Antenna-coupled microbridge structure for a small-pixel microbolometer and method of fabrication

Abstract

The application discloses an antenna-coupled micro-bridge structure for a small-pixel microbolometer and a preparation method thereof, and belongs to the technical field of photoelectric detection. The spiral antenna and the electrode bridge leg are arranged alternately, the proportion of the small-pixel micro-bridge structure thermal isolation support bridge leg is improved, the bridge leg is lengthened, the thermal conductivity is reduced, and the temperature rise of the microbolometer is improved; when the spiral antenna arm is used for coupling the thermal sensitive unit to receive infrared radiation, the absorption of light energy can be more concentrated on the thermal sensitive unit, the temperature rise of the thermal sensitive unit is further improved under the condition that the total light absorption rate of the device is similar, the effective absorption area of the micro-bridge structure is equivalent to being increased, compared with the traditional microbolometer, energy can be better collected, and the detection efficiency is improved; while low thermal conductivity and high absorption rate are obtained, the thermal mass of the micro-bridge structure is reduced; the double-layer micro-bridge structure of the traditional upper absorption layer and the lower thermal isolation layer is replaced, the preparation process is simplified, and the device manufacturing cost can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, and more specifically, relates to an antenna coupling microbridge structure and its fabrication method for a small pixel microbolometer. Background Technology

[0002] Infrared thermal imaging technology extends human visual perception beyond the visible wavelength, enabling us to see in the dark, identify targets in dust or smoke, measure heat, and detect and identify chemical substances. The core detection element of an infrared thermal imaging system is the infrared detector, which can be categorized as cooled or uncooled detectors based on its operating temperature. A microbolometer is a typical example of a resistive uncooled infrared detector, utilizing the temperature-dependent changes in the thermistor value to convert photothermal signals into electrical signals for infrared detection. Uncooled microbolometer infrared focal plane arrays offer advantages such as small size, light weight, low cost, and low power consumption, and have been widely applied in thermal imaging fields such as medical imaging, thermal imaging, night vision, firefighting, surveillance, predictive maintenance, and industrial process control.

[0003] Uncooled infrared focal plane arrays (IRFPAs) have been continuously evolving towards smaller pixel pitches, from the early 50μm pitch to the current mainstream 12μm and 10μm pitches, with further reductions to 8μm and 6μm underway. As pixel pitches shrink, the yield of FPAs per wafer increases, which reduces the manufacturing cost of uncooled FPAs. However, developing uncooled microbolometer infrared focal plane arrays with pixel pitches of 12μm and below without sacrificing sensitivity presents a significant challenge. This is because reducing pixel pitch decreases the effective absorption area and the space occupied by the microbridge legs, directly leading to a reduction in detector signal response.

[0004] Without considering material-related properties and back-end circuit configuration, there are two well-known approaches to improving the responsivity of small-pixel microbolometers (FPAs): increasing the fill factor or decreasing the thermal conductivity (G). th Increasing the fill factor directly expands the effective absorption area and improves the light absorption rate. Generally, single-layer microbridge structures are fabricated as double-layer microbridge structures with upper and lower bridge surfaces, allowing the high fill factor absorption layer and low thermal conductivity support leg structure to be implemented on the upper and lower layers respectively. This achieves both high light absorption and high thermal isolation characteristics, thereby improving the detector's sensitivity. Reducing the thermal conductivity G... th This can be achieved by extending the length of the thermally insulated support legs of the microbridge structure, reducing the leg linewidth, or thinning the thickness of the leg structure layer. However, a double-layer design requires more processing steps than a single-layer design, leading to process complexity, lower yield, and difficulty in ensuring mechanical stability.

[0005] While the fabrication process for single-layer microbolometer pixels is relatively simple, the need to simultaneously perform absorption and thermal isolation functions within the same layer, coupled with the inherent trade-off between the absorption bridge area and the leg ratio, exacerbates the sensitivity disadvantage of single-layer microbolometers as pixel sizes decrease. This is primarily because a high fill factor equates to a large absorption bridge area, while low thermal conductivity necessitates a long leg length. Traditional single-layer structures struggle to simultaneously meet both high fill factor and low thermal conductivity requirements. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides an antenna coupling microbridge structure and its fabrication method for a small pixel microradiometric calorimeter, the purpose of which is to solve the problem that traditional single-layer structures cannot simultaneously meet the requirements of high fill factor and low thermal conductivity.

