Gas sensor

Abstract

The durability can be improved.SOLUTION: The gas sensor 10 includes a gas sensor device 20 containing a ceramic material, and a substrate 30 having a cavity 31A surrounded by a frame 31. The gas sensor 10 is provided with a cantilevered beam portion 32 extending from the frame 31 toward the inside of the frame 31. The gas sensor device 20 is connected to the beams 32 on the side of the beams 32 not facing the 31A of the cavity. The gas sensor element 20 has a heater 26.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to gas sensors. [Background technology]

[0002] Patent Document 1 discloses a gas sensor. This gas sensor includes a substrate and a heater disposed on the substrate with a first insulating layer interposed therebetween. The gas sensor further includes a gas inlet passage disposed on the heater with a second insulating layer interposed therebetween for introducing a gas to be measured, a lower electrode disposed on the gas inlet passage, a solid electrolyte layer disposed on the lower electrode, and an upper electrode disposed on the surface of the solid electrolyte layer facing the lower electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 014033 Summary of the Invention [Problem to be solved by the invention]

[0004] In the gas sensor of Patent Document 1, if there is a large difference in the thermal expansion coefficient between a component on the substrate side (e.g., the first insulating layer) and a component of the gas sensor element (e.g., the solid electrolyte layer), the difference in thermal expansion between the two components before and after heating by the heater may cause stress to be applied to the gas sensor element. There is a demand for a gas sensor that can suppress the occurrence of such stress and has high durability. The present disclosure has been made in view of the above circumstances, and aims to provide a gas sensor that can improve durability. The present disclosure can be realized in the following aspects. [Means for solving the problem]

[0005] The gas sensor of the present disclosure comprises: a gas sensor element including a ceramic material; a substrate having a cavity surrounded by a frame; A gas sensor comprising: a cantilever beam portion extending inward from the frame body, the gas sensor element is connected to the beam portion on a side of the beam portion that does not face the cavity, The gas sensor element includes a heater. [Effects of the Invention]

[0006] The present disclosure can provide a gas sensor that can improve durability. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a side cross-sectional view of a gas sensor according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a plan view of the gas sensor of FIG. [Figure 3] FIG. 2 is a side cross-sectional view of the gas sensor element of FIG. [Figure 4] FIG. 2 is a bottom view of the gas sensor element of FIG. [Figure 5] FIG. 2 is a side cross-sectional view of the substrate of FIG. [Figure 6] FIG. 2 is a plan view of the substrate of FIG. [Figure 7] FIG. 4 is a side cross-sectional view of a gas sensor according to a second embodiment of the present disclosure. [Figure 8] FIG. 8 is a plan view of the gas sensor of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the following, embodiments of the present disclosure are listed and illustrated. [1] A gas sensor element including a ceramic material; a substrate having a cavity surrounded by a frame; A gas sensor comprising: a cantilever beam portion extending inward from the frame body, the gas sensor element is connected to the beam portion on a side of the beam portion that does not face the cavity, The gas sensor, wherein the gas sensor element has a heater.

[0009] According to the gas sensor of the above [1], the gas sensor element is connected to a cantilevered beam portion extending inward from the frame body on the side that does not face the cavity. This allows the beam portion to easily deform three-dimensionally, and the deformation of the beam portion can suppress stress concentration at the connection portion between the gas sensor element and the beam portion. This suppresses the generation of stress in the gas sensor element and improves the durability of the gas sensor.

[0010] [2] The beam portion is plural, The gas sensor according to [1], wherein each of the beam portions is connected to the gas sensor element at a different connection position.

[0011] According to the gas sensor of the above item [2], the gas sensor element is supported by a plurality of beams, so that the gas sensor element can be stably supported on the substrate. Moreover, since the plurality of beams are connected to the gas sensor element at different connection positions, the three-dimensional deformation of each beam can suppress stress concentration at the connection portions between the gas sensor element and each beam.

[0012] [3] The gas sensor according to [2], wherein, when viewed in a plan view from the thickness direction of the substrate, the different connection positions are rotationally symmetrical with the center of gravity of the gas sensor element as the center of rotation.

