Electromagnetic wave detection element and electromagnetic wave sensor equipped therewith

Abstract

To improve the efficiency of electromagnetic wave absorption. [Solution] The electromagnetic wave detection element 11 has an electromagnetic wave detection unit 12. The electromagnetic wave detection unit 12 has a first surface 21 to which the electromagnetic wave to be measured is incident, a second surface 22 which is the back surface of the first surface 21, a temperature sensing film 14 located between the first surface 21 and the second surface 22, a first conductive layer 15 connected to the temperature sensing film 14, a dielectric layer 18 covering the first conductive layer 15 and the temperature sensing film 14, and an overlapping portion 31 that overlaps the temperature sensing film 14 and the first conductive layer 15 when viewed in the film thickness direction of the temperature sensing film 14. In the overlapping portion 31, the average thickness Z1 of the dielectric layer 18 between the first conductive layer 15 and the first surface 21 is greater than the average distance Z2 in the film thickness direction between the first conductive layer 15 and the second surface 22.

Description

Technical Field

[0001] The present disclosure relates to an electromagnetic wave detection element and an electromagnetic wave sensor including the same.

Background Art

[0002] An electromagnetic wave sensor that detects electromagnetic waves such as infrared rays is known. Patent Document 1 describes an electromagnetic wave sensor including a temperature detection element, a conductive layer electrically connected to the electromagnetic wave incident surface of the temperature detection element, and a dielectric layer covering the temperature detection element and the conductive layer. The temperature detection element has a thermistor film whose electrical resistance changes according to temperature. The thermistor film undergoes a temperature change due to electromagnetic waves incident from the outside. There is a correlation (Stefan-Boltzmann's law) between the temperature of the measurement target and the radiant energy radiated from the measurement target. Based on this principle, the temperature of the measurement target can be measured from the electrical resistance of the thermistor film.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electromagnetic wave sensor described in Patent Document 1, since the conductive layer is provided on the electromagnetic wave incident surface of the temperature detection element, a part of the incident electromagnetic wave is reflected by the conductive layer and does not sufficiently contribute to the temperature change of the temperature detection element. The present disclosure aims to provide an electromagnetic wave detection element capable of enhancing the absorption efficiency of electromagnetic waves.

Means for Solving the Problems

[0005] The electromagnetic wave detection element of this disclosure has an electromagnetic wave detection unit. The electromagnetic wave detection unit has a first surface to which the electromagnetic wave to be measured is incident, a second surface which is the back surface of the first surface, a temperature sensing film located between the first surface and the second surface, a first conductive layer connected to the temperature sensing film, a dielectric layer covering the first conductive layer and the temperature sensing film, and an overlapping portion that overlaps the temperature sensing film and the first conductive layer when viewed in the film thickness direction of the temperature sensing film. In the overlapping portion, the average thickness of the dielectric layer between the first conductive layer and the first surface is greater than the average distance between the first conductive layer and the second surface in the film thickness direction. [Effects of the Invention]

[0006] According to this disclosure, it is possible to provide an electromagnetic wave detection element that can improve the absorption efficiency of electromagnetic waves. [Brief explanation of the drawing]

[0007] [Figure 1] This is an exploded perspective view of the infrared sensor according to the first embodiment. [Figure 2] This is a schematic diagram of an electromagnetic wave detection element according to the first embodiment. [Figure 3] Figure 2 is a schematic plan view of the electromagnetic wave detection element shown. [Figure 4] Figure 2 is a schematic cross-sectional view of the electromagnetic wave detection element shown. [Figure 5] This is a schematic cross-sectional view of an electromagnetic wave detection element in a comparative example. [Figure 6] This is a schematic cross-sectional view showing other configurations of the dielectric layer. [Figure 7] Figure 2 is a schematic cross-sectional view showing a manufacturing method for the electromagnetic wave detection element shown. [Figure 8] This is a schematic plan view of an electromagnetic wave detection element according to the second embodiment. [Figure 9] Figure 8 is a schematic cross-sectional view of the electromagnetic wave detection element shown. [Figure 10] This is a schematic cross-sectional view showing other configurations of the dielectric layer. [Figure 11] Figure 8 is a schematic cross-sectional view showing a manufacturing method for the electromagnetic wave detection element. [Figure 12]This is a schematic cross-sectional view of a modified electromagnetic wave detection element. [Figure 13] This is a schematic cross-sectional view of another modified electromagnetic wave detection element. [Modes for carrying out the invention]

[0008] Several embodiments of the electromagnetic wave detection element and electromagnetic wave sensor of this disclosure will be described below with reference to the drawings. In the following description and drawings, the X and Y directions are parallel to the main surfaces of the first substrate 2 and the second substrate 3, the X direction corresponds to the row direction of the array of electromagnetic wave detection elements 11, and the Y direction corresponds to the column direction of the array of electromagnetic wave detection elements 11. The main surfaces are the mutually opposing surfaces of the first substrate 2 and the second substrate 3. The X and Y directions are orthogonal to each other. The Z direction is orthogonal to the X and Y directions and is perpendicular to the main surfaces of the first substrate 2 and the second substrate 3, or the thickness direction of the temperature detection film 14 of the electromagnetic wave detection element 11. The +Z direction is the direction from the second substrate 3 toward the first substrate 2, or the direction from the first arm surface 24 of the arm portion 13 toward the second arm surface 25. The -Z direction is the direction from the first substrate 2 to the second substrate 3, or the direction from the second arm surface 25 of the arm portion 13 to the first arm surface 24. For convenience, the perspective views and cross-sectional views from Figure 2 onward are shown upside down compared to Figure 1.

