Gas sensor module and method for producing gas sensor module

Abstract

To provide a gas sensor module that is small in size, has high resolution, enables low power consumption, and exhibits superior waterproof properties.SOLUTION: A gas sensor module 1 includes a filter substrate 40 having a plurality of holes 42, and a wiring substrate 20 equipped with a first wire 22A on a first wiring surface 20A. The gas sensor module also includes a gas sensor substrate 10 provided with multiple silicon nanowires 11, being surface-coated with a gas adsorption film and extending in a direction intersecting the first wiring surface, and an electrode wire 12 electrically connected to the first wire 22A and configured to detect the surface resistance of the silicon nanowires 11. The gas sensor module further includes a sensor chamber 50, which is a space communicating with external air through the holes 42, the sensor chamber being provided with a gap between the holes 42 and the silicon nanowires 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas sensor module and a method for manufacturing the gas sensor module. [Background technology]

[0002] Various sensors, such as gas sensor modules, have been used in the past. For example, Patent Document 1 discloses a gas sensor that utilizes differences in the thermal conductivity of the gas to be measured to heat the gas and measure the concentration of the target gas from the difference in the rate of temperature rise. Furthermore, Patent Document 2 discloses a waterproof pressure sensor that transmits external air pressure to the air pressure sensor and achieves waterproof functionality by covering the air pressure sensor with a soft, gel-like polymer resin material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-106348 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-64299 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the gas sensor of Patent Document 1 uses electrical heating, which tends to consume a lot of power. Furthermore, the waterproof pressure sensor of Patent Document 2 is difficult to implement because the gas components themselves cannot reach the sensor. While CO2 sensors using Si nanowires and other materials have been developed, these sensors require a large silicon surface area because the amount of gas molecules adsorbed per unit area is very small, making miniaturization difficult. For this reason, it has been difficult to obtain conventional gas sensor modules that are small, have high resolution, consume little power, and are highly waterproof. [Means for solving the problem]

[0005] The gas sensor module of the present invention, which solves the above-mentioned problems, is characterized by comprising: a filter substrate having a large number of breathable holes; a wiring substrate having a first wiring provided on a first wiring surface on the side where the filter substrate is placed; a gas sensor substrate which is a semiconductor substrate adhered to the first wiring surface, the surface of which is covered with a gas adsorption film and which is provided with a plurality of silicon nanowires extending in a direction intersecting the first wiring surface, and electrode wiring which is electrically connected to the first wiring and which detects the surface resistance of the silicon nanowires; and a sensor chamber which is a space connected to the outside air through the holes and has a gap between the holes and the silicon nanowires.

[0006] Furthermore, a manufacturing method of a gas sensor module of the present invention for solving the above-mentioned problems comprises a filter substrate manufacturing step of manufacturing a breathable filter substrate having a large number of pores, a gas sensor substrate manufacturing step of manufacturing a gas sensor substrate, and a bonding step of bonding the gas sensor substrate to a wiring substrate, wherein the gas sensor substrate manufacturing step comprises a SiO2 film forming step of forming a pattern including a pore pattern on a first region on a silicon substrate and a second region outside the first region, an Au film forming step of forming an Au film as a catalyst film on the SiO2 film and on the silicon substrate exposed from the SiO2 film, a silicon nanowire forming step of forming silicon nanowires on the silicon substrate in the first region by metal-assisted chemical etching, in which the Au film is etched using the pore pattern as a mask, a ZnO2 film forming step of forming a ZnO2 film on the silicon nanowires in the first region, and an electrode wiring forming step of forming electrode wiring from the ZnO2 film in the first region to the second region. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating a gas sensor module according to a first embodiment of the present invention. [Figure 2]FIG. 2 is a schematic diagram illustrating a gas sensor substrate of the gas sensor module of FIG. 1. [Figure 3] 4 is a flowchart showing an example of a method for manufacturing the gas sensor module of FIG. 1. [Figure 4] FIG. 4 is a transition diagram for explaining the flowchart of FIG. 3. [Figure 5] 4 is a flowchart showing an example of a filter substrate manufacturing process in the flowchart of FIG. 3. [Figure 6] 6 is a transition diagram for explaining the filter substrate manufacturing process shown in the flowchart of FIG. 5. [Figure 7] 4 is a flowchart showing an example of the gas sensor substrate manufacturing process of the flowchart in FIG. 3. [Figure 8] FIG. 8 is a transition diagram for explaining the gas sensor substrate manufacturing process shown in the flowchart of FIG. 7. [Figure 9] 4 is a flowchart showing an example of a joining step in the flowchart of FIG. 3. [Figure 10] FIG. 5 is a schematic diagram illustrating a gas sensor module according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] First, the present invention will be briefly described. The gas sensor module of the first aspect of the present invention for solving the above problem is characterized by comprising: a filter substrate having a large number of breathable holes; a wiring substrate having a first wiring provided on a first wiring surface on the side where the filter substrate is placed; a gas sensor substrate which is a semiconductor substrate adhered to the first wiring surface and has a surface covered with a gas adsorption film and is provided with a plurality of silicon nanowires extending in a direction intersecting the first wiring surface, and electrode wiring which is electrically connected to the first wiring and detects the surface resistance of the silicon nanowires; and a sensor chamber which is a space connected to the outside air via the holes and has a gap between the holes and the silicon nanowires.

