Device, concentration measuring apparatus provided with the same, and concentration measuring method using the same

Abstract

[Problem] The present application provides a device that can be used in a concentration measuring device and a concentration measuring method, and can detect a threshold voltage Vth with high sensitivity even if a target object in a fluid under test is in a trace amount th , and can rapidly measure the concentration of the target object in the fluid under test. [Solution] A device has an insulating substrate, a gate electrode formed on the insulating substrate, at least one insulating composite layer formed on the gate electrode in an insulating state, and a storage portion capable of holding a fluid under test, the insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes, the semiconductor layer is composed of an oxide containing an indium (In) element, a zinc (Zn) element, and an additive element (X), the additive element (X) contains at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb), and a sensitive film having selectivity to a target object in the fluid under test is provided between the insulating composite layer and the storage portion.

Description

Technical Field

[0001] This invention relates to the voltage value of the gate electrode, i.e., the threshold voltage V, during the switching of current between a pair of electrodes. th Devices that vary according to the concentration of the analyte in the fluid being tested, more specifically, those involving a threshold voltage V th A concentration measuring device and method for determining the concentration of the target substance in a test fluid by measuring changes in its concentration. Background Technology

[0002] In the coming super-intelligent society, Society 5.0, with the goal of balancing economic development and solving social issues, the Internet of Things (IoT) that supports this goal will require sensors for acquiring data.

[0003] Previously, electrochemical sensors using semiconductors were known as methods for detecting the presence or concentration of a target substance in a liquid.

[0004] For example, sensors with field-effect transistor (FET) structures are disclosed in Patent Documents 1 and 2.

[0005] like Figure 5 As shown, the sensor 100 with such a FET structure has a gate electrode 102 formed on a substrate 101, and an insulating film 103 formed to cover the gate electrode 102. In addition, a semiconductor layer 104 is formed on the insulating film 103, and a drain electrode 105 and a source electrode 106 are formed in contact with the semiconductor layer 104.

[0006] In addition, such as Figure 5 As shown, the sensitive membrane 107 can be disposed separately, covering the gate electrode 102, or the insulating membrane 103 can be used as the sensitive membrane. The sensitive membrane 107 can selectively detect the target object in the liquid to be tested. Moreover, due to the threshold voltage V of the gate voltage... th The threshold voltage V of the gate voltage varies depending on the amount of the object to be detected, such as the liquid to be detected adsorbed on or permeated into the sensitive membrane 107. Therefore, the threshold voltage V of the gate voltage is measured while the liquid to be detected is in contact with the sensitive membrane 107. th This allows for the determination of the concentration of the target substance in the liquid being tested.

[0007] Sensors utilizing semiconductors are highly sensitive and compact, enabling micro-level detection and serving as portable detection devices. Furthermore, because they use semiconductors, the detection results are output as electrical signals, resulting in high compatibility with communication devices and allowing for remote measurement.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2011-043420

[0011] Patent Document 2: Japanese Patent Application Publication No. 2012-122749 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] In Patent Documents 1 and 2, the semiconductor layer 104 uses an oxide semiconductor that contains gallium (Ga), aluminum (Al), iron (Fe), etc., in an oxide containing indium (In) and zinc (Zn), particularly an oxide semiconductor containing In, Ga, and Zn (hereinafter referred to as "InGaZnO"). Alternatively, crystalline Si (silicon) has been commonly used as the semiconductor layer 104 in the past.

[0014] However, using crystalline Si presents limitations in applications due to its opacity to visible light and inability to bend. Furthermore, the cutoff current (when the gate voltage is set to the threshold voltage V) is also a factor. th In the following case, the leakage current flowing from the drain electrode to the source electrode is relatively large, approximately 1.0 × 10⁻⁶. -12 A / μm~1.0×10 -7 The A / μm value affects noise during measurement, making it difficult to perform trace detection.

[0015] On the other hand, because InGaZnO is transparent to visible light and is flexible, its applications are not limited. Furthermore, the cutoff current is approximately 1.0 × 10⁻⁶. -16 A / μm~1.0×10 -11 A / μm is smaller than that of crystalline Si, so there is less noise influence during measurement.

[0016] However, due to the low field-effect mobility of InGaZnO, approximately 10 cm⁻¹, 2 / Vs, therefore, if the drain-source voltage V is not sufficiently increased DS Therefore, it is difficult to detect the threshold voltage V with good accuracy. th The changes.

