JP6184366B2 - Electromagnetic wave sensor device - Google Patents

Description

  The present invention relates to an electromagnetic wave sensor device including one or a plurality of electromagnetic wave sensors, and more particularly to an infrared sensor device including a thermal infrared sensor.

  In the conventional thermal type (non-cooled type) infrared sensor device, an optical filter is mounted in front of the infrared sensor in order to select the wavelength of the infrared ray to be detected. However, thermal infrared sensor devices that select a detection wavelength using only an infrared sensor without using an optical filter have been developed for reasons such as a complicated structure and reduced detection efficiency.

  For example, Patent Document 1 discloses an infrared sensor device in which an infrared absorber is provided with a corrugated structure made of a curved surface, and selectively absorbs only infrared rays having a wavelength equal to the period of the corrugated structure. Carbon is used instead of metal as a material constituting the infrared absorber.

  Further, in Non-Patent Documents 1 and 2, detection is performed by a metal plate (multi-layer structure in which metal plates / insulating films / metal structures are sequentially laminated) arranged on an insulating film formed on a flat metal and periodically separated. A light absorber for selecting a wavelength is disclosed. Specifically, the detection wavelength is selected depending on the size of the metal plate.

Japanese Patent Laid-Open No. 1-142418

J. Hao, J. Wang, X. Liu, W. J. Padilla, L. Zhou, and M. Qiu, Appl. Phys. Lett. Vol. 96, p. 251104 (2010). T. Maier and H. Brueckl, Opt. Lett.vol. 35 p. 3766 (2010).

  However, in the case of the infrared sensor device described in Patent Document 1, first, the size of the periodic structure of the infrared absorber cannot be made smaller than the detection wavelength, and thus it is difficult to reduce the size of the absorber. There was a problem. Secondly, as a result of using carbon as a material constituting the absorber, the material itself absorbs infrared rays having wavelengths other than the detection wavelength, resulting in a problem that wavelength selectivity deteriorates.

  On the other hand, in the case of a multi-layered absorber including an insulating film described in Non-Patent Documents 1 and 2, first, the insulating film itself absorbs infrared light having a wavelength other than the detection wavelength, and the wavelength selectivity is high. There was a problem of getting worse. Secondly, because of the multi-layer structure, there is a problem in that the entire volume is increased, and thus the heat capacity is increased and the response speed is reduced.

  These problems also apply to electromagnetic waves in a wavelength range other than infrared.

  An object of the present invention is to provide an electromagnetic wave sensor device having a high response speed and excellent wavelength selectivity.

  In order to achieve the above object, a first aspect of the present invention relates to an electromagnetic wave sensor device including one or a plurality of electromagnetic wave sensors. The electromagnetic wave sensor includes a temperature detection unit and an electromagnetic wave absorption unit thermally connected to the temperature detection unit. The electromagnetic wave absorption unit includes a plurality of isolated plates including metal, which are periodically spaced apart, a reflecting plate which is disposed opposite to the isolated plate and whose surface is metal, and a surface in the in-plane direction of the isolated plate It has a connecting column for connecting between the isolated plate and the reflector so that plasmon resonance occurs. The in-plane dimension of the isolated plate is 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.

  By the way, in the electromagnetic wave absorber according to the prior art, it is necessary to provide a periodic structure in one pixel, and the size of one pixel cannot be sufficiently reduced, and therefore the pixel resolution of the electromagnetic wave sensor device cannot be improved. It was.

  Then, the 2nd aspect of this invention is related with the electromagnetic wave sensor apparatus provided with the several electromagnetic wave sensor. Each of the plurality of electromagnetic wave sensors includes a temperature detection unit and an electromagnetic wave absorption unit thermally connected to the temperature detection unit. The electromagnetic wave absorber includes an isolated plate containing metal, a reflecting plate disposed opposite to the isolated plate and having at least a surface of metal, and the isolated plate and the reflecting plate so that surface plasmon resonance occurs in the in-plane direction of the isolated plate. Connecting pillars connecting the two. The in-plane dimension of the isolated plate is 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. In addition, the isolated plates are arranged at a constant period in one direction or in two directions intersecting each other across the plurality of electromagnetic wave sensors.

  In the electromagnetic wave sensor device according to the second aspect of the present invention, the electromagnetic wave absorber has, for example, one or two isolated plates.

  According to the first aspect of the present invention, surface plasmon resonance corresponding to the wavelength determined by the in-plane dimension of the isolated plate occurs mainly in the in-plane direction of the isolated plate, and an electromagnetic wave having a specific wavelength is generated by the electromagnetic wave absorber. It can be absorbed selectively and efficiently. Further, by utilizing surface plasmon resonance, the period of the isolated plate can be made smaller than the specific wavelength, and the sensor can be miniaturized.

  Moreover, according to the 1st aspect, at least one part of the electromagnetic wave absorption part is comprised with a metal. In particular, when at least the surfaces of the isolated plate and the connecting pillar are made of metal, at least the surface of the electromagnetic wave absorbing portion is made of metal. Thereby, absorption of the electromagnetic wave by the material itself which comprises an electromagnetic wave absorption part can be prevented. Moreover, the whole volume can be made small by connecting between an isolated plate and a reflecting plate with a connection pillar. In this way, an electromagnetic wave sensor having a high response speed and excellent wavelength selectivity is realized.

  According to the second aspect of the present invention, the isolated plate is periodically arranged over the plurality of electromagnetic wave sensors. Thereby, the same effect as the first aspect is obtained.

  In addition, according to the second aspect, a periodic structure is provided over a plurality of electromagnetic wave sensors, and it is not necessary to provide a periodic structure in one pixel (one electromagnetic wave sensor), and thus the size of one pixel is reduced. Can be made. In particular, when only one isolated plate is provided in the electromagnetic wave absorber, the size of one pixel can be made smaller than the cycle of the isolated plate. In this way, the pixel resolution of the electromagnetic wave sensor device can be improved.

1 is a perspective view of an infrared sensor device according to an embodiment of the present invention. It is a top view in the state without an absorber of the infrared sensor by Embodiment 1 of this invention. It is the II sectional view taken on the line of FIG. 2 in a state with 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 the II-II sectional view taken on the line of FIG. It is a figure which shows a part of FIG. 5 and demonstrates surface plasmon resonance. It is a graph which shows the absorption characteristic of the absorber by Embodiment 1 of this invention. It is a graph which shows the absorption characteristic of the absorber by Embodiment 1 of this invention. It is a graph which shows the absorption characteristic of the absorber by Embodiment 1 of this invention. It is a graph which shows the absorption characteristic of the absorber by Embodiment 1 of this invention. It is a graph which shows the absorption characteristic of the absorber by Embodiment 1 of this invention. It is a top view of the absorber by the 1st modification of Embodiment 1 of this invention. It is a graph which shows the absorption characteristic of the absorber by the 1st modification of Embodiment 1 of this invention. It is sectional drawing of the absorber by the 2nd modification of Embodiment 1 of this invention. It is a graph which shows the absorption characteristic of the absorber by the 2nd modification of Embodiment 1 of this invention. It is a figure which shows each manufacturing process (a)-(d) of the manufacturing method of the absorber of FIG. It is a perspective view of the absorber by Embodiment 2 of this invention. It is sectional drawing equivalent to FIG. 5 of the absorber by Embodiment 2 of this invention. It is explanatory drawing which shows the area | region which can form a through-hole. It is a top view of the absorber by Embodiment 2 of this invention. It is a top view of another absorber by Embodiment 2 of the present invention. It is a graph which shows the absorption characteristic of the absorber by Embodiment 2 of this invention. It is a top view of the absorber by the modification of Embodiment 2 of this invention. It is the IV-IV sectional view taken on the line of FIG. It is a top view of the absorber by Embodiment 3 of this invention. It is the VV sectional view taken on the line of FIG. It is sectional drawing of the absorber by Embodiment 5 of this invention, and the coating layer is provided in the whole surface of the isolated board. It is sectional drawing of the absorber by Embodiment 5 of this invention, and the coating layer is provided in the upper surface (a), side surface (b), and lower surface (c) of the isolated board. It is a graph which shows the absorption characteristic of the absorber by Embodiment 5 of this invention. It is the figure which provided the coating layer in the structure of FIG. It is the figure which provided the coating layer in the structure of FIG. It is a top view of the infrared sensor array by Embodiment 6 of this invention. It is a top view of the infrared sensor array by Embodiment 7 of this invention. It is the VI-VI sectional view taken on the line of FIG. It is principal part sectional drawing equivalent to a part of FIG. 3 of the infrared sensor by Embodiment 8 of this invention. It is a top view of the infrared sensor array with which each infrared sensor has two isolated plates by Embodiment 9 of this invention. It is the VII-VII sectional view taken on the line of FIG. It is a top view of the infrared sensor array in which each infrared sensor has one isolated board by Embodiment 9 of this invention. It is the VIII-VIII sectional view taken on the line of FIG. It is a graph which shows the absorption characteristic by the infrared sensor array of FIG.

  A thermal infrared sensor device according to an embodiment of the present invention will be described below with reference to the drawings. In each embodiment, the same components are denoted by the same reference numerals, and description thereof is omitted.

First, surface plasmon resonance will be briefly described.
In general, surface plasmons are excited when the wavelength of an evanescent wave generated when electromagnetic waves are totally reflected at a boundary surface is combined with the surface plasmon waves. As the surface plasmon is derived from the dispersion relation, a phenomenon in the visible to near-infrared region is common. On the other hand, by introducing a periodic structure on the surface, in a wavelength region other than the visible to near-infrared wavelength region, for example, in the visible, middle wavelength infrared, long wavelength infrared, far infrared, terahertz (THz), microwave region Approximately the same phenomenon occurs. Since this can be treated approximately as surface plasmon, it is also called pseudo surface plasmon. Therefore, the present invention is not limited to the infrared sensor described below, but can be applied to sensors for wavelength regions other than infrared rays.

