Temperature sensor and biosensor including the same

Abstract

To provide a temperature sensor capable of highly accurate measurement by protecting a pattern wire and preventing a damage while suppressing the increase in manufacturing cost, and a biosensor including the temperature sensor.SOLUTION: A temperature sensor includes a substrate at least an upper surface of which is formed of an insulating material, a pair of measurement counter electrodes 3A formed to face each other on the upper surface of the substrate, a pair of measurement pattern wires 4A formed on the upper surface of the substrate and having one end connected to the pair of measurement counter electrodes, a pair of measurement pad parts 5A formed on the upper surface of the substrate and connected to the other end of the pair of measurement pattern wires, and a thin-film heat-sensitive part 6 formed covering an upper surface and a side surface of the pair of measurement counter electrodes. The heat sensitive part is formed so as to cover an upper surface and a side surface of the pair of measurement pattern wires.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a highly durable temperature sensor and a biosensor equipped with the same. [Background technology]

[0002] Conventionally, a thin-film biosensor has been known that has a thermistor, electrodes, and an enzyme (glucose oxidase (GOD) that has the ability to identify glucose) on a substrate. In such a biosensor, an enzyme reaction occurs when a test solution (glucose solution) is passed through the biosensor, and the thermistor senses the heat of this enzyme reaction, measuring the change in resistance to determine the concentration of the target substance.

[0003] For example, Patent Documents 1 and 2 describe a biosensor that includes a thin-film thermistor heat-sensing section, a pair of counter electrodes formed on the heat-sensing section facing each other, and enzymes immobilized on the surfaces of the heat-sensing section and the counter electrode. This biosensor is small and has a small heat capacity, and can be immobilized with many enzymes, enabling high-density, high-precision measurements.

[0004] Patent document 3 also describes a biosensor that employs a lower electrode structure in which a thin-film thermistor (heat-sensing part) is formed after the electrode part is formed, thereby suppressing fluctuations in resistance value due to side reactions of the enzyme reaction and enabling accurate measurement of the heat of the enzyme reaction. This biosensor is composed of three parts: a pair of opposing electrodes formed on a sensor substrate (insulating film) as the electrode part of the sensor, a pad part provided to ensure electrical continuity with the outside, and pattern wiring extending from the opposing electrodes to ensure electrical continuity with the pad part.

[0005] On the other hand, for example, Patent Document 4 describes a temperature sensor in which a thin-film thermistor portion is formed on an insulating film, and a counter electrode and a connection electrode are formed on the thin-film thermistor portion. In this temperature sensor, the thin-film thermistor portion is formed on the entire lower surface of the counter electrode and the connection electrode. Furthermore, Patent Document 5 describes a temperature sensor with high moisture resistance, which has a structure including a first thin-film thermistor portion formed on an insulating film, a pair of opposing electrodes formed opposite each other on the first thin-film thermistor portion, and a second thin-film thermistor portion formed by patterning on the first thin-film thermistor portion and the opposing electrode. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-117171 [Patent Document 2] Patent Publication No. 2021-117172 [Patent Document 3] Japanese Patent Publication No. 2023-077607 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-96719 [Patent Document 5] Japanese Patent Application Publication No. 2018-044946 Summary of the Invention [Problem to be solved by the invention]

[0007] The above conventional techniques still have the following problems. In other words, if the above-mentioned conventional temperature sensor is used in an environment where the metal forming the pattern wiring is corrosive, the exposed pattern wiring may come into contact with corrosive liquid or the like, damaging the pattern wiring and causing a sudden increase in resistance or, in the worst case, causing a break in the wiring. In particular, in biosensors equipped with the above-mentioned temperature sensor, if the viscosity of the test liquid is low or if there is a large amount of it, the test liquid may flow out to places other than the counter electrode covered by the thin-film thermistor, and come into contact with the exposed pattern wiring.If current is passed through in this state, the pattern wiring may be damaged by the components in the liquid and the voltage applied when current is applied, resulting in a sudden increase in resistance or, in the worst case, a break in the wiring. For this reason, there is a method of coating a protective film to protect the exposed pattern wiring, but this requires a patterning step using lithography, which is inconvenient as it increases the manufacturing cost. Furthermore, when an enzyme reacts with a target substance (substrate), a by-product may be generated. For example, when measuring glucose (blood sugar level) using glucose oxidase, the following reaction is selectively catalyzed: β-D-glucose + O2 → β-D-gluconolactone + H2O2 When a voltage is applied to the generated hydrogen peroxide through the electrodes, an oxidation-reduction reaction occurs, causing a current to flow through the measuring meter. Anode: H2O2→ 2H + +O2+2e - Cathode:O2+4H + +4e - → 2H2O This reduces the apparent resistance, making it difficult to measure the resistance change caused by the exothermic / endothermic reaction itself.

