Gas concentration measuring device and method for measuring concentration of target gas in measured gas

Abstract

A gas concentration measurement device having a heating resistor that generates heat when current is applied and a stage that supports the heating resistor. 。 The heating resistor overlaps with the stage in a plan view. The area S of the stage in a plan view is 3.6×10 7 μm 2 When the total volume of the heating resistor and the stage is V, S / V is 0.0010 μm or less. ―1 More than 0010μm ―1 The gas concentration measuring device measures the concentration of a target gas in a measurement gas based on the resistance value of the heating resistor.

Description

[Technical field]

[0001] The present invention relates to a gas concentration measuring device used for measuring the concentration of a target gas in a measurement gas, and also to a method for measuring the concentration of a target gas in a measurement gas. [Background technology]

[0002] Conventionally, various devices for measuring the gas concentration in a measurement gas are known. One such device is a thermal conduction gas sensor. In a thermal conduction gas sensor, heat from a heating resistor is conducted to the measurement gas, and the gas concentration in the measurement gas is measured by utilizing the heat lost from the heating resistor.

[0003] For example, Patent Document 1 describes a combustible gas detection device equipped with a thermal conduction type gas detection unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-156364 A Summary of the Invention

[0005] As exemplified by Patent Document 1, various gas sensors have been proposed up to now, but these gas sensors have room for improvement in terms of ease of manufacture.

[0006] Therefore, an object of the present invention is to provide a gas concentration measurement device that can be easily manufactured.

[0007] The present invention provides a heating resistor that generates heat when current is applied, and a stage that supports the heating resistor, the heating resistor overlaps with the stage in a plan view, The area S of the stage in plan view is 3.6×10 7 μm 2is as follows: When the total volume of the heating resistor and the stage is V, S / V is 0.0010μm -1 More than 10μm -1 is as follows: The present invention provides a gas concentration measuring device that measures the concentration of a target gas in a measurement gas based on the resistance value of the heating resistor.

[0008] The present invention also provides a method for measuring the concentration of a target gas in a measurement gas, using the gas concentration measuring device. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a schematic diagram of a preferred embodiment of a gas concentration measuring device of the present invention. [Diagram 2] FIG. 2 is a plan view showing the position and shape of a heating resistor in the gas concentration measuring device shown in FIG. [Figure 3-1] FIG. 3-1 is a cross-sectional view of the gas concentration measuring device shown in FIG. 1 taken along line III-III. [Figure 3-2] 3-2 is a cross-sectional view of the gas concentration measuring device shown in FIG. 1 taken along line IV-IV. [Figure 3-3] FIG. 3-3 is a cross-sectional view showing another embodiment of the gas concentration measuring device of the present invention, and corresponds to FIG. 3-2. [Diagram 3-4] FIG. 3-4 is a cross-sectional view showing another embodiment of the gas concentration measuring device of the present invention, and corresponds to FIG. 3-2. [Figure 4] FIG. 4 is a perspective view that typically illustrates a preferred method for producing the gas concentration measuring device shown in FIG. [Diagram 5] FIG. 5 is a perspective view illustrating a gas concentration measuring device according to another embodiment of the present invention. [Figure 6] FIG. 6 is a plan view of the stage of the gas concentration measuring device shown in FIG. 5 as seen from the rear side. [Figure 7]7 is a cross-sectional view of the gas concentration measuring device shown in FIG. 5 taken along line VII-VII. [Figure 8] FIG. 8 is a cross-sectional view of the gas concentration measuring device of Comparative Example 1, and corresponds to FIG. [Figure 9] FIG. 9 is a perspective view diagrammatically illustrating another embodiment of the gas concentration measuring device of the present invention, and corresponds to FIG. [Figure 10] 10 is a plan view showing the position and shape of the heating resistor in the gas concentration measuring device shown in FIG. 9, and corresponds to FIG. [Figure 11] FIG. 11 is a cross-sectional view taken along line XI-XI of the gas concentration measuring device shown in FIG. 9, and corresponds to FIG. 3-1. [Figure 12] FIG. 12 is a perspective view diagrammatically illustrating another embodiment of a gas concentration measuring device of the present invention, and corresponds to FIG. [Figure 13] 13 is a plan view showing the position and shape of the heating resistor in the gas concentration measuring device shown in FIG. 12, and corresponds to FIG. [Figure 14] FIG. 14 is a cross-sectional view taken along line XIV-XIV of the gas concentration measuring device shown in FIG. 12, and corresponds to FIG. 3-1. [Figure 15] FIG. 15 is a graph showing the relationship between the measurement time and the resistance change rate of the heating resistor when electricity is applied to the gas concentration measuring devices of Examples 1 to 3 at a constant power of 80 mW. [Figure 16] FIG. 16 is a graph showing the relationship between the oxygen gas concentration of the measurement gas and the resistance change rate of the heating resistor when the gas concentration measuring devices of Examples 1 to 3 are energized at a constant power of 80 mW. [Figure 17] FIG. 17 is a graph showing the relationship between the measurement time and the rate of resistance change of the heating resistor when electricity is passed through the gas concentration measuring devices of Examples 2, 4 and 6 in a mixed gas flow of argon and nitrogen. [Figure 18] FIG. 18 is a graph showing the relationship between the measurement time and the rate of resistance change of the heating resistor when current is passed through the gas concentration measuring devices of Examples 2, 4 and 6 in a mixed gas flow of helium and nitrogen. [Figure 19] FIG. 19 is a graph showing the relationship between the measurement time and the rate of resistance change of the heating resistor when electricity is applied to the gas concentration measuring devices of Examples 2, 4 and 6 in a mixed gas flow of hydrogen and nitrogen. [Figure 20] FIG. 20 is a graph showing the relationship between the measurement time and the rate of resistance change of the heating resistor when electricity is passed through the gas concentration measuring device of Example 4 in an atmosphere of a mixed gas of water vapor and nitrogen. [Figure 21] FIG. 21 is a graph showing the relationship between the argon gas concentration of the measurement gas and the resistance change rate of the heating resistor when current is applied to the gas concentration measurement devices of Examples 2, 4 and 6 in a mixed gas flow of argon and nitrogen. [Figure 22] FIG. 22 is a graph showing the relationship between the helium gas concentration of the measurement gas and the resistance change rate of the heating resistor when current is applied to the gas concentration measurement devices of Examples 2, 4 and 6 in a mixed gas flow of helium and nitrogen. [Figure 23] FIG. 23 is a graph showing the relationship between the hydrogen gas concentration of the measurement gas and the resistance change rate of the heating resistor when current is applied to the gas concentration measurement devices of Examples 2, 4 and 6 in a mixed gas flow of hydrogen and nitrogen. [Figure 24] FIG. 24 is a graph showing the relationship between the relative humidity of the measurement gas and the resistance change rate of the heating resistor when electricity is passed through the gas concentration measuring device of Example 4 in an atmosphere of a mixed gas of water vapor and nitrogen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will now be described based on preferred embodiments with reference to the drawings. A preferred embodiment of the gas concentration measuring device of the present invention is shown in Fig. 1, Fig. 2, Fig. 3-1 and Fig. 3-2. The gas concentration measuring device 10 (hereinafter also referred to as "device 10") of this embodiment includes a stage 21 and one or more bridges 22 extending from the periphery of the stage 21 to form a bridge structure 20. In the device 10 shown in Fig. 1, the bridge structure 20 includes the stage 21 made of a rectangular plate-like body in a plan view and four bridges 22 extending from the periphery of the stage 21. The bridges 22 extend from the four corners of the stage 21. The device 10 also includes a peripheral portion 24 that is connected to the bridges 22 and surrounds the stage 21. The shape of the stage 21 in a plan view is not limited to a rectangle.

[0011] 3-1, the stage 21 has a multi-layer structure. In detail, the stage 21 has a four-layer structure including a first insulating layer 121, a second insulating layer 122 arranged on the first insulating layer 121, a third insulating layer 123 arranged on the second insulating layer 122, and a fourth insulating layer 124 arranged on the third insulating layer 123. However, the layer structure of the stage 21 is not limited thereto, and the stage 21 may have, for example, a single-layer structure, a two-layer structure, or a three-layer structure. In the device 10 shown in FIG. 2, a fourth insulating layer 124 and a second adhesive layer 34 described later are omitted in order to clearly show the position and shape of a heating resistor 31 described later.

[0012] The device 10 has a heating resistor 31 that generates heat when electricity is applied. The heating resistor 31 is supported by the stage 21 and overlaps the stage 21 in a plan view. More specifically, in the embodiment shown in FIGS. 1, 2, 3-1, and 3-2, the stage 21 includes the heating resistor 31 inside in the thickness direction. In this embodiment, the heating resistor 31 is disposed on the third insulating layer 123, and the fourth insulating layer 124 is disposed above and to the side of the heating resistor 31. In this way, the heating resistor 31 is surrounded by the third insulating layer 123 and the fourth insulating layer 124, and contact with the surrounding gas is prevented, whereby the durability of the heating resistor 31 can be improved.

[0013] The heating resistor 31 is preferably made of one or more filaments, and more preferably made of a series of filaments. In this specification, the term "series of filaments" refers to a single filament or a plurality of filaments having at least both ends in common. The series of wires arranged inside the stage 21 in the thickness direction form a heating resistor 31 inside the stage 21 in the thickness direction. The series of wires extends to the two bridges 22, 22 and the peripheral portion 24 to form two wirings 312, 312. That is, the series of wires is composed of the heating resistor 31 arranged inside the stage 21 in the thickness direction and the bridge 22 and the wiring 312 extending to the peripheral portion 24. In order to be able to form the two wirings 312, 312, it is preferable that two or more bridges 22 extend from the peripheral portion of the stage 21. In addition, from the viewpoint of supporting the stage 21 more stably, it is preferable that three or more, more preferably four or more bridges 22 extend from the peripheral portion of the stage 21. The heating resistor 31 is connected to two wires 312, 312, which are further connected via the two wires 312, 312 to two wire bonding pads 32, 32 (hereinafter also simply referred to as "pads 32") arranged on the peripheral portion 24. The wires 312 have a shape extending in one direction on the bridge 22.

