Infrared detection element, infrared sensor, and method for manufacturing infrared detection element

Abstract

The present disclosure addresses the problem of increasing the sensitivity of an infrared detection element. An infrared detection element (10) comprises a pyroelectric substrate (1), a first electrode (2), a second electrode (3), and an infrared absorption layer (4). The pyroelectric substrate (1) has a first surface (11) and a second surface (12) in the thickness direction (D1). The first electrode (2) is provided on the first surface (11) of the pyroelectric substrate (1). The second electrode (3) is provided on the second surface (12) of the pyroelectric substrate (1) so as to overlap the first electrode (2) in the thickness direction (D1). The infrared absorption layer (4) is provided on the first electrode (2). The pyroelectric substrate (1) has through holes (19) penetrating the pyroelectric substrate (1) in the thickness direction (D1). The through holes (19) are formed around a specific part (13) of the pyroelectric substrate (1), the specific part (13) being a portion sandwiched between the first electrode (2) and the second electrode 3. The through holes (19) each have a tapered structure in which the first surface (11) side thereof has a narrower width than the second surface (12) side thereof.

Description

Infrared detection element, infrared sensor, and method for manufacturing infrared detection element

[0001] The present disclosure generally relates to an infrared detection element, an infrared sensor, and a method for manufacturing an infrared detection element. More specifically, the present disclosure relates to an infrared detection element, an infrared sensor, and a method for manufacturing an infrared detection element using a pyroelectric substrate.

[0002] Patent Document 1 discloses a pyroelectric infrared detection element. In this infrared detection element, a pair of upper and lower electrodes are formed on the front and back surfaces of a pyroelectric substrate to form a light receiving portion, and infrared rays are incident on the light receiving portion to generate charges. The light receiving portion has a structure in which a part of the pyroelectric substrate is cantilever-supported by a through hole surrounding the front three directions thereof.

[0003] In the field of infrared detection elements using a pyroelectric substrate, higher sensitivity may be desired. [[ID=X]] [[ID=Y]]

[0004] Japanese Patent Laid-Open No. 10-2793

[0005] An object of the present disclosure is to achieve higher sensitivity of an infrared detection element.

[0006] An infrared detection element according to one aspect of the present disclosure includes a pyroelectric substrate, a first electrode, a second electrode, and an infrared absorption layer. The pyroelectric substrate has a first surface and a second surface in a thickness direction. The first electrode is provided on the first surface of the pyroelectric substrate. The second electrode is provided on the second surface of the pyroelectric substrate so as to overlap the first electrode in the thickness direction. The infrared absorption layer is provided on the first electrode. The pyroelectric substrate has a through hole penetrating the pyroelectric substrate in the thickness direction. The through hole is formed around a specific portion sandwiched between the first electrode and the second electrode in the pyroelectric substrate. The through hole has a tapered structure in which the width on the first surface side is narrower than that on the second surface side.

[0007] An infrared sensor according to one aspect of the present disclosure includes the infrared detection element, a mounting substrate, and a package. The mounting substrate has the infrared detection element mounted thereon. The package houses the infrared detection element and the mounting substrate.

[0008] A method for manufacturing an infrared detection element according to one aspect of the present disclosure includes a first electrode formation step, a second electrode formation step, an infrared absorption layer formation step, and a through-hole formation step. The first electrode formation step includes forming a first electrode on the first surface of a pyroelectric substrate having a first surface and a second surface in the thickness direction. The second electrode formation step includes forming a second electrode on the second surface of the pyroelectric substrate so as to overlap with the first electrode in the thickness direction. The infrared absorption layer formation step includes forming an infrared absorption layer on the first electrode. The through-hole formation step is performed after the infrared absorption layer formation step. The through-hole formation step includes forming a through-hole in the pyroelectric substrate having a tapered structure in which the width on the first surface side is narrower than the width on the second surface side, around a specific portion which is sandwiched between the first electrode and the second electrode.

[0009] Figure 1 is a top view of an infrared detection element according to one embodiment of the present disclosure. Figure 2 is a bottom view of the same infrared detection element. Figure 3 is a cross-sectional view taken along the line III-III in Figure 1. Figure 4 is a cross-sectional view taken along the line IV-IV in Figure 1. Figure 5 is an exploded perspective view of an infrared sensor equipped with the same infrared detection element. Figure 6 is a flowchart of the method for manufacturing the same infrared detection element. Figure 7 is an explanatory diagram illustrating the through-hole formation step in the method for manufacturing the same infrared detection element. Figure 8 is a cross-sectional view of an infrared detection element of Modification 1. Figure 9 is an explanatory diagram showing one step in the method for manufacturing an infrared detection element of Modification 2. Figure 10 is an explanatory diagram showing one step in the method for manufacturing an infrared detection element of a Comparative Example.

[0010] The infrared detection element and infrared sensor of the embodiments of this disclosure will be described with reference to the drawings. The figures described in the embodiments below are schematic diagrams, and the ratios of the size and thickness of each component in the figures do not necessarily reflect the actual dimensional ratios.

[0011] (1) Embodiment (1.1) Overview As shown in Figures 1 to 4, the infrared detection element 10 of this embodiment comprises a pyroelectric substrate 1, a first electrode 2, a second electrode 3, and an infrared absorption layer 4.

[0012] The pyroelectric substrate 1 has a first surface 11 and a second surface 12 in the thickness direction D1.

[0013] The first electrode 2 is provided on the first surface 11 of the pyroelectric substrate 1. The second electrode 3 is provided on the second surface 12 of the pyroelectric substrate 1 so as to overlap with the first electrode 2 in the thickness direction D1. The infrared absorption layer 4 is provided on the first electrode 2.

