Gas sensor

Abstract

To provide a gas sensor capable of enhancing adhesion between an electrode layer and a sensitive layer.SOLUTION: A gas sensor 100 comprises: an isolation layer 20; an electrode layer 30 laminated on the isolation layer 20; and a sensitive layer 40 laminated on the electrode layer 30 and reacting to gas to be measured. In the gas sensor 100, the isolation layer 20 comprises: a first insulation part 21; a second insulation 22 having a thickness in a laminating direction greater than that of the first insulation 21; and a third insulation part 23 which is a portion where the thickness in the laminating direction has changed, and is disposed between the first insulation part 21 and the second insulation part 22. The electrode layer 30 comprises: a first electrode part 31 laminated on the first insulation part 21; and a second electrode part 32 laminated on the second insulation part 22. A gap S in which the third insulation part 23 is exposed, is disposed between an end face 31C of the first electrode part 31 and an end face 32C2 of the second electrode part 32. The sensitive layer 40 is in contact with a portion of the end face 31C and a portion of the end face 32C2. A portion of the sensitive layer 40 is disposed in the gap S.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, as a sensor, the technology described in Patent Document 1 is known. Specifically, Patent Document 1 discloses a sensor in which a first Au layer is formed on a silicon substrate, and a second Au layer is formed by separating it from the first Au layer using Al2O3, thereby forming a nanogap corresponding to the thickness of Al2O3. When a solution is injected between the nanogaps, this sensor can detect a specific substance through changes in the electrical characteristics at both ends of the nanogap.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration disclosed in Patent Document 1, improvement in the detection sensitivity of a specific substance is desired. Therefore, in the sensor, for example, it is conceivable to provide a sensitive layer (sensitive film) that is in contact with two electrode layers (metal layers) and reacts with a specific substance. In this case, it is said that the adhesion between the electrode layer and the sensitive layer should be high, and improvement in adhesion is desired.

[0005] The present disclosure is a technology completed based on the above circumstances, and an object thereof is to provide a gas sensor capable of improving the adhesion between an electrode layer and a sensitive layer.

Means for Solving the Problems

[0006] The gas sensor of the present disclosure is a gas sensor including an insulating layer, an electrode layer laminated on the insulating layer, and a sensitive layer laminated on the electrode layer and reacting with a gas to be measured, wherein the insulating layer includes a first insulating portion, a second insulating portion having a thickness greater than that of the first insulating portion in the stacking direction in which the insulating layer, the electrode layer, and the sensitive layer are stacked, and a third insulating portion disposed between the first insulating portion and the second insulating portion and being a portion where the thickness changes in the stacking direction; the electrode layer includes a first electrode portion laminated on the first insulating portion and a second electrode portion laminated on the second insulating portion; a gap where the third insulating portion is exposed is disposed between an end face of the first electrode portion and an end face of the second electrode portion; and the sensitive layer is in contact with a part of an end face of the first electrode portion and a part of an end face of the second electrode portion, and a part of the sensitive layer is disposed in the gap.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide a gas sensor capable of improving the adhesion between the electrode layer and the sensitive layer.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] First, embodiments of the present disclosure will be listed and described. (1) The gas sensor of the present disclosure is a gas sensor including an insulating layer, an electrode layer laminated on the insulating layer, and a sensitive layer laminated on the electrode layer and reacting with a gas to be measured, wherein the insulating layer includes a first insulating portion, a second insulating portion having a thickness greater than that of the first insulating portion in the stacking direction in which the insulating layer, the electrode layer, and the sensitive layer are stacked, and a third insulating portion disposed between the first insulating portion and the second insulating portion and being a portion where the thickness changes in the stacking direction. The electrode layer includes a first electrode portion laminated on the first insulating portion and a second electrode portion laminated on the second insulating portion. A gap where the third insulating portion is exposed is provided between the end surfaces of the first electrode portion and the second electrode portion. The sensitive layer is in contact with a part of the end surface of the first electrode portion and a part of the end surface of the second electrode portion, and a part of the sensitive layer is disposed in the gap.

[0010] (2) In the gas sensor according to (1), the end surfaces of the first electrode portion and the second electrode portion may have a curved portion when viewed from the stacking direction.

[0011] (3) In the gas sensor according to (1) or (2), the end surfaces of the first electrode portion and the second electrode portion may be inclined with respect to the stacking direction.

[0012] (4) In the gas sensor according to any one of (1) to (3), at least one of silicon nitride and silicon oxide is used as the material of the insulating layer, and platinum may be used as the material of the electrode layer.

