JP2514280B2 - Integrated ion sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated ion sensor, and more particularly to an integrated ion sensor for measuring electrolyte components and the like in solutions such as blood, urine and rivers.

[0002]

2. Description of the Related Art In an IS (Ion Sensitive) FET which is an ion sensor using a MOSFET, a structure in which an ion sensitive film is directly formed on a gate insulating film without forming a gate electrode is general. . I with this structure
As a measurement circuit using SFET, for example, IEEE Trans
actions on Electron Devices, vol.ED-26, No.12 (1979)
There is one described in pp1939-1944. In the measurement circuit described in this document, a power supply for keeping a voltage and a current between a drain and a source of an ISFET constant and a reference electrode attached for the purpose of activating a sensor circuit for signal processing are provided. A power supply was needed to apply the appropriate voltage to the.

As another example of the configuration of the conventional ion sensor,
Sensors and Actuators, 4, (1983), pp 291-298. In this ion sensor,
As shown in g.2, the signal related to the ion concentration detected by the ion-sensitive film is sent to the MOSFE through the signal line.
It is configured to transmit to the gate electrode of T.

[0004]

In the configuration of the measuring circuit of the ISFET described above, two power sources, that is, the power source for the sensor circuit and the power source for the reference electrode are required, which increases the number of connections,
The device becomes complicated and large. In the case of an ion sensor that simultaneously measures multiple types of ions in a solution using multiple sensors with different ion-sensitive membranes,
Although one reference electrode is commonly used, the same number of measurement sensor circuits as the number of sensors are required, which further complicates the sensor device configuration. In particular, when making the above-mentioned ion sensor, in order to connect to an external power supply or measurement circuit when incorporating the sensor circuit and reference electrode into the catheter and micronizing the ion sensor for in vivo measurement in the living body. However, there is a problem in that the number of lead wires is increased.

Further, in the conventional ion sensor having a structure in which the ion sensitive film and the gate electrode of the MOSFET are electrically connected via a signal line formed of, for example, polysilicon, the ion sensor is used for a long time. Then, water molecules and the like of the measurement solution permeate the ion sensitive film and enter the inside of the signal line and the gate electrode to oxidize or dissolve them. For this reason, the interface state between the ion sensitive film and the signal line or the gate electrode becomes unstable, and there is a drawback that the response characteristics of the ion sensor greatly change with time.

By the way, conventionally, a voltage follower circuit is known as an electric circuit configuration in which a gain is set to 1. In this voltage follower circuit, 2
One MOSFET when equipped with two MOSFETs
If is replaced with ISFET, an ion sensor using ISFET that produces an output with a gain of 1 can be produced. Actually, in order to realize the voltage follower circuit that generates the above output, the structural characteristics of the MOSFET and ISFET arranged in the input stage, that is, the thickness of the oxide film of the gate and the length of the channel are set. The gate structures such as the width of the channel must be exactly matched with each other. However, in the conventional ion sensor in which the ion sensitive film is electrically connected to the gate electrode via the signal line, as described above, the change with time of the response characteristic is large, and therefore, when the voltage follower circuit is configured,
When used for a long time, the characteristics of ISFET are MOSFET
No longer matches the characteristics of. As a result, since the gain of the circuit deviates from 1, it becomes necessary to correct the output of the sensor, and the circuit configuration becomes complicated due to the correction circuit.

A first object of the present invention is to provide an ion sensor equipped with a reference electrode, which can be operated by a single power source, which can simplify the circuit structure and wiring and can be compactly constructed. To provide.

A second object of the present invention is to provide an integrated ion sensor which has stable and accurate measurement operation with little change in measurement characteristics over time even when used for a long time.

