Microbolometer and method of manufacturing the same

Abstract

The application discloses a microbolometer, comprising a substrate and a bridge pier, a bridge leg layer, a first support column, a bridge deck layer, a second support column and a canopy layer arranged in sequence on the front surface of the substrate. The bridge deck layer is provided with a first release hole, and the canopy layer is provided with a second release hole. The microbolometer can increase the infrared absorption area and improve the infrared absorption rate by arranging the canopy layer above the bridge deck layer. Meanwhile, the bridge deck layer is provided with the first release hole, and the canopy layer is provided with the second release hole, so that the release rate of the sacrificial layer is accelerated, the sacrificial layer is released more cleanly, the risk of interlayer adhesion or deformation caused by release stress is reduced, and the process reliability and yield are improved. In addition, the hole arrangement can reduce the weight of the bridge deck layer and the canopy layer, thereby reducing the weight borne by the bridge leg layer and improving the structural stability. The application further discloses a microbolometer preparation method.

Description

Technical Field

[0001] This application belongs to the field of infrared detection technology, specifically relating to a microbolometer and its preparation method. Background Technology

[0002] A microbolometer is a photodetector that converts incident infrared radiation into temperature changes, and then detects these temperature changes by detecting changes in the resistance of a thermistor. It is a core component of uncooled infrared imaging systems. Its core structure is a microbridge structure suspended above a substrate.

[0003] Traditional microbridge structures are mostly single-layer or double-layer structures. Single-layer structures typically integrate the support legs (bridge legs) and the absorption / thermosensitive area (bridge surface) in the same plane. This severely limits the reduction of support leg length and thermal conductivity due to the limited planar area, and also restricts the further expansion of the bridge surface (thermosensitive area) area, affecting infrared absorption efficiency and fill factor. While double-layer structures can improve some of these issues, they still have limitations in improving infrared absorption rate. Summary of the Invention

[0004] Therefore, this application needs to provide a microbolometer that can further improve infrared absorption rate and its preparation method.

[0005] The technical solution proposed in this application is as follows: A microbolometer, comprising: Substrate; Bridge piers are disposed on the substrate; A bridge leg layer, supporting the end of the bridge pier away from the substrate; The first support column is located on the side of the bridge leg layer opposite to the bridge pier; The bridge deck layer is supported on the end of the first support column away from the bridge leg layer; The second support column is disposed on the side of the bridge deck layer opposite to the first support column; An umbrella-shaped layer is supported on the end of the second support column away from the bridge deck layer; The bridge deck layer has a first release hole, and the umbrella cover layer has a second release hole.

[0006] Using the aforementioned microbolometer and placing a canopy layer above the bridge deck layer increases the infrared absorption area, thereby improving the infrared absorption rate. Simultaneously, the first release hole in the bridge deck layer and the second release hole in the canopy layer accelerate the release rate of the sacrificial layer and ensure a cleaner release, reducing the risk of interlayer adhesion or deformation due to stress release, thus improving process reliability and yield. Furthermore, the openings reduce the weight of the bridge deck layer and the canopy layer, thereby reducing the weight borne by the bridge leg layers and improving structural stability.

[0007] Furthermore, there are two piers and two first support columns, with the two piers spaced apart on the substrate and the two first support columns spaced apart.

[0008] Furthermore, the bridge leg layer includes a first bridge leg and a second bridge leg, both of which extend in a tortuous manner. One end of the first bridge leg is connected to one of the bridge piers, and the other end is connected to one of the first support columns. One end of the second bridge leg is connected to another of the bridge piers, and the other end is connected to another of the first support columns.

[0009] Furthermore, there are two of each of the canopy layer and the second support column. The two second support columns are arranged at intervals on the bridge deck layer, and the two canopy layers are respectively supported by the two second support columns and are arranged at intervals.

[0010] Furthermore, the second support column is integrally formed with the umbrella cover layer.

