Infrared sensor

Abstract

An infrared sensor is provided with a light receiving unit and a thermoelectric conversion unit (60) that generates an infrared detection signal on the basis of heat generated by the light receiving unit. The thermoelectric conversion unit (60) has an n-type MOSFET (61), a p-type MOSFET (62), a warm contact metal electrode (63), a first cold contact metal electrode (64), and a second cold contact metal electrode (65). The temperature contact metal electrode (63) is located on or adjacent to the light receiving unit, and forms an ohmic junction with the drain (61d) of the n-type MOSFET (61) and the drain (62d) of the p-type MOSFET (62). The first cold contact metal electrode (64) forms an ohmic junction with the source (61s) of the n-type MOSFET (61). The second cold contact metal electrode (65) forms an ohmic junction with the source (62s) of the p-type MOSFET (62).

Description

Technical Field

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

[0002] An infrared sensor using an infrared sensor element is known. The infrared sensor element detects infrared rays by heat generated when receiving infrared rays by a light-receiving unit. In addition, as such an infrared sensor, an infrared imaging element (infrared image sensor) obtained by arranging infrared sensor elements as pixels in an array is known. In order to arrange many 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 converter (Analog-to-Digital). 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 the plurality of infrared sensor elements is provided between the infrared sensor and the AFE. When switching the pixels selected by the pixel selection switch 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. 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 of them can be manufactured as other chips and integrated by mounting.

[0003] On the other hand, if the area of the light-receiving part of the infrared sensor element is reduced, the infrared energy (power) received by the light becomes weak. Furthermore, it is difficult to obtain a spatial temperature difference when using a light-receiving part with a small area. In an infrared sensor element such as a thermocouple or a thermopile that uses the Seebeck effect, that is, an electromotive force based on a temperature difference, as an infrared detection signal, if the temperature difference becomes small, the electromotive force becomes weak and the S / N (Signal / Noise; signal-to-noise ratio) decreases. In view of this problem, Patent Document 1 discloses a technique of hollowly supporting a light-receiving part 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 a 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 upward from the substrate, a phonon crystal structure is provided in the hollow support part, a cold junction is provided on the substrate side, and a hot junction is provided on the light-receiving part side. As a result, the temperature of the hot junction on the light-receiving part whose temperature has changed due to the radiation of infrared rays can easily maintain a temperature difference from the temperature of the cold junction due to the high adiabatic property 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

[0007] Non-Patent Documents

[0008] Non-Patent Document 1: S. Basu, B. J. Lee and M. Zhang, “Infrared Radiative Properties of Heavily Doped Silicon at Room Temperature”, Journal of Heat Transfer, Vol. 132, FEBRUARY 2010.

[0009] Non-Patent Document 2: D. Kobayashi, C.-J. Kim and H. Fujita, “Photoresist-Assisted Release of Movable Microstructures”, Jpn. J. Appl. Phys. Vol. 32 (1993) pp. L1642 - L1644. Summary of the Invention

[0010] In the present disclosure, an infrared sensor capable of improving the detection accuracy of infrared rays is provided.

[0011] An infrared sensor according to one aspect of the present disclosure includes a light receiving unit and a thermoelectric conversion unit that generates an infrared detection signal based on heat generated by the light receiving unit. The thermoelectric conversion unit includes an n-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a p-type MOSFET, a warm junction metal electrode, a first cold junction metal electrode, and a second cold junction metal electrode. The warm junction metal electrode is located on the light receiving unit or adjacent to the light receiving unit, and forms an ohmic junction with the drain of the n-type MOSFET and the drain of the p-type MOSFET. The first cold junction metal electrode forms an ohmic junction with the source of the n-type MOSFET, and the second cold junction metal electrode forms an ohmic junction with the source of the p-type MOSFET.

[0012] According to the present disclosure, the detection accuracy of infrared rays can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a block diagram showing the overall configuration of the infrared sensor according to Embodiment 1.

[0014] Figure 2 is a cross-sectional view showing the infrared sensor element according to Embodiment 1.

[0015] Figure 3 is a plan view of the infrared sensor element according to Embodiment 1 when viewed from above.

[0016] Figure 4A is a diagram for explaining the operation in the noise measurement mode of the infrared sensor according to Embodiment 1.

[0017] Figure 4B is a diagram for explaining the operation in the infrared measurement mode of the infrared sensor according to Embodiment 1.

[0018] Figure 5 is a block diagram showing the overall configuration of the infrared sensor according to Embodiment 2.

[0019] Figure 6A is a diagram for explaining the operation in the noise measurement mode of the infrared sensor according to Embodiment 2.

[0020] Figure 6B is a diagram for explaining the operation in the infrared measurement mode of the infrared sensor according to Embodiment 2.

[0021] Figure 7 is a diagram showing the configuration of the infrared sensor according to Embodiment 3.

[0022] Figure 8 This is a diagram showing an example of the waveform of the voltage output by the voltage supply circuit of Embodiment 3.

[0023] Figure 9 This is a cross-sectional view showing the infrared sensor element of Embodiment 4.

[0024] Figure 10 This is a plan view of the infrared sensor element of Embodiment 4 when viewed from above.

[0025] Figure 11 This is a cross-sectional view showing the infrared sensor element of a modified example of Embodiment 4.

[0026] Figure 12 This is a cross-sectional view showing the infrared sensor element of Embodiment 5.

[0027] Figure 13 This is a cross-sectional view showing the infrared sensor element of a modified example of Embodiment 5.

[0028] Figure 14 This is a cross-sectional view showing the infrared sensor element of Embodiment 6.

[0029] Figure 15A This is a plan view of a part of the channel region of the n-type MOSFET of Embodiment 6 when viewed from above.

[0030] Figure 15B This is a plan view of a part of the channel region of the p-type MOSFET of Embodiment 6 when viewed from above.

[0031] Figure 16A This is a cross-sectional view of a part of the channel region of the n-type MOSFET of Embodiment 6.

[0032] Figure 16B This is a cross-sectional view of a part of the channel region of the p-type MOSFET of Embodiment 6. Detailed Embodiments

[0033] (Insights underlying the present disclosure)

[0034] In an infrared sensor, there is a pursuit of improving the detection accuracy of infrared rays. The technique described in the above Patent Document 1 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 (decreasing) 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 (i.e., the offset component) generated by the amplifier and the 1 / f noise by signal processing. As an example of a specific method, a method can be cited in which a mechanical shutter is provided between the infrared sensor and the infrared source and the signal obtained by opening and closing the mechanical shutter is subjected to signal processing.

[0035] In this method, as the first stage, the output information of the AFE when the shutter is "closed" is obtained. 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 obtained. 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 and the 1 / f noise of the amplifier and does not include information from infrared rays.

[0036] Next, as the second stage, the output information of the AFE when the shutter is "open" is obtained. That is, an infrared detection signal is output from the infrared sensor element to the AFE, and the output information obtained by processing the infrared detection signal by the AFE is obtained. 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 and the 1 / f noise of the amplifier to the information from infrared rays.

[0037] 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. Regardless of 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.

[0038] Since the mechanical shutter is not suitable for a small imaging element, the opening and closing of the shutter can be analogously replaced by a semiconductor switch, and the noise measurement mode and the infrared ray measurement mode are implemented using the semiconductor switch. For example, the noise measurement mode and the infrared ray measurement mode can be switched by the operation of 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.

[0039] The inventors of the present application have found the following problems in the case of switching the measurement mode using such a semiconductor switch.

[0040] 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 current leakage 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 greater the signal leaking from the measurement mode switching switch in the off state. 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.

[0041] 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.

[0042] The inventors of the present application focused on the problem that when realizing an infrared sensor with high detection accuracy, the detection accuracy of the infrared sensor decreases due to the leakage of the infrared detection signal caused by the characteristics of the semiconductor switch. As a result of intensive research by the inventors of the present application, it was found that the above problem can be solved by having a configuration that can temporarily eliminate the function of the infrared sensor element to generate an infrared detection signal, and thus one aspect of the present disclosure was obtained. The details are described below.

[0043] (Summary of the present disclosure)

[0044] An example of the infrared sensor of the present disclosure is shown below.

[0045] The infrared sensor according to the first aspect of the present disclosure includes a light-receiving portion and a thermoelectric conversion portion that generates an infrared detection signal based on heat generated by the light-receiving portion. The thermoelectric conversion portion includes an n-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a p-type MOSFET, a warm-junction metal electrode, a first cold-junction metal electrode, and a second cold-junction metal electrode. The warm-junction metal electrode is located on the light-receiving portion or at a position adjacent to the light-receiving portion, and forms an ohmic junction with the drain of the n-type MOSFET and the drain of the p-type MOSFET. The first cold-junction metal electrode forms an ohmic junction with the source of the n-type MOSFET, and the second cold-junction metal electrode forms an ohmic junction with the source of the p-type MOSFET.

[0046] According to this configuration, the mixing of unintended infrared detection signals can be suppressed, and the detection accuracy of infrared rays can be improved.

[0047] Specifically, in a case such as the noise measurement mode where it is not desired to output an infrared detection signal from the thermoelectric conversion unit, by applying a gate voltage that does not form an n-type channel to the n-type MOSFET and a gate voltage that does not form a p-type channel to the p-type MOSFET, a configuration having a thermoelectric conversion function that is electrically connected in series with "cold junction - n-type semiconductor - warm junction - p-type semiconductor - cold junction" is not formed in the thermoelectric conversion unit. That is, even if the light receiving unit receives infrared rays and a temperature difference is generated between the warm junction and the cold junction, thermoelectric conversion based on the Seebeck effect is not performed in the thermoelectric conversion unit. Therefore, for example, in the noise measurement mode, the offset component and 1 / f noise of the amplifier can be measured without mixing in the infrared detection signal from the thermoelectric conversion unit.

