Microbolometer structure and method of fabrication thereof

Abstract

The microbolometer structure comprises, from bottom to top, a substrate (1), a polyhedral structure layer (2), a silica aerogel layer (3), a reflective layer (4), a protective layer (5), a heat-sensitive layer (6), an electrode (7) and a light-absorbing layer (8). The polyhedral structure layer (2) is formed by a plurality of polyhedral structures arranged in an array and is etched on the substrate (1). The silica aerogel layer (3) is deposited on the polyhedral structure layer (2) and the upper surface of the substrate (1), and the height of the silica aerogel layer (3) is greater than that of the polyhedral structure layer (2). The heat-sensitive layer (6) is deposited on a first predetermined area on the upper surface of the protective layer (5), and the area of the first predetermined area is smaller than that of the protective layer (5). The electrode (7) is deposited between the protective layer (5), the heat-sensitive layer (6) and the light-absorbing layer (8).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of infrared thermal radiation, in particular to a microbolometer structure and a manufacturing method thereof. BACKGROUND

[0002] The uncooled infrared thermal radiation detector has a wide application prospect due to its portability, excellent performance and low cost. However, the traditional single-sacrificial layer micro-bridge structure used by the microbolometer for a long time, the mismatch between the length and width of the micro-bridge bridge leg and the heat-sensitive effective detection area affects the performance of the device to some extent. The microbolometer with the best thermal performance should have the narrowest and longest bridge leg and the largest heat-sensitive effective detection area, but this will make the mechanical performance of the structure worse and the traditional single-layer micro-bridge structure cannot meet these conditions. In recent years, the microbolometer with a multi-layer structure has alleviated these problems, but the multi-layer structure also exposes problems such as complex manufacturing process and unstable mechanical performance. SUMMARY

[0003] (I) Technical problems to be solved

[0004] Therefore, the present disclosure provides a microbolometer structure and a manufacturing method thereof, which at least partially solve the problems of low detection efficiency, poor film formation quality of the silica aerogel layer, complex process and poor stability of the current microbolometer.

[0005] (II) Technical solutions

[0006] In order to achieve the above-mentioned purpose, the present disclosure provides a microbolometer structure, which comprises, from bottom to top, a substrate, a polyhedral structure layer, a silica aerogel layer, a reflective layer, a protective layer, a heat-sensitive layer, an electrode and a light absorption layer; wherein the polyhedral structure layer is composed of a plurality of polyhedral structure arrays arranged in an array, and is etched on the substrate; the silica aerogel layer is deposited on the polyhedral structure layer and the upper surface of the substrate, and the height of the silica aerogel layer is greater than the height of the polyhedral structure layer; the heat-sensitive layer is deposited on a first predetermined area of the upper surface of the protective layer, and the area of the first predetermined area is smaller than the area of the protective layer; the electrode is deposited on the protective layer, heat-sensitive layer and light absorption.

[0007] According to the embodiment of the present disclosure, the material of the substrate is silicon and silicon oxide.

[0008] According to the embodiment of the present disclosure, the electrode comprises a first electrode and a second electrode, the first electrode and the second electrode are symmetrically arranged at the edge of the upper surface of the protective layer and cover part of the upper surface of the heat-sensitive layer.

[0009] According to an embodiment of the present disclosure, the material of the polyhedral structure layer is one or more of silicon nitride, polysilicon and metal.

[0010] According to an embodiment of the present disclosure, the edge length of the polyhedral structure is 1 nm-1 um, and the interval period is 1 nm-1 um.

[0011] According to an embodiment of the present disclosure, the material of the reflective layer is one of aluminum, chromium and gold.

[0012] According to an embodiment of the present disclosure, the material of the heat-sensitive layer is vanadium oxide.

[0013] According to an embodiment of the present disclosure, the material of the protective layer and the light-absorbing layer is silicon nitride.

[0014] A second aspect of the present disclosure provides a manufacturing method of a microbolometer, comprising: coating and etching a polyhedral structure layer on a substrate according to a preset mask, the polyhedral structure layer being composed of a plurality of polyhedral structures arranged in an array; preparing a silica aerogel layer and spin coating the silica aerogel layer on the polyhedral structure layer and the upper surface of the substrate, the height of the silica aerogel layer being greater than the height of the polyhedral structure layer; sequentially depositing, from bottom to top, a reflective layer, a protective layer, a heat-sensitive layer, an electrode and a light-absorbing layer on the upper surface of the silica aerogel layer; wherein the heat-sensitive layer is deposited on a first predetermined area on the upper surface of the protective layer, the area of the first predetermined area being less than the area of the protective layer; and the electrode is deposited between the protective layer, the heat-sensitive layer and the light-absorbing layer.

