JP5706174B2 - Infrared sensor and infrared sensor array - Google Patents

Description

  The present invention relates to an infrared sensor and an infrared sensor array.

  A conventional thermal infrared sensor does not have a function of detecting the polarization of incident light. For this reason, specific polarized light has been detected by providing a polarizing filter separately from the thermal infrared sensor (see, for example, Patent Document 1).

JP-A-3-29824

  However, in a structure in which a polarizing filter and a thermal infrared sensor are combined, first, a polarizing filter is required in addition to the thermal infrared sensor, and the structure becomes complicated. Second, what kind of polarizing filter is used. However, some of the necessary wavelength components are absorbed by the change filter, which lowers the detection efficiency. Third, to detect a plurality of polarized lights, it is necessary to attach a polarization filter having a different structure for each thermal infrared sensor. There was a problem such as having to.

  Accordingly, an object of the present invention is to provide a thermal infrared sensor and a thermal infrared sensor array that can be miniaturized and have high detection efficiency for polarized light.

  The present invention relates to an infrared sensor for detecting infrared rays, a substrate having a hollow part, a temperature detection part provided on the hollow part, including a detection film, and connected to the temperature detection part, on the hollow part. A support leg for holding the temperature detection unit; and an umbrella structure unit provided on the temperature detection unit and including a plate-shaped absorption umbrella, wherein the absorption umbrella is a plurality of slits arranged in parallel at regular intervals. And an infrared sensor that selectively absorbs an electric field component of incident infrared rays in a direction perpendicular to the longitudinal direction of the slit.

  The present invention also relates to an infrared sensor array in which the above infrared sensors are arranged in an array (matrix).

  As described above, in the infrared sensor of the present invention, it is possible to selectively absorb only the electric field component of the incident infrared ray perpendicular to the slit, and it is possible to detect only specific polarized light.

  Moreover, in the infrared sensor array of the present invention, it is possible to detect polarization information of incident infrared rays.

It is a top view of the thermal type infrared sensor concerning Embodiment 1 of the present invention. It is sectional drawing at the time of seeing the thermal infrared sensor of FIG. 1 in the II direction. The absorption characteristic of the absorber umbrella concerning Embodiment 1 of this invention is shown. The polarization characteristic of the absorptivity of the absorber according to the first embodiment of the present invention is shown. The relationship between the rotation angle at the time of rotating the thermal type infrared sensor concerning Embodiment 1 of this invention and a sensor output is shown. It is a top view of the thermal type infrared sensor array concerning Embodiment 2 of this invention. It is a top view of the thermal type infrared sensor array concerning Embodiment 3 of this invention. It is sectional drawing at the time of seeing the thermal infrared sensor array of FIG. 7 toward VII-VII. It is a top view of the thermal type infrared sensor array concerning Embodiment 4 of this invention. It is a figure explaining the polarization angle detected by the thermal type infrared sensor array concerning Embodiment 4 of this invention. It is a figure explaining the polarization angle detected by the thermal type infrared sensor array concerning Embodiment 4 of this invention. It is a top view of the thermal type infrared sensor array concerning Embodiment 5 of this invention. It is sectional drawing of the temperature detection part of the thermal type infrared sensor concerning Embodiment 6 of this invention.

Embodiment 1 FIG.
FIG. 1 is a top view of the thermal infrared sensor according to the first embodiment of the present invention, the whole being represented by 100, and FIG. 2 is a cross-sectional view when FIG. 1 is viewed in the II direction. is there.

  As shown in FIGS. 1 and 2, the thermal infrared sensor 100 includes a substrate 1 made of, for example, silicon. A hollow portion 2 is provided in the substrate 1, and a temperature detection unit 4 is supported on the hollow portion 2 by a support leg 3. The support leg 3 includes a thin film metal wiring 6 and a dielectric film 16 that supports the thin film metal wiring 6. The support legs 3 are two here, and are bent in an L shape when viewed from above. The support legs 3 are disposed substantially symmetrically with respect to the central axis of the temperature detection unit 4.

