sensor

Abstract

To provide a sensor capable of obtaining high detection sensitivity.SOLUTION: According to an embodiment, the sensor includes a substrate, a fixed electrode, a first fixing part, a first support part, and a movable part. The substrate includes a first region and a second region. The fixed electrode is fixed to the first region. The first fixing part is fixed to the second region. The first support part is connected to the first fixing part. The first support part includes a first support layer and a first layer fixed to the first support layer. The first layer includes oxygen and at least one metal selected from the group consisting of Pt, Pd, and Ti. The movable part is supported by the first support part. A first air gap is provided between the fixed electrode and the movable part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to sensors.

Background Art

[0002] For example, there are sensors that apply MEMS structures. In sensors, high detection sensitivity is desired.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Embodiments of the present invention provide a sensor capable of obtaining high detection sensitivity.

Means for Solving the Problems

[0005] According to an embodiment of the present invention, a sensor includes a substrate, a fixed electrode, a first fixing portion, a first support portion, and a movable portion. The substrate includes a first region and a second region. The fixed electrode is fixed to the first region. The first fixing portion is fixed to the second region. The first support portion is connected to the first fixing portion. The first support portion includes a first support layer and a first layer fixed to the first support layer. The first layer includes at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen. The movable portion is supported by the first support portion. A first gap is provided between the fixed electrode and the movable portion.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a sensor according to a first embodiment. [Figure 2]Figure 2 is a graph illustrating the characteristics of the sensor according to the first embodiment. [Figure 3] Figures 3(a) to 3(c) are schematic cross-sectional views illustrating a method for manufacturing a sensor according to the first embodiment. [Figure 4] Figures 4(a) to 4(c) are schematic cross-sectional views illustrating a method for manufacturing a sensor according to the first embodiment. [Figure 5] Figures 5(a) to 5(c) are schematic cross-sectional views illustrating a method for manufacturing a sensor according to the first embodiment. [Modes for carrying out the invention]

[0007] Embodiments of the present invention will be described below with reference to the drawings. Drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of different parts, are not necessarily identical to those of reality. Even when representing the same part, the dimensions and ratios may be depicted differently in different drawings. In this specification and in each figure, elements similar to those described above are denoted by the same reference numerals with respect to previously shown figures, and detailed explanations are omitted as appropriate.

[0008] (First Embodiment) Figure 1 is a schematic cross-sectional view illustrating a sensor according to the first embodiment. As shown in Figure 1, the sensor 110 according to this embodiment includes a base 40, a fixed electrode 55, a first fixed part 21, a first support part 31s, and a movable part 30M.

[0009] The substrate 40 includes a first region 41 and a second region 42. The substrate 40 may be, for example, a silicon substrate.

[0010] The fixed electrode 55 is fixed to the first region 41. An insulating film 55a may be provided on the fixed electrode 55.

[0011] The first fixing portion 21 is fixed to the second region 42. The first support portion 31s is connected to the first fixing portion 21. The first support portion 31s includes a first support layer 31L and a first layer 31. The first layer 31 is fixed to the first support layer 31L.

[0012] The first layer 31 comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen. For example, the first layer 31 comprises an oxide of the above metal. The first layer 31 comprises a bond between the above metal and oxygen.

[0013] The movable part 30M is supported by the first support part 31s. A first gap G1 is provided between the fixed electrode 55 and the movable part 30M.

[0014] For example, the first layer 31 is reduced by the target gas surrounding the first layer 31. The target gas includes, for example, hydrogen. When the first layer 31 is reduced, for example, oxygen contained in the first layer 31 is released from the first layer 31. The structure of the first layer 31 changes. For example, the volume of the first layer 31 changes.

[0015] A change in the structure of the first layer 31 generates stress between the first layer 31 and the first support layer 31L. This stress is, for example, tensile stress. For example, the first layer 31 tries to contract relative to the first support layer 31L. This changes the shape of the first support portion 31s. This change in shape changes the distance between the movable portion 30M and the fixed electrode 55. The capacitance changes in accordance with the change in distance. By detecting the change in capacitance, the target gas can be detected. According to this embodiment, a sensor with high detection sensitivity can be provided.

[0016] As shown in Figure 1, the movable part 30M may include a movable electrode 35. The capacitance may be the capacitance between the fixed electrode 55 and the movable electrode 35.

[0017] Figure 2 is a graph illustrating the characteristics of the sensor according to the first embodiment. The horizontal axis of FIG. 2 is the concentration parameter CP1. The concentration parameter CP1 is the square root of the concentration of the gas to be detected. An increase in the concentration parameter CP1 corresponds to an increase in the concentration of the gas to be detected. The vertical axis is the change in capacitance ΔC. The change ΔC is based on the capacitance when the concentration of the gas to be detected is 0. A negative change ΔC corresponds to a decrease in capacitance.

