JP4040548B2 - Infrared imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an infrared imaging device, and more particularly to an infrared imaging device including a thermal infrared sensor that does not require a cooling device.
[0002]
[Prior art]
In recent years, as thermal infrared image sensors (imaging devices) that do not require cooling devices, vanadium oxide bolometers using micromachining technology and BSTO (Barium-Strontium-Titanium Oxide) pyroelectric infrared A sensor is realized. These infrared sensors have a heat-sensitive part that absorbs infrared light to raise the temperature, support legs for thermally separating the heat-sensitive part from the silicon substrate, and horizontal address lines and vertical signal lines for selecting pixels. And is composed of.
[0003]
These thermal infrared sensors detect infrared rays by absorbing infrared rays radiated from a subject and detecting changes in resistance of the counter electrode, spontaneous polarization changes, and the like caused by the temperature rise.
[0004]
In the case of a bolometer-type infrared sensor that detects a resistance change, when vanadium oxide, which is the most commonly used material, is used, the resistance temperature change is about minus 2%, and the signal amount is large. . However, in order to detect a resistance change, it is necessary to pass a current of several tens of microamperes or more to the infrared sensor, and heat generation from the sensor itself increases. For this reason, it is necessary to remove noise generated by the heat generation, and there is a drawback that a temperature stabilizer such as a Peltier element is necessary to keep the element temperature constant.
[0005]
On the other hand, in the case of a pyroelectric infrared sensor that detects a spontaneous polarization change, when a certain infrared ray is incident on the pyroelectric material, it takes about 1 second to neutralize the generated charge. There is a disadvantage that a chopper for modulating the incident light is required.
[0006]
On the other hand, an infrared sensor that detects a change in vibration frequency has also been proposed (see, for example, Patent Document 1). In this infrared sensor, since both ends of the beam, which is an infrared light receiving portion, are fixed to the fixed frame, stress is generated inside the beam instead of thermal expansion of the beam due to a temperature change of the light receiving portion due to infrared absorption. Due to this stress, the axial force of the beam changes, and the resonance frequency change and Q value (sharpness) change of the vibrator are detected. For the light receiving portion, silicon doped with boron at a high concentration is used, and for the heat insulating portion, a silicon oxide film is used.
[0007]
Additive-free silicon is transparent to infrared rays having a wavelength of 8 μm or more. On the other hand, when an impurity is added to silicon, the absorption rate of infrared rays is improved, but infrared rays cannot be absorbed unless the thickness is increased to several hundred μm or more. Therefore, the heat capacity of the light receiving portion is increased, the response speed as a sensor is lowered, and there is a disadvantage that it cannot be used for a high-speed scanning application such as a two-dimensionally arranged imager.
[0008]
In addition, since the detection principle is to generate internal stress, it is necessary to support at a plurality of fixed points. For this reason, there has been a problem that the “escape” of heat from the light receiving portion becomes large. Furthermore, since the light receiving part and the part that generates stress are the same, if the light receiving surface is enlarged two-dimensionally, the stress due to thermal expansion escapes in a direction perpendicular to the direction supported by the fixed frame, and the fixed part is There was also a drawback that the axial force was not sufficient.
[0009]
On the other hand, a sensor that reads the “deflection” as a change in the capacitance with the substrate has also been proposed due to the temperature rise caused by the absorbed infrared rays, which causes a “deflection” due to the difference between the linear thermal expansion coefficients of the two substances. (For example, refer to Patent Document 2).
However, because “deflection” due to the difference in the linear thermal expansion coefficient between the two substances is detected, it cannot respond to the fast response speed required for the image sensor, and the capacitance change with the substrate changes linearly with the temperature rise of the sensor. It was a problem not to.
[0010]
[Patent Document 1]
JP-A-7-83756 [Patent Document 2]
U.S. Patent No. 6,498,347.
[0011]
[Problems to be solved by the invention]
As described above, the conventional thermal infrared imaging device has problems such as large noise, poor sensor sensitivity, and poor linearity of the output signal with respect to the temperature rise of the sensor.
The present invention has been made on the basis of recognition of such a problem. The object of the present invention is to provide a thermal infrared sensor that has low noise, good sensor sensitivity, and good linearity of an output signal with respect to temperature rise of the sensor. Another object is to provide an infrared imaging device.