[0013] According to the gas sensor of the above item [3], the gas sensor element is supported in a well-balanced manner by the multiple beams, so that the gas sensor element can be supported on the substrate in a more stable manner. Moreover, deformation is likely to occur equally in each beam, so that stress concentration at the connection portions between the gas sensor element and each beam can be further suppressed.

[0014] [4] A gas sensor according to any one of [1] to [3], wherein the gas sensor element and the substrate are connected via a connecting portion, and at least a portion of the gas sensor element is spaced apart from the substrate.

[0015] According to the gas sensor of the above item [4], the gas sensor element having the heater is separated from the substrate via the connecting portion, so that the conduction of heat generated by the heater to the substrate can be suppressed.

[0016] [5] The gas sensor according to [4], wherein the connecting portion is at least one selected from the group consisting of a conductive bump and a conductive wire.

[0017] According to the gas sensor of the above item [5], the connecting portion can support the gas sensor element relative to the substrate while ensuring electrical continuity between the substrate and the gas sensor element.

[0018] [6] The gas sensor according to any one of [1] to [5], wherein the gas sensor element comprises a solid electrolyte body made of zirconia and an electrode mainly composed of metal formed on the surface of the solid electrolyte body.

[0019] According to the gas sensor of the above [6], the zirconia type gas sensor element can be driven well by heating with the heater.

[0020] First Embodiment 1. Configuration of the gas sensor 10 A gas sensor 10 according to a first embodiment of the present invention will be described below with reference to FIGS. 1 to 6. The gas sensor 10 according to the first embodiment shown in FIG. 1 is an example of a gas sensor according to the present disclosure. In the following description, for convenience of explanation, the up-down direction shown in FIG. 1 is defined as the up-down direction, but it does not have to coincide with the up-down direction in the actual arrangement of the gas sensor 10. The up-down direction corresponds to the thickness direction of the substrate 30.

[0021] 1 and 2, the gas sensor 10 includes a gas sensor element 20 and a substrate 30. The gas sensor element 20 includes a ceramic material. The gas sensor 10 measures the concentration of a measurement target gas, such as oxygen.

[0022] 1-1. Configuration of the substrate 30 The substrate 30 shown in FIGS. 5 and 6 is, for example, a MEMS (Micro Electro Mechanical Systems) chip. FIG. 5 is a diagram showing a cross section taken along line BB in FIG. 6. The substrate 30 has a frame 31 and beam portions 32. The frame 31 is, for example, in the shape of a rectangular ring. A rectangular parallelepiped cavity 31A is formed inside the frame 31. The beam portions 32 are cantilevered and extend inward from the frame 31. Hereinafter, the front end of the beam portions 32 in the extension direction (the end facing inward) will also be referred to as the tip.

[0023] Specifically, as shown in Fig. 1, the substrate 30 has a semiconductor substrate 33A and insulating layers 33B-33F. The substrate 30 further has a pair of signal leads 34, a pair of signal pads 35, a pair of signal electrodes 36 (see Fig. 6), a pair of heater leads 37, a pair of heater pads 38, and a pair of heater electrodes 39 (see Fig. 6). Note that Fig. 1 is a cross section taken along line AA in Fig. 2, and shows one signal lead 34, one signal pad 35, one signal electrode 36, one heater lead 37, one heater pad 38, and one heater electrode 39.

[0024] The material of the semiconductor substrate 33A includes, for example, silicon (Si). An opening 33G is formed in the semiconductor substrate 33A so as to penetrate the substrate so as to open to both the top and bottom surfaces. The opening 33G has, for example, a rectangular shape in a plan view. A portion of the insulating layer 33B is exposed in the opening 33G.

