JPH08327583A - Solid-film type ion sensor and method for stabilizing the same - Google Patents

Abstract

PURPOSE: To reduce the influence of interfering ions for the stabilization of sensor outputs and as to enhance measuring accuracy by providing a water- insoluble material that has higher reactivity to the interfering ions than to ions to be detected, on the surface of or inside a solid sensitive film containing an ion-sensitive material. CONSTITUTION: An Ag lead wire 2 is pressed into an Ag/AgCl-sensitive film 1, and the connection of them is molded with a polyvinyl chloride 3. Next, potassium bromide and iodide ions are dissolved in pure water to prepare an aqueous solution containing bromide ions and iodide ions by 0.1mol/L each, and the sensitive film 1 is immersed in the aqueous solution for about 30 minutes to accumulate, on the surface of the sensitive film 1, a water-insoluble material made up of a bromide and an iodide which have higher reactivity to interfering ions than to ions to be detected. An ion sensor using the sensitive film 1 does not show draft for a solution to be detected that contains the interfering ions, and has little fluctuation in output voltage, so that its measuring accuracy can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid film type ion sensor suitable for detecting various ions in a solution, and a method for using the solid film type ion sensor for measuring a test liquid containing interfering ions. The present invention relates to a stabilizing method for obtaining a stable output.

[0002]

2. Description of the Related Art Conventionally, as an ion sensor for detecting various ions in a solution, a liquid film type ion sensor in which an ion sensitive substance is supported on a polymer support material such as PVC (polyvinyl chloride), or a solid ion sensitive sensor A solid film type ion sensor using a substance is known. For example, as a chlorine ion sensor, a liquid film type sensor in which a sensitive substance such as a quaternary ammonium salt which is an ion exchanger is supported on PVC together with a plasticizer, or a solid film type sensor in which AgCl (silver chloride) is a sensitive substance is used. A sensor is typical. The detection principle of these sensors is to measure the interfacial potential difference due to the dissociation equilibrium reaction of the detection target ions at the interface between the sensitive film and the test liquid. Here, an example of a conventional solid film type chlorine ion sensor is shown in FIG. In FIG. 12, an Ag lead wire 2 is press-fitted into a predetermined hole provided in the Ag / AgCl sensitive film 1, and a connecting portion between the two is molded with polyvinyl chloride 3.

In the measurement using these ion sensors, when there are interfering ions other than the detection target ions in the test liquid, a dissociation equilibrium reaction of the interfering ions simultaneously occurs at the interface between the sensitive film and the test liquid. , Its effects cannot be avoided altogether. However, in the case of the liquid film type chlorine ion sensor described above, Analytical Chemistry, 41, 5 (199
2) or Analytical Chemistry, 42, 77 (1993), by selecting a sensitizer or a plasticizer,
The selectivity of target ions for detection with respect to interfering ions can be improved to some extent.

However, since AgCl, which is a sensitizer of a solid film type sensor, has a higher reactivity with Br ⁻ and I ⁻ which are halogen ions of the same family than Cl ⁻ , these ions are contained in the test solution. In that case, the output potential becomes unstable and the measurement accuracy decreases. For example, when the solid-film sensor is clinically applied to the measurement of Cl ⁻ concentration in blood, when a patient takes a sedative containing Br ⁻ , the Br ⁻ in blood is temporarily increased.
^- to produce hinder the measurement of the concentration, in particular Br ^{- -} concentration rises Cl has been desired to improve the selectivity for.

As one type of solid film type ion sensor, there is known a solid film type FET ion sensor having an FET as a means for converting an interface potential difference between a solid sensitive film and a test liquid into an electric signal. In this solid film type FET ion sensor, the method of forming a sensitive film on a minute sensitive gate portion poses a problem. Conventionally, a vapor deposition method, a sputtering method, an electrolytic polymerization method or the like, which has good compatibility with the device manufacturing process, has been used.

[0006] For example, the inventors of the present invention disclosed in Japanese Patent Laid-Open No. 62-75.
No. 250 disclosed a method of vapor-depositing an Ag film and then electrolytically chlorinating the surface of the Ag film in order to realize a FET chlorine ion sensor. That is, as shown in FIG.
Vapor deposition Ag film 11 and electrolytic chloride AgCl on the sensitive gate section
The film 12 is formed.