[0017] In view of the current situation, the present invention aims to provide a concentration measuring device and a device that can be used in a concentration measuring method, which can detect the threshold voltage V with high sensitivity even when the amount of the analyte in the fluid being tested is trace. th It can quickly determine the concentration of the target substance in the fluid being tested.

[0018] Solution for solving the problem

[0019] The present invention was invented to solve the problems in the prior art as described above. The device, the concentration measuring apparatus having the same, and the concentration measuring method using the same include the following configurations.

[0020] [1] A device comprising: an insulating substrate, a gate electrode formed on the insulating substrate, at least one insulating composite layer formed on the gate electrode in a state of being insulated from the gate electrode, and a storage portion capable of holding a fluid to be tested.

[0021] The aforementioned insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes. The semiconductor layer is composed of an oxide containing indium (In), zinc (Zn), and an additive element (X).

[0022] The aforementioned added element (X) includes at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb).

[0023] A sensitive membrane that is selective for the object to be tested in the fluid to be tested is provided between the aforementioned insulating composite layer and the aforementioned storage section.

[0024] [2] According to the device described in [1], the aforementioned sensitive membrane is an ion carrier.

[0025] [3] According to the device described in [1], the aforementioned sensitive membrane is a lipid membrane.

[0026] [4] According to the device described in [1], the aforementioned sensitive membrane is a nucleic acid probe.

[0027] [5] The device according to any one of [1] to [4] further comprises an insulating film between the aforementioned insulating substrate and the aforementioned gate electrode.

[0028] [6] The device according to any one of [1] to [5], wherein the field-effect mobility of the aforementioned semiconductor layer is 20 cm⁻¹. 2 / Vs and above.

[0029] [7] The device according to any one of [1] to [6], wherein,

[0030] The cutoff current between the aforementioned pair of electrodes in the aforementioned semiconductor layer is 1×10 -12 Below A.

[0031] [8] A concentration measuring device comprising:

[0032] The device described in any one of [1] to [7]; and

[0033] Control device,

[0034] The aforementioned control device includes:

[0035] A voltage application unit that causes a change in the voltage between the current-flow side electrode and the gate electrode of the aforementioned pair of electrodes;

[0036] A current measuring unit that measures the current flowing between the aforementioned pair of electrodes;

[0037] The threshold voltage detection unit detects the voltage value of the gate electrode, i.e., the threshold voltage V, when the current switching occurs between the aforementioned pair of electrodes, based on the voltage value applied by the aforementioned voltage application unit and the current value measured by the aforementioned current measurement unit. th ;as well as

[0038] The concentration calculation unit is based on the threshold voltage V detected by the aforementioned threshold voltage detection unit. th Calculate the concentration of the target substance in the aforementioned fluid.

[0039] [9] A concentration determination method, which uses any one of [1] to [7] to detect the concentration of the analyte in the fluid to be tested.

[0040] The threshold voltage V is the voltage value of the gate electrode when the current switching occurs between the aforementioned pair of electrodes. th Based on this threshold voltage V th The concentration of the target substance in the aforementioned test fluid was determined.

[0041] The effects of the invention

[0042] According to the present invention, by employing an oxide comprising indium (In), zinc (Zn), and an additive element (X) as the semiconductor layer, wherein the additive element (X) is at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb), the cutoff current can be reduced, and the field-effect mobility can be increased compared to that using conventional oxide semiconductors. Therefore, it is possible to fabricate a system that can detect the threshold voltage V with high sensitivity even when the amount of the detectable object in the fluid being tested is minute. th Components.

[0043] Furthermore, a concentration measuring device and a concentration measuring method can be manufactured that, by using such a device, can quickly measure the concentration of the target substance in the fluid being tested, even if the amount of the target substance in the fluid being tested is trace. Attached Figure Description

[0044] Figure 1 This is a schematic diagram illustrating the configuration of the concentration measuring device in this embodiment.

[0045] Figure 2 It is used for explanation Figure 1 A front view schematic diagram of the components used in the concentration measuring device.

[0046] Figure 3 yes Figure 2 A side view diagram.

[0047] Figure 4 It shows the use Figure 1 When the concentration measuring device measures the concentration of the target substance in the test liquid L, the concentration of the target substance and the threshold voltage V are compared. th A diagram showing the relationships between them.

