JP5943764B2 - Electromagnetic wave sensor and electromagnetic wave sensor device - Google Patents

Description

  The present invention relates to an electromagnetic wave sensor and an electromagnetic wave sensor device, and more particularly to a thermal type infrared sensor and an infrared sensor device.

  In the conventional thermal infrared sensor device, an optical filter is mounted in front of the infrared sensor in order to select an infrared wavelength to be detected. However, a thermal infrared sensor device that selects a detection wavelength using only an infrared sensor without using an optical filter has been developed for reasons such as a complicated structure and reduced detection efficiency.

  For example, Patent Document 1 discloses an infrared sensor in which a corrugated structure including a curved surface is provided in an infrared absorbing portion, and selectively absorbs only infrared light having a wavelength equal to the period of the corrugated structure.

Japanese Patent Laid-Open No. 1-142418

  However, in the case of the infrared sensor described in Patent Document 1, first, it is difficult to reduce the area of the absorption part because the period of the periodic structure of the infrared absorption part cannot be made smaller than the detection wavelength. There was a problem. Secondly, when carbon or the like is used as the material constituting the absorption part, the material itself absorbs wavelengths other than the detection wavelength, and the wavelength selectivity is deteriorated. Third, the corrugated structure has a problem that it is difficult to manufacture.

  Then, an object of this invention is to provide the electromagnetic wave sensor which selectively detects a predetermined wavelength, without using an optical filter, and the electromagnetic wave sensor apparatus provided with this electromagnetic wave sensor.

  In order to achieve the above object, an electromagnetic wave sensor according to the present invention comprises a temperature detection part, and an electromagnetic wave absorption part thermally connected to the temperature detection part and having at least an electromagnetic wave incident surface made of metal. An electromagnetic wave sensor for detecting an electromagnetic wave incident on the electromagnetic wave absorption part through the electromagnetic wave absorption part, each having a plurality of groove parts formed in parallel with each other at a constant groove period in two directions intersecting each other, The groove depth, groove width, and groove period of the groove are selected so as to induce surface plasmons that combine with electromagnetic waves of a specific wavelength included in the electromagnetic waves incident on the electromagnetic wave absorber.

  The electromagnetic wave sensor device according to the present invention is characterized in that a plurality of the electromagnetic wave sensors are arranged in an array.

  According to the present invention, surface plasmon resonance occurs in the depth direction or in-plane direction of the groove portion, so that the absorption amount of electromagnetic waves of a specific wavelength is larger than the absorption amount of electromagnetic waves other than the specific wavelength without providing an optical filter. Accordingly, an electromagnetic wave having a desired wavelength can be selected and detected. Moreover, since surface plasmon resonance is used and the magnitude of the period can be made smaller than the detection wavelength, the area of the electromagnetic wave absorber can be reduced.

  Further, at least the electromagnetic wave incident surface is a metal, and it is possible to suppress wavelength absorption other than the detection wavelength due to the material itself constituting the electromagnetic wave absorbing portion, and therefore it is possible to improve the selectivity of the absorption wavelength. Further, such a groove can be easily produced by a general etching process.

1 is a perspective view of an infrared sensor device according to Embodiment 1 of the present invention. The top view of the infrared sensor by Embodiment 1 of this invention is shown in the state without an absorber. The II sectional view of FIG. 2 is shown in a state where there is an absorber. It is a perspective view of the absorber by Embodiment 1 of this invention. It is a top view of the absorber by Embodiment 1 of this invention. It is II-II sectional drawing of FIG. 4b. It is sectional drawing corresponding to FIG. 5 of the alternative absorber by Embodiment 1 of this invention. It is sectional drawing corresponding to FIG. 5 of the alternative absorber by Embodiment 1 of this invention. The absorption characteristic of the absorber by Embodiment 1 of this invention is shown. FIG. 9 shows the absorption characteristics when h = 0.8 μm. FIG. 9A shows the case where the electric field is parallel to the x direction, and FIG. 9B shows the case where it is perpendicular. . The absorption characteristic of the absorber by Embodiment 1 of this invention is shown. The absorption characteristic of the absorber by Embodiment 1 of this invention is shown. It is a top view of the infrared sensor array by Embodiment 2 of this invention. It is a top view of the infrared sensor array by Embodiment 3 of this invention. It is III-III sectional drawing of FIG. It is sectional drawing of the temperature detection part of the infrared sensor by Embodiment 4 of this invention.