[0008] The above biosensor employs temperature sensor technology that combines a thin-film thermistor to measure the heat of enzyme reaction. However, when conventional temperature sensor technology such as that disclosed in Patent Documents 4 and 5 is employed, the following inconveniences arise. In other words, the technology of Patent Document 4 has an upper electrode structure in which a thin-film thermistor is formed on an insulating film and an opposing electrode is further formed on top of that, so there is a risk that the measurement solution will come into contact with the electrode portion, damaging the opposing electrode and causing the above-mentioned sudden increase in resistance value or breakage. Furthermore, in the technology of Patent Document 5, the second thin-film thermistor covers the counter electrode, but does not cover the pattern wiring, so it still comes into contact with the measurement solution.

[0009] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a temperature sensor and a biosensor equipped with the same that can protect pattern wiring and prevent damage while suppressing increases in manufacturing costs, and that are capable of highly accurate measurements. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention employs the following configuration: That is, a temperature sensor according to a first aspect of the present invention includes a substrate having at least an upper surface made of an insulating material, a pair of measurement counter electrodes formed on the upper surface of the substrate so as to face each other, a pair of measurement pattern wirings formed on the upper surface of the substrate and connected at one ends to the pair of measurement counter electrodes, a pair of measurement pad portions formed on the upper surface of the substrate and connected at the other ends of the pair of measurement pattern wirings, and a thin-film heat-sensing portion formed of a thermistor material and covering the upper and side surfaces of the pair of measurement counter electrodes, wherein the heat-sensing portion is formed to cover the upper and side surfaces of the pair of measurement pattern wirings.

[0011] In this temperature sensor, the heat-sensing portion is formed to cover the top and side surfaces of a pair of measurement pattern wirings, so that the measurement pattern wirings are protected by the heat-sensing portion and have no exposed portions, preventing damage to the measurement pattern wirings and causing a sudden increase in resistance value or breakage, even in a corrosive environment.

[0012] A temperature sensor according to a second invention is the temperature sensor of the first invention, characterized in that the heat-sensing portion is formed to cover the entire upper surface of the substrate except for the pair of measurement pad portions. In other words, in this temperature sensor, the heat-sensing part is formed to cover the entire upper surface of the substrate except for a pair of measurement pad parts, so it is only necessary to expose the measurement pad parts, eliminating the need for fine patterning processes such as lithography, and thereby suppressing increases in production costs.

[0013] The biosensor according to the third invention is a biosensor equipped with an enzyme, characterized in that it comprises the temperature sensor of the first or second invention, and the enzyme fixed directly to the heat-sensing part or fixed to the underside of the substrate opposite the pair of measurement counter electrodes. Specifically, this biosensor includes the temperature sensor and an enzyme fixed directly to the heat-sensing unit or fixed to the underside of the substrate, facing a pair of counter electrodes for measurement. Because the heat-sensing unit, made of a thermistor material, covers the measurement pattern wiring, the test solution (e.g., glucose solution) does not penetrate the heat-sensing unit and does not come into contact with the measurement pattern wiring. This prevents the test solution from coming into contact with the measurement pattern wiring, which could damage the measurement pattern wiring due to the influence of components in the solution and the voltage applied when current is applied, resulting in a sudden increase in resistance or disconnection. Furthermore, because hydrogen peroxide generated in the solution by the enzyme reaction is not decomposed on the surface of the measurement pattern wiring and does not generate electrons, the heat-sensing unit can detect only the heat generated by the enzyme reaction, enabling highly accurate measurement of the enzyme reaction heat. Furthermore, noise due to side reactions other than hydrogen peroxide is reduced, enabling accurate measurement of the enzyme reaction heat.

[0014] A biosensor according to a fourth invention is the biosensor according to the third invention, characterized in that the thermistor material is a nitride. In other words, in this biosensor, the thermistor material is a nitride, and by protecting the measurement pattern wiring with a heat-sensing part formed of a nitride thermistor material having a dense structure, it is possible to better prevent the infiltration of the measurement liquid.

