TW202542516A - Device, concentrating measuring apparatus including the same, and concentration measuring method using the same - Google Patents

Abstract

Provided is a device that can be used in a concentration measuring apparatus and a concentration measuring method that can detect a threshold voltage V_thwith high sensitivity even if the amount of a target substance in a test fluid is minute and also can quickly measure the concentration of the target substance in the test fluid. The provided device has an insulating substrate, a gate electrode formed on the insulating substrate, at least one insulating composite layer formed in an insulated state on the gate electrode, and a reservoir capable of holding the test fluid. 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) that contains at least one element selected from tantalum (Ta), strontium (Sr) and niobium (Nb). A sensitive membrane having selectivity for the target substance in the test fluid is provided between the insulating composite layer and the reservoir.

Description

Device, concentration measuring apparatus having the device, and concentration measuring method using the device.

This invention relates to a device in which the threshold voltage _Vth of the gate electrode, which controls whether current flows between a pair of electrodes, varies depending on the concentration of the test object in the tested fluid. More specifically, it relates to a concentration measuring apparatus and method for measuring the concentration of the test object in the tested fluid based on such a change in threshold voltage _Vth .

In the upcoming super-smart society, Society 5.0, which aims to balance economic development and the resolution of social issues, the Internet of Things (IoT) that supports this goal must have useful sensors to acquire data.

In the past, known methods for detecting the presence and concentration of the analyte in a sample fluid included electrochemical sensors using semiconductors. For example, patents 1 and 2 disclose sensors constructed using field-effect transistors (FETs).

As shown in FIG5, 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.

Furthermore, as shown in Figure 5, the sensing membrane 107 can be provided separately in the form of 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 fluid. Moreover, since the threshold voltage _Vth of the gate voltage varies depending on the amount of the analyte adsorbed on or penetrating into the sensing membrane 107, the concentration of the analyte in the sample fluid can be measured by measuring the threshold voltage _Vth of the gate voltage while the sample fluid is in contact with the sensing membrane 107.

Because of their high sensitivity and small size, semiconductor sensors can perform micro-detection and can be made into portable detection devices. Furthermore, since semiconductors are used, the detection results are output as electrical signals, resulting in high compatibility with communication devices and enabling remote measurement. [Previous Art Documents][Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2011-043420 [Patent Document 2] Japanese Patent Application Publication No. 2012-122749

[Problem to be Solved by the Invention] Patents 1 and 2 use oxide semiconductors containing indium (In) and zinc (Zn) with gallium (Ga), aluminum (Al), and iron (Fe) as the semiconductor layer 104, especially oxide semiconductors containing In, Ga, and Zn (hereinafter referred to as "InGaZnO"). In the past, crystalline silicon was mostly used as the semiconductor layer 104.

However, when using crystalline silicon, it is not transparent to visible light and cannot be bent, thus limiting its applications. In addition, the OFF current (the leakage current from the drain to the source when the gate voltage is below the threshold voltage _Vth ) is a relatively large value of about 1.0× ^10⁻¹² A/μm to 1.0× ^10⁻⁷ A/μm, which will become noise during measurement and affect the measurement, making it difficult to achieve micro-scale detection.

On the other hand, InGaZnO is transparent to visible light and flexible, thus its applications are not limited. The OFF current is also much smaller than that of crystalline silicon, ranging from about 1.0 × ^10⁻¹⁶ A/μm to 1.0 × ^10⁻¹¹ A/μm, and its influence as noise during measurement is also smaller.

However, the field effect mobility of InGaZnO is a low value of about 10 ^cm² /Vs. Therefore, without a sufficiently large drain-source voltage _VDS , it is difficult to accurately detect changes in the threshold voltage _Vth .

In view of the current situation, this invention aims to provide a device and method for concentration measurement that can detect the threshold voltage V _{_th} with high sensitivity even when the amount of the analyte in the tested fluid is very small, and can quickly determine the concentration of the analyte in the tested fluid. [Means of Solving the Problem]

This invention was made to solve the problems faced by the prior art as described above. The device of this invention, the concentration measuring apparatus having the device, and the concentration measuring method using the device are comprised as described below.

[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 for holding a tested fluid, wherein the insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes, and the semiconductor layer is composed of an indium-containing... The composite material is composed of oxides of elements (In), zinc (Zn), and additive element (X), wherein the additive element (X) includes at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb). A sensing film is provided between the insulating composite layer and the storage portion, and the sensing film is selective for the analyte in the tested fluid.

