Infrared sensor

Abstract

This infrared sensor comprises a base substrate, a wall substrate, a plurality of infrared detection elements, a roof substrate, and a semiconductor lens. The wall substrate is provided on the base substrate. The wall substrate has a through-hole constituting a cavity. The plurality of infrared detection elements are disposed on the base substrate so as to be accommodated in the cavity. The roof substrate is provided on the wall substrate so as to close the cavity. The semiconductor lens is provided on one main surface of the main surfaces on both sides of the roof substrate. The semiconductor lens has a plurality of uneven parts. The plurality of uneven parts are provided on the one main surface of the roof substrate.

Description

Infrared sensor

[0001] The present disclosure relates generally to infrared sensors, and more particularly to infrared sensors with semiconductor lenses.

[0002] The thermal infrared detection device described in Patent Document 1 includes a thermal infrared detection element and a package. The thermal infrared detection element is formed from a first wafer. An infrared detection section is formed on one surface of the thermal infrared detection element. The package is formed from a second wafer. The package is sealed to one surface of the thermal infrared detection element in a manner that surrounds the infrared detection section. A semiconductor lens, which is a convex lens, is provided in the package. This thermal infrared detection device is manufactured using a semiconductor process.

[0003] Japanese Patent Application Laid-Open No. 2007-171170

[0004] In the thermal infrared detector described in Patent Document 1, a semiconductor lens that is a convex lens (i.e., a curved lens) is formed by a semiconductor process. When a semiconductor lens that is a convex lens is formed by a semiconductor process, there is a problem that the control variation of the curved surface shape of the convex lens becomes large, resulting in a decrease in yield.

[0005] An infrared sensor according to one aspect of the present disclosure includes a base substrate, a wall substrate, a plurality of infrared detection elements, a roof substrate, and a semiconductor lens. The wall substrate is provided on the base substrate and has through holes that form a cavity. The plurality of infrared detection elements are arranged on the base substrate so as to be housed within the cavity. The roof substrate is provided on the wall substrate so as to close the cavity. The semiconductor lens is provided on one of the main surfaces on both sides of the roof substrate. The semiconductor lens has a plurality of concave and convex portions provided on the one main surface of the roof substrate.

[0006] An infrared sensor according to an aspect of the present disclosure has an advantage in that the semiconductor lens can be formed with an increased yield by utilizing a semiconductor process.

[0007] FIG. 1 is a cross-sectional view of an infrared sensor according to an embodiment. FIG. 2 is a perspective view of a pillar constituting a semiconductor lens of the infrared sensor according to the embodiment. FIG. 3 is a cross-sectional view of an infrared sensor according to a first modified example of the embodiment. FIG. 4 is a partial cross-sectional view showing a part of a cross-section of an infrared sensor according to a second modified example of the embodiment. FIG. 5 is a partial cross-sectional view showing a part of a cross-section of an infrared sensor according to a third modified example of the embodiment. FIG. 6 is a partial cross-sectional view showing a part of a cross-section of an infrared sensor according to a fourth modified example of the embodiment. FIG. 7 is a partial cross-sectional view showing a part of a cross-section of an infrared sensor according to a fifth modified example of the embodiment. FIG. 8 is a cross-sectional view showing a plurality of pillars of an infrared sensor according to a sixth modified example of the embodiment.

[0008] Hereinafter, an infrared sensor according to an embodiment will be described with reference to the drawings.

[0009] (Embodiment) (1) Overview An infrared sensor 1 according to an embodiment of the present disclosure will be described with reference to FIG. 1 . As shown in FIG. 1 , the infrared sensor 1 includes a base substrate 21, a wall substrate 22, a plurality of infrared detection elements 3, a roof substrate 23, and a semiconductor lens 5. The wall substrate 22 is provided on the base substrate 21. The wall substrate 22 has through holes 22d that form cavities 22c. The plurality of infrared detection elements 3 are disposed on the base substrate 21 so as to be housed within the cavities 22c. The roof substrate 23 is provided on the wall substrate 22 so as to close the cavities 22c. The semiconductor lens 5 is provided on at least one of the main surfaces 23a, 23b on both sides of the roof substrate 23 (the main surface 23b facing the cavity 22c in the example of FIG. 1 ). The semiconductor lens 5 has a plurality of concave-convex portions 5a. The plurality of concave-convex portions 5a are provided on at least one of the main surfaces 23b of the roof substrate 23.

[0010] According to this configuration, the infrared sensor 1 includes the base substrate 21, the wall substrate 22, and the roof substrate 23, and therefore can be configured as a WLP (Wafer Level Package). Furthermore, the semiconductor lens 5 provided on the roof substrate 23 has a plurality of concave and convex portions 5a, and therefore the semiconductor lens 5 can be formed with an increased yield by utilizing the semiconductor process for manufacturing the infrared sensor 1.

[0011] (2) Detailed Description The infrared sensor 1 according to the embodiment is an infrared sensor that receives infrared rays C1 (i.e., far-infrared rays) emitted from a thermal object. More specifically, the infrared sensor 1 detects a mosaic thermal image of N rows and N columns by receiving the far-infrared rays with a plurality of pixels (a plurality of infrared detection elements) arranged in a matrix of N rows and N columns (N: an integer, for example, N=8).

[0012] 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.

[0013] 1, the infrared sensor 1 is packaged by WLP. More specifically, the infrared sensor 1 includes a semiconductor package 2, a plurality of infrared detection elements 3, a plurality of reference detection elements 4, a semiconductor lens 5, a getter material 7, an anti-reflection film (also called an "AR (Anti Reflection) coat") 8, and a sealing member 9.

[0014] The semiconductor package 2 includes a base substrate 21 , a wall substrate 22 , and a roof substrate 23 .