[0011] Furthermore, the umbrella cover layer has a plurality of second release holes.

[0012] Furthermore, the total opening area of ​​the plurality of second release holes does not exceed 30% of the area of ​​the umbrella cover layer.

[0013] Furthermore, the bridge deck layer is provided with a plurality of the first release holes.

[0014] Furthermore, in a direction perpendicular to the front side of the substrate, the first release hole and the second release hole are at least partially staggered.

[0015] A method for preparing a microbolometer includes the following steps: S110, a reflective layer, an insulating dielectric layer and a first sacrificial layer are sequentially formed on the front side of the substrate, and the first sacrificial layer is etched to obtain a first via; S120, a pier is formed in the first through hole, and a leg layer connected to the pier is formed on the first sacrificial layer. S130, a second sacrificial layer is formed on the bridge leg layer and the first sacrificial layer, and the second sacrificial layer is etched to form a second via that exposes the bridge leg layer; S140, a first support column is formed in the second through hole, and then a bridge deck layer connected to the first support column is formed on the second sacrificial layer, and the bridge deck layer is etched to form a first release hole; S150, a third sacrificial layer is formed on the bridge deck layer and the second sacrificial layer, and the third sacrificial layer is etched to form a third through-hole that exposes the bridge deck layer; S160, a second support post is formed in the third through hole, and an umbrella layer is formed on the third sacrificial layer. The umbrella layer is etched to form a second release hole. S170, the first sacrificial layer, the second sacrificial layer and the third sacrificial layer are removed by a release process.

[0016] In summary, the microbolometer and its preparation method provided in this application have at least the following advantages: 1. By setting up an umbrella layer, the infrared absorption area can be increased, thereby improving the infrared absorption rate.

[0017] 2. The first release hole is opened on the bridge deck layer and the second release hole is opened on the umbrella layer. This can reduce the weight and the weight borne by the bridge leg layer, improve the structural stability, accelerate the release rate of the sacrificial layer in the release process, and make the sacrificial layer release more cleanly. This reduces the risk of interlayer adhesion or deformation caused by release stress, and improves the reliability and yield of the process.

[0018] 3. Both the first and second bridge legs are S-shaped, which extends the length of the bridge legs, reduces thermal conductivity, and improves the response speed of the microbolometer.

[0019] 4. The canopy layer is divided into two parts, which can significantly reduce the thermal stress of the canopy layer, reduce the probability of deformation of the canopy layer, and further reduce the heat capacity of the canopy layer, thereby accelerating the response speed. Attached Figure Description

[0020] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0021] Figure 1 This is a schematic diagram of the structure of a microbolometer provided in an embodiment of this application; Figure 2 This is a flowchart illustrating a method for preparing a microbolometer according to an embodiment of this application.

[0022] Label Explanation: 110, Substrate; 120, Pier; 130, Leg Layer; 131, First Leg; 132, Second Leg; 140, First Support Post; 150, Bridge Surface Layer; 151, First Release Hole; 160, Second Support Post; 170, Umbrella Layer; 171, Second Release Hole. Detailed Implementation

[0023] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0024] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0026] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0027] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0028] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0029] This application provides a microbolometer that, compared to existing double-layer microbridge structures, can further improve infrared absorption rate and further reduce thermal conductivity, thereby improving response speed.

[0030] like Figure 1 As shown, in one embodiment, the microbolometer includes a substrate 110, a pier 120, a leg layer 130, a first support column 140, a deck layer 150, a second support column 160, and a canopy layer 170. The pier 120 is disposed on the substrate 110, and the leg layer 130 is supported at the end of the pier 120 away from the substrate 110. The first support column 140 is disposed on the side of the leg layer 130 opposite to the pier 120, the deck layer 150 is supported at the end of the first support column 140 away from the leg layer 130, the second support column 160 is disposed on the side of the deck layer 150 opposite to the first support column 140, and the canopy layer 170 is supported at the end of the second support column 160 away from the deck layer 150. By providing the canopy layer 170, the infrared absorption area is increased, thereby improving the infrared absorption rate.

