Device, concentration measurement device provided with same, and concentration measurement method using same

Abstract

Provided is a device that can be used in a concentration measurement device and a concentration measurement method, that can detect a threshold voltage (Vth) with high sensitivity even when a small amount of a subject is contained in a sample solution, and that can quickly measure the concentration of the subject in the sample solution. A device having an insulating substrate, at least one insulating composite layer, and a liquid reservoir capable of holding a sample liquid, the insulating composite layer having a pair of electrodes and a semiconductor layer in contact with the pair of electrodes, the liquid reservoir having a reference electrode in contact with the sample liquid, the semiconductor layer comprising an oxide containing an indium (In) element, a zinc (Zn) element, and an additive element (X), the additive element (X) is at least one element selected from the group consisting of tantalum (Ta), strontium (Sr), and niobium (Nb), and a sensing film that is selective with respect to an object to be detected in the sample liquid is provided between the insulating composite layer and the liquid reservoir.

Description

Technical Field

[0001] This invention relates to the voltage value of a reference electrode, i.e., the threshold voltage V, when the condition of whether current flows between a pair of electrodes changes. th Devices that change based on the concentration of the detected object in the sample solution, more specifically, involving a threshold voltage V. th A concentration measuring device and method for measuring the concentration of the tested object in a sample solution by measuring changes in concentration. Background Technology

[0002] In Society 5.0, which is poised to become an ultra-intelligent society, the IoT, which aims to balance economic development with addressing social issues, will require sensors to acquire data.

[0003] Previously, methods for detecting the presence or concentration of a analyte in a sample solution included electrochemical sensors using semiconductors.

[0004] For example, Patent Documents 1 and 2 disclose a sensor with a field-effect transistor (FET) structure.

[0005] like Figure 8 As shown, the sensor 100 with this FET structure has a gate electrode 102 formed on a substrate 101, and an insulating film 103 is 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 8 As shown, the sensing membrane 107 can be provided separately, covering the gate electrode 102, or the insulating membrane 103 can be used as the sensing membrane. The sensing membrane 107 can selectively detect the analyte in the sample solution. Furthermore, 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 analyte adsorbed on the sensing membrane 107. Therefore, the threshold voltage V of the gate voltage can be measured while the sample liquid is in contact with the sensing membrane 107. th To determine the concentration of the tested object in the sample solution.

[0007] This semiconductor-based sensor boasts high sensitivity and a small size, enabling micro-level detection and allowing for the creation of portable detection devices. Furthermore, by using semiconductors, the detection results are output as electrical signals, thus offering high compatibility with communication devices and facilitating 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, as the semiconductor layer 104, oxide semiconductors containing gallium (Ga), aluminum (Al), iron (Fe), etc., are used in oxides containing indium (In) and zinc (Zn), and in particular, oxide semiconductors containing In, Ga, and Zn (hereinafter referred to as "InGaZnO") are used. In addition, crystalline Si (silicon) has been commonly used as the semiconductor layer 104 in the past.

[0014] However, when using crystalline Si, it is opaque to visible light and cannot be bent, thus limiting its applications. Furthermore, due to the cutoff current (when the gate voltage is set to the threshold voltage V), th The following is the leakage current flowing from the drain electrode to the source electrode, which is relatively large, approximately 1.0 × 10⁻⁶. -12 A / μm ~1.0×10 -7 The value is A / μm, therefore, it has the disadvantage of being affected by noise during measurement and being difficult to perform trace detection.

[0015] On the other hand, InGaZnO is transparent to visible light and is flexible, thus its applications are not limited. Additionally, 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 it has less influence on noise during measurement.

[0016] However, because the electron mobility of InGaZnO is low, approximately 10 cm⁻¹ 2 / Vs, so 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 device that can be used in concentration measuring apparatus and concentration measuring methods, which can detect the threshold voltage V with high sensitivity even when the analyte in the sample solution is in trace amounts. th It can quickly determine the concentration of the tested object in the sample solution.

[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 of the present invention, as well as the concentration measuring apparatus having the same and the concentration measuring method using the same, comprises the following technical solutions.

[0020] [1] A device having an insulating substrate, at least one insulating composite layer, and a reservoir capable of holding a sample solution.

[0021] The insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes.

[0022] The liquid storage section has a reference electrode that is in contact with the sample liquid.

[0023] The semiconductor layer is composed of an oxide containing indium (In), zinc (Zn), and an additive element (X).