  Hereinafter, in an embodiment of the present invention, a thermal infrared sensor will be described as an example of an electromagnetic wave sensor. As an example, the case where the temperature detection unit is a silicon diode will be described. However, the present invention is not limited to this, and the present invention is also effective when an absorber structure such as a thermopile or a bolometer is used as the absorber structure of incident light. It is. That is, the present invention does not depend on the thermal infrared sensor system itself. Furthermore, the present invention is also effective as a sensor in a wavelength range other than infrared, for example, visible, near infrared, and terahertz (THz).

  Moreover, in each embodiment, the same code | symbol is attached | subjected to the same structure and description is abbreviate | omitted.

Embodiment 1 FIG.
First, the configuration of the infrared sensor device according to the first embodiment of the present invention will be described.
FIG. 1 is a perspective view of an infrared sensor device according to Embodiment 1 of the present invention, the whole being represented by 1000. FIG. In the infrared sensor device 1000, a plurality of infrared sensors 100 are arranged on the substrate 1 in a matrix (array) in the x-axis and y-direction, and light is incident from a direction parallel to the z-axis. Around the infrared sensor 100, a detection circuit 1010 that processes a signal detected by the infrared sensor 100 and detects an image is provided.

  Although the infrared sensor 100 is two-dimensionally arranged in the infrared sensor device 1000, a configuration in which the infrared sensor device 1000 is arranged one-dimensionally may be used.

  FIG. 2 is a top view of the infrared sensor 100 with the absorber 10 removed. In FIG. 2, the protective film and the reflective film on the wiring are omitted for clarity. FIG. 3 shows a cross-sectional view of the infrared sensor 100 in the II direction shown in FIG. 2 and the II-II direction shown in FIG.

  As shown in FIGS. 2 and 3, the infrared sensor 100 includes a substrate 1 made of, for example, silicon. A hollow portion 2 is provided in the substrate 1. Further, a temperature detection unit 4 that detects the temperature is provided above the hollow portion 2. The temperature detection unit 4 is supported by two support legs 3. As shown in FIG. 2, the support leg 3 has a bridge shape that is bent in an L shape when viewed from above. The support leg 3 includes a thin film metal wiring 6 and an insulating layer 14 that supports the wiring 6.

  The temperature detection unit 4 includes a detection film 5 and a thin-film metal wiring 6 whose electric resistance value changes with temperature. The detection film 5 is made of, for example, a diode using crystalline silicon, that is, a silicon diode. As described above, the thin-film metal wiring 6 is also provided on the support leg 3 and electrically connects the aluminum wiring 7 covered with the insulating layer 17 and the detection film 5. The thin film metal wiring 6 is made of, for example, a titanium alloy having a thickness of about 100 nm. The electric signal output from the detection film 5 is transmitted to the aluminum wiring 7 through the thin film metal wiring 6 formed on the support leg 3, and is taken out by the detection circuit (1010 in FIG. 1). Electrical connection between the thin-film metal wiring 6 and the detection film 5 and between the thin-film metal wiring 6 and the aluminum wiring 7 is performed via a conductor (not shown) extending in the vertical direction as necessary. You may go.

  The reflective film 8 that reflects infrared rays is disposed so as to cover the hollow portion 2. However, the reflective film 8 is disposed so as to cover at least a part of the support leg 3 in a state where it is not thermally connected to the temperature detector 4.