[0025] The insulating layers 33B-33F may be made of any material, as long as they have sufficient insulating properties. The insulating layers 33B-33E are stacked on the upper surface of the semiconductor substrate 33A. From the upper surface of the semiconductor substrate 33A, the insulating layer 33B, the insulating layer 33C, the insulating layer 33D, and the insulating layer 33E are stacked in this order. The insulating layers 33B and 33D are formed of, for example, silicon oxide (SiO2). The insulating layer 33B is formed by, for example, thermal oxidation (such as thermal oxidation of a silicon substrate). The insulating layers 33C and 33E are made of, for example, silicon nitride (Si3N4). The insulating layers 33C and 33E are formed by, for example, low-pressure CVD. The insulating layer 33D is formed by, for example, plasma CVD using TEOS (Si(OC2H5)4) as a liquid source. The insulating layer 33D is formed by, for example, two film deposition processes, one of which sandwiches the process of forming the pair of signal leads 34 and the pair of signal pads 35.

[0026] The insulating layer 33F is laminated on the lower surface of the semiconductor substrate 33A. The material of the insulating layer 33F includes, for example, silicon oxide (SiO2). The insulating layer 33F is formed by, for example, thermal oxidation (thermal oxidation of a silicon substrate, etc.).

[0027] The pair of signal leads 34 and the pair of heater leads 37 are embedded in the insulating layer 33D. The signal leads 34 and the heater leads 37 extend horizontally from the outside to the inside of the insulating layer 33D when viewed from the top-bottom direction. Specifically, one end portion (the tip portion in the extension direction) of the signal leads 34 and one end portion (the tip portion in the extension direction) of the heater leads 37 are embedded in the beam portion 32. The signal leads 34 and the heater leads 37 extend in a direction parallel to the extension direction of the beam portion 32.

[0028] The signal lead 34 is connected to the signal pad 35 and the signal electrode 36. The signal lead 34 is a conductive path for extracting an electric signal such as a current from the gas sensor element 20 that measures the gas concentration. The signal lead 34 has a two-layer structure, for example, a layer containing titanium (Ti) and a layer containing platinum (Pt) formed thereon.

[0029] A signal pad 35 is connected to one end (outer end) of the signal lead 34. The signal pad 35 has a two-layer structure, for example, a layer containing chromium (Cr) and a layer containing gold (Au) formed thereon. Wiring (not shown) for supplying power from an external circuit is connected to the signal pad 35. The signal pad 35 is formed at a position that overlaps the semiconductor substrate 33A (frame body 31) in the vertical direction.

[0030] A signal electrode 36 is connected to the other end (inner end) of the signal lead 34. The signal electrode 36 is formed on the upper surface of the beam portion 32 near the tip. The material of the signal electrode 36 contains, for example, gold (Au). The signal electrode 36 is disposed in a hole 30A formed on the upper surface of the substrate 30. The hole 30A is formed on the upper surface of the beam portion 32 near the tip. The hole 30A penetrates the insulating layers 33D and 33E, and the other end of the signal lead 34 is exposed at the bottom. The thickness of the signal electrode 36 is, for example, the same as the thickness of the insulating layer 33D. A connection portion 40, which will be described later, is connected to the signal electrode 36.

[0031] The heater lead 37 is connected to the heater pad 38 and the heater electrode 39. The heater lead 37 is a conductive path for passing a current to the heater 26 of the gas sensor element 20, which will be described later. The heater lead 37 has a two-layer structure, for example, a layer containing titanium (Ti) and a layer containing platinum (Pt) formed thereon.

[0032] A heater pad 38 is connected to one end (outer end) of the heater lead 37. The heater pad 38 has a two-layer structure, for example, a layer containing chromium (Cr) and a layer containing gold (Au) formed thereon. Wiring (not shown) for supplying power from an external circuit is connected to the heater pad 38. The heater pad 38 is formed at a position that overlaps the semiconductor substrate 33A (frame 31) in the vertical direction.

[0033] A heater electrode 39 is connected to the other end (inner end) of the heater lead 37. The heater electrode 39 is formed on the upper surface of the beam portion 32 near the tip. The material of the heater electrode 39 contains, for example, gold (Au). The heater electrode 39 is disposed in a hole 30B formed on the upper surface of the substrate 30. The hole 30B is formed on the upper surface of the beam portion 32 near the tip. The hole 30B penetrates the insulating layers 33D and 33E, and the other end of the heater lead 37 is exposed at the bottom. The thickness of the heater electrode 39 is, for example, the same as the thickness of the insulating layer 33D. A connection portion 40, which will be described later, is connected to the heater electrode 39.

