Sensor

Abstract

A sensor 1 comprises: a field-effect-transistor-type sensor element 10 including a semiconductor layer 11, and a source electrode 12 and a drain electrode 13 that are electrically connected to the semiconductor layer 11 and are disposed facing each other across a gap in the channel length direction of the semiconductor layer 11; and an insulation coat layer 20 covering at least part of one or both of the source electrode 12 and the drain electrode 13. As seen in a cross-section in a direction crossing the gap between the source electrode 12 and the drain electrode 13, an insulating film continuous with the insulating coat layer 20 is not provided around the semiconductor layer 11.

Description

Sensor

[0001] The present invention relates to sensors such as biosensors.

[0002] As a sensor for detecting a substance to be detected (also called a target molecule) in a solution, a field effect transistor (FET) type sensor using a probe molecule that specifically interacts with the target molecule is known. In such a FET type sensor, the probe molecule is disposed on the surface of a sensor element.

[0003] One example of an FET that constitutes an FET-type sensor is a graphene FET, which uses graphene for the channel formed between the source electrode and the drain electrode. Graphene is a two-dimensional material consisting of carbon atoms bonded in a hexagonal mesh. Graphene has a very large specific surface area (surface area per volume) and very high electrical mobility. Therefore, in a graphene FET, the charge of a target molecule is easily converted into a current signal.

[0004] Patent Literature 1 discloses a sensor including a substrate, a plurality of graphene FETs, at least one source electrode, at least one drain electrode, and at least one gate electrode. In the sensor described in Patent Literature 1, the source electrode is connected to the graphene FET via at least one first metal track, and the drain electrode is connected to the graphene FET via at least one second metal track.

[0005] US Patent Application Publication No. 2022 / 0136996

[0006] US Patent Application Publication No. 2009 / 0129994 describes an embodiment in which at least one first metal track and at least one second metal track are encapsulated by covering them with an organic or inorganic dielectric material to avoid degradation and reduce leakage currents.

[0007] In FIGS. 8G and 8H of Patent Document 1, an example of encapsulation is shown in which an electrode 83 and a substrate 80 are covered with a sealing layer 74 and a portion of graphene 82 is covered with a sealing layer 75.

[0008] However, it has been found that a structure in which an insulating member such as a sealing layer is disposed around the sensing portion, such as the sensor described in Patent Document 1, causes a problem of a long detection time. The detection time of a sensor is strongly dependent on the time it takes for a substance to be detected (target molecule) in a solution to reach the sensing portion. Therefore, in a sensor such as that described in Patent Document 1, it is thought that the time it takes for the target molecule to reach the sensing portion after being introduced is long.

[0009] It can be said that the above problem is not limited to graphene FET type sensors, but occurs in FET type sensors in general.

[0010] The present invention has been made to solve the above problems, and aims to provide a sensor with a short detection time by shortening the time it takes for the target molecule to reach the sensing portion after being introduced.

[0011] The sensor of the present invention comprises a field-effect transistor-type sensor element including a semiconductor layer, a source electrode and a drain electrode electrically connected to the semiconductor layer and arranged opposite each other with a gap in the channel length direction of the semiconductor layer, and an insulating coating layer covering at least a portion of one or both of the source electrode and the drain electrode. When viewed in a cross section across the gap between the source electrode and the drain electrode, no insulating film that is integrally continuous with the insulating coating layer is provided around the semiconductor layer.

[0012] According to the present invention, the time required for the target molecule to reach the sensing portion after being introduced is shortened, thereby providing a sensor with a short detection time.

[0013] FIG. 1 is a schematic perspective view showing an example of a sensor according to a first embodiment of the present invention. FIG. 2 is a schematic plan view showing an example of a sensor according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of the sensor shown in FIG. 2 taken along line A-A. FIG. 4 is a schematic cross-sectional view of the sensor shown in FIG. 2 taken along line B-B. FIG. 5 is a schematic perspective view showing a first modified example of the sensor according to the first embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of the sensor shown in FIG. 5. FIG. 7 is a perspective view of a calculation model for confirming the relationship between a convex portion formed by an insulating film and flow velocity. FIG. 8 is an xy cross-sectional view of the calculation model shown in FIG. 7. FIG. 9 is an xz cross-sectional view of the calculation model shown in FIG. 7. FIG. 10 is a graph showing simulation results of flow velocity at a monitoring position. FIG. 11 is an enlarged view of the graph shown in FIG. 10. FIG. 12 is a schematic cross-sectional view showing an example of an insulating film that may be provided at a location away from the semiconductor layer. FIG. 13 is a schematic plan view showing an example of an insulating film provided at a location away from the semiconductor layer. FIG. 14 is a schematic cross-sectional view showing an example of an insulator that may be provided around the semiconductor layer 11. FIG. 15 is a schematic plan view showing modified examples of the source electrode and the drain electrode. FIG. 16 is a schematic cross-sectional view showing a second modified example of the sensor according to the first embodiment of the present invention. FIG. 17 is a schematic cross-sectional view showing a third modified example of the sensor according to the first embodiment of the present invention. FIG. 18 is a schematic cross-sectional view showing a fourth modified example of the sensor according to the first embodiment of the present invention. FIG. 19 is a schematic plan view showing an example of a sensor according to the second embodiment of the present invention. FIG. 20 is a schematic plan view showing another example of the sensor according to the second embodiment of the present invention. FIG. 21 is a schematic plan view showing an example of the vector direction of the principal component of the flow velocity of the flow channel. FIG. 22 is a schematic plan view showing an example of a sensor according to the third embodiment of the present invention. FIG. 23 is a schematic plan view showing another example of the sensor according to the third embodiment of the present invention.