[0048] Figure 5 This is a schematic diagram illustrating the configuration of a sensor with an existing FET structure. Detailed Implementation

[0049] Hereinafter, embodiments (examples) of the present invention will be described in more detail based on the accompanying drawings.

[0050] Figure 1 This is a schematic diagram illustrating the configuration of the concentration measuring device in this embodiment. Figure 2 It is used for explanation Figure 1 A front view schematic diagram of the components used in the concentration measuring device. Figure 3 yes Figure 2 A side view diagram.

[0051] like Figure 1 As shown, the concentration measuring device 50 of this embodiment includes a device 10 and a control device 60. The device 10 includes an insulating substrate 12, a gate electrode layer 13, at least one insulating composite layer 14, and a reservoir 16 capable of holding the test liquid L, which is the test fluid.

[0052] It should be noted that, as Figure 2 , 3 The device 10 configured as shown can also be made into semiconductor elements such as field-effect transistors (FETs) and metal oxide semiconductor field-effect transistors (MOSFETs).

[0053] The gate electrode layer 13 has a gate electrode 131 and an insulating film 132 formed on the insulating substrate 12. It should be noted that in this embodiment, an insulating film 12a is provided between the insulating substrate 12 and the gate electrode 131 to prevent the intrusion of various gases, water vapors, etc., but the gate electrode 131 can also be formed directly on the insulating substrate 12.

[0054] The insulating composite layer 14 has a pair of electrodes (first electrode 141 and second electrode 142) and a semiconductor layer 144 in contact with the pair of electrodes 141 and 142.

[0055] The configuration of the liquid storage section 16 is not particularly limited as long as it can hold the liquid to be tested L. However, in this embodiment, in order to hold the liquid to be tested L in contact with the sensitive membrane 18 described later, the liquid storage section 16 is composed of a partition section 16a that is provided around the sensitive membrane 18.

[0056] It should be noted that, in this embodiment, although the concentration of the target substance contained in the test liquid L is determined by measuring the liquid L containing the target substance as the test fluid stored in the liquid storage unit 16, it is also possible to, for example, provide a storage unit capable of storing gas instead of the liquid storage unit 16, and measure the concentration of the target substance contained in the gas by measuring the gas containing the target substance as the test fluid stored in the storage unit.

[0057] In addition, a sensitive membrane 18 is provided between the insulating composite layer 14 and the liquid storage section 16.

[0058] The sensitive membrane 18 is selective for the analyte in the test liquid L. Specifically, it has the property of selectively allowing ions of the analyte to pass through or selectively capturing the constituent components (e.g., nucleic acids) of the analyte. Such a sensitive membrane 18 can be made from ion carriers such as lithium ion carriers, potassium ion carriers, sodium ion carriers, calcium ion carriers, ammonium ion carriers, chloride ion carriers, and magnesium ion carriers. Alternatively, lipid membranes and nucleic acid probes can also be used.

[0059] There are no particular limitations on the manufacturing method of such a sensitive membrane 18. For example, when using an ion carrier, it can be manufactured through the following steps.

[0060] First, weigh the polyvinyl chloride (PVC) in a beaker. Here, from the viewpoint of ease of handling and smooth adhesion to the insulating composite layer 14, it is preferable to use PVC with a degree of polymerization of about 1050.

[0061] Next, tetrahydrofuran was added to the beaker as a solvent, and the mixture was stirred until the polyvinyl chloride dissolved.

[0062] After the polyvinyl chloride is dissolved, plasticizers and ion carriers are added. If the target to be tested is a cationic substance, an anion excluding agent is added; if the target to be tested is an anionic substance, a cation excluding agent is added. Then, the mixture is stirred using a stirrer.

[0063] It should be noted that, for example, 2-nitrophenyl octyl ether (NPOE) and bis(2-ethylhexyl) sebacate can be used as plasticizers.

[0064] In addition, potassium tetra(4-chlorophenyl)borate can be used as an anion scavenger, and tris(dodecyl)methylammonium chloride (TDDMACl) can be used as a cation scavenger.