Also, Sensors & Actuat
Ors, 9 (1986) 179-197, one purpose is to realize a FET ion sensor and a FET reference electrode, and an Ag film and an AgCl film are sequentially deposited on a Si substrate to form a micro chlorine electrode having a laminated structure. A method of forming the is proposed. That is, as shown in FIG. 14, the vapor deposition Ag film 11 and the vapor deposition AgCl film 13 are formed in the sensitive gate portion.

The FET ion sensor manufactured by these methods is manufactured in order to form the sensitive film by using the vapor deposition device used in the manufacturing process of the element (a) such as formation of the source / drain electrodes as described above. In addition to good compatibility with the process, there are advantages that (b) the controllability of the film thickness of the sensitive film is good, and (c) the response film can be expected to have an improved response speed by thinning the sensitive film.

However, when the film thickness of the sensitive film is thin as in these conventional FET ion sensors, the ion sensitive material is dissolved in the test solution or the storage solution, and the sensor sensitivity is gradually lowered. The problem occurs that the sensor deteriorates in about a month. Therefore, it is conceivable to increase the thickness of the vapor deposition film in order to extend the life of the sensor.
10 to form a solid sensitive film having a thickness of about m by a vapor deposition method
It takes about a long time. Moreover, if the film thickness is increased, the adhesion between the film and the sensor base tends to decrease,
There is also a problem that the film is easily peeled off.

[0010]

As described above, in the conventional solid film type ion sensor, if interfering ions other than the detection target ions are present in the test liquid, the output becomes unstable and the measurement accuracy becomes low. There was a problem of lowering. In addition, a solid film type FET which is a kind of solid film type ion sensor
In ion sensors, vapor deposition and electrolysis have been tried as a method of forming a sensitive film, but since a sensitive film having a sufficient film thickness cannot be obtained, the sensitive component is likely to be eluted into the solution and the sensitivity is likely to be lowered. There was a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a solid film type ion sensor having excellent output stability and long life even when interfering ions are present in a test solution. And

[0012]

The solid film type ion sensor of the present invention is a solid film type ion sensor provided with a solid sensitive film containing an ion sensitive substance, and the solid purpose type ion sensor has a detection object on the surface or inside of the solid sensitive film. It is characterized in that a poorly water-soluble substance having a higher reactivity with an interfering ion than an ion is present.

Further, the solid film type ion sensor of the present invention is
A solid sensitive film containing an ion sensitive substance, and an FET for converting an interface potential difference between the solid sensitive film and a test liquid into an electric signal
In the solid film type ion sensor including the above, the solid sensitive film is fixed to the gate portion of the FET via a non-conductive adhesive. Also in such a so-called solid film type FET ion sensor, it is effective to allow a hardly water-soluble substance having higher reactivity with interfering ions than the detection target ions to exist on the surface or inside of the solid sensitive film.

Further, according to the method for stabilizing a solid film type ion sensor of the present invention, the solid sensitive film constituting the solid film type ion sensor as described above is immersed in an aqueous solution containing interfering ions and detected on the surface thereof. Characterized by forming a poorly water-soluble substance that has a higher reactivity with interfering ions than the target ion, or by including a poorly water-soluble substance that has a higher reactivity with the interfering ions than the detection target ion in the solid sensitive film. It is what

It is also possible to use a method of vapor-depositing or sputtering a poorly water-soluble substance on the surface of the sensitive film.
In the present invention, the poorly water-soluble substance is not particularly limited as long as it satisfies the condition that it has a higher reactivity with the interfering ion than the detection target ion, and may be a poorly water-soluble salt of the interfering ion. Other poorly water-soluble salts may be used. Further, in the solid film type FET ion sensor of the present invention, the material of the non-conductive adhesive used for fixing the solid sensitive film to the gate portion of the FET is not particularly limited.

[0016]

When used in the solid film type ion sensor of the present invention, by interfering the reaction site of the interfering ion on the surface or inside of the solid sensitive film with a poorly water-soluble substance having a high reactivity with the interfering ion, the interfering ion can be obtained. It is possible to stabilize the sensor output by reducing the influence of, and improve the measurement accuracy.