  As shown in FIG. 3, a support column 9 is provided on the upper side of the temperature detection unit 4, and the absorber 10 is supported on the support column 9. That is, the absorber 10 is connected by the support pillar 9 on the upper side of the temperature detection unit 4. The absorber 10 is thermally connected to the temperature detection unit 4 and has a configuration in which a temperature change generated in the absorber 10 is transmitted to the temperature detection unit 4.

  On the other hand, the absorber 10 is held above the reflective film 8 in a state where it is not thermally connected to the reflective film 8, and spreads laterally so as to cover at least a part of the reflective film 8. Therefore, when the infrared sensor 100 is viewed from above, only the absorber 10 is visible as shown in FIG. 4b. Note that, when the absorber 10 can sufficiently absorb incident light, the reflective film 8 may be omitted. Therefore, whether to provide the reflective film 8 can be selected as necessary.

  In the infrared sensor 100, incident infrared rays (electromagnetic waves) are mainly absorbed by the absorber 10. The infrared rays absorbed by the absorber 10 are converted into heat and transmitted to the temperature detection unit 4 via the support column 9. In the temperature detection unit 4, since the electrical resistance of the detection film 5 changes depending on the temperature, the amount of infrared rays absorbed by the absorber 10 is detected by detecting a change in the value of the electrical resistance by the detection circuit 1010 provided outside. Can be detected.

Next, the structure of the absorber 10 will be described.
4a and 4b are a perspective view and a top view of an absorber provided in the infrared sensor according to Embodiment 1 of the present invention. In FIG. 4a and FIG. 4b, in order to clarify the structure of the absorber 10, the hole of the connecting portion that connects the absorber 10 and the support column 9 described later is omitted, but the existence of this hole Is not required.

  As shown in FIGS. 4a and 4b, the absorber 10 is periodically formed with grooves 11 (11a, 11b) that do not penetrate the absorber 10 in the z direction, respectively in the x direction and the y direction. As shown in FIG. 4a, the groove 11 has a predetermined groove depth h, groove width w, and groove period p. Further, the groove portions 11a and 11b extending in the x direction and the y direction respectively intersect with each other, and preferably are orthogonal to each other. Furthermore, the groove period p is set to a size smaller than the desired absorption wavelength. Moreover, it is preferable that the number of periods of the grooves 11a and 11b, that is, the number of convex portions of the absorber is equal. However, if the number of periods is sufficiently large, for example, if the product of the number of periods and the groove period p is generally a value that is several times the detection wavelength, the asymmetry of the absorption characteristics even if the number of periods of the grooves 11a and 11b is different. Sex can be ignored. 4a and 4b illustrate the case where the groove portions 11a and 11b are orthogonal to each other and the number of convex portions of the absorber is the same.

  By forming the groove portions 11a and 11b so as to intersect with each other and making the number of periods of the groove portions 11a and 11b equal, there is an effect that the polarization dependency of incident light in absorption is reduced and the absorption rate is increased. Further, when the grooves 11a and 11b are orthogonal, the dependency of the incident light on the polarization is lost, and the absorption rate is increased most.

  FIG. 5 is a cross-sectional view (xz plane) of the absorber 10 of the infrared sensor 100 shown in FIG. 4B when viewed in the II-II direction. In FIG. 4b, since the groove portions 11a and 11b are orthogonal to each other and the number of convex portions of the absorber is equal to each other, FIG. Further, as already described, the groove 11 is provided in the absorber 10 so as to form a two-dimensional periodic structure, and the cross section perpendicular to the longitudinal direction of the groove 11 is rectangular. Preferably it is formed. That is, it is preferable that the groove part 11 has a side wall orthogonal to the infrared absorption surface and the bottom surface.

  As shown in FIG. 5, the absorber 10 is made of a metal film 12. Moreover, it is preferable that the metal film 12 is comprised with the metal which is easy to produce surface plasmon resonance. Such metals are, for example, Au, Ag, Cu, Al, Ni, Cr and the like. The overall film thickness of the absorber 10 can be appropriately determined in consideration of the absorption rate, thermal time constant, material stress, and the like.