[0015] The base substrate 21 is a substrate on which multiple infrared detection elements 3 are disposed. The base substrate 21 is formed in a flat plate shape from a semiconductor material (e.g., silicon). The base substrate 21 has a first main surface 21a and a second main surface 21b. Multiple recesses 21c are provided on the first main surface 21a of the base substrate 21. The multiple recesses 21c correspond one-to-one to multiple elements, including multiple infrared detection elements 3 and multiple reference detection elements 4. Each of these elements overlaps a corresponding one of the multiple recesses 21c when viewed in direction D1. The multiple recesses 21c are located behind the hot junctions (described below) of the corresponding elements (i.e., between the hot junctions and the base substrate 21) and function as a heat insulating structure to prevent heat from escaping from the hot junctions. A wiring substrate 6 is attached to the second main surface 21b of the base substrate 21 via an adhesive 6b.

[0016] The base substrate 21 includes a signal processing unit. The signal processing unit includes, for example, a MEMS (Micro Electro Mechanical Systems) and an ASIC (Application Specific Integrated Circuit). The signal processing unit converts the infrared rays C1 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, and converts the output values ​​of each of the multiple infrared detection elements 3 into digital values ​​(digital output values) and outputs them. The signal processing unit also converts the infrared rays C1 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 signals of each of the multiple reference detection elements 4 into digital values ​​(dental output signals) and outputs them. The signal processing unit removes noise from the digital output signals of each of the multiple infrared detection elements 3 by subtracting the digital output signal of the corresponding reference detection element 4 from the digital output signal of each of the multiple infrared detection elements 3. The signal processing unit then outputs the noise-removed digital output signals of the infrared detection elements 3 to the external wiring board 6.

[0017] The signal processing unit and the wiring substrate 6 are electrically connected by, for example, via electrodes 6a (for example, TSVs (Through Silicon Vias)). Note that the signal processing unit and the wiring substrate 6 may be electrically connected by wire bonding instead of the via electrodes 6a.

[0018] The wall substrate 22 is a substrate for forming a cavity 22c, which is an accommodation space for accommodating the multiple infrared detection elements 3. The wall substrate 22 is a flat substrate having, for example, the same shape and size as the base substrate 21, and is formed from a semiconductor material (e.g., silicon). The wall substrate 22 is provided on the first main surface 21a of the base substrate 21. The wall substrate 22 has a through hole 22d that forms the cavity 22c. The through hole 22d penetrates the wall substrate 22 in the thickness direction D1 (the vertical direction in FIG. 1 ). The internal space of the through hole 22d forms the cavity 22c. The through hole 22d is, for example, a circular through hole. The cavity 22c functions as an incident optical path when infrared rays C1 from outside pass through the roof substrate 23 and enter the multiple infrared detection elements 3 in the cavity 22c. The cavity 22c is sealed by the base substrate 21, the wall substrate 22, and the roof substrate 23 described below, and is maintained at a vacuum.

[0019] The wall substrate 22 has an aperture portion 24. The aperture portion 24 functions as an aperture for restricting the incident optical path of the infrared ray C1 within the cavity 22c. The aperture portion 24 protrudes from the center of the wall substrate 22 in the thickness direction D1 toward the cavity 22c on the inner circumferential surface of the through hole 22d. The aperture portion 24 is formed over the entire circumferential direction of the inner circumferential surface of the through hole 22d. The aperture portion 24 is formed in the shape of an annular flat plate with an aperture hole 24a at its center. The aperture hole 24a is a portion through which the infrared ray C1 passes and is, for example, circular. The wall substrate 22 has a first main surface 22a and a second main surface 22b. The second main surface 22b is the main surface on the base substrate 21 side, and the first main surface 22a is the main surface opposite the base substrate 21.

[0020] The infrared detection elements 3 are detectors that detect infrared rays C1 (more specifically, far-infrared rays) that pass through the roof substrate 23 from the outside and enter the cavity 22c. When receiving the infrared rays C1 from the outside, each of the infrared detection elements 3 outputs an electrical signal corresponding to the intensity of the received infrared rays C1. The infrared detection elements 3 are thermocouple-type infrared detection elements having hot junctions 3a and cold junctions 3b. The infrared detection elements 3 are arranged on the first main surface 21a of the base substrate 21 so as to be housed in the cavity 22c of the wall substrate 22. The infrared detection elements 3 are arranged in a matrix of, for example, N rows and N columns (N: an integer, for example, 8). By arranging the infrared detection elements 3 in this matrix of N rows and N columns, the infrared detection elements 3 form an N-row, N-column mosaic thermal image sensor. The infrared detection elements 3 are arranged in the thickness direction D1 of the base substrate 21 (the vertical direction in FIG. 1 ) so as not to overlap with the narrowed portion 24 of the wall substrate 22.

[0021] The multiple infrared detection elements 3 are arranged so as to overlap corresponding recesses 21c in the base substrate 21 in the direction D1. More specifically, hot junctions 3a are arranged in the central portion of each infrared detection element 3, and cold junctions 3b are arranged in the peripheral portion. The central portion of each infrared detection element 3, where the hot junctions 3a are arranged, is arranged so as to overlap the corresponding recesses 21c in the direction D1, and the peripheral portion, where the cold junctions 3b are arranged, is arranged so as to overlap the base substrate 21 on the outer periphery of the corresponding recesses 21c. Therefore, the recesses 21c corresponding to the infrared detection elements 3 are arranged between the hot junctions 3a and the base substrate 21. As a result, heat from the hot junctions 3a is insulated by the recesses 21c, preventing it from escaping to the base substrate 21.

[0022] The multiple reference detection elements 4 are thermocouple-type infrared detection elements having hot junctions 4a and cold junctions 4b. The multiple reference detection elements 4 are arranged so as to overlap corresponding recesses 21c in the base substrate 21 in the direction D1. More specifically, the hot junctions 4a are arranged in the center of the reference detection elements 4, and the cold junctions 4b are arranged in the peripheral portions. The central portions of the reference detection elements 4, where the hot junctions 4a are arranged, are arranged so as to overlap the corresponding recesses 21c in the direction D1, and the peripheral portions, where the cold junctions 4b are arranged, are arranged so as to overlap the base substrate 21 on the outer periphery of the corresponding recesses 21c. Therefore, the recesses 21c corresponding to the reference detection elements 4 are arranged between the hot junctions 4a and the base substrate 21. As a result, heat from the hot junctions 4a is insulated by the recesses 21c, preventing it from escaping to the base substrate 21.

