Microbolometer and method of manufacturing the same

Abstract

The application provides a microbolometer and a manufacturing method thereof, the microbolometer comprising: a substrate with two readout circuits arranged oppositely inside, the readout circuits being used to obtain the temperature of a target object according to infrared radiation of the target object; a microbridge structure with a bridge surface and two support columns, the bridge surface being used to absorb the infrared radiation, the two support columns being respectively located on opposite sides of the surface of the substrate, used to support the bridge surface to be suspended on the substrate, and used to electrically connect the bridge surface and the corresponding readout circuit; and a getter film formed on the surface of the substrate and located between the two support columns, the getter film being used to absorb gas when the microbolometer is vacuum packaged. The above technical scheme sets the getter film between the bridge surface and the substrate, does not need additional space to store the getter, and reduces the overall size of the microbolometer after packaging.

Description

Technical Field

[0001] This invention relates to the field of infrared sensor technology, and in particular to a microbolometer and its manufacturing method. Background Technology

[0002] Infrared detectors are one of the important sensors in industrial, Internet of Things, security, and home applications. They can be widely used in many fields with huge market demand and development potential, such as industrial inspection, home security, smart homes, energy-saving control, medical care, flow counting, gas detection, fire monitoring, and consumer electronics.

[0003] Commonly used infrared detectors are generally uncooled, also known as room-temperature infrared sensors. Uncooled infrared sensors operate at room temperature without cooling, thus offering advantages such as small size, low power consumption, low cost, and portability. Uncooled infrared sensors are generally thermal sensors, meaning they work by detecting the thermal effects of infrared radiation. Commonly used uncooled infrared thermal sensors include thermopile, pyroelectric, and microbolometers.

[0004] Microbolometers detect radiation intensity by sensing changes in the resistance of a thermistor caused by the infrared radiation thermal effect. To maximize the conversion of infrared radiation energy absorbed by the pixel into temperature changes, microbolometers require vacuum encapsulation. Traditional vacuum encapsulation uses a metal casing with an exhaust tailpipe. After surface mounting, wire bonding, and capping, the casing is evacuated through the exhaust tailpipe and then sealed to achieve vacuum encapsulation. To further reduce the encapsulation size and improve efficiency, the industry has developed mass-producible evacuation metal vacuum encapsulation, ceramic vacuum encapsulation, and wafer-level vacuum encapsulation for microbolometers. To maintain the vacuum level within the encapsulation cavity long-term, a getter is typically placed inside. Figure 1 As shown, a cylindrical pre-formed getter 102 is generally used when performing metal vacuum encapsulation on the microbolometer 101. Figure 2 As shown, in the ceramic vacuum encapsulation of the microbolometer 201, a strip-shaped pre-formed getter or a thin-film getter 202 plated on the inner surface of the cover plate is generally used. Wafer-level vacuum encapsulation, on the other hand, generally uses a thin-film getter plated on the inner surface of the wafer cap.

[0005] However, any of the above solutions has the following problems: (1) the getter requires additional space, which increases the overall size of the packaged product; and (2) additional process assembly or manufacturing steps are added, which increases production costs.

[0006] Therefore, providing a microbolometer and its manufacturing method that do not require additional space to store getter, in order to reduce the overall size of the packaged product, is an urgent technical problem to be solved. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a microbolometer and its manufacturing method to solve the problem that the getter requires additional space, which increases the overall size of the packaged product.

[0008] To address the aforementioned problems, this invention provides a microbolometer, comprising: a substrate having two readout circuits disposed opposite to each other, the readout circuits being used to acquire the temperature of a target object based on infrared radiation from the target object; a microbridge structure having a bridge surface and two support pillars, the bridge surface being used to absorb the infrared radiation, the two support pillars being respectively located on opposite sides of the substrate surface, used to support the bridge surface suspended on the substrate, and used to electrically connect the bridge surface to the corresponding readout circuit; and a getter film formed on the substrate surface and located between the two support pillars, the getter film being used to absorb gas during vacuum sealing of the microbolometer.

