Thermoelectric device

Abstract

The present invention provides a thermoelectric device in which a reduction in size is possible using a simple configuration. The thermoelectric device 1X is provided with a sheet-shaped or plate-shaped thermoelectric conversion film 15 having a thermoelectric conversion element comprising a material exhibiting an abnormal Nernst effect, and a high-thermal-conductivity insulating film 16X provided on at least a first surface of the thermoelectric conversion film 15 and made of an insulator having a thermal conductivity higher than the material constituting the thermoelectric conversion element. The thermoelectric device is further provided with a catalyst part comprising a catalyst that can be applied to a gas sensor and that reacts to the heat of a gas. The catalyst part is provided, so as to face a gas flow path, on at least a partial region of the surface of the high-thermal-conductivity insulating film.

Description

[Technical Field]

[0001] The present invention relates to thermoelectric devices. [Background technology]

[0002] The Seebeck effect is known as a thermoelectric mechanism that generates a voltage when a temperature gradient is applied to a substance (see, for example, Patent Document 1). Thermometers using thermocouples that utilize the Seebeck effect and Peltier elements for temperature control and cooling of various devices have already been put to practical use. Furthermore, various configurations have been proposed for gas sensors that combine the Seebeck effect with a catalyst to measure the heat generated by the gas to be detected by the catalyst (see Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-156461 [Patent Document 2] International Publication No. 2016 / 181777 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because the Seebeck effect generates a voltage in the same direction as the temperature gradient, it is necessary to fabricate a structure in which p-type and n-type modules are alternately arranged in the vertical direction from the heat source surface, which makes miniaturization difficult, limits the degree of freedom in device design, results in a complex structure, and raises the issue of high manufacturing costs.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a thermoelectric device that can be downsized with a simple configuration. [Means for solving the problem]

[0006] A thermoelectric device according to one embodiment of the present invention comprises a sheet-like or plate-like thermoelectric conversion film having a thermoelectric conversion element made of a material that exhibits the anomalous Nernst effect, and a highly thermally conductive insulating film provided on at least a first surface of the thermoelectric conversion film and made of an insulator with a thermal conductivity higher than that of the material of the thermoelectric conversion element. [Effects of the Invention]

[0007] According to the present invention, it is possible to realize a compact thermoelectric device with a simple configuration. [Brief explanation of the drawings]

[0008] [Figure 1] 1A and 1B are schematic diagrams for explaining the thermoelectric mechanism of a thermoelectric conversion film according to an embodiment. [Figure 2A] 1 is a cross-sectional view of a main part of an example of a thermoelectric device according to an embodiment. [Figure 2B] FIG. 10 is a cross-sectional view of a main part of another example of the thermoelectric device according to the embodiment. [Figure 3] FIG. 1 is a perspective view showing the configuration of a gas sensor according to a first embodiment. [Figure 4] FIG. 1 is a perspective view showing the configuration of a sensor unit of a gas sensor according to a first embodiment. [Figure 5] 1 is a cross-sectional view of a sensor portion of a gas sensor according to a first embodiment of the present invention. [Figure 6A] FIG. 2 is a diagram showing the layout of a part of the thermoelectric conversion film of the gas sensor of the first embodiment. [Figure 6B] FIG. 2 is a schematic diagram showing an example of a connection portion between adjacent thermoelectric conversion elements. [Figure 7] FIG. 4 is a diagram showing the layout of another part of the thermoelectric conversion film of the gas sensor of the first embodiment. [Figure 8] FIG. 2 is a diagram illustrating a readout circuit of the gas sensor according to the first embodiment. [Figure 9] 5A to 5C are cross-sectional views illustrating a method for manufacturing the gas sensor of the first embodiment. [Figure 10] FIG. 10 is a diagram showing the layout of a part of a thermoelectric conversion film of a gas sensor according to a second embodiment of the present invention. [Figure 11]FIG. 10 is a diagram showing the layout of another part of the thermoelectric conversion film of the gas sensor of the second embodiment. [Figure 12] FIG. 10 is a diagram showing the layout of a part of a thermoelectric conversion film of a gas sensor according to a third embodiment. [Figure 13] FIG. 10 is a diagram showing the layout of another part of the thermoelectric conversion film of the gas sensor of the third embodiment. [Figure 14] FIG. 10 is a diagram illustrating a readout circuit of a gas sensor according to a fourth embodiment. [Figure 15] FIG. 10 is a cross-sectional view of a sensor portion of a gas sensor according to a fifth embodiment. [Figure 16] FIG. 10 is a diagram showing the layout of a part of a thermoelectric conversion film of a gas sensor according to a fifth embodiment. [Figure 17] FIG. 10 is a perspective view showing the configuration of a sensor unit of a gas sensor according to a sixth embodiment. [Figure 18] FIG. 10 is a cross-sectional view of a sensor portion of a gas sensor according to a sixth embodiment. [Figure 19] FIG. 13 is a diagram showing the layout of a part of a thermoelectric conversion film of a gas sensor according to a sixth embodiment. [Figure 20] 10A to 10C are cross-sectional views illustrating manufacturing steps of a manufacturing method for the gas sensor of the sixth embodiment. [Figure 21] FIG. 13 is a perspective view showing the configuration of a gas sensor according to a seventh embodiment. [Figure 22] FIG. 13 is a cross-sectional view of a sensor portion of a gas sensor according to a seventh embodiment. [Figure 23] FIG. 13 is a diagram showing the layout of a part of a thermoelectric conversion film of a gas sensor according to a seventh embodiment. [Figure 24] 13A to 13C are cross-sectional views illustrating steps in a method for manufacturing the gas sensor of the seventh embodiment. [Figure 25] FIG. 25 is a cross-sectional view showing a step subsequent to that shown in FIG. 24. [Figure 26] FIG. 26 is a cross-sectional view showing a step subsequent to that shown in FIG. 25. [Figure 27] FIG. 13 is a cross-sectional view of a sensor portion of a gas sensor according to an eighth embodiment. [Figure 28] FIG. 13 is a cross-sectional view of a sensor portion of a gas sensor according to a ninth embodiment. [Figure 29]FIG. 13 is a diagram showing the layout of a thermoelectric conversion film of a gas sensor according to a ninth embodiment. [Figure 30] FIG. 13 is a cross-sectional view illustrating a noise cancellation method for a thermoelectric conversion film of a gas sensor according to a ninth embodiment. [Figure 31] FIG. 13 is a cross-sectional view of a sensor portion of a gas sensor according to a modified example of the ninth preferred embodiment. [Figure 32] FIG. 23 is a cross-sectional view of a sensor portion of a gas sensor according to a tenth embodiment, taken along a plane parallel to the gas flow. [Figure 33] FIG. 23 is a cross-sectional view of a sensor portion of a gas sensor according to a tenth embodiment, taken along a plane perpendicular to the gas flow. [Figure 34] FIG. 23 is a cross-sectional view of a sensor portion of a gas sensor according to an eleventh embodiment. [Figure 35] FIG. 23 is a diagram showing the layout of a thermoelectric conversion film of a gas sensor according to an eleventh embodiment. [Figure 36] FIG. 23 is a cross-sectional view of a sensor portion of a gas sensor according to a twelfth embodiment. [Figure 37] FIG. 22 is a cross-sectional view of a gas sensor according to a thirteenth embodiment. [Figure 38] FIG. 23 is a diagram showing the layout of a thermoelectric conversion film of a gas sensor according to a fourteenth embodiment. [Figure 39] FIG. 23 is a diagram showing the layout of a thermoelectric conversion film of a gas sensor according to a fifteenth embodiment. [Figure 40] FIG. 23 is a diagram showing the layout of a thermoelectric conversion film of a gas sensor according to a sixteenth embodiment. [Figure 41] FIG. 23 is a diagram illustrating a readout circuit of the gas sensor according to the seventeenth embodiment. [Figure 42] FIG. 20 is a cross-sectional view of the cooling device of the eighteenth embodiment. [Figure 43] FIG. 20 is a cross-sectional view of a cooling device according to a 19th embodiment. [Figure 44] FIG. 20 is a cross-sectional view of a heat flow sensor according to a twentieth embodiment. [Figure 45] FIG. 21 is a diagram showing the layout of the thermoelectric conversion film of the heat flow sensor of the 21st embodiment. [Figure 46] 21 is a graph showing an output signal versus heat flux of the heat flow sensor of the 21st embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, the same or similar components are designated by the same reference numerals throughout the drawings. The drawings are schematic, and the relationship between planar dimensions and thickness, and the thickness ratio of each component, differ from the actual ones. Furthermore, it goes without saying that the dimensional relationships and ratios of each component differ between the drawings.

[0010] First, with reference to FIG. 1, a thermoelectric conversion element and its thermoelectric mechanism according to an embodiment of the present invention will be described.

[0011] (Configuration of thermoelectric conversion element) The thermoelectric conversion element 101 according to this embodiment is made of a material that exhibits the anomalous Nernst effect. As shown in FIG. 1 , the thermoelectric conversion element 101 has a rectangular parallelepiped shape extending in one direction (X direction), a predetermined thickness (length in the Z direction), and is magnetized in the -Y direction. When a heat flow Q (∝∇T) flows through the thermoelectric conversion element 101 in the +Z direction, a temperature difference occurs in the +Z direction. As a result, an electromotive force E (∝M × ∇T) is generated in the thermoelectric conversion element 101 due to the anomalous Nernst effect in the direction of the cross product perpendicular to both the direction of the heat flow Q (+Z direction) and the direction of the magnetization M (-Y direction). Specifically, depending on the Nernst coefficient of the material of the thermoelectric conversion element 101, an electromotive force E is generated that causes a current to flow in the +X direction or the -X direction.

[0012] Examples of materials that exhibit the anomalous Nernst effect and that form the thermoelectric conversion element 101 include Fe—Ga alloys such as Fe 3 Ga, Fe—Al alloys such as Fe 3 Al, Co 2 MnGa, Fe—Ni alloys, Mn 3 Sn, and Mn 3 Ge.

[0013] (Configuration of thermoelectric device) Next, a thermoelectric device in which the thermoelectric conversion element 101 of this embodiment is modularized will be described.

[0014] 2A shows a cross-sectional view of a main portion of an example of a thermoelectric device according to this embodiment. The thermoelectric device 1X includes a thermoelectric conversion film 15 and a highly thermally conductive insulating film 16X provided on a first surface of the thermoelectric conversion film 15. The thermoelectric conversion film 15 is a sheet-like or plate-like film having a thermoelectric conversion element made of a material that exhibits the anomalous Nernst effect shown in FIG. 1. The highly thermally conductive insulating film 16X is made of an insulator having a higher thermal conductivity than the material of the thermoelectric conversion element of the thermoelectric conversion film 15.

[0015] 2B shows a cross-sectional view of a main portion of another example of a thermoelectric device according to this embodiment. The thermoelectric device 1Y includes a thermoelectric conversion film 15, a first highly thermal conductive insulating film 16 provided on a first surface of the thermoelectric conversion film 15, and a second highly thermal conductive insulating film 11 provided on a second surface of the thermoelectric conversion film 15 opposite the first surface. The thermoelectric conversion film 15 is a sheet-like or plate-like film having thermoelectric conversion elements made of a material that exhibits the anomalous Nernst effect, as shown in FIG. 1. The first highly thermal conductive insulating film 16 and the second highly thermal conductive insulating film 11 are made of insulators with higher thermal conductivity than the material of the thermoelectric conversion elements of the thermoelectric conversion film 15.

