Gas sensor

Abstract

The invention provides a gas sensor with good detection responsiveness. The gas sensor is provided with: a substrate in which an opening is formed; an insulating film disposed at a position overlapping the opening in plan view; and a gas detection unit provided on a surface on the upper side of the insulating film, the gas detection unit being configured so that the insulating film is curved so as to protrude toward the upper side during gas detection in which gas can be detected by the gas detection unit.

Description

Technical Field

[0001] The present disclosure relates to a gas sensor. Background Art

[0002] Gas sensors detect the presence of gases in the atmosphere, converting information such as their type and concentration into electrical signals for output. These sensors are installed in household appliances, industrial equipment, and environmental monitoring devices to detect the concentration of specific gases that may affect humans and the environment.

[0003] As a gas sensor, there is disclosed a gas sensor in which an opening is formed in a substrate and a detection portion is arranged on a flat insulating film arranged in the opening (see Patent Document 1, etc.).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5100733 Summary of the Invention

[0007] Technical problem to be solved by the invention

[0008] However, conventional gas sensors with a detection unit mounted on a flat insulating film sometimes suffer from insufficient exposure to airflow. For example, when airflow parallel to the flat insulating film occurs around the gas sensor, the area of ​​the detection unit exposed to the airflow is limited, sometimes leading to issues with high-speed responsiveness.

[0009] In view of such actual conditions, the present disclosure provides a gas sensor that can increase the chances of a gas detection portion being exposed to airflow and has appropriate responsiveness.

[0010] Means for solving technical problems

[0011] The gas sensor involved in the present disclosure has:

[0012] a substrate having an opening formed therein;

[0013] an insulating film disposed at a position overlapping with the opening in a plan view; and a gas detection portion provided on an upper surface of the insulating film,

[0014] When the gas detection unit is capable of detecting gas, the insulating film has a shape that is curved so as to protrude upward.

[0015] In such a gas sensor, since the insulating film on which the gas detection unit is placed is bent upward, the gas detection unit can be more likely to be exposed to airflow approaching the gas detection unit from the side.

[0016] Furthermore, for example, the insulating film may be a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film.

[0017] The gas detection unit may be provided on the upper surface of the first insulating film, and may include: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film.

[0018] The first heater wire and the second heater wire may be electrically connected in series, and the resistance value of the first heater wire may be greater than the resistance value of the second heater wire.

[0019] This gas sensor can generate a greater amount of heat than the second heater wiring by generating a greater amount of heat. The heat generated by these heater wirings can be used to deform the insulating film into a curved, upwardly protruding shape. Furthermore, in this gas sensor, the heat used to heat the gas detection unit is used to deform the insulating film into the curved shape, thereby achieving efficient energy utilization.

[0020] Furthermore, for example, the insulating film may be a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film.

[0021] The gas detection unit may be provided on the upper surface of the first insulating film, and may include: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film.

[0022] The first heater wire and the second heater wire may be electrically connected in parallel, and a resistance value of the first heater wire may be smaller than a resistance value of the second heater wire.

[0023] In this gas sensor, the heating value generated by the first heater wiring is greater than that generated by the second heater wiring. The heat generated by these heater wirings can deform the insulating film into a curved shape that protrudes upward. Furthermore, in this gas sensor, the heat used to heat the gas detection unit is used to deform the insulating film into the curved shape, thereby achieving efficient energy utilization.

[0024] Furthermore, for example, the insulating film may be a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film.

[0025] The gas detection unit may be provided on the upper surface of the first insulating film, and may include: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film.

[0026] The amount of expansion of the first heater wire in the film surface direction during heating relative to the non-heating state may be greater than the amount of expansion of the second heater wire in the film surface direction during heating relative to the non-heating state.

[0027] This gas sensor achieves a predetermined relationship between the expansion amounts of the first and second heater wires in the film plane. As these heater wires deform during heating, the insulating film is bent into an upwardly protruding shape. Furthermore, in this gas sensor, heat used to heat the gas detection unit is used to deform the insulating film into the curved shape, achieving efficient energy utilization.

[0028] Furthermore, for example, the insulating film may be a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film.

[0029] The gas detection unit may be provided on the upper surface of the first insulating film, and may include: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film.

[0030] The first heater wiring and the second heater wiring may also be electrically independent.

[0031] This gas sensor can independently control the current or voltage applied to the first and second heater wires, utilizing the heat generated by these heater wires to deform the insulating film into a curved, upwardly protruding shape. Furthermore, in this gas sensor, heat used to heat the gas detection unit is used to deform the insulating film into the curved shape, thereby achieving efficient energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic plan view of the gas sensor according to the first embodiment of the present disclosure.

[0033] Figure 2 yes Figure 1 Schematic diagram of the cross section of the gas sensor along line II-II is shown.

[0034] Figure 3 yes Figure 1 Schematic diagram of a cross section of the gas sensor along line III-III is shown.

[0035] Figure 4 yes Figure 1 Schematic diagram of the cross section of the gas sensor along line IV-IV is shown.

[0036] Figure 5 is Figure 1 The enlarged cross-sectional view of the insulating film and the gas detection portion in the gas sensor shown shows a state before gas detection.

[0037] Figure 6 Yes Figure 5 A conceptual diagram of the insulating film and the gas detection unit during gas detection is shown.

[0038] Figure 7 Yes Figure 1 A top view showing the shape of the gas sensor substrate.

[0039] Figure 8A as well as Figure 8B Yes Figure 1 A top view showing the shape of the third insulating film of the gas sensor shown.

[0040] Figure 9A as well as Figure 9B Yes Figure 1 A top view of the shape of the second heater wiring of the gas sensor shown.

[0041] Figure 10A as well as Figure 10B Yes Figure 1 A top view showing the shape of the second insulating film of the gas sensor shown.

[0042] Figure 11A and Figure 11B Yes Figure 1 A top view showing the shape of the first heater wiring of the gas sensor shown.

[0043] Figure 12A as well as Figure 12B Yes Figure 1 A top view showing the shape of the first insulating film of the gas sensor.

[0044] Figure 13A as well as Figure 13B Yes Figure 1 A top view showing the shape of the detection electrode of the gas sensor shown.

[0045] Figure 14A as well as Figure 14B Yes Figure 1 A top view showing the shape of the thermistor film of a gas sensor.

[0046] Figure 15 This is a conceptual diagram showing the shape of the gas sensor according to the first embodiment during gas detection and the flow of gas around the gas sensor.

[0047] Figure 16A as well as Figure 16B It is a plan view showing the shape of a gas detection portion in a gas sensor according to a second embodiment of the present disclosure.

[0048] Figure 17A is a plan view showing the shapes of heater wiring and an insulating film in a gas sensor according to a third embodiment of the present disclosure. Figure 17B yes Figure 17A An enlarged cross-sectional view of the heater wiring, insulating film, etc. shown.

[0049] Figure 18A is a plan view showing the shapes of heater wiring and an insulating film in a gas sensor according to a fourth embodiment of the present disclosure. Figure 18B yes Figure 18A An enlarged cross-sectional view of the heater wiring and insulating film is shown.

[0050] Figure 19A is a plan view showing the shapes of heater wiring and an insulating film in a gas sensor according to a fifth embodiment of the present disclosure. Figure 19B yes Figure 19A An enlarged cross-sectional view of the heater wiring and insulating film is shown.

