Infrared sensor and method of manufacturing the same

Abstract

To enhance airtightness of an internal space of an infrared sensor.SOLUTION: The infrared sensor 1 includes an infrared detecting element 3, an element substrate 21, a spacer layer 22, a lens substrate 23, and an antireflection film 8. The element substrate 21 is made of silicon, and the infrared detecting element 3 is disposed thereon. The spacer layer 22 is made of silicon, and is bonded to the element substrate 21 so as to surround the infrared detecting element 3. The lens substrate 23 is made of silicon and is bonded to the spacer layer 22. The antireflection film 8 is disposed on the lens substrate 23. The antireflection film 8 is disposed on the inner face of the lens substrate 23 facing the cavity 9, and is not disposed on the inner face 22c of the spacer layer 22 facing the cavity 9, the first joint face 25 between the device substrate 21 and the spacer layer 22, and the second joint face 26 between the spacer layer 22 and the lens substrate 23.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an infrared sensor and a method for manufacturing the same. [Background technology]

[0002] Patent Document 1 describes an optical lens usable in an infrared sensor and a manufacturing method thereof. The manufacturing method of the optical lens described in Patent Document 1 includes a lens surface forming step, a lens region forming step, and a lens holder forming step. In the lens surface forming step, a lens surface is formed on the surface of an SOI (silicon on insulator) layer of a substrate consisting of an SOI layer, an SiO2 layer, and a Si layer. In the lens region forming step, the SOI layer other than the lens region is removed until the SiO2 layer is exposed, so that the SOI layer remains only in the lens region including the lens surface and its edge. In the lens holder forming step, the Si layer other than the lens holder is removed until the SiO2 layer is exposed from the back surface of the substrate, so as to form a lens holder that holds the lens region. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-101649 (see FIG. 1) Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical lens described in Patent Document 1, it is conceivable to provide an anti-reflection film according to the target wavelength in order to effectively transmit only the target wavelength. In this case, the anti-reflection film is provided on the back surface of the substrate.

[0005] When an anti-reflection film is provided on the rear surface of the substrate (lens substrate), an anti-reflection film is also provided on the bonding surface between the substrate and the lens holding part, so it is necessary to remove the anti-reflection film on the bonding surface.

[0006] However, in the configuration described in Patent Document 1, there is a large step between the back surface of the substrate (lens substrate) and the back surface (bonding surface) of the lens holding portion (spacer layer), making it difficult to clean and flatten the bonding surface when removing the anti-reflection film formed on the bonding surface.As a result, when the lens substrate is bonded to an element substrate on which an infrared detection element is arranged, it is difficult to improve the airtightness of the internal space.

[0007] An object of the present disclosure is to provide an infrared sensor that can increase the airtightness of the internal space of the infrared sensor, and a method for manufacturing the same. [Means for solving the problem]

[0008] An infrared sensor according to one aspect of the present disclosure includes an infrared detection element, an element substrate, a spacer layer, a lens substrate, and an anti-reflection film. The element substrate has the infrared detection element disposed thereon and is made of silicon. The spacer layer is bonded to the element substrate so as to surround the infrared detection element and is made of silicon. The lens substrate is bonded to the spacer layer and is made of silicon and has a lens. The anti-reflection film is disposed on the lens substrate. The element substrate, the spacer layer, and the lens substrate form a cavity. The anti-reflection film is disposed on an inner surface of the lens substrate facing the cavity. The anti-reflection film is not disposed on an inner surface of the spacer layer facing the cavity, a first bonding surface between the element substrate and the spacer layer, or a second bonding surface between the spacer layer and the lens substrate.

[0009] A method for manufacturing an infrared sensor according to one embodiment of the present disclosure includes a first step, a second step, a third step, a fourth step, a fifth step, a sixth step, a seventh step, and an eighth step. In the first step, a first silicon wafer, a second silicon wafer, and a third silicon wafer are prepared. In the second step, an element substrate is formed by arranging infrared detection elements on the first silicon wafer. In the third step, a spacer layer is formed using the second silicon wafer as a base material. In the fourth step, a lens substrate having lenses is formed on the third silicon wafer. In the fifth step, an anti-reflection film is formed on the lens substrate formed in the fourth step. In the sixth step, a bonding region with the spacer layer is formed on the lens substrate by removing a portion of the anti-reflection film formed in the fifth step. In the seventh step, the bonding region of the lens substrate and the spacer layer are bonded. In the eighth step, the spacer layer is bonded to the element substrate formed in the second step so that the spacer layer surrounds the infrared detection elements. [Effects of the Invention]

[0010] According to the present disclosure, the airtightness of the internal space of the infrared sensor can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of an infrared sensor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view of the infrared sensor. [Figure 3] FIG. 3 is a first explanatory diagram of the method for manufacturing the infrared sensor. [Figure 4] FIG. 4 is a second explanatory diagram of the method for manufacturing the infrared sensor. [Figure 5] FIG. 5 is a third explanatory diagram of the method for manufacturing the infrared sensor. [Figure 6] FIG. 6 is a fourth explanatory diagram of the method for manufacturing the infrared sensor. [Figure 7]FIG. 7 is a fifth explanatory diagram of the method for manufacturing the infrared sensor. [Figure 8] FIG. 8 is a sixth explanatory diagram of the method for manufacturing the infrared sensor. [Figure 9] FIG. 9 is a seventh explanatory diagram of the method for manufacturing the infrared sensor. [Figure 10] FIG. 10 is a first explanatory diagram of a method for manufacturing an infrared sensor according to a first modified example of the embodiment of the present disclosure. [Figure 11] FIG. 11 is a second explanatory diagram of the method for manufacturing the infrared sensor. [Figure 12] FIG. 12 is a first explanatory diagram of a method for manufacturing an infrared sensor according to a second modified example of the embodiment of the present disclosure. [Figure 13] FIG. 13 is a second explanatory diagram of the method for manufacturing the infrared sensor. [Figure 14] FIG. 14 is a third explanatory diagram of the method for manufacturing the infrared sensor. [Figure 15] FIG. 15 is an explanatory diagram of a method for manufacturing an infrared sensor according to a comparative example of the embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an infrared sensor and a manufacturing method thereof according to an embodiment will be described in detail with reference to the drawings. However, each drawing described in the following embodiments is a schematic diagram, and the dimensional ratios of the sizes of the components and the like do not necessarily reflect the actual dimensional ratios. Furthermore, the configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0013] (Embodiment) (1) Overview An infrared sensor 1 according to an embodiment of the present disclosure will be described with reference to FIG.