[0034] The pair of signal pads 35 and the pair of heater pads 38 are positioned in rotational symmetry around the center (center of gravity) C of the gas sensor 10 (specifically, the gas sensor element 20 and the substrate 30) when viewed from above in the thickness direction (vertical direction) of the substrate 30. As shown in Fig. 6, the pair of signal electrodes 36 and the pair of heater electrodes 39 are positioned in rotational symmetry around the center (center of gravity) C of the gas sensor 10 (specifically, the gas sensor element 20 and the substrate 30) when viewed from above in the thickness direction (vertical direction) of the substrate 30.

[0035] The frame 31 is composed of a semiconductor substrate 33A and an insulating layer 33F. The beam 32 is composed of an inner portion (excluding the portion that vertically overlaps with the frame 31) of the portion composed of the insulating layers 33B-33E, a pair of signal electrodes 36, and a pair of heater electrodes 39. The four beams 32 are linear and extend horizontally from the four corners of the opening 33G of the semiconductor substrate 33A. In a plan view, the four beams 32 extend along the diagonals of the quadrangle (such as a square) that is the outer shape of the frame 31. The four beams 32 have the same extension length.

[0036] The tip surfaces of the beam portions 32 are surfaces perpendicular to the extension direction of the beam portions 32. The tips of a pair of beam portions 32 facing each other in the extension direction are spaced apart. The distance between the tips of one pair of beam portions 32 is the same as the distance between the tips of the other pair of beam portions 32. The tips of adjacent beam portions 32 around the center C are also spaced apart. The four beam portions 32 are rotationally symmetric with the center C as the center of rotation.

[0037] 1-2. Configuration of the gas sensor element 20 3 and 4, the gas sensor element 20 includes a solid electrolyte body 21, a detection electrode 22, a reference electrode 23, insulating layers 24 and 25, a heater 26, a pair of element-side pads 27, and a pair of element-side electrodes 28. The gas sensor element 20 has, for example, a quadrangular (square) plate shape in plan view.

[0038] The solid electrolyte body 21 contains a material that is activated by heating to a high temperature and exhibits ion conductivity. The solid electrolyte body 21 is preferably made of zirconia (ZrO2). The solid electrolyte body 21 contains, for example, stabilized zirconia. The stabilized zirconia is, for example, yttria-stabilized zirconia (YSZ). The solid electrolyte body 21 has, for example, a quadrangular (e.g., square) plate shape in plan view. The solid electrolyte body 21 is, for example, not a layer formed by sputtering, but a bulk ceramic (ceramic sintered body) formed by sintering a ceramic material. The solid electrolyte body 21 has better detection accuracy than a structure formed by sputtering.

[0039] The detection electrode 22 and the reference electrode 23 are electrodes mainly composed of metal and formed on the surface of the solid electrolyte body 21. The detection electrode 22 is laminated on one surface (upper surface) of the solid electrolyte body 21. The material of the detection electrode 22 contains, for example, platinum (Pt). The detection electrode 22 is, for example, a porous body. The reference electrode 23 is laminated on the other surface (lower surface) of the solid electrolyte body 21. The material of the reference electrode 23 contains, for example, platinum (Pt). The reference electrode 23 is, for example, a porous body. The solid electrolyte body 21 is sandwiched between the detection electrode 22 and the reference electrode 23.

[0040] The detection electrode 22 is exposed to a gas to be measured (detection gas). A reference gas (oxygen, etc.) of a predetermined concentration is introduced into the reference electrode 23. The structure for introducing the gas to be measured into the detection electrode 22 and the structure for introducing the reference gas into the reference electrode 23 are not shown in the figure.