[0015] According to an embodiment of the present disclosure, the preparation of the silica aerogel layer and the spin coating of the silica aerogel layer on the polyhedral structure layer and the upper surface of the substrate comprises: mixing and stirring tetraethyl orthosilicate, anhydrous ethanol and deionized water to generate a silicic acid gel, adding a catalyst hydrochloric acid to adjust the pH, and stirring for a first time; adding anhydrous ethanol and deionized water to the silicic acid gel and stirring to generate a silica aerogel, and adding a catalyst ammonia water to adjust the pH to neutral and stirring for a second time; and spin coating the prepared silica aerogel on the polyhedral structure layer at a preset rotation speed.

[0016] (III) Beneficial Effects

[0017] The microbolometer structure and the manufacturing method thereof provided by the present disclosure overcome the deficiencies in the prior art, remove the traditional cavity heat insulation structure, solve the problems of unstable bridge legs and fracture, use efficient silica aerogel as a heat insulation film, improve the detection efficiency and stability of the device, and use a standard semiconductor manufacturing process to simplify the device manufacturing process; on the other hand, before spin coating the silica aerogel film on the substrate, a polyhedral structure layer is first etched as a stress release structure of the silica aerogel film, which avoids problems such as warping deformation and cracking of the silica aerogel film, and also serves as an adhesion layer between the two materials to firmly adhere the silica aerogel material to the substrate, thereby improving the quality and stability of the film. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A cross-sectional process flow diagram of the microbolometer structure provided by the embodiment of the present disclosure is schematically shown;

[0019] Figure 2 An SEM test diagram of the aerogel spin-coated on the substrate without the polyhedral structure layer etched on the substrate is schematically shown;

[0020] Figure 3 An SEM test diagram of the aerogel spin-coated on the substrate with the polyhedral structure layer etched on the substrate is schematically shown;

[0021] Figure 4 A model diagram of the polyhedral structure layer is schematically shown;

[0022] Figure 5 An etching mask diagram during preparation of the polyhedral structure layer is schematically shown.

[0023] REFERENCE SIGNS:

[0024] 1 - substrate;

[0025] 2 - polyhedral structure layer;

[0026] 3 - silica aerogel layer;

[0027] 4 - reflective layer;

[0028] 5 - protective layer;

[0029] 6 - heat-sensitive layer;

[0030] 7 - electrode;

[0031] 8 - light-absorbing layer. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent, however, that one or more embodiments can be practiced without these specific details. In other instances, well-known structures and functions are not described in detail in order to avoid obscuring the concept of the present disclosure.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present disclosure. The terms "comprises", "comprising", "includes", "including" and the like are meant to be interpreted broadly to include the presence of zero or more steps, features, operations, and / or components, as well as the presence of one or more steps, features, operations, and / or components.

[0034] All terms used herein, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the present specification, and should not be interpreted in an idealized or overly formal manner.

[0035] Figure 1 A cross-sectional process flow diagram of a microbolometer structure provided by embodiments of the present disclosure is schematically shown.

[0036] As shown in Figure 1 The microbolometer structure comprises, in order from bottom to top, a substrate 1, a polyhedral structure layer 2, a silica aerogel layer 3, a reflective layer 4, a protective layer 5, a heat-sensitive layer 6, an electrode 7, and a light-absorbing layer 8.

[0037] Further, the polyhedral structure layer 2 is composed of a plurality of polyhedral structure arrays arranged in an array, and is etched on the substrate 1. The silica aerogel layer 3 is deposited on the polyhedral structure layer 2 and the upper surface of the substrate 1, and the height of the silica aerogel layer 3 is greater than the height of the polyhedral structure layer 2.