[0016] Examples of materials for the high thermal conductive insulating film 16X in FIG. 2A and the first and second high thermal conductive insulating films 16 and 11 in FIG. 2B include SiC, AlN, SiN, and BN.

[0017] Moreover, examples of materials for the high thermal conductive insulating film 16X in FIG. 2A and the first and second high thermal conductive insulating films 16 and 11 in FIG. 2B include Al2O3 and MgO.

[0018] Assuming that the longitudinal length of the rectangular parallelepiped thermoelectric conversion element 101 shown in FIG. 1 is L and its thickness is H, the electromotive force generated by the anomalous Nernst effect is proportional to L / H when the temperature difference between the top and bottom surfaces of the thermoelectric conversion element 101 is constant. In other words, the longer and thinner the thermoelectric conversion element 101 constituting the thermoelectric conversion film 15, the greater the generated electromotive force. This not only improves the performance of the thermoelectric device, but also enables it to be made thinner and more compact. Furthermore, the highly thermally conductive insulating film provided on the thermoelectric conversion film allows for uniform and efficient heat conduction, thereby further improving the performance of the thermoelectric device.

[0019] Materials that exhibit the anomalous Nernst effect are also known to exhibit the Ettingshausen effect, which is the reverse process of the anomalous Nernst effect. Thermoelectric devices that utilize the Ettingshausen effect can also be made thinner and more compact, and efficient heat transport is possible through highly thermally conductive insulating films, leading to the realization of high performance thermoelectric devices.

[0020] Hereinafter, an example in which the thermoelectric device of this embodiment is applied to a fluid sensor that detects a fluid, an example in which it is applied to a cooling device, and an example in which it is applied to a heat flow sensor will be described. As the fluid sensor, a gas sensor that detects gas will be described, but the fluid to be detected may also be a liquid.

[0021] First, an example in which the thermoelectric device of this embodiment is applied to a gas sensor will be described. (First Example) 3 is a schematic diagram showing the configuration of the gas sensor according to the first embodiment. The gas sensor 1 includes a substantially cylindrical sensor section 2, a power supply signal processing section 4 provided on the outer circumferential surface of the sensor section 2 and having a readout circuit (described later), wiring 3 connecting the sensor section 2 and the power supply signal processing section 4, and a fan 5. The sensor section 2 is open at both ends, with one open end serving as a gas intake path 6 and the other open end serving as a gas exhaust path 7.

[0022] The gas sensor 1 is configured such that, by operating the fan 5, gas outside the sensor unit 2 is introduced into the sensor unit 2 along the intake path 6, passes through the inside of the sensor unit 2, and then is exhausted to the outside of the sensor unit 2 along the exhaust path 7. Although the fan 5 is provided on the exhaust path 7 side in FIG. 3, it may also be provided on the intake path 6 side.

[0023] FIG. 4 shows a schematic diagram of the sensor section 2 of the gas sensor of the first embodiment. A thermoelectric conversion film 15 is provided on the inner periphery of a substantially cylindrical heat-insulating substrate 10. A first highly thermally conductive insulating film 16 is provided on a first surface of the thermoelectric conversion film 15 on the inner periphery. A second highly thermally conductive insulating film 11 is provided between the heat-insulating substrate 10 and a second surface of the thermoelectric conversion film 15 opposite the first surface. The inner periphery of the first highly thermally conductive insulating film 16 is partitioned into two equal-area regions at a position intersecting a plane passing through the central axis of the cylinder. One region is provided with a catalyst portion 17, and the other region is provided with a non-catalytic portion 18 that does not exhibit catalytic activity against the gas to be detected. The non-catalytic portion 18 is made of a material similar to that of the catalyst portion 17 but without the catalyst. The non-catalytic portion 18 does not necessarily have to be formed; the surface of the first highly thermally conductive insulating film 16 may be exposed. The inner periphery of the catalyst portion 17 and the non-catalytic portion 18 is hollow, forming a gas flow path. A cylindrical heater 19 is provided in the center of this hollow portion.

[0024] The sensor structure 40 is formed by the second highly thermal conductive insulating film 11, the thermoelectric conversion film 15, the first highly thermal conductive insulating film 16, and the catalyst portion 17, and the sensor structure 41 is formed by the second highly thermal conductive insulating film 11, the thermoelectric conversion film 15, the first highly thermal conductive insulating film 16, and the non-catalytic portion 18.

[0025] The sensor unit 2 is provided with legs 20 and is installed with its open end parallel to the floor where the gas sensor 1 is installed. The legs 20 provide a gap between the bottom and the floor, preventing the opening on the bottom from being blocked. For example, gas outside the sensor unit 2 is drawn into the sensor unit 2 from the bottom along the intake path 6, passes through the inside of the sensor unit 2, and is then exhausted to the outside of the sensor unit 2. By creating an updraft inside the sensor unit 2 due to the chimney effect, the efficiency of gas intake into the sensor unit 2 can be improved. While FIG. 4 shows a configuration in which the open end of the sensor unit 2 is installed parallel to the floor where the gas sensor 1 is installed, the open end may also be installed perpendicular to the floor where the gas sensor 1 is installed.

[0026] Fig. 5 shows a cross-sectional view taken along line VV in Fig. 4. The thermoelectric conversion film 15 is configured such that first thermoelectric conversion elements 12 and second thermoelectric conversion elements 13 extending in a direction parallel to the circumference of the cylindrical sensor part 2 are insulated from each other by a low thermal conductive insulating film 14 serving as an interlayer insulating film and are alternately arranged in a direction perpendicular to the circumferential direction.

[0027] The first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 are made of a material that exhibits the anomalous Nernst effect. The first high thermal conductive insulating film 16 and the second high thermal conductive insulating film 11 are made of an insulator having a thermal conductivity higher than that of the material of the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13. The low thermal conductive insulating film 14 is made of an insulator having a thermal conductivity lower than that of the material of the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13, and is made of an insulating film such as porous silica.

[0028] The catalyst section 17 is composed of a film of the catalyst itself or a film supporting the catalyst. The catalyst has the property of generating heat in response to the gas to be detected by the gas sensor 1. For example, Pt is used as the catalyst. When the catalyst is supported on a film, it is preferably supported on a film with a large surface area, for example, a porous film. The catalyst section 17 is composed of, for example, a porous Al2O3 film supporting Pt.

[0029] The non-catalytic portion 18 is made of a material obtained by removing the catalyst from the catalytic portion 17, and is made of, for example, a porous Al2O3 film that does not support Pt.

[0030] The heater 19 is connected to the power supply signal processing unit 4 via wiring 3, and is made of a material that generates heat when electricity is applied.

[0031] FIG. 6A shows a layout (developed view) of the catalyst portion 17 region of the thermoelectric conversion film 15 of the gas sensor 1 of the first embodiment.

[0032] A plurality of first thermoelectric conversion elements 12 and a plurality of second thermoelectric conversion elements 13 are provided, each forming an L-shaped three-dimensional shape. The first thermoelectric conversion elements 12 and the second thermoelectric conversion elements 13 are alternately arranged in parallel in a direction perpendicular to the longitudinal direction (X direction). Here, a side portion of the first thermoelectric conversion element 12 near one end portion in the longitudinal direction (-X direction) is connected to a side portion of the second thermoelectric conversion element 13 adjacent on one side (+Y direction), and a side portion of the first thermoelectric conversion element 12 near the other end portion in the longitudinal direction (+X direction) is connected to a side portion of the second thermoelectric conversion element 13 adjacent on the other side (-Y direction). A side portion near one end portion in the longitudinal direction (-X direction) of the second thermoelectric conversion element 13 is connected to a side portion of the first thermoelectric conversion element 12 adjacent on the other side (-Y direction), and a side portion near the other end portion in the longitudinal direction of the second thermoelectric conversion element 13 (+X direction) is connected to a side portion of the first thermoelectric conversion element 12 adjacent on one side (+Y direction). The first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 are insulated from each other except for the connection points.

[0033] The connection between adjacent thermoelectric conversion elements is not limited to the example shown in Fig. 6A. For example, the upper surface end of the thermoelectric conversion element may be etched to form a step, and the end of the adjacent thermoelectric conversion element may be connected so as to fill this step area (e.g., an area of ​​20 µm x 20 µm x 10 nm). Fig. 6B shows an example in which the end of the first thermoelectric conversion element 12 is connected to the step area 131 at the upper surface end of the second thermoelectric conversion element 13.

[0034] In this manner, the plurality of first thermoelectric conversion elements 12 and the plurality of second thermoelectric conversion elements 13 are electrically connected in series and arranged in a serpentine pattern. The ends of the outermost first thermoelectric conversion elements 12 and the second thermoelectric conversion elements 13 that are not connected to the first thermoelectric conversion elements 12 or the second thermoelectric conversion elements 13 serve as terminals of a power generator consisting of the plurality of first thermoelectric conversion elements 12 and the plurality of second thermoelectric conversion elements 13 connected in series. A catalyst portion 17 is formed in the area covering the first thermoelectric conversion elements 12 and the second thermoelectric conversion elements 13. The first thermoelectric conversion elements 12 are magnetized in the -Y direction (direction of magnetization M12). The second thermoelectric conversion elements 13 are magnetized in the +Y direction (direction of magnetization M13). The number of first thermoelectric conversion elements 12 and the number of second thermoelectric conversion elements 13 are not limited. The plurality of first thermoelectric conversion elements 12 and the plurality of second thermoelectric conversion elements 13 have Nernst coefficients of the same sign.

[0035] When catalyst section 17 reacts with the gas flowing through the flow path and generates heat, the heat is conducted from catalyst section 17 to the first surface of thermoelectric conversion film 15 via first high thermal conductive insulating film 16, causing a heat flow in the Z direction to first thermoelectric conversion element 12 and second thermoelectric conversion element 13. When a temperature difference occurs due to the heat flow, an electromotive force E12 is generated in first thermoelectric conversion element 12 in a direction (-X direction) perpendicular to both the direction of magnetization M12 (-Y direction) and the direction of heat flow Q (+Z direction) due to the anomalous Nernst effect. In second thermoelectric conversion element 13, an electromotive force E13 is generated in a direction (+X direction) perpendicular to both the direction of magnetization M13 (+Y direction) and the direction of heat flow Q (+Z direction) due to the anomalous Nernst effect.

[0036] Here, the heat conducted to the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 includes heat due to the reaction between the catalytic portion 17 and the gas, heat from the non-catalytic portion 18, or heat from other sources in the environment, and the sum of these heat sources generates a temperature difference in the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13, which generates an electromotive force due to the anomalous Nernst effect in the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13. The electromotive force thus obtained is an output resulting from the heat generated by the catalytic portion 17 reacting with the gas and the heat of environmental fluctuations.

[0037] As described above, the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 arranged in parallel are electrically connected in series, so that the electromotive force E12 generated in the first thermoelectric conversion element 12 can be applied to the adjacent second thermoelectric conversion element 13. Furthermore, since the electromotive force E12 generated in the first thermoelectric conversion element 12 and the electromotive force E13 generated in the adjacent second thermoelectric conversion element 13 are in opposite directions, the electromotive forces of the adjacent first thermoelectric conversion element 12 and second thermoelectric conversion element 13 are added together, thereby increasing the output voltage V. The first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 are connected to the wiring 3 shown in FIG. 3 via through holes 21 and 22 penetrating the heat insulating substrate 10, and the electromotive forces generated in the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 are detected by the power supply signal processing unit 4.