[0041] The insulating layers 24 and 25 are laminated on the other surface (lower surface) of the solid electrolyte body 21 and one surface (lower surface) of the reference electrode 23. The insulating layer 24 and the insulating layer 25 are laminated in this order from top to bottom. The material of the insulating layers 24 and 25 contains aluminum oxide (Al2O3). When viewed from above and below, the insulating layers 24 and 25 overlap the solid electrolyte body 21.

[0042] The heater 26 is embedded in the insulating layer 25. The heater 26 has, for example, a strip shape. The heater 26 has, for example, a rectangular spiral shape or a meandering shape when viewed from above and below. The heater 26 is made of a material containing, for example, platinum (Pt). The heater 26 generates heat to activate the solid electrolyte body 21.

[0043] 4, the pair of element-side pads 27 and the pair of element-side electrodes 28 are arranged, for example, at the four corners of the lower surface of the insulating layer 25. The pair of element-side pads 27 and the pair of element-side electrodes 28 have a two-layer structure, for example, a layer containing gold (Au) and a layer formed thereunder containing platinum (Pt). When the pair of element-side pads 27 and the pair of element-side electrodes 28 have a two-layer structure, it is preferable that the material of the upper layer is the same as the material of the connection part 40, which will be described later.

[0044] One of the element-side pads 27 is a pad for extracting a signal obtained from the detection electrode 22. Although not shown, the element-side pad 27 is electrically connected to the detection electrode 22 via a through-hole formed in the gas sensor element 20 (insulating layers 24, 25, etc.).

[0045] The other element-side pad 27 is a pad for extracting a signal obtained from the reference electrode 23. Although not shown, the other element-side pad 27 is electrically connected to the reference electrode 23 via a through-hole formed in the gas sensor element 20 (insulating layers 24, 25, etc.).

[0046] The pair of element-side electrodes 28 are electrodes for passing current through the heater 26. One of the element-side electrodes 28 is connected to one end of the heater 26. The other element-side electrode 28 is connected to the other end of the heater 26. Conduction between the pair of element-side electrodes 28 and the heater 26 is ensured via through holes formed in the gas sensor element 20 (insulating layers 24, 25, etc.).

[0047] The gas sensor element 20 is formed, for example, by a sheet molding process or a printing process. For example, the gas sensor element 20 can be formed by preparing a sheet formed from a ceramic raw material that forms the base of the solid electrolyte body 21, a sheet that forms the base of the insulating layers 24 and 25, etc., printing various electrodes on the sheets, and then sintering the sheets.

[0048] The gas sensor element 20 outputs a signal (voltage signal) based on the difference between the concentration of the measurement gas to which the detection electrode 22 is exposed and the concentration of the reference gas introduced into the reference electrode 23. For example, when the measurement gas is oxygen, the solid electrolyte body 21 can be made ion-conductive by maintaining it at a high temperature, and oxygen ions are conducted from the reference electrode 23 side, where the oxygen concentration is high, to the detection electrode 22 side, generating a current. Because the oxygen ions have a negative charge, an electromotive force is generated between the two electrodes 22, 23.

[0049] The operating temperature of the gas sensor element 20 (the surface temperature of the solid electrolyte body 21 when heated by the heater 26) is preferably 550° C. to 800° C., more preferably 600° C. to 750° C., and even more preferably 650° C. to 700° C. The surface temperature of the frame body 31 (semiconductor substrate 33A) when the gas sensor element 20 is operated is preferably room temperature (e.g., 25° C.) to 50° C.

[0050] 1-3. Support structure of the gas sensor element 20 by the substrate 30 As shown in FIG. 1, the gas sensor element 20 is connected to the four beams 32 (only two are shown in FIG. 1) on the sides (upper surface sides) of the four beams 32 that do not face the cavity 31A. In a plan view seen from the top-bottom direction, the center (center of gravity) of the gas sensor element 20 overlaps with the center (center of gravity) C of the substrate 30. The gas sensor 10 further includes four connection portions 40 (two connection portions 40 appear in FIG. 1). The gas sensor element 20 and the substrate 30 (beams 32) are connected via the connection portions 40, and the entire gas sensor element 20, except for the portions in contact with the connection portions 40, faces the substrate 30 (beams 32) while being spaced apart. A space exists between the gas sensor element 20 and the substrate 30 (beams 32).