[0014] The sensor of the present invention will be described below. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied within the scope of the present invention. A combination of two or more of the individual desirable configurations of the present invention described in the following embodiments also constitutes the present invention.

[0015] The sensor of the present invention is preferably a sensor for detecting a substance to be detected (target molecule) in a solution. The sensor of the present invention is, for example, an FET-type biosensor for detecting viruses, etc. An FET-type biosensor forms a mechanism in the channel portion that mimics a living organism, and detects the reaction that occurs there using the electrical characteristics of the FET. The sensor of the present invention may also be applied to sensors other than biosensors. For example, the sensor of the present invention may be an FET-type chemical sensor that detects ions, etc.

[0016] The following embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. From the second embodiment onwards, descriptions of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned one after the other for each embodiment.

[0017] In the following description, when no particular distinction is made between the embodiments, they will simply be referred to as "the sensor of the present invention."

[0018] The drawings shown below are schematic diagrams, and the sensor configuration has been modified as appropriate for clarity and simplification of the drawings. In the drawings, the same or corresponding parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and duplicate explanations will be omitted.

[0019] First Embodiment FIG. 1 is a schematic perspective view showing an example of a sensor according to a first embodiment of the present invention.

[0020] The sensor 1 shown in FIG. 1 includes a field effect transistor type sensor element 10 and an insulating coating layer 20 .

[0021] The sensor element 10 includes, for example, a semiconductor layer 11, and a source electrode 12 and a drain electrode 13 electrically connected to the semiconductor layer 11. The semiconductor layer 11 between the source electrode 12 and the drain electrode 13 forms a channel of the sensor element 10. As shown in Fig. 1 , the source electrode 12 and the drain electrode 13 are arranged opposite to each other with a gap therebetween in the channel length direction of the semiconductor layer 11 (the x direction in Fig. 1 ).

[0022] The semiconductor layer 11 includes, for example, graphene.

[0023] The source electrode 12 and the drain electrode 13 are electrodes with a multilayer structure in which, for example, a titanium (Ti) layer and a gold (Au) layer are stacked. As the electrode material, in addition to titanium and gold, metals such as gold, platinum, titanium, and palladium may be used in a single layer, or two or more metals may be combined to form a multilayer structure.

[0024] The sensor 1 preferably further includes an insulating substrate 15. In this case, the sensor element 10 is disposed on the insulating substrate 15.

[0025] The insulating substrate 15 is, for example, a silicon oxide (SiO ２ Examples of the insulating substrate 15 include a thermally oxidized silicon substrate or a boron nitride (BN) substrate on which a thermally oxidized silicon (Si) layer is formed. The material of the insulating substrate 15 is not particularly limited, and examples thereof include inorganic compounds such as silicon oxide, silicon nitride, aluminum oxide, titanium oxide, and calcium fluoride, and organic compounds such as acrylic resin, polyimide, and fluororesin. The shape of the insulating substrate 15 is not particularly limited, and may be a flat plate or a curved plate. The insulating substrate 15 may be flexible.

[0026] 1 , the source electrode 12 and the drain electrode 13 are disposed on an insulating substrate 15 at a distance from each other, and the insulating substrate 15 is exposed between the source electrode 12 and the drain electrode 13. The semiconductor layer 11 is disposed on the insulating substrate 15 so as to cover the exposed portions of the insulating substrate 15. As shown in FIG. 1 , the semiconductor layer 11 may be disposed continuously on the insulating substrate 15 so as to cover the end of the source electrode 12, the exposed portion of the insulating substrate 15, and the end of the drain electrode 13. In other words, the semiconductor layer 11 may be disposed in a continuous state on the insulating substrate 15 so as to cover the end of the source electrode 12, the exposed portion of the insulating substrate 15, and the end of the drain electrode 13.

[0027] A drain-source voltage Vds is applied between the source electrode 12 and the drain electrode 13. The semiconductor layer 11 is preferably placed in an electrolyte solution 30. A gate electrode 31 is preferably placed in the electrolyte solution 30. The gate electrode 31 is an electrode for applying a gate voltage Vg.

[0028] The gate electrode 31 applies a potential to the source electrode 12 and the drain electrode 13, and generally uses a noble metal or a silver / silver chloride reference electrode. The gate electrode 31 is provided at a location other than where the source electrode 12 and the drain electrode 13 are formed. Usually, the gate electrode 31 is provided on the insulating substrate 15 or at a location other than the insulating substrate 15, but it is preferable to provide the gate electrode 31 above the source electrode 12 or the drain electrode 13.

[0029] Fig. 2 is a schematic plan view showing an example of a sensor according to the first embodiment of the present invention. Fig. 3 is a schematic cross-sectional view taken along line AA of the sensor shown in Fig. 2. Fig. 4 is a schematic cross-sectional view taken along line BB of the sensor shown in Fig. 2.

[0030] 2, the insulating coating layer 20 is provided so as to cover at least a portion of one or both of the source electrode 12 and the drain electrode 13. By providing the insulating coating layer 20, the insulation properties of the portions other than the sensing portion are improved, thereby improving the reliability of the sensor.