[0007] To achieve the above objectives, one aspect of the present invention provides an antenna-coupled microbridge structure for a small-pixel microbolometer, comprising an antenna-coupled receiving unit, a bridge surface, and electrode bridge legs:

[0008] The antenna coupling receiving unit includes a helical antenna arm and a feed point region. The helical antenna arm extends from the center of the bridge deck, grows by rotation within the bridge deck area, and extends beyond the bridge deck area. It continues to rotate to the end of the antenna arm outside the bridge deck area according to the same rotation rule. The feed point region is formed by the gap region at the starting end of the helical antenna arm, and the electrode bridge legs are arranged alternately in the gap region of the helical antenna arm.

[0009] Furthermore, the bridge surface area ranges from 1% to 50% of the area of ​​a single pixel.

[0010] Furthermore, the width of the spiral antenna arm is 0.05μm-0.4μm.

[0011] Furthermore, the spacing between adjacent antennas arranged in the spiral antenna arm is 0.3μm-1.5μm.

[0012] Furthermore, the width of the electrode bridge leg is 0.08μm-0.5μm.

[0013] Furthermore, the feed point area and the thermal unit are connected vertically by an insulating layer; the thermal unit is disposed on the entire bridge surface.

[0014] Furthermore, the feed point area is laterally distributed with the thermal unit; the thermal unit is disposed in a portion of the bridge deck area.

[0015] The present invention also provides a method for fabricating the antenna coupling microbridge structure for a small pixel microbolometer as described above, comprising:

[0016] Step 1: Integrate the readout circuit on the substrate and fabricate a metal total reflection layer;

[0017] Step 2: Prepare and pattern a sacrificial layer on the substrate surface where the readout circuit and the metal total reflection layer are fabricated, exposing the holes of the support pillars and the electrodes of the readout circuit;

[0018] Step 3: Prepare and pattern the dielectric support layer of the bridge surface on the patterned sacrificial layer. The pattern of the support layer is determined by the shape of the electrode bridge legs, thermistor unit, and the spiral antenna arm itself. Etch the part of the readout circuit electrode covered by the dielectric support layer to expose the readout circuit electrode.

[0019] Step 4: Fabricate and pattern the electrode bridge leg layer on the dielectric support layer, so that one end of the electrode bridge leg is connected to the electrode of the readout circuit, and the other end covers both sides of the bridge surface to form two electrode leads.

[0020] Step 5: Fabricate and pattern a thermistor unit layer on the dielectric support layer so that the thermistor unit layer covers the electrode leads and forms an electrical connection with the electrode bridge legs;

[0021] Step 6: Coat and pattern a dielectric passivation layer on the electrode bridge leg layer and the thermistor unit layer so that the dielectric passivation layer covers the electrode bridge leg layer and the thermistor unit layer.

[0022] Step 7: Fabricate an antenna coupling receiving unit on the dielectric passivation layer and dielectric support layer, and after patterning, form a spiral antenna arm structure and a feed point region. The spiral antenna arm is located in the gap region on the same plane as the electrode bridge leg.

[0023] Step 8: Release the sacrificial layer to form an antenna-coupled microbridge structure containing a cavity.

[0024] Overall, the above-described technical solutions conceived by this invention can achieve the following beneficial effects compared with the prior art.

[0025] (1) The antenna-coupled microbridge structure adopted in this invention arranges the helical antenna and electrode bridge legs alternately, which increases the proportion of thermally isolated support bridge legs of the small pixel microbridge structure, makes the bridge legs longer and reduces the thermal conductivity, thereby improving the temperature rise of the microbolometer. When the helical antenna arm is used to couple the thermistor unit to receive infrared radiation, the absorption of light energy can be more concentrated in the thermistor unit. Under the condition that the total light absorption rate of the device is similar, the temperature rise of the thermistor unit is further improved, which is equivalent to increasing the effective absorption area of ​​the microbridge structure. Compared with the traditional microbolometer, it can collect energy better and improve the detection efficiency, thereby realizing more efficient and higher resolution infrared detection and infrared imaging.