[0038] The heater 19 is provided to face the surfaces of the catalytic section 17 and the non-catalytic section 18, and can heat the region of the sensor section 2 inside the heat insulating substrate 10 to a predetermined temperature. For example, it is configured to heat the region of the sensor section 2 inside the heat insulating substrate 10 to 100°C. If moisture is adsorbed onto the catalytic section 17, the reactivity of the catalyst will decrease, so by evaporating the moisture through heating, it is possible to prevent a decrease in catalytic function. Furthermore, by controlling the region of the sensor section 2 inside the heat insulating substrate 10 to a constant temperature, it is possible to ensure the stability of the characteristics of the gas sensor.

[0039] 6A, for example, a temperature sensor 24 is mounted on the heat insulating substrate 10 outside the area of ​​the catalyst section 17, and temperature detection is possible in the power supply signal processing section 4 through a through hole 23. The mounting position of the temperature sensor 24 is not particularly limited, and it may be formed inside the area of ​​the catalyst section 17. In this case, the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 are laid out so as to avoid the mounting position of the temperature sensor 24.

[0040] Fig. 7 shows a layout (developed view) of the region of the non-catalytic portion 18 of the thermoelectric conversion film 15 of the gas sensor 1 of the first embodiment. The configuration shown in Fig. 7 is substantially the same as the configuration shown in Fig. 6A, except that the non-catalytic portion 18 is provided instead of the catalytic portion 17 of Fig. 6A. Needless to say, the connection between thermoelectric conversion elements shown in Fig. 6B can also be used in Fig. 7.

[0041] In the non-catalytic section 18, no heat is generated by reaction with the gas flowing in the flow path, but heat from the non-catalytic section 18 or heat from other environments is conducted to the thermoelectric conversion film 15, generating an electromotive force E12 in the first thermoelectric conversion element 12 and an electromotive force E13 in the second thermoelectric conversion element 13. The electromotive forces of the adjacent first thermoelectric conversion element 12 and second thermoelectric conversion element 13 are added together and output as an output voltage V. The electromotive forces of the first thermoelectric conversion element 12 and second thermoelectric conversion element 13 obtained in this manner are outputs resulting from environmental fluctuations.

[0042] The heat insulating substrate 10 has a thickness of 25 μm to 1 mm, for example, 100 μm. The second high thermal conductive insulating film 11 has a thickness of 10 nm to 1 μm, for example, 0.1 μm. The thermoelectric conversion film 15 has a thickness of 10 nm to 10 μm, for example, 0.1 μm. The first high thermal conductive insulating film 16 has a thickness of 10 nm to 1 μm, for example, 0.1 μm. The catalyst portion 17 has a thickness of 5 nm to 10 μm, for example, 5 μm.

[0043] 6A and 7, the length in the X direction of the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 is 1 mm to 100 mm, for example, 1 mm to 3 mm. The width in the Y direction of the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 is 0.1 μm to 100 μm, for example, 20 μm. The spacing in the Y direction between the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13, in other words, the width in the Y direction of the low thermal conductive insulating film 14, is 0.1 μm to 100 μm, for example, 10 μm. The repeat width d in the Y direction of the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 (the sum of the width in the Y direction of the first thermoelectric conversion element 12 or the second thermoelectric conversion element 13 and the spacing between the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13) is 0.1 μm to 100 μm, for example, 30 μm.

[0044] In the gas sensor 1, it is preferable that the temperature of the region inside the heat insulating substrate 10 can be heated from, for example, 25°C to 100°C in a short time of less than 1 second by heating with a heater 19 that consumes low power, about 50 mW. To achieve this, it is important to reduce the total volume Vd of the second high thermal conductive insulating film 11, thermoelectric conversion film 15, first high thermal conductive insulating film 16, catalyst portion 17, and non-catalytic portion 18 in the region inside the heat insulating substrate 10. The condition for the volume Vd when the rise time from 25°C to 100°C is t (s) and the power consumption of the heater 19 is P (W) is expressed by equation (1).

number

[0045] When the rise time from 25°C to 100°C is 1 s and the power consumption of the heater 19 is 50 mW, the condition for Vd is Vd<0.27 mm. 3 This becomes:

[0046] In the first example, of the total heat capacity of the thermoelectric conversion film 15, the first high thermal conductive insulating film 16, the second high thermal conductive insulating film 11, and the catalyst section 17, the proportion of the heat capacity of the catalyst section 17 made of Pt is 95%, the proportion of the heat capacity of the second high thermal conductive insulating film 11 made of AlN is 1.6%, the proportion of the heat capacity of the thermoelectric conversion film 15 is 1.8%, and the proportion of the heat capacity of the first high thermal conductive insulating film 16 made of AlN is 1.6%. Note that there are no particular limitations on the proportions of the heat capacities of the films constituting the sensor section.

[0047] 8 shows the configuration of a readout circuit 80 of the gas sensor 1 of the first embodiment. The readout circuit 80 is provided in the power supply signal processing unit 4. One terminal of the thermoelectric conversion film 15 of the sensor structure 41 is connected to the source of the transistor TRa1, and the other terminal is connected to the source of the transistor TRa2 and the gate of the transistor TRa3. The transistor TRa3 is a source follower amplifier that amplifies the output from the sensor structure 41. The transistors TRa1 and TRa2 are reset transistors. The output of the sensor structure 41 is input to the (-) side of the differential amplifier DA.

[0048] The source of transistor TRb1 is connected to one terminal of the thermoelectric conversion film 15 of the sensor structure 40, and the source of transistor TRb2 and the gate of transistor TRb3 are connected to the other terminal. Transistor TRb3 is a source follower amplifier that amplifies the output from the sensor structure 40. Transistors TRb1 and TRb2 are reset transistors. The output of the sensor structure 40 is input to the (+) side of differential amplifier DA.

[0049] In the read circuit 80, an emitter follower amplifier may be used instead of the source follower amplifier.

[0050] Next, we will explain the operation of the read circuit 80. First, before reading, reset transistors TRa1, TRa2, TRb1, and TRb2 are turned on and left for a predetermined time (CR time constant), thereby resetting the potentials of the sensor structures 41 and 40 to a predetermined potential.

[0051] At the start of measurement, each reset transistor is turned OFF, and the output of sensor structure 41, which corresponds to the environmental fluctuation output, is amplified by transistor TRa3 and input to the (-) side of differential amplifier DA. Meanwhile, the output of sensor structure 40, which corresponds to the sum of the heat generated in catalyst unit 17 and the heat of environmental fluctuation, is amplified by transistor TRb3 and input to the (+) side of differential amplifier DA.

[0052] Next, the differential amplifier DA amplifies the difference between the output from the sensor structure 41 and the output from the sensor structure 40, and the output of the gas sensor 1 is read out from the differential amplifier DA.

[0053] In this way, by subtracting the output signal of the non-catalytic region 18 from the output signal of the catalytic region 17, background noise can be removed and the S / N ratio of the gas sensor output can be increased.

[0054] The readout circuit 80 shown in FIG. 8 can also be applied to gas sensors having a catalytic portion and a non-catalytic portion, as shown in the following examples.

[0055] 9, a method for manufacturing the gas sensor 1 will be described. First, a release layer made of a deliquescent material such as MgO is formed on the transfer substrate 100. After that, a 0.1 μm-thick AlN film is formed by, for example, sputtering to form the first highly thermal conductive insulating film 16. Next, a resist film is applied to the first highly thermal conductive insulating film 16 and a photolithography process is performed to form a resist film that opens the regions for the first thermoelectric conversion elements 12 and the second thermoelectric conversion elements 13. A 0.1 μm-thick film of a material exhibiting the anomalous Nernst effect is then formed by, for example, sputtering, and the material exhibiting the anomalous Nernst effect formed on the resist film is removed together with the resist film by lift-off to form the first thermoelectric conversion elements 12 and the second thermoelectric conversion elements 13 in a predetermined pattern.

[0056] Next, a porous insulating film is formed in a thickness of 0.1 μm in the region between the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13, for example, by plasma enhanced chemical vapor deposition (CVD) or spin coating, and then polished by chemical mechanical polishing (CMP) until the upper surfaces of the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 are exposed, forming the low thermal conductive insulating film 14. Next, a 0.1 μm thick AlN film is formed on the first thermoelectric conversion element 12, the second thermoelectric conversion element 13, and the low thermal conductive insulating film 14, for example, by sputtering, to form the second high thermal conductive insulating film 11. Each of the above layers may be formed by other film formation methods, such as molecular beam epitaxy (MBE), vacuum evaporation using resistance heating, or thermal CVD. Next, the first thermoelectric conversion element 12 and the second thermoelectric conversion element 13 are magnetized in the predetermined directions shown in FIGS. 6A and 7.

[0057] Next, the laminate of the second high thermal conductive insulating film 11, first thermoelectric conversion element 12, second thermoelectric conversion element 13, low thermal conductive insulating film 14, and first high thermal conductive insulating film 16 is peeled off at the interface of the peel-off layer and transferred to the outer peripheral surfaces of the catalytic portion 17 and non-catalytic portion 18, which have been machined into a cylindrical shape in advance. After the transfer, the first high thermal conductive insulating film 16 is positioned on the inner peripheral side, and the second high thermal conductive insulating film 11 is positioned on the outer peripheral side. A heat insulating substrate 10 is attached to the outer peripheral side of the second high thermal conductive insulating film 11.

[0058] Next, a through-hole is formed through the heat insulating substrate 10, and the through-hole is filled with wire 3 to form the wiring. A temperature sensor may be mounted on the heat insulating substrate 10 at a position to be connected to the through-hole, and the wiring may be connected via the through-hole. Next, a power supply signal processing unit 4 is connected to the wiring 3. In this manner, the gas sensor 1 shown in FIGS. 3 and 4 can be manufactured.

[0059] (Second Example) FIG. 10 shows the layout of the catalyst region of the thermoelectric conversion film of the gas sensor of the second embodiment. In the thermoelectric conversion film of the second embodiment, similar to the first embodiment, multiple first thermoelectric conversion elements 12a and multiple second thermoelectric conversion elements 13a are alternately arranged in parallel in a direction perpendicular to the longitudinal direction (X direction), electrically connected in series, and formed into a serpentine shape. The second embodiment differs from the first embodiment shown in FIG. 6A in that the first thermoelectric conversion elements 12a and the second thermoelectric conversion elements 13a have Nernst coefficients of different signs and are magnetized in the same direction. In FIG. 10, the first thermoelectric conversion element 12a has a Nernst coefficient of (-), and the second thermoelectric conversion element 13a has a Nernst coefficient of (+). Both the first thermoelectric conversion element 12a and the second thermoelectric conversion element 13a are magnetized in the +Y direction (the direction of magnetization M12a and M13a).

[0060] A catalyst portion 17a is provided in an area covering the first thermoelectric conversion element 12a and the second thermoelectric conversion element 13a. When the catalyst portion 17a reacts with the gas flowing through the flow path and generates heat, an electromotive force E12a is generated in the −X direction in the first thermoelectric conversion element 12a, and an electromotive force E13a is generated in the +X direction in the second thermoelectric conversion element 13a due to the anomalous Nernst effect. The electromotive forces of the adjacent first thermoelectric conversion element 12a and second thermoelectric conversion element 13a are added together, thereby increasing the output voltage V.