[0065] As an ion carrier, it can be appropriately selected according to the ion of the target ion. For example, in the case of lithium ions (Li₂O₃), it can be used as an ion carrier. + When detecting potassium ions (K+), dibenzyl-14-crown-4 or TTD-14-crown-4 can be used. + When detecting sodium ions (Na+), bis(benzo-15-crown-5) can be used. + When detecting calcium ions (Ca), double (12-crown-4) can be used. 2+ When detecting ammonium ions (NH4+), HDOPP-Ca can be used. + When detecting chloride ions (Cl), nonactin can be used. - When detecting magnesium ions (Mg), Bisthiourea-1 (chloride ion carrier IV) can be used. 2+ When using C14-K22B5, K22B1B5, or K22B9, you can use these options.

[0066] Next, the sensitive membrane 18 can be formed by spreading the solution thus prepared on a glass petri dish and allowing it to air dry. It should be noted that from the viewpoint of further accelerating the response speed (establishing ion diffusion equilibrium), it is effective to make the sensitive membrane 18 thinner, but in this case, it is preferable to form the sensitive membrane 18 by spin coating.

[0067] The sensitive membrane 18 thus made is cut to a suitable size and adhered to the insulating composite layer 14 in a manner that does not trap air. For example, the liquid reservoir 16 is adhered to the adhered sensitive membrane 18 using epoxy resin, thereby making the device 10.

[0068] It should be noted that the insulating composite layer 14 has an insulating film 146 at least in the area in contact with the sensitive film 18. The insulating film 146 also serves as a protective layer for protecting the semiconductor layer 144 from the influence of the liquid L being tested. By providing the insulating film 146, corrosion of the semiconductor layer 144 can be prevented, thereby improving the durability and reliability of the semiconductor layer 144. As for the material of the insulating film 146, any known material that has insulating properties can be used, but a corrosion-resistant material is preferred. As for insulating materials, Ta2O5, Si3N4, SiO2, etc. are preferred, and their thickness is preferably 0.01 μm or more and 0.5 μm or less, more preferably 0.03 μm or more and 0.2 μm or less.

[0069] Furthermore, the field-effect mobility of the semiconductor layer 144 is preferably 20 cm⁻¹. 2 / Vs or higher, especially preferably 60cm 2 / Vs and above.

[0070] Furthermore, regarding the semiconductor layer 144, in the device 10 configured as described above, the voltage applied to the gate electrode 131 is set to the threshold voltage V. th In the following case, the current flowing from the first electrode 141 to the second electrode 142 or from the second electrode 142 to the first electrode 141, i.e., the cutoff current, is preferably 1×10⁻⁶. -12 A and below, especially preferably 1×10 -14 Below A. Because the cutoff current is made so small, the threshold voltage V is detected as follows. th Even with a small voltage applied between the first electrode 141 and the second electrode 142, the threshold voltage V can be detected with higher accuracy. th .

[0071] Such a semiconductor layer 144 is composed of an oxide containing indium (In), zinc (Zn) and an additive element (X), wherein the additive element (X) is at least one element selected from tantalum (Ta), strontium (Sr) and niobium (Nb).

[0072] Specifically, regarding In and X, the atomic ratio shown in equation (1) is preferred (where X is the sum of the contents of the aforementioned added elements. Equations (2) and (3) are the same below).

[0073] 0.4≤(In+X) / (In+Zn+X)≤0.8 (1)

[0074] Regarding Zn, the atomic ratio shown in equation (2) is preferred.

[0075] 0.2≤Zn / (In+Zn+X)≤0.6 (2)

[0076] Regarding X, the atomic ratio shown in equation (3) is preferred.

[0077] 0.001≤X / (In+Zn+X)≤0.015 (3)

[0078] By making the atomic ratio of In, Zn and X satisfy equations (1) to (3), the semiconductor layer 144 can reliably exhibit the field-effect mobility and cutoff current as described above.

[0079] In order for the semiconductor layer 144 to exhibit higher field-effect mobility and lower cutoff current, it is preferable that the atomic ratio of In, Zn and X satisfies Equations (1-2), (2-2) and (3-2).

[0080] 0.43≤(In+X) / (In+Zn+X)≤0.79 (1-2)

[0081] 0.21≤Zn / (In+Zn+X)≤0.57 (2-2)

[0082] 0.0015≤X / (In+Zn+X)≤0.013 (3-2)

[0083] Furthermore, it is preferable that the atomic ratio of In, Zn and X satisfies equations (1-3), (2-3), and (3-3).