[0023] The multiple (e.g., 1 to 3) reference detection elements 4 are infrared detection 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 C1 that pass through the roof substrate 23 from the outside and enter the cavity 22c. 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 are emitted from the roof substrate 23 (e.g., the semiconductor lens 5 and its surrounding area) 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.

[0024] The plurality of reference detection elements 4 are arranged on the first main surface 21a of the base substrate 21 so as to be housed in the cavity 22c of the wall substrate 22. The plurality of reference detection elements 4 are arranged in a region (opposing region) 21e facing the diaphragm portion 24 on the first main surface 21a of the base substrate 21. In this way, by arranging the plurality of reference detection elements 4 in the opposing region 21e, the diaphragm portion 24 suppresses reception of infrared light C1 that has passed through the roof substrate 23 from the outside and entered the cavity 22c.

[0025] The getter material 7 adsorbs gas present in the cavity 22c, thereby increasing the degree of vacuum within the cavity 22c. The getter material 7 is disposed on the first main surface 21a of the base substrate 21 so as to be housed in the cavity 22c of the wall substrate 22. In the example of FIG. 1 , the getter material 7 is disposed in a region 21e (opposing region) facing the narrowed portion 24 on the first main surface 21a of the base substrate 21.

[0026] The roof substrate 23 is provided on the first main surface 22a of the wall substrate 22 so as to close the cavity 22c. The roof substrate 23 is a flat substrate having, for example, the same shape and size as the wall substrate 22, and is made of a semiconductor material (for example, silicon). The roof substrate 23 has a first main surface 23a and a second main surface 23b that are opposite to each other. The second main surface 23b is the main surface on the wall substrate 22 side (i.e., the main surface facing the cavity 22c), and the first main surface 23a is the main surface on the opposite side to the wall substrate 22 (i.e., the external side).

[0027] A semiconductor lens 5 is provided on at least one of the first main surface 23a and the second main surface 23b of the roof substrate 23 (the second main surface 23b in the example of FIG. 1 ). The semiconductor lens 5 is a lens that focuses infrared light C1 that passes through the roof substrate 23 from the outside and enters the cavity 22c onto the multiple infrared detection elements 3. The semiconductor lens 5 is a lens having a metamaterial structure (a metamaterial lens). More specifically, the semiconductor lens 5 has multiple concave-convex portions 5a provided on the second main surface 23b of the roof substrate 23. Here, "the semiconductor lens 5 has multiple convex portions 5a" includes cases where the semiconductor lens 5 has multiple convex portions and multiple concave portions, cases where the semiconductor lens 5 includes only multiple convex portions, and cases where the semiconductor lens 5 includes only multiple concave portions.

[0028] More specifically, the semiconductor lens 5 has a plurality of pillars 51 as a metamaterial structure (see FIG. 2 ). Each of the plurality of pillars 51 is columnar (e.g., cylindrical) and protrudes into the cavity 22c from the second main surface 23b of the roof substrate 23. The width D1 of the pillar 51 is, for example, 1.5 μm or more and 5 μm or less. The height H1 of the pillar 51 is, for example, 6 μm or more and 7 μm or less. The pitch P1 of the pillars 51 is, for example, 6 μm or more and 8 μm or less. The pitch P1 is the center-to-center distance between adjacent pillars 51. For example, the plurality of pillars 51 form a plurality of convex portions. Note that in this embodiment, the pillars 51 are cylindrical, but may be elliptical, triangular, or polygonal.

[0029] The multiple pillars 51 are arranged vertically and horizontally at intervals in an arrangement region 23c (region facing the cavity 22c) of the second main surface 23b of the roof substrate 23. The optical axis L1 of the semiconductor lens 5 passes through the center of the arrangement region 23c. The center of the diaphragm hole 24a and the center of the arrangement of the multiple infrared detection elements 3 are arranged, for example, on an extension of the optical axis L1 of the semiconductor lens 5. At least one of the height H1 and width D1 of each of the multiple pillars 51 varies periodically in the circumferential direction around the optical axis L1. Furthermore, at least one of the height H1 and width D1 of each of the multiple pillars 51 may vary periodically in the radial direction around the optical axis L1. In this way, the height H1 and width D1 of each of the multiple pillars 51 vary in the circumferential and radial directions, thereby achieving the function of focusing infrared light C1 that passes through the roof substrate 23 from the outside and enters the cavity 22c onto the multiple infrared detection elements 3.

[0030] The provision of the plurality of uneven portions 5a (i.e., metamaterial structure) on the second main surface 23b of the roof substrate 23 reduces the change in refractive index at the boundary surface between the cavity 22c and the second main surface 23b of the roof substrate 23. This suppresses the reflection of the infrared ray C1 at the boundary surface, making it easier for the infrared ray C1 to pass through the boundary surface.

[0031] An anti-reflection film 8 is provided on the first main surface 23a of the roof substrate 23. The anti-reflection film 8 prevents reflection of the infrared rays C1, which makes it easier for the infrared rays C1 from outside to pass through the roof substrate 23 and enter the cavity 22c.

[0032] The sealing member 9 is a member that seals the outer peripheral surface of the semiconductor package 2. The sealing member 9 is made of insulating resin. The sealing member 9 is provided so as to cover the entire outer peripheral surface of the base substrate 21, the entire outer peripheral surface of the wall substrates 22, and almost the entire outer peripheral surface of the roof substrate 23 (approximately half of the outer peripheral surface of the roof substrate 23 on the base substrate 21 side in the example of FIG. 1 ).

[0033] (3) Description of Operation The operation of the infrared sensor 1 will be described with reference to FIG.

