JP2018205078A - Semiconductor gas detection element and manufacturing method of semiconductor gas detection element - Google Patents

Abstract

A semiconductor gas detection element capable of improving the selectivity of a gas to be detected is provided. The semiconductor gas detection element 100 is heated by a substrate 1, a detection gas detection electrode 2 including a heater portion disposed on the substrate 1 so that an upper surface is exposed, and a heater portion. A sensitive portion 3 that contacts the detection gas, and the sensitive portion 3 is adjacent to the detection electrode 2 in the direction along the surface of the substrate 1 and is in contact with the inner surface of the detection electrode 2 on the substrate 1. Is arranged. [Selection] Figure 1

Description

  The present invention relates to a semiconductor gas detection element and a method for manufacturing a semiconductor gas detection element, and more particularly to a semiconductor gas detection element including a substrate and a method for manufacturing the semiconductor gas detection element.

  Conventionally, a semiconductor type gas detection element provided with a substrate is known (for example, refer to patent documents 1).

  Patent Document 1 discloses a semiconductor-type gas detection element including a substrate, a detection electrode, a heater provided in the substrate, and a gas sensitive part disposed on the substrate in contact with the detection electrode. .

Japanese Patent Laid-Open No. 2006-70704

  In the field of the semiconductor gas detection element disclosed in Patent Document 1, it has been desired to improve the selectivity of the gas to be detected (property to appropriately select the target gas to be detected from the atmosphere gas). ing. Specifically, in a gas sensor using a semiconductor gas detection element, if a flammable gas (for example, an interfering gas such as alcohol or hydrogen) having a lower combustion temperature than the gas to be detected (for example, methane) exists, Even if the concentration does not reach the predetermined threshold value, if the detected gas exists, it may be erroneously detected. Therefore, there is a problem to improve the selectivity of the detected gas.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a semiconductor type gas detection element capable of improving the selectivity of a gas to be detected. It is.

  A semiconductor gas detection element according to a first aspect of the present invention is heated by a substrate, a detection electrode of a detection gas including a heater portion arranged on the substrate so that the upper surface is exposed, and a detection target. A sensitive portion that contacts the gas, and the sensitive portion is disposed on the substrate in a direction along the surface of the substrate, adjacent to the detection electrode and in contact with the side surface of the detection electrode.

  In the semiconductor-type gas detection element according to the first aspect of the present invention, as described above, the detection electrode of the gas to be detected including the heater unit disposed on the substrate so that the upper surface is exposed, and the heater unit are heated, A sensitive portion that is in contact with the gas to be detected, and the sensitive portion is disposed on the substrate adjacent to the detection electrode and in contact with the side surface of the detection electrode in a direction along the surface of the substrate. Thereby, since the detection electrode contains the heater part, the upper surface which a detection electrode exposes can be heated. For this reason, since the flammable gas can be burned and removed on the upper surface of the detection electrode, the concentration of the flammable gas with respect to the detected gas can be lowered. As a result, the selectivity of the gas to be detected can be improved. Further, if almost all of the upper surface of the detection electrode is exposed, the flammable gas can be burned and removed more effectively than in the case where a part of the upper surface of the detection electrode is not exposed. Therefore, the selectivity of the gas to be detected can be improved more effectively. Further, since the detection electrode includes the heater part, the sensitive part can be heated from the side surface via the side surface of the detection electrode.

  In the semiconductor gas detection element according to the first aspect, preferably, the detection electrode is formed of a detection electrode pattern having a meandering shape on the substrate, and the sensitive portion is arranged to be filled between the detection electrode patterns. Has been. If comprised in this way, the length of a detection electrode can be ensured large without enlarging the area of a board | substrate by meandering a detection electrode on a board | substrate. For this reason, it is possible to further reduce the size of the semiconductor gas detection element. In addition, the semiconductor gas detection element can be configured so that the detection electrode pattern and the sensitive portion are in contact with each other in a larger area by meandering the detection electrode on the substrate and disposing the sensitive portion between the detection electrodes. it can.

  In this case, it is preferable that the detection electrode pattern having a meandering shape is connected to a plurality of first portions arranged adjacent to each other substantially in parallel in a plan view, and a second portion connecting ends of the first portions adjacent to each other. The sensitive portion is disposed between the detection electrode patterns in contact with the inner surface of the first portion and the inner surface of the second portion that are adjacent to each other. If comprised in this way, since the circumference | surroundings of a sensitive part can be substantially enclosed by the 1st part which mutually adjoins, and the 2nd part which connects the edge part of a 1st part, the heat | fever from a detection electrode is efficient. Can be transmitted to the sensitive part to heat the sensitive part efficiently.

  In the semiconductor gas detection element according to the first aspect, preferably, the sensitive portion has a thickness larger than that of the detection electrode. With this configuration, the contact area between the sensitive portion and the detection electrode can be secured larger than when the thickness of the sensitive portion is smaller than the thickness of the detection electrode. Can be transmitted to the sensitive part and the sensitive part can be heated. Moreover, since the surface area which contacts the gas of a sensitive part can be enlarged compared with the case where the thickness of a sensitive part is smaller than the thickness of a detection electrode, gas sensitivity can be raised.