[0061] Fig. 11 shows the layout of the non-catalytic region of the thermoelectric conversion film of the gas sensor of Example 2. The configuration shown in Fig. 11 is the same as the configuration shown in Fig. 10, except that non-catalytic region 18a is provided instead of catalytic region 17a in Fig. 10.

[0062] In the non-catalytic portion 18a, heat is not generated by reaction with the gas flowing in the flow path, but heat from the non-catalytic portion 18a or heat from other environments is conducted to the thermoelectric conversion film, generating an electromotive force E12a in the first thermoelectric conversion element 12a and an electromotive force E13a in the second thermoelectric conversion element 13a. The electromotive forces of the adjacent first thermoelectric conversion element 12a and second thermoelectric conversion element 13a are added together and output as an output voltage V.

[0063] In the second embodiment, the connection between the thermoelectric conversion elements shown in FIG. 6B can also be adopted.

[0064] (Third Example) FIG. 12 shows the layout of the catalytic region of the thermoelectric conversion film of the gas sensor of the third embodiment. In the third embodiment, multiple thermoelectric conversion elements 12b are arranged in parallel in a direction perpendicular to the longitudinal direction (X direction), and wiring 25 is provided so that one longitudinal end (-X direction) of each thermoelectric conversion element 12b is connected to the other longitudinal end (+X direction) of the adjacent thermoelectric conversion element 12b on one side (-Y direction). The connection between the thermoelectric conversion element 12b and the wiring 25 is similar to the connection between adjacent thermoelectric conversion elements shown in FIG. 6B. A stepped region is provided at the end of the top surface of the thermoelectric conversion element 12b, and the end of the wiring 25 is connected to fill this stepped region. The thermoelectric conversion elements 12b and the wiring 25 are insulated from each other except for the connection points. In this way, multiple thermoelectric conversion elements 12b are electrically connected in series and arranged in a serpentine pattern. The thermoelectric conversion elements 12b are magnetized in the +Y direction (the direction of magnetization M12b).

[0065] A catalyst portion 17b is provided in the region covering the thermoelectric conversion element 12b. When the catalyst portion 17b reacts with the gas flowing in the flow path and generates heat, an electromotive force E12b is generated in the +X direction in the thermoelectric conversion element 12b due to the anomalous Nernst effect. The electromotive forces of the adjacent thermoelectric conversion elements 12b are added together, and the output voltage V can be increased.

[0066] Fig. 13 shows the layout of the non-catalytic region of the thermoelectric conversion film of the gas sensor of Example 3. The configuration shown in Fig. 13 is the same as the configuration shown in Fig. 12, except that non-catalytic region 18b is provided instead of catalytic region 17b in Fig. 12.

[0067] In the non-catalytic portion 18b, heat is not generated by reaction with the gas flowing in the flow path, but heat from the non-catalytic portion 18b or heat from other environments is conducted to the thermoelectric conversion film, and an electromotive force E12b is generated in the thermoelectric conversion element 12b. The electromotive forces of adjacent thermoelectric conversion elements 12b are added together and output as a voltage V.

[0068] (Fourth Example) A readout circuit 81 of a fourth embodiment shown in FIG. 14 can be used in place of the readout circuit 80 (FIG. 8) of the gas sensor 1 of the first embodiment.

[0069] 14, in the readout circuit 81, the source of the transistor TRc1 is connected to one terminal of the thermoelectric conversion film of the sensor structure 41, and the source of the transistor TRc2 and the gate of the transistor TRc3 are connected to the other terminal. The transistor TRc3 is a source follower amplifier that amplifies the output of the sensor structure 41. The transistors TRc1 and TRc2 are reset transistors. The output of the sensor structure 41 is connected to the transistors TRc4 and V OD It passes through a circuit (Voltage Oscillator) and is input to the (-) side of the differential amplifier DA.

[0070] The source of transistor TRd1 is connected to one terminal of the thermoelectric conversion film of the sensor structure 40, and the source of transistor TRd2 and the gate of transistor TRd3 are connected to the other terminal. Transistor TRd3 is a source follower amplifier that amplifies the output of the sensor structure 40. Transistors TRd1 and TRd2 are reset transistors. The output of the sensor structure 40 amplified by transistor TRd3 is input to the (+) side of a differential amplifier DA via transistor TRd4. Transistor TRe1, a clamp capacitance element CA, and transistor TRe2 are connected between transistor TRd4 and the (+) side of the differential amplifier DA.

[0071] In the read circuit 81, an emitter follower amplifier may be used instead of the source follower amplifier.

[0072] Next, a description will be given of the operation of the read circuit 81. For simplicity, the transistors TRc1, TRd1, TRc2, TRd2, TRc4, TRd4, TRe1, and TRe2 will be denoted as φ1, φ2, φ3, φ4, φ5, φ6, φ7, and φ8, respectively.

[0073] First, before reading, φ1, φ2, φ3, and φ4 are turned on and left for a predetermined time (CR time constant), thereby resetting the potential of the sensor structure 41 and the potential of the sensor structure 40 to a predetermined potential.

[0074] Next, φ1, φ2, φ3, φ4, and φ6 are turned OFF, and φ7 and φ8 are turned ON, and measurement is performed by the sensor structure 41, and the clamp capacitance element CA is reset.

[0075] After the measurement by the sensor structure 41 is completed, φ7 and φ8 are turned OFF, φ1 and φ5 are turned ON, and the output of the sensor structure 41 corresponding to the environmental fluctuation output is read out to the clamp capacitance element CA.

[0076] Next, the signal level read out to the clamp capacitance element CA is V OD Set the initial value of the circuit's sweep voltage and prepare a μV-level sweep from that voltage.

[0077] Next, φ5 is turned OFF and φ8 is turned ON to reset the (+) input terminal of the differential amplifier DA to the ground voltage.

[0078] Next, φ8 is turned OFF, and in order to read the output of the sensor structure 40, which corresponds to the sum of the heat generated in the catalyst section and the heat generated by environmental fluctuations, φ2 and φ6 are turned ON, and the output signal resulting from the heat generated in the catalyst section, with the signal due to environmental fluctuations subtracted, is output to the (+) input terminal of the differential amplifier DA.

[0079] Next, V OD The circuit outputs a fine range sweep signal, and the points at which the sign of the difference changes in the differential amplifier DA are counted by a counter, which outputs digital data and reads out the output of the gas sensor 1.

[0080] In this way, by subtracting the output signal of the non-catalytic region from the output signal of the catalytic region, background noise can be removed and the S / N ratio of the gas sensor output can be increased.

[0081] (Fifth Example) FIG. 15 shows a cross-sectional view of the sensor section of the gas sensor of the fifth embodiment. The sensor section shown in FIG. 15 has a substantially cylindrical shape, and a second highly thermally conductive insulating film 11c, a thermoelectric conversion film 15c, and a first highly thermally conductive insulating film 16c are laminated on the inner circumferential side of a heat insulating substrate 10. On the inner circumferential side of the first highly thermally conductive insulating film 16c, a catalyst section 17c is provided in the upper half region, and a non-catalytic section 18c is provided in the lower half region. The catalyst section 17c and the non-catalytic section 18c have substantially the same area. The inner circumferential sides of the catalyst section 17c and the non-catalytic section 18c are hollow, forming a gas flow path. A cylindrical heater 19 is provided in the center of this hollow section.

[0082] 16 shows the layout (developed view) of the thermoelectric conversion film 15c. In each of the catalytic portion 17c and non-catalytic portion 18c, a plurality of pairs of first thermoelectric conversion elements 12c and second thermoelectric conversion elements 13c are arranged in parallel in a direction perpendicular to their longitudinal direction (X direction), electrically connected in series, and form a serpentine shape. The layout of the thermoelectric conversion film 15c shown in FIG. 16 is equivalent to the layouts shown in FIGS. 6A and 7 or the layouts shown in FIGS. 10 and 11.

[0083] In the region of catalyst section 17c, terminals of a power generator consisting of multiple sets of first thermoelectric conversion elements 12c and second thermoelectric conversion elements 13c connected in series are connected to power supply signal processing section 4 through through holes 21c1 and 22c1. Also, for example, in a region outside catalyst section 17c, temperature sensor 24c1 is mounted on heat insulating substrate 10, and temperature can be detected in power supply signal processing section 4 through through hole 23c1.

[0084] In the region of non-catalytic section 18c, the terminals of a power generator consisting of multiple sets of first thermoelectric conversion elements 12c and second thermoelectric conversion elements 13c connected in series are connected to power supply signal processing section 4 via through holes 21c2 and 22c2. Also, for example, in a region outside non-catalytic section 18c, a temperature sensor 24c2 is mounted on heat insulating substrate 10, and temperature detection is possible in power supply signal processing section 4 via through hole 23c2.

[0085] (Sixth Example) Fig. 17 shows a perspective view of a sensor unit of a gas sensor according to the sixth embodiment. The sensor unit according to the sixth embodiment has a substantially cylindrical shape, and a layered heater 19d is provided between the heat insulating substrate 10 and the second highly thermal conductive insulating film 11d. Except for the heater 19d, the sensor unit according to the sixth embodiment has substantially the same configuration as the sensor unit 2 according to the first embodiment (Fig. 4).

[0086] Fig. 18 shows a cross-sectional view taken along line XVIII-XVIII in Fig. 17. A heater 19d, a second highly thermally conductive insulating film 11d, a thermoelectric conversion film 15d, and a first highly thermally conductive insulating film 16d are laminated on the inner circumferential side of heat insulating substrate 10. The surface on the inner circumferential side of first highly thermally conductive insulating film 16d is partitioned into two regions of equal area at a position where it intersects with a plane passing through the central axis of the cylindrical shape, with catalyst portion 17d provided in one region and non-catalytic portion 18d provided in the other region.

[0087] 19 shows a layout (developed view) of a thermoelectric conversion film 15d of a gas sensor of Example 6. In each of the catalytic portion 17d and non-catalytic portion 18d, a plurality of pairs of first thermoelectric conversion elements 12d and second thermoelectric conversion elements 13d are arranged in parallel in a direction perpendicular to their longitudinal direction (X direction), electrically connected in series, and formed in a serpentine shape. The layout of the thermoelectric conversion film 15d shown in FIG. 19 is equivalent to the layouts shown in FIGS. 6A and 7 or the layouts shown in FIGS. 10 and 11.

[0088] 19, the heat insulating substrate 10 is provided with through holes 22 and 26. The thermoelectric conversion film 15d is connected to a power supply signal processing unit provided on the outer peripheral surface of the cylindrical sensor unit via the through hole 22. The heater 19d is connected to the power supply signal processing unit via the through hole 26.

[0089] Next, a brief description will be given of a method for manufacturing the gas sensor of Example 6. In the following, an example will be described in which a plurality of sensor structures each having a catalyst portion 17d are simultaneously manufactured on the same heat insulating substrate 10.

[0090] First, as shown in Figures 19 and 20, a through-hole 22 for the thermoelectric conversion film 15d and a through-hole 26 for the heater 19d are formed in the heat insulating substrate 10 for each sensor structure. Then, wiring is formed to connect the heater 19d and the through-hole 26. Next, as in the first embodiment, a second high thermal conductive insulating film 11d and a thermoelectric conversion film 15d (first thermoelectric conversion element 12d, second thermoelectric conversion element 13d, and low thermal conductive insulating film 14d) are formed. Then, wiring is formed so that the thermoelectric conversion film 15d and the through-hole 22 make ohmic contact. Next, a first high thermal conductive insulating film 16d is formed on the thermoelectric conversion film 15d.