[0009] According to this aspect, a gas sensor substrate having silicon nanowires and electrode wiring can be used to achieve high resolution and low power consumption. Furthermore, by placing the gas sensor substrate in the sensor chamber, a compact configuration can be achieved. Furthermore, by making the sensor chamber a space that communicates with the outside air through a large number of breathable holes provided in the filter substrate, a highly waterproof configuration can be achieved by, for example, adjusting the hole diameter or applying a water-repellent treatment to the periphery of the holes.

[0010] A gas sensor module according to a second aspect of the present invention is an aspect dependent on the first aspect, and is characterized in that the wiring substrate has a second wiring electrically connected to the first wiring and provided on a second wiring surface opposite to the first wiring surface.

[0011] According to this aspect, the wiring board has second wiring electrically connected to the first wiring and provided on a second wiring surface opposite to the first wiring surface, and this configuration allows wiring to pass from the first wiring surface to the second wiring surface.

[0012] The gas sensor module of the third aspect of the present invention is an aspect dependent on the first aspect, characterized in that the silicon nanowires have a diameter of 20 nm or more and 300 nm or less and a length of 0.5 μm or more and 50 μm or less.

[0013] According to this embodiment, the silicon nanowires have a diameter of 20 nm to 300 nm and a length of 0.5 μm to 50 μm, which provides excellent water resistance while improving communication with the outside air.

[0014] A fourth aspect of the gas sensor module of the present invention is an aspect dependent on the first aspect, characterized in that the gas sensor substrate has a first region in which the silicon nanowires are arranged and a second region that is a region outside the first region, and the electrode wiring has wiring provided in the second region and an electrode electrically connected to the wiring and provided over the end surface of the silicon nanowires in the first region.

[0015] According to this aspect, the electrode wiring includes a wiring provided in the second region and an electrode electrically connected to the wiring and provided across the end surface of the silicon nanowire in the first region. This configuration allows the electrode wiring to be efficiently arranged, and allows for a compact configuration while maintaining high resolution.

[0016] A gas sensor module according to a fifth aspect of the present invention is an aspect dependent on the first aspect, and is characterized in that a water-repellent film having a contact angle with water of 90° or more is provided on the surface of the filter substrate facing the outside air.

[0017] According to this aspect, a water-repellent film having a contact angle of 90° or more with respect to water is provided on the surface of the filter substrate facing the outside air. This configuration makes it possible to provide a configuration that is particularly excellent in waterproofing.

[0018] A gas sensor module according to a sixth aspect of the present invention is an aspect dependent on the first aspect, characterized in that the diameter of the hole is 50 nm or more and 300 nm or less.

[0019] According to this aspect, the pore diameter is 50 nm or more and 300 nm or less. With this configuration, it is possible to particularly effectively increase communication with the outside air and achieve a configuration with excellent waterproofing.

[0020] A gas sensor module according to a seventh aspect of the present invention is an aspect dependent on the first aspect, characterized in that the gas adsorption film is a ZnO2 film having a film thickness of 10 nm or more and 40 nm or less.

[0021] According to this aspect, the gas adsorption film is a ZnO2 film having a thickness of 10 nm to 40 nm, which allows for a particularly high resolution.

[0022] The gas sensor module of the eighth aspect of the present invention is an aspect dependent on any one of the first to seventh aspects, and is characterized in that the sensor chamber is formed between the filter substrate and the wiring substrate by joining the filter substrate and the wiring substrate.

[0023] According to this aspect, the sensor chamber is formed between the filter substrate and the wiring substrate by joining the filter substrate and the wiring substrate, and this configuration makes it possible to provide a gas sensor module that is highly versatile and can be used in a variety of devices.

[0024] A gas sensor module according to a ninth aspect of the present invention is an aspect dependent on any one of the first to seventh aspects, characterized in that the sensor chamber is configured by joining a housing that houses the wiring board and the gas sensor board therein and a lid portion that has the filter board.

[0025] According to this aspect, the sensor chamber is configured by joining a housing that houses the wiring board and the gas sensor board inside, and a lid that has a filter board. With this configuration, the housing can also serve as an outer case of the device in which it is used, thereby achieving miniaturization of the device in which it is used.

[0026] A tenth aspect of the present invention provides a method for manufacturing a gas sensor module, comprising: a filter substrate manufacturing step of manufacturing a breathable filter substrate having a large number of pores; a gas sensor substrate manufacturing step of manufacturing a gas sensor substrate; and a bonding step of bonding the gas sensor substrate to a wiring substrate, wherein the gas sensor substrate manufacturing step comprises: an SiO2 film forming step of forming an SiO2 film in a first region on a silicon substrate and in a second region outside the first region, thereby forming a pattern including a pore pattern; an Au film forming step of forming an Au film as a catalyst film on the SiO2 film and on the silicon substrate exposed from the SiO2 film; a silicon nanowire forming step of forming silicon nanowires on the silicon substrate in the first region by metal-assisted chemical etching, in which the Au film is etched using the pore pattern as a mask; a ZnO2 film forming step of forming a ZnO2 film on the silicon nanowires in the first region; and an electrode wiring forming step of forming electrode wiring from the ZnO2 film in the first region to the second region.