[0009] The following embodiments focus on infrared sensors in which electromagnetic wave detection elements 11 are arranged in a two-dimensional array. Infrared sensors primarily detect long-wavelength infrared radiation. The wavelength of long-wavelength infrared radiation is generally 8 to 14 μm. Such infrared sensors are mainly used as image sensors in infrared cameras. Infrared cameras can be used as night vision scopes and night vision goggles in dark places, as well as for measuring the temperature of people and objects. Furthermore, infrared sensors in which multiple electromagnetic wave detection elements 11 are arranged in a one-dimensional array can be used as sensors for measuring various temperatures or temperature distributions. Although not explained in detail, infrared sensors in which multiple electromagnetic wave detection elements 11 are arranged in a one-dimensional array are also included in the scope of this disclosure. The electromagnetic waves to be detected are not limited to infrared radiation; for example, terahertz waves with wavelengths of 100 μm to 1 mm may also be used.

[0010] (First Embodiment) (Overall structure) Figure 1 is an exploded perspective view of an infrared sensor 1 according to a first embodiment of the present disclosure, showing the second substrate 3 separated from the electrical connection member 7. The arm portion 13 of the electromagnetic wave detection element 11 is omitted from the illustration in Figure 1. The infrared sensor 1 has a first substrate 2 and a second substrate 3 facing the first substrate 2. Side walls (not shown) are connected to the first substrate 2 and the second substrate 3, and the first substrate 2, the second substrate 3 and the side walls form a sealed internal space 4. The internal space 4 is under negative pressure or vacuum. This prevents or suppresses gas convection in the internal space 4, thereby reducing the thermal influence on the electromagnetic wave detection element 11.

[0011] The first substrate 2 has a silicon substrate and an insulating film (not shown). Elements 5 such as a readout IC (ROIC), wiring (not shown), etc. are formed on the surface of the silicon substrate or inside the insulating film. The ROIC includes a regulator, A / D converter, multiplexer, etc. The second substrate 3 mainly has a silicon substrate and an insulating film (not shown). Leads 6 are formed inside or on the surface of the insulating film of the second substrate 3.

[0012] Multiple electromagnetic wave detection elements 11 are provided in the internal space 4. The multiple electromagnetic wave detection elements 11 form a two-dimensional grid array consisting of multiple rows extending in the X direction and multiple columns extending in the Y direction. Each row consists of multiple electromagnetic wave detection elements 11 arranged at regular intervals in the X direction, and each column consists of multiple electromagnetic wave detection elements 11 arranged at regular intervals in the Y direction. The electromagnetic wave detection unit 12 (see Figure 2) of each electromagnetic wave detection element 11 constitutes one cell or pixel in this array. The number of rows and columns of the array can be, for example, 640 rows × 480 columns, 1024 rows × 768 columns, etc., but is not limited to these.

[0013] Leads 6 are formed on the second substrate 3. The leads 6 connect an electric connection member 7, which will be described later, to the electromagnetic wave detection element 11 and supply a sense current to the electromagnetic wave detection element 11. The leads 6 are formed of a conductor such as copper. The leads 6 are provided for each row and each column of the electromagnetic wave detection element 11 and are formed in a grid pattern. That is, the leads 6 include row leads 6X extending in the row direction (X direction) and column leads 6Y extending in the column direction (Y direction). The row leads 6X sequentially connect the electromagnetic wave detection elements 11 included in the corresponding rows, and the column leads 6Y sequentially connect the electromagnetic wave detection elements 11 included in the corresponding columns. The row leads 6X and the column leads 6Y extend at different positions in the Z direction so as to cross without being directly electrically connected to each other.

[0014] The first substrate 2 and the second substrate 3 are connected by a plurality of electric connection members 7. The electric connection members 7 are conductors having a pillar shape with a circular cross section and can be manufactured, for example, by plating. Elements 5 such as ROICs are connected to the electric connection members 7 via internal wirings of the first substrate 2. Some of the plurality of electric connection members 7 are connected to the row leads 6X, and the rest of the plurality of electric connection members 7 are connected to the column leads 6Y. Although not shown, the plurality of electric connection members 7X respectively connected to the plurality of row leads 6X are alternately arranged on one end side and the other end side of the plurality of row leads 6X. Similarly, the plurality of electric connection members 7Y respectively connected to the plurality of column leads 6Y are alternately arranged on one end side and the other end side of the plurality of column leads 6Y. Thereby, it is possible to suppress an increase in the size of the infrared sensor 1 while ensuring a sufficient cross-sectional area of the electric connection members 7.