[0048] In addition, according to this configuration, for example, when used in an application where one thermoelectric conversion unit is selected from multiple thermoelectric conversion units to output an infrared detection signal, in the selected thermoelectric conversion unit, by applying a gate voltage that forms an n-type channel to the n-type MOSFET and a gate voltage that forms a p-type channel to the p-type MOSFET, a configuration having a thermoelectric conversion function that is electrically connected in series with "cold junction - n-type semiconductor - warm junction - p-type semiconductor - cold junction" is formed in the thermoelectric conversion unit. Therefore, thermoelectric conversion based on the Seebeck effect is performed in the thermoelectric conversion unit to generate an infrared detection signal. On the other hand, in the non-selected thermoelectric conversion unit, by applying a gate voltage that does not form an n-type channel to the n-type MOSFET and a gate voltage that does not form a p-type channel to the p-type MOSFET, a configuration having a thermoelectric conversion function as described above is not formed, and thermoelectric conversion is not performed. Therefore, in the non-selected thermoelectric conversion unit, an infrared detection signal is not generated, and interference with the infrared detection signal generated from the selected thermoelectric conversion unit can be suppressed.

[0049] In addition, for example, the infrared sensor according to the second aspect of the present disclosure further includes an amplifier that amplifies the infrared detection signal generated by the thermoelectric conversion unit based on the infrared sensor according to the first aspect, and the amplifier is a voltage input type amplifier.

[0050] According to this configuration, when the thermoelectric conversion unit outputs an infrared detection signal to the amplifier, due to the high input impedance of the voltage input type amplifier, almost no current flows from the thermoelectric conversion unit to the amplifier. Therefore, when the thermoelectric conversion unit outputs an infrared detection signal to the amplifier, it is difficult to generate a current that contributes to the manifestation of the Peltier effect opposite to the Seebeck effect in the thermoelectric conversion unit. Therefore, the temperature distribution of the thermoelectric conversion unit hardly changes, and it is difficult to generate an error even when reading the output of the amplifier immediately after outputting this infrared detection signal. For example, when switching from the noise measurement mode to the infrared measurement mode, the magnitude of the current flowing through the thermoelectric conversion unit hardly changes before and after this switching moment. Therefore, the temperature distribution of the thermoelectric conversion unit hardly changes. Therefore, even when reading the output from the amplifier immediately after switching, it is possible to suppress the error generated during the redistribution process of the temperature distribution and ensure a high S / N. Thus, the infrared sensor of this solution can perform a high-precision and high-speed detection operation.

[0051] In addition, for example, the infrared sensor according to the third aspect of the present disclosure, based on the infrared sensor according to the first aspect or the second aspect, further includes a substrate, and the light receiving portion, the n-type MOSFET, and the p-type MOSFET are located above the substrate, and a gap is formed between the light receiving portion, the n-type MOSFET, and the p-type MOSFET and the substrate.

[0052] According to this configuration, the periphery of the light receiving portion is a gas such as air with a low thermal conductivity or a gas such as air after being decompressed. Therefore, most of the heat generated in the light receiving portion due to infrared irradiation will flow only to the cold junction side via the p-type MOSFET and the n-type MOSFET, and it is easy to ensure the temperature difference between the warm junction and the cold junction. Thus, an infrared detection signal with a high S / N can be obtained.

[0053] In addition, for example, the infrared sensor according to the fourth aspect of the present disclosure, based on the infrared sensor according to the third aspect, at least one of the gates of the n-type MOSFET and the p-type MOSFET has a phononic crystal structure.

[0054] According to this configuration, since the adiabatic property of at least one of the gates of the p-type MOSFET and the n-type MOSFET becomes higher, it is easy to ensure the temperature difference between the warm junction and the cold junction. Thus, an infrared detection signal with a high S / N can be obtained.

[0055] In addition, for example, the infrared sensor according to the fifth aspect of the present disclosure, based on the infrared sensor according to the third aspect or the fourth aspect, at least one of the source, drain, and channel regions of the n-type MOSFET and the p-type MOSFET has a phononic crystal structure.

[0056] According to this configuration, the adiabatic property of the portions with a phononic crystal structure in the p-type MOSFET and the n-type MOSFET becomes higher. Therefore, it is easy to ensure the temperature difference between the hot junction and the cold junction. Thus, an infrared detection signal with a high S / N can be obtained.

[0057] Further, for example, in the infrared sensor according to the sixth aspect of the present disclosure, based on the infrared sensor according to any one of the third to fifth aspects, at least one of the channel regions of the n-type MOSFET and the p-type MOSFET has a phononic crystal structure, and a gate of at least one of the n-type MOSFET and the p-type MOSFET is formed on the inner wall of the pores of the phononic crystal structure.

[0058] According to this configuration, it is possible to minimize the volume of the gate in at least one of the p-type MOSFET and the n-type MOSFET, and the adiabatic property of at least one of them becomes higher. Therefore, it is easy to ensure the temperature difference between the hot junction and the cold junction. Thus, an infrared detection signal with a high S / N can be obtained.

[0059] Further, for example, in the infrared sensor according to the seventh aspect of the present disclosure, based on the infrared sensor according to any one of the first to sixth aspects, a part of the gate oxide film of at least one of the n-type MOSFET and the p-type MOSFET is removed.

[0060] According to this configuration, in at least one of the p-type MOSFET and the n-type MOSFET, the gate oxide film is removed and replaced with a gas such as air having a lower thermal conductivity than the gate oxide film or a gas such as air after being decompressed. Therefore, it is easy to ensure the temperature difference between the hot junction and the cold junction. Thus, an infrared detection signal with a high S / N can be obtained.

[0061] Further, for example, in the infrared sensor according to the eighth aspect of the present disclosure, based on the infrared sensor according to any one of the first to seventh aspects, a voltage having a periodic repetitive waveform is applied to the gate of the n-type MOSFET and the gate of the p-type MOSFET.

[0062] According to this configuration, by performing signal processing in the frequency band of the frequency of the repetitive waveform, noise components can be removed, and even a weak infrared detection signal can be extracted with high accuracy.

[0063] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0064] In addition, the embodiments described below are all embodiments showing general or specific examples. The numerical values, shapes, materials, constituent elements, arrangement positions of the constituent elements, connection methods, 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.

[0065] In addition, each figure is a schematic diagram and is not necessarily drawn precisely. Therefore, for example, the scales in each figure are not necessarily the same. In addition, in each figure, substantially the same constituent elements are denoted by the same reference numerals, and repeated descriptions are omitted or simplified.

[0066] In addition, in this specification, terms indicating the relationship between elements such as parallel, and terms indicating the shape of elements such as rectangle, and numerical ranges are not expressions indicating only strict meanings, but are expressions meaning that they also include substantially equivalent ranges, for example, ranges with a difference of about several %.

[0067] 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 always used to specify the mutual arrangement between members and are not intended to limit the posture during the use of the infrared sensor. In addition, terms such as "above" and "below" are applicable not only to the case where two constituent elements are arranged at intervals and there are other constituent elements between the two constituent elements, but also to the case where two constituent elements are arranged closely and the two constituent elements are in contact.

[0068] In addition, in this specification, unless otherwise specified, "planar observation" means 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).

[0069] In addition, in this specification, unless otherwise specified, ordinal numbers such as "first" and "second" do not mean the number or order of the constituent elements, but are used for the purpose of distinguishing the constituent elements to avoid confusion of the same kind of constituent elements.

[0070] (Embodiment 1)

[0071] Hereinafter, the infrared sensor of Embodiment 1 will be described.

[0072] [Overall Configuration]

[0073] First, the overall configuration of the infrared sensor of Embodiment 1 will be described.

[0074] Figure 1 It is a block diagram showing the overall configuration of the infrared sensor 1 of Embodiment 1.

[0075] As Figure 1 shown, the infrared sensor 1 includes an infrared sensor element 10, a switch 11, an amplifier 12, and a control circuit 13. The infrared sensor 1 includes, for example, a semiconductor substrate 30 described later and is an infrared sensor chip formed on one semiconductor substrate 30. In addition, a part of the infrared sensor 1 may 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 semiconductor substrate 30 on which the infrared sensor element 10 and the switch 11 are formed.

[0076] The infrared sensor element 10 generates an infrared detection signal corresponding to the amount of infrared light received and outputs the generated infrared detection signal. The infrared sensor element 10 is configured to be able to temporarily disable the function of generating the infrared detection signal. Details of the infrared sensor element 10 will be described later.

[0077] The switch 11 is a switch disposed on the path between the infrared sensor element 10 and the amplifier 12. The switch 11 switches the conduction and non - conduction between the infrared sensor element 10 and the amplifier 12. In addition, the infrared sensor 1 may not include the switch 11.

[0078] The amplifier 12 amplifies the infrared detection signal generated by the infrared sensor element 10. The amplifier 12 is, for example, a part of an AFE. Although not shown, the infrared sensor 1 may include, in addition to the amplifier 12, a filter and an AD converter included in the AFE. The amplifier 12 outputs the amplified infrared detection signal. The output from the amplifier 12 is input to, for example, the signal processing circuit 100. The output information from the amplifier 12 can be converted into encoded digital information by an AD converter.

[0079] In the present embodiment, the infrared sensor element 10 and the amplifier 12 are in a one - to - one configuration. In addition, as long as the infrared sensor element 10 and the amplifier 12 are in a one - to - one relationship, the infrared sensor 1 may also be an array sensor including a plurality of infrared sensor elements 10 and a plurality of amplifiers 12.

[0080] The control circuit 13 controls the entirety of the infrared sensor 1. For example, the control circuit 13 controls, by outputting a control signal, whether to disable the function of causing the infrared sensor element 10 to generate an infrared detection signal and the operation of the switch 11. The control circuit 13 supplies, for example, control signals (such as high-level or low-level voltages) for controlling the infrared sensor element 10 and the switch 11 to the infrared sensor element 10 and the switch 11. Details of the control performed by the control circuit 13 will be described later. 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 an infrared measurement mode and a 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.

[0081] The control circuit 13 includes, for example, one or more microcomputers or processors having a program for performing control processing of the infrared sensor 1 built therein. The control circuit 13 can include a dedicated logic circuit for performing control processing of the infrared sensor 1.

[0082] The signal processing circuit 100 performs various signal processes on the output from the amplifier 12. The signal processing circuit 100 performs, for example, a process of 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 between the output information of the amplifier 12 (AFE) in the infrared measurement mode and the noise measurement mode.

