A dual-cavity metasurface uncooled infrared detector and its fabrication method

Abstract

This invention discloses a dual-cavity metasurface uncooled infrared detector and its fabrication method. The detector includes a substrate and a detector body, the detector body comprising two resonant cavity structures. The first resonant cavity structure includes a reflective layer, a dielectric layer, an electrical connection structure, a first cavity support layer, a thermistor layer, a thermistor protection layer, a spectral tuning layer, and a metasurface absorption structure. The second resonant cavity structure includes a support layer and a metasurface antenna structure. The support layer and the metasurface antenna structure of the second cavity together constitute the second cavity metasurface absorption structure. The first cavity metasurface absorption structure adopts a "MIM" sandwich structure, and the second cavity metasurface absorption structure adopts an "IMI" structure. This dual-cavity metasurface uncooled infrared detector effectively improves the problem of uneven heat absorption in the photosensitive layer of common "umbrella"-shaped double-layer uncooled detectors, greatly enhancing the absorption rate of the uncooled detector and achieving dual-band broadband absorption.

Description

Technical Field

[0001] This invention belongs to the field of infrared detection, and particularly relates to a dual-cavity metasurface uncooled infrared detector and its preparation method. Background Technology

[0002] An uncooled detector is a detector that operates at room temperature and converts incident infrared thermal radiation signals into electrical signals. It requires no cooling device, operates at room temperature, and boasts numerous advantages such as fast start-up, low power consumption, small size, light weight, long lifespan, and low cost. Among these, the VOx microbolometer is the most widely used uncooled detector, finding broad application in both military and civilian fields. However, as detector pixel sizes continue to shrink, their effective absorption area decreases sharply with the square of the side length, severely hindering the development of uncooled detectors. Enhancing the absorption efficiency of the surface elements is crucial for improving the performance of uncooled detectors. Generally, absorption enhancement structures are added during the design of infrared detectors to compensate for the insufficient absorption characteristics of the sensing element itself.

[0003] Multi-band detection enables the detection of multiple different types of targets using a single detector. This results in a wider operating band and superior detection performance, making it a crucial research direction for infrared detectors. Currently, imaging techniques targeting mid-wave and long-wave frequencies are hot topics in infrared research, each offering unique advantages. Long-wave technology has strong smoke penetration capabilities, providing excellent imaging results; mid-wave technology, in environments such as rain, offers superior imaging performance compared to long-wave infrared and is widely used in missile early warning systems. However, most current uncooled detectors are single-band; dual-band uncooled detectors still require further development and refinement.

[0004] A metasurface is a combination of subwavelength unit cells arranged on a plane according to specific requirements. Through the rational design of the unit cell structure, arrangement, and material selection, various properties of light can be modulated. Metasurfaces possess the characteristics of "artificial atoms," meaning that we can independently design the structure and arrangement of each unit cell at a microscopic level, thereby achieving independent control of light. Therefore, metasurfaces provide a universal platform for developing detection devices. Compared with traditional modulation methods, metasurfaces can be mass-produced using semiconductor chip industry standards, which not only reduces device size and cost but also provides a new solution for mass production and improved efficiency. In recent years, people have gradually recognized the application prospects of metasurfaces in this field, and the concept of "metasurface perfect absorbers" has been proposed.

[0005] As detector pixel sizes continue to decrease, their effective absorption area sharply diminishes with the square of the side length, severely restricting the development of uncooled detectors. Enhancing the absorption efficiency of surface elements is crucial for improving the performance of uncooled detectors. Generally, absorption enhancement structures are added during the design of infrared detectors to compensate for the insufficient absorption characteristics of the sensing elements themselves.

[0006] Most current uncooled detectors are single-band. Dual-band uncooled detectors often have insufficient absorption bands or absorption effects, and require further development and improvement. For example, CN 103776546 A, CN 110118604 A, CN115406540 ​​A, and CN 205246224U only target single-band absorption enhancement in the long infrared region, limiting their application scenarios. CN107741278A also uses a metasurface structure (single layer) to enhance and regulate the absorption of uncooled detectors, but it reflects that the absorption band is the entire single band. This means that there are interference bands other than the useful mid-infrared band (3um-5um) and long infrared band (8um-14um). In addition, there are also problems such as either only being able to achieve single-band absorption or having poor absorption effects. Summary of the Invention

[0007] The technical problem to be solved by this invention is: how to improve the problem of uneven heat absorption of the photosensitive layer in common "umbrella"-shaped double-layer uncooled detectors, overcome the problem of sharp reduction in absorption rate as the detector pixel size continues to decrease, and achieve dual-band broadband absorption. The purpose is to provide a dual-cavity metasurface uncooled infrared detector that can achieve dual-band broadband absorption.

