Infrared sensor

Abstract

An infrared sensor (201) is provided with: a substrate; an infrared sensor element (10) that generates an infrared detection signal; a parallel switch (SW2) that is connected to the infrared sensor element (10); and an amplifier (112) that amplifies the infrared detection signal generated by the infrared sensor element (10). An infrared sensor element (10) has a light receiving unit, a hollow support unit that hollowly supports the light receiving unit so that a gap is formed between a substrate and the light receiving unit, and a thermoelectric conversion unit that generates an infrared detection signal on the basis of heat generated by the light receiving unit. The thermoelectric conversion unit includes a first terminal (T1) that outputs an infrared detection signal, and a second terminal (T2) that is held at a predetermined potential. The parallel switch (SW2) connects the first terminal (T1) and the second terminal (T2) in a short-circuited manner. The amplifier (112) is a current input type amplifier.

Description

Technical Field

[0001] The present disclosure relates to an infrared sensor. Background Art

[0002] There is known an infrared sensor using an infrared sensor element that detects infrared rays by heat generated when a light-receiving portion receives infrared rays. Further, as such an infrared sensor, there is known an infrared imaging element (infrared image sensor) in which infrared sensor elements are arranged in an array as pixels. In order to arrange a large number of pixels at high density and obtain a high-definition infrared image with a small imaging element, there is a means of reducing the area of the infrared sensor element per pixel on average. This can be achieved by miniaturization of semiconductor manufacturing processes. A signal generated from the infrared sensor element per pixel on average is processed by an analog front end. Hereinafter, the analog front end will be referred to as "AFE". The AFE mainly consists of, for example, an amplifier, a filter, and an AD (Analog-to-Digital) converter. In the case where the infrared sensor has one AFE with respect to a plurality of infrared sensor elements, a pixel selection switch for selecting a part of the pixels connected to the AFE from among the plurality of infrared sensor elements is provided between the infrared sensor element and the AFE. When the pixels selected by the pixel selection switch are switched at a certain time interval, scanning of the pixels can be achieved. That is, an infrared detection signal is output from the sequentially selected pixels to the AFE. The pixel selection switch and the AFE can also be realized by a fine semiconductor manufacturing process. The infrared sensor element, the pixel selection switch, and the AFE can be integrated on the same semiconductor substrate, or a part thereof can be fabricated as another chip and integrated by mounting.

[0003] On the other hand, if the light-receiving area of the infrared sensor element is reduced, the infrared energy (power) received becomes weak. Furthermore, if a light-receiving part with a small area is used, it is difficult to obtain a spatial temperature difference. In an infrared sensor element such as a thermocouple or a thermopile that uses the Seebeck effect, i.e., the electromotive force based on the temperature difference, as the infrared detection signal, if the temperature difference becomes small, the electromotive force becomes weak and the S / N (Signal / Noise) decreases. To address this problem, Patent Document 1 discloses a technique in which a light-receiving part is hollow-supported by a hollow support part having a phonon crystal structure with excellent adiabatic properties in an infrared sensor. Thereby, it is possible to maintain a spatial temperature difference and suppress the decrease in S / N. Specifically, in a thermopile-type infrared sensor structure having a substrate, a light-receiving part separated from the substrate, and a hollow support part that supports the light-receiving part so as to be separated above the substrate, a phonon crystal structure is provided in the hollow support part, a cold junction is provided on the substrate side, and a warm junction is provided on the light-receiving part side. As a result, the temperature of the warm junction on the light-receiving part whose temperature has changed due to the radiation of infrared rays can easily maintain the temperature difference from the cold junction temperature due to the high adiabaticity of the phonon crystal structure, and the electromotive force generated by the Seebeck effect can be effectively obtained.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication No. 2019 / 225058 Summary of the Invention

[0007] In the present disclosure, an infrared sensor capable of improving the detection accuracy of infrared rays is provided.

[0008] An infrared sensor according to an aspect of the present disclosure includes a substrate, a sensor element that generates an infrared detection signal, a first switch connected to the sensor element, and an amplifier that amplifies the infrared detection signal generated by the sensor element. The sensor element has a light-receiving part located above the substrate, a hollow support part that binds the substrate and the light-receiving part and hollow-supports the light-receiving part so as to form a gap between the substrate and the light-receiving part, and a thermoelectric conversion part that generates the infrared detection signal based on the heat generated by the light-receiving part. The thermoelectric conversion part includes a first terminal that outputs the infrared detection signal and a second terminal that is held at a predetermined potential. The first switch connects the first terminal and the second terminal in a short-circuitable manner. The amplifier is a current-input type amplifier.

[0009] An infrared sensor according to one aspect of the present disclosure includes: a substrate; a plurality of sensor elements that generate infrared detection signals; a plurality of first switches, each connected to one of the plurality of sensor elements in a one-to-one manner; an amplifier that amplifies the infrared detection signals generated by the plurality of sensor elements; a plurality of second switches, each connected to one of the plurality of sensor elements in a one-to-one manner, and independently switching the conduction and non-conduction between each of the plurality of sensor elements and the amplifier; and a third switch, connected to the input terminal of the amplifier, capable of shorting the input terminal to a reference potential. Each of the plurality of sensor elements has: a light-receiving portion located above the substrate; a hollow support portion that combines the substrate and the light-receiving portion and hollowly supports the light-receiving portion so as to form a gap between the substrate and the light-receiving portion; and a thermoelectric conversion portion that generates the infrared detection signal based on heat generated by the light-receiving portion. The thermoelectric conversion portion includes a first terminal that outputs the infrared detection signal and a second terminal that is held at a predetermined potential. Each of the plurality of first switches connects the first terminal and the second terminal in a short-circuitable manner. Each of the plurality of second switches is a semiconductor-type switch, and the amplifier is a voltage-input type amplifier.

[0010] According to the present disclosure, the detection accuracy of infrared rays can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A It is a diagram showing the circuit configuration of the infrared sensor constituting Example 1.

[0012] Figure 1B It is a diagram showing the circuit configuration of the infrared sensor constituting Example 2.

[0013] Figure 1C It is a diagram showing the circuit configuration of the infrared sensor constituting Example 3.

[0014] Figure 1D It is a diagram showing the circuit configuration of the infrared sensor constituting Example 4.

[0015] Figure 1E It is a diagram showing the circuit configuration of the infrared sensor constituting Example 5.

[0016] Figure 1F It is for explaining Figures 1A - 1E the result obtained by calculating the leakage of the infrared detection signal in the shown configuration example.

[0017] Figure 2 It is a block diagram showing the overall configuration of the infrared sensor of Embodiment 1.

[0018] Figure 3AIt is a cross-sectional view showing the infrared sensor element of Embodiment 1.

[0019] Figure 3B It is a plan view when observing the infrared sensor element of Embodiment 1 from above.

[0020] Figure 4A It is a cross-sectional view for explaining the manufacturing method of the infrared sensor of Embodiment 1.

[0021] Figure 4B It is a cross-sectional view for explaining the manufacturing method of the infrared sensor of Embodiment 1.

[0022] Figure 4C It is a cross-sectional view for explaining the manufacturing method of the infrared sensor of Embodiment 1.

[0023] Figure 5 It is a diagram showing the circuit configuration of the infrared sensor of Embodiment 1.

[0024] Figure 6 It is a diagram showing the circuit configuration of the infrared sensor of Comparative Example 1.

[0025] Figure 7 It is a diagram showing the circuit configuration of the infrared sensor of Comparative Example 2.

[0026] Figure 8 It is a diagram for explaining the result obtained by calculating the leakage of the infrared detection signal in the infrared sensors of Embodiment 1, Comparative Example 1, and Comparative Example 2.

[0027] Figure 9 It is a block diagram showing the overall configuration of the infrared sensor of Embodiment 2.

[0028] Figure 10 It is a diagram showing the circuit configuration of the infrared sensor of Embodiment 2.

[0029] Figure 11 It is a diagram for explaining the result obtained by calculating the leakage of the infrared detection signal in the infrared sensor of Embodiment 2.

[0030] Figure 12A It is a diagram showing an example of the switching operation in the infrared detection mode of the infrared sensor of Embodiment 2.

[0031] Figure 12B It is a diagram showing another example of the switching operation in the infrared detection mode of the infrared sensor of Embodiment 2.

[0032] Figure 12C It is a plan view showing an example of the arrangement of the infrared sensor elements in the element array.

[0033] Figure 13 It is a block diagram showing the overall configuration of the infrared sensor of Embodiment 3.

[0034] Figure 14 It is a diagram showing the circuit configuration of the infrared sensor of Embodiment 3.

[0035] Figure 15 It is a diagram for explaining the result obtained by calculating the leakage of the infrared detection signal in the infrared sensor of Embodiment 3. Detailed Embodiment

[0036] (Insight underlying the present disclosure)

[0037] In an infrared sensor, improvement in the detection accuracy of infrared rays has been constantly sought. The technique described in Patent Document 1 above is a technique for improving the detection accuracy of infrared rays by improving (increasing) the S component of the S / N. On the other hand, it is also possible to improve (reduce) the N component of the S / N to improve the detection accuracy of infrared rays. For example, as a method for improving the N component of the S / N, there is a method of eliminating the drift of the offset voltage generated by an amplifier (that is, the offset component) and 1 / f noise by signal processing. As an example of a specific method, a method of providing a mechanical shutter between the infrared sensor and the infrared source and performing signal processing on the signal obtained by opening and closing the mechanical shutter can be cited.

[0038] In this method, as the first stage, the output information of the AFE when the shutter is "closed" is acquired. That is, the output information output from the AFE in a state where no infrared detection signal is output from the infrared sensor element to the AFE is acquired. Sometimes, the processing method of outputting information from the AFE in a state where no infrared detection signal is output from the infrared sensor element to the AFE as described above is hereinafter referred to as the "noise measurement mode". The output information of the AFE when the shutter is "closed" becomes the offset component of the amplifier and 1 / f noise and does not include information from infrared rays.

[0039] Next, as the second stage, the output information of the AFE when the shutter is "open" is acquired. That is, an infrared detection signal is output from the infrared sensor element to the AFE, and the output information output by processing the infrared detection signal by the AFE is acquired. Sometimes, the processing method of outputting an infrared detection signal from the infrared sensor element to the AFE and outputting information by processing the infrared detection signal by the AFE as described above is hereinafter referred to as the "infrared measurement mode". The output information of the AFE when the shutter is "open" is information obtained by adding the offset component of the amplifier and 1 / f noise to the information from infrared rays.

[0040] Finally, as the third stage, the output information of the second stage is subtracted from the output information of the first stage. The subtracted output information becomes the infrared ray information after eliminating (removing) the offset component of the amplifier and the 1 / f noise from the information based on the infrared ray detection signal. As a result, the N component of the S / N can be reduced, and the detection accuracy of the infrared ray sensor can be improved. The output information of the AFE obtained in the first stage and the second stage can be converted into encoded digital information by an AD converter. Thereby, the differential operation processing in the third stage becomes easy. In addition, the order of the noise measurement mode and the infrared ray measurement mode can be reversed. No matter which of the noise measurement mode and the infrared ray measurement mode is performed first, the two measurement modes of the noise measurement mode and the infrared ray measurement mode are performed during a short period in which the drift of the offset voltage of the amplifier and the change of the 1 / f noise can be ignored.

[0041] Since the mechanical shutter is not suitable for a small imaging element, the opening and closing of the shutter can be simulated by a semiconductor switch, and the semiconductor switch is used to implement the noise measurement mode and the infrared ray measurement mode. For example, the noise measurement mode and the infrared ray measurement mode can be switched by turning on (conducting) and off (cutting off) the semiconductor switch. Hereinafter, such a semiconductor switch may sometimes be referred to as a "measurement mode switching switch". The aforementioned pixel selection switch also functions as the measurement mode switching switch, for example. For example, even when an infrared ray detection signal is being generated by the infrared ray sensor element, the noise measurement mode is realized by turning off (closing) the measurement mode switching switch provided between the infrared ray sensor element and the AFE so that the infrared ray sensor element and the AFE are non-conductive, and the infrared ray measurement mode is realized by turning on (opening) the measurement mode switching switch so that the infrared ray sensor element and the AFE are conductive.

[0042] The inventors of the present application have found the following problems in the case of switching the measurement mode using such a semiconductor switch.

[0043] A semiconductor switch using a general semiconductor device is excellent in the high speed of the switch as a whole compared with a mechanical switch, but has a problem in isolation (insulation). Poor isolation means that even in the off state of the switch, there is a slight leakage of current and the resistance of the switch cannot be regarded as infinite. Therefore, the stronger the signal intensity of the infrared ray detection signal generated by the infrared ray sensor element, the larger the signal leaking from the off-state measurement mode switching switch. That is, when the signal intensity of the infrared ray detection signal generated by the infrared ray sensor element is strong, in the noise measurement mode, the infrared ray detection signal that cannot be completely blocked by the measurement mode switching switch is output to the AFE, and the offset component of the amplifier and the 1 / f noise cannot be accurately obtained.

[0044] In addition, in the case of a configuration in which a plurality of pixels are connected to one AFE, in the infrared measurement mode, if an infrared detection signal that cannot be completely blocked leaks from the pixel selection switch of a non-selected pixel and is input to the AFE in a superimposed manner with the infrared detection signal of the selected pixel, the infrared information of the selected pixel cannot be accurately obtained.