[0009] To address the aforementioned problems, the present invention also provides a method for manufacturing a microbolometer, the method comprising: providing a substrate having two readout circuits disposed opposite to each other inside the substrate, the readout circuits being used to acquire the temperature of a target object based on infrared radiation from the target object; forming a getter film on the surface of the substrate, the getter film being located between the two oppositely disposed readout circuits; forming a sacrificial layer, the sacrificial layer covering the getter film and the substrate; partially etching the sacrificial layer covering the substrate to form two vias, each via exposing a corresponding readout circuit; forming a support post in each via; forming a bridge surface on the surfaces of the two support posts and the remaining surface of the sacrificial layer, and removing the remaining sacrificial layer, the bridge surface being used to absorb the infrared radiation and electrically connected to the corresponding readout circuit through the support post, the getter film being used to absorb gas during vacuum sealing of the microbolometer.

[0010] To address the aforementioned problems, the present invention also provides a method for manufacturing a microbolometer, the method comprising: providing a substrate having two readout circuits disposed opposite to each other inside the substrate, the readout circuits being used to obtain the temperature of a target object based on infrared radiation from the target object; sequentially forming a getter film and a metal layer on the surface of the substrate, the getter film and the metal layer being located between the two oppositely disposed readout circuits; forming a sacrificial layer covering the metal layer and the substrate; partially etching the sacrificial layer covering the substrate to form two vias, each via exposing a corresponding readout circuit; forming a support pillar in each via; forming a bridge surface on the surfaces of the two support pillars and the remaining surface of the sacrificial layer, and removing the remaining sacrificial layer, the bridge surface being used to absorb the infrared radiation and electrically connected to the corresponding readout circuit through the support pillars, the surface of the bridge surface near the substrate and the surface of the metal layer away from the substrate forming a resonant cavity to enhance the absorption capacity of the bridge surface of the infrared radiation, the getter film being used to absorb gas during vacuum sealing of the microbolometer.

[0011] The above technical solution, by placing the getter film between the bridge surface and the substrate, eliminates the need for additional space to store the getter, thereby reducing the overall size of the microbolometer after packaging.

[0012] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of a metal vacuum-encapsulated microbolometer in the prior art;

[0015] Figure 2 This is a schematic diagram of a ceramic vacuum-encapsulated microbolometer in the prior art;

[0016] Figure 3 This is a schematic diagram of a microbolometer in one embodiment of the present invention;

[0017] Figure 4This is a flowchart of a method for manufacturing a microbolometer according to an embodiment of the present invention;

[0018] Figure 5 This is a flowchart of a method for manufacturing a microbolometer according to another embodiment of the present invention;

[0019] Figures 6 to 11 This is a schematic diagram of the device structure formed by the main steps of the manufacturing method of a microbolometer in one embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments 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.

[0021] To address the issues in existing technologies where the getter requires additional space, increasing the overall size of the packaged product, this invention provides a microbolometer and its manufacturing method.

[0022] The following is a description of a microbolometer provided in an embodiment of the present invention.

[0023] Please see Figure 3 This is a schematic diagram of a microbolometer in one embodiment of the present invention. Figure 3 As shown, the microbolometer described in this embodiment includes a substrate 31, a microbridge structure 32, and a getter film 33. The substrate 31 has two readout circuits 35 arranged opposite each other, which are used to obtain the temperature of a target object based on its infrared radiation. The microbridge structure 32 has a bridge surface 34 and two support pillars 36. The bridge surface 34 absorbs the infrared radiation, and the two support pillars 36 are located on opposite sides of the surface of the substrate 31, supporting the bridge surface 34 suspended on the substrate and electrically connecting the bridge surface 34 to the corresponding readout circuit 35. The getter film 33 is formed on the surface of the substrate 31 and located between the two support pillars 36 to absorb gas during vacuum sealing of the microbolometer.

[0024] In some embodiments, the getter film 33 is a pixel-level getter film, and its material can be one or more of alloys such as titanium zirconium vanadium, zirconium iron vanadium, and zirconium vanadium.

[0025] like Figure 3As shown, in this embodiment, the bridge surface 34 has an infrared thermistor layer 37 on the side away from the substrate 31, and cantilever beams 42 at both ends of the bridge surface 34. The resistance value of the thermistor in the infrared thermistor layer 37 changes according to the infrared radiation of the target object, and the change in electrical signal caused by the change in resistance value is transmitted to the readout circuit 35 through the support pillar 36. The readout circuit 35 outputs a result signal to reflect the temperature of the target object. The bridge surface 34 is coupled to the corresponding support pillar 36 through the cantilever beams 42.