[0008] The technical solution of this invention is as follows:

[0009] A dual-cavity metasurface uncooled infrared detector includes a semiconductor substrate, a readout circuit, and a detector body with an integrated metasurface dual-cavity structure. The detector body includes a first cavity structure and a second cavity structure, with the second cavity structure disposed on the first cavity structure. The first cavity structure includes a reflective layer, a dielectric layer, an electrical connection structure, a first cavity support layer, a thermistor layer, a thermistor protection layer, a spectral tuning layer, and a "MIM" (metal / insulator / metal) metasurface absorption layer. The second cavity structure includes a second cavity support layer and a second cavity metasurface antenna structure, which together constitute the second cavity "IMI" (insulator / metal / insulator) metasurface absorption structure.

[0010] Furthermore, in the dual-cavity metasurface uncooled infrared detector, the semiconductor substrate has a reflective layer, which is deposited from highly reflective metal Al and has a thickness of 50nm-200nm.

[0011] Furthermore, the reflective layer is provided with the dielectric layer, which is a SiNx insulating dielectric layer with a thickness of 20nm-100nm.

[0012] Furthermore, the first cavity support layer is provided directly above the dielectric layer, and the material of the first cavity support layer is SiNx with a thickness of 100nm-300nm.

[0013] Furthermore, an electrical connection structure is provided between the dielectric layer and the first cavity support layer. The electrical connection structure includes two electrode connection piers located on the diagonal of the dielectric layer, and bridge legs connecting the piers to the first cavity support layer / thermosensitive layer / thermosensitive protective layer. The diagonal piers include a first pier and a second pier; the bridge legs include a first bridge leg and a second bridge leg; the piers are hollow octagonal prisms with SiNx / Ti / SiNx sandwich structure; the bridge legs are slender "U"-shaped strips composed of SiNx / Ti / SiNx film system.

[0014] Furthermore, the first cavity support layer is provided with the thermosensitive layer, the thermosensitive layer material is VOx, and the thickness is 50nm-200nm.

[0015] Furthermore, the thermal protective layer is provided on the thermal layer, and the thermal protective layer is made of SiNx with a thickness of 100nm-300nm.

[0016] Furthermore, a spectral adjustment layer is provided on the thermal protective layer, the spectral adjustment layer is made of SiO2 and has a thickness of 10nm-50nm.

[0017] Furthermore, the spectral adjustment layer is provided with a "MIM" metasurface absorption layer, the film system of which is a Ti / SiNx / Ti sandwich layer. The bottom Ti is an ultrathin continuous film, and a blocky / cylindrical SiNx / Ti film antenna is provided on the bottom Ti. The antenna period is 0.5um-3um, the antenna duty cycle is 0.5-0.9, and the thickness of the Ti / SiNx / Ti sandwich film system is 5nm-20nm, 20nm-100nm, and 5nm-10nm, respectively.

[0018] Furthermore, the "MIM" metasurface absorption layer is provided with a second cavity support layer, which is a SiNx continuous film with a thickness of 50nm-100nm.

[0019] Furthermore, the second cavity support layer is provided with the "MI" (i.e., "metal / insulator") metasurface absorbing antenna structure. At the same time, the second cavity support layer and the metasurface absorbing antenna structure together constitute an "IMI" metasurface absorbing structure. The metasurface absorbing antenna structure is a block / cylindrical SiNx / Ti film antenna with an antenna period of 0.5um-5um, an antenna duty cycle of 0.5-0.9, and SiNx / Ti / SiNx sandwich film thicknesses of 50nm-200nm, 5nm-10nm, and 10nm-100nm, respectively.

[0020] The spectral modulation layer of this invention is provided with a "MIM" metasurface absorption layer, the film system of which is a Ti / SiNx / Ti sandwich layer. The bottom Ti is an ultrathin continuous film, and a blocky / cylindrical SiNx / Ti film antenna is provided on the bottom Ti. The antenna period is 0.5um-3um, the antenna duty cycle is 0.5-0.9, and the thickness of the Ti / SiNx / Ti sandwich film system is 5nm-20nm, 20nm-100nm, and 5nm-10nm, respectively.

