JPH041301B2 - - Google Patents

Abstract

PURPOSE:To reduce power consumption, to enhance mass productivity, and to improve gas sensitivity, by forming a gas sensitive material between a pair of conducting layers, and performing gas detection based on the change in resistance value of the material due to the contact reaction with the gas. CONSTITUTION:On a substrate 1 and an insulating layer 2, metal layers 3 are formed into three patterns each having two electrode parts and one thin wire part, respectively. Heaters 7 and 9, a gas-detecting lead 8, a gas-detecting semiconductor layer 6, and an insulating layer 4 are formed. A bump 5 is formed on each electrode part (7a, 8b, 9c, 7d, 8e, and 9f) after the opening of a window in the insulating layer 4. The width (m) of the gas-detecting lead pattern 8 is 1-3mum, which is narrow. This is because the output voltage across the electrodes 8b-8e is increased by increasing the resistance value of the gas-detecting lead pattern, S/N of the detected voltage is improved, and the temperature distribution is improved. The width of the heaters 7 and 9 are wide in the vicinity of the center of a bridge. This is because the cross sectional areas of the heaters 7 and 9 are increased, and the current density must be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to gas detection devices, and more particularly to gas detection devices.
This invention relates to a gas detection device that can be applied to gas leak alarms for LP gas and city gas.

Conventional technology Conventional gas detection devices include a heater coil that also serves as an electrode inside a metal oxide semiconductor.
There is a method that takes advantage of the fact that the resistance value of a metal oxide semiconductor heated by a heater coil decreases due to gas adsorption on the surface, but this method consumes a large amount of power and is not suitable for battery operation.

Purpose The present invention has been made in view of the above points, and is capable of reducing power consumption, enabling dry battery operation, easy mass production, good gas sensitivity, stable operation at all times, and long life. The purpose of the present invention is to provide a gas detection device that has the following characteristics.

Configuration The configuration of the present invention will be described below based on specific examples. FIG. 1 is a schematic diagram showing the internal structure of a gas detector using a gas detection device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line - in FIG. 1. The gas detection device in this embodiment is indicated by 10 in FIG. 1, where 1 is a substrate, 2 is an insulating layer, and 3 is a metal layer. The metal layer 3 is formed into three patterns each having two electrode parts and one thin wire part, 7 and 9 are heaters, 7a,
7d, 9c, and 9f are heater electrodes, 8 is a gas detection lead, and 8b and 8e are detection electrodes. 6 is a semiconductor layer for gas detection. 4 is an insulating layer;
Bumps 5 are formed on each electrode portion 7a, 8b, 9c, 7d, 8e, and 9f after opening a window in the insulating layer 4. This gas detection device 10 has lead foils 26 (six pieces) bonded on a film 20 to each electrode portion 7.
It is mounted on the film 20 by heat bonding to the bumps 5 of a, 8b, 9c, 7d, 8e, and 9f, and is covered with a lower cover 21 on the lower side and an explosion-proof net 24 and a dust-proof filter 25 on the upper side. There is. Explosion-proof net 24 and dust-proof filter 2
5 is an upper cover work 2 provided on the film 20;
2 and is fixed. Explosion-proof net 2
4 is for preventing ignition. The dust filter 25 is used to prevent the gas detection device 10 from being affected by dust attached to its surface, such as shortening its life or making the operation unstable. When the detection device 10 is attached to the film 20, glass wool is used which does not allow dust of 0.1 .mu.m or larger to pass therethrough and does not impede the inflow and outflow of gas. Gas is adsorbed by the gas detection semiconductor 6 through the explosion-proof net 24 and the dust-proof filter 25.