[0051] Each of the pair of connection portions 40 is disposed between the signal electrode 36 of the substrate 30 and the element-side pad 27 of the gas sensor element 20. The connection portion 40 is connected to the signal electrode 36 and the element-side pad 27. The connection portion 40 is inserted into the hole 30A in which the signal electrode 36 is disposed. A part of the connection portion 40 may protrude onto the insulating layer 33E.

[0052] The other pair of connecting portions 40 are respectively disposed between the heater electrode 39 of the substrate 30 and the element-side electrode 28 of the gas sensor element 20. The connecting portions 40 are connected to the heater electrode 39 and the element-side electrode 28. The connecting portions 40 are inserted into the holes 30B in which the heater electrodes 39 are disposed. Parts of the connecting portions 40 may protrude onto the insulating layer 33E.

[0053] The connection portions 40 are conductive bumps. The material of the connection portions 40 includes, for example, precious metals and base metals. The material of the connection portions 40 is preferably gold (Au), nickel (Ni), or metallic glass. The material of the connection portions 40 is preferably the same as the material of the pair of element-side pads 27 and the material of the pair of element-side electrodes 28. If the pair of element-side pads 27 and the pair of element-side electrodes 28 have a two-layer structure, the material of the connection portions 40 is preferably the same as the material of the layer on the connection portion 40 side.

[0054] The four beam portions 32 are connected to different connection positions of the gas sensor element 20. Specifically, the four beam portions 32 are connected to a pair of element-side pads 27 and a pair of element-side electrodes 28 formed at different positions of the gas sensor element 20.

[0055] 2, when viewed from above in the thickness direction (vertical direction) of the substrate 30, the different connection positions of the gas sensor element 20 to the beam portion 32 (the positions of the pair of element-side pads 27 and the pair of element-side electrodes 28) are rotationally symmetrical with respect to the center (center of gravity) C of the gas sensor element 20. The different connection positions of the gas sensor element 20 to the beam portion 32 (the positions of the pair of element-side pads 27 and the pair of element-side electrodes 28) are located on the same plane (horizontal plane) and are arranged at equal intervals (equal angles) around the center (center of gravity) C of the gas sensor element 20.

[0056] In plan view, the diagonal lines of the quadrangle (square) that is the outer shape of the gas sensor element 20 overlap with the diagonal lines of the quadrangle (square) that is the outer shape of the substrate 30.

[0057] The gas sensor 10 shown in FIGS. 1 and 2 is fabricated by fabricating the gas sensor element 20 shown in FIGS. 3 and 4 and the substrate 30 shown in FIGS. 5 and 6, respectively, and then connecting the gas sensor element 20 to the substrate 30 via the connecting portion 40.

[0058] 2. Effects of the First Embodiment The gas sensor 10 of the first embodiment includes a gas sensor element 20 containing a ceramic material and a substrate 30 having a cavity 31A surrounded by a frame 31. The gas sensor 10 is provided with a cantilevered beam portion 32 extending from the frame 31 toward the inside of the frame 31. The gas sensor element 20 is connected to the beam portion 32 on the side of the beam portion 32 that does not face the cavity 31A. The gas sensor element 20 includes a heater 26.

[0059] With this configuration, the gas sensor element 20 is connected to the cantilevered beam portion 32 extending inward from the frame 31 on the side that does not face the cavity 31A. This allows the beam portion 32 to deform easily in three dimensions, and the deformation of the beam portion 32 can suppress stress concentration at the connection portion between the gas sensor element 20 and the beam portion 32 (the connection portion between the element-side pad 27 and the signal electrode 36 via the connection portion 40, and the connection portion between the element-side electrode 28 and the heater electrode 39 via the connection portion 40). This suppresses stress generation in the gas sensor element 20, and improves the durability of the gas sensor 10.