[0026] (2) While achieving low thermal conductivity and high absorption rate, the present invention also reduces the thermal mass of the microbridge structure, making it easy to obtain fast response devices.

[0027] (3) The present invention realizes the alternating arrangement of electrode bridge legs and helical antenna in a single-layer microbridge structure, replacing the traditional double-layer microbridge structure of upper absorption layer and lower thermal isolation layer, which simplifies the fabrication process and can reduce the device manufacturing cost. Attached Figure Description

[0028] Figure 1 This is a top view of the antenna coupling microbridge structure of the present invention. The coupling method is that the feed point area of ​​the antenna coupling receiving unit and the thermal unit are connected vertically through a dielectric insulating layer.

[0029] Figure 2 The antenna-coupled microbridge structure of the present invention is coupled in such a way that the feed point region of the antenna-coupled receiving unit and the thermal unit are laterally distributed. (a) is a top view and (b) is a front view.

[0030] Figure 3 This is a cross-sectional schematic diagram of the fabrication process of the antenna coupling microbridge structure of the present invention when the coupling mode is top and bottom connection. In the diagram, (a) is a substrate with the readout circuit and metal reflective layer already fabricated, (b) is a substrate with the sacrificial layer fabricated, (c) is a substrate with the dielectric support layer fabricated, (d) is a substrate with the electrode bridge legs and electrode leads fabricated, (e) is a substrate with the thermal unit fabricated, (f) is a substrate with the dielectric passivation layer fabricated, (g) is a substrate with the antenna coupling receiving unit fabricated (the antenna in the figure is a set of spiral antenna arms), and (h) is a cross-sectional schematic diagram of the antenna coupling microbridge structure device with cavity after the sacrificial layer is released.

[0031] Figure 4 The antenna-coupled microbridge structure of the present invention is compared with the structure of the uncoupled antenna in terms of light absorption and temperature rise performance under incident radiation of 8-14μm long-wave infrared. (a) is the light absorption rate and temperature rise curve, and (b) is the change of light power absorption of the substrate, bridge leg, thermistor unit and antenna arm of the microbolometer microbridge structure after antenna coupling.

[0032] The markings in the diagram are: 10-substrate, 20-readout circuit, 21-metal total reflection layer, 30-sacrificial layer, 40-dielectric support layer, 41-dielectric passivation layer, 50-electrode bridge leg, 51-electrode lead, 60-thermal element, 70-antenna coupling receiver element, 71-spiral antenna arm, 72-feed area, 80-support post. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] To address the issues of low effective light absorption and high thermal conductivity in small-pixel single-layer microbolometers caused by the decreasing effective absorption area and bridge leg ratio in existing single-layer pixel microbridge structures as pixel spacing shrinks, and the mutual constraint between the bridge surface and thermally isolated bridge legs, this invention provides an antenna-coupled microbridge structure for small-pixel microbolometers. The difference from existing technologies lies in that it includes an antenna-coupled receiving unit, a bridge surface, and electrode bridge legs.

[0035] The antenna coupling receiving unit includes a helical antenna arm and a feed point region. The helical antenna arm extends from the center of the bridge deck, grows by rotation within the bridge deck area, and extends beyond the bridge deck area. It continues to rotate to the end of the antenna arm outside the bridge deck area according to the same rotation rule. The feed point region is formed by the gap region at the starting end of the helical antenna arm, and the electrode bridge legs are arranged alternately in the gap region of the helical antenna arm.

[0036] Preferably, the bridge surface area ranges from 1% to 50% of the area of ​​a single pixel. The bridge surface area is smaller than that of traditional structures, providing space for the alternating arrangement of the helical antenna structure and the electrode bridge legs.