[0014] The heating resistor 31 shown in Fig. 2 is composed of a single filament. This filament extends in the stage 21, meandering in one direction and then the opposite direction repeatedly without crossing. The shape of the filament increases the resistance of the heating resistor 31. This makes it possible to measure the gas concentration with less power consumption.

[0015] An example of an embodiment in which the heating resistor 31 is composed of a plurality of filaments having at least both ends in common is an embodiment (not shown) in which the filaments are arranged so as not to intersect with each other in the stage 21, and the portions of the filaments arranged in the bridges 22 are common (overlapping each other).

[0016] From the viewpoint of sufficiently increasing the physical strength of the heating resistor 31 and sufficiently increasing the resistance value of the heating resistor 31 to reduce the power consumption of the device 10, the thickness of the heating resistor 31 is preferably 0.01 μm or more and 100 μm or less, more preferably 0.02 μm or more and 75 μm or less, and even more preferably 0.05 μm or more and 50 μm or less. The thicknesses of the heating resistor and the first adhesive layer 33 and second adhesive layer 34 described below can be measured by a stylus type step gauge, an electron microscope, or an optical three-dimensional measuring device.

[0017] When the heating resistor 31 is made of one or more wires, the resistance value of the wiring 312 at the portion overlapping the bridge 22 in a plan view is R B The resistance value of the heating resistor 31 is R S Then, R B R S Ratio of R S / R B is preferably within a predetermined numerical range. S / R B is preferably 0.01 or more, more preferably 0.1 or more, and even more preferably 1 or more. S / R B By setting the value to 0.01 or more, heat radiation from the portion of the wiring 312 overlapping with the bridge 22 in a plan view is reduced, thereby improving the accuracy and sensitivity in measuring the concentration of the detection target gas. Also, R S / R B is preferably 10,000 or less, more preferably 1,000 or less, and even more preferably 100 or less. S / R BBy setting the value to 10,000 or less, the wiring 312 and the heating resistor 31 can be appropriately designed, and the device 10 can be easily formed. R S / R B In order to set within the above-mentioned numerical range, for example, the width or thickness of the filaments on the stage 21 and the bridge 22 may be appropriately adjusted.

[0018] When electricity is applied to the heating resistor 31 to generate heat, the amount of heat generated eventually balances with the amount of heat absorbed by the surrounding measured gas, and a steady state is reached. The temperature of the heating resistor 31 at this time depends on the thermal conductivity (heat absorption) of the measured gas. Since the thermal conductivity of the measured gas varies with the composition of the gas, the temperature of the heating resistor in the steady state changes depending on the composition of the measured gas. Therefore, the gas concentration in the measured gas can be measured based on the resistance value of the heating resistor 31 at this time.

[0019] As a result of the inventors' investigations, it was found that by setting the heat capacity of the heating resistor 31 and its surroundings to a predetermined value or less, the amount of temperature change of the heating resistor 31 in response to changes in the concentration of the target gas to be detected can be sufficiently increased, thereby improving the measurement accuracy and measurement sensitivity of the target gas concentration in the measured gas. In detail, the total heat capacity of the heating resistor 31 and the stage 21 is 3.2×10 -2 J / K or less is preferable, and 2.2×10 -2 J / K or less is more preferable, and 1.5×10 -2 J / K or less is more preferable, and 1.0×10 -3 J / K or less is more preferable, and 1.0×10 -4 It is even more preferable that the concentration is 4.0×10 J / K or less. -5 It is particularly preferable that the ratio is J / K or less. In order to reduce power consumption, the total heat capacity of the heating resistor 31 and the stage 21 is set to 1.0×10 -10 J / K or more is preferable, and 1.0×10 -9 J / K or more is more preferable, and 2.0×10 -9J / K or more is more preferable, and 1.0×10 -8 J / K or more is more preferable, and 1.0×10 -7 It is particularly preferable that it is J / K or more. As already explained, the device 10 shown in Figures 1, 2, 3-1 and 3-2 has a stage 21 containing a heating resistor 31 therein, and a bridge structure 20 consisting of a bridge 22. By employing the device 10 having such a structure as the gas concentration measurement device of the present invention, the total heat capacity of the heating resistor 31 and the stage 21 can be easily controlled within the above-mentioned range.

[0020] From the viewpoint of controlling the total heat capacity of the heating resistor 31 and the stage 21 within the above-mentioned range and from the viewpoint of ensuring sufficient mechanical strength, the area S of the stage 21 in a plan view is set to 3.6×10 7 μm 2 It is preferable that the value is less than 3.0×10 7 μm 2 More preferably, it is 2.5×10 7 μm 2 More preferably, it is 9.0×10 or less. 6 μm 2 More preferably, it is 4.0×10 or less. 6 μm 2 It is particularly preferred that: In order to improve the efficiency of heat transfer with the measured gas, S is set to 100 μm. 2 It is preferable that the thickness is 200 μm or more. 2 More preferably, it is 400 μm or more. 2 More preferably, it is 2.5×10 or more. 3 μm 2 More preferably, it is 1.5×10 or more. 4 μm 2 More preferably, it is equal to or greater than this.

[0021] From a similar viewpoint, when stage 21 is rectangular, the length of one side of stage 21 is preferably 10 μm or more and 3000 μm or less, more preferably 12.5 μm or more and 2500 μm or less, and even more preferably 20 μm or more and 2000 μm or less, provided that S is within the above-mentioned range.

[0022] In order to ensure a sufficient amount of heat absorption by the gas to be measured and to improve the measurement accuracy and sensitivity of the concentration of the gas to be detected, when the total volume of the heating resistor 31 and the stage 21 is V, S / V is set to 0.0010 μm -1 It is preferable that the thickness is 0.00125 μm or more. -1 More preferably, it is 0.0016 μm or more. -1 More preferably, it is 0.010 μm or more. -1 More preferably, the above is true. In addition, from the viewpoint of reducing power consumption, S / V is set to 10 μm -1 Preferably, it is 7.0 μm or less. -1 More preferably, it is 5.0 μm or less. -1 More preferably, it is 3.0 μm or less. -1 More preferably, it is 1.0 μm or less. -1 It is particularly preferred that:

[0023] From the viewpoint of further improving the measurement accuracy and sensitivity of the concentration of the target gas, it is preferable that the resistance value of the heating resistor 31 has a high temperature dependency. t is preferably 100 ppm / °C or more, more preferably 500 ppm / °C or more, and even more preferably 1000 ppm / °C or more. Temperature coefficient of resistance α at 25℃ tExamples of materials having a solubility of 100 ppm / °C or more include platinum, tungsten, copper, gold, silver, molybdenum, aluminum, and tantalum, as well as alloys thereof. Examples of alloys containing platinum include Pt-Nb, Pt-Rh, and Pt-W. Another example is a cermet of platinum group elements (platinum, palladium, rhodium, ruthenium, iridium, and osmium) and / or alloys containing these and metal oxides. Therefore, it is preferable that the heating resistor 31 contains one or more materials selected from the group consisting of these materials. Among them, it is particularly preferable that the heating resistor 31 contains platinum or an alloy containing platinum, from the viewpoint of stability in a high-temperature environment.

[0024] In order to increase the adhesion between the heating resistor 31 and the third insulating layer 123 and the fourth insulating layer 124, and thereby improve the durability of the device 10, it is preferable that a first adhesion layer 33 and a second adhesion layer 34 are arranged in positions in contact with the lower and upper surfaces of the heating resistor 31, respectively. When the first adhesion layer 33 and the second adhesion layer 34 are arranged in a position contacting the lower and upper surfaces of the heating resistor 31, it is preferable that the first adhesion layer 33 and the second adhesion layer 34 are also arranged in a position contacting the lower and upper surfaces of the wiring 312 and the pad 32. In order to sufficiently increase the adhesion between the heating resistor 31 and the third insulating layer 123 and the fourth insulating layer 124, the thicknesses of the first adhesive layer 33 and the second adhesive layer 34 are each independently preferably 1 nm or more and 200 nm or less, more preferably 2 nm or more and 150 nm or less, and even more preferably 10 nm or more and 100 nm or less.

[0025] 1 and 3-1, a part of the fourth insulating layer 124 disposed on the pad 32 is removed, which causes the second adhesive layer 34 (in an embodiment in which the second adhesive layer does not exist, a part of the pad 32) to be exposed to the outside.

[0026] As described above, the device 10 has a periphery 24 that surrounds the stage 21. The periphery 24 is preferably spaced apart from the stage 21, and the two are preferably connected via a bridge 22. The peripheral portion 24 preferably includes a substrate 11 and a plurality of insulating layers formed above and below the substrate 11. In detail, as shown in Fig. 3-1, a first insulating layer 121, a second insulating layer 122, a third insulating layer 123, and a fourth insulating layer 124 are disposed in this order above the substrate 11. Also, a fifth insulating layer 125 and a sixth insulating layer 126 are disposed in this order below the substrate 11.

[0027] The device 10 may or may not have the fifth insulating layer 125 and the sixth insulating layer 126. Depending on the presence or absence of the fifth insulating layer 125 and the sixth insulating layer 126, the stress applied to the substrate 11 can be adjusted. In device 10, the upper surface of peripheral portion 24 (the surface on the fourth insulating layer 124 side) has a substantially flat shape except for the positions of pads 32. In addition, the lower surface of peripheral portion 24 (the surface on the sixth insulating layer 126 side) also has a substantially flat shape.

[0028] 3-2, in the device 10 of this embodiment, the stage 21 and the bridge 22 have the same thickness, and both are smaller than the thickness of the peripheral portion 24. However, the relationship in thickness between the stage 21, the bridge 22, and the peripheral portion 24 is not limited to this. For example, as shown in Fig. 3-3, the thicknesses of the stage 21, the bridge 22, and the peripheral portion 24 may all be the same. Alternatively, as shown in Fig. 3-4, the thicknesses of the bridge 22 and the peripheral portion 24 may be the same, and the thickness of the stage 21 may be smaller than the thicknesses of the bridge 22 and the peripheral portion 24.