[0083] The signal processing circuit 100 includes, for example, one or more microcomputers or processors having a program for performing control processing built therein. The signal processing circuit 100 can include a dedicated logic circuit for performing signal processing.

[0084] The signal processing circuit 100 is provided, for example, in an external signal processing device, but can 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 can be implemented by one microcomputer or processor, or can be implemented by one or more microcomputers or processors that are respectively independent.

[0085] [Infrared sensor element]

[0086] Next, the detailed configuration of the infrared sensor element 10 included in the infrared sensor 1 will be described.

[0087] Figure 2 is a cross-sectional view showing the infrared sensor element 10 of Embodiment 1. Figure 3This is a plan view of the infrared sensor element 10 of Embodiment 1 when viewed from above. In addition, Figure 2 represents Figure 3 a cross-section taken along line II-II shown in the figure. In addition, in Figure 3 the outlines of the reflective surface 42 and the gate electrodes 61g, 62g that are actually covered by the insulating film 41 are shown by dashed lines.

[0088] As Figure 2 and Figure 3 shown, the infrared sensor element 10 includes a light-receiving unit 40 and a thermoelectric conversion unit 60. The infrared sensor element 10 is formed, for example, on the upper surface of the semiconductor substrate 30 included in the infrared sensor 1.

[0089] The semiconductor substrate 30 is a substrate for forming the infrared sensor element 10 and peripheral circuits, etc. The semiconductor substrate 30 is, for example, a p-type silicon substrate made of single-crystalline silicon, but may also be an n-type semiconductor substrate or a semiconductor substrate made of a semiconductor material other than single-crystalline silicon, etc., i.e., a semiconductor substrate other than a p-type silicon substrate. Hereinafter, it will be described assuming that the semiconductor substrate 30 is a substrate made of a p-type semiconductor.

[0090] On the semiconductor substrate 30, a reflective surface 42, an n-type MOSFET 61, and a p-type MOSFET 62, which will be described later, are formed. In addition, although not shown, at least one of a switch 11, an amplifier 12, a configuration of an AFE other than the amplifier 12, a control circuit 13, and a signal processing circuit 100 may be formed on the semiconductor substrate 30.

[0091] The thermoelectric conversion unit 60 generates an infrared detection signal based on the heat generated by the light-receiving unit 40. The thermoelectric conversion unit 60 includes an n-type MOSFET 61, a p-type MOSFET 62, a hot-junction metal electrode 63, a first cold-junction metal electrode 64, and a second cold-junction metal electrode 65.

[0092] The n-type MOSFET 61 includes a source 61s, a drain 61d, and a gate 61g. Additionally, a gate oxide film is disposed between the gate 61g, which is a conductive layer, and the channel region located between the source 61s and the drain 61d. The source 61s and the drain 61d of the n-type MOSFET 61 are n-type impurity regions formed by diffusing n-type impurities into the semiconductor substrate 30. The channel region of the n-type MOSFET 61 is a part of the semiconductor substrate 30 that is a p-type semiconductor. The channel region is the region in the MOSFET where a channel is formed. The gate 61g of the n-type MOSFET 61 is, for example, a conductive material such as polysilicon. The gate 61g is connected to a metal electrode 61e disposed on the insulating film 41. The metal electrode 61e is connected to the control circuit 13 via, for example, wiring (not shown). A voltage from the control circuit 13 is applied to the gate 61g via the metal electrode 61e. The metal electrode 61e is made of, for example, a metal such as aluminum.

[0093] The p-type MOSFET 62 includes a source 62s, a drain 62d, a gate 62g, and a well region 62w. Additionally, a gate oxide film is disposed between the gate 62g, which is a conductive layer, and the channel region located between the source 62s and the drain 62d. The well region 62w of the p-type MOSFET 62 is an n-type impurity region formed by diffusing n-type impurities into the semiconductor substrate 30. The source 62s and the drain 62d of the p-type MOSFET 62 are p-type impurity regions formed by diffusing p-type impurities into the well region 62w. The channel region of the p-type MOSFET 62 is a part of the well region 62w that is an n-type semiconductor. The gate 62g of the p-type MOSFET 62 is, for example, a conductive material such as polysilicon. The gate 62g is connected to a metal electrode 62e disposed on the insulating film 41. The metal electrode 62e is connected to the control circuit 13 via, for example, wiring (not shown). A voltage from the control circuit 13 is applied to the gate 62g via the metal electrode 62e. The metal electrode 62e is made of, for example, a metal such as aluminum.

[0094] In Figure 2 the example shown, the gate 61g and the gate 62g are buried in the insulating film 41, but in the case where the insulating film 41 is thin, they may be formed on the insulating film 41.

[0095] The thermocouple metal electrode 63 is located on the light-receiving portion 40. In addition, the thermocouple metal electrode 63 may be located at any position as long as its temperature changes synchronously with the temperature of the light-receiving portion 40, and there is no particular limitation. For example, it may also be located at a position adjacent to the light-receiving portion 40.

[0096] The thermocouple metal electrode 63 forms an ohmic junction with the drain 61d of the n-type MOSFET 61 and the drain 62d of the p-type MOSFET 62. The thermocouple metal electrode 63 forms a thermocouple through this ohmic junction.

[0097] The first cold-junction metal electrode 64 and the second cold-junction metal electrode 65 are located outside the light-receiving portion 40 in a plan view. The first cold-junction metal electrode 64 and the second cold-junction metal electrode 65 are arranged so as to sandwich the light-receiving portion 40 in a plan view, for example.

[0098] The first cold-junction metal electrode 64 forms an ohmic junction with the source 61s of the n-type MOSFET 61. The first cold-junction metal electrode 64 forms a cold junction through this ohmic junction.

[0099] The second cold-junction metal electrode 65 forms an ohmic junction with the source 62s of the p-type MOSFET 62. The second cold-junction metal electrode 65 forms a cold junction through this ohmic junction.

[0100] If the n-type MOSFET 61 forms an n-type channel and the p-type MOSFET 62 forms a p-type channel, a configuration electrically connected in series as "cold junction - n-type semiconductor - warm junction - p-type semiconductor - cold junction" is formed, and the thermoelectric conversion unit 60 can exhibit a thermoelectric conversion function. That is, by the n-type MOSFET 61 forming an n-type channel and the p-type MOSFET 62 forming a p-type channel, the thermoelectric conversion unit 60 can generate an infrared detection signal. It can also be said that the "thermoelectric conversion function" is the function of the thermoelectric conversion unit 60 (infrared sensor element 10) to generate an infrared detection signal.

[0101] The warm-junction metal electrode 63, the first cold-junction metal electrode 64, and the second cold-junction metal electrode 65 are each composed of, for example, a metal via extending in the thickness direction of the insulating film 41 in the insulating film 41 and a metal wiring disposed on the insulating film 41. The metal via is in contact and connected to each of the drain 61d, the drain 62d, the source 61s, or the source 62s, and the metal wiring. The metal via is made of a high-melting-point metal such as tungsten, for example. The metal wiring is made of a metal such as aluminum, for example.

[0102] The light-receiving portion 40 generates heat by absorbing infrared rays, and the temperature of the light-receiving portion 40 rises due to this heat. The amount of heat generated by the light-receiving portion 40 depends on the amount of infrared ray absorption in the light-receiving portion 40. The light-receiving portion 40 is located above the semiconductor substrate 30. By the temperature rise of the light-receiving portion 40, a temperature difference can be imparted between the warm junction and the cold junction.

[0103] In the present embodiment, the light-receiving portion 40 includes a portion on the reflecting surface 42 in the insulating film 41. In Figure 3In the example shown, the light-receiving part 40 is an area on the semiconductor substrate 30 where a reflecting surface 42 and a hot-junction metal electrode 63 are formed in a plan view. Additionally, for example, a plurality of reflecting surfaces 42 are formed, and in a plan view, the hot-junction metal electrode 63 is sandwiched by the reflecting surfaces 42. The hot-junction metal electrode 63 is disposed, for example, in an area including the center of the light-receiving part 40 in a plan view.

[0104] The insulating film 41 is disposed above the semiconductor substrate 30. The insulating film 41 is formed of, for example, silicon oxide, but may also be formed of an insulating material other than silicon oxide (e.g., silicon nitride).

[0105] The reflecting surface 42 is, for example, the upper surface of a high-concentration impurity region in the upper surface of the semiconductor substrate 30 where the infrared reflectivity is increased by doping the semiconductor substrate 30 with a high concentration of p-type impurities. This is also a technique described in Non-Patent Document 1. For example, compared with an undoped silicon substrate, the infrared reflectivity of a silicon substrate doped with boron (B) at a high concentration of about 10 20 cm -3 is greater. The impurity concentration in the high-concentration impurity region is higher than that in the portion of the semiconductor substrate 30 below the high-concentration impurity region. The impurity concentration in the high-concentration impurity region is, for example, 10 19 cm -3 or more and 10 21 cm -3 or less. The stacked structure of the reflecting surface 42 and the dielectric (here, the insulating film 41) stacked thereon forms a dielectric thin-film type infrared absorption structure.

[0106] If the light-receiving part 40 absorbs infrared rays and as a result, the temperature of the hot junction is higher than the temperature of the cold junction, many carriers gather toward the cold-junction side. As a result, if the n-type MOSFET 61 forms an n-type channel and the p-type MOSFET 62 forms a p-type channel, the cold junction of the n-type MOSFET 61 has a negative electromotive force with respect to the cold junction of the p-type MOSFET 62. That is, a potential difference corresponding to the heat generated by the light-receiving part 40 is generated between the first cold-junction metal electrode 64 and the second cold-junction metal electrode 65. At this time, if the second cold-junction metal electrode 65 is maintained at a reference potential, an infrared detection signal corresponding to this electromotive force is output from the first cold-junction metal electrode 64. In addition, the temperature relationship between the "hot junction" and the "cold junction" of the thermoelectric conversion part 60 is not necessarily that the temperature of the hot junction is higher than the temperature 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 hot junction is lower than the temperature of the cold junction. At this time, the polarity of the electromotive force of the thermoelectric conversion part 60 is reversed.

[0107] Such an infrared sensor element 10 can be manufactured by using a processing technique used for manufacturing semiconductor devices, for example.