[0051] Explanation of symbols:

[0052] 10, 110, 210, 310, 410…gas sensors

[0053] 20…base material

[0054] 22…Opening

[0055] 24…Substrate upper surface

[0056] 30, 230…Insulation film

[0057] 31a, 31b, 31c, 31d, 32a, 32b, 32c, 32d, 33a, 33b, 33c, 33d... beams

[0058] 33e, 32e, 31e, 232e…Central

[0059] 31f, 31g, 31h, 31i, 32f, 32g, 32h, 32i, 33f, 33g, 33h, 33i…peripheral holes

[0060] 31…first insulating film

[0061] 32, 232…Second insulating film

[0062] 33…third insulating film

[0063] 32j…heater connection hole

[0064] 32k, 31k, 31l, 232k, 232l, 431k, 431l, 431m, 431n…heater insertion hole

[0065] 35, 435…Insulation film peripheral portion

[0066] 36 ... first insulating film peripheral portion

[0067] 37, 237 ...Second insulating film peripheral portion

[0068] 38 ...third insulating film peripheral portion

[0069] 40, 240, 340...First heater wiring

[0070] 40a, 50a, 250a, 250c, 240a, 240c, 350a, 340a...heating part

[0071] 40b, 50b, 250b, 240b, 350b, 340b... flat part

[0072] 44, 244a, 244b...first heater lead-out portion

[0073] 45…discontinuous part

[0074] 46, 246a, 246b ... first heater terminal portion

[0075] 50, 250, 350... Second heater wiring

[0076] 54, 454a, 454b...second heater lead-out portion

[0077] 56, 456a, 456b...second heater terminal portion

[0078] 60, 160…Gas detection unit

[0079] 61…Thermistor film

[0080] 62a, 62b...electrode portion

[0081] 64a, 64b...Electrode lead portion

[0082] 66a, 66b...Electrode terminal portion

[0083] 71, 72, 73, 74... surface electrode parts

[0084] 91, 92, 93…arrows

[0085] D1…up and down direction

[0086] D2… membrane surface direction

[0087] 161…MOx material membrane DETAILED DESCRIPTION

[0088] Hereinafter, the present disclosure will be described in detail based on specific embodiments and the like in the following order.

[0089] 1. First Implementation

[0090] 1.1. Overall structure

[0091] 1.2. Substrate

[0092] 1.3. Insulating film

[0093] 1.4. Heater wiring

[0094] 1.5. Gas detection unit

[0095] 1.6. Manufacturing method

[0096] 1.7. Action

[0097] 2. Second Implementation

[0098] 3. Third Implementation

[0099] 4. Fourth Implementation

[0100] 5. Fifth Implementation

[0101] (1. First embodiment)

[0102] Figure 1 1 is a schematic top view of the gas sensor 10 according to the first embodiment, and is a diagram showing the gas sensor 10 as viewed from above. Figure 1 In FIG. 1 , among the components included in the gas sensor 10 , only the base material 20 and the third insulating film 33 are shown opaquely, and the other components are shown superimposed on the outline so that the shapes of the underlying components can be seen.

[0103] Figure 2 It is along Figure 1The cross-sectional view of the gas sensor 10 taken along the cross-sectional line II-II is shown. Figure 1 and Figure 2 As shown, the gas sensor 10 includes a substrate 20 having an opening 22 formed therein; an insulating film 30 disposed so as to overlap the opening 22 when viewed from above in a direction perpendicular to the substrate upper surface 24; and a gas detection portion 60 provided on the upper surface of the insulating film 30. An example of a gas to be detected by the gas detection portion 60 is carbon dioxide (CO2).

[0104] As described in detail later, the gas sensor 10 includes a gas detection unit 60 having a thermistor film 61 whose resistance changes due to contact with the gas to be detected. As the concentration of the target gas changes and the thermal conductivity of the gas in contact with the thermistor film 61 changes, the temperature of the thermistor film 61 changes, and the resistance of the thermistor film 61 changes. The gas detection unit 60 also includes at least a pair of electrodes 62a and 62b in contact with the thermistor film 61. The gas sensor 10 detects gas concentration by connecting the changes in the resistance of the thermistor film 61 between the electrodes 62a and 62b.

[0105] In addition, the gas detection portion 60 of the gas sensor involved in the present disclosure is not limited to the one having the thermistor film 61 and a pair of electrode portions 62a, 62b, but also includes MOx (metal oxide) and the like that use a thin film instead of the thermistor film 61 (refer to the second embodiment, etc.). In particular, as the gas sensor involved in the present disclosure, it is preferred that the portion that reacts with the gas in contact with the gas is a thin film. However, the gas sensor involved in the present disclosure includes a gas sensor having a reference element that does not directly have a gas detection capability, or a gas sensor having a plurality of gas detection portions that are different from each other, and other gas sensors having arbitrary gas detection portions. In addition, as the gas detection portion 60 of the gas sensor involved in the present invention, a heat conduction type gas detection portion using a Pt wire instead of a thermistor film and an electrode, or a contact combustion type gas detection portion using a catalyst material and an electrode, etc. can be cited. Examples of catalyst materials include catalysts in which noble metal particles such as platinum (Pt), palladium (Pd), ruthenium (Ru), and rhodium (Rh) are supported on a carrier of an oxide material such as alumina (gamma alumina, etc.) or silica.

[0106] (1.1. Overall structure)

[0107] Figure 3 It is along Figure 1 A schematic cross-sectional view of the gas sensor 10 taken along the plane of line III-III is shown in FIG. Figure 4 It is along Figure 1Schematic cross-sectional view of the gas sensor 10 taken along line IV-IV in FIG. In the description of the gas sensor 10, the direction perpendicular to the substrate upper surface 24 is referred to as the vertical direction D1, and the direction parallel to the substrate upper surface 24 is referred to as the film surface direction D2. Regarding the vertical direction D1, the direction away from the substrate 20 relative to the substrate upper surface 24 where the insulating film peripheral portion 35 is formed is referred to as the upper side, and the direction toward the interior of the substrate 20 relative to the substrate upper surface 24 is referred to as the lower side.

[0108] like Figure 1 and Figure 2 As shown, the gas sensor 10 includes a substrate 20 having an opening 22 formed therein. Other components of the gas sensor 10 are arranged at positions overlapping with the opening 22 of the substrate 20 in a plan view and at a substrate upper surface 24 extending around the opening 22. Examples of other components of the gas sensor 10 other than the substrate 20 include an insulating film 30 arranged at a position overlapping with the opening 22 in a plan view, a first heater wiring 40, a second heater wiring 50, a gas detection portion 60, an insulating film peripheral portion 35 arranged on the substrate upper surface 24, a first heater terminal portion 46, a second heater terminal portion 56, and electrode terminal portions 66a and 66b.

[0109] (1.2. Base material)

[0110] Figure 7 1 is a top view showing the shape of the substrate 20 of the gas sensor 10. Figure 1 and Figure 7 As shown in FIG. 1 , the opening 22 is formed near the center of the substrate 20. Figure 2 As shown in FIG. 1 , an insulating film 30 and the like are disposed in the region above the opening 22. Figure 1 and Figure 2 As shown, the insulating film 30 is arranged so as to overlap with the opening 22 when viewed from the up-down direction D1 .

[0111] like Figure 1 、 Figure 2 as well as Figure 7 As shown, the opening 22 in the substrate 20 is formed by a through hole having a substantially rectangular shape when viewed from above in the substrate 20, but the shape of the opening 22 when viewed from above is not limited to a rectangle. Figure 2 and Figure 4 In the through hole shown, the opening 22 may be formed by a recessed portion recessed downward from the upper surface 24 of the substrate.

[0112] The material of the substrate 20 is not particularly limited as long as it is composed of a material having a sufficient mechanical strength to support the position overlapping with the opening 22 in a plan view and the components formed on the substrate upper surface 24, and is suitable for micro-processing such as etching. In this embodiment, examples of the substrate 20 include a single crystal silicon substrate, a single crystal sapphire substrate, a ceramic substrate, a quartz substrate, a glass substrate, a ferrite substrate, and the like.

[0113] (1.3. Insulating film)

[0114] like Figure 1 and Figure 2 As shown, in the gas sensor 10, an insulating film 30 is arranged at a position overlapping with the opening 22 formed in the center of the substrate 20 in a plan view. Furthermore, a gas detection portion 60 is provided on the upper surface of the insulating film 30. The insulating film 30 is a multilayer film composed of a first insulating film 31, a second insulating film 32, and a third insulating film 33. A first heater wiring 40 is provided between the first insulating film 31 and the second insulating film 32, and a second heater wiring 50 is provided between the second insulating film 32 and the third insulating film 33.