Further, according to the solid film type FET ion sensor of the present invention, a solid film having a sufficient film thickness can be obtained by a simple means of fixing the solid sensitive film to the gate portion of the FET via a non-conductive adhesive. Since a sensitive membrane can be used,
Even if the ion sensitive substance is gradually dissolved in the solution, a sufficient sensitive substance is secured as a reservoir, and high sensor sensitivity can be maintained for a long period of time. Moreover, the sensor characteristics such as sensitivity and response characteristics are not adversely affected even though the non-conductive adhesive is interposed to fix the solid sensitive film to the gate portion of the FET. Further, also in the solid film type FET ion sensor, if a hardly water-soluble substance is present on the surface or inside of the solid sensitive film, the influence of interfering ions can be reduced and the sensor output can be stabilized to improve the measurement accuracy. You can

[0018]

Embodiments of the present invention will be described below. In the following examples, solid film type chlorine ion sensors will be described, and bromine ions and iodine ions are assumed as interfering ions.

Example 1 FIG. 1 shows the structure of a solid film type chlorine ion sensor in this example. In FIG. 1, an Ag lead wire 2 is press-fitted into a predetermined hole provided in an Ag / AgCl sensitive film 1, and a connecting portion between the two is molded with polyvinyl chloride 3. Further, a poorly water-soluble substance 4 having high reactivity with interfering ions is formed on the exposed surface of the Ag / AgCl sensitive film 1.

This solid film type chloride ion sensor was manufactured as follows. First, A formed by pressure molding
Ag / A by slicing and polishing g / AgCl
A gCl sensitive film 1 was prepared. After making a predetermined hole in this Ag / AgCl sensitive film 1 and press-fitting the Ag lead wire 2, the connection between both was molded with polyvinyl chloride 3. Also,
Potassium bromide and potassium iodide were dissolved in pure water to prepare an aqueous solution containing bromine ion and iodine ion in an amount of 0.1 mol / L each. This aqueous solution was placed in a beaker, and the Ag / AgCl sensitive film 1 was immersed for 30 minutes while stirring with a stirrer to perform surface treatment. A after surface treatment
Yellow-green deposits were formed on the surface of the g / AgCl sensitive film 1. From the result of elemental analysis, this deposit was confirmed to be bromide and iodide which are poorly water-soluble substances.

On the other hand, for comparison, A as shown in FIG.
A conventional solid film type chloride ion sensor (Comparative Example 1) in which a hardly water-soluble substance does not exist on the surface or inside of the g / AgCl sensitive film 1 was prepared.

Using the solid film type chloride ion sensor of Example 1, chloride ion was measured at a liquid temperature of 37 ° C. for a solution of [Cl ⁻ ] = 10 ⁻⁵ to 10 ⁻¹ mol / L to examine a sensitivity characteristic curve. The results are shown in FIG. As shown in FIG. 2, this sensitivity characteristic curve shows [Cl ⁻ ] = 10 ⁻⁴ to 10 ⁻¹ mol /
Shows linearity in the L concentration range and has a slope sensitivity of 51 mV
Was / dec. It was confirmed that this sensitivity characteristic is equivalent to that of the solid film type chlorine ion sensor of Comparative Example 1, and that the sensitivity characteristic is not deteriorated by the surface treatment of the sensitive film.

Next, using the solid film type chlorine ion sensors of Comparative Example 1 and Example 1, the chlorine ion concentration was 1 in both cases.
11.0 mmol / L, but (1) a test liquid containing no interfering ions, (2) bromine ions as an interfering ion of 0.
3 of a test solution containing 1 mmol / L and (3) a test solution containing 0.1 mmol / L of iodine ion as an interfering ion
The response curve to the test liquid of each species was continuously measured. The measurement was carried out 5 times for the test liquid of (1), 5 times for the test liquid of (2),
The test liquid of (3) was repeated in the order of 5 times, and the sensor was immersed in the calibration liquid (N) having a Cl ⁻ concentration of 100 mmol / L during each measurement. These response curves are shown in FIGS. 3 and 4.

As shown in FIG. 3, when the solid film type chlorine ion sensor of Comparative Example 1 was used, an output drift appeared with respect to the test liquid containing interfering ions, and particularly iodine ions were contained. The output drift with respect to the test liquid is extremely remarkable. Further, it can be seen that the output voltage value greatly fluctuates with respect to the test liquid containing the interfering ions, and is greatly affected by the interfering ions.