[0029] Next, the materials of each layer described above will be described. The substrate 11 preferably comprises silicon (Si). The insulating layers formed on the upper and lower surfaces of the substrate 11 preferably contain a silicon (Si) compound from the viewpoints of availability, ease of formation, and chemical stability. Examples of suitable insulating layers include silicon dioxide (SiO2) and silicon nitride (SiN x, x is a number between 0.100 and 1.667.) More specifically, the first insulating layer 121, the third insulating layer 123, the fourth insulating layer 124, and the fifth insulating layer 125 are made of SiO2, and the second insulating layer 122 and the sixth insulating layer 126 are made of SiN x It is preferable that the composition comprises:

[0030] In order to enhance adhesion to the third insulating layer 123 and the fourth insulating layer 124, the first adhesion layer 33 and the second adhesion layer 34 preferably contain one or more selected from tantalum (Ta), titanium (Ti), titanium nitride, titanium oxide, titanium oxynitride, tantalum oxide, zirconium, zirconium oxide, yttrium, yttrium oxide, tungsten, tungsten oxide, chromium, chromium oxide, nickel, nickel oxide, and alloys thereof.

[0031] The material of the heating resistor 31 is as already described. The material of the pad 32 can be the same as that of the heating resistor 31. The heating resistor 31 and the pad 32 may be made of different materials or the same material. From the viewpoint of enabling simple manufacture and reducing manufacturing costs, it is preferable that the heating resistor 31 and the pad 32 are made of the same material.

[0032] Fig. 5 shows a device 10 according to another embodiment of the present invention. Fig. 6 shows a plan view of a stage 21 (described in detail below) constituting the device 10 according to the embodiment shown in Fig. 5, as viewed from the rear side. Furthermore, Fig. 7 shows a cross-sectional view of the device 10 according to the embodiment shown in Fig. 5 taken along line VII-VII. In the following, the present embodiment will be described mainly with respect to the differences from the embodiment shown in Figures 1, 2, 3-1, and 3-2. For the points of the present embodiment that are not specifically described, the explanations of the embodiment shown in Figures 1, 2, 3-1, and 3-2 will be applied as appropriate.

[0033] The device 10 of this embodiment has a terminal block 50 and a plurality of pillar members 51 penetrating the terminal block 50 in the thickness direction. A terminal 52 for wire bonding is provided on the upper surface of each pillar member 51. The device 10 has a stage 21 and a plurality of bridges 22 extending from the periphery of the stage 21. The stage 21 is fixed to a terminal 52 via the plurality of bridges 22. In detail, as shown in FIG. 5, on the upper surface of the stage 21, the stage 21 and the bridges 22 (hereinafter also referred to as "first support 35") are joined at joints 37 provided at two locations. Also, as shown in FIG. 6, on the rear surface of the stage 21, the stage 21 and the bridges 22 (hereinafter also referred to as "second support 36") are joined at joints 37 provided at two locations. As shown in FIG. 5, the bridge 22 in this embodiment has a wire shape.

[0034] 6 and 7, a heating resistor 31 and two pads 32 are formed on one surface of the stage 21. In other words, the stage 21 supports the heating resistor 31 and the pads 32. The above-mentioned joint 37 is provided on the pad 32, and the pad 32 and the second support 36 are joined at the joint 37. When a conductor is used as the material of the second support 36, the heating resistor 31 is electrically connected to the columnar member 51 via the second support 36, so that electricity can be passed through the heating resistor 31 by connecting the columnar member 51 to a power source. For this purpose, the second support 36 preferably contains, for example, platinum. In contrast to this, in this embodiment, the first support 35 is used solely for the purpose of supporting the stage 21. Therefore, the material of the first support 35 is not limited to a conductor. The heating resistor 31 in this embodiment is made up of a single wire, which does not extend to the bridge 22 .

[0035] The stage 21 may have a single-layer structure or a multi-layer structure, but from the viewpoint of easier manufacture, it is preferable that the stage 21 has a single-layer structure. Examples of materials for the stage 21 include silicon, alumina, glass, forsterite, polyimide, polyamide, polycarbonate, polyamideimide, polyacetal, polyphenylene ether, polybutylene terephthalate, fluororesin, epoxy resin, and phenolic resin.

[0036] From the viewpoint of ensuring sufficient physical strength and reducing the heat capacity of the stage 21, the thickness of the stage 21 is preferably 0.5 μm or more and 2000 μm or less, more preferably 1.0 μm or more and 1000 μm or less, and even more preferably 1.5 μm or more and 500 μm or less.

[0037] From the viewpoint of increasing the physical strength of the first support 35 and the second support 36 and suppressing heat radiation from the heating resistor, the wire diameters of the first support 35 and the second support 36 are each independently preferably 1.0 μm or more and 100 μm or less, more preferably 5.0 μm or more and 80 μm or less, and even more preferably 10 μm or more and 50 μm or less.

[0038] The terminal block 50 is preferably made of an insulator, and the columnar members 51 and the terminals 52 are preferably made of conductors. The columnar members 51 and the terminals 52 may be made of the same material or different materials.

[0039] Figures 9 to 11 show a device 10 according to yet another embodiment of the present invention. In the following, the present embodiment will be described, focusing mainly on the differences from the embodiment shown in Figures 1, 2, 3-1 and 3-2. For points not specifically described in this embodiment, the descriptions of the embodiment shown in Figures 1, 2, 3-1 and 3-2 apply as appropriate. Figures 9 to 11 correspond to Figures 1, 2 and 3-1, respectively.

[0040] 1, 2, 3-1 and 3-2, the device 10 of this embodiment has a first insulating layer 121, a second insulating layer 122 and a third insulating layer 123 arranged over the entire area of ​​the device 10 in the planar direction (FIG. 11). The fourth insulating layer 124 is also arranged over the entire area of ​​the device 10 in the planar direction, except for the portion where the pad 32 is located. Due to having such a structure, the device 10 of this embodiment does not have a bridge 22 and a bridge structure 20 (FIGS. 9 and 10).

[0041] That is, the device 10 has a diaphragm 23 having a first insulating layer 121, a second insulating layer 122, a third insulating layer 123, and a fourth insulating layer 124, a peripheral portion 24 surrounding the diaphragm 23, and a heating resistor 31 is provided at any position in the thickness direction of the diaphragm 23. The diaphragm 23 is made of a thin film, and the thickness thereof can be the same as that of the stage 21 described above. The diaphragm 23 has a rectangular shape, and the length of one side is preferably 100 μm or more and 4500 μm or less, more preferably 150 μm or more and 3000 μm or less, and even more preferably 200 μm or more and 1500 μm or less. However, the shape of the diaphragm 23 is not limited to a rectangular shape.

[0042] 9 and 10, the device 10 of this embodiment has a heating resistor 31 and two wires 312, 312 that connect the heating resistor 31 and a pad 32. The heating resistor 31 has each end connected to each end of the two wires 312, 312, respectively, and forms a single filament as a whole. In this embodiment, when the heating resistor 31 and the wirings 312, 312 are made of the same material, the portion of the filament that is densely packed due to meandering or the like is defined as the heating resistor 31, and the portion extending outward from the heating resistor 31 is defined as the wiring 312. The heating resistor 31 is located approximately in the center of the diaphragm 23.

[0043] 10, in this embodiment, when a figure obtained by connecting the outer edges of the heating resistor 31 in a plan view of the device 10 is defined as K, the portion that overlaps with the figure K in a plan view (excluding the heating resistor 31) is defined as the stage 21 of the device 10. In Fig. 10, the figure K is indicated by a dashed line and has a rectangular shape. Therefore, in this embodiment, the above-mentioned "area S of the stage 21 in a plan view" is synonymous with "the area of ​​the figure K." Also, in this embodiment, the above-mentioned "total volume V of the heating resistor 31 and the stage 21" is synonymous with "the volume of the portion overlapping with the figure K in a plan view."

[0044] Figures 12 to 14 show a device 10 according to yet another embodiment of the present invention. In the following, the present embodiment will be described, focusing mainly on the differences from the embodiment shown in Figures 1, 2, 3-1, and 3-2. For points not specifically described in this embodiment, the descriptions of the embodiment shown in Figures 1, 2, 3-1, and 3-2 apply as appropriate. Note that Figures 12 to 14 correspond to Figures 1, 2, and 3-1, respectively.

[0045] The device 10 of this embodiment includes a stage 21 and at least two bridges 22 extending from the periphery of the stage 21. The stage 21 and the bridges 22 form a bridge structure 20. The bridges 22 have a shape extending in one direction. The device 10 also has a periphery 24 that is spaced apart from the stage 21 and surrounds the stage 21, and the bridges 22 are connected to the periphery 24. In a plan view, the peripheral portion 24 has a hollow rectangular shape defined by a first rectangular portion 26 having four sides and forming an outer contour, and a second rectangular portion 27 having four sides and forming an inner contour. The stage 21 is located inside the second rectangular portion 27. Each side of the second rectangular portion 27 in the peripheral portion 24 and each side of the stage 21 are non-parallel and non-orthogonal to each other. In detail, the stage 21 is disposed inside the second rectangular portion 27 in such a positional relationship that each corner of the stage 21 faces each side of the second rectangular portion 27. Each bridge 22 extends from a corner of the stage 21 along the extension direction of a diagonal of the stage 21. Each bridge 22 extends from a corner of the stage 21 and is bent 90 degrees midway, changing the direction of extension, and is connected to the wall surface of the peripheral portion 24 located on the extension line of the bent direction, i.e., the above-mentioned second rectangular portion 27.

[0046] 13, the peripheral portion 24 surrounding the stage 21 has a pair of first portions 24a, 24a that extend in the same direction and face each other at a distance, and a pair of second portions 24b, 24b that extend in a direction perpendicular to the extension direction of the first portions 24a, 24a and face each other at a distance. Each end of the first portions 24a, 24a is connected to each end of the second portions 24b, 24b.

[0047] 12 to 14, the device 10 has a portion (hereinafter also referred to as a "partition wall 25") that extends inward from the wall of the peripheral portion 24 toward the stage 21. The partition wall 25 is disposed in the space between adjacent bridges 22, 22 in a plan view so as to separate the bridges 22, 22 from each other. As shown in FIG. 14, similar to the peripheral portion 24, the partition 25 has a first insulating layer 121, a second insulating layer 122, a third insulating layer 123, a fourth insulating layer 124, a substrate 11, a fifth insulating layer 125 and a sixth insulating layer 126 along its thickness direction, and extends from the upper end to the lower end of the device 10.