FIG. 3 is a schematic diagram for explaining the operating principle of the gas detection device 10, and FIG. 4 is a block diagram showing a method of driving the gas detector. Between electrodes 7a-7d and 9
Heaters 7 and 9 are extended between electrodes 8b and 8e, and gas detection leads 8 are provided between electrodes 8b and 8e.
11 is a power supply and a pulse drive circuit. The reason why the gas detection lead 8 is sandwiched between the two heaters 7 and 9 is to make the temperature distribution of the gas detection semiconductor layer 6 uniform.If the conditions for uniform temperature distribution are satisfied, the heater pattern is Any number of lead patterns and gas detection lead patterns may be alternately arranged. Between electrodes 9c-9f (7a-7
When a pulse voltage of 1.5 to 3 V is applied between
9 reaches 350 to 400° C. At the same time, the gas detection semiconductor layer 6 is also heated via the insulating layer 2, and its resistance value decreases. Furthermore, a gas detection semiconductor layer 6 that adsorbs gas
The resistance value eventually decreases by two to three orders of magnitude, and as a result, the current icf of the heater 7 (the same applies to 9) flows in the form of Icbef on the gas detection lead 8 side, and appears as a pulse voltage change between the electrodes 8b and 8e. Therefore, the gas concentration can be detected as a voltage change between electrodes 8b-8e. Figure 5a shows the output voltage waveform V _OUT (at gas concentration 0%) and V _OUT1 (at gas concentration 0.35%) between electrodes 8b-8e with respect to the voltage waveform V _IN input between electrodes 9c-9f. When a highly concentrated gas, for example 100% gas, is adsorbed, Icbef increases and Icf decreases.If Icf decreases, the temperature of the heaters 7 and 9 decreases, and accordingly the gas detection semiconductor As the temperature of the layer 6 decreases, the resistance value starts to increase and Icbef becomes small again.This decrease is due to the small heat capacity of the heaters 7 and 9 and the short time to reach thermal equilibrium, as well as the driving method. -8e has the advantage of shortening the time required to stabilize the output voltage and suppressing the temperature rise of the heaters 7 and 9. Fig. 6 is an enlarged view of Fig. 3, and the dimensions in this example are...
100~500μm, m...1~3μm, n...5~20μm, s
...10 to 50 μm, t...15 to 50 μm, u...1 to 3 μm. The width m of the gas detection lead pattern 8 is 1 to 3 μm.
The reason why it is narrow is that by increasing the resistance value of the gas detection lead pattern 8, the output voltage across the electrodes 8b-8e in FIG. 4 increases, improving the S/N ratio of the detection voltage. be. heater 7,
The reason why the width of heater 9 becomes wider near the center of the bridge is to increase the cross-sectional area of heaters 7 and 9 and lower the current density at the center of the heater, where the temperature is highest. As a result, the amount of heat generated at the center of the bridge is reduced, which has the effect of making the temperature distribution of the heaters 7 and 9 uniform, and at the same time prevents the promotion of electromigration under high temperatures, thereby improving the life of the heaters 7 and 9. I can do it. Furthermore, since the heaters 7 and 9 and the gas detection lead 8 are brought closest to each other at the center of the bridge where the temperature is highest, the resistance value of the gas detection semiconductor layer 6 becomes the lowest due to a synergistic effect, and the electrode 8b-
Since the detection voltage between 8e and 8e becomes larger, the S/N ratio improves, and there is an effect of reducing the effect of lowering the sensitivity of the gas detection device 10 to the temperature and alcohol that react at low temperatures.

Next, an example of the manufacturing process of the gas detection device having the above-mentioned configuration will be explained in detail with reference to FIGS. 7 to 14. First, as shown in FIG. 7, an insulating layer 2, a metal 3, and a resist layer 4 are formed on a substrate 1. The substrate 1 is the base of the gas detection device, and electrode pads of a heater pattern and a gas detection lead pattern are formed on the substrate 1. It is easy to undercut etching without affecting the upper layer material, and deforms at high temperature (heating at 500℃ for several to 10 hours).
Use materials that do not deteriorate. In this example, Si
(100), but other materials include Al, Cu, N,
Cr is also possible. Dimensions are 1 to 4 mm square and 0.1
It is best to have a thickness of ~1 mm. However, the thinner the better for easier braking. 2 is an insulating layer that supports the heater pattern and provides insulation between each electrode. Use a heat-resistant material with high insulation properties and a coefficient of linear expansion close to that of the heater material. For example Al ₂
O ₃ , MgO, Si ₃ N ₄ , Ta ₂ O ₅ may also be used. In this example, SiO ₂ was sputtered using known RF sputtering (Ar pressure 0/
1 to 0.01 Torr, input power density 1 to 10 W/cm ² ,
It is formed to a thickness of 0.3 to 2 μm depending on the substrate temperature (350 to 400° C.). 3a is a diffusion layer for increasing the adhesion between the heater material layer 3b and the insulating layer 2;
Both the substrate 1 and the insulating layer 2 are made of materials that are resistant to etching solutions. In this example, Mo was deposited by RF sputtering (the conditions are the same as above) to
It is formed to a thickness of 800 Å. In addition, Cr, Ni,
Ti is also good. 3b is a heater material layer, which is made of a material that is stable for a long time. In this example, Pt is RF
0.0 by sputtering (conditions are the same as above)
It is formed to a thickness of 3 to 2 μm. Besides that
SiC, TaN2 _, etc. can also be used. 4 is a resist layer, which serves as a mask when dry etching the metal layer 3, as will be described later, and also serves as insulation for the lead layer for gas detection and as a solder bump glass dam when forming bumps on each electrode portion. . In this example, SiO ₂ is formed to a thickness of 0.5 to 1 μm by RF sputtering (under the same conditions as above).
All of the above processes can be performed continuously in the same batch and are suitable for mass production. Since it is continuous, the interface between the layers is clean and has excellent adhesion. Also
As a condition for RF sputtering, the substrate temperature should be 350~
The reason why the temperature was set at 400°C is that in addition to the well-known advantage that heating the substrate makes the film denser and reduces the range of fluctuations in the resistance value of the metal layer 3 over time, the operating temperature of the gas detection device is 350 to 400°C. This is because it has the advantage of minimizing the stress exerted on the membrane during operation, resulting in improved reliability.