  Such an absorber 10 can be produced by patterning a metal by photolithography. In other words, 1) a mask pattern of the groove portion 11 is created, 2) a photoresist is applied to the metal film, 3) the photoresist is irradiated with light, and the mask pattern of the groove portion 11 is transferred to the metal film. Development is performed. 5) The exposed metal portion is processed by dry etching using a halogen-based gas. 6) Finally, the resist is removed with an organic solvent. The above 5) may be performed by wet etching using an etching solution.

Here, it is sufficient that the absorber 10 has at least an infrared absorption surface made of metal. For example, as shown in FIG. 6, only the infrared absorption surface is made of the metal film 12, and the inside is silicon oxide SiO ₂ , silicon nitride SiN, silicon It may be composed of a dielectric 13 such as. In this case, if the metal film 12 has a sufficient thickness not to transmit incident light, there is no optical influence such as absorption of the internal dielectric 13 itself.

For example, the metal film 12 of the absorber 10 has a thickness (about several tens of nanometers) that is about twice or more the skin depth expressed by δ = (2 / μσω) ^1/2 with respect to the detection wavelength. In general, it can be said that leakage of incident light is sufficiently small. Here, μ and σ are the magnetic permeability and electrical conductivity of the metal film 12, respectively, and ω is the angular frequency of the electromagnetic wave having the detection wavelength.

  Therefore, the absorber 10 may have a two-layer structure in which a metal film is formed on a dielectric film, or a three-layer structure in which a dielectric film made of silicon oxide or the like is sandwiched between metal films. May be.

  When the absorber 10 has such a multilayer structure, the heat capacity is generally smaller than that of a single metal due to the fact that the dielectric has a larger volume specific heat than the metal. This has the effect of increasing the response speed. The two-layer structure and the three-layer structure can be manufactured by forming a metal on the surface by sputtering or the like after processing the dielectric by patterning and etching by photolithography. Therefore, the fabrication becomes easier than the case where the groove is formed of a single metal as shown in FIG.

  Further, as shown in FIG. 7, the absorber 10 may have a structure in which the internal dielectric is removed from the structure shown in FIG. In the case of this structure, since the volume of the absorber 10 itself is reduced as compared with the structures shown in FIGS. 5 and 6, the heat capacity is minimized and the response speed is further increased. Here, the thickness of the metal film 12 in FIG. 7 may be a thickness that does not transmit the target incident electromagnetic wave. As described above, this thickness can be a value of about twice or more the thickness of the skin effect.

Next, the absorption characteristic of the absorber 10 will be described.
In general, when the wavelength of the evanescent wave generated when the electromagnetic wave is totally reflected at the boundary surface matches the wavelength of the surface plasmon wave, the surface plasmon is excited. In addition, as in the present invention, when a fine and periodic groove is provided on the surface of the absorber (infrared absorbing surface), it is known that surface plasmons are excited and coupled to the surface in normal incident light. . Due to such coupling, the electromagnetic wave having the resonance wavelength is strongly localized on the surface and is consequently absorbed, so that the absorption increases at the resonance wavelength. Here, for simplicity, description will be made using a one-dimensional periodic structure. In the case of a one-dimensional periodic structure, if the wave number of the induced surface plasmon is k _sp , the wave number of incident light is k ₀ , the incident angle is θ, and m is an integer, the following equation is established.

  Therefore, it can be seen that the wavelength determined by the groove period p is strongly localized on the surface and consequently absorbed. In the case of a two-dimensional periodic structure, the reciprocal lattice vector in the above equation is two-dimensional. In the case of a structure in which isolated dents are periodically arranged two-dimensionally, for example, a square lattice or a triangular lattice, surface plasmon resonance occurs in the in-plane direction and in the depth direction, but surface plasmon resonance in the in-plane direction. Is dominant, and the main absorption wavelength is determined by the period. In the absorber structure of the present invention as shown in FIG. 4a, when the groove width w is smaller than the groove depth h, the surface plasmon resonance in the depth direction becomes dominant, so the absorption wavelength is determined by the depth. Is done. Therefore, absorption can occur even at wavelengths longer than the period p.