[0012]
[Means for Solving the Problems]
The present invention includes a plurality of infrared sensors provided in a substantially matrix form on a substrate, a frequency sweep circuit, and storage means, and each of the plurality of infrared sensors is provided on a surface of the substrate. A first electrode and a second electrode; a third electrode provided on the substrate opposite to and spaced from the first and second electrodes; and the third electrode provided on the third electrode, An infrared absorption layer that absorbs infrared rays and converts the infrared rays into heat; and a support leg that supports the third electrode and the infrared absorption layer in a state of being separated from the first and second electrodes, and the infrared ray The absorption layer absorbs incident infrared rays and converts it into heat, whereby the temperature of the support leg changes, and the Young's modulus of the material constituting the support leg changes in response to the change in temperature, whereby the support leg The fixed end of The resonance frequency of the third electrode and the infrared absorption layer changes, and the frequency sweep circuit is an alternating current having a variable frequency between the first electrode and the third electrode of each of the plurality of infrared sensors. The infrared rays obtained by applying a voltage to vibrate the third electrode and the infrared absorption layer with the fixed end of the support leg as a fulcrum, and causing a certain level of infrared rays to enter each of the plurality of infrared sensors. The resonance frequency of the absorption layer is stored in the storage means as a reference value, the resonance frequency of the infrared absorption layer measured by the frequency sweep circuit for each of the plurality of infrared sensors, and the reference value stored in the storage means An infrared imaging device is provided.
[0014]
By providing a plurality of these infrared sensors in a substantially matrix shape, it is possible to provide a thermal infrared imaging device that is also low in noise, has good sensitivity, and has good linearity of an output signal with respect to temperature rise.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 1 is a schematic cross-sectional view showing a part of a thermal infrared imaging device according to an embodiment of the present invention.
FIG. 2 is a plan view of the infrared imaging device of the present embodiment. That is, these drawings show a part of an image sensor in which infrared sensors are arranged in a substantially two-dimensional matrix.
[0017]
The infrared sensor 101 constituting the infrared imaging element includes a counter electrode 103 in which a vibration lower electrode 108 and an amplitude measurement lower electrode 107 are provided on a silicon substrate 102 and an infrared absorption layer 112 is stacked with a cavity 106 interposed therebetween. It has a structure supported by support legs 104 with low heat conduction. The counter electrode 103 is connected to a ground electrode (not shown) of the silicon substrate 102 and has a ground potential. The adjacent vertical signal line 105 is connected to the amplitude measuring electrode 107, and the horizontal signal line 115 is connected to the excitation lower electrode 108. The excitation lower electrode 108 and the amplitude measurement lower electrode 107 are insulated from each other by an insulating layer 111 made of silicon oxide or the like provided on the surface of the silicon substrate 102.
[0018]
The counter electrode 103 is made of titanium, titanium nitride, polycrystalline silicon, or the like, and an infrared absorption layer 112 made of silicon oxide, silicon nitride, or a laminate of these is overlaid and laminated on the surface. The infrared absorption layer 112 can absorb as much infrared rays 109 as possible, and the temperature rise efficiency of the support legs 104 can be increased by the absorbed heat.
[0019]
In addition, a part of the counter electrode 103 made of titanium, titanium nitride, or the like extends to the support leg 104 as a wiring portion and is electrically connected to the silicon substrate 102 via the support column 110. By applying an AC voltage having a frequency of about 100 kHz to 10 MHz between the counter electrode 103 and the excitation lower electrode 108, the counter electrode 103 and the infrared absorption layer 112 laminated thereon are fixed to the support leg 104. It vibrates using the end 104A as a fulcrum. By designing the shape of the counter electrode 103 and the mass of the infrared absorption layer 112 so as to resonate at a frequency of 100 kHz to 10 MkHz just around room temperature, a large amplitude can be obtained even with a slight electrostatic force.
[0020]
FIG. 3 is a graph showing an example of the relationship between the temperature of the counter electrode 103 and the resonance frequency in the present invention.