[0091] Then, as shown in FIG. 20, a catalyst portion 17d is formed on the first high thermal conductive insulating film 16d. In this manner, a plurality of sensor structures are fabricated on the same heat insulating substrate 10. Individual sensor structures are obtained by cutting the heat insulating substrate 10 at the boundaries between these sensor structures. A plurality of sensor structures having non-catalytic portions 18d are also fabricated on the same heat insulating substrate in the same manner. A cylindrical gas sensor is fabricated by bending a sensor structure having catalyst portion 17d and a sensor structure having non-catalytic portions 18d into a cylinder and combining them.

[0092] (Seventh Example) Fig. 21 shows a schematic diagram of a gas sensor 1e according to a seventh embodiment, and Fig. 22 shows a cross-sectional view taken along line XXII-XXII in Fig. 21. The gas sensor 1e includes a sensor unit 2e having a generally rectangular cylindrical shape, a power supply signal processing unit 4e having a readout circuit and provided on the outer surface of the sensor unit 2e, wiring 3e connecting the sensor unit 2e and the power supply signal processing unit 4e, and a fan 5e. The sensor unit 2e is open at both ends, with one open end serving as a gas intake path 6e and the other open end serving as a gas exhaust path 7e.

[0093] In the gas sensor 1e, the operation of the fan 5e causes gas outside the sensor unit 2e to be introduced into the sensor unit 2e along the intake path 6e, pass through the inside of the sensor unit 2e, and then be exhausted to the outside of the sensor unit 2e along the exhaust path 7e. Note that although the fan 5e is provided on the exhaust path 7e side in FIG. 21, it may also be provided on the intake path 6e side.

[0094] The sensor unit 2e is configured by combining sensor structures 2ea, 2ea2, 2eb, and 2eb2 in a rectangular cylindrical shape on each of the four inner surfaces parallel to the gas flow. Each sensor structure has a heater 19e, an insulating film 28, a second highly thermal conductive insulating film 11e, a thermoelectric conversion film 15e, and a first highly thermal conductive insulating film 16e stacked on the inside of a heat insulating substrate 10.

[0095] 23, the thermoelectric conversion film 15e is composed of a serpentine first thermoelectric conversion section 15ea consisting of a plurality of sets of first thermoelectric conversion elements 12e and second thermoelectric conversion elements 13e, and a serpentine second thermoelectric conversion section 15eb consisting of a plurality of sets of first thermoelectric conversion elements 12e and second thermoelectric conversion elements 13e, and the first thermoelectric conversion section 15ea and the second thermoelectric conversion section 15eb are arranged so as to interdigitate with each other. The first thermoelectric conversion elements 12e and the second thermoelectric conversion elements 13e are arranged in parallel with their longitudinal directions perpendicular to the gas flow, are electrically connected in series, and are insulated from each other by a low thermal conductive insulating film 14e.

[0096] On the inside (gas flow path side) of the first high thermal conductive insulating film 16e, a catalytic portion 17e is provided in an area corresponding to the first thermoelectric conversion portion 15ea, and a non-catalytic portion 18e is provided in an area corresponding to the second thermoelectric conversion portion 15eb, and the catalytic portion 17e and the non-catalytic portion 18e face the inside of the rectangular cylindrical shape which is the gas flow path.

[0097] The first thermoelectric conversion element 12e and the second thermoelectric conversion element 13e are made of the same material as the thermoelectric conversion elements of the first embodiment, and when the catalyst section 17e reacts with the gas flowing through the flow path and generates heat, an electromotive force is generated in each of the adjacent first thermoelectric conversion element 12e and second thermoelectric conversion element 13e due to the anomalous Nernst effect. Because the first thermoelectric conversion element 12e and the second thermoelectric conversion element 13e are electrically connected in series, the electromotive forces are added together, and the output voltage V can be increased.

[0098] In the non-catalytic portion 18e, heat is not generated by reaction with the gas flowing in the flow path, but heat from the non-catalytic portion 18e or heat from other environments is conducted to the thermoelectric conversion film 15e. An electromotive force is generated in each of the adjacent first thermoelectric conversion element 12e and second thermoelectric conversion element 13e, and these electromotive forces are added together and output.

[0099] 22, the catalyst portion 17e of the sensor structures 2ea and 2eb and the catalyst portions of the other sensor structures 2ea2 and 2eb2 may be configured to be made of catalysts of different materials. In this way, by providing a gas sensor with multiple catalyst portions made of different catalysts, it becomes possible to detect the components of a mixed gas.

[0100] Next, a method for manufacturing the gas sensor of the seventh embodiment will be described with reference to FIGS. First, in the sensor region R1 and the transistor region R2, an insulating film 28 made of silicon oxide is formed on the silicon substrate 27 by a CVD method or the like. In reality, the transistor region R2 is provided on both sides of the sensor region R1 (both horizontal ends in the figure), but one of the transistor regions R2 is not shown in Figures 24 to 26. In the transistor region R2, the insulating film 28 serves as the gate insulating film of the transistor. In the sensor region R1, an insulating film made of silicon nitride may be further formed on the insulating film 28. The silicon nitride film not only serves as a highly thermally conductive insulating film but also functions as a tensile stress film when forming the sensor region R1 into a membrane, as described below. Next, a conductive layer such as polysilicon is formed by a CVD method or the like, and a resist pattern is formed by a photolithography process and an etching process such as RIE (Reactive Ion Etching) is performed to pattern the gate electrode 29, forming the gate electrode. Next, source / drain regions 30 are formed in the silicon substrate 27 on both sides of the gate electrode by ion implantation or the like. In this manner, a transistor is formed in the transistor region R2.

[0101] 25, a second high thermal conductive insulating film 11e, a thermoelectric conversion film 15e having a first thermoelectric conversion element 12e, a second thermoelectric conversion element 13e, and a low thermal conductive insulating film 14e, and a first high thermal conductive insulating film 16e are formed on the insulating film 28 of the silicon substrate 27 in the same manner as in the first embodiment. Subsequently, a catalyst portion 17e is formed on the first high thermal conductive insulating film 16e in the region of the catalyst portion 17e. Furthermore, a non-catalytic portion 18e is formed on the first high thermal conductive insulating film 16e in the region of the non-catalytic portion 18e.

[0102] 26, in the sensor region R1, the silicon substrate 27 is removed from the back side thereof by etching such as RIE until the insulating film 28 is exposed. Subsequently, in the sensor region R1, a heater 19e is formed on the back side of the insulating film 28. In the process of forming the heater 19e, wiring 31 connected to the heater 19e is formed in the transistor region R2. Next, in the sensor region R1 and the transistor region R2, a heat insulating substrate 10 is formed on the back side of the heater 19e and wiring 31. In this manner, the sensor structure of the gas sensor of the seventh embodiment can be manufactured.

[0103] (Eighth Example) 27 shows a cross-sectional view of the sensor portion of the gas sensor of the eighth embodiment. The sensor portion of the eighth embodiment is provided with a plurality of sensor structures 2ec, 2ed, 2ee, and 2ef held by a holder 32 at a distance from one another. The sensor structures 2ec, 2ed, 2ee, and 2ef have the same configuration as the sensor structures 2ea and 2eb of the seventh embodiment (FIG. 22). Each of the sensor structures 2ec, 2ed, 2ee, and 2ef detects gas trapped in the gaps between these sensor structures.

[0104] The number of sensor structures constituting the gas sensor of the eighth embodiment is not particularly limited. Furthermore, the catalyst portions of the multiple sensor structures may be configured to be made of catalysts of different materials. This makes it possible to detect the components of a mixed gas.

[0105] (Ninth Example) 28 shows a cross-sectional view of a sensor portion of a gas sensor according to a ninth embodiment. The sensor portion includes a sensor structure 2fa. The sensor structure 2fa includes a first thermoelectric conversion film 15f including a first thermoelectric conversion element 12f, a second thermoelectric conversion element 13f, and a low thermal conductive insulating film 14f. A first high thermal conductive insulating film 16f is provided on a first surface of the thermoelectric conversion film 15f, and a catalyst portion 17f is provided on the first high thermal conductive insulating film 16f. Furthermore, a second high thermal conductive insulating film 11f is provided on a second surface of the thermoelectric conversion film 15f, and a non-catalytic portion 18f is provided on the surface of the second high thermal conductive insulating film 11f opposite to the thermoelectric conversion film 15f side.

[0106] FIG. 29 shows the layout of the thermoelectric conversion film 15f of the gas sensor of the ninth embodiment shown in FIG.

[0107] The plurality of pairs of first and second thermoelectric conversion elements 12f and 13f are arranged in parallel in a direction perpendicular to their longitudinal direction (X direction), electrically connected in series, and formed in a serpentine shape. The first and second thermoelectric conversion elements 12f and 13f are connected to a power supply signal processing unit via through holes 21f and 22f. The layout of the thermoelectric conversion film 15f shown in FIG. 28 is equivalent to the layouts shown in FIGS. 6A and 7 or the layouts shown in FIGS. 10 and 11.

[0108] Next, with reference to FIG. 30, a noise cancellation method for the gas sensor of the ninth embodiment shown in FIG. 28 will be described. When the catalyst portion 17f generates heat in response to gas in the flow path, an electromotive force is generated in the first thermoelectric conversion element 12f in the -X direction, and an electromotive force is generated in the second thermoelectric conversion element 13f in the +X direction due to the anomalous Nernst effect. Here, the heat generated by the catalyst portion 17f in response to gas flowing in the flow path and the heat Q1 and Q3 due to environmental fluctuations are conducted from the first surface of the thermoelectric conversion film 15f, and the heat Q2 and Q4 due to environmental fluctuations are conducted from the second surface of the thermoelectric conversion film 15f to the non-catalytic portion 18f. The heat Q1 and Q3 from the first surface of the thermoelectric conversion film 15f and the heat Q2 and Q4 from the second surface are conducted in opposite directions, canceling out the heat component due to environmental fluctuations in the film thickness direction.

[0109] In this way, heat caused by environmental fluctuations is canceled in the film thickness direction, and electromotive forces caused by heat generated when catalyst portion 17f reacts with gas are generated in first thermoelectric conversion element 12f and second thermoelectric conversion element 13f. The electromotive forces in adjacent first thermoelectric conversion element 12f and second thermoelectric conversion element 13f are added together to obtain output voltage V.

[0110] 31 shows a cross-sectional view of a sensor portion of a gas sensor according to a modification of the ninth embodiment. In the sensor portion of this modification, a first sensor structure 2ff is provided on a first surface of a silicon substrate 27fa, and a second sensor structure 2fg is provided on a second surface of the silicon substrate 27fa.

[0111] The first sensor structure 2ff has a silicon oxide insulating film 28fa and a silicon nitride insulating film 28fb stacked in this order on a silicon substrate 27fa, a thermoelectric conversion film having a first thermoelectric conversion element 12fa and a second thermoelectric conversion element 13fa provided on the silicon nitride insulating film 28fb, and a high thermal conductive insulating film 16fa provided on the thermoelectric conversion film. Furthermore, a low thermal conductive insulating film 28fc is provided on the silicon nitride insulating film 28fb to insulate the first thermoelectric conversion element 12fa from the second thermoelectric conversion element 13fa, which are adjacent to each other. A catalyst portion 17fa is provided on the high thermal conductive insulating film 16fa.