[0037] Preferably, the width of the spiral antenna arm is 0.05μm-0.4μm. A sufficiently wide antenna arm can excite the local field enhancement effect, and for microbridge structures with small pixels of 12μm and below, the antenna arm width does not exceed 400nm.

[0038] Preferably, the width of the electrode bridge leg is 0.08μm-0.5μm. In order to ensure the stability of the microbridge structure, the width of the electrode bridge leg is slightly larger than the width of the antenna arm.

[0039] Preferably, the spacing between adjacent antennas in the spiral antenna arm is 0.3μm-1.5μm. Since the electrode bridge legs are distributed in the gap area of ​​the spiral antenna arm, the spacing between adjacent antennas should be greater than the width of the electrode bridge legs, approximately three times the width of the electrode bridge legs.

[0040] The antenna-coupled microbridge structure employed in this invention arranges the helical antenna and electrode bridge legs alternately, increasing the proportion of thermally isolated support bridge legs in the geometric space. This elongates the bridge legs and reduces their thermal conductivity, thereby improving the temperature rise of the microbolometer. When the helical antenna arm couples the thermistor to receive infrared radiation, the optical antenna can excite local surface plasmons under the action of incident electromagnetic waves, realizing the conversion between the incident wave's free field and the local field. The absorbed electromagnetic waves excite photocurrents on the surface of the optical antenna and propagate along the antenna arm towards the antenna feed point. Therefore, the incident infrared light absorbed by the antenna is transferred to the thermistor on the bridge surface. Furthermore, the antenna-coupled receiving unit can also collect the light energy originally absorbed by the support bridge legs and the substrate and transfer it to the thermistor, resulting in the thermistor absorbing more light energy and the bridge legs absorbing less energy. This is equivalent to increasing the effective absorption area of ​​the microbridge structure, further improving the temperature rise of the thermistor. With similar total absorption across devices, the antenna-coupled receiving unit collects relatively more light energy and focuses it onto the thermistor. This coupling method reduces light energy loss on the bridge legs and concentrates energy in the thermistor to achieve localized heating. Compared with other antenna-coupled microbolometer methods, this method has a greater advantage in improving device responsivity.

[0041] This invention employs a bridge surface with a smaller fill factor, thus achieving low thermal conductivity and high absorptivity while reducing the bridge surface thermal mass of the microbridge structure, facilitating the development of fast-response devices. The bridge surface used in this invention is smaller than that of traditional microbolometers because it maximizes the coverage area of ​​the helical antenna structure within a single pixel (the light energy collection effect of the helical antenna structure is positively correlated with the coverage area within a single pixel). A smaller bridge surface provides space for a larger coverage area of ​​the helical antenna structure and for the helical antenna arms to extend beyond the bridge surface, allowing for alternating electrode legs and antenna arms, which facilitates leg extension and thus reduces thermal conductivity and improves responsivity. The detector's responsivity is proportional to the bridge surface area. While a smaller bridge surface area traditionally reduces sensitivity, the antenna structure, when coupled, concentrates light energy collection onto the bridge surface, effectively increasing the effective absorption area of ​​the bridge surface.

[0042] This invention achieves the alternating arrangement of electrode bridge legs and helical antenna in a single-layer microbridge structure, which can replace the traditional double-layer microbridge structure with an upper absorption layer and a lower thermal isolation layer, simplifying the fabrication process and reducing device manufacturing costs.

[0043] As an optional embodiment of the present invention, such as Figure 1As shown, the structure mainly includes a substrate 10, two support pillars 80 containing conductive layers, two electrode bridge legs 50, a thermistor unit 60, and an antenna coupling receiving unit 70 composed of a helical antenna arm 71 and a feed point region 72. Among them, a readout circuit 20 and a metal total reflection layer 21 are fabricated on the substrate 10. One end of each of the two electrode bridge legs 50 is fixed to the support pillar 80, and the other end is connected to both sides of the thermistor unit 60, forming a levitable bridge surface with electrical connections. The feed point region 72 of the antenna coupling receiving unit 70 is connected to the thermistor unit 60 vertically through a dielectric passivation layer 41.