[0015] The biosensor according to the fifth invention is characterized in that, in the third or fourth invention, the enzyme is contained and immobilized in an enzyme recess formed on the lower surface of the substrate. That is, in this biosensor, the enzyme is accommodated and immobilized in an enzyme recess formed on the underside of the substrate. By disposing the enzyme on the underside of the substrate, hydrogen peroxide is also generated on the underside of the substrate, further reducing the impact on the measurement pattern wiring on the upper surface. Furthermore, by accommodating the enzyme in the enzyme recess, immobilization and positioning of the enzyme is facilitated. Even if the enzyme is disposed on the underside of the substrate, the enzyme recess brings the enzyme and the heat-sensing unit closer together through the substrate, which has been thinned by the enzyme recess, making it easier to transfer the heat of the enzyme reaction to the heat-sensing unit. Furthermore, by forming an enzyme recess on the substrate, the heat capacity of the substrate itself can be reduced, improving responsiveness.

[0016] The biosensor of the sixth invention, in any of the third to fifth inventions, comprises a pair of compensation counter electrodes formed on the upper surface of the substrate facing each other and spaced apart from the enzyme, a pair of compensation pattern wirings formed on the upper surface of the substrate and connected at one end to the pair of compensation counter electrodes, and a pair of compensation pad portions formed on the upper surface of the substrate and connected at the other end to the pair of compensation pattern wirings, and is characterized in that the heat-sensing portion covers the upper and side surfaces of the pair of compensation counter electrodes and the upper and side surfaces of the pair of compensation pattern wirings. That is, in this biosensor, the heat-sensing part covers the upper and side surfaces of the pair of compensation counter electrodes and the upper and side surfaces of the pair of compensation pattern wirings, so that not only the measurement counter electrodes and measurement pattern wirings but also the compensation counter electrodes and compensation pattern wirings are protected by the heat-sensing part and there are no exposed parts, which prevents the compensation pattern wirings from being damaged and causing a sudden increase in resistance value or breakage, etc. [Effects of the Invention]

[0017] According to the present invention, the following effects are achieved. In other words, according to the temperature sensor of the present invention, the heat-sensing portion is formed to cover the top and side surfaces of a pair of measurement pattern wirings, so that the measurement pattern wirings are protected by the heat-sensing portion and have no exposed portions, thereby preventing damage to the measurement pattern wirings and the occurrence of a sudden increase in resistance value or breakage, etc. Furthermore, the biosensor of the present invention is equipped with the above-mentioned temperature sensor and an enzyme fixed directly to the heat-sensing part or fixed to the underside of the substrate opposite a pair of measurement opposing electrodes, so that the measurement liquid does not pass through the heat-sensing part and does not come into contact with the measurement pattern wiring, preventing damage to the measurement pattern wiring and preventing decomposition of hydrogen peroxide on the surface of the measurement pattern wiring, thereby enabling highly accurate measurement of the enzyme reaction heat. Therefore, the biosensor of the present invention has high durability and can accurately measure heat generation / absorption, enabling highly accurate measurement of minute amounts of biological substances such as glucose, making it suitable for use in blood glucose self-monitoring devices, triglyceride measuring devices, urine testing devices, etc. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic cross-sectional view of a space between opposing measurement electrodes in a first embodiment of a temperature sensor according to the present invention and a biosensor including the same. [Figure 2] 1A is a plan view showing a temperature sensor according to a first embodiment and a biosensor including the same, and FIG. 1B is an enlarged view of a main part thereof. [Figure 3] FIG. 10 is a schematic cross-sectional view of a portion between opposing measurement electrodes in a second embodiment of a temperature sensor according to the present invention and a biosensor including the same. [Figure 4] 10A and 10B are a plan view and a bottom view showing a temperature sensor according to a second embodiment and a biosensor including the same. [Figure 5] 1 is a schematic cross-sectional view of a temperature sensor according to the present invention and a biosensor including the same in Comparative Example 1 between opposing measurement electrodes. [Figure 6] 1 is a graph showing the change in resistance value in a PBS dropping test in Example 1 of the temperature sensor according to the present invention and the biosensor including the same. [Figure 7] 1 is a graph showing the change in resistance value in a glucose dropping test in Example 1 of the temperature sensor according to the present invention and the biosensor including the same. [Figure 8] 10 is a graph showing the change in resistance value in a PBS dropping test in a temperature sensor according to the present invention and a biosensor including the same in Comparative Example 1. [Figure 9] 10 is a graph showing the change in resistance value in a glucose dropping test in a temperature sensor according to the present invention and a biosensor including the same in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0019] A first embodiment of a temperature sensor and a biosensor including the same according to the present invention will be described below with reference to Figures 1 and 2. Note that in some of the drawings used in the following description, the scale has been changed as necessary to make each part recognizable or easily recognizable.