[0060] For example, when yttria-stabilized zirconia (YSZ) is used for the solid electrolyte body 21, the thermal expansion coefficient of YSZ is approximately 10 ppm / °C, while the thermal expansion coefficient of the oxide film and nitride film used for the insulating layers 33B-33E constituting the beam portion 32 is approximately 3 ppm / °C. Since the difference in thermal expansion coefficient between the solid electrolyte body 21 and the beam portion 32 is large, the difference in thermal expansion due to thermal strain between the solid electrolyte body 21 and the beam portion 32 increases. However, the occurrence of stress on the gas sensor element 20 due to deformation of the beam portion 32 can be suppressed. In particular, when the gas sensor element 20 needs to be heated to a temperature between 650°C and 700°C inclusive in order to function, the temperature difference from room temperature (e.g., 25°C) is large, and therefore the configuration of the first embodiment is effective for driving the gas sensor element 20.

[0061] Furthermore, since the gas sensor element 20 is supported by the beam portion 32, the proportion of the portion constituting the substrate 30 is small, making it easier to suppress the conduction of heat generated by the heater 26 to the installation side (lower surface side) of the substrate 30.

[0062] The gas sensor 10 of the first embodiment includes a plurality of beam portions 32, each of which is connected to a different connection position (the position of a pair of element-side pads 27 and a pair of element-side electrodes 28) of the gas sensor element 20. With this configuration, the gas sensor element 20 is supported by the plurality of beam portions 32, and therefore the gas sensor element 20 can be stably supported on the substrate 30. Furthermore, because the plurality of beam portions 32 are connected to the gas sensor element 20 at different connection positions, the three-dimensional deformation of each beam portion 32 can suppress stress concentration at the connection portion between the gas sensor element 20 and each beam portion 32.

[0063] In the gas sensor 10 of the first embodiment, when viewed from above in the thickness direction of the substrate 30, the different connection positions of the gas sensor element 20 (the positions of the pair of element-side pads 27 and the pair of element-side electrodes 28) are rotationally symmetrical with respect to the center (center of gravity) C of the gas sensor element 20. With this configuration, the gas sensor element 20 is supported in a well-balanced manner by the multiple beams 32, and the gas sensor element 20 can be supported more stably on the substrate 30. Furthermore, deformation is likely to occur in each beam 32 in the same manner, and stress concentration at the connection portions between the gas sensor element 20 and each beam 32 can be further suppressed.

[0064] In the gas sensor 10 of the first embodiment, the gas sensor element 20 and the substrate 30 are connected via a connecting portion 40. The entire gas sensor element 20 is spaced apart from the substrate 30. With this configuration, the gas sensor element 20 having the heater 26 is spaced apart from the substrate 30 via the connecting portion 40, so that conduction of heat generated by the heater 26 to the substrate 30 can be suppressed.

[0065] In the gas sensor 10 of the first embodiment, the connecting portions 40 are conductive bumps. With this configuration, the connecting portions 40 can support the gas sensor element 20 on the substrate 30 while ensuring electrical continuity between the substrate 30 and the gas sensor element 20.

[0066] In the gas sensor 10 of the first embodiment, the gas sensor element 20 includes a solid electrolyte body 21 made of zirconia, and a detection electrode 22 and a reference electrode 23, each of which is mainly made of metal and formed on the surface of the solid electrolyte body 21. With this configuration, the zirconia-type gas sensor element 20 can be driven well by heating with the heater 26.

[0067] Second Embodiment A second embodiment of the present disclosure will be described below with reference to FIGS. 7 and 8. The gas sensor of the second embodiment differs from the first embodiment in the configuration of the connection portion, but is otherwise the same. Note that the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Note that FIG. 7 is a view showing a cross section taken along CC in FIG. 8.

[0068] The gas sensor 210 of the second embodiment includes a gas sensor element 20, a substrate 30, and four connecting portions 240. The connecting portions 240 are conductive wires. The connecting portions 240 are made of a material such as gold (Au), copper (Cu), or aluminum (Al). The gas sensor element 20 is supported on the substrate 30 by the four connecting portions 240.