[0115] Figure 5 It will Figure 2 FIG. 1 is an enlarged cross-sectional view showing the gas detection portion 60, the insulating film 30, the first heater wiring 40, and the second heater wiring 50 in the gas sensor 10. Figure 5 As shown, the insulating film 30 includes a first insulating film 31 , a second insulating film 32 provided on the lower side of the first insulating film 31 , and a third insulating film 33 provided on the lower side of the second insulating film 32 .

[0116] Figure 8A 3 is a top view of the third insulating film 33 and the third insulating film peripheral portion 38 formed of the same layer as the third insulating film 33. Figure 8B It will Figure 8A The third insulating film 33 is arranged at the bottom of the first insulating film 31, the second insulating film 32 and the third insulating film 33 constituting the insulating film 30. Figures 2 to 4 As shown, the third insulating film peripheral portion 38 is arranged below the first insulating film peripheral portion 36 and the second insulating film peripheral portion 37 .

[0117] from Figure 8A and Figure 1 As can be understood from the comparison, the third insulating film 33 is arranged at a position overlapping with the opening 22 of the substrate 20 in a plan view, and the third insulating film peripheral portion 38 is provided on the substrate upper surface 24 of the substrate 20. The third insulating film 33 and the third insulating film peripheral portion 38 are composed of an integral film formed simultaneously. Figure 2As shown, the lower surface of the third insulating film peripheral portion 38 is in direct contact with the substrate upper surface 24 .

[0118] like Figure 8B As shown, the third insulating film 33 has a substantially rectangular central portion 33e and a plurality of (four in the embodiment) beam portions 33a, 33b, 33c, and 33d connecting the central portion 33e to the third insulating film peripheral portion 38. The beam portions 33a, 33b, 33c, and 33d are provided at the four corners of the central portion 33e. Furthermore, peripheral holes 33f, 33g, 33h, and 33i are formed in portions of the central portion 33e other than the four corners to surround the central portion 33e. The third insulating film 33 is disposed at a position that overlaps with the opening 22 when viewed from above. By surrounding the central portion 33e with the peripheral holes 33f, 33g, 33h, and 33i, heat transfer between the third insulating film 33 and the third insulating film peripheral portion 38 can be suppressed.

[0119] Figure 10A 3 is a top view of the second insulating film 32 and the second insulating film peripheral portion 37 formed of the same layer as the second insulating film 32. Figure 10B It will Figure 10A The second insulating film 32 is arranged between the first insulating film 31, the second insulating film 32 and the third insulating film 33 constituting the insulating film 30. Figures 2 to 4 As shown, the second insulating film peripheral portion 37 is arranged between the first insulating film peripheral portion 36 and the third insulating film peripheral portion 38 .

[0120] from Figure 10A and Figure 8A As can be understood from the comparison, the planar shape of the second insulating film 32 is the same as that of the third insulating film 33, except that the heater connection hole 32j is formed in the central portion 32e. In addition, the planar shape of the second insulating film peripheral portion 37 is the same as that of the third insulating film peripheral portion 38, except that the heater insertion hole 32k is formed. Figure 10A and Figure 1 As can be understood from the comparison, the second insulating film 32 is arranged at a position overlapping with the opening 22 of the substrate 20 when viewed from above, and the second insulating film peripheral portion 37 is provided on the upper side of the substrate upper surface 24 of the substrate 20 and the third insulating film peripheral portion 38. The second insulating film 32 and the second insulating film peripheral portion 37 are composed of an integral film formed simultaneously. Figure 2 As shown, the lower surface of the second insulating film peripheral portion 37 is in direct contact with the upper surface of the third insulating film peripheral portion 38 .

[0121] like Figure 10BAs shown, the second insulating film 32 has a generally rectangular central portion 32e and a plurality (four in the embodiment) of beams 32a, 32b, 32c, and 32d connecting the central portion 32e to the second insulating film peripheral portion 37. The beams 32a, 32b, 32c, and 32d are located at the four corners of the central portion 32e. Furthermore, peripheral holes 32f, 32g, 32h, and 32i are formed in portions of the central portion 32e other than the four corners, surrounding the central portion 32e. Thus, by surrounding the central portion 32e with the peripheral holes 32f, 32g, 32h, and 32i, heat transfer between the second insulating film 32 and the second insulating film peripheral portion 37 can be suppressed.

[0122] Figure 12A 3 is a top view of the first insulating film 31 and the first insulating film peripheral portion 36 formed of the same layer as the first insulating film 31. Figure 12B It will Figure 12A The first insulating film 31 is arranged on the uppermost side among the first insulating film 31, the second insulating film 32 and the third insulating film 33 constituting the insulating film 30. Figures 2 to 4 As shown, the first insulating film peripheral portion 36 is arranged above the second insulating film peripheral portion 37 and the third insulating film peripheral portion 38 .

[0123] from Figure 12A and Figure 8A As can be understood from the comparison, the planar shape of the first insulating film 31 is the same as that of the third insulating film 33. In addition, the planar shape of the first insulating film peripheral portion 36 is the same as that of the third insulating film peripheral portion 38 except that the heater insertion holes 31k and 31l are formed. Figure 12A and Figure 1 As can be understood from the comparison, the first insulating film 31 is arranged at a position overlapping with the opening 22 of the substrate 20 when viewed from above, and the first insulating film peripheral portion 36 is provided on the upper side of the substrate upper surface 24, the third insulating film peripheral portion 38, and the second insulating film peripheral portion 37 of the substrate 20. The first insulating film 31 and the first insulating film peripheral portion 36 are composed of an integral film formed simultaneously. Figure 2 As shown, the lower surface of the first insulating film peripheral portion 36 is in direct contact with the upper surface of the second insulating film peripheral portion 37 .

[0124] like Figure 12BAs shown, the first insulating film 31 has a substantially rectangular central portion 31e and a plurality (four in the embodiment) of beams 31a, 31b, 31c, and 31d connecting the central portion 31e to the first insulating film peripheral portion 36. The beams 31a, 31b, 31c, and 31d are provided at the four corners of the central portion 31e. Furthermore, peripheral holes 31f, 31g, 31h, and 31i are formed in portions of the central portion 31e other than the four corners, surrounding the central portion 31e. Thus, by surrounding the central portion 31e with the peripheral holes 31f, 31g, 31h, and 31i, heat transfer between the first insulating film 31 and the first insulating film peripheral portion 36 can be suppressed.

[0125] As described above, the insulating film 30 is a multilayer film including the first insulating film 31, the second insulating film 32, and the third insulating film 33. Figure 1 、 Figure 8A 、 Figure 10A as well as Figure 12A As shown, the insulating film 30 is connected to the first to third insulating film peripheral portions 36 to 38 provided on the substrate upper surface 24 via the beam portions 31a to 31d, 32a to 32d, and 33a to 33d of the first to third insulating films 31 to 33. Therefore, the insulating film 30 supports the first to third insulating film peripheral portions 36 to 38 and the substrate 20 via the beam portions 31a to 31d, 32a to 32d, and 33a to 33d. Figure 2 As shown, it is held at a position overlapping with the opening 22 in a plan view.

[0126] like Figure 5 As shown in FIG. 1 , the thicknesses of the first insulating film 31, the second insulating film 32, and the third insulating film 33 may be different from each other. In addition, when the thicknesses of the first insulating film 31, the second insulating film 32, and the third insulating film 33 are different from each other, the strength of the gas sensor 10 is ensured, and as shown in FIG. Figure 6 From the perspective of deforming the insulating film 30 into a curved shape that protrudes upward, the thickness of the third insulating film 33 is preferably thicker than the thicknesses of the first insulating film 31 and the second insulating film 32. Furthermore, from the perspective of reducing the height difference generated by the flat portion 40b at the connection point between the first heater wire 40 and the second heater wire 50, the thickness of the second insulating film 32 is preferably thinner than the thicknesses of the third insulating film 33 and the first insulating film 31. However, the first insulating film 31, the second insulating film 32, and the third insulating film 33 may have the same thickness.