On the other hand, as shown in FIG. 4, when the solid film type chlorine ion sensor of Example 1 is used,
It can be seen that no output drift was observed with respect to the test liquid containing interfering ions, and the fluctuation of the output voltage value was small.

Further, regarding the solid film type chlorine ion sensors of Comparative Example 1 and Example 1, the selection coefficient (K _{Cl, X} ) is set as follows as a scale showing the influence of interfering ions, based on the evaluation result of the above response characteristics. It was obtained by a method such as. First,
Based on the measurement results of 5 times for each test liquid of (1) to (3), the average concentration of chlorine ions for each test liquid of (1) to (3) is obtained. Next, the difference between the two is obtained by subtracting the average concentration in the case of (1) not containing the interfering ions from the average concentration in the case of (2) or (3) containing the interfering ions (X). A value obtained by dividing the difference in average concentration obtained as described above by the concentration of interfering ions is used as the selection coefficient. The values of the selection coefficient thus obtained are shown in Table 1 below. From these results, it can be seen that in Example 1 in which the sensitive film is surface-treated, the selection coefficient is improved by about one digit as compared with Comparative Example 1, and the influence of interfering ions can be significantly reduced.

[0027] Example 2 FIG. 5 shows a solid film type chlorine ion sensor in this example. In FIG. 5, the Ag lead wire 2 is press-fitted into a predetermined hole provided in the Ag / AgCl sensitive film 5 containing silver bromide and silver iodide as poorly water-soluble substances, and the connection between both is made of polyvinyl chloride. It is molded with.

The solid film type chloride ion sensor was manufactured as follows. First, after mixing silver bromide and silver iodide as a poorly water-soluble salt with silver bromide and silver iodide, a molded body formed by pressure molding is sliced and polished to obtain Ag / containing a slightly water-soluble salt of interfering ions. AgCl sensitive film 5
Was produced. After making a predetermined hole in this Ag / AgCl sensitive film 5 and press-fitting the Ag lead wire 2, the connection between both was molded with polyvinyl chloride 3.

Using the solid film type chlorine ion sensor of Example 2, chlorine ion was measured at a liquid temperature of 37 ° C. for a solution of [Cl ⁻ ] = 10 ⁻⁵ to 10 ⁻¹ mol / L to examine the sensitivity characteristic curve. As a result, similar results to those in FIG. 2 were obtained. This sensitivity characteristic curve shows linearity in the concentration range of [Cl ⁻ ] = 10 ⁻⁴ to 10 ⁻¹ mol / L, and the slope sensitivity is 50 mV / d.
It was ec. This sensitivity characteristic is equivalent to that of the solid film type chlorine ion sensor of Comparative Example 1, and it was confirmed that the sensitivity characteristic is not deteriorated even if a poorly water-soluble salt is contained in the sensitive film.

Next, using the solid-film type chlorine ion sensor of Example 2, (1) a test liquid containing no interfering ions, and (2) bromine ion 0 as interfering ions, in exactly the same manner as in Example 1. 0.1 mmol / L of test liquid, and (3) test liquid containing iodine ion 0.1 mmol / L as interfering ions (all have chloride ion concentrations of 11
The response curve to (1.0 mmol / L) was continuously measured. This response curve is shown in FIG. As shown in FIG. 6, even when the solid film type chlorine ion sensor of Example 2 was used, no output drift was observed with respect to the test liquid containing interfering ions, and the fluctuation of the output voltage value was small. I understand.

Further, the results of _{obtaining the} selection coefficient (K _{Cl, X} ) for the solid film type chlorine ion sensor of Example 2 by the same method as in Example 1 are shown in Table 2 below. From these results, it can be seen that even in Example 2 in which the sensitive film contains a poorly water-soluble salt, the selectivity coefficient is improved by about one digit as compared with Comparative Example 1, and the influence of interfering ions can be significantly reduced.

