excitation source (sine wave symbol in the figure) are integrated in the loop. Specifically, a preset charge is applied by the control voltage source V, and a transverse repulsive force (indicated by the outward thick arrow in the figure) is generated by the interaction between the charges. The repulsive force acts on the film plane of the reflective structure, generating a mechanical stress similar to "stretching outward". The above-mentioned stress can actively offset the residual stress inside the first reflective structure 11, thereby correcting the plane deviation thereof. Through such in-plane stress adjustment, combined with the longitudinal spacing control between the first and second calibration electrodes, the present application not only solves the overall parallelism problem between the two reflective structures, but also ensures the absolute flatness of each reflective surface within the light spot irradiation range from a microscopic point of view, so that the Fabry-Perot resonant cavity can always maintain extremely high spectral resolution.

[0051] Referring to Table 1 below, the multi-component gas concentration detection device based on the Fabry-Perot resonant cavity 1 includes two Fabry-Perot resonant cavities 1 arranged side by side, and the two Fabry-Perot resonant cavities 1 correspond to different infrared spectral bands respectively, for covering the characteristic absorption intervals of different gas components in the cleaning process. In this embodiment, one of the Fabry-Perot resonant cavities 1 constitutes a mid-infrared channel, and the target gases corresponding thereto include gas components having significant absorption characteristics in the mid-infrared region. The optical center wavelength of the mid-infrared channel is set to about 4.42 The corresponding Fabry-Perot resonant cavity 1 adjusts the cavity length so that the resonant transmission peak thereof is located near the above-mentioned center wavelength.

[0052] In some embodiments of the present application, the DBR reflectivity of the first reflective structure 11 and the second reflective structure 12 exceeds 99.5%, which can meet the detection requirements for a detection range of 0-1000 ppm and an accuracy of 5 ppm. In order to meet the requirement for high reflectivity in this band, the first reflective structure 11 and the second reflective structure 12 of the mid-infrared channel both adopt a distributed Bragg reflector (DBR) formed by alternately stacking high-refractive-index materials and low-refractive-index materials. The high-refractive-index material is preferably silicon, and the low-refractive-index material is preferably silicon dioxide. The single-layer optical thickness of each layer is set to one-fourth of the center wavelength, and the corresponding physical thickness is, for example, about 325 nm for a silicon layer and about 762 nm for a silicon dioxide layer. By setting about 20 to 24 pairs of alternately stacked reflective layers, the total physical thickness of the distributed Bragg reflector of the mid-infrared channel is about 20 μm to 26 μm, so as to ensure the reflectivity while taking into account the manufacturability of the structure.

[0053] In the middle-wave infrared channel, the movable structure layer 13 for carrying the first reflective structure 11 is made of low-stress silicon nitride material, and its thickness is set to about 2.0-2.5 μm, so as to reduce the overall structure mass while ensuring that the cantilever film has sufficient mechanical strength, thereby facilitating the realization of high-response-speed cavity length modulation. The first driving electrode is provided in the form of a metal grid structure, for example, formed of aluminum material with a thickness of 100-200 nm, so as to provide electrostatic driving force while reducing the shielding effect on light transmission.

[0054] In the above embodiment, another Fabry-Perot resonant cavity 1 is configured as a long-wave infrared channel, and the corresponding target gas includes gas components having characteristic absorption in the long-wave infrared region. The optical center wavelength of the long-wave infrared channel is set to about 10.15 μm, and the corresponding Fabry-Perot resonant cavity 1 is adjusted in cavity length so that its resonance condition covers the absorption band of the above-mentioned gas. In order to adapt to the high reflectivity requirement under longer wavelength conditions, the first reflective structure 11 and the second reflective structure 12 of the long-wave infrared channel are formed of a distributed Bragg reflector structure in which germanium is used as a high-refractive-index material and zinc sulfide is used as a low-refractive-index material. The single-layer optical thickness of each layer is also set to one-fourth of the center wavelength, and the corresponding physical thickness is, for example, about 634 nm for a germanium layer and about 1153 nm for a zinc sulfide layer. By setting about 16-20 pairs of reflective layers, the total physical thickness of the distributed Bragg reflector structure of the long-wave infrared channel is about 28-36 μm.

[0055] Since the overall thickness of the distributed Bragg reflector structure of the long-wave infrared channel is larger and the mass is higher, in order to ensure the mechanical stability of the movable structure layer 13 during driving, the corresponding movable structure layer 13 of the long-wave infrared channel is also made of low-stress silicon nitride material, but its thickness is increased to about 3.0-3.5 μm, so as to improve the carrying capacity of the cantilever film and suppress undesired deformation. In this channel, the first driving electrode is also provided in the form of a metal grid structure, for example, formed of aluminum material with a thickness of 100-200 nm, so as to realize the same electrostatic driving mode as the middle-wave infrared channel. By arranging the above-mentioned middle-wave infrared channel and the Fabry-Perot resonant cavity 1 of the long-wave infrared channel in parallel, the detection of different gas components is functionally partitioned in the spectral dimension, which not only avoids the structural and control difficulties brought by the tuning of a single resonant cavity in an ultra-wide wavelength band, but also enables high-sensitivity detection of multiple clean gases and reaction byproducts in the same detector device, thereby improving the adaptability of the system to complex semiconductor cleaning conditions.