[0034] Infrared rays C1 from outside pass through the roof substrate 23 and enter the cavity 22c. At this time, the infrared rays C1 are hardly reflected by the first main surface 23a of the roof substrate 23 and pass through the first main surface 23a due to the anti-reflection coating 8 provided on the first main surface 23a of the roof substrate 23. Furthermore, the infrared rays C1 are not reflected by the second main surface 23b of the roof substrate 23 and pass through the second main surface 23b due to the multiple uneven portions 5a (semiconductor lenses 5) provided on the second main surface 23b of the roof substrate 23. Furthermore, when the infrared rays C1 from outside pass through the semiconductor lenses 5 (multiple uneven portions 5a), they are focused by the semiconductor lenses 5 onto the multiple infrared detection elements 3 arranged on the first main surface 21a of the base substrate 21. The infrared rays C1 that have passed through the roof substrate 23 then travel toward the base substrate 21 in the cavity 22c, are narrowed by the narrowing section 24, and are received by the plurality of infrared detection elements 3 arranged on the first main surface 21a of the base substrate 21. The infrared rays C1 received by each of the plurality of reference detection elements 4 are output to the signal processing section of the base substrate 21, and are subjected to required processing (signal processing, amplification, AD (analog-to-digital) conversion, noise removal, etc.) by the signal processing section in the base substrate 21, converted into a digital output signal, and output to the wiring substrate 6.

[0035] (4) Advantages (4-1) Advantage 1 Consider Comparative Example 1, in which the semiconductor lens 5 is a curved lens. Forming the semiconductor lens 5 in Comparative Example 1 using a semiconductor process results in significant control variability when controlling the curved shape of the semiconductor lens 5. Furthermore, when the semiconductor lens 5 in Comparative Example 1 is a lens with a large curvature, Comparative Example 1 has the disadvantage of reducing the yield of the semiconductor lens 5. Therefore, when the semiconductor lens 5 is a curved lens as in Comparative Example 1, the design freedom is reduced. Furthermore, providing the semiconductor lens 5 on the roof substrate 23 as in Comparative Example 1 requires a short focal length, but when the semiconductor lens 5 is a curved lens, achieving a short focal length is difficult. As a result, in Comparative Example 1, it is difficult to use a curved lens as the semiconductor lens 5 in WLP.

[0036] In contrast, in this embodiment, the semiconductor lens 5 is a metamaterial lens having multiple pillars 51, and therefore treats light as waves rather than lines. Therefore, in this embodiment, the optical characteristics of the semiconductor lens 5 depend on the periodic arrangement pattern of the width D1 and height H1 of the pillars 51. Since both the width D1 and the height H1 of the pillars 51 are unlikely to vary during the semiconductor process, this embodiment has the advantages of ensuring high design freedom while maintaining a high yield and facilitating a short focal length.

[0037] (4-2) Advantage 2 In the present embodiment, the case where the semiconductor lens 5 is provided only on the second main surface 23b out of both surfaces (the first main surface 23a and the second main surface 23b) of the roof substrate 23 has been exemplified, but there is an advantage in that it is easy to provide the semiconductor lens 5 on both surfaces of the roof substrate 23. In order to explain this point in more detail, first consider Comparative Example 2 in which the roof substrate 23 has semiconductor lenses that are curved lenses on both surfaces. If the roof substrate 23 has semiconductor lenses that are curved lenses on both surfaces, as in Comparative Example 2, there is a disadvantage in that it is difficult to realize due to the constraints of the semiconductor process, as explained in the [Background Art] section. Even if it were realized, there would be a disadvantage in that the number of manufacturing steps would increase and the process cost would be high.

[0038] In contrast, when semiconductor lenses 5 are provided on both sides of the roof substrate 23 in this embodiment, since the semiconductor lens 5 has a metamaterial structure, multiple pillars 51 can be formed on the second main surface 23b of the roof substrate 23 as a metamaterial structure, as described in this embodiment, and a semiconductor lens 5 having only multiple recesses instead of multiple pillars 51 as a metamaterial structure can be provided on the first main surface 23a. In this way, the manufacturing method for providing a semiconductor lens 5 having a metamaterial structure on both sides of the roof substrate 23 is as follows. First, before providing the roof substrate 23 on the wall substrate 22, a semiconductor lens 5 having only multiple recesses is formed on the first main surface 23a of the roof substrate 23, and then a semiconductor lens 5 having multiple pillars 51 is formed on the second main surface 23b of the roof substrate 23. At this time (when forming the semiconductor lens 5 having the multiple pillars 51 on the second main surface 23b), the first main surface 23a on which the multiple recesses are formed needs to be placed in contact with the floor surface, but the multiple recesses are less likely to be damaged when contacting the floor surface than are protrusions. Therefore, in this embodiment, there is an advantage that it is easy to provide the semiconductor lenses 5 on both sides of the roof substrate 23.

[0039] (4-3) Advantage 3 Consider Comparative Example 3 in which, instead of the semiconductor lens 5, an anti-reflection film is provided on the second main surface 23b of the roof substrate 23, which prevents external infrared rays C1 from being reflected by the second main surface 23b of the roof substrate 23. When an anti-reflection film is provided on the second main surface 23b of the roof substrate 23, as in Comparative Example 3, there is a disadvantage that gas is generated from the anti-reflection film, reducing the degree of vacuum within the cavity 22c. In other words, Comparative Example 3 has the disadvantage that it is difficult to simultaneously create a vacuum within the cavity 22c and prevent external infrared rays C1 from being reflected by the second main surface 23b of the roof substrate 23.

[0040] In contrast to this, in the embodiment, the semiconductor lens 5 having a metamaterial structure is provided on the second main surface 23b of the roof substrate 23. The semiconductor lens 5 having a metamaterial structure has a function of improving the transmittance of infrared rays (i.e., a function of suppressing reflection of infrared rays), and does not generate gas. Therefore, in the embodiment, by providing the semiconductor lens 5 having a metamaterial structure on the second main surface 23b of the roof substrate 23, there is an advantage in that it is possible to simultaneously create a vacuum inside the cavity 22c and suppress a decrease in the transmittance of infrared rays for the roof substrate 23.

[0041] (4-4) Advantage 4 Consider Comparative Example 4, in which the semiconductor lens 5 is a curved lens. Curved lenses are usually circular, and therefore have the disadvantage that the four corners of the main surface (rectangular main surface) on which the curved lens is formed cannot be effectively used as a lens.