[0048] In a plan view, the partition wall 25 has a shape defined by four sides: a wall surface (second rectangular portion 27) of the peripheral portion 24, a pair of parallel protruding sides 28, 28 extending from the wall surface toward the stage 21, and a connecting side portion 29 connecting the tips of the protruding sides. The pair of protruding sides 28, 28 are perpendicular to the wall surface of the peripheral portion 24. The lengths of the pair of protruding sides 28, 28 are different from each other. As a result, the connecting side portion 29 is not parallel to the peripheral portion 24. The connecting side portion 29 faces one side of the stage 21 formed of a quadrangle. The connecting side portion 29 and the side of the stage 21 facing it are parallel to each other at a distance. Of the pair of protruding sides 28, 28, the protruding side portion 28a having a longer length is parallel to the side adjacent to the side from which the protruding side portion 28a protrudes, and is separated by a distance from each other, among the four sides constituting the second rectangular portion 27 described above. On the other hand, of the pair of protruding sides 28, 28, the protruding side portion 28b having a shorter length is spaced apart from and parallel to the bridge 22 extending from the corner of the stage 21. The fact that the partition wall 25 has such a shape in a plan view is advantageous in that it is possible to effectively control V', which will be described later, while ensuring an appropriate distance between the stage 21 and the bridge 22.

[0049] From the viewpoint of suppressing heat conduction from bridge 22 to partition 25, in the case where device 10 has partition 25, the minimum distance between bridge 22 and partition 25 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. Furthermore, from the viewpoint of reliably forming the partition 25 and efficiently controlling V' described below, when the device 10 has the partition 25, the minimum distance between the bridge 22 and the partition 25 is preferably 1500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, and particularly preferably 200 μm or less. The above-mentioned “minimum distance between the bridge 22 and the partition wall 25 ” refers to the minimum distance between any point on the bridge 22 and any point on the partition wall 25 .

[0050] From the viewpoint of suppressing heat conduction from the stage 21 to the partition wall 25, when the device 10 has the partition wall 25, the minimum distance between the stage 21 and the partition wall 25 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. Furthermore, from the viewpoint of reliably forming the partition 25 and efficiently controlling V, which will be described later, in the case where the device 10 has the partition 25, the minimum distance between the stage 21 and the partition 25 is preferably 1500 μm or less, more preferably 400 μm or less, even more preferably 300 μm or less, and particularly preferably 200 μm or less. The above-mentioned “minimum distance between the stage 21 and the partition wall 25 ” refers to the minimum distance between any point on the stage 21 and any point on the partition wall 25 .

[0051] In device 10, from the viewpoint of improving the measurement sensitivity and accuracy of the concentration of the target gas, it is preferable that there be a predetermined relationship between the volume of the space within device 10 and the area of ​​device 10 in a planar view. In detail, when the total volume of space A1 located below stage 21 and space A2 between stage 21 and peripheral portion 24 in device 10 is V' and the area of ​​stage 21 in a planar view is S, the value of V' / S is 10 or more and 2.0×10 or less. 9 It is preferable that V' / S is set within this range. By setting V' / S within this range, heat transfer from the underside of the stage 21 can be suppressed, which can improve the measurement sensitivity and accuracy of the target gas concentration. From the viewpoint of making this effect even more pronounced, the value of V' / S is preferably 10 or more and 1.6×10 or less. 6 More preferably, it is 50 or more and 7.3×10 or less. 5 More preferably, it is 1.0×10 2 More than 1.8 x 10 5 More preferably, it is 5.0×10 or less. 2 Above 1.0×10 4 It is particularly preferred that:

[0052] 14, the space A1 is a space surrounded by the stage 21, an extension P1 of the lower surface of the stage 21, the peripheral portion 24, the partition wall 25, and an extension P2 of the lower surface of the peripheral portion 24. The space A2 is a space surrounded by the stage 21, an extension P1 of the lower surface of the stage 21, the peripheral portion 24, the partition wall 25, and an extension P3 of the upper surface of the stage 21. It is preferable that all of the extensions P1 to P3 extend in the horizontal direction.

[0053] In order to set V' / S within the above-mentioned numerical range, for example, V' may be appropriately adjusted. The adjustment of V' can be performed, for example, by appropriately setting the size of the partition 25. Alternatively, the distance d1 between the pair of opposing first regions 24a, 24a and the distance d2 between the pair of opposing second regions 24b, 24b may be appropriately set. In detail, d1 and d2 are each independently preferably 100 μm or more and 4500 μm or less, more preferably 150 μm or more and 3000 μm or less, and further preferably 200 μm or more and 1500 μm or less.

[0054] From the viewpoint of shortening the time required to reach a steady state in which the amount of heat generated by the heating resistor 31 and the amount of heat absorbed by the surrounding gas to be measured are balanced, V' is set to 1.8×10 11 It is preferable that the value is 1.6×10 or more. 10 μm 3 It is preferable that the value is less than 7.2×10 9 μm 3 More preferably, it is 1.8×10 or less. 9 μm 3 It is even more preferred that:

[0055] In plan view, the minimum width of the bridge 22 is preferably 5 μm or more, more preferably 7.5 μm or more, even more preferably 10 μm or more, even more preferably 20 μm or more, and particularly preferably 30 μm or more. By setting the minimum width of the bridge 22 to 5 μm or more, the physical strength of the bridge 22 can be sufficiently ensured. This effect can be obtained. Moreover, the minimum width of the bridge 22 is preferably 1500 μm or less, more preferably 450 μm or less, even more preferably 300 μm or less, and even more preferably 200 μm or less. By setting the minimum width of the bridge 22 to 450 μm or less, the heat conduction from the stage 21 to the bridge 22 can be further suppressed. The "minimum width of the bridge 22" refers to the width at the position where the width of the bridge 22 (the length in the direction perpendicular to the longitudinal direction of the bridge 22) is minimum when the device 10 is viewed in a plan view.

[0056] The above discussion regarding V' / S, V' and the minimum width of bridge 22 also applies to embodiments that do not include a bulkhead 25 (eg, device 10 shown in FIG. 1 and device 10 shown in FIG. 9).

[0057] From the viewpoint of improving the measurement accuracy and measurement sensitivity of the concentration of the target gas in the measurement gas, the total heat capacity of the heating resistor 31 and the stage 21 in the device 10 shown in FIGS. 12 to 14 is 8.3×10 -6 J / K or less is preferable, and 3.9×10 -6 J / K or less is more preferable, and 9.4×10 -7 It is more preferable that the ratio is J / K or less. From the viewpoint of reducing power consumption, the total heat capacity of the heating resistor 31 and the stage 21 in the device 10 shown in FIGS. 12 to 14 is 9.0×10 -10 J / K or more is preferable, and 1.8×10 -9 J / K or more is preferable, and 3.7×10 -9 It is more preferable that it is J / K or more.

[0058] From the viewpoint of controlling the total heat capacity of the heating resistor 31 and the stage 21 within the above-mentioned range and from the viewpoint of ensuring sufficient mechanical strength, the area S of the stage 21 in a plan view in the device 10 shown in FIGS. 12 to 14 is 3.6×10 7 μm 2 It is preferable that the value is less than 9.0×10 6 μm 2 More preferably, it is 4.0×10 or less. 6 μm 2 More preferably, it is 1.0×10 6 μm 2 More preferably, it is 4.9×10 or less. 5 μm 2 It is particularly preferred that: In order to increase the efficiency of heat transfer with the gas to be measured, the area S of the stage 21 in the device 10 shown in FIGS. 12 to 14 in a plan view is set to 1.0×10 2 μm 2 More preferably, it is 2.0×10 2 More preferably, it is 4.0×10 or more. 2 μm 2 More preferably, it is 1.0×10 3 μm 2 More preferably, it is 1.0×10 or more. 4 μm 2 More preferably, it is 1.0×10 5 μm 2 More preferably, it is equal to or greater than this.

[0059] In order to ensure a sufficient amount of heat absorption by the gas to be measured and to improve the measurement accuracy and sensitivity of the concentration of the gas to be detected, the above-mentioned S / V in the device 10 shown in FIGS. 12 to 14 is set to 0.020 μm. -1 It is preferable that the thickness is 0.040 μm or more. -1 More preferably, it is 0.050 μm or more. -1 More preferably, it is equal to or greater than this. From the viewpoint of reducing power consumption, the above-mentioned S / V in the device 10 shown in FIGS. -1 Preferably, it is 7.0 μm or less. -1 More preferably, it is 5.0 μm or less. -1 It is even more preferable that:

[0060] Next, a method for measuring the concentration of a target gas in a measurement gas using the device 10 will be described. The measurement gas includes the gas to be detected and the remainder consisting of other gases. The remainder may include only one type of gas, or may include two or more types of gas. When the remainder includes two or more types of gas, it is preferable that the ratio of each gas included in the remainder is constant during the measurement of the gas to be detected, from the viewpoint of improving the measurement accuracy of the concentration of the gas to be detected. However, when the remainder includes two or more types of gas with similar thermal conductivities (for example, when it includes nitrogen gas and oxygen gas), the ratio of each gas component included in the remainder does not necessarily have to be constant.

[0061] When the device 10 is used to measure the concentration of the target gas in the measured gas, the heating resistor 31 is energized to heat the heating resistor 31. The energization conditions are not particularly limited as long as a good linear relationship is established between the concentration of the target gas in the measured gas and the resistance value of the heating resistor. For example, the energization can be performed under constant power conditions, i.e., under conditions where the amount of heat generated from the heating resistor 31 due to energization is constant even if the concentration of the target gas in the measured gas changes. Alternatively, the energization can be performed under constant voltage conditions, i.e., under conditions where the voltage applied to the heating resistor 31 is constant even if the concentration of the target gas in the measured gas changes, or under constant current conditions, i.e., under conditions where the current flowing through the heating resistor 31 is constant even if the concentration of the target gas in the measured gas changes. "Constant power" here does not require that the power be strictly constant during measurement of the target gas concentration. For example, if the change in power during measurement is 1% or less, more preferably 0.5% or less, the target gas concentration can be measured with sufficient accuracy. Therefore, even if a power change of this magnitude occurs during measurement of the target gas concentration, the measurement is considered to have been performed under constant power conditions. The same applies to the "constant voltage" and "constant current" described above.

