FET sensor

Abstract

To provide a technique for improving the sensitivity of a sensor.SOLUTION: A sensor is a FET sensor comprising a substrate including a source electrode, a drain electrode, and a channel region electrically connected to the source electrode and the drain electrode, an insulating layer covering at least the channel region and formed to be stacked on the substrate, and a gate electrode facing the substrate and disposed to be spaced apart from the insulating layer at least in an overlapping region where the channel region and the insulating layer overlap in a stacking direction. The gate electrode has a protrusion protruding toward the channel region, and a metal layer and a capture film for capturing a target are stacked in order from a surface in contact with the gate electrode in the protrusion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to FET sensors. [Background technology]

[0002] FET sensors using field-effect transistors have been proposed. For example, Non-Patent Document 1 discloses a sensor in which a layer is provided on the channel region to prevent the influence of outside air and the adhesion of dust. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] M. Burgmair, et al., Sensors and Actuators, B 95, (2003) 183-188. Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology described in Patent Document 1 has room for improvement in terms of improving the sensitivity of the sensor, and therefore there has been a demand for a technology that can improve the sensitivity of the sensor. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one aspect of the present disclosure, there is provided a FET sensor comprising: a substrate including a source electrode, a drain electrode, and a channel region electrically connected to the source electrode and the drain electrode; an insulating layer formed on the substrate and covering at least the channel region; and a gate electrode facing the substrate and spaced apart from the insulating layer at least in an overlapping region where the channel region and the insulating layer overlap in the stacking direction. The gate electrode has a protrusion protruding toward the channel region, and the protrusion is formed by stacking, in order from the surface in contact with the gate electrode, a metal layer and a trapping film for trapping a target. In this aspect of the sensor, the metal layer between the gate electrode and the trapping film can reduce the distance between the trapping film and the channel region, thereby improving the sensitivity of the sensor.

[0007] (2) In the sensor described in (1) above, the area of ​​the metal layer may be larger than the area of ​​the channel region. According to this form of sensor, the sensitivity of the sensor can be efficiently improved.

[0008] (3) In the sensor described in (1) or (2), the capture membrane may contain a molecularly imprinted polymer having a space formed therein for capturing the target substance, thereby improving the sensitivity of the sensor.

[0009] (4) In the sensor according to any one of (1) to (3), the metal layer may be made of a noble metal. This sensor can improve the sensitivity of the sensor.

[0010] (5) In the sensor according to any one of (1) to (4), the gate electrode may be made of a base metal. This sensor can improve the sensitivity of the sensor.

[0011] The present disclosure can be realized in various forms, for example, a method for manufacturing a sensor, a method for monitoring a target substance using a sensor, and the like. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a cross-sectional view schematically illustrating the general configuration of a sensor. DETAILED DESCRIPTION OF THE INVENTION

[0013] A. First embodiment FIG. 1 is a cross-sectional view schematically illustrating the general configuration of a sensor 100 according to an embodiment of the present disclosure. For convenience of illustration, FIG. 1 illustrates only the essential components of the sensor 100. The sensor 100 detects a target substance contained in a sample. The sample is not particularly limited, but examples thereof include gases such as air and exhaled breath, and liquids such as water. The sensor 100 of this embodiment is a FET sensor including a field-effect transistor.

[0014] The sensor 100 of this embodiment includes: (i) a substrate 10 including a source electrode 30, a drain electrode 40, and a channel region 20 electrically connected to the source electrode 30 and the drain electrode 40; (ii) an insulating layer 15 formed on the substrate 10 and covering at least the channel region 20; and (iii) a gate electrode 50 facing the substrate 10 and spaced apart from the insulating layer 15 at least in an overlap region R where the channel region 20 and the insulating layer 15 overlap in the stacking direction. The gate electrode 50 also includes a protrusion C protruding toward the channel region 20. The protrusion C has, in order from the surface in contact with the gate electrode 50, a metal layer 55 and a capture film 60 for capturing a target stacked thereon.

[0015] The capture membrane 60 of this embodiment is a membrane containing a molecularly imprinted polymer (MIP). A space for capturing a target substance is formed in this molecularly imprinted polymer. This space is formed according to the size and surface structure of the target substance by a method described below. The molecularly imprinted polymer recognizes and captures the target substance by chemically interacting with the target substance in this space. The chemical interaction is not particularly limited, but examples thereof include hydrogen bonding.