[0031] Furthermore, the bridge deck layer 150 has a first release hole 151 through it, and the umbrella layer 170 has a second release hole 171 through it, so as to facilitate the release of the sacrificial layer after the preparation is completed, accelerate the release rate of the sacrificial layer, and make the release of the sacrificial layer cleaner, reduce the risk of interlayer adhesion or deformation caused by release stress, and improve process reliability and yield.

[0032] Using the aforementioned microbolometer, an umbrella layer 170 is placed above the bridge deck layer 150, which increases the infrared absorption area and thus improves the infrared absorption rate. Simultaneously, the bridge deck layer 150 has a first release hole 151, and the umbrella layer 170 has a second release hole 171. This accelerates the release rate of the sacrificial layer and ensures a cleaner release, reducing the risk of interlayer adhesion or deformation due to stress release, thereby improving process reliability and yield. Furthermore, the openings reduce the weight of the bridge deck layer 150 and the umbrella layer 170, thereby reducing the weight borne by the bridge leg layer 130 and improving structural stability.

[0033] To facilitate understanding of the technical effects of the microbolometer in this embodiment, such as Figure 2As shown, this application also provides a method for fabricating a microbolometer, the method comprising the following steps: S110, forming a reflective layer, an insulating dielectric layer and a first sacrificial layer sequentially on the front side of a substrate 110, and etching the first sacrificial layer to obtain a first through-hole; S120, forming a pier 120 in the first through-hole, and simultaneously forming a leg layer 130 connected to the pier 120 on the first sacrificial layer; S130, forming a second sacrificial layer on the leg layer 130 and the first sacrificial layer, and etching the second sacrificial layer to form a second through-hole exposing the leg layer 130; S140, forming a first support post in the second through-hole. 140, then form a bridge deck layer 150 connected to the first support column 140 on the second sacrificial layer, and etch the bridge deck layer 150 to form a first release hole 151; S150, form a third sacrificial layer on the bridge deck layer 150 and the second sacrificial layer, and etch the third sacrificial layer to form a third through hole exposing the bridge deck layer 150; S160, form a second support column 160 in the third through hole, and at the same time form a canopy layer 170 on the third sacrificial layer, and etch the canopy layer 170 to form a second release hole 171; S170, remove the first sacrificial layer, the second sacrificial layer and the third sacrificial layer by a release process.

[0034] Specifically, the bridge leg layer 130 is composed of a silicon nitride support layer, a metal interconnect layer and a silicon nitride passivation layer deposited sequentially, the bridge surface layer 150 is composed of a silicon nitride support layer, a vanadium oxide thermistor layer (or a polycrystalline silicon thermistor layer), a metal (Ti) interconnect layer and a silicon nitride passivation layer deposited sequentially, and the umbrella layer 170 is composed of a silicon nitride support layer, a metal (Ti) absorber layer and a silicon nitride passivation layer deposited sequentially.

[0035] It should be noted that the etching and release processes are conventional methods, and the materials used for the sacrificial layer are also conventional choices, which will not be elaborated upon here. Furthermore, in S140, the first support pillar 140 and the bridge deck layer 150 can be deposited and formed simultaneously. In S160, the second support pillar 160 and the umbrella layer 170 are deposited and formed simultaneously, i.e., they are integrally molded.

[0036] Therefore, by opening the first release hole 151 and the second release hole 171, the release rate of the sacrificial layers is faster and the release is cleaner when releasing the first, second, and third sacrificial layers through the release process. Furthermore, it should be noted that in this embodiment, the reflective layer is disposed on the front side of the substrate 110, and a resonant cavity is formed between the front side of the substrate 110 and the bridge layer 150, with the height of this resonant cavity being 1 / 4 wavelength.