  The temperature detection unit 4 includes a detection film 5 and a thin film metal wiring 6, and the detection film 5 and the thin film metal wiring 6 are covered with an insulating layer 18 such as silicon oxide. The detection film 5 is made of, for example, a diode using crystalline silicon. The thin film metal wiring 6 is formed simultaneously with the thin film metal wiring 6 included in the support leg 3 and electrically connects the detection film 5 and the aluminum wiring 7. The thin film metal wiring 6 is made of, for example, a titanium alloy having a film thickness of 100 nm. The aluminum wiring 7 is covered with an insulating layer 17.

  The electrical signal output from the detection film 5 is transmitted to the aluminum wiring 7 via the thin film metal wiring 6 formed on the support leg 3, and is detected by a detection circuit (not shown). The electrical connection between the thin-film metal wiring 6 and the detection film 5 and the electrical connection between the thin-film metal wiring 6 and the aluminum wiring 7 are made of a conductor (not shown) extending in the vertical direction as necessary. ).

  On the insulating layer 17, a reflective film 8 that reflects infrared rays is disposed so as to cover the hollow portion 2. The reflective film 8 is disposed so as to cover at least a part of the upper portion of the support leg 3 in a state where it is not thermally connected to the temperature detection unit 4. The reflective film 7 is made of a metal such as aluminum.

  On the temperature detection unit 4, an umbrella structure unit 20 including a support column 9 and a plate-shaped absorbent umbrella 10 supported by the support column 9 is provided. As shown in FIG. 1, the thermal infrared sensor 100 can only see the umbrella structure 20 when viewed from above. The absorber 10 is made of, for example, a metal thin film such as Au, Ag, Cu, and Al. The film thickness is about several nm to several hundred nm, and the film thickness that does not leak incident light at the absorption wavelength to be measured. Is desirable. Here, the absorbing umbrella 10 is a single-layered metal thin film 6. However, for example, a three-layer structure in which a metal thin film 6 is sandwiched between dielectric thin films such as silicon oxide having a film thickness of about 100 to 200 nm, or a dielectric. A two-layer structure in which the metal thin film 6 is formed on the thin film may be used.

  The absorbent umbrella 10 is provided with a plurality of linear slits 11 formed in parallel at regular intervals to form a one-dimensional periodic structure. The film thickness of the absorber 10 is appropriately determined in consideration of absorption, thermal time constant, material stress, and the like. As can be seen from FIG. 2, the absorbent umbrella 10 is connected to the temperature detection unit 4 by the support pillar 9, that is, the absorption umbrella 10 and the temperature detection unit 4 are thermally connected. On the other hand, the absorbing umbrella 10 is held above the reflecting film 8 in a state where it is not thermally connected to the reflecting film 8, and spreads in a plate shape in the lateral direction so as to cover at least part of the reflecting film 8. .

  In such a thermal infrared sensor element 100, incident infrared rays are mainly absorbed by the absorber 10. On the other hand, the infrared light transmitted through the absorber 10 is reflected by the reflective film 8 and is incident on the absorber 10 again from the back surface and is absorbed. Infrared rays absorbed by the absorber 10 are converted into heat and transmitted to the temperature detection unit 4 through 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 is detected by detecting a change in the electrical resistance of the detection film 5 with an external detection circuit (not shown). it can. Although the structure provided with the reflective film 8 is shown here, the reflective film 8 may not be provided.

Next, the absorption structure of the absorbent umbrella 11 will be described in detail. FIG. 3 is a result of obtaining the absorption characteristics of the absorber having a one-dimensional periodic structure formed of Au using strict coupled wave analysis. Here, when d: slit depth (Z-axis direction), p: slit period, w: slit width (X-axis direction), and λ _ab : absorption wavelength, d = 1 μm, p = 3 μm, w = The thickness was 0.1 μm. Further, the incident light was only an electric field component (X-axis direction) perpendicular to the slit.