[0027] According to this aspect, a gas sensor module can be configured with a gas sensor substrate having silicon nanowires and electrode wiring, thereby achieving high resolution and low power consumption. Furthermore, for example, a gas sensor substrate can be disposed in a sensor chamber, thereby enabling a compact gas sensor module. Furthermore, for example, the sensor chamber can be configured as a space that communicates with the outside air through a large number of breathable holes provided in a filter substrate. For example, by adjusting the hole diameter or by applying a water-repellent treatment to the periphery of the holes, the gas sensor module can be configured with excellent waterproofing.

[0028] A manufacturing method of a gas sensor module according to an eleventh aspect of the present invention is an aspect dependent on the tenth aspect, and the filter substrate manufacturing process includes a pore pattern forming step of applying a resist to a first surface of the silicon substrate and forming a pore pattern thereon; a first Au film attaching step of attaching an Au film to the pores of the pore pattern formed in the pore pattern forming step by electroless Au plating; a metal-assisted chemical etching step of performing metal-assisted chemical etching using a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide; and a metal-assisted chemical etching step of removing the resist applied in the pore pattern forming step and the Au film attached in the first Au film attaching step. an opening formation step of applying resist to a region on a second surface of the silicon substrate opposite the first surface, the region including at least a region corresponding to the first region, to form an opening; a second Au film deposition step of depositing an Au film in the opening by an electroless Au plating method; a connecting step of thinning the opening that constitutes the sensor chamber to communicate with the hole by a metal-assisted chemical etching method; and a second peeling step of removing the resist applied in the opening formation step and the Au film deposited in the second Au film deposition step with an etching solution.

[0029] According to this aspect, a sensor chamber is formed in the opening, which allows a gas sensor substrate to be disposed in the sensor chamber, thereby enabling the gas sensor module to be made compact.

[0030] A twelfth aspect of the present invention is a method for manufacturing a gas sensor module that is dependent on the eleventh aspect, and is characterized in that the filter substrate manufacturing process further includes a water-repellent process of performing a water-repellent treatment on the surface.

[0031] According to this aspect, the filter substrate manufacturing process further includes a water-repellent process of performing a water-repellent treatment on the surface, which allows the gas sensor module to have a particularly excellent waterproof structure.

[0032] A thirteenth aspect of the present invention is a method for manufacturing a gas sensor module that is dependent on the tenth aspect, and is characterized in that the joining step includes a surface-bonding step of surface-bonding the gas sensor substrate to the wiring board, and a connecting step of connecting a first wiring provided on the wiring board to the electrode wiring by wire bonding.

[0033] According to this aspect, the bonding step includes a surface-bonding step of bonding the gas sensor substrate to the wiring board and a connection step of connecting the first wiring provided on the wiring board to the electrode wiring by wire bonding. By performing these steps, the adhesive strength between the gas sensor substrate and the wiring board and the connection strength between the first wiring and the electrode wiring are increased. This allows the manufacture of a highly durable gas sensor module.

[0034] A fourteenth aspect of the method for manufacturing a gas sensor module according to the present invention is an aspect dependent on any one of the tenth to thirteenth aspects, and is characterized by further comprising a first filter substrate bonding step of bonding the filter substrate to the wiring substrate to which the gas sensor substrate is bonded.

[0035] According to this aspect, the method further includes a first filter substrate bonding step of bonding a filter substrate to the wiring substrate to which the gas sensor substrate is bonded, whereby the sensor chamber is formed between the filter substrate and the wiring substrate by bonding them together, thereby making it possible to provide a gas sensor module that is highly versatile and can be used in a variety of devices.

[0036] A fifteenth aspect of the method for manufacturing a gas sensor module according to the present invention is an aspect dependent on any one of the tenth to thirteenth aspects, and is characterized by further comprising a second filter substrate bonding step of bonding the filter substrate to a housing that accommodates the gas sensor substrate and the wiring substrate.

[0037] According to this aspect, the method further includes a second filter substrate bonding step of bonding a filter substrate to a housing that houses the gas sensor substrate and the wiring substrate. Therefore, the sensor chamber is formed by bonding the housing that houses the wiring substrate and the gas sensor substrate inside to the lid that has the filter substrate, and the housing can also serve as an outer case for the device that uses it, thereby achieving miniaturization of the device that uses it.

[0038] [Example 1] Hereinafter, a gas sensor module 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings. First, the overall configuration of a gas sensor module 1A according to a first embodiment of the present invention will be described with reference to FIG.

[0039] In the gas sensor module 1A of this embodiment, a gas sensor 10 (gas sensor substrate), which is a CO2 sensor capable of detecting CO2, is bonded by an adhesive to a first wiring surface 20A of a wiring substrate 20 having a control circuit 21. The wiring substrate 20 is wired to a second wiring surface 20B by a through electrode 22. More specifically, the through electrode 22 connects a first wiring 22A on the first wiring surface 20A to a second wiring 22B on the second wiring surface 20B. A wire 13 is connected to the first wiring 22A by wire bonding to the gas sensor 10. An FPC (flexible printed cable) 51 is attached to the second wiring surface 20B.

[0040] A filter substrate 40 is bonded to the first wiring surface 20A of the wiring substrate 20. By bonding the filter substrate 40 and the wiring substrate 20 together, a sensor chamber 50 is formed between the filter substrate 40 and the wiring substrate 20. With this configuration, the gas sensor module 1A of this embodiment is a highly versatile gas sensor module 1 that can be used with a variety of devices, such as mobile phones.