[0021]
That is, the counter electrode 103 and the infrared absorption layer 112 laminated thereon vibrate using the fixed end 104A of the support leg 104 as a fulcrum. At this time, when the infrared ray absorbing layer 112 absorbs incident infrared rays and the temperature thereof changes, the temperature of the support leg 104 also changes. When the temperature of the support leg 104 changes, the Young's modulus changes, so the resonance frequency also changes. As shown in FIG. 3, the resonance frequencies of the counter electrode 103 and the infrared absorption layer 112 have a negative correlation with the temperature of the support leg 104. Then, by appropriately selecting the material, size, thickness, and the like of the support leg 104, the counter electrode 103, and the infrared absorption layer 112 laminated thereon, the resonance frequency is about 50 kHz when the temperature of the support leg 104 changes by 0.4K. It is also possible to change.
[0022]
For example, the Young's modulus near room temperature of titanium is 60 GPa, and the temperature coefficient is about minus 0.4% / K. Accordingly, a silicon oxide film having a planar size of about 20 μm × 20 μm and a thickness of 500 nm and a silicon thickness of 300 nm are formed on the tip of a cantilever (support leg 104) made of titanium having a length of 2 μm and a cross-sectional area of 0.3 μm ^2. When the infrared absorption layer 112 having a laminated structure of nitride films is provided, the resonance frequency of the counter electrode 103 is about 2.3 MHz.
[0023]
When titanium nitride is used instead of titanium, the Young's modulus is about 120 Gpa and the temperature coefficient is minus 0.3% / K. In order to obtain a resonance frequency similar to that of titanium, the length of the cantilever (support leg 104) needs to be 4 μm. By doing so, the thermal resistance of the cantilever is increased, so the “escape” of heat from the counter electrode 103 is reduced, and the sensitivity is improved by about 1.5 times.
[0024]
As another specific example, the above-described infrared absorbing layer 112 is supported by a support leg 104 made of titanium nitride having a length of 7 μm and a cross-sectional area of 0.3 μm ² , and an infrared optical system having an F value of 1.0 for an infrared wavelength of 10 μm band. When the light is condensed, approximately 85% of the light is absorbed by the infrared absorption layer 112, and the 1K temperature change of the subject becomes a 1 mK temperature change at the counter electrode. Converting this to a change in resonance frequency corresponds to a change of about 5 Hz. This changes the amplitude by about 7%. When this is measured as the integral value of the capacitance between the amplitude measuring lower electrode 107 and the counter electrode 103 over a certain period of time, a change of approximately 5% is obtained.
[0025]
When this capacitance change is expressed by NETD (noise equivalent temperature difference) used as an index of sensitivity of the infrared imaging device, it corresponds to about 10 mK. This sensitivity is very good. Further, the linearity is also good within the range of the subject temperature difference of 10K.
[0026]
FIG. 4 is a schematic diagram illustrating an example of a circuit configuration of the infrared imaging element of the present embodiment.
Each row is selected by the vertical shift register 404, and an AC voltage is applied from the oscillator 410 to the sensor 101 in each row via the buffer 405. The selection time can be set to about 25 microseconds, for example. The sensor 101 is designed in advance to vibrate at a predetermined resonance frequency. The oscillator 410 applies an alternating voltage with a constant frequency to each sensor and vibrates at a constant frequency. The frequency of the AC voltage applied from the oscillator 410 can typically be set as a resonance frequency of each sensor set in advance.
[0027]
When infrared rays are incident on each sensor vibrating at a constant frequency in this way, the frequency shift amount from the resonance frequency differs depending on the amount of incident infrared rays in each sensor. The amplitude differs for each sensor) and the capacitance changes. This is converted into a voltage signal or current signal using a capacitance change detection circuit 407 using an RC oscillation circuit, etc., sequentially selected by a horizontal shift register 406, amplified by an output amplifier 408, and output to an output terminal 409. .
[0028]
FIG. 5 is a graph showing the relationship between the temperature of the counter electrode and the capacitance in the infrared imaging device of this example. In the figure, the state represented by the symbol P corresponds to the resonance frequency. The sensor temperature varies depending on the amount of infrared light incident on each pixel (counter electrode), and the frequency that vibrates correspondingly deviates from the resonance frequency.