[0015] (Configuration of the electromagnetic wave detection element 11) FIG. 2 is a perspective view of the electromagnetic wave detecting element 11. FIG. 3 is a plan view of the electromagnetic wave detecting element 11 viewed from the -Z direction to the +Z direction, in which the illustration of the first dielectric layer 19 is omitted, and the internal temperature detecting film 14 and the first conductive layer 15 are illustrated. FIG. 4(a) is a cross-sectional view of the electromagnetic wave detecting element 11 along the line A-A in FIG. 3, FIG. 4(b) is an enlarged view of part C in FIG. 4(a), and FIG. 4(c) is a cross-sectional view of the electromagnetic wave detecting element 11 along the line B-B in FIG. 3. The electromagnetic wave detecting element 11 includes an electromagnetic wave detecting unit 12, two arm portions 13 connected to the electromagnetic wave detecting unit 12 and supporting the electromagnetic wave detecting unit 12, and two conductive columns 30 respectively connected to corresponding ones of the two arm portions 13. In the example shown in FIGS. 2 and 3, the arm portion 13 has a linear shape. As shown in FIGS. 4(a) and 4(b), the electromagnetic wave detecting unit 12 has a first surface 21 and a second surface 22. The first surface 21 is the surface on which the electromagnetic wave to be measured in the electromagnetic wave detecting unit 12 is incident, and faces the second substrate 3 in the Z direction. The second surface 22 is the back surface of the first surface 21 and faces the first substrate 2 in the Z direction. The conductive column 30 connects the second substrate 3 and the arm portion 13. Thereby, the first surface 21 of the electromagnetic wave detecting unit 12 is provided at a position separated from the second substrate 3 in the Z direction. The conductive column 30 is electrically connected to the lead 6 formed on the second substrate 3. The two arm portions 13 have the same shape and configuration, and the two conductive columns 30 also have the same shape and configuration.

[0016] The electromagnetic wave detecting unit 12 includes a temperature detecting film 14, two first conductive layers 15, and a dielectric layer 18. One of the two first conductive layers 15 is referred to as the other first conductive layer 15. The temperature detecting film 14 is, for example, a thermistor film having a square or rectangular shape. The planar shape of the thermistor film is not limited to a square or rectangular shape and can take any shape. The thermistor film is, for example, a film of vanadium oxide, amorphous silicon, polycrystalline silicon, an oxide having a spinel-type crystal structure containing manganese, titanium oxide, or yttrium-barium-copper oxide. The temperature detecting film 14 may be, instead of the thermistor film, for example, a diode film such as a silicon diode film, a thermocouple film, a thermopile film, or a pyroelectric film such as a lead zirconate titanate film.

[0017] Each of the two first conductive layers 15 includes a conductive terminal layer 16 and a wiring layer 17 electrically connected to the terminal layer 16. Therefore, the electromagnetic wave detection unit 12 includes two terminal layers 16 and two wiring layers 17. The first conductive layers 15 can be formed from, for example, a metal such as titanium or a conductive nitride such as titanium nitride. The sense current flows in the direction connecting the two first conductive layers 15, i.e., in the in-plane direction (XY plane) of the temperature detection film 14. The end of the wiring layer 17 opposite to the terminal layer 16 is electrically connected to the second conductive layer 26, which will be described later. The connection between the wiring layer 17 and the second conductive layer 26, i.e., the connection between the electromagnetic wave detection unit 12 and the arm portion 13, is located near the center of each of the two opposing sides of the electromagnetic wave detection unit 12 in a view in the Z direction, but the position of the connection is not limited. The two first conductive layers 15 have the same configuration.

[0018] Referring to Figure 4, the temperature sensing film 14 is located between the first surface 21 and the second surface 22 of the electromagnetic wave detection unit 12. The temperature sensing film 14 has an electromagnetic wave incident surface 23 on the electromagnetic wave incident side (-Z side) that faces the first surface 21. The two first conductive layers 15 are provided on the electromagnetic wave incident side (-Z side) of the temperature sensing film 14, and the terminal layers 16 of the two first conductive layers 15 are connected to the electromagnetic wave incident surface 23. This is because, as will be described later, the electromagnetic wave detection unit 12 is manufactured in the +Z direction from the first surface 21 toward the second surface 22. By providing the two first conductive layers 15 on the -Z side of the temperature sensing film 14, it is possible to avoid the temperature sensing film 14 being affected when the two first conductive layers 15 are formed by patterning.

[0019] The dielectric layer 18 is formed from aluminum oxide, silicon oxide, aluminum nitride, silicon nitride, etc., and functions as an electromagnetic wave absorber. The dielectric layer 18 covers the first conductive layer 15 and the temperature sensing film 14. Specifically, the dielectric layer 18 has a first dielectric layer 19 that covers the first conductive layer 15 and the temperature sensing film 14 on the -Z side of the first conductive layer 15 and the temperature sensing film 14, and a second dielectric layer 20 that covers the first conductive layer 15 and the temperature sensing film 14 on the +Z side of the first conductive layer 15 and the temperature sensing film 14.