[0032] Example 3 FIG. 7 shows the structure of a solid film type FET chlorine ion sensor in this example. This solid film type FET chlorine ion sensor is a rear gate type ISFE in which a signal extraction electrode and a sensitive gate portion are separately formed on the front and back surfaces of a wafer.
T (Ion Sensitive Field Eff)
ect Transistor: ion sensitive field effect transistor). In FIG. 7, the first silicon substrate 21 and the second silicon substrate 22 are the SiO ₂ film 23.
It is adhered to each other by sandwiching. These silicon substrates 21 and 22 are etched into a predetermined shape. S between the second silicon substrate 22 and the first silicon substrate 21
The portion completely removed to reach the iO ₂ film 23 becomes the sensitive gate portion. The source is on the first silicon substrate 21,
Drain regions 24 and 25 are formed. A portion of the first silicon substrate 21 between these source / drain regions 24 and 25 becomes a channel region 26. A SiN _x film 28 is formed on the exposed surfaces of the first and second silicon substrates 21 and 22 including the sensitive gate portion via a SiO ₂ film 27. Signal extraction electrodes 29 and 30 are formed on the first silicon substrate 21 through contact holes formed in the SiO ₂ film 27 and the SiN _x film 28 formed on the surface opposite to the sensitive gate portion. . In addition, the sensitive gate is provided with an epoxy resin 31 with a thickness of about 200 μm.
The g / AgCl sensitive film 32 is adhered.

Using the solid film type FET chlorine ion sensor of Example 3, chlorine ion was measured at a liquid temperature of 37 ° C. for a solution of [Cl ⁻ ] = 10 ⁻⁵ to 10 ⁻¹ mol / L, and a sensitivity characteristic curve was obtained. Was examined, the result similar to that of FIG. 2 was obtained. This sensitivity characteristic curve is [Cl ⁻ ] = 10 ⁻⁴ to 10 ⁻¹ m
Shows linearity in the concentration range of ol / L and has a slope sensitivity of 5
It was 1 mV / dec. This sensitivity characteristic is the solid film type F of FIG. 13 having an electrolytic chloride AgCl film on the surface of a vapor deposited Ag film.
It was equivalent to the ET chlorine ion sensor (Comparative Example 2) or the solid film type FET chlorine ion sensor of FIG. 14 (Comparative Example 3) having the vapor deposited AgCl film on the vapor deposited Ag film. As described above, it was confirmed that the sensor of this example exhibits a good sensitivity characteristic despite the structure in which the non-conductive epoxy adhesive is interposed between the gate insulating film and the ion sensitive film. It was

Next, using the solid film type FET chlorine ion sensor of the present embodiment, the measurement for two test liquids having [Cl ⁻ ] concentrations of 10 ⁻³ mol / L and 10 ⁻² mol / L was continuously performed. FIG. 8 shows the response characteristics in the case of performing the same. As is clear from this figure, the sensor of this embodiment has a thickness of 200 μm.
95% despite using a thick sensitive film
It was confirmed that the response time was within 1 second, and high-speed response could be realized. The response speed was also equal to that of the sensors of Comparative Example 2 and Comparative Example 3.

Further, in the sensors of Comparative Example 2 and Example 3, the [Cl ⁻ ] concentration was 10 ⁻³ mol / every few days.
The slope sensitivity was measured using two test liquids of L and 10 ^-2 mol / L, and the lifetime was evaluated by examining the change over time. The result is shown in FIG. In the case of Comparative Example 2, the sensor sensitivity gradually decreased and the sensor deteriorated in about one month. This is probably because the sensitive component of the sensitive membrane was dissolved in the test solution or the storage solution. On the other hand, in the sensor of Example 3, the sensitivity was hardly decreased even after the lapse of 3 months, and the sensor had a long life. This is considered to be due to the fact that even if the sensitive component of the sensitive membrane is dissolved in the test liquid or the preservative liquid, a sufficient sensitive substance is secured as a reservoir. It should be noted that although a slight decrease in sensitivity is observed in the initial stage, the sensor sensitivity fluctuates little after that, indicating that stable sensitivity is maintained.
It is considered that this is because the sensitive substance is sufficiently uniformly distributed in the sensitive film.

Embodiment 4 FIG. 10 shows the structure of the solid film type FET chlorine ion sensor of this embodiment. This sensor is the same as Example 3 shown in FIG. 7, except that the slightly water-soluble substance 33 is formed on the surface of the sensitive film 32.
It has the same structure as the sensor of. The sensor of this embodiment is
The ion-sensitive membrane of the sensor of Example 3 shown in FIG. 7 was prepared by immersing the ion-sensitive membrane in an aqueous solution containing 0.1 mol / L each of bromine ion and iodine ion for 30 minutes for surface treatment.