[0014] The pyroelectric substrate 1 has through holes 19 that penetrate the pyroelectric substrate 1 in the thickness direction D1, formed around a specific portion 13 that is sandwiched between the first electrode 2 and the second electrode 3 in the pyroelectric substrate 1. As shown in Figures 3 and 4, the through holes 19 have a tapered structure in which the width is narrower on the first surface 11 side than on the second surface 12 side.

[0015] As shown in Figure 5, the infrared sensor 20 comprises an infrared detection element 10, a mounting substrate 8 on which the infrared detection element 10 is mounted, and a package 9 that houses the infrared detection element 10 and the mounting substrate 8.

[0016] According to the infrared detection element 10 and infrared sensor 20 of this embodiment, the infrared detection element 10 is equipped with an infrared absorption layer 4, which improves the absorption rate of infrared rays and thereby enables higher sensitivity. Furthermore, as will be described in detail later, the through hole 19 has a tapered structure in which the width is narrower on the first surface 11 side than on the second surface 12 side, which also enables higher sensitivity.

[0017] (1.2) Details Below, each component of the infrared detection element 10 and the infrared sensor 20 will be described in more detail.

[0018] For convenience, in the following, the direction of the infrared detection element 10 along the thickness direction D1 of the pyroelectric substrate 1 will be referred to as the "up and down direction," the direction from the second surface 12 toward the first surface 11 will be referred to as "up," and the direction from the first surface 11 toward the second surface 12 will be referred to as "down." Also, in the following, viewing in the thickness direction D1 of the pyroelectric substrate 1 (i.e., viewing from above or below) will be referred to as a "plan view." However, the definition of direction in this disclosure merely indicates the relative positional relationship between the components of the infrared detection element 10 and the infrared sensor 20, and does not limit the orientation of the infrared detection element 10 and the infrared sensor 20 when they are in use.

[0019] (1.2.1) Infrared detection element As shown in Figures 1 to 4, the infrared detection element 10 comprises a pyroelectric substrate 1, four first electrodes 2, four second electrodes 3, and four infrared absorption layers 4.

[0020] The pyroelectric substrate 1 is rectangular in shape. The planar shape of the pyroelectric substrate 1 is, for example, square, but is not particularly limited. The pyroelectric substrate 1 is a substrate that possesses pyroelectric properties. The pyroelectric substrate 1 is made of, for example, a single-crystal LiTaO3 substrate. The direction of spontaneous polarization of the pyroelectric substrate 1 is one direction along the thickness direction D1 of the pyroelectric substrate 1, for example, upward.

[0021] The thickness of the pyroelectric substrate 1 is, for example, 50 μm, but is not limited to this value. From the viewpoint of infrared detection sensitivity and the intensity of the pyroelectric substrate 1, it is preferable to set the thickness of the pyroelectric substrate 1 in the range of approximately 30 μm to 150 μm.

[0022] The first electrode 2 is a conductive layer formed from a material that is conductive and absorbs infrared rays. The material of the first electrode 2 is Ni, but is not limited to Ni; for example, NiCr, gold black, etc., may also be used.

[0023] The four first electrodes 2 are provided on the first surface 11 (top surface) of the pyroelectric substrate 1. The four first electrodes 2 are provided in four different regions of the first surface 11. The four first electrodes 2 are arranged in a 2x2 matrix. The four first electrodes 2 are spaced apart from each other.

[0024] The planar shape of each first electrode 2 is, for example, rectangular or square. The thickness of the first electrode 2 is, for example, 0.05 μm or more and 5 μm or less. The four first electrodes 2 are identical in shape, size, thickness, and material to each other.

[0025] The second electrode 3 is made of a conductive material. The second electrode 3 is made of the same material as the first electrode 2, but is not limited to this, and may be made of a different material than the first electrode 2.

[0026] The four second electrodes 3 are provided on the second surface 12 (bottom surface) of the pyroelectric substrate 1. The four second electrodes 3 correspond one-to-one with the four first electrodes 2. As shown in Figures 3 and 4, each second electrode 3 is provided on the second surface 12 of the pyroelectric substrate 1 such that it overlaps with the corresponding first electrode 2 in the thickness direction D1. The four second electrodes 3 are spaced apart from each other. In this disclosure, "the second electrodes 3 overlap with the first electrodes 2 in the thickness direction D1" means that, when viewed along the thickness direction D1, at least a portion (part or all) of the second electrodes 3 overlaps with the first electrodes 2.

[0027] The planar shape of each second electrode 3 is, for example, rectangular or square. The thickness of the second electrode 3 is, for example, 0.05 μm or more and 5 μm or less. The thickness of each second electrode 3 may be the same as or different from the thickness of the corresponding first electrode 2. The four second electrodes 3 are identical to each other in shape, size, thickness and material.

[0028] Each second electrode 3 is formed to have the same shape and size as the corresponding first electrode 2. In this embodiment, in a plan view, the outer edge of each second electrode 3 coincides with the outer edge of the corresponding first electrode 2. That is, in this embodiment, when viewed along the thickness direction D1, the entirety of the second electrode 3 overlaps with the first electrode 2.

[0029] The infrared absorption layer 4 is a resin layer in which conductive fine powder is dispersed in the resin. The thickness of the infrared absorption layer 4 is, for example, 0.1 μm or more and 5 μm or less.