[0084] 0.48≤(In+X) / (In+Zn+X)≤0.78 (1-3)

[0085] 0.22≤Zn / (In+Zn+X)≤0.52 (2-3)

[0086] 0.002 <X / (In+Zn+X)≤0.012 (3-3)

[0087] Furthermore, it is preferable that the atomic ratio of In, Zn and X satisfies equations (1-4), (2-4), and (3-4).

[0088] 0.53≤(In+X) / (In+Zn+X)≤0.75 (1-4)

[0089] 0.25≤Zn / (In+Zn+X)≤0.47 (2-4)

[0090] 0.0025≤X / (In+Zn+X)≤0.010 (3-4)

[0091] Furthermore, it is preferable that the atomic ratio of In, Zn and X satisfies equations (1-5), (2-5), and (3-5).

[0092] 0.58≤(In+X) / (In+Zn+X)≤0.70 (1-5)

[0093] 0.30≤Zn / (In+Zn+X)≤0.42 (2-5)

[0094] 0.003≤X / (In+Zn+X)≤0.009 (3-5)

[0095] The added element (X) is selected from Ta, Sr, and Nb as described above. These elements can be used individually or in combination of two or more. It should be noted that the added element (X) may also include elements other than Ta, Sr, and Nb, but it is preferred to include only these elements.

[0096] Furthermore, regarding the thickness of the semiconductor layer 144, the thinner it is, the greater the change in surface conductivity, thus increasing the change in migrated charge as described later, and improving measurement accuracy. The thickness of this semiconductor layer 144 is preferably 0.5 μm or less, more preferably 0.1 μm or less, and particularly preferably 0.05 μm or less. It should be noted that the lower limit of the thickness of the semiconductor layer 144 is not specifically defined, but it is typically 0.005 μm or more.

[0097] Furthermore, the surface 144a of the semiconductor layer 144 on the sensitive film 18 side is preferably as smooth as possible. If the surface 144a of the semiconductor layer 144 is not smooth, for example, a gap may form between it and the insulating film 146, or the insulating film 146 may be discontinuous, resulting in reduced adhesion between the insulating film 146 and the sensitive film 18, making it impossible to accurately capture potential changes from the sensitive film 18. This leads to reduced measurement accuracy or unstable operation.

[0098] Specifically, the maximum height Sz of the surface 144a of the semiconductor layer 144 is preferably 0.05 μm or less, more preferably 0.01 μm or less, and most preferably 0.003 μm or less. The lower limit of this maximum height Sz is not particularly specified, and is generally 0.0005 μm or more. Furthermore, the arithmetic mean height Sa of the surface 144a on the sensitive film 18 side of the semiconductor layer 144 is preferably 0.03 μm or less, more preferably 0.005 μm or less, and most preferably 0.002 μm or less. The lower limit of this arithmetic mean height Sa is not particularly specified, and is generally 0.0002 μm or more.

[0099] Here, the maximum height Sz and the arithmetic mean height Sa are surface roughness parameters specified by ISO 25178. These parameters can be measured, for example, using a 3D surface roughness shape measuring machine (manufactured by Zygo, NexView, etc.). It should be noted that the measurement conditions are preferably as follows.

[0100] The measurements were performed according to ISO 25178, with an objective lens of 50x, a zoom lens of 20x, and a measurement range of 89μm × 87μm. A roughness curve with a range of 3μm × 3μm was extracted from the obtained three-dimensional surface shape. Using the analytical program "Mx" provided with the 3D surface roughness shape measuring machine, the roughness curve was corrected under the following correction conditions, and the maximum height Sz and the arithmetic mean height Sa were calculated.

[0101] <Calibration conditions>

[0102] -Remove: Form Removal

[0103] - Filter Type: Spline

[0104] - Filter: Low-pass

[0105] - Type: Gaussian Spline Filter (Auto)

[0106] It should be noted that when the device 10 described above is formed as a FET structure, it can be formed using the same methods as conventionally known FETs, MOSFETs, etc. For example, a conductive metal thin film serving as the first electrode 141 and the second electrode 142 can be formed on an insulating substrate 12 using a sputtering apparatus, and then an oxide thin film configured as described above can be formed as the semiconductor layer 144 using a sputtering apparatus. It should be noted that a shadow mask can be used for patterning in the formation of the first electrode 141 and the second electrode 142 and in the formation of the semiconductor layer 144.