[0108] [action]

[0109] Next, the operation of the infrared sensor 1 according to the present embodiment will be described.

[0110] Figure 4A This is a diagram for explaining the operation of the infrared sensor 1 according to the first embodiment in the noise measurement mode. Figure 4B 1 is a diagram for explaining the operation of the infrared sensor 1 according to the first embodiment in the infrared measurement mode. Figure 4A as well as Figure 4B , a cross section of the infrared sensor element 10 and a schematic circuit configuration of the switch 11 , the amplifier 12 , and wiring connected to the infrared sensor element 10 are schematically shown.

[0111] like Figure 4A as well as Figure 4B As shown, a bias voltage V is applied to the second cold junction metal electrode 65 connected to the source 62s of the p-type MOSFET 62. bias Furthermore, the first cold junction metal electrode 64 connected to the source 61s of the n-type MOSFET 61 is connected to the input terminal of the amplifier 12 via the switch 11. The infrared detection signal generated by the infrared sensor element 10 is output from the first cold junction metal electrode 64 to the amplifier 12.

[0112] The amplifier 12 is, for example, a voltage input amplifier with high input impedance. In the example shown in the figure, the amplifier 12 is a voltage input / voltage output type voltage amplifier. The voltage amplifier is, for example, composed of a non-inverting amplifier circuit using an operational amplifier. In the example shown in the figure, the non-inverting input terminal of the operational amplifier is connected to the switch 11, and the inverting input terminal of the operational amplifier is connected to the switch 11 via the resistor R 1 Connect to bias voltage V bias , and, through the resistor R 2 Connect to the output terminal of the operational amplifier. 1 and resistor R 2 The voltage gain G of the non-inverting amplifier circuit becomes 1+(R 2 / R 1 ). Regarding the input impedance Z of amplifier 12 in , the input resistance between the two input terminals of the operational amplifier is set to R i , set the open-loop gain to A 0 When Z in =R i ·A 0 / G is established. For example, in Ri = 100 MΩ, A 0 = 120 dB, G = 1000, Z in = 100 GΩ. Therefore, the input impedance of amplifier 12 is very high. In addition, there is no particular limitation on amplifier 12. For example, an active element with a high input impedance may be used for amplifier 12, and amplifier 12 may be a transconductance amplifier (voltage input / current output type amplifier) or a voltage follower (amplifier with a magnification of 1).

[0113] Switch 11 is provided in front of the input terminal of amplifier 12. Switch 11 is connected to infrared sensor element 10 and amplifier 12 in such a way that it can block the transmission of the infrared detection signal from infrared sensor element 10 to amplifier 12. Switch 11 is, for example, a single-pole double-throw (SPDT (Single-Pole Double-Throw)) type switch. Switch 11 can switch the connection destination of the input terminal of amplifier 12 to the first cold-junction metal electrode 64 and the bias voltage V bias Switching. Switch 11 corresponds to the measurement mode switching switch described above. Switch 11 may be a mechanical switch, but from the perspective of compatibility with the semiconductor manufacturing process for manufacturing infrared sensor 1, for example, it is a semiconductor switch. Generally speaking, the isolation in the closed state of a semiconductor switch is worse than that of a mechanical switch. In addition, in this specification, "blocking" and "non-conduction" of the switch indicate substantially blocked and non-conductive states, and are expressions that also include cases where signals leak out even though they do not completely become blocked and non-conductive states.

[0114] First, the operation of infrared sensor 1 in the noise measurement mode will be described. As Figure 4A shown, in the noise measurement mode, switch 11 connects the bias voltage V bias to the input terminal of amplifier 12. In addition, in the noise measurement mode, the gate voltage V L that does not form an n-channel is applied to the gate 61g of n-type MOSFET 61 by control circuit 13. In addition, in the noise measurement mode, the gate voltage V H that does not form a p-channel is applied to the gate 62g of p-type MOSFET 62 by control circuit 13. As specific examples of gate voltage V L and gate voltage V H , gate voltage V L is at the GND level, and gate voltage V H is 2 V bias . In addition, the gate voltage may be applied to only one of n-type MOSFET 61 and p-type MOSFET 62 in such a way that no channel is formed.

[0115] As a result of such an operation, channels are not formed in the n-type MOSFET 61 and the p-type MOSFET 62 of the infrared sensor element 10. Therefore, a configuration in which "cold junction - n-type semiconductor - warm junction - p-type semiconductor - cold junction" is electrically connected in series is not formed, and the thermoelectric conversion function of the thermoelectric conversion unit 60 is not exhibited. Therefore, even if the insulation of the switch 11 is poor, the infrared detection signal is not transmitted to the amplifier 12. In Figure 4A the example shown, a bias voltage V is applied to both differential input terminals of the operational amplifier of the amplifier 12. bias As a result, the input to the amplifier 12 becomes zero. As a result, the offset component and 1 / f noise generated by the amplifier 12 appear in the output of the amplifier 12. These noise components are encoded by, for example, an AD converter and output to the signal processing circuit 100 as digital information. The digital information of the output noise measurement mode is stored by the signal processing circuit 100.

[0116] Next, the operation of the infrared sensor 1 in the infrared measurement mode will be described. As Figure 4B shown, in the infrared measurement mode, the switch 11 connects the first cold junction metal electrode 64 to the input terminal of the amplifier 12. Further, in the infrared measurement mode, the control circuit 13 applies a gate voltage V to the gate 61g of the n-type MOSFET 61 to form an n-type channel 61c in the n-type MOSFET 61. H Further, in the infrared measurement mode, the control circuit 13 applies a gate voltage V to the gate 62g of the p-type MOSFET 62 to form a p-type channel 62c in the p-type MOSFET 62. L In addition, the value of the gate voltage V applied to the gate 61g in the noise measurement mode L may be different from the value of the gate voltage V applied to the gate 62g in the infrared measurement mode. Further, the value of the gate voltage V applied to the gate 62g in the noise measurement mode L may be different from the value of the gate voltage V applied to the gate 61g in the infrared measurement mode. H In addition, the value of the gate voltage V applied to the gate 62g in the noise measurement mode H may be different from the value of the gate voltage V applied to the gate 61g in the infrared measurement mode.

[0117] As a result of such an operation, channels are formed in the n-type MOSFET 61 and the p-type MOSFET 62 of the infrared sensor element 10, and a configuration is formed that is electrically connected as "cold junction - n-type semiconductor - warm junction - p-type semiconductor - cold junction", presenting the thermoelectric conversion function of the thermoelectric conversion unit 60. The infrared detection signal generated by the thermoelectric conversion function flows out as a large number of carriers (electrons) of the n-type MOSFET 61 from the first cold junction metal electrode 64 connected to the n-type MOSFET 61 and is input to the amplifier 12. The output information of the amplifier 12 is information obtained by adding the offset component and 1 / f noise generated by the amplifier 12 to the infrared information. This output information is encoded by, for example, an AD converter and output as digital information to the signal processing circuit 100. The digital information output in the infrared measurement mode is stored by the signal processing circuit 100.

[0118] Finally, after subtracting the output of the amplifier 12 in the noise measurement mode from the output of the amplifier 12 in the infrared measurement mode, infrared information from which the offset component and 1 / f noise generated by the amplifier 12 are removed is obtained. This operation is performed by, for example, the signal processing circuit 100.

[0119] In addition, in Figure 4A and Figure 4B it is shown that voltages are independently applied to the gate 61g and the gate 62g, but it is also possible that a voltage conversion circuit is provided between one of the gate 61g and the gate 62g and the control circuit 13, and the control circuit 13 supplies voltages to the gate 61g and the gate 62g together.

[0120] As described above, in the infrared sensor 1, the thermoelectric conversion unit 60 includes an n-type MOSFET 61 and a p-type MOSFET 62. Thus, it is possible to determine whether to form a series connection configuration of "cold junction - n-type semiconductor - warm junction - p-type semiconductor - cold junction" according to whether channels are formed in the n-type MOSFET 61 and the p-type MOSFET 62, and control whether to present the thermoelectric conversion function of the thermoelectric conversion unit 60. Therefore, when it is not desired to input the infrared detection signal to the amplifier 12, it is possible not to present the thermoelectric conversion function of the thermoelectric conversion unit 60. As a result, there is no leakage of the infrared detection signal as in the case of blocking the infrared detection signal by a semiconductor switch. As a result, for example, it is possible to measure the offset component and 1 / f noise of the amplifier 12 without being affected by the leakage of the infrared detection signal from the infrared sensor element 10 in the noise measurement mode. Therefore, it is possible to effectively remove the offset component and 1 / f noise of the amplifier 12 from the output in the infrared measurement mode. Thus, according to the infrared sensor 1, the detection accuracy of infrared rays can be improved.

[0121] In addition, the infrared sensor 1 includes an amplifier 12, and the amplifier 12 is a voltage-input type amplifier. By using such a voltage-input type amplifier with a high input impedance Z in high, in the infrared sensor 1, the current flowing through the infrared sensor element 10 can be regarded as the same in the noise measurement mode and the infrared measurement mode. Specifically, in the noise measurement mode, the infrared sensor 1 does not cause the thermoelectric conversion function of the thermoelectric conversion unit 60 to appear. Therefore, the current flowing out of the infrared sensor element 10 is zero. In addition, in the infrared measurement mode, the infrared sensor 1 causes the thermoelectric conversion function of the thermoelectric conversion unit 60 to appear. Therefore, an electromotive force is generated in the thermoelectric conversion unit 60. However, due to the high input impedance Z in of the amplifier 12, almost no current flows from the infrared sensor element 10 and is close to zero.

[0122] The current flowing inside the thermoelectric conversion unit 60 due to the thermoelectric conversion function acts in the direction of eliminating the temperature difference between the hot junction and the cold junction through the Peltier effect opposite to the Seebeck effect. That is, if the amount of current flowing inside the thermoelectric conversion unit 60 changes, the temperature distribution between the hot junction and the cold junction is disrupted. However, as described above, in the infrared sensor 1, this current is zero or close to zero in both the noise measurement mode and the infrared measurement mode and can be regarded as the same. Therefore, even if the switch 11 is switched in such a way that the mode changes from the noise measurement mode to the infrared measurement mode, the phenomenon that the temperature distribution between the hot junction and the cold junction is temporarily disrupted due to the change in the amount of current and then redistributes over time will not occur. That is, when switching from the noise measurement mode to the infrared measurement mode, without waiting for the time required for the temperature distribution between the hot junction and the cold junction to redistribute and stabilize in a stable state, even if the output information from the amplifier 12 of the infrared sensor 1 is read, the detection accuracy of infrared rays can be maintained.