[0026] like Figure 3 As shown, the microbolometer further includes a metal layer 38, which is located on the side of the getter film 33 near the bridge surface 34. The metal layer 38 forms a resonant cavity with the bridge surface, and is used to reflect the infrared radiation to enhance the absorption capacity of the bridge surface 34 for infrared radiation. The metal layer 38 can be made of one or more metals such as nickel, chromium, gold, and silver. For example, by optimizing the fabrication process of the titanium-zirconium-vanadium alloy thin film and the porous nickel, gold, and aluminum layers, the getter film 33 can function as a getter while also maintaining the reflectivity of the metal layer 38 in the 8–14 μm wavelength range.

[0027] like Figure 3 As shown, the metal layer 38 is located on the surface of the getter film 33 to protect it. In this embodiment, the metal layer 38 has a plurality of pore structures 39, which increase the contact area between the getter film 33 and the air. While retaining the metal layer 38 as a reflective layer to enhance the absorption capacity of the bridge surface 34 for infrared radiation, this avoids the metal layer 38 affecting the getter film 33's air-absorbing performance when it covers the surface of the getter film 33 as a reflective layer. In other embodiments, there is a gap between the metal layer 38 and the getter film 33 to further increase the contact area between the getter film 33 and the air, thereby preventing the metal layer 38 from affecting the getter film 33's air-absorbing performance when it covers the surface of the getter film 33 as a reflective layer.

[0028] In other embodiments, the getter film 33 is a thin film. By adjusting the manufacturing process of the getter film 33 to improve its surface reflectivity, the metal layer 38 does not need to be provided on the surface of the getter film 33. In this case, a resonant cavity is formed between the getter film 33 and the bridge surface 34, and the getter film 33 is used to reflect the infrared radiation to enhance the absorption capacity of the bridge surface 34 for the infrared radiation.

[0029] In some embodiments, the surface of the getter film 33 has nanostructures to increase its surface area. The size of the nanostructures is smaller than the wavelength dimension of 10 μm to reduce the impact on the reflectivity of infrared radiation. Taking a sensor chip with 12 μm pixels and a 640×512 array as an example, the area of ​​the getter film 33 under each pixel is approximately 100 square micrometers, and the total area of ​​the getter film 33 for 640×512 pixels is approximately 30 square centimeters, which is much larger than the getter area made on the inner surface of the cap in metal vacuum packaging, ceramic vacuum packaging, and wafer-level vacuum packaging.

[0030] In this embodiment, the microbolometer is a single-layer microbridge structure. In other embodiments, the microbolometer may also be a multi-layer microbridge structure.

[0031] The above technical solution, by placing the getter film 33 between the bridge surface 34 and the substrate 31, eliminates the need for additional space to store the getter, thus reducing the overall size of the encapsulated microbolometer. Furthermore, by increasing the air absorption area of ​​the getter film 33, the performance of the vacuum encapsulation is improved. Compared to the use of columnar pre-formed getter 102 for metal vacuum encapsulation of microbolometers and strip-shaped pre-formed getter or thin-film getter 202 plated on the inner surface of the cover plate for ceramic vacuum encapsulation, the microbolometer of this invention can reduce production costs.

[0032] Based on the same inventive concept, this invention also provides a method for manufacturing a microbolometer. Please refer to [link to relevant documentation]. Figure 4 This is a flowchart illustrating a method for manufacturing a microbolometer according to an embodiment of the present invention. Figure 4 As shown, the manufacturing method of the microbolometer includes: step S41, providing a substrate, the substrate having two readout circuits disposed opposite to each other, the readout circuits being used to obtain the temperature of a target object based on the infrared radiation of the target object; step S42, forming a getter film on the surface of the substrate, the getter film being located between the two readout circuits disposed opposite to each other; step S43, forming a sacrificial layer, the sacrificial layer covering the getter film and the substrate; step S44, partially etching the sacrificial layer covering the substrate to form two vias, each via exposing a corresponding readout circuit; step S45, forming a support pillar in each via; step S46, forming a bridge surface on the surfaces of the two support pillars and the remaining surface of the sacrificial layer, and removing the remaining sacrificial layer, the bridge surface being used to absorb the infrared radiation and electrically connected to the corresponding readout circuit through the support pillar, the getter film being used to absorb gas during vacuum sealing of the microbolometer.

[0033] In this embodiment, the getter film 33 is a thin film, and its surface reflectivity is improved by adjusting the manufacturing process of the getter film 33. At this time, a resonant cavity is formed between the getter film 33 and the bridge surface 34, and the getter film 33 is used to reflect the infrared radiation to enhance the absorption capacity of the bridge surface 34 for the infrared radiation.