[0042] In contrast, in the embodiment, the semiconductor lens 5 is a semiconductor lens having a metamaterial structure, and therefore the metamaterial structure (plural uneven portions 5a) can be provided over the entire placement area 23c (e.g., a rectangular area) of the second main surface 23b of the roof substrate 23, which has the advantage that the main surface (placement area 23c) on which the semiconductor lens 5 is provided can be effectively utilized without waste.

[0043] (5) Effects The infrared sensor 1 according to this embodiment includes a base substrate 21, a wall substrate 22, a plurality of infrared detection elements 3, a roof substrate 23, and a semiconductor lens 5. The wall substrate 22 is provided on the base substrate 21. The wall substrate 22 has through holes 22d that form cavities 22c. The plurality of infrared detection elements 3 are disposed on the base substrate 21 so as to be housed within the cavities 22c. The roof substrate 23 is provided on the wall substrate 22 so as to close the cavity 22c. The semiconductor lens 5 is provided on at least one of the main surfaces 23a, 23b on both sides of the roof substrate 23 (the second main surface 23b in the example of FIG. 1). The semiconductor lens 5 has a plurality of concave-convex portions 5a. The plurality of concave-convex portions 5a are provided on at least one of the main surfaces (the second main surface 23b) of the roof substrate 23.

[0044] According to this configuration, the infrared sensor 1 includes the base substrate 21, the wall substrate 22, and the roof substrate 23, and therefore the infrared sensor 1 can be configured using WLP. Furthermore, the semiconductor lens 5 provided on the roof substrate 23 has a plurality of concave and convex portions 5a, and therefore the semiconductor lens 5 can be formed with a higher yield by utilizing the semiconductor process for manufacturing the infrared sensor 1, compared to a semiconductor lens having a curved lens.

[0045] Furthermore, in the infrared sensor 1 according to this embodiment, the semiconductor lens 5 is provided on one of the main surfaces (first main surface 23a and second main surface 23b) on both sides of the roof substrate 23, that is the main surface facing the cavity 22c (second main surface 23b). With this configuration, the semiconductor lens 5 having the multiple concave and convex portions 5a has relatively high infrared transmittance. Therefore, the semiconductor lens 5 can be used as an anti-reflection film that suppresses reflection of infrared rays (C1) at the boundary surface between the second main surface 23b of the roof substrate 23 and the cavity 22c. This eliminates the need to provide an anti-reflection film on the second main surface 23b of the roof substrate 23, and makes it possible to suppress a decrease in the degree of vacuum in the cavity 22c that would be caused by providing an anti-reflection film.

[0046] Moreover, the infrared sensor 1 according to this embodiment further includes an anti-reflection film 8. The anti-reflection film 8 is provided on the main surface (first main surface 23a) of the roof substrate 23 opposite to the cavity 22c. According to this configuration, the anti-reflection film 8 can suppress reflection of infrared rays C1 from the outside on the first main surface 23a of the roof substrate 23. This allows the infrared rays C1 from the outside to be transmitted through the first main surface 23a of the roof substrate 23 efficiently.

[0047] The infrared sensor 1 according to this embodiment further includes an aperture section 24 and a reference detection element 4. The aperture section 24 protrudes from the inner peripheral surface of the through-hole 22d of the wall substrate 22 into the cavity 22c and limits the incident optical path of the infrared ray C1 within the cavity 22c. The reference detection element 4 is disposed in an opposing region 21f of the base substrate 21 that faces the aperture section 24. With this configuration, the aperture section 24 can be used to provide the reference detection element 4 on the base substrate 21 so that the reference detection element 4 does not receive the infrared ray C1 from outside.

[0048] (6) Modifications Modifications of the embodiment will be described. The following modifications can be implemented in combination.

[0049] 3 , the infrared sensor 1 according to the first modification includes a semiconductor lens 5B having a plurality of recesses 5b (metamaterial structure) on the first main surface 23a of the roof substrate 23 in the infrared sensor 1 according to the embodiment. The recesses 5b are provided in an arrangement region 23d on the first main surface 23a. The arrangement region 23d coincides with, for example, the arrangement region 23c on the second main surface 23b in the thickness direction D1 of the roof substrate 23. The optical axis L2 of the semiconductor lens 5B passes through the center of the arrangement region 23d and coincides with the optical axis L1 of the semiconductor lens 5B.

[0050] The recess 5b is a columnar (for example, cylindrical) recess, but is not limited to a cylindrical shape and may be an elliptical, triangular, or polygonal columnar recess.

[0051] At least one of the depth H2 and the width D2 of each of the plurality of recesses 5b varies periodically in the circumferential direction around the optical axis L2. Furthermore, at least one of the depth H2 and the width D2 of each of the plurality of recesses 5b may vary periodically in the radial direction around the optical axis L2. In this way, the depth H2 and the width D2 of each of the plurality of recesses 5b vary in the circumferential direction and the radial direction, thereby achieving the function of focusing infrared rays C1 from outside onto the plurality of infrared detection elements 3.

[0052] The infrared sensor 1 according to the first modification further includes a second semiconductor lens 5B. The second semiconductor lens 5B is a lens separate from the first semiconductor lens, which is the semiconductor lens 5. The second semiconductor lens 5B is provided on the main surface (first main surface 23a) of the roof substrate 23 opposite the cavity 22c. The second semiconductor lens 5B has a plurality of recesses 5b. With this configuration, as described in Advantage 3, semiconductor lenses (the first semiconductor lens 5 and the second semiconductor lens 5B) can be easily provided on both sides of the roof substrate 23.

[0053] In the first modification, an example is shown in which the second semiconductor lens 5B is provided in the arrangement region 23d of the first main surface 23a of the roof substrate 23, but the second semiconductor lens 5B may be provided over the entire first main surface 23a of the roof substrate 23. Furthermore, an anti-reflection film 8 may be provided on the first main surface 23a of the roof substrate 23 including the semiconductor lens 5B.