[0029]
However, since this detection circuit only measures the absolute value of the difference from the resonance frequency, if the absolute value is the same, the temperature of the subject is higher and lower than the reference temperature (temperature corresponding to the resonance frequency). It will be reflected in the same way. In order to prevent this, it is necessary to set on the basis of photographing a uniform subject at a high temperature exceeding the temperature range of the subject, for example, 100 ° C. The fact that the reference temperature is high requires that the resonance frequency be set to a lower frequency, as can be seen from FIG. However, even in such a case, if the subject has a part higher than the reference temperature (for example, 100 ° C.), the part appears to be a part having a low temperature.
[0030]
FIG. 6 is a schematic diagram showing an infrared imaging device that solves this problem as a second specific example of the present invention.
[0031]
That is, an AC voltage of, for example, 2 MHz to 2.5 MHz is applied to one row of pixels (sensor 101) selected by the vertical shift register 504 from the frequency sweep circuit 510 via the buffer 505 while sequentially changing the frequency.
[0032]
First, prior to photographing (measurement), the shutter is closed in advance and a certain level of infrared (reference infrared) is incident on each pixel, and the resonance frequency at that time is stored as a reference value in the camera circuit. Next, the shutter is opened to start photographing, and an alternating voltage of 2 MHz to 2.5 MHz, for example, is sequentially applied from the frequency sweep circuit 510 to the pixels in each row, and the displacement of the resonance frequency due to the incidence of infrared rays is detected by the capacitance peak detection circuit 507. Are detected as electrical signals.
[0033]
That is, the resonance frequency of each pixel 101 in a state where infrared rays are irradiated is measured. Then, the direction and amount of “deviation” are detected by comparing with the reference value of the resonance frequency based on the reference infrared rays measured in advance. These signals are sequentially selected by the horizontal shift register 506, amplified by the output amplifier 508, and output to the output terminal 509.
[0034]
Using this embodiment, not only the absolute value of the temperature change but also the height can be discriminated. In addition, since the resonance frequency of the reference infrared rays is measured in advance, it is also effective when there is a “variation” in the resonance frequency of individual pixels or when the temperature of the entire image sensor changes during operation. Furthermore, the dynamic range of the infrared imaging device can be adjusted by changing the frequency range to be swept.
[0035]
However, the present invention is not limited to those using reference infrared rays. In other words, in the case where influences such as “variation” of each sensor and the ambient temperature can be ignored, infrared irradiation may be started immediately without measuring the reference value of the resonance frequency by the reference infrared rays in advance. .
[0036]
Next, one embodiment of the method for manufacturing an infrared imaging device of the present invention will be described.
[0037]
7 to 23 are process diagrams showing a method for manufacturing an infrared imaging device of the present invention.
[0038]
That is, in these figures, a process of forming a complementary metal-oxide-semiconductor (CMOS) transistor that constitutes a signal processing circuit and a scanner circuit for performing X and Y addresses on a silicon substrate and a counter electrode are formed. Represents a process.
[0039]
First, as shown in FIG. 7, a p-type silicon substrate is prepared. Then, after forming the element isolation region 802 as shown in FIG. 8, the n-MOS region is masked with a photoresist 803 to form a well of the p-MOS region as shown in FIG. Phosphorus ions 804 are implanted.
[0040]
Thereafter, as shown in FIG. 10, a gate oxide film 805 and a polycrystalline silicon 806 serving as a gate material are stacked. Next, as shown in FIG. 11, in order to simultaneously form the source / drain region 807 of the n-MOS region and the region 808 to be the ground electrode of the counter electrode 103, the p-MOS region is masked with a photoresist 809, Arsenic ions 810 are implanted.
[0041]
Next, as shown in FIG. 12, in order to form the source / drain region 811 of the p-MOS region, the n-MOS region in which the transistor has already been formed is masked with a photoresist 812, and boron ions 813 are implanted. Thereafter, as shown in FIG. 13, the photoresist 812 is removed by oxygen plasma etching, and the n-MOS transistor 814 and the p-MOS transistor 815 are completed.
[0042]
Next, as shown in FIG. 14, a silicon oxide film 816 is stacked on these transistors. Further, as shown in FIG. 15, openings are formed in the silicon oxide film 816, and plugs 817A serving as contacts are embedded in the gates, sources, and drains of the transistors 814 and 815, respectively. At that time, a contact 817B to be a wiring of the upper electrode of the sensor is also formed.