[0056]

[0057] In some embodiments of the present application, the multi-component gas concentration detection device based on the Fabry-Perot resonant cavity 1 is controlled by an internal control algorithm to realize the selective detection of different gas components. Specifically, when a target gas needs to be detected, the control algorithm first determines the characteristic absorption band of the target gas according to the type of the gas to be detected by calling the preset gas-infrared absorption band mapping relationship. For example, when the target gas is , the algorithm determines that its main absorption is located in the mid-infrared band, and accordingly selects the Fabry-Perot resonant cavity 1 matched with the band as the current working cavity. After determining the target resonant cavity, the control algorithm applies a driving signal to the corresponding first calibration electrode 31 and second calibration electrode 32 to make the cantilever reflection structure of the resonant cavity enter the adjustable working state; at the same time, the other Fabry-Perot resonant cavity 1 arranged in parallel remains stationary or in a non-working state, thereby avoiding the electrical or optical interference introduced by the simultaneous response of different detection channels. In some embodiments, the incident infrared light can also be mainly coupled into the selected resonant cavity through optical or circuit switching. Subsequently, the control algorithm applies a time-varying scanning voltage to the driving electrode of the selected resonant cavity to make the cantilever reflection structure produce periodic micro-displacement within a small preset range, thereby continuously changing the cavity length of the Fabry-Perot resonant cavity 1 and making its transmission center wavelength scan around the characteristic absorption peak of the target gas. For example, for , the transmission wavelength can reciprocate around about 4.26 μm. The infrared detector located below the Fabry-Perot resonant cavity 1 synchronously collects the light intensity signal transmitted through the resonant cavity. When the transmission wavelength coincides with the absorption peak of the target gas, the transmission light intensity will produce a characteristic attenuation change. The control algorithm demodulates and analyzes the collected light intensity signal, and calculates the actual concentration value of the target gas according to the corresponding relationship between the light intensity change amplitude and the gas concentration.

[0058] After completing the detection of the current gas, if another gas needs to be detected, for example , the control algorithm will stop driving the mid-infrared resonant cavity and switch to another Fabry-Perot resonant cavity 1 corresponding to the long-infrared band, and repeat the above cavity selection, driving scanning and signal demodulation process, thereby realizing the cyclic detection of different gas components. Through the above method, the selective and high-precision detection of multi-band and multi-component gas can be realized in a single device.

[0059] In some embodiments of the present application, the pyroelectric unit 2 comprises a pyroelectric layer 21, a micro-bridge 22 and a supporting substrate layer 23 arranged in sequence along the light incident direction, wherein the micro-bridge 22 is arranged between the pyroelectric layer 21 and the supporting substrate layer 23 to form a thermal isolation structure therebetween, thereby reducing the conduction loss of heat to the substrate, enhancing the temperature response amplitude of the pyroelectric unit 2 to the modulated light signal, and improving the detection sensitivity. In some specific embodiments, the micro-bridge 22 is a thin film suspended structure, and a lower electrode layer is formed on the surface of the micro-bridge 22. The lower electrode layer is directly deposited on the surface of the micro-bridge 22 during the manufacturing process, and forms a physical connection with the micro-bridge 22 material in a close combination, thereby ensuring good mechanical stability and electrical continuity. The lower electrode is electrically connected to the electrode pad on the supporting substrate layer 23 through the metal wiring or embedded wire arranged on the supporting beam of the micro-bridge 22, and is further connected to the back-end signal readout circuit to realize effective extraction of the pyroelectric signal. Above the micro-bridge 22, the pyroelectric layer 21 is formed on the lower electrode for generating a polarization charge corresponding to the temperature change after absorbing the modulated infrared light. An upper electrode is formed on the upper surface of the pyroelectric layer 21, which directly covers and is electrically connected to the pyroelectric layer 21 for efficiently collecting the charge signal generated by the pyroelectric effect.

[0060] In some embodiments, the pyroelectric unit 2 is also arranged opposite to the lower reflective structure of the Fabry-Perot resonant cavity 1. The lower reflective structure is a distributed Bragg reflector composed of multiple layers of dielectric materials, which is an electrically insulating structure itself. The upper electrode and the lower reflective structure do not form a direct electrical connection, but form a capacitive coupling relationship through the pyroelectric layer 21 and the spacing medium therebetween, thereby ensuring normal output of the pyroelectric signal while achieving electrical isolation to avoid interference of the driving voltage or parasitic electrical signal on the pyroelectric signal acquisition. Through the above structure arrangement, the micro-bridge 22 provides good thermal isolation effect while ensuring reliable electrical connection between the lower electrode and the substrate, and the electrical isolation between the upper electrode and the lower reflective structure effectively improves the anti-interference ability of the pyroelectric signal, thereby further improving the signal-to-noise ratio and detection sensitivity of the pyroelectric unit 2 in the modulated infrared detection scenario.