[0018] As shown in FIG. 2, when the concentration parameter CP1 increases, the change in capacitance ΔC is negative and the absolute value of the change ΔC increases. That is, when the concentration of the gas to be detected increases, the capacitance decreases.

[0019] As shown in FIG. 2, the concentration of the gas to be detected in the first state ST1 (high concentration) is higher than the concentration of the gas to be detected in the second state ST2 (low concentration). The first capacitance between the fixed electrode 55 and the movable part 30M in the first state ST1 is smaller than the second capacitance between the fixed electrode 55 and the movable part 30M in the second state ST2.

[0020] Thus, the change in capacitance corresponds to the concentration of the gas to be detected. By detecting the change in capacitance, the gas to be detected can be detected. For example, the gas to be detected can be detected with high sensitivity of about 1 ppm to 10 ppm.

[0021] As shown in FIG. 1, the sensor 110 may further include a control unit 70. The control unit 70 can detect capacitance (for example, the first capacitance and the second capacitance, etc.).

[0022] The change in capacitance corresponds to the change in the distance dz between the fixed electrode 55 and the movable part 30M (movable electrode 35). For example, the first distance between the fixed electrode 55 and the movable part 30M in the first state ST1 (high concentration) is longer than the second distance between the fixed electrode 55 and the movable part 30M in the second state ST2 (low concentration). <0​​​

[0024] As described above, the change in distance dz may be based on the stress resulting from the change in the volume of the first layer 31. For example, the first volume of the first layer 31 in the first state ST1 (high concentration) is smaller than the second volume of the first layer 31 in the second state ST2 (low concentration).

[0025] As shown in Figure 1, in this example, the first support layer 31L is provided between the base 40 and the first layer 31. A second void G2 is provided between the base 40 and the first support layer 31L.

[0026] In this example, the sensor 110 further includes a first connection portion 31c. A portion of the first connection portion 31c is connected to a first support portion 31s. Another portion of the first connection portion 31c is connected to a movable portion 30M. A third gap G3 is provided between the base 40 and the first connection portion 31c. For example, the first connection portion 31c may have a meander structure.

[0027] As shown in Figure 1, the sensor 110 may include a second fixing portion 22 and a second support portion 32s. The base 40 further includes a third region 43. The first region 41 is located between the second region 42 and the third region 43. The second fixing portion 22 is fixed to the third region 43. The second support portion 32s is connected to the second fixing portion 22. The second support portion 32s includes a second support layer 32L and a second layer 32. The second layer 32 is fixed to the second support layer 32L.

[0028] The second layer 32 comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen. The second layer 32 comprises, for example, an oxide of the above metal. The second layer 32 comprises, for example, the above metal and acid Basic Includes combination with.

[0029] The movable part 30M is provided between the first support part 31s and the second support part 32s. The movable part 30M is supported by the first support part 31s and the second support part 32s. A fourth gap G4 is provided between the base body 40 and the second support part 32s. A cantilever beam type structure may be applied.

[0030] In this example, the sensor 110 further includes a second connection portion 32c. A portion of the second connection portion 32c is connected to a second support portion 32s. Another portion of the second connection portion 32c is connected to a movable portion 30M. A fifth gap G5 is provided between the base 40 and the second connection portion 32c. The second connection portion 32c has, for example, a meander structure.

[0031] As shown in Figure 1, the first support portion 31s may include a first conductive member 31h. The second support portion 32s may include a second conductive member 32h. For example, the temperature of the first support portion 31s can be increased by a current flowing through the first conductive member 31h. For example, the temperature of the second support portion 32s can be increased by a current flowing through the second conductive member 32h. For example, by heating the support portion, various substances (including hydrogen, for example) adsorbed on the first layer 31 and the second layer 32 can be released.

[0032] As shown in Figure 1, the first layer 31 includes a first surface F1 and a first portion P1. The first portion P1 is located between the first support layer 31L and the first surface F1. The first portion P1 is the center of the first layer 31 in a first direction D1 from the first support layer 31L to the first surface F1. The first direction D1 is, for example, the Z-axis direction. One direction perpendicular to the Z-axis direction is defined as the X-axis direction. The direction perpendicular to the Z-axis direction and the X-axis direction is defined as the Y-axis direction. The direction from the first support portion 31s to the movable portion 30M is, for example, the X-axis direction.