[0062] Regardless of the condition under which electricity is passed, the resistance value of the heating resistor 31 changes depending on the temperature of the heating resistor 31, and the concentration of the target gas to be detected can be measured based on the resistance value.

[0063] From the viewpoint of promoting heat absorption by the measurement gas from the heating resistor 31 and further improving the measurement accuracy of the concentration of the target gas, it is preferable to sufficiently increase the temperature of the heating resistor 31 by passing current through it while the concentration of the target gas is being measured. In detail, when measuring the concentration of the target gas in the measurement gas, it is preferable to pass current through the heating resistor 31 so that the temperature difference between the heating resistor 31 and the measurement gas is preferably 30° C. or more, more preferably 60° C. or more, and even more preferably 100° C. or more. To prevent deterioration of the heating resistor 31 due to heat, the temperature difference between the heating resistor 31 and the measurement gas is preferably 800° C. or less, more preferably 750° C. or less, and even more preferably 700° C. or less.

[0064] Examples of gases to be detected in the measurement gas include, but are not limited to, oxygen gas, nitrogen gas, argon gas, helium gas, water vapor, hydrogen gas, and carbon dioxide gas. Measurement can be performed if there is a difference in thermal conductivity between the gases to be detected contained in the measurement gas and other gases. Preferred gases to be detected are oxygen gas, argon gas, helium gas, water vapor, or carbon dioxide gas, and particularly preferred are oxygen gas, water vapor, or carbon dioxide gas. When the gas to be detected is oxygen gas, the thermal conductivity of oxygen gas is relatively low, so the temperature change of the heating resistor 31 accompanying the change in oxygen gas concentration is small. Due to this, there is a problem that the measurement accuracy of the oxygen gas concentration is easily reduced in conventional thermal conduction gas sensors. In addition, when the measurement target gas contains oxygen gas and nitrogen gas, such as air, it is particularly difficult to measure the oxygen gas concentration with high accuracy using conventional thermal conduction gas sensors, because the thermal conductivities of oxygen gas and nitrogen gas are close to each other. In contrast, in device 10, the amount of temperature change of heating resistor 31 in response to changes in the concentration of the target gas is sufficiently increased as described above, so that even if the target gas is oxygen gas, the concentration can be measured with high accuracy. Furthermore, device 10 can measure the oxygen gas concentration with high accuracy even if the target gas contains oxygen gas and nitrogen gas. In order to utilize the advantages of the device 10 described above, the total content of oxygen gas and nitrogen gas in the gas to be measured is preferably 0.00001 vol. % or more, more preferably 0.0001 vol. % or more, and even more preferably 0.001 vol. % or more. In addition, water vapor has a thermal conductivity close to that of oxygen gas and nitrogen gas, so the device 10 is also excellent in that it can measure the humidity in a measurement target gas (for example, air) containing oxygen gas and / or nitrogen gas with high accuracy.

[0065] As described above, the device 10 can measure the concentration of the target gas in the measurement gas with high accuracy even if it has only the heating resistor 31 as a member sensitive to the target gas. In this way, the device 10 can be constructed from a relatively small number of members, and therefore can be manufactured more easily. In this specification, the term "a member sensitive to a target gas" refers to a member whose properties change in response to the concentration of the target gas in the measurement gas. The heating resistor 31 corresponds to a member sensitive to a target gas because the resistance value of the heating resistor 31 changes in response to the concentration of the target gas in the measurement gas when a current is applied. Another example of a component sensitive to the target gas is an electrode portion consisting of a positive electrode, a negative electrode, and an electrolyte disposed between them, in which the value of the current flowing through the electrode portion changes depending on the concentration of the target gas in the measured gas. Further, examples of materials sensitive to oxygen gas include semiconductors such as tin oxide and zinc oxide, and piezoelectric materials such as barium titanate, zirconium titanate and zinc oxide.

[0066] Next, a preferred method for manufacturing the gas concentration measurement device of the present invention will be described using the method for manufacturing the device 10 shown in Figures 1, 2, 3-1 and 3-2 as an example. Figures 4(a) to (e) show a preferred manufacturing procedure for the device 10 shown in Figures 1, 2, 3-1 and 3-2. This manufacturing method includes the following steps in this order: 1. Step of forming an insulating layer on the substrate 11 2. Step of forming the heating resistor 31 on the insulating layer 3. Step of forming the fourth insulating layer 124 on the sides and above the heating resistor 31 4. Step of forming bridge structure 20

[0067] 1. Step of forming an insulating layer on the substrate 11 First, the substrate 11 is thermally oxidized by heating it to 700° C. or higher and 1400° C. or lower in an atmosphere containing oxygen or water vapor, and a first insulating layer 121 and a fifth insulating layer 125 made of SiO2 are formed on the surface of the substrate 11. Next, a second insulating layer 122 and a sixth insulating layer 126 made of SiNx are formed on the surfaces of the first insulating layer 121 and the fifth insulating layer 125 using a thin film forming means described later.

[0068] As a thin film forming means, physical vapor deposition (PVD) methods such as vapor deposition, sputtering, and ion plating, and chemical vapor deposition (CVD) methods can be used. Among them, it is preferable to form the second insulating layer 122 and the sixth insulating layer 126 by using a PECVD (plasma enhanced chemical vapor deposition) method or an LP-CVD (low pressure chemical vapor deposition) method, from the viewpoint of the possibility of adjusting the residual stress and from the viewpoint of mass productivity. 4(a) to 4(e), the first insulating layer 121, the second insulating layer 122, the third insulating layer 123, the fifth insulating layer 125, and the sixth insulating layer 126 are omitted from the illustration.

[0069] Next, a third insulating layer 123 is formed on the second insulating layer 122 (FIG. 4(a)). The third insulating layer 123 is formed on the entire surface of the substrate 11. The above-mentioned thin film forming means can be used to form the third insulating layer 123. Among them, when forming the third insulating layer 123 made of SiO2, it is preferable to use the PECVD method from the viewpoint of the ability to adjust residual stress and from the viewpoint of mass productivity.

[0070] 2. Step of forming the heating resistor 31 on the insulating layer Prior to the formation of the heating resistor 31, the first adhesive layer 33 is formed as necessary. The first adhesive layer 33 can be formed by patterning using a lift-off method. In detail, a layer (not shown) made of photoresist is first provided over the entire area on the third insulating layer 123, and then exposed and developed to form a mask (not shown) having a shape complementary to the shape of the first adhesive layer 33 by patterning. Next, with the third insulating layer 123 covered with the mask, the first adhesive layer 33 is formed by a thin film forming means. As the thin film forming means, it is particularly preferable to use a sputtering method from the viewpoint of mass productivity. Finally, the layer made of photoresist is removed to obtain the first adhesive layer 33 having a desired shape.

[0071] Next, the heating resistor 31 is formed (FIG. 4(b)). In this manufacturing method, in order to simplify the manufacturing process, the heating resistor 31, the wiring 312, and the pads 32 are formed simultaneously. In forming the heating resistor 31, the wiring 312, and the pads 32, it is preferable to first form the heating resistor 31, the wiring 312, and the pads 32 on the entire surface of the substrate 11 using any of the above-mentioned thin film forming means, and then perform patterning. As a means for forming the thin film, it is particularly preferable to use a sputtering method from the viewpoint of mass productivity. As the patterning method, it is particularly preferable to use a milling method from the viewpoint of suppressing burrs generated at the ends of the heating resistor 31. Also, a lift-off method can be used instead of the milling method. When the lift-off method is used, the method of forming the heating resistor 31 is similar to the method of forming the first adhesive layer 33, and therefore a description thereof will be omitted here.

[0072] After forming the heating resistor 31, the second adhesive layer 34 is formed as necessary. The second adhesive layer 34 can be formed by the same method as the first adhesive layer 33. In FIG. 4(b), the first adhesive layer 33 and the second adhesive layer 34 are omitted.

[0073] 3. Step of forming the fourth insulating layer 124 on the sides and above the heating resistor 31 After forming the heating resistor 31 and, if necessary, the first adhesive layer 33 and the second adhesive layer 34, the fourth insulating layer 124 is formed. The fourth insulating layer 124 is formed on the entire surface of the substrate 11 (FIG. 4(c)). The fourth insulating layer 124 can be formed by the same method as the third insulating layer 123. Through the above steps, a structure 40 including each insulating layer and the heating resistor 31 can be obtained.

[0074] 4. Step of forming bridge structure 20 First, unnecessary portions of the first insulating layer 121, the second insulating layer 122, the third insulating layer 123, and the fourth insulating layer 124, which are insulating layers located above the substrate 11, are removed (FIG. 4(d)). The unnecessary portions here refer to portions of the target device 10 (FIG. 1) that do not overlap with the bridge structure 20 or the peripheral portion 24 in a plan view. In this step, in parallel with removing the unnecessary portions, a part of the fourth insulating layer 124 formed on the pad 32 can be removed to expose the pad 32 to the outside. At this time, if necessary, in addition to the part of the fourth insulating layer 124, a part of the second adhesive layer 34 may be removed.

[0075] The unnecessary portions can be removed by an etching method such as a dry etching method or a wet etching method. Dry etching can be performed using reactive ion etching (RIE) with fluorocarbon or halogen gas, while wet etching can be performed using isotropic etching with hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, etc., or anisotropic etching with alkaline solutions such as KOH (potassium hydroxide), TMAH (tetramethylammonium hydroxide), and EDP (ethylenediamine pyrocatechol). Among these, from the viewpoint of preventing etching of the structure 40, RIE can be preferably used to remove the unnecessary portions.

[0076] Next, unnecessary portions of the fifth insulating layer 125 and the sixth insulating layer 126, which are insulating layers located below the substrate 11, are removed, and then unnecessary portions of the substrate 11 are removed (FIG. 4(e)). The unnecessary portions here refer to portions that do not overlap with the peripheral edge portion 24 in a plan view.