[0021] The "MIM" metasurface absorption layer of the present invention is provided with a second cavity support layer, which is a SiNx continuous film with a thickness of 50nm-100nm.

[0022] The second cavity support layer of the present invention is provided with the "MI" metasurface absorbing antenna structure. At the same time, the second cavity support layer and the metasurface absorbing antenna structure thereon together constitute the "IMI" metasurface absorbing structure. The metasurface absorbing antenna structure is a block / cylindrical SiNx / Ti film antenna with an antenna period of 0.5um-5um, an antenna duty cycle of 0.5-0.9, and SiNx / Ti / SiNx sandwich film thicknesses of 50nm-200nm, 5nm-10nm, and 10nm-100nm, respectively.

[0023] The beneficial effects of this invention include:

[0024] The dual-cavity metasurface structure of this invention, on the one hand, effectively improves the problem of uneven heat absorption in the photosensitive layer of common "umbrella"-shaped dual-layer uncooled detectors through the design of the lower metasurface structure; on the other hand, under the integrated and optimized dual-cavity height of the two metasurface structures, it further enhances the absorptivity of the uncooled detector, enabling the detector to achieve near-perfect absorption in the long-infrared band and also exhibiting excellent broadband absorption characteristics in the mid-infrared band. This effectively improves the optical and thermal performance of long-wave infrared uncooled detectors and dual-band (mid-wave and long-wave) uncooled detectors. Attached Figure Description

[0025] Figure 1This is a schematic cross-sectional view of the first cavity structure in this invention.

[0026] Figure 2 This is a schematic cross-sectional view of the dual-cavity metasurface uncooled infrared detector in this invention.

[0027] Figure 3 This is a schematic diagram of the first cavity structure in this invention.

[0028] Figure 4 This is a schematic diagram of the dual-cavity metasurface uncooled infrared detector in this invention.

[0029] Figure 5 This is a comparison of the infrared absorption spectra of the dual-cavity metasurface uncooled infrared detector in this invention and a conventional uncooled detector (without integrated dual-cavity metasurface).

[0030] The components include: 1. Semiconductor substrate; 2. Readout circuit; 3. Reflective layer; 4. Dielectric layer; 5. First cavity support layer; 61. First pier Ti electrode layer; 62. Second pier Ti electrode layer; 71. First pier SiNx electrode protective layer; 71. Second pier SiNx electrode protective layer; 81. First leg Ti electrode layer; 82. Second leg Ti electrode layer; 91. First leg SiNx electrode protective layer; 92. Second leg SiNx electrode protective layer; 10. Thermistor layer; 11. 12. Thermal protection layer; 13. Spectral modulation layer; 14. "MIM" metasurface bottom layer Ti ultrathin continuous film; 15. "MIM" metasurface intermediate dielectric antenna layer; 16. "MIM" metasurface upper layer Ti antenna layer; 17. Second cavity support layer; 18. Second cavity metasurface antenna structure thermal conductive layer; 19. Second cavity metasurface antenna structure thermal conductive protection layer; 20. "MI" metasurface absorbing antenna structure intermediate Ti antenna layer; 11. "MI" metasurface absorbing antenna structure upper layer SiNx layer; Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1-4As shown, a dual-cavity metasurface uncooled infrared detector includes a semiconductor substrate 1, a readout circuit 2, and a detector body with an integrated metasurface dual-cavity structure. The detector body includes a first cavity structure and a second cavity structure, with the second cavity structure disposed on the first cavity structure. The first cavity structure includes a reflective layer 3, a dielectric layer 4, an electrical connection structure, a first cavity support layer 5, a thermistor layer 10, a thermistor protection layer 11, a spectral adjustment layer 12, and a "MIM" metasurface absorption layer. The second cavity structure includes a second cavity support layer 16 and a second cavity metasurface antenna structure. The second cavity support layer and the second cavity metasurface antenna structure together constitute the second cavity "IMI" metasurface absorption structure.

[0033] The semiconductor substrate has a reflective layer 3, which makes the overall transmittance of the detector zero by reflecting optical light back to the absorption film system. The reflective layer 3 is deposited from highly reflective metal Al and has a thickness of 50nm-200nm.