  The semiconductor-type gas detection element according to the first aspect is preferably a MEMS sensor formed using MEMS technology. If comprised in this way, since a semiconductor type gas detection element can be reduced in size, when an electric current is sent and heated to the detection electrode containing a heater part, a flammable gas can be combusted with a small amount of electric current. The temperature of the sensing electrode can be increased to the temperature. Moreover, the temperature of the sensitive part can be raised through the detection electrode to a temperature at which the gas to be detected can be detected with a small amount of current. That is, it is possible to save power of the gas sensor including the semiconductor type gas detection element.

  According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor gas detection element, wherein a detection electrode pattern of a detection gas including a heater portion disposed on a substrate is formed so as to be water-repellent and exposed on an upper surface. And a step of forming a sensitive part by filling a semiconductor paste between detection electrode patterns.

  In the method of manufacturing a semiconductor type gas detection element according to the second aspect of the present invention, as described above, the step of forming the detection electrode pattern of the detection gas including the heater portion arranged on the substrate so that the upper surface is exposed. And a step of forming a sensitive part by filling a semiconductor paste between detection electrode patterns. Thereby, since the detection electrode pattern includes the heater part, the upper surface where the detection electrode pattern is exposed can be heated. For this reason, since the flammable gas can be burned and removed on the upper surface of the detection electrode pattern, the concentration of the flammable gas with respect to the detected gas can be lowered. As a result, the selectivity of the gas to be detected can be improved. Further, if almost all of the upper surface of the detection electrode is exposed, the flammable gas can be burned and removed more effectively than in the case where a part of the upper surface of the detection electrode is not exposed. Therefore, the selectivity of the gas to be detected can be improved more effectively.

  According to the present invention, the selectivity of the gas to be detected can be improved as described above.

It is the top view which showed the whole structure of the semiconductor type gas detection element by one Embodiment of this invention. 1 is a schematic cross-sectional view illustrating an overall configuration of a semiconductor gas detection element according to an embodiment of the present invention. It is sectional drawing along the 500-500 line | wire of FIG. It is sectional drawing along the 600-600 line of FIG. It is an enlarged view of the X section of FIG. It is a circuit diagram of the gas sensor containing the semiconductor type gas detection element by one Embodiment of this invention. It is the figure which showed the manufacturing process of the 1st step of the semiconductor type gas detection element by one Embodiment of this invention in order to (a)-(d). It is the figure which showed the manufacturing process of the 2nd step of the semiconductor type gas detection element by one Embodiment of this invention in order to (a)-(c). It is the top view which showed the whole structure of the semiconductor type gas detection element by a comparative example. It is the graph which showed the relationship between the gas concentration of the semiconductor type gas detection element by a comparative example, and a sensor output. It is the graph which showed the relationship between the gas concentration of the semiconductor type gas detection element by the Example of this invention, and a sensor output.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.

  With reference to FIGS. 1-8, the structure of the semiconductor type gas detection element 100 by one Embodiment of this invention is demonstrated.

(Configuration of semiconductor gas detector)
As shown in FIG. 1, the semiconductor gas detection element 100 includes a substrate 1, a detection electrode 2, and a sensitive part 3. The detection electrode 2 and the sensitive portion 3 are in contact with one surface of the substrate 1 (surface on the A1 direction side described later). The semiconductor gas detection element 100 is provided with a lead wire 4 disposed on the substrate 1.

  In FIG. 1, for convenience, the sensitive unit 3 is hatched. The hatching in FIG. 1 does not show a cross section.

  The semiconductor gas detection element 100 is formed by a MEMS (Micro Electro Mechanical Systems) technique that is a technique for manufacturing an ultra-fine electronic component. That is, the semiconductor gas detection element 100 is an extremely small element (MEMS sensor) formed based on a semiconductor manufacturing process or the like. The semiconductor gas detection element 100 (a supported portion 11a to be described later of the substrate 1) has, for example, a rectangular (substantially square) flat plate shape with a side L of about 0.1 mm.

  The semiconductor gas detection element 100 is connected to a power supply unit (not shown) and is configured to be supplied with current from the power supply unit. For example, the semiconductor gas detection element 100 is configured such that a pulse current is supplied from a small-sized lithium ion battery as a power supply unit for 0.1 seconds every 10 seconds (in a cycle of 10 seconds).

  The semiconductor gas detection element 100 is used for detection of a gas to be detected, which is performed by measuring the electrical resistance between both ends 21 of the detection electrode 2 with a voltmeter (not shown). The electrical resistance between both ends 21 of the detection electrode 2 is a combined resistance of the detection electrode 2 and the sensitive part 3. The circuit configuration will be described later.

(Substrate structure)
As shown in FIG. 1, a substrate 1 includes an insulating film 11 provided on one surface side of the substrate 1 and a support substrate portion 12 that supports the insulating film 11 in contact with the A2 direction described below (see FIG. 2). ). The insulating film 11 is made of, for example, silicon dioxide. The support substrate portion 12 is made of, for example, a material whose main component is silicon (silicon).

  The insulating film 11 includes a supported portion 11a disposed on one surface side (A1 direction side described below) and a supporting portion 11b that supports the supported portion 11a while the detection electrode 2 and the sensitive portion 3 are in contact with each other. Contains.