[0054] (6-2) Modification 2 As shown in FIG. 4 , the infrared sensor 1 according to Modification 2 is the same as the infrared sensor 1 of the embodiment, except that the aperture section 24 has a facing surface 24b facing the base substrate 21 and further includes a plurality of second concave-convex portions 30 arranged, for example, on the entire surface of the aperture section 24 facing the base substrate 21. The plurality of second concave-convex portions 30 form a metamaterial structure. The plurality of second concave-convex portions 30 are different from the plurality of first concave-convex portions 5a, which are the plurality of concave-convex portions 5a. The height difference H3 of each of the plurality of second concave-convex portions 30 is ¼ the wavelength of the infrared ray C1 from the outside. Note that FIG. 4 illustrates an example in which the second concave-convex portions 30 are, for example, a plurality of convex portions having a height difference (height) H3.

[0055] The infrared sensor 1 according to the second modification further includes a plurality of second uneven portions 30. The second uneven portions 30 are separate from the first uneven portions 5a, which are the plurality of uneven portions 5a. The second uneven portions 30 are disposed on the surface 24b of the aperture portion 24 facing the base substrate 21. The height difference H3 between the second uneven portions 30 is ¼ of the wavelength of the infrared ray C1 passing through the cavity 22c. This configuration prevents the infrared ray C1, which has passed through the semiconductor lens 5 from the outside and entered the cavity 22c, from passing through the aperture portion 24. This prevents the infrared ray C1 from entering the reference detection element 4 from being received from the outside.

[0056] 5, the infrared sensor 1 according to the third modification is the infrared sensor 1 of the embodiment, further including a reflective film 31 that reflects infrared rays C1, for example, on the entire surface 24b of the aperture portion 24 that faces the base substrate 21. The reflective film 31 is made of, for example, a metal (for example, aluminum).

[0057] The infrared sensor 1 according to the third modification includes a reflective film 31. The reflective film 31 is disposed on the surface 24b of the aperture section 24 facing the base substrate 21, and reflects infrared rays. With this configuration, the reflective film 31 can prevent external infrared rays from passing through the aperture section 24. This prevents infrared rays C1 that have passed through the semiconductor lens 5 from the outside and entered the cavity 22c from being received by the reference detection element 4. This improves the detection accuracy of the reference detection element 4.

[0058] (6-4) Modification 4 As shown in FIG. 6 , in the infrared sensor 1 according to Modification 4, in the infrared sensor 1 of the embodiment, the distance M1 of the gap S1 between the diaphragm portion 24 and the base substrate 21 is ¼ of the wavelength of the infrared ray C1 passing through the cavity 22c. With this configuration, the distance M1 of the gap S1 between the diaphragm portion 24 and the base substrate 21 is ¼ of the wavelength of the infrared ray C1 passing through the cavity 22c from the outside, and therefore the infrared ray C1 that has passed through the semiconductor lens 5 and entered the cavity 22c from the outside can be prevented from passing through the diaphragm portion 24. This prevents the infrared ray C1 from entering the reference detection element 4 from being received from the outside. As a result, the detection accuracy of the reference detection element 4 can be improved.

[0059] (6-5) Modification 5 As shown in FIG. 7 , the infrared sensor 1 according to Modification 5 has the same configuration as the infrared sensor 1 of the embodiment, except for the arrangement of the getter material 7. In Modification 5, the getter material 7 is arranged on the first main surface 21a of the base substrate 21 so as to be housed in the cavity 22c, as in the embodiment. Also, in Modification 5, the getter material 7 is arranged in a region (facing region) 21f facing the diaphragm portion 24 on the first main surface 21a of the base substrate 21, between one of the plurality of infrared detection elements 3 (for example, the infrared detection element 3p arranged closest to the getter material 7) and the reference detection element 4. Here, "A is arranged between B and C" means that at least one of a plurality of line segments connecting an arbitrary point in region B and an arbitrary point in region C passes through region A.

[0060] The infrared sensor 1 according to the fifth modification includes a getter material 7 disposed on the base substrate 21 so as to be housed within the cavity 22c. The getter material 7 is disposed in a facing region 21f of the base substrate 21 facing the aperture portion 24, between one of the plurality of infrared detection elements 3 (infrared detection element 3p in the example of FIG. 7) and the reference detection element 4. This configuration utilizes the getter material 7 to prevent infrared rays C1 that have passed through the semiconductor lens 5 from entering the cavity 22c from entering the gap S1 between the aperture portion 24 and the base substrate 21. This prevents the reference detection element 4 from receiving the infrared rays C1 from outside. As a result, the detection accuracy of the reference detection element 4 can be improved.

[0061] (6-6) Modification 6 As shown in FIG. 8, the infrared sensor 1 according to modification 6 is configured in the same manner as the infrared sensor 1 according to the embodiment, except that the shapes of the plurality of uneven portions 5a (i.e., the plurality of pillars 51) are different.

[0062] In Modification 6, each of the multiple uneven portions 5a (multiple pillars 51) has a tip side portion 52 and a base side portion 53. The tip side portion 52 is the tip half of the pillar 51. The tip side portion 52 is, for example, columnar (e.g., cylindrical, elliptical, triangular, or polygonal). The example in FIG. 8 illustrates a case where the tip side portion 52 is columnar. The base side portion 53 is the base half of the pillar 51 and, in the embodiment, is connected to the main surface of the roof substrate 23. The base side portion 53 is, for example, columnar (e.g., cylindrical, elliptical, triangular, or polygonal). The example in FIG. 8 illustrates a case where the base side portion 53 is columnar.

[0063] The width D4 of the base side portion 53 is larger than the width D3 of the tip side portion 52. In other words, the width D3 of the tip side portion 52 is smaller than the width D4 of the base side portion 53. The base side portion 53 has a tip surface 53a and a bottom surface 53b. The bottom surface 53b is connected to the second main surface 23b of the roof substrate 23. The tip side portion 52 is provided at the tip surface 53a of the base side portion 53 so as to protrude from the tip surface 53a concentrically with the base side portion 53. The width D3 of the tip side portion 52 is formed to be a width suitable for collecting infrared rays C1 that pass through the semiconductor lens 5 from the outside and enter the cavity 22c. The width D4 of the base side portion 53 is formed to be a width suitable for transmitting infrared rays C1 from the outside.