[0033] The ratio of the absolute difference between the first partial oxygen concentration in the first part P1 and the first surface oxygen concentration in the first surface F1 to the first partial oxygen concentration is between 0.1 and 10. The oxygen concentration is relatively uniform in the thickness direction of the first layer 31.

[0034] The thickness of the first layer 31 is, for example, 1 nm to 1 μm. The thickness of the first support layer 31L is, for example, 10 nm to 10 μm. m The following applies: The first support layer 31L contains, for example, silicon oxide.

[0035] Several examples of methods for manufacturing the sensor 110 are described below.

[0036] Figures 3(a) to 3(c) are schematic cross-sectional views illustrating a method for manufacturing a sensor according to the first embodiment. As shown in Figure 3(a), a first metal film 31M, which will become the first layer 31, is provided on the first support layer 31L. The first metal film 31M contains at least one metal selected from the group consisting of Pt, Pd, and Ti. A mask M1 (e.g., a resist layer) is formed on the first metal film 31M.

[0037] As shown in Figure 3(b), the first metal film 31M is processed using mask M1 as a mask. Dry etching or wet etching is performed during processing. After that, mask M1 is removed.

[0038] As shown in Figure 3(c), the first metal film 31M is oxidized by heat treatment in an oxygen atmosphere. The first layer 31 is obtained from the first metal film 31M.

[0039] Figures 4(a) to 4(c) are schematic cross-sectional views illustrating a method for manufacturing a sensor according to the first embodiment. As shown in Figure 4(a), a metal film is formed on the first support layer 31L in an oxygen-containing atmosphere. This yields a metal oxide layer 31A. As shown in Figure 4(b), a mask M1 is formed on the metal oxide layer 31A. As shown in Figure 4(c), the first layer 31 is obtained by processing the metal oxide layer 31A using the mask M1 as a mask.

[0040] Figures 5(a) to 5(c) are schematic cross-sectional views illustrating a method for manufacturing a sensor according to the first embodiment. As shown in Figure 5(a), a metal oxide layer 31A is formed on the first support layer 31L using a target containing a metal oxide. As shown in Figure 5(b), a mask M1 is formed on the metal oxide layer 31A. As shown in Figure 5(c), the first layer 31 is obtained by processing the metal oxide layer 31A using the mask M1 as a mask.

[0041] The target gas for detection is, for example, hydrogen. Hydrogen is produced from various resources, such as fossil fuels, by-product gases from factories, biomass, or renewable energy. Hydrogen is attracting attention as a clean energy source. Since hydrogen is a flammable gas, it is desirable to detect it with high sensitivity. For example, a high-speed, low-power hydrogen sensor is required.

[0042] For example, hydrogen is produced simultaneously with carbon monoxide during incomplete combustion. Detecting hydrogen can help detect the initial stages of a fire. For example, measuring hydrogen gas in exhaled breath can predict gut health. For example, highly sensitive hydrogen detection can advance healthcare. In these various applications, the concentration of hydrogen is low. For instance, detecting hydrogen at low concentrations of around 1 ppm is desirable.

[0043] There are resistive and semiconductor type hydrogen sensors. However, there are limitations to reducing power consumption in these hydrogen sensors.

[0044] In this embodiment, for example, the first layer 31 is reduced by the target gas (hydrogen). As a result, the first support portion 31s, which includes the first layer 31, deforms. This deformation of the first support portion 31s is detected, for example, as a change in electrical capacitance.

[0045] In this embodiment, the first layer 31 (sensitive film) contains a metal oxide. The metal oxide has catalytic properties. When a reducing gas such as hydrogen approaches the sensitive film, the film stress changes in the direction of the tensile stress. The concentration of oxygen in the sensitive film changes depending on the concentration (including presence or absence) of the target gas to be detected.

[0046] For example, when a reducing gas such as hydrogen approaches the sensitive film, hydrogen molecules dissociate into hydrogen atoms at the film surface. These hydrogen atoms reduce metal oxides, forming water and detaching. The frequency of this reaction depends on the hydrogen concentration. When the amount of oxygen in the sensitive film decreases, the film stress changes in the tensile direction.

[0047] In this embodiment, for example, the reducing action of a catalytic metal oxide is utilized. For instance, the metal oxide is reduced by the reducing gas to be detected. This changes the volume of the layer containing the catalyst metal. This change in volume is detected as a change in capacitance. By utilizing the reducing action, even extremely small concentrations of reducing gas, such as 1 ppm, can be detected with high sensitivity.