  Here, in the following description, the thickness direction of the substrate 1 is the A direction, the insulating film 11 side of the substrate 1 is the A1 direction, and the opposite direction of the A1 direction is the A2 direction. Further, a direction in which a pair of one end faces 10a of the supported portion 11a of the substrate 1 which are orthogonal to the A direction extend is defined as a B direction. In addition, a direction in which a pair of the other end surfaces 10b of the supported portion 11a of the substrate 1 which are orthogonal to the A direction extends is defined as a C direction. That is, let the direction orthogonal to the A direction and the B direction be the C direction. The B direction and the C direction are directions along the surface of the substrate 1.

  The supported portion 11a has a rectangular shape in plan view (viewed from the direction A). As shown in FIG. 2, the support substrate portion 12 is provided with a recess 12a that is recessed in the A2 direction in a range that overlaps the supported portion 11a in the A direction and a predetermined range that surrounds the range that overlaps the supported portion 11a. ing. That is, the supported portion 11a and the support substrate portion 12 are arranged with a space therebetween and are separated from each other.

  As shown in FIG. 1, the support part 11b is provided with two or more (four pieces). In addition, each of the plurality of support portions 11b has one inner end connected to different corners (corner portions) of the rectangular supported portion 11a. In addition, one end of each of the plurality of support portions 11b (on the side opposite to the side connected to the supported portion 11a) is fixed to the support substrate portion 12. Further, as shown in FIG. 2, as described above, since the support substrate portion 12 and the supported portion 11a are separated from each other by the recess 12a, the supported portion 11a is supported in a floating state by the support portion 11b. ing. Moreover, as shown in FIG. 1, the some support part 11b is integrally formed with the to-be-supported part 11a. Each of the plurality of support portions 11b has an L shape that is bent in the same direction (counterclockwise as viewed from the A1 direction side) centered on the supported portion 11a in plan view (viewed from the A direction). Have.

(Lead wire configuration)
As shown in FIG. 1, the lead wire 4 is provided on the A1 direction side on the support portion 11b connected to the corner portion (corner portion) on the B1 direction side and the C1 direction side of the supported portion 11a. The lead wire 4 is also provided on the A1 direction side on the support portion 11b connected to the corner portion (corner portion) on the B2 direction side and the C2 direction side of the supported portion 11a. That is, the two lead wires 4 are respectively provided on the pair of support portions 11b facing each other in the diagonal direction of the supported portion 11a. The lead wire 4 is disposed on the surface of the substrate 1 in contact with the substrate 1 (insulating film 11).

(Configuration of detection electrode)
As a material of the detection electrode 2 shown in FIG. 1, for example, platinum or gold can be used, but is not particularly limited thereto. The detection electrode 2 is disposed on the A1 direction side on the substrate 1 (insulating film 11) in contact with the sensitive portion 3. The detection electrode 2 is arranged on the surface of the substrate 1 in contact with the substrate 1 (insulating film 11). The detection electrode 2 is formed integrally with the lead wire 4 (see FIG. 1). Further, the detection electrode 2 is formed thinner than the lead wire 4 and is configured to have an electric resistance larger than that of the lead wire 4.

  As shown in FIG. 1, the detection electrode 2 is formed of a detection electrode pattern P having a meandering shape on the substrate 1.

  Specifically, the detection electrode 2 (detection electrode pattern P) includes a plurality of first portions 22 each having a rectangular flat plate shape whose longitudinal direction is the B direction and a plurality of first portions having a rectangular flat plate shape having the C direction as the longitudinal direction. The two portions 23 are included, and a plurality of first portions 22 and a plurality of second portions 23 are alternately connected to form a meandering shape. The plurality of first portions 22 are arranged adjacent to each other in the C direction so as to be substantially parallel to each other in plan view. In FIG. 1, the detection electrode 2 includes nine first portions 22 as an example. The plurality of first portions 22 are arranged at substantially equal intervals in the C direction. Further, each of the plurality of first portions 22 extends linearly in the B direction. Each of the plurality of first portions 22 extends from the vicinity of the end portion on the B1 direction side of the supported portion 11a of the substrate 1 to the vicinity of the end portion on the B2 direction side.

  The second portion 23 is configured to connect the ends of the first portions 22 adjacent to each other. The plurality of second portions 23 alternately connect one end and the other end of the first portion 22 in the C direction. Further, the size D1 of the second portion 23 in the longitudinal direction (C direction) is smaller than the size D2 of the first portion 22 in the longitudinal direction (B direction).

  The plurality of second portions 23 and the first portion 22 at the C1 direction end portion and the C2 direction end portion are disposed along the outer edge of the supported portion 11a of the substrate 1. That is, the outer edge of the detection electrode 2 (detection electrode pattern P) is generally formed to have a similar shape to the outer edge of the supported portion 11 a of the substrate 1.

  As shown in FIG. 3, the detection electrode 2 is arranged on the substrate 1 such that the upper surface 2 a (end surface in the A1 direction) is exposed without being covered by the sensitive portion 3. That is, the detection electrode 2 is configured such that the upper surface 2a is in contact with the atmospheric gas (including the gas to be detected and the flammable gas) in the region where the semiconductor gas detection element 100 is disposed. The detection electrode 2 is exposed without being covered with the sensitive portion 3 in substantially the entire area (including the entire area) of the upper surface 2a. That is, the detection electrode 2 is disposed so as not to substantially overlap the sensitive portion 3 in the A direction. Further, the upper surface 2 a of the detection electrode 2 is not covered with a configuration other than the sensitive portion 3.