[0041] The filter substrate 40 is provided with a hole formation section 41 that is open to the outside air, and a large number of breathable holes 42 are formed in the hole formation section 41. Here, the diameter of the holes 42 is 120 nm in this embodiment, but it is preferable that it be 50 nm or more and 300 nm or less. This is because such a configuration can provide a configuration that is particularly effective in increasing communication with the outside air and also has excellent waterproof properties.

[0042] Furthermore, a water-repellent film 44 having a contact angle with water of 90° or more is provided on the surface 40A of the filter substrate 40 that is open to the outside air. With this configuration, it is possible to achieve a configuration that is particularly excellent in waterproofing. As the water-repellent film 44, for example, a water-repellent film containing fluorine, such as Cytop (registered trademark) by AGC Inc., can be used.

[0043] As shown in FIG. 1 , the gas sensor module 1A of this embodiment includes a wiring board 20 and a filter board 40 housed in a case 30. The case 30 includes a top cover 30A having an opening 31 that exposes the hole formation portion 41 to the outside air, a bottom cover 30C in which an insulating sheet 32 ​​is disposed and which has an opening 34 through which an FPC 51 passes, a side portion 30B that connects the top cover 30A and the bottom cover 30C, and a fixing portion 30D that is a bolt that fixes the side portion 30B. That is, the hole formation portion 41 is open to the outside air through the opening 31, and gas, water, and the like reach the hole formation portion 41 through the opening 31. However, as described above, the diameter of the holes 42 in the hole formation portion 41 is adjusted to be 150 nm or more and 250 nm or less, and the surface 40A is provided with a water-repellent film 44 with a contact angle of 90° or more. Therefore, the gas sensor module 1A of this embodiment is configured such that water does not reach the sensor chamber 50 through the hole formation portion 41.

[0044] Here, the top cover 30A and the surface 40A of the filter substrate 40 are sealed with a sealing member, an O-ring 33. In other words, the gas sensor module 1A of this embodiment is mounted such that the case 30 and the filter substrate 40 are tightly attached with the O-ring 33 using multiple plate-like members and bolts, preventing water from entering unnecessary areas.

[0045] Next, the gas sensor 10 will be described in detail with reference to Fig. 2. The gas sensor 10 of this embodiment is a silicon substrate as a semiconductor substrate bonded to a first wiring surface 20A. As shown in Fig. 2, the gas sensor 10 of this embodiment is provided with a plurality of silicon nanowires 11 whose surface is covered with a gas adsorption film and which extend in a direction intersecting with the first wiring surface 20A. Furthermore, the gas sensor 10 of this embodiment is provided with electrode wiring 12 that is electrically connected to the first wiring 22A via wire 13 and that detects the surface resistance of the silicon nanowires 11.

[0046] More specifically, the surface of the silicon nanowires 11 of the gas sensor 10 is coated with a ZnO film 106 (described later) using atomic layer deposition (ALD) to a thickness of 20 nm. The ZnO film 106 has the ability to adsorb CO2, and the adsorption of CO2 gas molecules changes the surface resistance of the ZnO2 film 106. The gas sensor 10 of this embodiment detects this change using electrode wiring 12.

[0047] 2, the gas sensor 10 of this embodiment has a plurality of electrode wirings 12, including electrode wirings 12A, 12B, 12C, and 12D, each of which includes an electrode 121 provided in a first region R1 where the silicon nanowires 11 are arranged and wirings 122 provided in a second region R2 that is an area outside the first region R1. Each electrode wiring 12 has a wiring 122 provided in the second region R2 and an electrode 121 electrically connected to the wiring 122 and provided across the end surfaces of the silicon nanowires 11 in the first region R1. This configuration allows the electrode wirings 12 to be efficiently arranged, enabling a compact configuration while maintaining high resolution.

[0048] Here, the electrode wiring 12A is made up of an electrode 121A and a wiring 122A, the electrode wiring 12B is made up of an electrode 121B and a wiring 122B, the electrode wiring 12C is made up of an electrode 121C and a wiring 122C, and the electrode wiring 12D is made up of an electrode 121D and a wiring 122D. The wiring 122A, the wiring 122B, the wiring 122C, and the wiring 122D are all connected to a wire 13. The gas sensor 10 of this embodiment is configured to be able to measure changes in the surface resistance of the ZnO film 106, for example, by passing a current between the electrodes 121A and 121B and between the electrodes 121C and 121D, converting the current into a voltage, and evaluating the voltage.

[0049] 2, the gas sensor 10 of this embodiment has two reference resistors, which form a Wheatstone bridge together with the resistors between the electrodes 121A and 121B and between the electrodes 121C and 121D. The gas sensor 10 of this embodiment is configured to convert the resistance change between these electrodes 121 into a voltage change, and perform AD (analog-to-digital) conversion in the control circuit 21, thereby enabling measurement of the CO2 concentration.