[0064] In the infrared sensor 1 according to the sixth modification, each of the plurality of concave-convex portions 5a is a pillar 51. The pillar 51 has a tip side portion 52 and a base side portion 53. The base side portion 53 has a width D4 that is larger than the width D3 of the tip side portion 52. With this configuration, the width D3 of the tip side portion 52 is narrower than the width D4 of the base side portion 53, so the width D3 of the tip side portion 52 can be formed to a width suitable for collecting infrared rays C1 from the outside. Furthermore, the width D4 of the base side portion 53 is wider than the width D3 of the tip side portion 52, so the width D4 of the base side portion 53 can be formed to a width suitable for transmitting infrared rays C1 from the outside. As a result, the plurality of concave-convex portions 5a (i.e., the plurality of pillars 51) can be formed into a metamaterial structure that has excellent light-collection and transmission functions.

[0065] (Aspects) As is clear from the above-described embodiments and modifications, the present specification discloses the following aspects.

[0066] The infrared sensor (1) of the first aspect includes a base substrate (21), a wall substrate (22), a plurality of infrared detection elements (3), a roof substrate (23), and a first semiconductor lens (5). The wall substrate (22) is provided on the base substrate (21) and has through holes (22d) that form a cavity (22c). The plurality of infrared detection elements (3) are arranged on the base substrate (21) so as to be housed within the cavity (22c). The roof substrate (23) is provided on the wall substrate (22) so as to close the cavity (22c). The roof substrate (23) has a first main surface (23b) facing the cavity (22c) and a second main surface (23a) opposite the first main surface (23b). The first semiconductor lens (5) is provided on one of the first and second main surfaces (23a and 23b) of the roof substrate (23). The first semiconductor lens (5) has a plurality of concave and convex portions (5a) provided on the one main surface (23b) of the roof substrate (23).

[0067] According to this configuration, the infrared sensor (1) can be configured as a wafer level package (WLP) because it includes the base substrate (21), the wall substrate (22), and the roof substrate (23). Furthermore, since the semiconductor lens (5) provided on the roof substrate (23) has a plurality of concave and convex portions (5a), the semiconductor lens (5) can be formed with a higher yield by utilizing the semiconductor process for manufacturing the infrared sensor (1) compared to a semiconductor lens that is a curved lens.

[0068] The infrared sensor (1) of the second aspect is the same as that of the first aspect, except that the first semiconductor lens (5) is provided on the first main surface (23b) of the roof substrate (23).

[0069] According to this configuration, the semiconductor lens (5) having the plurality of concave and convex portions (5 a) has a relatively high infrared transmittance. Therefore, the semiconductor lens (5) can be used as an anti-reflection film that suppresses reflection of infrared rays at the boundary between the cavity (22 c) and the first main surface (23 b) of the roof substrate (23) that faces the cavity (22 c). This eliminates the need to provide an anti-reflection film on the main surface (23 b) of the roof substrate (23) that faces the cavity (22 c), and can suppress a decrease in the degree of vacuum in the cavity (22 c) that would be caused by providing an anti-reflection film.

[0070] The infrared sensor (1) of the third aspect is the second aspect, further comprising an anti-reflection film (8). The anti-reflection film (8) is provided on the second main surface (23a) of the roof substrate (23).

[0071] According to this configuration, the anti-reflection film (8) can suppress reflection of external infrared rays (C1) on the second main surface (23 a) of the roof substrate (23) opposite to the cavity (22 c), thereby allowing the external infrared rays (C1) to efficiently transmit through the main surface (23 a) of the roof substrate (23).

[0072] The infrared sensor (1) of the fourth aspect is the same as that of the second or third aspect, and further includes a second semiconductor lens (5B). The second semiconductor lens (5B) is a lens separate from the first semiconductor lens (5). The second semiconductor lens (5B) is provided on a second main surface (23a) of the roof substrate (23) on the side opposite to the cavity (22c). The second semiconductor lens (5B) has a plurality of recesses (5b).

[0073] According to this configuration, semiconductor lenses (5, 5B) can be easily provided on both surfaces (23a, 23b) of the roof substrate (23). More specifically, after forming a second semiconductor lens (5B) having only a plurality of recesses (5b) on the main surface (first main surface) (23a) of the roof substrate (23) opposite the cavity (22c), a first semiconductor lens (5) having a plurality of concave-convex portions (5a) can be formed on the main surface (second main surface) (23b) of the roof substrate (23) facing the cavity (22c) with the first main surface (23a) in contact with the floor surface. As described above, even if the first main surface (23a) on which the plurality of recesses (5b) are formed is brought into contact with the floor surface, the plurality of recesses are less likely to be damaged by contact with the floor surface than convex portions. Therefore, as described above, a plurality of concave-convex portions (5a) can be formed on the second main surface (23b) with the first main surface (23a) in contact with the floor surface. This makes it possible to easily provide the semiconductor lenses (5, 5B) on both surfaces (23a, 23b) of the roof substrate (23).

[0074] The infrared sensor (1) of a fifth aspect is the same as any one of the first to fourth aspects, further comprising an aperture section (24) and a reference detection element (4). The aperture section (24) protrudes from the inner peripheral surface of the through-hole (22d) of the wall substrate (22) into the cavity (22c) and limits the incident optical path of the infrared ray (C1) within the cavity (22c). The reference detection element (4) is disposed in a facing region (21f) of the base substrate (21) facing the aperture section (24).

[0075] According to this configuration, the diaphragm portion (24) can be used to provide the reference detection element (4) on the base substrate (21) so that the reference detection element (4) does not receive infrared rays (C1) from outside.

[0076] The infrared sensor (1) of the sixth aspect is the fifth aspect, further comprising a plurality of second uneven portions (30). The plurality of second uneven portions (30) are separate from the plurality of first uneven portions (5a). The plurality of second uneven portions (30) are arranged on a surface (24b) of the diaphragm portion (24) facing the base substrate (21). A height difference (H3) of the plurality of second uneven portions (30) is ¼ of the wavelength of the infrared ray (C1) passing through the cavity (22c).