[0043]
Next, as shown in FIG. 16, a first aluminum layer 818B to be a wiring is laminated together with a titanium (Ti) -based barrier metal 818A and a cap metal 818C. At this time, the excitation electrode 108 and the amplitude measurement electrode 107 of the sensor lower electrode are also formed. Further, an interlayer film 821 made of a silicon oxide film is also formed.
[0044]
Next, as shown in FIG. 17, a portion of the interlayer film 821 above the lower electrodes 107 and 108 in the sensor region is subjected to oxide film RIE (reactive ion etching) to form a lower electrode cap metal 818C. Etching is performed until a cavity 822 is formed. More preferably, silicon oxide or silicon nitride is laminated to a thickness of about 50 nm as a protective film for the lower electrodes 107 and 108 on the surface of the titanium-based cap metal 818C.
[0045]
Next, as shown in FIG. 18, amorphous silicon 823 serving as a sacrificial layer is embedded in the cavity 822 once formed. Next, as shown in FIG. 19, a second aluminum layer 824 serving as a wiring layer, 825A to 825C serving as an upper electrode (counter electrode 103) of the sensor, and bonding pads 826A to 826C are formed, and an interlayer made of silicon oxide is formed. A film 827 is stacked. Here, the electrode 825A is a titanium metal, the electrode 825B is aluminum, and the electrode 825C is a cap metal layer made of titanium or the like. Similarly, the bonding pad 826 (826A to 826C) is a cap metal layer made of titanium metal, the electrode 826B is aluminum, and the electrode 826C is titanium. Note that it is more preferable that silicon oxide or silicon nitride is stacked to a thickness of about 50 nm as a protective film for the counter electrode 103 before the second aluminum layer 824 is formed.
[0046]
Next, in order to increase the thermal resistance of the support legs of the sensor, as shown in FIG. 20, the interlayer film 827, the cap metal 825C, and the aluminum electrode 825B are sequentially etched while changing the etching conditions, so that titanium ( An upper electrode wiring 828 made of Ti) metal is formed. Further, in order to protect the whole, a silicon nitride film 829 is formed as shown in FIG.
[0047]
Next, as illustrated in FIG. 22, the nitride film 829, the interlayer film 827, and the cap metal layer 826 </ b> C are sequentially etched by RIE also on the bonding pad 826 to form the opening 830. In addition, in order to perform thermal separation of the counter electrode, the nitride film 829 and the interlayer film 827 around the counter electrode are selectively RIE etched to form an etching hole 831 that reaches the sacrifice layer 823. During this etching, the bonding pad 826 is masked with a photoresist (not shown).
[0048]
Finally, the sacrificial layer 823 is etched away by silicon etching using XeF ₂ (xenon difluoride) to form the cavity 106, so that the infrared imaging element of the present invention as shown in FIG. Department is completed.
[0049]
The embodiments of the present invention have been described above by exemplifying specific examples. However, the present invention is not limited to the specific examples described above.
[0050]
For example, the materials, shapes, thicknesses, arrangement relationships, etc. of each semiconductor layer, insulating layer, metal layer, etc. constituting the infrared sensor or infrared imaging device are appropriately designed and implemented by those skilled in the art. As long as a summary is included, it is included in the scope of the present invention.
[0051]
In addition, the present invention can be implemented with various modifications without departing from the spirit thereof, and these embodiments are also included in the scope of the present invention.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an infrared sensor and an infrared imaging device having excellent low noise characteristics, high sensitivity, and good linearity of an output signal with respect to a temperature rise. Industrial benefits are tremendous.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a part of a thermal infrared imaging device according to an embodiment of the present invention.
FIG. 2 is a plan view of the infrared imaging device of the present embodiment.
FIG. 3 is a graph showing an example of the relationship between the temperature of the counter electrode 103 and the resonance frequency in the present invention.
FIG. 4 is a schematic diagram illustrating an example of a circuit configuration of the infrared imaging element according to the embodiment of the present invention.
FIG. 5 is a graph showing the relationship between the temperature of a counter electrode and capacitance in an infrared imaging device of a specific example of the present invention.
FIG. 6 is a schematic diagram illustrating an infrared imaging device according to a second specific example of the present invention.