[0044] Preferably, the electrode bridge leg 50, the thermal unit 60 and the antenna coupling receiving unit 70 contain a dielectric support layer 40 of the same thickness, but the planar shape of the dielectric support layer 40 is determined by the shape of the three components.

[0045] Specifically, the thermistor 50 is vanadium oxide, and the feed point region is a vacuum;

[0046] Preferably, the helical antenna arm 71 is a metal thin film with a thickness of 10-300 nm, including gold, silver, titanium, aluminum, nickel-chromium, or any alloy of the above metals with suitable properties; the helical antenna arm is in the form of a square helix, a circular helix, or a logarithmic periodic helix, or any effective combination thereof.

[0047] As another optional embodiment of the present invention, such as Figure 2 As shown in (a)-(b), with Figure 1 In comparison, except that the feed region 72 of the antenna coupling receiving unit 70 and the thermal unit 60 are arranged in parallel on the same dielectric layer, the other structures are similar. The structure of this embodiment mainly includes a substrate 10, two support pillars 80 containing conductive layers, two electrode bridge legs 50, a thermal unit 60, and an antenna coupling receiving unit 70 composed of a helical antenna arm 71 and a feed region 72; wherein, a readout circuit 20 and a metal total reflection layer 21 are fabricated on the substrate 10; one end of each of the two electrode bridge legs 50 is fixed to the support pillar 80, and the other end is connected to both sides of the thermal unit 60, forming a levitable bridge surface with electrical connections;

[0048] Detailed process steps

[0049] A method for fabricating an antenna-coupled microbridge structure for a small-pixel microbolometer, wherein the feed region 72 of the antenna-coupled receiving unit 70 and the thermistor unit 60 are connected vertically via a dielectric passivation layer 41, includes the following fabrication steps, corresponding to ah in the attached figures:

[0050] Step 1: Fabricate a patterned metallic total reflective layer on a silicon substrate with readout circuitry using a lift-off process, such as... Figure 3 As shown in (a);

[0051] Step 2: Clean the surface of the substrate 10 on which the readout circuit 20 and the metal total reflection layer 21 were prepared, and dry the surface of the substrate 10 with a nitrogen gun to enhance adhesion. Activate the surface of the cleaned substrate 10 using a plasma stripper. Spin coat polyimide (PI) onto the activated substrate 10 surface using a spin coater to prepare the sacrificial layer 30, controlling the spin speed at 2000 rms. Pre-bake the coated polyimide at 135°C for 10 mins, expose the polyimide using a stepper lithography machine, develop it with MIF developer for 45 s, then dry the developed substrate 10 with a nitrogen gun and continuously heat it at 145°C for 15 mins. After baking at ℃, the substrate 10 with the prepared sacrificial layer 30 was placed in a high-temperature annealing furnace filled with flowing nitrogen or argon protective gas for thermal curing. The thermal curing temperature was set to increase in stages, with a maximum temperature of 300℃ and a holding time of 75 min. The thickness of the polyimide after thermal curing was 2.2 μm. Then, a reactive ion etching process was performed. The etching gas was a mixture of CHF3 and O2, with a CHF3:O2 flow ratio of 15 sccm:20 sccm, an RF power of 150 W, and a reaction chamber pressure of 4 Pa. After etching, the sacrificial layer 30 exposed the support pillar holes and readout circuit electrode parts, which appeared as an inverted trapezoidal pattern in the imaging. Figure 3 As shown in (b);

[0052] Step 3: A low-stress silicon nitride dielectric support layer 40 was deposited at 300°C using an Oxford PlasmaPro 800 PECVD system at a deposition rate of 11.7 nm / min. The thickness of the dielectric support layer 40 ranged from 0.1 to 0.3 μm. Then, the dielectric support layer 40 was subjected to photolithography and etching to obtain its pattern. Simultaneously, the portion of the readout circuit electrodes covered by the dielectric support layer 40 was etched away to expose the readout circuit electrodes. Figure 3 As shown in (c), the pattern of the dielectric support layer 40 is determined by the planar shape of the electrode bridge leg 50, the thermal element 60, and the spiral antenna arm 71.