The sensor of this embodiment has almost the same sensor characteristics as the sensor of the third embodiment, and [Cl ⁻ ] = 10 ^{−4 -10.}
-Slope sensitivity in the concentration range of ^-1 mol / L is 51 mV /
dec, 95% response time was within 1 second, and there was almost no deterioration in sensitivity even after 3 months, and the life was long.

Next, using the sensors of Comparative Example 2 and Example 4 and in exactly the same manner as in Example 1, (1) a test liquid containing no interfering ions, (2) bromine ions (Br) as interfering ions. ^-) the sample liquid containing 0.1 mmol / L, and (3) iodide ions as an interfering ion ^(I -) 0.1 mm
When the response curves to three types of test solutions containing ol / L (all have chloride ion concentrations of 111.0 mmol / L) were continuously measured, the response curves similar to those in FIGS. 3 and 4 were obtained. was gotten. Furthermore, Table 3 below shows the results of obtaining the selection coefficients for the sensors of Comparative Example 2 and Example 4 by the same method as in Example 1. From these results, the solid film type FET chlorine ion sensor of Example 4 in which the poorly water-soluble substance was formed on the surface of the sensitive film had a selectivity coefficient improved by about an order of magnitude as compared with that of Comparative Example 2, and the interfering ions were It can be seen that the effect of can be significantly reduced.

[0039] Example 5 FIG. 11 shows the structure of a solid film type FET chlorine ion sensor of this example. This sensor has the same structure as the sensor of Example 3 shown in FIG. 7, except that the Ag / AgCl sensitive film 34 containing the hardly water-soluble substances silver bromide and silver iodide was used.

The sensor of this example has almost the same sensor characteristics as the sensor of Example 3, and [Cl ⁻ ] = 10 ⁻⁴ to 10 ⁻¹⁰
-Slope sensitivity is 50 mV / in the concentration range of ^-1 mol / L
dec, 95% response time was within 1 second, and there was almost no deterioration in sensitivity even after 3 months, and the life was long.

Next, using the sensor of Example 5, Example 1
In exactly the same manner as in (1) the test liquid containing no interfering ions, (2) the bromine ion (Br ⁻ ) 0.
Three types of test liquids (all having a chloride ion concentration of 11), a test liquid containing 1 mmol / L and (3) a test liquid containing iodine ion (I ⁻ ) 0.1 mmol / L as interfering ions.
When the response curve to 1.0 mmol / L) was continuously measured, a response curve similar to that in FIG. 6 was obtained. Furthermore, Table 4 below shows the results of obtaining the selection coefficient for the sensor of Example 5 by the same method as in Example 1. From this result, the selection coefficient of the solid film type FET chlorine ion sensor of Example 5 using the sensitive film containing the poorly water-soluble substance was improved by about one digit as compared with that of Comparative Example 2, and the interfering ions It can be seen that the effect of can be significantly reduced.

[0042] In addition, in the above-mentioned Examples 3 to 5, the rear gate type ISFET in which the signal extraction electrode and the sensitive gate portion are separately formed on the front and back surfaces of the wafer has been described, but the present invention is also applied to the ISFET having other structures. Of course, it can be applied.

[0043]

As described above in detail, according to the present invention, it is possible to provide a solid film type ion sensor having excellent output stability even when interfering ions are present in a test liquid and having a long life. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a solid film type chloride ion sensor of Example 1.

FIG. 2 is a diagram showing a sensitivity characteristic curve of chlorine ion measured by using the solid film type chlorine ion sensor of Example 1.

FIG. 3 is a diagram showing a response curve to a test liquid containing interfering ions, which is measured using the solid film type chloride ion sensor of Comparative Example 1.

FIG. 4 is a diagram showing a response curve to a test liquid containing interfering ions, which is measured using the solid film type chloride ion sensor of Example 1.

FIG. 5 is a cross-sectional view of a solid film type chloride ion sensor of Example 2.

FIG. 6 is a view showing a response curve to a test liquid containing interfering ions, which is measured by using the solid film type chloride ion sensor of Example 2;

FIG. 7 is a cross-sectional view showing the structure of a solid film type FET chlorine ion sensor of Example 3.

8 is a solid-state FET chlorine ion sensor of Example 3 with [Cl ⁻ ] concentration of 10 ⁻³ mol / L and 10 ^−2.
The figure which shows the response characteristic at the time of measuring continuously about two to-be-tested liquids which are mol / L.