[0050] As described above, the gas sensor module 1A of this embodiment is configured to have high resolution and low power consumption by including a gas sensor 10 (gas sensor substrate) having silicon nanowires 11 and electrode wiring 12. Furthermore, the gas sensor module 1A of this embodiment can be configured to be compact by arranging the gas sensor 10 in the sensor chamber 50. Furthermore, the gas sensor module 1A of this embodiment has the sensor chamber 50 as a space that communicates with the outside air via a large number of breathable holes 42 provided in the filter substrate 40. Therefore, the gas sensor module 1A of this embodiment can be configured to have excellent waterproof properties by, for example, adjusting the hole diameter or applying a water-repellent treatment to the periphery of the holes 42.

[0051] In the gas sensor module 1A of this embodiment, the wiring board 20 has second wiring 22B that is electrically connected to the first wiring 22A and is provided on the second wiring surface 20B opposite to the first wiring surface 20A. With this configuration, the gas sensor module 1A of this embodiment is configured so that wiring passes from the first wiring surface 20A to the second wiring surface 20B.

[0052] In this embodiment, the silicon nanowires 11 have a diameter of 100 nm and a length of 10 μm, but preferably have a diameter of 20 nm to 300 nm and a length of 0.5 μm to 50 μm, because such a configuration can provide excellent waterproofing while improving communication with the outside air.

[0053] In this embodiment, the gas adsorption film is a ZnO film 106 having a thickness of 20 nm, but the thickness is preferably 10 nm to 40 nm, because this configuration allows for a particularly high resolution.

[0054] In the filter structure of the filter substrate 40 described above, the relationship between the radius of curvature of the curved surface of the water and the internal / external pressure difference is determined by the Young-Laplace equation. If the internal / external pressure difference is ΔP (Pa), the surface tension of the water is σ (N / m), and the radius of curvature is r (m), then ΔP can be calculated as ΔP = 2σ / r. Substituting 10 atmospheres (= 1,013,250 Pa) and σ = 0.0728 N / m for ΔP in this formula, a filter structure waterproof to 10 atmospheres can be achieved if the radius of the holes 42 in the filter substrate 40 is 0.143 μm or less, i.e., if the diameter of the holes 42 is 0.286 μm or less.

[0055] Next, a method for manufacturing the gas sensor module 1A of this embodiment will be described with reference to Fig. 3 to Fig. 9. Below, an outline of the method for manufacturing the gas sensor module 1A of this embodiment will be described with reference to Figs.

[0056] 3 and 4, when the manufacturing method of the gas sensor module 1A of this embodiment is started, first, in the filter substrate manufacturing process of step S10, a breathable filter substrate 40 having a large number of holes 42 is manufactured. Next, in the gas sensor substrate manufacturing process of step S20, the gas sensor 10 (gas sensor substrate) is manufactured.

[0057] Next, in the bonding process of step S30, the gas sensor 10 is bonded to the wiring board 20. The upper diagram in Fig. 4 shows the state after this step is completed, in which the gas sensor 10 is bonded to the wiring board 20. The gas sensor 10 and the wiring board 20 can be bonded together using an adhesive or the like.

[0058] Next, in the filter substrate bonding step of step S40, a filter substrate 40 is bonded to the wiring substrate 20 to which the gas sensor 10 has been bonded. The diagram in the middle of Fig. 4 shows the state after this step is completed, in which the filter substrate 40 has been bonded to the wiring substrate 20 to which the gas sensor 10 has been bonded. The wiring substrate 20 and the filter substrate 40 can be bonded together using an adhesive or the like.

[0059] Finally, in step S50, an FPC attachment process, FPC 51 is attached to second wiring 22B provided on second wiring surface 20B of wiring board 20. The lower diagram in FIG. 4 shows the state after this step is completed, in which FPC 51 is attached to second wiring 22B provided on second wiring surface 20B of wiring board 20.

[0060] The filter substrate manufacturing process in step S10 of the flowchart in FIG. 3 will be described below with reference to FIGS. 5 and 6. When the filter substrate manufacturing process starts, first, in step S110, the pore pattern forming process, resist 401 is applied to the first surface 400A of the silicon substrate 400 to form a pore pattern 402. The top diagram in FIG. 6 shows the state after this step is completed. Here, the pores are circular with a diameter of 250 nm, but this is not a limitation. However, a pore diameter of 50 nm or more and 300 nm or less is preferable.

[0061] Next, in step S120, a first Au film deposition process, an Au film 403 is deposited in the holes 402A of the pore pattern 402 by electroless Au plating. The second diagram from the top in FIG. 6 shows the state after this step is completed. Here, the Au film 403 has a thickness of 30 nm, but is not limited to this configuration. However, a thickness of 30 nm to 90 nm is preferable.

[0062] Next, in step S130, a metal-assisted chemical etching (MACE) process is performed using a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide. The third diagram from the top of FIG. 6 shows the state after this step is completed. Here, for example, a mixed aqueous solution of 4.6 mol / L hydrofluoric acid and 0.3 mol / L hydrogen peroxide is used. Note that, although the depth of the holes 42 formed in the silicon substrate 400 is 60 μm, this is not a limitation.

[0063] Next, in a first stripping step S140, the resist 401 and the Au film 403 are stripped using, for example, a commercially available etching solution, etc. The fourth diagram from the top in Fig. 6 shows the state after this step is completed.

[0064] Next, in the opening formation process of step S150, resist 401 is applied to a region R3 on the second surface 400B of the silicon substrate 400 opposite to the first surface 400A, the region R3 including at least a region corresponding to the first region R1 of the gas sensor 10, and a pattern corresponding to the opening 405 is formed by photolithography. The fifth diagram from the top in Figure 6 shows the state after this step is completed.