[0024] The added element (X) comprises at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb).

[0025] A sensing membrane selective for the object being tested in the sample liquid is provided between the insulating composite layer and the liquid reservoir.

[0026] [2] According to the device described in [1], the sensing membrane is an ion carrier.

[0027] [3] According to the device described in [1], the aforementioned sensing membrane is a nucleic acid probe.

[0028] [4] The device according to [1] to [3], wherein the field-effect mobility of the semiconductor layer is 20 cm⁻¹. 2 / Vs and above.

[0029] [5] According to the device described in [1] to [4], wherein the cutoff current between the pair of electrodes of the semiconductor layer is 1 × 10⁻⁶. -12 Below A.

[0030] [6] A concentration measuring device, comprising:

[0031] The device described in any one of [1] to [5]; and

[0032] Control device,

[0033] The control device has:

[0034] A voltage application unit that varies the voltage applied between the current-flow-side electrode and the reference electrode in the pair of electrodes;

[0035] A current measuring unit that measures the current flowing between the pair of electrodes;

[0036] The threshold voltage detection unit detects the voltage value of the reference electrode, i.e., the threshold voltage V, when the current flow between the pair of electrodes changes, 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

[0037] The concentration calculation unit is based on the threshold voltage V detected by the threshold voltage detection unit. th The concentration of the tested object in the sample solution is calculated.

[0038] [7] A concentration determination method, which uses the device described in any one of [1] to [5] to detect the concentration of the analyte in a sample solution.

[0039] The threshold voltage V is the voltage value of the reference electrode when the current flowing between the pair of electrodes changes. th Based on this threshold voltage V th The concentration of the target substance in the sample solution is determined.

[0040] The effects of the invention

[0041] According to the present invention, an oxide comprising indium (In), zinc (Zn), and an additive element (X) is used as the semiconductor layer, wherein the additive element (X) is at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb). This reduces the cutoff current and increases the electron mobility compared to 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 analyte in the sample solution is minute. th Devices.

[0042] Furthermore, by using such a device, it is possible to realize a concentration measuring apparatus and concentration measuring method that can rapidly measure the concentration of the target substance in the sample solution even when the target substance in the sample solution is in trace amounts. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating the structure of the concentration measuring device in this embodiment.

[0044] Figure 2 It is used to explain in Figure 1 A schematic diagram of the structure of the device used in the concentration measuring apparatus.

[0045] Figure 3 It means to use Figure 1A graph showing the relationship between the concentration of the target (LiCl) and the threshold voltage Vth when the concentration of the target in sample solution L (LiCl aqueous solution) is measured using a concentration measuring device.

[0046] Figure 4 It means to use Figure 1 A graph showing the relationship between the concentration of the target (LiCl) and the threshold voltage Vth when the concentration of the target in sample solution L (LiCl aqueous solution) is measured using a concentration measuring device.

[0047] Figure 5 This is a graph showing the relationship between the concentration of the target substance and the threshold voltage Vth when using crystalline Si as the semiconductor layer of the concentration measuring device to measure the concentration of the target substance in sample solution L.

[0048] Figure 6 It means to use Figure 1 A graph showing the relationship between the concentration of the target (NH4Cl) and the threshold voltage Vth when the concentration measuring device is used to measure the concentration of the target in other sample solutions L (NH4Cl aqueous solution).

[0049] Figure 7 It means to use Figure 1 A graph showing the relationship between the concentration of the target (NH4Cl) and the threshold voltage Vth when the concentration measuring device is used to measure the concentration of the target in other sample solutions L (NH4Cl aqueous solution).

[0050] Figure 8 This is a schematic diagram illustrating the structure of a sensor based on an existing FET structure. Detailed Implementation

[0051] Hereinafter, embodiments (examples) of the present invention will be described in more detail based on the accompanying drawings.

[0052] Figure 1 This is a schematic diagram illustrating the structure of the concentration measuring device in this embodiment. Figure 2 It is used to explain in Figure 1 A schematic diagram of the structure of the device used in the concentration measuring apparatus.

[0053] 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 has an insulating substrate 12, at least one insulating composite layer 14, and a liquid storage section 16 capable of holding the sample liquid.

[0054] It should be noted that, as Figure 2The device 10 configured as shown can also be made into a semiconductor element such as a field-effect transistor (FET) or a metal oxide semiconductor field-effect transistor (MOSFET).

[0055] The insulating substrate 12 is, for example, a substrate formed of insulating materials such as glass or ceramic.