  The semiconductor-type gas detection element 100 is configured such that substantially the entire area (including the entire area) of the upper surface 2a is exposed without being covered by another structure such as the sensitive portion 3, so that a part of the upper surface 2a or Compared to the case where the entire region is covered with the sensitive part 3 or the like, a large contact area of the detection electrode 2 with the flammable gas can be ensured. For this reason, flammable gas (interfering gas) can be burned and removed effectively. As a result, the selectivity of the gas to be detected can be improved more effectively.

  Further, the semiconductor gas detection element 100 is configured so that substantially the entire area (including the entire area) of the upper surface 2a is exposed without being covered by the sensitive portion 3, so that a part or the entire area of the upper surface 2a is sensitive. Compared with the case where it is covered with the part 3, the size of the sensitive part 3 can be reduced. For this reason, the temperature of the sensitive part 3 can be raised to a temperature at which the gas to be detected can be detected with a smaller amount of heat. For this reason, in order to heat the sensitive part 3, the electric current sent through the detection electrode 2 can be made small. That is, the power saving of the gas sensor including the semiconductor gas detection element 100 can be achieved.

  Both the inner side surface 2 b of the first portion 22 and the inner side surface 2 c (see FIG. 4) of the second portion 23 are in contact with the sensitive portion 3. Further, both the inner side surface 2b and the inner side surface 2c are in contact with the sensitive portion 3 over substantially the entire surface.

  The inner side surface 2b of the first portion 22 refers to all of the side surfaces of the plurality of first portions 22 arranged in the C direction that are located on the inner side of the side surface (outer surface 20a) that is the outermost side of the substrate 1. It is the side of the.

  As shown in FIG. 4, the inner side surface 2 c of the second portion 23 is a side surface located on the inner side of the two side surfaces (the inner side surface 2 c and the outer side surface 20 b) of the second portion 23 aligned in the B direction. That is. The inner side surface 2b and the inner side surface 2c extend in the A direction.

  The detection electrode 2 shown in FIG. 1 is configured to be heated when a current is passed through a lead wire 4 from a power supply unit (not shown). Specifically, the detection electrode 2 is configured to be heated to a temperature equal to or higher than the combustion temperature of the flammable gas whose combustion temperature is lower than that of the detected gas and lower than the combustion temperature of the detected gas.

  For example, when the gas to be detected is methane, the combustion temperature is at least 500 ° C. or more, and when the flammable gas is alcohol or hydrogen, the combustion temperature is about 300 ° C. For this reason, the detection electrode 2 is configured to be heated to about 400 ° C., for example. As a result, the detection electrode 2 can come into contact with the flammable gas at the upper surface 2a in contact with the atmospheric gas, so that the flammable gas is burned and removed at the upper surface 2a and the detected gas is substantially burned. It is configured not to be removed. The detection electrode 2 is also configured to function as a heater unit that heats the sensitive unit 3. That is, at least the upper surface 2a and the outer surface 20a of the detection electrode 2 are made of gas combustion means (means for contacting the flammable gas contained in the atmospheric gas and removing the flammable gas by burning (that is, the gas to be detected). The inner side surface 2b of the detection electrode 2 is configured to function as a heater portion.

(Configuration of sensitive part)
The sensitive part 3 shown in FIG. 1 is formed of a metal oxide semiconductor. As a material of the metal oxide semiconductor, for example, tin oxide, indium oxide, zinc oxide, or the like can be used, but is not particularly limited thereto. The sensitive part 3 has a characteristic that, when heated by the detection electrode 2, reacts with the detected gas contained in the atmospheric gas in contact with the sensitive part 3 to change the resistance value. The semiconductor gas detection element 100 is configured to detect the gas to be detected using the characteristics of the sensitive portion 3.

  The sensitive portion 3 is adjacent to the detection electrode 2 in the direction along the surface of the substrate 1 (surface direction along the B direction and the C direction), and the inner side surfaces 2b (see FIG. 3) and 2c (see FIG. 3) of the detection electrode 2. 4 is arranged on the substrate 1 in contact with the substrate 1. Moreover, the sensitive part 3 is arrange | positioned in the state which contacted the board | substrate 1 (insulating film 11) on the surface of the board | substrate 1 (insulating film 11).

  One sensitive portion 3 is disposed between each of the first portions 22 of the detection electrodes 2 adjacent to each other. For example, eight sensitive portions 3 are arranged between the nine first portions 22. That is, the semiconductor gas detection element 100 includes a plurality of sensitive portions 3 that are separated from each other. The sensitive part 3 is arranged so as to be filled between the detection electrode patterns P.

  The sensitive portion 3 is in contact with the inner surface 2b (see FIG. 3) of the first portion 22 adjacent to the detection electrode 2 and the inner surface 2c (see FIG. 4) of the second portion 23 of the detection electrode 2. , Between the detection electrode patterns P. In addition, the sensitive portion 3 is provided between two adjacent first portions 22 over a range from the inner side surface 2 b of one first portion 22 to the inner side surface 2 b of the other first portion 22. That is, both end sides in the C direction of the second portion 23 are in contact with the inner side surfaces 2b of the separate first portions 22, respectively. The sensitive portion 3 extends in the B direction over a range from one end to the other end of the first portion 22, and one end surface in the B direction (the end surface on the B1 direction side or the end surface on the B2 direction side) is the second portion. 23 is in contact with the inner side surface 2c.

