JP2017138191A - Gas sensor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor and a manufacturing method therefor, wherein the gas sensor is downsized and detects multiple kinds of gases with stable sensitivity.SOLUTION: The gas sensor is configured to comprise: a nano-hole array 13 in which a first face of a conductive substrate is divided into a plurality of sensing blocks electrically insulated by a first insulator 12; a pair of electrodes 14, 17 provided on the surface of the first insulator for each of the plurality of sensing blocks; and a heater 16 provided via a second insulator 15 on a second face of the conductive substrate that is opposite to the first face. Each of the plurality of sensing blocks includes a plurality of nano-holes formed in the first face, and a gas sensitive film 13B formed on the first face of the conductive substrate including the wall face that forms the plurality of nano-holes and electrically connected to the pair of electrodes. Between at least two sensing blocks among the plurality of sensing blocks, gas sensitive films are formed with different gas sensitive materials.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas sensor and a manufacturing method thereof.

  Conventionally, analyzers such as a gas chromatograph and a mass spectrometer are used for highly sensitive detection of air pollutants. However, in addition to the expensive analysis apparatus, a carrier gas such as He is necessary to separate the contaminants, and therefore, analysis at the contamination site is difficult. Contaminated gases are collected by a method such as leaving a Tenax tube or a substrate that easily adsorbs harmful substances at the contamination site, and extracting a sample collected at the site at a specific facility. For this reason, it is impossible to analyze in real time the pollution state that changes every moment.

  There are various real-time analysis methods for air pollutants, such as a method using a QCM sensor using a quartz crystal (QCM), an optical change method, a resistance change method, and a surface photo voltage (SPV) method. Various detection methods have been proposed.

  A QCM sensor detects a change in vibration frequency when a substance adheres. For this reason, in addition to requiring a sensing probe for each substance to be detected, the size of the frequency counter, which is a detector, is large, resulting in poor portability.

  On the other hand, a gas sensor element that detects with high sensitivity by a surface photovoltage (SPV) method has been proposed (see, for example, Patent Document 1). However, as in the case of the QCM sensor, this gas sensor element also requires a sensing probe for each detection substance, and the size of the detector is large, making it difficult to reduce the size.

  A semiconductor gas sensor is known as a portable small environmental sensor. A semiconductor gas sensor uses a metal oxide as a gas-sensitive material, and detects the gas concentration based on a change in electrical resistance caused by the reaction between oxygen adsorbed on the surface of the gas-sensitive material heated by the heater and the reducing gas (or target gas). To do. Although the semiconductor gas sensor is smaller than the detector as described above, it can detect with high sensitivity. However, the semiconductor gas sensor can detect only one kind of gas. For this reason, when detecting a plurality of types of gases, one semiconductor gas sensor is required for each type of gas, resulting in an increase in the size of the probe portion. In addition, since heaters corresponding to the number of semiconductor gas sensors are required, it is difficult to reduce power consumption.

  A gas detection element having a nanohole structure in a sensitive part that reacts with a gas to be detected and a method for manufacturing the same have also been proposed (see, for example, Patent Document 2). In this gas detection element, a gas-sensitive portion is formed by sintering after dropping a tin oxide precursor solution into nanoholes formed by aluminum anodization. Further, in the manufacturing process of the gas detection element, a dense barrier layer is formed at the interface with the aluminum plate, and after removing the barrier layer by etching from the back surface, a platinum electrode is formed. However, since a heater for heating the gas detection element is not mounted, there is a concern that the sensitivity may be lowered during continuous use due to the influence of moisture in the atmosphere and the influence of gas component adsorption.

  In addition, there has been proposed a sensor device having a structure in which porous silicon oxide is used for the gas sensitive part and a plurality of types of gas detection are performed with one chip (for example, see Patent Document 3). However, since this sensor device is a capacitive sensor, it is easily affected by moisture in the atmosphere. Furthermore, since the gas sensitive part has an irregular porous structure, individual differences in sensitivity occur between the sensor devices. For this reason, it is difficult to detect a plurality of types of gases with stable sensitivity.

JP 2004-93469 A JP 2007-322342 A JP 2011-196835 A JP 2005-283159 A JP 2008-39508 A

  In the prior art, it is difficult to downsize a gas sensor that can detect a plurality of types of gases with stable sensitivity.

  Therefore, an object of one aspect is to provide a gas sensor capable of downsizing that detects a plurality of types of gases with stable sensitivity, and a manufacturing method thereof.