[0037] In one embodiment, there are two piers 120 and two first support columns 140, with the two piers 120 spaced apart on the substrate 110 and the two first support columns 140 spaced apart. Further, the leg layer 130 includes a first leg 131 and a second leg 132. Both the first leg 131 and the second leg 132 extend in a zigzag pattern. One end of the first leg 131 is connected to one of the piers 120, and the other end is connected to one of the first support columns 140. One end of the second leg 132 is connected to the other pier 120, and the other end is connected to the other first support column 140, to further reduce thermal conductivity and improve response speed. Specifically, both the first leg 131 and the second leg 132 are S-shaped, and the width at the bend of the leg is greater than the width at other locations on the leg, to reduce stress concentration and improve structural strength.

[0038] In one embodiment, the umbrella layer 170 has multiple second release holes 171. This further reduces weight and improves the structural stability of the bridge leg layer 130. It also reduces heat capacity, thereby further improving response speed.

[0039] Preferably, the total opening area of ​​the multiple second release holes 171 does not exceed 30% of the area of ​​the umbrella layer 170. If the proportion of the second release holes 171 is too large, the infrared absorption area of ​​the umbrella layer 170 will be reduced. At the same time, by controlling the opening area to not exceed 30% of the area of ​​the umbrella layer 170, a diffraction window can be created through the opening. Infrared radiation is reflected multiple times in the resonant cavity below through the diffraction window formed by the second release holes 171, increasing the path length of the light and improving the infrared absorption rate. For specific effects, please refer to the simulation data in Table 1.

[0040] Table 1 Simulation Data It should be noted that the area and other structures of the umbrella layer 170 in Examples 1 and 2 are the same. The only difference is that in Example 2, the umbrella layer 170 has multiple second release holes 171, which are arranged in an array, and the total area of ​​the holes accounts for 20% of the area of ​​the umbrella layer 170. As can be seen from Examples 1 and 2, when the umbrella layer 170 has second release holes 171, the stress and deformation of the bridge leg can be effectively reduced, and the infrared absorption rate in the corresponding band (8~14μm) can also be improved to a certain extent.

[0041] In one embodiment, the bridge deck layer 150 has multiple first release holes 151 to further reduce weight and improve the structural stability of the bridge leg layer 130. Similarly, the total area of ​​the first release holes 151 should not be too large to avoid affecting the infrared absorption rate. Preferably, the total opening area of ​​the first release holes 151 accounts for 10-60% of the area of ​​the bridge deck layer 150.

[0042] In one embodiment, in the direction perpendicular to the front side of the substrate 110, the first release hole 151 and the second release hole 171 are at least partially staggered to further accelerate the flow rate of the etchant or etching plasma in the release process, thereby further accelerating the release efficiency of the sacrificial layer. It should be noted that in the illustrated embodiment, the first release hole 151 is circular and located in the middle of the bridge layer 150. In other embodiments, the first release hole 151 may also be rectangular and arranged in the same way as the second release hole 171 in the figure; this is not a limitation.

[0043] In one embodiment, there are two umbrella layers 170 and two second support columns 160. The two second support columns 160 are spaced apart on the bridge deck layer 150, and the two umbrella layers 170 are supported by the two second support columns 160, respectively, and are arranged at intervals. This not only further reduces weight and accelerates the release rate of the sacrificial layer, but also significantly reduces the thermal stress of the umbrella layer 170 and lowers the probability of bending deformation. Simultaneously, it further reduces the heat capacity of the umbrella layer 170, thereby accelerating the response speed. Specifically, the two umbrella layers 170 are arranged symmetrically.

[0044] In summary, the microbolometer and its preparation method provided in this application have at least the following advantages: 1. By setting the umbrella layer 170, the infrared absorption area can be increased, thereby improving the infrared absorption rate.