  As shown in FIG. 5, the sensitive portion 3 generally has a rectangular parallelepiped shape with a surface perpendicular to the B direction and a rectangular parallelepiped shape (see FIG. 1) with the B direction as the longitudinal direction. In the A direction, the thickness d1 of the sensitive portion 3 is larger than the thickness d2 of the detection electrode 2. Although it is an example, the thickness d1 of the sensitive part 3 is about twice as large as the thickness d2 of the detection electrode 2.

  The sensitive portion 3 extends in the A direction, contacts the detection electrode 2 (covered), and extends in the A direction, and does not contact the detection electrode 2 (not covered). And the exposed second side face 30b. The first side surface 30a and the second side surface 30b are provided on the same plane. The first side surface 30a is arranged on the substrate 1 side (A2 direction side) of the second side surface 30b.

  The sensitive unit 3 is configured to be heated by the detection electrode 2 through the first side surface 30 a that contacts the detection electrode 2. In addition, the sensitive unit 3 is configured to come into contact with the detected gas contained in the atmospheric gas via the second side surface 30b and the upper surface 30c.

(Circuit configuration of gas sensor including semiconductor type gas detection element)
Next, an example of a circuit configuration of the semiconductor gas sensor G including the hot-wire semiconductor gas detection element 100 will be described with reference to FIG. The circuit configuration of the semiconductor gas sensor G including the semiconductor gas detection element 100 shown below is an example, and is not limited to the configuration shown below.

  As shown in FIG. 6, a hot-wire semiconductor gas detection element resistance R (hereinafter referred to as element resistance R), which is a combined resistance of the detection electrode 2 and the sensitive portion 3, is a bridge circuit together with fixed resistances R1, R2, and R3. The semiconductor type gas sensor G is built in. The element resistance R is connected in series to the fixed resistance R3. In addition, fixed resistors R1 and R2 connected in series are provided on opposite sides of the element resistor R and the fixed resistor R3. Then, a voltage is applied to the bridge circuit by the power source E. At this time, the sensor output V is the potential difference between the midpoint P1 between the element resistance R and the fixed resistance R3 and the midpoint P2 between the fixed resistance R1 and the fixed resistance R2.

  Specifically, the element resistance R and the fixed resistance R3 are connected in series, so that one end r1 of the element resistance R and one end r31 of the fixed resistance R3 are equipotential. Further, the fixed resistor R1 and the fixed resistor R2 are connected in series, so that one end r11 of the fixed resistor R1 and one end r21 of the fixed resistor R2 are equipotential.

  The other end r2 of the element resistor R and the other end r12 of the fixed resistor R1 are connected so as to be equipotential. The midpoint P3 between the other end r2 of the element resistor R and the other end r12 of the fixed resistor R1 (a wiring connecting the other end r2 of the element resistor R and the other end r12 of the fixed resistor R1) is a positive electrode of the power source E. Connected to the side.

  The other end r32 of the fixed resistor R3 and the other end r22 of the fixed resistor R2 are connected so as to be equipotential. The midpoint P4 between the other end r32 of the fixed resistor R3 and the other end r22 of the fixed resistor R2 (a wiring connecting the other end r32 of the fixed resistor R3 and the other end r22 of the fixed resistor R2) is a negative electrode of the power source E. Connected to the side.

  The midpoint P2 (the wiring connecting the one end r11 of the fixed resistor R1 and the one end r21 of the fixed resistor R2) between the one end r11 of the fixed resistor R1 and the one end r21 of the fixed resistor R2 is one end on the positive electrode side of the power source E. Is connected to a resistor R0 connected to the negative side of the power supply E. Thereby, the midpoint P2 between the one end r11 of the fixed resistor R1 and the one end r21 of the fixed resistor R2 becomes a predetermined reference potential (set to zero).

  The bridge circuit is energized constantly or intermittently by a power source E, and the semiconductor gas detection element 100 is configured to have a predetermined temperature suitable for detection. Further, the resistance value of the semiconductor gas detection element 100 (the sensitive unit 3 (see FIG. 1)) changes when the gas to be detected is adsorbed. For this reason, in the semiconductor type gas sensor G according to the present embodiment, the change in the element resistance R of the semiconductor type gas detection element 100 is extracted as a deviation voltage, and this is used as the sensor output V to measure the gas concentration of the detected gas. It is configured as possible.

(Manufacturing method of gas sensor including semiconductor type gas detection element)
Next, with reference to FIG. 7 (a)-(d) and FIG. 8 (a)-(c), the manufacturing method of the semiconductor type gas detection element 100 by MEMS technique is demonstrated. The manufacturing method will be described in two stages: a first stage shown in FIGS. 7A to 7D and a second stage shown in FIGS. 8A to 8C. The first step is a step of forming the detection electrode 2 (detection electrode pattern P) on the substrate 1, and the second step is sensitive between the detection electrodes 2 (detection electrode pattern P) formed in the first step. This is a step of forming the portion 3.

  FIGS. 7A to 7D and FIGS. 8A to 8C show the manufacturing process of the semiconductor gas detection element 100, respectively. The manufacturing process is performed in the order of FIGS. 7A to 7D and FIGS. 8A to 8C. In addition, the manufacturing method of the semiconductor type gas detection element 100 shown below is an example, and the manufacturing method of the semiconductor type gas detection element 100 of this invention is not limited to the manufacturing method shown below.