  According to one proposal, a nanohole array in which a first surface of a conductor substrate is divided into a plurality of sensing blocks electrically insulated by a first insulator, and a surface of the first insulator, A heater provided via a second insulator on a pair of electrodes provided for each of a plurality of sensing blocks and a second surface opposite to the first surface of the conductor substrate And each of the plurality of sensing blocks is formed on the first surface including a plurality of nanoholes formed on the first surface and a wall surface of the conductor substrate forming the plurality of nanoholes. A gas-sensitive film electrically connected to the pair of electrodes, wherein the gas-sensitive film of each sensing block is electrically connected to the pair of electrodes, and at least two of the plurality of sensing blocks Senshin Between blocks gas sensor the sensitive gas film is formed in a different gas-sensitive material is provided.

  According to one aspect, it is possible to reduce the size of a gas sensor that detects a plurality of types of gases with stable sensitivity.

It is sectional drawing which shows an example of the gas sensor in one Example. It is a top view of the gas sensor shown in FIG. It is a bottom view of the gas sensor shown in FIG. It is a bottom view of the gas sensor in a modification. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example. It is sectional drawing explaining the process of the manufacturing method of the gas sensor in one Example.

  The disclosed gas sensor includes a nanohole array in which a first surface of a conductive substrate is divided into a plurality of sensing blocks electrically insulated by a first insulator, and a surface of the first insulator on each sensing block. A pair of electrodes provided on the second substrate and a heater provided on a second surface opposite to the first surface of the conductor substrate via a second insulator are provided. Each sensing block includes a plurality of nanoholes formed on the first surface and a gas-sensitive film electrically connected to the pair of electrodes formed on the first surface including the wall surface of the conductive substrate forming the plurality of nanoholes. The gas sensitive film is formed of different gas sensitive materials between at least two sensing blocks.

  Embodiments of the disclosed gas sensor and its manufacturing method will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of a gas sensor in one embodiment. As shown in FIG. 1, the nanohole array type gas sensor 1 includes a conductive substrate 11, a first insulator 12, a nanohole array 13, an electrode 14, a second insulator 15, a heater 16, and an electrode 17. And have. The conductor substrate 11 is made of metal, for example. The first insulator 12 and the nanohole array 13 are provided on the upper surface which is an example of the first surface of the conductor substrate 11.

  The nanohole array 13 includes a plurality of nanoholes 13A regularly formed on the conductor substrate 11, and a gas sensitive film 13B formed of a gas sensitive material that reacts with the detection target gas. The gas sensitive film 13B is formed on the first surface (surface between adjacent nanoholes 13A) of the conductive substrate 11 including the wall surface of the conductive substrate 11 forming the nanoholes 13A. The gas sensitive material is, for example, an oxide whose main component is a metal selected from titanium, tin, aluminum, copper, and nickel. The main component of the gas-sensitive material refers to a component whose component amount exceeds 50% in the gas-sensitive material. Therefore, the surface of the nanohole array 13 is formed of, for example, a metal oxide.

  The diameter when the nanohole 13A is cylindrical is not particularly limited as long as it is in the range of, for example, several nm to several hundred nm, and is preferably in the range of 10 nm to 200 nm. When the diameter of the nanohole 13A is smaller than several nanometers, the detection target gas hardly penetrates into the nanohole 13A. On the other hand, when the diameter of the nanohole 13A exceeds several hundreds of nanometers, the surface area of the sensitive portion that reacts with the detection target gas of the nanohole array 13 is reduced, and the detection sensitivity is lowered. For this reason, the diameter of the nanohole 13A is selected in the range as described above. The depth of the nanohole 13A is not particularly limited. Further, the shape of the nanohole 13A is not particularly limited.

  The electrode 14 is formed of an electrode material such as metal, for example, and is provided on the first insulator 12. Since the gas sensor 1 is a kind of resistance change detection type sensor, the electrode material is preferably a metal. Examples of the metal that can be used for the electrode material include gold, platinum, silver, copper, aluminum, cobalt, nickel, and alloys containing at least one of these metals. Although the electrode 14 is provided on the first insulator 12 in this example, a metal film (not shown) is provided between the electrode 14 and the first insulator 12 in order to prevent peeling of the electrode 14. ) May be formed. The metal coating can be formed of, for example, Ti, TiN, Ta, TaN, Mn, W, WN, TiW, Cr, or the like. However, when the metal film is formed so that the metal film does not increase the resistance of the electrode 14 and decrease the detection sensitivity, the thickness of the metal film is preferably 50 nm or less.