[2] The device as described in [1], wherein the aforementioned sensing film is an ionophore.

[3] The device as described in [1], wherein the aforementioned sensing membrane is a lipid membrane.

[4] The device as described in [1], wherein the aforementioned sensing membrane is a nucleic acid probe.

[5] The device as described in any of [1] to [4], wherein an insulating film is further provided between the aforementioned insulating substrate and the aforementioned gate electrode.

[6] The device as described in any of [1] to [5], wherein the field-effect mobility of the aforementioned semiconductor layer is above 20 ^cm² /Vs.

[7] The device as described in any of [1] to [6], wherein the OFF current between the aforementioned pair of electrodes of the aforementioned semiconductor layer is less than 1 × ^10⁻¹² A.

[8] A concentration measuring device comprising: a device as described in any one of [1] to [7], and a control device comprising: a voltage applying means for changing the voltage between the current-flow-side electrode of the pair of electrodes and the gate electrode; a current measuring means for measuring the current flowing between the pair of electrodes; and a threshold voltage detecting means for detecting, based on the voltage value applied by the voltage applying means and the current value measured by the current measuring means, a threshold voltage _Vth belonging to the voltage value of the gate electrode at the time of switching whether to allow current to flow between the pair of electrodes. ; and the concentration calculation method is to calculate the concentration of the object to be tested in the fluid to be tested based on the threshold voltage V _th detected by the aforementioned threshold voltage detection method.

[9] A concentration measurement method, which uses a device as described in any one of [1] to [7] to detect the concentration of a test object in a test fluid, the concentration measurement method comprising: detecting a threshold voltage _Vth of the voltage value belonging to the gate electrode when switching whether current flows between the aforementioned pair of electrodes, and measuring the concentration of the test object in the test fluid based on the threshold voltage _Vth . [Effects of the Invention]

According to the present invention, an oxide containing 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 OFF current and increases the field-effect mobility compared to conventional oxide semiconductors. As a result, a device can be obtained that can detect the threshold voltage _Vth with high sensitivity even when the amount of the analyte in the detected fluid is very small.

Furthermore, by using such a device, a concentration measuring apparatus and concentration measuring method can be obtained to quickly measure the concentration of the test object in the test fluid, even if the amount of the test object in the test fluid is very small.

The embodiments of the present invention will now be described in more detail with reference to the figures. Figure 1 is a schematic diagram illustrating the configuration of the concentration measuring device of the present embodiment, Figure 2 is a front view illustrating the configuration of the device used in the concentration measuring device of Figure 1, and Figure 3 is a side view of Figure 2.

As shown in Figure 1, 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 storage section 16 for holding the test liquid L, which is the test fluid.

The device 10 configured as shown in Figures 2 and 3 can be a semiconductor device such as a field-effect transistor (FET) or a metal oxide semiconductor field-effect transistor (MOSFET).

The gate electrode layer 13 has a gate electrode 131 and an insulating film 132 formed on the insulating substrate 12. 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 and water vapors, but the gate electrode 131 can also be formed directly on the insulating substrate 12.

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.

The liquid storage section 16 is only required to hold the sample liquid L and there are no particular restrictions. However, in this embodiment, in order to keep the sample liquid L in contact with the sensing membrane 18 described later, the liquid storage section 16 is configured as a partition section 16a surrounding the sensing membrane 18.

Although this embodiment is configured to measure the concentration of the test object contained in the test liquid L by storing the test liquid L in the liquid storage unit 16 as the test fluid, it can also be configured to replace the liquid storage unit 16 by providing a gas storage unit, and measure the concentration of the test object contained in the gas by storing the gas containing the test object in the storage unit as the test fluid.

Furthermore, a sensing membrane 18 is provided between the insulating composite layer 14 and the liquid storage portion 16. The sensing membrane 18 is selective for the analyte in the sample solution L. Specifically, it has the property of selectively allowing ions of the analyte to penetrate or selectively capturing the constituent components of the analyte (e.g., nucleic acids). Such a sensing membrane 18 can be an ion carrier such as a lithium ion carrier, potassium ion carrier, sodium ion carrier, calcium ion carrier, ammonium ion carrier, chloride ion carrier, magnesium ion carrier, etc., or it can be a lipid membrane or a nucleic acid probe.