[0069] One pair of connecting portions 240 is connected to the signal electrode 36 of the substrate 30 and the element-side pad 27 of the gas sensor element 20, respectively. The other pair of connecting portions 240 is connected to the heater electrode 39 of the substrate 30 and the element-side electrode 28 of the gas sensor element 20, respectively.

[0070] Even with this configuration, the beam portion 32 is easily deformed three-dimensionally, and the deformation of the beam portion 32 can suppress stress concentration at the connection portion between the gas sensor element 20 and the beam portion 32 (the connection portion between the element-side pad 27 and the signal electrode 36 via the connection portion 240, and the connection portion between the element-side electrode 28 and the heater electrode 39 via the connection portion 240). Furthermore, the difference in thermal expansion between the beam portion 32 and the gas sensor element 20 can be absorbed by the deformation of the connection portion 240. Therefore, the generation of stress in the gas sensor element 20 can be suppressed, and the durability of the gas sensor 210 can be improved.

[0071] <Other embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or following embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or following embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiment may be modified as follows.

[0072] In the first and second embodiments, the gas sensor includes four beams, but the number of beams is not limited to this. For example, the gas sensor may include one beam, two beams, six beams, or eight beams.

[0073] In the first and second embodiments, the different connection positions of the gas sensor element are rotationally symmetrical with respect to the center (center of gravity) C of the gas sensor element in a plan view. However, the different connection positions may be non-rotationally symmetrical. For example, the different connection positions of the gas sensor element may be line-symmetrical with respect to a line that passes through the center (center of gravity) C of the gas sensor element and is parallel to a horizontal plane in a plan view.

[0074] In the first and second embodiments, the beam portions extend linearly, but may have a shape other than a linear shape, such as a curved shape or a meandering shape (meandering shape).

[0075] In the first and second embodiments, the gas sensor element and the beam portion are connected via the connecting portion, but they may be connected without the connecting portion.

[0076] In the first and second embodiments, the entire gas sensor element is separated from the substrate (beam portion), but a part of the gas sensor element may be separated from the substrate (beam portion). That is, a part of the gas sensor element may be in contact with the substrate (beam portion).

[0077] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0078] 10: Gas sensor 20: Gas sensor element 21: Solid electrolyte body 22: Sensing electrode 23: Reference electrode 24: Insulating layer 25: Insulating layer 26: Heater 27: Element side pad 28: Element side electrode 30: Circuit board 30A: Hole 30B: Hole 31: Frame 31A: Cavity 32: Beam section 33A: Semiconductor substrate 33B-33F: Insulating layer 33G: Opening 34: Signal lead 35: Signal pad 36: Signal electrode 37: Heater lead 38: Heating pad 39: Heater electrode 40: Connection 210: Gas sensor 240: Connection C: Center (center of gravity)

Claims

1. a gas sensor element including a ceramic material; a substrate having a cavity surrounded by a frame; A gas sensor comprising: a cantilever beam portion extending inward from the frame body, the gas sensor element is connected to the beam portion on a side of the beam portion that does not face the cavity, The gas sensor, wherein the gas sensor element has a heater.

2. The beam portion is plural, 2. The gas sensor according to claim 1, wherein each of the beam portions is connected to the gas sensor element at a different connection position.

3. 3. The gas sensor according to claim 2, wherein, when viewed from above in a thickness direction of the substrate, the different connection positions are rotationally symmetrical with the center of gravity of the gas sensor element as a center of rotation.

4. 3. The gas sensor according to claim 1, wherein the gas sensor element and the substrate are connected via a connecting portion, and at least a part of the gas sensor element is spaced apart from the substrate.

5. 5. The gas sensor according to claim 4, wherein the connecting portion is at least one selected from the group consisting of a conductive bump and a conductive wire.

6. 3. The gas sensor according to claim 1, wherein the gas sensor element comprises a solid electrolyte body made of zirconia and an electrode mainly made of metal formed on a surface of the solid electrolyte body.

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