[0065] Next, in step S160, a second Au film deposition process, an Au film 403 is deposited by electroless Au plating in the opening 405. The sixth diagram from the top in Fig. 6 shows the state after this step is completed.

[0066] Next, in the connecting process of step S170, metal-assisted chemical etching is performed using a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide. The seventh diagram from the top of Figure 6 shows the state after this step is completed. Here, the thickness of the silicon substrate 400 is 400 μm, the depth of the hole 42 is 60 μm, and the hole 406 corresponding to the opening 405 is 350 μm. In this way, the thickness of the portion where the pore pattern 402 is formed is thinned to 50 μm, and a through hole corresponding to the hole 402A is formed.

[0067] Next, in the second stripping step of step S180, the resist 401 and the Au film 403 are stripped using, for example, a commercially available etching solution etc. The eighth diagram from the top of Fig. 6 shows the state after this step is completed.

[0068] Finally, in a water-repellent process of step S190, first surface 400A as the surface of silicon substrate 400 is subjected to a water-repellent treatment by forming water-repellent film 44. The diagram at the bottom of Figure 6 shows the state after this step is completed.

[0069] The gas sensor substrate manufacturing process in step S20 of the flowchart in FIG. 3 will be described below with reference to FIGS. 7 and 8. The gas sensor 10 is manufactured using the MACE technique and an ALD film formation apparatus, etc. When the gas sensor substrate manufacturing process starts, first, in the SiO2 film formation process in step S210, an SiO2 film 101 is formed in the first region R1 and the second region R2 on the silicon substrate 100, forming a pattern including a pore pattern. The top diagram in FIG. 8 shows the state after this step is completed. Specifically, after forming a thermal oxide film (SiO2 film 101) with a thickness of 1 μm, a resist 102 is applied, and a portion of the silicon substrate 100 that will become the first region R1 is opened using photolithography.

[0070] Next, in step S220, an Au film 104 is formed as a catalyst film on the SiO film 101 and on the silicon substrate 100 exposed by the SiO film 101. Specifically, the SiO film 101 in the opening 103 is removed using hydrofluoric acid, and the Au film 104 is deposited using vacuum evaporation. During deposition of the Au film 104, a film that has evolved from multiple islands into a continuous film during film growth is used. In this type of film, the islands are partially connected, resulting in a porous Au film 104 with Au-free areas. Because the thickness of such a film varies depending on the vacuum deposition equipment, the thickness of the Au film 104 must be adjusted in advance and the appropriate thickness determined by SEM (Scanning Electron Microscope) observation. Here, a film with a thickness of 12 nm is deposited. The second diagram from the top of Figure 8 shows the state after this step is completed.

[0071] Next, in step S230, a metal-assisted chemical etching process is performed to etch the Au film 104 in the first region R1 using the pore pattern as a mask. Here, MACE is performed at room temperature using, for example, a mixed aqueous solution of 4.6 mol / L hydrofluoric acid and 0.3 mol / L hydrogen peroxide. The etching rate is evaluated in advance, and the etching time is adjusted so that the length of the silicon nanowires 11 becomes 50 μm. The third diagram from the top in Figure 8 shows the state after this step is completed.

[0072] Next, in step S240, a silicon nanowire formation process, the Au film 104 is peeled off using a commercially available etching solution. The fourth diagram from the top in Fig. 8 shows the state after this step is completed.

[0073] Next, in step S250, a ZnO film is formed on the surface of the silicon nanowires 11 in the first region R1 using ALD to form a 30 nm ZnO film 106. The unnecessary resist 102 is then removed using a resist stripper. The fifth diagram from the top in Figure 8 shows the state after this step is completed.

[0074] Finally, in step S260, the electrode wiring formation process, electrode wiring 12 is formed from the ZnO film 106 in the first region R1 to the second region R2. Specifically, an Al electrode is formed by a mask deposition method, for example. For example, a sputtering device can be used as the deposition device, and the film thickness can be set to 500 nm. The bottom diagram in Figure 8 shows the state after this step is completed.

[0075] The bonding process in step S30 of the flowchart in Fig. 3 will be described below with reference to Fig. 9. When the bonding process starts, first, in a surface bonding process in step S310, the gas sensor 10 is surface-bonded to the wiring substrate 20. Then, in a connection process in step S320, the first wiring 22A provided on the wiring substrate 20 and the electrode wiring 12 are connected by wire bonding.

[0076] As described above, the manufacturing method of the gas sensor module of this embodiment includes a filter substrate manufacturing process in step S10, a gas sensor substrate manufacturing process in step S20, and a bonding process in step S30. The gas sensor substrate manufacturing process in step S20 further includes a SiO film forming process in step S210, an Au film forming process in step S220, a silicon nanowire forming process in step S240, a ZnO film forming process in step S250, and an electrode wiring forming process in step S260. By performing the manufacturing method of the gas sensor module of this embodiment, a gas sensor 10 having silicon nanowires 11 and electrode wiring 12 can be configured, thereby achieving high resolution and low power consumption for the gas sensor module 1. Furthermore, for example, the gas sensor 10 can be disposed in the sensor chamber 50, thereby enabling the gas sensor module 1 to be compact. Furthermore, for example, the sensor chamber 50 can be configured as a space that is in communication with the outside air via a large number of breathable holes 42 provided in the filter substrate 40, and the gas sensor module 1 can be configured to have excellent waterproof properties, for example, by adjusting the hole diameter or by applying a water-repellent treatment to the areas around the holes 42.