[0031] The insulating coating layer 20 is preferably provided so as to cover at least a part of the source electrode 12 and at least a part of the drain electrode 13. The insulating coating layer 20 covering the source electrode 12 and the insulating coating layer 20 covering the drain electrode 13 may or may not be continuous.

[0032] As shown in FIG. 3, when viewed in a cross section in the channel length direction (x direction in FIGS. 2 and 3 ) where the source electrode 12 and the drain electrode 13 face each other, it is preferable that an insulating coating layer 20 be provided around the semiconductor layer 11.

[0033] On the other hand, as shown in Figure 4, when viewing a cross section in a direction across the gap between the source electrode 12 and the drain electrode 13 (the y direction in Figures 2 and 4), no insulating film that is continuous and integral with the insulating coating layer 20 is provided around the semiconductor layer 11.

[0034] As described above, the detection time of the sensor 1 strongly depends on the time it takes for the substance to be detected (target molecule) in a solution such as the electrolyte solution 30 to reach the sensing portion (semiconductor layer 11). Therefore, when the insulating coating layer 20 is provided all around the semiconductor layer 11, the flow of the solution is hindered by the insulating coating layer 20, which tends to reduce the flow rate at the sensing portion. As a result, the time it takes for the target molecule to reach the sensing portion after being introduced tends to be longer.

[0035] In contrast, the flow velocity at the sensing portion in the direction (e.g., the y direction) across the gap between the source electrode 12 and the drain electrode 13 is increased because no protrusions made of insulating film are provided. As a result, the time it takes for the target molecules to reach the sensing portion after being introduced is shortened, thereby shortening the detection time of the sensor.

[0036] Fig. 5 is a schematic perspective view showing a first modified example of the sensor according to the first embodiment of the present invention. Fig. 6 is a schematic cross-sectional view of the sensor shown in Fig. 5. The sensor 1A shown in Figs. 5 and 6 is a biosensor that detects target molecules 41 such as viruses.

[0037] 5 and 6, the probe molecules 40 are disposed on at least a part of the surface of the sensor element 10. The other configuration of the sensor 1A is the same as that of the sensor 1.

[0038] Examples of the probe molecules 40 to be placed on the surface of the sensor element 10 include antibodies, enzymes, sugar chains, aptamers (nucleic acids), lectins, oligonucleotides, peptides, and low-molecular-weight organic polymers.

[0039] The probe molecules 40 may be movable with a certain degree of freedom as long as they remain on the surface of the sensor element 10. The probe molecules 40 may be disposed directly or indirectly on the surface of the sensor element 10.

[0040] 5 and 6 , the probe molecules 40 are disposed on at least a portion of the surface of the semiconductor layer 11. The probe molecules 40 capture target molecules 41. The probe molecules 40 are preferably disposed in the electrolyte solution 30.

[0041] When the probe molecule 40 specifically binds to the target molecule 41, the conduction characteristics are modulated by the charge of the target molecule 41. By observing this modulation, the presence or concentration of the target molecule 41 can be sensed.

[0042] An example of a method for detecting a substance to be detected (target molecules 41) in a solution (electrolyte solution 30) using the sensor 1A will be described below.

[0043] First, using the sensor 1A, the target molecules 41 in the electrolyte 30 are captured by the probe molecules 40.

[0044] For example, a sample containing target molecules 41 is supplied to the sensor 1A. This brings the sample into contact with the sensor element 10. The sample containing the target molecules 41 is preferably a liquid. In this case, the sample may be dropped onto the sensor element 10 using a dropper or the like, or the sample may be introduced into the sensor element 10 using a flow channel.

[0045] Examples of samples containing target molecules 41 include body fluids such as the subject's saliva, throat swabs, nasal mucus, tears, and blood, biological samples such as urine and feces, suspensions of cells or viruses themselves, drinking water, sewage, and exhaled breath.

[0046] Subsequently, the electrical change caused by the target molecule 41 is measured in the sensor element 10 .

[0047] Examples of electrical physical quantities that change due to the interaction between the target molecule 41 and the probe molecule 40 include voltage value, current value, frequency characteristics, electrical resistance value, and conductivity.

[0048] For example, a voltage is applied between the source electrode 12 and the drain electrode 13 to measure the value of the current (drain current value) flowing between the source electrode 12 and the drain electrode 13. In this case, the gate voltage (Dirac voltage V Ｄｉｒａｃ The change in the temperature over time is obtained as an example of the sensor output.

[0049] In a method for detecting target molecules 41 in an electrolyte solution 30 using the sensor 1A, a background may be measured using a sample that does not contain the target molecules 41 before supplying a sample containing the target molecules 41 to the sensor 1A.

[0050] When measuring the background, it is preferable to remove the sample not containing the target molecules 41 from the sensor 1A before supplying the sample containing the target molecules 41 to the sensor 1A.

[0051] The present inventors performed a simulation using the calculation model shown in FIGS. 7 to 9 in order to confirm the relationship between the convex portions formed by the insulating film and the flow velocity.

[0052] Fig. 7 is a perspective view of a calculation model for confirming the relationship between the convex portion due to the insulating film and the flow velocity. Fig. 8 is an xy cross-sectional view of the calculation model shown in Fig. 7. Fig. 9 is an xz cross-sectional view of the calculation model shown in Fig. 7.