There are no particular limitations on the manufacturing method of such a sensing film 18. When using, for example, an ion carrier, it can be manufactured according to the steps described below. First, weigh polyvinyl chloride (PVC) in a beaker. Here, from the viewpoint of ease of handling and smooth bonding to the insulating composite layer 14, it is preferable to use PVC with a degree of polymerization of approximately 1050.

Next, add tetrahydrofuran to the beaker as a solvent and stir with a stirrer until the polyvinyl chloride is dissolved.

After the polyvinyl chloride is dissolved, plasticizer and ion carrier are added. If the object being tested is cationic, anion scavenger is added; if the object being tested is anionic, a cation scavenger is added. Then, stir with a stirring rod.

Plasticizers such as 2-nitrophenyl octyl ether (NPOE) and bis(2-ethylhexyl) sebacate can be used. Anion scavengers such as tetrakis(4-chlorophenyl)boron potassium can be used, and cation scavengers such as tris(dodecyl)methylammonium chloride (TDDMACl) can be used.

The ion support can be appropriately selected according to the ions of the analyte. For example, dibenzyl-14-crown-4 or TTD-14-crown-4 can be used to detect lithium ions (Li ⁺ ), bis(benzo-15-crown-5) can be used to detect potassium ions (K ⁺ ), bis(12-crown-4) can be used to detect sodium ions (Na ⁺ ), HDOPP-Ca can be used to detect calcium ions (Ca2 ⁺ ), and ammonium ions (NH4+) can be used to detect ammonium ions ( _NH4 ^+). For the detection of chloride ions ( ^Cl- ), nonanol can be used; for the detection of magnesium ions (Mg2+), Bisthiourea-1 can be used; and for the detection of magnesium ions (Mg2 ⁺ ), C14-K22B5, K22B1B5, or K22B9 can be used.

Next, the prepared solution is spread evenly on a glass petri dish and air-dried to produce the sensing membrane 18. From the perspective of accelerating the response speed (establishing ion diffusion equilibrium), the thinner the sensing membrane 18 is, the better. However, it is better to use the spin coating method to produce the sensing membrane 18.

The sensing film 18, which is thus made, is cut to an appropriate size and attached to the insulating composite layer 14 in a way that does not trap air. Then, the liquid storage part 16 is attached to the sensing film 18 using, for example, epoxy resin, to make the device 10.

The insulating composite layer 14 has an insulating film 146 at least in the area that contacts the sensing membrane 18. The insulating film 146 also serves as a protective layer to prevent the semiconductor layer 144 from contacting the sample fluid L. By providing the insulating film 146, corrosion and other damage to the semiconductor layer 144 can be prevented, thereby improving the durability and reliability of the semiconductor layer 144. The insulating film 146 can be made of any insulating material, and known materials can be used, with those having corrosion resistance being preferred. Materials with insulating properties include _Ta₂O₅ , _Si₃N₄ , _{and SiO₂} , with _a thickness preferably between 0.01μm and 0.5μm, and even better between 0.03μm and 0.2μm.

The field-effect mobility of semiconductor layer 144 is preferably above 20 ^cm² /Vs, especially above 60 ^cm² /Vs.

Furthermore, in the device 10 configured as described above, the OFF current of semiconductor layer 144, which is the current flowing from the first electrode 141 to the second electrode 142 or from the second electrode 142 to the first electrode 141 when the voltage applied to the gate electrode 131 is less than the threshold voltage _Vth , is preferably less than 1× ^10⁻¹² A, and more preferably less than 1× ^10⁻¹⁴ A. Because the OFF current is small, the threshold voltage _Vth can be detected with higher accuracy even when the voltage applied between the first electrode 141 and the second electrode 142 is small, as described _later .

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).

Specifically, for In and X, the atomic ratio expressed by the following formula (1) is preferred (where X is the sum of the contents of the aforementioned added elements, which is also the case in formulas (2) and (3) below). 0.4≦(In+X)/(In+Zn+X)≦0.8 …(1) For Zn, the atomic ratio expressed by the following formula (2) is preferred. 0.2≦Zn/(In+Zn+X)≦0.6 …(2) For X, the atomic ratio expressed by the following formula (3) is preferred. 0.001≦X/(In+Zn+X)≦0.015 …(3)

If the atomic ratios of In, Zn, and X satisfy equations (1) to (3), then semiconductor layer 144 will indeed exhibit the field-effect mobility and OFF current described above.