[0009]

A first integrated ion sensor according to the present invention comprises at least one ion sensitive film which is sensitive to ions contained in a measurement object and detects the concentration of the ions, and an ion sensitive film. The obtained detection signal is input through a conductive member, and the detection signal is included in the MO included in the input stage.
A signal processing circuit for taking in and processing via SFET and the like,
It has a reference electrode that is placed in the measurement environment created by the measurement target and is set to have a predetermined voltage relationship with the ion-sensitive membrane, and has two terminals, positive and negative, and is driven by the signal processing circuit via the two terminals. By supplying power, one of two terminals is provided with a power source connected to the reference electrode, and further, by controlling at least one threshold value of the MOSFET or the like of the signal processing circuit, the reference electrode is connected to the reference electrode. It is configured to set the signal processing circuit to an active state at a set voltage.

In the integrated ion sensor according to the present invention, preferably, in the first configuration, the ion sensitive film and the signal processing circuit are formed as one semiconductor integrated circuit device,
The reference electrode is formed as a separate member.

In the integrated ion sensor according to the present invention, more preferably, in the first configuration, the electric circuit section including the ion sensitive film and the signal processing circuit and the reference electrode are mounted in the same catheter. Is composed of. In this configuration, the ion sensitive film, the signal processing circuit, and the reference electrode can be further formed as one sensor device.

In each of the above configurations, the input stage MOSFET
For example, if the depletion type is made by controlling the threshold value of the sensor at the time of manufacturing, the power source for the sensor circuit can be commonly used as the power source of the reference electrode, the overall sensor circuit can be made compact, and the number of lead wires can be reduced. Can be reduced.

In the second integrated ion sensor according to the present invention, preferably, in the first configuration, the signal processing circuit is composed of a voltage follower circuit or a non-inverting amplifier circuit.

In the integrated ion sensor according to the present invention, preferably, in the first configuration, the conductive member is covered with an ion sensitive film and is connected to a gate electrode of a MOSFET, a platinum group metal, gold, A metal film of one of silver and an alloy of silver, or a metal oxide film of one of palladium oxide, platinum oxide, and iridium oxide is used.

In the integrated ion sensor according to the present invention, preferably, in the second configuration, the conductive member is covered with an ion sensitive film and is connected to the gate electrode of the MOSFET, a platinum group metal, gold, A metal film of one of silver and an alloy of silver, or a metal oxide film of one of palladium oxide, platinum oxide, and iridium oxide is used.

[0016]

In the integrated ion sensor according to the present invention, the ion sensitive film and the gate electrode of the MOSFET provided in the input stage of the signal processing circuit are connected by a conductive member and MOSFE.
By controlling the threshold value of T, it is possible to perform the detection operation by not providing a dedicated power source for the reference electrode and sharing the power source of the signal processing circuit. Therefore, the number of power sources can be reduced, which is convenient for downsizing. The ion-sensitive film, the signal processing circuit, and these and the reference electrode can be made into a chip as one semiconductor device.

Further, a protective layer such as a platinum layer is provided between the ion sensitive film and the gate electrode of the MOSFET, so that water molecules and the like penetrating through the ion sensitive film may affect the signal line and the gate electrode. Block. The ion sensor has multiple MOSFETs (or insulated gate structure ISF) in the input stage.
ET element), especially when configured as a voltage follower circuit or a non-inverting amplifier circuit, an ion sensitive film and an M
A protective layer, such as a platinum layer, is provided between the gate electrode of the OSFET and the protective layer to protect the sensor device as required.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a cross section of a semiconductor element of various elements forming a sensor circuit of an integrated ion sensor according to the present invention. The sensor circuit is a circuit that processes a detected signal. In FIG. 1, reference numeral 1 is a silicon substrate, and a plurality of various semiconductor elements are formed on the silicon substrate 1. Two
Is a CM composed of nMOS (2A) and pMOS (2B)
OS element, 3 is a MOSFET, as will be described later.
Is an ISFET element formed by providing an ion sensitive film on the gate electrode of the above through a conductive member. The p
The MOS (2B) is an nWE formed on the silicon substrate 1.
It is separated from other semiconductor elements by LL4. pM
The source and drain of the OS (2B) are each formed of the p ⁺ diffusion layer 5, and the gate insulating film 6 thereof is made of SiO ₂ . On the other hand, nMOS (2A) and ISFET element 3
Are separated from other semiconductor elements by pWELL 7 formed on the silicon substrate 1, and n ⁺ diffusion layers 8 are used for their sources and drains, respectively. The ISFET element 3 basically has the same configuration as the MOSFET element. Further, an aluminum wiring 10a is formed on the gate electrode 9 formed of polysilicon, the aluminum wiring 10a is connected to the gate electrode 9, and the titanium layer 10 is further formed.
The platinum layer 11 connected to the aluminum wiring 10a via b is provided on the aluminum wiring 10a. The titanium layer 10b acts as an adhesive layer.