In FIG. 8, when the material constituting the absorber 10 is Au, the absorptance when p = 6 μm, w = 0.1 μm, and h = 0.5, 0.8, 1.0 μm is electromagnetic. The result obtained by the field analysis is shown. In FIG. 8, the vertical axis represents the electromagnetic wave absorption rate, and the horizontal axis represents the absorption wavelength. The grooves 11a and 11b are orthogonal to each other, have the same number of periods, and have a rectangular cross section perpendicular to the longitudinal direction of the grooves 11. When the absorption wavelength is lambda _ab, for each h, lambda _ab was 6.3,8.6,10.0Myuemu.

  Further, in the case of h = 0.8 μm, the absorption characteristics when the electric field is parallel to and perpendicular to the x direction are shown in FIGS. 9A and 9B by the same electromagnetic field analysis. ). 9A and 9B, the vertical axis represents the electromagnetic wave absorption rate, and the horizontal axis represents the wavelength. 9 (a) and 9 (b) gave the same result. Since the absorption characteristics are the same for the electric fields in directions orthogonal to each other, it is recognized that the direction of the electric field with respect to the groove 11 has no polarization dependency. In this case, it is clear from symmetry that there is no polarization dependence for the direction of other electric fields.

  Here, as in the example shown in FIG. 5, when the groove width w is sufficiently smaller than the groove depth h, it depends on the groove depth h rather than the in-plane resonance depending on the groove period p of the surface. The resonance in the depth direction becomes dominant. Therefore, the wavelength determined by the groove depth h is strongly localized on the surface and is consequently absorbed.

Next, the case where the groove width w is changed will be considered.
FIG. 10 shows the results of the absorption rate obtained when h = 0.8 μm and p = 6 μm are fixed and w is changed to 50, 100, 200, and 400 nm. In FIG. 10, the vertical axis represents the electromagnetic wave absorption rate, and the horizontal axis represents the wavelength. As shown in FIG. 10, the absorption wavelength shifts to the short wavelength side as the groove width w increases. This is considered to be a result of an increase in resonance in the in-plane direction in addition to resonance in the depth direction due to an increase in the groove width. Thus, it can be seen that the absorption wavelength can be controlled by changing the groove width w in addition to the groove depth h. Even at this time, if the groove width w is smaller than the groove depth h, absorption occurs at a wavelength having a period greater than or equal to the period p. Further, as shown in FIG. 10, in order to increase the absorption rate, it is preferable that the groove width w is sufficiently smaller than the groove depth h.

Further, a case where the groove width w is larger than the groove depth h will be considered.
FIG. 11 shows the absorptance when h = 0.8 μm and p = 6 μm and w is set to 2.0 μm and 3.0 μm as an example. In FIG. 11, the vertical axis represents the electromagnetic wave absorption rate, and the horizontal axis represents the wavelength. In FIG. 11, main absorption wavelengths are multi-wavelength. This is presumably because the surface plasmon resonance in the depth direction (z direction) and the in-plane direction (x direction, y direction) acts when the groove width w increases. Using this characteristic, absorption wavelength control at multiple wavelengths can be performed. For example, a two-wavelength absorption structure called an atmospheric window can be realized at a wavelength of about 3 μm to about 5 μm and about 8 μm to about 12 μm without atmospheric absorption. The light in the wavelength range between the above wavelengths corresponds to the absorption wavelength in the atmosphere and can be noise. However, the structure of the present invention can suppress absorption in the wavelength range that becomes noise and absorb a desired wavelength. .

  As described above, even when the groove width w is larger than the groove depth h, the absorption wavelength can be determined by the surface plasmon mode determined by the surface structure, and the absorption of the material itself constituting the absorber 10 is prevented. You can see that you can. In general, detection wavelengths tend to be multi-wavelength, and simultaneous detection of multi-wavelengths is possible using the above-described absorption wavelength control at multiple wavelengths. Furthermore, in this case, as shown in FIG. 11, it is possible to absorb wavelengths longer than the groove period p of the groove portion 11.