[0013] <Embodiment> Embodiments of the present disclosure will be described with reference to FIG. 1 and the like. In this embodiment, a gas sensor 100 capable of detecting a specific gas (gas to be measured) will be exemplified. In FIGS. 2 and 3, the Z direction is the stacking direction, and the X direction perpendicular to the Z direction is the horizontal direction. Also, in FIGS. 1 and 4, the front side of the paper is the front side (upper side in the stacking direction) of the gas sensor 100, and in FIGS. 2 and 3, the upper side of the paper is the front side (upper side in the stacking direction) of the gas sensor 100. The back side of the paper in FIGS. 1 and 4 and the lower side of the paper in FIGS. 2 and 3 are the back side (lower side in the stacking direction) of the gas sensor 100.

[0014] As shown in FIG. 1, the gas sensor 100 includes a flat substrate 10, a laminate 11 laminated on the surface of the substrate 10, and a first wiring 15 and a second wiring 16 disposed on the surface of the substrate 10 and connected to the laminate 11. The substrate 10 is made of, for example, silicon. The gas sensor 100, together with the power supply 2 and the ammeter 3, constitutes the gas sensor device 1. The power supply 2 is connected to the first wiring 15 and the ammeter 3. The ammeter 3 is connected to the second wiring 16.

[0015] As shown in FIG. 2, the laminate 11 includes an insulating layer 20 laminated on the substrate 10 (disposed above the substrate 10) and an electrode layer 30 laminated on the insulating layer 20 (disposed above the insulating layer 20). A sensitive layer 40 is laminated above the electrode layer 30.

[0016] The insulating layer 20 includes a first insulating portion 21, a second insulating portion 22 having a thickness L2 in the stacking direction (Z direction) in which the insulating layer 20, the electrode layer 30, and the sensitive layer 40 are laminated is thicker than the thickness L1 of the first insulating portion 21, and a third insulating portion 23 disposed between the first insulating portion 21 and the second insulating portion 22 and having a varying thickness in the stacking direction. The third insulating portion 23 is a stepped portion that forms a stepped portion in the insulating layer 20. As shown in FIG. 3, the third insulating portion 23 includes a low surface 23A that is a plane continuous with the upper surface 21A of the first insulating portion 21, a standing upper surface 23B that is a plane rising upward in the stacking direction from the low surface 23A, and a high surface 23C that is a plane continuous with the upper surface 22A of the second insulating portion 22 and the standing upper surface 23B and is disposed above the low surface 23A (disposed at a higher position than the low surface 23A) in the stacking direction.

[0017] The electrode layer 30 includes a first electrode portion 31 laminated on the upper surface 21A of the first insulating portion 21 and a second electrode portion 32 laminated on the upper surface 22A of the second insulating portion 22. The first wiring 15 shown in FIG. 1 is connected to the first electrode portion 31. The second wiring 16 is connected to the second electrode portion 32. As shown in FIG. 3, the second electrode portion 32 is in contact with the standing upper surface 23B and the high surface 23C of the third insulating portion 23. A gap S is provided between the end surface 31C of the first electrode portion 31 and the end surface (lower end surface) 32C2 of the second electrode portion 32, where the low surface 23A of the third insulating portion 23 is exposed toward the sensing layer 40 side.

[0018] The end surface 31C of the first electrode portion 31 and the lower end surface 32C2 of the second electrode portion 32 face each other and are inclined with respect to the stacking direction. The end surface 31C in the first electrode portion 31 is a surface that rises from the upper surface 31A with the corner portion 31B as a base point, and is inclined so as to approach the standing upper surface 23B more as it goes downward in the stacking direction. The second electrode portion 32 includes end surfaces 32C1 and 32C2 that rise from the upper surface 32A with the curved surface 32B as a base point. The end surfaces 32C1 and 32C2 include an upper end surface 32C1 continuous with the curved surface 32B and a lower end surface 32C2 that is disposed below the upper end surface 32C1, is continuous with the upper end surface 32C1, and is in contact with the third insulating portion 23. The end surfaces 32C1 and 32C2 are inclined so as to approach the standing upper surface 23B more as they go downward in the stacking direction. The lower end surface 32C2 is more inclined with respect to the stacking direction so as to be closer to the standing upper surface 23B than the upper end surface 32C1.

[0019] As shown in FIG. 4, when the gap S of the electrode layer 30 and its peripheral portion are viewed from above in the stacking direction, the end face 31C of the first electrode portion 31 and the upper end face 32C1 of the second electrode portion 32 each have curved portions 31D and 32D. The curved portions 31D and 32D are not parallel to the orthogonal line Y orthogonal to the stacking direction (the depth direction of the paper surface of FIG. 4), but are curved portions. The curved portion 31D corresponds to the upper end portion (corner portion 31B) of the end face 31C shown in FIG. 3. The curved portion 32D corresponds to the upper end portion (curved surface 32B) of the upper end face 32C1. The distance of the gap S (the distance between the end face 31C and the lower end face 32C2) is on the order of nanometers. The distance of this gap S may be, for example, 1 nm or more and less than 1000 nm, may be less than 100 nm, or may be several tens of nm.