[0045] Here, an example of the circuit configuration of an infrared sensor element, a measurement mode switching switch, and an amplifier will be shown, and the results of the research by the inventor of the present application on the relationship between the circuit configuration and the leakage of the above-described infrared detection signal will be described.

[0046] Figure 1A FIG. shows the circuit configuration of the infrared sensor according to Configuration Example 1. Figure 1B FIG. shows the circuit configuration of the infrared sensor according to Configuration Example 2. Figure 1C FIG. shows the circuit configuration of the infrared sensor according to Configuration Example 3. Figure 1D FIG. is a circuit diagram showing the circuit configuration of the infrared sensor according to Configuration Example 4. Figure 1E FIG. shows the circuit configuration of the infrared sensor according to Configuration Example 5. In addition, in Figures 1A - 1E , regarding the switch, in order to easily understand On and Off, it is shown as a mechanical switch, but in reality, it is a semiconductor type switch. The same applies to the subsequent figures showing the circuit configuration. In addition, in Figures 1A - 1E , the state of the switch in the noise measurement mode is shown.

[0047] As Figures 1A - 1E shown, Configuration Examples 1 to 5 are configuration examples of an infrared sensor in the case where one infrared sensor element 10 is connected to one amplifier 12.

[0048] As Figure 1A shown, the infrared sensor according to Configuration Example 1 includes one infrared sensor element 10, one series switch SW1, and one amplifier 12. The amplifier 12 is at least a part of the AFE. The AFE may have a filter and an AD converter (not shown in Figure 1A ) in addition to the amplifier 12. The same applies to Configuration Examples 2 to 5 described later.

[0049] The infrared sensor element 10 is, for example, an infrared sensor element including a light receiving portion and a thermopile that performs thermoelectric conversion of the heat of the light receiving portion. The thermopile of the infrared sensor element 10 is represented by a series connection of a voltage source that equivalently generates an electromotive force V Figure 1A as shown in IR and an internal resistance R 0 . The electromotive force V IRdepending on the amount of infrared absorption in the light-receiving section. The infrared sensor element 10 outputs an infrared detection signal corresponding to the electromotive force V IR The internal resistance R0 is mainly the resistance of the semiconductor that constitutes the thermopile.

[0050] The thermopile of the infrared sensor element 10 includes a first terminal T1 that outputs an infrared detection signal and a second terminal T2 that is maintained at a predetermined potential. In the illustrated example, the second terminal T2 is connected to the ground (ground wire), and the predetermined potential is the ground level. In the infrared sensor element 10, an electromotive force V is generated between the first terminal T1 and the second terminal T2 IR . In addition, the second terminal T2 can be maintained at a predetermined potential by applying a predetermined bias voltage to the second terminal T2.

[0051] The series switch SW1 is a semiconductor switch. For example, it is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The series switch SW1 is connected to the infrared sensor element 10 and the amplifier 12 in such a way that it can block the transmission of the infrared detection signal from the infrared sensor element 10 to the amplifier 12. The series switch SW1 is connected in series between the infrared sensor element 10 and the amplifier 12. One end of the series switch SW1 is connected to the first terminal T1, and the other end of the series switch SW1 is connected to the input terminal of the amplifier 12. In Figure 1A the illustrated example, the other end of the series switch SW1 is connected to the non-inverting input terminal of the operational amplifier. The series switch SW1 switches the conduction and non-conduction between the infrared sensor element 10 and the amplifier 12. In addition, in this specification, "blocking" and "non-conduction" of the switch indicate a state that is substantially blocking and non-conduction, and are expressions that also include the case where the signal leaks out without completely becoming non-conduction and blocking.

[0052] In Figure 1A the illustrated example, the amplifier 12 is a voltage amplifier. The voltage amplifier has, for example, an operational amplifier and two resistors. The voltage amplifier is constituted by, for example, a non-inverting amplifier circuit using an operational amplifier. Using the resistors R 1 and the resistor R 2 , the voltage gain G of this non-inverting amplifier circuit becomes 1 + (R 2 / R 1 ). Regarding the input impedance Z in of the amplifier 12, when the input resistance between the two input terminals of the operational amplifier is set to R i and the open-loop gain is set to A 0 , Zin = R i ·A 0 / G holds. For example, when R i = 100 MΩ, A 0 = 120 dB, and G = 1000, Z in = 100 GΩ. Therefore, the input impedance of amplifier 12 is very high.

[0053] Here, the resistance R SW1 of the series switch SW1 is assumed to be an ideal value that is infinite when the series switch SW1 is off and zero when the series switch SW1 is on. In this case, in the noise measurement mode, the infrared sensor turns off the series switch SW1 to make the infrared sensor element 10 non-conductive with the amplifier 12. As a result, the voltage applied to the input of the amplifier 12 becomes V IR ·Z in / (R 0 + R SW1 + Z in ) = 0, and no component corresponding to the electromotive force V IR generated by infrared irradiation appears at the output of the amplifier 12, and the offset component and 1 / f noise of the amplifier 12 are output from the amplifier 12.

[0054] In addition, in the infrared measurement mode, the infrared sensor turns on the series switch SW1 to connect the infrared sensor element 10 to the amplifier 12. As a result, the voltage applied to the input of the amplifier 12 becomes V IR ·Z in / (where R 0 << Z in ), and the sum of the signal obtained by multiplying the electromotive force V IR by the gain G and the offset component and 1 / f noise of the amplifier is output from the amplifier 12. If the output value of the amplifier 12 obtained in the infrared measurement mode is subtracted from the output value of the amplifier 12 obtained in the noise measurement mode, the infrared information G·V IR after eliminating the offset component and 1 / f noise of the amplifier 12 can be obtained.

[0055] However, in reality, the resistance R SW1 of the series switch SW1 is different from the ideal one and does not become infinite when the series switch SW1 is off. The resistance component of the series switch SW1 depends on the size and operating speed of the switching element.

[0056] Figure 1F is a diagram for explaining the result of calculating the leakage of the infrared detection signal in the configuration example shown in Figures 1A - 1E . InFigure 1F In Table 1, the states of the switches and the leakage rates of the infrared detection signals in the noise measurement mode, and the states of the switches and the errors of the infrared detection signals in the infrared measurement mode of the infrared sensors of Configuration Examples 1 to 5 are shown in tabular form in the rows marked "Configuration Example 1" to "Configuration Example 5". In Figure 1F Table 1, the leakage rates of the infrared detection signals are recorded in the column marked "Leakage Rate of Detection Signal (%)", and the errors of the infrared detection signals are recorded in the column marked "Error (%)".

[0057] The leakage rate of the infrared detection signal in the noise measurement mode is the ratio (%) of the voltage applied to the input of the amplifier 12 in the noise measurement mode to the electromotive force V IR generated by the infrared sensor element 10. In addition, the error of the infrared detection signal in the infrared measurement mode is the error (%) of the voltage applied to the input of the amplifier 12 in the infrared measurement mode with respect to the electromotive force V IR generated by the infrared sensor element 10. That is, the value obtained by subtracting the voltage applied to the input of the amplifier 12 from the electromotive force V IR generated by the infrared sensor element 10 is the ratio (%) with respect to the electromotive force V IR generated by the infrared sensor element 10. In addition, in Figure 1F Table 1, it is shown that: when the resistance when the series switch SW1 and the parallel switches SW2 and SW3 described later are off is set to 1 GΩ, the resistance when on is set to 100 Ω, and the input impedance Z in of the amplifier 12 is set to 100 GΩ, the leakage rate of the infrared detection signal and the error of the infrared detection signal are calculated.

[0058] As Figure 1F shown in the row of Configuration Example 1 in Table 1, in the infrared sensor of Configuration Example 1, the leakage rate of the infrared detection signal is 99.0%, and the voltage applied to the input of the amplifier 12 in the noise measurement mode also reaches 99.0% of the electromotive force V IR generated by the infrared sensor element 10. On the other hand, in the infrared sensor of Configuration Example 1, the error of the infrared detection signal is 0.0%, and in the infrared measurement mode, a voltage with an error of 0.0% with respect to the electromotive force V IR generated by the infrared sensor element 10 is applied to the input of the amplifier 12. Thus, in Figure 1AIn the infrared sensor of Configuration Example 1 shown, a large amount of infrared detection signals leak in the noise measurement mode and are applied to the input of the amplifier 12. Therefore, even if the difference (difference amount) of the output of the amplifier 12 is obtained in the infrared measurement mode and the noise measurement mode, it is impossible to accurately cancel the offset component and 1 / f noise of the amplifier 12. This is caused by the following reasons: the resistance value when the series switch SW1 is Off is not an ideal infinite value, and is not even a value sufficiently higher than the input impedance Z in compared to the amplifier 12.

[0059] Next, the infrared sensor of Configuration Example 2 will be described. As Figure 1B shown, the infrared sensor of Configuration Example 2 is a configuration in which a parallel switch SW2 is added to the configuration of the infrared sensor of Configuration Example 1.

[0060] The parallel switch SW2 is a semiconductor switch, for example, a MOSFET. The parallel switch SW2 connects the first terminal T1 and the second terminal T2 of the infrared sensor element 10 in a short-circuitable manner. The parallel switch SW2 is connected in parallel with the infrared sensor element 10 between the infrared sensor element 10 and the series switch SW1. One end of the parallel switch SW2 is connected to the first terminal T1 and one end of the series switch SW1, and the other end of the parallel switch SW2 is connected to the ground in the same manner as the second terminal T2. The other end of the parallel switch SW2 and the second terminal T2 are electrically connected in a manner of commonly connecting to the ground. Therefore, the other end of the parallel switch SW2 is also connected to the second terminal T2. By turning on the parallel switch SW2, the first terminal T1 and the second terminal T2 of the infrared sensor element 10 are short-circuited.

[0061] As Figure 1F shown, the infrared sensor of Configuration Example 2 turns off the series switch SW1 and turns on the parallel switch SW2 in the noise measurement mode. Thus, in the noise measurement mode, the infrared sensor element 10 is short-circuited by the parallel switch SW2. In addition, the infrared sensor of Configuration Example 2 turns on the series switch SW1 and turns off the parallel switch SW2 in the infrared measurement mode. Thus, the infrared detection signal from the infrared sensor element 10 is input to the amplifier 12.

[0062] As a result of such an operation, as Figure 1FAs shown in the row of "Configuration Example 2", the leakage rate of the infrared detection signal in the noise measurement mode is 0.1%, which is improved compared with Configuration Example 1. This is because: by turning the parallel switch SW2 to the On state, the infrared sensor element 10 is short-circuited, and it is difficult for the infrared detection signal to leak from the infrared sensor element 10. In addition, the error of the infrared detection signal in the infrared measurement mode is 0.0%. Therefore, by obtaining the difference between the outputs of the amplifier 12 in the infrared measurement mode and the noise measurement mode, the offset component and 1 / f noise of the amplifier 12 can be eliminated.

[0063] Next, the infrared sensor of Configuration Example 3 will be described. As Figure 1C shown, the infrared sensor of Configuration Example 3 is a configuration in which a parallel switch SW3 is added to the configuration of the infrared sensor of Configuration Example 1.

[0064] The parallel switch SW3 is a semiconductor switch, for example, a MOSFET. The parallel switch SW3 connects the input terminal of the amplifier 12 to the reference potential in a short-circuitable manner. The parallel switch SW3 is connected in parallel with the infrared sensor element 10 between the series switch SW1 and the amplifier 12. One end of the parallel switch SW3 is connected to the other end of the series switch SW1 and the input terminal of the amplifier 12, and the other end of the parallel switch SW3 is connected to the ground. In Figure 1C the example shown, one end of the parallel switch SW3 is connected to the non-inverting input terminal of the operational amplifier. The parallel switch SW3 switches the conduction and non-conduction between the input terminal of the amplifier 12 and the ground. By turning the parallel switch SW3 to the On state, the input terminal of the amplifier 12 is connected to the ground level as the reference potential. In addition, the reference potential is not limited to the ground level, and a predetermined value can be arbitrarily set. For example, in the case of driving the amplifier 12 in a single-pole manner, the reference potential can be set to approximately half of the driving DC (Direct Current) voltage of the amplifier 12.

[0065] As Figure 1F shown, in the infrared sensor of Configuration Example 3, the series switch SW1 is turned to Off and the parallel switch SW3 is turned to On in the noise measurement mode. Thus, in the noise measurement mode, the input terminal of the amplifier 12 is short-circuited to the reference potential by the parallel switch SW3. In addition, in the infrared sensor of Configuration Example 3, the series switch SW1 is turned to On and the parallel switch SW3 is turned to Off in the infrared measurement mode. Thus, the infrared detection signal from the infrared sensor element 10 is input to the amplifier 12.

[0066] As a result of such an operation: As Figure 1FAs shown in the row of "Constitution Example 3", the leakage rate of the infrared detection signal in the noise measurement mode is 0.0%, which is improved compared with Constitution Example 1. This is because: by turning the parallel switch SW3 to the On state, the input terminal of the amplifier 12 is short-circuited to the reference potential, and it is difficult for the infrared detection signal leaking from the infrared sensor element 10 to affect the input to the amplifier 12. In addition, the error of the infrared detection signal in the infrared measurement mode is 0.0%. Therefore, by obtaining the difference between the outputs of the amplifier 12 in the infrared measurement mode and the noise measurement mode, the offset component and 1 / f noise of the amplifier 12 can be eliminated.