To achieve higher field-effect mobility and lower OFF current in semiconductor layer 144, the atomic ratios of In, Zn, and X are optimized to satisfy equations (1-2), (2-2), and (3-2). 0.43≦(In+X)/(In+Zn+X)≦0.79 …(1-2) 0.21≦Zn/(In+Zn+X)≦0.57 …(2-2) 0.0015≦X/(In+Zn+X)≦0.013 …(3-2)

The atomic ratios of In, Zn, and X should satisfy equations (1-3), (2-3), and (3-3) to be optimal. 0.48≦(In+X)/(In+Zn+X)≦0.78 …(1-3) 0.22≦Zn/(In+Zn+X)≦0.52 …(2-3) 0.002＜X/(In+Zn+X)≦0.012 …(3-3)

The atomic ratios of In, Zn, and X are preferred to satisfy equations (1-4), (2-4), and (3-4). 0.53≦(In+X)/(In+Zn+X)≦0.75 …(1-4) 0.25≦Zn/(In+Zn+X)≦0.47 …(2-4) 0.0025≦X/(In+Zn+X)≦0.010 …(3-4)

The atomic ratios of In, Zn, and X are preferred to satisfy equations (1-5), (2-5), and (3-5). 0.58≦(In+X)/(In+Zn+X)≦0.70 …(1-5) 0.30≦Zn/(In+Zn+X)≦0.42 …(2-5) 0.003≦X/(In+Zn+X)≦0.009 …(3-5)

The added element (X) uses at least one of the elements selected from Ta, Sr, and Nb as described above. Any one of these elements may be used alone, or in combination of two or more. Additionally, the added element (X) may also contain elements other than Ta, Sr, and Nb, but it is preferable to contain only these elements.

Furthermore, the thinner the semiconductor layer 144, the greater the change in surface conductivity, thus increasing the variation in moving charges as described later, and improving measurement accuracy. A thickness of less than 0.5 μm is preferred, less than 0.1 μm is even better, and less than 0.05 μm is ideal. There is no specific lower limit for the thickness of the semiconductor layer 144, but it is generally above 0.005 μm.

Furthermore, the surface 144a of the sensing film 18 side of the semiconductor layer 144 should be as smooth as possible. If the surface 144a of the semiconductor layer 144 is not smooth, gaps may occur between it and the insulating film 146, or the insulating film 146 may be discontinuously formed, resulting in reduced adhesion between the insulating film 146 and the sensing film 18. Consequently, it will be impossible to accurately measure potential changes from the sensing film 18. Therefore, measurement accuracy will decrease, or the operation will become unstable.

Specifically, the maximum height Sz of the surface 144a of the semiconductor layer 144 is preferably below 0.05 μm, more preferably below 0.01 μm, and best of all below 0.003 μm. There is no specific requirement for the lower limit of this maximum height Sz, but it is generally above 0.0005 μm. Furthermore, the arithmetic mean height Sa of the surfaces 144a on the 18 sides of the sensing film 18 of the semiconductor layer 144 is preferably below 0.03 μm, more preferably below 0.005 μm, and best of all below 0.002 μm. There is no specific requirement for the lower limit of this arithmetic mean height Sa, but it is generally above 0.0002 μm.

Here, the maximum height Sz and the arithmetic mean height Sa are surface roughness parameters specified in ISO 25178. Such parameters can be measured using, for example, a 3D surface roughness shape measuring machine (NexView manufactured by Zygo). Moreover, the measurement conditions in this case are preferably performed as follows.

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

＜Correction conditions＞-Remove：Form Remove-Filter Type：Spline-Filter：Low Pass-Type：Gaussian Spline Auto

When the device 10 described above is formed as a FET structure, it can be formed using the same methods as known FETs and MOSFETs. For example, a conductive metal thin film can be formed on the insulating substrate 12 using a sputtering apparatus as the first electrode 141 and the second electrode 142. Then, an oxide thin film as described above can be formed using a sputtering apparatus as the semiconductor layer 144. A shadow mask can be used in the patterning of the first electrode 141 and the second electrode 142 and the semiconductor layer 144.