[0030] The four infrared absorption layers 4 correspond one-to-one with the four first electrodes 2. Each infrared absorption layer 4 is provided on the corresponding first electrode 2. In this embodiment, each infrared absorption layer 4 covers the upper surface 21 of the corresponding first electrode 2. Also, each infrared absorption layer 4 covers the side surface 23 of the corresponding first electrode 2. In this embodiment, as shown in Figures 1, 3, and 4, each infrared absorption layer 4 covers the entire corresponding first electrode 2 (i.e., the entire surface of the first electrode 2 except for the surface in contact with the pyroelectric substrate 1). Note that each infrared absorption layer 4 does not have to cover the entire upper surface of the corresponding first electrode 2; it is sufficient to cover a part of the upper surface of the first electrode 2. That is, each infrared absorption layer 4 is provided on at least a part of the upper surface of the corresponding first electrode 2. In addition, in this embodiment, the infrared absorption layer 4 covers all four side surfaces 23 of the rectangular first electrode 2, but is not limited to this, and may cover one or more of the four side surfaces 23 of the first electrode 2. Furthermore, in this embodiment, the infrared absorbing layer 4 covers the entire surface 23 of each side 23, but is not limited to this, and may cover only a part of the surface 23.

[0031] The resin in the infrared absorption layer 4 is, for example, a thermosetting resin. Examples of thermosetting resins include phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane resin, and thermosetting polyimide resin. As the resin for the infrared absorption layer 4, it is preferable to use a thermosetting resin from among these thermosetting resins that has a higher absorption rate of the infrared radiation to be detected by the infrared detection element 10. For example, when the infrared sensor 20 is used for applications such as gas detection and the wavelength of the infrared radiation to be detected is in the range of 3 to 8 μm, the resin for the infrared absorption layer 4 is preferably a resin containing hydroxyl groups. For example, when the infrared sensor 20 is used for applications such as human body detection and the wavelength of the infrared radiation to be detected is in the range of 8 to 13 μm, the resin for the infrared absorption layer 4 is preferably an aromatic resin.

[0032] Examples of conductive fine powders dispersed in the resin in the infrared absorption layer 4 include carbon-based fine powders, metal-based fine powders, and metal oxide-based fine powders. The volume concentration of the conductive fine powder can be set, for example, within a range of about 1 to 30%. As a result, the infrared absorption layer 4 is conductive, but its resistivity is higher than that of the first electrode 2.

[0033] The infrared detection element 10 comprises four detection units 100. Each of the four detection units 100 includes a first electrode 2, a second electrode 3 corresponding to the first electrode 2, an infrared absorption layer 4 provided on the first electrode 2, and a portion of the pyroelectric substrate 1 sandwiched between the first electrode 2 and the second electrode 3 (hereinafter also referred to as the "specific unit 13"). In this case, the planar shape of the specific unit 13 is rectangular. Hereafter, the four detection units 100 will be referred to as detection units 101 to 104 to distinguish them from one another.

[0034] As shown in Figures 1 and 2, the four detection units 101 to 104 are arranged in a 2x2 matrix such that detection unit 101 is located on the left front side, detection unit 102 on the right front side, detection unit 103 on the left rear side, and detection unit 104 on the right rear side. The four detection units 101 to 104 are arranged to be 2 rotationally symmetric in a plan view. Furthermore, the four detection units 101 to 104 are arranged to be line-symmetric in a plan view with respect to two directions (front-to-back and left-to-right) that are perpendicular to the vertical direction and mutually perpendicular to each other.

[0035] In the pyroelectric substrate 1, four through-holes 19 that penetrate the pyroelectric substrate 1 in the thickness direction D1 are formed around each of the four specific portions 13. For convenience, the four portions of the pyroelectric substrate 1 surrounded by the four through-holes 19 will be referred to as the "predetermined portion 15," and the portion supporting the predetermined portion 15 will be referred to as the "support portion 16" (see Figures 3 and 4). The predetermined portion 15 may coincide with the specific portion 13, or it may be different from the specific portion 13. In this embodiment, the predetermined portion 15 is different from the specific portion 13 and is slightly larger than the specific portion 13 in a plan view. As shown in Figures 1 and 4, the predetermined portion 15 is cantilevered to the support portion 16 by the beam portion 17. The predetermined portion 15 is thermally insulated from the support portion 16 by the through-holes 19, except for the beam portion 17. As a result, the four detection portions 100 of the infrared detection element 10 are thermally insulated from each other.

[0036] Each through-hole 19 is formed around the corresponding specific portion 13 (the portion sandwiched between the first electrode 2 and the second electrode 3 in the pyroelectric substrate 1) along three sides of the specific portion 13. By forming the through-holes 19 along the three sides of the specific portion 13, the thermal insulation of the detection unit 100 is improved, and the sensitivity of the infrared detection element 10 can be further increased.

[0037] Each through-hole 19 is formed at a distance from the corresponding specific part 13 in a plan view. In other words, the inner surface of each through-hole 19 in the pyroelectric substrate 1 is separated from the first electrode 2 and the second electrode 3 in a plan view. Furthermore, as shown in Figures 3 and 4, in the pyroelectric substrate 1, each through-hole 19 is formed at an outer position in a plan view from the side surface 43 of the infrared absorption layer 4 in the corresponding detection part 100.