[0056] The insulating composite layer 14 has a pair of electrodes (a first electrode 141 and a second electrode 142) and a semiconductor layer 144 in contact with the pair of electrodes 141 and 142.

[0057] The reservoir 16 is not particularly limited in structure as long as it can hold the sample solution L. However, in this embodiment, in order to hold the sample solution L in contact with the sensing membrane 18 (described later), it is composed of a partition 16a that surrounds the sensing membrane 18. Furthermore, a reference electrode 161 is provided in the reservoir 16 in contact with the sample solution L.

[0058] In addition, a sensing membrane 18 is provided between the insulating composite layer 14 and the liquid storage section 16.

[0059] The sensing membrane 18 is selective relative to the analyte in the sample solution L. Specifically, it has the property of selectively allowing ions of the analyte to pass through or selectively capturing components of the analyte (e.g., nucleic acids). For example, lithium ion carriers, potassium ion carriers, sodium ion carriers, calcium ion carriers, ammonium ion carriers, chloride ion carriers, magnesium ion carriers, etc., can be used as such sensing membranes 18. Additionally, nucleic acid probes can also be used.

[0060] There are no particular limitations on the manufacturing method of such a sensing film 18. For example, when using an ion carrier, it can be manufactured through the following process.

[0061] 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, PVC with a degree of polymerization of about 1050 is preferred.

[0062] Next, tetrahydrofuran was added to the beaker as a solvent, and the mixture was stirred until the polyvinyl chloride dissolved.

[0063] After the polyvinyl chloride is dissolved, plasticizers, ion carriers, and anion scavengers are added, and the mixture is further stirred using a stirrer.

[0064] It should be noted that, for example, 2-nitrophenyl octyl ether (NPOE) and bis(2-ethylhexyl) sebacate can be used as plasticizers.

[0065] In addition, potassium tetra(4-chlorophenyl)borate can be used as an anion scavenger, for example.

[0066] As an ion carrier, it can be appropriately selected according to the ion of the target being detected. For example, when you want to detect lithium ions (Li... + In cases where potassium ions (K+) are to be detected, dibenzyl-14-crown-4 or TTD-14-crown-4 can be used. + In cases where sodium ions (Na+) are to be detected, bis(benzo-15-crown-5) can be used. + In cases where calcium ions (Ca) are to be detected, dual (12-crown-4) can be used. 2+ In cases where it is desired to detect ammonium ions (NH4+), HDOPP-Ca can be used. + In cases where viable bacteria are required, a non-viable bacterium can be used to detect chloride ions (Cl). - In cases where it is desired to detect magnesium ions (Mg), dithiourea-1 can be used. 2+ In the case of ), C14-K22B5, K22B1B5, and K22B9 can be used.

[0067] Next, the solution prepared in this way is spread out in a glass petri dish and allowed to air dry, thereby forming the sensing membrane 18. It should be noted that from the viewpoint of making the response speed (the establishment of ion diffusion equilibrium) faster, it is effective to make the sensing membrane 18 thinner, but in this case, it is preferable to form the sensing membrane 18 by spin coating.

[0068] The sensing film 18 thus made is cut to an appropriate size and pasted onto the insulating composite layer 14 in a manner that does not trap air. The liquid reservoir 16 is then bonded onto the pasted sensing film 18, for example, using epoxy resin, thereby enabling the fabrication of the device 10.

[0069] It should be noted that the insulating composite layer 14 has an insulating film 146 at least in the portion that contacts the sensing film 18. The insulating film 146 also serves as a protective layer for protecting the semiconductor layer 144 from the influence of the sample liquid L. 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 with insulating properties can be used, and 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.

[0070] Furthermore, the field-effect mobility of the semiconductor layer 144 is preferably 20 cm⁻¹. 2 / Vs or higher, especially preferably 60cm2 / Vs and above.

[0071] Furthermore, regarding the semiconductor layer 144, in the device 10 with the structure described above, the voltage applied to the reference electrode 161 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 the current flowing 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. In this way, because the cutoff current is small, the threshold voltage V is detected as described later. 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 .

[0072] 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).

[0073] Specifically, regarding In and X, it is preferable to satisfy the atomic ratio shown in the following equation (1) (where X is set as the sum of the contents of the above-mentioned added elements, and the same applies to equations (2) and (3) below).

[0074] 0.4≤(In+X) / (In+Zn+X)≤0.8 (1)

[0075] Regarding Zn, the atomic ratio shown in equation (2) is preferred.