<First stage>
First, as shown in FIG. 7A, a platinum metal layer K having a predetermined thickness d2 (see FIG. 5) is formed on the insulating film 11 of the substrate 1.

  Next, as shown in FIG. 7B, a mask M is formed at a predetermined position on the substrate 1. The mask M is formed at least at a position overlapping the detection electrode 2 to be formed on the substrate 1 in plan view (viewed from the direction A).

  Next, as shown in FIG. 7C, the metal layer K located between the masks M is removed by etching in plan view (viewed from the direction A). As a result, the detection electrode 2 (detection electrode pattern P (see FIG. 1)) is formed on the substrate 1.

  Next, as shown in FIG. 7D, the mask M on the substrate 1 is removed, and the upper surface 2a (end surface in the A1 direction) of the detection electrode 2 is exposed.

<Second stage>
Next, as shown in FIG. 8A, a water repellent material R is formed on the upper surface 2 a of the substrate 1. The water repellent material R is formed at least at a position overlapping the detection electrode 2 in a plan view (viewed from the direction A). The water repellent material R has a property of repelling the material solution of the sensitive part 3 containing tin oxide, which is the material of the sensitive part 3.

  Next, as shown in FIG. 8B, the material solution of the sensitive portion 3 containing tin oxide is formed on the substrate 1 and the detection electrode 2 from above the central portion of the substrate 1 (A1 direction side of the substrate 1). It is applied by dropping. At this time, the material solution of the sensitive portion 3 containing tin oxide is repelled by the water repellent material R, whereby the material solution of the sensitive portion 3 containing tin oxide on the water repellent material R (A1 direction side of the water repellent material R) is repelled. Flows between the detection electrode patterns P. In addition, the amount of the material solution of the sensitive part 3 containing tin oxide is adjusted so that the thickness d1 (see FIG. 5) of the sensitive part 3 is larger than the thickness d2 (see FIG. 5) of the detection electrode 2. . Thereby, the material solution of the sensitive part 3 containing tin oxide is filled between the detection electrode patterns P. As a result, the material solution of the sensitive portion 3 containing tin oxide comes into contact with the surface of the substrate 1 (insulating film 11) and the inner side surfaces 2b and 2c of the detection electrode 2 (see FIG. 4).

  Next, as shown in FIG.8 (c), the material solution of the sensitive part 3 containing a tin oxide is baked, and the sensitive part 3 is formed. Further, during firing, the water repellent material R is burned and removed, and the upper surface 2a of the detection electrode 2 is exposed. That is, the upper surface 2a of the detection electrode 2 is not covered with the water repellent material R and the sensitive portion 3 and is in contact with the atmospheric gas (including the detected gas and the flammable gas). Thus, the manufacture of the semiconductor gas detection element 100 is completed.

(Effect of this embodiment)
In the present embodiment, the following effects can be obtained.

  In the present embodiment, as described above, the detection electrode 2 of the gas to be detected including the heater portion disposed on the substrate 1 so that the upper surface 2a is exposed, and the sensitivity that is heated by the heater portion and contacts the gas to be detected. Part 3, and the sensitive part 3 is adjacent to the detection electrode 2 in the direction along the surface of the substrate 1 and in contact with the side surfaces (inner side surfaces 2 b and 2 c) of the detection electrode 2. To place. Thereby, since the detection electrode 2 contains the heater part, the upper surface 2a which the detection electrode 2 exposes can be heated. For this reason, since the flammable gas can be burned and removed on the upper surface 2a of the detection electrode 2, the concentration of the flammable gas with respect to the gas to be detected can be lowered. As a result, the selectivity of the gas to be detected can be improved. Further, if almost all of the upper surface 2a of the detection electrode 2 is exposed, the flammable gas can be burned and removed more effectively than when a part of the upper surface 2a of the detection electrode 2 is not exposed. Therefore, the selectivity of the gas to be detected can be improved more effectively. Moreover, since the detection electrode 2 includes the heater part, the sensitive part 3 can be heated from the side surface via the side surfaces (inner side surfaces 2b and 2c) of the detection electrode 2.

  In the present embodiment, as described above, the detection electrode 2 is formed from the detection electrode pattern P having a meandering shape on the substrate 1, and the sensitive portion 3 is filled between the detection electrode patterns P. Deploy. Thereby, by making the detection electrode 2 meander on the substrate 1, it is possible to ensure a large length of the detection electrode 2 without increasing the area of the substrate 1. For this reason, it is possible to further reduce the size of the semiconductor gas detection element 100. Further, by detecting the sensing electrode 2 in a meandering manner on the substrate 1 and disposing the sensitive part 3 between the sensing electrodes 2, the semiconductor gas detection is performed so that the sensing electrode pattern P and the sensitive part 3 are in contact with each other in a larger area. The element 100 can be configured.

  In the present embodiment, as described above, the detection electrode pattern P having a meandering shape has a plurality of first portions 22 arranged adjacent to each other in a plan view and the first portions 22 adjacent to each other. The sensing electrode pattern P is provided in a state in which the second portion 23 is connected to each other, and the sensitive portion 3 is in contact with the inner surface of the first portion 22 and the inner surface of the second portion 23 that are adjacent to each other. Place between. Accordingly, the first portion 22 adjacent to each other and the second portion 23 connecting the end portions of the first portion 22 can substantially surround the periphery of the sensitive portion 3, so that the heat from the detection electrode 2 can be efficiently used. Therefore, the sensitive part 3 can be efficiently heated and efficiently heated.