[0053] 7 to 9, a pair of insulating films 21, each having a dimension of 100 μm in the x direction and a dimension of 100 μm in the y direction, are arranged facing each other with a gap in the x direction. The dimension (thickness T) of the insulating film 21 in the z direction is 10 μm. The distance between the insulating films 21 in the x direction (facing distance L) is 400 μm.

[0054] As shown in Figures 7 to 9, water was flowed in the x direction from the inlet to the outlet at a flow rate of 1 mm / s. The flow rate distribution in this case was calculated using COMSOL Multiphysics 3.5, a finite element method simulation software. The position indicated by the dashed line in Figure 9 (distance from the bottom surface: z = 100 nm) was set as the monitoring position, and the flow rate at the monitoring position was calculated.

[0055] Figure 10 is a graph showing the simulation results of the flow velocity at the monitoring position, and Figure 11 is an enlarged view of the graph shown in Figure 10.

[0056] 10 and 11 show that the flow velocity is significantly reduced near the end of the insulating film 21 (the boundary with the insulating film 21) where the horizontal axis is 0 μm or 400 μm. In other words, the target molecules have difficulty reaching the end of the insulating film 21 (the boundary with the insulating film 21). From these results, it is thought that by not locating the sensing portion (semiconductor layer 11) near the insulating film 21, the time it takes for the target molecules to reach the sensing portion is shortened.

[0057] As shown in FIG. 11, the flow velocity at a position sufficiently far from the end of the insulating film 21 is 525 nm / s (100%), whereas the flow velocity at a position 50 μm away from the end of the insulating film 21 is 510 nm / s (approximately 97%), and the flow velocity at a position 20 μm away from the end of the insulating film 21 is 325 nm / s (approximately 60%).

[0058] From the above, in a sensor such as the sensor 1 shown in Figure 1, when viewing a cross section in a direction across the gap between the source electrode 12 and the drain electrode 13 (for example, the y direction), the effect of the insulating film 21 in reducing the flow rate is small in locations away from the semiconductor layer 11, so an insulating film 21 that is continuous and integral with the insulating coating layer 20 may be provided.

[0059] From the results shown in Figure 11, it is preferable that the insulating film 21 is not provided within a range of 20 μm around the semiconductor layer 11, and it is more preferable that the insulating film 21 is not provided within a range of 50 μm around the semiconductor layer 11.

[0060] Fig. 12 is a schematic cross-sectional view showing an example of an insulating film that may be provided at a location away from the semiconductor layer, and Fig. 13 is a schematic plan view showing an example of an insulating film that is provided at a location away from the semiconductor layer.

[0061] 12 , when viewed in a cross section in a direction across the gap between the source electrode 12 and the drain electrode 13 (the y direction in FIGS. 12 and 13 ), an insulating film 21 may be provided that is continuous and integral with the insulating coating layer 20, as long as it is located away from the semiconductor layer 11. In this case, the distance D between the semiconductor layer 11 and the insulating film 21 is preferably greater than 20 μm, and more preferably greater than 50 μm.

[0062] The thickness of the insulating film 21 is not particularly limited, and may be the same as the thickness of the insulating coating layer 20 , may be smaller than the thickness of the insulating coating layer 20 , or may be larger than the thickness of the insulating coating layer 20 .

[0063] FIG. 14 is a schematic cross-sectional view showing an example of an insulator that may be provided around the semiconductor layer 11. As shown in FIG.

[0064] 14 , even if the insulator 22 is located close to the semiconductor layer 11, it may be provided around the semiconductor layer 11 as long as it is not continuous with the insulating coating layer 20. Examples of such an insulator 22 include resist residues.

[0065] The thickness of the insulator 22 is preferably smaller than the thickness of the semiconductor layer 11. In addition, the total area of ​​the insulator 22 is preferably smaller than the area of ​​the semiconductor layer 11 when viewed in the thickness direction of the semiconductor layer 11.

[0066] FIG. 15 is a schematic plan view showing a modified example of the source electrode and the drain electrode.

[0067] 15, the source electrode 12 and the drain electrode 13 may have a comb-like shape. Note that, for the comb-like electrodes shown in Fig. 15, the x direction in which each comb tooth extends is defined as the channel length direction of the semiconductor layer 11, and the y direction is defined as the direction perpendicular thereto.

[0068] 1, the semiconductor layer 11 preferably contains graphene. By using a FET transistor with graphene as the channel, the sensitivity of the sensor can be increased.

[0069] Graphene is a two-dimensional material consisting of carbon atoms bonded in a hexagonal network, which has a very large specific surface area (surface area per volume) and very high electrical mobility.

[0070] Furthermore, since graphene is a thin and flat material, the flow rate is less likely to decrease in the semiconductor layer 11, which is the sensing portion.

[0071] Generally, graphene refers to a carbon-based sheet material in which one layer of carbon atoms has a honeycomb structure. However, in this specification, the following materials are also broadly defined as graphene: - A carbon-based sheet material in which graphene is multilayered or partially multilayered up to 100 layers. - A polycrystalline carbon-based sheet material having grain boundaries and further having partial breaks and edges. - A carbon-based sheet material in which elements are partially substituted or the honeycomb structure is broken. - Graphene oxide and reduced graphene oxide obtained by reducing it. - Ribbon-shaped (strip-shaped) graphene. - Carbon nanotubes in which sheet-shaped graphene is shaped into a cylinder, and materials in which graphene is wrapped around itself.