  The above phenomenon is often classified into surface plasmon resonance and plasmonics regardless of the wavelength range, including the meaning of strong resonance on the metal surface. Alternatively, as mentioned above, it may be called a metamaterial, pseudo surface plasmon, etc., but the essential phenomenon in absorption is the same. In the present specification, these are not distinguished and are expressed as surface plasmon, plasmon resonance, or simply resonance.

Embodiment 1 FIG.
The configuration of the infrared sensor device will be described.
FIG. 1 is a perspective view showing an infrared sensor device according to an embodiment of the present invention. In the infrared sensor device 1000, a plurality of infrared sensors 100 are arranged on the substrate 1 in a matrix (array) in two directions (x direction and y direction) orthogonal to each other, and from a direction parallel to the z axis. Make light incident. 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.

Next, the configuration of the infrared sensor will be described.
FIG. 2 is a top view of the infrared sensor according to Embodiment 1 of the present invention in a state where there is no absorber. In FIG. 2, the protective film and the reflective film on the wiring are omitted for the sake of clarity. 3 is a cross-sectional view taken along the line II of FIG. 2 in a state where there is an absorber. The absorber 10 corresponds to an electromagnetic wave absorber in the claims.

  As shown in FIG. 3, the infrared sensor 100 includes a substrate 1 made of, for example, silicon. A hollow portion 2 is provided in the substrate 1. A temperature detection unit 4 having a temperature detection function is provided on the upper side of 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 insulating layer 14 is made of, for example, silicon oxide.

  The temperature detection unit 4 includes a detection film 5 whose electric resistance value varies with temperature and the thin-film metal wiring 6 described above. The detection film 5 is made of, for example, a silicon diode using crystalline silicon. 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 reflection film 8 has a function of reflecting incident light and 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 can be seen as shown in FIG. In the configuration of the embodiment of the present invention, the reflecting film 8 is not essential because the absorber 10 can sufficiently absorb incident light having a specific wavelength. In particular, in order to prevent absorption on the back surface, it may be better not to have the reflective film 8. Whether or not to provide the reflective film 8 can be selected as necessary in consideration of the yield in manufacturing the hollow structure.

  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. It can be detected.

Next, the structure of the absorber 10 will be described in detail.
4a and 4b are a perspective view and a top view of the absorbent body 10 according to Embodiment 1 of the present invention. FIG. 5 is a cross-sectional view taken along line II-II in FIG. 4B. Note that in the perspective views of FIGS. 4a and 16, the period p is drawn larger than the other figures in order to make the figures easier to see.

  As shown in FIGS. 4a, 4b, and 5, the absorber 10 has a plurality of isolated elements arranged in two directions (x direction and y direction) perpendicular to (or intersecting) each other with a constant period p. It has the board 11, the flat reflecting plate 13 arranged facing the isolated plate 11, and the connection pillar 12 which supports the isolated plate 11 while connecting between the isolated plate 11 and the reflecting plate 13, respectively.

  The isolated plates 11 are arranged in a square lattice as shown in FIG. 4a. However, in order not to have polarization dependency as described later, it may be arranged in a two-dimensional periodic manner, for example, in a triangular lattice shape or a hexagonal lattice shape. Further, from the viewpoint of eliminating the polarization dependency, it is preferable that the number of periods (the number of isolated plates 11 in one direction) is equal in two orthogonal directions. However, for example, if the number of periods is sufficiently large in both directions, the polarization dependence may be almost negligible. Further, since absorption occurs even if the number of periods is different, it is not essential that the number of periods is equal in both directions. What is necessary is just to select suitably each period number of two orthogonal directions according to the shape of the absorber 10, a magnitude | size, polarization dependence, etc. which are needed.

  Incident infrared light having a wavelength smaller than the period p is diffracted and therefore reflected by the absorber 10 and hardly absorbs. Therefore, the period p is preferably set to be equal to or less than the wavelength in order to increase the infrared absorption amount of the detection wavelength. Thus, according to the structure of the absorber 10 using surface plasmon resonance, it is possible to absorb a wavelength longer than the period p. In addition, light having a wavelength other than the resonance wavelength among the incident light is reflected by the absorber 10.

  The isolated plate 11 is a circular plate. However, if the shape is symmetrical in two orthogonal directions, the polarization dependency can be eliminated, and for example, a square plate or a cross plate may be used. Furthermore, the shape which a some blade | wing extends radially from a certain point may be sufficient. The connection column 12 is, for example, a cylinder or a square column. As shown in FIG. 5 and the like, the in-plane dimension of the isolated plate 11 is L, the thickness is t, the height of the connecting column 12 is h, and the thickness is w. The “in-plane dimension of the isolated plate 11” represents a representative dimension in the in-plane direction of the isolated plate 11. If the isolated plate 11 is a disk, it is the diameter of the circle, and if it is a square plate, Let it be a length. The “thickness of the connecting column 12” is the diameter of a circle on the bottom surface (cross section) of the column in the case of a cylinder, and the length of one side of the bottom surface in the case of a square column.

  As will be described in detail below, the connection column 12 connects the isolated plate 11 and the reflecting plate 13 so that surface plasmon resonance in the in-plane direction of the isolated plate 11 occurs predominantly. Then, by suitably selecting the in-plane dimension L of the isolated plate 11, surface plasmons that couple with infrared rays of a specific wavelength included in the light incident on the absorber 10 are induced.

  When the isolated plate 11 is used for a thermal infrared sensor for normal use, it is preferable to eliminate the polarization dependency as a symmetrical shape in two orthogonal directions such as a circular plate, a square plate or a cross plate. However, even if it is a square at the time of design, the manufacturing process of the absorber 10 described below may include a step of rounding the corners of the isolated plate 11. In that case, by designing the isolated plate 11 in a circular shape in advance, the shape can be made as designed. However, according to the configuration of the absorber 10, the absorption wavelength (detection wavelength) is determined by the in-plane direction dimension L regardless of whether the isolated plate 11 is a circular plate or a square plate.

  In the first embodiment, the isolated plate 11, the connecting column 12, and the reflecting plate 13 are all made of the same metal, but the present invention is not limited to this. The metal is preferably a metal that generates surface plasmons. The metal is a metal having a negative dielectric constant, such as Au, Ag, Cu, Al, Cr, and Ni. However, these materials include those that have a large half-width of resonance and can broaden the absorption wavelength, and those that can easily oxidize the surface and cause broad absorption in the infrared wavelength region. In consideration of the manufacturing process of the absorber 10 and the detection wavelength, a metal suitable for wavelength selection by surface plasmons is appropriately selected so that these do not cause a problem. In this specification, the “metal generating surface plasmon” refers to a metal selected in consideration of the manufacturing process of the absorber 10 and the detection wavelength.

  In the configuration described above, the polarization dependency of incident light in absorption is reduced by setting the number of periods of the isolated plate 11 equal to p in two orthogonal directions. Further, by arranging the isolated plates 11 in a square lattice pattern (two-dimensionally periodically) and making the in-plane direction dimensions of the isolated plates 11 the same in two orthogonal directions, absorption, which is the main light incident direction, in particular. In the normal incidence direction (z direction) to the body 10, the polarization dependency is reduced.

  By reducing the polarization dependency in this way, the overall absorption amount for incident light can be increased, and as a result, the output can be increased. Further, when an image sensor is configured with the infrared sensor 100, it is advantageous because polarized light is not reflected.

  On the other hand, the number of periods of the isolated plate 11 in two orthogonal directions (x direction and y direction) is made different, or the isolated plate 11 is made asymmetric in two orthogonal directions such as an elliptical plate, a rectangular plate, and a triangular plate. As a result, asymmetry also occurs in the resonance direction, resulting in polarization dependence, and absorption of only specific polarized light increases. In this way, it is possible to configure a sensor that detects specific polarized light. When the isolated plate 11 is an elliptical plate, a rectangular plate, or a triangular plate, the in-plane dimension of the isolated plate 11 can be the major axis of the ellipse, the long side of the rectangle, and one side of the triangle, respectively. By detecting the specific polarization (polarization imaging), for example, it is also possible to distinguish between the two by utilizing the fact that the polarization characteristics of the reflected light are different between a natural object and an artificial object.

  Next, the dimensions (in-plane dimension L and thickness t) of the isolated plate 11 and the dimensions (height h and thickness w) of the connecting column 12 will be described in detail. These are important for the establishment of plasmon resonance in the absorber 10 and the determination of the absorption wavelength. As a premise, first, general surface plasmon resonance will be described.

In general, when fine and periodic irregularities are provided on the surface of an absorber (infrared absorbing surface), it is known that surface plasmons are excited by normal incident light and bonded to the surface. By this coupling, the infrared light having the resonance wavelength is strongly localized on the surface and is consequently absorbed. This increases the absorption at the resonance wavelength. When the period of the irregularities is p, the reciprocal lattice vector in that case is G, the wave number vector of the induced surface plasmon is K _sp , the wave number vector of the incident light toward the absorber surface is K _x , and m is an integer, Formula (1) is materialized. In equation (1), the vector is given an up arrow.

  Further, when the unevenness is one-dimensional (slit structure), the vector display can be omitted and expressed as the following formula (2).

Note that the wave vector of the incident light K _0, can be expressed as K _{x =} K ₀ sinθ as (a 0 ° direction perpendicular to the absorber plane) the incident angle theta.

  Thus, it can be seen that the wavelength determined by the period p of the unevenness is strongly localized on the surface and consequently absorbed. In the case of a two-dimensional periodic structure, the reciprocal lattice vector G in the above equation (1) is a two-dimensional vector. When isolated irregularities are two-dimensionally arranged, surface plasmon resonance occurs in the in-plane direction and the height direction, but surface plasmon resonance in the in-plane direction is dominant, and the main absorption wavelength is the period p. Determined by.