[0045] 2. A first release hole 151 is opened on the bridge deck layer 150 and a second release hole 171 is opened on the umbrella layer 170. This can reduce the weight, reduce the weight borne by the bridge leg layer 130, improve the structural stability, accelerate the release rate of the sacrificial layer in the release process, and make the sacrificial layer release more cleanly, reduce the risk of interlayer adhesion or deformation caused by release stress, and improve process reliability and yield.

[0046] 3. Both the first bridge leg 131 and the second bridge leg 132 are S-shaped, which extends the length of the bridge leg, reduces thermal conductivity, and improves the response speed of the microbolometer.

[0047] 4. The umbrella layer 170 is divided into two parts, which can significantly reduce the thermal stress of the umbrella layer 170, reduce the probability of deformation of the umbrella layer 170, and further reduce the heat capacity of the umbrella layer 170, thereby accelerating the response speed.

[0048] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A microbolometer, characterized in that, include: Substrate; Bridge piers are disposed on the substrate; A bridge leg layer, supporting the end of the bridge pier away from the substrate; The first support column is located on the side of the bridge leg layer opposite to the bridge pier; The bridge deck layer is supported on the end of the first support column away from the bridge leg layer; The second support column is disposed on the side of the bridge deck layer opposite to the first support column; An umbrella-shaped layer is supported on the end of the second support column away from the bridge deck layer; The bridge deck layer has a first release hole, and the umbrella cover layer has a second release hole.

2. The microbolometer according to claim 1, characterized in that, The number of bridge piers and the number of the first support columns are both two, with the two bridge piers arranged alternately on the substrate and the two first support columns arranged alternately.

3. The microbolometer according to claim 2, characterized in that, The bridge leg layer includes a first bridge leg and a second bridge leg. Both the first bridge leg and the second bridge leg extend in a curved manner. One end of the first bridge leg is connected to one of the bridge piers, and the other end is connected to one of the first support columns. One end of the second bridge leg is connected to another of the bridge piers, and the other end is connected to another of the first support columns.

4. The microbolometer according to claim 1, characterized in that, The number of the umbrella layer and the number of the second support column are both two. The two second support columns are arranged at intervals on the bridge deck layer. The two umbrella layers are respectively supported by the two second support columns and are arranged at intervals.

5. The microbolometer according to claim 1, characterized in that, The second support column is integrally formed with the umbrella cover layer.

6. The microbolometer according to claim 1, characterized in that, The umbrella cover layer has multiple second release holes.

7. The microbolometer according to claim 6, characterized in that, The total opening area of ​​the plurality of second release holes does not exceed 30% of the area of ​​the umbrella cover layer.

8. The microbolometer according to claim 6, characterized in that, The bridge deck layer has multiple first release holes.

9. The microbolometer according to claim 8, characterized in that, In a direction perpendicular to the front side of the substrate, the first release hole and the second release hole are at least partially staggered.

10. A method for preparing a microbolometer, characterized in that, Including the following steps: S110, a reflective layer, an insulating dielectric layer and a first sacrificial layer are sequentially formed on the front side of the substrate, and the first sacrificial layer is etched to obtain a first via; S120, a pier is formed in the first through hole, and a leg layer connected to the pier is formed on the first sacrificial layer. S130, a second sacrificial layer is formed on the bridge leg layer and the first sacrificial layer, and the second sacrificial layer is etched to form a second via that exposes the bridge leg layer; S140, a first support column is formed in the second through hole, and then a bridge deck layer connected to the first support column is formed on the second sacrificial layer, and the bridge deck layer is etched to form a first release hole; S150, a third sacrificial layer is formed on the bridge deck layer and the second sacrificial layer, and the third sacrificial layer is etched to form a third through-hole that exposes the bridge deck layer; S160, a second support post is formed in the third through hole, and an umbrella layer is formed on the third sacrificial layer. The umbrella layer is etched to form a second release hole. S170, the first sacrificial layer, the second sacrificial layer and the third sacrificial layer are removed by a release process.

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