[0038] As shown in Figures 3 and 4, each through-hole 19 has a tapered structure in which the width W1 on the first surface 11 side is narrower than the width W2 on the second surface 12 side. The tapered structure of each through-hole 19 includes a portion in which the width gradually narrows from the second surface 12 side toward the first surface 11 side. In the extension direction of the through-hole 19 (the direction perpendicular to the plane of the paper in Figure 3), the shape of the through-hole 19 (the shape of the through-hole 19 in the cross-section shown in Figure 3) is substantially constant. Through-holes 19 having such a tapered structure can be formed, for example, by irradiating the pyroelectric substrate 1 with laser light L1 (see Figure 7) from the second surface 12 side of the pyroelectric substrate 1 (laser processing). That is, a through-hole 19 can be formed by scanning the laser light L1 along the edge of the second electrode 3 while irradiating the pyroelectric substrate 1, on which the second electrode 3 is provided, with laser light L1 from the second surface 12 side. Note that in laser processing, it is not limited to performing only one scan, but multiple scans may be performed.

[0039] As shown in Figures 1 and 2, the infrared detection element 10 further comprises a first wiring 5 and a second wiring 6. Note that the first wiring 5 and the second wiring 6 are not shown in Figures 3 and 4.

[0040] As shown in Figure 1, the first wiring 5 is provided on the first surface 11 of the pyroelectric substrate 1 corresponding to the support portion 16. The first wiring 5 is connected to the first electrode 2. The first wiring 5 is formed of the same material and to the same thickness as the first electrode 2. The first wiring 5 can be formed at the same time as the first electrode 2.

[0041] As shown in Figure 1, the infrared detection element 10 of this embodiment is equipped with two first wirings 5. Hereinafter, the two first wirings 5 ​​will be referred to as first wirings 51 and 52 to distinguish them.

[0042] The first wiring 51 connects the first electrode 2 of the detection unit 101 and the first electrode 2 of the detection unit 104. The first wiring 52 connects the first electrode 2 of the detection unit 102 and the first electrode 2 of the detection unit 103.

[0043] As shown in Fig. 2, the second wiring 6 is provided on the second surface 12 of a portion of the pyroelectric substrate 1 corresponding to the support portion 16. The second wiring 6 is connected to the second electrode 3. The second wiring 6 is formed of the same material and the same thickness as the second electrode 3. The second wiring 6 can be formed simultaneously with the second electrode 3.

[0044] As shown in Fig. 2, the infrared detection element 10 of the present embodiment includes two second wirings 6. Hereinafter, when distinguishing the two second wirings 6, they are denoted as second wirings 61 and 62.

[0045] The second wiring 61 connects between the second electrodes 3 of the detection unit 101 and the detection unit 104. The second wiring 62 connects between the second electrodes 3 of the detection unit 102 and the detection unit 103.

[0046] (1.2.2) Method for manufacturing an infrared detection element The method for manufacturing the infrared detection element 10 will be described with reference to Figs. 6 and 7.

[0047] As shown in the flowchart of Fig. 6, the method for manufacturing the infrared detection element 10 includes a first electrode forming step ST1, a second electrode forming step ST2, an infrared absorption layer forming step ST3, and a through hole forming step ST4.

[0048] In the first electrode forming step ST1, the first electrode 2 is formed on the first surface 11 of the pyroelectric substrate 1 having the first surface 11 and the second surface 12 in the thickness direction D1. In the first electrode forming step ST1, the first electrode 2 is formed using a vapor deposition method, a sputtering method, or the like. Note that the first wiring 5 can also be formed simultaneously with the first electrode 2 in the first electrode forming step ST1.

[0049] In the second electrode forming step ST2, the second electrode 3 is formed on the second surface 12 of the pyroelectric substrate 1. The second electrode 3 is formed so as to overlap the first electrode 2 in the thickness direction D1 of the pyroelectric substrate 1. In the second electrode forming step ST2, the second electrode 3 is formed using a vapor deposition method, a sputtering method, or the like. Note that the second wiring 6 can also be formed simultaneously with the second electrode 3 in the second electrode forming step ST2.

[0050] In the infrared absorption layer formation step ST3, an infrared absorption layer 4 is formed on the first electrode 2. In the infrared absorption layer formation step ST3, the infrared absorption layer 4 is formed by printing a paste, which is made by dispersing conductive fine powder in a resin and mixing it with an organic solvent, using a screen printing method, gravure printing method, etc., and then curing it by baking.

[0051] The through-hole formation process ST4 is performed after the infrared absorption layer formation process ST3. In the through-hole formation process ST4, through-holes 19 are formed in the pyroelectric substrate 1. The through-holes 19 are formed around a specific portion 13, which is the part of the pyroelectric substrate 1 sandwiched between the first electrode 2 and the second electrode 3. The through-holes 19 have a tapered structure in which the width is narrower on the first surface 11 side than on the second surface 12 side.

[0052] In the through-hole formation process ST4, for example, a through-hole 19 is formed by irradiating the pyroelectric substrate 1 with laser light L1. That is, the through-hole formation process ST4 includes a laser processing process. In the laser processing process, a through-hole 19 having a tapered structure, where the first surface 11 side is narrower than the second surface 12 side, is formed by irradiating the pyroelectric substrate 1 with laser light L1 from the second surface 12 side (see Figure 7). For convenience, in Figure 7, the area of ​​the pyroelectric substrate 1 where the through-hole 19 is to be formed is shown by a dashed line.

[0053] Note that the flowchart shown in Figure 6 is just one example, and the order of the processes may be changed or additional processes may be added as appropriate. Furthermore, multiple infrared detection elements 10 may be manufactured simultaneously by forming multiple infrared detection elements 10 on a wafer that will serve as the base for the pyroelectric substrate 1 and then dicing it.

[0054] (1.2.3) Advantages of the infrared detection element In the infrared detection element 10 of this embodiment, the pyroelectric substrate 1 has through holes 19 with a tapered structure in which the width W1 on the first surface 11 side is narrower than the width W2 on the second surface 12 side, thereby enabling high sensitivity. This point will be explained below in comparison with the infrared detection element of Comparative Example 1 and the infrared detection element of Comparative Example 2.