[0072] The number of layers in the semiconductor layer 11 is not limited to one, and may be two or three or more. The number of layers in the semiconductor layer 11 is preferably 10 or less, and more preferably 5 or less. The number of layers does not need to be uniform throughout the semiconductor layer 11; for example, one layer portion and two or more layers portion may be mixed. The number of layers in the semiconductor layer 11 can be measured, for example, by Raman spectroscopy or cross-sectional observation using a transmission electron microscope (TEM).

[0073] For example, when the semiconductor layer 11 includes graphene, as shown in Fig. 3, when a cross section in the channel length direction (e.g., x direction) in which the source electrode 12 and the drain electrode 13 face each other is viewed, the semiconductor layer 11 preferably covers a part of one or both of the source electrode 12 and the drain electrode 13. Specifically, the semiconductor layer 11 preferably covers the ends of one or both of the source electrode 12 and the drain electrode 13 in a connected state.

[0074] Graphene is hydrophobic. A hydrophobic surface has the effect of reducing flow resistance (laminar flow resistance). Therefore, by covering electrodes such as the source electrode 12 and the drain electrode 13 with the semiconductor layer 11, the flow resistance of the entire system is reduced, thereby shortening the detection time.

[0075] Furthermore, as shown in FIG. 3, when viewed in a cross section in the channel length direction (e.g., x direction) where the source electrode 12 and the drain electrode 13 face each other, it is preferable that the semiconductor layer 11 is arranged at a distance from the insulating coating layer 20.

[0076] 10 and 11, the flow rate decreases near the end of the insulating film 21 (the boundary with the insulating film 21), making it difficult for target molecules to reach there. Therefore, if the sensing portion (semiconductor layer 11) is located near the insulating coating layer 20, it may become a noise source. Therefore, by arranging the semiconductor layer 11 at a distance from the insulating coating layer 20, the accuracy of the sensor can be improved.

[0077] Furthermore, as will be described later, when the end of the insulating coating layer 20 is inclined, if the inclined portion of the insulating coating layer 20 is covered with the semiconductor layer 11, the semiconductor layer 11 is likely to break due to the flow along the inclination. Therefore, from the viewpoint of making the semiconductor layer 11 less likely to break, it is preferable that the semiconductor layer 11 be disposed at a distance from the insulating coating layer 20.

[0078] The size of the gap between the semiconductor layer 11 and the insulating coating layer 20 is not particularly limited and is adjusted as appropriate, for example, by the thickness of the insulating coating layer 20. The size of the gap between the semiconductor layer 11 and the insulating coating layer 20 on the source electrode 12 side and the drain electrode 13 side may be the same or different.

[0079] The semiconductor layer 11 may cover a portion of the source electrode 12 but not the drain electrode 13, or may cover a portion of the drain electrode 13 but not the source electrode 12; however, it is preferable that the semiconductor layer 11 cover a portion of the source electrode 12 and a portion of the drain electrode 13.

[0080] FIG. 16 is a schematic cross-sectional view showing a second modified example of the sensor according to the first embodiment of the present invention.

[0081] As in the sensor 1B shown in Figure 16, when viewed in a cross section in the channel length direction (x direction in Figure 16) where the source electrode 12 and the drain electrode 13 face each other, the semiconductor layer 11 does not need to cover the source electrode 12 and the drain electrode 13.

[0082] FIG. 17 is a schematic cross-sectional view showing a third modified example of the sensor according to the first embodiment of the present invention.

[0083] As in the sensor 1C shown in Figure 17, when viewed in cross section in the channel length direction (x direction in Figure 17) where the source electrode 12 and the drain electrode 13 face each other, the end of the insulating coating layer 20 may be inclined.

[0084] If the end of the insulating coating layer 20 is inclined, the flow resistance is reduced, and the reduction in flow velocity is alleviated.

[0085] The angle of inclination at the end of the insulating coating layer 20 is not particularly limited and may be adjusted as appropriate depending on, for example, the thickness of the insulating coating layer 20. The angle of inclination at the end of the insulating coating layer 20 on the source electrode 12 side and the drain electrode 13 side may be the same or different.

[0086] In the example shown in Figure 17, the ends of the insulating coating layer 20 on the source electrode 12 side and the drain electrode 13 side are sloped, but it is also possible to slope only the end of the insulating coating layer 20 on the source electrode 12 side, or only the end of the insulating coating layer 20 on the drain electrode 13 side.

[0087] 17 , the end of the insulating coating layer 20 is inclined so that the dimension of the x direction of the insulating coating layer 20 increases as it approaches the source electrode 12 or the drain electrode 13 in the z direction (i.e., toward the negative direction of the z axis), but the end of the insulating coating layer 20 may also be inclined so that the dimension of the x direction of the insulating coating layer 20 decreases as it approaches the source electrode 12 or the drain electrode 13 in the z direction (i.e., toward the negative direction of the z axis). In this case, the direction of the inclination may be the same or different between the end of the insulating coating layer 20 on the source electrode 12 side and the end of the insulating coating layer 20 on the drain electrode 13 side.

[0088] The insulating coating layer 20 may be made of, for example, SiO ２ , Si ３ N ４ , Al ２ O ３ , HfO ２ Examples of insulating materials include ceramic materials such as those mentioned above, and resin materials such as epoxy resin, polyimide resin, silicone resin, fluororesin, acrylic resin, and photoresist. When forming a pattern by photolithography, the material forming the insulating coating layer 20 is preferably a photosensitive material.