  On the other hand, in the case of a structure in which the isolated plate 11 made of a metal that generates surface plasmons, such as the absorber 10, is periodically arranged, and the reflecting plate 13 is arranged to face the isolated plate 11, the surface plasmon resonance is Resonance occurs three-dimensionally in the in-plane (xy plane) direction of the isolated plate 11 and the height h direction of the connecting column 12. The state of the electromagnetic field localized in the vicinity of the isolated plate 11 by this three-dimensional resonance is shown in FIG. However, as will be described later, the resonance in the height direction of the connecting column 12 is not dominant. On the other hand, the resonance in the height direction plays a role of confining resonant light that is strongly localized in the plane of the isolated plate 11. Therefore, it is mainly surface plasmon resonance that occurs in the in-plane direction of the isolated plate 11 that leads to wavelength selective absorption of infrared rays in the absorber 10.

  As will be described below, by adjusting the dimensions of the isolated plate 11 and the connecting column 12, a cavity is formed between the isolated plate 11 and a region of the reflecting plate 13 immediately below the isolated plate 11. Then, surface plasmon resonance occurs predominantly in the in-plane direction (in the xy plane) of the isolated plate 11, and the absorption wavelength of the absorber 10 can be selected mainly by the in-plane direction dimension L of the isolated plate 11.

  Below, the dimension (thickness t) of the said isolated plate 11 and the dimension (height h and thickness w) of the connection pillar 12 are demonstrated with respect to the in-plane direction dimension L of the isolated plate 11. FIG.

First, the thickness t of the isolated plate 11 will be described.
As the thickness t of the isolated plate 11 increases, the heat capacity of the absorber 10 increases and the response speed of the sensor 100 decreases. Therefore, from the viewpoint of response speed, it is preferable to reduce the thickness t as much as possible.

  Further, when the thickness t of the isolated plate 11 increases, resonance also occurs in the thickness direction, so that the wavelength selection effect is weakened and the absorption itself is weakened, or broad absorption occurs in a wide wavelength range. That is, in addition to the resonance in the height direction of the connecting column 12, resonance in the thickness direction of the isolated plate 11 occurs, and the resonance in the vertical direction (z direction) may be dominant over the resonance in the in-plane direction. There is. In this case, since the dependency of absorption on the incident angle increases, the detection wavelength may shift. In addition, the amount of light absorption at a desired detection wavelength decreases, and the output decreases. In order to suppress resonance in the thickness direction and the height direction, it is preferable to satisfy t <L.

  Furthermore, in order to make resonance in the in-plane direction of the isolated plate 11 dominant and to make the incident angle dependency of absorption sufficiently small, it is preferable to satisfy t <L / 4.

Next, the height h of the connecting column 12 will be described.
The absorber 10 absorbs infrared rays by resonance that occurs in the in-plane direction of the isolated plate 11. The resonance generated in the in-plane direction of the isolated plate 11 is confined in the height direction by the reflecting plate 13 and held. Therefore, the resonance in the height direction (h direction) of the connecting column 12 should not be dominant. When the height h is too large, the resonance in the height direction competes with the resonance in the in-plane direction of the isolated plate 11. Thereby, strong resonance does not occur in the in-plane direction, the absorptance is greatly reduced, or broad absorption occurs over a wide wavelength range, and wavelength-selective absorption becomes difficult. In order to generate wavelength selective absorption, it is preferable to satisfy h <L.

  Furthermore, since it is generally a condition that the dimension is smaller than ¼ of the wavelength so as not to cause resonance or resonance, in order to prevent resonance in the height direction (h direction), h <L / 4 is preferably satisfied.

Next, the thickness w of the connecting column 12 will be described.
When the thickness w approaches the in-plane dimension L of the isolated plate 11, particularly when the connecting column 12 is made of metal, no light can exist in the metal, so the isolated plate 11 and the reflecting plate 13 below the isolated plate 11. Surface plasmon resonance between the two becomes difficult to occur, and the amount of infrared absorption at the detection wavelength is greatly reduced. In order to sufficiently establish absorption by resonance, it is preferable to satisfy at least w <L.

  Furthermore, it is preferable to satisfy w <L / 4 in order to ignore the influence of the connecting pillar 12 on the in-plane resonance of the isolated plate 11.

  As described above, by adjusting the dimensions of the isolated plate 11 and the connecting column 12, the resonance caused by the surface plasmon coupled with the infrared ray having the wavelength determined by the in-plane dimension L is caused in the in-plane direction of the isolated plate 11. It comes to dominate.

  As a result of electromagnetic field analysis, the wavelength at which surface plasmon resonance occurs by changing the period p, the thickness t of the isolated plate 11 and the height h of the connecting column 12 in addition to the in-plane direction dimension L of the isolated plate 11 It is known that can be changed slightly.

The upper limit of the preferable values of the thickness t of the isolated plate 11 and the height h and thickness w of the connecting column 12 has been described above. Next, the lower limit of these preferable values will be described.
In order to improve the infrared absorption rate of the detection wavelength by the absorber 10, it is preferable that the infrared of the detection wavelength does not substantially pass through the absorber 10. The thickness t of the isolated plate 11 and the height h and thickness w of the connecting column 12 are more than twice the thickness δ (skin depth) of the skin effect expressed by the following formula (3) with respect to the detection wavelength. In general, it can be said that the light leakage is sufficiently small and the absorption rate can be improved. On the other hand, if it is less than this value, light leaks and a sufficient reflection effect cannot be obtained, and therefore the resonance effect is lowered, so that sufficient absorption may not be obtained.
δ = (2 / μσω) ^1/2 (3)

  In addition, the height h of the connecting column 12 is set to a thickness that is at least twice the thickness δ of the skin effect, so that the isolation plate 11 and the region immediately below the isolation plate 11 in the reflection plate 13 It has been found that this is the preferred condition for forming cavities in between.

  Here, μ and σ are the magnetic permeability and electrical conductivity of the metal constituting the isolated plate 11, the connecting column 12, and the reflecting plate 13, respectively, and ω is the angular frequency of infrared rays of the detection wavelength.

  As can be seen from the above formula (3), the magnitude of δ varies depending on the wavelength, but t is preferably about several tens of nm to several hundreds of nm in the infrared wavelength region. Further, as shown in the following electromagnetic field analysis, in the infrared wavelength region, if it is about 50 to 100 nm or more, sufficient absorption occurs, and if it is about 200 nm, it is more sufficient.

  Moreover, it is known from the electromagnetic field analysis that the height h of the connecting column 12 is preferably about several hundred nm or less. Further, it has been found that sufficiently strong absorption occurs in the infrared wavelength region when the wavelength is about several tens of nm to several hundreds of nm, and the medium wavelength and long wavelength infrared regions are about 50 nm to 250 nm.

Next, the thickness of the reflecting plate 13 will be described.
The thickness of the reflecting plate 13 may be as long as it does not transmit infrared light having a detection wavelength. Thereby, sufficient reflection can be obtained. This size is about twice as large as the thickness δ of the skin effect, and is about several tens of nm to several hundreds of nm in the infrared wavelength region, and in the middle wavelength infrared region to long wavelength infrared wavelength region. Although about 200 nm is desirable, this is a value in consideration of strength, and the minimum thickness is essentially determined by the thickness δ of the skin effect.

  Similarly to the description of the thickness t of the isolated plate 11, the thickness of the reflecting plate 13 is preferably as small as possible from the viewpoint of response speed. Ultimately, the thickness is determined in consideration of the mechanical strength of the hollow portion 2.

  In addition, when a plurality of isolated plates 11 having different in-plane direction dimensions L are periodically arranged, resonance occurs at a plurality of wavelengths corresponding to the in-plane direction dimensions, thereby causing absorption at a plurality of wavelengths. Absorption in a broad wavelength region occurs. In this case, it is important to make the in-plane dimension L of each isolated plate 11 included in an independent pixel (sensor) constant in order to realize a wavelength selection function with excellent monochromaticity.

Next, an exemplary method for manufacturing the absorber 10 will be described. This manufacturing method includes the following steps S1 to S10.
First, the reflecting plate 13 is formed by a film forming apparatus such as a sputtering apparatus (S1). A sacrificial layer such as a resist or oxide film is applied or formed thereon (S2). A hole corresponding to the connection column 12 is formed at a position where the connection column 12 is provided in the sacrifice layer. For forming the holes, ordinary photolithography, electron beam exposure, or the like is used (S3). The hole is filled with metal by sputtering or the like, and a metal film is formed on the entire surface of the sacrificial layer (S4). A photoresist is applied to the metal film (S5). The photoresist is irradiated with light to transfer the mask pattern of the isolated plate 11 to the metal film (S6). The photoresist is developed (S7). The exposed metal portion is processed by dry etching using a halogen-based gas (S8). The resist is removed with an organic solvent (S9). Finally, the sacrificial layer is removed by an organic solvent or dry etching (S10).

The step S10 may be performed by wet etching using an etchant. Alternatively, a structure in which a metal portion is removed in advance by resist instead of metal etching is formed on the connection pillars 12 and the isolated plate 11 of S3 and S4 by photolithography, and then a metal layer is formed by sputtering (or plating). Finally, a lift-off method for removing the resist may be used. Alternatively, after the connection pillar 12 is formed by filling with sputtering or plating, a polishing step may be performed to flatten the upper surface portion of the connection pillar 12.
Thereafter, the isolated plate 11 can be formed in the same manner as described above. The optimum manufacturing method can be appropriately selected depending on the size of the absorber 10, the material constituting the absorber 10, and the like.

  Next, effects obtained by the infrared sensor 100 according to the first embodiment will be described.

  First, the results of electromagnetic field analysis of absorption characteristics in the absorber 10 will be described with reference to FIGS. 7 to 11 are graphs (absorption spectra) showing the absorption characteristics of the absorber according to Embodiment 1 of the present invention. The horizontal axis of the graph represents the wavelength of incident light, and the vertical axis represents the absorptance. In these analyses, the period p was 4 μm, the thickness t of the isolated plate 11 was 100 nm, the thickness of the reflecting plate 13 was 200 nm, the metal constituting the absorber 10 was Au, and the connecting column 12 was a cylinder.