[0020] Each of the two arm portions 13 has a second conductive layer 26 electrically connected to a wiring layer 17 of a corresponding first conductive layer 15, a third dielectric layer 27 covering the second conductive layer 26 on the electromagnetic wave incident side (-Z side), and a fourth dielectric layer 28 covering the second conductive layer 26 on the opposite side of the third dielectric layer 27 in the Z direction (+Z side). The second conductive layer 26 is electrically connected to the conductive support column 30. The arm portion 13 has a first arm surface 24 located on the electromagnetic wave incident side, and a second arm surface 25 which is the back surface of the first arm surface 24. The first arm surface 24 is formed by the third dielectric layer 27 (the third dielectric layer 27 and the second conductive layer 26 at the connection point with the conductive support column 30), and the second arm surface 25 is formed by the fourth dielectric layer 28.

[0021] (Configuration of the dielectric layer 18 of the electromagnetic wave detection unit 12) The electromagnetic wave detection unit 12 has an overlapping portion 31 (the dashed-dotted line portion in Figure 3) that overlaps with the temperature detection film 14 and the first conductive layer 15 when viewed in the Z direction. Since the electromagnetic wave detection unit 12 has two first conductive layers 15, it has two overlapping portions 31. As shown in Figure 3, the terminal layer 16 is generally circular when viewed in the Z direction, and the wiring layer 17 has a width (dimension in the X direction) that covers the terminal layer 16 when viewed from the -Z direction. Therefore, the overlapping portion 31 is rectangular when viewed in the Z direction, but the shape of the overlapping portion 31 is not limited to this.

[0022] In at least one, preferably in each overlapping portion 31, the average thickness Z1 (dimension in the Z direction) of the dielectric layer 18 (first dielectric layer 19) between the first conductive layer 15 and the first surface 21 is greater than the average distance Z2 (distance in the Z direction) between the first conductive layer 15 and the second surface 22 in the film thickness direction of the temperature sensing film 14. Here, the average thickness Z1 can be calculated as Z1 = Σ(ΔX × ΔY × D1(X,Y)) / Σ(ΔX × ΔY) when the first dielectric layer 19 (dielectric layer 18 between the first conductive layer 15 and the first surface 21) in the overlapping portion 31 is divided into a small volume with an X-direction dimension ΔX, a Y-direction dimension ΔY, and a distance D1(X,Y) between the first conductive layer 15 and the first surface 21. Similarly, the average spacing Z2 can be calculated as Z1 = Σ(ΔX × ΔY × D2(X,Y)) / Σ(ΔX × ΔY) when the portion between the first conductive layer 15 and the second surface 22 in the superimposed portion 31 is divided into infinitesimal volumes with dimensions ΔX in the X direction, ΔY in the Y direction, and a distance D2(X,Y) between the first conductive layer 15 and the second surface 22.

[0023] A portion of the electromagnetic wave detection unit 12 protrudes in the +Z direction beyond the second arm surface 25. More specifically, the electromagnetic wave detection unit 12 has a base portion 32 that coincides with the arm portion 13 in the Z direction, and a protruding portion 33 provided on the +Z side of the base portion 32 in contact with the base portion 32. In the example shown in Figures 4(a) and 4(b), the protruding portion 33 includes a temperature sensing film 14, a terminal layer 16, and a portion of the wiring layer 17. The protruding portion 33 is generally a shape combining a truncated square pyramid and a rectangular parallelepiped, but the shape of the protruding portion 33 is not limited and may be, for example, a rectangular parallelepiped. The planar shape of the protruding portion 33 is also not limited and may be a quadrilateral, a polygon other than a quadrilateral, a circle, an ellipse, etc. The base portion 32 is a flat plate. Except for the overlapping portion 31, it is not necessary to satisfy the relationship Z1 > Z2, so for example, a recess may be provided on the first surface 21 in a portion away from the temperature sensing film 14 in the X direction. In the examples shown in Figures 4(a) and 4(b), the wiring layer 17 is bent inside the dielectric layer 18. That is, the wiring layer 17 extends inside the electromagnetic wave detection unit 12, from the boundary between the electromagnetic wave detection unit 12 and the arm unit 13 in the Y direction within the XY plane, extends diagonally in the Y direction and the +Z direction along the way, and then extends again in the Y direction within the XY plane to connect to the terminal layer 16.

[0024] As described above, since the dielectric layer 18 functions as an electromagnetic wave absorber, it is preferable that the electromagnetic wave absorption efficiency is high. Here, it is known that electromagnetic waves attenuate according to Lambert-Beer's law when traveling inside a medium. If the electromagnetic wave intensity at the incident surface of a certain medium is I and the electromagnetic wave intensity at the exit surface of the medium is I0, then I = I0 × exp(-α), and α is proportional to the distance between the incident surface and the exit surface of the medium. That is, when the distance between the incident surface and the exit surface is large, the electromagnetic wave energy absorbed by the dielectric layer becomes large.