[0112] The second sensor structure 2fg has the same structure as the first sensor structure 2ff, excluding the catalyst portion 17fa. The first sensor structure 2ff and the second sensor structure 2fg are arranged such that the catalyst portion 17fa of the first sensor structure 2ff and the high thermal conductive insulating film 11fa of the second sensor structure 2fg face in opposite directions.

[0113] In the gas sensor shown in FIG. 31, the heat component of the environmental fluctuation can be cancelled in the film thickness direction, similar to the noise cancellation method shown in FIG.

[0114] (Tenth Example) Fig. 32 shows a cross-sectional view of the sensor portion of the gas sensor of the tenth embodiment, taken along a plane parallel to the gas flow. Fig. 33 shows a cross-sectional view of the sensor portion of the gas sensor of the tenth embodiment, taken along a plane perpendicular to the gas flow. The sensor portion of the gas sensor of the tenth embodiment has a plurality of sensor structures 2fb, 2fc, 2fd, and 2fe held by a holder 32f at a distance from one another. Each of the sensor structures 2fb, 2fc, 2fd, and 2fe has a configuration similar to that of the sensor structure 2fa of the ninth embodiment. The sensor structures 2fb, 2fc, 2fd, and 2fe detect gas trapped in the gaps between these sensor structures.

[0115] The number of sensor structures constituting the gas sensor of the tenth embodiment is not particularly limited. Furthermore, the catalyst portions of the multiple sensor structures may be configured to be made of catalysts of different materials. This makes it possible to detect the components of a mixed gas.

[0116] (Eleventh Example) 34 shows a cross-sectional view of a sensor portion of the gas sensor according to the eleventh embodiment. The sensor portion has a sensor structure 2ga. The sensor structure 2ga has an insulating film 28g, a second high thermal conductive insulating film 11g, a thermoelectric conversion film 15g having a first thermoelectric conversion element 12ga, a second thermoelectric conversion element 12gb, and a low thermal conductive insulating film 14g, and a first high thermal conductive insulating film 16g stacked on a silicon substrate 27g.

[0117] As shown in FIG. 35, the thermoelectric conversion film 15g has multiple sets of first thermoelectric conversion elements 12ga and second thermoelectric conversion elements 12gb extending in one direction (X direction), insulated from each other by low-thermal-conductivity insulating films 14g, and arranged alternately in parallel in a direction (Y direction) perpendicular to the one direction. The multiple sets of first thermoelectric conversion elements 12ga and second thermoelectric conversion elements 12gb are electrically connected in series and form a serpentine shape. The first thermoelectric conversion elements 12ga and second thermoelectric conversion elements 12gb are made of the same material and magnetized in the same direction (direction of magnetization M12g). The first thermoelectric conversion elements 12ga and second thermoelectric conversion elements 12gb are connected to a power supply signal processing unit via through holes 21g and 22g.

[0118] On first high thermal conductive insulating film 16g, catalytic portion 17g is provided at a position corresponding to first thermoelectric conversion element 12ga, and non-catalytic portion 18g is provided at a position corresponding to second thermoelectric conversion element 12gb. Furthermore, on first high thermal conductive insulating film 16g, heater 19g is provided in a serpentine shape so as to weave between catalytic portion 17g and non-catalytic portion 18g.

[0119] Next, a noise cancellation method for the thermoelectric conversion film 15g of the gas sensor of the eleventh embodiment will be described. When the catalyst portion 17g generates heat in response to the gas flowing through the flow path, an electromotive force E12ga is generated in the first thermoelectric conversion element 12ga in the +X direction due to the anomalous Nernst effect. The electromotive force E12ga is an electromotive force resulting from the heat generated by the catalyst portion 17g in response to the gas and the heat of environmental fluctuations. On the other hand, when heat from the non-catalytic portion 18g is conducted to the second thermoelectric conversion element 12gb, an electromotive force E12gb is generated in the +X direction. The electromotive force E12gb is an electromotive force resulting from the heat of environmental fluctuations. The electromotive forces generated in the first thermoelectric conversion element 12ga and the second thermoelectric conversion element 12gb tend to cancel each other out. In this way, the electromotive force caused by environmental fluctuations in the in-plane direction is canceled, and the electromotive forces caused by the heat generated when the catalyst portion 17g reacts with the gas are added together in each of the multiple first thermoelectric conversion elements 12ga, resulting in an output voltage V.

[0120] (Twelfth Example) Figure 36 shows a cross-sectional view of the sensor portion of the gas sensor of the twelfth embodiment, taken along a plane perpendicular to the gas flow. The sensor portion of the gas sensor of the twelfth embodiment has a plurality of sensor structures 2gb, 2gc, 2gd, and 2ge held by a holder 32g at a distance from one another. The sensor structures 2gb, 2gc, 2gd, and 2ge have the same configuration as the sensor structure 2ga of the eleventh embodiment (Figure 34). The sensor structures 2gb, 2gc, 2gd, and 2ge detect gas trapped in the gaps between these sensor structures.

[0121] The number of sensor structures constituting the gas sensor of the twelfth embodiment is not particularly limited. Furthermore, the catalyst portions of the multiple sensor structures may be made of different catalyst materials. This makes it possible to detect the components of a mixed gas.

[0122] (13th Example) 37 shows a cross-sectional view of the gas sensor of the thirteenth embodiment taken along a plane parallel to the gas flow. The gas sensor of the thirteenth embodiment includes a first sensor structure 2ha and a second sensor structure 2hb. The first sensor structure 2ha and the second sensor structure 2hb are held by a holder 32h so as to face each other across the gas flow path. A shutter 33 is provided on the gas inlet side of the holder 32h, and a fan 5h is provided on the gas outlet side.

[0123] The first sensor structure 2ha and the second sensor structure 2hb have the same configuration as the sensor structure 2ga of the eleventh embodiment (FIG. 34). The first sensor structure 2ha has a catalyst portion 17ha and a non-catalytic portion 18h on the gas flow path side. The second sensor structure 2hb has a catalyst portion 17hb and a non-catalytic portion 18h on the gas flow path side. The catalyst portion 17ha of the first sensor structure 2ha and the catalyst portion 17hb of the second sensor structure 2hb are made of catalysts made of different materials and react to different components that make up the gas. This makes it possible to detect each component of a mixed gas.

[0124] (14th Example) Fig. 38 shows the layout of the thermoelectric conversion film of the gas sensor of Example 14. The thermoelectric conversion film of Example 14 has a first thermoelectric conversion section consisting of a plurality of thermoelectric conversion elements 12i and a second thermoelectric conversion section consisting of a plurality of thermoelectric conversion elements 13i. The first and second thermoelectric conversion sections have the same configuration as the thermoelectric conversion film shown in Fig. 35 and are arranged so as to interdigitate with each other.

[0125] In the first thermoelectric conversion unit, catalytic portions 17i are provided in regions corresponding to the odd-numbered thermoelectric conversion elements 12i, and non-catalytic portions 18i are provided in regions corresponding to the even-numbered thermoelectric conversion elements 12i. Similarly, in the second thermoelectric conversion unit, catalytic portions 17i are provided in regions corresponding to the odd-numbered thermoelectric conversion elements 13i, and non-catalytic portions 18i are provided in regions corresponding to the even-numbered thermoelectric conversion elements 13i.

[0126] In the first thermoelectric conversion unit consisting of multiple thermoelectric conversion elements 12i, background noise can be removed in the in-plane direction by subtracting the electromotive force caused by the heat of the non-catalytic region 18i from the electromotive force caused by the heat of the catalytic region 17i. The output from the first thermoelectric conversion unit is output to the outside from terminals T3 and T4.

[0127] Similarly, in the second thermoelectric conversion unit consisting of multiple thermoelectric conversion elements 13i, background noise can be removed in the in-plane direction by subtracting the electromotive force caused by the heat of the non-catalytic region 18i from the electromotive force caused by the heat of the catalytic region 17i. The output from the second thermoelectric conversion unit is output to the outside from terminals T1 and T2.

[0128] (15th Example) Fig. 39 shows the layout of the thermoelectric conversion film of the gas sensor of the fifteenth embodiment. The thermoelectric conversion film of the fifteenth embodiment has thermoelectric conversion elements 12j with the same or different longitudinal lengths arranged side by side in the longitudinal direction (column direction), arranged in parallel in a direction perpendicular to the longitudinal direction (row direction), and electrically connected in series, forming a serpentine shape. Each thermoelectric conversion element 12j has the same configuration as the first thermoelectric conversion element 12ga and the second thermoelectric conversion element 12gb shown in Fig. 35, except for the longitudinal length.

[0129] Catalyst portions 17j are provided in regions corresponding to the thermoelectric conversion elements 12j in odd-numbered rows, and non-catalytic portions 18j are provided in regions corresponding to the thermoelectric conversion elements 12j in even-numbered rows. In the thermoelectric conversion film of the 15th embodiment, background noise can also be removed in the in-plane direction by subtracting the electromotive force caused by heat in the non-catalytic portions 18j from the electromotive force caused by heat in the catalytic portions 17j. In particular, the thermoelectric conversion film of the 15th embodiment has more connections (foldbacks) between adjacent thermoelectric conversion elements 12j in the row direction than the thermoelectric conversion film shown in FIG. 35, which allows for localized noise cancellation.

[0130] (16th Example) Fig. 40 shows the layout of the thermoelectric conversion film of the gas sensor of the 16th embodiment. The thermoelectric conversion film of the 16th embodiment is formed by arranging two thermoelectric conversion films (hereinafter referred to as the first thermoelectric conversion section and the second thermoelectric conversion section) having the same configuration as the thermoelectric conversion film of the 15th embodiment shown in Fig. 39 so as to be interdigitated with each other. The first thermoelectric conversion section has a plurality of first thermoelectric conversion elements 12k, and the second thermoelectric conversion section has a plurality of second thermoelectric conversion elements 13k.

[0131] Catalyst portions 17k are provided in regions corresponding to the first thermoelectric conversion elements 12k and second thermoelectric conversion elements 13k in the odd-numbered rows, and non-catalytic portions 18k are provided in regions corresponding to the first thermoelectric conversion elements 12k and second thermoelectric conversion elements 13k in the even-numbered rows. One terminal of the first thermoelectric conversion portion and one terminal of the second thermoelectric conversion portion are connected. In FIG. 40, the other terminals of the first thermoelectric conversion portion and the second thermoelectric conversion portion are denoted as T5 and T6, respectively.

[0132] In each of the first thermoelectric conversion element 12k and the second thermoelectric conversion element 13k, background noise can be removed in the in-plane direction by subtracting the electromotive force caused by the heat of the non-catalytic portion 18k from the electromotive force caused by the heat of the catalytic portion 17k. In particular, the thermoelectric conversion film of the 16th embodiment has more connections (folds) between the first thermoelectric conversion elements 12k adjacent in the row direction and more connections (folds) between the second thermoelectric conversion elements 13k adjacent in the row direction, thereby enhancing the effect of local noise cancellation.

[0133] (17th Example) 41 shows the configuration of a readout circuit 82 of the gas sensor of the seventeenth embodiment. The readout circuit 82 of the seventeenth embodiment is provided in the power supply signal processing section, and is a readout circuit that is particularly applicable to the thirteenth embodiment (FIG. 37).