[0067] Next, the infrared sensor of Constitution Example 4 will be described. As Figure 1D shown, the infrared sensor of Constitution Example 4 is a configuration in which the series switch SW1 is removed from the configuration of the infrared sensor of Constitution Example 2, and only the parallel switch SW2 is arranged as the switch connected to the infrared sensor element 10.

[0068] In the infrared sensor of Constitution Example 4, since the series switch SW1 is removed, one end of the parallel switch SW2 is connected not to one end of the series switch SW1 but to the input terminal of the amplifier 12. Therefore, the parallel switch SW2 also has the same function as the parallel switch SW3, and also functions to switch the conduction and non-conduction between the input terminal of the amplifier 12 and the ground.

[0069] As Figure 1F shown, the infrared sensor of Constitution Example 4 turns the parallel switch SW2 to On in the noise measurement mode. As a result, the second terminal T2 of the infrared sensor element 10 and the input terminal of the amplifier 12 are connected to the reference potential (ground level in the example shown in Figure 1F ). In addition, the first terminal T1 is short-circuited to the second terminal T2. In addition, the infrared sensor of Constitution Example 4 turns the parallel switch SW2 to Off in the infrared measurement mode. As a result, the infrared detection signal from the infrared sensor element 10 is input to the amplifier 12.

[0070] As a result of such an operation, as Figure 1F shown in the row of "Constitution Example 4", the leakage rate of the infrared detection signal in the noise measurement mode is 0.1%, which is improved compared with Constitution Example 1. The reason is the same as the explanation in Constitution Example 2 and Constitution Example 3. In addition, the error of the infrared detection signal in the infrared measurement mode is 0.0%. Therefore, by obtaining the difference between the outputs of the amplifier 12 in the infrared measurement mode and the noise measurement mode, the offset component and 1 / f noise of the amplifier 12 can be eliminated.

[0071] Next, the infrared sensor of Constitution Example 5 will be described. As Figure 1EAs shown, the infrared sensor of Configuration Example 5 is a configuration in which a parallel switch SW2 and a parallel switch SW3 are added to the configuration of the infrared sensor of Configuration Example 1, and the parallel switch SW2, the series switch SW1, and the parallel switch SW3 are connected in a π shape.

[0072] The infrared sensor of Configuration Example 5 performs an operation that combines the operations of the switches of the infrared sensor of Configuration Example 2 and the infrared sensor of Configuration Example 3. Specifically, as Figure 1F shown, the infrared sensor of Configuration Example 5 turns on the parallel switch SW2, turns off the series switch SW1, and turns on the parallel switch SW3 in the noise measurement mode. In addition, the infrared sensor of Configuration Example 5 turns off the parallel switch SW2, turns on the series switch SW1, and turns off the parallel switch SW3 in the infrared measurement mode.

[0073] As a result of such an operation, as Figure 1F shown in the row of "Configuration Example 5", the leakage rate of the infrared detection signal in the noise measurement mode is 0.0%, which is improved compared to Configuration Example 1. The reason is the same as the explanation in Configuration Example 2 and Configuration Example 3. In addition, the error of the infrared detection signal in the infrared measurement mode is 0.0%. Therefore, by obtaining the difference in the outputs of the amplifier 12 in the infrared measurement mode and the noise measurement mode, the offset component and 1 / f noise of the amplifier 12 can be eliminated.

[0074] From the above, it is shown that the problem of the configuration of the infrared sensor of Configuration Example 1 caused by the fact that the resistance value when the semiconductor switch is off is not an ideal infinite value can be solved by the configurations of the infrared sensors of Configuration Examples 2 to 5 that use at least one of the parallel switch SW2 and the parallel switch SW3. The inventors of the present application focused on: "the problem that the detection accuracy of the infrared sensor is reduced due to the leakage of the infrared detection signal caused by the characteristics of the semiconductor switch as described above", and "it can be improved by the configuration of the switch used in the infrared sensor".

[0075] In addition, the inventors of the present application studied applying the above research results to an infrared sensor having a plurality of infrared sensor elements 10. When the infrared sensor element 10 includes a plurality of infrared sensor elements 10, by connecting the infrared sensor elements 10 to the amplifier 12 in a multiple-to-one manner, it is not necessary to have the same number of amplifiers 12 as the number of pixels (infrared sensor elements 10), so that the current consumption required for driving the amplifier 12 can be suppressed. That is, a plurality of pixels are allocated to one amplifier 12 in a time-sharing manner. Therefore, it takes a certain amount of time to switch the pixel selection switch to scan the pixels. However, from the perspective of the current consumption of the amplifier 12, it is preferably configured such that the infrared sensor elements 10 and the amplifier 12 are connected in a multiple-to-one manner within the range that can ensure the number of frames per second required for shooting.

[0076] However, if the configuration is such that the infrared sensor elements 10 and the amplifier 12 are connected in a multiple-to-one manner, it is expected that in the noise measurement mode, the infrared detection signals leaking from many infrared sensor elements 10 are likely to be superimposed and transmitted to the amplifier 12. In addition, it is expected that in the infrared measurement mode, the infrared detection signals leaking from many infrared sensor elements 10 other than the selected infrared sensor element 10 are likely to be superimposed and transmitted to the amplifier 12.

[0077] Then, the inventors of the present application studied applying the research results of the switch configuration in the above circuit configuration to an infrared sensor having a plurality of infrared sensor elements 10, thereby obtaining one aspect of the present disclosure. In addition, as a countermeasure against the leakage of the above infrared detection signal, research was also conducted on the amplifier, thereby obtaining one aspect of the present disclosure. The following details will be described.

[0078] (Summary of the present disclosure)

[0079] An example of the infrared sensor of the present disclosure is shown below.

[0080] The infrared sensor according to the first aspect of the present disclosure includes a substrate, a sensor element that generates an infrared detection signal, a first switch connected to the sensor element, and an amplifier that amplifies the infrared detection signal generated by the sensor element. The sensor element has: a light-receiving portion located above the substrate; a hollow support portion that combines the substrate and the light-receiving portion and hollowly supports the light-receiving portion so as to form a gap between the substrate and the light-receiving portion; and a thermoelectric conversion portion that generates the infrared detection signal based on heat generated by the light-receiving portion. The thermoelectric conversion portion includes a first terminal that outputs the infrared detection signal and a second terminal that is held at a predetermined potential. The first switch connects the first terminal and the second terminal so as to be short-circuitable. The amplifier is a current-input type amplifier.

[0081] Thus, without outputting the infrared detection signal from the sensor element to the amplifier, by short-circuiting the thermoelectric conversion portion using the first switch, it is difficult for the infrared detection signal generated by the sensor element to be output to the amplifier. Therefore, it is difficult to generate an error in the output from the amplifier without outputting the infrared detection signal from the sensor element to the amplifier. As a result, for example, in the noise measurement mode, the influence of the leakage of the infrared detection signal from the sensor element can be reduced, and the offset component and 1 / f noise of the amplifier can be measured. Therefore, according to the infrared sensor of the present aspect, the detection accuracy of infrared rays can be improved.

[0082] In addition, since the amplifier is a current-input type amplifier with a low input impedance, when the first switch is changed from the On state to the Off state when switching from the noise measurement mode to the infrared measurement mode, a current of approximately the same magnitude as the short-circuit current flowing in the thermoelectric conversion portion of the sensor element in the noise measurement mode flows from the sensor element to the amplifier in the infrared measurement mode. Therefore, for example, before and after this switching, the magnitude of the current flowing in the thermoelectric conversion portion of the sensor element hardly changes. Therefore, it is difficult for the Peltier effect opposite to the Seebeck effect to change in the thermoelectric conversion portion, and the temperature distribution of the thermoelectric conversion portion hardly changes. Therefore, even if the infrared information output from the amplifier immediately after this switching is read, an error generated during the redistribution process of the temperature distribution will not occur, and a good S / N can be ensured. Therefore, the infrared sensor of the present aspect can perform a highly accurate and high-speed detection operation.

[0083] Further, for example, the infrared sensor according to the second aspect of the present disclosure includes, based on the infrared sensor according to the first aspect, a plurality of the sensor elements and a plurality of the first switches. The infrared sensor further includes a plurality of second switches each connected to one of the plurality of sensor elements in a one-to-one manner. Each of the plurality of second switches is a semiconductor switch and independently switches the conduction and non-conduction between each of the plurality of sensor elements and the amplifier.

[0084] In this aspect, the plurality of second switches for selecting the sensor elements that output the infrared detection signal to the amplifier are semiconductor switches. Even when the plurality of second switches are in the off state, the resistance does not become an ideal infinite value, and the infrared detection signal leaks from the unselected sensor elements. Even in such a case, since the first switch is connected to each of the plurality of sensor elements and the amplifier is a current input type amplifier, similarly to the above, it is difficult to generate an error in the output from the amplifier when the infrared detection signals from the plurality of sensor elements are not output to the amplifier. As a result, for example, in the noise measurement mode, the influence of the leakage of the infrared detection signal from the sensor elements can be reduced, and the offset component and 1 / f noise of the amplifier can be measured. Further, for example, in the infrared measurement mode, the influence of the leakage of the infrared detection signal from the non-selected sensor elements can be reduced, and the infrared detection signal of the selected sensor element can be measured. Therefore, according to the infrared sensor of this aspect, the detection accuracy of infrared rays can be improved.

[0085] Further, for example, the infrared sensor according to the third aspect of the present disclosure includes, based on the infrared sensor according to the second aspect, a control circuit. The control circuit makes two or more of the plurality of second switches simultaneously conductive, so that two or more of the plurality of sensor elements connected to the two or more second switches output the infrared detection signal to the amplifier simultaneously.

[0086] Thereby, the infrared detection signals from two or more sensor elements are added and input to the amplifier, so that the output from the amplifier can be increased. Therefore, for example, even when the infrared detection signal generated by one sensor element is weak, the infrared detection signal can be increased and the S / N can be improved.

[0087] Further, for example, the infrared sensor according to the fourth aspect of the present disclosure includes, based on the infrared sensor according to any one of the first to third aspects, at least a part of the thermoelectric conversion unit is provided in the hollow support portion, and the hollow support portion has a phononic crystal structure.

[0088] Due to the heat insulation property of the phonon crystal structure of such a hollow support portion, it is difficult to release the heat of the light-receiving portion whose temperature has changed due to infrared irradiation. Therefore, the infrared detection sensitivity of the thermoelectric conversion portion is improved. On the other hand, if the hollow support portion has a phonon crystal structure, the thermal resistance of the hollow support portion increases due to the high heat insulation property of the phonon crystal structure. As a result, the thermal time constant of the thermal circuit composed of the hollow support portion and the light-receiving portion increases, and it takes time for the temperature distribution of the hollow support portion where the thermoelectric conversion portion is provided to redistribute. However, when switching from the noise measurement mode to the infrared measurement mode, it is difficult to change in terms of the Peltier effect opposite to the Seebeck effect in the thermoelectric conversion portion as described above, and the temperature distribution of the thermal circuit composed of the hollow support portion and the light-receiving portion where the thermoelectric conversion portion is provided hardly changes before and after this switching. Therefore, the increase in the thermal time constant caused by the phonon crystal structure hardly deteriorates the S / N and the high-speed detection operation.

[0089] In addition, the infrared sensor according to the fifth aspect of the present disclosure includes: a substrate; a plurality of sensor elements that generate infrared detection signals; a plurality of first switches each connected to one of the plurality of sensor elements in a one-to-one manner; an amplifier that amplifies the infrared detection signals generated by the plurality of sensor elements; a plurality of second switches each connected to one of the plurality of sensor elements in a one-to-one manner and independently switching the conduction and non-conduction between each of the plurality of sensor elements and the amplifier; and a third switch connected to the input terminal of the amplifier and capable of short-circuiting the input terminal to a reference potential. Each of the plurality of sensor elements has: a light-receiving portion located above the substrate; a hollow support portion that combines the substrate and the light-receiving portion and hollowly supports the light-receiving portion so as to form a gap between the substrate and the light-receiving portion; and a thermoelectric conversion portion that generates the infrared detection signal based on the heat generated by the light-receiving portion. The thermoelectric conversion portion includes a first terminal that outputs the infrared detection signal and a second terminal that is held at a predetermined potential. Each of the plurality of first switches connects the first terminal and the second terminal in a short-circuitable manner. Each of the plurality of second switches is a semiconductor type switch, and the amplifier is a voltage input type amplifier.

[0090] In this solution, the multiple second switches for selecting the sensor elements that output the infrared detection signal to the amplifier are semiconductor switches. Even in the Off state, the resistance of the multiple second switches does not become an ideal infinite value, and the infrared detection signal leaks from the unselected sensor elements. Even in such a case, when the infrared detection signal from the sensor element is not output to the amplifier, by short-circuiting the thermoelectric conversion unit using the first switch, the infrared detection signal generated by the sensor element is also difficult to be output to the amplifier. Moreover, even when the infrared detection signal leaks from the sensor element to the amplifier, the input terminal of the amplifier can be short-circuited to the reference potential through the third switch. Therefore, the leaked infrared detection signal is difficult to affect the input to the amplifier. As a result, it is difficult to generate an error in the output from the amplifier when the infrared detection signal from the sensor element is not output to the amplifier. Consequently, for example, in the noise measurement mode, the influence of the infrared detection signal leaking from the sensor element can be reduced, and the offset component and 1 / f noise of the amplifier can be measured. Additionally, for example, in the infrared measurement mode, the influence of the infrared detection signal leaking from the unselected sensor element can be reduced, and the infrared detection signal of the selected sensor element can be measured. Thus, according to the infrared sensor of this solution, the detection accuracy of infrared rays can be improved.