[0076] 0.2≤Zn / (In+Zn+X)≤0.6 (2)

[0077] Regarding X, the atomic ratio shown in equation (3) is preferred.

[0078] 0.001≤X / (In+Zn+X)≤0.015 (3)

[0079] By making the atomic ratio of In, Zn and X satisfy equations (1) to (3), the semiconductor layer 144 exhibits the field-effect mobility and cutoff current as described above.

[0080] In order to make the semiconductor layer 144 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).

[0081] 0.43≤(In+X) / (In+Zn+X)≤0.79 (1-2)

[0082] 0.21≤Zn / (In+Zn+X)≤0.57 (2-2)

[0083] 0.0015≤X / (In+Zn+X)≤0.013 (3-2)

[0084] In addition, the atomic ratios of In, Zn and X are more preferably satisfied by equations (1-3), (2-3), and (3-3).

[0085] 0.48≤(In+X) / (In+Zn+X)≤0.78 (1-3)

[0086] 0.22≤Zn / (In+Zn+X)≤0.52 (2-3)

[0087] 0.002 <X / (In+Zn+X)≤0.012 (3-3)

[0088] In addition, the atomic ratio of In, Zn and X is more preferably satisfied by equations (1-4), (2-4), and (3-4).

[0089] 0.53≤(In+X) / (In+Zn+X)≤0.75 (1-4)

[0090] 0.25≤Zn / (In+Zn+X)≤0.47 (2-4)

[0091] 0.0025≤X / (In+Zn+X)≤0.010 (3-4)

[0092] In addition, the atomic ratio of In, Zn and X is more preferably satisfied by equations (1-5), (2-5), and (3-5).

[0093] 0.58≤(In+X) / (In+Zn+X)≤0.70 (1-5)

[0094] 0.30≤Zn / (In+Zn+X)≤0.42 (2-5)

[0095] 0.003≤X / (In+Zn+X)≤0.009 (3-5)

[0096] 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 contain elements other than Ta, Sr, and Nb, but it is preferable to contain only these elements.

[0097] Furthermore, the thinner the semiconductor layer 144, the greater the change in surface conductivity. Therefore, the change in migrated charge, as described later, becomes larger, 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 particularly limited, and is typically 0.005 μm or more.

[0098] Furthermore, the surface 144a of the semiconductor layer 144 on the sensing 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 be formed between it and the insulating film 146, or the insulating film 146 may be discontinuously formed. This reduces the adhesion between the insulating film 146 and the sensing film 18, making it impossible to accurately capture potential changes from the sensing film 18. Consequently, measurement accuracy decreases, or operation becomes unstable.

[0099] 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 sensing 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.

[0100] Here, the maximum height Sz and the arithmetic mean height Sa are surface roughness parameters specified in ISO 25178. These parameters can be measured, for example, using a 3D surface roughness shape measuring machine (Zygo, NexView, etc.). It should be noted that the measurement conditions are preferably as follows.

[0101] 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. The roughness curve was then corrected using the analysis program "Mx" attached to the 3D surface roughness shape measuring machine under the following correction conditions, and the maximum height Sz and arithmetic mean height Sa were calculated.

[0102] <Calibration conditions>

[0103] -Remove: Form Remove (Format Removal)

[0104] - Filter Type: Spline

[0105] -Filter: Low Pass

[0106] -Type: Gaussian Spline Auto

[0107] 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 can be formed on an insulating substrate 12 using a sputtering apparatus as the first electrode 141 and the second electrode 142, and then an oxide thin film of the structure 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 in the patterning of the first electrode 141 and the second electrode 142 and in the formation of the semiconductor layer 144.

[0108] 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) and tungsten (W) can be used. In addition, alloys of these metals with cerium oxide (CeO2), copper (Cu), silver (Ag) and the like can also be used.

[0109] The insulating film 146 can then 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 SiH4 / N2O / N2 mixed gas, 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.

[0110] In addition, the control device 60 of the concentration measuring device 50 in this embodiment includes: a variable voltage source 32 for applying voltage between the first electrode 141 and the second electrode 142, a variable voltage source 34 (voltage application unit) for applying voltage between the first electrode 141 and the reference electrode 161, 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 reference electrode 161.

[0111] 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.

[0112] 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.