[0016] The molecularly imprinted polymer is not particularly limited, but preferably has a non-covalent functional group in the main chain or branched chain. Examples of the non-covalent functional group include, but are not particularly limited to, an OH group. Examples of the molecularly imprinted polymer include, but are not particularly limited to, polypyrrole, polyaniline, acrylic polymers, photocurable polymers, and photosolubilizable polymers. The monomer for forming the molecularly imprinted polymer is not particularly limited, but preferably has a double bond for polymerization. The double bond may be present in the molecular chain or may be a double bond of an aromatic ring. Furthermore, from the viewpoint of the polymerization reaction, a monomer having an amino group is preferred. Therefore, the monomer for forming the molecularly imprinted polymer is preferably a compound having a double bond, an OH group, and an amino group.

[0017] Although one type of monomer may be used as the monomer for forming the molecularly imprinted polymer, it is preferable to use two or more types of monomers. When two or more types of monomers are used, a monomer without a non-covalent functional group may be included. The monomer for forming the molecularly imprinted polymer may be either water-soluble or water-insoluble, but a water-soluble monomer is preferable from the viewpoint of ease of handling. Specific examples of the monomer for forming the molecularly imprinted polymer include pyrrole, aniline, ortho-phenylenediamine, acrylamide, N,N'-methylenebisacrylamide, aminophenylboronic acid, aminophenol, aminobenzoic acid, and dopamine.

[0018] The target substance is not particularly limited, and examples thereof include substances having a three-dimensional structure, chemical substances, fine particles, etc. The substances having a three-dimensional structure are not particularly limited, and examples thereof include viruses, fungi, microorganisms, proteins, antigens, etc. The fungi are not particularly limited, and examples thereof include bacteria, fungi, archaea, etc. The viruses and fungi may be pathogenic to animals such as humans. The microorganisms are not particularly limited, and examples thereof include yeast and algae, etc. The proteins are not particularly limited, and examples thereof include disease-related proteins and antibodies, etc. The chemical substances are not particularly limited, and examples thereof include drugs and hormones, etc. The fine particles are not particularly limited, and examples thereof include pollen, PM2.5, yellow sand, aerosols, etc.

[0019] The target substance may be one or more types, but is preferably one type from the viewpoint of preventing a decrease in detection accuracy. In an embodiment in which two or more types of target substances are detected, two or more types of spaces are formed in the molecular imprinted polymer according to the target substances.

[0020] The thickness of the trapping film 60 is not particularly limited, but is preferably 0.05 μm to 3 μm, more preferably 0.08 μm to 2 μm, and even more preferably 0.1 μm to 1 μm. By setting the thickness within these preferred ranges, the sensitivity of the sensor 100 can be further improved.

[0021] The gate electrode 50 faces the substrate 10 and is spaced apart from the insulating layer 15 at least in the overlap region R where the channel region 20 and the insulating layer 15 overlap in the stacking direction. When a target substance is captured in the space formed in the capture film 60, the value of the current flowing through the gate electrode 50 changes, and the target substance can be detected based on this value.

[0022] The gate electrode 50 is not particularly limited as long as it is conductive, and may be formed from, for example, a metal, conductive carbon, a conductive polymer, or the like. The metal is not particularly limited, and examples thereof include noble metals and base metals. In this specification, the term "base metal" refers to a metal having a higher ionization tendency than hydrogen. Examples of base metals include alkali metals, alkaline earth metals, aluminum, zinc, and lead. Examples of alkali metals include lithium, sodium, and potassium. Examples of alkaline earth metals include magnesium and calcium. In this specification, the term "noble metal" refers to a metal having a lower ionization tendency than hydrogen. Examples of noble metals include copper, silver, gold, and platinum. From the viewpoint of reducing manufacturing costs, the gate electrode 50 is preferably formed from a base metal. The gate electrode 50 of this embodiment is formed from aluminum.

[0023] The gate electrode 50 has a protrusion C that protrudes toward the channel region 20. On the protrusion C, a metal layer 55 and a capture film 60 for capturing a target are stacked in this order from the surface that contacts the gate electrode 50.

[0024] The metal layer 55 is not particularly limited, but may be formed of, for example, a base metal or a precious metal. From the viewpoint of improving the sensitivity of the sensor 100, the metal layer 55 is preferably formed of a precious metal.

[0025] The thickness of the metal layer 55 is not particularly limited, but is preferably 10 nm to 200 nm, more preferably 30 nm to 150 nm, and even more preferably 50 nm to 120 nm. By setting the thickness within the above preferred range, the sensitivity of the sensor 100 can be further improved.

[0026] The area of ​​the metal layer 55 is not particularly limited, and may be equal to or larger than the area of ​​the channel region 20. In this specification, the area of ​​the metal layer 55 and the area of ​​the channel region 20 both refer to the area in a plane perpendicular to the stacking direction of the metal layer 55 and the trapping film 60. In this embodiment, the area of ​​the metal layer 55 is larger than the area of ​​the channel region 20.