[0025] FIG. 5 shows the electromagnetic wave detection unit 112 of the comparative example. In the comparative example, in the overlapping portion 31, the average thickness Z1 of the dielectric layer 18 between the first conductive layer 15 and the first surface 21 is small, and Z1 < Z2. Therefore, in the overlapping portion 31, before the electromagnetic wave is sufficiently absorbed by the dielectric layer 18, it is reflected by the first conductive layer 15, making it difficult to increase the electromagnetic wave absorption efficiency of the dielectric layer 18. On the other hand, in the present embodiment, since Z1 > Z2, more electromagnetic waves are absorbed by the dielectric layer 18 (the first dielectric layer 19) on the incident side before being reflected by the first conductive layer 15 compared to the comparative example. Therefore, in the present embodiment, the electromagnetic wave absorption efficiency of the dielectric layer 18 can be increased compared to the comparative example.

[0026] When the volume of the dielectric layer 18 increases, the heat capacity of the electromagnetic wave detection unit 12 including the dielectric layer 18 increases, and the temperature change of the electromagnetic wave detection unit 12 becomes less likely to occur. As described above, since Z2 < Z1 in the overlapping portion 31, an increase in the heat capacity of the electromagnetic wave detection unit 12 can be suppressed, and the electromagnetic wave detection sensitivity of the electromagnetic wave detection element 11 can be increased.

[0027] (Configuration of the dielectric layer of the arm portion 13) Since the arm portion 13 serves as a heat transfer path from the electromagnetic wave detection unit 12, it is preferable to minimize heat transfer from the arm portion 13. To achieve this, it is preferable to make the third dielectric layer 27 and the fourth dielectric layer 28 of each arm portion 13 as thin as possible, to the extent necessary to protect the second conductive layer 26. In this embodiment, the average thickness Z1 of the dielectric layer 18 in the superimposed portion 31 is greater than the average thickness Z3 of the third dielectric layer 27, so that the amount of heat dissipated from the arm portion 13 can be suppressed while increasing the electromagnetic wave absorption efficiency of the dielectric layer 18. Also, as shown in Figure 4(a), the average thickness Z4 of the arm portion 13 is smaller than the average thickness Z5 of the electromagnetic wave detection unit 12. This also suppresses the amount of heat dissipated from the arm portion 13, thereby increasing the electromagnetic wave detection sensitivity of the electromagnetic wave detection element 11.

[0028] (Modified example of dielectric layer 18 of electromagnetic wave detection unit 12) The dielectric layer 18 can be composed of two or more dielectric films. As described above, since infrared sensors detect long-wavelength infrared radiation with wavelengths of approximately 8 to 14 μm, it is preferable that the dielectric layer 18 has high infrared absorption efficiency over a wide range within the 8 to 14 μm wavelength range. Since the infrared absorption efficiency is wavelength-dependent for each material, the wavelength range with high absorption efficiency can be broadened by having two or more dielectric films with different wavelength ranges for high absorption efficiency. For example, the dielectric layer 18 can be composed of a laminate of two or more dielectric films.

[0029] The dielectric layer 18 can have two or more of the following: a silicon oxide film, an aluminum oxide film, and a silicon nitride film. All of these are chemically stable materials. Silicon oxide has high infrared absorption efficiency in the wavelength range of approximately 8 to 10.5 μm, with a peak in infrared absorption efficiency around 10 μm. Aluminum oxide has high infrared absorption efficiency in the wavelength range of approximately 10.5 to 20 μm, with a peak in infrared absorption efficiency around 14 μm. Silicon nitride has high infrared absorption efficiency in the wavelength range of approximately 8 to 15 μm, with a peak in infrared absorption efficiency around 13 μm. Therefore, when the dielectric layer 18 has two dielectric films, it is preferable to combine silicon oxide with either aluminum oxide or silicon nitride, which have similar absorption efficiency peaks.

[0030] Figure 6 shows the structure of a laminate 34 (first dielectric layer 19) consisting of an aluminum oxide film 35 and a silicon oxide film 36. The silicon oxide film 36 is provided between the aluminum oxide film 35 and the temperature sensing film 14, in contact with the temperature sensing film 14. Since silicon oxide has less chemical influence on the temperature sensing film 14 than aluminum oxide, this method can suppress the performance degradation of the temperature sensing film 14 over time. In addition, aluminum oxide has higher strength than silicon oxide, and by using it as the dielectric layer 18, the physical strength of the electromagnetic wave detection unit 12 can be increased. As will be described later, the first dielectric layer 19 is divided into a first portion 43, a second portion 44, and a dielectric layer 49A for manufacturing process reasons. In the example shown in Figure 6(a), the aluminum oxide film 35 corresponds to the first portion 43, and the silicon oxide film 36 corresponds to the second portion 44 and the dielectric layer 49A. Therefore, the dielectric layer 18 can be manufactured using the same manufacturing process as when the first portion 43, the second portion 44, and the dielectric layer 49A are made from the same material. In the example shown in Figure 6(b), the first portion 43 consists of an aluminum oxide film 35, and the portion of the second portion 44 that is in contact with the first portion 43 consists of an aluminum oxide film 35, while the portion that is in contact with the temperature sensing film 14 consists of a silicon oxide film 36. In this example as well, the dielectric layer 18 can be manufactured using the same manufacturing process as when the first portion 43, the second portion 44, and the dielectric layer 49A are made from the same material.