[0077] According to this configuration, the plurality of second concave-convex portions (30) can prevent the infrared rays (C1) that have passed through the semiconductor lens (5) from the outside and entered the cavity (22c) from passing through the aperture portion (24). This prevents the infrared rays (C1) from the outside from being received by the reference detection element (4). This improves the detection accuracy of the reference detection element (4).

[0078] The infrared sensor (1) of a seventh aspect is the fifth aspect, further comprising a reflective film (31) that reflects infrared light (C1). The reflective film (31) is disposed on a surface (24b) of the diaphragm portion (24) facing the base substrate (21).

[0079] According to this configuration, the reflective film 31 can prevent the infrared rays C1 that have passed through the semiconductor lens 5 from entering the cavity 22c from passing through the aperture 24. This prevents the infrared rays C1 from the outside from being received by the reference detection element 4. This improves the detection accuracy of the reference detection element 4.

[0080] In the infrared sensor (1) of the eighth aspect, in the fifth aspect, the distance (M1) of the gap (S1) between the diaphragm portion (24) and the base substrate (21) is 1 / 4 the wavelength of the infrared ray (C1) passing through the cavity (22c).

[0081] This configuration prevents the infrared rays (C1) that have passed through the semiconductor lens (5) from the outside and entered the cavity (22c) from passing through the aperture section (24). This prevents the infrared rays (C1) from the outside from being received by the reference detection element (4). As a result, the detection accuracy of the reference detection element (4) can be improved.

[0082] The infrared sensor (1) of a ninth aspect is the fifth aspect, further comprising a getter material (7). The getter material (7) is arranged on the base substrate (21) so as to be housed in the cavity (22c). The getter material (7) is arranged between one of the plurality of infrared detection elements (3) (infrared detection element 3p) and the reference detection element (4) in a region (21f) of the base substrate (21) facing the diaphragm portion (24).

[0083] According to this configuration, the getter material (7) can be used to prevent infrared rays (C1) that have passed through the semiconductor lens (5) from entering the cavity (22c) from entering the gap (S1) between the diaphragm portion (24) and the base substrate (21) and being received by the reference detection element (4), thereby improving the detection accuracy of the reference detection element (4).

[0084] In the infrared sensor (1) of a tenth aspect, in any one of the first to ninth aspects, each of the plurality of first concave-convex portions (5 a) is a pillar (51). The pillar (51) has a tip side portion (52) and a base side portion (53). The base side portion (53) has a width (D4) larger than the width (D3) of the tip side portion (52).

[0085] According to this configuration, the width (D3) of the tip side portion (52) is narrower than the width (D4) of the base side portion (53), so the width (D3) of the tip side portion (52) can be formed to a width (D4) suitable for collecting infrared rays (C1). Also, the width (D4) of the base side portion (53) is wider than the width (D3) of the tip side portion (52), so the width (D4) of the base side portion (53) can be formed to a width suitable for transmitting infrared rays (C1) from outside. As a result, the multiple pillars (51) can be formed in a shape that has excellent light collecting and transmitting functions.

[0086] DESCRIPTION OF SYMBOLS 1 Infrared sensor 5 Semiconductor lens (first semiconductor lens) 5B Semiconductor lens (second semiconductor lens) 5a Concave / convex portion 5b Concave portion 7 Getter material 8 Anti-reflection film 21 Base substrate 21f Opposing region 22 Wall substrate 22c Cavity 23 Roof substrate 23a First main surface (main surface) 23b Second main surface (main surface) 24 Constriction portion 24b Opposing surface 30 Second concave / convex portion 31 Reflection film 51 Pillar 52 Tip side portion 53 Base side portion C1 Infrared light D3, D4 Width H3 Height difference M1 Spacing S1 Gap

Claims

1. A base substrate, a wall substrate provided on the base substrate and having a through hole forming a cavity, a plurality of infrared detection elements arranged on the base substrate so as to be accommodated in the cavity, a roof substrate provided on the wall substrate so as to close the cavity and having a first main surface facing the cavity and a second main surface on the opposite side of the first main surface, and a first semiconductor lens provided on one of the main surfaces of the roof substrate. The first semiconductor lens has a plurality of first uneven portions provided on the one main surface of the roof substrate. An infrared sensor.

2. The infrared sensor according to claim 1, wherein the first semiconductor lens is provided on the first main surface of the roof substrate.

3. The infrared sensor according to claim 2, further comprising an antireflection film provided on the second main surface of the roof substrate.

4. The infrared sensor according to claim 2 or 3, further comprising a second semiconductor lens provided on the second main surface of the roof substrate, the second semiconductor lens having a plurality of concave portions.

5. A diaphragm portion protruding from the inner peripheral surface of the through hole of the wall substrate into the cavity to limit the incident optical path of infrared rays in the cavity, and a reference detection element arranged in a facing region of the base substrate facing the diaphragm portion. The infrared sensor according to any one of claims 1 to 3.

6. The infrared sensor according to claim 5, further comprising a plurality of second uneven portions arranged on a surface of the diaphragm portion facing the base substrate, and a height difference between the plurality of second uneven portions being 1 / 4 of the wavelength of infrared rays passing through the cavity.

7. The infrared sensor according to claim 5, further comprising a reflection film arranged on a surface of the diaphragm portion facing the base substrate to reflect infrared rays.

8. The infrared sensor according to claim 5, wherein a distance between the diaphragm portion and the base substrate is 1 / 4 of the wavelength of infrared rays passing through the cavity.

9. The infrared sensor according to claim 5, further comprising a getter material arranged on the base substrate so as to be accommodated in the cavity, the getter material being arranged between any one of the plurality of infrared detection elements and the reference detection element in a region of the base substrate facing the diaphragm portion.

10. Each of the plurality of first concavo-convex portions is a pillar, and the pillar has a tip side portion and a base end side portion having a width larger than the width of the tip side portion. The infrared sensor according to any one of claims 1 to 3.

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