[0020] As shown in FIGS. 1 and 2, the temperature sensor 1 of this embodiment comprises a substrate 2 having at least an upper surface made of an insulating material, a pair of measurement counter electrodes 3A formed opposite each other on the upper surface of the substrate 2, a pair of measurement pattern wirings 4A formed on the upper surface of the substrate 2 and connected at one end to the pair of measurement counter electrodes 3A, a pair of measurement pad portions 5A formed on the upper surface of the substrate 2 and connected at the other end to the pair of measurement pattern wirings 4A, and a thin-film heat-sensing portion 6 formed of a thermistor material and covering the upper and side surfaces of the pair of measurement counter electrodes 3A. The heat-sensing portion 6 is formed to cover the upper and side surfaces of the pair of measurement pattern wirings 4A. In particular, the heat-sensing portion 6 is formed to cover the entire upper surface of the substrate 2 except for the pair of measurement pad portions 5A. When the heat-sensing part 6 covers the entire upper surface of the substrate 2 except for the pair of measurement pad parts 5A, it is not necessary to remove only the pair of measurement pad parts 5A, and the area including the pair of measurement pad parts 5A may be exposed in a rectangular shape as shown in Figure 2, and as long as it is sufficiently spaced from the measurement counter electrode 3A, a portion of the pair of measurement pattern wirings 4A on the pair of measurement pad parts 5A side does not have to be covered by the heat-sensing part 6.

[0021] Furthermore, the biosensor 10 of this embodiment is a biosensor equipped with an enzyme that selectively reacts to a specific substrate component to be measured, and as shown in Figures 1 and 2, is equipped with the above-mentioned temperature sensor 1 and an enzyme G directly fixed to the heat-sensing part 6 opposite a pair of measurement counter electrodes 3A.

[0022] Furthermore, the biosensor 10 of this embodiment is equipped with a pair of compensation counter electrodes 3B formed on the upper surface of the substrate 2 facing each other and spaced apart from the enzyme G, a pair of compensation pattern wirings 4B formed on the upper surface of the substrate 2 and connected at one end to the pair of compensation counter electrodes 3B, and a pair of compensation pad portions 5B formed on the upper surface of the substrate 2 and connected at the other end to the pair of compensation pattern wirings 4B. The heat-sensitive portion 6 also covers the upper and side surfaces of the pair of compensation counter electrodes 3B and the upper and side surfaces of the pair of compensation pattern wirings 4B. The pair of compensation counter electrodes 3B are spaced apart from the enzyme G in the planar direction of the substrate 2 by a distance sufficient to prevent the enzyme G from being affected by the heat of the enzyme reaction at least in terms of measurement.

[0023] The substrate 2 is, for example, a Si substrate having an insulating material such as SiN or SiO2 formed on the upper surface thereof. Note that the substrate 2 may also be an insulating film such as a polyimide resin sheet. As shown in FIG. 2, the substrate 2 extends in a strip shape, and the measurement counter electrode 3A is disposed on one end side of the substrate 2. The measurement pad portion 5A and the compensation pad portion 5B are terminal portions formed on the other end side of the substrate 2, wider than the main portions of the extending measurement pattern wiring 4A and compensation pattern wiring 4B, in order to connect external lead wires, etc.