First, FIG. 7 in which the in-plane dimension L of the isolated plate 11 is changed will be described.
In FIG. 7, h = 0.15 μm and w = 200 nm. The results for L = 2.0 μm (solid line) and 3.5 μm (broken line) are shown. Hereinafter, unless otherwise specified, in this specification, when the isolated plate 11, the connecting column 12, and the reflecting plate 13 are metal, the material is analyzed as Au.

When the absorption wavelength of a peak and lambda _ab, for each L, λ _ab = 4.8μm, was 8.6 [mu] m. That is, under the conditions of FIG. 7, it can be expressed as λ _ab = 2.5 × L by rough approximation. The value 2.5 shown here is a value in the structure analyzed in FIG. 7, and is not a value to be applied to the entire structure. However, it is known that under other conditions, when L is continuously changed, if n is a positive real number, λ _ab = n × L. Thus, it can be seen that the absorption wavelengths _λab and L are in a substantially proportional relationship. Thus, the absorption wavelength lambda _ab by the absorbent body 10 is said to be determined by the in-plane direction dimension L of the isolated plates 11 rather than period p.

That is, in the absorber 10, the conditions represented by the following formulas (4) and (5) are satisfied.
λ _ab = n × L (4)
λ _ab > p (5)

Next, FIGS. 8 and 9 in which the height h of the connecting column is changed will be described.
In FIGS. 8 and 9, L = 2.0 μm. h = 150 nm (FIG. 8) and 200 nm (FIG. 9). 8 and 9, it can be seen that the larger the h, the absorptance can be slightly reduced, but the absorption wavelength λ _ab is hardly changed.

Next, FIGS. 10 and 11 in which the thickness w of the connecting column is changed will be described.
10 and 11, h = 0.15 μm and L = 2.0 μm. w = 200 nm (FIG. 10) and 500 nm (FIG. 11). In FIG. 10 and FIG. 11, there was no significant difference between the absorption rate and the absorption wavelength.

As a result of the same electromagnetic field analysis, when p = 4 μm and L = 2.0 μm, if the connection column height h is in the range of about 100 to 250 nm, the absorption rate of 80% or more is maintained. It is known that the absorption wavelength is almost unchanged. However, it is also known that depending on the conditions, the absorption wavelength _λab slightly changes by changing the height h. Similarly, when the thickness w of the connecting pillar is about 20 to 500 nm, it is known that a high absorption rate of 80% or more is maintained and the absorption wavelength is not substantially changed.

As described above, as described based on the result of the electromagnetic field analysis, the infrared sensor 100 causes surface plasmon resonance according to the wavelength mainly determined by the in-plane direction dimension L of the isolated plate 11, and the selective infrared rays. Absorption is possible. That is, as the infrared sensor 100, detection wavelength in the absorption wavelength lambda _ab is selected. Further, the surface plasmon resonance in the in-plane direction of the isolated plate 11 can be dominant, and the infrared rays having the detection wavelength can be efficiently absorbed.

Next, the effect obtained by the first embodiment will be described by comparing the prior art with the first embodiment.
In the case of an absorber having a wave-like periodic structure as in Patent Document 1, first, the size of the periodic structure of the absorber cannot be made smaller than the detection wavelength, so the absorber is downsized. There was a problem that it was difficult. Second, as a result of using carbon as a material constituting the absorber, there is a problem that the material itself absorbs wavelengths other than the wavelength to be detected, and wavelength selectivity is deteriorated. Thirdly, in order to manufacture the corrugated structure, a special mask formation such as a gray scale mask and an etching process are required, which makes it difficult to manufacture.

  On the other hand, in the case of a multi-layered absorber including an insulating film described in Non-Patent Documents 1 and 2, first, the insulating film itself absorbs infrared light having a wavelength other than the detection wavelength, and the wavelength selectivity is high. There was a problem of getting worse. Second, in order to maximize the absorptance at a specific wavelength, it is necessary to control the thickness of the insulating film, that is, the thickness of the insulating film must be changed depending on the wavelength of the detection target, and thus the detection wavelength. When pixels with different ranges are integrated, there is a problem in that integration is difficult because the thickness needs to be controlled for each pixel. Thirdly, because of the multilayer structure, the portion corresponding to the connecting pillar 12 becomes a flat film, so that the entire volume is increased, so that the heat capacity is increased and the response speed is reduced.

  In addition, for example, when a periodic refractive index distribution structure using a photonic crystal is provided in the infrared absorber, thereby realizing wavelength selectivity, the following problem arises. In other words, the absorption wavelength of a dielectric film that is an absorber material, for example, silicon oxide, exists in the vicinity of 8 μm to 14 μm. Therefore, for example, when the absorption peak wavelength is set to 6 μm, the absorption wavelength (8 μm to 14 μm) of silicon oxide as a material is detected at the same time due to the structure of the periodic refractive index distribution and the photonic band gap. As described above, the wavelength selectivity is deteriorated by increasing the absorption wavelength.

  With respect to these problems, the first embodiment uses surface plasmon resonance and can absorb wavelengths having a period of p or more. In other words, the period p of the isolated plate 11 can be made smaller than the detection wavelength. Therefore, the area of the absorber 10 can be reduced as compared with the structure in which the period and the absorption wavelength are the same as in Patent Document 1. Therefore, when a thermal imager is constituted by the size of the infrared sensor 100 and a plurality of infrared sensors, the pixels can be reduced.

  Further, since the absorber 10 is made of a metal that generates surface plasmons, absorption by the insulator material itself when an insulating film or the like is used is prevented, and the wavelength selectivity is improved. The same effect can be obtained when at least the surface of the absorber 10 is covered with the metal.

  Moreover, since the absorber 10 does not have a special shape such as a wave shape, the manufacture becomes easier.

  Further, in the absorber 10, the absorption wavelength does not change greatly depending on the height h of the connecting column 12, so that when the sensors (pixels) having different detection wavelengths are integrated, it is not necessary to change the height h for each pixel. The structure is easy to integrate.

  Further, instead of providing a layer between the isolated plate 11 and the reflecting plate 13 as in Non-Patent Documents 1 and 2, the connection column 12 is used for connection, and the height h and thickness w of the connection column 12 are further reduced. Thus, the volume of the absorber 10 can be sufficiently reduced, and therefore the response speed of the infrared sensor 100 can be increased.

  The response speed is particularly effective as follows. Generally, when selecting a wavelength according to the uneven structure on the surface of the absorber, the depth of the concave portion (height of the convex portion) needs to be at least about 1/4 of the detection wavelength. The thickness (dimension in the z direction) of the absorber 10 is about 100 nm + 150 nm + 200 nm = 450 nm even when the thickness t of the isolated plate 11, the height h of the connecting column 12, and the thickness of the reflecting plate 13 are added (example in FIG. 7). ) And very thin. Thus, since the thickness can be reduced as compared with the case of a general periodic concavo-convex structure, the thermal time constant can be reduced, thereby increasing the response speed.

Furthermore, the following effects can be obtained as compared with the metal / insulating film / metal structure (multilayer structure) described in Non-Patent Documents 1 and 2.
When an insulating film is used, if the thickness of the insulating film changes, the absorptance and the absorption wavelength shift, so that the manufacturing error range becomes narrow. However, in the case of the structure using the connection pillar 12 like the absorber 10 Even if the height h changes, the absorptance and the absorption wavelength hardly change, so that the manufacturing error range is widened.

  As described above, by introducing the connection column 12 as in the first embodiment, the change in the absorptivity and the absorption wavelength at the height h is reduced because the isolated plate 11 and the reflection plate 13 connected by the connection column 12 are reduced. This is probably because air occupies between the two. Since the refractive index of air is smaller than that of an insulator, the optical length is also reduced. Therefore, the change in the resonance wavelength with respect to the change in the thickness of the air layer, that is, the height h of the connecting column 12 is also reduced.

  Next, a modified example of the absorbent body 10 will be described.

  FIG. 12a is a top view of the absorber according to the first modification example of the first embodiment of the present invention. In the first modification, the isolated plate 11 is arranged not in a two-dimensional manner but in a one-dimensional manner (for example, only in the x direction). As shown in FIG. 12a, when the isolated plates 11 each having a rectangular shape are arranged in a stripe shape, an electromagnetic wave having an electric field component in a direction perpendicular to the long side of the rectangle (a direction parallel to the x direction). Since only the field is absorbed, only specific polarized light can be absorbed (detected). 12a is a top view corresponding to FIG. 4b, and a cross-sectional view taken along line III-III in FIG. 12a is the same as FIG.

  FIG. 12b is a graph showing the absorption characteristics of the absorbent body according to the first modification of the first embodiment of the present invention. The horizontal axis of the graph indicates the wavelength of incident light normalized by the wavelength giving the maximum absorption rate, and the vertical axis indicates the absorption rate. The metal constituting the absorber 10 is Au. As described above, the wavelength giving the maximum absorption rate is selected mainly by the in-plane direction dimension (the length of the short side in the case of a rectangle).

  From FIG. 12b, it can be seen that the electric field component (broken line) parallel to the longitudinal direction of the rectangle is hardly absorbed. In this way, when the isolated plate 11 is arranged one-dimensionally periodically (for example, periodically only in the x direction), the polarization direction can be detected. The specific polarization detection and characteristics for a one-dimensional arrangement apply to all embodiments described herein. Since only the arrangement direction of the isolated plates 11 is different, in this specification, a two-dimensional arrangement will be described as a representative example.