  The second insulator 15 is provided on the lower surface of the conductor substrate 11. The lower surface of the conductor substrate 11 is an example of a second surface opposite to the upper surface (that is, the first surface) of the conductor substrate 11. The second insulator 15 may be formed of the same insulating material as that of the first insulator 12. The heater 16 is provided on the lower surface of the second insulator 15. A pair of electrodes 17 is electrically connected to the heater 16. The electrode 17 may be formed of the same electrode material as the electrode 14. By supplying a current to the heater 16 via the electrode 17, the heater 16 generates heat and heats the entire nanohole array 13. Specifically, the heater 16 heats the gas sensitive film 13 </ b> B through the conductor substrate 11. For example, due to the reaction between oxygen and the gas to be detected, an oxidation reaction due to adsorbed oxygen occurs on the surface of the heated gas-sensitive film 13B, and electrons flow into the gas-sensitive film 13B to change the conductivity of the gas-sensitive film 13B. To do. Such a change in the conductivity of the gas sensitive film 13B causes a change in electrical resistance in the gas sensitive film 13B. Therefore, the gas concentration of the detection target gas can be detected by detecting the change in the electric resistance of the gas-sensitive film 13B via the electrode 14.

  FIG. 2 is a top view of the gas sensor shown in FIG. As shown in FIG. 2, the first surface of the conductor substrate 11 is divided into a plurality of sensing blocks 13-1 to 13-4 that are electrically insulated from each other by the first insulator 12. That is, the gas sensitive film 13 </ b> B in each of the sensing blocks 13-1 to 13-4 is surrounded by the first insulator 12 embedded in the conductor substrate 11. In this example, each sensing block 13-1 to 13-4 forms a resistance change detection type sensor element. A pair of electrodes 14 electrically connected to both ends of the gas sensitive film 13B is provided for each sensing block 13-1 to 13-4.

  In this example, the electrode 14 is provided so as to contact the entire length of the opposing sides of the outer peripheral portion of the gas sensitive film 13B (in this example, a rectangular region) in each sensing block. It may be provided so as to contact only a part. That is, the electrode 14 should just be provided so that it may contact with at least one part of the edge | side which the outer peripheral part of the gas sensitive film | membrane 13B in each sensing block 13-1 to 13-4 opposes. In this example, the electrode 14 extends in the vertical direction in FIG. 3, but may extend in the direction well. Furthermore, in the sensing blocks 13-1 to 13-4, the direction in which the electrode 14 extends between at least two sensing blocks may be different from each other.

  In this example, the planar shape of the conductor substrate 11 and each of the sensing blocks 13-1 to 13-4 is a quadrilateral, but the planar shape is not particularly limited. In this example, each of the sensing blocks 13-1 to 13-4 has the same planar shape and the same size (or area). However, the sensing blocks 13-1 to 13-4 may have different planar shapes or different sizes. good. In the plurality of sensing blocks 13-1 to 13-4, gas sensitive films 13 </ b> B formed of different gas sensitive materials can be provided on the surface of the nanohole array 13. Therefore, the gas sensor 1 can detect a maximum of four types of detection target gases in this example. The number of sensing blocks is not particularly limited and may be two or more.

  As the surface area of each of the sensing blocks 13-1 to 13-4 increases, the detection target gas can be detected with high sensitivity. For this reason, the size of each sensing block 13-1 to 13-4 can be selected according to the sensitivity with which the detection target gas should be detected. In addition, at least one of the planar shape and size of each sensing block 13-1 to 13-4 and the diameter, depth, and shape of the nanohole 13A in each sensing block 13-1 to 13-4 is the type of detection target gas. It can be selected according to.

  In the example shown in FIG. 1, the upper surface of the gas sensor 1 (that is, the upper surface of the conductor substrate 11, the surface including the surface of the first insulator 12, and the surface of the nanohole array 13) has a planar shape or a substantially planar shape. In order to increase the surface area of each of the sensing blocks 13-1 to 13-4, the upper surface of the gas sensor 1 may be curved. In this case, the curved surface shape may be a convex shape or a concave shape.

  By the way, when the heater 16 heats the gas-sensitive film 13B through the conductor substrate 11, the resistance value of the gas-sensitive film 13B changes, specifically, increases as the temperature of the gas-sensitive film 13B increases. On the other hand, for example, when an oxidation reaction due to adsorbed oxygen occurs on the surface of the heated gas-sensitive film 13B due to a reaction between oxygen and a gas to be detected, electrons flow to the gas-sensitive film 13B and the gas-sensitive film 13B conducts. Since the rate changes, an electric resistance change occurs in the gas sensitive film 13B. For example, the change in electrical resistance of the gas-sensitive film 13B caused by the reaction between oxygen and the detection target gas is divided into a case where it increases according to the type of detection target gas and a case where it decreases. Therefore, it is desirable to exclude a change in resistance value due to heating of the gas-sensitive film 13B from a change in electric resistance of the gas-sensitive film 13B due to detection of the detection target gas.