[0024] The measurement counter electrode 3A, the compensation counter electrode 3B, the measurement pattern wiring 4A, and the compensation pattern wiring 4B each have, for example, a first bonding layer 3a made of Cr or NiCr and having a thickness of 5 to 100 nm, an electrode layer 3b made of Au and having a thickness of 50 to 1000 nm formed on the first bonding layer 3a, and a second bonding layer 3c made of Ti and having a thickness of 5 nm formed on the electrode layer 3b. The total thickness of the measurement counter electrode 3A, the compensation counter electrode 3B, the measurement pattern wiring 4A, and the compensation pattern wiring 4B is not particularly limited, but is about 50 nm to 10 μm. Although Au is used for the electrode layer 3b, this is not limiting. For example, metals such as Pt, Cu, and Al, and conductive oxides such as ITO can be used for the electrode layer 3b as highly conductive materials. Furthermore, in addition to Ti, which has good bonding properties with the heat-sensitive part 6, materials such as Cr or NiCr with a film thickness of 5 to 100 nm can also be used for the second bonding layer 3c. The pair of measurement counter electrodes 3A and the pair of compensation counter electrodes 3B are comb-shaped electrodes having a plurality of comb portions 3d and arranged opposite to each other.

[0025] The thermistor material of the heat-sensing part 6 is an Al-containing nitride, such as a metal nitride M-Al-N (wherein M represents at least one of Ti, Fe, Co, Mn, Cu, Ni, Zr, Nb, Mo, Hf, Ta, W, Zn, V, and Cr). In this embodiment, the thermistor material of the heat-sensing part 6 is, for example, a material having the general formula: Ti x Al y N z The thermistor material is made of a metal nitride with the formula (0.70≦y / (x+y)≦0.95, 0.4≦z≦0.5, x+y+z=1) and has a hexagonal wurtzite single-phase crystal structure. This thermistor material is a film with a high degree of c-axis orientation in the film thickness direction.

[0026] The heat-sensing part 6 is formed by reactive sputtering in a nitrogen-containing atmosphere, for example. The sputtering conditions are, for example, using a Ti-Al alloy sputtering target with a composition ratio of Al / (Al+Ti)=0.85, and an ultimate vacuum of 4×10 -5 The sputtering gas pressure was 0.2 Pa, the target input power (output): 200 W, and the nitrogen gas partial pressure was 30% in an atmosphere of a mixed gas of Ar gas and nitrogen gas.

[0027] The composition of the upper surface of the heat-sensitive part 6 may be an inorganic material containing oxygen atoms. That is, the heat-sensing part 6 may be formed of a thermistor material of an Al-containing nitride containing Al, and an Al-containing oxynitride film may be formed on the upper surface of the heat-sensing part 6 by oxidizing the Al-containing nitride by heat treatment in the atmosphere or the like. The Al-containing oxynitride film has higher hydrophilicity than Al-containing nitride. The material of the Al-containing oxynitride film contains M-Al-NO (where M represents at least one of Ti, Fe, Co, Mn, Cu, Ni, Zr, Nb, Mo, Hf, Ta, W, Zn, V, and Cr). In this way, when the composition of the upper surface of the heat-sensitive part 6 is an inorganic material containing oxygen atoms, the enzyme is more likely to bind to the highly hydrophilic inorganic material containing oxygen atoms, improving the adhesion of the enzyme.

[0028] When the biosensor 10 of this embodiment is used as a glucose sensor that detects glucose as the substrate component, the enzyme G can be, for example, glucose oxidase (GOD). This glucose oxidase (enzyme G) is immobilized on the heat-sensing part 6 by dissolving glucose oxidase in a phosphate buffer solution (pH=7) to prepare a solution, and dropping this solution onto the heat-sensing part 6 .

[0029] Enzyme G glucose oxidase exhibits the following enzymatic reaction: (glucose oxidase) Glucose + O2 → Gluconolactone + H2O2 The glucose concentration can be measured by detecting the change in resistance of the heat-sensitive part 6 due to the heat generated during this reaction process. A glucose solution can be measured using the biosensor 10 of this embodiment fabricated in this manner. That is, the glucose concentration is determined using the difference in resistance between the measurement counter electrode 3A and the compensation counter electrode 3B when the biosensor 10 is immersed in the glucose solution. Even if a compensation counter electrode is not provided, the glucose concentration can be determined from the change in resistance when the biosensor 10 is alternately immersed in a glucose solution and a phosphate buffer solution maintained at 25°C.

[0030] It is preferable that the thickness of the heat-sensing part 6 is 3 to 20 times the thickness of the measurement pad part 5A and the compensation pad part 5B, the measurement counter electrode 3A and the compensation counter electrode 3B, the measurement pattern wiring 4A and the compensation pattern wiring 4B. If the thickness of the thermal sensing part 6 is less than three times that of the counter electrode or pattern wiring, etc., the sputtering process may result in poor adhesion and inability to completely cover the sides of the measurement pad 5A and compensation pad 5B, the measurement counter electrode 3A and compensation counter electrode 3B, the measurement pattern wiring 4A, and the compensation pattern wiring 4B. If the thickness of the thermal sensing part 6 is more than 20 times, stress is generated in the thin film-like thermal sensing part 6, which may cause cracks.