[0123] On the other hand, assuming that the amplifier 12 is a current-input type amplifier with an input impedance close to zero (for example, a transimpedance amplifier), then from the moment of switching from the noise measurement mode to the infrared measurement mode, a current obtained by dividing the electromotive force by the internal resistance of the thermoelectric conversion unit 60 starts to flow in the thermoelectric conversion unit 60, and the temperature distribution between the hot junction and the cold junction is redistributed. The output information from the amplifier 12 read without waiting for the time required for this redistribution may contain errors. However, in applications where the time for switching from the noise measurement mode to the infrared measurement mode can be ensured, even if the amplifier 12 is a current-input type amplifier, there is no problem.

[0124] (Embodiment 2)

[0125] Next, the infrared sensor of Embodiment 2 will be described. In the infrared sensor of Embodiment 1, the configuration is such that there is one amplifier for one infrared sensor, but in Embodiment 2, a configuration in which there is one amplifier for a plurality of infrared sensors will be described. In the following description, the focus will be on the differences from Embodiment 1, and the description of common points will be omitted or simplified.

[0126] Figure 5 FIG. is a block diagram showing the overall configuration of the infrared sensor 101 of Embodiment 2.

[0127] As Figure 5 shown, the infrared sensor 101 of the present embodiment is different in that it includes an element array 10A composed of a plurality of infrared sensor elements 10 instead of the infrared sensor element 10. The infrared sensor 101 is, for example, an infrared image sensor (infrared imaging element) in which a plurality of infrared sensor elements 10 are arranged as pixels.

[0128] The element array 10A is composed of a plurality of infrared sensor elements 10 that are arranged in an array shape while sharing the semiconductor substrate 30. In the Figure 5 block diagram, for the sake of 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 shape in multiple columns in the longitudinal and lateral directions when viewed from 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. Each of the plurality of infrared sensor elements 10 is connected to the amplifier 12 via a switch 11. In the present embodiment, the number of infrared sensor elements 10 is N (N is an integer of 2 or more).

[0129] When the element array 10A is composed of N infrared sensor elements 10, the infrared sensor element 10 and the amplifier 12 are configured in a ratio of N to 1. According to this N-to-1 configuration, in an array sensor in which N infrared sensors are arranged in an array, it is not necessary to provide N amplifiers 12 that consume a large amount of current, which is effective for power saving. In this case, for one amplifier 12, a part of the plurality of infrared sensor elements 10 is sequentially allocated in a time-sharing manner. Therefore, it is necessary to sequentially switch the infrared sensor elements 10 that output the infrared detection signals and perform pixel scanning for a certain period of time. However, from the viewpoint of the current consumption of the amplifier 12, it is preferable to configure the infrared sensor elements 10 and the amplifier 12 in a multi-to-one manner within the range where the required number of frames per second can be ensured.

[0130] In addition, the infrared sensor element 10 and the amplifier 12 are not limited to the N-to-1 configuration, and the infrared sensor 101 may also include a plurality of amplifiers 12. In this case, for example, the amplifiers 12 are provided for each pixel column, pixel row, or pixel block.

[0131] Next, the operation of the infrared sensor 101 of the present embodiment will be described.

[0132] Figure 6A FIG. is a diagram for explaining the operation of the infrared sensor 101 in the noise measurement mode according to Embodiment 2. Figure 6B FIG. is a diagram for explaining the operation of the infrared sensor 101 in the infrared measurement mode according to Embodiment 2. In addition, in Figure 6A and Figure 6B in order to make a distinction, a plurality of infrared sensor elements 10 are denoted by reference numerals of a plurality of infrared sensor elements 10_1 to 10_N. In addition, in Figure 6A and Figure 6B each infrared sensor element 10 (denoted as "sensor element" in the figure) is schematically illustrated as a block having four terminals, namely, a first cold-junction metal electrode 64, a second cold-junction metal electrode 65, a gate 61g, and a gate 62g. The first cold-junction metal electrode 64 is a terminal connected to the source 61s of the n-type MOSFET 61. The second cold-junction metal electrode 65 is a terminal connected to the source 62s of the p-type MOSFET 62.

[0133] The first cold-junction metal electrodes 64 of the respective plurality of infrared sensor elements 10_1 to 10_N, which are connected to the n-type MOSFET 61, are connected in parallel and are connected to the input terminal of the amplifier 12 via the switch 11. A bias voltage V is applied to the second cold-junction metal electrodes 65 of the respective plurality of infrared sensor elements 10_1 to 10_N, which are connected to the p-type MOSFET 62. bias In addition, in Figure 6B a case is shown in which only the infrared sensor element 10_1 among the plurality of infrared sensor elements 10_1 to 10_N is selected to output an infrared detection signal. That is, in Figure 6B 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. In Figure 6B a dotted pattern is marked on the selected infrared sensor element 10_1.

[0134] In the noise measurement mode, as shown in Figure 6AAs shown, in each of the plurality of infrared sensor elements 10_1 to 10_N, the gate 61g of the n-type MOSFET 61 is applied with a gate voltage V by the control circuit 13 in such a manner that no pyroelectric conversion function is exhibited in all of the infrared sensor elements 10_1 to 10_N L and the gate 62g of the p-type MOSFET 62 is applied with a gate voltage V by the control circuit 13 H . In the noise measurement mode, the switch 11 connects the bias voltage V bias to the input terminal of the amplifier 12. Since no pyroelectric conversion function is exhibited in all of the infrared sensor elements 10_1 to 10_N, even if the isolation of the switch 11 is poor, the infrared detection signals of N quantities are not transmitted to the amplifier 12. In addition, in the example shown in Figure 6A , for the differential input terminals of the operational amplifier of the amplifier 12, in either case, the bias voltage V bias is applied, so that the input to the amplifier 12 becomes a zero state. As a result, the offset component generated by the amplifier 12 and 1 / f noise appear in the output of the amplifier 12. These noise components are encoded by, for example, an AD converter and output to the signal processing circuit 100 as digital information. The digital information in the output noise measurement mode is stored by the signal processing circuit 100

[0135] Next, in the infrared measurement mode, as shown in Figure 6B , only a part of the infrared sensor elements 10_1 to 10_N, i.e., the infrared sensor element 10_1, is selected to output an infrared detection signal, and the other infrared sensor elements 10_2 to 10_N are not selected at all and do not output an infrared detection signal

[0136] Specifically, in the example shown in Figure 6B , since the infrared sensor element 10_1 is selected, in the infrared sensor element 10_1, the gate 61g of the n-type MOSFET 61 and the gate 62g of the p-type MOSFET 62 are applied with a gate voltage V by the control circuit 13 in such a manner that only the n-type MOSFET 61 and the p-type MOSFET 62 of the infrared sensor element 10_1 form channels to exhibit a pyroelectric conversion function H and the gate 62g of the p-type MOSFET 62 is applied with a gate voltage V by the control circuit 13 L . In addition, in such a manner that the n-type MOSFET 61 and the p-type MOSFET 62 of the unselected infrared sensor elements 10_2 to 10_N do not form channels and do not exhibit a pyroelectric conversion function, the gate 61g of the n-type MOSFET 61 is applied with a gate voltage V by the control circuit 13 L, in each of the infrared sensor elements 10_2 to 10_N, a gate voltage V is applied to the gate 62g of the p-type MOSFET 62 by the control circuit 13 H . Further, in the infrared measurement mode, the switch 11 connects the first cold-junction metal electrode connected to the n-type MOSFET 61 to the input terminal of the amplifier 12. The infrared detection signal of the infrared sensor element 10_1 flows out as a large number of carriers (electrons) of the n-type MOSFET 61 from the first cold-junction metal electrode 64 connected to the n-type MOSFET 61, and is input to the amplifier 12. The output information of the amplifier 12 is information obtained by adding an offset component and 1 / f noise generated by the amplifier 12 to the infrared information of the infrared sensor element 10_1. This output information is encoded by, for example, an AD converter and output as digital information to the signal processing circuit 100. The digital information corresponding to the infrared sensor element 10_1 output in the infrared measurement mode is stored by the signal processing circuit 100.

[0137] In addition, in Figure 6A and Figure 6B , by changing the positions of the wirings connected to the gate 61g and the gate 62g in the infrared sensor element 10_1, the voltages applied to the gate 61g and the gate 62g are switched, but actually the positions of the wirings are not changed. In practice, for example, by switching a switch, or by independently applying voltages to the gate 61g and the gate 62g by connecting control lines to the gate 61g and the gate 62g of each of the infrared sensor elements 10_1 to 10_N, etc., the voltages applied to the gate 61g and the gate 62g are switched.

[0138] Finally, after subtracting the output of the amplifier 12 in the noise measurement mode from the output of the amplifier 12 corresponding to the infrared sensor element 10_1 in the infrared measurement mode, the infrared information of the infrared sensor element 10_1 from which the offset component and 1 / f noise generated by the amplifier 12 are removed is obtained. This operation is performed by, for example, the signal processing circuit 100. When the infrared sensor element 10_1 is selected, the pyroelectric conversion function is not exhibited in the infrared sensor elements 10_2 to 10_N. Therefore, there is no situation where the infrared detection signals of the infrared sensor elements 10_2 to 10_N leak out and are mixed as noise into the infrared detection signal of the infrared sensor element 10_1. Therefore, the error in the detection of infrared rays in the infrared measurement mode can be reduced, and thus, according to the infrared sensor 101, the detection accuracy of infrared rays can be improved.

[0139] In addition, in the infrared measurement mode, for each of the plurality of infrared sensor elements 10_1 to 10_N, the same operations as those of the infrared sensor element 10_1 described above are sequentially performed, and infrared information of each of the plurality of infrared sensor elements 10_1 to 10_N can be obtained.