  In this case, as shown in FIG. 1 and FIG. 2, in parallel to detecting the gas concentration of the detection target gas on the surface of the first insulator 12 by the sensing blocks 13-1 to 13-4, the sensing block You may further provide the resistance temperature sensor 50 which detects the temperature of 13-1 to 13-4. The position where the resistance temperature sensor 50 is provided is not particularly limited as long as it does not contact the electrode 14 on the surface of the insulator. For example, the resistance temperature sensor 50 may be disposed on the surface of the first insulator 12 at a position different from that in FIGS. If there is a region that can be disposed on the surface of the second insulator 15, the resistance temperature sensor 50 may be disposed at a position that does not contact the electrode 17 on the surface of the second insulator 15.

  The material forming the resistance temperature sensor 50 is not particularly limited as long as it is a material that can utilize the temperature characteristic of resistivity. Further, the resistance temperature sensor 50 may have a resistance pattern as shown in FIG. 2, for example. When the resistance temperature sensor 50 is provided, the resistance value of the gas sensitive film 13 </ b> B that changes according to the temperature detected by the resistance temperature sensor 50 is canceled based on the detection result of the gas concentration by the sensing blocks 13-1 to 13-4. can do. That is, since the resistance value of the gas sensitive film 13B that changes according to the temperature can be obtained in advance, the resistance value of the gas sensitive film 13B that changes according to the temperature can be cancelled. Specifically, in an external device (not shown), the resistance value of the gas-sensitive film 13B obtained in advance according to the detected temperature obtained from the electrodes (for example, both ends) of the resistance temperature sensor 50 is acquired. Based on the detection results of the gas concentrations obtained from the electrodes 14 of the sensing blocks 13-1 to 13-4, a gas sensor that depends on the temperature change is performed by performing a process of canceling the acquired resistance value of the gas sensitive film 13B. The sensitivity reduction of 1 can be compensated.

  As described above, the gas sensor 1 outputs information indicating the gas concentration of the detection target gas detected by the sensing blocks 13-1 to 13-4 (that is, the resistance value of the gas-sensitive film 13 </ b> B) from the electrode 14. Further, by providing the resistance temperature sensor 50, the temperature information for canceling the resistance value of the gas-sensitive film 13B that changes according to the temperature, that is, the information indicating the canceling information, the information indicating the gas concentration detected is the electrode 14. In parallel with the output from each pair, the resistance temperature sensor 50 can output.

  FIG. 3 is a bottom view of the gas sensor shown in FIG. In this example, the electrode 17 is provided so as to be in contact with only the central portions on both sides of the heater 16 (left side and right side in FIG. 3). That is, the electrode 17 is provided so as to be in contact with only a part of the opposing sides of the outer peripheral portion of the heater 16 (rectangular region in this example). The heater 16 is disposed so as to heat the entire nanohole array 13, that is, all the sensing blocks 13-1 to 13-4. In this example, the region of the heater 16 on the bottom view includes the entire nanohole array 13. In addition, the electrode 17 may extend in a direction parallel to the electrode 14 so as to be in contact with at least the entire length of opposing sides (that is, both sides) of the outer peripheral portion of the heater 16. Moreover, the heater 16 may be formed with the heat ray which has a pattern suitable for heating each sensing block 13-1 to 13-4.

  FIG. 4 is a bottom view of a gas sensor according to a modification. 4, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted. In this modification, the electrode 17 extends in a direction perpendicular to the electrode 14 so as to be in contact with the length of the heater 16 along the top and bottom of the heater 16 (upper side and lower side in FIG. 4). That is, the electrode 17 is provided so that it may contact over the full length of the edge | side (namely, upper and lower sides) which the outer peripheral part of the heater 16 (rectangular area in this example) opposes. However, the electrode 17 may be provided so as to contact only the central portions of the upper side and the lower side of the heater 16.

  As described above, the electrode 17 is provided so as to be in contact with at least the entire length of the opposing sides of the outer peripheral portion of the heater 16 (in this example, a rectangular region) or in part. In other words, the electrode 17 may be provided so as to be in contact with at least a part of the opposing sides of the outer peripheral portion of the heater 16.