[0113] The threshold voltage detection unit 62 applies a predetermined voltage V between the first electrode 141 and the second electrode 142 through the variable voltage source 32. ds Under these conditions, the voltage V applied between the first electrode 141 and the reference electrode 161 through the variable voltage source 34 is gradually increased. g Therefore, the threshold voltage detection unit 62 uses the ammeter 36 to detect the current I flowing between the first electrode 141 and the second electrode 142. d The change in voltage is detected using voltmeter 38, and the voltage V between the first electrode 141 and the reference electrode 161 is also detected. g The change in threshold voltage V was used to determine the threshold voltage V. th .

[0114] It is known that in the device 10 with the structure described above, the threshold voltage V th The threshold voltage V varies depending on the amount of the detected object present on or inside the sensing membrane 18. Therefore, by measuring this threshold voltage V... th It can detect the concentration of the target substance contained in sample solution L.

[0115] It should be noted that the threshold voltage V th The measurement method is not particularly limited; for example, the initial current I flowing between the first electrode 141 and the second electrode 142 can be detected. d Voltage V at time g It can also be determined from the current I flowing through it. d The voltage V gradually decreases from the state of being. g Detecting current I d Voltage V when no longer flowing g Alternatively, voltage V can be used. g Changes and current I d Reaching the specified value (e.g., 1×10) -9 V at time A) ds The value is set as the threshold voltage Vth While methods known previously are acceptable, 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 Furthermore, the current I flowing at this time is measured. d Calculate √I within the specified range using the least squares method. d Compared to V g The fitted straight line, the √I of the fitted straight line d V when =0 g Set as threshold voltage V th .

[0116] Figure 3 This refers to the relationship between the concentration of the target substance and the threshold voltage V when the concentration measuring device 50 of this embodiment is used to measure the concentration of the target substance in the sample solution L. th A diagram showing the relationship between the two.

[0117] In this determination (Example 1), an aqueous solution of lithium chloride (LiCl) was used as the sample solution L, lithium chloride (LiCl) was used as the analyte, and a lithium ion carrier was used as the sensing membrane 18, which was used to generate a voltage V. ds The voltage is 5V, so that the voltage V g The specified range for changes is -3V to 3V, and √I is applied within the range of 2V to 3V. d Linear fitting.

[0118] like Figure 3 As shown, the higher the LiCl concentration, the higher the threshold voltage V. th The lower.

[0119] Therefore, for example, by pre-creating a representation of the concentration of the object being detected relative to the threshold voltage V... th The standard curve of the relationship can be based on the threshold voltage V measured using the concentration measuring device 50. th The concentration of the tested object, LiCl, is then determined.

[0120] Alternatively, the concentration of the object to be detected can be correlated with the threshold voltage V. th These data are used as training data for machine learning, thereby using artificial intelligence (AI) to calculate the threshold voltage V based on the concentration measuring device 50. th The concentration of the object being tested.

[0121] 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. thThe concentration of the object being detected is calculated as described above. This concentration calculation unit 64 can be implemented using a computer or similar device assembled in the control unit 60.

[0122] Figure 4 This refers to the relationship between the concentration of the target substance and the threshold voltage V when the concentration measuring device 50 of this embodiment is used to measure the concentration of the target substance in the sample solution L. th A diagram showing the relationship between the two.

[0123] In this determination, an aqueous solution of lithium chloride (LiCl) was used as the sample solution L, lithium chloride (LiCl) was used as the analyte, a lithium ion carrier was used as the sensing membrane 18, and a voltage V was applied. ds Set to 1V or 5V. Additionally, perform √I within the range of 2V~3V or 1.5V~2.5V. d The linear fit is shown in Table 1. The specific combinations of conditions are presented in Table 1.

[0124] [Table 1]

[0125]

[0126] like Figure 4 As shown, even if the voltage V g Changes occur, and even if it is used to calculate the threshold voltage V th However, the specified range changes, and the LiCl concentration is related to the threshold voltage V. th There is also a correlation between them.

[0127] As a comparative example (Comparative Example 1), Figure 5 (A) shows the determination of LiCl concentration and threshold voltage V using the following concentration measuring device. th The diagram shows the relationship between the concentration measuring devices. The concentration measuring device is a concentration measuring device with the same structure as the concentration measuring device 50 described above. It has a sensing membrane 18 and a liquid storage section 16 on an ISFET electrode (pH measurement: No. 001314) manufactured by BAS Corporation.