FIG. 9 is a diagram showing a change in sensitivity with time for solid film type FET chlorine ion sensors of Example 3 and Comparative Example 2.

FIG. 10 is a cross-sectional view showing the structure of a solid film type FET chlorine ion sensor of Example 4.

FIG. 11 is a cross-sectional view showing the structure of a solid film type FET chlorine ion sensor of Example 5.

FIG. 12 is a cross-sectional view showing the structure of a solid film type chloride ion sensor of Comparative Example 1.

FIG. 13 is a cross-sectional view showing the structure of a solid film type FET chlorine ion sensor of Comparative Example 2.

14 is a cross-sectional view showing the structure of a solid film type FET chlorine ion sensor of Comparative Example 3. FIG.

[Explanation of symbols]

1 ... Ag / AgCl sensitive film, 2 ... Ag lead wire, 3 ... Polyvinyl chloride, 4 ... Slightly water-soluble substance, 5 ... Ag / AgCl sensitive film containing silver bromide and silver iodide, 11 ... Evaporated Ag
Film, 12 ... Electrolytic chlorinated AgCl film, 13 ... Evaporated AgCl
Film, 21 ... First silicon substrate, 22 ... Second silicon substrate, 23 ... SiO ₂ film, 24 ... Source region, 25 ... Drain region, 26 ... Channel region, 27 ... SiO ₂ film,
28 ... SiN _x film, 29, 30 ... Signal extraction electrode, 3
1 ... Epoxy resin, 32 ... Ag / AgCl sensitive film, 33
... Slightly water-soluble substance, 34 ... Ag / AgCl sensitive film containing silver bromide and silver iodide.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromitsu Tokunaga 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock company Toshiba Nasu factory (72) Inventor Wakako Shinaga 1385-1 Shimoishi, Otawara, Tochigi Company Toshiba Nasu Factory

Claims (7)

[Claims] 1. A solid film type ion sensor comprising a solid sensitive film containing an ion sensitive substance, wherein the surface or the interior of the solid sensitive film is highly water-reactive and has a higher reactivity with an interfering ion than a target ion for detection. A solid film type ion sensor characterized by the presence of a substance. 2. A method for stabilizing the output of a solid film type ion sensor equipped with a solid sensitive film containing an ion sensitive substance, comprising immersing the solid sensitive film in an aqueous solution containing interfering ions, the method comprising: A method for stabilizing a solid film type ion sensor, comprising forming a hardly water-soluble substance having a higher reactivity with an interfering ion than a target ion on a surface. 3. A method for stabilizing the output of a solid film type ion sensor comprising a solid sensitive film containing an ion sensitive substance, comprising a reactivity with an interfering ion rather than a detection target ion in the solid sensitive film. A method for stabilizing a solid film type ion sensor, which comprises containing a poorly water-soluble substance having a high content. 4. A solid film type ion sensor comprising a solid sensitive film containing an ion sensitive substance and an FET for converting an interface potential difference between the solid sensitive film and a test liquid into an electric signal. Is fixed to the gate portion of the FET via a non-conductive adhesive agent, a solid film type ion sensor. 5. The solid film type ion according to claim 4, wherein a poorly water-soluble substance having a higher reactivity with an interfering ion than a detection target ion is present on the surface or inside of the solid sensitive film. Sensor. 6. A solid sensitive film containing an ion sensitive substance, and a FET for converting an interface potential difference between the solid sensitive film and a test liquid into an electric signal, wherein the solid sensitive film is the F
A method for stabilizing the output of a solid film type ion sensor fixed to a gate portion of an ET via a non-conductive adhesive, comprising immersing the solid sensitive film in an aqueous solution containing interfering ions, A method for stabilizing a solid film type ion sensor, which comprises forming a hardly water-soluble substance having a higher reactivity with an interfering ion than a target ion. 7. A solid sensitive film containing an ion sensitive substance, and a FET for converting an interfacial potential difference between the solid sensitive film and a test liquid into an electric signal, wherein the solid sensitive film is the F
A method for stabilizing the output of a solid film type ion sensor fixed to a gate portion of an ET via a non-conductive adhesive, which has higher reactivity with interfering ions than detection target ions in the solid sensitive film. A method for stabilizing a solid film type ion sensor, characterized by containing a poorly water-soluble substance.