[0140] (Embodiment 3)

[0141] Next, the infrared sensor of Embodiment 3 will be described. In the following description, the differences from Embodiments 1 and 2 will be mainly described, and the description of the common points will be omitted or simplified.

[0142] Figure 7 is a diagram showing the configuration of the infrared sensor 201 of Embodiment 3. In Figure 7 it schematically shows a cross-section of the infrared sensor element 10 and a schematic circuit configuration of the amplifier 12 and the control circuit 213.

[0143] As Figure 7 shown, the infrared sensor 201 of the present embodiment is different from the infrared sensor 1 of Embodiment 1 in that it does not have the switch 11 and in that it has the control circuit 213 instead of the control circuit 13.

[0144] In the infrared sensor 201, the first cold-junction metal electrode 64 connected to the source 61s of the n-type MOSFET 61 is connected to the input terminal of the amplifier 12 without passing through the switch.

[0145] The control circuit 213 has a voltage supply circuit 214 and an inverter 215. The control circuit 213 may also have a microcomputer, a processor, or a logic circuit in the same manner as the control circuit 13.

[0146] The voltage supply circuit 214 supplies a voltage having a periodic repetitive waveform to the infrared sensor element 10. The voltage supply circuit 214 is connected to the gate 61g of the n-type MOSFET 61 and the gate 62g of the p-type MOSFET 62. In Figure 7 the example shown, the voltage supply circuit 214 is connected to the gate 61g without passing through the inverter 215 and is connected to the gate 62g through the inverter 215.

[0147] The inverter 215 modulates the waveform of the voltage supplied from the voltage supply circuit 214, specifically, inverts it. The inverter 215 is disposed between the voltage supply circuit 214 and the gate 62g. A voltage having a waveform inverted with respect to the voltage applied to the gate 61g is applied to the gate 62g. Further, the inverter 215 may be disposed between the voltage supply circuit 214 and the gate 61g instead of between the voltage supply circuit 214 and the gate 62g. Additionally, the control circuit 213 may not include the inverter 215, and waveforms different voltages, specifically, voltages with inverted waveforms, may be independently applied to the gate 61g and the gate 62g through two voltage supply circuits 214.

[0148] Figure 8 FIG. is an example showing the waveform of the voltage output from the voltage supply circuit 214. In the infrared sensor 201, by utilizing the fact that the thermoelectric conversion function can be controlled by the control signals (voltages) applied to the gate 61g of the n-type MOSFET 61 and the gate 62g of the p-type MOSFET 62, it is possible to reduce the switches provided between the input terminal of the amplifier 12 and the infrared sensor element 10 and omit the noise measurement mode.

[0149] Specifically, a voltage having a periodic repetitive waveform, for example, Figure 8 a pulse voltage having a frequency f (period T) as shown, is applied to the gate 61g of the n-type MOSFET 61 and the gate 62g of the p-type MOSFET 62 (for the gate 62g, it is a voltage with an inverted waveform with respect to Figure 8 ). In the example shown in Figure 8 , the voltage value of the pulse voltage is the gate voltage V L at the Low level (low level), and the gate voltage V H at the High level (high level). Since an inverter 215 is inserted between the gate 62g and the voltage supply circuit 214, when the gate voltage V H is applied to the gate 61g of the n-type MOSFET 61, the gate voltage V L is applied to the gate 62g of the p-type MOSFET 62. As a result, the thermoelectric conversion function is presented in the infrared sensor element 10. Conversely, when the gate voltage V L is applied to the gate 61g of the n-type MOSFET 61, the gate voltage V H is applied to the gate 62g of the p-type MOSFET 62. As a result, the thermoelectric conversion function disappears and is not presented in the infrared sensor element 10. The presentation and disappearance of this thermoelectric conversion function are repeated at the frequency f.

[0150] Even if the frequency f is on the order of kHz, the appearance and disappearance of this thermoelectric conversion function can be followed. Therefore, if the peak value of the output of the amplifier 12 is measured in the frequency region of kHz where the 1 / f noise is sufficiently attenuated in the amplifier 12, the infrared information after removing the 1 / f noise and the offset component of the amplifier 12 can be obtained. The peak can be read by reading the peak-to-peak value through a narrow band-pass type band-pass filter having a center frequency that passes through the frequency f, or synchronous detection using a pulse of the frequency f as a reference signal can be performed.

[0151] As described above, in the infrared sensor 201, a voltage having a periodic repetitive waveform is applied to the gate 61g of the n-type MOSFET 61 and the gate 62g of the p-type MOSFET 62. Thereby, by performing signal processing in the frequency band of the repetition frequency, noise components can be removed, and thus even a weak infrared detection signal can be extracted with high accuracy.

[0152] (Embodiment 4)

[0153] Next, the infrared sensor of Embodiment 4 will be described. In Embodiment 4, a configuration in which the light-receiving portion is hollowly supported will be described. In the following description, the description will focus on the differences from Embodiments 1 to 3, and the description of common points will be omitted or simplified.

[0154] Figure 9 It is a cross-sectional view showing the infrared sensor element 310 of Embodiment 4. Figure 10 It is a plan view when observing the infrared sensor element 310 of Embodiment 4 from above. In addition, Figure 9 represents Figure 10 the cross-section at the IX-IX line shown. Additionally, in Figure 10 in order to facilitate observation, a dotted pattern is marked on the region where the slit 52 is formed.

[0155] The infrared sensor of the present embodiment has a configuration in which the infrared sensor element 10 of the infrared sensor of any one of Embodiments 1 to 3 is changed to the infrared sensor element 310.

[0156] The infrared sensor element 310 of the present embodiment is different from the infrared sensor element 10 of Embodiments 1 to 3 in that it is formed on the laminated substrate 335 instead of the semiconductor substrate 30, has a light-receiving portion 340 instead of the light-receiving portion 40, and has a void 51 and a slit 52 formed.

[0157] As Figure 9 and Figure 10As shown, the infrared sensor element 310 is formed using the laminated substrate 335 included in the infrared sensor of the present embodiment. In Figure 9 the example shown, the laminated substrate 335 is a three-layer substrate in which a semiconductor substrate 330, a buried oxide film layer 331, and a semiconductor layer 332 are laminated in this order from the lower side. The laminated substrate 335 is, for example, an SOI (Silicon On Insulator) substrate. In addition, the laminated substrate 335 may be a laminated substrate other than the SOI substrate. Hereinafter, it is assumed that the laminated substrate 335 is an SOI substrate for explanation.

[0158] The semiconductor substrate 330 is an example of a substrate and is made of, for example, single crystal silicon. Although not shown, in the semiconductor substrate 330, similar to the semiconductor substrate 30, a reflective surface 42 that has increased infrared reflectivity by doping a high concentration of p-type impurities is formed. In a plan view, the oxide film layer 331 is made of, for example, silicon oxide at a position overlapping with the metal film 342. The semiconductor layer 332 is, for example, an SOI layer and is a p-type silicon layer using single crystal silicon.

[0159] The n-type MOSFET 61 and the p-type MOSFET 62 formed in the semiconductor substrate 30 in the infrared sensor element 10 are formed in the p-type semiconductor layer 332 in the infrared sensor element 310. Therefore, the thermoelectric conversion unit 60 having the n-type MOSFET 61 and the p-type MOSFET 62 is located above the semiconductor substrate 330. In the infrared sensor element 310, the n-type MOSFET 61 and the p-type MOSFET 62 bond the light-receiving unit 340 to the laminated substrate 335 and also function as arms that hollowly support the light-receiving unit 340. In addition, in the infrared sensor element 310, a part of the insulating film 41 is disposed as the gate oxide film of the n-type MOSFET 61 and the p-type MOSFET 62. In addition, in the infrared sensor element 310, the hot-junction metal electrode 63, the first cold-junction metal electrode 64, and the second cold-junction metal electrode 65 are made of, for example, aluminum as a whole.

[0160] In this embodiment, the oxide film layer 331 under the n-type MOSFET 61, the hot junction metal electrode 63, and the p-type MOSFET 62 is removed, and a gap 51 is formed between the n-type MOSFET 61, the p-type MOSFET 62, and the light-receiving portion 340 and the semiconductor substrate 330. The gap 51 is filled with a gas such as air or air under reduced pressure. For example, in a plan view, the gap 51 overlaps with the light-receiving portion 40, the hot junction metal electrode 63, the gate 61g, and the gate 62g, and does not overlap with the first cold junction metal electrode 64 and the second cold junction metal electrode 65. The first cold junction metal electrode 64 and the second cold junction metal electrode 65 are located outside the gap 51 in a plan view.

[0161] The gap 52 is a region where the semiconductor layer 332 and the insulating film 41 on the semiconductor layer 332 are removed together, for example, by dry etching. The gap 52 is formed so as to sandwich the light-receiving portion 340 and the gates 61g and 62g on the insulating film 41 in a plan view.

[0162] The oxide film layer 331 is locally etched in such a way as to pass through the gap 52 to form the gap 51. Therefore, the gap 52 is connected to the gap 51. In the etching for forming the gap 51, for example, hydrofluoric acid is used. Although the oxide film layer 331 and the insulating film 41 on the semiconductor layer 332 are etched by hydrofluoric acid, in order to provide regions in the oxide film layer 331 and the insulating film 41 that are not etched, it is effective to apply a method of film protection using a photoresist as disclosed in Non-Patent Document 2. For example, in a plan view, the gap 51 is formed in the region sandwiched by the gap 52.

[0163] The light-receiving portion 340 is located above the semiconductor substrate 330. In this embodiment, the light-receiving portion 340 includes the insulating film 41 and the metal film 342 on the insulating film 41. In Figure 10 the example shown, the light-receiving portion 340 is a region where the metal film 342 and the hot junction metal electrode 63 are formed on the insulating film 41 above the semiconductor substrate 330 in a plan view.

[0164] The metal film 342 is located near the hot junction metal electrode 63 on the insulating film 41 in a plan view. The light-receiving portion 340 includes, for example, a plurality of metal films 342, and the hot junction metal electrode 63 is sandwiched by the metal films 342 in a plan view. The hot junction metal electrode 63 is disposed, for example, in a region including the center of the light-receiving portion 340 in a plan view. In a plan view, the metal film 432 overlaps with the reflecting surface 42. The metal film 342 absorbs at least a part of the infrared rays irradiated to the infrared sensor element 310. The metal film 342 is made of, for example, titanium, titanium nitride, tungsten, or the like.