[0055] Each of the infrared detection elements of Comparative Example 1 and Comparative Example 2 has basically the same configuration as the infrared detection element 10 of this embodiment, but differs in that a through-hole with a tapered structure in which the width on the first surface side is wider than the width on the second surface side is formed in the pyroelectric substrate. A through-hole with a tapered structure in which the width on the first surface side is wider than the width on the second surface side can be formed by processing from the first surface side of the pyroelectric substrate. Furthermore, the infrared detection element of Comparative Example 1 and the infrared detection element of Comparative Example 2 differ from each other mainly in the method of forming the through-hole.

[0056] In the infrared detection element of Comparative Example 1, the through-hole is formed by sandblasting from the first surface side using a blasting process.

[0057] Referring to Figure 10, the method for manufacturing the infrared detection element of Comparative Example 1 will be briefly described.

[0058] In the manufacturing method of the infrared detection element of Comparative Example 1, first, a first electrode 2 and an infrared absorption layer 4 are formed on the first surface 211 of a wafer 201, which is the base of the pyroelectric substrate 1 and has a first surface 211 and a second surface 212 in the thickness direction D1. In Figure 10, for the sake of explanation, one first electrode 2 is shown covering the entire first surface 211 of the wafer 201, but in reality, multiple first electrodes 2 corresponding to multiple detection units 100 are provided on the first surface 211 of the wafer 201, and adjacent first electrodes 2 are spaced apart from each other.

[0059] Furthermore, in the method for manufacturing the infrared detection element of Comparative Example 1, a resist film 71 is attached to the first surface 211 side of the wafer 201 as a mask for blast processing. Also, in the method for manufacturing the infrared detection element of Comparative Example 1, holes corresponding to the shape of the through holes are formed in the resist film 71 by exposure and development processes. Then, in the method for manufacturing the infrared detection element of Comparative Example 1, through holes are formed in the wafer 201 by projecting an abrasive such as sand through the holes in the resist film 71 from the first surface 211 side of the wafer 201 (sandblasting).

[0060] The through-hole formed in this manner has a tapered structure, with the first surface 211 side (the side onto which the abrasive is projected) being wider than the second surface 212 side.

[0061] In the infrared detection element of Comparative Example 1, which is formed by this manufacturing method, it is necessary to attach a resist film 71 on the first electrode 2 and the infrared absorption layer 4, as described above. However, in the manufacturing method of the infrared detection element of Comparative Example 1, as shown in Figure 10, the resist film 71 may float, and a gap 711 may be created between the resist film 71 and the first surface 211 of the wafer 201. If an abrasive is projected from the first surface 211 side in this state, the abrasive may enter the gap 711 and come into contact with areas of the wafer 201 other than the area where the through-hole is to be formed, making it impossible to obtain a through-hole of the desired shape. In addition, the abrasive that enters the gap 711 may cause defects such as deformation in the infrared absorption layer 4. Therefore, the sensitivity of the infrared detection element of Comparative Example 1 may decrease.

[0062] In contrast, the infrared detection element 10 of this embodiment does not use the resist film 71 and abrasive in the manufacturing method of the infrared detection element of Comparative Example 1, so problems such as deformation of the infrared absorption layer 4 are less likely to occur. Therefore, the infrared detection element 10 of this embodiment can be made more sensitive compared to the infrared detection element of Comparative Example 1.

[0063] Next, in the manufacturing method of the infrared detection element of Comparative Example 2, a through hole is formed by irradiating the pyroelectric substrate 1 with laser light from the first surface 11 side of the pyroelectric substrate 1. The through hole formed in this way has a tapered structure in which the first surface 11 side (the side irradiated with laser light) is wider than the second surface 12 side.

[0064] In the infrared detection element of Comparative Example 2, the second electrode 3 on the second surface 12 may be altered (oxidized, peeled off, etc.) due to the heat generated by the energy of the laser light irradiated from the first surface 11. If the second electrode 3 is altered, the sensitivity of the infrared detection element may decrease.

[0065] In contrast, in the infrared detection element 10 of this embodiment, the through-hole 19 is formed by irradiating the pyroelectric substrate 1 with laser light L1 from the second surface 12 side of the pyroelectric substrate 1, as shown in Figure 7. In this case, the heat due to the energy of the laser light L1 irradiated from the second surface 12 side is mainly absorbed by the infrared absorption layer 4. Therefore, deterioration of the first electrode 2 and the second electrode 3 is less likely to occur. As a result, the infrared detection element 10 of this embodiment may have improved sensitivity compared to the infrared detection element of Comparative Example 2.

[0066] In particular, because the side surface 23 of the first electrode 2 is covered with the infrared absorption layer 4, the heat generated by the energy of the laser light L1 is more easily absorbed by the infrared absorption layer 4 than by the first electrode 2. This makes it even less likely for the first electrode 2 to deteriorate, making it possible to further increase the sensitivity of the infrared detection element 10.

[0067] Thus, the infrared detection element 10 of this embodiment has the advantage of being able to achieve higher sensitivity compared to the infrared detection element of Comparative Example 1 and the infrared detection element of Comparative Example 2.

[0068] (1.2.4) Infrared Sensor The infrared sensor 20 of this embodiment will be described with reference to Figure 5.