[0031] (Manufacturing method for the electromagnetic wave detection element 11 of the first embodiment) A method for manufacturing an electromagnetic wave detection element 11 according to the first embodiment will be described with reference to Figure 7. Normally, multiple electromagnetic wave detection elements 11 are fabricated on a wafer to form a two-dimensional array, but here the main manufacturing process of a single electromagnetic wave detection element 11 will be described. First, as shown in Figure 7(a), two conductive pillars 30 are fabricated on the second substrate 3, and an organic sacrificial layer 41 such as photoresist is fabricated between the two conductive pillars 30, i.e., on the -Z side of the region that will become the electromagnetic wave detection part 12. Leads 6 (not shown) of the second substrate 3 are fabricated in advance. Next, as shown in Figure 7(b), a dielectric layer 42 is formed on the two conductive pillars 30 and the organic sacrificial layer 41. Next, as shown in Figure 7(c), a part of the dielectric layer 42 is removed by milling to fabricate a first portion 43 in the shape of a truncated square pyramid in the center of the region that will become the electromagnetic wave detection part 12. Next, as shown in Figure 7(d), a dielectric layer is formed on the first portion 43 to fabricate a second portion 44. In this way, a dielectric layer 45 with a central portion protruding in the +Z direction is fabricated.

[0032] Next, as shown in Figure 7(e), a conductive layer 46 including a terminal layer 16 and a wiring layer 17 is fabricated on the dielectric layer 45. At this time, a hole 47 reaching the conductive support 30 is formed in the portion of the dielectric layer 45 that covers the conductive support 30, and a conductive layer 46 electrically connected to the conductive support 30 is also fabricated in the hole 47. Next, as shown in Figure 7(f), a dielectric layer 49A is formed on the gap 48 between the two terminal layers 16 (see Figure 7(e)) and on the wiring layer 17. Next, as shown in Figure 7(g), a temperature sensing film 14 is formed on the terminal layer 16 and the dielectric layer 49A. Next, as shown in Figure 7(h), a dielectric layer 49B is formed so as to cover the conductive layer 46 and the temperature sensing film 14. Next, by fabricating the pattern for the arm portion 13, an electromagnetic wave detection unit 12 comprising the first and second dielectric layers 19, 20 and the first conductive layer 15, and two arm portions 13 comprising the third and fourth dielectric layers 27, 28 and the second conductive layer 26 are formed. Next, by removing the organic sacrificial layer 41, the electromagnetic wave detection element 11 shown in Figure 4 is obtained. After that, although not shown in the diagram, the second substrate 3 is joined to the first substrate to complete the infrared sensor 1.

[0033] (Second embodiment) Next, the second embodiment will be described, focusing on the differences from the first embodiment. Configurations and effects that have been omitted from the description are the same as in the first embodiment. Figure 8 is a plan view of the electromagnetic wave detection element 11 according to the second embodiment, viewed from the -Z direction to the +Z direction, with the first dielectric layer 19 not shown, and the internal temperature sensing film 14 and the first conductive layer 15 shown. Figure 9(a) is a cross-sectional view of the electromagnetic wave detection element 11 along the DD line in Figure 8, Figure 9(b) is an enlarged view of section F in Figure 9(a), and Figure 9(c) is a cross-sectional view of the electromagnetic wave detection element 11 along the EE line in Figure 8. In this embodiment as well, in the superimposed portion 31, the average thickness Z1 of the dielectric layer 18 (first dielectric layer 19) between the first conductive layer 15 and the first surface 21 is greater than the average distance Z2 in the film thickness direction of the temperature sensing film 14 between the first conductive layer 15 and the second surface 22. However, in this embodiment, a portion of the electromagnetic wave detection unit 12 protrudes in the -Z direction beyond the first arm surface 24, and another portion of the electromagnetic wave detection unit 12 protrudes in the +Z direction beyond the second arm surface 25. In this embodiment as well, the average thickness Z4 of the arm portion 13 is smaller than the average thickness Z5 of the electromagnetic wave detection unit 12, thereby suppressing the amount of heat dissipated from the arm portion 13 and increasing the electromagnetic wave detection sensitivity of the electromagnetic wave detection element 11.