[0077] The method for removing the unnecessary portions can be the same as the method for removing the insulating layer located above the substrate 11. In particular, RIE can be preferably used as a method for removing unnecessary portions of the insulating layer located below the substrate 11. Also, deep recess etching (DRIE) can be preferably used as a method for removing unnecessary portions of the substrate 11, in which an etching process using SF6 (sulfur hexafluoride) and a passivation process using a fluoroalkane gas such as C4F8 (octafluorocyclobutane) are alternately performed.

[0078] When manufacturing the device 10 shown in Fig. 9 instead of the device 10 shown in Fig. 1, it is only necessary to not remove unnecessary portions in the "step of forming the bridge structure 20" shown in Fig. 4(d). Even in this case, it is preferable to expose the pad 32 to the outside by removing a part of the fourth insulating layer 124 formed on the pad 32 and, if necessary, a part of the second adhesive layer 34, as in Fig. 4(d).

[0079] When manufacturing the device 10 shown in FIG. 12 instead of the device 10 shown in FIG. 1, unnecessary portions may be removed in the "step of forming the bridge structure 20" shown in FIG. 4(d) so as to form the partition wall 25 shown in FIG. 12.

[0080] Although the gas concentration measuring device of the present invention has been described above based on the preferred embodiments, the present invention is not limited to such embodiments.

[0081] The above-described embodiment of the present invention encompasses the following technical ideas. [1] A heating resistor that generates heat when current is applied and a stage that supports the heating resistor; the heating resistor overlaps with the stage in a plan view, A gas concentration measuring device that measures the concentration of a target gas in a measurement gas based on the resistance value of the heating resistor. [2] The total heat capacity of the heating resistor and the stage is 1.0×10 -10 J / K or above 3.2×10 -2 The gas concentration measurement device according to [1], wherein the concentration is less than or equal to J / K. [3] The gas concentration measurement device according to [1] or [2], further comprising one or more bridges extending from the periphery of the stage to form a bridge structure. [4] The gas concentration measurement device according to any one of [1] to [3], wherein the detection target gas is oxygen gas, argon gas, helium gas, water vapor or carbon dioxide gas. [5] The gas concentration measurement device according to any one of [1] to [4], wherein the detection target gas is oxygen gas. [6] The heating resistor is composed of a series of filaments, The series of filaments may be a single filament or a plurality of filaments having at least both ends in common, At least two of the bridges extend from a periphery of the stage; The gas concentration measurement device described in [3], wherein the series of wires extend to each of the two bridges. [7] The area S of the stage in a plan view is 3.6 × 10 7 μm 2 A gas concentration measurement device according to [3] or [6], which is as follows: [8] The total volume of the heating resistor and the stage is V, When the area of ​​the stage in a plan view is S, S / V is 0.0010μm -1 More than 10μm -1 A gas concentration measurement device according to any one of claims [3], [6] and [7], which is as follows: [9] The gas concentration measurement device according to any one of [1] to [8], wherein the heating resistor has a temperature coefficient of resistance αt of 100 ppm / °C or more at 25°C.

[10] The gas concentration measurement device according to any one of [1] to [9], wherein the heating resistor comprises platinum or an alloy containing platinum.

[11] A gas concentration measurement device according to any one of [1] to

[10] , having only the heating resistor as a component sensitive to a gas to be detected.

[0082]

[12] A peripheral portion spaced apart from the stage and surrounding the stage in a plan view; At least two bridges extending from and connected to the periphery of the stage; V' is the total volume of the space below the stage and the space between the stage and the peripheral portion, When the area of ​​the stage in a plan view is S, V' / S value is 10μm or more 2.0×10 9 The gas concentration measurement device according to any one of [1] to

[12] , wherein the particle size is equal to or less than 1 μm.

[13] The gas concentration measurement device according to

[12] , wherein the heating resistor is connected to wiring extending to the bridge and the peripheral portion.

[14] The heating resistor comprises one or more filaments, The resistance value R of the wiring at the portion overlapping with the bridge in a plan view B The resistance value R of the heating resistor S R is the ratio of S / R B The gas concentration measurement device according to

[13] , wherein the value of is 0.01 or more and 10,000 or less.

[15] The total volume V' is 2.5 × 10 4 μm 3 More than 1.8 x 10 11 μm 3 is as follows: The area S is 1.0×10 2 μm 2 More than 3.6 x 10 7 μm 2 The gas concentration measurement device according to

[12] or

[13] , wherein:

[16] The stage has a rectangular shape in a plan view, The bridge extends from each of the four corners of the stage, A partition wall is disposed in a space between adjacent bridges in a plan view to separate the bridges, The gas concentration measurement device according to any one of

[12] to

[15] , wherein the minimum distance between the bridge and the partition wall in a plan view is 5 μm or more and 1500 μm or less.

[17] The gas concentration measurement device according to

[16] , wherein the minimum width of the bridge is 5 μm or more and 1500 μm or less in a plan view.

[18] The gas concentration measurement device according to

[16] or

[17] , wherein the minimum distance between the stage and the partition wall in a plan view is 5 μm or more and 1500 μm or less.

[19] The area S of the stage in a plan view is 3.6 × 10 7 μm 2 is as follows: When the total volume of the heating resistor and the stage is V, S / V is 0.0010μm -1 More than 10μm -1 is as follows: A gas concentration measuring device according to any one of [1] to

[18] , which measures the oxygen gas concentration in a measured gas based on the resistance value of the heating resistor.

[20] A method for measuring a concentration of a target gas in a measurement gas using the gas concentration measuring device according to any one of [1] to

[19] .

[21] The measurement method according to

[20] , wherein the concentration of a target gas in the measured gas is measured in a state where a temperature difference between the heating resistor and the measured gas is set to 30°C or more by passing an electric current through the heating resistor.

[22] The measurement method according to

[20] or

[21] , wherein the measurement gas contains oxygen gas and nitrogen gas.

[23] A heating resistor that generates heat when electricity is passed through it; a stage for supporting the heating resistor; a peripheral portion spaced apart from the stage and surrounding the stage in a plan view; At least two bridges extending from and connected to the periphery of the stage; A gas concentration measuring device comprising: the heating resistor overlaps with the stage in a plan view, V' is a total volume of a space located below the stage and a space between the stage and the peripheral portion in the gas concentration measurement device, When the area of ​​the stage in a plan view is S, V' / S value is 10μm or more 2.0×10 9 μm or less, A gas concentration measuring device that measures the concentration of a target gas in a measurement gas based on the resistance value of the heating resistor.

[24] A heating resistor that generates heat when current is applied, and a stage that supports the heating resistor, the heating resistor overlaps with the stage in a plan view, The area S of the stage in plan view is 3.6×10 7 μm 2 is as follows: When the total volume of the heating resistor and the stage is V, S / V is 0.0010μm -1 More than 10μm -1 is as follows: A gas concentration measuring device that measures the concentration of a target gas in a measurement gas based on the resistance value of the heating resistor. EXAMPLES

[0083] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0084] Example 1 In this example, a device 10 shown in FIG. 1 was manufactured.

[0085] <Formation of insulating layer> Silicon crystal orientation <100> A substrate 11 having a thickness of 500 μm was prepared. The substrate 11 was thermally oxidized to form a first insulating layer 121 and a fifth insulating layer 125 made of SiO2 on the surface of the substrate 11. The first insulating layer 121 and the fifth insulating layer 125 each had a thickness of 600 nm. Next, a SiN x A second insulating layer 122 and a sixth insulating layer 126 made of SiO2 were formed. The second insulating layer 122 and the sixth insulating layer 126 each had a thickness of 200 nm. Furthermore, a third insulating layer 123 made of SiO2 was formed on the second insulating layer 122 by using a PECVD method. The third insulating layer 123 had a thickness of 1000 nm.

[0086] <Formation of Heating Resistor 31> According to the above-mentioned method, the first adhesive layer 33, the heating resistor 31 and the pad 32, and the second adhesive layer 34 were formed in this order on the third insulating layer 123 by sputtering. The first adhesive layer 33 and the second adhesive layer 34 were patterned by a lift-off method, and the heating resistor 31 and the pad 32 were patterned by a milling method. When forming the heating resistor 31 and the pad 32, a target material made of platinum was used as the sputtering target material. When forming the first adhesive layer 33 and the second adhesive layer 34, sputtering was carried out using a target material made of tantalum. The heating resistor 31 had a thickness of 0.3 μm, and the first adhesive layer 33 and the second adhesive layer 34 had a thickness of 0.02 μm.

[0087] <Formation of fourth insulating layer 124> A fourth insulating layer 124 made of SiO2 was formed on the third insulating layer 123 by the same method as the third insulating layer 123. The thickness of the fourth insulating layer 124 was 4000 nm. The thickness of each layer was calculated based on the film formation speed and the film formation time.

[0088] <Formation of Bridge Structure 20> Using RIE, unnecessary portions of the first insulating layer 121, the second insulating layer 122, the third insulating layer 123, and the fourth insulating layer 124, which are insulating layers located above the substrate 11, were removed. Next, unnecessary portions of the fifth insulating layer 125 and the sixth insulating layer 126, which are insulating layers located below the substrate 11, were removed. The unnecessary portions of the fifth insulating layer 125 and the sixth insulating layer 126 were removed by RIE to obtain a gas concentration measurement device. The unnecessary portions of the substrate 11 were removed by DRIE, which alternated between an etching process using SF6 and a passivation process using C4F8.

[0089] Example 2 In this example, the gas concentration measuring device shown in FIGS. 5 to 7 was manufactured. First, the crystal orientation of silicon <100> A stage 21 having a thickness of 290 μm was prepared. On one side of the stage 21, a heating resistor 31 and a pad 32 having a thickness of 0.3 μm were formed by sputtering. A 2-inch target material made of platinum and a 2-inch target material made of Y2O3 were used as target materials for the sputtering method. The film was formed by a co-sputtering method in which power is supplied to the two targets simultaneously. DC sputtering was used for platinum, and RF sputtering was used for Y2O3. The sputtering was performed using argon gas, with the flow rate of the argon gas being 50 sccm and the pressure of the argon gas being 4 Pa. The powers were 90 W and 200 W, respectively, and the sputtering was performed at room temperature. The heating resistor 31 contained 25 volume % of Y2O3 and 75 volume % of platinum.