[0038] In embodiments of the present disclosure, the material of the substrate 1 is silicon and silicon oxide, and the silicon oxide is located above the silicon and serves as a physical support. At the same time, since the silica aerogel layer 3 has the defects of being brittle and having poor mechanical properties, it is easy to cause the skeleton structure to expand and break, so the silica aerogel layer 3 is prepared on the substrate 1. Compared with other substrates, at this time, the quality of the silica aerogel film is the best.

[0039] The silica aerogel layer 3 serves as a device insulation layer, reducing heat loss from the thermosensitive device to the substrate. It also lacks microbridge structures, offers high stability, and eliminates the need for complex microfabrication. Besides silica aerogel, the insulation layer can also be made of PET plastic, polyimide, and other porous materials, but silica aerogel offers the best insulation performance (its thermal conductivity is 0.018 W / mK, lower than the thermal conductivity of still air in the microbridge resonant cavity (0.023 W / mK)).

[0040] Furthermore, when the silica aerogel layer 3 is deposited on the substrate 1, insufficient adhesion to the substrate 1 may occur, resulting in a gap between the film and the substrate 1, such as Figure 2 As shown, the film may warp and crack due to stress, which may easily lead to film deformation or even shedding, thus seriously affecting the subsequent process and stability of the device. Therefore, a polyhedral structure layer 2 is deposited between the substrate 1 and the silica aerogel layer 3.

[0041] Figure 3 The SEM test image of the aerogel provided by the embodiment of the present disclosure is schematically shown, in which the polyhedron structure layer 2 is prepared and spin-coated on the substrate 1.

[0042] like Figure 3 As shown, the polyhedral structure layer 2 acts as a stress release structure for the silica aerogel film, preventing warping, deformation, cracking, and other problems in the silica aerogel film. It also serves as an adhesion layer between the two layers of material, firmly adhering the silica aerogel material to the substrate and improving the film quality of the silica aerogel film, thereby reducing the heat dissipation of the microbolometer and the thermal response time of the device. Furthermore, by removing the traditional cavity insulation structure and adopting the efficient silica aerogel layer 3 as the thermal insulation film, problems such as unstable and broken bridge legs are solved, while also improving the stability and detection efficiency of the microbolometer. Figure 4 A schematic diagram of a model of a polyhedron structure layer provided by an embodiment of the present disclosure is schematically shown.

[0043] like Figure 4 As shown, the structural size of the polyhedral structure layer 2 should not be too large. The side length of a single polyhedral structure is 1nm-1μm, and the interval period is 1nm-1μm. The side length and interval width of the polyhedral structure can be consistent or inconsistent. The shape of the polyhedral structure can be rectangular, prism-shaped, conical, pyramidal, etc.

[0044] In the embodiment of the present disclosure, the material of the reflective layer 4 is one of aluminum, chromium and gold. When infrared energy is radiated, part of the energy is absorbed by the light-absorbing layer 8 and can be converted into resistance change in the heat-sensitive layer 6, and the other part of the energy can pass through the light-absorbing layer 8 and the heat-sensitive layer 6, at this time the reflective layer 4 reflects the part of the energy to the light-absorbing layer 8 and the heat-sensitive layer 6, thereby enhancing the absorption effect.

[0045] In the embodiment of the present disclosure, the material of the protective layer 5 is silicon nitride, which is used as a buffer layer to protect the material of the heat-sensitive layer 6.

[0046] In the embodiment of the present disclosure, the material of the heat-sensitive layer 6 is vanadium oxide, which is deposited on the first predetermined area of the upper surface of the protective layer 5, and the area of the first predetermined area is smaller than the area of the protective layer 5. The function of the heat-sensitive layer 6 is mainly to absorb the thermal radiation of the target to be measured or the environment, so that the temperature of the material rises, thereby causing the resistance of the heat-sensitive layer 6 to change.

[0047] In the embodiment of the present disclosure, the electrode 7 is deposited between the protective layer 5, the heat-sensitive layer 6 and the light-absorbing layer 8, and includes a first electrode and a second electrode, which are symmetrically arranged at the edges of the upper surface of the protective layer 5 and cover part of the upper surface of the heat-sensitive layer 6. The main function of the electrode 7 is to provide the required electrical signal for measurement.

[0048] In the embodiment of the present disclosure, the material of the light-absorbing layer 8 is silicon nitride, which is used to absorb the thermal radiation of the target to be measured or the environment.