[0107] It should be noted that there are no particular limitations on the conductive metals used as the first electrode 141 and the second electrode 142. For example, molybdenum (Mo), tungsten (W), etc. can be used. In addition, alloys of these metals with cerium oxide (CeO2), copper (Cu), silver (Ag), etc. can also be used.

[0108] Next, an insulating film 146 can be formed by depositing a ceramic thin film thereon. Specifically, for example, an insulating film 146 can be formed by depositing a SiOx thin film under the conditions of a film-forming gas mixture of SiH4 / N2O / N2, a film-forming pressure of 110 Pa, and a substrate temperature of 250°C to 400°C using a plasma CVD apparatus such as the PD-2202L manufactured by SAMCO Inc.

[0109] In addition, the control device 60 of the concentration measuring device 50 in this embodiment includes: a variable voltage source 32 for applying a voltage between the first electrode 141 and the second electrode 142; a variable voltage source 34 (voltage application unit) for applying a voltage between the first electrode 141 and the gate electrode 131; a current meter 36 (current measuring unit) for measuring the current value between the first electrode 141 and the second electrode 142; and a voltage meter 38 (voltage measuring unit) for measuring the voltage value between the first electrode 141 and the gate electrode 131.

[0110] The control device 60 has a computer with an arithmetic unit, a storage unit, an input / output unit, etc., and is configured to perform voltage control of the variable voltage source 32 and the variable voltage source 34, current measurement based on the ammeter 36, and voltage measurement based on the voltmeter 38 based on the program stored in the storage unit.

[0111] Furthermore, the control device 60 also includes a threshold voltage detection unit 62. The threshold voltage detection unit 62 is configured to control the voltage applied by the variable voltage source 32 and the variable voltage source 34, and to receive the current and voltage values ​​measured by the ammeter 36 and the voltmeter 38 in the form of electrical signals. Such a threshold voltage detection unit 62 can be implemented using a computer or the like assembled in the control device 60.

[0112] The threshold voltage detection unit 62 applies a predetermined voltage V between the first electrode 141 and the second electrode 142 by the variable voltage source 32. ds In this state, the voltage V applied by the variable voltage source 34 between the first electrode 141 and the gate electrode 131 is... g The voltage gradually increases. Furthermore, the threshold voltage detection unit 62 detects the current I flowing between the first electrode 141 and the second electrode 142 by the ammeter 36. d The change is detected by voltmeter 38, and the voltage V between the first electrode 141 and the gate electrode 131 is measured. g The change in threshold voltage V was used to determine the threshold voltage V. th .

[0113] It is known that in the device 10 configured as described above, the threshold voltage V th The threshold voltage V varies depending on the amount of the object to be detected present on or inside the sensitive membrane 18. Therefore, by measuring this threshold voltage V... th This allows for the detection of the concentration of the target substance contained in the liquid L being tested.

[0114] It should be noted that the threshold voltage V th The measurement method is not particularly limited; for example, the current I between the first electrode 141 and the second electrode 142 can be detected. d Voltage V at the start of flow g It can also be obtained from the current I d The flow state causes the voltage V g Gradually decrease, until no current I is detected. d Voltage V during flow g Additionally, voltage V can be used. g The current I changes d Reaching the specified value (e.g., 1×10) -9 V at time A) ds The value of V is used as the threshold voltage. th While existing known methods exist, from the viewpoint of more accurate measurement, it is preferable to use voltage V. ds Set to constant, apply voltage V within a specified range. g And measure the current I flowing at this time. d√I within the specified range is calculated using the least squares method. d Compared to V g An approximate straight line, and the √I of this approximate straight line. d V when =0 g As the threshold voltage V th .

[0115] Figure 4 This illustrates the relationship between the concentration of the target substance and the threshold voltage V when measuring the concentration of the target substance in the test liquid L using the concentration measuring device 50 of this embodiment. th A diagram showing the relationships between them.

[0116] The determination (example) was performed as follows: An aqueous solution of ammonium chloride (NH4Cl) was used as the test liquid L, and ammonium ions (NH4Cl) were used as the test solution L. + Using ammonium ion carrier as the target of detection and ammonium ion carrier as the sensitive membrane 18, voltage V is applied. ds Set it to 1V, so that the voltage V g The specified range for the change is 1.3V to 1.5V.

[0117] like Figure 4 As shown, NH4 + The higher the concentration, the higher the threshold voltage V. th The lower.