  FIG. 13 is a cross-sectional view of an absorbent body according to a second modification of the first embodiment of the present invention. It is known that the electromagnetic field concentrates on the edge portion of the isolated plate 11 in the electromagnetic field (see FIG. 6) localized in the vicinity of the isolated plate 11 due to surface plasmon resonance. Therefore, it can be said that the influence of the electromagnetic field in the vicinity of the connecting column 12 on the plasmon resonance is small. Therefore, in the second modification, as shown in FIG. 13, a hollow region 26 is provided in the vicinity of the center of the connection column 12. FIG. 14 shows the absorption characteristics of the absorber according to the second modification. In FIG. 14, p = 3 μm, h = 0.15 μm, L = 2.0 μm, and w = 500 nm. The hollow region 26 was a cylinder having a diameter of 250 nm. FIG. 14 shows that wavelength selective absorption occurs even when the hollow region 26 is provided near the center of the connecting column 12.

  In the case where the hollow region 26 is provided near the center of the connecting column 12, the following effects can be further obtained. First, since the volume of the solid part of the absorber 10 is reduced by the amount of the hollow region 26, the heat capacity is lowered and the response speed is increased. Second, the absorber 10 can be easily manufactured. The second effect will be specifically described with reference to FIG.

FIG. 15A corresponds to the state after steps S1 to S3 of the manufacturing method, and a hole corresponding to the connection pillar 12 is formed in the sacrificial layer 24. FIG. In FIG. 15B, a metal layer 25 is provided on the hole formed in the sacrificial layer and the sacrificial layer surface. In FIG. 15C, the metal layer 25 on the surface of the sacrificial layer is etched away in accordance with the in-plane dimension L of the isolated plate 11 by photolithography. In FIG. 15D, the sacrificial layer 24 is removed by oxygen ashing, wet etching, or the like, and the absorber 10 corresponding to FIG. 13 is manufactured.
According to the described manufacturing method, it is not necessary to fill the connection pillars 12, so that the metal material can be saved. Moreover, since it is not necessary to manufacture the connection pillar 12 part separately and to perform a polishing process etc., the absorber 10 can be manufactured easily by reducing the number of processes.

Next, a third modification of the first embodiment will be described.
In the third modified example, the connection column 12 is made of an insulator, a semiconductor, or a dielectric. The volume of the connecting column 12 is made sufficiently small so that the influence of absorption by these materials can be almost ignored. In this structure, since the volumetric heat capacity (heat capacity per unit volume) can be reduced, a faster response than the structures of Non-Patent Documents 1 and 2 is possible.

For example, it is known that wavelength selective absorption also occurs when the connecting pillar 12 is made of silicon as a semiconductor. However, when the analysis is performed with a structure in which the isolated plate 11 and the reflective plate 13 are connected by a flat layer as in Non-Patent Documents 1 and 2, since silicon is not an insulator, the isolated plate 11 and the reflective plate It was found that a thickness of about 300 nm was necessary to generate plasmon resonance with 13 and to obtain sufficient absorption. On the other hand, when the connection column 12 is formed in a columnar shape, air as an insulator is present between the isolated plate 11 and the reflection plate 13 in addition to silicon, so that insulation is increased and plasmon resonance is increased. For this reason, the height of the connection pillar 12 can be reduced to about 100 nm. That is, when the connecting pillar 12 is made of an insulator, a semiconductor, or a dielectric, the height necessary for obtaining sufficient absorption can be made lower (thinner) than that of a flat layer.
By using the column-shaped connecting column 12 in this manner, the volumetric heat capacity can be reduced, and the absorption of the material itself can be suppressed and the response speed can be increased.

  In the following second to sixth embodiments, only the configuration different from the first embodiment will be described, and the description of the same configuration will be omitted.

Embodiment 2. FIG.
As described above, in the absorber 10, surface plasmon resonance mainly occurs between the isolated plate 11 and a region of the reflector 13 immediately below the isolated plate 11. Therefore, even if no metal is provided in the reflecting plate 13 other than the region directly below the isolated plate 11, the influence on the infrared absorption can be ignored.

  FIG. 16 is a perspective view of an absorbent body according to Embodiment 2 of the present invention, and FIG. 17 is a cross-sectional view corresponding to FIG. 5 of the absorbent body. Moreover, FIG. 18 is explanatory drawing which shows the area | region which can form a through-hole. In the second embodiment, by utilizing the above characteristics, the through-holes in the reflector 13 are located at positions other than the region immediately below the isolated plate 11, in other words, in a range that does not overlap with the isolated plate 11 in the in-plane direction of the reflector 13. 19 is formed.

  As described above, in principle, the surface plasmon resonance in the in-plane direction of the isolated plate 11 is not affected even if the through hole 19 is formed at a position other than the region directly below the isolated plate 11, and the absorption characteristics. Does not deteriorate.

  Thus, by forming the through-hole 19, the area (volume) of the reflecting plate 13 can be reduced, the heat capacity can be reduced, and the response speed can be increased. From the viewpoint of reducing the area of the reflector 13, it is preferable to increase the area where the through holes 19 are formed as much as possible.

  However, in order to hold the isolated plate 11 and the connection column 12, it is necessary to provide a frame region in the reflective plate 13 with a certain area to connect the periodic isolated plate 11 to each other in the plane of the reflective plate 13.

  FIG. 19 is a top view of an absorbent body according to Embodiment 2 of the present invention. FIG. 19 corresponds to the configuration of FIG. In order to achieve both the increase in the area for forming the through hole 19 and the necessity of the frame region, the through hole 19 can be formed, for example, two-dimensionally periodically. For example, as shown in FIG. 19, they may be formed in two directions orthogonal to each other with the same period p as that of the isolated plate 11. Moreover, as shown in FIG. 20, you may form apart from the isolated plate 11 with a different period. 19 and 20, a portion surrounded by a dotted line indicates a unit cycle unit. However, the non-periodic arrangement and random arrangement do not affect the absorption characteristics. Thus, the through holes 19 can be arranged in various ways. Further, even if the sizes of the through holes 19 are not the same, the absorption characteristics are not affected, and the shape of the through holes 19 may be any shape such as a polygon such as a rectangle or a rectangle, or an ellipse.

  The arrangement, size, and period of the through holes 19 may be determined in consideration of parameters such as the material, thickness, size, and warpage when the absorber 10 is held hollow.

  FIG. 21 is a graph showing the absorption characteristics of the absorbent body according to Embodiment 2 of the present invention. In FIG. 21, t = 100 nm, L = 2.0 μm, d = 1.0 μm, h = 150 nm, and the thickness of the reflector 13 is 200 nm. The through hole 19 was circular when viewed from the main surface of the reflector 13. The diameter of the through hole 19 is d.

As shown in FIG. 21, the absorption wavelength λ _ab (about 5 μm) of the peak hardly changes even when the through hole 19 is formed, compared to the absorption characteristic when the through hole 19 is not formed (FIG. 7). I understand. At the absorption wavelength λ _ab , the absorptance is 1, indicating that 100% incident light is absorbed.

  Also in the second embodiment, the detection wavelength can be selected by changing the size L of the isolated plate 11 based on the above-described principle of surface plasmon resonance.

  In general, when the through hole 19 is formed in the absorber 10 having the absorption rate A and the volume of the absorber 10 is 80%, the amount of absorption is reduced to A × 80%, and the sensitivity is lowered. However, in the absorber 10, the absorption wavelength is determined by surface plasmon resonance that occurs in the in-plane direction of the isolated plate 11, so that the reflector 13 in a region other than directly below the isolated plate 11 contributes to absorption regardless of the surface plasmon resonance. do not do. Therefore, even if the through hole 19 is formed and the volume is reduced, the absorption rate does not change.

  That is, according to the configuration of the second embodiment, even when the through hole 19 is formed in the reflecting plate 13, the heat capacity can be reduced and the response speed can be increased without reducing the sensitivity.

  Such an absorption phenomenon that does not depend on the aperture ratio is a special effect inherent to plasmon resonance. Conventionally, an oxide film or a metal thin film has been used as an absorber for an infrared sensor. However, when an etching hole or the like is formed in these, the amount of absorption is always reduced by the amount of volume reduction, and the sensitivity is lowered.

  On the other hand, by using plasmon resonance like the absorber 10, the volume can be reduced and the response speed can be increased without causing a decrease in sensitivity.

  Moreover, in the absorber 10, since the influence which it has on the optical characteristic regarding the size and shape of the through hole 19 can be almost ignored, the through hole 19 can be appropriately formed in consideration of stress so that the warp of the hollow structure does not occur. This is advantageous for maintaining a good hollow structure.

  Here, for example, in order to form a structure in which the absorber 10 or the like is supported on the hollow portion 2 in the infrared sensor 100 shown in FIG. 3, a hollowing method called bulk micromachining or surface micromachining can be employed. In the former, a hollow region is formed by deep digging with a technique such as anisotropic etching. In the latter case, a hollow region is previously filled with a sacrificial layer such as a resist, a structure is formed thereon by vapor deposition, etc., and only the sacrificial layer is etched away so that the structure is supported on the hollow part. To manufacture.

  In the technique using the sacrificial layer etching as described above, the sacrificial layer can be removed by wet etching or dry etching, but the etchant wraps around from the side of the absorber to remove the sacrificial layer. At this time, if the sacrificial layer remains, for example, a portion where the temperature rises due to light incidence and a portion where the temperature does not rise are thermally connected by the residue, and it is assumed that the performance of the sensor is significantly deteriorated. .

  When the through hole 19 is formed in the reflecting plate 13 of the absorber 10 as in the second embodiment, the etching gas or the wet etching solution easily reaches the lower sacrificial layer from the upper part of the sensor during the sacrificial layer etching. In addition, no sacrificial layer residue is generated, and a sensor with good characteristics can be manufactured.

Next, a modification of the second embodiment will be described.
22 is a top view of an absorbent body according to a modification of the second embodiment of the present invention, and FIG. 23 is a cross-sectional view taken along line IV-IV in FIG. In Non-Patent Documents 1 and 2, infrared absorption at a wavelength other than the plasmon resonance wavelength due to the material of the insulating layer on the flat metal layer (corresponding to the reflector 13 in the present invention) has become a problem. As in the structure of the absorber 10 according to the second embodiment, when the region of the through hole 19 is formed sufficiently wide in the reflector 13 and the volume of the insulating layer is reduced as much as possible, the amount of the insulating layer depends on the material itself. Since the absorption is reduced, the influence of the material is almost negligible.