FIG. 7 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 8 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 9 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 10 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 11 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 12 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 13 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 14 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 15 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 16 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 17 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 18 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 19 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 20 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 21 is a process diagram illustrating the manufacturing method of the infrared imaging element of the present invention.
FIG. 22 is a process diagram illustrating a method for manufacturing an infrared imaging device of the present invention.
FIG. 23 is a process diagram illustrating the manufacturing method of the infrared imaging element of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 Infrared sensor 102 Silicon substrate 103 Opposite electrode 104 Support leg 105 Vertical signal line 106 Hollow structure 106 Hollow part 107 Amplitude measurement lower electrode 108 Excitation lower electrode 110 Post 112 Infrared absorption layer 210 Infrared 404 Vertical shift register 406 Horizontal shift register 407 Capacitance change detection circuit 408 Sequential output amplifier 409 Output terminal 410 Oscillator 504 Vertical shift register 506 Horizontal shift register 507 Capacitance peak detection circuit 508 Output amplifier 509 Output terminal 510 Frequency sweep circuit 802 Element isolation region 803 Photoresist 804 Phosphorus ion 805 Gate oxide film 806 Polycrystalline silicon 807 Drain region 808 Region 809 Photoresist 810 Arsenic ion 811 Drain region 812 Photoresist 813 Boron ion 14,815 Transistor 816 Silicon oxide film 817 Plug 818A Barrier metal 818B Aluminum layer 818C Cap metal 821 Interlayer film 822 Cavity 823 Amorphous silicon 823 Sacrificial layer 824 Aluminum layer 825A Electrode 825B Aluminum electrode 825C Cap metal 826 Bonding pad 826C Cap metal layer 827 Interlayer film 828 Upper electrode wiring 829 Silicon nitride film 830 Opening 831 Etching hole

Claims (9)

A plurality of infrared sensors provided in a substantially matrix on the substrate;
A frequency sweep circuit;
Storage means;
With
Each of the plurality of infrared sensors is
First and second electrodes provided on the surface of the substrate;
A third electrode provided on the substrate spaced apart from the first and second electrodes and facing the electrodes;
An infrared absorbing layer provided on the third electrode for absorbing incident infrared radiation and converting it into heat;
A support leg for supporting the third electrode and the infrared absorption layer in a state of being separated from the first and second electrodes;
Have
When the infrared absorbing layer absorbs incident infrared rays and converts it into heat, the temperature of the support leg changes, and the Young's modulus of the material constituting the support leg changes in response to the change in temperature. The resonance frequency of the third electrode and the infrared absorption layer generated using the fixed end of the support leg as a fulcrum changes,
The frequency sweep circuit applies the AC voltage having a variable frequency between the first electrode and the third electrode of each of the plurality of infrared sensors, thereby using the fixed end of the support leg as a fulcrum. 3 and the infrared absorbing layer are vibrated,
The storage means stores the resonance frequency of the infrared absorption layer obtained by making a certain level of infrared rays enter each of the plurality of infrared sensors as a reference value,
An infrared imaging device, wherein the resonance frequency of the infrared absorption layer measured by the frequency sweep circuit for each of the plurality of infrared sensors is compared with a reference value stored in the storage means.   The infrared imaging device according to claim 1, further comprising a capacitance detection circuit that measures a capacitance between the second electrode and the third electrode.   The infrared imaging device according to claim 1, wherein the support leg is formed as a part of the third electrode extending.   The infrared imaging element according to claim 1, wherein the support leg includes a portion made of at least one of titanium, titanium nitride, and a composite thereof.   The infrared imaging element according to claim 1, wherein the infrared absorption layer is formed by stacking silicon oxide and silicon nitride.   The infrared imaging device according to claim 1, further comprising selection means for selecting any of the plurality of infrared sensors.   The infrared imaging element according to claim 1, wherein each of the plurality of infrared sensors has a single support leg. The third electrode has a first layer made of a metal having a relatively high thermal conductivity, and a second layer made of a metal having a relatively low thermal conductivity,
The infrared imaging device according to claim 1, wherein the support leg includes the second layer extending from the third electrode.   The infrared absorption layer is formed by projecting both sides of the support leg from above the third electrode toward a fixed end of the support leg. An infrared imaging device according to 1.

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