  In the present embodiment, the gas sensor 1 integrally including the plurality of sensing blocks 13-1 to 13-4 can be formed by one chip. Thus, a plurality of types of detection gases can be detected by the one-chip gas sensor 1, and a one-chip multimodal sensor can be formed. Further, even if the size of each of the sensing blocks 13-1 to 13-4 is reduced with the downsizing of the gas sensor 1, the diameter, depth, and shape of the nanohole 13A of the nanohole array 13 are controlled, and each sensing block 13- By increasing the surface area of 1 to 13-4, the detection target gas can be detected with high sensitivity. When the planar shape of the gas sensor 1 formed with one chip is a square, the area of the square is, for example, several millimeters to several tens of millimeters, and is smaller than, for example, a QCM sensor.

  The gas sensor 1 can be carried by forming it with one chip and reducing the size. Further, since the plurality of sensing blocks 13-1 to 13-4 for detecting a plurality of types of detection target gases are heated by the single heater 16, it is possible to reduce power consumption. Furthermore, the gas sensor 1 can detect a plurality of types of detection target gases in real time. Therefore, the gas sensor 1 is an air pollutant such as volatile organic compounds (VOC), NOx, SOx such as formhouse, benzene and toluene, which are one of the causes of sick house syndrome, chemical sensitivity and air pollution. It is suitable for use as a small environmental sensor for detecting temperature, humidity and the like.

  Next, a method for manufacturing a gas sensor in one embodiment will be described with reference to FIGS. 5 to 12 are cross-sectional views illustrating the steps of the gas sensor manufacturing method according to one embodiment. 5 to 12, the same parts as those in FIGS. 1 to 4 are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 5, first, a photoresist 21 is patterned on the upper surface of the conductor substrate 11 so as to cover a region where the nanohole array 13 is to be formed. The photoresist 21 is not particularly limited as long as it is a photosensitive resin, and a dry film resist, a liquid resist, or the like can be used. Further, the light source used for exposing the photoresist 21 may irradiate any of g-line, h-line, i-line, electron beam, and X-ray, and any of positive type and negative type It can also be used for the photoresist 21.

  Specifically, for example, a positive resist (for example, AZP-4620 manufactured by AZ Electronic Materials Co., Ltd.) is spin-coated by a spin coater at 5000 rpm for 60 seconds on an aluminum substrate having a thickness of 1 mm, and then 110 ° C. And pre-bake for 60 seconds. Then, using a contact aligner with i-line mounted on the light source, ultraviolet irradiation was performed outside the region where the nanohole array 13 was formed, and a 2.38% tetramethylammonium hydroxide (TMAH) solution The positive resist is patterned so as to cover the region where the nanohole array 13 is to be formed by performing alkali development in.

  Next, as shown in FIG. 6, using the patterned photoresist 21 as a mask, the surface of the conductor substrate 11 is etched to form a groove 22 for embedding the first insulator 12. The etching method of the conductor substrate 11 is not particularly limited as long as the groove 22 for embedding the first insulator 12 can be formed, and may be wet etching or dry etching. The depth of the groove 22 is not particularly limited as long as it can be electrically separated from the conductor substrate 11 and the electrode 14, and may be shallower than the depth of the nanohole 13 </ b> A. As a method for forming the groove 22 for embedding the first insulator 12, focused ion beam processing, laser processing, or the like may be used.

  Specifically, for example, dry etching using chlorine gas plasma is performed using a patterned positive resist on an aluminum substrate as a mask to form a groove 22 for embedding the first insulator 12 having a depth of 1 μm. To do. Thereafter, an SOG (Spin On Glass) solution formed by a sol-gel method is spin-coated with a spin coater at 2000 rpm for 60 seconds, and further annealed at 150 ° C. for 30 minutes.

  Next, as shown in FIG. 7, the photoresist 21 is removed, and the first insulator 12 is embedded in the groove 22 formed in the conductor substrate 11. The first insulator 12 to be embedded is not particularly limited as long as it is an insulating material. Insulating materials include, for example, organic materials such as phenol resin, epoxy resin, polyimide resin, polymaleimide resin, melamine resin, acrylic resin, polybenzocyclobutene, parylene resin, polyphenylene ether resin, silicon oxide, organic content Examples thereof include inorganic materials such as silicon oxide, silicon nitride, alumina, and titanium oxide. The method of embedding the first insulator 12 is not particularly limited, and for example, spin coating, spray coating, dip coating, screen printing, vacuum lamination, vapor deposition, sputtering, plasma CVD (Chemical Vapor Deposition), thermal CVD, etc. are used. May be. The embedding of the first insulator 12 is preferably formed only in the portion of the groove 22. However, when the entire surface of the conductor substrate 11 is covered when forming the first insulator 12, the groove 22 is formed. The first insulator 12 formed in the other portion may be removed by polishing, etching, or the like.