[0127] The material of the first insulating film 31 , the second insulating film 32 , and the third insulating film 33 is not particularly limited as long as it is an insulating film, and examples thereof include SiO 2 (silicon oxide) and SiN x (silicon nitride).

[0128] (1.4. Heater wiring)

[0129] like Figure 5 As shown, the gas sensor 10 includes a first heater wiring 40 provided between the first insulating film 31 and the second insulating film 32 , and a second heater wiring 50 provided between the second insulating film 32 and the third insulating film 33 . Figure 9A : is a top view of the second heater wiring 50, the second heater lead portion 54 and the second heater terminal portion 56, which are formed of the same layer as the second heater wiring 50. Figure 9B It will Figure 9A FIG. 1 is a partially enlarged view showing the second heater wiring 50 and its surroundings. FIG.

[0130] From 9A and Figure 1 As can be understood from the comparison, the second heater wiring 50 is arranged at a position overlapping with the opening 22 of the substrate 20 when viewed from above, and the second heater terminal portion 56 is provided on the upper side of the substrate upper surface 24 of the substrate 20. The second heater lead portion 54 connects the second heater wiring 50 and the second heater terminal portion 56. A portion of the second heater lead portion 54 is arranged at a position overlapping with the opening 22 when viewed from above, and is provided between the second insulating film 32 and the third insulating film 33. In addition, another portion of the second heater lead portion 54 is provided on the upper side of the substrate upper surface 24 at the second insulating film peripheral portion 37 (see Figure 10A ) and the third insulating film peripheral portion 38 (refer to Figure 8A )between.

[0131] like Figure 9B as well as Figure 5 As shown, the second heater wire 50 includes a flat portion 50b disposed in the center of the insulating film 30 and a heating portion 50a formed in a spiral shape around the flat portion 50b. The heating portion 50a has a smaller cross-sectional area perpendicular to the direction of conduction than the flat portion 50b or the second heater lead portion 54. Therefore, when current flows through the second heater wire 50 and the second heater lead portion 54, the heating portion 50a effectively generates heat.

[0132] Figure 11A FIG. 4 is a plan view of the first heater wiring 40 and the first heater lead portion 44 , the first heater terminal portion 46 , and the discontinuous portion 45 , which are formed of the same layer as the first heater wiring 40 . Figure 11B It will Figure 11A A partially enlarged view showing the first heater wiring 40 and its surroundings. Figure 11A and Figure 9A As can be understood from the comparison of FIG. 4 , the planar shape of the first heater wire 40 is similar to the planar shape of the second heater wire 50 .

[0133] That is, from Figure 11A and Figure 1 As can be understood from the comparison, the first heater wiring 40 is arranged at a position overlapping with the opening 22 of the substrate 20 when viewed from above, and the first heater terminal portion 46 is provided on the upper side of the substrate upper surface 24 of the substrate 20. The first heater lead-out portion 44 connects the first heater wiring 40 and the first heater terminal portion 46. A portion of the first heater lead-out portion 44 is arranged at a position overlapping with the opening 22 when viewed from above, and is provided between the first insulating film 31 and the second insulating film 32. In addition, another portion of the first heater lead-out portion 44 is provided on the upper side of the substrate upper surface 24 at the first insulating film peripheral portion 36 (see Figure 12A ) and the second insulating film peripheral portion 37 (refer to Figure 10A ). The discontinuous portion 45 is formed between the second heater terminal portion 56 (refer to Figure 9A ) and connected to the surface electrode portion 74 exposed on the surface (refer to Figure 1 ) and the second heater terminal portion 56 (refer to Figure 3 ).

[0134] like Figure 5 As shown, the flat portion 40b of the first heater wire 40 is in direct contact with the flat portion 50b of the second heater wire 50, and the first heater wire 40 and the second heater wire 50 are electrically connected in series. Figure 10A as well as Figure 10B As shown, a heater connection hole 32j is formed in the second insulating film 32 disposed between the first heater wiring 40 and the second heater wiring 50. Figure 5 As shown, the second insulating film 32 insulates the heat generating portion 40a of the first heater wiring 40 and the heat generating portion 50a of the second heater wiring 50, but the first heater wiring 40 and the second heater wiring 50 are in contact with each other through the heater connection hole 32j. Figure 1 A potential difference is formed between the illustrated first heater terminal portion 46 and the second heater terminal portion 56 , and current flows through the first heater wire 40 and the second heater wire 50 connected in series.

[0135] Here, Figure 11B The resistance value of the first heater wire 40 shown is greater than Figure 9B The resistance value of the second heater wiring 50 is shown in FIG. Figure 5 As shown, since the film thickness of the first heater wire 40 is thinner than that of the second heater wire 50, the cross-sectional area of ​​the heat-generating portion 40a of the first heater wire 40, which is perpendicular to the direction of conduction, is smaller than that of the heat-generating portion 50a of the second heater wire 50. When current flows through the first heater wire 40 and the second heater wire 50, the heat generated in the first heater wire 40 is greater than that in the second heater wire 50.

[0136] like Figure 5 As shown in FIG, the insulating film 30 sandwiching the first heater wiring 40 and the second heater wiring 50 is substantially flat relative to the first heater wiring 40 and the second heater wiring 50 when no power is supplied. On the other hand, when power is supplied to the first heater wiring 40 and the second heater wiring 50 during gas detection, the insulating film 30 and the first heater wiring 40 and the second heater wiring 50 will thermally expand in accordance with the amount of heat generated. At this time, the amount of thermal expansion of the first heater wiring 40 and its surrounding area on the upper side is greater than the amount of thermal expansion of the second heater wiring 50 and its surrounding area on the lower side. Therefore, as shown in FIG. Figure 6 As shown, the insulating film 30 is curved and convex upward during gas detection.

[0137] Furthermore, the method of making the resistance value of the first heater wiring 40 greater than the resistance value of the second heater wiring 50 is not limited to the method of making the film thickness of the first heater wiring 40 and the second heater wiring 50 different. For example, the width of the heat generating portions 50a, 40a in the film surface direction D2 or the wiring length may be made different between the first heater wiring 40 and the second heater wiring 50, or the materials of the first heater wiring 40 and the second heater wiring 50 may be made different.

[0138] The material of the first heater wiring 40, the first heater lead-out portion 44, the first heater terminal portion 46, the discontinuous portion 45, the second heater wiring 50, the second heater lead-out portion 54, and the second heater terminal portion 56 is not particularly limited as long as it is conductive, but from the perspective of being able to perform a high-temperature process in the formation process of the gas detection portion 60, a material with a relatively high melting point is preferably used. Examples of such materials include molybdenum (Mo), platinum (Pt), nickel (Ni), chromium (Cr), tungsten (W), tantalum (Ta), palladium (Pd), iridium (Ir), or alloys containing two or more of these (for example, nickel-chromium alloy (NiCr)). In this embodiment, platinum (Pt) is particularly preferred because it allows for high-precision patterning such as peeling and has high durability. The first heater wiring 40 and the second heater wiring 50 may be made of the same material, or the first heater wiring 40 and the second heater wiring 50 may be made of different materials.

[0139] (1.5. Gas Detection Unit)

[0140] like Figure 2 As shown in FIG. 1 , the gas detection unit 60 is provided on the upper surface of the insulating film 30. Figure 5As shown, in a gas sensor 10 in which the insulating film 30 is a multilayer film composed of first to third insulating films 31, 32, and 33, a gas detection portion 60 is provided on the upper surface of the first insulating film 31 above the first heater wiring 40. The gas detection portion 60 includes a thermistor film 61 and electrode portions 62a and 62b for detecting changes in resistance of the thermistor film 61.