  Thus, the surface plasmon is induced by the groove portion 11 formed in the absorber 10, and only a desired detection wavelength can be selectively absorbed. When the groove width w is sufficiently smaller than the groove depth h, the detection wavelength is determined by the groove depth. In other words, the detection wavelength is selected as the infrared sensor. This phenomenon is called surface plasmon, metamaterial, pseudo surface plasmon, etc., but the essential phenomenon is the same. In the present invention, these are not distinguished and are described as surface plasmons.

  In the case of an infrared sensor provided with an absorber having a wave-like periodic structure as in Patent Document 1, firstly, since the magnitude of the period of the periodic structure of the absorber cannot be made equal to or less than the detection wavelength, absorption is performed. There was a problem that it was difficult to reduce the body area. Secondly, when carbon or the like is used as the material constituting the absorber, the absorption wavelength of the material itself is added to the absorption wavelength determined by the structure, so the selectivity of the absorption wavelength, that is, the detection wavelength is selected. There was a problem of getting worse. Third, there is a problem that a special mask formation / etching process such as a gray scale mask is required, which makes it difficult to manufacture. Fourth, there is a problem that the absorptance becomes small because resonance in the groove is disturbed.

  Similarly to the second problem, as already known, in the case where wavelength selectivity is realized by providing a periodic refractive index distribution structure including a photonic crystal in the infrared absorption section, an absorber Since the absorption wavelength of a dielectric film such as a dielectric film such as silicon oxide exists in the vicinity of 8 μm to 14 μm, the absorption peak wavelength is 6 μm depending on the periodic refractive index distribution and the structure of the photonic band gap. Even if it is set, 8 μm to 14 μm, which is the absorption wavelength of silicon oxide as a material, is also detected at the same time. Thus, the selectivity deteriorates as the detection wavelength is increased.

  With respect to these problems, in the present embodiment, surface plasmon resonance is used, and the period of the groove portion 11 can be made equal to or less than the detection wavelength. Therefore, compared to a structure in which the period coincides with the absorption wavelength, the absorber The area of 10 can be reduced. Therefore, it is possible to reduce the size of the infrared sensor 100, and hence the pixel size when a thermal imager or the like is constituted by a plurality of infrared sensors.

  Further, by using the metal film 12 on the surface corresponding to the infrared absorption surface and utilizing the absorption by the surface plasmon resonance determined by the surface structure, the absorption of the material itself constituting the absorber 10 is prevented, and an unintended wavelength. This has the effect of preventing the detection.

  In addition, since it does not have a special shape such as a corrugated shape, it is easy to manufacture the absorber 10, and in particular, since a cross section perpendicular to the longitudinal direction of the groove 11 is formed in a rectangular shape, It can be easily manufactured by dry etching using photolithography.

  Further, if the side wall is in a wedge shape or a curved surface, the resonance between the side walls is disturbed and the absorptance is lowered. However, the groove 11 is formed in a rectangular shape, and the side wall is orthogonal to the infrared absorption surface and the bottom surface. Therefore, the distance between the side walls becomes constant in the depth direction (z direction), and the bottom surface of the groove portion 11 is flat. Therefore, the distance between the groove top surface and the groove bottom surface is in the in-plane direction (x direction, It becomes constant in the y direction). As a result, the resonance is not disturbed, and therefore, strong resonance is generated in the groove 11 and the absorptance is increased.

Embodiment 2. FIG.
FIG. 12 is a top view of a thermal-type infrared sensor array according to the second embodiment of the present invention, indicated as a whole by 200. FIG. In the present specification, the “infrared sensor array” refers to a structure in which the infrared sensors mounted in the infrared sensor device described in FIG. 1 are arranged in an array (matrix).