[0091] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0092] In addition, the embodiments described below are all embodiments showing general or specific examples. The numerical values, shapes, materials, constituent elements, arrangement positions and connection methods of the constituent elements, steps (processes), the order of steps (processes), etc. shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, among the constituent elements of the following embodiments, the constituent elements not described in the independent claims are described as optional constituent elements.

[0093] In addition, the drawings are schematic diagrams and are not necessarily drawn precisely. Therefore, for example, the scales in the respective drawings are not necessarily the same. In addition, in the respective drawings, the same reference numerals are assigned to substantially the same constituent elements, and repeated descriptions are omitted or simplified.

[0094] In addition, in this specification, terms indicating the relationality between elements such as parallelism, terms indicating the shapes of elements such as rectangles, and numerical ranges are not expressions indicating only strict meanings, but mean expressions including substantially equivalent ranges, for example, expressions with a difference of about several percent.

[0095] In addition, in this specification, terms such as "above" and "below" do not refer to the upward direction (vertically above) and downward direction (vertically below) in the absolute spatial sense, but are used as terms defined by the relative positional relationship. Specifically, the light-receiving side of the infrared sensor is set as "above", and the side opposite to the light-receiving side is set as "below". In addition, terms such as "above" and "below" are only used to specify the mutual configuration between components, and are not intended to limit the posture when the infrared sensor is used. In addition, terms such as "above" and "below" are applicable not only to the case where two components are arranged at intervals and there are other components between the two components, but also to the case where two components are arranged in close contact and the two components are in contact with each other.

[0096] In addition, in this specification, unless otherwise specified, "planar observation" refers to the case when observed from a direction perpendicular to the upper surface of the semiconductor substrate (that is, the thickness direction of the semiconductor substrate).

[0097] In addition, in this specification, unless otherwise specified, ordinal numbers such as "first" and "second" do not mean the number or order of components, but are used for the purpose of distinguishing components to avoid confusion of the same type of components.

[0098] (Embodiment 1)

[0099] Hereinafter, the infrared sensor of Embodiment 1 will be described.

[0100] [Overall Configuration]

[0101] First, the overall configuration of the infrared sensor of Embodiment 1 will be described.

[0102] Figure 2 It is a block diagram showing the overall configuration of the infrared sensor 1 of Embodiment 1.

[0103] As Figure 2 shown, the infrared sensor 1 includes an element array 10A composed of a plurality of infrared sensor elements 10, a switch circuit 11, an amplifier 12, and a control circuit 13. The infrared sensor element 10 is an example of a sensor element. The infrared sensor 1 is, for example, an infrared image sensor (infrared imaging element) in which a plurality of infrared sensor elements 10 are arranged as pixels. The infrared sensor 1 is, for example, an infrared sensor chip formed on a substrate 30 described later. In addition, a part of the infrared sensor 1 may also be formed on another substrate. For example, at least one of the amplifier 12 and the control circuit 13 may be formed on a substrate different from the substrate 30 on which the element array 10A and the switch circuit 11 are formed.

[0104] The element array 10A is composed of a plurality of infrared sensor elements 10 arranged in an array on a common substrate 30. In Figure 2 the block diagram, for convenience, the plurality of infrared sensor elements 10 are shown overlapping, but in reality, the plurality of infrared sensor elements 10 are arranged in an array in multiple columns in the longitudinal and transverse directions when viewed in a plane. Each of the plurality of infrared sensor elements 10 generates an infrared detection signal corresponding to the amount of infrared light received and outputs the generated infrared detection signal. In the present embodiment, the number of infrared sensor elements 10 is N (N is an integer of 2 or more).

[0105] The switch circuit 11 is a circuit having a plurality of switches and wirings and connecting the element array 10A to the amplifier 12. By turning on / off (connecting / disconnecting) the switches of the switch circuit 11, switching between the noise measurement mode and the infrared measurement mode, and scanning of pixels, etc. are performed. The detailed configuration of the switch circuit 11 will be described later.

[0106] The amplifier 12 amplifies the infrared detection signals generated by the plurality of infrared sensor elements 10. The amplifier 12 is a voltage input type amplifier with a high input impedance. The amplifier 12 is, for example, a voltage amplifier (voltage input / voltage output type amplifier), but as long as it is an active element with a high input impedance, it is not limited to a voltage amplifier and can also be a transconductance amplifier (voltage input / current output type amplifier) or a voltage follower (amplifier with a magnification of 1). The amplifier 12 is, for example, a part of the AFE. Although not shown, the infrared sensor 1 may also include a filter and an AD converter included in the AFE in addition to the amplifier 12. The amplifier 12 outputs the amplified infrared detection signal. The output from the amplifier 12 is, for example, input to the signal processing circuit 100. The output information from the amplifier 12 can be converted into encoded digital information by the AD converter.

[0107] The control circuit 13 controls the whole infrared sensor 1. For example, the control circuit 13 controls the operation of the switches of the switch circuit 11 by outputting a control signal. The control circuit 13 supplies, for example, a control signal (such as a voltage of high level or low level) for controlling the operation of the switches of the switch circuit 11 to the control terminals (such as gates) of the switches. In addition, the control circuit 13 can output a control signal for controlling the AFE. The control circuit 13 causes the infrared sensor 1 to operate in the infrared measurement mode and the noise measurement mode, and causes the output information in each of the infrared measurement mode and the noise measurement mode to be output to the amplifier 12. In addition, the infrared sensor 1 may not include the control circuit 13, and the infrared sensor 1 may be controlled by an external control device having the function of the control circuit 13.

[0108] The control circuit 13 includes, for example, one or more microcomputers or processors with a program for controlling the infrared sensor 1 built therein. The control circuit 13 may include a dedicated logic circuit for controlling the infrared sensor 1.

[0109] The signal processing circuit 100 performs various signal processes on the output from the amplifier 12. For example, the signal processing circuit 100 performs the following process: eliminating (removing) the offset component and 1 / f noise of the amplifier 12 from the output information in the infrared measurement mode by obtaining the difference in the output information of the amplifier 12 (AFE) in the infrared measurement mode and the noise measurement mode.

[0110] The signal processing circuit 100 includes, for example, one or more microcomputers or processors with a program for controlling processes built therein. The signal processing circuit 100 may include a dedicated logic circuit for performing signal processing.

[0111] The signal processing circuit 100 is provided, for example, in an external signal processing device, but may also be provided in the infrared sensor 1. When the signal processing circuit 100 is provided in the infrared sensor 1, the control circuit 13 and the signal processing circuit 100 may be implemented by one microcomputer or processor, or may be respectively implemented by one or more independent microcomputers or processors.

[0112] [Infrared sensor element]

[0113] Next, the detailed configuration of the infrared sensor element 10 included in the infrared sensor 1 will be described.

[0114] Figure 3A is a cross-sectional view showing the infrared sensor element 10 of Embodiment 1. Figure 3B is a plan view when observing the infrared sensor element 10 of Embodiment 1 from above. In addition, in Figure 3A and Figure 3B , in addition to the infrared sensor element 10, the substrate 30 and the transistor 80 serving as the switch of the switch circuit 11 are also shown. In addition, in Figure 3A and Figure 3B , one infrared sensor element 10 is shown, but the other infrared sensor elements 10 constituting the element array 10A are also arranged in an array shape in a plan view while sharing the substrate 30. In addition, Figure 3A indicates: in Figure 3BIn the structure shown, a cross-section in the case of slicing with a line passing through the metal wiring 84, metal wiring 83, metal wiring 71, cold-junction metal electrode 63p, P-type semiconductor 65p, warm-junction metal electrode 61, warm-junction metal electrode 62, P-type semiconductor 66p, and cold-junction metal electrode 64p in this order. Additionally, in Figure 3B the positions of the N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p that are actually covered by the insulating film 41 are shown by thick dashed lines. Additionally, in Figure 3B the outline of the semiconductor 42 in the light-receiving portion 40 that is actually covered by the insulating film 41 is shown by a dashed line.

[0115] As Figure 3A and Figure 3B shown, the infrared sensor element 10 includes a light-receiving portion 40, a hollow support portion 50, and a thermoelectric conversion portion 60. The infrared sensor element 10 is located above the substrate 30. The infrared sensor element 10 is formed, for example, at least partially on the substrate 30. The plurality of infrared sensor elements 10 included in the infrared sensor 1 all have the same configuration, for example.

[0116] The substrate 30 is a substrate for forming the infrared sensor element 10 and peripheral circuits, etc. The substrate 30 has a semiconductor substrate 31 and an insulating film 32 laminated on the upper surface of the semiconductor substrate 31.

[0117] The semiconductor substrate 31 is, for example, a silicon substrate, but it can also be a semiconductor substrate other than a silicon substrate. A transistor 80 is formed on the upper surface of the semiconductor substrate 31.

[0118] The transistor 80 is a MOSFET. The transistor 80 includes a source 80s, a drain 80d, a gate 80g, and a well region 80w. Additionally, a gate oxide film is disposed between the gate 80g, which is a conductive layer, and the channel region of the transistor 80. Furthermore, depending on the type and concentration of impurities in the semiconductor substrate 31, the transistor 80 may not include the well region 80w.

[0119] The transistor 80 is one of the switches of the switch circuit 11. In the present embodiment, the transistor 80 is a parallel switch SW2 for short-circuiting the series switch SW1 provided between the infrared sensor element 10 and the amplifier 12 or the infrared sensor element 10. Additionally, MOSFETs other than the transistor 80 may also be formed on the semiconductor substrate 31 as switches of the switch circuit 11. Moreover, the MOSFETs formed on the semiconductor substrate 31 other than the transistor 80 may perform functions other than those of the switches of the switch circuit 11. For example, they may undertake logical functions for pixel selection or amplification functions for detection signals, etc.

[0120] The insulating film 32 is located above the semiconductor substrate 31. More specifically, it is located on the upper surface of the semiconductor substrate 31. The insulating film 32 is made of, for example, an oxide such as silicon oxide (SiO 2 ), etc., but it can also be made of an insulating material other than silicon oxide.

[0121] The light-receiving portion 40 generates heat due to the absorption of infrared rays, and the temperature of the light-receiving portion 40 rises due to this heat. In the infrared sensor element 10, infrared incident light Lin is incident from above, and at least a part of the infrared incident light Lin is absorbed by the light-receiving portion 40. The amount of heat generated by the light-receiving portion 40 depends on the amount of infrared absorption in the light-receiving portion 40.

[0122] The light-receiving portion 40 is located above the substrate 30. The light-receiving portion 40 has a two-dimensional extension. The shape of the light-receiving portion 40 in plan view is, for example, a square, but it can also be other shapes such as a rectangle. The light-receiving portion 40 is separated from the substrate 30, and a gap 51 is formed between the light-receiving portion 40 and the substrate 30.

[0123] In the present embodiment, the light-receiving portion 40 includes a part of the insulating film 41 and a part of the thin-film semiconductor 42. The light-receiving portion 40 has a sandwich structure in which the semiconductor 42 is sandwiched by the insulating film 41.

[0124] The insulating film 41 and the semiconductor 42 are disposed above the substrate 30. The insulating film 41 is formed on the gap 51 and on the insulating film 32. The semiconductor 42 is sandwiched by the insulating film 41 from above and below. In a part of the semiconductor 42, N-type semiconductors 65n, 66n and P-type semiconductors 65p, 66p, which will be described later, are formed. The insulating film 41 is made of, for example, silicon nitride (SiN), but it can also be made of an insulating material other than silicon nitride (for example, silicon oxide). The semiconductor 42 is, for example, polysilicon, but it can also be a semiconductor other than polysilicon.

[0125] The hollow support portion 50 hollowly supports the light-receiving portion 40 in such a manner that a gap 51 is formed between the substrate 30 and the light-receiving portion 40. The gap 51 is located between the light-receiving portion 40 and the hollow support portion 50 and the substrate 30. In the present embodiment, the hollow support portion 50 is two arms that bond the light-receiving portion 40 to the insulating film 32. The hollow support portion 50 includes a part of the insulating film 41, and N-type semiconductors 65n, 66n and P-type semiconductors 65p, 66p that are part of the semiconductor 42. The side wall of the gap 51 is made of the insulating film 32. The gap 51 is, for example, a recess formed in the substrate 30 by removing a part of the insulating film 32. Even if the insulating film 32 below the light-receiving portion 40 is removed in this way to form the gap 51, the light-receiving portion 40 can be hollowly supported by the hollow support portion 50. In addition, through the gap 51, the transfer of heat from the light-receiving portion 40 to the substrate 30 is suppressed, and the decrease in the temperature of the light-receiving portion 40 that has risen due to the reception of infrared rays is suppressed.

[0126] The thermoelectric conversion unit 60 generates an infrared detection signal based on the heat generated by the light receiving unit 40. The infrared detection signal is, for example, a voltage signal or a current signal. At least a part of the thermoelectric conversion unit 60 is provided in the hollow support unit 50. In the present embodiment, the thermoelectric conversion unit 60 is a thermopile-type thermoelectric conversion element utilizing the Seebeck effect. The thermoelectric conversion unit 60 includes hot junction metal electrodes 61, 62, cold junction metal electrodes 63p, 63n, 64p, 64n, N-type semiconductors 65n, 66n, P-type semiconductors 65p, 66p, and metal wirings 67.