The upper surface of the device of the ion sensor is almost entirely covered with the polyimide film 12, and the entire upper surface of the device is protected by the polyimide film 12. At least one circular groove, for example, is formed in a part of the polyimide film 12, and the ion sensitive film 13 is provided in the groove. While the platinum layer 11 is covered with the polyimide film 12, the circular groove, that is, the ion sensitive film 13 is formed.
Is extended to the location where The tip portion of the platinum layer 11 has substantially the same shape as the ion sensitive film 13, and the tip portion is covered with the ion sensitive film 13. Thus the platinum layer 11
Is substantially electrically connected to the gate electrode 9 in a state where the tip portion thereof is covered with the ion sensitive film 13. The platinum layer 11 corresponds to the above-mentioned conductive member arranged between the gate electrode 9 and the ion sensitive film 13.

The entire sensor circuit formed in the ion sensor device having the above structure is shown in FIG. As is apparent from this electric circuit diagram, the sensor circuit 17 of the ion sensor is configured as a voltage follower circuit using the CMOS element 2 and the ISFET element 3.
In this voltage follower circuit, the input stage has nM
Two semiconductor elements, OS (2A) and ISFET element 3, are arranged, ISFET element 3 is formed as a non-inverting input terminal portion, and nMOS (2A) is formed as an inverting input terminal portion. In the voltage follower circuit shown in FIG. 2, a DC power source such as a battery is connected between the terminals 14 and 15, and the measured output voltage is taken out from the output terminal 16. Here, 14 is a power supply terminal and 15 is a ground terminal. The sensor circuit having the above circuit configuration is
It has a function of processing a detection signal output from the ion sensitive film 13.

FIG. 3 is a perspective view showing the appearance of the above-mentioned device of the ion sensor. CM on the silicon substrate 1
The voltage follower circuit portion shown in FIG. 2 including the OS element 2 and the ISFET element 3 is formed inside the device as indicated by reference numeral 17, and the sensor circuit 17 is further formed on the upper surface thereof from the measurement solution. A polyimide film 12 for protection is coated. As described above, the polyimide film 12
A groove having a circular opening is formed at a predetermined position on the substrate, and the ion sensitive film 13 is provided in this groove. As described with reference to FIG. 1, the ISFET element is provided with a platinum layer 11 connected to the gate electrode of the underlying MOSFET element, and the platinum layer 11 is provided with an ion-sensitive film 13 located on the front side in FIG. It is extended to the location. The shape of the tip of the platinum layer 11 is almost the same as the shape of the ion-sensitive film 13, and
Is formed so as to cover the tip of the platinum layer 11. In this way, the gate electrode of the ISFET element 3 and the ion sensitive film 13 are electrically connected via the platinum layer 11. In addition, the power supply terminal 14 and the ground terminal 1 described above.
5, the output terminal 16 is the ion sensitive film 1 on the silicon substrate 1.
3 are arranged side by side at the end located on the side opposite to the end on which 3 is arranged.

In the integrated ion sensor having the above structure, the gate electrode 9 and the ion sensitive film 13 of the ISFET element are provided.
A platinum layer 11 having a function of protecting the sensor circuit 17 is provided between and, and the platinum layer 11 covered with the ion sensitive film 13 is electrically connected to the gate electrode 9. According to the platinum layer 11, when the device is immersed in the measurement solution for a long period of time, alkali ions, water molecules, etc., which may pass through the ion sensitive film 13 and enter the sensor circuit, are blocked, The insulating film and the like can be protected. Therefore, the platinum layer 11 can prevent deterioration of the gate electrode, the gate insulating film and the like below the ion sensitive film 13.