There are no particular restrictions on the conductive metals used as the first electrode 141 and the second electrode 142. For example, molybdenum (Mo) or tungsten (W) can be used, as well as alloys of these metals with cerium oxide (CeO ₂ ), copper (Cu), silver (Ag), etc.

Next, a ceramic thin film is deposited on it to form an insulating film 146. Specifically, a plasma CVD apparatus such as the PD-2202L manufactured by SAMCO Corporation of Japan can be used to deposit a SiOx thin film to form the insulating film 146 under the following conditions: film-forming gas: _SiH4 / _N2O / _N2 mixed gas, film-forming pressure: 110Pa, and substrate temperature: 250°C to 400°C.

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 means) for applying a voltage between the first electrode 141 and the gate electrode 131; a current meter 36 (current measuring means) for measuring the current value between the first electrode 141 and the second electrode 142; and a voltmeter 38 (voltage measuring means) for measuring the voltage value between the first electrode 141 and the gate electrode 131.

The control device 60 is configured to have a computer equipped with calculation means, memory means, input and output means, etc., and to control the applied voltage of the variable voltage source 32 and the variable voltage source 34 according to the program stored in the memory means, or to measure the current value using the ammeter 36 and the voltage value using the voltmeter 38.

The control device 60 is further equipped with a threshold voltage detection means 62. The threshold voltage detection means 62 is configured to control the voltage applied by the variable voltage source 32 and the variable voltage source 34, and receive the current and voltage values measured by the ammeter 36 and the voltmeter 38 as electrical signals. Such a threshold voltage detection means 62 can be implemented by a computer or the like integrated into the control device 60.

The threshold voltage detection means 62, while applying a predetermined voltage _Vds between the first electrode 141 and the second electrode 142 using a variable voltage source 32, gradually increases the voltage _Vg applied between the first electrode 141 and the gate electrode 131 using a variable voltage source 34. Then, the threshold voltage detection means 62 uses a current meter 36 to detect the change in the current _Id flowing between the first electrode 141 and the second electrode 142, and a voltmeter 38 to detect the change in the voltage _Vg between the first electrode 141 and the gate electrode 131, thereby measuring the threshold voltage _Vth .

In the device 10 configured as described above, it is known that the threshold voltage _Vth varies depending on the amount of the analyte present on or inside the sensing membrane 18. Therefore, the concentration of the analyte in the sample fluid L can be detected by detecting the threshold voltage _Vth .

There are no particular limitations on the method for measuring the threshold voltage _Vth . For example, it can be used to detect the voltage _Vg when the current _Id begins to flow between the first electrode 141 and the second electrode 142, or it can be used to gradually decrease the voltage _Vg while the current _Id is flowing, and then detect the voltage _Vg when the current _Id no longer flows. While conventional methods such as varying the voltage _Vg and using the value of _Vds when the current _Id reaches a predetermined value (e.g., 1 × ^10⁻⁹ A) as the threshold voltage _Vth can be employed, from a more accurate measurement perspective, it is preferable to keep the voltage _Vds constant, apply the voltage _Vg within a predetermined range, measure the current _Id flowing at that time, calculate an approximate straight line of _√Id relative to the predetermined range of _Vg using the least squares method, and then use the _Vg at the point where _√Id = 0 of the approximate straight line as the threshold voltage _Vth .

Figure 4 is a graph showing the relationship between the concentration of the test subject and the threshold voltage _Vth during the concentration measurement of the test subject in the sample solution L using the concentration measuring device 50 of this embodiment. In this measurement (example), an ammonium chloride ( _NH4Cl ) aqueous solution is used as the sample solution L, ammonium ions ( _NH4 ⁺ ) are used as the test subject, an ammonium ion carrier is used as the sensing membrane 18, and the voltage _Vds is set to 1V, while the voltage _Vg is varied within a predetermined range of 1.3V to 1.5V for measurement.

As shown in Figure 4, the higher ^the _NH₄⁺ concentration, the lower the threshold voltage _V₁th . Therefore, a calibration curve representing the relationship between the concentration of the tested object and the threshold voltage _V₁th can be prepared in advance, and then the concentration of the tested object can be determined based on the threshold voltage _V₁th measured using the concentration measuring device 50.

Alternatively, the concentration of the object being tested can be correlated with a threshold voltage V _th and used as training data for machine learning. Then, artificial intelligence (AI) can be used to calculate the concentration of the object being tested based on the threshold voltage V _th measured using the concentration measuring device 50.