[0049] In the embodiment of the present disclosure, the material of the polyhedral structure layer is one or more of silicon nitride, polysilicon and metal. The above-mentioned material is first deposited on the substrate 1, and then etched to form a polyhedral structure, thereby enhancing the tightness of the adhesion between the silica aerogel layer 3 and the substrate 1, and enhancing the spin-coating film quality of the silica aerogel thin film.

[0050] Another aspect of the embodiment of the present disclosure provides a manufacturing method of a microbolometer, which comprises S1-S3.

[0051] In operation S1, the polyhedral structure layer 2 is coated and etched on the substrate 1 according to a predetermined mask, and the polyhedral structure layer 2 is composed of a plurality of polyhedral structures arranged in an array.

[0052] In operation S2, the silica aerogel layer 3 is prepared and spin-coated on the upper surface of the polyhedral structure layer 2 and the substrate 1, and the height of the silica aerogel layer 3 is greater than the height of the polyhedral structure layer 2.

[0053] In operation S3, a reflective layer 4, a protective layer 5, a heat-sensitive layer 6, an electrode 7, and a light-absorbing layer 8 are sequentially deposited on the upper surface of the silica aerogel layer 3 from bottom to top. The heat-sensitive layer 6 is deposited in a first predetermined region on the upper surface of the protective layer 5, the area of ​​the first predetermined region being smaller than the area of ​​the protective layer 5; and the electrode 7 is deposited between the protective layer 5, the heat-sensitive layer 6, and the light-absorbing layer 8.

[0054] Figure 5 A schematic diagram of an etching mask for preparing a polyhedral structure layer provided in an embodiment of the present disclosure is shown.

[0055] like Figure 5 As shown, a plurality of polyhedral structures are arranged in an array on the mask, and the polyhedral structure layer 2 is precisely positioned and manufactured on the substrate 1 through the photolithography mask, thereby improving the manufacturing efficiency and meeting the needs.

[0056] The polyhedral structure layer 2 is etched by dry etching, whereby plasma reacts with the surface film to form volatile substances, or directly bombards the surface of the etched material.

[0057] Furthermore, operation S2 specifically includes S21-S23.

[0058] In operation S21, tetraethyl silicate, anhydrous ethanol and deionized water are mixed and stirred to generate silica gel, and catalyst hydrochloric acid is added to adjust the pH, and stirred for a first time.

[0059] In operation S22, anhydrous ethanol and deionized water are added to the silicic acid gel and stirred to generate silica aerogel, and ammonia water as a catalyst is added to adjust the pH to neutral, and stirred for a second time.

[0060] In operation S23 , the prepared silica aerogel is spin-coated on the polyhedral structure layer at a preset rotation speed.

[0061] Specifically, at a temperature of 40 degrees Celsius, 2.23 ml of tetraethyl silicate, 1.75 ml of anhydrous ethanol, and 0.18 ml of deionized water were mixed and stirred to perform a hydrolysis reaction of the silica aerogel, followed by adding a catalyst of 10 ul of hydrochloric acid to adjust the pH to 2-3, and continuing to stir for a first time, the first time being 0.5-4 hours. 7.64 ml of anhydrous ethanol and 0.54 ml of deionized water were then added and stirred to perform a polycondensation reaction of the silica aerogel, followed by adding a catalyst of 10 ul of ammonia water to adjust the pH to neutral, and stirring for a second time, the second time being 0.5-2 hours. Finally, the silica aerogel was spin-coated on the polyhedral structure layer 2 at 500 r / min 30 s + 1000 r / min 30 s.

[0062] According to the microbolometer structure and the manufacturing method thereof provided by the present disclosure, the polyhedral structure layer 2 is prepared between the substrate 1 and the silica aerogel layer 3 as a stress release structure of the silica aerogel film, which avoids the problems such as warping deformation and cracks of the silica aerogel layer 3, and can also be used as an adhesive layer between the two layers of materials to firmly adhere the silica aerogel material on the substrate 1, thereby improving the quality and stability of the film. The present disclosure removes the traditional cavity heat insulation structure, solves the problems such as unstable bridge legs and breakage, uses efficient silica aerogel as the heat insulation film, improves the detection efficiency and stability of the device, and simplifies the device manufacturing process, which is suitable for large-scale batch array preparation.