[0069] As shown in Figure 5, the infrared sensor 20 comprises an infrared detection element 10, a mounting substrate 8 on which the infrared detection element 10 is mounted, and a package 9 that houses the infrared detection element 10 and the mounting substrate 8. For convenience, Figure 5 omits the illustration of the first wiring 5 of the infrared detection element 10.

[0070] As shown in Figure 5, the infrared sensor 20 further comprises a signal processing unit 200. The signal processing unit 200 is composed of, for example, a single-chip IC (Integrated Circuit) element. The signal processing unit 200 processes the output signal consisting of the output current of the infrared detection element 10. The signal processing unit 200 outputs a human body detection signal to an external device based on the output signal of the infrared detection element 10. For example, the signal processing unit 200 outputs a human body detection signal as an output signal when the signal level of the output signal of the infrared detection element 10 exceeds a threshold.

[0071] The mounting board 8 is a MID (Molded Interconnect Device). In the infrared sensor 20, the infrared detection element 10 and the signal processing unit 200 are mounted on the mounting board 8.

[0072] Package 9 is a so-called can package. Package 9 includes a base 91, a cap 92, a window material 93, and multiple (three) lead terminals 94.

[0073] The base 91 is conductive. The base 91 is made of, for example, metal. The base 91 is disc-shaped. The mounting substrate 8 is supported on the upper surface of the base 91.

[0074] The cap 92 is conductive. The cap 92 is made of, for example, metal. The cap 92 is cylindrical with a bottom. The cap 92 is fixed to the base 91 so as to cover the mounting substrate 8, the signal processing unit 200, and the infrared detection element 10. A window opening corresponding to the shape of the infrared detection element 10 is formed in the upper wall 921 of the cap 92.

[0075] The window material 93 is an infrared-transmitting member that transmits infrared rays. The window material 93 is conductive. The window material 93 includes, for example, a silicon substrate and an infrared optical filter laminated on the silicon substrate. The infrared optical filter is an optical multilayer film that transmits infrared rays in the wavelength range to be detected by the infrared sensor 20.

[0076] The window material 93 is positioned to cover the window opening in the upper wall 921 of the cap 92. The window material 93 is positioned above the infrared detection element 10.

[0077] The three lead terminals 94 are held by the base 91. Each of the three lead terminals 94 is pin-shaped. Each of the three lead terminals 94 penetrates the base 91 in the thickness direction. The three lead terminals 94 are, for example, a power supply lead terminal, a signal output lead terminal, and a ground lead terminal.

[0078] (2) Modifications The above embodiments are only one of many embodiments of the present disclosure. The above embodiments can be modified in various ways depending on the design, etc., as long as the objectives of the present disclosure are achieved. Modifications of the embodiments are listed below. The above embodiments and the modifications described below can be combined and applied as appropriate.

[0079] (2.1) Modification 1 The infrared detection element 10 of this modification will be described with reference to Figure 8.

[0080] In the infrared detection element 10 of this modified example, as shown in Figure 8, the first electrode 2 and the second electrode 3 are provided on the entire predetermined portion 15 of the pyroelectric substrate 1, which is the part surrounded by the through-hole 19. That is, in this modified example, the predetermined portion 15 coincides with the specific portion 13 (the part of the pyroelectric substrate 1 sandwiched between the first electrode 2 and the second electrode 3). Also, as shown in Figure 8, the side surface 23 of the first electrode 2, the inner surface of the through-hole 19 in the pyroelectric substrate 1, and the side surface 33 of the second electrode 3 are continuously connected. In this disclosure, "two surfaces are continuously connected" means that the two surfaces are connected substantially without any step. Furthermore, in this embodiment, the infrared absorption layer 4 is provided only on the upper surface 21 (the entire surface) of the first electrode 2, and the side surface 43 of the infrared absorption layer 4 and the side surface 23 of the first electrode 2 are continuously connected.

[0081] The through-hole 19, as in this modified example, can be formed by laser processing. For example, first, a first conductive layer, which will serve as the base for the first electrode 2, and a conductive resin layer, which will serve as the base for the infrared absorption layer 4, are provided on the first surface 11 of the pyroelectric substrate 1, and a second conductive layer, which will serve as the base for the second electrode 3, is provided on the second surface 12 of the pyroelectric substrate 1. Then, laser light is irradiated from the second surface 12 side of the pyroelectric substrate 1, and the edges of the first conductive layer, the edges of the second conductive layer, the portion of the pyroelectric substrate 1 corresponding to the through-hole 19, and the edges of the conductive resin layer are removed collectively by the laser light. In this way, a structure (see Figure 8) is formed in which the side surface 23 of the first electrode 2, the inner surface of the through-hole 19 in the pyroelectric substrate 1, the side surface 33 of the second electrode 3, and the side surface 43 of the infrared absorption layer 4 are continuously connected.

[0082] In this modified infrared detection element 10, just like in the embodiment, it is possible to achieve high sensitivity.

[0083] Furthermore, in the infrared detection element 10 of this modified example, the outer shape of the infrared absorption layer 4 is determined by laser processing, which suppresses variations in the size of the infrared absorption layer 4 for each element. This makes it possible to reduce variations in sensitivity for each element.

[0084] (2.2) Modification 2 The infrared detection element 10 of this modification will be described with reference to Figure 9. The structure of the infrared detection element 10 of this modification is the same as the structure of the infrared detection element 10 of the embodiment (see Figures 1 to 4). The infrared detection element 10 of this modification differs from the structure of the infrared detection element 10 of the embodiment in the method of forming the through hole 19.

[0085] In this modified infrared detection element 10, through holes 19 are formed by blasting. That is, in the manufacturing method of this modified infrared detection element 10, the through hole formation step ST4 includes a blasting step.