[0034] The reflective layer 3 is provided with the dielectric layer 4, which is a SiNx insulating dielectric layer with a thickness of 20nm-100nm, and is used to protect the structure below the reflective layer 3.

[0035] The first cavity support layer 5 is provided directly above the dielectric layer 4. The first cavity support layer 5 is made of SiNx and has a thickness of 100nm-300nm, which serves to support the entire upper structure.

[0036] An electrical connection structure is provided between the dielectric layer 4 and the first cavity support layer 5. The electrical connection structure includes two electrode connecting piers located on the diagonal of the dielectric layer and bridge legs connecting the piers to the first cavity support layer / thermosensitive layer / thermosensitive protective layer. The diagonal piers are the first pier and the second pier; the bridge legs are the first bridge leg and the second bridge leg. The piers are SiNx / Ti / SiNx sandwich hollow octagonal prisms. The first pier includes a part of the first cavity support layer 5, a first pier Ti electrode layer 61, and a first pier SiNx electrode protective layer 71; the second pier includes a part of the first cavity support layer 5, a second pier Ti electrode layer 62, and a second pier SiNx electrode protective layer 72. The two piers together serve as the support columns for the entire upper layer and are also electrically connected to the bridge legs and the readout circuit 2. The bridge legs are U-shaped elongated strips composed of SiNx / Ti / SiNx film systems. The first bridge leg includes a portion of the first cavity support layer 5, a first bridge leg Ti electrode layer 81, and a first bridge leg SiNx electrode protective layer 91. The second bridge leg includes a portion of the second cavity support layer 5, a second bridge leg Ti electrode layer 82, and a second bridge leg SiNx electrode protective layer 92. The two bridge legs electrically connect the bridge pier and the thermistor layer 10, and reduce the thermal conductivity of the device, thereby improving the overall detector performance.

[0037] The first cavity support layer 5 is provided with the thermosensitive layer 10. The thermosensitive layer is made of VOx material and has a thickness of 50nm-200nm. The resistance of the thermosensitive layer 10 changes after receiving radiant heat, thereby generating information that can be converted.

[0038] The thermal protective layer 11 is provided on the thermal layer 10. The thermal protective layer is made of SiNx and has a thickness of 100nm-300nm.

[0039] The thermal protective layer 11 is provided with a spectral adjustment layer 12. The spectral adjustment layer is made of SiO2 and has a thickness of 10nm-50nm. SiO2 is not only an excellent passivation material, but also plays a key role in adjusting the spectrum and stress.

[0040] The spectral adjustment layer 12 is provided with a "MIM" metasurface absorption layer, which is a Ti / SiNx / Ti sandwich layer. The bottom Ti layer is an ultrathin continuous film, which can uniformly transfer the heat absorbed by the upper "MIM" metasurface absorption structure to the thermistor layer 10 through the thermistor protection layer 11 and the spectral adjustment layer 12. A blocky / cylindrical SiNx / Ti film antenna is provided on the bottom Ti layer. The "MIM" metasurface absorption layer includes a "MIM" metasurface bottom Ti ultrathin continuous film 13, a "MIM" metasurface intermediate dielectric antenna layer 14, and a "MIM" metasurface upper Ti antenna layer 15. The antenna period is 0.5um-3um, the antenna duty cycle is 0.5-0.9, and the thickness of the Ti / SiNx / Ti sandwich film system is 5nm-20nm, 20nm-100nm, and 5nm-10nm, respectively.

[0041] The "MIM" metasurface absorption layer is provided with a second cavity support layer 16, which is a SiNx continuous film with a thickness of 50nm-100nm.

[0042] The second cavity support layer 16 is provided with the "MI" metasurface absorbing antenna structure. The second cavity support layer 16 and the metasurface absorbing antenna structure together constitute the "IMI" metasurface absorbing structure. At the same time, the heat absorbed by the "IMI" metasurface absorbing structure is transferred to the lower layer through the thermal conductive layer 17 of the second cavity metasurface antenna structure. The thermal conductive layer 17 of the second cavity metasurface antenna structure is protected by the thermal conductive protection layer 18 of the second cavity metasurface antenna structure. The metasurface absorbing antenna structure is a block / cylindrical SiNx / Ti film antenna. The metasurface absorbing antenna structure includes the middle Ti antenna layer 19 of the "MI" metasurface absorbing antenna structure and the upper SiNx layer 20 of the "MI" metasurface absorbing antenna structure. The antenna period is 0.5um-5um, the antenna duty cycle is 0.5-0.9, and the thickness of the SiNx / Ti / SiNx sandwich film system is 50nm-200nm, 5nm-10nm, and 10nm-100nm, respectively.