[0141] Figure 13A 62a, 62b, electrode lead portions 64a, 64b, and electrode terminal portions 66a, 66b, which are formed of the same film as the electrode portions 62a, 62b, are shown in FIG. Figure 13B It will Figure 13A A partially enlarged view showing the periphery of the electrode portions 62a and 62b in FIG.

[0142] like Figure 13A As shown, the electrode terminal portions 66a and 66b are arranged on the upper side of the substrate upper surface 24 of the substrate 20. The electrode lead portion 64a connects the electrode portion 62a provided on the first insulating film 31 to the electrode terminal portion 66a. The electrode lead portion 64b connects the electrode portion 62b provided on the first insulating film 31 to the electrode terminal portion 66b. Figure 13B As shown, the electrode portion 62 a and the electrode portion 62 b are formed on the first insulating film 31 at a predetermined distance from each other.

[0143] Figure 14A 2 is a plan view showing the planar shape of the thermistor film 61 and its arrangement in the substrate 20. Figure 14B It will Figure 14A Thermistor film 61 is provided on the upper side of the insulating film 30, and in particular, Figure 5 As shown in FIG. 1 , the electrode portion 62a and the electrode portion 62b are connected to each other on the first insulating film 31 and are provided at the center of the first insulating film 31. Figure 1 and Figure 5 As shown, the thermistor film 61 is arranged so as to at least partially overlap with the flat portions 40 b and 50 b of the first heater wire 40 and the second heater wire 50 as viewed from above.

[0144] When the gas detection unit 60 is capable of detecting gas, the first heater wire 40 and the second heater wire 50 are energized and generate heat, thereby heating the gas detection unit 60 to a temperature at which it can properly detect gas. Examples of materials for the thermistor film 61 in the gas detection unit 60 include CoNiMnOx, but other materials whose resistance value changes when exposed to a specific gas may also be used. Examples of materials for the electrodes 62a, 62b, the electrode lead portions 64a, 64b, and the electrode terminals 66a, 66b include conductive materials such as platinum (Pt), silver (Ag), gold (Au), and aluminum (Al).

[0145] In addition, if Figure 1 and Figure 3 As shown, surface electrodes 71, 72, 73, and 74 are formed on the uppermost layer of the electrode terminals 66a and 66b and the first and second heater terminals 46 and 56. The surface electrodes 71, 72, 73, and 74 can be made of a conductive material such as platinum (Pt), silver (Ag), gold (Au), or aluminum (Al).

[0146] (1.6. Manufacturing method)

[0147] An example of a method for manufacturing the gas sensor 10 is described below. However, the method for manufacturing the gas sensor 10 is not limited to the method described below. In manufacturing the gas sensor 10, first, a substrate material serving as a raw material for the substrate 20 is prepared. The substrate material is in the form of a flat plate without an opening 22 formed thereon. Next, a third insulating film 33 and a third insulating film peripheral portion 38 are formed on one main surface of the prepared substrate material, i.e., the substrate upper surface 24 (see FIG. 1 ). Figure 8A As a method for forming the third insulating film 33 and the third insulating film peripheral portion 38 , a well-known film forming method such as a thermal oxidation method or a CVD (Chemical Vapor Deposition) method can be used.

[0148] Next, the second heater wiring 50 is formed on the third insulating film 33. In the process of forming the second heater wiring 50, a second heater lead portion 54 and a second heater terminal portion 56 (see FIG. 5 ) made of the same film as the second heater wiring 50 are also formed simultaneously. Figure 9A). The shapes of the second heater wiring 50, the second heater lead-out portion 54, and the second heater terminal portion 56 are formed, for example, by a stripping method. In the stripping process, first, a resist is applied to the entire surface on which a predetermined pattern is formed, and the resist is exposed and developed in such a manner as to form a predetermined pattern shape. By development, the resist corresponding to the predetermined pattern shape is dissolved, and the predetermined pattern shape is patterned. After the resist is dissolved, a film of the material constituting the pattern is formed by a film-forming method such as sputtering or evaporation. After the film is formed, the remaining resist is removed by a stripping solution, and the material formed on the resist is also removed, leaving the material formed only in the patterned area, thereby forming a predetermined pattern.

[0149] Next, the second insulating film 32 is formed on the second heater wiring 50. In the process of forming the second insulating film 32, the second insulating film peripheral portion 37 (see FIG. 1 ) made of the same film as the second insulating film 32 is also formed simultaneously. Figure 10A In the process of forming the second insulating film 32 and the second insulating film peripheral portion 37 , similarly to the formation of the third insulating film 33 , they are formed using a known film forming method or the like.

[0150] Next, the first heater wiring 40 is formed on the second insulating film 32. In the process of forming the first heater wiring 40, the first heater lead portion 44, the first heater terminal portion 46, and the discontinuous portion 45 (see FIG. 1 ) made of the same film as the first heater wiring 40 are also formed simultaneously. Figure 11A The method for forming the first heater wiring 40 and the like is the same as the method for forming the second heater wiring 50 described above.

[0151] Next, the first insulating film 31 is formed on the first heater wiring 40. In the process of forming the first insulating film 31, the first insulating film peripheral portion 36 (see FIG. 1 ) made of the same film as the first insulating film 31 is also formed simultaneously. Figure 12A In the process of forming the first insulating film 31 and the first insulating film peripheral portion 36 , similar to the formation of the third insulating film 33 and the second insulating film 32 , a known film forming method or the like can be used.

[0152] Next, the gas detection portion 60 is formed on the first insulating film 31. In the process of forming the gas detection portion 60, the gas detection portion 60 is formed in the same film forming process. Figure 13A After the electrode portions 62a, 62b, the electrode lead portions 64a, 64b and the electrode terminal portions 66a, 66b are formed, the thermistor film 61 is formed on the electrode portions 62a, 62b (see FIG. Figure 14AThe shapes of the electrode portions 62a, 62b, etc. are formed by a lift-off method, etc., similar to the first and second heater wirings 40, 50. Furthermore, surface electrode portions 71 to 74 are formed above the first and second heater terminal portions 46, 56 and the electrode terminal portions 66a, 66b. Alternatively, the thermistor film 61 may be formed on the electrode portions 62a, 62b after the step of forming the surface electrode portions 71 to 74 or the step of forming the opening 22, which will be described later.

[0153] Next, an etching mask is applied to a predetermined area of ​​the main surface of the base material where the third insulating film 33 and the third insulating film peripheral portion 38 are not formed, and the base material is etched until the third insulating film 33 formed on the opposite main surface (base material upper surface 24) is exposed, thereby forming an opening 22. Figure 2 As shown, the gas sensor 10 is obtained in which the insulating film 30 is arranged at a position overlapping with the opening 22 in a plan view.

[0154] (1.7. Action)

[0155] In the gas sensor 10, the first heater wire 40 and the second heater wire 50 are connected to an external circuit (not shown) via the first and second heater lead portions 44 and 54, the first and second heater terminal portions 46 and 56, and the surface electrodes 71 and 72. Furthermore, the electrodes 62a and 62b of the gas detection unit 60 are connected to an external circuit (not shown) via the electrode lead portions 64a and 64b, the electrode terminal portions 66a and 66b, and the surface electrodes 73 and 74. When the gas sensor 10 is activated, power is supplied to the first and second heater wires 40 and 50 from the control unit and the external circuit, heating the gas detection unit 60 and its surroundings to a predetermined temperature, thereby enabling the gas detection unit 60 to detect gas.

[0156] like Figure 5 As shown in FIG. 1 , the insulating film 30 sandwiching the first heater wire 40 and the second heater wire 50 is substantially flat relative to the first heater wire 40 and the second heater wire 50 when no power is supplied. However, after the first and second heater wires 40 and 50 are energized, the insulating film 30 becomes substantially flat when the gas detection unit 60 is capable of detecting gas. Figure 6 This is because, of the first and second heater wires 40 and 50 connected in series, the resistance of the first heater wire 40 is greater than that of the second heater wire 50 , and the amount of heat generated by the first heater wire 40 is greater than that of the second heater wire 50 .