[0128] In this determination, an aqueous solution of lithium chloride (LiCl) was used as the sample solution L, lithium chloride (LiCl) was used as the analyte, and a lithium ion carrier was used as the sensing membrane 18 to transmit voltage V. ds Set it to 5V, so that the voltage V g The specified range for changes is set to -3V to 3V, and √I is performed within the range of 1.5V to 2.5V. d Linear fitting.

[0129] like Figure 5 As shown in (A), when using crystalline Si as the semiconductor layer 144, the LiCl concentration is related to the threshold voltage V. thThere is no correlation between them, making it difficult to determine the threshold voltage V. th To determine the concentration of LiCl.

[0130] As another comparative example (Comparative Example 2), the concentration measuring device used in Comparative Example 1 was used to measure the concentration of voltage V. ds The LiCl concentration at 1V and the threshold voltage V th The relationship, the resulting chart is placed on Figure 5 (B)

[0131] like Figure 5 As shown in (B), even if the voltage V is changed ds , also with Figure 5 Similarly, the results shown indicate that the LiCl concentration is related to the threshold voltage V. th There is no correlation between them, making it difficult to determine the threshold voltage V. th To determine the concentration of LiCl.

[0132] Figure 6 , Figure 7 This refers to the ratio of the concentration of the target substance to the threshold voltage V when using the concentration measuring device 50 of this embodiment to measure the concentration of the target substance in other sample solutions L. th A diagram showing the relationship between the two.

[0133] In this determination (Examples 6 and 7), an aqueous solution of ammonium chloride (NH4Cl) was used as the sample solution L, ammonium chloride (NH4Cl) was used as the analyte, and the ammonium ion carrier was used as the sensing membrane 18. The voltage Vds was set to 5V, and the voltage Vg was varied within the range of -3V to 3V, specifically within the range of 2V to 3V. Figure 6 ) or 1.3V~1.5V ( Figure 7 Within the range of √I d Linear fitting.

[0134] like Figure 6 , Figure 7 As shown, the higher the NH4Cl concentration, the higher the threshold voltage V. th The lower.

[0135] That is, the concentration of NH4Cl is related to the threshold voltage V. th The relationship between LiCl concentration and threshold voltage V is similar to that shown in Examples 1-5. th The relationship tends to be similar. Therefore, based on the threshold voltage V measured using the concentration measuring device 50 of this embodiment... th It can determine the concentration of the object being tested, namely NH4Cl.

[0136] 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.

[0137] Explanation of reference numerals in the attached figures

[0138] 10 devices

[0139] 12 Insulating Substrates

[0140] 14 Insulation Composite Layer

[0141] 141 First Electrode

[0142] 142 Second Electrode

[0143] 144 semiconductor layers

[0144] 144a surface

[0145] 146 insulating film

[0146] 16Liquid storage part

[0147] 16a partition

[0148] 161 reference electrode

[0149] 18-sensor film

[0150] 32 Variable Voltage Source

[0151] 34 Variable Voltage Sources

[0152] 36 Ammeter

[0153] 38 Voltmeter

[0154] 50 Concentration Measuring Device

[0155] 60 control devices

[0156] 62 Threshold Voltage Detection Unit

[0157] 64 concentration calculation units

[0158] 100 sensors

[0159] 101 substrate

[0160] 102 gate electrode

[0161] 103 insulating film

[0162] 104 semiconductor layer

[0163] 105 drain electrode

[0164] 106 source electrode

[0165] 107 ion sensing membrane

Claims

1. A device comprising an insulating substrate, at least one insulating composite layer, and a reservoir capable of holding a sample solution. The insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes. The liquid storage section has a reference electrode that is in contact with the sample liquid. 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 sensing membrane selective for the object being tested in the sample liquid is provided between the insulating composite layer and the liquid reservoir.

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

3. The device according to claim 1, wherein, The sensing membrane is a nucleic acid probe.

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

5. 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.

6. A concentration measuring device, comprising: The device according to any one of claims 1 to 5; and Control device, The control device has: A voltage application unit that varies the voltage applied between the current-flow-side electrode and the reference electrode in 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 reference electrode, i.e., the threshold voltage V, when the current flow between the pair of electrodes changes, 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 The concentration of the tested object in the sample solution is calculated.

7. A concentration determination method, comprising using the device according to any one of claims 1 to 5 to detect the concentration of the analyte in a sample solution. The threshold voltage V is the voltage value of the reference electrode when the current flowing between the pair of electrodes changes. th Based on this threshold voltage V th The concentration of the target substance in the sample solution is determined.

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