FIG. 3 shows that strong absorption occurs at a specific wavelength (approximately 5.6 to 5.7 μm). This absorption can be explained by the following equation 1 in principle, where the absorption wavelength is λ _ab with the slit depth direction as the resonance direction.

  However, as shown in FIG. 3, the absorption wavelength is made longer than the result obtained by Equation 1. This can be explained by the fact that a part of the electromagnetic field resonating in the slit leaks out of the slit, so that the depth of the slit becomes equivalently deep. Further, in order to realize absorption without generating not only the slit depth but also higher-order diffraction, the relationship of the following formula 2 must be satisfied.

λ _ab > p (Formula 2)

  The width of the slit 11 depends on the depth in order to maintain the resonance state. For example, when d = 1 μm, w is preferably thinner than 200 nm.

  Next, with respect to the absorption structure of the absorber used in FIG. 3, strict wave coupling analysis is performed on incident light when the electric field component is perpendicular to the slit (X-axis direction) and parallel to the slit (Y-axis direction). FIG. 4 shows the absorption rate obtained by use.

  From FIG. 4, the absorber 10 according to the first embodiment selectively absorbs incident light (solid line) having an electric field component in the direction (X-axis direction) perpendicular to the longitudinal direction (Y-axis direction) of the slit 11. And it turns out that incident light (broken line) which has an electric field component of the direction (Y-axis direction) parallel to the slit 11 hardly absorbs. That is, it can be seen that polarized light is separated and absorbed. Thus, by using the absorber 10 according to the first embodiment, polarized light can be separated and detected.

  This phenomenon is also called surface plasmon, plasmonics, or metamaterial in the physical field. These are called different terms, but in any case, when a one-dimensional periodic structure is formed by a metal such as gold, silver, and aluminum, the surface mode strongly localized on the surface is generated, and the mechanism of selective absorption is the same. It is.

  FIG. 5 shows the relationship between the rotation angle and the sensor output when the thermal infrared sensor having such an absorbing umbrella 10 is rotated about the Z axis. As can be seen from FIG. 5, the polarization of the incident light can be obtained by measuring the output of the sensor at each rotation angle.

  As described above, in the infrared sensor 100 according to the first embodiment of the present invention, first, a polarizing filter as in the conventional structure is not required, and the polarization detection system can be formed from a minimum structure including only the infrared sensor alone. it can. Secondly, the infrared rays are not absorbed by the polarizing filter, and the infrared detection efficiency is increased. Third, even in a system that detects a plurality of different polarized lights, it is possible to detect a desired polarized light without using a polarizing filter by simply changing the slit structure.

Embodiment 2. FIG.
FIG. 6 is a top view of the thermal infrared sensor array according to the second exemplary embodiment of the present invention, indicated as a whole by 200, and the thermal infrared sensor 100 shown in FIG. 1 is arranged in an array (matrix). It is a thing. In FIG. 6, for the sake of simplicity, a thermal infrared sensor array 200 including a total of four thermal infrared sensors 100 of 2 rows × 2 columns is shown. There is no limit to the number.

  The thermal infrared sensor array 200 selects thermal infrared sensors in each row and each column by an external scanning circuit (not shown) or the like, and takes out information detected by each sensor in time series. Information detected by each sensor may be read out in parallel.

  Thus, by arranging the thermal infrared sensors 100 in an array and detecting only the electric field component perpendicular to the slit, it can be used as a thermal image imager for detecting an image having polarization information. Further, by rotating the array around the Z axis, the polarization angle in each sensor (pixel) can be obtained as described in the first embodiment of the present invention. As a result, each pixel can be used as a thermal imager that detects an image having information on the polarization angle and incident light intensity.

Embodiment 3 FIG.
FIG. 7 is a top view of the thermal infrared sensor array according to the third embodiment of the present invention, the whole being represented by 300, and FIG. 8 is a cross-sectional view when FIG. 7 is viewed in the VII-VII direction. It is.