[0014] The infrared sensor 1 includes an infrared detection element 3, an element substrate 21, a spacer layer 22, a lens substrate 23, and an antireflection film 8. The element substrate 21 is made of silicon, and has the infrared detection element 3 disposed thereon. The spacer layer 22 is made of silicon, and is bonded to the element substrate 21 so as to surround the infrared detection element 3. The lens substrate 23 is made of silicon, and is bonded to the spacer layer 22. The antireflection film 8 is disposed on the lens substrate 23. The element substrate 21, the spacer layer 22, and the lens substrate 23 form a cavity 9. The antireflection film 8 is disposed on the inner surface of the lens substrate 23 facing the cavity 9. The antireflection film 8 is not disposed on an inner surface 22c of the spacer layer 22 facing the cavity 9, a first bonding surface 25 between the element substrate 21 and the spacer layer 22, or a second bonding surface 26 between the spacer layer 22 and the lens substrate 23.

[0015] According to this configuration, the antireflection film 8 disposed on the lens substrate 23 is not disposed on the inner surface 22c of the spacer layer 22 facing the cavity 9. This makes it possible to bond the lens substrate 23 and the spacer layer 22 after manufacturing them in separate processes. Furthermore, since the antireflection film 8 is not disposed on the first bonding surface 25 between the element substrate 21 and the spacer layer 22 and the second bonding surface 26 between the spacer layer 22 and the lens substrate 23, it is easier to maintain the cleanliness and flatness of the first bonding surface 25 and the second bonding surface 26. This makes it possible to ensure a high level of airtightness in the cavity 9 (internal space) of the infrared sensor 1.

[0016] (2) Details The infrared sensor 1 according to the embodiment will be described in detail below with reference to FIGS.

[0017] (2.1) Configuration The infrared sensor 1 according to the embodiment is an infrared sensor that receives infrared rays 30 (i.e., far-infrared rays) emitted from an object (including a person or an animal). More specifically, the infrared sensor 1 detects a mosaic thermal image of N rows and N columns by receiving far-infrared rays with a plurality of pixels (a plurality of infrared detection elements 3, described later) arranged in a matrix of N rows and N columns (N: an integer, for example, N=8).

[0018] The infrared sensor 1 can be installed in, for example, an indoor air conditioner to detect the temperature distribution in the room or to detect the presence of a person in the room. It can also be used to detect the temperature distribution inside a microwave oven.

[0019] More specifically, the infrared sensor 1 includes a plurality of infrared detection elements 3, an element substrate 21, a spacer layer 22, a lens substrate 23, a lens 5, a getter material 7, and a plurality of anti-reflection films (also called AR (Anti Reflection) coats) 8. The infrared sensor 1 is an infrared sensor with an integrated lens.

[0020] The element substrate 21, the spacer layer 22, and the lens substrate 23 are packaged using wafer-level packaging (WLP). More specifically, a sealing member (not shown) is used to seal the outer peripheral surfaces of the element substrate 21, the spacer layer 22, and the lens substrate 23. The sealing member is made of, for example, an insulating resin. The element substrate 21, the spacer layer 22, and the lens substrate 23 are flat substrates of the same shape and size, and are formed into a rectangular shape in plan view (see FIG. 2). By packaging the element substrate 21, the spacer layer 22, and the lens substrate 23 using WLP, the package size of the infrared sensor 1 can be made close to the chip size of the infrared sensor 1.

[0021] The element substrate 21, the spacer layer 22, and the lens substrate 23 form a cavity 9. More specifically, the cavity 9 is a space enclosed by the first main surface 21a of the element substrate 21, the inner surface 22c of the spacer layer 22, and the second main surface 23b of the lens substrate 23. The cavity 9 is an internal space that houses a plurality of infrared detection elements 3, and in this embodiment, is a substantially rectangular parallelepiped space. The cavity 9 is sealed by the element substrate 21, the spacer layer 22, and the lens substrate 23, and is maintained at a vacuum. The cavity 9 functions as an incident optical path when infrared rays 30 from outside pass through the lens substrate 23 and enter the plurality of infrared detection elements 3 therein.

[0022] The element substrate 21 has a first main surface 21a and a second main surface 21b that face each other in the thickness direction. A plurality of infrared detection elements 3 are arranged on the first main surface 21a of the element substrate 21. More specifically, a plurality of infrared detection elements 3 and a plurality of reference detection elements 4 (only one is shown in FIG. 1 ) are arranged on the first main surface 21a of the element substrate 21.

[0023] The multiple infrared detection elements 3 are detection elements that detect infrared rays 30 (more specifically, far-infrared rays) that have passed through the lens substrate 23 from the outside and entered the cavity 9. When the multiple infrared detection elements 3 receive infrared rays 30 from the outside, they each output an electrical signal according to the intensity of the received infrared rays 30. The multiple infrared detection elements 3 are thermocouple-type infrared detection elements having hot junctions and cold junctions. In this way, the multiple infrared detection elements 3 are arranged in a matrix of N rows and N columns, and the multiple infrared detection elements 3 form an N-row and N-column thermal image sensor.

[0024] A plurality of recesses 21c are provided on the first main surface 21a of the element substrate 21. The plurality of infrared detection elements 3 are arranged so as to overlap with corresponding recesses 21c in the element substrate 21 in the thickness direction of the element substrate 21. More specifically, in each infrared detection element 3, a hot junction is arranged in the center and a cold junction is arranged in the peripheral portion. The central portion of the infrared detection element 3 where the hot junction is arranged is arranged so as to overlap with the corresponding recess 21c, and the peripheral portion where the cold junction is arranged is arranged so as to overlap with the element substrate 21 around the corresponding recess 21c. Therefore, the recess 21c corresponding to the infrared detection element 3 is arranged between the hot junction and the element substrate 21 in the thickness direction of the element substrate 21. As a result, heat from the hot junction is insulated by the recess 21c and is prevented from escaping to the element substrate 21.

[0025] The multiple reference detection elements 4 are elements that detect infrared rays that cause noise included in the output signals of each of the multiple infrared detection elements 3. The infrared rays that cause the noise are infrared rays other than the infrared rays 30 that pass through the lens substrate 23 from the outside and enter the cavity 9. More specifically, the infrared rays that cause the noise include infrared rays that cause temperature changes at the cold junctions of each of the multiple infrared detection elements 3, and light (infrared rays) that is emitted from the lens substrate 23 (e.g., the lens 5 and its surroundings) when heated. Each of the multiple infrared detection elements 3 corresponds to one of the multiple reference detection elements 4 (e.g., the nearest reference detection element 4). The output signal (digital output signal) of the corresponding one reference detection element 4 is subtracted from the output signal (digital output signal) of each of the multiple infrared detection elements 3, thereby removing the noise from the output signal (digital output signal) of each of the multiple infrared detection elements 3.

[0026] A signal processing unit (not shown) is formed on the first main surface 21a of the element substrate 21. The signal processing unit includes, for example, an ASIC (Application Specific Integrated Circuit). The signal processing unit converts the infrared rays 30 detected by each of the multiple infrared detection elements 3 into a voltage, amplifies the converted voltage, converts the amplified voltage into a digital signal, converts the output value of each of the multiple infrared detection elements 3 into a digital value, and outputs the digital value. The signal processing unit converts the infrared rays 30 detected by each of the multiple reference detection elements 4 into a voltage, amplifies the converted voltage, converts the amplified voltage into a digital signal, and converts the output value of each of the multiple reference detection elements 4 into a digital value and outputs the digital value.