  Specifically, for example, the SOG coated on the entire upper surface of the aluminum substrate by spin coating is removed by polishing the SOG coated on the portion other than the groove 22, thereby embedding the first insulator 12. An aluminum substrate is produced.

  Next, as shown in FIG. 8, a photoresist 23 is patterned on the conductor substrate 11 embedded with the first insulator 12 so as to cover a region other than the region where the nanohole array 13 is formed. The photoresist 23 is not particularly limited as long as it is a photosensitive resin, and a dry film resist, a liquid resist or the like can be used. Further, the light source used for exposing the photoresist 23 may irradiate any of g-line, h-line, i-line, electron beam, and X-ray, and any of positive type and negative type It can also be used for the photoresist 23.

  Specifically, for example, a positive resist (for example, AZP-4620 manufactured by AZ Electronic Materials) is spin-coated with a spin coater at 5000 rpm for 60 seconds, and then pre-baked at 110 ° C. for 60 seconds. Thereafter, using a contact aligner equipped with i rays as a light source, the region where the nanohole array 13 is to be formed is irradiated with ultraviolet rays, and alkali development is performed with a 2.38% TMAH solution, thereby forming the nanohole array 13. The positive resist is patterned so as to cover areas other than the area.

  Next, as shown in FIG. 9, the nanohole array 13 is formed at the place where the conductor substrate 11 is exposed. The method for forming the nanohole array 13 is not particularly limited as long as nanoholes 13A having a diameter of several nanometers to several hundred nanometers can be formed. Anodization, focused ion beam processing, laser processing, and the like can be used. For example, the nanohole 13A may be formed by dry etching using a resist pattern formed in a nanohole array as a mask. However, since the sidewall of the nanohole 13A needs to be a metal oxide, an anodic oxidation method in which the formation of the nanohole 13A and the oxidation of the conductor (that is, the sidewall of the conductor substrate 11 forming the nanohole 13A) proceed simultaneously is used. Is preferred. When the nanohole array 13 is formed by the anodic oxidation method, an acidic aqueous solution such as oxalic acid, sulfuric acid, phosphoric acid or the like is used as the electrolytic solution, and the voltage applied between the conductor substrate 11 and the cathode electrode is in the range of 10V to 80V. It is preferable that In addition, when the nanohole 13A does not become a desired size in this anodizing step, the nanohole 13A may be widened by immersing in an acidic solution such as a phosphoric acid aqueous solution. Further, annealing may be performed after the formation of the nanohole 13A for the purpose of improving the characteristics of the oxide.

  Specifically, for example, a 0.5 mol oxalic acid aqueous solution is held at 10 ° C. by a constant temperature water bath, and the aluminum substrate is immersed in the oxalic acid aqueous solution in the constant temperature water bath. Further, a nanohole array 13 is formed by applying a voltage of DC 80 V between the aluminum substrate and the cathode electrode using a platinum cathode electrode. When the size of the nanohole array 13 at this time was measured with an electron microscope, it was confirmed that the diameter was about 50 nm.

  Next, as shown in FIG. 10, a gas sensitive film 13 </ b> B of a gas sensitive material is formed so as to cover the formed nanohole array 13. The gas sensitive film 13B is formed on the first surface (surface between adjacent nanoholes 13A) of the conductor substrate 11 in each of the sensor blocks 13-1 to 13-4 including the wall surface of the conductor substrate 11 that forms the nanoholes 13A. Is done. The gas sensitive material is not particularly limited as long as it can adsorb the detection target gas. The method of forming the gas sensitive film 13B is not particularly limited as long as the gas sensitive material can be fixed to the wall surface on which the nanohole 13A is formed. For example, the nanohole array 13 may be impregnated with a solution containing the gas sensitive material. The array 13 may be exposed to vapors of gas sensitive material.

Specifically, for example, the gas-sensitive material is formed by exposing the vapor of SnCl ₄ and WCl ₆ to the nanohole array 13.

  Next, as shown in FIG. 11, the photoresist 23 is removed, and the electrode 14 is electrically connected to both ends of the gas-sensitive film 13B in the corresponding sensing block on the first insulator 12. Form each pair.

  Next, as shown in FIG. 12, the second insulator 15 is formed on the lower surface of the conductor substrate 11, and the heater 16 is formed on the lower surface (that is, the exposed surface) of the second insulator 15.

  Further, the electrode 17 is formed in the arrangement shown in FIG. 3 or FIG. 4 so as to be connected to the heater 16, and the resistance temperature sensor 50 is formed on the surface of the second insulator 15 as necessary. 1 can be produced.