Further, the sensor circuit is constructed as a voltage follower circuit, and the polymer-supported ion-sensitive film 13 is provided on the gate electrode 9 of the ISFET element 3 at the non-inverting input terminal portion thereof.
Since the platinum layer 11 coated with is electrically connected, the potential change in the ion sensitive film 13 corresponding to the target ion concentration in the measurement solution can be directly output as it is. Further, in the sensor circuit, since the sensor output can be made to have a low impedance by using the voltage follower circuit, noise can be reduced and an external measuring circuit having a simple structure can be used. A non-inverting amplifier circuit can be used instead of the voltage follower circuit. In this case,
The detection signal output from the ion sensitive film 13 is amplified by the non-inverting amplifier circuit, and then signal processed.

In the above embodiment, as the conductive member for protecting the sensor circuit, other metal film or metal oxide film having similar characteristics can be used instead of the platinum layer 11. As the other metal film, for example, a platinum group metal, gold, silver, or an alloy of silver is used. As the metal oxide film, palladium oxide (P _d O), platinum oxide (P _t O _2), iridium oxide (I _r O ₂₎ is used.

In the above-mentioned embodiment, in order to be able to use it in a measurement requiring high accuracy such as a clinical test, the ion-sensitive membrane is not made of an inorganic material but is made of, for example, an ion-sensitive substance. It is necessary to employ a polymer-supported ion-sensitive membrane dispersed in a polymer together with the agent.

Next, a method of using the integrated ion sensor having the above structure will be described with reference to FIG. FIG. 4 shows the device configuration of the integrated ion sensor according to the present invention in use.

In FIG. 4, 20 is a container and 21 is a container 2.
This is the measurement solution housed in 0. The ion concentration of the measurement solution 21 is measured using the ion sensor according to the present invention. In the measurement solution 21, a sensor device 22 having a built-in sensor circuit 17 is arranged in a substantially upright state so that the portion of the ion sensitive film 13 is immersed in the measurement solution 21,
In addition, the reference electrode 23 is arranged at a required distance from the sensor device 22. In such a usage state, the sensor device 22 actually has the configuration shown in FIG. 3, and in the package 24, only the portion of the ion-sensitive film 13 is exposed and the other portions are hidden.
It is implemented in. Three lead wires 14A, 15A, 16A are drawn from the upper surface of the package of the sensor device 22. The lead wire 14A is drawn from the power supply terminal 14 of the voltage follower circuit and is connected to the positive terminal of the battery 25. The lead wire 15A is drawn out from the ground terminal 15 of the voltage follower circuit and is connected to the negative terminal of the battery 25.
Is drawn out from the output terminal 16 of the voltage follower circuit, and is connected to one input terminal 26 a of the voltmeter 26. The voltmeter 26 inputs the output signal of the sensor device 22 and displays it as voltage data. Lead wire 23 from the power supply terminal of the reference electrode 23
A is connected to the negative terminal of the battery 25. Battery 25
The negative terminal of is connected to the other input terminal 26b of the voltmeter 26.

In the ion sensor, the measurement operation cannot be performed only by the sensor device 22 including the sensor circuit 17 that performs signal processing, but the measurement operation is performed in combination with the reference electrode 23. That is, the sensor circuit 17 can be set to the active state for the first time by setting a predetermined voltage relationship with the reference electrode 23 and using the reference electrode 23.