  The thermal infrared sensor array 300 is configured by arranging four types of thermal infrared sensors 100, 110, 120, and 130 that differ only in slit depth in an array. FIG. 7 shows a thermal infrared sensor array 300 composed of a total of four thermal infrared sensors of 2 rows × 2 columns for the sake of simplicity. There is no limit. The thermal infrared sensor array 300 selects a thermal infrared sensor in each row and each column by an external scanning circuit (not shown) or the like, and takes out information detected by each sensor in time series. Information detected by each sensor may be read out in parallel.

  In the thermal infrared sensor, the detection wavelength in the sensor (pixel) can be changed by changing the depth of the slit. That is, by providing a slit in each pixel, the polarization angle can be detected, and it can be used as a thermal image imager for detecting an image having incident light intensity information at a different wavelength for each pixel.

Embodiment 4 FIG.
FIG. 9 is a top view of the thermal infrared sensor array according to the fourth embodiment of the present invention, indicated as a whole by 400. FIG. In FIG. 9, the concave portion of the support column 9 is omitted.

  As shown in FIG. 9, in the thermal infrared sensor array 400, the longitudinal directions of the slits 11 are all different, the thermal infrared sensors 100 and 140 are orthogonal to each other, and the thermal infrared sensors 150 and 160 are orthogonal to each other. On the other hand, the thermal infrared sensors 100 and 150 are at an angle of 45 °, and the thermal infrared sensors 140 and 160 are at an angle of 45 °.

  If the four thermal infrared sensors (pixels) are taken as one unit, polarized light can be detected by this unit. The mechanism is shown in FIGS. 10 and 11, as is clear from the symmetry, the orthogonal coordinate system (indicated by the solid line in FIG. 10 and the broken line in FIG. 11) formed by the thermal infrared sensors 100 and 140 and the thermal infrared sensors 150 and 160 are formed. The polarization angle of incident light is uniquely determined by the orthogonal coordinate system (solid line in FIG. 11). Therefore, the polarization angle can be obtained by incorporating the following algorithms (1) to (3) into a readout circuit that reads out the electrical characteristics of the thermal infrared sensor.

(1) The polarization angle detected by the thermal infrared sensors 100 and 140 is θ or −θ (see FIG. 10).
(2) The polarization angle detected by the thermal infrared sensors 150 and 160 is Φ or −Φ (see FIG. 11).
(3) If 45−Φ> 0, the polarization angle is θ, and if 45−Φ <0, the polarization angle is −θ.

  In this way, by using four thermal infrared sensors (pixels) having a one-dimensional periodic structure forming different orthogonal coordinate systems as one unit, the polarization angle can be obtained without rotating the thermal infrared sensor. It becomes possible.

Embodiment 5 FIG.
FIG. 12 is a top view of the thermal infrared sensor array according to the fifth embodiment of the present invention, the whole being represented by 500. FIG. In FIG. 12, the concave portion of the support column 9 is omitted.

  The thermal infrared sensor array 500 has a structure in which two units of the thermal infrared sensor array 400 according to the fourth embodiment are arranged. Here, for simplicity of explanation, the thermal infrared sensor array 500 including two units, that is, a total of eight thermal infrared sensors is shown, but the number of thermal infrared sensors arranged is not limited. These thermal infrared sensor arrays select thermal infrared sensors in each row and each column by an external scanning circuit (not shown) or the like, and take out information detected by each sensor in time series. Information detected by each sensor may be read out in parallel.

  When four thermal infrared sensors (four pixels) are arranged in an array as one unit, it can be considered that each unit corresponds to one pixel. Then, by applying the above-described algorithm of Embodiment 4 to each unit, polarization angle information can be obtained in each unit. Therefore, an image including the polarization angle information of the object to be observed can be obtained without rotating the thermal infrared sensor.

Embodiment 6 FIG.
FIG. 13: is sectional drawing of the temperature detection part 4 of the thermal type infrared sensor concerning Embodiment 6 of this invention. The structure other than the temperature detection unit 4 is the same as that in FIG. 2, and the temperature detection unit 4 is supported on the upper portion of the hollow portion 2 by the support legs 3.