[0027] The signal processing unit subtracts the digital output signal of the corresponding reference detection element 4 from the digital output signal of each of the plurality of infrared detection elements 3, thereby removing noise from the digital output signal of each of the plurality of infrared detection elements 3. Then, the signal processing unit outputs the digital output signal of the infrared detection element 3 from which the noise has been removed to an external wiring board (not shown).

[0028] The spacer layer 22 has a first main surface 22a and a second main surface 22b that face each other in the thickness direction. The spacer layer 22 is bonded to the element substrate 21 so as to surround the plurality of infrared detection elements 3. More specifically, the infrared detection elements 3 are surrounded by an inner surface 22c of the spacer layer 22 that forms the cavity 9 on the first main surface 21a of the element substrate 21. The second main surface 22b of the spacer layer 22 and the first main surface 21a of the element substrate 21 are bonded at a first bonding surface 25.

[0029] The getter material 7 is disposed on the first main surface 21a of the element substrate 21. The getter material 7 is housed in the cavity 9 together with the plurality of infrared detection elements 3. The getter material 7 adsorbs gas present in the cavity 9. This makes it possible to increase the degree of vacuum within the cavity 9.

[0030] The lens substrate 23 has a first main surface 23a and a second main surface 23b that face each other in the thickness direction. The second main surface 23b is the main surface of the lens substrate 23 that faces the cavity 9, and the first main surface 23a is the main surface of the lens substrate 23 on the side opposite to the cavity 9. The second main surface 23b of the lens substrate 23 closes the cavity 9. The lens substrate 23 is bonded to the spacer layer 22. More specifically, the first main surface 22a of the spacer layer 22 and the second main surface 23b of the lens substrate 23 are bonded at a second bonding surface 26.

[0031] The lens substrate 23 has a lens 5. More specifically, the lens 5 is provided on the second main surface 23b of the lens substrate 23. The lens 5 is a silicon lens. More specifically, the lens 5 is formed, for example, in the shape of a plano-convex aspherical lens on the second main surface 23b of the lens substrate 23. The lens 5 faces the cavity 9. The lens 5 is a lens that focuses infrared rays 30 that pass through the lens substrate 23 from the outside and enter the cavity 9 onto the multiple infrared detection elements 3.

[0032] The antireflection coating 8 is disposed on the lens substrate 23. A first antireflection coating 8a is disposed on the second main surface 23b of the lens substrate 23. More specifically, the first antireflection coating 8a covers the lenses 5 formed on the second main surface 23b of the lens substrate 23. In other words, the first antireflection coating 8a is disposed on the inner surface of the lens substrate 23 facing the cavity 9. Furthermore, a second antireflection coating 8b is disposed on the first main surface 23a of the lens substrate 23. The second antireflection coating 8b has a rectangular shape in plan view (see FIG. 2). Hereinafter, the first antireflection coating 8a and the second antireflection coating 8b may be collectively referred to as the antireflection coating 8.

[0033] The antireflection film 8 is not disposed on the inner surface 22c of the spacer layer 22 facing the cavity 9. In addition, the antireflection film 8 is not disposed on the first bonding surface 25 between the element substrate 21 and the spacer layer 22, and on the second bonding surface 26 between the spacer layer 22 and the lens substrate 23.

[0034] In the present disclosure, "the anti-reflection coating 8 is not disposed on the first bonding surface 25 and the second bonding surface 26" means that the first bonding surface 25 and the second bonding surface 26 contain few impurities made of the same material as the anti-reflection coating 8. When the above impurities are present on the first bonding surface 25 and the second bonding surface 26, the cleanliness and flatness of the first bonding surface 25 and the second bonding surface 26 decrease compared to when the above impurities are not present, which deteriorates the airtightness of the cavity 9 of the infrared sensor 1 and increases the internal pressure.

[0035] The anti-reflection coating 8 is made of, for example, a multilayer film in which thin films with different refractive indices are stacked. In this embodiment, the anti-reflection coating 8 has a first thin film layer and a second thin film layer. For example, a ZnS (zinc sulfide) layer is used as the first thin film layer. For example, a Ge (germanium) layer or a layer containing titanium dioxide (TiO2) is used as the second thin film layer. The anti-reflection coating 8 of this embodiment achieves anti-reflection function by adjusting the film thickness, refractive index, etc. The film thickness of the anti-reflection coating 8 is appropriately set depending on the infrared wavelength range in which the transmittance is to be increased. This prevents reflection of infrared rays 30, making it easier for external infrared rays 30 to pass through the lens substrate 23 and enter the cavity 9.

[0036] (2.2) Operation explanation The operation of the infrared sensor 1 will be described with reference to FIG.

[0037] Infrared rays 30 from outside pass through the lens substrate 23 and enter the cavity 9. At this time, the infrared rays 30 are transmitted through the first main surface 23a of the lens substrate 23 without being reflected by the first main surface 23a of the lens substrate 23 due to the second antireflection film 8b provided on the first main surface 23a of the lens substrate 23. Furthermore, the infrared rays 30 are transmitted through the second main surface 23b of the lens substrate 23 without being reflected by the second main surface 23b of the lens substrate due to the lens 5 and the first antireflection film 8a provided on the second main surface 23b of the lens substrate 23. Furthermore, when the infrared rays 30 from outside pass through the lens 5, the lens 5 focuses the infrared rays 30 onto the multiple infrared detection elements 3 arranged on the first main surface 21a of the element substrate 21. The infrared rays 30 transmitted through the lens substrate 23 then travel toward the element substrate 21 in the cavity 9, are narrowed by a diaphragm section (not shown), and are received by the multiple infrared detection elements 3 arranged on the first main surface 21a of the element substrate 21. The infrared light 30 received by each of the multiple reference detection elements 4 is output to a signal processing unit arranged on the element substrate 21, where it is subjected to the required processing, converted into a digital output signal, and output to a wiring board (not shown).

[0038] (2.3) Manufacturing method Next, a method for manufacturing the infrared sensor 1 according to the embodiment will be described with reference to FIGS.

[0039] (2.3.1) First step First, in the first step, a first silicon wafer 11, a second silicon wafer 12, and a third silicon wafer 13 are prepared as shown in Fig. 3. The first silicon wafer 11, the second silicon wafer 12, and the third silicon wafer 13 have the same shape and size.

[0040] The first silicon wafer 11 is a substrate material for forming the element substrate 21 (see FIG. 1) of the infrared sensor 1. More specifically, the first silicon wafer 11 is a disk-shaped substrate material, and has a first main surface 11a and a second main surface 11b that face each other in the thickness direction.

[0041] The second silicon wafer 12 is a substrate material for forming the spacer layer 22 (see FIG. 1) of the infrared sensor 1. More specifically, the second silicon wafer 12 is a disk-shaped substrate material, and has a first main surface 12a and a second main surface 12b that face each other in the thickness direction.