[0020] Platinum is used as the material for the electrode layer 30 and the respective wirings 15 and 16. Note that the material for the electrode layer 30 and the respective wirings 15 and 16 is not limited to platinum, and a conductive material can be adopted. For example, one or two or more of metals such as aluminum, copper, and gold can be adopted. As the material for the insulating layer 20, at least one of silicon nitride (for example, Si3N4) and silicon oxide (for example, SiO2) is used. Note that the material for the insulating layer 20 is not limited to these, and a non-conductive material can be adopted. A heater capable of heating the stacked body 11 may be provided inside the insulating layer 20.

[0021] As shown in FIGS. 2 and 3, the gas sensor 100 includes a sensitive layer 40 laminated on the electrode layer 30 and reacting to the gas to be measured. The sensitive layer 40 includes a first sensitive portion 41 disposed above the upper surface 31A of the first electrode portion 31, a second sensitive portion 42 disposed above the upper surface 32A of the second electrode portion 32 and above the first sensitive portion 41 in the stacking direction, and a third sensitive portion 43 disposed between the first sensitive portion 41 and the second sensitive portion 42. The third sensitive portion 43 includes a main body portion 43A continuous with the first sensitive portion 41 and the second sensitive portion 42, and a bulging portion 43B bulging in a shape that enters the gap S from the main body portion 43A. The main body portion 43A is in contact with the curved surface 32B and the upper end surface 32C1. The bulging portion 43B is in contact with a part of the end surface 31C of the first electrode portion 31 (corner portion 31B and curved portion 31D) and a part of the lower end surface 32C2 of the second electrode portion 32 (the upper end portion of the lower end surface 32C2), and the bulging portion 43B (a part of the sensitive layer 40) is disposed in the gap S. The lower end (lower surface) of the bulging portion 43B is located below the upper surface 31A of the first electrode portion 31 in the stacking direction. A low surface 23A is disposed below the bulging portion 43B.

[0022] The sensitive layer 40 is configured such that its electrical characteristics (e.g., resistance value) change in response to a specific gas (the gas to be measured). The material of the sensitive layer 40 may be appropriately selected according to the gas to be detected and is not particularly limited. For example, an oxide semiconductor film can be adopted. As the oxide semiconductor film, any one of ZnO, SnO2, WO3, In2O3, TiO2, and V2O5 can be adopted. In the gas sensor 100, when a specific gas reacts with the sensitive layer 40 and the resistance value of the sensitive layer 40 changes, in the gas sensor device 1, the current value of the ammeter 3 connected to the power supply 2 changes. Thereby, the gas sensor device 1 can detect a specific gas.

[0023] The manufacturing method of the gas sensor 100 is not particularly limited. For example, it may include a first step of forming a laminate 11 on a substrate 10 and a second step of forming a sensitive layer 40 on the laminate 11. In the first step, an insulating layer 20 may be formed on the substrate 10, and an electrode layer 30 may be formed on the insulating layer 20. In this case, when forming the electrode layer 30 on the insulating layer 20 in the first step, the laminate 11 may be heated (annealing treatment is performed), and the portion disposed on the first insulating portion 21 (the first electrode portion 31) and the portion disposed on the second insulating portion 22 (the second electrode portion 32) in the electrode layer 30 may be cracked by the heating to form a gap S. Thereby, the manufacturing process of the gas sensor 100 having the gap S as a nanogap can be simplified, and cost reduction and shortening of the manufacturing time can be achieved.

[0024] Subsequently, the effects of the present embodiment will be described. The gas sensor 100 of the present embodiment is a gas sensor 100 including an insulating layer 20, an electrode layer 30 laminated on the insulating layer 20, and a sensitive layer 40 laminated on the electrode layer 30 and reacting to the gas to be measured. The insulating layer 20 includes a first insulating portion 21, a second insulating portion 22 having a thickness in the stacking direction in which the insulating layer 20, the electrode layer 30, and the sensitive layer 40 are stacked being thicker than that of the first insulating portion 21, and a third insulating portion 23 disposed between the first insulating portion 21 and the second insulating portion 22 and having a varying thickness in the stacking direction. The electrode layer 30 includes a first electrode portion 31 laminated on the first insulating portion 21 and a second electrode portion 32 laminated on the second insulating portion 22. A gap S in which the third insulating portion 23 is exposed is disposed between the end face 31C of the first electrode portion 31 and the end face 32C2 of the second electrode portion 32. The sensitive layer 40 is in contact with a part of the end face 31C of the first electrode portion 31 and a part of the end face 32C2 of the second electrode portion 32, and a part of the sensitive layer 40 is disposed in the gap S.