[0034] The electromagnetic wave detection unit 12 has a base portion 37 including a first conductive layer 15, and a protruding portion 38 provided on the -Z direction side of the base portion 37 in contact with the base portion 37. The protruding portion 38 is generally truncated square pyramidal, but the shape of the protruding portion 38 is not limited and may be, for example, a rectangular parallelepiped. The planar shape of the protruding portion 38 is also not limited and may be a quadrilateral, a polygon other than a quadrilateral, a circle, an ellipse, etc. In the protruding portion 38, the area other than the overlapping portion 31 may be thinner than the overlapping portion 31. For example, a recess may be provided on the first surface 21 in the X direction, away from the temperature detection film 14.

[0035] Figure 10 shows the structure of a laminate 34 (first dielectric layer 19) consisting of an aluminum oxide film 35 and a silicon oxide film 36. In this embodiment as well, the silicon oxide film 36 can be provided between the aluminum oxide film 35 and the temperature sensing film 14, in contact with the temperature sensing film 14. In the example shown in Figure 10(a), the aluminum oxide film 35 corresponds to the protruding portion 38 and the silicon oxide film 36 corresponds to the base portion 37, so the dielectric layer 18 can be manufactured using the same manufacturing process as when the protruding portion 38 and the base portion 37 are made from the same material. In the example shown in Figure 10(b), the protruding portion 38 is made of the aluminum oxide film 35, the part of the base portion 37 that contacts the protruding portion 38 is made of the aluminum oxide film 35, and the part that contacts the temperature sensing film 14 is made of the silicon oxide film 36. In this example as well, the dielectric layer 18 can be manufactured using the same manufacturing process as when the protruding portion 38 and the base portion 37 are made from the same material.

[0036] (Manufacturing method for the electromagnetic wave detection element 11 of the second embodiment) A method for manufacturing the electromagnetic wave detection element 11 of the second embodiment will be described with reference to Figure 11. First, two conductive pillars 30 and an organic sacrificial layer 41 are fabricated on the second substrate 3. This step is the same as the step shown in Figure 7(a). Next, as shown in Figure 11(a), a recess 51 is formed in the organic sacrificial layer 41, and a first portion 52 of the first dielectric layer 19 is formed in the recess 51. Next, as shown in Figure 11(b), a second portion 53 of the first dielectric layer 19 is formed on the organic sacrificial layer 41 and the first portion 52.

[0037] The following steps are basically the same as in the first embodiment. That is, as shown in Figure 11(c), a conductive layer 54 including a terminal layer 16 and a wiring layer 17 is fabricated on the second portion 53, and the conductive layer 54 is electrically connected to the conductive support column 30. At this time, a dielectric layer 55 is formed in the gap between the two terminal layers 16 and on the wiring layer 17. Next, as shown in Figure 11(d), a temperature sensing film 14 is formed on the terminal layer 16 and the dielectric layer 55, and a dielectric layer 56 is formed so as to cover the dielectric layer 55 and the temperature sensing film 14. Next, the pattern of the arm portion 13 is fabricated to form the electromagnetic wave detection portion 12 and the two arm portions 13. Next, the organic sacrificial layer 41 is removed to obtain the electromagnetic wave detection element 11 shown in Figure 9. After that, the second substrate 3 is joined to the first substrate to complete the infrared sensor 1.

[0038] As described above, in the first embodiment, a portion of the electromagnetic wave detection unit 12 protrudes beyond the second arm surface 25 in the +Z direction, and in the second embodiment, a portion of the electromagnetic wave detection unit 12 protrudes beyond the first arm surface 24 in the -Z direction. Both embodiments can improve the electromagnetic wave absorption efficiency compared to the comparative example, but the first embodiment is more advantageous than the second embodiment in terms of the manufacturing process. That is, in the second embodiment, in Figure 11(a), a photoresist is fabricated on the organic sacrificial layer 41 to create a recess 51 in the organic sacrificial layer 41, and after forming the first portion 52, the photoresist is removed. However, the dielectric layer attached to the side wall of the photoresist may remain after the photoresist is removed. In the first embodiment, such a step is unnecessary.

[0039] On the other hand, in the second embodiment, the wiring layer 17 extends planarly in the XY plane, resulting in even higher reliability of the wiring layer 17 compared to the first embodiment. Furthermore, since the temperature sensing film 14 can be formed over a wider area, it is also preferable in terms of the operational stability of the electromagnetic wave sensing element 11.

[0040] (modified version) FIG. 12 shows a cross-sectional view of the electromagnetic wave detection element 11 of a modified example. In this modified example, a backside conductive layer 40 (another conductive layer) is added to the electromagnetic wave detection element 11 of the first embodiment. The backside conductive layer 40 is connected to the back surface 39 of the electromagnetic wave incident surface 23 of the temperature detection film 14. The sense current flows through the temperature detection film 14 in the film thickness direction (Z direction). This modified example can also be applied to the second embodiment.