[0034] Based on the same inventive concept, the present invention also provides a method for manufacturing a microbolometer. Figure 5 This is a flowchart of a method for manufacturing a microbolometer according to another embodiment of the present invention. Figures 6 to 11 This is a schematic diagram of the device structure formed by the main steps of the manufacturing method of the microbolometer in one embodiment of the present invention. Please refer to it as well. Figure 5 and Figures 6 to 11 The manufacturing method of the microbolometer includes: step S51, providing a substrate 31, wherein the substrate 31 has two readout circuits 35 disposed opposite to each other, the readout circuits 35 being used to obtain the temperature of a target object based on the infrared radiation of the target object, such as... Figure 6 As shown; in step S52, a getter film 33 and a metal layer 38 are sequentially formed on the surface of the substrate 31. The getter film 33 and the metal layer 38 are located between two oppositely disposed readout circuits 35, as shown. Figure 7 As shown; in step S53, a sacrificial layer 40 is formed, which covers the metal layer 38 and the substrate 31, as shown. Figure 8 As shown; in step S54, the sacrificial layer 40 covering the substrate 31 is partially etched to form two vias 41, each via 41 exposing a corresponding readout circuit 35, as shown. Figure 9 As shown; in step S55, a support post 36 is formed in each of the through holes 41, as follows. Figure 10 As shown; in step S56, a bridge surface 34 is formed on the surfaces of the two support columns 36 and the remaining surface of the sacrificial layer 40, as follows. Figure 11 As shown; and the remaining sacrificial layer 40 is removed, the bridge surface 34 is used to absorb the infrared radiation and is electrically connected to the corresponding readout circuit 35 through the support pillar 36, the surface of the bridge surface 34 near the substrate 31 and the surface of the metal layer 38 away from the substrate 31 form a resonant cavity to enhance the absorption capability of the bridge surface 34 for the infrared radiation, the getter film 33 is used to absorb gas during vacuum sealing of the microbolometer, such as Figure 3 As shown.

[0035] In this embodiment, the getter film 33 is a pixel-level getter film, and its material can be one or more alloys such as titanium-zirconium-vanadium, zirconium-iron-vanadium, and zirconium-vanadium. The metal layer 38 is located on the side of the getter film 33 near the bridge surface 34, and a resonant cavity is formed between the metal layer 38 and the bridge surface 34. The metal layer 38 is used to reflect the infrared radiation to enhance the absorption capacity of the bridge surface 34 for the infrared radiation. The material of the metal layer 38 can be one or more metals such as nickel, chromium, gold, and silver. For example, by optimizing the manufacturing process of the titanium-zirconium-vanadium alloy thin film and the porous nickel, gold, and aluminum layers, the getter film 33 can be used as a getter while also taking into account the reflectivity of the metal layer 38 in the 8-14 μm wavelength band.

[0036] like Figure 3 As shown, the metal layer 38 is located on the surface of the getter film 33 to protect it. In this embodiment, multiple pore structures 39 can be formed on the metal layer 38. These pore structures 39 increase the contact area between the getter film 33 and the air. While retaining the metal layer 38 as a reflective layer to enhance the absorption capacity of the bridge surface 34 for infrared radiation, this avoids the metal layer 38 affecting the getter film 33's air-absorbing performance when it covers the surface of the getter film 33 as a reflective layer. In other embodiments, a gap exists between the metal layer 38 and the getter film 33 to further increase the contact area between the getter film 33 and the air, thereby preventing the metal layer 38 from affecting the getter film 33's air-absorbing performance when it covers the surface of the getter film 33 as a reflective layer. Specifically, photoresist can be spin-coated over the getter film 33, the photoresist can be etched to form a connection hole, a metal layer 38 can be formed on the surface of the photoresist away from the substrate 31, and the suspended metal layer 38 can be formed after the photoresist is released.

[0037] In this embodiment, the manufacturing method of the microbolometer further includes: forming an infrared thermistor layer 37 on the side of the bridge surface 34 away from the substrate 31, and forming cantilever beams 42 at both ends of the bridge surface 34. The resistance value of the thermistor in the infrared thermistor layer 37 changes according to the infrared radiation change of the target object, and the change in electrical signal caused by the resistance change is transmitted to the readout circuit 35 through the support column 36. The readout circuit 35 outputs a result signal to reflect the temperature of the target object. The bridge surface 34 is coupled to the corresponding support column 36 through the cantilever beams 42.