[0027] The substrate 10 includes a source region 35, a drain region 45, and a channel region 20 electrically connected to the source region 35 and the drain region 45. The substrate 10 also includes a source electrode 30 in electrical contact with the source region 35, and a drain electrode 40 in electrical contact with both the source region 35 and the drain region 45. Therefore, in other words, the channel region 20 is electrically connected to the source electrode 30 and the drain electrode 40.

[0028] The substrate 10 is not particularly limited and may be made of an inorganic material or an organic material. Examples of inorganic materials include, but are not particularly limited to, glass, ceramics, and metal. Examples of organic materials include, but are not particularly limited to, resin and paper. The substrate 10 of this embodiment is made of silicon.

[0029] The source electrode 30 and the drain electrode 40 are not particularly limited, and may be formed of, for example, a metal, a conductive polymer, conductive carbon, a conductive organic-inorganic composite material, or the like. Examples of metals include, but are not particularly limited to, gold, silver, copper, platinum, aluminum, and titanium. Examples of conductive polymers include, but are not particularly limited to, PEDOT and PSS. Examples of conductive carbon include, but are not particularly limited to, conductive carbon nanotubes and graphene. The source electrode 30 and the drain electrode 40 of this embodiment are both formed of gold.

[0030] The insulating layer 15 is formed on the channel region 20. This prevents the channel region 20 from being affected by the outside air and from being contaminated by dust. The insulating layer 15 is not particularly limited, and may be formed from, for example, hafnium oxide, silicon nitride, silica (silicon oxide), alumina (aluminum oxide), a self-assembled monolayer, polystyrene, polyvinylphenol, polyvinyl alcohol, polymethyl methacrylate, polydimethylsiloxane, polysilsesquioxane, an ionic liquid, polytetrafluoroethylene, or the like. The insulating layer 15 of this embodiment is formed from silicon nitride.

[0031] In this embodiment, a guard ring 25 is formed on the insulating layer 15. The guard ring 25 is provided so as to surround the channel region 20. The material of the guard ring 25 is not particularly limited. The guard ring 25 may be formed of, for example, a metal, a conductive polymer, a conductive carbon, a conductive organic-inorganic composite material, or the like. In this embodiment, the guard ring 25 is formed of gold.

[0032] In this embodiment, the gate electrode 50 and the substrate 10 are bonded via a spacer 90. In this embodiment, the spacer 90 is formed of a material that insulates the gate electrode 50 from the substrate 10. The spacer 90 is not particularly limited, but may contain, for example, silicon nitride, silica (silicon oxide), alumina (aluminum oxide), a self-assembled monolayer, polystyrene, polyvinylphenol, polyvinyl alcohol, polymethyl methacrylate, polydimethylsiloxane, polysilsesquioxane, an ionic liquid, polytetrafluoroethylene, or the like. The spacer 90 is bonded to the insulating layer 15 by an adhesive layer 70 and to the gate electrode 50 by an adhesive layer 80. The adhesive layer 70 is not particularly limited as long as it is made of a material that can bond the insulating layer 15 and the spacer 90, and the adhesive layer 80 is not particularly limited as long as it is made of a material that can bond the gate electrode 50 and the spacer 90. In this embodiment, both the adhesive layers 70 and 80 are made of gold.

[0033] In the sensor 100 of this embodiment, the metal layer 55 is provided between the gate electrode 50 and the trapping film 60, which causes the trapping film 60 to protrude toward the channel region 20. As a result, the sensor 100 of this embodiment can reduce the distance between the trapping film 60 and the channel region 20, thereby improving the sensitivity of the sensor 100.

[0034] Furthermore, in the sensor 100 of this embodiment, the area of ​​the metal layer 55 is larger than the area of ​​the channel region 20, so the trapping film 60 protrudes toward the channel region 20 on the surface where the channel region 20 is present. As a result, the sensor 100 of this embodiment can reduce the distance between the trapping film 60 and the channel region 20 over a wide area, thereby improving the sensitivity of the sensor 100. The areas of the metal layer 55 and the trapping film 60 are both larger than the area of ​​the overlapping region R. Therefore, the area of ​​the convex portion C is larger than the area of ​​the overlapping region R. Furthermore, the convex portion C is formed above the entire overlapping region R.