Next, the SiO ₂ of No. 4 is photoetched using a known photolithography technique. A general buffered hydrofluoric acid (HF+NH ₄ F) is used as the etching solution. The photomask pattern consists of a heater pattern having two electrode parts and one thin line part and a plurality of gas detection patterns, and the temperature distribution of the gas detection lead pattern is made uniform by the heat generated by the heater pattern. FIG. 8 shows a photomask pattern 12 in which the substrate 1 around the heater pattern, except for the electrode portion, is undercut etched during the anisotropic etching of the substrate 1. As shown in FIG. Since Si (100) is used as the substrate 1, the electrode part 1 is placed in the direction where the (111) plane, which is difficult to be etched, appears.
2', a (110) surface that is easily etched appears on the underside of the bridge portion 12'' that forms an angle of 45° with respect to the electrode portion, and is easily undercut etched to form a cavity. As Si
(111), photomask pattern 1
The angle between the electrode part 12' and the bridge part 12'' of No. 2 is
By setting the angle to 15°, undercut etching can be performed. Figure 9 shows the photo-etching of SiO ₂ in step 4.
FIG. 8 is a sectional view taken along the line FIG. 4 in Figure 9
FIG. 10 shows dry etching of the metal layer 3 using SiO ₂ as a resist. Dry etching was used because wet etching is difficult for 3a Pt. In this example, the well-known Ar sputter etching (Ar pressure 0,
1 to 0.01Torr, input power density 1 to 10W/cm ² ,
Although the substrate temperature was room temperature), CF ₄ +O ₂ plasma etching is also possible. Here, the first
Using the photomask pattern 13 shown in FIG. 1, photoetch the SiO ₂ layers 2 and 4 in FIG. 10 to open windows 7a'', 8b'', 9c'', 7d'',
8e″, 9f″, etching window opening 14 for substrate 1,
15. FIG. 12 is a sectional view taken along the - line in FIG. 11 after photo-etching, in which windows 16 are opened on the heater pattern and the gas detection lead pattern. 3 is a metal layer, 3b is Mo, 3a is Pt,
It is composed of Mo of 3b. Using SiO ₂ of 2 and 4 in Fig. 12 as a resist, further substrate 1 (Si)
Perform anisotropic etching. The etching solution is KOH or NaOH, which is a known anisotropic etching solution.
(30-60% aqueous solution, liquid temperature 80-150℃), APW (ethylenediamine + pyrocatechol + water, liquid temperature 90-150℃)
110℃), hydrazine aqueous solution (64mo1%, liquid temperature 90~
110℃) etc. As shown in Figure 13,
By etching for 20 to 40 minutes, the substrate 1 existing under the SiO ₂ layer 2' is undercut to a depth of 50 to 300 μm to form a cavity, and the heater patterns 7 and 9 and the gas detection pattern 8 are bridged. A profile with a similar structure is obtained. This is due to the relationship between the crystal orientation of the substrate 1 and the photomask pattern as described above. The window opening indicated by 14 in FIG. 11 has the effect of finishing the etching profile of the substrate 1 well. For example, in this example, Si (111) tends to remain at both ends of the bridge-like part, but the etching time required to prevent this from remaining can be reduced to about half, and the etching time for other layers can be reduced by half. Damage from liquid can be further reduced. In addition, if the etching profile is good, heat diffusion due to heat conduction from the heater layer 3 to the substrate 1 via the insulating layer 2 is prevented from occurring near both ends of the bridge-like portion, and the efficiency of the heaters 7 and 9 is improved. As the temperature becomes better, the temperature distribution tends to become more uniform. Furthermore, although both ends of the bridge-shaped portion are relatively low temperature, since the gas detection semiconductor layer 6 is not formed in these portions, the influence of humidity and alcohol that react at low temperatures can be reduced. 1st
Figure 13 is a version of Figure 2 with undercut etching applied. Next, in the electrode windows 17a and 17b
Sn and Au are each deposited to a thickness of several to 10 μm, and the substrate 1 is heated to 400 to 600°C to form dome-shaped bumps 5.
form. In this case, _the Au-Sn eutectic alloy bumps 5 are formed into a dome shape as shown in FIG. I can do that. Reference numeral 6 in FIG. 14 is a semiconductor layer for gas detection, which is formed astride between the heater patterns 7 and 9 and the lead pattern 8 for gas detection. _SnO2 ,
Using a semiconductor material for gas detection made of metal oxides such as Fe ₂ O ₃ and ZnO, it is formed to a thickness of 0.3 to 3 μm by sputtering or vapor deposition, or by dispersing fine powder in water and alcohol. Form by spin coding. The above process can be easily completed using two types of photomasks and two types of vapor deposition masks, and the upper mask alignment accuracy is approximately ±3 μm. This is much simpler than other IC and LSI manufacturing processes, so it is low cost and highly reliable.