[0031] In this way, in the temperature sensor 1 of this embodiment, the heat-sensing portion 6 is formed to cover the top and side surfaces of a pair of measurement pattern wirings 4A, so that the measurement pattern wirings 4A are protected by the heat-sensing portion 6 and have no exposed portions, and therefore, even in a corrosive environment, the measurement pattern wirings 4A can be prevented from being damaged and causing a sudden increase in resistance value, breakage, etc. Furthermore, since the heat-sensing portion 6 is formed to cover the entire upper surface of the substrate 2 except for the pair of measurement pad portions 5A, it is only necessary to expose the measurement pad portions 5A, which eliminates the need for fine patterning processes such as lithography, thereby suppressing increases in production costs.

[0032] Furthermore, the biosensor 10 of this embodiment includes the temperature sensor 1 and the enzyme G directly fixed to the heat-sensing part 6 facing the pair of measurement counter electrodes 3A, and the heat-sensing part 6 made of a thermistor material covers the measurement pattern wiring 4A, so that the measurement liquid (glucose solution, etc.) does not pass through the heat-sensing part 6 and does not come into contact with the measurement pattern wiring 4A. Therefore, it is possible to prevent the measurement pattern wiring 4A from being damaged by the components in the liquid and the voltage applied when current is applied when the measurement liquid comes into contact with the measurement pattern wiring 4A, and to prevent a sudden increase in resistance value, breakage, etc. In particular, since the thermistor material is a nitride, the measurement pattern wiring 4A can be protected by the heat-sensing part 6 formed from a nitride thermistor material having a dense structure, thereby making it possible to better prevent the intrusion of the measurement liquid.

[0033] In addition, because the hydrogen peroxide in the solution produced by the enzyme reaction is not decomposed on the surface of the measurement pattern wiring 4A and does not generate electrons, only the heat generated by the enzyme reaction can be detected by the heat-sensing unit 6, enabling highly accurate measurement of the enzyme reaction heat. Furthermore, noise from side reactions other than hydrogen peroxide is also reduced, enabling accurate measurement of the enzyme reaction heat. Furthermore, since the heat-sensitive part 6 covers the upper and side surfaces of the pair of compensation counter electrodes 3B and the upper and side surfaces of the pair of compensation pattern wirings 4B, not only the measurement counter electrode 3A and the measurement pattern wiring 4A but also the compensation counter electrode 3B and the compensation pattern wiring 4B are protected by the heat-sensitive part 6 and no exposed parts are left, which prevents damage to the compensation pattern wiring 4B and the occurrence of a sudden increase in resistance value, breakage, etc.

[0034] Next, a second embodiment of a temperature sensor and a biosensor including the same according to the present invention will be described below with reference to Figures 3 and 4. In the description of the following embodiment, the same components as those described in the above embodiment will be denoted by the same reference numerals, and their description will be omitted.

[0035] The difference between the second embodiment and the first embodiment is that in the first embodiment, the enzyme G is directly fixed to the heat-sensing part 6, whereas in the biosensor 20 of the second embodiment, the enzyme G is stored and fixed in the enzyme recess 22a formed on the underside of the substrate 22, as shown in Figures 3 and 4. That is, in the second embodiment, an enzyme recess 22a having a rectangular shape in plan view is formed on the lower surface of the substrate 22 opposite the pair of measurement counter electrodes 3A, and an enzyme G is stored therein.

[0036] On the lower surface of the substrate 22, a compensation recess 22b, to which the enzyme G is not immobilized, is formed in the same shape as the enzyme recess 22a, directly below the compensation counter electrode 3B. The enzyme recesses 22 a and the compensation recesses 22 b are formed by partially etching the lower surface of the substrate 22 . In this way, in the biosensor 20 of the second embodiment, the enzyme G is stored and fixed in the enzyme recess 22a formed on the underside of the substrate 22. Therefore, since the enzyme G is arranged on the underside of the substrate 22, hydrogen peroxide is also produced on the underside of the substrate 22, further reducing the impact on the measurement pattern wiring 4A on the upper surface.