[0042] The third silicon wafer 13 is a substrate material for forming the lens substrate 23 (see FIG. 1) of the infrared sensor 1. More specifically, the third silicon wafer 13 is a disk-shaped substrate material, and has a first main surface 13a and a second main surface 13b that face each other in the thickness direction.

[0043] (2.3.2) Second step 4, in the second step, the infrared detection elements 3 are disposed on the first silicon wafer 11 to form an element substrate 21. Hereinafter, the substrate before the infrared detection elements 3 are disposed will be referred to as the first silicon wafer 11, and the substrate after the infrared detection elements 3 are disposed will be referred to as the element substrate 21 to distinguish between the two. In other words, the element substrate 21 is the first silicon wafer 11 on which the infrared detection elements 3 are disposed.

[0044] More specifically, on the first main surface 11a of the first silicon wafer 11, as shown in Fig. 4, a plurality of infrared detection elements 3, a plurality of reference detection elements 4 (only one of which is shown in Fig. 4), and a signal processing unit (not shown) are arranged on the first main surface 21a of the element substrate 21. Then, a plurality of recesses 21c are formed. Then, a getter material 7 is arranged around the plurality of infrared detection elements 3 arranged on the first main surface 21a of the element substrate 21.

[0045] Of the first main surface 21a of the element substrate 21, the area around the area where the multiple infrared detection elements 3, the getter material 7, the multiple reference detection elements 4, and the signal processing unit are arranged (hereinafter also referred to as the "element arrangement area") is referred to as a bonding area 21d with the spacer layer 22, which will be described later. In other words, the bonding area 21d is an area of ​​the first main surface 21a of the element substrate 21 where the multiple infrared detection elements 3, the getter material 7, the multiple reference detection elements 4, and the signal processing unit are not arranged. The bonding area 21d is the bonding area of ​​the element substrate 21 with the spacer layer 22.

[0046] (2.3.3) Third step 5, in the third step, a spacer layer 22 is formed using the second silicon wafer 12 as a base material. Hereinafter, the substrate before the through-holes 12c are formed will be referred to as the second silicon wafer 12, and the substrate after the through-holes 12c are formed will be referred to as the spacer layer 22 to distinguish between the two. In other words, the spacer layer 22 is the second silicon wafer 12 in which the through-holes 12c are formed.

[0047] 5, the spacer layer 22 is formed by forming through holes 12c in the thickness direction of the second silicon wafer 12. More specifically, the through holes 12c penetrate the first main surface 22a and the second main surface 22b, which face each other in the thickness direction of the spacer layer 22. The through holes 12c are holes for surrounding the infrared detection elements 3 arranged on the element substrate 21 in an eighth step, which will be described later. Therefore, the openings of the through holes 12c cover at least the region (element arrangement region) on the first main surface 21a of the element substrate 21 where the infrared detection elements 3 are arranged. The inner walls of the through holes 12c correspond to the inner surfaces 22c of the spacer layer 22.

[0048] An area adjacent to the through-hole 12c on the first main surface 22a of the spacer layer 22 is referred to as a first bonding area 22d with the lens substrate 23, which will be described later. An area adjacent to the through-hole 12c on the second main surface 22b of the spacer layer 22 is referred to as a second bonding area 22e with the element substrate 21, which will be described later. The first bonding area 22d is an area of ​​the spacer layer 22 that is bonded to the lens substrate 23. The second bonding area 22e is an area of ​​the spacer layer 22 that is bonded to the element substrate 21.

[0049] (2.3.4) Fourth step Next, as shown in FIG. 6, in the fourth step, a lens substrate 23 having lenses 5 is formed on the third silicon wafer 13.

[0050] Hereinafter, to distinguish between the substrate before the lens 5 is formed, the substrate is referred to as the third silicon wafer 13, and the substrate after the lens 5 is formed is referred to as the lens substrate 23. In other words, the lens substrate 23 is the third silicon wafer 13 on which the lens 5 is formed.

[0051] The lens 5 is a curved lens made of silicon. More specifically, as shown in FIG. 6, a plano-convex aspherical lens is formed on the second main surface 23b of the lens substrate 23. The peripheral shape of the lens 5 is, for example, rectangular in plan view. The lens 5 can be formed by etching, polishing, or the like. For example, a lens made of a diffractive optical element can be formed by repeating photolithography and etching processes using photolithography-etching technology used in semiconductor technology. Note that the method for forming the lens 5 is not limited to the above, and the lens can be formed on the lens substrate 23 using other known techniques. The region adjacent to the lens 5 on the second main surface 23b of the lens substrate 23 is referred to as a bonding region 23d with the spacer layer 22, which will be described later.

[0052] (2.3.5) Fifth step Next, as shown in FIG. 7, in a fifth step, an anti-reflection film 8 is formed on the lens substrate 23 formed in the fourth step.

[0053] 7, a first antireflection film 8a is formed on the second main surface 23b of the lens substrate 23, and a second antireflection film 8b is formed on the first main surface 23a of the lens substrate 23. On the second main surface 23b of the lens substrate 23, the first antireflection film 8a is formed so as to cover the bonding region 23d between the lens 5 and the spacer layer 22. Meanwhile, the second antireflection film 8b is formed so as to cover the entire first main surface 23a of the lens substrate 23.

[0054] The anti-reflection coating 8 is formed by laminating thin films with different refractive indices. In this embodiment, the anti-reflection coating 8 is composed of a first thin film layer and a second thin film layer. For example, a ZnS (zinc sulfide) layer is formed on the main surface of the lens substrate 23 as the first thin film layer. Then, a Ge (germanium) layer or a layer made of titanium dioxide (TiO2) is formed on top of the first thin film layer as the second thin film layer. Vacuum deposition or sputtering, which do not require high heat, is preferably used to form each layer constituting the anti-reflection coating 8. The anti-reflection coating 8 of this embodiment achieves anti-reflection function by adjusting the film thickness, refractive index, etc. The film thickness of the anti-reflection coating 8 is appropriately set depending on the infrared wavelength region in which the transmittance is to be increased.

[0055] (2.3.6) 6th step Next, as shown in FIG. 7, in a sixth step, a part of the antireflection film 8 formed in the fifth step is removed to form a bonding region 23d between the lens substrate 23 and the spacer layer 22.

[0056] 7, part of the antireflection film 8 is a portion of the first antireflection film 8a formed on the second main surface 23b of the lens substrate 23, which covers the bonding region 23d with the spacer layer 22. In other words, part of the antireflection film 8 is a portion of the first antireflection film 8a formed on the second main surface 23b of the lens substrate 23 excluding the portion that covers the lens 5.

[0057] Using photolithography, a resist layer (not shown) is formed on the first antireflection film 8a, which covers the lenses 5 and the bonding region 23d on the second main surface 23b of the lens substrate 23. Then, using the resist layer as a mask, unnecessary portions of the first antireflection film 8a (more specifically, the portions covering the bonding region 23d) are etched away by, for example, wet etching or dry etching. This exposes the bonding region 23d with the spacer layer 22 on the lens substrate 23. Then, the resist layer is removed. This forms the bonding region 23d with the spacer layer 22 on the second main surface 23b of the lens substrate 23.