[0134] 41, the source of transistor TRf1 is connected to one terminal of the first and second sensor structures 2ha, 2hb, and the source of transistor TRf2 is connected to the other terminal, and the gate of transistor TRf4 is connected via transistor TRf3, and the gate of transistor TRf6 is connected via transistor TRf5. Transistors TRf4 and TRf6 form a source follower amplifier that amplifies the outputs of the first and second sensor structures 2ha, 2hb. Transistor TRf4 is connected to be input to the (-) side of differential amplifier DA. Transistor TRf6 is connected to be input to the (+) side of differential amplifier DA.

[0135] In the read circuit 82, an emitter follower amplifier may be used instead of the source follower amplifier.

[0136] Next, the operation of the readout circuit 82 will be described with reference to Figures 37 and 41. First, the first and second sensor structures 2ha, 2hb are initialized as follows: The shutter 33 at the gas inlet is turned OFF, the fan 5h is turned ON, and the holder 32h is filled with a standard gas (e.g., air) that does not contain the gas to be detected. If it takes a long time to replace the gas, a method of adding a standard gas from a cylinder through the gas inlet is also possible. At this time, the transistors TRf1, TRf2 connected to both ends of the first and second sensor structures 2ha, 2hb are turned ON, and the potentials at both ends are reset to a desired voltage, for example, ground potential.

[0137] Next, a heater provided near the catalyst section is turned on, and the system waits until the heater temperature reaches a desired temperature (for example, 100°C). Here, since the first and second sensor structures 2ha and 2hb have a membrane structure, their total heat capacity is extremely small, and they reach the desired temperature in 0.1 seconds.

[0138] Next, the signal before gas introduction is read. This signal corresponds to the noise component due to environmental fluctuations. As described above, after the initialization of the first and second sensor structures 2ha and 2hb is completed, the signal when the holder 32h is filled with standard gas is read. Specifically, transistor TRf1 is turned ON, TRf2 is turned OFF, transistor TRf3 is turned ON, and transistor TRf5 is turned OFF. This inputs the signal before gas introduction, i.e., the signal corresponding to the noise component due to environmental fluctuations, to the (-) side of the differential amplifier DA. Ideally, the electromotive force generated by the thermoelectric conversion element would cancel out internally, resulting in a zero potential output. However, asymmetrical portions of the thermoelectric conversion element may prevent this from occurring. Therefore, as described above, by reading the signal before gas introduction, i.e., the signal containing the noise component due to environmental fluctuations, temperature variations within the gas sensor can be corrected.

[0139] Next, the signal at the time of gas introduction is read out. Transistor TRf1 is turned ON, TRf2 is turned OFF, transistor TRf3 is turned OFF, and simultaneously transistor TRf5 is turned ON. At the same time, the shutter 33 at the gas inlet is turned ON and the fan 5h is turned ON. This allows gas to be introduced into the holder 32h. The catalyst section is heated to 100°C by the heater, and since the heat capacity of the catalyst section is greater than that of the gas, the temperature drop due to the gas is negligible. As a result, the signal after gas introduction, i.e., a signal corresponding to the noise components caused by the reaction heat from the catalyst section and environmental fluctuations, is input to the (+) side of the differential amplifier DA.

[0140] Next, the signal generated when gas was introduced is read out by the differential amplifier DA. The transistor TRf3 is turned OFF, and at the same time, the transistor TRf5 is turned OFF, and the difference between the outputs of the two source follower amplifiers is output from the differential amplifier DA. Then, the transistors TRf1 and TRf2 are turned ON, and the shutter 33 is turned OFF, resetting the first and second sensor structures 2ha and 2hb for the next sensing operation.

[0141] In this way, background noise can be removed by reading the difference between the electromotive force generated in the thermoelectric conversion element before the gas is introduced into the gas sensor and the electromotive force generated in the thermoelectric conversion element when the gas is introduced into the gas sensor.

[0142] According to the gas sensors of the first to seventeenth embodiments, the following effects can be obtained. (1) It becomes possible to thin the thermoelectric conversion film that exhibits the anomalous Nernst effect, thereby enabling the miniaturization of the entire sensor. (2) The miniaturization allows for a design that reduces the heat capacity of the sensor unit, and power consumption can be reduced even when a heater is built in. Furthermore, the miniaturization allows the sensor unit to be incorporated into mobile devices, etc., and can be used for, for example, analyzing the components of human breath and managing health. (3) By eliminating background noise, even low-concentration gases (e.g., about 1 ppm) can be detected with high sensitivity and a high S / N ratio. (4) In a structure in which a plurality of sensor structures are stacked, by disposing various catalysts in each sensor structure, it becomes possible to identify the mixed gas from the signal output of each sensor structure. (5) The film of the roughly cylindrical sensor structure can be formed on a large flexible substrate in a roll-to-roll manner. After the film is produced, it can be connected to an external power supply signal processing unit via through holes formed on the flexible substrate. This allows the two processes to be separated, enabling production using a high-yield manufacturing process. (6) The continuous film formation process is utilized in existing semiconductor processes (some MEMS processes), which can prevent problems such as poor mechanical thermal contact. (7) The area per device can be easily expanded, and the catalytic reaction rate can be adjusted with a heater, allowing the concentration of the gas to be detected to be adjusted.

[0143] The features of the gas sensors of the first to seventeenth embodiments may be combined in any desired manner, thereby achieving a gas sensor with higher performance.

[0144] Next, an example in which the thermoelectric device of this embodiment is applied to a cooling device will be described. (18th Example) 42 shows a cross-sectional view of a cooling device 70 of the 18th embodiment. In the cooling device 70 of the 18th embodiment, a first high thermal conductive insulating film 60 is provided on a first surface of a thermoelectric conversion film 61, and a second high thermal conductive insulating film 62 is provided on a second surface. Wirings 63 and 64 are connected to the thermoelectric conversion film 61. The thermoelectric conversion film 61 has a configuration similar to that of the thermoelectric conversion film 15 described in the first embodiment. The surface of the first high thermal conductive insulating film 60 opposite to the thermoelectric conversion film 61 is a cooling surface, and the surface of the second high thermal conductive insulating film 62 opposite to the thermoelectric conversion film 61 is a heat dissipation surface.

[0145] In the cooling device 70, when a current is passed through the thermoelectric conversion film 61 from the wiring 63, 64, heat is transported by the Ettingshausen effect in the thermoelectric conversion elements included in the thermoelectric conversion film 61. As a result, heat on the cooling side can be transported to the heat dissipation side. In Fig. 42, arrow Q5 represents heat transport by the Ettingshausen effect, arrow Q6 represents thermal conduction (heat inflow from a high temperature), and arrows Q7 and Q8 represent Joule heat.

[0146] According to the cooling device 70 of the eighteenth embodiment, by passing a current from an external power source through the thermoelectric conversion element, a heat flow in a predetermined direction can be generated in the thermoelectric conversion element, and heat can be transported via the highly thermally conductive insulating film. The cooling device 70 has a simple configuration, and the longitudinal length of the thermoelectric conversion element can be easily increased, thereby improving the performance of the cooling device 70. Furthermore, since the cooling device 70 can be made thinner, it can be made more compact. Furthermore, efficient heat transport with the outside is possible via the first highly thermally conductive insulating film 60 and the second highly thermally conductive insulating film 62, and the cooling device 70 can achieve high performance.

[0147] (19th Example) 43 shows a cross-sectional view of a cooling device 71 of the 19th embodiment. In the cooling device 71 of the 19th embodiment, a first high thermal conductive insulating film 65 is provided on a first surface of a thermoelectric conversion film 66, and a second high thermal conductive insulating film 67 is provided on a second surface. Wiring 68, 69 are connected to both ends of the thermoelectric conversion film 66. The thermoelectric conversion film 66 has a configuration similar to that of the thermoelectric conversion film 15 of the first embodiment. The surface of the first high thermal conductive insulating film 65 opposite the thermoelectric conversion film 66 is a cooling surface, and the surface of the second high thermal conductive insulating film 67 opposite the thermoelectric conversion film 66 is a heat dissipation surface.

[0148] In the cooling device 71, by passing a current through the wiring 68, 69 to the thermoelectric conversion film 66, the heat in the cooling region 52 can be transported to the heat dissipation region 53 due to the Ettingshausen effect in the thermoelectric conversion element included in the thermoelectric conversion film 66.

[0149] (20th Example) FIG. 44 shows a cross-sectional view of a heat flow sensor 90X according to the twentieth embodiment. The heat flow sensor 90X of the twentieth embodiment has a first highly thermally conductive insulating film 90 provided on a first surface of a thermoelectric conversion film 91, and a second highly thermally conductive insulating film 92 provided on a second surface. Wiring 93 and 94 are connected to the thermoelectric conversion film 91. The thermoelectric conversion film 91 has a configuration similar to that of the thermoelectric conversion film 15 described in the first embodiment. The first highly thermally conductive insulating film 90 is made of, for example, Al2O3. The second highly thermally conductive insulating film 92 is made of, for example, MgO, and serves as a support substrate for supporting the thermoelectric conversion film 91. Highly thermally conductive silicone rubber sheets 90T and 92B are provided on the surface of the first highly thermally conductive insulating film 90 opposite the thermoelectric conversion film 91 and on the surface of the second highly thermally conductive insulating film 92 opposite the thermoelectric conversion film 91, respectively.

[0150] In the heat flow sensor 90X, a heat source 95 is disposed on the surface of the high thermal conductivity silicone rubber sheet 90T opposite the first high thermal conductivity insulating film 90, and a heat bath 96 is disposed on the surface of the high thermal conductivity silicone rubber sheet 92B opposite the second high thermal conductivity insulating film 92. When a heat flux Q9 flows from the heat source 95 to the heat bath 96, an electromotive force is generated in the thermoelectric conversion element included in the thermoelectric conversion film 91, which is magnetized in a predetermined direction, due to the anomalous Nernst effect. The voltage difference between the wiring 93 and 94 is output as an output signal of the heat flow sensor 90X. The positions of the heat source 95 and the heat bath 96 may be interchanged, in which case an output signal with an inverted sign is output. The heat source 95 is the same size as the sensor surface of the heat flow sensor 90X and is configured to apply a uniform heat flux across the entire sensor surface.

[0151] According to the heat flow sensor 90X of the twentieth embodiment, when a heat flux flows to a thermoelectric conversion element due to heat conduction through the high thermal conductive insulating film, an electromotive force is generated in the thermoelectric conversion element, which outputs an output signal corresponding to the magnitude of the heat flux, thereby detecting the heat flow. The heat flow sensor 90X has a simple configuration, and the longitudinal length of the thermoelectric conversion element can be easily increased, thereby improving the performance of the heat flow sensor 90X. Furthermore, since the heat flow sensor 90X can be made thinner, it can be made more compact. Furthermore, efficient heat conduction is possible through the first high thermal conductive insulating film 90 and the second high thermal conductive insulating film 92, thereby improving the performance of the heat flow sensor 90X.