[0077] In the manufacturing method of the gas sensor module of this embodiment, the filter substrate manufacturing process of step S10 includes a pore pattern forming process of step S110, a first Au film deposition process of step S120, a metal-assisted chemical etching process of step S130, a first peeling process of step S140, an opening forming process of step S150, a second Au film deposition process of step S160, a communication process of step S170, and a second peeling process of step S180. By performing this manufacturing method of the gas sensor module, a sensor chamber 50 can be formed in the opening 31. Therefore, for example, a gas sensor 10 can be disposed in the sensor chamber 50, and the gas sensor module 1 can be configured to be compact.

[0078] Furthermore, in the manufacturing method of the gas sensor module of this embodiment, the filter substrate manufacturing process of step S10 further includes a water-repellent process of step S190, which allows the gas sensor module 1 to have a particularly excellent waterproofing property.

[0079] In the manufacturing method of the gas sensor module of this embodiment, the bonding step of step S30 includes a surface bonding step of step S310 and a connection step of step S320. By performing these steps, the adhesive strength between the gas sensor 10 and the wiring substrate 20 is increased, and the connection strength between the first wiring 22A and the electrode wiring 12 is also increased. This makes it possible to manufacture a highly durable gas sensor module 1.

[0080] The manufacturing method of the gas sensor module of this embodiment also includes a filter substrate bonding step of step S40. The filter substrate bonding step of step S40 is a first filter substrate bonding step of bonding the filter substrate 40 to the wiring substrate 20 to which the gas sensor 10 is bonded when manufacturing a gas sensor module 1A as the gas sensor module 1. Therefore, by employing such a first filter substrate bonding step as the filter substrate bonding step of step S40, the sensor chamber 50 is formed between the filter substrate 40 and the wiring substrate 20 by bonding them together, and it is possible to manufacture a gas sensor module 1A that is highly versatile and can be used in a variety of devices.

[0081] [Example 2] Next, a gas sensor module 1B of Example 2 will be described with reference to FIG. 10. A manufacturing method for the gas sensor module 1B of this example, if expressed in the form of a flowchart, would be similar to the flowcharts in FIGS. 3, 5, 7, and 9. FIG. 10 corresponds to FIG. 1 showing the gas sensor module 1A of Example 1. Except for the following description, the gas sensor module 1B of this example is similar to the gas sensor module 1A of Example 1, and therefore has the same features as the gas sensor module 1A of Example 1. Therefore, in FIG. 10, parts common to those of Example 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0082] As shown in Fig. 10, the gas sensor module 1 of this embodiment has the filter substrate 40 attached to a lid 30E that forms part of the product housing. The gas sensor 10 is housed in a space in the housing 30F together with the wiring board 20 and other components. With this configuration, the gas sensor module 1 of this embodiment does not need to individually seal the gas sensor 10. Furthermore, with this configuration, the filter substrate 40 can be replaced if damaged, making the module applicable to products that require reliability, such as wearable devices.

[0083] From another perspective, in the gas sensor module 1B of this embodiment, the sensor chamber 50 is configured by joining a housing 30F that houses the wiring board 20 and the gas sensor 10 (gas sensor board) therein, and a lid 30E that has the filter board 40. With this configuration, the gas sensor module 1B of this embodiment can also use the housing 30F as an outer case for the device in which it is used, thereby achieving miniaturization of the device in which it is used.

[0084] 3 corresponds to a second filter substrate bonding step of bonding the filter substrate 40 to the housing 30F that houses the gas sensor 10 and the wiring board 20. To reiterate, by employing such a second filter substrate bonding step as the filter substrate bonding step of step S40, the sensor chamber 50 is configured by bonding the housing 30F that houses the wiring board 20 and the gas sensor 10 therein to the lid 30E that has the filter substrate 40. This allows the housing 30F to also serve as the outer case of the device that uses it, thereby achieving miniaturization of the device that uses it.

[0085] The present invention is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present invention. The technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0086] 1...gas sensor module, 1A...gas sensor module, 1B...gas sensor module, 10...gas sensor (gas sensor substrate), 11...silicon nanowire, 12...electrode wiring, 13...wire, 20...wiring substrate, 20A...first wiring surface, 20B...second wiring surface, 21...control circuit, 22...through electrode, 22A...first wiring, 22B...second wiring, 30...case, 30A...top cover, 30B...side portion, 30C...bottom cover, 30D...fixing portion, 30E...lid portion, 30F...housing, 31...opening, 32...insulating sheet, 33...O-ring, 34...opening, 40...filter substrate, 41...hole forming portion , 42...hole, 44...water-repellent film, 50...sensor chamber, 51...FPC, 100...silicon substrate, 101...SiO2 film, 102...resist, 103...opening, 104...Au film, 106...ZnO2 film (gas adsorption film), 121...electrode, 121A...electrode, 121B...electrode, 121C...electrode, 121D...electrode, 122...wiring, 122A...wiring, 122B...wiring, 122C...wiring, 122D...wiring, 400...silicon substrate, 400A...first surface, 400B...second surface, 401...resist, 402...pore pattern, 403...Au film, 405...opening, 406...hole, R1...first region, R2...second region, R3...region