[0089] In particular, it is preferable that the insulating coating layer 20 is made of a polymer such as a resin material, since the use of a polymer makes it possible to easily form the inclined portion of the insulating coating layer 20 .

[0090] The thickness of the insulating coating layer 20 is not particularly limited, and may be greater than, smaller than, or the same as the thickness of the semiconductor layer 11. The thickness of the insulating coating layer 20 may be greater than, smaller than, or the same as the thickness of the source electrode 12 and the drain electrode 13. The thickness of the insulating coating layer 20 is, for example, 100 nm or more and 10 μm or less.

[0091] FIG. 18 is a schematic cross-sectional view showing a fourth modified example of the sensor according to the first embodiment of the present invention.

[0092] As in a sensor 1D shown in FIG. 18, at least a portion of the surface of the insulating coating layer 20 may be covered with a hydrophilic material 25 that is more hydrophilic than the material that constitutes the insulating coating layer 20.

[0093] For example, when a solution such as the electrolyte solution 30 is introduced into the sensor element 10 using a flow path, if the surface of the insulating coating layer 20 is hydrophobic, the capillary force is weak, making it difficult for the solution to enter the flow path. On the other hand, if the surface of the insulating coating layer 20 is covered with a hydrophilic material 25, the capillary force is strong, making it easier for the solution to spontaneously enter the flow path. This eliminates the need to introduce the solution using a means such as a pump.

[0094] Furthermore, if the surface of the insulating coating layer 20 is hydrophobic, the flow resistance decreases, resulting in a higher flow rate than on the surface of the insulating substrate 15, which is hydrophilic. Since the target molecules 41 flow through areas with a high flow rate, they tend to flow more easily on the surface of the insulating coating layer 20, making it difficult for the target molecules 41 to reach the sensing portion on the insulating substrate 15. On the other hand, if the surface of the insulating coating layer 20 is covered with a hydrophilic material 25, the flow rate on the insulating coating layer 20 can be made closer to the flow rate on the insulating substrate 15. Therefore, the target molecules 41 tend to reach the sensing portion on the insulating substrate 15.

[0095] Examples of the hydrophilic material 25 include proteins (e.g., bovine serum albumin (BSA), hemoglobin, skim milk, etc.), surfactants (e.g., Tween (trade name), Triton (trade name), sodium dodecyl sulfate (SDS), etc.), and polymers (e.g., PEG, PVP, etc.). These may be used alone or in combination of two or more. The hydrophilic material 25 may be negatively or positively charged.

[0096] Second Embodiment A sensor according to a second embodiment of the present invention further includes a flow path for introducing a solution into the sensor element.

[0097] FIG. 19 is a schematic plan view showing an example of a sensor according to the second embodiment of the present invention.

[0098] 19 further includes a flow channel 50 for introducing a solution into the sensor element 10. The other configuration of the sensor 2 is the same as that of sensors such as the sensor 1.

[0099] 19 , when viewed from the thickness direction of the semiconductor layer 11 (z direction in FIG. 19 ), it is preferable that the angle formed between the vector direction of the main component of the flow velocity of the flow channel 50 flowing over the semiconductor layer 11 (Dc direction in FIG. 19 ) and the direction crossing the gap between the source electrode 12 and the drain electrode 13 (y direction in FIG. 19 ) is 45 degrees or less. In the sensor 2 shown in FIG. 19 , the angle formed between the vector direction of the main component of the flow velocity of the flow channel 50 flowing over the semiconductor layer 11 (Dc direction in FIG. 19 ) and the direction crossing the gap between the source electrode 12 and the drain electrode 13 (y direction in FIG. 19 ) is 0 degrees.

[0100] When the angle formed by the vector direction of the main component of the flow velocity of the flow channel 50 flowing on the semiconductor layer 11 and the direction crossing the gap between the source electrode 12 and the drain electrode 13 is 45 degrees or less, no protrusions due to the insulating film exist in the direction in which the solution flows on the semiconductor layer 11, which is the sensing portion, and therefore the effect of shortening the detection time is easily obtained.

[0101] FIG. 20 is a schematic plan view showing another example of the sensor according to the second embodiment of the present invention.

[0102] As in the sensor 2A shown in Figure 20, the angle formed by the vector direction of the main component of the flow velocity of the flow path 50 flowing over the semiconductor layer 11 (the Dc direction in Figure 20) and the direction crossing the gap between the source electrode 12 and the drain electrode 13 (the y direction in Figure 20) may be greater than 0 degrees and less than 45 degrees.

[0103] In addition, the vector direction Dc of the main component of the flow velocity of the flow path 50 flowing over the semiconductor layer 11 may or may not coincide with the direction parallel to the line segment connecting the inlet 51 and the outlet 52.

[0104] FIG. 21 is a schematic plan view showing an example of the vector direction of the principal component of the flow velocity in the flow channel.