In the device configuration of the ion sensor, the reference electrode 23 can be operated by simply connecting the reference electrode 23 to the negative terminal of the battery 25 for supplying power to the sensor device 22. There is no need to provide a dedicated power source. Also, in this way, the reference electrode 2
3 is connected to the negative terminal of the battery 25 for the sensor circuit.
Since it is possible to control the threshold value of one or both of the nMOS (2A) and the ISFET element 3 provided at the input stage of the voltage follower circuit at the stage of manufacturing 2, it is possible to set to an appropriate value. Is. This will be generally described with reference to FIG. FIG. 5 shows the static characteristics of the output of the integrated ion sensor. Reference numeral 27 in the figure shows a change in the output voltage of the sensor with respect to the reference electrode voltage when the threshold value of the sensor device 22 is not controlled. in this case,
The power supply voltage of the sensor circuit is 5 volts, and the measurement solution is p
H7.0 Tris borate buffer is used. As is clear from the static characteristic 27, no sensor output occurs when the voltage applied to the reference electrode is 0 volt. for that reason,
Unless the applied voltage value of the reference electrode is set to an intermediate value of the power supply voltage of the sensor circuit by providing a dedicated power supply for the reference electrode, it cannot be used as an ion sensor. On the other hand, when the threshold value of the ISFET element is controlled and the ISFET element is configured as the depletion type as described above at the stage of manufacturing the sensor device 22, the characteristic curve becomes negative as shown by 28 in the figure. Can be shifted. Therefore, according to the characteristic 28 thus shifted, it is possible to operate as an ion sensor even when the voltage of the reference electrode is 0 volt, that is, the ground potential. That is, in the integrated ion sensor according to the present invention, it is not necessary to provide a dedicated power source for the reference electrode 23, and if the reference electrode 23 is connected to the negative terminal of the battery 25 of the sensor device 22 and set to 0 volt, The sensor circuit 17 can be operated, which can simplify the device configuration. In particular, the number of lead wires between the battery 25 as a power source and the sensor device 22 including the sensor circuit 17 and the reference electrode 23 can be reduced, which is very convenient when performing in vivo measurement. It is also possible to operate the sensor circuit 17 by connecting the reference electrode 23 to the positive terminal of the battery 25 simply by changing the control of the threshold value.

As described above, according to the integrated ion sensor of the present invention, at least the threshold value of the ISFET element in the input stage can be controlled at the time of manufacturing the device. Therefore, the voltage relationship between the reference electrode and the sensor circuit is adjusted. Then
The power source for the sensor circuit can be used together with the reference electrode, and it is possible to reduce the power source, simplify the circuit configuration, and reduce the number of lead wires. Further, by providing a platinum layer or the like between the gate electrode and the ion sensitive film, the measurement of the ion sensor can be stabilized for a long period of time.

6 and 7 show the measurement results by the integrated ion sensor according to the present invention. FIG. 6 shows the response characteristics of a K ⁺ sensor using a K ⁺ ion sensitive film. Valinomycin as a ligand and TOT as a plasticizer as a K ⁺ ion sensitive membrane
M, PVC was used as the base material. As is clear from the measurement results, according to this sensor, a linear response was obtained in the range of 10 ^-1 to 10 ^-5 mol / l, and a sensitivity of 59.4 mV / decade was obtained. FIG. 7 shows the response characteristics of the Na ⁺ sensor using the Na ⁺ ion sensitive membrane. Bis (12-crown-4) ether was used as the ligand, TOTM was used as the plastic material, and PVC was used as the base material as the Na ⁺ ion sensitive film. As is clear from the measurement results, the linear range was slightly narrower than K ⁺ , but 10 ^-1
A linear response was obtained in the range of ^{-10 -4} mol / l, and a sensitivity of 56.5 mV / decade was obtained.

A second embodiment of the integrated ion sensor according to the present invention will be described with reference to FIGS. 8 and 9. Elements that are substantially the same as the elements described in the above embodiments are assigned the same reference numerals.

In FIG. 8, a Na ion sensitive film 29, a K ion sensitive film 30 and a reference electrode 31 are provided at the tip of the sensor device 22. Therefore, in this example,
Two kinds of ion-sensitive films 29 and 30 and a reference electrode 31 are formed on one sensor device 22. As shown in FIG. 9, the sensitive portion of the sensor device 22 has a structure in which various ion sensitive films 29 and 30 and a reference electrode 31 are separately formed on an oxide film 32 formed on a silicon substrate 1. For separation, a polyimide film 33 in which holes for filling various ion-sensitive films and gel for the reference electrode are patterned is used.
To use. Each of the ion-sensitive films 29 and 30 is formed of a mixed material of a ligand and a plastic material, using polyvinyl chloride as a base material. Further, the Na ion sensitive film 29 and the K ion sensitive film 30 are respectively coated on the platinum layer 11. Since each platinum layer 11 is hard to directly contact the silicon oxide film 32, the titanium layer 10b is provided as an adhesive layer.