[0037] Furthermore, storing the enzyme G in the enzyme recess 22a facilitates the fixing and positioning of the enzyme G. Even if the enzyme G is placed on the underside of the substrate 22, the enzyme recess 22a brings the enzyme G and the heat-sensing unit 6 closer together across the substrate 22, which has been made thinner by the enzyme recess 22a, making it easier to transfer the heat of the enzyme reaction to the heat-sensing unit 6. Furthermore, by forming the enzyme recess 22a in the substrate 22, the heat capacity of the substrate 22 itself can be reduced, improving responsiveness. [Example]

[0038] Example 1 of the biosensor of the present invention was prepared as follows. First, a first bonding layer of Cr (20 nm thick), an electrode layer of Au (50 nm thick), and a second bonding layer of Ti (5 nm thick) were deposited by sputtering on a 300 μm thick SiN / Si substrate or SiO2 / Si substrate, and then a pair of opposing measurement electrodes, measurement pattern wiring, and measurement pads were patterned on the substrate by etching.

[0039] Furthermore, a film of Al-Ti-N (thickness: 300 nm) was formed by sputtering as a heat-sensitive part so as to cover the measurement counter electrode and the measurement pattern wiring. In this sputtering, the measurement pad portion was simply masked so as not to be covered with Al-Ti-N. Thereafter, the substrate was cut into rectangular pieces measuring 2 cm in length and 8 mm in width using a dicing device, and these were used as temperature sensors of full-surface thermistors having a bottom electrode structure. Furthermore, an enzyme was immobilized on the heat-sensing part located on the counter electrode for measurement of this temperature sensor, to form Example 1 having a full-surface thermistor structure.

[0040] The biosensor of Example 1 thus fabricated was measured for resistance change as follows. <Measurement A> (PBS drip test) First, prepare phosphate buffered saline (PBS) (pH = 7.3) and then use a micropipette to apply 3 μL of this solution to the heat-sensing part located above the counter electrode for measurement. -1 It dripped. A constant current of 10 μA was applied to the biosensor of Example 1, and the change in resistance value from the time when the PBS came into contact until 400 seconds later was measured as "Measurement A."

[0041] <Measurement B> (Glucose drip test) In addition, a test was conducted as "Measurement B" using the biosensor of Example 1, except that glucose was dissolved in phosphate-buffered saline (PBS) (pH = 7.3) as the solution to be dropped and the glucose concentration was adjusted to 400 mM. In "Measurement A" and "Measurement B," each measurement pad was clamped to an external connector, and electrical continuity was established by contacting the connector pins.

[0042] <Measurement C> (PBS immersion test) Furthermore, using the biosensor of Example 1, PBS was poured into a 50 mL beaker, and the entire sensor except for the pad portion was immersed in PBS and fixed in the beaker. In this state, a constant current of 10 μA was applied, and the change in resistance value from the start of measurement until 400 seconds later was measured as "Measurement C." In "Measurement C," electrical continuity was achieved by soldering external lead wires to each measurement pad.

[0043] Furthermore, a biosensor of Comparative Example 1 of the present invention was fabricated as follows, and "Measurement A," "Measurement B," and "Measurement C" were carried out in the same manner as in Example 1. The biosensor 100 of Comparative Example 1 was fabricated in the same manner as in Example 1 above, by depositing a heat-sensing part 6 of Al-Ti-N (film thickness 300 nm) on the entire surface of the substrate 2, then patterning it by etching so that the heat-sensing part 6 covers only the upper surface of the measurement counter electrode 3A, as shown in Figure 5, and immobilizing enzyme G on the heat-sensing part 6 located on the measurement counter electrode 3A.

[0044] For Example 1 of the present invention thus prepared, a graph of the change in resistance value in "Measurement A" measured continuously is shown in FIG. 6, and a graph of the change in resistance value in "Measurement B" is shown in FIG. Also, for the produced Comparative Example 1 of the present invention, a graph of the change in resistance value in "Measurement A" measured continuously is shown in FIG. 8, and a graph of the change in resistance value in "Measurement B" is shown in FIG. Table 1 also shows the results of evaluation of the rate of change in resistance value in the above "Measurement A," "Measurement B," and "Measurement C" for Example 1 and Comparative Example 1.