[0058] (2.3.7) 7th step Next, as shown in FIG. 8, in a seventh step, the bonding region 23d of the lens substrate 23 and the first bonding region 22d of the spacer layer 22 are bonded together.

[0059] 8, the bonding region 23d on the second main surface 23b of the lens substrate 23 is bonded to the first bonding region 22d on the first main surface 22a of the spacer layer 22. This forms a second bonding surface 26 between the spacer layer 22 and the lens substrate 23.

[0060] In this embodiment, the bonding between the lens substrate 23 and the spacer layer 22 at the second bonding surface 26 is a direct bonding between the lens substrate 23 and the spacer layer 22. In this disclosure, "direct bonding" refers to directly bonding silicon substrates together without an adhesive layer. The anti-reflection film 8 is not formed on the first bonding region 22d of the spacer layer 22 and the bonding region 23d of the lens substrate 23, and therefore the surfaces are regions of pure silicon. This enables direct bonding between the lens substrate 23 and the spacer layer 22, both of which are silicon.

[0061] In this embodiment, the direct bonding between the lens substrate 23 and the spacer layer 22 is low-temperature activated bonding. In this disclosure, "low-temperature activated bonding" refers to a technique for activating the surfaces of silicon substrates at a temperature of 200°C or less and bonding the substrates together. In this embodiment, a temperature of 200°C or less may be referred to as "low temperature," and a temperature higher than 200°C may be referred to as "high temperature." For example, in surface activated bonding, the substrate surfaces are activated at room temperature using an argon fast atom beam, an ion beam, plasma, or the like, and the substrates are pressed together in a vacuum to bond them together. Note that "room temperature" in this disclosure refers to room temperature. Since surface activated bonding can bond the lens substrate 23 and the spacer layer 22 at room temperature, it has less of an effect on the anti-reflection coating 8 of the lens substrate 23.

[0062] (2.3.8) 8th step Next, as shown in FIG. 9, in an eighth step, the spacer layer 22 and the element substrate 21 formed in the second step are bonded together so that the spacer layer 22 surrounds the infrared detection element 3.

[0063] 9, the second bonding region 22e on the second main surface 22b of the spacer layer 22 bonded to the lens substrate 23 is bonded to the bonding region 21d on the first main surface 21a of the element substrate 21. This forms a first bonding surface 25 between the spacer layer 22 and the element substrate 21.

[0064] In this embodiment, the bonding between the element substrate 21 and the spacer layer 22 at the first bonding surface 25 is a direct bonding between the element substrate 21 and the spacer layer 22. The bonding region 21d of the element substrate 21 and the second bonding region 22e of the spacer layer 22 are regions whose surfaces are made of pure silicon because no antireflection film 8 is formed thereon. This enables a direct bonding between the element substrate 21 and the spacer layer 22 made of silicon.

[0065] Furthermore, the direct bonding between the element substrate 21 and the spacer layer 22 is low-temperature activated bonding. For example, surface activated bonding can bond the element substrate 21 and the spacer layer 22 at room temperature, which reduces the influence on the circuit elements (such as the infrared detection element 3) of the element substrate 21 compared to fusion bonding, which requires heat treatment at high temperatures.

[0066] In the final step, the element substrate 21, the spacer layer 22, and the lens substrate 23 are cut along the dicing lines. The infrared sensors 1 are cut so as to have a rectangular shape in a plan view (see FIG. 2). As a result, the infrared sensors 1 are formed individually in chip units (see FIG. 1).

[0067] According to the manufacturing method of this embodiment, wafer level package (WLP) technology can be applied to manufacture the lens-integrated infrared sensor 1. The internal pressure of the cavity 9 (internal space) of the infrared sensor 1 can be reduced to 10 Pa or less.

[0068] In this embodiment, a method for manufacturing a single infrared sensor 1 has been described, but by arranging more infrared detection elements 3 on the first silicon wafer 11, multiple infrared sensors 1 can be manufactured at once by cutting.

[0069] (3.1) Advantage 1 A configuration in which an antireflection film corresponding to a target wavelength is formed on a lens substrate integrally formed with a spacer layer will be considered as Comparative Example 1. As shown in Fig. 15, an optical lens 118 and an edge portion 120 are formed on a lens substrate 124 of Comparative Example 1, and a spacer layer 122 is formed on the back surface of the lens substrate 124. In Comparative Example 1, antireflection films 80a and 80b corresponding to a target wavelength are formed on both surfaces of the lens substrate 124, as shown in Fig. 15.

[0070] Thereafter, the antireflection film 80a is removed from the back surface 122a of the spacer layer 122. The back surface 122a of the spacer layer 122 corresponds to the bonding surface of the lens substrate 124 with the element substrate. In this case, the antireflection film 80a is covered with a resist layer, and part of the antireflection film 80a (the part covering the back surface 122a of the spacer layer 122) is patterned and etched away.

[0071] However, in the lens substrate 124 of Comparative Example 1, there is a large step H between the lens rear surface 118a and the rear surface 122a of the spacer layer 122. This makes it difficult to accurately apply a resist layer (not shown) to the antireflection film 80a from the rear surface of the lens substrate 124, and it is difficult to clean and flatten the rear surface 122a (bonding surface) of the spacer layer 122 when selectively removing a portion of the antireflection film 80a. As a result, in Comparative Example 1, it is difficult to increase the airtightness of the internal space when the element substrate is bonded to the lens substrate 124.

[0072] In contrast, in the manufacturing method of the infrared sensor 1 according to this embodiment, the lens substrate 23 and the spacer layer 22 are formed in separate processes, the anti-reflection coating 8 is formed only on the lens substrate 23, and a portion of the anti-reflection coating 8 is selectively removed. As shown in FIG. 7 , the step between the lens 5 and the bonding region 23d on the second main surface 23b of the lens substrate 23 is small. This makes it easy to accurately apply a resist layer (not shown) to the first anti-reflection coating 8a covering the lens 5 and the bonding region 23d of the lens substrate 23. This allows the bonding region 23d of the spacer layer 22 to be clean and flat when selectively removing a portion of the first anti-reflection coating 8a (the portion covering the bonding region 23d of the spacer layer 22). As a result, in this embodiment, the first anti-reflection coating 8a is not formed on the second bonding surface 26 between the lens substrate 23 and the spacer layer 22, making it easier to increase the airtightness of the internal space of the infrared sensor 1.

[0073] (3.2) Advantage 2 Consider Comparative Example 2, a configuration in which the anti-reflection film is an oxide film. In Comparative Example 2, if the anti-reflection film is formed of, for example, SiO2, the SiO2 layer has the disadvantages of being limited in the transmission wavelength range and of being difficult to adjust the film thickness by etching or the like. For this reason, the anti-reflection effect or transmission efficiency of the anti-reflection film of Comparative Example 2 is limited.