  In the infrared sensor array 200, the infrared sensors 100 are arranged in an array. FIG. 12 shows an infrared sensor array 200 including a total of four infrared sensors 100 of 2 rows × 2 columns for the sake of simplicity. However, the present invention is not limited to this, and infrared rays to be arranged are arranged. There is no limit to the number of sensors 100. Further, it is not necessarily a two-dimensional array, and may be a one-dimensional array. The infrared sensor array 200 selects an infrared sensor in each row and / or each column by an external scanning circuit (not shown) or the like, and extracts information detected by each sensor 100 in time series. Information detected by each sensor may be read out in parallel.

  In this way, the infrared sensor device equipped with the infrared sensor array 200 can be used as a thermal imager for detecting images. At this time, an image having wavelength information and information on incident light intensity can be detected by using the absorber 10 shown in FIG. 4A as an infrared absorber. As an application other than the image sensor, it can be used as an array sensor for position detection with a small number of pixels.

Embodiment 3 FIG.
FIG. 13 is a top view of the infrared sensor array according to the third embodiment of the present invention, which is generally indicated by 300, and FIG. 14 is a cross section of the infrared sensor array 300 as viewed in the III-III direction shown in FIG. FIG.

  The infrared sensor array 300 is an array of four types of infrared sensors 100, 110, 120, and 130 that differ only in the groove depth h of the groove. In FIG. 13, for simplicity of explanation, an infrared sensor array 300 including a total of four infrared sensors of 2 rows × 2 columns is illustrated, but the present invention is not limited to this, and the arranged infrared sensor is shown. There is no limit to the number of sensors. Further, it is not necessarily a two-dimensional array, and may be a one-dimensional array. The infrared sensor array 300 selects an infrared sensor in each row and / or each column by an external scanning circuit (not shown) or the like, and extracts information detected by each sensor in time series. Information detected by each sensor may be read out in parallel.

  As already described, when the groove width w is sufficiently smaller than the groove depth h, the detection wavelength of the sensor constituting the pixel is changed by changing the groove depth h of the groove formed in the absorber of the infrared sensor. be able to. That is, by providing grooves having different depths in the absorber of each sensor, it is possible to use as a thermal image imager for detecting images having incident light intensity information of different wavelengths depending on pixels.

  Alternatively, the absorptance or the absorption wavelength may be controlled by changing not only the groove depth h but also the groove period p and the groove width w. That is, in the present embodiment, pixels having sensor structures in which at least one of the groove depth h, the groove width w, and the groove period p is different from each other are arrayed in the two-dimensional groove portion periodic structure shown in FIG. This makes it possible to use the image as a thermal imager that can obtain information having different wavelength information.

  Then, by arraying pixels having different detection wavelengths in this way, it is possible to obtain a color image in the infrared wavelength region as in the case of the image sensor in the visible light region. As an application other than the image sensor, it can be used as an array sensor for position detection with a small number of pixels.

Embodiment 4 FIG.
FIG. 15 is a cross-sectional view of a temperature detection unit of a thermal infrared sensor according to Embodiment 4 of the present invention. Structures other than the temperature detection unit 54 are the same as those in FIGS. 2 and 4, and the temperature detection unit 54 is supported on the upper portion of the hollow portion 2 by the support legs 3.

  A temperature detection unit 54 shown in FIG. 15 includes a detection film 5 and a thin-film metal wiring 6 whose electric resistance value changes depending on the temperature. The detection film 5 is, for example, a silicon diode. The thin film metal wiring 6 is made of, for example, a titanium alloy having a thickness of about 100 nm. The detection film 5 and the thin metal wiring 6 are covered with an insulating layer 14 made of, for example, silicon oxide.

  Furthermore, the temperature detection part 54 is directly equipped with the absorber 10 which absorbs infrared rays (electromagnetic waves) in the upper part. Infrared rays absorbed by the absorber 10 are converted into heat and transmitted to the temperature detector 54. By this action, incident electromagnetic waves can be detected. The structure of the absorber 10 is the same as that described in the first embodiment, and absorbs a specific wavelength by controlling the groove depth h, the groove width w, and the groove period p.