[0053] Step 4: Fabricate and pattern the electrode bridge legs on the support layer, such as... Figure 3 As shown in (d), a titanium nitride thin film with a thickness of 10-50 nm was prepared as electrode leg 50 using a reactive ion beam sputtering deposition machine. Then, the electrode leg layer 50 was patterned by photolithography and reactive ion etching processes. The reactive ion etching gases were BCl3, Cl2 and N2, and the flow rate ratio of BCl3, Cl2 and N2 was set to 20 sccm: 20 sccm: 5 sccm. The RF power was 200 W and the reaction chamber pressure was 4 Pa. After patterning, the width of the electrode leg 50 was 0.2 μm.

[0054] Step 5: Fabricate and pattern the thermal cells on the support layer, such as... Figure 3 As shown in (e), a thermistor layer 60 formed by depositing vanadium oxide was formed using a reactive ion beam sputtering device. The sputtering power was 20W, the oxygen partial pressure was 8%, the sputtering time was 30min, the annealing temperature was 300℃, and the annealing time was 60min. The thermistor layer 60 was patterned using photolithography and reactive ion etching processes. The reactive ion etching gases were BCl3, Cl2, and N2, and the flow ratio of BCl3, Cl2, and N2 was set to 40sccm:25sccm:5sccm. The RF power was 200W, and the reaction chamber pressure was 4Pa. After patterning, the thermistor layer 60 was a rectangular pattern that covered the electrode leads 51 of the electrode bridge leg layer 50.

[0055] Step 6: Apply a passivation layer and pattern it onto the bridge legs and vanadium oxide, such as... Figure 3 As shown in (f), a low-stress silicon nitride layer 41 with a thickness of 50-200 nm is prepared by depositing low-stress silicon nitride using a PECVD equipment. The dielectric passivation layer 41 is patterned using photolithography and reactive ion etching processes. The etching gas is a mixture of CHF3 and O2, with a CHF3 to O2 flow rate ratio of 15 sccm:20 sccm, an RF power of 200 W, and a reaction chamber pressure of 4 Pa. After etching the dielectric passivation layer 41, a pattern determined by the planar shape of the electrode bridge legs and the thermistor unit itself is formed to cover the electrode bridge leg layer 50 and the thermistor unit layer 60.

[0056] Step 7: Fabricate a helical antenna structure on the passivation layer. A thin titanium film with a thickness of 100 nm is prepared using electron beam evaporation deposition equipment to serve as the helical antenna arm 71. Then, the helical antenna arm 71 is patterned using photolithography and reactive ion etching (RIE). The RIE gases are BCl3, Cl2, and N2, with a flow rate ratio of 25 sccm:25 sccm:5 sccm. The RF power is 200 W, and the reaction chamber pressure is 4 Pa. After patterning, the helical antenna arm 71 is a right-angle helical antenna, as shown below. Figure 1 As shown, the gap in the feed point region 72 is 0.1 μm, the antenna width and thickness are 0.15 μm and 0.1 μm respectively, the spacing between adjacent antenna arms is 0.5 μm, the number of antenna coils is 1.75 turns, and the patterned spiral antenna structure is partially placed on the passivation layer of the thermal element 60, and partially located in the gap region on the same plane as the electrode bridge leg 50, as shown. Figure 3 As shown in (g).

[0057] Step 8: Release the sacrificial layer to form a suspended microbridge structure. Use oxygen plasma to release the polyimide layer in the microbridge structure of the antenna-coupled receiving unit 70. The RF power is 250W, the O2:N2 flow ratio is set to 90 sccm:10 sccm, the working pressure is 500Pa, and intermittent ashing is performed for 15 minutes. This process is repeated multiple times to remove the thermosetting polyimide sacrificial layer 30, forming an antenna-coupled microbridge structure detection unit with a suspended support structure. A cross-sectional schematic diagram of this detection unit is shown below. Figure 3 As shown in (h).