[0118] Therefore, for example, by pre-creating a representation of the concentration of the object to be detected relative to the threshold voltage V... th The standard curve of the relationship is obtained, thereby enabling the determination of the threshold voltage V measured using the concentration measuring device 50. th To determine the concentration of the object to be tested.

[0119] Alternatively, by varying the concentration of the target object with a threshold voltage V th This data is used as training data for machine learning, thereby enabling the use of artificial intelligence (AI) and based on the threshold voltage V measured using the concentration measuring device 50. th Determine the concentration of the object to be tested.

[0120] The control device 60 in this embodiment further includes a concentration calculation unit 64, which is configured to calculate the concentration based on the threshold voltage V detected by the threshold voltage detection unit 62. th The concentration of the object to be detected is calculated as described above. Such a concentration calculation unit 64 can be implemented by a computer or the like assembled in the control device 60.

[0121] The preferred embodiments of the present invention have been described above, but the present invention is not limited thereto, and various modifications can be made without departing from the purpose of the present invention.

[0122] Explanation of reference numerals in the attached figures

[0123] 10 devices

[0124] 12 Insulating substrate

[0125] 13 Gate electrode layer

[0126] 131 Gate electrode

[0127] 132 Insulating Film

[0128] 14 Insulating composite layer

[0129] 141 First Electrode

[0130] 142 Second Electrode

[0131] 144 Semiconductor Layer

[0132] 144a surface

[0133] 146 Insulating film

[0134] 16 Liquid storage part

[0135] 16a Separator

[0136] 18 Sensitive membrane

[0137] 32 Variable Voltage Source

[0138] 34 Variable Voltage Source

[0139] 36 Ammeter

[0140] 38 Voltmeter

[0141] 50 Concentration measuring device

[0142] 60 Control device

[0143] 62 Threshold Voltage Detection Unit

[0144] 64 Concentration Calculation Unit

[0145] 100 sensors

[0146] 101 substrate

[0147] 102 gate electrode

[0148] 103 Insulating film

[0149] 104 Semiconductor Layer

[0150] 105 Drain electrode

[0151] 106 source electrode

[0152] 107 Ion-sensitive membrane.

Claims

1. A device comprising: an insulating substrate, a gate electrode formed on the insulating substrate, at least one insulating composite layer formed on the gate electrode in a state of insulation from the gate electrode, and a storage portion capable of holding a fluid to be tested. The insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes. The semiconductor layer is composed of an oxide containing indium (In), zinc (Zn), and an additive element (X). The added element (X) comprises at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb). A sensitive membrane selectively reacts to the object to be tested in the fluid being tested is provided between the insulating composite layer and the storage section.

2. The device according to claim 1, wherein, The sensitive membrane is an ion carrier.

3. The device according to claim 1, wherein, The sensitive membrane is a lipid membrane.

4. The device according to claim 1, wherein, The sensitive membrane is a nucleic acid probe.

5. The device according to claim 1, wherein an insulating film is further provided between the insulating substrate and the gate electrode.

6. The device according to claim 1, wherein, The field-effect mobility of the semiconductor layer is 20 cm⁻¹. 2 / Vs and above.

7. The device according to claim 1, wherein, The cutoff current between the pair of electrodes in the semiconductor layer is 1×10⁻⁶. -12 Below A.

8. A concentration measuring device, comprising: The device according to any one of claims 1 to 7; and Control device, The control device includes: A voltage application unit that causes a change in the voltage between the current-flow side electrode and the gate electrode of the pair of electrodes; A current measuring unit that measures the current flowing between the pair of electrodes; The threshold voltage detection unit detects the voltage value of the gate electrode, i.e., the threshold voltage V, when a current switching occurs between the pair of electrodes, based on the voltage value applied by the voltage application unit and the current value measured by the current measurement unit. th ; as well as The concentration calculation unit is based on the threshold voltage V detected by the threshold voltage detection unit. th Calculate the concentration of the target substance in the fluid to be tested.

9. A concentration determination method, comprising using the device according to any one of claims 1 to 7 to detect the concentration of a target substance in a test fluid. The threshold voltage V is the voltage value of the gate electrode detected when the current switching occurs between the pair of electrodes. th Based on this threshold voltage V th The concentration of the target substance in the fluid to be tested is determined.

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