[0048] The embodiment may include the following configuration (e.g., proposed technical details). (Composition 1) A substrate including a first region and a second region, A fixed electrode fixed in the first region, The first fixing part fixed to the second region, A first support portion connected to the first fixed portion, the first support portion comprising a first support layer and a first layer fixed to the first support layer, wherein the first layer comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen, the first support portion, A movable part supported by the first support part, wherein a first gap is provided between the fixed electrode and the movable part, A sensor equipped with this feature.

[0049] (Configuration 2) The sensor according to configuration 1, wherein the first layer is reduced by the target gas surrounding the first layer.

[0050] (Composition 3) The sensor according to configuration 2, wherein the target gas for detection contains hydrogen.

[0051] (Composition 4) The concentration of the target gas in the first state is higher than the concentration of the target gas in the second state. The sensor according to configuration 1, wherein the first distance between the fixed electrode and the movable part in the first state is longer than the second distance between the fixed electrode and the movable part in the second state.

[0052] (Composition 5) The concentration of the target gas in the first state is higher than the concentration of the target gas in the second state. The sensor according to configuration 1, wherein the first volume of the first layer in the first state is smaller than the second volume of the first layer in the second state.

[0053] (Composition 6) The concentration of the target gas in the first state is higher than the concentration of the target gas in the second state. The sensor according to configuration 1, wherein the first capacitance between the fixed electrode and the movable part in the first state is smaller than the second capacitance between the fixed electrode and the movable part in the second state.

[0054] (Composition 7) The sensor according to configuration 6, further comprising a control unit capable of detecting the first electrical capacitance and the second electrical capacitance.

[0055] (Composition 8) The sensor according to any one of configurations 1 to 7, wherein the first layer comprises an oxide of the metal.

[0056] (Composition 9) The sensor according to any one of configurations 1 to 7, wherein the first layer includes a bond between the metal and oxygen.

[0057] (Composition 10) The first layer includes a first surface and a first portion, The first portion is located between the first support layer and the first surface, The first portion is the center of the first layer in a first direction from the first support layer to the first surface, The sensor according to any one of configurations 1 to 9, wherein the ratio of the absolute value of the difference between the first part concentration of oxygen in the first part and the first surface concentration of oxygen in the first surface to the first part concentration is 0.1 or more and 10 or less.

[0058] (Composition 11) The thickness of the first layer is 1 nm to 1 μm. mThe sensor described in one of the following configurations 1 to 10.

[0059] (Composition 12) The sensor according to configuration 11, wherein the thickness of the first support layer is 10 nm or more and 10 μm or less.

[0060] (Composition 13) The first support portion further includes a first conductive member, The sensor according to any one of configurations 1 to 12, wherein the temperature of the first support portion can be raised by the current flowing through the first conductive member.

[0061] (Composition 14) The sensor according to any one of configurations 1 to 13, wherein the first support layer comprises silicon oxide.

[0062] (Composition 15) The first support layer is provided between the substrate and the first layer. A sensor according to any one of configurations 1 to 14, wherein a second void is provided between the substrate and the first support layer.

[0063] (Composition 16) Further comprising a first connection section, A portion of the first connecting portion is connected to the first support portion, Another part of the first connection is connected to the movable part, The sensor according to configuration 15, wherein a third gap is provided between the base and the first connecting portion.

[0064] (Composition 17) The first connection portion is the sensor according to configuration 16, having a meander structure.

[0065] (Composition 18) The second fixing part, The second support section and Furthermore, The substrate further includes a third region, The first region is located between the second region and the third region. The second fixing part is fixed to the third region, The second support portion is connected to the second fixing portion, The second support portion includes a second support layer and a second layer fixed to the second support layer, wherein the second layer includes at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen. The movable part is provided between the first support part and the second support part and is further supported by the second support part, the sensor according to any one of configurations 1 to 17.

[0066] (Composition 19) Further equipped with a second connection section, A portion of the second connecting portion is connected to the second support portion, Another part of the second connection is connected to the movable part, The sensor according to configuration 18, wherein a gap is provided between the base and the second connecting portion.

[0067] (Composition 20) The second connection portion is the sensor according to configuration 19, having a meander structure.

[0068] According to this embodiment, a sensor with high detection sensitivity can be provided.

[0069] Embodiments of the present invention have been described above with reference to examples. However, the present invention is not limited to these examples. For example, the specific configuration of each element included in the sensor, such as the substrate, fixed part, support part, movable part, fixed electrode, and control unit, is included within the scope of the present invention as long as those skilled in the art can appropriately select from the known range to implement the present invention and obtain similar effects.

[0070] Combinations of two or more elements from each example, to the extent technically feasible, are also included within the scope of the present invention, insofar as they encompass the gist of the invention.