[0058] Figure 4 As shown in Figure (a), the light absorptivity and temperature rise curves of the antenna-coupled microbridge structure and the uncoupled antenna structure of the present invention under incident radiation in the 8-14 μm long-wave infrared range are presented. Figure 4 Figure (b) shows the incremental curves of optical power absorption by the substrate, bridge legs, thermistor, and antenna arm of the microbolometer after antenna coupling. It can be seen that the antenna-coupled microbridge structure improves the temperature rise of the microbolometer while maintaining a high absorptivity. The spiral antenna structure collects the light energy originally absorbed by the supporting bridge legs and substrate and transfers it to the thermistor, resulting in the thermistor absorbing more light energy and the bridge legs absorbing less. With similar total absorption, the antenna-coupled receiving unit collects relatively more light energy and focuses it on the thermistor. This coupling method concentrates heat in the thermistor to achieve localized heating, which has a greater advantage in improving the device responsivity compared to other antenna-coupled microbolometer methods.

[0059] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An antenna-coupled microbridge structure for a small-pixel microbolometer, characterized in that, Includes antenna-coupled receiving unit, bridge deck, and electrode bridge legs: The antenna coupling receiving unit includes a helical antenna arm and a feed point region. The helical antenna arm extends from the center of the bridge surface, grows by rotation within the bridge surface area, and extends beyond the bridge surface area. It continues to rotate to the end of the antenna arm outside the bridge surface area according to the same rotation rule. The feed point region is formed by the gap region at the starting end of the helical antenna arm, and the electrode bridge legs are arranged alternately in the gap region of the helical antenna arm. The bridge surface area ranges from 1% to 50% of the area of ​​a single pixel; The feed point area and the thermal unit are connected vertically by an insulating layer, and the thermal unit is disposed on the entire bridge surface; or, the feed point area and the thermal unit are distributed laterally, and the thermal unit is disposed on a portion of the bridge surface.

2. The antenna coupling microbridge structure for a small-pixel microbolometer according to claim 1, characterized in that, The width of the spiral antenna arm is 0.05μm-0.4μm.

3. The antenna coupling microbridge structure for a small-pixel microbolometer according to claim 2, characterized in that, The spacing between adjacent antennas in the spiral antenna arm is 0.3μm-1.5μm.

4. The antenna coupling microbridge structure for a small-pixel microbolometer according to claim 3, characterized in that, The width of the electrode bridge leg is 0.08μm-0.5μm.

5. A method for fabricating an antenna coupling microbridge structure for a small-pixel microbolometer as described in any one of claims 1-4, characterized in that, include: Step 1: Integrate the readout circuit on the substrate and fabricate a metal total reflection layer; Step 2: Prepare and pattern a sacrificial layer on the substrate surface where the readout circuit and the metal total reflection layer are fabricated, exposing the holes of the support pillars and the electrodes of the readout circuit; Step 3: Prepare and pattern the dielectric support layer of the bridge surface on the patterned sacrificial layer. The pattern of the support layer is determined by the shape of the electrode bridge legs, thermistor unit, and the spiral antenna arm itself. Etch the part of the readout circuit electrode covered by the dielectric support layer to expose the readout circuit electrode. Step 4: Fabricate and pattern the electrode bridge leg layer on the dielectric support layer, so that one end of the electrode bridge leg is connected to the electrode of the readout circuit, and the other end covers both sides of the bridge surface to form two electrode leads. Step 5: Fabricate and pattern a thermistor unit layer on the dielectric support layer so that the thermistor unit layer covers the electrode leads and forms an electrical connection with the electrode bridge legs; Step 6: Coat and pattern a dielectric passivation layer on the electrode bridge leg layer and the thermistor unit layer so that the dielectric passivation layer covers the electrode bridge leg layer and the thermistor unit layer. Step 7: Fabricate an antenna coupling receiving unit on the dielectric passivation layer and dielectric support layer, and after patterning, form a spiral antenna arm structure and a feed point region. The spiral antenna arm is located in the gap region on the same plane as the electrode bridge leg. Step 8: Release the sacrificial layer to form an antenna-coupled microbridge structure containing a cavity.

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