  Note that the timing of forming the heater 16 and the electrode 17 is not limited to the above timing, and the heater 16 and the electrode 17 may be formed at any timing of the steps described with reference to FIGS.

  In addition, at least one of the planar shape and size of each sensing block 13-1 to 13-4 and the diameter, depth, and shape of the nanohole 13A in each sensing block 13-1 to 13-4 is determined according to the type of detection target gas. Control may be performed according to the above.

  Next, the evaluation result of the produced gas sensor will be described. For example, the sensing blocks 13-1 and 13-2 are formed with a gas-sensitive film 13B of a gas-sensitive material that detects formaldehyde, and the sensing blocks 13-3 and 13-4 have a gas-sensitive material that detects toluene. The gas sensor 1 on which the film 13B was formed was manufactured by the above manufacturing method. The electrode 14 of the gas sensor 1 produced in this way was connected to an LCR meter, placed in a sealed chamber, and then the detection range was measured using formaldehyde and toluene diluted with nitrogen gas. As a result of this measurement, formaldehyde was 0.1 ppm to 200 ppm and toluene was 0.5 ppm to 100 ppm, and it was confirmed that a plurality of types of gases could be detected with stable sensitivity. Moreover, when this gas sensor 1 was continuously driven for one month, it was confirmed that the detection sensitivity did not decrease. Furthermore, since the nanoholes 13A are provided regularly (for example, at a constant pitch) in each of the sensing blocks 13-1 to 13-4, the sensitivity to each detection target gas among the plurality of gas sensors 1 produced. It was also confirmed that individual differences were less likely to occur.

  As described above, according to the disclosed gas sensor, an example of an environmental sensor device that can detect a plurality of types of detection target gas in real time in a small size can be formed. For this reason, the gas sensor can be incorporated in a small mobile electronic device such as a mobile phone, a PDA (Personal Digital Assistant), a notebook PC (Personal Computer), or an electronic dictionary. Further, by incorporating the gas sensor in an electronic device having a wired or wireless communication function, it is possible to grasp the air pollution status at each measurement point. Furthermore, by statisticalizing the data acquired from the gas sensor through the wide area network, it can be applied to a system or service for identifying a pollution source or transmitting wide area information.

The following additional notes are further disclosed with respect to the embodiment including the above examples.
(Appendix 1)
A nanohole array divided into a plurality of sensing blocks in which a first surface of a conductor substrate is electrically insulated by a first insulator;
A pair of electrodes provided for each of the plurality of sensing blocks on the surface of the first insulator;
A heater provided on a second surface opposite to the first surface of the conductive substrate via a second insulator;
With
Each of the plurality of sensing blocks is formed on the first surface including the plurality of nanoholes formed on the first surface and the wall surface of the conductive substrate forming the plurality of nanoholes. And a gas sensitive film electrically connected to
The gas sensor, wherein the gas sensitive film is formed of different gas sensitive materials between at least two sensing blocks among the plurality of sensing blocks.
(Appendix 2)
The first insulator is embedded in the first surface of the conductor substrate so as to electrically insulate the plurality of sensing blocks;
The gas sensor according to claim 1, wherein in each of the plurality of sensing blocks, the gas sensitive film is surrounded by the first insulator.
(Appendix 3)
The gas sensor according to appendix 1 or 2, wherein each of the plurality of sensing blocks forms a resistance change detection type sensor element.
(Appendix 4)
4. The appendix according to claim 1, wherein each of the plurality of sensing blocks is in contact with at least a part of opposing sides of the outer peripheral portion of the gas-sensitive film. Gas sensor.
(Appendix 5)
A resistance temperature sensor is provided on the surface of the first insulator and further detects a temperature of the plurality of sensing blocks in parallel with detecting the gas concentration of the detection target gas by the plurality of sensing blocks. ,
The temperature sensor for canceling the resistance value of the gas sensitive film that changes according to the temperature, the resistance temperature sensor in parallel with the information indicating the detected gas concentration being output from each pair of electrodes. The gas sensor according to any one of appendices 1 to 4, wherein the gas sensor is output from
(Appendix 6)
The gas sensor according to any one of appendices 1 to 5, wherein the gas-sensitive material is an oxide mainly composed of a metal selected from titanium, tin, aluminum, copper, and nickel. .
(Appendix 7)
At least one of the planar shape and size of each of the plurality of sensing blocks and the diameter, depth, and shape of the nanohole in each of the plurality of sensing blocks is selected according to the type of detection target gas. The gas sensor according to any one of appendices 1 to 6, characterized in that:
(Appendix 8)
The gas sensor according to any one of appendices 1 to 7, further comprising a pair of electrodes electrically connected to the heater.
(Appendix 9)
The first surface of the conductive substrate, the surface of the first insulator, and the surface including the surface of the nanohole array have a planar shape, a substantially planar shape, or a curved surface shape. The gas sensor according to any one of 8.
(Appendix 10)
Forming a groove in the first surface of the conductor substrate;
Burying a first insulator in the groove and dividing the first surface into a plurality of sensing blocks electrically insulated by the first insulator;
Forming a plurality of nanoholes formed on the first surface in a plurality of regions surrounded by the first insulator;
Forming a nanohole array by forming a gas sensitive film on the first surface including the wall surface of the conductive substrate forming the nanohole;
Forming a pair of electrodes in contact with the gas-sensitive film for each of the plurality of sensing blocks;
Forming a second insulator on a second surface of the conductor substrate opposite to the first surface;
Forming a heater on the surface of the second insulator;
A gas sensor manufacturing method, wherein the gas sensitive film is formed of different gas sensitive materials between at least two sensing blocks among the plurality of sensing blocks.
(Appendix 11)
11. The method of manufacturing a gas sensor according to appendix 10, wherein the gas sensitive material is an oxide mainly composed of a metal selected from titanium, tin, aluminum, copper, and nickel.
(Appendix 12)
Using an anodic oxidation method in which the formation of the nanoholes and the oxidation of the side walls proceed simultaneously,
12. The method for manufacturing a gas sensor according to appendix 10 or 11, wherein a metal oxide is formed on the side wall.
(Appendix 13)
Controlling at least one of the planar shape and size of each of the plurality of sensing blocks and the diameter, depth, and shape of the nanohole in each of the plurality of sensing blocks according to the type of detection target gas. The method of manufacturing a gas sensor according to any one of appendices 10 to 12, which is characterized in that