[0043] This invention also relates to a method for fabricating a dual-cavity metasurface uncooled infrared detector, comprising the following steps:

[0044] Step 1: Clean the substrate containing the readout circuit, deposit 50nm-200nm Al, deposit 20nm-100nm SiNx, use a photolithography mask to create electrode patterns, and etch the corresponding Al and SiNx to expose the readout circuit electrode pairs.

[0045] Step 2: Spin-coat polyimide on the dielectric layer 4 to form a first cavity sacrificial layer with a thickness of 1um-4um. Use a photolithography mask to create the contact hole pattern of the bridge pier and readout circuit. Etch the first cavity sacrificial layer at the contact hole to expose the electrode pair.

[0046] Step 3: Deposit 100nm-300nm SiNx, 50nm-200nm VOx, 100nm-300nm SiNx, and 10nm-50nm SiO2 on the sacrificial layer of the first cavity, respectively. Use a photolithography mask to fabricate the pattern of the first cavity support layer 5, thermistor layer 10, thermistor protection layer 11, and spectral adjustment layer 12. Etch excess SiNx, VOx, and SiO2 materials to form the first cavity support layer 5, the thermistor layer 10, the thermistor protection layer 11, the spectral adjustment layer 12, and the thermal insulation microbridges and corresponding electrical connection holes.

[0047] Step 4: After completing the previous step, deposit Ti of 50nm-200nm and SiNx of 100nm-300nm respectively. Use a photolithography mask to fabricate the electrode pattern of the electrical connection structure, and etch the excess Ti and SiNx materials to form the electrical connection structure (including the pier and the leg).

[0048] Step 5: Deposit 5nm-20nm Ti on the thermal protective layer 11, use a photolithography mask to create an ultrathin continuous Ti film pattern, etch excess Ti material, and form the "MIM" metasurface bottom layer Ti ultrathin continuous film 13.

[0049] Step 6: Deposit 20nm-100nm SiNx and 5nm-10nm Ti on the bottom Ti ultrathin continuous film 13 of the “MIM” metasurface, respectively. Use a photolithography mask to fabricate the block / cylindrical SiNx / Ti film antenna pattern, and etch excess Ti and SiNx materials to form the “MIM” metasurface intermediate dielectric antenna layer 14 and the “MIM” metasurface upper Ti antenna layer 15.

[0050] Step 7: After completing the previous step, spin-coat polyimide to create a second cavity sacrificial layer with a thickness of 1um-4um. Use a photolithography mask to create contact holes between the second cavity support layer 16 and the upper Ti antenna layer 15 of the "MIM" metasurface. Etch the exposed second cavity sacrificial layer to expose the contact holes.

[0051] Step 8: After completing the previous step, deposit 50nm-200nm SiNx, 5nm-10nm Ti, and 10nm-100nm SiNx respectively. Use a photolithography mask to fabricate the metasurface absorbing antenna structure pattern, and etch excess Ti and SiNx materials to form the “IMI” metasurface absorbing structure.

[0052] Step 9: Remove the sacrificial layer to complete the fabrication of the dual-cavity metasurface uncooled infrared detector of the present invention.