[0090] Platinum paste was applied to the two pads 32 and two points on the surface opposite to the pads 32, and then fired in air at 700°C for 1 hour to form joints 37. Next, a Pt wire (bridge 22) with a wire diameter of 50 μm was bonded to each platinum paste by resistance welding. The other end of the Pt wire was bonded to a terminal 52 by resistance welding, thereby fixing the stage 21 to the terminal 52 via the bridge 22, and a gas concentration measuring device was obtained.

[0091] Example 3 A gas concentration measurement device was manufactured in the same manner as in Example 2, except that a 0.26 mm thick substrate made of alumina was used as the stage 21, and a 13 μm thick heating resistor 31 and pad 32 were formed on one surface of the substrate by screen printing using Pt paste.

[0092] Example 4 The substrate 11 used had a thickness of 300 μm, and the fourth insulating layer 124 had a thickness of 1000 nm. Other than this, the device 10 shown in FIG.

[0093] Example 5 A substrate 11 with a thickness of 300 μm was used, the thickness of the fourth insulating layer 124 was set to 1000 nm, and in <Formation of the bridge structure 20>, only the removal of the fourth insulating layer 124 located above the pad 32 was performed to expose the pad 32 to the outside. The bridge structure 20 was not formed. Except for the above points, in the same manner as in Example 1, a device 10 shown in FIGS. 9 to 11 without a bridge 22 was manufactured.

[0094] [Example 6] Except for changing the position and size of the unnecessary portions to be removed in <Formation of the bridge structure 20>, in the same manner as in Example 4, a device 10 shown in FIG. 1 was manufactured. The stage 21 and the bridge 22 in the device 10 of Example 6 were similar in plan view to the stage 21 and the bridge 22 in the device 10 of Example 4, and when comparing their sizes in plan view, the former was 0.3 times that of the latter.

[0095] [Comparative Example 1] A gas concentration measurement device shown in FIG. 8 was manufactured. In Example 3, after forming the heating resistor 31 on one surface of the stage 21, on the other surface of the stage 21, an electrode 61a made of platinum and a perovskite-type La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ A cell composed of a solid electrolyte 62 made of lanthanum silicate disposed between the composite oxide electrodes 61b was adhered to one surface of the stage 21 using a Pt paste. Next, in an air atmosphere, a sealing material 63 made of glass was applied to seal the electrode 61a located closer to the stage 21 among the two electrodes 61a and 61b. Except for this, in the same manner as in Example 3, a gas concentration measurement device was obtained. The gas concentration measurement device of Comparative Example 1 can measure the oxygen concentration based on the concentration difference electromotive force generated between the two electrodes 61a and 61b, and the heating resistor 31 is used to heat the solid electrolyte 62.

[0096] [Evaluation] <Measurement of S, V, and Heat Capacity> In Examples 1 and 4 to 6, the thicknesses of the layers constituting the stage 21 and the heating resistor 31 were calculated from the previously calculated film formation speeds of the layers and the heating resistor 31. In Examples 2 and 3, the thicknesses of the stage 21 and the heating resistor 31 were measured using calipers. The dimensions of the stage 21 and the heating resistor 31 other than the thickness were measured using a microscope (VHX-8000 manufactured by Keyence Corporation) or a vernier caliper. Based on the dimensions measured as described above, and the specific heat and density of the materials constituting each layer, the area S of the stage 21 in a plan view, and the total volume V and total heat capacity of the heating resistor 31 and the stage 21 were calculated. These results are shown in Table 1.

[0097] <Oxygen gas concentration response measurement> The oxygen gas concentration response of the heating resistor 31 was measured when a current was applied to the heating resistor 31. The measurement was performed using the gas concentration measuring devices of Examples 1 to 5 under the following conditions. Current supply conditions: Atmospheric pressure, constant power drive at applied voltages of 40mW, 50mW, 80mW, 700mW or 1300mW Gas flow rate: 100sccm Measurement gas: Oxygen and nitrogen gas mixture Room temperature (temperature of the gas to be measured): 25℃ The oxygen gas concentrations in the gases to be measured were as follows: 140 to 240 seconds after measurement begins: 100% by volume 240 to 340 seconds after measurement begins: 80% by volume 340 to 440 seconds after measurement begins: 60% by volume 440~540 seconds after measurement starts: 40% by volume 540-640 seconds after measurement begins: 21% by volume 640 to 740 seconds after measurement begins: 10% by volume 740-800 seconds after measurement begins: 21% by volume The resistance change rate of the heating resistor 31 when a current is applied to the heating resistor 31 under a constant power condition of 80 mW is shown in Fig. 15. The resistance change rate is a value (ppm) based on the resistance value of the heating resistor 31 when the oxygen concentration in the measurement gas is 21 volume %, and is calculated based on the following formula. In the formula, R x represents the resistance value at oxygen concentration x volume percent, and R 21 indicates the resistance value at an oxygen concentration of 21 volume %. Resistance change rate = (R x -R 21 ) / R 21 ×10 6 Table 2 shows the temperature of the heating resistor 31 and the temperature difference between the heating resistor 31 and room temperature (temperature of the gas to be measured) during current flow under each constant power condition. The temperature of the heating resistor 31 was measured in an environment with an oxygen concentration of 21% using a radiation thermometer (FLIR T640, CLOSE-UP LENS). The emissivity was measured as 0.66 for Example 1, 0.63 for Example 2, 0.88 for Example 3 and Comparative Example 1, and 0.70 for Examples 4 and 5. In Tables 1 and 2, "-" indicates that the measurement was not performed.

[0098] <Calculating sensitivity> The resistance change rate (ppm) of the heating resistor 31 obtained in the above <Oxygen gas concentration response measurement> was plotted against the oxygen concentration (%) of the measured gas. A regression line was then obtained by the least squares method, and the slope of the regression line was calculated as the sensitivity. The results are shown in Table 2. Also, a graph showing the relationship between the resistance change rate of the heating resistor 31 and the oxygen concentration when electricity is applied to the heating resistor 31 under a constant power condition of 80 mW is shown in FIG. 16.

[0099] <Response speed evaluation> In the gas concentration measuring devices of Example 3 and Comparative Example 1, the oxygen gas concentration was changed from 60% to 90%, and the time it took for the sensor output to respond from 10% to 90% was compared as the response speed (sec). The sensor output of Example 3 is the resistance value of the heating resistor, and the sensor output of Comparative Example 1 is the electromotive force value generated between the two electrodes. The current supply condition was a constant power condition of 1300 mW. The flow rate of Comparative Example 1 was 50 sccm. The other conditions were the same as those in the above <Measurement of oxygen gas concentration response>. The results are shown in Table 2.

[0100] <Temperature coefficient of resistance of heating resistor α t Measurements > Using a hot-cold stage (manufactured by INSTEC), the resistance value of the heating resistor 31 when the oxygen concentration in the measurement gas is 21% by volume and 25°C is used as the reference, and the rate of change in the resistance value of the heating resistor when heated to 500°C (R 500 -R 25 ) / R 25 / (500-25)×10 6 (ppm / ℃) (in the formula, R 500 represents the resistance value at 500°C, and R 25 indicates the resistance value at a reference temperature of 25°C.) was measured. The results are shown in Table 1.

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in Fig. 13 and Table 2, there was a good linear relationship between the oxygen gas concentration in the measurement gas and the resistance value of the heating resistor 31. Therefore, it is understood that the gas concentration measurement device of the present invention can measure the oxygen gas concentration with high accuracy even when the measurement gas contains oxygen gas and nitrogen gas, despite being easily manufactured. In contrast, the gas concentration measurement device of Comparative Example 1 has room for improvement in that the manufacturing process is complicated.

[0104] <Measurement of hydrogen gas, helium gas, argon gas and water vapor concentration response> Hydrogen gas, helium gas, argon gas or water vapor was used as the detection target gas, and the detection target gas concentration response was measured in the same manner as in the case of oxygen gas. The measurement was performed using the gas concentration measurement devices of Examples 2, 4 and 6 under the following conditions. -Power supply conditions: Atmospheric pressure, constant power drive at an applied voltage of 30mW Gas flow rate: 200sccm Measurement gas: A mixture of the gas to be detected and nitrogen gas Room temperature (temperature of the gas to be measured): 25℃ The concentrations of the target gases to be detected in the measurement gas were as follows: [When the gas to be detected is hydrogen gas] 0 to 180 seconds after measurement begins: 0% by volume 180 to 360 seconds after measurement begins: 2% by volume 360 to 540 seconds after measurement begins: 3% by volume 540 to 720 seconds after measurement begins: 4% by volume 720 to 900 seconds after measurement begins: 0% by volume [When the gas to be detected is helium gas or argon gas] 0 to 180 seconds after measurement begins: 0% by volume 180 to 360 seconds after measurement begins: 5% by volume 360 to 540 seconds after measurement begins: 10% by volume 540 to 720 seconds after measurement begins: 20% by volume 720 to 900 seconds after measurement begins: 50% by volume 900 to 1080 seconds after measurement begins: 100% by volume 1080~1260 seconds after measurement starts: 0% by volume [When the gas to be detected is water vapor] Instead of performing measurements under a flow of the target gas, a thermo-hygrostat chamber housing the gas concentration measuring device was filled with the target gas at 25°C, and the relative humidity in the thermo-hygrostat chamber was then changed as follows: ·0 to 4 hours after start of measurement: 10%RH ·4 to 7 hours after start of measurement: 20%RH ·710 hours after start of measurement: 40%RH ·10~13 hours after start of measurement: 60%RH ·13~16 hours after start of measurement: 80%RH ·16~19 hours after start of measurement: 60%RH

[0105] The resistance change rate of the heating resistor 31 for each detection target gas when a current is passed through the heating resistor 31 under the above-mentioned conditions is shown in Fig. 17 to Fig. 20. The resistance change rate is a value (ppm) based on the resistance value of the heating resistor 31 when the detection target gas concentration in the measurement target gas is 0 volume % (10% RH when the detection target gas is water vapor), and is calculated based on the following formula. In the formula, R x represents the resistance value when the detection target gas concentration is x% by volume (x% RH when the detection target gas is water vapor), and R0 represents the resistance value when the detection target gas concentration is 0% by volume (10% RH when the detection target gas is water vapor). Resistance change rate = (R x -R0) / R0×10 6

[0106] <Calculating sensitivity> The resistance change rate (ppm) of the heating resistor 31 obtained in the above <Measurement of hydrogen gas, helium gas, argon gas, and water vapor concentration response> was plotted against the detection target gas concentration (%) in the measurement gas. Next, a regression line was obtained by the least squares method, and the slope of the regression line was calculated as the sensitivity. The calculated sensitivity is shown in Table 3. In addition, graphs showing the relationship between the resistance change rate of the heating resistor 31 and the detection target gas concentration when current is applied to the heating resistor 31 under the above-mentioned conditions are shown in Figures 21 to 24 for each detection target gas. In Table 3, "-" indicates that the measurement was not performed.