Therefore, in this modification, the connection column 12 is made of a material such as an insulator. The material may be, for example, an insulator such as silicon oxide (SiO ₂ ), silicon nitride (SiN), or aluminum oxide (Al ₂ O ₃ ), a semiconductor such as silicon, or a dielectric. The structural parameters as the absorbent body 10, for example, the height of the connecting column 12 can be appropriately adjusted according to the respective physical property values.

  In this case, plasmon resonance occurs inside the connecting column 12 made of an insulator or the like. Therefore, the thickness w of the connecting column 12 may be approximately the same as the in-plane dimension L of the isolated plate 11, for example, the same thickness.

Next, the height h of the connecting column 12 made of an insulator will be described.
As described above, in the absorber 10, surface plasmon resonance occurs in the in-plane direction of the isolated plate 11. At this time, when resonance in the height direction occurs, a plurality of resonance wavelengths are generated, and the wavelength selectivity is deteriorated. Alternatively, for example, when the connecting column 12 is made of silicon oxide, absorption occurs in a wide wavelength range of 8 to 14 μm.

  Therefore, in order to prevent resonance in the height direction, the height h of the connecting column 12 is preferably smaller than L / 4. According to the analysis result, it is about 200 nm or less in the infrared wavelength region. Is known to be preferred. However, the height h of the connection column 12 may be changed depending on the material constituting the connection column 12 and the optical length in the infrared insulating layer of the detection wavelength as long as the wavelength selective effect is obtained. The optical length refers to the wavelength of light in a substance determined by the refractive index and the dielectric constant.

  Further, the height h of the connecting column 12 is a value determined from the evanescent wavelength of the metal (skin) in order to form a cavity between the isolated plate 11 and a region of the reflector 13 immediately below the isolated plate 11. The thickness is preferably about twice or more the thickness (δ) of the effect.

Next, the manufacturing method of the absorber 10 according to this modification will be described in the case where the in-plane dimension L of the isolated plate 11 and the thickness w of the connecting column 12 are equal.
First, a reflector 13 made of metal and an insulating layer (a layer corresponding to the connection column 12) are formed by sputtering or the like. Next, the pattern of the isolated plate 11 is formed by pattern processing by lift-off and dry etching. Next, the insulating plate 22 is excluded in a region other than directly below the isolated plate 11 by photolithography and wet etching. Finally, the through hole 19 is formed by, for example, photolithography and wet etching.

  Thus, compared with the manufacturing method of the absorber 10 demonstrated in Embodiment 1, since the process of manufacturing the metal connection pillar 12 is abbreviate | omitted, a manufacturing method is simplified.

  As described above, in the second embodiment, the configuration in which the through hole 19 penetrating the reflection plate 13 in the z direction has been described. However, if only the purpose of increasing the response speed is achieved, the reflection plate 13 is penetrated. The structure in which the recessed part which does not perform was formed may be sufficient.

Embodiment 3 FIG.
In the first and second embodiments, the connecting column 12 is provided between each isolated plate 11 and the reflecting plate 13. By the way, as described in the first and second embodiments, the surface plasmon resonance generated between the isolated plate 11 and the reflecting plate 13 is adjusted by adjusting the dimensions of the isolated plate 11 and the connecting column 12. Can be made independent of This is because resonance occurs only between the isolated plate 11 and the region of the reflector 13 immediately below the isolated plate 11 (see FIG. 18). This is because it is unnecessary. That is, this effect can be exhibited even if an object or structure that does not inhibit plasmon resonance exists between the isolated plate 11 and the region of the reflector 13 immediately below the isolated plate 11.

  Therefore, in the third embodiment, an insulating plate 22 is provided between the isolated plate 11 and the reflecting plate 13. FIG. 24 is a top view of the absorber according to the third embodiment of the present invention, and FIG. 25 is a cross-sectional view taken along the line VV in FIG. Even in this configuration, the wavelength selective absorption as described above can be realized by adjusting the dimension of the insulating plate 22.

The insulating plate 22 may be made of, for example, an insulator such as silicon oxide (SiO ₂ ), silicon nitride (SiN), aluminum oxide (Al ₂ O ₃ ), a semiconductor such as silicon, or a dielectric.

  24 and 25, the insulating plate 22 is provided over the entire surface of the reflecting plate 13 in a region other than the region directly below the isolated plate 11, but as described above, the insulating plate 22 is essentially unnecessary in this region. Therefore, it may be provided only on a part of the reflector 13. That is, it can be considered that the insulating plate 22 provided in the third embodiment is a connecting pillar connecting the plurality of isolated plates 11 and the reflecting plate 13.

Next, the thickness of the insulating plate 22 will be described.
The thickness of the insulating plate 22 directly below the isolated plate 11 can be considered in the same manner as the height h of the connecting column 12 described in the modification of the second embodiment. That is, in order to prevent the plasmon resonance in the in-plane direction of the isolated plate 11 from being disturbed as much as possible, it is only necessary to make the resonance in the height direction as difficult as possible. Therefore, the thickness of the insulating plate 22 is preferably smaller than L / 4, and according to the analysis result, it is known that about 200 nm or less is preferable in the infrared wavelength region. However, the thickness of the insulating plate 22 may be changed depending on the material constituting the insulating plate 22 and the optical length in the infrared insulating layer of the detection wavelength as long as a wavelength selective effect is obtained.

  Further, the thickness of the insulating plate 22 is a value determined from the evanescent wavelength of the metal (skin effect) in order to form a cavity between the isolated plate 11 and the region of the reflector 13 immediately below the isolated plate 11. The thickness δ) is preferably about twice or more.

  Since the insulating plate 22 in the region other than directly below the isolated plate 11 is not essentially necessary for plasmon resonance, the thickness of the insulating plate 22 in this region should be smaller than the thickness of the insulating plate 22 directly below the isolated plate 11. Is possible. Thereby, since the volume of the absorber 10 is reduced and the heat capacity is reduced, the sensor 100 having a high response speed is realized.

  In addition, when stress is applied to the absorber 10, a warp having a size corresponding to the material constituting the absorber 10 is generated. However, the region where the insulating plate 22 is provided can be prevented from warping due to stress. Thereby, a design range becomes wide and it can contribute to the performance enhancement of the infrared sensor 100. FIG. As described in the second embodiment, from the viewpoint of the response speed of the sensor 100, it is preferable to form the through hole 19 in as wide a region as possible, but at the same time, it is necessary to consider the strength of the reflector 13. The strength can be reinforced by providing the insulating plate 22 on the reflecting plate 13 as in the third embodiment.

  In addition, silicon oxide, which is an example of an insulator constituting the insulating plate 22, mainly has a strong absorption peak in the long-wavelength infrared (8 μm to 14 μm) region. Therefore, absorption of the insulator inhibits wavelength selectivity. . Therefore, it is preferable to reduce the volume of the insulating plate 22 as much as possible.

Next, the manufacturing method of the absorber 10 by this modification is demonstrated.
First, the reflecting plate 13 and the insulating plate 22 made of metal are formed by sputtering or the like. Next, the pattern of the isolated plate 11 is formed by pattern processing by lift-off and dry etching. Finally, the through hole 19 is formed by, for example, photolithography and wet etching. Thus, the manufacturing method is further simplified as compared with the manufacturing method of the absorbent body 10 described in the first and second embodiments.

  In the embodiment described below, the absorber 10 in which the through hole 19 is not formed in the reflecting plate 13 will be described. However, when the through hole 19 is formed, the same effects as those described in the second and third embodiments are provided. The effect of can be obtained.

Embodiment 4 FIG.
In the first embodiment, the isolated plate 11, the connecting column 12, and the reflecting plate 13 of the absorber 10 are all made of a metal that generates the same surface plasmon resonance. In the modification of the second embodiment and the third embodiment, the case where the connecting column 12 is made of an insulator or the like has been described. The isolated plate 11, the connecting column 12, and the reflecting plate 13 of the absorber 10 according to the fourth embodiment are selected from the group consisting of a metal surface layer, a dielectric, an insulator, and a semiconductor as in the first embodiment. And an inner layer made of a material. The material of the inner layer may be an insulator that absorbs in the infrared wavelength region such as silicon oxide (SiO ₂ ), silicon nitride (SiN), aluminum oxide (Al ₂ O ₃ ), a semiconductor such as silicon, or a dielectric. . These are the materials of the connecting column 12 exemplified in the modification of the second embodiment. The inner layer material includes air.

  Further, the surface layer is made of a metal that causes surface plasmon resonance, and the thickness thereof is determined to be equal to or greater than the thickness that is determined from the skin effect and does not transmit infrared light having a detection wavelength. Thereby, infrared rays do not transmit the surface layer, and the influence on the surface plasmon resonance by the material constituting the inner layer is eliminated.

  Materials such as dielectrics, insulators, and semiconductors generally have a smaller volumetric heat capacity than metals. Therefore, according to the fourth embodiment, the connection pillar 12 includes the inner layer, whereby the heat capacity of the absorber 10 can be reduced and the response speed can be increased.

Embodiment 5. FIG.
FIG. 26 is a cross-sectional view of an absorbent body according to Embodiment 5 of the present invention.
In the fifth embodiment, the isolated plate 11 is provided with a coating layer 23 covering the surface thereof. In FIG. 26, the coating layer 23 is provided on the entire surface excluding the connection pillar 12 portion, but may be provided on the entire surface including the portion. However, the coating layer 23 does not have to be provided on the entire surface of the isolated plate 11, and as shown in FIGS. 27A to 27C, at least one of the upper surface, the side surface, and the lower surface of the isolated plate 11, or What is necessary is just to be provided in these edge parts at least.