[0025] According to such a gas sensor 100, since the sensitive layer 40 is in contact with a part of the end face 31C of the first electrode portion 31 and a part of the end face of the second electrode portion, and a part of the sensitive layer 40 is disposed in the gap S, the anchor effect can be exerted in the gap S of the electrode layer 30, thereby improving the adhesion between the electrode layer 30 and the sensitive layer 40.

[0026] The end face 31C of the first electrode portion 31 and the end face 32C1 of the second electrode portion 32 have bent portions 31D and 32D when viewed in the stacking direction.

[0027] According to such a gas sensor 100, at a portion where the sensing layer 40 is in contact with a part of the end faces 31C and 32C1 of the electrode portions 31 and 32, it is possible to improve the anchor effect and increase the contact area, and thus further improve the adhesion between the electrode layer 30 and the sensing layer 40.

[0028] The end face 31C of the first electrode portion 31 and the end face 32C2 of the second electrode portion 32 are inclined with respect to the stacking direction.

[0029] According to such a gas sensor 100, for example, compared with the case where the end faces 31C and 32C2 of the electrode portions 31 and 32 constituting the gap S extend in the stacking direction, at a portion where the sensing layer 40 is in contact with the inclined surfaces of the electrode portions 31 and 32, it is possible to improve the anchor effect and increase the contact area, and thus improve the adhesion between the electrode layer 30 and the sensing layer 40.

[0030] As the material of the insulating layer 20, at least one of silicon nitride and silicon oxide is used, and as the material of the electrode layer 30, platinum is used.

[0031] According to such a configuration, a practical gas sensor 100 can be obtained.

[0032] <Other Embodiments> The present disclosure is not limited to the embodiments described above with reference to the description and the drawings. For example, the following embodiments are also included in the technical scope of the present disclosure, and various modifications can be made without departing from the gist of the present disclosure other than those described below.

[0033] (1) In addition to the above-described embodiments, the configuration of the third insulating portion and the gap can be appropriately changed. The gas sensor may be configured such that the standing surface or the high surface of the third insulating portion is exposed from the gap, or the entire upper surface (low surface, standing surface, and high surface) of the third insulating portion may be exposed from the gap. Further, a plurality of third insulating portions and gaps may be provided. The third insulating portion may have a convex or concave shape with two standing surfaces. The standing surface may rise perpendicular to the low surface, or may be inclined or curved with respect to the stacking direction.

[0034] (2) The configuration of the sensing layer can be appropriately changed. The sensing layer may be disposed in the gap so as to fill the gap. In that case, the sensing layer may be in contact with the third insulating portion.

[0035] (3) The configuration of the wiring can be appropriately changed. In the above-described embodiment, the wiring is routed to be connected to both lateral sides (left and right sides of the paper surface in FIG. 1) of the laminate, but is not limited thereto. For example, the wiring may be routed to be connected to the front side of the laminate (lower side of the paper surface in FIG. 1).

[0036] (4) In the gas sensor device, the device for measuring the electrical characteristics is not limited to an ammeter for measuring current, and various measuring instruments for measuring electrical characteristics such as a voltmeter and an ohmmeter may be employed.

Description of Reference Numerals

[0037] 1... Gas sensor device, 20... Insulating layer, 21... First insulating portion, 22... Second insulating portion, 23... Third insulating portion, 30... Electrode layer, 31... First electrode portion, 31C... End face, 31D, 32D... Curved portion, 32... Second electrode portion, 32C2... End face, 40... Sensing layer, 100... Gas sensor, S... Gap

Claims

1. An insulating layer, An electrode layer laminated on the insulating layer, A gas sensor comprising a sensing layer laminated on the electrode layer and reacting with a gas to be measured, The insulating layer is A first insulating portion, A second insulating portion having a thickness greater than that of the first insulating portion in the stacking direction in which the insulating layer, the electrode layer, and the sensing layer are stacked, A third insulating portion disposed between the first insulating portion and the second insulating portion and having a variable thickness in the stacking direction, The electrode layer is A first electrode portion laminated on the first insulating portion, A second electrode portion laminated on the second insulating portion, A gap is provided between the end faces of the first electrode portion and the second electrode portion, through which the third insulating portion is exposed, The sensing layer is in contact with a part of the end face of the first electrode portion and a part of the end face of the second electrode portion, and a part of the sensing layer is disposed in the gap. A gas sensor.

2. The end faces of the first electrode portion and the second electrode portion have curved portions when viewed from the stacking direction. The gas sensor according to claim 1.

3. The end faces of the first electrode portion and the second electrode portion are inclined with respect to the stacking direction. The gas sensor according to claim 1 or claim 2.

4. As the material of the insulating layer, at least one of silicon nitride and silicon oxide is used, As the material of the electrode layer, platinum is used. The gas sensor according to claim 1 or claim 2.

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