[0165] In the light-receiving section 340, a multilayer structure composed of a metal film 342, an insulating film 41 below the metal film 342, a semiconductor layer 332 below the insulating film 41, a gap 51 below the semiconductor layer 332, and a reflecting surface 42 below the gap 51 forms an infrared interference absorption structure. Heat generated in the metal film 342 that has absorbed infrared rays is difficult to release to the surrounding air or the decompressed air. Therefore, by forming the gap 51, it is easy to ensure the temperature difference between the hot junction and the cold junction. Thus, by using the infrared sensor element 310, an infrared detection signal with a high S / N can be obtained. The lower the pressure in the gap 51, the higher this effect.

[0166] In this way, in the infrared sensor element 310, the n-type MOSFET 61 and the p-type MOSFET 62 support the light-receiving section 340 in a hollow manner, forming the gap 51, thereby ensuring the temperature difference between the hot junction and the cold junction. Therefore, by reducing the heat conduction of the n-type MOSFET 61 and the p-type MOSFET 62 located between the hot junction and the cold junction, it is easier to ensure the temperature difference between the hot junction and the cold junction. For example, by removing a part of the gate oxide film of the n-type MOSFET 61 and the p-type MOSFET 62, the heat conductivity of the n-type MOSFET 61 and the p-type MOSFET 62 can be reduced.

[0167] Figure 11 It is a cross-sectional view of an infrared sensor element 310a which is a modification of Embodiment 4. As Figure 11 shown, the infrared sensor element 310a has a configuration in which a part of the gate oxide film of the n-type MOSFET 61 and the p-type MOSFET 62 is removed from the infrared sensor element 310. In Figure 11 the example shown, as the gate oxide film, a part below the gate 61g in the insulating film 41 is removed to form a gap 351, and a part below the gate 62g is removed to form a gap 352. A part of the portion of the insulating film 41 that overlaps with the gate 61g in plan view and a part of the portion that overlaps with the gate 62g are removed. If all of the gate oxide film of the n-type MOSFET 61 and the p-type MOSFET 62 is removed, the gates 61g and 62g warp upward due to the release of the internal stress of the polysilicon in the semiconductor layer 332, which hinders the transistor operation. Therefore, by removing only a part of the gate oxide film of the n-type MOSFET 61 and the p-type MOSFET 62, such upward warping can be suppressed. The gaps 351 and 352 are filled with a gas such as air or decompressed air that has a lower heat conductivity than the insulating film 41.

[0168] In addition, in the infrared sensor elements 10 of Embodiments 1 to 3 and the infrared sensor element of Embodiment 5 described later, the gate oxide film may be removed in the same manner as the infrared sensor element 310a.

[0169] (Embodiment 5)

[0170] Next, the infrared sensor of Embodiment 5 will be described. In Embodiment 5, a configuration in which the light-receiving portion is hollow-supported and has a phononic crystal structure will be described. In the following description, the differences from Embodiments 1 to 4 will be mainly described, and the description of common points will be omitted or simplified.

[0171] Figure 12 is a cross-sectional view showing the infrared sensor element 410 of Embodiment 5. In addition, in Figure 12 the illustration of the pores of the phononic crystal structure described later is omitted.

[0172] The infrared sensor of the present embodiment has a configuration in which the infrared sensor element 10 of the infrared sensor of any one of Embodiments 1 to 3 is changed to the infrared sensor element 410.

[0173] As Figure 12 shown, the infrared sensor element 410 of the present embodiment is different from the infrared sensor element 310 of Embodiment 4 in that it includes a thermoelectric conversion unit 460 instead of the thermoelectric conversion unit 60.

[0174] The thermoelectric conversion unit 460 has a configuration in which the n-type MOSFET 61 and the p-type MOSFET 62 of the thermoelectric conversion unit 60 are changed to an n-type MOSFET 461 and a p-type MOSFET 462. The n-type MOSFET 461 has a gate 461g formed by providing a phononic crystal structure on at least a part of the gate 61g of the n-type MOSFET 61. In addition, the p-type MOSFET 462 has a gate 462g formed by providing a phononic crystal structure on at least a part of the gate 62g of the p-type MOSFET 62. That is, the gate 461g of the n-type MOSFET 461 and the gate 462g of the p-type MOSFET 462 have a phononic crystal structure.

[0175] In order to ensure the temperature difference between the warm junction and the cold junction to improve the S / N of the infrared detection signal, it is effective to form a phonon crystal structure with high adiabaticity in the semiconductor (MOSFET in this embodiment) located between the warm junction and the cold junction. A doped semiconductor has conductivity, and since carriers also transport heat, generally the thermal insulation is low. However, by providing a phonon crystal structure in at least a part of the gate 461g and the gate 462g, it is possible to improve the thermal insulation while having conductivity. Thus, by using the infrared sensor element 410, the adiabaticity of the n-type MOSFET 461 and the p-type MOSFET 462 can be improved, and the temperature difference between the warm junction and the cold junction can be ensured to improve the S / N of the infrared detection signal. In addition, one of the gate 461g and the gate 462g may not have a phonon crystal structure.

[0176] An artificial phonon crystal structure processed by semiconductor manufacturing processes is a structure obtained by digging out 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. The aperture of the fine holes is, for example, 10 nm or more and 50 nm or less.

[0177] 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. In addition, 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 materials of the gate 461g and the gate 462g are, for example, polysilicon, and the above-mentioned lithography and dry etching can be applied to dig out fine through-holes. At this time, if the aspect ratio (hole depth / aperture) is 5 or less, the etching gas is likely to travel into the holes and the holes 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 an aperture of 20 nm.

[0178] In addition, in order to further improve the adiabaticity of the n-type MOSFET 461 and the p-type MOSFET 462, a phonon crystal structure may also be provided in parts other than the gate 461g and the gate 462g of the n-type MOSFET 461 and the p-type MOSFET 462.

[0179] Figure 13 It is a cross-sectional view of the infrared sensor element 410a which is a modification of Embodiment 5. In addition, in Figure 13 the illustration of the fine holes of the phonon crystal structure described later is omitted.

[0180] The infrared sensor element 410a has a configuration in which a phonon crystal structure is provided in the semiconductor layer 332 of the infrared sensor element 410. As Figure 13 shown, the infrared sensor element 410a has a configuration in which the thermoelectric conversion unit 460 of the infrared sensor element 410 is changed to a thermoelectric conversion unit 460a. The thermoelectric conversion unit 460a is formed by providing phonon crystal structures also in the n-type MOSFET 461 and the p-type MOSFET 462 for the thermoelectric conversion unit 460, other than at the gate 461g and the gate 462g.

[0181] The thermoelectric conversion unit 460a includes an n-type MOSFET 461a and a p-type MOSFET 462a. The source 461s, the drain 461d, the gate 461g of the n-type MOSFET 461a, and the channel region between the source 461s and the drain 461d have a phonon crystal structure. The source 462s, the drain 462d, the gate 462g of the p-type MOSFET 462a, and the channel region between the source 462s and the drain 462d have a phonon crystal structure. The channel region of the p-type MOSFET 462a is part of the well region 462w of the p-type MOSFET 462a. Thus, by using the infrared sensor element 410a, the adiabatic properties of the n-type MOSFET 461a and the p-type MOSFET 462a can be further improved, the temperature difference between the hot junction and the cold junction can be ensured, and the S / N of the infrared detection signal can be further improved. In addition, at least one of the source 461s, the drain 461d, the gate 461g, and the channel region of the n-type MOSFET 461a, and the source 462s, the drain 462d, the gate 462g, and the channel region of the p-type MOSFET 462a may not have a phonon crystal structure.

[0182] (Embodiment 6)

[0183] Next, the infrared sensor of Embodiment 6 will be described. In the following description, the description will focus on the differences from Embodiments 1 to 5, and the description of common points will be omitted or simplified.

[0184] Figure 14 is a cross-sectional view showing the infrared sensor element 510 of Embodiment 6. In addition, in Figure 14 the illustration of the pores of the phonon crystal structure described later is omitted.

[0185] The infrared sensor of the present embodiment has a configuration in which the infrared sensor element 10 of the infrared sensor of any one of Embodiments 1 to 3 is changed to an infrared sensor element 510.

[0186] As Figure 14As shown, the infrared sensor element 510 of the present embodiment is different from the infrared sensor element 410 of Embodiment 5 in that it includes a thermoelectric conversion section 560 instead of the thermoelectric conversion section 460.

[0187] In the infrared sensor element 510, a phonon crystal structure is provided in the semiconductor layer 332 in the same manner as in the infrared sensor element 410a of the modification of Embodiment 5.

[0188] The thermoelectric conversion section 560 has a configuration in which the n-type MOSFET 461 and the p-type MOSFET 462 of the thermoelectric conversion section 460 are changed to an n-type MOSFET 561 and a p-type MOSFET 562.

[0189] The n-type MOSFET 561 includes a source 461s, a drain 461d, a gate 561g, and a channel region 561c between the source 461s and the drain 461d. The channel region 561c is formed by providing a phonon crystal structure in a portion between the source 461s and the drain 461d in the semiconductor layer 332. The source 461s, the drain 461d, the gate 561g, and the channel region 561c have a phonon crystal structure. In Figure 14 the example shown, the thickness of the channel region 561c is the same as the thickness of the semiconductor layer 332. That is, the channel region 561c is formed throughout the entire thickness direction of the semiconductor layer 332. In addition, in Figure 14 the gate 561g on the channel region 561c is shown as a configuration having no thickness because the thickness is very thin.

[0190] The p-type MOSFET 562 includes a source 462s, a drain 462d, a gate 562g, and a channel region 562c between the source 462s and the drain 462d. The channel region 562c is a portion between the source 462s and the drain 462d in the well region 462w of the above-described p-type MOSFET 462a. The source 462s, the drain 462d, the gate 562g, and the channel region 562c have a phonon crystal structure. In Figure 14 the example shown, the thickness of the channel region 562c is the same as the thickness of the semiconductor layer 332. That is, the channel region 562c is formed throughout the entire thickness direction of the semiconductor layer 332. In addition, in Figure 14 the gate 562g on the channel region 562c is shown as a configuration having no thickness because the thickness is very thin.