[0157] Figure 151 is a conceptual diagram showing the shape of the gas sensor 10 during gas detection and the flow of gas in the gas sensor 10. Figure 15 As shown, during gas detection, consideration is given to the possibility of generating gas flows in the vertical direction D1 as indicated by arrows 91, and gas flows in the membrane surface direction D2 as indicated by arrows 92 and 93. If the insulating film 30 of the gas sensor 10 is flat even during gas detection, the gas detection unit 60 of the gas sensor 10 will have fewer opportunities to detect gas flows in the membrane surface direction D2 as indicated by arrows 92 and 93, and there is a concern that the detection output may be delayed.

[0158] However, if Figure 15 As shown, the insulating film 30 of the gas sensor 10 is curved and convex upward during gas detection. Therefore, compared to a case where the insulating film 30 is flat, the gas sensor 10 increases the chances of the gas detection unit 60 detecting airflow in the film surface direction D2, as indicated by arrows 92 and 93. This also enables the gas sensor 10 to achieve high-speed responsiveness to airflow in the film surface direction D2. Furthermore, the gas sensor 10 achieves the same responsiveness to airflow in the vertical direction D1, as indicated by arrow 91, as when the insulating film 30 is flat.

[0159] (2. Second embodiment)

[0160] Figure 16A is a plan view showing the shape of the gas detection unit 160 in the gas sensor 110 according to the second embodiment of the present disclosure. Figure 16B It will Figure 16A The gas sensor 110 is different from the gas sensor 10 according to the first embodiment in that the gas detection portion 160 includes the MOx material film 161 as a metal oxide film instead of the thermistor film 61, but is similar in other respects. Figure 1 The gas sensor 10 shown in FIG. 1 is the same as the gas sensor 10 shown in FIG. 1 . In addition, the gas detection unit 160 causes an oxidation-reduction reaction by contact with the gas to be detected, thereby changing the resistance value of the metal oxide film. The gas to be detected by the gas detection unit 160 is, for example, a combustible gas and a reducing gas. Specifically, examples include carbon monoxide (CO), methane (CH4), propane (C3H8), ethanol (C2H5OH), hydrogen (H2), etc. As the MOx material film 161 of the metal oxide film, tin oxide (SnO2), zirconium oxide (ZrO2), iron oxide (Fe2O3), tungsten oxide (WO3), indium oxide (In2O3), cobalt oxide (Co3O4), etc. can be cited. Noble metal particles such as platinum (Pt) and palladium (Pd) can also be supported on the MOx material film 161.

[0161] Figure 16AThe MOx material film 161 shown is Figure 14A The thermistor film 61 shown is similarly provided on the upper surface of the insulating film 30 (see FIG. Figure 5 ). In particular, Figure 5 and Figure 16A As shown, the MOx material film 161 is provided on the first insulating film 31 in the center portion of the first insulating film 31 so as to connect the electrode portion 62 a and the electrode portion 62 b .

[0162] Gas sensor 110 and Figure 1 The illustrated gas sensor 10 similarly includes a first heater wiring 40 and a second heater wiring 50 provided in a multilayer film, namely an insulating film 30. Similar to the gas sensor 10, the gas sensor 110 heats the gas detection portion 160 to a temperature capable of appropriately detecting gas by energizing the first heater wiring 40 and the second heater wiring 50 and generating heat during gas detection.

[0163] Gas sensor 110 and Figure 15 Similarly, the gas sensor 10 shown in FIG. 1 has an insulating film 30 that is curved and protrudes upward during gas detection, thereby increasing the response speed during gas detection. Figure 16A and Figure 16B The gas sensor 110 is shown with Figure 1 The same points as the gas sensor 10 shown in the above are achieved, and the same effects as the gas sensor 10 are achieved.

[0164] (3. Third embodiment)

[0165] Figure 17A It is a top view showing the planar shapes of the first heater wiring 240, first heater lead portions 244a, 244b, first heater terminal portions 246a, 246b, second insulating film 232, and second insulating film peripheral portion 237 in the gas sensor 210 involved in the third embodiment of the present disclosure. Figure 17B 2 is a cross-sectional view showing the first insulating film 31, the second insulating film 232, the third insulating film 33, the first heater wiring 240, and the second heater wiring 250 in the gas sensor 210. Figure 17A In order to be able to see the shape of the second insulating film 232 of the lower layer, the outlines of each component are overlapped and shown. Figure 17A and Figure 17B In the figure, the gas detection portion and substrate of the gas sensor 210 are omitted.

[0166] The gas sensor 210 according to the third embodiment differs from the gas sensor 10 in that the first heater wire 240 and the second heater wire 250 are electrically connected in parallel, and the resistance of the first heater wire 240 is lower than that of the second heater wire 250. However, other than the connection method between the first heater wire 240 and the second heater wire 250, the gas sensor 210 is identical to the gas sensor 10 according to the first embodiment. The description of the gas sensor 210 focuses on the differences from the gas sensor 10, and description of the commonalities with the gas sensor 10 is omitted.

[0167] The insulating film 230 of the gas sensor 210 is a multilayer film having a first insulating film 31, a second insulating film 232 provided on the lower side of the first insulating film 31, and a third insulating film 33 provided on the lower side of the second insulating film 232. The planar shapes of the first insulating film 31 and the third insulating film 33 are the same as those of the gas sensor 10. Figure 17A Although not shown in the figure, the planar shapes of the first insulating film peripheral portion 36 formed of the same film as the first insulating film 31 and the third insulating film peripheral portion 38 formed of the same film as the third insulating film 33 are also the same as those of the gas sensor 10 .

[0168] On the other hand, Figure 17A In the second insulating film 232 of the gas sensor 210 shown in FIG. Figure 10A The second insulating film 32 shown is different in that no heater connection hole 32j is formed in the central portion. Figure 17B As shown, no through hole is formed in the central portion 232 e of the second insulating film 232 , and the second insulating film 232 electrically insulates the upper first heater wire 240 from the lower second heater wire 250 .

[0169] In addition, if Figure 17A As shown, heater insertion holes 2321 and 232k are formed in the peripheral portion 237 of the second insulating film made of the same film as the second insulating film 232. As will be described later, the first heater wiring 240 is inserted from the opening 22 (see FIG. Figure 1 ) is led out to two first heater terminals 246a and 246b formed on the upper side of the substrate upper surface 24. Two heater insertion holes 232l and 232k corresponding to the two first heater terminals 246a and 246b are formed in the second insulating film peripheral portion 237.

[0170] Figure 17A as well as Figure 17B The first heater wire 240 is shown with Figure 11A as well as Figure 5The first heater wiring 40 shown is similarly provided between the first insulating film 31 and the second insulating film 232. As viewed from above, the first heater wiring 240 is disposed in the opening 22 of the substrate 20, and the first heater terminal portions 246a and 246b are provided above the substrate upper surface 24 of the substrate 20. The first heater wiring 240 has a central flat portion 240b and heating portions 240a and 240c formed in a spiral shape so as to surround the flat portion 240b.

[0171] The heating parts 240a and 240c are centered on the central flat part 240b and are formed into two non-overlapping spiral plane shapes when viewed from above. The outer end of the heating part 240a is connected to Figure 17A The first heater lead-out portion 244a at the lower right is connected to the first heater terminal portion 246a via the first heater lead-out portion 244a. On the other hand, the outer end of the heating portion 240c is connected to the Figure 17A The upper left first heater lead-out portion 244b is connected to the first heater terminal portion 246b via the first heater lead-out portion 244b.

[0172] Figure 17B The second heater wiring 250 is shown with Figure 9A as well as Figure 5 The second heater wiring 50 shown is also provided between the second insulating film 232 and the third insulating film 33. Figure 17A Although not shown, the second heater wire 250 has the same planar shape as the first heater wire 240, including a central flat portion 250b and heating portions 250a and 250c formed in a spiral shape to surround the flat portion 250b. Similarly to the first heater wire 240, the second heater wire is connected to two second heater terminal portions located below the first heater terminal portions 246a and 246b via two second heater lead portions.