On the other hand, the reference electrode 31 has a structure in which an electrolyte gel 34 mixed with potassium chloride is coated on a silver electrode 36 having silver chloride 35 formed on its surface.

As described above, the two ion-sensitive films 29, 30
Since the sensor device 22 is provided in one sensor device 22, each sensor device 22 is provided with two dedicated sensor circuits 17. In FIG. 8, 37 and 38 are output terminals corresponding to the sensor circuits 17 of the ion sensitive films 29 and 30, respectively. Further, since the reference electrode 31 is integrally incorporated in the sensor device 22,
The reference electrode 31 is directly connected to the ground terminal 15 on the sensor device 22, which is connected to the negative terminal of the battery 25. The ground terminal 15 is the ground terminal of the buffer amplifier of each sensor circuit 17.

The change in the potential of the ion-sensitive film generated in the ion-sensitive part by contacting the measurement solution is transmitted through the platinum layer 11 to the ISFET of the non-inverting input terminal part in the sensor circuit 17 corresponding to each ion-sensitive film. Is transmitted to the device. The power source of each sensor circuit 17 is the sensor device 2
It is supplied by an external power source through each lead wire connected to the second power supply terminal 14 and the ground terminal 15. An output signal from each sensor circuit 17, that is, a sensor detection signal is transmitted to an external measurement circuit via a lead wire connected to each output terminal 37, 38, and Na ions and K in the measurement solution are mixed.
Each concentration of ions is calculated.

As with the ion sensor of the first embodiment, the ion sensor of the above embodiment has a Na sensor of 58.2 mV /
Decade has been obtained, 59.3 mV / decade has been obtained with the K sensor, sensitivity close to the theoretical value can be obtained, and problems such as crosstalk between sensors have not occurred.

In the second embodiment, when the number of ISFET elements is generally n, the number of lead wires required for external extraction is n + 2. Further, when the conventional insulated gate ISFET is used, a drain lead wire and a source lead wire are required for each ISFET. Therefore, in the sensor device 22, one lead wire for the ISFET and one lead wire for the reference electrode are required. Was needed. Therefore, according to the integrated ion sensor of the present invention, the number of lead wires can be significantly reduced.

In the above-mentioned embodiment, the electrolyte component in the solution was used as the object to be measured, but the structure is such that the hydrophobic porous membrane is provided on the upper part of the ion sensitive part so as to hold the various internal solution layers, so that ammonia can be obtained. Similarly, dissolved gas components such as gas or biochemical components such as glucose can be measured by forming an immobilized enzyme membrane instead of the ion-sensitive membrane.

[0041]

As is apparent from the above description, according to the present invention, the dedicated power source for the reference electrode can be omitted and the reference electrode can be operated by a single power source. Therefore, the ion sensor can be downsized,
The number of lead wires for pulling out can be reduced, and the overall size can be made compact. In particular, in an ion sensor having a plurality of ion sensitive films, the integration as a sensor device can be enhanced, and such an effect is remarkably exhibited. Further, since a protective conductive member such as platinum is provided between the ion sensitive film and the gate electrode of the MOSFET provided at the input stage of the signal processing circuit, the gate electrode, etc. due to water molecules that permeate through the ion sensitive film can be provided. Can be prevented, the life of the ion sensor can be extended, and stable and accurate measurement operation can be performed for a long period of time.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of an integrated ion sensor according to the present invention.

FIG. 2 is an electric circuit diagram of an integrated ion sensor.

FIG. 3 is an external perspective view of an integrated ion sensor.

FIG. 4 is a diagram showing a measurement state and a wiring relation of the integrated ion sensor according to the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a reference electrode voltage and a sensor output.