Next, examples of the present invention will be described. 1st
FIG. 5 is a schematic diagram thereof, and FIGS. 16 and 17 are sectional views taken along the - line and '-' line in FIG. 15, respectively. 21 is a substrate, 22 is an insulating layer, 23
is the metal layer. A circular electrode 29 is provided on the metal layer 23.
f, a circular heater 27 spirally extending from 29f to form a concentric circle outside 29f, another electrode 29b protruding from the circular heater 27, and a gas detection electrode forming a concentric circle between the circular electrode 29f and the circular heater 27. Lead 28, electrode 28e extending from gas detection lead 28, independent electrode 29
g is formed in a pattern. As shown in FIG. 17, a window is formed in the insulating layer 22 so that the circular electrode 29f can be electrically connected to the independent electrode 29g via the substrate 1. Electrode 2 of gas detection lead 28
The lead end other than the 9e side is connected to the circular electrode 29f. 26 is a semiconductor layer for gas detection. The substrate 21 is undercut-etched to form a cavity at the outer portion of the concentric circular heater 27 and the gas detection lead 28. Therefore, as shown in FIG. 16, the circular heater 27 and the gas detection leads 28 are mounted on the periphery of the disc-shaped insulating layer 22 extending above the cavity of the substrate 21. That is, the heating portion is not in contact with the substrate 21 which is a support. Electrode 29b
serves as both a heater electrode and a detection electrode. Further, the electrode 29g is a heater electrode and is electrically connected to the circular electrode 29f via the substrate 21. The electrode 29e is a detection electrode. The driving circuit and the principle of gas concentration detection are exactly the same as those shown in FIG. 4 in the embodiment described above. That is, in FIG.
The circular heater 27 generates heat due to the pulse voltage applied between 9b and 29f, and the gas detection semiconductor layer 2
6 is heated. As the gas detection semiconductor layer 26 reaches a high temperature and gas is adsorbed, the resistance value decreases by two to three orders of magnitude, so the electrode of the heater 27 flows on the gas detection lead 28 side, causing a pulse voltage change between the electrodes 29b-29e. Detected as .