Claims

1. A dual-cavity metasurface uncooled infrared detector, characterized in that: The dual-cavity metasurface uncooled infrared detector includes a semiconductor substrate (1), a readout circuit (2), and a detector body. The detector body includes a first cavity structure and a second cavity structure arranged sequentially from bottom to top. The first cavity structure includes a first cavity body, which consists of a reflective layer (3) located below, a dielectric layer (4) located in the middle, a first cavity support layer (5) located directly above the dielectric layer (4), and electrical connection structures located at the left and right ends of the first cavity body for connecting the dielectric layer (4) and the first cavity support layer (5); the reflective layer (3) is disposed on a semiconductor substrate, and the dielectric layer (4) is disposed on the reflective layer (3); The first cavity structure further includes a thermosensitive layer (10) disposed on the first cavity support layer (5), a thermosensitive protective layer (11) disposed on the thermosensitive layer (10), a spectral adjustment layer (12) disposed on the thermosensitive protective layer (11), and a "MIM" metasurface absorption layer disposed on the spectral adjustment layer (12); The second cavity structure includes a second cavity support layer (16) and a second cavity metasurface antenna structure. The second cavity support layer (16) is provided with a "MI" metasurface absorbing antenna structure. The second cavity support layer (16) and the second cavity metasurface antenna structure together constitute the second cavity "IMI" metasurface absorbing structure. The "MIM" metasurface absorption layer is a Ti / SiNx / Ti sandwich structure. The bottom Ti layer is an ultrathin continuous film used to uniformly transfer the heat absorbed by the upper "MIM" metasurface absorption structure to the thermal layer (10) through the thermal protection layer (11) and the spectral adjustment layer (12). A block or cylindrical SiNx / Ti film antenna is provided on the bottom Ti layer. The "MIM" metasurface absorption layer includes a "MIM" metasurface bottom Ti ultrathin continuous film (13), a "MIM" metasurface intermediate dielectric antenna layer (14), and a "MIM" metasurface upper Ti antenna layer (15) arranged sequentially. The thickness of the ultrathin continuous film is 5nm-10nm. It also includes a heat-conducting layer (17) for transferring the heat absorbed by the "IMI" metasurface absorbing structure to the lower second cavity metasurface antenna structure heat-conducting layer (17), which is protected by a second cavity metasurface antenna structure heat-conducting protection layer (18); the second cavity "IMI" metasurface absorbing structure includes a second cavity support layer (16) and the "MI" metasurface absorbing antenna structure, the "MI" metasurface absorbing antenna structure includes an intermediate Ti antenna layer (19) and an upper SiNx layer (20) of the "MI" metasurface absorbing antenna structure, and the "MI" metasurface absorbing antenna structure is a block or cylindrical Ti / SiNx film antenna.

2. The dual-cavity metasurface uncooled infrared detector according to claim 1, characterized in that: The electrical connection structure includes two electrode connection piers located on the diagonal of the dielectric layer (4) that are electrically connected to the readout circuit (2), and two bridge legs that realize the electrical connection between the two electrode connection piers and the thermistor layer (10).

3. The dual-cavity metasurface uncooled infrared detector according to claim 2, characterized in that: The pier is a hollow octagonal prism, which is composed of a sandwich structure formed by a first cavity support layer (5), a pier electrode layer (61, 62) and a pier electrode protective layer (71, 72). The first cavity support layer (5) is located on the outer layer of the pier, the pier electrode protective layer (71, 72) is located on the inner layer of the pier, and the pier electrode layer (61, 62) is located between the first cavity support layer (5) and the pier electrode protective layer (71, 72). The bottom of the pier is connected to the dielectric layer (4) by the first cavity support layer (5), and the bottom of the pier is connected to the readout circuit (2) by the pier electrode layer (61, 62) and the pier electrode protective layer (71, 72). The bridge leg is a U-shaped slender strip, which is composed of a sandwich structure formed by a first cavity support layer (5), a bridge leg electrode layer (81,82) and a bridge leg electrode protective layer (91,92). The bridge leg is connected to the bridge pier electrode layer (61,62) by the bridge leg electrode layer (81,82), and the bridge leg is connected to the bridge pier electrode protective layer (71,72) by the bridge leg electrode protective layer (91,92). The first cavity support layer (5) is located inside the first cavity body of the bridge leg, and the bridge leg electrode protective layer (91,92) is located outside the first cavity body.

4. The dual-cavity metasurface uncooled infrared detector according to claim 2, characterized in that: The two electrode-connected piers are the first pier and the second pier, respectively. The first pier includes a first pier electrode layer (61) and a first pier electrode protective layer (71); the second pier includes a second pier electrode layer (62) and a second pier electrode protective layer (72). The two piers together serve as the supporting columns of the entire superstructure. The bridge legs include a first bridge leg and a second bridge leg. The first bridge leg includes a first bridge leg electrode layer (81) and a first bridge leg electrode protection layer (91). The second bridge leg includes a second bridge leg electrode layer (82) and a second bridge leg electrode protection layer (92). The two bridge legs are electrically connected to the two bridge piers and the thermistor layer (10) on the one hand, and on the other hand, they are used to reduce the thermal conductivity of the device and improve the overall detector performance.