[0074] In contrast, in the infrared sensor 1 according to this embodiment, the antireflection coating 8 is made of a multilayer film in which thin films with different refractive indices are stacked. This allows infrared light in a desired wavelength range to pass through and infrared light in an unnecessary wavelength range to be suitably reflected. Furthermore, the thickness of the antireflection coating 8 can be appropriately set depending on the infrared wavelength range in which the transmittance is to be increased.

[0075] (4) Effects In the infrared sensor 1 according to this embodiment, as shown in FIG. 1, the anti-reflection coating 8 disposed on the lens substrate 23 is not disposed on the inner surface 22c of the spacer layer 22 facing the cavity 9. This allows the lens substrate 23 and the spacer layer 22 to be manufactured in separate processes and then bonded together, as shown in FIGS. 5 to 7. Furthermore, since the anti-reflection coating 8 is not disposed on the first bonding surface 25 between the element substrate 21 and the spacer layer 22 and the second bonding surface 26 between the spacer layer 22 and the lens substrate 23, the cleanliness and flatness of the first bonding surface 25 and the second bonding surface 26 can be easily maintained. This allows the element substrate 21, the spacer layer 22, and the lens substrate 23 to be bonded together by direct bonding of silicon. In other words, this embodiment ensures a high level of airtightness in the cavity 9 (internal space) of the infrared sensor 1.

[0076] In the infrared sensor 1 according to this embodiment, the antireflection coating 8 is made of a multilayer film in which thin films with different refractive indices are stacked. This allows infrared light in a desired wavelength range to pass through and infrared light in an unnecessary wavelength range to be suitably reflected. The thickness of the antireflection coating 8 can be appropriately set depending on the infrared wavelength range in which the transmittance is to be increased.

[0077] Furthermore, in the infrared sensor 1 according to this embodiment, anti-reflection films 8 are disposed on both surfaces (the first main surface 23a and the second main surface 23b) of the lens substrate 23. This makes it possible to cut out infrared rays in unnecessary wavelength ranges, thereby increasing the infrared sensitivity.

[0078] In this embodiment, the bonding between the element substrate 21 and the spacer layer 22 at the first bonding surface 25 is a direct bonding between the element substrate 21 and the spacer layer 22. The bonding region 21d of the element substrate 21 and the second bonding region 22e of the spacer layer 22 are regions whose surfaces are made of pure silicon because the anti-reflection film 8 is not formed thereon. This enables a direct bonding between the element substrate 21 and the spacer layer 22 made of silicon.

[0079] In this embodiment, the direct bonding between the element substrate 21 and the spacer layer 22 is low-temperature activated bonding. For example, surface activated bonding can bond the element substrate 21 and the spacer layer 22 at room temperature, which reduces the influence of the element substrate 21 on the infrared detection element 3 compared to fusion bonding, which requires heat treatment at high temperature.

[0080] Furthermore, in this embodiment, the bonding between the lens substrate 23 and the spacer layer 22 at the second bonding surface 26 is a direct bond between the lens substrate 23 and the spacer layer 22. The first bonding region 22d of the spacer layer 22 and the bonding region 23d of the lens substrate 23 are regions whose surfaces are made of pure silicon because no antireflection film 8 is formed thereon. This enables direct bonding between the lens substrate 23 and the spacer layer 22, both made of silicon.

[0081] In this embodiment, the direct bonding between the lens substrate 23 and the spacer layer 22 is low-temperature activated bonding. For example, surface activated bonding allows the lens substrate 23 and the spacer layer 22 to be bonded at room temperature, which reduces the effect on the anti-reflection film 8 of the lens substrate 23 compared to fusion bonding, which requires heat treatment at high temperatures.

[0082] (5) Variations The above embodiment is merely one of various embodiments of the present disclosure. The embodiment can be modified in various ways depending on the design and the like as long as the object of the present disclosure can be achieved.

[0083] The following modifications may be implemented in appropriate combination. The same components as those in the above-described embodiment are denoted by the same reference numerals and will not be described again.

[0084] (5.1) Variation 1 In the manufacturing method of the infrared sensor 1 of this embodiment, in the third step, the spacer layer 22 is formed by forming through holes 12c in the thickness direction in the second silicon wafer 12 (see Figure 5), but the method of forming the spacer layer 22 is not limited to the method of forming through holes 12c.

[0085] A method for manufacturing an infrared sensor 1 according to a first modified example of the present embodiment will be described below with reference to Figures 10 and 11. In the method for manufacturing an infrared sensor 1 according to the first modified example, the third and seventh steps are different from the method for manufacturing an infrared sensor 1 according to the present embodiment.

[0086] 10, in the third step of the first modified example, a recess 12d is formed in the thickness direction on the first main surface 12a of the second silicon wafer 12. This forms a first bonding region 22d in the spacer layer 22 with the lens substrate 23.

[0087] 11, the bonding region 23d of the lens substrate 23 is bonded to the first bonding region 22d of the spacer layer 22. This forms a second bonding surface 26 between the spacer layer 22 and the lens substrate 23. Then, the second main surface 12b of the second silicon wafer 12 is polished in the thickness direction. This forms a second bonding region 22e between the spacer layer 22 and the element substrate 21.

[0088] When forming the second bonding region 22e, for example, a CMP (Chemical Mechanical Polishing) method is used to polish the second main surface 12b of the second silicon wafer 12. This makes it possible to increase the cleanliness and flatness of the surface of the second bonding region 22e.

[0089] In the eighth step of the first modified example, similarly to the embodiment (FIG. 9), the second bonding region 22e of the spacer layer 22 bonded to the lens substrate 23 is bonded to the bonding region 21d of the element substrate 21 formed in the second step. This makes it easier to maintain the cleanliness and flatness of the second bonding surface 26 between the spacer layer 22 and the element substrate 21. That is, the first modified example can also achieve the same effects as the embodiment.

[0090] (5.2) Variation 2 In the infrared sensor 1 of this embodiment, the lens substrate 23 has the convex aspherical lens 5 facing the cavity 9 (see FIG. 1), but the lens 5 is not limited to facing the cavity 9.

[0091] In the infrared sensor 1A according to the second variant of this embodiment, as shown in the lower diagram of Figure 14, the lens substrate 23A differs from the infrared sensor 1 according to the embodiment in that it has a convex aspherical lens 5 on the second main surface 23b opposite the cavity 9.

[0092] A method for manufacturing the infrared sensor 1A according to the second modification will be described below with reference to Figures 12 to 14. In the method for manufacturing the infrared sensor 1A according to the second modification, the sixth, seventh, and eighth steps are different from the method for manufacturing the infrared sensor 1 according to the embodiment.

[0093] In the sixth step of the second modified example, a portion of the antireflection film 8 (see FIG. 12) formed in the fifth step is removed. More specifically, in the second modified example, as shown in FIG. 12, the portion of the antireflection film 8 is a portion of the second antireflection film 8b formed on the first main surface 23a of the lens substrate 23 that covers the bonding region 23d with the spacer layer 22.