18 to 21 are cross-sectional views taken along the - line of the gas detection device shown in FIG. 15, showing the manufacturing process. In FIG. 18, an insulating layer 22 of SiO ₂ is formed on a substrate 21 of Si (100) by sputtering, and a window 22 for undercut etching is formed in the substrate 21 by photoetching using the photomask pattern 14 of FIG. ' and electrode 29f-29
g Opening window 22f for contact hole for continuity,
Do 22g. Next, as shown in Figure 19,
Diffusion layer 23a using Mo, heater material layer 23b using Pt, and resist layer 24 using SiO ₂
The circular heater 2 is formed by sputtering, and the resist layer 24 is photoetched using the photomask pattern 15 shown in FIG.
7', gas detection lead 28', electrode 29e', 29
Mask patterns b', 29f', and 29g' are formed.
Using this mask pattern as a resist, the diffusion layer 2a
FIG. 20 shows the dry etching of the metal layer 23 consisting of the heater material 2b and the diffusion layer 2a. Since the SiO ₂ in the resist layer 24 on the metal layer 23 is extremely thin, it is removed by immersing it in an SiO ₂ etching solution, and then the Si substrate 21 is undercut etched using anisotropic etching to form a cavity. When the gas detection semiconductor layer 26 is formed so as to cover the heater pattern 27 and the gas detection pattern 28 on the same circumference, the final result is as shown in FIG. 21. Note that since the electrodes 29g to 29f are electrically connected through the substrate 21, the material of the substrate 21 must have high electrical conductivity. For example, in addition to Si doped with impurities such as B or P at high density, Al,
Use Cu, Ni, Cr, etc.

Photomask pattern 1 in Figures 22 and 23
The dimensions at 4 and 15 are preferably as follows. In FIG. 23, the diameter φ ₁ of the circular electrode 29f is 30~
800 μm, and a gas detection lead 28 with a width of 1 to 10 μm on the outside, and a heater 2 with a width of 3 to 50 μm on the outside.
7 is formed concentrically with the circular electrode 29f. The clearance between the gas detection lead 28 and the pattern of the heater 27 is 1 to 10 μm. The disc-shaped insulating layer 22 supporting the heater 27 and the gas detection lead 28 is also concentric with the circular electrode 29f, and has a diameter φ ₂ of 50 to 1,000 μm. The electrode 29e and the electrode 29b each protrude from the concentric circle, and the angle α between the protruding portion and the electrode in FIG.
This is to ensure that the bottom of the overhanging portion is undercut due to the relationship between the Si(100)NO crystal orientation and anisotropic etching. The length q of the overhang is 5~
50 μm is appropriate.

Since the circular heater as in this embodiment has the same heat diffusion concentrically with respect to the center of the circle, it is far superior to the linear heater in terms of uniform temperature distribution. Also, regarding the load applied to the heater support layer (insulating layer), a linear heater has a bridge-like structure, whereas a circular heater only has a bridge-like structure that rests on the protruding part of the circumferential edge. Therefore, it can be said that the circular type has a much smaller load and greater strength. Furthermore, the length of the heater must be longer than a certain level (for example, when the width of the heater is 3 μm to 10 μm, the thickness is 0.3 μm, and the resistance value is 200 Ω, the length must be 0.5 mm or more).
With linear heaters, the longer they are, the greater the effect of thermal expansion.Particularly with pulse drive, the heater vibrates in synchronization with the pulses, and the vibrations can cause the heater to separate from the semiconductor layer for gas detection, or to support the heater. This may cause cracks in the insulation layer. Since a coil type heater can absorb thermal expansion, the gas detection device of this embodiment is designed to have a spiral shape to absorb vibrations. For the above reasons, making the heater circular means that the temperature distribution
It is effective in improving strength, life, etc.

In FIG. 15, a heater 27 and a gas detection lead 28 are mounted on the circumferential edge of the disc-shaped insulating layer 22, but conversely, a heater 27 and a gas detection lead 28 are mounted on an overhang extending into the cavity of the substrate. A form in which a lead is mounted may also be used. As an example, the gas detection device 30
The plane is shown in FIG. 24, and the cross section is shown in FIG. In this case, it is easy to make the electrode portion protrude from the circular portion 33 that is undercut by the anisotropic etching, and the inside of the substrate 21 is exposed as shown between the electrodes 29g and 29f in FIG. It does not need to be a conductive part. 31 is the board, 3
2 is an insulating layer, 33 is a metal layer, 37 is a circular heater, 38 is a lead for gas detection, 36 is a semiconductor layer for gas detection, 39b and 39e are detection electrodes, 39
c and 39f are heater electrodes.