FIG. 6 is a diagram showing an example of measurement results of the integrated ion sensor according to the present invention.

FIG. 7 is a diagram showing an example of measurement results of the integrated ion sensor according to the present invention.

FIG. 8 is an electric circuit diagram showing another embodiment of the integrated ion sensor according to the present invention.

FIG. 9 is a cross-sectional view showing a cross-sectional structure of a sensitive part of an integrated ion sensor of another embodiment.

[Explanation of symbols]

 1 Silicon Substrate 2 CMOS Element 3 ISFET Element 9 Gate Electrode 10a Aluminum Wiring 11 Platinum Layer 12 Polyimide Film 13 Ion Sensitive Film 14 Power Terminal 15 Earth Terminal 16 Output Terminal 17 Sensor Circuit 20 Container 21 Measuring Solution 22 Sensor Device 23 Reference Electrode 25 Battery 26 Voltmeter 29 Ion Sensitive Membrane 30 Ion Sensitive Membrane 31 Reference Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshio Watanabe Yoshio Watanabe 1-280, Higashi Koikekubo, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-60-120240 (JP, A) JP-A-61 -106649 (JP, A) JP 61-155851 (JP, A) JP 62-144059 (JP, A) JP 2-32245 (JP, A) JP 62-185160 (JP, A) ) JP-A-63-210656 (JP, A) JP-A-3-502135 (JP, A)

Claims (10)

(57) [Claims] 1. An at least one ion-sensitive film that detects the concentration of the ions in response to the ions contained in a measurement target, and a detection signal obtained by the ion-sensitive film is input via a conductive member, A predetermined voltage is provided between the signal processing circuit that receives and processes the detection signal via the field effect semiconductor element included in the input stage and the measurement environment created by the measurement target, and the ion sensitive film. A reference electrode that is set in a relationship, and two positive and negative terminals, supply drive power to the signal processing circuit via the two terminals, and one of the two terminals serves as the reference electrode. And at least one of the field effect semiconductor elements of the signal processing circuit, wherein
An integrated ion sensor, wherein the signal processing circuit is set to an active state at a voltage set on the reference electrode by controlling two threshold values. 2. The integrated ion sensor according to claim 1, wherein the ion sensitive film and the signal processing circuit are formed as one semiconductor integrated circuit device, and the reference electrode is formed as a separate member. Integrated ion sensor. 3. The integrated ion sensor according to claim 1, wherein the electric circuit portion including the ion sensitive film and the signal processing circuit and the reference electrode are mounted in the same catheter. Integrated ion sensor. 4. The integrated ion sensor according to claim 3, wherein the ion sensitive film, the signal processing circuit, and the reference electrode are formed as one semiconductor integrated circuit device. Sensor. 5. The integrated ion sensor according to claim 1, wherein the signal processing circuit is composed of a voltage follower circuit. 6. The integrated ion sensor according to claim 1, wherein the signal processing circuit is composed of a non-inverting amplifier circuit. 7. The integrated ion sensor according to claim 1, wherein the conductive member is coated with the ion sensitive film and is connected to a gate electrode of the field effect semiconductor element, a platinum group metal, gold, An integrated ion sensor characterized by being a metal film of one of silver and a silver alloy. 8. The integrated ion sensor according to claim 1, wherein the conductive member is covered with the ion-sensitive film and is connected to a gate electrode of the field-effect semiconductor element, palladium oxide, platinum oxide, An integrated ion sensor characterized by being a metal oxide film of any one of iridium oxides. 9. The integrated ion sensor according to claim 5, wherein the conductive member is coated with the ion sensitive film and is connected to a gate electrode of the field effect semiconductor element, a platinum group metal, gold, An integrated ion sensor characterized by being a metal film of one of silver and a silver alloy. 10. The integrated ion sensor according to claim 6, wherein the conductive member is covered with the ion-sensitive film and is connected to a gate electrode of the field-effect semiconductor element, palladium oxide, platinum oxide, An integrated ion sensor characterized by being a metal oxide film of any one of iridium oxides.