[0094] Using photolithography, a resist layer (not shown) is formed on the second antireflection film 8b covering the second main surface 23b of the lens substrate 23. Then, using the resist layer as a mask, unnecessary portions of the second antireflection film 8b (more specifically, portions covering the bonding region 23d) are etched away. This exposes the bonding region 23d of the lens substrate 23 with the spacer layer 22. Then, the resist layer is removed. As a result, the bonding region 23d with the spacer layer 22 is formed on the first main surface 23a of the lens substrate 23, as shown in the lower diagram of FIG. 12.

[0095] Next, in the seventh step of the second modified example, the bonding region 23d of the lens substrate 23 is bonded to the spacer layer 22. More specifically, as shown in Fig. 13 , the bonding region 23d on the first main surface 23a of the lens substrate 23 is bonded to the first bonding region 22d on the first main surface 22a of the spacer layer 22. This forms a second bonding surface 26 between the spacer layer 22 and the lens substrate 23.

[0096] Next, in an eighth step of the second modified example, the spacer layer 22 is bonded to the element substrate 21 formed in the second step so that the spacer layer 22 surrounds the infrared detection element 3. More specifically, as shown in Fig. 14, the second bonding region 22e on the second main surface 22b of the spacer layer 22 bonded to the lens substrate 23A is bonded to the bonding region 21d on the first main surface 21a of the element substrate 21. This forms a first bonding surface 25 between the spacer layer 22 and the element substrate 21.

[0097] The infrared sensor 1A according to the second modification of this embodiment can also achieve the same effects as those of the embodiment.

[0098] In the infrared sensor 1 of this embodiment (see FIG. 1) and the infrared sensor 1A according to the second modification (see FIG. 14), the lenses 5 are formed on one main surface of the lens substrate 23, but the position where the lenses 5 are formed is not limited to one main surface of the lens substrate 23. The lenses 5 may be formed on both sides (the first main surface 23a and the second main surface 23b) of the lens substrate 23.

[0099] (5.3) Other Modifications In this embodiment, the second step of forming the element substrate 21, the third step of forming the spacer layer 22, and the fourth step of forming the lens substrate 23 are performed in this order, but the order of the second to fourth steps is not limited to this. That is, the steps may be performed in the following order: second step - fourth step - third step, third step - second step - fourth step, third step - fourth step - second step, fourth step - second step - third step, fourth step - third step - second step.

[0100] In this embodiment, the lens substrate 23 and the spacer layer 22 are bonded together in the seventh step (see FIG. 8), and then the spacer layer 22 bonded to the lens substrate 23 is bonded to the element substrate 21 in the eighth step (see FIG. 9). However, the seventh step and the eighth step may be reversed. That is, the element substrate 21 and the spacer layer 22 may be bonded together, and then the spacer layer 22 bonded to the element substrate 21 may be bonded to the lens substrate 23.

[0101] In this embodiment, the anti-reflection coating 8 is described as being made up of a multilayer film in which a plurality of thin films are stacked, but the configuration of the anti-reflection coating 8 is not limited to a multilayer film. For example, the anti-reflection coating 8 may be made up of at least one thin film. In this case, the anti-reflection coating 8 may be made up of a first thin film layer consisting of, for example, only a ZnS layer.

[0102] In the seventh step of this embodiment, the direct bonding between the element substrate 21 and the spacer layer 22 is surface activated bonding, but the direct bonding is not limited to surface activated bonding. The direct bonding between the element substrate 21 and the spacer layer 22 may be any low-temperature activated bonding, such as plasma activation bonding or cryogenic bonding.

[0103] In the eighth step of this embodiment, the bonding between the element substrate 21 and the spacer layer 22 at the first bonding surface 25 is direct bonding between the element substrate 21 and the spacer layer 22, but the bonding between the element substrate 21 and the spacer layer 22 is not limited to direct bonding. The bonding between the element substrate 21 and the spacer layer 22 may be bonding via, for example, a metal intermediate layer.

[0104] (summary) The above-described embodiments and the like disclose the following aspects.

[0105] The infrared sensor (1, 1A) of the first embodiment includes an infrared detection element (3), an element substrate (21), a spacer layer (22), a lens substrate (23, 23A), and antireflection films (8a, 8b). The element substrate (21) is made of silicon, and has the infrared detection element (3) disposed thereon. The spacer layer (22) is made of silicon and is bonded to the element substrate (21) so as to surround the infrared detection element (3). The lens substrate (23, 23A) is made of silicon and is bonded to the spacer layer (22). The antireflection films (8a, 8b) are disposed on the lens substrate (23, 23A). The element substrate (21), the spacer layer (22), and the lens substrate (23, 23A) form a cavity (9). The antireflection film (8a) is disposed on the inner surface of the lens substrate (23, 23A) facing the cavity (9). The anti-reflection film (8a) is not disposed on the inner surface (22c) of the spacer layer (22) facing the cavity (9), the first bonding surface (25) between the element substrate (21) and the spacer layer (22), or the second bonding surface (26) between the spacer layer (22) and the lens substrate (23).

[0106] According to this embodiment, the antireflection film (8a) is not disposed on the inner surface (22c) of the spacer layer (22) facing the cavity (9). This allows the lens substrate (23, 23A) on which the antireflection films (8a, 8b) are disposed and the spacer layer (22) on which the antireflection films (8a, 8b) are not disposed to be manufactured in separate processes, and then the two substrates can be bonded together. Furthermore, the antireflection film (8a) is not disposed on the first bonding surface (25) between the element substrate (21) and the spacer layer (22) and the second bonding surface (26) between the spacer layer (22) and the lens substrate (23, 23A). This makes it easier to maintain the cleanliness and flatness of the first bonding surface (25) and the second bonding surface (26). As a result, it is possible to ensure a high level of airtightness of the cavity (9) of the infrared sensor (1, 1A).

[0107] The manufacturing method of the infrared sensor (1, 1A) of the second aspect includes first to eighth steps. In the first step, a first silicon wafer (11), a second silicon wafer (12), and a third silicon wafer (13) are prepared. In the second step, an element substrate (21) is formed by arranging infrared detection elements (3) on the first silicon wafer (11). In the third step, a spacer layer (22) is formed using the second silicon wafer (12) as a base material. In the fourth step, a lens substrate (23, 23A) having lenses (5) is formed on the third silicon wafer (13). In the fifth step, antireflection films (8a, 8b) are formed on the lens substrate (23, 23A) formed in the fourth step. In the sixth step, a bonding region (23d) with the spacer layer (22) is formed on the lens substrate (23, 23A) by removing a portion of the antireflection films (8a, 8b) formed in the fifth step. In a seventh step, the bonding regions (23d) of the lens substrates (23, 23A) are bonded to the spacer layer (22). In an eighth step, the spacer layer (22) is bonded to the element substrate (21) formed in the second step so that the spacer layer (22) surrounds the infrared detection element (3).