[0107] [Table 3]

[0108] As shown in Table 3, even when hydrogen gas, helium gas, argon gas, and water vapor are used as the detection target gas, it is possible to measure the detection target gas concentration with high sensitivity.

[0109] [Examples 7 to 16] In Examples 7 to 16, the devices 10 shown in FIGS. 12 to 14 were manufactured. The distances d1 and d2 (d1=d2 in each example) and R S / R B , the minimum width of bridge 22, the minimum distance between bridge 22 and partition 25, S, V', and V' / S are shown in Table 4. The minimum distance between the stage 21 and the partition wall 25 is the same as the minimum distance between the bridge 22 and the partition wall 25 . Additionally, the devices 10 of Examples 7 and 10 to 16 did not have a partition 25 .

[0110] <Formation of insulating layer> Silicon crystal orientation <100> A substrate 11 having a thickness of 300 μm was prepared. The substrate 11 was thermally oxidized to form a first insulating layer 121 and a fifth insulating layer 125 made of SiO2 on the surface of the substrate 11. The first insulating layer 121 and the fifth insulating layer 125 each had a thickness of 600 nm. Next, a SiN x A second insulating layer 122 and a sixth insulating layer 126 made of SiO2 were formed. The second insulating layer 122 and the sixth insulating layer 126 each had a thickness of 200 nm. Furthermore, a third insulating layer 123 made of SiO2 was formed on the second insulating layer 122 by using a PECVD method. The third insulating layer 123 had a thickness of 1000 nm.

[0111] <Formation of Heating Resistor 31> According to the above-mentioned method, the first adhesive layer 33, the heating resistor 31 and the pad 32, and the second adhesive layer 34 were formed in this order on the third insulating layer 123 by sputtering. The first adhesive layer 33 and the second adhesive layer 34 were patterned by a lift-off method, and the heating resistor 31 and the pad 32 were patterned by a milling method. When forming the heating resistor 31 and the pad 32, a target material made of platinum was used as the sputtering target material. When forming the first adhesive layer 33 and the second adhesive layer 34, sputtering was carried out using a target material made of tantalum. The heating resistor 31 had a thickness of 0.20 μm, and the first adhesive layer 33 and the second adhesive layer 34 had a thickness of 0.020 μm.

[0112] <Formation of fourth insulating layer 124> A fourth insulating layer 124 made of SiO2 was formed on the third insulating layer 123 by the same method as the third insulating layer 123. The thickness of the fourth insulating layer 124 was 1000 nm. The thickness of each layer was calculated based on the film formation speed and the film formation time.

[0113] <Formation of Bridge Structure 20> Using RIE, unnecessary portions of the first insulating layer 121, the second insulating layer 122, the third insulating layer 123, and the fourth insulating layer 124, which are insulating layers located above the substrate 11, were removed. Next, unnecessary portions of the fifth insulating layer 125 and the sixth insulating layer 126, which are insulating layers located below the substrate 11, were removed. The unnecessary portions of the fifth insulating layer 125 and the sixth insulating layer 126 were removed by RIE to obtain a gas concentration measurement device. The unnecessary portions of the substrate 11 were removed by DRIE, which alternated between an etching process using SF6 and a passivation process using C4F8.

[0114] 〔evaluation〕 <Oxygen gas concentration response measurement> The oxygen gas concentration response of the heating resistor 31 was measured when a current was applied to the heating resistor 31. The measurement was performed under the following conditions. -Power supply conditions: Atmospheric pressure, constant power drive at an applied voltage of 50mW Gas flow rate: 300sccm Measurement gas: Oxygen and nitrogen gas mixture Room temperature (temperature of the gas to be measured): 25℃ The oxygen gas concentrations in the gases to be measured were as follows: 180 to 360 seconds after measurement begins: 100% by volume 360-540 seconds after measurement begins: 80% by volume 540 to 720 seconds after measurement begins: 60% by volume 720 to 900 seconds after measurement begins: 40% by volume 900 to 1080 seconds after measurement begins: 21% by volume 1080~1260 seconds after measurement starts: 10% by volume 1260-1440 seconds after measurement started: 21% by volume The resistance change rate is a value (ppm) based on the resistance value of the heating resistor 31 when the oxygen concentration in the measurement gas is 21 volume %, and is calculated based on the following formula: x represents the resistance value at oxygen concentration x volume percent, and R 21 indicates the resistance value at an oxygen concentration of 21 volume %. Resistance change rate = (R x -R 21 ) / R 21 ×10 6

[0115] <Calculating sensitivity> The resistance change rate (ppm) of the heating resistor 31 obtained in the above <Oxygen gas concentration response measurement> was plotted against the oxygen concentration (%) of the measured gas. Next, a regression line was obtained by the least squares method, and the slope of the regression line was calculated as the sensitivity. The results are shown in Table 4.

[0116] [Table 4]

[0117] As shown in Table 4, the gas concentration measurement devices of the examples in which V' / S was within the specified range showed excellent measurement sensitivity. S / R B The larger the value, the higher the sensitivity. Also, the smaller the stage area S, the higher the sensitivity tends to be. [Industrial Applicability]

[0118] According to the present invention, a gas concentration measuring device that can be easily manufactured is provided.

Claims

1. The heater includes a heating resistor that generates heat when an electric current is applied thereto, and a stage that supports the heating resistor; the heating resistor overlaps with the stage in a plan view, The area S of the stage in a plan view is 3.6×10 ７ μm ２ is as follows: When the total volume of the heating resistor and the stage is V, S / V is 0.0010 μm －１ 10 μm or more －１ is as follows: A gas concentration measuring device that measures the concentration of a detection target gas (excluding helium gas) in a measurement gas based on the resistance value of the heating resistor.

2. The total heat capacity of the heating resistor and the stage is 1.0×10 －１０ J / K or above 3.2×10 －２ The gas concentration measurement device according to claim 1 , wherein the resistance is equal to or less than J / K.

3. 10. The gas concentration measurement device of claim 1, further comprising one or more bridges extending from a periphery of the stage to form a bridge structure.

4. 2. The gas concentration measuring device according to claim 1, wherein the gas to be detected is oxygen gas, argon gas, water vapor or carbon dioxide gas.

5. 2. The gas concentration measuring device according to claim 1, wherein the detection target gas is oxygen gas.

6. The heating resistor is made of a series of wires, The series of filaments may be a single filament or a plurality of filaments having at least both ends in common, At least two of the bridges extend from a periphery of the stage; The gas concentration measurement device according to claim 3 , wherein the series of wires extend to each of the two bridges.

7. 2. The gas concentration measuring device according to claim 1, wherein the heating resistor has a temperature coefficient of resistance αt at 25° C. of 100 ppm / ° C. or more.

8. The gas concentration measurement device according to claim 1 , wherein the heating resistor comprises platinum or an alloy containing platinum.

9. 2. The gas concentration measuring device according to claim 1, wherein the heating resistor is the only member sensitive to the target gas.

10. a peripheral portion spaced apart from the stage and surrounding the stage in a plan view; At least two bridges extending from and connected to the periphery of the stage; When the total volume of the space below the stage and the space between the stage and the peripheral portion is V', The value of V' / S is 10 μm or more and 2.0×10 ９ The gas concentration measuring device according to claim 1 , wherein the particle size is equal to or smaller than 1 μm.

11. The gas concentration measurement device according to claim 10 , wherein the heating resistor is connected to wiring extending to the bridge and the peripheral portion.

12. The heating resistor is composed of one or more filaments, The resistance value R of the wiring at the portion overlapping with the bridge in a plan view Ｂ The resistance value R of the heating resistor Ｓ R is the ratio of Ｓ / R Ｂ The gas concentration measurement device according to claim 11 , wherein the value of is 0.01 or more and 10,000 or less.

13. The total volume V′ is 2.5×10 ４ μm ３ That's 1.8 x 10 １１ μm ３ is as follows: The area S is 1.0×10 ２ μm ２ The gas concentration measuring device according to claim 10 .

14. The stage has a rectangular shape in a plan view, The bridge extends from each of the four corners of the stage, A partition wall is disposed in a space between adjacent bridges in a plan view to separate the bridges, 11. The gas concentration measurement device according to claim 10, wherein a minimum distance between the bridge and the partition wall is 5 μm or more and 1500 μm or less in a plan view.

15. The gas concentration measurement device according to claim 14 , wherein the minimum width of the bridge is 5 μm or more and 1500 μm or less in a plan view.

16. 15. The gas concentration measurement device according to claim 14, wherein a minimum distance between the stage and the partition wall is 5 μm or more and 1500 μm or less in a plan view.

17. A method for measuring a concentration of a target gas in a measurement gas, using the gas concentration measuring device according to claim 1 .

18. 18. The method according to claim 17, further comprising the step of: measuring a concentration of the target gas in the measurement gas by passing a current through the heating resistor so that a temperature difference between the heating resistor and the measurement gas is set to 30° C. or more.

19. 18. The measurement method according to claim 17, wherein the measurement gas contains oxygen gas and nitrogen gas.

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