  In the present embodiment, as described above, the sensitive portion 3 is formed to have a larger thickness than the detection electrode 2. Thereby, compared with the case where the thickness of the sensitive part 3 is smaller than the thickness of the detection electrode 2, since the contact area of the sensitive part 3 and the detection electrode 2 can be ensured large, the heat | fever from the detection electrode 2 is reduced. The sensitive part 3 can be effectively transmitted to the sensitive part 3 and heated. Moreover, since the surface area which contacts the gas of the sensitive part 3 can be enlarged compared with the case where the thickness of the sensitive part 3 is smaller than the thickness of the detection electrode 2, gas sensitivity can be improved.

  In the present embodiment, as described above, the semiconductor gas detection element 100 is formed as a MEMS sensor using the MEMS technology. Thereby, since the semiconductor gas detection element 100 can be reduced in size, when a current is supplied to the detection electrode 2 including the heater and heated, the flammable gas can be combusted with a small amount of current. The temperature of the detection electrode 2 can be increased. Moreover, the temperature of the sensitive part 3 can be raised through the detection electrode 2 to a temperature at which the gas to be detected can be detected with a small amount of current. That is, the power saving of the gas sensor including the semiconductor gas detection element 100 can be achieved.

(Example)
Next, examples and comparative examples of the present invention will be described with reference to FIGS.

  In the example, the sensing electrode 2 shown in FIG. 1 was made of platinum, and the sensitive part 3 was made of tin oxide.

  As shown in FIG. 9, as a comparative example, a semiconductor gas detection element 200 including a detection electrode 202 made of the same material as that of the example and a sensitive part 203 made of the same material as that of the example was manufactured. Unlike the embodiment, the sensitive unit 203 covers the entire detection electrode 202. That is, the semiconductor gas detection element 200 of the comparative example does not include a portion where the detection electrode 2 is exposed as in the embodiment (the upper surface 2a is not exposed), and the detection electrode 202 is an atmospheric gas (detected). Gas and flammable gas).

(Measurement results and evaluation of examples and comparative examples)
The semiconductor gas detection element 100 of the example and the semiconductor gas detection element 200 of the comparative example are respectively disposed in a sealed measurement tank (not shown), and methane, hydrogen, and ethanol are placed in the measurement tank. Were sealed in the same amount (gas concentration), and the sensor output (mV) was measured with a voltmeter (not shown).

  The measurement was performed under the conditions where the gas concentrations of methane, hydrogen and ethanol were 500 ppm, 1000 ppm, 3000 ppm, 5000 ppm and 10000 ppm, respectively. That is, the gas concentration of methane is 500 (1000, 3000, 5000, 10000) ppm, the gas concentration of hydrogen is 500 (1000, 3000, 5000, 10000) ppm, and the gas concentration of ethanol is 500 (1000, 3000, 5000). The sensor output (mV) was measured for a gas having a concentration of 10,000) ppm.

<Measurement results of methane, hydrogen and ethanol in comparative example>
As shown in FIG. 10, in the comparative example, when the gas concentration is 500 ppm, each sensor output of methane, hydrogen, and ethanol is within the range of 40 to 80 mV, and when the gas concentration is 1000 ppm, each of methane, hydrogen, and ethanol When the sensor output is in the range of 80 to 120 mV and the gas concentration is 3000 ppm, each sensor output of methane, hydrogen, and ethanol is in the range of 120 to 160 mV, and when the gas concentration is 5000 ppm, each of methane, hydrogen, and ethanol When the sensor output was in the range of 140 to 180 mV and the gas concentration was 10,000 ppm, the sensor outputs of methane, hydrogen, and ethanol were in the range of 160 to 200 mV. That is, it was found that methane, hydrogen and ethanol show sensor outputs relatively close to each other at any gas concentration. In addition, methane showed the smallest sensor output at any gas concentration.

<Measurement results of methane in Examples>
As shown in FIG. 11, in the example, when the gas concentration is 500 ppm, the sensor output of methane shows about 18 mV, and when the gas concentration is 1000 ppm, the sensor output of methane shows about 30 mV, and the gas concentration is 3000 ppm. In this case, when the sensor output of methane is about 68 mV, the gas concentration is 5000 ppm, the sensor output of methane is about 92 mV, and when the gas concentration is 10000 ppm, the sensor output of methane is about 132 mV.

<Measurement results of hydrogen in Examples>
When the gas concentration is 500 ppm, the hydrogen sensor output shows about 5 mV, when the gas concentration is 1000 ppm, the hydrogen sensor output shows about 8 mV, and when the gas concentration is 3000 ppm, the hydrogen sensor output shows about 15 mV. When the gas concentration was 5000 ppm, the hydrogen sensor output showed about 23 mV, and when the gas concentration was 10,000 ppm, the hydrogen sensor output showed about 35 mV.

<Measurement results of ethanol in Examples>
When the gas concentration is 500 ppm, the ethanol sensor output is about 3 mV. When the gas concentration is 1000 ppm, the ethanol sensor output is about 4 mV. When the gas concentration is 3000 ppm, the ethanol sensor output is about 10 mV. When the gas concentration was 5000 ppm, the ethanol sensor output was about 13 mV, and when the gas concentration was 10,000 ppm, the ethanol sensor output was about 21 mV.