[0041] FIG. 13(a) shows a cross-sectional view of the electromagnetic wave detection element 11 of another modified example. In this modified example, the first conductive layer 15 is provided on substantially the entire electromagnetic wave incident surface 23 of the temperature detection film 14, and two terminal layers 16 and two wiring layers 17 are provided on the back surface 39 of the electromagnetic wave incident surface 23. The terminal layer 16 becomes the backside conductive layer 40. In this modified example, since the first conductive layer 15 also covers the central portion of the temperature detection film 14, the overlapping portion 31 is wider than that in the modified example shown in FIG. 12. FIG. 13(b) shows a cross-sectional view of the electromagnetic wave detection element 11 of still another modified example. In this modified example, the first conductive layer 15 shown in FIG. 13(a) is not provided. Therefore, two terminal layers 16 and two wiring layers 17 constitute two first conductive layers 15, and two overlapping portions 31 are provided. Also in this case, since Z2 < Z1, an increase in the heat capacity of the electromagnetic wave detection unit 12 can be suppressed, and the electromagnetic wave detection sensitivity of the electromagnetic wave detection element ********** 11 can be enhanced. Each of the modified examples shown in FIG. 13 can also be applied to the second embodiment.

Description of Reference Numerals

[0042] 1 Infrared sensor (electromagnetic wave sensor) 2 First substrate 3 Second substrate 11 Electromagnetic wave detection element 12 Electromagnetic wave detection unit 13 Arm portion 14 Temperature detection film 15 First conductive layer 18 Dielectric layer 21 First surface 22 Second surface 23 Electromagnetic wave incident surface 26 Second conductive layer 24 First arm surface 25 Second arm surface 30 Conductive Post 31. Overlapping portion

Claims

1. It has an electromagnetic wave detection unit, The electromagnetic wave detection unit is The first surface into which the electromagnetic wave to be measured is incident, The second surface is the back surface of the first surface, A temperature sensing film located between the first surface and the second surface, A first conductive layer connected to the temperature sensing film, A dielectric layer covering the first conductive layer and the temperature sensing film, The temperature sensing film has an overlapping portion that overlaps the temperature sensing film and the first conductive layer when viewed in the film thickness direction of the temperature sensing film, An electromagnetic wave detection element wherein, in the superimposed portion, the average thickness of the dielectric layer between the first conductive layer and the first surface is greater than the average distance in the film thickness direction between the first conductive layer and the second surface.

2. It has an arm portion that supports the electromagnetic wave detection unit, The electromagnetic wave detection element according to claim 1, wherein the average thickness of the arm portion is smaller than the average thickness of the electromagnetic wave detection portion.

3. The arm portion has a first arm surface located on the incident side of the electromagnetic wave, and a second arm surface which is the back surface of the first arm surface. The electromagnetic wave detection element according to claim 2, wherein a part of the electromagnetic wave detection unit protrudes from the second arm surface in a direction toward the second arm surface from the first arm surface.

4. The arm portion has a first arm surface located on the incident side of the electromagnetic wave, and a second arm surface which is the back surface of the first arm surface. The electromagnetic wave detection element according to claim 2, wherein a part of the electromagnetic wave detection unit protrudes from the first arm surface in a direction toward the first arm surface from the second arm surface.

5. It has an arm portion that supports the electromagnetic wave detection unit, The arm portion has a second conductive layer electrically connected to the first conductive layer, and a dielectric layer covering the second conductive layer on the incident side of the electromagnetic wave. The electromagnetic wave detection element according to claim 1, wherein the average thickness of the dielectric layer between the first conductive layer and the first surface in the superimposed portion is greater than the average thickness of the dielectric layer in the arm portion.

6. The arm portion supporting the electromagnetic wave detection unit, A substrate provided facing the first surface in the film thickness direction and away from the first surface, A support column connecting the substrate and the arm portion, An electromagnetic wave detection element according to claim 1, having the following characteristics.

7. It has another first conductive layer connected to the temperature sensing film, The temperature sensing film includes an electromagnetic wave incident surface facing the first surface, The electromagnetic wave detection element according to any one of claims 1 to 6, wherein the first conductive layer and the other first conductive layer are connected to the electromagnetic wave incident surface.

8. It has a back-side conductive layer connected to the temperature sensing film, The temperature sensing film includes an electromagnetic wave incident surface facing the first surface, The electromagnetic wave detection element according to any one of claims 1 to 6, wherein the first conductive layer is connected to the electromagnetic wave incident surface, and the back conductive layer is connected to the back surface of the electromagnetic wave incident surface.

9. The electromagnetic wave detection element according to any one of claims 1 to 6, wherein the dielectric layer has two or more types of dielectric films.

10. The electromagnetic wave detection element according to claim 9, wherein the dielectric layer comprises an aluminum oxide film and a silicon oxide film.

11. The electromagnetic wave detection element according to claim 10, wherein the silicon oxide film is provided between the aluminum oxide film and the temperature detection film, in contact with the temperature detection film.

12. An electromagnetic wave sensor comprising an electromagnetic wave detection element according to any one of claims 1 to 6.

13. A plurality of electromagnetic wave detection elements according to any one of claims 1 to 5 are provided, The electromagnetic wave sensor comprises multiple electromagnetic wave detection elements arranged in an array.

Images