Claims

1. a filter substrate having a large number of breathable holes; a wiring substrate having a first wiring provided on a first wiring surface on the side where the filter substrate is disposed; a gas sensor substrate, which is a semiconductor substrate adhered to the first wiring surface, the gas sensor substrate including a plurality of silicon nanowires whose surface is covered with a gas adsorption film and which extend in a direction intersecting the first wiring surface, and electrode wiring electrically connected to the first wiring and which detects the surface resistance of the silicon nanowires; a sensor chamber that is a space that communicates with the outside air through the hole and has a gap between the hole and the silicon nanowire; A gas sensor module comprising:

2. 2. The gas sensor module according to claim 1, The gas sensor module is characterized in that the wiring board has second wiring electrically connected to the first wiring and provided on a second wiring surface opposite to the first wiring surface.

3. 2. The gas sensor module according to claim 1, The silicon nanowires have a diameter of 20 nm to 300 nm and a length of 0.5 μm to 50 μm.

4. 2. The gas sensor module according to claim 1, the gas sensor substrate has a first region in which the silicon nanowires are arranged and a second region that is a region outside the first region; The gas sensor module is characterized in that the electrode wiring includes a wiring provided in the second region and an electrode electrically connected to the wiring and provided across the end surface of the silicon nanowire in the first region.

5. 2. The gas sensor module according to claim 1, A gas sensor module characterized in that a water-repellent film having a contact angle with water of 90° or more is provided on the surface of the filter substrate facing the outside air.

6. 2. The gas sensor module according to claim 1, The gas sensor module is characterized in that the diameter of the holes is 50 nm or more and 300 nm or less.

7. 2. The gas sensor module according to claim 1, The gas adsorption film is made of ZnO ２ A gas sensor module comprising a film having a thickness of 10 nm or more and 40 nm or less.

8. 8. The gas sensor module according to claim 1, The gas sensor module is characterized in that the sensor chamber is formed between the filter substrate and the wiring substrate by joining the filter substrate and the wiring substrate.

9. 8. The gas sensor module according to claim 1, a housing that houses the wiring board and the gas sensor board therein, and a lid portion that has the filter board joined to the housing;

10. a filter substrate manufacturing process for manufacturing a filter substrate having a large number of holes and having breathability; a gas sensor substrate manufacturing process for manufacturing a gas sensor substrate; a bonding step of bonding the gas sensor substrate to a wiring substrate; and The gas sensor substrate manufacturing process includes: A first region on a silicon substrate and a second region outside the first region are provided with SiO ２ A film is formed to form a pattern including a pore pattern. ２ a film forming step; The SiO ２ On the film, and the SiO ２ an Au film forming step of forming an Au film as a catalyst film on the silicon substrate exposed from the film; a silicon nanowire formation step of forming silicon nanowires on the silicon substrate in the first region by a metal-assisted chemical etching method in which the Au film is etched using the pore pattern as a mask; ZnO on the silicon nanowires in the first region ２ ZnO film formation ２ a film forming step; The ZnO in the first region ２ an electrode wiring forming step of forming an electrode wiring from the film to the second region; 1. A method for manufacturing a gas sensor module, comprising:

11. The method for manufacturing a gas sensor module according to claim 10, The filter substrate manufacturing process includes: a hole pattern forming step of applying a resist to a first surface of the silicon substrate and forming a hole pattern; a first Au film deposition step of depositing an Au film into the holes of the pore pattern formed in the pore pattern formation step by an electroless Au plating method; A metal-assisted chemical etching process using a mixed aqueous solution of hydrofluoric acid and hydrogen peroxide; a first stripping step of stripping the resist applied in the hole pattern forming step and the Au film attached in the first Au film attaching step with an etching solution; an opening forming step of applying a resist to a region including at least a region corresponding to the first region on a second surface of the silicon substrate opposite to the first surface to form an opening; a second Au film deposition step of depositing an Au film in the opening by electroless Au plating; a connecting step of thinning the opening that defines the sensor chamber to communicate with the hole by a metal-assisted chemical etching method; a second stripping step of stripping the resist applied in the opening formation step and the Au film attached in the second Au film attachment step with an etching solution; 1. A method for manufacturing a gas sensor module, comprising:

12. The method for manufacturing a gas sensor module according to claim 11, 10. A method for manufacturing a gas sensor module, wherein the filter substrate manufacturing process further comprises a water-repellent process of subjecting the surface to a water-repellent treatment.

13. The method for manufacturing a gas sensor module according to claim 10, The joining step includes: a surface-bonding step of surface-bonding the gas sensor substrate to the wiring substrate; a connecting step of connecting a first wiring provided on the wiring board and the electrode wiring by wire bonding; 1. A method for manufacturing a gas sensor module, comprising:

14. 14. The method for manufacturing a gas sensor module according to claim 10, a first filter substrate bonding step of bonding the filter substrate to the wiring substrate to which the gas sensor substrate has been bonded;

15. 14. The method for manufacturing a gas sensor module according to claim 10, a second filter substrate bonding step of bonding the filter substrate to a housing that accommodates the gas sensor substrate and the wiring substrate;

Images