[0127] The hot junction metal electrodes 61, 62 are located on the light receiving unit 40. In addition, the hot junction metal electrodes 61, 62 are located near the connection portion between the light receiving unit 40 and the hollow support unit 50. Furthermore, the hot junction metal electrodes 61, 62 may be located at positions where the temperature changes synchronously with the temperature of the light receiving unit 40, and there is no particular limitation. For example, they may be located at positions adjacent to the light receiving unit 40.

[0128] The cold junction metal electrodes 63p, 63n, 64p, 64n are located outside the light receiving unit 40 in a plan view. In addition, the cold junction metal electrodes 63p, 63n, 64p, 64n are located outside the gap 51 in a plan view. In addition, the cold junction metal electrodes 63p, 63n, 64p, 64n are located near the connection portion between the substrate 30 and the hollow support unit 50. The hot junction metal electrode 61 and the cold junction metal electrodes 63p, 64n are arranged so as to sandwich one arm of the hollow support unit 50. The hot junction metal electrode 62 and the cold junction metal electrodes 63n, 64p are arranged so as to sandwich the other arm of the hollow support unit 50.

[0129] The N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p are respectively provided in the insulating film 41. The N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p are respectively linear and extend along the hollow support unit 50. The N-type semiconductor 66n and the P-type semiconductor 65p pass through one arm of the hollow support unit 50. In addition, the N-type semiconductor 65n and the P-type semiconductor 66p pass through the other arm of the hollow support unit 50. The N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p are respectively formed by doping impurities (such as boron (B) or phosphorus (P)) in the semiconductor 42.

[0130] One end of the N-type semiconductor 66n and one end of the P-type semiconductor 65p are connected to the warm-junction metal electrode 61 and are joined to the warm-junction metal electrode 61. The N-type semiconductor 66n and the P-type semiconductor 65p are electrically connected via the warm-junction metal electrode 61 to form a warm junction. Further, one end of the N-type semiconductor 65n and one end of the P-type semiconductor 66p are connected to the warm-junction metal electrode 62 and are joined to the warm-junction metal electrode 62. The N-type semiconductor 65n and the P-type semiconductor 66p are electrically connected via the warm-junction metal electrode 62 to form a warm junction.

[0131] The other end of the P-type semiconductor 65p is connected to the cold-junction metal electrode 63p and is joined to the cold-junction metal electrode 63p, thereby forming a cold junction. The other end of the N-type semiconductor 66n is connected to the cold-junction metal electrode 64n and is joined to the cold-junction metal electrode 64n, thereby forming a cold junction. The other end of the P-type semiconductor 66p is connected to the cold-junction metal electrode 64p and is joined to the cold-junction metal electrode 64p, thereby forming a cold junction. The other end of the N-type semiconductor 65n is connected to the cold-junction metal electrode 63n and is joined to the cold-junction metal electrode 63n, thereby forming a cold junction.

[0132] The connections of the N-type semiconductors 65n, 66n and the P-type semiconductors 65p, 66p to the warm-junction metal electrodes 61, 62 and the cold-junction metal electrodes 63p, 63n, 64p, 64n are ohmic connections. The N-type semiconductor 66n and the P-type semiconductor 65p that have made ohmic connections to the same warm-junction metal electrode 61 form a thermocouple. Further, the N-type semiconductor 65n and the P-type semiconductor 66p that have made ohmic connections to the same warm-junction metal electrode 62 form a thermocouple.

[0133] When the light-receiving part 40 absorbs infrared rays and as a result the temperature of the warm junction is higher than that of the cold junction, many carriers gather on the cold-junction side. As a result, the cold junctions of the N-type semiconductors 65n and 66n have a negative electromotive force with respect to the cold junctions of the P-type semiconductors 65p and 66p. In the illustrated example, there are 2 pairs of cold junctions and warm junctions, and the metal wiring 67 electrically connects the cold-junction metal electrode 64n and the cold-junction metal electrode 64p. Therefore, the two thermocouples with electromotive forces are in a series-connected state, and the cold-junction metal electrode 63n has a negative electromotive force with respect to the cold-junction metal electrode 63p. That is, a potential difference corresponding to the heat generated by the light-receiving part 40 is generated between the cold-junction metal electrode 63p and the cold-junction metal electrode 63n. At this time, if the cold-junction metal electrode 63n is maintained at the reference potential, an infrared detection signal corresponding to this electromotive force is output from the cold-junction metal electrode 63p. In addition, the temperature relationship between the "warm junction" and the "cold junction" of the thermoelectric conversion part 60 is not necessarily such that the temperature of the warm junction is higher than that of the cold junction. For example, when the infrared sensor 1 is used to detect the temperature of an object lower than the temperature of the infrared sensor 1 itself, sometimes the temperature of the warm junction is lower than that of the cold junction. At this time, the polarity of the electromotive force of the thermoelectric conversion part 60 is reversed.

[0134] The source 80s of the transistor 80 is electrically connected to the metal wiring 83 located above the insulating film 32 through a metal via 81 extending in the thickness direction of the insulating film 32 in the insulating film 32. The metal wiring 83 is electrically connected to the cold-junction metal electrode 63p through the metal wiring 71. The drain 80d of the transistor 80 is electrically connected to the metal wiring 84 located above the insulating film 32 through a metal via 82 extending in the thickness direction of the insulating film 32 in the insulating film 32. The transistor 80, the metal vias 81 and 82, and the metal wirings 83 and 84 are part of the switching circuit 11.

[0135] The warm-junction metal electrodes 61 and 62, the cold-junction metal electrodes 63p, 63n, 64p, and 64n, the metal wiring 67, the metal wiring 71, the metal wiring 83, and the metal wiring 84 are each made of a metal such as aluminum, for example. In addition, the metal vias 81 and 82 are made of a high-melting-point metal such as tungsten, for example.

[0136] In addition, the hollow support part 50 may have a phononic crystal structure. For example, a phononic crystal structure is formed by the N-type semiconductors 65n and 66n and the P-type semiconductors 65p and 66p passing through the hollow support part 50. By having a phononic crystal structure in the hollow support part 50, the temperature difference between the warm junction and the cold junction is maintained by using the high heat insulation of the phononic crystal structure, so that the sensitivity of the infrared sensor 1 can be improved.

[0137] An artificial phonon crystal structure processed by a semiconductor manufacturing process is a structure obtained by digging fine holes with a diameter on the order of several tens of nm and arranging them periodically. The period of the fine holes is, for example, 1 nm or more and 300 nm or less. In addition, the pore diameter of the fine holes is, for example, 10 nm or more and 50 nm or less.

[0138] Since the wavelength of phonons that transport heat mainly ranges from 1 nm to 300 nm, if the period is within such a range, the phonon crystal structure is likely to have high adiabaticity. Electron beam lithography is suitable for forming a phonon crystal structure with a period of 100 nm or more and 300 nm or less. Block copolymer (BCP) lithography is suitable for forming a phonon crystal structure with a period of 1 nm or more and 100 nm or less. The semiconductor 42 (including doped regions) made of polysilicon or the like included in the hollow support portion 50 can be used to dig fine through-holes using the above-mentioned lithography and dry etching. At this time, if the aspect ratio (hole depth / hole diameter) is 5 or less, the etching gas is likely to travel into the hole and the hole can be easily processed. For example, the etching gas can etch a 20-nm diameter hole and penetrate a 100-nm thick polysilicon film to form a phonon crystal structure with a pore diameter of 20 nm. Processing holes with an aspect ratio greater than 5 is difficult to balance the processing shape and productivity. Therefore, it is appropriate that the film thickness of the hollow support portion 50 having the phonon crystal structure is at most about 100 nm.

[0139] [Manufacturing method of infrared sensor]

[0140] Next, the manufacturing method of the infrared sensor 1 will be described. In addition, the manufacturing method described below is an example, and the manufacturing method of the infrared sensor 1 is not limited to the following examples.

[0141] Figures 4A - 4C It is a cross-sectional view for explaining the manufacturing method of the infrared sensor 1 of Embodiment 1.

[0142] First, as Figure 4A shown, an insulating film 32 is formed by CVD (Chemical Vapor Deposition) on the semiconductor substrate 31 on which the transistor 80 is formed. The insulating film 32 is, for example, a silicon oxide film. On the semiconductor substrate 31, circuit elements included in the infrared sensor 1 such as MOSFETs other than the transistor 80 may also be formed. Next, the portion below the light-receiving portion 40 and the hollow support portion 50 (the portion where the gap 51 will be formed later) is excavated by dry etching to form a concave space 53. Further, a thin protective film 33 is deposited by CVD on the insulating film 32 on which the concave space 53 is formed. The protective film 33 is, for example, a silicon oxide film.

[0143] Next, as Figure 4BAs shown, the material of the sacrificial layer 55 is deposited in such a way as to fill the recessed space 53, and the upper surfaces of the insulating film 32 and the sacrificial layer 55 are exposed by CMP (Chemical Mechanical Polishing). The material of the sacrificial layer 55 is, for example, polysilicon.

[0144] Next, as Figure 4C shown, after forming via holes in the insulating film 32 by dry etching for wiring the transistor 80, tungsten is buried in the via holes and CMP is performed again, thereby forming metal vias 81 and 82. In addition, in the formation of the metal vias 81 and 82, a titanium nitride film or the like may be formed as a base adhesion layer before depositing tungsten in the via holes.

[0145] After that, after forming the light-receiving portion 40, the hollow support portion 50, the thermoelectric conversion portion 60, and various metal wirings, the sacrificial layer 55 is etched by xenon fluoride (XeF 2 ) to form voids 51, thereby obtaining Figure 3A and Figure 3B the structure shown. In addition, such a manufacturing process is also performed at other portions of the semiconductor substrate 31 to form the infrared sensor 1 including a plurality of infrared sensor elements 10. In the formation of the light-receiving portion 40, the hollow support portion 50, the thermoelectric conversion portion 60, and various metal wirings, for example, the processing techniques used in semiconductor device manufacturing are used.

[0146] [Circuit Configuration and Operation]

[0147] Next, the detailed circuit configuration and operation of the infrared sensor 1 of the present embodiment will also be described with reference to the infrared sensor of the comparative example.

[0148] Figure 5 is a diagram showing the circuit configuration of the infrared sensor 1 of Embodiment 1. In addition, in Figure 5 , the circuit configurations of the element array 10A, the switch circuit 11, and the amplifier 12 are shown, and the illustration of other circuit configurations in the infrared sensor 1 is omitted. In addition, in Figure 5 , for the sake of distinction, a plurality of infrared sensor elements 10 are denoted by reference numerals 10_1 to 10_N of a plurality of infrared sensor elements. In addition, in Figure 5 , each of the plurality of infrared sensor elements 10_1 to 10_N is equivalent to Figures 1A - 1E similarly, and is equivalently represented by a series connection of a voltage source that generates an electromotive force V IR and an internal resistance R 0 . This is the same in the diagrams showing the circuit configuration hereafter. In addition, in Figure 5In [it], the states of the switches in the noise measurement mode are shown.

[0149] As Figure 5 shown, the infrared sensor 1 includes a plurality of series switches SW1_1 to SW1_N, a plurality of parallel switches SW2_1 to SW2_N, and a parallel switch SW3 as the switches included in the switch circuit 11. The plurality of series switches SW1_1 to SW1_N are an example of a plurality of second switches. The plurality of parallel switches SW2_1 to SW2_N are an example of a plurality of first switches. The parallel switch SW3 is an example of a third switch.

[0150] Each of the plurality of series switches SW1_1 to SW1_N corresponds to the series switch SW1 described in the above-mentioned “(Insight underlying the present disclosure)”. Hereinafter, each of the plurality of series switches SW1_1 to SW1_N may be simply referred to as “series switch SW1”. In addition, each of the plurality of parallel switches SW2_1 to SW2_N corresponds to the parallel switch SW2 described in the above-mentioned “(Insight underlying the present disclosure)”. Hereinafter, each of the plurality of parallel switches SW2_1 to SW2_N may be simply referred to as “parallel switch SW2”. In addition, the content described in the above-mentioned “(Insight underlying the present disclosure)” can be applied to the parallel switch SW3. In addition, the content described in the above-mentioned “(Insight underlying the present disclosure)” can also be applied to the plurality of infrared sensor elements 10_1 to 10_N and the amplifier 12. Therefore, the description of the matters that have been described is omitted or simplified.

[0151] The infrared sensor 1 has a configuration in which one infrared sensor element 10 of the infrared sensor of the above-described Configuration Example 5 is expanded into a plurality of infrared sensor elements 10_1 to 10_N (in other words, a plurality of pixels).

[0152] In the infrared sensor 1, the N infrared sensor elements 10_1 to 10_N are connected in parallel to one amplifier 12 via the switch circuit 11. That is, the infrared sensor elements 10_1 to 10_N and the amplifier 12 have a configuration of multiple to one.

[0153] A plurality of series switches SW1_1 to SW1_N are connected to respective ones of a plurality of infrared sensor elements 10_1 to 10_N in a one-to-one manner. Each of the plurality of series switches SW1_1 to SW1_N is connected to an amplifier 12 in such a way that the transmission of infrared detection signals from respective ones of the plurality of infrared sensor elements 10_1 to 10_N to the amplifier 12 can be independently interrupted. Each of the plurality of series switches SW1_1 to SW1_N independently switches the conduction and non-conduction between respective ones of the plurality of infrared sensor elements 10_1 to 10_N and the amplifier 12. The other ends of each of the plurality of series switches SW1_1 to SW1_N are connected to each other. Further, one end of a parallel switch SW3 is connected between the other ends of the plurality of series switches SW1_1 to SW1_N and the amplifier 12.