[0086] In the through-hole formation step ST4 of this modified example, as shown in Figure 9, a resist film 71 is attached to the second surface 12 side of the pyroelectric substrate 1 as a mask for blasting. In the example in Figure 9, the resist film 71 is attached on the second electrode 3 formed on the second surface 12 of the pyroelectric substrate 1. Note that in Figure 9, for the sake of explanation, one first electrode 2 and one second electrode 3 are shown on the entire first surface 11 and second surface 12 of the pyroelectric substrate 1, respectively. However, in reality, multiple first electrodes 2 and second electrodes 3 corresponding to multiple detection units 100 are provided on the pyroelectric substrate 1, and adjacent first electrodes 2 are spaced apart from each other, and adjacent second electrodes 3 are spaced apart from each other.

[0087] Furthermore, in the through-hole formation step ST4 of this modified example, holes 710 corresponding to the shape of the through-holes 19 are formed in the resist film 71 by exposure and development processes.

[0088] Then, in the through-hole formation step ST4 of this modified example, a through-hole 19 is formed in the pyroelectric substrate 1 by projecting an abrasive such as sand through the resist film 71 from the second surface 12 side of the pyroelectric substrate 1 (sandblasting).

[0089] The through-hole 19 formed in this manner has a tapered structure in which the width on the first surface 11 side is narrower than the width on the second surface 12 side (the side to which the abrasive is projected) (see Figures 3 and 4).

[0090] In the manufacturing method of the infrared detection element 10 of this modified example, the resist film 71 is attached to the second surface 12 side, which does not have the infrared absorption layer 4. Therefore, compared to the manufacturing method of the infrared detection element of Comparative Example 1, a gap (see gap 711 in Figure 10) is less likely to occur between the resist film 71 and the pyroelectric substrate 1. As a result, in the infrared detection element 10 of this modified example, defects such as deformation of the infrared absorption layer 4 are less likely to occur compared to the infrared detection element of Comparative Example 1. In addition, the infrared detection element 10 of this modified example has the advantage of making it easier to obtain through holes 19 of a desired shape.

[0091] (2.3) Other Modifications In one modification, the side surface 23 of the first electrode 2 is covered with the infrared absorbing layer 4, and the side surface 43 of the infrared absorbing layer 4 and the inner surface of the through hole 19 in the pyroelectric substrate 1 are continuously connected.

[0092] In one modified example, the side surface 23 of the first electrode 2 is not covered by the infrared absorption layer 4, and the through hole 19 may be formed at a distance from the side surface 23 of the first electrode 2.

[0093] In one modified example, the first electrode 2 and the second electrode 3 may differ in size or shape. In this case, the specific portion 13 is defined by the region of the pyroelectric substrate 1 that overlaps with both the first electrode 2 and the second electrode 3.

[0094] In one modified example, the plan view shape of the specific part 13 is not limited to a rectangle, but may be, for example, a circle, a semicircle, an ellipse, a semi-ellipse, a polygon other than a rectangle, etc.

[0095] (3) Embodiments As can be seen from the above embodiments and modifications, the following embodiments are disclosed herein.

[0096] The infrared detection element (10) of the first embodiment comprises a pyroelectric substrate (1), a first electrode (2), a second electrode (3), and an infrared absorption layer (4). The pyroelectric substrate (1) has a first surface (11) and a second surface (12) in the thickness direction (D1). The first electrode (2) is provided on the first surface (11) of the pyroelectric substrate (1). The second electrode (3) is provided on the second surface (12) of the pyroelectric substrate (1) so as to overlap with the first electrode (2) in the thickness direction (D1). The infrared absorption layer (4) is provided on the first electrode (2). The pyroelectric substrate (1) has a through hole (19) that penetrates the pyroelectric substrate (1) in the thickness direction (D1). The through-hole (19) is formed around a specific portion (13) in the pyroelectric substrate (1) that is sandwiched between the first electrode (2) and the second electrode (3). The through-hole (19) has a tapered structure in which the width is narrower on the first surface (11) side than on the second surface (12) side.

[0097] According to this embodiment, it becomes possible to increase the sensitivity of the infrared detection element (10).

[0098] In the infrared detection element (10) of the second embodiment, the specific portion (13) is rectangular in shape, as in the first embodiment. The through hole (19) is formed around the specific portion (13) along three sides of the specific portion (13).

[0099] According to this embodiment, it becomes possible to further increase the sensitivity of the infrared detection element (10).

[0100] In the infrared detection element (10) of the third embodiment, in the first or second embodiment, the thickness of the first electrode (2) is 0.05 μm or more and 5 μm or less. The thickness of the second electrode (3) is 0.05 μm or more and 5 μm or less.

[0101] According to this embodiment, it becomes possible to increase the sensitivity of the infrared detection element (10).

[0102] In the infrared detection element (10) of the fourth embodiment, in any one of the first to third embodiments, the infrared absorption layer (4) is a resin layer in which conductive fine powder is dispersed in the resin. The thickness of the infrared absorption layer (4) is 0.1 μm or more and 5 μm or less.

[0103] According to this embodiment, it becomes possible to increase the sensitivity of the infrared detection element (10).

[0104] In the fifth embodiment of the infrared detection element (10), in any one of the first to fourth embodiments, the infrared absorption layer (4) is provided so as to cover the side surface (23) of the first electrode (2).

[0105] According to this embodiment, it becomes possible to further increase the sensitivity of the infrared detection element (10).

[0106] In the sixth embodiment of the infrared detection element (10), in any one of the first to fifth embodiments, the through hole (19) is formed at a distance from the specific part (13).