  The temperature detection unit 4 in FIG. 13 includes a detection film 5 and a thin film metal wiring 6. The detection film 5 is a diode made of, for example, silicon. The thin film metal wiring 6 is made of, for example, a titanium alloy having a film thickness of 100 nm. The detection film 5 and the thin metal wiring 6 are covered with an insulating layer 18 made of, for example, silicon oxide.

  Furthermore, the temperature detection part 4 is directly equipped with the absorption film 21 which absorbs infrared rays in the upper part. The absorption film 21 is made of a metal such as Au or Ag. The absorption film 21 is formed with a one-dimensional periodic slit 11 as shown in the first embodiment, and absorbs a specific wavelength and polarized light.

  In the thermal infrared sensor element having the temperature detection unit 4 integrally formed with the absorption film 21 as in the present embodiment, the desired infrared wavelength resonates and the amount of absorption is selectively increased, so that only a specific wavelength is obtained. Can be selectively detected. Further, the process of supporting the absorbent umbrella with the support pillar is not required, the manufacturing process is simplified, and the product can be manufactured at a lower cost.

  The thermal infrared sensor array according to the second to fifth embodiments may be formed by arranging thermal infrared sensors including the temperature detection unit 4 having such a structure in an array.

  DESCRIPTION OF SYMBOLS 1 Board | substrate, 2 Hollow part, 3 Support leg, 4 Temperature detection part, 5 Detection film, 6 Thin film metal wiring, 7 Aluminum wiring, 8 Reflective film, 9 Support pillar, 10 Absorbing umbrella, 11 Slit, 12 Insulating film, 16 Dielectric Body membrane, 17, 18 insulating layer, 20 umbrella structure, 100 thermal infrared sensor.

Claims (7)

An infrared sensor for detecting infrared rays,
A substrate having a hollow portion;
A temperature detector provided on the hollow portion and including a detection film;
A support leg connected to the temperature detection unit and holding the temperature detection unit on the hollow part;
An umbrella structure part provided on the temperature detection part and including a plate-shaped absorption umbrella;
The absorbent umbrella has a plurality of rectilinear grooves that are arranged in parallel at regular intervals and do not penetrate the bottom surface. Within the absorbent umbrella surface, the direction of the groove is one direction, of incident infrared radiation, the concave grooves not penetrating the straight and bottom longitudinally selectively absorb to the vertical direction of the electric field component is converted into heat, the wavelength of the absorbed electric field components of the constant An infrared sensor characterized by being longer than the interval .   The infrared sensor according to claim 1, wherein the absorbing umbrella is directly disposed on the temperature detection unit.   An infrared sensor array in which the infrared sensors according to claim 1 or 2 are arranged in an array. Including first and second infrared sensors;
It provided the infrared sensor of the first, and a concave groove which does not penetrate the straight and bottom, provided on the infrared sensor of the second, the depth of the groove of the concave does not penetrate the straight and bottom differ The infrared sensor array according to claim 3. Including first, second, third, and fourth infrared sensors having concave grooves that are linear and do not penetrate the bottom surface, the longitudinal directions of which are different from each other;
It provided the infrared sensor of the first, straight and the longitudinal recessed grooves not penetrating the bottom surface, provided on the infrared sensor of the second longitudinal grooves of the concave does not penetrate the straight and bottom And are orthogonal
Provided the infrared sensor of the third linear and the longitudinal recessed grooves not penetrating the bottom surface, provided on the infrared sensor fourth longitudinal groove recessed not penetrating straight and bottom The infrared sensor array according to claim 3, wherein and are orthogonal to each other. Provided in the first infrared sensor, the longitudinal direction of the concave groove which does not penetrate the straight and bottom, provided on the third infrared sensor, longitudinal grooves recessed not penetrating straight and bottom The infrared sensor array according to claim 5, wherein and form an angle of 45 °.   7. An infrared sensor array comprising the first, second, third and fourth infrared sensors according to claim 5 or 6 as one unit, and a plurality of the units arranged in an array.

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