[0061] In the present application, unless otherwise explicitly specified and limited, the terms "connection", "fixation" and the like should be understood in a broad sense, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection; can be direct connection, or indirect connection through intermediate medium; can be internal communication of two elements or interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0062] In addition, if the description of "first", "second" and the like is involved in the embodiments of the present application, the description of "first", "second" and the like is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of the ordinary skilled in the art, when the combination of technical solutions appears contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist, nor in the protection scope of the present application.

[0063] The above is only a specific implementation of the embodiments of the present application, but the protection scope of the embodiments of the present application is not limited to this, any change or replacement within the technical scope disclosed by the embodiments of the present application should be covered in the protection scope of the embodiments of the present application. Therefore, the protection scope of the embodiments of the present application should be subject to the protection scope of the claims.

Claims

1. A multi-component gas concentration detector based on a Fabry-Perot resonator, characterized by, The application relates to a Fabry-Perot resonant cavity, which comprises a first reflecting structure and a second reflecting structure arranged oppositely, a working cavity is formed between the first reflecting structure and the second reflecting structure, and the cavity length of the working cavity is adjustable. A pyroelectric unit has a sensing area in an optical path, the pyroelectric unit is located behind the optical path of the Fabry-Perot resonant cavity, is used for receiving light selected by the Fabry-Perot resonant cavity and generating an electric signal. A driving member is connected with the first reflecting structure or the second reflecting structure, is used for driving the movement of the first reflecting structure or the second reflecting structure to change the cavity length, and has a first driving mode and a second driving mode. The first driving mode is used for adjusting the cavity length to a resonant length corresponding to a characteristic absorption wave band of a target gas component. The second driving mode drives the first reflecting structure or the second reflecting structure to perform periodic micro-displacement on the basis of the resonant length set by the first driving mode, so as to modulate the intensity of incident light. The Fabry-Perot resonant cavity further comprises:

2. The Fabry-Perot resonant cavity-based multi-component gas concentration detector according to claim 1, wherein, A movable structure layer, the first reflecting structure is fixedly connected with the movable structure layer and is arranged on the lower surface of the movable structure layer, and the second reflecting structure is located between the first reflecting structure and the pyroelectric unit. The driving member is connected with the movable structure layer, is used for driving the movable structure layer to displace along a direction perpendicular to the second reflecting structure, and changes the cavity length of the Fabry-Perot resonant cavity. The movable structure layer comprises an electric functional layer and a mechanical support layer, the mechanical support layer is arranged at the bottom of the electric functional layer, is used for providing elastic force and supporting the electric functional layer, and the movable structure layer is a light-transmitting layer.

3. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 2, wherein, Further comprising:

4. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 2, wherein, A sealed cavity is arranged in the light incidence direction of the Fabry-Perot resonant cavity, is used for providing a vacuum-sealed space for the movement of the movable structure layer. The Fabry-Perot resonant cavity has a plurality of Fabry-Perot resonant cavities, and the plurality of Fabry-Perot resonant cavities are respectively used for allowing light in different wave band ranges to transmit through.

5. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 3, wherein, The driving member comprises a first driving electrode and a second driving electrode, the first driving electrode is arranged on the electric functional layer, the second driving electrode is arranged on the pyroelectric unit, and the first driving electrode and the second driving electrode are electrically connected and are used for driving the linear displacement of the movable structure layer.

6. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 5, wherein, The driving member further comprises a plurality of first calibration electrodes and a plurality of second calibration electrodes, the plurality of first calibration electrodes are uniformly arranged on the first reflecting structure, the plurality of second calibration electrodes are uniformly arranged on the second reflecting structure, the plurality of first calibration electrodes and the plurality of second calibration electrodes are arranged one by one and are electrically connected.

7. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 6, wherein, An attractive force can be generated between each first calibration electrode and second calibration electrode, and the attractive force is independently adjustable.

8. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 7, wherein, The mechanical support layer comprises a cantilever membrane and a cantilever elastic beam, the first driving electrode can drive the cantilever membrane to perform periodic vibration, the cantilever elastic beam is arranged along a direction perpendicular to the cantilever membrane, and the cantilever elastic beam is used for providing elastic support force for the cantilever membrane.

9. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 6, wherein, ​ 10. The Fabry-Perot resonant cavity-based multi-component gas concentration detector of claim 1, wherein, The pyroelectric unit comprises a pyroelectric layer, a microbridge and a support substrate layer distributed along the light incidence direction, the microbridge being used to thermally isolate the pyroelectric layer from the support substrate layer.

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