5. The dual-cavity metasurface uncooled infrared detector according to claim 3, characterized in that: The reflective layer (3) is deposited from highly reflective metal Al, the dielectric layer (4) is a SiNx insulating dielectric layer, the first cavity support layer (5), the pier electrode protection layer (71,72) and the leg electrode protection layer (91,92) are made of SiNx, the pier electrode layer (61,62) and the leg electrode layer (81,82) are made of Ti, the thermistor layer (10) is made of VOx, the thermistor protection layer (11) is made of SiNx, and the spectral adjustment layer (12) is made of SiO2.

6. The dual-cavity metasurface uncooled infrared detector according to claim 1, characterized in that: The thickness of the reflective layer (3) is 50nm-200nm; The thickness of the dielectric layer (4) is 20nm-100nm; The thickness of the first cavity support layer (5) is 100nm-300nm; The thickness of the thermal layer (10) is 50nm-200nm; The thickness of the thermal protective layer (11) is 100nm-300nm; The thickness of the spectral adjustment layer (12) is 10nm-50nm.

7. The dual-cavity metasurface uncooled infrared detector according to claim 1, characterized in that: The second cavity support layer is a SiNx continuous film with a thickness of 50nm-100nm; The Ti / SiNx film antenna has an antenna period of 0.5µm–5µm and an antenna duty cycle of 0.5–0.

9. The thicknesses of the SiNx / Ti / SiNx interlayers in the "IMI" metasurface absorption structure are 50nm-200nm, 5nm-10nm, and 10nm-100nm, respectively.

8. A method for fabricating a dual-cavity metasurface uncooled infrared detector as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Clean the substrate containing the readout circuit, deposit 50nm-200nm Al, deposit 20nm-100nm SiNx, use a photomask to fabricate the electrode pattern, and etch the corresponding Al and SiNx to expose the readout circuit electrode pair. Step 2: Spin-coat polyimide to form a first cavity sacrificial layer on the dielectric layer (4) with a thickness of 1um-4um. Use a photolithography mask to form the contact hole pattern of the bridge pier and the readout circuit. Etch the first cavity sacrificial layer at the contact hole to expose the electrode pair. Step 3: Deposit 100nm-300nm SiNx, 50nm-200nm VOx, 100nm-300nm SiNx, and 10nm-50nm SiO2 on the sacrificial layer of the first cavity, respectively. Use a photolithography mask to fabricate the pattern of the first cavity support layer (5), thermistor layer (10), thermistor protection layer (11), and the spectrum adjustment layer (12). Etch excess SiNx, VOx, and SiO2 materials to form the first cavity support layer (5), the thermistor layer (10), the thermistor protection layer (11), the spectrum adjustment layer (12), and the thermal insulation microbridge and corresponding electrical connection holes. Step 4: After completing the previous step, deposit Ti of 50nm-200nm and SiNx of 100nm-300nm respectively. Use a photolithography mask to fabricate the electrode pattern of the electrical connection structure, and etch the excess Ti and SiNx materials to form the electrical connection structure including the bridge pier and the bridge leg. Step 5: Deposit 5nm-20nm Ti on the thermal protective layer (11), use a photolithography mask to create an ultrathin continuous Ti film pattern, etch excess Ti material, and form the "MIM" metasurface bottom layer Ti ultrathin continuous film (13). Step 6: Deposit 20nm-100nm SiNx and 5nm-10nm Ti on the bottom Ti ultrathin continuous film (13) of the "MIM" metasurface, respectively. Use a photolithography mask to fabricate a block or cylindrical SiNx / Ti film antenna pattern, and etch excess Ti and SiNx materials to form the "MIM" metasurface intermediate dielectric antenna layer (14) and the "MIM" metasurface upper Ti antenna layer (15). Step 7: After completing the previous step, spin-coat polyimide to create a second cavity sacrificial layer with a thickness of 1um-4um. Use a photolithography mask to create contact holes between the second cavity support layer (16) and the upper Ti antenna layer (15) of the "MIM" supersurface. Etch the exposed second cavity sacrificial layer to expose the contact holes. Step 8: After completing the previous step, deposit 50nm-200nm SiNx, 5nm-10nm Ti, and 10nm-100nm SiNx respectively. Use a photolithography mask to fabricate the metasurface absorption antenna structure pattern, and etch excess Ti and SiNx materials to form the "IMI" metasurface absorption structure. Step 9: Remove the sacrificial layer to prepare a dual-cavity metasurface uncooled infrared detector.

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