The control device 60 of this embodiment further includes a concentration calculation means 64, which is configured to calculate the concentration of the detected object as described above based on the threshold voltage _Vth detected by the threshold voltage detection means 62. This concentration calculation means 64 can be implemented by a computer or the like integrated into the control device 60.

The above describes the preferred embodiment of the invention, but the invention is not limited thereto, and various changes can be made without departing from the purpose of the invention.

10: Device; 12: Insulating substrate; 12a: Insulating film; 13: Gate electrode layer; 14: Insulating composite layer; 16: Liquid storage section; 16a: Spacer section; 18: Sensing film; 32: Variable voltage source; 34: Variable voltage source; 36: Ammeter; 38: Voltmeter; 50: Concentration measuring device; 60: Control device; 62: Threshold voltage detection method; 64: Concentration calculation method 100: Sensor; 101: Substrate; 102: Gate electrode; 103: Insulating film; 104: Semiconductor layer; 105: Drain electrode; 106: Source electrode; 107: Ion sensing film (sensing film); 131: Gate electrode; 132: Insulating film; 141: First electrode; 142: Second electrode; 144: Semiconductor layer; 144a: Surface; 146: Insulating film.

Figure 1 is a schematic diagram illustrating the configuration of the concentration measuring device of this embodiment. Figure 2 is a front schematic diagram illustrating the configuration of the device used in the concentration measuring device of Figure 1. Figure 3 is a side schematic diagram of Figure 2. Figure 4 is a graph showing the relationship between the concentration of the test object and the threshold voltage _Vth when measuring the concentration of the test object in the sample fluid L using the concentration measuring device of Figure 1. Figure 5 is a schematic diagram illustrating the configuration of a conventional FET sensor.

10: Devices

12: Insulating substrate

13: Gate electrode layer

14: Insulating Composite Layer

16: Liquid Storage Section

32: Variable Voltage Power Supply

34: Variable Voltage Power Supply

36: Ammeter

38: Voltmeter

50: Concentration measuring device

60: Control Device

62: Threshold Voltage Detection Methods

64: Concentration Calculation Method

Claims (9)

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 an insulated state from the gate electrode; and a storage portion for holding a tested fluid, wherein the insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes, the semiconductor layer being composed of a substrate containing a metal layer ... It is composed of oxides of indium (In), zinc (Zn) and additive element (X), wherein the additive element (X) includes at least one element selected from tantalum (Ta), strontium (Sr) and niobium (Nb), and a sensing film is provided between the aforementioned insulating composite layer and the aforementioned storage portion, the sensing film being selective for the analyte in the aforementioned test fluid. The device as described in claim 1, wherein the aforementioned sensing membrane is an ion carrier. The device as described in claim 1, wherein the aforementioned sensing membrane is a lipid membrane. The device as described in claim 1, wherein the aforementioned sensing membrane is a nucleic acid probe. The device as described in claim 1, wherein an insulating film is further provided between the aforementioned insulating substrate and the aforementioned gate electrode. The device as described in claim 1, wherein the field-effect mobility of the aforementioned semiconductor layer is above 20 ^cm² /Vs. The device as described in claim 1, wherein the OFF current between the aforementioned pair of electrodes of the aforementioned semiconductor layer is less than 1 × ^10⁻¹² A. A concentration measuring device comprises: the device described in any one of claims 1 to 7, and a control device, wherein the control device comprises: a voltage application means for changing the voltage applied between the current-flow-side electrode of the pair of electrodes and the gate electrode; a current measurement means for measuring the current flowing between the pair of electrodes; and a threshold voltage detection means for detecting, based on the voltage value applied by the voltage application means and the current value measured by the current measurement means, a threshold voltage _Vth belonging to the gate electrode at the time of switching whether to allow current to flow between the pair of electrodes. ; and the concentration calculation method is to calculate the concentration of the object to be tested in the fluid to be tested based on the threshold voltage V _th detected by the aforementioned threshold voltage detection method. A concentration measurement method uses the device described in any one of claims 1 to 7 to detect the concentration of a test object in a test fluid. The concentration measurement method includes: detecting a threshold voltage _Vth of the voltage value belonging to the gate electrode when switching whether current flows between the aforementioned pair of electrodes, and measuring the concentration of the test object in the aforementioned test fluid based on the threshold voltage _Vth .