[0152] (21st Example) FIG. 45 shows the layout of the thermoelectric conversion film 91 of the heat flow sensor fabricated in Example 21. In Example 21, multiple thermoelectric conversion elements 12M are arranged in parallel on a support substrate 10M in a direction perpendicular to the longitudinal direction (X direction), and wiring 25M is provided so that one longitudinal end (-X direction) of each thermoelectric conversion element 12M is connected to the other longitudinal end (+X direction) of the adjacent thermoelectric conversion element 12M on one side (-Y direction). The first high thermal conductive insulating film 90 is removed from the top surface end of the thermoelectric conversion element 12M at the connection portion with the wiring 25M, and the thermoelectric conversion element 12M and the wiring 25M are electrically connected. The thermoelectric conversion element 12M and the wiring 25M are insulated from each other except for the connection portion. In this way, multiple thermoelectric conversion elements 12M are electrically connected in series and arranged in a serpentine pattern. The thermoelectric conversion element 12M is magnetized in the +Y direction (direction of magnetization M12M).

[0153] The configuration other than the thermoelectric conversion film 91 is the same as that of the twentieth embodiment, and a first highly thermal conductive insulating film 90 is provided on a first surface of the thermoelectric conversion film 91, and a second highly thermal conductive insulating film 92 is provided on a second surface. In this embodiment, the second highly thermal conductive insulating film 92 also serves as a support substrate 10M that supports the thermoelectric conversion film 91.

[0154] When a heat flux occurs in thermoelectric conversion element 12M, an electromotive force E12M is generated in thermoelectric conversion element 12M in the +X direction due to the anomalous Nernst effect. The electromotive force E12M is output to the outside through wiring 93, 94 (see FIG. 44) connected at connection points 21M, 22M, and the electromotive forces of adjacent thermoelectric conversion elements 12M are added together, thereby increasing the output voltage V.

[0155] The second high thermal conductive insulating film 92 has a thickness of 0.5 mm and is made of MgO. The first high thermal conductive insulating film 90 has a thickness of 5 nm and is made of Al2O3. The thermoelectric conversion element 12M has a thickness of 200 nm and is made of Co2MnGa. The wiring 25M is formed of a laminate of Au with a thickness of 400 nm and Ti with a thickness of 4 nm. The area of ​​the sensor surface of the heat flow sensor is 20 mm x 20 mm. The length of the thermoelectric conversion element 12M in the X direction is 16 mm. The width of the thermoelectric conversion element 12M in the Y direction is 20 μm. The width of the wiring 25M in the Y direction is 20 μm. The distance between the thermoelectric conversion element 12M and the wiring 25M in the Y direction is 5 μm. The repeat width d of the thermoelectric conversion elements 12M in the Y direction (the sum of the width of the thermoelectric conversion elements 12M in the Y direction, the width of the wiring 25M in the Y direction, and the spacing between the thermoelectric conversion elements 12M and the wiring 25M in the Y direction) is 50 μm. The film thickness of the high thermal conductive silicone rubber sheets 90T and 92B is 0.5 mm.

[0156] The heat flow sensor of this example was fabricated as follows. A 200-nm-thick layer of Co2MnGa and a 5-nm-thick layer of Al2O3 were deposited on the second high-thermal-conductivity insulating film 92 (support substrate 10M) by sputtering. A resist pattern for the thermoelectric conversion element 12M was then formed by photolithography, followed by Ar dry etching to form the thermoelectric conversion element 12M and the first high-thermal-conductivity insulating film 90. Next, a resist pattern for the wiring 25M was formed by photolithography, and a 400-nm-thick layer of Au and a 4-nm-thick layer of Ti were deposited by sputtering. The wiring 25M was then formed by lift-off. In the above process, the first high-thermal-conductivity insulating film 90 was formed to have the same pattern as the thermoelectric conversion element 12M. However, it is also possible to form the first high-thermal-conductivity insulating film 90 over the entire sensor surface by forming the first high-thermal-conductivity insulating film 90 after the pattern etching of the thermoelectric conversion element 12M.

[0157] A predetermined amount of heat was applied from heat source 95 to the heat flow sensor configured as described above, and the output signal of the heat flow sensor relative to the heat flux was examined. An auxiliary heat source (not shown) was provided on the side of heat source 95 opposite the first high thermal conductive insulating film 90, and adjustments were made to prevent heat flow between the auxiliary heat source and heat source 95, so that all of the heat generated by heat source 95 was applied to the heat flow sensor and the heat application was uniform across the sensor surface. As a heat bath 96, an oxygen-free copper plate was placed on the side of thermally conductive silicone rubber sheet 92B opposite the second high thermal conductive insulating film 92.

[0158] The amount of heat transfer (W) applied to the heat flow sensor is calculated by the (current consumption) of the heater incorporated in the heat source 95. 2 The calculation was made by multiplying the resistance by 1. The heater resistance is 200 Ω. The amount of heat transfer was changed by changing the heater current consumption.

[0159] FIG. 46 shows a graph of the output signal versus heat flux of the heat flow sensor of the 21st embodiment. The horizontal axis of the graph represents the heat flux (W / m 2 ) and is the value obtained by dividing the amount of heat transfer (W) applied to the heat flow sensor by the area of ​​the sensor surface of the heat flow sensor (20mm x 20mm), and is also called the heat flux density. The vertical axis of the graph is the output signal (mV) of the heat flow sensor. The output signal was obtained by calculating half of the voltage difference that occurs when the magnetization direction of the thermoelectric conversion element 12M is changed by 180°.

[0160] As shown in Figure 46, the output signal of the heat flow sensor was proportional to the heat flux. The sensitivity of the heat flow sensor is indicated by the slope of the graph in Figure 46 (output voltage / heat flux), and is 2.1 μV / (W / m 2 ) and it was confirmed that it has high sensitivity as a 20mm square heat flow sensor. [Explanation of symbols]

[0161] 1, 1e gas sensor 2 Sensor section 3 Wiring 4 Power signal processing section 5 Fans 6 Intake path 7 Exhaust route 10. Heat insulating substrate 11 Second high thermal conductive insulating film 12 First thermoelectric conversion element 13 Second thermoelectric conversion element 14 Low thermal conductive insulating film 15 Thermoelectric conversion film 16. First high thermal conductive insulating film 17 Catalyst section 18 Non-catalyst part 19 Heater 70, 71 Cooling device 80, 81, 82 Readout circuit 90X Heat Flow Sensor

Claims

1. a sheet-like or plate-like thermoelectric conversion film having a thermoelectric conversion element made of a material that exhibits the anomalous Nernst effect; a highly thermally conductive insulating film provided on a first surface of the thermoelectric conversion film and made of an insulator having a thermal conductivity higher than that of a material of the thermoelectric conversion element; a catalyst portion disposed in a partial area of ​​the surface of the highly thermal conductive insulating film so as to face a fluid flow path, the catalyst portion comprising a catalyst that generates heat in response to a gas contained in the fluid; a non-catalytic portion that is disposed at a position different from the catalytic portion on the surface of the highly thermal conductive insulating film and is made of a material that does not exhibit catalytic activity against the gas; a readout circuit connected to the thermoelectric conversion element for reading out an electromotive force generated in the thermoelectric conversion element due to the anomalous Nernst effect, the readout circuit reading out a difference between an electromotive force generated in the thermoelectric conversion element by heat from the catalytic portion and an electromotive force generated in the thermoelectric conversion element by heat from the non-catalytic portion; A thermoelectric device comprising:

2. a structure including the thermoelectric conversion film, the highly thermal conductive insulating film, the catalytic portion, and the non-catalytic portion has a cylindrical shape; a hollow portion of the structure serves as a flow path for the fluid, The thermoelectric device of claim 1 , wherein the readout circuitry is provided outside the structure.

3. Further provided is a second catalyst portion made of a catalyst material different from that of the catalyst portion, The thermoelectric device according to claim 1 , wherein the catalytic portion and the second catalytic portion react with different components that make up the fluid.

4. A sheet-like or plate-like thermoelectric conversion film having a thermoelectric conversion element made of a material that exhibits the anomalous Nernst effect; a first high thermal conductive insulating film provided on a first surface of the thermoelectric conversion film and made of an insulator having a thermal conductivity higher than that of a material of the thermoelectric conversion element; a catalyst portion disposed on a surface of the first highly thermal conductive insulating film facing a fluid flow path, the catalyst portion comprising a catalyst that generates heat in response to a gas contained in the fluid; a second high thermal conductive insulating film provided on a second surface of the thermoelectric conversion film opposite to the first surface, the second high thermal conductive insulating film being made of an insulator having a thermal conductivity higher than that of a material of the thermoelectric conversion element; a non-catalytic portion disposed on a surface of the second high thermal conductive insulating film and made of a material that does not exhibit catalytic activity against the gas; A thermoelectric device comprising:

5. A substrate, a first structure provided on a first surface of the substrate; a second structure provided on a second surface of the substrate opposite to the first surface; A thermoelectric device comprising: Each of the first structure and the second structure is a silicon insulating film provided on the substrate; a sheet-like or plate-like thermoelectric conversion film provided on the silicon insulating film and having a thermoelectric conversion element made of a material that exhibits the anomalous Nernst effect; a highly thermally conductive insulating film provided on the thermoelectric conversion film and made of an insulator having a thermal conductivity higher than that of a material of the thermoelectric conversion element; and The first structure is The thermally conductive insulating film further includes a catalyst portion disposed on a surface thereof facing a fluid flow path, the catalyst portion being made of a catalyst that generates heat in response to a gas contained in the fluid, The thermoelectric device, wherein the first structure and the second structure are arranged such that the catalyst portion of the first structure and the highly thermal conductive insulating film of the second structure face opposite each other.

6. the thermoelectric conversion film includes, as the thermoelectric conversion elements, a first thermoelectric conversion element and a second thermoelectric conversion element that are formed in a shape extending in one direction, are made of the same material, and have magnetization in the same direction perpendicular to the one direction; the first thermoelectric conversion element and the second thermoelectric conversion element are arranged in parallel in a direction perpendicular to the one direction and are electrically connected in series to form a serpentine shape; The thermoelectric device according to claim 1 , wherein the catalyst portion is disposed on the surface of the highly thermal conductive insulating film at a position corresponding to the first thermoelectric conversion element.

7. A thermoelectric device as described in Claim 6, wherein the non-catalytic portion is arranged at a position on the surface of the high thermal conductive insulating film corresponding to the second thermoelectric conversion element.

8. 8. The thermoelectric device according to claim 1, wherein the highly thermally conductive insulating film has a tensile stress.

9. The thermoelectric device according to any one of claims 1 to 3 and 6 to 8, further comprising a heater for setting the fluid at a predetermined temperature.

10. The thermoelectric device of claim 9 , wherein the heater is disposed within the flow path of the fluid.

11. The thermoelectric device according to claim 9 , wherein the heater is disposed on a second surface side of the thermoelectric conversion film opposite to the first surface on the catalyst portion side.

12. The thermoelectric device according to claim 9 , wherein the heater is disposed on the surface of the highly thermally conductive insulating film so as to be along the catalyst portion.

13. 13. The thermoelectric device according to claim 1, wherein the highly thermally conductive insulating film is made of AlN, SiC, SiN, or BN.

14. The high thermal conductive insulating film is made of Al ２ O ３ The thermoelectric device according to any one of claims 1 to 3 and 5 to 12, wherein the thermoelectric device is made of a material selected from the group consisting of SiO2, ...

15. The thermoelectric device according to any one of claims 1 to 14, wherein the thermoelectric conversion film is provided with a low thermal conductive insulating film made of an insulator having a thermal conductivity lower than that of the material of the thermoelectric conversion element as an interlayer insulating film.

16. The thermoelectric device according to any one of claims 1 to 15, wherein the thermoelectric device is a gas sensor that detects the gas.

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