[0035] The uses of the sensor 100 of this embodiment are not particularly limited, but may be applied to, for example, monitoring of viruses and bacteria, disease testing by measuring breath and detection of illegal drugs such as narcotics, detection of dangerous materials such as landmines and explosives, personal authentication by measuring multiple odor components, air quality monitoring, drone inspection and monitoring, food hygiene management, water quality management, and health management of humans, animals, and plants.

[0036] The method for manufacturing the sensor 100 of this embodiment is not particularly limited, but it can be manufactured, for example, by the following method: An example of the method for manufacturing the sensor 100 will be described below.

[0037] First, a substrate 10 including a source region 35, a drain region 45, and a channel region 20 is prepared. Next, an insulating layer 15 is formed on the substrate 10. After that, holes are formed in the insulating layer 15 above the source region 35 and above the drain region 45, and then a source electrode 30, a drain electrode 40, a guard ring 25, and an adhesive layer 70 are formed by vacuum deposition. The substrate 10 is then diced into chips. This allows a member including the substrate 10 to be manufactured.

[0038] Next, an aluminum substrate is prepared as the gate electrode 50. Then, a metal layer 55 and an adhesive layer 80 are formed on the gate electrode 50. After that, a trapping film 60 is formed on the metal layer 55. Here, the trapping film 60 can be formed, for example, by the following method. Specifically, after plasma treatment of the aluminum substrate, it is immersed in a 1 mM aminoethanethiol solution overnight (about 12 hours), and then washed with ethanol and ultrapure water. Next, it is reacted with a 0.4 vol% Nafion solution for 3 hours, and then 1 × 10 9 After adding CFU / mL of E. coli and 100 mM pyrrole, 30 minutes later, a 120 mM aqueous solution of ammonium persulfate was added and the pyrrole was polymerized overnight (approximately 12 hours). After that, the substrate was washed with ultrapure water and then ultrasonically cleaned in water for 5 minutes (or with 1 × 10 -3By performing incubation in a surfactant containing M, the E. coli used for template formation is removed from the capture membrane 60, thereby forming the capture membrane 60. In this way, a member having a gate electrode 50 can be produced.

[0039] Then, in a state where the member including the gate electrode 50 and the spacer 90 are temporarily fixed together, the member including the gate electrode 50 and the spacer 90 are bonded together by the adhesive layer 80, thereby manufacturing a member including the spacer 90 and the gate electrode 50. In this embodiment, Au-Au bonding is used for bonding.

[0040] Thereafter, the member including the spacer 90 and the gate electrode 50 is made into a chip, and the member including the spacer 90 and the gate electrode 50 is bonded to a member including the substrate 10 via the adhesive layer 70, thereby manufacturing the sensor 100 of this embodiment. In this embodiment, Au-Au bonding is used for bonding.

[0041] B. Variations The configuration of the sensor 100 in the above embodiment is merely an example and can be modified in various ways. For example, the sensor 100 may be configured such that the insulating layer 15 and the spacer 90 are integrally formed, so that the end of the gate electrode 50 and the insulating layer 15 are in contact with each other. Furthermore, for example, in the above embodiment, the trapping film 60 is a film containing a molecularly imprinted polymer, but this is not limiting. For example, a metal complex such as copper phthalocyanine may be used as the trapping film 60.

[0042] 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. For example, the technical features in the embodiments and examples corresponding to the technical features in each aspect described in the Summary of the Invention section 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]

[0043] 10...substrate, 15...insulating layer, 20...channel region, 25...guard ring, 30...source electrode, 35...source region, 40...drain electrode, 45...drain region, 50...gate electrode, 55...metal layer, 60...trapping film, 70, 80...adhesion layer, 90...spacer, 100...sensor, C...protrusion, R...overlap region

Claims

1. a substrate including a source electrode, a drain electrode, and a channel region electrically connected to the source electrode and the drain electrode; an insulating layer covering at least the channel region and laminated on the substrate; a gate electrode facing the substrate and spaced apart from the insulating layer at least in an overlapping region where the channel region and the insulating layer overlap in a stacking direction, the gate electrode has a protrusion protruding toward the channel region, the protrusion has a metal layer and a capture film for capturing a target laminated on it in this order from the surface in contact with the gate electrode; FET sensor characterized by:

2. 2. The FET sensor according to claim 1, The area of ​​the metal layer is larger than the area of ​​the channel region. FET sensor characterized by:

3. 3. The FET sensor according to claim 1, the capture membrane contains a molecularly imprinted polymer having spaces formed therein for capturing a target substance; FET sensor characterized by:

4. 3. The FET sensor according to claim 1, The metal layer is formed of a noble metal. FET sensor characterized by:

5. 3. The FET sensor according to claim 1, the gate electrode is formed of a base metal; FET sensor characterized by:

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