[0191] In this embodiment, the gate 561g is formed not only on the upper surface of the channel region 561c but also on the inner walls of the pores ch1 of the phononic crystal structure in the channel region 561c. Further, the gate 562g is formed not only on the upper surface of the channel region 562c but also on the inner walls of the phononic crystal structure in the channel region 562c.

[0192] Figure 15A It is a plan view when a part of the channel region 561c of the n-type MOSFET 561 is observed from above. Figure 15B It is a plan view when a part of the channel region 562c of the p-type MOSFET 562 is observed from above. Figure 16A It is a cross-sectional view of a part of the channel region 561c of the n-type MOSFET 561. Figure 16B It is a cross-sectional view of a part of the channel region 562c of the p-type MOSFET 562. Further, in Figure 15A the outline of the channel region 561c covered by the gate 561g is shown by a dashed line. Additionally, in Figure 15B the outline of the channel region 562c covered by the gate 562g is shown by a dashed line. Additionally, Figure 16A represents Figure 15A the cross-section at the XVIa-XVIa line shown in. Additionally, Figure 16B represents Figure 15B the cross-section at the XVIb-XVIb line shown in.

[0193] As Figure 15A and Figure 16A shown, in the n-type MOSFET 561, the gate 561g is formed not only on the upper surface of the channel region 561c but also on the inner walls of the periodic plurality of pores ch1 of the phononic crystal structure in the channel region 561c. Further, a plurality of pores gh1 are periodically formed in the gate 561g. Moreover, although not shown in Figure 15A and Figure 16A a thin gate oxide film is formed between the gate 561g and the channel region 561c.

[0194] As Figure 15B and Figure 16B shown, in the p-type MOSFET 562, the gate 562g is formed not only on the upper surface of the channel region 562c but also on the inner walls of the periodic plurality of pores ch2 of the phononic crystal structure in the channel region 562c. Further, a plurality of pores gh2 are periodically formed in the gate 562g. Moreover, although not shown in Figure 15B and Figure 16B a thin gate oxide film is formed between the gate 562g and the channel region 562c.

[0195] With such a configuration, the gate 561g and the gate 562g can be formed with the minimum volume required for the control of the MOSFET, and the gate 561g and the gate 562g also have a phonon crystal structure with periodically formed fine pores. Thus, the adiabatic properties of the gate 561g and the gate 562g can be improved.

[0196] In addition, when a signal voltage is applied to the gate 561g and the gate 562g, the channel regions 561c and 562c are formed throughout the entire thickness region of the semiconductor layer 332. Therefore, the resistance of the channel regions 561c and 562c decreases, and when a voltage is applied to the gate 561g and the gate 562g to control the thermoelectric conversion unit 560, the thermal noise generated from the resistance of the channel can be reduced. Thus, based on the temperature difference between the warm junction and the cold junction ensured by the adiabatic properties of the gate 561g and the gate 562g, and the effect of reducing the thermal noise generated from the resistance of the channel, high S / N infrared information can be obtained by using the infrared sensor element 510.

[0197] In addition, in the infrared sensor element 510, at least one of the source 461s, the drain 461d, the gate 561g, the source 462s, the drain 462d, and the gate 562g may not have a phonon crystal structure. Also, one of the channel regions 561c and 562c may not have a phonon crystal structure.

[0198] (Other embodiments)

[0199] 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 other solutions constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present disclosure.

[0200] For example, in the above embodiment, the first cold-junction metal electrode 64 outputs an infrared detection signal to the amplifier 12, and a bias voltage V is applied to the second cold-junction metal electrode 65 bias , but it is not limited thereto. It may also be that the second cold-junction metal electrode 65 outputs an infrared detection signal to the amplifier 12, and a bias voltage V is applied to the first cold-junction metal electrode 64 bias .

[0201] In addition, in the above-described embodiments, the thermoelectric conversion units 60, 460, 460a, 560 each have one n-type MOSFET 61, 461, 461a, 561 and one p-type MOSFET 62, 462, 462a, 562, but are not limited thereto. The thermoelectric conversion units 60, 460, 460a, 560 may have a plurality of at least one of the n-type MOSFETs 61, 461, 461a, 561 and the p-type MOSFETs 62, 462, 462a, 562. In this case, the n-type MOSFETs 61, 461, 461a, 561 among themselves and the p-type MOSFETs 62, 462, 462a, 562 among themselves are connected in series. As a result, the total channel length in the thermoelectric conversion units 60, 460, 460a, 560 becomes longer, the distance between the hot junction and the cold junction can be increased, and it is easy to ensure the temperature difference between the hot junction and the cold junction. In addition, some of the plurality of n-type MOSFETs 61, 461, 461a, 561 may be changed to n-type semiconductors. In addition, some of the plurality of p-type MOSFETs 62, 462, 462a, 562 may be changed to p-type semiconductors.

[0202] In addition, in the above-described embodiments, the infrared sensor elements 10, 310, 310a, 410, 410a, 510 each have one thermoelectric conversion unit 60, 460, 460a, 560, but are not limited thereto. The infrared sensor elements 10, 310, 310a, 410, 410a, 510 may also have a plurality of thermoelectric conversion units 60, 460, 460a, 560. In this case, the thermoelectric conversion units 60, 460, 460a, 560 are connected in series in such a way that the n-type MOSFETs 61, 461, 461a, 561 and the p-type MOSFETs 62, 462, 462a, 562 are connected. As a result, compared with the case where there is one thermoelectric conversion unit 60, 460, 460a, 560, the electromotive force of the infrared sensor element 10 can be made several times the number of the thermoelectric conversion units 60, 460, 460a, 560. In addition, some of the plurality of thermoelectric conversion units 60, 460, 460a, 560 may have a configuration in which an n-type semiconductor and a p-type semiconductor are used instead of the n-type MOSFETs 61, 461, 461a, 561 and the p-type MOSFETs 62, 462, 462a, 562.

[0203] In addition, in the above-described embodiment, FETs other than MOSFETs, such as junction FETs (Field Effect Transistors), may be used instead of the n-type MOSFETs 61, 461, 461a, 561 and the p-type MOSFETs 62, 462, 462a, 562.

[0204] Industrial Applicability

[0205] 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.

[0206] Description of Reference Numerals

[0207] 1, 101, 201 Infrared sensor

[0208] 10, 10_1 to 10_N, 310, 310a, 410, 410a, 510 Infrared sensor element

[0209] 10A Element array

[0210] 11 Switch

[0211] 12 Amplifier

[0212] 13, 213 Control circuit

[0213] 30, 330 Semiconductor substrate

[0214] 40, 340 Light receiving part

[0215] 41 Insulating film

[0216] 42 Reflecting surface

[0217] 51, 351, 352 Gap

[0218] 52 Gap

[0219] 60, 460, 460a, 560 Thermoelectric conversion part

[0220] 61, 461, 461a, 561 n-type MOSFET

[0221] 61c n-type channel

[0222] 61d, 62d, 461d, 462d Drain

[0223] 61e and 62e metal electrodes

[0224] 61g, 62g, 461g, 462g, 561g, 562g gates

[0225] 61s, 62s, 461s, 462s sources

[0226] 62, 462, 462a, 562 p-type MOSFETs

[0227] 62c p-type channel

[0228] 62w, 462w well regions

[0229] 63 hot-junction metal electrode

[0230] 64 first cold-junction metal electrode

[0231] 65 second cold-junction metal electrode

[0232] 100 signal processing circuit

[0233] 214 voltage supply circuit

[0234] 215 inverter

[0235] 331 oxide film layer

[0236] 332 semiconductor layer

[0237] 335 laminated substrate

[0238] 561c, 562c channel regions

[0239] ch1, ch2, gh1, gh2 pores

Claims

1. An infrared sensor, comprising: a light-receiving portion; and a thermoelectric conversion portion that generates an infrared detection signal based on heat generated by the light-receiving portion, wherein the thermoelectric conversion portion includes an n-type metal oxide semiconductor field effect transistor, i.e., an n-type MOSFET, a p-type MOSFET, a warm-junction metal electrode, a first cold-junction metal electrode, and a second cold-junction metal electrode, the warm-junction metal electrode is located on the light-receiving portion or at a position adjacent to the light-receiving portion, and forms an ohmic junction with the drain of the n-type MOSFET and the drain of the p-type MOSFET, the first cold-junction metal electrode forms an ohmic junction with the source of the n-type MOSFET, the second cold-junction metal electrode forms an ohmic junction with the source of the p-type MOSFET.

2. The infrared sensor according to claim 1, wherein the infrared sensor further includes an amplifier that amplifies the infrared detection signal generated by the thermoelectric conversion portion, and the amplifier is a voltage input type amplifier.

3. The infrared sensor according to claim 1 or 2, wherein the infrared sensor further includes a substrate, the light-receiving portion, the n-type MOSFET, and the p-type MOSFET are located above the substrate, and a gap is formed between the light-receiving portion, the n-type MOSFET, the p-type MOSFET, and the substrate.

4. The infrared sensor according to claim 3, wherein at least one of the gates of the n-type MOSFET and the p-type MOSFET has a phononic crystal structure.

5. The infrared sensor according to claim 3, wherein at least one of the source, drain, and channel regions of the n-type MOSFET and the p-type MOSFET has a phononic crystal structure.

6. The infrared sensor according to claim 3, wherein the channel region of at least one of the n-type MOSFET and the p-type MOSFET has a phononic crystal structure, and the gate of at least one of the n-type MOSFET and the p-type MOSFET is formed on the inner wall of the pores of the phononic crystal structure.

7. The infrared sensor according to claim 1 or 2, wherein a part of the gate oxide film of at least one of the n-type MOSFET and the p-type MOSFET is removed.

8. The infrared sensor according to claim 1 or 2, wherein a voltage having a periodic repetitive waveform is applied to the gates of the n-type MOSFET and the p-type MOSFET.

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