[0071] All sensors that a person skilled in the art can implement by appropriately modifying the design based on the sensors described above as embodiments of the present invention also fall within the scope of the present invention, insofar as they encompass the gist of the present invention.

[0072] Within the scope of the concept of this invention, a person skilled in the art would be able to conceive of various modifications and alterations, and it is understood that such modifications and alterations also fall within the scope of this invention.

[0073] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0074] 21, 22: First and second fixed parts, 30M: Movable part, 31, 32: First and second layers, 31A: Metal oxide layer, 31L, 32L: First and second support layers, 31M: First metal film, 31c, 32c: First and second connection parts, 31h, 32h: First and second conductive members, 31s, 32s: First and second support parts, 35: Movable electrode, 40: Substrate, 41-43: First to third regions, 55: Fixed electrode, 55a: Insulating film, 70: Control unit, 110: Sensor, CP1: Concentration parameter, D1: First direction, F1: First plane, G1-G5: First to fifth voids, M1: Mask, P1: First part, ST1, ST2: First and second states, dz: Distance ΔC: Change

Claims

1. A substrate including a first region and a second region, A fixed electrode fixed in the first region, The first fixing part fixed to the second region, A first support portion connected to the first fixed portion, the first support portion comprising a first support layer and a first layer fixed to the first support layer, wherein the first layer comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen, A movable part supported by the first support part, wherein a first gap is provided between the fixed electrode and the movable part, Equipped with, The first layer is reduced by the target gas surrounding the first layer, and is a sensor.

2. The sensor according to claim 1, wherein the gas to be detected includes hydrogen.

3. A substrate comprising a first region and a second region, A fixed electrode fixed in the first region, The first fixing part fixed to the second region, A first support portion connected to the first fixed portion, the first support portion comprising a first support layer and a first layer fixed to the first support layer, wherein the first layer comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen, A movable part supported by the first support part, wherein a first gap is provided between the fixed electrode and the movable part, Equipped with, The concentration of the target gas in the first state is higher than the concentration of the target gas in the second state. A sensor in which the first distance between the fixed electrode and the movable part in the first state is longer than the second distance between the fixed electrode and the movable part in the second state.

4. A substrate comprising a first region and a second region, A fixed electrode fixed in the first region, The first fixing part fixed to the second region, A first support portion connected to the first fixed portion, the first support portion comprising a first support layer and a first layer fixed to the first support layer, wherein the first layer comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen, A movable part supported by the first support part, wherein a first gap is provided between the fixed electrode and the movable part, Equipped with, The concentration of the target gas in the first state is higher than the concentration of the target gas in the second state. A sensor in which the first volume of the first layer in the first state is smaller than the second volume of the first layer in the second state.

5. A substrate comprising a first region and a second region, A fixed electrode fixed in the first region, The first fixing part fixed to the second region, A first support portion connected to the first fixed portion, the first support portion comprising a first support layer and a first layer fixed to the first support layer, wherein the first layer comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen, A movable part supported by the first support part, wherein a first gap is provided between the fixed electrode and the movable part, Equipped with, The concentration of the target gas in the first state is higher than the concentration of the target gas in the second state. A sensor in which the first capacitance between the fixed electrode and the movable part in the first state is smaller than the second capacitance between the fixed electrode and the movable part in the second state.

6. The sensor according to claim 5, further comprising a control unit capable of detecting the first capacitance and the second capacitance.

7. A substrate comprising a first region and a second region, A fixed electrode fixed in the first region, The first fixing part fixed to the second region, A first support portion connected to the first fixed portion, the first support portion comprising a first support layer and a first layer fixed to the first support layer, wherein the first layer comprises at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen, A movable part supported by the first support part, wherein a first gap is provided between the fixed electrode and the movable part, Equipped with, The first layer includes a first surface and a first portion, The first portion is located between the first support layer and the first surface, The first portion is the center of the first layer in a first direction from the first support layer to the first surface, A sensor in which the ratio of the absolute value of the difference between the first part concentration of oxygen in the first part and the first surface concentration of oxygen in the first surface to the first part concentration is 0.1 or more and 10 or less.

8. The first support layer is provided between the substrate and the first layer. The sensor according to claim 1, wherein a second void is provided between the substrate and the first support layer.

9. The second fixing part and The second support section and Furthermore, The substrate further includes a third region, The first region is located between the second region and the third region. The second fixing portion is fixed to the third region, The second support portion is connected to the second fixing portion, The second support portion includes a second support layer and a second layer fixed to the second support layer, wherein the second layer includes at least one metal selected from the group consisting of Pt, Pd, and Ti, and oxygen. The sensor according to claim 1, wherein the movable part is provided between the first support part and the second support part and is further supported by the second support part.

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