The coating layer 23 is made of a material that can transmit the inside without totally reflecting electromagnetic waves and has a refractive index larger than the refractive index of air (about 1.0). The material is silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), other insulators (dielectrics), and semiconductors.

  As described with reference to FIG. 6, when surface plasmon resonance occurs, the electromagnetic field concentrates particularly on the edge portion of the isolated plate 11. At this time, the optical length of the electromagnetic wave localized in the coating layer 23 made of a material having a refractive index n is approximately the wavelength xn in vacuum (or air). As a result of at least the edge portion being covered with the coating layer 23 having a high refractive index, the electromagnetic waves localized by plasmon resonance are confined in the coating layer 23, so that the resonance wavelength is also increased to the refractive index times of the coating layer 23 as described above. Become. In this way, the resonance wavelength is shifted to the long wavelength side. The magnitude of the shift also depends on the degree of electric field enhancement due to surface plasmon resonance.

The thickness of the coating layer 23 will be described.
When the thickness of the covering layer 23 is large, absorption due to the material of the covering layer 23 occurs, and further, the volume of the absorbent body 10 increases and the response speed decreases. Therefore, it is preferable to make the thickness of the coating layer 23 as small as possible. As a result of the electromagnetic field analysis described with reference to FIGS. 7 to 11, it is known that when surface plasmon resonance occurs, the electromagnetic field is localized in the range of about 100 nm ³ around the isolated plate 11. Therefore, if the detection wavelength is in the infrared region, the thickness of the coating layer 23 is preferably about 50 to 300 nm. This preferable thickness varies depending on the material constituting the coating layer 23.

FIG. 28 is a graph showing the absorption characteristics of the absorbent body according to Embodiment 5 of the present invention. The horizontal axis of the graph indicates the wavelength of incident light, and the vertical axis indicates the normalized absorption rate. In FIG. 28, the electromagnetic field analysis was performed by setting the diameter of the isolated plate 11 (disk) to 1.5 μm and the period p to 4 μm. Moreover, the thickness of the coating layer 23 was 50 nm. Moreover, the metal which comprises the isolated plate 11 and the reflecting plate 13 was Au, and the coating layer 23 and the connection pillar 23 were silicon oxide. FIG. 28 shows the results when the coating layer 23 is not provided (short broken line), when it is provided only on the lower surface of the isolated plate 11 (long broken line), and when provided over the entire surface (solid line). The absorption wavelength λ _{ab of the} peak was about 3.5 μm, about 5.0 μm, and about 5.5 μm, respectively.

Further, as a result of conducting the same electromagnetic field analysis with the diameter of the isolated plate 11 (disk) being 2.0 μm, the peak absorption wavelength λ _ab was about 4.5 μm when the coating layer 23 was not provided. . Comparing this result with the case where the l coating layer 23 is provided only on the lower surface of the isolated plate 11 (long broken line), the same absorption wavelength λ _ab can be obtained by providing the coating layer 23 on the lower surface of the isolated plate 11. It can be said that the diameter of the isolated plate 11 to be obtained can be reduced by at least 0.5 μm. It can also be seen that the effect of increasing the detection wavelength is greatest when the coating layer 23 is provided on the entire surface of the isolated plate 11.

  By increasing the detection wavelength in this way, the period p for obtaining the same detection wavelength can be reduced. Therefore, when a thermal image imager is constituted by the infrared sensor 100 described, the pixel can be reduced.

  Note that the effect of increasing the detection wavelength may be obtained even in the metal / insulating film / metal structure (multilayer structure) described in Non-Patent Documents 1 and 2. However, in the fifth embodiment, the coating layer 23 is provided only in at least one of the area region sufficiently smaller than the insulating film, that is, the upper surface, the side surface, and the lower surface. The effect of wavelength conversion can be obtained.

  In general, a metal such as gold has a larger volumetric heat capacity than an insulator such as silicon oxide. Therefore, if the volume is the same, the heat capacity of the isolated plate 11 can be reduced by providing the covering layer 23.

  29 and 30, a coating layer 23 is provided in addition to the structures of FIGS. 29 and 30, the detection wavelength can be increased. In these drawings, the connecting pillar 12 (or insulating plate 22) made of an insulator and the covering layer 23 are shown as separate bodies, but they may be the same insulator.

Embodiment 6 FIG.
FIG. 31 is a top view of an infrared sensor array according to the sixth embodiment of the present invention. 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).

  The infrared sensor array 200 is obtained by arranging the infrared sensors 100 according to the first embodiment in an array. FIG. 31 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 the arranged infrared sensor is shown. 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. Furthermore, the arrangement is not necessarily a square lattice arrangement, and may be any other arrangement such as a triangular lattice arrangement, a hexagonal lattice arrangement, or an aperiodic arrangement.

  The infrared sensor array 200 selects an infrared sensor in each row and / or each column by an external scanning circuit (not shown) and takes out information detected by each sensor 100 in time series. At this time, each sensor 100 can be considered as one pixel. 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 incident light intensity information 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 7 FIG.
32 is a top view of the infrared sensor array according to the seventh embodiment of the present invention, and FIG. 33 is a sectional view taken along line VI-VI in FIG.

  The infrared sensor array 300 is an array of four types of infrared sensors 110, 120, 130, and 140 that differ only in the in-plane direction dimension L of the isolated plate 11. Although different from the fifth embodiment in that the in-plane dimension L of the isolated plate is changed for each sensor, the other configuration is the same as that of the fifth embodiment, and the description is omitted.

  By changing the in-plane dimension L of the isolated plates 11, 21, 31, 41 formed on the absorber of the infrared sensor, the detection wavelength of each sensor constituting the pixel can be changed.

  Further, the detection wavelength of each sensor can be changed by changing the period p, the thickness t of the isolated plate 11 and the height h of the connecting column with respect to the in-plane dimension L of the isolated plate 11. . However, as described in the first embodiment, the change in the period p, the thickness t, and the height h has a smaller influence on the determination of the absorption wavelength than the change in the in-plane direction dimension L. For example, it can be used for fine adjustment of the absorption wavelength.

  That is, the absorptance at a desired wavelength can be maximized by optimizing p / L, t / L, and h / L. As described above, by arraying pixels in which at least one of L, p, t, and h has a different sensor structure, it is used as a thermal image imager that detects an image having incident light intensity information of a different wavelength depending on the pixel. It becomes possible.

  Then, by arraying pixels having different detection wavelengths in this way, a color image can be obtained in the infrared wavelength region as well as in 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 8 FIG.
FIG. 34 is a cross-sectional view of a principal part corresponding to a part of FIG. 3 of the infrared sensor according to the eighth embodiment of the present invention. Except for the structure around the temperature detector 54, the configuration is the same as that of the other embodiment shown in FIG.

  The temperature detection unit 54 shown in FIG. 34 includes the detection film 5 and the thin film metal wiring 6 covered with the insulating layer 14. Although not shown, the temperature detection unit 54 is supported on the upper portion of the hollow portion 2 by the support legs 3 as in FIG.

  FIG. 3 shows a configuration in which the 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. On the other hand, in the eighth embodiment, the absorber 10 is formed integrally with the temperature detection unit 54 or directly provided on the temperature detection unit 54. And the infrared rays absorbed by the absorber 10 are converted into heat and directly transmitted to the temperature detector 54, and the incident infrared rays are detected. The structure of the absorber 10 is the same as the structure described in the first embodiment, and by controlling the in-plane dimension L of the isolated plate 11, infrared light having a specific wavelength is absorbed.

  Even in the infrared sensor having the temperature detection unit 54 integrally formed with the absorber 10 as in the eighth embodiment, the infrared of the detection wavelength resonates and the amount of absorption is selectively increased, so that the infrared of the detection wavelength is selectively selected. Can be detected.

  Furthermore, since the process of attaching the absorber 10 on the support pillar 9 becomes unnecessary, the manufacturing process can be simplified and the product can be manufactured at a lower cost than the case of manufacturing the infrared sensor according to the first to fifth embodiments.

  The infrared sensor 600 including the temperature detection unit 54 described above may be arranged in an array to form the infrared sensor array according to the sixth and seventh embodiments.

  Further, as described in the sixth embodiment, it is possible to configure an image sensor by arraying infrared sensors having the same structure with respect to the absorber 10. Further, as described in the seventh embodiment, infrared sensors having different in-plane direction dimensions L, periods p, or connecting column heights h of the isolated plate 11 are arrayed (pixels having different absorption wavelength ranges are arrayed). ), 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.

Embodiment 9 FIG.
First, the relationship between the ninth embodiment and the first to eighth embodiments will be described.
In the infrared absorbers (light absorbers) disclosed in Patent Literature 1 and Non-Patent Literatures 1 and 2, it is necessary to provide a periodic structure in one pixel (one infrared sensor in the present specification). In the first to eighth embodiments, a plurality of isolated plates 11 are periodically provided in one infrared sensor. In this case, there is a problem that the size of the infrared sensor cannot be sufficiently reduced, and therefore the pixel resolution of the infrared sensor device 1000 cannot be sufficiently improved.

  On the other hand, as described so far, the absorption wavelength by the absorber 10 changes according to the in-plane direction dimension L rather than the period p. Further, it has been found that the region other than the region immediately below the isolated plate 11 in the reflecting plate 13 does not greatly affect the plasmon resonance.

  Based on this, as a result of diligent studies to solve the above problems, the present inventors have found that the isolated plate has not been provided over a plurality of electromagnetic wave sensors without providing the periodic structure of the isolated plate in one infrared sensor. When the periodic structure is provided, it has been found that the same effects as those described in the first to eighth embodiments can be obtained. The ninth embodiment is based on this new knowledge.