[0173] As described above, the second insulating film 232 between the first heater wiring 240 and the second heater wiring 250 does not form a heater connection hole. Therefore, the first heater wiring 240 and the second heater wiring 250 are connected at Figure 17B The interior of the insulating film 30 shown is electrically insulated.

[0174] but, Figure 17A The first heater terminal 246a is electrically connected to the second heater terminal disposed below it, and the first heater terminal 246b is electrically connected to the second heater terminal disposed below it. Thus, the first heater wire 240 and the second heater wire 250 of the gas sensor 210 are electrically connected in parallel.

[0175] In addition, Figure 17BThe first heater wiring 240 and the second heater wiring 250 of the gas sensor 210 shown in FIG. Figure 5 The illustrated gas sensor 10 differs from the first heater wire 40 and the second heater wire 50 in that the resistance value of the first heater wire 240 is smaller than the resistance value of the second heater wire 250. When current flows through the first heater wire 240 and the second heater wire 250, the amount of heat generated in the first heater wire 240 is greater than that in the second heater wire 250.

[0176] In addition, in the gas sensor 210, Figure 5 The gas sensor 10 shown in FIG. 1 is similar to the gas sensor 10 in that the gas detection unit is provided on the upper surface of the first insulating film 31. Therefore, the gas sensor 210 is also similar to the gas sensor 10 in that when the gas detection unit can detect gas, the insulating film 230 is in contact with the gas sensor 210. Figure 6 The insulating film 30 shown is similarly curved and convex upward, which increases the chances of detecting the target gas. Figure 17A and Figure 17B The gas sensor 210 is shown with respect to Figure 1 The common points of the gas sensor 10 shown in the above examples provide the same effects as the gas sensor 10 .

[0177] (4. Fourth embodiment)

[0178] Figure 18A It is a top view showing the planar shape of the substrate 20, insulating film 30, insulating film peripheral portion 35, first heater wiring 340, first heater lead portion 44, first heater terminal portion 46, second heater wiring 350, second heater lead portion 54 and second heater terminal portion 56 in the gas sensor 310 involved in the fourth embodiment of the present invention. Figure 18B 3 is a cross-sectional view showing the first insulating film 31, the second insulating film 32, the third insulating film 33, the first heater wiring 340 and the second heater wiring 350 in the gas sensor 310. Figure 18A In FIG. 1 , only the base material 20 and the third insulating film 33 are shown in an opaque manner, and the outlines of other components are overlapped so that the shapes of the components below can be seen. Figure 18A and Figure 18B In the figure, the gas detection unit of the gas sensor 310 and the like are omitted.

[0179] like Figure 18BAs shown, the insulating film 30 of the gas sensor 310 is a multilayer film comprising a first insulating film 31, a second insulating film 32 provided below the first insulating film 31, and a third insulating film 33 provided below the second insulating film 32. Its planar shape is the same as that of the gas sensor 10. However, the upper surfaces of the first and second insulating films 31 and 32 of the gas sensor 310 are flattened to prevent unevenness from forming on the lower surface, which is the film-forming surface. In each embodiment of the gas sensor, whether or not the upper surfaces of the first and second insulating films 31 and 32 are flattened is optional. The gas sensor 310 may have both the upper surfaces of the first and second insulating films 31 and 32 flattened, or it may have a configuration where neither the upper surfaces of the first and second insulating films 31 and 32 are flattened. The description of the gas sensor 310 focuses on the differences from the gas sensor 10, and description of the similarities with the gas sensor 10 is omitted.

[0180] Figure 18A and Figure 18B The first heater wiring 340 is shown with Figure 11A and Figure 5 The first heater wiring 40 shown is similarly provided between the first insulating film 31 and the second insulating film 32. As viewed from above, the first heater wiring 340 is disposed in the opening 22 of the substrate 20, and the first heater terminal portion 46 is provided above the substrate upper surface 24 of the substrate 20. The first heater wiring 340 has a central flat portion 340b and a heating portion 340a formed in a spiral shape so as to surround the flat portion 340b.

[0181] The second heater wiring 350 and Figure 9A and Figure 5 The second heater wiring 50 shown is similarly provided between the second insulating film 32 and the third insulating film 33. As viewed from above, the second heater wiring 350 is disposed in the opening 22 of the substrate 20, and the second heater terminal portion 56 is provided above the substrate upper surface 24 of the substrate 20. The second heater wiring 350 includes a central flat portion 350b and a heating portion 350a formed in a spiral shape so as to surround the flat portion 350b.

[0182] like Figure 18BAs shown, the flat portion 340b of the first heater wire 340 is in direct contact with the flat portion 350b of the second heater wire 350, and the first heater wire 340 and the second heater wire 350 are electrically connected in series. That is, a heater connection hole 32j is formed in the second insulating film 32 disposed between the first heater wire 340 and the second heater wire 350, and the flat portion 340b of the first heater wire 340 and the flat portion 350b of the second heater wire 350 are connected via the heater connection hole 32j.

[0183] Here, if Figure 18B As shown, the cross-sectional shapes of the heating portion 340a of the first heater wire 340 and the heating portion 350a of the second heater wire 350, taken along a section passing through the center of the opening 22 and perpendicular to the substrate upper surface 24, are different. Specifically, the heating portion 340a of the first heater wire 340 is thinner in the vertical direction D1 and wider in the film surface direction D2 than the heating portion 350a of the second heater wire 350.

[0184] In the gas sensor 310, the amount of expansion in the film surface direction D2 of the first heater wire 340 during heating relative to the non-heating state is greater than the amount of expansion in the film surface direction D2 of the second heater wire 350 during heating relative to the non-heating state. This is because the amount of expansion in the film surface direction D2 of the heat generating portions 340a and 350a is proportional to the width in the film surface direction D2.

[0185] Although Figure 18A and Figure 18B The gas detection unit of the gas sensor 310 is not shown in the figure, but Figure 2 The gas detection portion 60 of the gas sensor 10 shown in FIG. 1 is similarly provided on the upper surface of the first insulating film 31. When the gas sensor 310 detects gas, if the first heater wire 340 and the second heater wire 350 are energized to generate heat, the insulating film 30 of the gas sensor 310 is bent into a shape that protrudes upward due to the difference in the amount of expansion (see FIG. 1 ). Figure 6 as well as Figure 15 ).

[0186] Therefore, the gas sensor 310 has more opportunities to detect the gas detection portion of the airflow in the film surface direction D2, and the output response speed is improved. Even if the first heater wiring 340 and the second heater wiring 350 have the same resistance value, the gas sensor 310 can cause the insulating film 30 to bend and protrude upward by making the ratio of the thickness in the vertical direction D1 to the width in the film surface direction D2 of the heating portion 340a and 350a different from each other. In addition, Figure 18A and Figure 18B The gas sensor 310 is shown with respect to Figure 1The common points of the gas sensor 10 shown in the above examples provide the same effects as the gas sensor 10 .

[0187] (5. Fifth embodiment)

[0188] Figure 19A It is a top view showing the planar shape of the substrate 20, insulating film 230, insulating film peripheral portion 435, first heater wiring 240, first heater lead-out portion 244a, 244b, first heater terminal portion 246a, 246b, second heater wiring 250, second heater lead-out portion 454a, 454b and second heater terminal portion 456a, 456b of the gas sensor 410 involved in the fifth embodiment of the present disclosure. Figure 19B 4 is a top view showing the first insulating film 31, the second insulating film 232, the third insulating film 33, the first heater wiring 240 and the second heater wiring 250 in the gas sensor 410. Figure 19A In FIG. 1 , only the base material 20 and the third insulating film 33 are shown in an opaque manner, and the outlines of other components are overlapped so that the shapes of the components below can be seen. Figure 19A and Figure 19B In the figure, the gas detection unit of the gas sensor 410 and the like are omitted.