[0107] According to this embodiment, it becomes possible to increase the sensitivity of the infrared detection element (10).

[0108] In the infrared detection element (10) of the seventh embodiment, in any one of the first to fifth embodiments, the side surface (23) of the first electrode (2), the inner surface of the through hole (19) in the pyroelectric substrate (1), and the side surface (33) of the second electrode (3) are continuously connected.

[0109] According to this embodiment, it is possible to reduce the variation in sensitivity between individual elements.

[0110] The infrared sensor (20) of the eighth embodiment comprises an infrared detection element (10) of any one of the first to seventh embodiments, a mounting substrate (8), and a package (9). The infrared detection element (10) is mounted on the mounting substrate (8). The package (9) houses the infrared detection element (10) and the mounting substrate (8).

[0111] According to this embodiment, it becomes possible to increase the sensitivity of the infrared detection element (10).

[0112] A method for manufacturing an infrared detection element (10) according to the ninth embodiment includes a first electrode formation step (ST1), a second electrode formation step (ST2), an infrared absorption layer formation step (ST3), and a through-hole formation step (ST4). The first electrode formation step (ST1) includes forming a first electrode (2) on the first surface (11) of a pyroelectric substrate (1) having a first surface (11) and a second surface (12) in the thickness direction (D1). The second electrode formation step (ST2) includes forming a second electrode (3) on the second surface (12) of the pyroelectric substrate (1) such that it overlaps with the first electrode (2) in the thickness direction (D1). The infrared absorption layer formation step (ST3) includes forming an infrared absorption layer (4) on the first electrode (2). The through-hole formation step (ST4) is performed after the infrared absorption layer formation step (ST3). The through-hole formation step (ST4) includes forming a through-hole (19) in the pyroelectric substrate (1) around a specific portion (13) which is sandwiched between the first electrode (2) and the second electrode (3), having a tapered structure in which the first surface (11) side is narrower than the second surface (12) side.

[0113] According to this embodiment, it becomes possible to increase the sensitivity of the infrared detection element (10).

[0114] In the manufacturing method of the infrared detection element (10) according to the tenth embodiment, in the ninth embodiment, the through-hole formation step (ST4) includes a laser processing step. The laser processing step includes forming a through-hole (19) by irradiating the pyroelectric substrate (1) with laser light (L1) from the second surface (12) side of the pyroelectric substrate (1).

[0115] 10 Infrared detection element 20 Infrared sensor 1 Pyroelectric substrate 11 First surface 12 Second surface 13 Specific part 19 Through hole 2 First electrode 23 Side surface 3 Second electrode 33 Side surface 4 Infrared absorption layer 8 Mounting substrate 9 Package D1 Thickness direction L1 Laser light ST1 First electrode formation process ST2 Second electrode formation process ST3 Infrared absorption layer formation process ST4 Through hole formation process

Claims

1. An infrared detection element comprising: a pyroelectric substrate having a first surface and a second surface in the thickness direction; a first electrode provided on the first surface of the pyroelectric substrate; a second electrode provided on the second surface of the pyroelectric substrate so as to overlap with the first electrode in the thickness direction; and an infrared absorbing layer provided on the first electrode, wherein the pyroelectric substrate has a through hole penetrating the pyroelectric substrate in the thickness direction, the through hole is formed around a specific portion of the pyroelectric substrate sandwiched between the first electrode and the second electrode, and the through hole has a tapered structure in which the width on the first surface side is narrower than the width on the second surface side.

2. The infrared detection element according to claim 1, wherein the specific portion is rectangular in shape, and the through hole is formed around the specific portion, along three sides of the specific portion.

3. The infrared detection element according to claim 1 or 2, wherein the thickness of the first electrode is 0.05 μm or more and 5 μm or less, and the thickness of the second electrode is 0.05 μm or more and 5 μm or less.

4. The infrared detection element according to any one of claims 1 to 3, wherein the infrared absorbing layer is a resin layer in which conductive fine powder is dispersed in the resin, and the thickness of the infrared absorbing layer is 0.1 μm or more and 5 μm or less.

5. The infrared detection element according to any one of claims 1 to 4, wherein the infrared absorbing layer is provided so as to cover the side surface of the first electrode.

6. The infrared detection element according to any one of claims 1 to 5, wherein the through hole is formed at a distance from the specific portion.

7. The infrared detection element according to any one of claims 1 to 5, wherein the side surface of the first electrode, the inner surface of the through hole in the pyroelectric substrate, and the side surface of the second electrode are continuously connected.

8. An infrared sensor comprising: an infrared detection element according to any one of claims 1 to 7; a mounting substrate on which the infrared detection element is mounted; and a package housing the infrared detection element and the mounting substrate.

9. A method for manufacturing an infrared detection element, comprising: a first electrode forming step of forming a first electrode on the first surface of a pyroelectric substrate having a first surface and a second surface in the thickness direction; a second electrode forming step of forming a second electrode on the second surface of the pyroelectric substrate so as to overlap with the first electrode in the thickness direction; an infrared absorption layer forming step of forming an infrared absorption layer on the first electrode; and a through hole forming step performed after the infrared absorption layer forming step of forming a through hole in the pyroelectric substrate having a tapered structure in which the width on the first surface side is narrower than the width on the second surface side, around a specific portion which is sandwiched between the first electrode and the second electrode.

10. The method for manufacturing an infrared detection element according to claim 9, wherein the through-hole forming step includes a laser processing step of irradiating the pyroelectric substrate with laser light from the second surface side of the pyroelectric substrate to form the through-hole.

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