[0154] A plurality of parallel switches SW2_1 to SW2_N are connected to respective ones of a plurality of infrared sensor elements 10_1 to 10_N in a one-to-one manner. One end of each of the plurality of parallel switches SW2_1 to SW2_N is connected between a group of the plurality of infrared sensor elements 10_1 to 10_N connected in a one-to-one manner and the plurality of series switches SW1_1 to SW1_N. Each of the plurality of parallel switches SW2_1 to SW2_N connects a first terminal T1 that outputs an infrared detection signal in the infrared sensor element 10 and a second terminal T2 held at a predetermined potential in such a way that they can be short-circuited.

[0155] The first terminal T1 and the second terminal T2 are included in the above-described thermoelectric conversion unit 60. The first terminal T1 is, for example, a cold-junction metal electrode 63p of the thermoelectric conversion unit 60 or a part of a wiring extending from the cold-junction metal electrode 63p to the amplifier 12. Further, the second terminal T2 is, for example, a cold-junction metal electrode 63n of the thermoelectric conversion unit 60 or a part of a wiring for connecting the cold-junction metal electrode 63n to a reference potential.

[0156] The parallel switch SW3 is connected to an input terminal of the amplifier 12 and can short-circuit the input terminal to a reference potential.

[0157] In the plurality of infrared sensor elements 10_1 to 10_N, the plurality of series switches SW1_1 to SW1_N, and the plurality of parallel switches SW2_1 to SW2_N, the ends of the reference numerals indicate their corresponding relationships. The components with the same ends of the reference numerals are connected to each other.

[0158] Next, the infrared sensor element of the comparative example will be described. Figure 6 FIG. shows a circuit configuration of an infrared sensor 1X of Comparative Example 1. Figure 7 FIG. shows a circuit configuration of an infrared sensor 1Y of Comparative Example 2. Further, in Figure 6 and Figure 7In this, the states of the switches in the noise measurement mode are shown.

[0159] As Figure 6 shown, the infrared sensor 1X of Comparative Example 1 has a configuration in which a plurality of parallel switches SW2_1 to SW2_N are removed from the infrared sensor 1 of Embodiment 1. The infrared sensor 1X has a configuration in which one infrared sensor element 10 of the infrared sensor of the above-described Configuration Example 3 is expanded into a plurality of infrared sensor elements 10_1 to 10_N (in other words, a plurality of pixels).

[0160] As Figure 7 shown, the infrared sensor 1Y of Comparative Example 2 has a configuration in which the parallel switch SW3 is removed from the infrared sensor 1 of Embodiment 1. The infrared sensor 1Y has a configuration in which one infrared sensor element 10 of the infrared sensor of the above-described Configuration Example 2 or Configuration Example 4 is expanded into a plurality of infrared sensor elements 10_1 to 10_N (a plurality of pixels).

[0161] In the infrared sensors of Comparative Example 1 and Comparative Example 2, since the change is made from a single infrared sensor element 10 (pixel) to a plurality of infrared sensor elements 10_1 to 10_N (a plurality of pixels), an error may occur in the output of the amplifier 12, but in the infrared sensor 1 of Embodiment 1, an error in the output of the amplifier 12 can be suppressed. Details regarding this will be described below together with the operations of the respective switches of the switch circuit 11. The operations of the respective switches of the switch circuit 11 described below are performed based on the control of the control circuit 13.

[0162] Figure 8 is a diagram for explaining the results of calculating the leakage of the infrared detection signal in the infrared sensors of Embodiment 1, Comparative Example 1, and Comparative Example 2. In Figure 8 this, the states of the switches in the noise measurement mode and the leakage rate of the infrared detection signal, and the states of the switches in the infrared measurement mode and the error of the infrared detection signal in the infrared sensors of Embodiment 1, Comparative Example 1, and Comparative Example 2 are shown in tabular form in the rows labeled "Comparative Example 1" to "Embodiment 1". The definitions of the leakage rate of the infrared detection signal and the error of the infrared detection signal are as Figure 1F described in the explanation in this.

[0163] In addition, in Figure 8In the following conditions, the leakage rate of the infrared detection signal and the error of the infrared detection signal are calculated. The resistance of the multiple series switches SW1_1 to SW1_N, the multiple parallel switches SW2_1 to SW2_N, and the parallel switch SW3 when off is set to 1 GΩ, and the resistance when on is set to 100 Ω. In addition, the number of infrared sensor elements 10_1 to 10_N is set to 20. In addition, the input impedance Z of the amplifier 12 in is set to 100 GΩ. In addition, in the infrared measurement mode, it is set to output the infrared detection signal by only selecting the infrared sensor element 10_1 among the multiple infrared sensor elements 10_1 to 10_N. That is, in the following description, the selected pixel is the infrared sensor element 10_1, and the unselected pixels are the infrared sensor elements 10_2 to 10_N. In addition, it is assumed that: the infrared sensor elements 10_2 to 10_N are irradiated with infrared rays that generate an electromotive force V RI 100 times stronger than the electromotive force V RI of the infrared sensor element 10_1.

[0164] First, the operation of the infrared sensor 1X in Comparative Example 1 and the result of calculating the leakage of the infrared detection signal are described.

[0165] As Figure 8 shown, in the noise measurement mode of the infrared sensor 1X in Comparative Example 1, each of the multiple series switches SW1_1 to SW1_N is turned off, and the parallel switch SW3 is turned on. In addition, in the infrared measurement mode of the infrared sensor 1X, only the series switch SW1_1 connected to the selected pixel among the multiple series switches SW1_1 to SW1_N is turned on, and the series switches SW1_2 to SW1_N connected to the unselected pixels are turned off. In addition, the infrared sensor 1X turns off the parallel switch SW3 in the infrared measurement mode.

[0166] As a result of such an operation, as shown in the row of "Comparative Example 1" in Figure 8 , the leakage rate of the infrared detection signal in the noise measurement mode is 0.0%. On the other hand, the error of the infrared detection signal in the infrared measurement mode reaches +19.0%, resulting in a large error. This is because: when the infrared detection signal generated from the unselected pixel is strong, the resistance of the series switches SW1_2 to SW1_N connected to the unselected pixel is not infinite when off, so the infrared detection signal leaks to the amplifier 12, and thus the infrared detection signal of the selected pixel is larger than the actual value.

[0167] Next, the operation of the infrared sensor 1Y in Comparative Example 2 and the result of calculating the leakage of the infrared detection signal are described.

[0168] As Figure 8 shown, in the noise measurement mode of the infrared sensor 1Y of Comparative Example 2, each of the plurality of parallel switches SW2_1 to SW2_N is turned on, and each of the plurality of series switches SW1_1 to SW1_N is turned on. Further, in the noise measurement mode, the infrared sensor 1Y may turn on each of the plurality of parallel switches SW2_1 to SW2_N and turn off each of the plurality of series switches SW1_1 to SW1_N. Further, in the infrared measurement mode, the infrared sensor 1Y turns off only the parallel switch SW2_1 connected to the selected pixel among the plurality of parallel switches SW2_1 to SW2_N and turns on the parallel switches SW2_2 to SW2_N connected to the non-selected pixels. Further, in the infrared measurement mode, the infrared sensor 1Y turns on only the series switch SW1_1 connected to the selected pixel among the series switches SW1_1 to SW1_N and turns off the series switches SW1_2 to SW1_N connected to the non-selected pixels.

[0169] As a result of such an operation, as shown in the row of Figure 8 "Comparative Example 2", the leakage rate of the infrared detection signal in the noise measurement mode reaches 9.5% whether each of the plurality of series switches SW1_1 to SW1_N is turned on or off. Further, the error of the infrared detection signal in the infrared measurement mode is -0.2%. The reason why the leakage rate of the infrared detection signal is high is that the infrared detection signals leaking from the respective infrared sensor elements 10_1 to 10_N are likely to be superimposed and transmitted to the amplifier 12. Specifically, in the infrared sensors of the above-described Configuration Example 2 and Configuration Example 4, by turning on the parallel switch SW2, the infrared detection signal hardly leaks from the infrared sensor element 10, and the leakage rate of the infrared detection signal becomes low. However, in the infrared sensor 1Y, since there are a plurality of infrared sensor elements 10_1 to 10_N, the leaked infrared detection signals are superimposed. As a result, in the infrared sensor 1Y, the leakage rate of the infrared detection signal becomes high.

[0170] Next, the operation of the infrared sensor 1 of Embodiment 1 and the result of calculating the leakage of the infrared detection signal will be described.

[0171] As Figure 8As shown, in the noise measurement mode, the infrared sensor 1 of Embodiment 1 turns on multiple parallel switches SW2_1 to SW2_N, turns off multiple series switches SW1_1 to SW1_N, and turns on parallel switch SW3. In addition, in the infrared measurement mode, the infrared sensor 1 only turns off the parallel switch SW2_1 connected to the selected pixel among the multiple parallel switches SW2_1 to SW2_N, and turns on the parallel switches SW2_2 to SW2_N connected to the non-selected pixels. In addition, in the infrared measurement mode, the infrared sensor 1 only turns on the series switch SW1_1 connected to the selected pixel among the multiple series switches SW1_1 to SW1_N, and turns off the series switches SW1_2 to SW1_N connected to the non-selected pixels. In addition, the infrared sensor 1 turns off the parallel switch SW3 in the infrared measurement mode.

[0172] As a result of such an operation, as shown in the row of " Figure 8 Embodiment 1", the leakage rate of the infrared detection signal in the noise measurement mode is 0.0%. In addition, the error of the infrared detection signal in the infrared measurement mode is -0.2%. Therefore, by obtaining the difference between the outputs of the amplifier 12 in the infrared measurement mode and the noise measurement mode, the offset component and 1 / f noise of the amplifier 12 can be eliminated. This elimination process is performed, for example, by the signal processing circuit 100.

[0173] In this way, the infrared sensor 1 improves the error of the infrared detection signal compared with the infrared sensor 1X by having multiple parallel switches SW2_1 to SW2_N. This is for the following reason. In the infrared detection mode, by turning on the parallel switches SW2_1 to SW2_N, the first terminal T1 and the second terminal T2 that output the infrared detection signal are short-circuited in the infrared sensor elements 10_2 to 10_N. As a result, the infrared detection signal generated by the infrared sensor elements 10_2 to 10_N, which are non-selected pixels, hardly leaks to the amplifier 12. Therefore, the error of the infrared detection signal in the infrared detection mode is improved.

[0174] In addition, the infrared sensor 1 is provided with a parallel switch SW3, thereby improving the leakage rate of the infrared detection signal compared to the infrared sensor 1Y. This is for the following reasons. In the noise measurement mode, by turning on the plurality of parallel switches SW2_1 to SW2_N, the first terminal T1 for outputting the infrared detection signal and the second terminal T2 are short-circuited among the plurality of infrared sensor elements 10_1 to 10_N. As a result, the infrared detection signals generated by the plurality of infrared sensor elements 10_1 to 10_N are less likely to leak to the amplifier 12. Moreover, in the infrared sensor 1, in the noise measurement mode, by turning on the parallel switch SW3, the input terminal of the amplifier 12 is short-circuited to the reference potential, and the infrared detection signals leaking from the plurality of infrared sensor elements 10_1 to 10_N are less likely to affect the input to the amplifier 12. Therefore, the leakage rate of the infrared detection signal in the noise measurement mode is improved.

[0175] As described above, as Figure 8 explained, in Comparative Example 1 and Comparative Example 2 in which the circuit configuration that improves the leakage rate and error of the infrared detection signal in the case where the number of infrared sensor elements 10 is 1, such as the infrared sensors of Configuration Example 2 to Configuration Example 4 described above, is extended to a circuit configuration having a plurality of infrared sensor elements 10, errors are likely to occur in the output of the amplifier 12. Specifically, an error in the infrared detection signal occurs in the infrared sensor 1X of Comparative Example 1 in the infrared measurement mode, and leakage of the infrared detection signal occurs in the infrared sensor 1Y of Comparative Example 2 in the noise measurement mode. In contrast, in the infrared sensor 1 of Embodiment 1, leakage of the infrared detection signal in the noise measurement mode and error of the infrared detection signal in the infrared measurement mode can be suppressed. Therefore, the infrared sensor 1 of Embodiment 1 can improve the detection accuracy of infrared rays.

[0176] (Embodiment 2)

[0177] Next, the infrared sensor of Embodiment 2 will be described. In the following description, the description will focus on the differences from Embodiment 1, and the description of the common points will be omitted or simplified.

[0178] [Overall Configuration]

[0179] Figure 9 is a block diagram showing the overall configuration of the infrared sensor 101 of Embodiment 2.

[0180] As Figure 9 shown, the infrared sensor 101 of the present embodiment is different from the infrared sensor 1 of Embodiment 1 in that it includes a switch circuit 111 and an amplifier 112 instead of the switch circuit 11 and the amplifier 12.

[0181] The switch circuit 111 is a circuit that has a plurality of switches and wirings and connects the element array 10A to the amplifier 112. The detailed configuration of the switch circuit 111 will be described later.