[0189] from Figure 19B and Figure 17B As can be understood from a comparison, the shapes of the insulating film 230, first heater wire 240, and second heater wire 250 of the gas sensor 410 are identical to those of the gas sensor 210 according to the third embodiment. However, the difference between the gas sensor 410 and the gas sensor 210 is that the second heater wire 250 of the gas sensor 410 is connected to second heater terminal portions 456a and 456b, which are separate from the first heater terminal portions 246a and 246b connected to the first heater wire 240. The description of the gas sensor 410 focuses on the differences from the gas sensor 210, and description of the commonalities with the gas sensor 210 is omitted.

[0190] like Figure 19B As shown, the insulating film 230 of the gas sensor 410 is a multilayer film having a first insulating film 31, a second insulating film 232 provided on the lower side of the first insulating film 31, and a third insulating film 33 provided on the lower side of the second insulating film 232. Figure 17A The second insulating film 232 shown similarly has no through-hole formed in the central portion 232 e and electrically insulates the upper first heater wire 240 from the lower second heater wire 250 .

[0191] On the other hand, Figure 19AAs shown, in gas sensor 410, when viewed from above, the positions of first heater terminals 246a and 246b do not overlap with the positions of second heater terminals 456a and 456b. Furthermore, the shape of second heater lead portion 454a, which connects heating element 250a and second heater terminal 456a, differs from that of first heater lead portion 244a. Furthermore, the shape of second heater lead portion 454b, which connects heating element 250c and second heater terminal 456b, differs from that of first heater lead portion 244b.

[0192] like Figure 19A As shown, heater insertion holes 431m and 431n are formed on the first and second insulating film peripheral portions of the insulating film peripheral portion 435 provided on the second heater terminal portions 456a and 456b, respectively, to provide electrical connection to the second heater terminal portions 456a and 456b. In the gas sensor 410, the first heater wire 240 and its connected first heater lead portions 244a and 244b, and first heater terminal portions 246a and 246b, are insulated from the second heater wire 250 and its connected second heater lead portions 454a and 454b, and second heater terminal portions 456a and 456b. Therefore, the first heater wire 240 and the second heater wire 250 are electrically independent.

[0193] exist Figure 19A In the illustrated gas sensor 410, the first heater wire 240 and the second heater wire 250 are independently connected to a control unit and an external circuit via first heater terminals 246a and 246b or second heater terminals 456a and 456b, respectively. Therefore, the current or voltage applied to the first heater wire 240 and the current or voltage applied to the second heater wire 250 can be independently controlled, for example, by independent control signals transmitted from the control unit.

[0194] In this gas sensor 410, even if the first heater wire 240 and the second heater wire 250 have the same material and shape, the heating value of the first heater wire 240 and the second heater wire 250 can be arbitrarily controlled. Therefore, the gas sensor 410 can control the current value and the like so that the heating value of the first heater wire 240 is greater than the heating value of the second heater wire 250. Figure 6 As shown, the insulating film 230 can be bent into a shape that protrudes upward. As a result, the gas sensor 410 can improve the response speed when detecting the target gas. Figure 19A and Figure 19B The gas sensor 410 is shown with Figure 17A and Figure 17BThe common points of the gas sensor 210 shown in the above examples have the same effects as the gas sensor 210 .

[0195] While the gas sensor disclosed herein has been described using embodiments, the gas sensor disclosed herein is not limited to these embodiments and naturally encompasses numerous other embodiments and variations. For example, the insulating film of the gas sensor is not limited to the three-layer multilayer film shown in the embodiments; it may also be a two-layer, four-layer, or more multilayer film. Furthermore, the gas sensor can be installed in any orientation; the vertical direction D1 of the gas sensor can be aligned with or different from the vertical direction.

[0196] Furthermore, the gas sensor disclosed herein is not limited to a gas sensor in which the insulating film bends upward when power is applied to the heater, as in the first to fifth embodiments. Embodiments in which the insulating film is already bent and convex before power is applied to the heater can also be considered. For example, by increasing the formation temperature (substrate temperature during film formation) of the upper insulating film, i.e., the first insulating film 31, to be higher than the formation temperature of the lower insulating film, i.e., the third insulating film 33, stress is generated in the third insulating film 33 and the first insulating film 31 to bend upward, thereby achieving an insulating film that is already bent and convex before power is applied to the heater. Furthermore, since the stress on such an insulating film is supported by the substrate 20 before the opening 22 is formed, no bending occurs in the third insulating film 33 and the first insulating film 31 during the manufacturing stage before the opening 22 is formed, and the formation process of the heater wiring or the gas detection unit is not hindered. Furthermore, in such a gas sensor, the heater wiring can be formed into a single-layer structure consisting of the second heater wiring 50 and the first heater wiring 40 can be omitted. The insulating film can be formed into a two-layer structure consisting of the first and third insulating films 31 and 33 and the second insulating film 32 can be omitted.

[0197] In addition, as another embodiment for causing the insulating film to bend so as to protrude upward when power is supplied to the heater, an embodiment can be cited in which the film density of the upper insulating film, namely the first insulating film 31, is higher than the film density of the lower insulating film, namely the third insulating film 33. The film density of the first and third insulating films 31 and 33 can be adjusted, for example, by making the gas pressures during the formation of these first and third insulating films 31 and 33 different from each other, thereby making the amount of gas components entering the first and third insulating films 31 and 33 different from each other. For example, if the gas pressure during film formation is relatively lowered, the film density becomes relatively higher, and if the gas pressure during film formation is relatively increased, the film density becomes relatively lower. In such a gas sensor, the heater wiring can be configured as a single-layer structure consisting of the second heater wiring 50 and the first heater wiring 40 can be omitted. The insulating film can be configured as a two-layer structure consisting of the first and third insulating films 31 and 33 and the second insulating film 32 can be omitted.

[0198] In the gas sensor according to the present disclosure, the degree to which the insulating film 30 is bent so as to protrude upward is not particularly limited. However, it is preferable that the protrusion amount (protrusion height H1) of the insulating film 30 upward during gas detection is, for example, 1% or more relative to the maximum width W1 of the insulating film 30 in the film surface direction D2 that overlaps with the opening 22 in a plan view (see FIG. Figure 15 ).

Claims

1. A gas sensor, wherein: have: a substrate having an opening formed therein; an insulating film disposed at a position overlapping with the opening in a plan view; and a gas detection portion provided on the upper surface of the insulating film; When the gas detection unit is capable of detecting gas, the insulating film has a shape that is curved so as to protrude upward.

2. The gas sensor according to claim 1, wherein The insulating film is a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film. The gas detection unit is provided on the upper surface of the first insulating film and includes: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film, The first heater wire and the second heater wire are electrically connected in series, and a resistance value of the first heater wire is greater than a resistance value of the second heater wire.

3. The gas sensor according to claim 1, wherein The insulating film is a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film. The gas detection unit is provided on the upper surface of the first insulating film and includes: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film, The first heater wire and the second heater wire are electrically connected in parallel, and a resistance value of the first heater wire is smaller than a resistance value of the second heater wire.

4. The gas sensor according to claim 1, wherein The insulating film is a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film. The gas detection unit is provided on the upper surface of the first insulating film and includes: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film, The amount of expansion of the first heater wire in the film surface direction during heating relative to the non-heating state is greater than the amount of expansion of the second heater wire in the film surface direction during heating relative to the non-heating state.

5. The gas sensor according to claim 1, wherein The insulating film is a multilayer film including a first insulating film, a second insulating film provided below the first insulating film, and a third insulating film provided below the second insulating film. The gas detection unit is provided on the upper surface of the first insulating film and includes: a first heater wiring provided between the first insulating film and the second insulating film; and a second heater wiring provided between the second insulating film and the third insulating film, The first heater wiring is electrically independent from the second heater wiring.

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