[0063] Those skilled in the art can understand that the features described in various embodiments and / or claims of the present disclosure can be combined or / and integrated in various combinations, even if such combinations are not explicitly described in the present disclosure. In particular, the features described in various embodiments and / or claims of the present disclosure can be combined and / or integrated in various combinations without departing from the spirit and teachings of the present disclosure. All these combinations and / or integrations fall within the scope of the present disclosure.

[0064] Although the present disclosure has been shown and described with reference to certain exemplary embodiments thereof, it should be understood by those skilled in the art that various changes in form and details can be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-described embodiments, but should be determined only by the appended claims, and should be defined by the equivalents of the appended claims.

Claims

1. A microbolometer structure, characterized in that From bottom to top, they include: A substrate (1), a polyhedral structure layer (2), a silica aerogel layer (3), a reflective layer (4), a protective layer (5), a heat-sensitive layer (6), an electrode (7) and a light-absorbing layer (8); wherein, The polyhedral structure layer (2) is composed of a plurality of polyhedral structures arranged in an array, and is formed by etching on the substrate (1); The silica aerogel layer (3) is deposited on the upper surface of the polyhedral structure layer (2) and the substrate (1), and the height of the silica aerogel layer (3) is greater than the height of the polyhedral structure layer (2); The heat-sensitive layer (6) is deposited on a first predetermined area on the upper surface of the protective layer (5), and the area of ​​the first predetermined area is smaller than the area of ​​the protective layer (5); The electrode (7) is deposited between the protective layer (5), the heat-sensitive layer (6) and the light-absorbing layer (8).

2. The microbolometer structure according to claim 1, wherein: The substrate (1) is made of silicon and silicon oxide.

3. The microbolometer structure according to claim 1, wherein: The electrodes (7) include a first electrode and a second electrode, wherein the first electrode and the second electrode are symmetrically arranged at the edge of the upper surface of the protective layer (5) and cover a portion of the upper surface of the heat-sensitive layer (6).

4. The microbolometer structure according to claim 1, wherein: The material of the polyhedral structure layer (2) is one or more of silicon nitride, polysilicon and metal.

5. The microbolometer structure according to claim 1, wherein: The side length of the polyhedral structure is 1 nm-1 um, and the interval period is 1 nm-1 um.

6. The microbolometer structure according to claim 1, wherein: The material of the reflective layer (4) is one of aluminum, chromium and gold.

7. The microbolometer structure according to claim 1, wherein: The material of the heat sensitive layer (6) is vanadium oxide.

8. The microbolometer structure according to claim 1, wherein: The protective layer (5) and the light absorbing layer (8) are made of silicon nitride.

9. A method for manufacturing a microbolometer, characterized in that: include: Laminating and etching a polyhedral structure layer (2) on a substrate (1) according to a preset mask, wherein the polyhedral structure layer (2) is composed of a plurality of polyhedral structures arranged in an array; A silica aerogel layer (3) is prepared and spin-coated on the polyhedral structure layer (2) and the upper surface of the substrate (1), wherein the height of the silica aerogel layer (3) is greater than the height of the polyhedral structure layer (2); A reflective layer (4), a protective layer (5), a heat-sensitive layer (6), an electrode (7) and a light-absorbing layer (8) are sequentially deposited on the upper surface of the silica aerogel layer (3) from bottom to top; wherein: The heat-sensitive layer (6) is deposited on a first predetermined area on the upper surface of the protective layer (5), and the area of ​​the first predetermined area is smaller than the area of ​​the protective layer (5); The electrode (7) is deposited between the protective layer (5), the heat-sensitive layer (6) and the light-absorbing layer (8).

10. The method for manufacturing a microbolometer according to claim 9, wherein: The method of preparing the silica aerogel layer (3) and spin-coating the layer on the polyhedral structure layer (2) and the upper surface of the substrate (1) comprises: Tetraethyl silicate, anhydrous ethanol and deionized water are mixed and stirred to generate silica gel, and hydrochloric acid catalyst is added to adjust the pH and stirred for the first time; adding anhydrous ethanol and deionized water to the silicic acid gel and stirring to generate silica aerogel, adding ammonia water as a catalyst to adjust the pH to neutral, and stirring for a second time; The prepared silica aerogel is spin-coated on the polyhedral structure layer (2) at a preset rotation speed.

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