[0182] The amplifier 112 amplifies the infrared detection signals generated by the plurality of infrared sensor elements 10. The amplifier 112 is a current input type amplifier with a low input impedance. The amplifier 12 is, for example, a transimpedance amplifier (current input / voltage output type amplifier), but as long as it is an active element with a low input impedance, it is not limited to a transimpedance amplifier and can also be a current amplifier (current input / current output type amplifier).

[0183] [Circuit Configuration and Operation]

[0184] Next, the circuit configuration of the infrared sensor 101 of the present embodiment will be described.

[0185] Figure 10 is a diagram showing the circuit configuration of the infrared sensor 101 of Embodiment 2. In addition, in Figure 10 , the circuit configurations of the infrared sensor element 10, the switch circuit 111, and the amplifier 112 are shown, and the illustration of other circuit configurations included in the infrared sensor 101 is omitted. Also, in Figure 10 , the states of the switches in the noise measurement mode are shown.

[0186] As Figure 10 shown, the infrared sensor 101 has a configuration in which the amplifier 12 of the infrared sensor 1Y of Comparative Example 2 described above is changed to the amplifier 112. The infrared sensor 101 includes a plurality of series switches SW1_1 to SW1_N and a plurality of parallel switches SW2_1 to SW2_N as the switches included in the switch circuit 111. The plurality of series switches SW1_1 to SW1_N are an example of a plurality of second switches. The plurality of parallel switches SW2_1 to SW2_N are an example of a plurality of first switches. The switch circuit 111 has a configuration in which the parallel switch SW3 is removed from the above-described switch circuit 11.

[0187] In the infrared sensor 101, N infrared sensor elements 10_1 to 10_N are connected in parallel to one amplifier 112 via the switch circuit 111. That is, the infrared sensor elements 10_1 to 10_N and the amplifier 112 are in a many-to-one configuration.

[0188] In Figure 10 the example shown, the amplifier 112 is a transimpedance amplifier. The transimpedance amplifier has, for example, an operational amplifier and a resistor. The transimpedance amplifier is, for example, an inverting amplifier using an operational amplifier. The input impedance Z of the transimpedance amplifier inis extremely low and can be regarded as zero. Figure 10 The output voltage of the transimpedance amplifier having the feedback resistor R shown 4 is -R times the current flowing into the input terminal of the transimpedance amplifier. 4 times.

[0189] Next, the operation of the infrared sensor 101 of Embodiment 2 and the results of calculating the leakage of the infrared detection signal will be described. The operations of the respective switches of the switch circuit 111 described below are performed based on the control of the control circuit 13.

[0190] Figure 11 is a diagram for explaining the results of calculating the leakage of the infrared detection signal in the infrared sensor 101 of Embodiment 2. In Figure 11 the states of the switches and the leakage rate of the infrared detection signal in the noise measurement mode, and the states of the switches and the error of the infrared detection signal in the infrared measurement mode in the infrared sensor 101 of Embodiment 2 are shown in tabular form in the row labeled "Embodiment 2".

[0191] Figure 11 The definition of the leakage rate of the infrared detection signal (the column of "Leakage rate of detection signal (%)" in the figure) and the error of the infrared detection signal (the column of "Error (%)" in the figure) in IR / R 0 is as described below. The leakage rate of the infrared detection signal in the noise measurement mode is the ratio (%) of the current flowing into the input of the amplifier 12 in the noise measurement mode to the induced current V IR / R 0 generated by the infrared sensor element 10. In addition, the error of the infrared detection signal in the infrared measurement mode is the error (%) of the current flowing into the input of the amplifier 12 in the infrared measurement mode with respect to the induced current V IR / R 0 generated by the infrared sensor element 10, that is, the value obtained by subtracting the current flowing into the input of the amplifier 12 from the induced current V IR / R 0 generated by the infrared sensor element 10, and the ratio (%) of this value to the induced current V

[0192] In addition, in Figure 11In this case, the leakage rate of the infrared detection signal and the error of the infrared detection signal are calculated under the following conditions. The resistance of the multiple series switches SW1_1 to SW1_N and the multiple parallel switches SW2_1 to SW2_N when off is set to 1 GΩ, and the resistance when on is set to 100 Ω. Additionally, the number of infrared sensor elements 10_1 to 10_N is set to 20. Further, the input impedance Z of the amplifier 112 in is set to 0 Ω. Additionally, in the infrared measurement mode, only the infrared sensor element 10_1 among the multiple infrared sensor elements 10_1 to 10_N is selected to output the infrared detection signal. That is, in the following description, the selected pixel is the infrared sensor element 10_1, and the non-selected pixels are the infrared sensor elements 10_2 to 10_N. Additionally, it is assumed that: the infrared sensor elements 10_2 to 10_N are irradiated with infrared rays that generate an electromotive force V RI which is 100 times the electromotive force V RI as strong.

[0193] As Figure 11 shown, in the noise measurement mode of the infrared sensor 101 of Embodiment 2, each of the multiple parallel switches SW2_1 to SW2_N is turned on, and each of the multiple series switches SW1_1 to SW1_N is turned off. Additionally, in the infrared measurement mode of the infrared sensor 101, only the parallel switch SW2_1 connected to the selected pixel among the multiple parallel switches SW2_1 to SW2_N is turned off, and the parallel switches SW2_2 to SW2_N connected to the non-selected pixels are turned on. Additionally, in the infrared measurement mode of the infrared sensor 101, only the series switch SW1_1 connected to the selected pixel among the multiple series switches SW1_1 to SW1_N is turned on, and the series switches SW1_2 to SW1_N connected to the non-selected pixels are turned off.

[0194] As a result of such an operation, as shown in the row of "Embodiment 2" in Figure 11 , the leakage rate of the infrared detection signal in the noise measurement mode is 0.0%. Additionally, the error of the infrared detection signal in the infrared measurement mode is -0.1%. Therefore, by obtaining the difference between the outputs of the amplifier 112 in the infrared measurement mode and the noise measurement mode, the offset component and 1 / f noise of the amplifier 112 can be eliminated. This elimination process is performed, for example, by the signal processing circuit 100.

[0195] Thus, by including the amplifier 112, the infrared sensor 101 improves the leakage rate of the infrared detection signal in the noise measurement mode as compared with the infrared sensor 1Y of Comparative Example 2. This is because: by making the input impedance of the amplifier 112 low, even if the infrared detection signal leaks from the infrared sensor element 10, it is difficult to appear as the voltage which is the product of the flowing current and the input impedance.

[0196] As described above, as used Figure 11 as described above, it is shown that: even for the infrared sensor 101 having the same switch circuit 111 as that of the infrared sensor 1Y of Comparative Example 2 in which leakage of the infrared detection signal in the noise measurement mode is a problem, by changing the voltage input type amplifier to a current input type amplifier, the problem can be eliminated. Therefore, the infrared sensor 101 of Embodiment 2 can improve the detection accuracy of infrared rays.

[0197] In addition, the number of switches of the switch circuit 11 included in the infrared sensor 1 of Embodiment 1 is 2N + 1, whereas the number of switches of the switch circuit 111 included in the infrared sensor 101 of Embodiment 2 is 2N, and the number of switches can be reduced.

[0198] In addition, the infrared sensor 101 of Embodiment 2 has the feature that the current flowing through the infrared sensor element 10 is substantially the same both in the noise measurement mode and in the infrared measurement mode. For example, if we focus on the infrared sensor element 10_1, in the noise measurement mode, the parallel switch SW2_1 is On and the series switch SW1_1 is Off, so the short-circuit current V IR / R 0 ( Figure 10 the I in) flows through the infrared sensor element 10_1. Then, when the infrared sensor element 10_1 is selected and the parallel switch SW2_1 is Off and the series switch SW1_1 is On in the infrared measurement mode, the input impedance Z in of the amplifier 112 can be regarded as zero, so the current of the same magnitude as the short-circuit current V IR / R 0 flows into the amplifier 112 in the noise measurement mode. The short-circuit current is, for example, the current flowing through the P-type semiconductors 65p, 66p and the N-type semiconductors 65n, 66n in the thermoelectric conversion section 60 of the infrared sensor element 10, and is the electromotive force V IR generated by the Seebeck effect based on the temperature difference between the hot junction and the cold junction and the total resistance value R 0 of the P-type semiconductors 65p, 66p and the N-type semiconductors 65n, 66n.

[0199] The flow of this short-circuit current acts in the direction of eliminating the temperature difference between the hot junction and the cold junction through the Peltier effect, which is opposite to the Seebeck effect. However, if the amount of infrared irradiation is constant, it will stabilize at a steady state where the expansion of the temperature difference caused by the irradiated infrared rays is balanced with the elimination of the temperature difference caused by the flowing short-circuit current. Thus, even when switching from the noise measurement mode to the infrared measurement mode, as long as the magnitude of the current flowing through the infrared sensor element 10 is the same short-circuit current V IR / R 0 , there will be no phenomenon such that the temperature distribution between the hot junction and the cold junction is temporarily disrupted and redistributed due to the switching of the measurement mode. That is, even when switching from the noise measurement mode to the infrared measurement mode, there is no need to wait for the time required for the temperature distribution to be redistributed and stabilized at the steady state. Even when reading the infrared information based on the current flowing from the selected infrared sensor element 10 into the amplifier 112, the detection accuracy of the infrared rays can be maintained.

[0200] On the other hand, in the infrared sensor 1 of the first embodiment, regarding the short-circuit current V IR / R 0 ( Figure 5 the I in), when switching to the infrared measurement mode by turning off the parallel switch SW2_1, turning on the series switch SW1_1, and turning off the parallel switch SW3, since the input impedance of the amplifier 12 is extremely high and decreases, redistribution occurs in the temperature distribution between the hot junction and the cold junction of the infrared sensor element 10_1. If the infrared information is read without waiting for the time required for this redistribution, an error will occur. However, in applications where the time for switching from the noise measurement mode to the infrared measurement mode can be ensured, there is no problem even in the infrared sensor 1.

[0201] In addition, the resistance value in the On state of an actual semiconductor switch is not ideally zero but on the order of several Ω to several hundred Ω. Therefore, strictly speaking, it is not a short-circuit current. However, if it is sufficiently small compared to the internal resistance R 0 of the infrared sensor, it can be substantially regarded as a short-circuit current. Also, in this specification, the expression "short circuit" also includes cases where it is substantially short-circuited by being connected via a semiconductor switch in the On state.

[0202] The effect that the temperature distribution between the warm and cold junctions hardly changes even when switching from the noise measurement mode to the infrared measurement mode is particularly effective when the hollow support portion 50 of the infrared sensor element 10 has a phononic crystal structure. If the hollow support portion 50 has a phononic crystal structure, due to the high heat insulation of the phononic crystal structure, the thermal resistance of the hollow support portion 50 provided with the thermoelectric conversion portion 60 increases. As a result, the thermal time constant of the thermal circuit including the hollow support portion 50 provided with the thermoelectric conversion portion 60 and the light receiving portion 40 generally increases, and it takes more time for the redistribution of the temperature distribution between the warm and cold junctions. However, in the infrared sensor 101 using the amplifier 112, the temperature distribution hardly changes before and after the switching from the noise measurement mode to the infrared measurement mode. Therefore, the increase in the thermal time constant caused by the phononic crystal structure hardly deteriorates the S / N and the high-speed shooting performance.

[0203] [Another example of operation]

[0204] Next, another example of the operation of the infrared sensor 101 according to the second embodiment will be described. In the above description, the number of infrared sensor elements 10 selected by the infrared sensor 101 in the infrared measurement mode is 1, but the infrared sensor 101 may also select a plurality of infrared sensor elements 10.

[0205] Figure 12A FIG. is an example of the switching operation in the infrared detection mode of the infrared sensor 101 according to the second embodiment. Figure 12B FIG. is another example of the switching operation in the infrared detection mode of the infrared sensor 101 according to the second embodiment. Figure 12C FIG. is a plan view showing an example of the arrangement of the infrared sensor elements 10 in the element array 10A. Figure 12A and Figure 12B FIG. illustrates nine infrared sensor elements 10_1 to 10_9 in the element array 10A and the switches corresponding to the infrared sensor elements 10_1 to 10_9, and shows the states of the switches of the switch circuit 111 in the infrared detection mode.

[0206] As Figure 12A shown, when only the infrared sensor element 10_1 is selected in the infrared measurement mode, the infrared sensor element 10_1 outputs a current I equivalent to the short-circuit current 1 , and the current I 1 flows into the amplifier 112. In the infrared measurement mode, such an operation is also sequentially performed on the infrared sensor elements 10_2 to 10_9, and infrared information of 9 pixels is obtained. Hereinafter, the operation of such a switch circuit 111 is sometimes referred to as an "independent (separate) output operation".

[0207] On the other hand, as Figure 12B shown, when all nine infrared sensor elements 10_1 to 10_9 are simultaneously selected in the infrared measurement mode, each of the infrared sensor elements 10_1 to 10_9 outputs a current I equivalent to a short-circuit current 1 ~I 9 , and the sum of the currents I 1 ~I 9 flows into the amplifier 112. Thus, even if the infrared detection signals from the respective infrared sensor elements 10_1 to 10_9 are weak, the intensity of the infrared detection signals can be increased as the sum of nine pixels for detection. Hereinafter, the operation of such a switch circuit 111 is sometimes referred to as a "block output operation".