[0045] [Table 1]

[0046] The resistance value when it comes into contact with the test solution is taken as the initial resistance value. If the change rate of the resistance value 400 seconds after the start of measurement falls within a 10% range of the initial resistance value, the test counter electrode and the test pattern wiring are deemed undamaged and are judged as "Good." If the change rate exceeds 10%, the test counter electrode and the test pattern wiring are deemed damaged and are judged as "Poor." The change in resistance was measured using a digital multimeter.

[0047] As a result of these evaluations, in Example 1 of the present invention, the sensor did not malfunction even after a long period of 400 seconds of current application, due to the effect of covering the measurement counter electrode and the measurement pattern wiring with the Al-Ti-N heat-sensitive part, as shown in Figures 6 and 7. That is, as shown in Table 1, in "Measurement A," "Measurement B," and "Measurement C" of Example 1, the rate of change in resistance value was within 10%. Furthermore, even in "Measurement C" of Example 1, in which the amount of contact with the test liquid was increased, the rate of change in resistance value was within 10%, indicating that it was not affected by the amount of contact with the test liquid.

[0048] On the other hand, in Comparative Example 1 of the present invention, the counter electrode for measurement and the pattern wiring for measurement come into contact with the test solution, causing the sensor to malfunction after a long period of 400 seconds of current application, as shown in Figures 8 and 9. That is, the resistance value suddenly increases at around 220 seconds in "Measurement A" of Comparative Example 1, around 291 seconds in "Measurement B" of Comparative Example 1, and around 90 seconds in "Measurement C" of Comparative Example 1, causing the sensor to malfunction. Furthermore, as shown in Table 1, in "Measurement A," "Measurement B," and "Measurement C" of Comparative Example 1, the resistance change rate exceeds 100%, which is significantly higher than 10%. In "Measurement C" of Comparative Example 1, in which the amount of contact with the test solution was increased, the rate of change in resistance was 198%, which was larger than "Measurement A" and "Measurement B." This is because the increased amount of test solution increased the contact area between the test solution and the counter electrode for measurement and the pattern wiring for measurement, accelerating damage.

[0049] The technical scope of the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0050] 1...Temperature sensor, 2, 22...Substrate, 3A...Counter electrode for measurement, 3B...Counter electrode for compensation, 4A...Measurement pattern wiring, 4B...Compensation pattern wiring, 5A...Measurement pad portion, 5B...Compensation pad portion, 6...Thermal sensing portion, 10, 20...Biosensor, 22a...Enzyme recess, G...Enzyme

Claims

1. a substrate having at least an upper surface made of an insulating material; a pair of measurement counter electrodes formed opposite to each other on the upper surface of the substrate; a pair of measurement pattern wirings formed on the upper surface of the substrate and having one ends connected to the pair of measurement opposing electrodes; a pair of measurement pad portions formed on the upper surface of the substrate and connected to the other ends of the pair of measurement pattern wirings; a thin-film heat-sensing portion formed of a thermistor material and covering the upper and side surfaces of the pair of measurement opposing electrodes; A temperature sensor characterized in that the heat-sensing portion is formed to cover the upper and side surfaces of the pair of measurement pattern wirings.

2. 2. The temperature sensor according to claim 1, A temperature sensor characterized in that the heat-sensing portion is formed to cover the entire upper surface of the substrate except for the pair of measurement pad portions.

3. A biosensor comprising an enzyme, The temperature sensor according to claim 1 or 2; A biosensor comprising the enzyme immobilized directly on the heat-sensitive portion or on the lower surface of the substrate, facing the pair of counter electrodes for measurement.

4. The biosensor according to claim 3, A biosensor characterized in that the thermistor material is a nitride.

5. The biosensor according to claim 3, A biosensor characterized in that the enzyme is accommodated and immobilized in an enzyme recess formed on the lower surface of the substrate.

6. The biosensor according to claim 3, a pair of compensation counter electrodes formed on the upper surface of the substrate so as to face each other and spaced apart from the enzyme; a pair of compensation pattern wirings formed on the upper surface of the substrate and having one ends connected to the pair of compensation counter electrodes; a pair of compensation pad portions formed on the upper surface of the substrate and connected to the other ends of the pair of compensation pattern wirings; A biosensor characterized in that the heat-sensitive portion covers the upper and side surfaces of the pair of compensation counter electrodes and the upper and side surfaces of the pair of compensation pattern wirings.

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