<Evaluation>
In the embodiment, at any gas concentration, the sensor output of methane is significantly larger than the sensor output of hydrogen and ethanol (more than three times the sensor output of hydrogen and more than five times the sensor output of ethanol). I understood. That is, it was found that the flammable gas (interfering gas) in the measurement tank was smaller than that at the time of gas filling, and methane was selectively detected. In contrast to the comparative example, it was found that methane showed the largest sensor output at any gas concentration.

(Modification)
The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments and examples but by the scope of claims for patent, and includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above-described embodiment, the example in which the sensitive part is disposed so as to contact the first part and the second part of the detection electrode has been described, but the present invention is not limited thereto. In the present invention, the sensitive part may be arranged so as to contact only one of the first part and the second part of the detection electrode.

  Moreover, in the said embodiment, although the example which detected methane as a to-be-detected gas by the semiconductor type gas detection element was shown, this invention is not limited to this. In the present invention, for example, a gas other than methane such as propane or butane may be detected as the gas to be detected. At this time, the flammable gas is a gas having a combustion temperature lower than that of propane or butane.

  Moreover, although the example which formed the detection pattern in the meandering shape was shown in the said embodiment, this invention is not limited to this. In the present invention, for example, the detection pattern may be formed in a shape other than a meandering shape such as a comb tooth shape.

  Moreover, although the example which formed the to-be-supported part of the board | substrate in the rectangular shape was shown in the said embodiment, this invention is not limited to this. In the present invention, for example, the supported portion of the substrate may be formed in a shape other than a rectangular shape such as a circular shape.

  In the above embodiment, the semiconductor gas detection element has a two-terminal configuration (a configuration in which two lead wires are provided for one detection electrode), but the present invention is not limited to this. . In the present invention, for example, the semiconductor gas detection element may have a four-terminal configuration (a configuration in which two lead wires are provided for two detection electrodes).

  Moreover, although the example which has arrange | positioned the sensitive part so that it may not contact the outer surface of a 1st part (2nd part) was shown in the said embodiment, this invention is not limited to this. In this invention, you may arrange | position a sensitive part so that the outer surface of a 1st part (2nd part) may be contacted.

  Moreover, in the said embodiment, although the example which formed the mask and the water repellent material separately on the upper surface of the detection electrode in the manufacturing process of the semiconductor type gas detection element was shown, this invention is not limited to this. In the present invention, the mask may be provided with water repellency, and only the mask may be formed on the upper surface of the detection electrode in the manufacturing process of the semiconductor gas detection element. Thereby, the sensitive part can be formed immediately after the etching for forming the detection electrode (the material of the sensitive part is dropped).

  Moreover, although the said embodiment showed the example comprised so that the substantially whole area of the upper surface of a detection electrode might be exposed without being covered with a sensitive part, this invention is not limited to this. In the present invention, the upper surface 2a of the detection electrode 2 may not be completely exposed. For example, the upper surface of the detection electrode may be partially covered by an adjacent sensitive part protruding on the upper surface of the detection electrode.

  Moreover, in the said embodiment, although the example which provided the sensitive part from one end of the longitudinal direction of the 1st part to the other end (namely, substantially full length of the 1st part) was shown, this invention is not limited to this. In the present invention, a sensitive portion may be provided in a part of the first portion in the longitudinal direction.

  Moreover, in the said embodiment, although the example which provided the several sensitive part was shown, this invention is not limited to this. In the present invention, only one sensitive part may be provided. In this case, for example, the sensitive part may be formed in a comb-like shape, and the sensitive part may be arranged between the meandering detection electrodes.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Detection electrode 2a Upper surface 2b Inner side surface of 1st part 2c Inner side surface of 2nd part 3 Sensing part 22 1st part 23 2nd part 100 Semiconductor type gas detection element P Detection electrode pattern

Claims (6)

A substrate,
A detection electrode of a gas to be detected including a heater portion disposed on the substrate such that an upper surface is exposed;
A sensitive part heated by the heater part and in contact with the detected gas,
The said sensitive part is a semiconductor-type gas detection element arrange | positioned on the said board | substrate in the state which touches the side surface of the said detection electrode adjacent to the said detection electrode in the direction along the surface of the said board | substrate. The sensing electrode is formed from a sensing electrode pattern having a meandering shape on the substrate,
The semiconductor-type gas detection element according to claim 1, wherein the sensitive part is disposed so as to be filled between the detection electrode patterns. The detection electrode pattern having the meandering shape includes a plurality of first portions arranged adjacent to each other substantially parallel to each other in plan view, and a second portion connecting the ends of the first portions adjacent to each other. ,
3. The semiconductor according to claim 2, wherein the sensitive portion is disposed between the detection electrode patterns in a state of being in contact with an inner side surface of the first part adjacent to each other and an inner side surface of the second part. Gas detection element.   The semiconductor type gas detection element according to claim 1, wherein the sensitive portion has a thickness larger than that of the detection electrode.   The semiconductor type gas detection element according to any one of claims 1 to 4, which is a MEMS sensor formed by using a MEMS technology. Forming a detection electrode pattern of a gas to be detected including a water repellent treatment and a heater portion disposed on the substrate so that the upper surface is exposed;
Forming a sensitive part by filling a semiconductor paste between the detection electrode patterns.

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