Further, as another embodiment, a gas detection device 40
26 shows its plan view, and FIG. 27 shows its cross-sectional view, 41 is a substrate, 42 and 42' are insulating layers, 43 is a metal layer, 46 is a semiconductor layer for gas detection,
47 is a circular heater, 48 is a gas detection lead,
49a, 49e, 49c, and 49g are heater electrodes, and 49b, 49f, 49d, and 49h are detection electrodes. The manufacturing method is to first form the insulating layers 42 and 42' on both sides of the substrate 41, photo-etch the insulating layer 42 on one side to open a window, and then etch until the surface of the insulating layer 42' on the other side remains. A drum-shaped structure is made by covering the insulating layer 42' on the wall. Next, a metal layer 43 is formed on the insulating layer 42', and a pattern of a circular heater 47, a gas detection lead 48, and each electrode 49a to 49h is formed. Finally, a gas detection semiconductor layer 46 is coated to complete the process. In FIG. 26, there are two circular heaters 47 and two gas detection leads 48, but any number can be used as long as the temperature distribution is uniform. The drum-shaped structure shown in FIG.
The strain imparted to the insulating layer 42' due to the thermal expansion of 7;
It is extremely strong against damage caused by external vibrations, and is effective in improving reliability and lifespan.

Effects Since the gas detection device of the present invention has a multilayer film structure, it can be easily miniaturized using known semiconductor technology, photolithography technology, and thin film formation technology.
As a result, the heat capacity of the heater can be reduced. Furthermore, since the heating section and the support are not in contact with each other, thermal diffusion due to thermal conduction is reduced, improving the efficiency of the heater and shortening the time it takes to reach thermal equilibrium.
As a result of the above, the power consumption of the gas detection device is significantly reduced and it becomes suitable for pulse drive.
It becomes possible to supply a dry battery-powered gas alarm that is much easier to set than the conventional AC100V-powered gas alarm. In addition, since the heater and gas detection leads are formed on the same metal layer, the manufacturing process is simple and effective, improving reliability and reducing costs during mass production.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a gas detector using the gas detection device of the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is a schematic diagram for explaining the operating principle, and Fig. 4 is a schematic diagram of a gas detector using the gas detection device of the present invention. The figure is a block diagram showing the driving method. 5a and 5b are graphs of the experimental data in FIG. 4, and FIG. 6 is an enlarged view of the center of FIG. 3. Figure 7, Figure 9, Figure 10, Figure 12, Figure 1
3 and 14 are cross-sectional views showing the manufacturing process of the gas detection device 10 of the present invention, FIGS. 8 and 11 are schematic diagrams of photomask patterns used during the manufacturing process, and FIG. Schematic diagrams showing other embodiments of the present invention, FIGS. 16 and 17 are respectively shown in FIG.
Cross-sectional views taken along line and '-' line, Figures 18 to 2
1 is a sectional view showing the manufacturing process, and FIGS. 22 and 23 are schematic views showing photomask patterns used during the manufacturing process. 24 and 25 are a plan view and a sectional view of a reference example related to the embodiment schematically shown in FIG. 15. FIG. 26 is a schematic diagram showing still another embodiment of the gas detection device of the present invention, and FIG. 27 is a sectional view of FIG. 26. Explanation of symbols, 1...Substrate, 2...Insulating layer, 3...
...Metal layer, 4...Resist layer, 5...Bump, 6
... Semiconductor layer for gas detection, 7, 9 ... Heater,
8...Gas detection lead, 7a, 7d, 9c, 9
f...Heater electrode, 8b, 8e...Detection electrode.

Claims (1)

[Scope of Claims] 1. A substrate, an insulating layer provided on the substrate and having a protruding portion extending into the air, and at least one conductive layer for a heater arranged in parallel and spaced apart from each other on the protruding portion. and at least one conductive layer for detection, and a gas-sensitive material layer formed in contact between the conductive layers, the resistance value of which changes as the gas-sensitive material layer contacts and reacts with the gas. A gas detection device characterized in that gas detection is performed by detecting a current flowing from the heater conductive layer to the detection conductive layer via the gas sensitive material layer. 2. The gas detection device according to claim 1, wherein the projecting portion has a crosslinked structure. 3. The gas detection device according to claim 1, wherein the projecting portion has a cantilever structure. 4. A gas detection device according to any one of claims 1 to 3, characterized in that the gas sensitive material layer is formed of a metal oxide semiconductor.