[0105] As shown in FIG. 21 , the flow channel 50 does not have to be linear, but may have a bent shape. In the example shown in FIG. 21 , the vector direction (Dc) of the principal component of the flow velocity of the flow channel 50 flowing over the semiconductor layer 11 varies depending on the location. For example, when the flow channel 50 is parallel to the y direction, the Dc direction is parallel to the y direction, and the angle formed with the direction crossing the gap between the source electrode 12 and the drain electrode 13 (the y direction in FIG. 21 ) is 45 degrees or less. On the other hand, when the flow channel 50 is parallel to the x direction, the Dc direction is parallel to the x direction, and the angle formed with the direction crossing the gap between the source electrode 12 and the drain electrode 13 (the x direction in FIG. 21 ) is 45 degrees or less.

[0106] As described above, the shape of the flow path 50 is not particularly limited, and may be, for example, linear, curved, or polygonal. Furthermore, the shape, number, etc. of the inlet 51 are not particularly limited, and for example, as shown in FIG. 21 , multiple inlets 51 may be provided. Alternatively, the inlets 51 may be connected to form a single large inlet 51. Similarly, the shape, number, etc. of the outlet 52 are not particularly limited, and for example, as shown in FIG. 21 , an outlet 52 larger than the inlet 51 may be provided. The shape, number, etc. of the outlet 52 may be the same as or different from the shape, number, etc. of the inlet 51.

[0107] Third Embodiment A sensor according to a third embodiment of the present invention has an array of sensor elements, and the other configurations are the same as those of the second embodiment.

[0108] FIG. 22 is a schematic plan view showing an example of a sensor according to a third embodiment of the present invention.

[0109] In the sensor 3 shown in FIG. 22, a plurality of sensor elements 10 are arranged along the vector direction (y direction in FIG. 22) of the main component of the flow velocity of the flow channel 50 flowing on the semiconductor layer 11.

[0110] In the example shown in FIG. 22, three sensor elements 10 are arranged, but two sensor elements 10 may be arranged, or four or more sensor elements 10 may be arranged.

[0111] FIG. 23 is a schematic plan view showing another example of the sensor according to the third embodiment of the present invention.

[0112] In the sensor 3A shown in FIG. 23, a plurality of sensor elements 10 are arranged in a plurality of rows along the vector direction (y direction in FIG. 22) of the main component of the flow velocity of the flow channel 50 flowing on the semiconductor layer 11.

[0113] 23, a plurality of sensor elements 10 are arranged in two rows, but they may be arranged in three or more rows. The number of sensor elements 10 arranged in each row is not particularly limited, and they may be the same, or some or all of them may be different. The number of sensor elements 10 arranged in each row may be one, or two or more.

[0114] 23, the plurality of sensor elements 10 are arranged symmetrically with respect to the flow path 50 as an axis, but the plurality of sensor elements 10 may also be arranged asymmetrically. For example, the sensor elements 10 may be arranged one by one on either side of the flow path 50. Alternatively, the sensor elements 10 may be arranged alternately (in a zigzag pattern) in the y direction on either side of the flow path 50.

[0115] 22 and 23 , when viewed from the thickness direction of the semiconductor layer 11, the angle formed between the vector direction of the principal component of the flow velocity of the flow channel 50 flowing on the semiconductor layer 11 and the direction crossing the gap between the source electrode 12 and the drain electrode 13 is 45 degrees or less. The angle may be the same for all of the sensor elements 10, or may be different for some or all of them. As long as the angle formed between the vector direction of the principal component of the flow velocity of the flow channel 50 flowing on the semiconductor layer 11 and the direction crossing the gap between the source electrode 12 and the drain electrode 13 is 45 degrees or less when viewed from the thickness direction of the semiconductor layer 11, the number, size, orientation, etc. of the sensor elements 10 are not particularly limited. Furthermore, as described in the second embodiment, the shape of the flow channel 50 is not particularly limited, and the vector direction of the principal component of the flow velocity of the flow channel 50 flowing on the semiconductor layer 11 may or may not coincide with the direction parallel to the line segment connecting the inlet and the outlet.

[0116] The sensor of the present invention is not limited to the above-described embodiment, and various applications and modifications can be made within the scope of the present invention with respect to the configuration of the sensor, manufacturing conditions, etc.

[0117] The sensor of the present invention can be produced, for example, by forming an electrode pattern including a source electrode and a drain electrode on an insulating substrate, then forming an insulating coating layer to cover the electrodes on the insulating substrate, and then forming a semiconductor layer on the insulating substrate.

[0118] The electrode pattern including the source electrode and the drain electrode can be formed, for example, by a general photolithography process. For example, a metal layer having a multilayer structure, such as a Ti layer and an Au layer, is formed on an insulating substrate using a method such as vacuum deposition, electron beam (EB) deposition, or sputtering. Then, the metal layer is patterned by photolithography and etching to form the electrode pattern including the source electrode and the drain electrode.

[0119] The insulating coating layer can be formed by, for example, a general photolithography process, for example, by applying an insulating coating material to an insulating substrate on which an electrode pattern has been formed, and then patterning the insulating coating material by photolithography and etching, thereby forming an insulating coating layer that covers at least a portion of one or both of the source electrode and the drain electrode.

[0120] The semiconductor layer can be formed, for example, by the following method. For example, a two-dimensional material such as graphene can be grown on copper foil. Therefore, for example, after forming an insulating coating layer that covers an electrode on an insulating substrate, the two-dimensional material such as graphene grown on the copper foil is transferred from the insulating coating layer to the insulating substrate, and then patterned by photolithography and etching, thereby forming a semiconductor layer on the insulating substrate.