  As mentioned above, although the gas sensor of the indication and its manufacturing method were explained by an example, the present invention is not limited to the above-mentioned example, and it cannot be overemphasized that various modification and improvement are possible within the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 Gas sensor 11 Conductor board | substrate 12 1st insulator 13 Nanohole array 13-1 to 13-4 Sensing block 13A Nanohole 13B Gas sensitive film | membrane 14, 17 Electrode 15 2nd insulator 16 Heater 50 Resistance temperature sensor

Claims (5)

A nanohole array divided into a plurality of sensing blocks in which a first surface of a conductor substrate is electrically insulated by a first insulator;
A pair of electrodes provided for each of the plurality of sensing blocks on the surface of the first insulator;
A heater provided on a second surface opposite to the first surface of the conductive substrate via a second insulator;
With
Each of the plurality of sensing blocks is formed on the first surface including the plurality of nanoholes formed on the first surface and the wall surface of the conductive substrate forming the plurality of nanoholes. And a gas sensitive film electrically connected to
The gas sensor, wherein the gas sensitive film is formed of different gas sensitive materials between at least two sensing blocks among the plurality of sensing blocks. The first insulator is embedded in the first surface of the conductor substrate so as to electrically insulate the plurality of sensing blocks;
The gas sensor according to claim 1, wherein in each of the plurality of sensing blocks, the gas sensitive film is surrounded by the first insulator.   The gas sensor according to claim 1, wherein each of the plurality of sensing blocks forms a resistance change detection type sensor element. A resistance temperature sensor is provided on the surface of the first insulator and further detects a temperature of the plurality of sensing blocks in parallel with detecting the gas concentration of the detection target gas by the plurality of sensing blocks. ,
The temperature information for canceling the resistance value of the gas-sensitive film, which changes according to the temperature, in parallel with the information indicating the detected gas concentration being output from each pair of the electrodes The gas sensor according to any one of claims 1 to 3, wherein the gas sensor outputs from the sensor. Forming a groove in the first surface of the conductor substrate;
Burying a first insulator in the groove and dividing the first surface into a plurality of sensing blocks electrically insulated by the first insulator;
Forming a plurality of nanoholes formed on the first surface in a plurality of regions surrounded by the first insulator;
Forming a nanohole array by forming a gas sensitive film on the first surface including the wall surface of the conductive substrate forming the nanohole;
Forming a pair of electrodes in contact with the gas-sensitive film for each of the plurality of sensing blocks;
Forming a second insulator on a second surface of the conductor substrate opposite to the first surface;
Forming a heater on the surface of the second insulator;
A gas sensor manufacturing method, wherein the gas sensitive film is formed of different gas sensitive materials between at least two sensing blocks among the plurality of sensing blocks.

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