[0108] According to this embodiment, the lens substrate (23, 23A) and the spacer layer (22) are formed in separate processes, so there are no steps on the main surfaces (23a and 23b) on both sides of the lens substrate (23, 23A). This makes it easy to accurately apply a resist layer (not shown) when selectively removing a portion of the anti-reflection film (8a, 8b) on the lens substrate (23, 23A), and makes it possible to keep the bonding region (23d) of the spacer layer (22) clean and flat. This also makes it easier to improve the airtightness of the internal space of the infrared sensor (1, 1A).

[0109] A third aspect of the manufacturing method for an infrared sensor (1) is the second aspect, and includes the steps of: forming a recess (12d) in the thickness direction on the first main surface (12a) of the second silicon wafer (12); thereby forming a first bonding region (22d) in the spacer layer (22) with the lens substrate (23, 23A); bonding the bonding region (23d) of the lens substrate (23, 23A) to the first bonding region (22d) of the spacer layer (22); and polishing the second main surface (12b) of the second silicon wafer (12) opposite the first main surface (12a) in the thickness direction; thereby forming a second bonding region (22e) in the spacer layer (22) with the element substrate (21); and bonding the second bonding region (22e) of the spacer layer (22) bonded to the lens substrate (23) to the element substrate (21) formed in the second step.

[0110] According to this embodiment, it becomes easier to maintain the cleanliness and flatness of the bonding surface between the spacer layer (22) and the element substrate (21).

[0111] The manufacturing method of the infrared sensor (1) of the fourth aspect is the same as that of the second or third aspect, and in the seventh step, the bonding between the lens substrate (23, 23A) and the spacer layer (22) is direct bonding between the lens substrate (23, 23A) and the spacer layer (22).

[0112] According to this embodiment, the first bonding region (22d) of the spacer layer (22) and the bonding region (23d) of the lens substrate (23, 23A) are regions with pure silicon surfaces because the antireflection films (8a, 8b) are not formed thereon, which allows direct bonding between the lens substrate (23, 23A) made of silicon and the spacer layer (22).

[0113] The manufacturing method of the infrared sensor (1) of the fifth aspect is the second or third aspect, in which in the eighth step, the bonding between the element substrate (21) and the spacer layer (22) is direct bonding between the element substrate (21) and the spacer layer (22).

[0114] According to this embodiment, the bonding region (21d) of the element substrate (21) and the second bonding region (22e) of the spacer layer (22) are regions with pure silicon surfaces because the antireflection films (8a, 8b) are not formed thereon, thereby enabling direct bonding between the element substrate (21) and the spacer layer (22) made of silicon.

[0115] The sixth aspect of the method for producing the infrared sensor (1) is the fourth aspect, in which the direct bonding in the seventh step is low-temperature activated bonding.

[0116] According to this embodiment, the lens substrate (23, 23A) and the spacer layer (22) can be bonded at room temperature, for example, by surface activated bonding, which reduces the impact on the antireflection films (8a, 8b) of the lens substrate (23, 23A) compared to bonding that requires heat treatment at high temperatures, for example.

[0117] The seventh aspect of the method for producing the infrared sensor (1) is the fifth aspect, wherein the direct bonding in the eighth step is low-temperature activated bonding.

[0118] According to this embodiment, the element substrate (21) and the spacer layer (22) can be bonded at room temperature, for example, by surface activated bonding, which reduces the impact on the circuit elements of the element substrate (21) compared to bonding that requires heat treatment at high temperatures, for example.

[0119] The features according to the third to seventh aspects are not essential features for the method of manufacturing an infrared sensor, and can be omitted as appropriate. [Explanation of symbols]

[0120] 1. 1A infrared sensor 3. Infrared detector 4 Reference detector 5 Lenses 7. Getter material 8 Anti-reflection coating 8a 1st anti-reflection coating 8b Second anti-reflection coating 9 Cavity 11 First silicon wafer 11a 1st principal surface 11b 2nd principal surface 12 Second silicon wafer 12a First principal surface 12b Second principal surface 12c through hole 12d recess 13 Third silicon wafer 13a First main surface 13b Second principal surface 21 Element substrate 21a 1st main surface 21b 2nd principal surface 21d Junction area (element substrate) 22 spacer layer 22a First main surface 22b 2nd principal surface 22c inner surface 22d First junction region (spacer layer) 22e Second junction region (spacer layer) 23, 23A Lens substrate 23a First principal surface 23b 2nd principal surface 23d Bonding area (lens substrate) 25 1st joint surface 26 Second joint surface 30 Infrared

Claims

1. an infrared detection element; an element substrate made of silicon on which the infrared detection element is disposed; a spacer layer made of silicon and bonded to the element substrate so as to surround the infrared detection element; a lens substrate bonded to the spacer layer, the lens substrate being made of silicon and having lenses; an anti-reflection film disposed on the lens substrate; The anti-reflection film is disposed on an inner surface of the lens substrate facing a cavity formed by the element substrate, the spacer layer, and the lens substrate; and the spacer layer is not disposed on an inner surface facing the cavity, a first bonding surface between the element substrate and the spacer layer, or a second bonding surface between the spacer layer and the lens substrate; Infrared sensor.

2. a first step of preparing a first silicon wafer, a second silicon wafer, and a third silicon wafer; a second step of forming an element substrate by arranging infrared detection elements on the first silicon wafer; a third step of forming a spacer layer using the second silicon wafer as a substrate; a fourth step of forming a lens substrate having lenses on the third silicon wafer; a fifth step of forming an anti-reflection film on the lens substrate formed in the fourth step; a sixth step of forming a bonding region between the lens substrate and the spacer layer by removing a portion of the anti-reflection film formed in the fifth step; a seventh step of bonding the bonding region of the lens substrate and the spacer layer; an eighth step of bonding the spacer layer to the element substrate formed in the second step so that the spacer layer surrounds the infrared detection element; A method for manufacturing an infrared sensor, comprising:

3. In the third step, a recess is formed in a thickness direction on a first main surface of the second silicon wafer to form a first bonding region of the spacer layer with the lens substrate; The seventh step is bonding the bonding region of the lens substrate to the first bonding region of the spacer layer; polishing a second main surface of the second silicon wafer opposite to the first main surface in a thickness direction to form a second bonding region of the spacer layer with the element substrate; In the eighth step, bonding the second bonding region of the spacer layer bonded to the lens substrate to the element substrate formed in the second step; The method for manufacturing the infrared sensor according to claim 2 .

4. In the seventh step, the bonding between the lens substrate and the spacer layer is direct bonding between the lens substrate and the spacer layer. The method for manufacturing the infrared sensor according to claim 2 or 3.

5. In the eighth step, the bonding between the element substrate and the spacer layer is direct bonding between the element substrate and the spacer layer. The method for manufacturing the infrared sensor according to claim 2 or 3.

6. The direct bonding in the seventh step is low-temperature activated bonding. The method for manufacturing the infrared sensor according to claim 4 .

7. The direct bonding in the eighth step is low-temperature activated bonding. The method for manufacturing the infrared sensor according to claim 5 .

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