[0121] The present specification discloses the following:

[0122] <1> A sensor comprising: a field-effect transistor type sensor element including a semiconductor layer; and a source electrode and a drain electrode electrically connected to the semiconductor layer and arranged opposite each other with a gap in the channel length direction of the semiconductor layer; and an insulating coating layer covering at least a part of one or both of the source electrode and the drain electrode, wherein, when viewed in a cross section across the gap between the source electrode and the drain electrode, no insulating film that is integrally continuous with the insulating coating layer is provided around the semiconductor layer.

[0123] <2> The sensor according to <1>, wherein the semiconductor layer contains graphene.

[0124] <3> The sensor according to <1> or <2>, wherein, when viewed in a cross section in the channel length direction in which the source electrode and the drain electrode face each other, the semiconductor layer covers a part of one or both of the source electrode and the drain electrode.

[0125] <4> The sensor according to <3>, wherein when viewed in a cross section in the channel length direction in which the source electrode and the drain electrode face each other, the semiconductor layer is disposed at a distance from the insulating coating layer.

[0126] <5> The sensor according to any one of <1> to <4>, wherein an end of the insulating coating layer is inclined when viewed in a cross section in the channel length direction in which the source electrode and the drain electrode face each other.

[0127] <6> The sensor according to <5>, wherein the insulating coating layer is made of a polymer.

[0128] <7> The sensor according to any one of <1> to <6>, wherein at least a portion of the surface of the insulating coating layer is covered with a hydrophilic material that is more hydrophilic than a material constituting the insulating coating layer.

[0129] <8> The sensor according to any one of <1> to <7>, wherein the insulating film is not provided within a range of 20 μm around the semiconductor layer when viewed in a cross section across the gap between the source electrode and the drain electrode.

[0130] <9> The sensor according to any one of <1> to <7>, wherein the insulating film is not provided within a range of 50 μm around the semiconductor layer when viewed in a cross section across the gap between the source electrode and the drain electrode.

[0131] <10> The sensor according to any one of <1> to <9>, further comprising a flow path for introducing a solution into the sensor element, wherein, when viewed from a thickness direction of the semiconductor layer, an angle formed between a vector direction of a main component of a flow velocity of the flow path flowing over the semiconductor layer and a direction crossing the gap between the source electrode and the drain electrode is 45 degrees or less.

[0132] <11> The sensor according to <10>, wherein a plurality of the sensor elements are arranged.

[0133] <12> The sensor according to any one of <1> to <11>, wherein a probe molecule is disposed on at least a part of the surface of the sensor element.

[0134] 1, 1A, 1B, 1C, 1D, 2, 2A, 3, 3A Sensor 10 Sensor element 11 Semiconductor layer 12 Source electrode 13 Drain electrode 15 Insulating substrate 20 Insulating coating layer 21 Insulating film 22 Insulator 25 Hydrophilic material 30 Electrolyte 31 Gate electrode 40 Probe molecule 41 Target molecule 50 Flow channel 51 Inlet 52 Outlet

Claims

1. A sensor comprising: a field effect transistor type sensor element including a semiconductor layer; a source electrode and a drain electrode electrically connected to the semiconductor layer and arranged opposite each other with a gap in the channel length direction of the semiconductor layer; and an insulating coating layer covering at least a portion of one or both of the source electrode and the drain electrode, wherein, when viewed in cross section across the gap between the source electrode and the drain electrode, no insulating film that is integrally continuous with the insulating coating layer is provided around the semiconductor layer.

2. The sensor of claim 1, wherein the semiconductor layer comprises graphene.

3. A sensor as described in claim 1 or 2, wherein when viewed in a cross section in the channel length direction where the source electrode and the drain electrode face each other, the semiconductor layer covers a portion of one or both of the source electrode and the drain electrode.

4. The sensor according to claim 3, wherein when viewed in a cross section in the channel length direction in which the source electrode and the drain electrode face each other, the semiconductor layer is disposed with a gap between it and the insulating coating layer.

5. A sensor according to any one of claims 1 to 4, wherein when viewed in a cross section in the channel length direction where the source electrode and the drain electrode face each other, the end of the insulating coating layer is inclined.

6. The sensor according to claim 5, wherein the insulating coating layer is made of a polymer.

7. The sensor according to any one of claims 1 to 6, wherein at least a portion of the surface of the insulating coating layer is covered with a hydrophilic material that is more hydrophilic than the material that constitutes the insulating coating layer.

8. A sensor according to any one of claims 1 to 7, wherein, when viewed in a cross section across the gap between the source electrode and the drain electrode, the insulating film is not provided within a range of 20 μm around the semiconductor layer.

9. A sensor according to any one of claims 1 to 7, wherein, when viewed in a cross section across the gap between the source electrode and the drain electrode, the insulating film is not provided within a range of 50 μm around the semiconductor layer.

10. A sensor according to any one of claims 1 to 9, further comprising a flow path for introducing a solution into the sensor element, wherein, when viewed from the thickness direction of the semiconductor layer, the angle formed between the vector direction of the main component of the flow velocity of the flow path flowing over the semiconductor layer and the direction crossing the gap between the source electrode and the drain electrode is 45 degrees or less.

11. The sensor of claim 10, wherein a plurality of said sensor elements are arranged in an array.

12. The sensor according to any one of claims 1 to 11, wherein probe molecules are disposed on at least a portion of the surface of the sensor element.

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