[0038] The above technical solution, by placing the getter film 33 between the bridge surface 34 and the substrate 31, eliminates the need for additional space to store the getter, thus reducing the overall size of the encapsulated microbolometer. Furthermore, by increasing the air absorption area of ​​the getter film 33, the performance of the vacuum encapsulation is improved. Compared to the use of columnar pre-formed getter 102 for metal vacuum encapsulation of microbolometers and strip-shaped pre-formed getter or thin-film getter 202 plated on the inner surface of the cover plate for ceramic vacuum encapsulation, the manufacturing method of the microbolometer in this invention reduces process steps and lowers production costs.

[0039] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "also includes a…" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0040] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microbolometer, characterized in that, include: A substrate having two readout circuits arranged opposite each other inside, the readout circuits being used to obtain the temperature of a target object based on the infrared radiation of the target object; A microbridge structure with a bridge surface and two support pillars is provided. The bridge surface absorbs the infrared radiation. The two support pillars are located on opposite sides of the substrate surface, supporting the bridge surface suspended on the substrate and electrically connecting the bridge surface to the corresponding readout circuit. An infrared thermistor layer is located on the side of the bridge surface away from the substrate. The resistance of the thermistor in the infrared thermistor layer changes according to the infrared radiation from the target object, and the resulting electrical signal change is transmitted to the readout circuit through the support pillars. The readout circuit outputs a result signal to reflect the infrared radiation emitted by the target object. The temperature of the target object; the bridge deck is coupled to the corresponding support column via a cantilever beam; a getter film is directly covered on the substrate surface and located between the two support columns, the surface of the getter film facing the substrate is in direct contact with the substrate, the getter film is used to absorb gas during vacuum sealing of the microbolometer, the getter film is a pixel-level getter film, and the surface of the getter film has a nanostructure to increase the surface area of ​​the getter film, the size of the nanostructure is less than the wavelength size of 10 μm to reduce the influence on the reflectivity of infrared radiation; A metal layer is located on the side of the getter film near the bridge surface, forming a resonant cavity between the metal layer and the bridge surface. The metal layer is used to reflect the infrared radiation to enhance the bridge surface's absorption capacity of the infrared radiation. The metal layer has multiple pore structures to increase the contact area between the getter film and the air. There are gaps between the metal layer and the getter film to increase the contact area between the getter film and the air. The getter film can function as a getter while also taking into account the reflectivity of the metal layer in the 8µm to 14µm wavelength range.

2. A method for manufacturing a microbolometer, characterized in that, The method includes: providing a substrate, the substrate having two readout circuits disposed opposite to each other, the readout circuits being used to obtain the temperature of a target object based on the infrared radiation of the target object; forming a getter film and a metal layer sequentially on the surface directly covering the substrate, the getter film and the metal layer being located between the two oppositely disposed readout circuits, the surface of the getter film facing the substrate being in direct contact with the substrate, the getter film being a pixel-level getter film, and the surface of the getter film having nanostructures to increase the surface area of ​​the getter film, the size of the nanostructures being less than the wavelength size of 10 μm to reduce the influence on the reflectivity of infrared radiation, the metal layer having multiple pore structures to increase the contact area between the getter film and air, gaps between the metal layer and the getter film to increase the contact area between the getter film and air, the getter film serving as a getter while also taking into account the reflectivity of the metal layer in the 8 μm to 14 μm wavelength band; forming a sacrificial layer, the sacrificial layer covering the metal layer and the metal layer. The substrate; a portion of the sacrificial layer covering the substrate is etched to form two vias, each via exposing a corresponding readout circuit; a support pillar is formed in each via; a bridge is formed on the surfaces of the two support pillars and the remaining surface of the sacrificial layer, and the remaining sacrificial layer is removed; the bridge absorbs the infrared radiation and is electrically connected to the corresponding readout circuit through the support pillar; the surface of the bridge near the substrate and the surface of the metal layer away from the substrate form a resonant cavity to enhance the absorption capacity of the bridge for the infrared radiation; the getter film is used for gas absorption during vacuum sealing of the microbolometer; the side of the bridge away from the substrate has an infrared thermistor layer, the resistance of the thermistor in the infrared thermistor layer changes according to the infrared radiation of the target object, and the change in electrical signal caused by the change in resistance is transmitted to the readout circuit through the support pillar; the readout circuit outputs a result signal to reflect the temperature of the target object; the bridge is coupled to the corresponding support pillar through a cantilever beam.

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