[0208] Here, as Figure 12C shown, it is configured as follows: One infrared sensor element 10 is regarded as one pixel, and an element array 10A of 9×9 = 81 pixels is partitioned into blocks of every adjacent 3×3 pixels. In Figure 12C , blocks A to I outlined by a single-dot chain line are shown. When performing the independent output operation described in Figure 12A for each of the blocks A to I, in the infrared measurement mode, only one pixel out of the nine pixels of each of the blocks A to I is selected, and infrared information of all 81 pixels is obtained by sequentially scanning them. On the other hand, when performing the block output operation described in Figure 12B for each of the blocks A to I, the sum of the infrared information of the nine pixels included in each of the blocks A to I is obtained. In this case, the spatial resolution that can be expressed by 81 pixels is reduced to 1 / 9, but even a weak infrared detection signal is enhanced for each of the blocks A to I, and infrared information with an improved S / N can be obtained. In addition, one amplifier 112 may be provided commonly for the blocks A to I, or may be provided for each of the blocks A to I.

[0209] In this way, in the block output operation, the control circuit 13 makes two or more of the parallel switches SW2 among the plurality of parallel switches SW2 simultaneously conductive, so that two or more infrared sensor elements 10 connected to the two or more parallel switches SW2 output infrared detection signals to the amplifier 112 simultaneously. Thereby, the amplifier 112 amplifies and outputs a signal obtained by adding the infrared detection signals generated by the respective two or more infrared sensor elements 10.

[0210] Whether it is the resolution that prioritizes spatiality or the S / N of infrared information is determined by the operation of the switch of the switch circuit 111. Therefore, the photographer can appropriately switch while observing the temperature distribution of the subject being photographed. For example, the control circuit 13 obtains an instruction signal from the photographer indicating which of the independent output operation and the block output operation is used to control the switch circuit 111, and controls the switch circuit 111 based on the obtained instruction signal.

[0211] In addition, the control circuit 13 can also switch the independent output operation and the block output operation by obtaining the output in the infrared detection mode from the amplifier 112. For example, when the output from the amplifier 112 (for example, the average value or the maximum value of the output) is equal to or greater than a predetermined value, the control circuit 13 operates the switch circuit 111 by the independent output operation, and when the output from the amplifier 112 (for example, the average value or the maximum value of the output) is less than the predetermined value, the control circuit 13 operates the switch circuit 111 by the block output operation.

[0212] The reason for being able to perform the block output operation as described above is that by using an amplifier 112 with a low input impedance such as a transimpedance amplifier, the infrared detection signals from the respective infrared sensor elements 10 can be processed as currents and added together.

[0213] (Embodiment 3)

[0214] Next, the infrared sensor of Embodiment 3 will be described. In the following description, the description will focus on the differences from Embodiment 1 and Embodiment 2, and the description of the common points will be omitted or simplified.

[0215] Figure 13 It is a block diagram showing the overall configuration of the infrared sensor 201 of Embodiment 3.

[0216] As Figure 13 shown, compared with the infrared sensor 101 of Embodiment 2, the infrared sensor 201 of the present embodiment is different in that it has one infrared sensor element 10 instead of the element array 10A composed of a plurality of infrared sensor elements 10, and in that it has a switch circuit 211 instead of the switch circuit 111.

[0217] The switch circuit 211 is a circuit having a switch and wiring and connecting the infrared sensor element 10 and the amplifier 112. The detailed configuration of the switch circuit 211 will be described later.

[0218] Next, the circuit configuration of the infrared sensor 201 of the present embodiment will be described.

[0219] Figure 14This is a diagram showing the circuit configuration of the infrared sensor 201 of Embodiment 3. In addition, in Figure 14 the circuit configurations of the infrared sensor element 10, the switch circuit 211, and the amplifier 112 are shown, and the illustration of other circuit configurations included in the infrared sensor 201 is omitted. In addition, in Figure 14 the state of the switch in the noise measurement mode is shown.

[0220] The infrared sensor 201 has a configuration in which a plurality of infrared sensor elements 10 of the infrared sensor 101 of Embodiment 2 are reduced to one infrared sensor element 10. In addition, the infrared sensor 201 also has a configuration in which the amplifier 12 of the infrared sensor of the above Configuration Example 4 is changed to the amplifier 112. In the infrared sensor 201, one infrared sensor element 10 is connected to one amplifier 112. That is, the infrared sensor element 10 and the amplifier 112 have a one-to-one configuration.

[0221] As Figure 14 shown, the infrared sensor 201 includes a parallel switch SW2 as the switch included in the switch circuit 211. The parallel switch SW2 is an example of the first switch. In addition, in the parallel switch SW2, the content described in the above “(Insight underlying the present disclosure)” can be applied.

[0222] Next, the operation of the infrared sensor 201 of Embodiment 3 and the result of calculating the leakage of the infrared detection signal will be described. The operation of the parallel switch SW2 of the switch circuit 211 described below is based on the control of the control circuit 13.

[0223] Figure 15 This is a diagram for explaining the result of calculating the leakage of the infrared detection signal in the infrared sensor 201 of Embodiment 3. In Figure 15 the state of the switch in the noise measurement mode, the leakage rate of the infrared detection signal, and the state of the switch in the infrared measurement mode and the error of the infrared detection signal in the infrared sensor 201 of Embodiment 3 are shown in tabular form in the row marked “Embodiment 3”. The definitions of the leakage rate of the infrared detection signal and the error of the infrared detection signal are as described in the explanation in Figure 11 .

[0224] In addition, in Figure 15 the leakage rate of the infrared detection signal and the error of the infrared detection signal are calculated under the following conditions. The resistance when the parallel switch SW2 is off is set to 1 GΩ, and the resistance when it is on is set to 100 Ω. In addition, the input impedance Z in of the amplifier 112 is set to 0 Ω.

[0225] AsFigure 15 As shown, in the noise measurement mode, the infrared sensor 201 of Embodiment 3 turns on the parallel switch SW2. In addition, in the infrared measurement mode, the infrared sensor 201 turns off the parallel switch SW2.

[0226] As a result of such an operation, as Figure 15 shown in the row of "Embodiment 3", the leakage rate of the infrared detection signal in the noise measurement mode is 0.0%. In addition, the error of the infrared detection signal in the infrared measurement mode is -0.1%. Therefore, by obtaining the difference between the outputs of the amplifier 112 in the infrared measurement mode and the noise measurement mode, the offset component and 1 / f noise of the amplifier 112 can be eliminated. This elimination process is performed by the signal processing circuit 100, for example.

[0227] As described above, as Figure 15 explained, the infrared sensor 201 of Embodiment 3 is less likely to cause an error in the output of the amplifier 112, and the detection accuracy of infrared rays can be improved.

[0228] In addition, in the infrared sensor 201, the amplifier 112, which is a current input type amplifier with a low input impedance, is also provided in the same manner as the infrared sensor 101 of Embodiment 2. Therefore, even if a short-circuit current V IR / R 0 ( Figure 14 wherein I) is generated in the noise measurement mode, a current of the same magnitude as the short-circuit current V IR / R 0 flows into the amplifier 112 in the infrared measurement mode. Thus, in the infrared sensor 201, the same effect as the above-described infrared sensor 101 is obtained: even when switching from the noise measurement mode to the infrared measurement mode, the temperature distribution between the warm junction and the cold junction is less likely to change.

[0229] (Other Embodiments)

[0230] As described above, the infrared sensor of the present disclosure has been described based on the embodiments, but the present disclosure is not limited to these embodiments. As long as it does not deviate from the gist of the present disclosure, the solutions obtained by applying various modifications conceived by those skilled in the art to the embodiments and the other solutions constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present disclosure.

[0231] For example, in the above embodiments, the thermoelectric conversion unit 60 is a thermopile type thermoelectric conversion element, but it is not limited thereto. The thermoelectric conversion unit 60 may also be a thermoelectric conversion element having a thermoelectric conversion structure other than the thermopile structure.

[0232] In addition, in the above-described embodiments, the number of amplifiers 12 and 112 included in the infrared sensors 1, 101, and 201 is one, but it is not limited thereto. As long as the relationship between the number of infrared sensor elements 10 and the number of amplifiers 12 and 112 is maintained, the number of amplifiers 12 and 112 included in the infrared sensors 1, 101, and 201 may also be plural. For example, in the infrared sensors 1 and 101, amplifiers 12 (AFE) may be provided for each pixel column, pixel row, or pixel block. Additionally, for example, the infrared sensor 201 may be an infrared image sensor including a plurality of infrared sensor elements 10 and the same number of amplifiers 112 as the plurality of infrared sensor elements 10.

[0233] Industrial Applicability

[0234] The infrared sensor of the present disclosure can be used for various applications including applications of conventional infrared sensors such as infrared imaging elements. In the infrared sensor of the present disclosure, an uncooled and highly accurate infrared sensor can be achieved. Therefore, it can also be applied to a driving monitor capable of detecting a person at night, a simple thermal imager capable of efficiently measuring the body temperature of a group, and the like.

[0235] Explanation of Reference Numerals

[0236] 1, 1X, 1Y, 101, 201 Infrared sensors

[0237] 10, 10_1 to 10_N Infrared sensor elements

[0238] 10A Element array

[0239] 11, 111, 211 Switching circuits

[0240] 12, 112 Amplifiers

[0241] 13 Control circuit

[0242] 30 Substrate

[0243] 31 Semiconductor substrate

[0244] 32, 41 Insulating films

[0245] 33 Protective film

[0246] 40 Light-receiving portion

[0247] 42 Semiconductor

[0248] 50 Hollow support portion

[0249] 51 Gap

[0250] 53 Recessed space

[0251] 55 Sacrificial layer

[0252] 60 Thermoelectric conversion section

[0253] 61, 62 Hot junction metal electrodes

[0254] 63n, 63p, 64n, 64p Cold junction metal electrodes

[0255] 65n, 66n N-type semiconductors

[0256] 65p, 66p P-type semiconductors

[0257] 67, 71, 83, 84 Metal wirings

[0258] 80 Transistor

[0259] 80d Drain

[0260] 80g Gate

[0261] 80s Source

[0262] 80w Well region

[0263] 100 Signal processing circuit

[0264] Lin Infrared incident light

[0265] SW1, SW1_1 to SW1_N Series switches

[0266] SW2, SW2_1 to SW2_N, SW3 Parallel switches

Claims

1. An infrared sensor, comprising: a substrate; a sensor element that generates an infrared detection signal; a first switch connected to the sensor element; and an amplifier that amplifies the infrared detection signal generated by the sensor element, wherein the sensor element has: a light-receiving portion located above the substrate; a hollow support portion that combines the substrate and the light-receiving portion and hollowly supports the light-receiving portion in such a manner that a gap is formed between the substrate and the light-receiving portion; and a thermoelectric conversion portion that generates the infrared detection signal based on heat generated by the light-receiving portion, the thermoelectric conversion portion includes a first terminal that outputs the infrared detection signal and a second terminal that is held at a predetermined potential, the first switch connects the first terminal and the second terminal in a short-circuitable manner, the amplifier is a current-input type amplifier.

2. The infrared sensor according to claim 1, the infrared sensor includes a plurality of the sensor elements and a plurality of the first switches, the infrared sensor further includes a plurality of second switches each connected to one of the plurality of sensor elements in a one-to-one manner, each of the plurality of second switches is a semiconductor-type switch and independently switches conduction and non-conduction between each of the plurality of sensor elements and the amplifier.

3. The infrared sensor according to claim 2, the infrared sensor further includes a control circuit that, by making two or more of the plurality of second switches simultaneously conductive, causes two or more of the plurality of sensor elements connected to the two or more second switches to simultaneously output the infrared detection signal to the amplifier.

4. The infrared sensor according to any one of claims 1 to 3, at least a part of the thermoelectric conversion portion is provided in the hollow support portion, the hollow support portion has a phononic crystal structure.

5. An infrared sensor, comprising: a substrate; a plurality of sensor elements that generate an infrared detection signal; a plurality of first switches each connected to one of the plurality of sensor elements in a one-to-one manner; an amplifier that amplifies the infrared detection signal generated by the plurality of sensor elements; a plurality of second switches each connected to one of the plurality of sensor elements in a one-to-one manner and independently switching conduction and non-conduction between each of the plurality of sensor elements and the amplifier; and a third switch connected to an input terminal of the amplifier and capable of short-circuiting the input terminal to a reference potential, each of the plurality of sensor elements has: a light-receiving portion located above the substrate; a hollow support portion that combines the substrate and the light-receiving portion and hollowly supports the light-receiving portion in such a manner that a gap is formed between the substrate and the light-receiving portion; and a thermoelectric conversion portion that generates the infrared detection signal based on heat generated by the light-receiving portion, the thermoelectric conversion portion includes a first terminal that outputs the infrared detection signal and a second terminal that is held at a predetermined potential, each of the plurality of first switches connects the first terminal and the second terminal in a short-circuitable manner, Each of the plurality of second switches is a semiconductor switch, The amplifier is a voltage-input type amplifier.

6. An infrared sensor, comprising: A substrate; A sensor element that generates an infrared detection signal; A first switch connected to the sensor element; and An amplifier that amplifies the infrared detection signal generated by the sensor element, The sensor element has: A light-receiving portion located above the substrate; A support portion that combines the substrate and the light-receiving portion and supports the light-receiving portion; and A thermoelectric conversion portion that generates the infrared detection signal based on heat generated by the light-receiving portion, The thermoelectric conversion portion includes a first terminal that outputs the infrared detection signal and a second terminal that is held at a predetermined potential, The first switch connects the first terminal and the second terminal so as to be short-circuitable, The amplifier is a current-input type amplifier.

Images