  Even in the infrared sensor having the temperature detection unit 54 integrally formed with the absorber 10 as in the present embodiment, the desired detection wavelength resonates and the amount of absorption is selectively increased, so that only the desired detection wavelength is selectively selected. It becomes possible to detect.

  Furthermore, since a process for realizing a structure for supporting the absorber 10 with the support pillar 9 is not required, the manufacturing process can be simplified as compared with the case of manufacturing the infrared sensor used in the first to third embodiments. Therefore, the product can be manufactured at a lower cost.

  Note that the infrared sensor array according to the second and third embodiments may be formed by arranging infrared sensors including the temperature detection unit 54 having such a structure in an array.

  As described in the second embodiment, an image sensor can be configured by arraying infrared sensors having the same structure as the absorber 10. Further, as described in the third embodiment, by arraying infrared sensors having different structures (at least one of groove period, groove depth, and groove width) (by arraying pixels having different detection wavelengths) Similar to the image sensor in the visible light region, a colored image can be obtained in the infrared wavelength region. As an application other than the image sensor, it can be used as an array sensor for position detection with a small number of pixels.

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 2 Hollow part, 3 Support leg, 4,54 Temperature detection part, 5 Detection film | membrane, 6 Thin film metal wiring, 7 Aluminum wiring, 8 Reflective film, 9 Support pillar, 10 Absorber, 11 (11a, 11b), 21, 31, 41 Groove, 12, 22, 32, 42 Metal film, 13 Dielectric film, 14, 17 Insulating layer, 18 Insulating film, 100, 110, 120, 130, 140 Infrared sensor, 200, 300 Infrared sensor array 1000 Infrared sensor device.

Claims (8)

An electromagnetic wave sensor that includes a temperature detection unit and an electromagnetic wave absorption unit that is thermally connected to the temperature detection unit and that has at least an electromagnetic wave incident surface made of metal, and detects an electromagnetic wave incident on the electromagnetic wave absorption unit through the electromagnetic wave incident surface. There,
The electromagnetic wave absorber is
The electromagnetic wave absorber has a plurality of grooves formed in parallel to each other at a constant groove period in two directions intersecting each other,
The groove depth, groove width, and groove period of the groove are selected so as to induce surface plasmons that combine with an electromagnetic wave having a single specific wavelength included in an electromagnetic wave having a wavelength range of 4 μm to 15 μm incident on the electromagnetic wave absorber. ,
Groove, the has the following groove cycle specific wavelength, and have a smaller groove width than the groove depth,
An electromagnetic wave sensor characterized in that the groove depth of the groove is smaller than the height of the electromagnetic wave absorber .   The electromagnetic wave sensor according to claim 1, wherein the electromagnetic wave absorption unit is directly disposed on the temperature detection unit.   The electromagnetic wave sensor according to claim 1, wherein the plurality of grooves are formed in two directions orthogonal to each other.   The electromagnetic wave sensor according to claim 1, wherein the electromagnetic wave absorber has a single layer structure made of a metal film or a multilayer structure including a metal film and a dielectric film.   The electromagnetic wave sensor according to any one of claims 1 to 4, wherein a cross section perpendicular to the longitudinal direction of the groove is formed in a rectangular shape. A substrate having a hollow portion;
A support leg connected to the temperature detection unit and holding the temperature detection unit above the hollow portion;
The temperature detection unit has a detection film whose electrical resistance value changes with temperature,
The electromagnetic wave sensor according to claim 1, wherein the electromagnetic wave absorber is provided on the upper side of the temperature detector.   An electromagnetic wave sensor device according to claim 1, wherein a plurality of the electromagnetic wave sensors according to claim 1 are arranged in an array.   The electromagnetic wave sensor device according to claim 7, comprising a plurality of electromagnetic wave sensors in which at least one of a groove depth, a groove width, and a groove period of the groove part is different from each other.

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