  FIG. 35 is a top view of an infrared sensor array according to the ninth embodiment of the present invention. 36 is a sectional view taken along line VII-VII in FIG. In the infrared sensor array 700, the infrared sensors 610 are arranged in a two-dimensional array. The infrared sensors 610 are arranged at a certain distance (spatial distance, clearance) d from each other. Two isolated plates 11 are provided for each infrared sensor 610.

When the interval between the isolated plates 11 in one infrared sensor 610 is p ₁ and the interval between two adjacent isolated plates 11 across two adjacent infrared sensors 610 is p ₂ , p ₁ = p ₂ (= p) Is established. FIG. 35 shows that this relationship is established in the x direction, but the same holds true in the y direction. Thus, since there are only two isolated plates 11 in one infrared sensor 610, the periodic structure of the isolated plate 11 is not formed. However, when viewed from a plurality of infrared sensors 610, the periodic structure of the isolated plate 11 is formed. Will be.

  Although FIG. 35 shows an infrared sensor array 700 including a total of four infrared sensors 610 in 2 rows × 2 columns, five or more infrared sensors 610 may be provided. In addition, in the infrared sensor 610, the absorber 10 and the temperature detection part 54 are integrally formed like the infrared sensor 600 demonstrated in Embodiment 8, However, This is not essential.

  In the example shown in FIGS. 37 and 38, one isolated plate 11 is provided for each infrared sensor 620. Also in this case, since there is only one isolated plate 11 in one infrared sensor 620, the periodic structure of the isolated plate 11 is not formed. However, when viewed from three or more adjacent infrared sensors 620, the isolated plate 11 A periodic structure is formed.

  Furthermore, it has been found that even when two adjacent infrared sensors are used, wavelength selectivity comparable to that of a periodic structure using three or more infrared sensors can be obtained. Therefore, in the ninth embodiment, it is assumed that a cycle p having a cycle number of 1 is constituted by two infrared sensors.

  FIG. 39 is a graph showing the absorption characteristics of the infrared sensor array shown in FIGS. In FIG. 39, the electromagnetic field analysis was performed with p = 3 μm, h = 0.15 μm, L = 2.0 μm, w = 500 nm, and d = 500 nm. From this result, it is understood that the infrared sensor array according to the ninth embodiment also has wavelength selective absorption as described above.

  As described above, even when the periodic structure is not provided in one infrared sensor, the periodic structure is provided over a plurality of adjacent infrared sensors, so that the wavelength selective operation is achieved by the infrared sensor array including a plurality of infrared sensors. Absorption is possible. Thus, since it is not necessary to provide a periodic structure in the infrared sensor that constitutes one pixel, the size of one pixel can be reduced. In particular, when only one isolated plate 11 is provided in the infrared sensor as shown in FIGS. 37 and 38, the size (area) of one pixel can be made smaller than the period p of the isolated plate 11, and absorption is performed. The volume of the body 10 is sufficiently reduced and the heat capacity is also reduced. In this way, the pixel resolution of the infrared sensor device 1000 can be improved.

  In the ninth embodiment, when the rectangular isolated plates 11 are arranged in stripes, only specific polarized light can be detected as described with reference to FIGS. 12a and 12b. .

  In the above description, the configuration in which one or two isolated plates 11 are provided in one infrared sensor (pixel) from the viewpoint of miniaturizing one pixel as much as possible has been described. It is important that a periodic structure is provided over three or more, and three or more isolated plates 11 may be provided in one infrared sensor.

  As described above, in the embodiments of the present invention, the case where the temperature detection unit is a silicon diode has been described. However, the present invention is not limited to this, and the present invention is also effective when used as an absorber structure for a thermopile, a bolometer, a thermistor, or the like. It is. That is, the present invention does not depend on the thermal infrared sensor system itself. Further, the configurations of the embodiments and the modifications described above may be freely combined, modified, or omitted.

  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, 21, 31, 41 Isolated plate, 12 connecting pillar, 13 reflector, 14, 17 insulating layer, 18 insulating film, 19 through-hole, 20 absorber, 22 insulating plate, 23 covering layer, 26 hollow region, 100, 110, 120, 130, 140 , 600, 610, 620 Infrared sensor, 200, 300, 700, 800 Infrared sensor array, 1000 Infrared sensor device.

Claims (23)

An electromagnetic wave sensor device comprising one or more electromagnetic wave sensors,
The electromagnetic wave sensor is
A temperature detector;
An electromagnetic wave absorber thermally connected to the temperature detector,
The electromagnetic wave absorber is
A plurality of isolated plates containing metal, spaced apart periodically;
A reflective plate disposed opposite to the isolated plate and having at least a surface of the metal;
A connecting column connecting the isolated plate and the reflector so that surface plasmon resonance occurs in the in-plane direction of the isolated plate;
The in-plane dimension of the isolated plate is 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 isolated plates are arranged in a certain period in one direction or in two directions intersecting each other,
The electromagnetic wave sensor device according to claim 1, wherein the certain period is smaller than the specific wavelength. An electromagnetic wave sensor device comprising a plurality of electromagnetic wave sensors,
Each of the plurality of electromagnetic wave sensors is
A temperature detector;
An electromagnetic wave absorber thermally connected to the temperature detector,
The electromagnetic wave absorber is
An isolated plate containing metal,
A reflective plate disposed opposite to the isolated plate and having at least a surface of the metal;
A connecting column connecting the isolated plate and the reflector so that surface plasmon resonance occurs in the in-plane direction of the isolated plate;
The in-plane dimension of the isolated plate is selected so as to induce a surface plasmon that couples with an electromagnetic wave having a specific wavelength included in the electromagnetic wave incident on the electromagnetic wave absorber,
The electromagnetic wave sensor device, wherein the isolated plates are arranged at a constant period in one direction or in two directions intersecting each other across the plurality of electromagnetic wave sensors.   The electromagnetic wave sensor device according to claim 3, wherein the electromagnetic wave absorber has one or two of the isolated plates.   The electromagnetic wave sensor device according to claim 3, wherein the certain period is smaller than the specific wavelength.   The electromagnetic wave sensor device according to claim 3, wherein two electromagnetic wave sensors are provided in one direction.   The electromagnetic wave sensor device according to claim 1, wherein the metal is a metal that generates surface plasmons. The isolated plate and the connecting pillar are:
The electromagnetic wave sensor device according to any one of claims 1 to 7, wherein the electromagnetic wave sensor device is made of a material selected from the group consisting of an insulator, a semiconductor, and a dielectric, or at least a surface thereof is a metal.   9. The electromagnetic wave sensor device according to claim 1, wherein a height and a thickness of the connection column are smaller than an in-plane dimension of the isolated plate.   The at least one of the thickness of the isolated plate, the height of the connecting column, and the thickness of the connecting column is smaller than ¼ of an in-plane dimension of the isolated plate. The electromagnetic wave sensor device according to any one of 9. The isolated plate, the connecting column, and the reflecting plate are at least surfaces of metal,
The magnetic permeability of the metal is μ, the electrical conductivity is σ, the angular frequency of the electromagnetic wave of the specific wavelength is ω, the thickness of the isolated plate, the height of the connecting column, the thickness of the connecting column, and the The thickness of each reflector is
2 × (2 / μσω) ^1/2
It is the above magnitude | size, The electromagnetic wave sensor apparatus of any one of Claims 1-10 characterized by the above-mentioned.   The coating layer made of a material having a higher refractive index than air is provided on at least one of the upper surface, the side surface, and the lower surface of the isolated plate. The electromagnetic wave sensor apparatus of description.   The electromagnetic wave sensor device according to any one of claims 1 to 12, wherein the reflection plate has a through hole formed in a range not overlapping with the isolated plate in an in-plane direction of the reflection plate. .   The through-holes are formed in one direction or in two directions intersecting each other, separated by a period in which the isolated plate is disposed or a period different from a period in which the isolated plate is disposed. The electromagnetic wave sensor device according to claim 13. The isolated plate, the reflecting plate and the connecting column are:
A surface layer made of metal,
The electromagnetic wave sensor device according to claim 1, comprising an inner layer made of a material selected from the group consisting of an insulator, a semiconductor, and a dielectric.   The electromagnetic sensor device according to claim 1, wherein the isolated plate has a symmetrical shape in two directions intersecting each other.   The electromagnetic sensor device according to claim 1, wherein the isolated plate has an asymmetric shape in two directions intersecting each other. The reflector has a through-hole formed in a range not overlapping with the isolated plate in the in-plane direction of the reflector,
The connecting pillar is made of a material selected from the group consisting of an insulator, a semiconductor, and a dielectric,
The height of the connecting column is less than 1/4 of the in-plane dimension of the isolated plate,
18. The electromagnetic wave sensor device according to claim 1, wherein a thickness of the connection column is equal to or less than a size in an in-plane direction of the isolated plate. A plurality of the isolated plates and the reflective plate are connected by the connecting pillars,
The reflector has a through-hole formed in a range not overlapping with the isolated plate in the in-plane direction of the reflector,
The connecting pillar is made of a material selected from the group consisting of an insulator, a semiconductor, and a dielectric,
18. The electromagnetic wave sensor device according to claim 1, wherein a height of the connection pillar is smaller than ¼ of an in-plane dimension of the isolated plate. 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 varies with temperature,
The electromagnetic wave sensor device according to any one of claims 1 to 19, wherein the electromagnetic wave absorber is provided on an upper side of the temperature detector.   The electromagnetic wave sensor device according to claim 20, wherein the electromagnetic wave absorber is provided directly on the temperature detector.   The electromagnetic wave sensor device according to claim 1, comprising a plurality of electromagnetic wave sensors arranged in an array. The plurality of electromagnetic wave sensors arranged in the array includes a first electromagnetic wave sensor and a second electromagnetic wave sensor,
The first electromagnetic wave sensor and the second electromagnetic wave sensor are at least one of a period in which the isolated plate is disposed, an in-plane direction dimension of the isolated plate, a thickness of the isolated plate, and a height of the connecting column. The electromagnetic wave sensor device according to claim 22, wherein one is different.

Images