JP2772833B2 - Method for manufacturing ion sensor, method for manufacturing sensor plate, and method for storing these - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion sensor with reduced variation in output characteristics, a method for manufacturing a sensor plate of a component thereof, and a method for storing them.

[Conventional technology]

An ion sensor is used to measure the ion concentration in a sample liquid. An ion-sensitive film is formed on the gate electrode of a field-effect transistor (FET) formed on a semiconductor. Transistor (IS
FET). This ISFET utilizes the fact that when a sample solution is brought into contact with an ion-sensitive membrane, the conductivity near the semiconductor surface changes according to the change in the electric field generated at the interface between the ion-sensitive membrane and the solution. This is to enable detection.

In this ISFET, a separate gate electrode is provided on another insulating substrate, not on the semiconductor substrate on which the FET is formed, an ion-sensitive film is provided on this, and a separate reference electrode is provided opposite to make an independent component. There is also known a so-called isolation gate type ISFET in which a transistor is connected to an FET.

The ion sensitive portion of such an isolation gate type ISFET ion sensor is formed by mounting a so-called printed wiring board in which a copper foil having a thickness of 35 μm is adhered on an insulating substrate, for example, a glass epoxy resin substrate, by a photolithographic method or the like. Etching to the copper conductive pattern of the shape, and then electrolytic plating using a commercially available silver plating bath for thickening, and several μm on the surface
A silver layer having a thickness of about m to 20 μm is formed, and further immersed in a hydrochloric acid solution or a sodium chloride solution and subjected to electrolytic conversion treatment to form a silver chloride layer of several μm on the surface of the silver layer. Next, after forming an embankment body with an insulating resin, for example, an epoxy resin so as to surround an electrode provided with a laminated structure of a silver layer and a silver chloride layer on a surface layer portion, a macrocyclic compound called an ionophore or an ion exchange resin is included. An ion-sensitive membrane was formed, and this structure was proposed in an earlier application.

[Problems to be solved by the invention]

However, an electrode having a laminated structure of a silver layer and a silver chloride layer constituting the above-mentioned ion-sensitive portion and an ion-sensitive film coated thereon are sensitive to moisture, and the variation in characteristics is increased due to moisture absorption. There is. However, conventionally, the process of coating the electrode with the ion-sensitive film in the atmosphere was performed in the air, and the output when used as an ion sensor varies due to the humidity of the work day, the time required for the work, and the like. I was

Also, an ion sensor in which the above-mentioned ion-sensitive part is integrally formed on the same substrate as the FET, or a part consisting of the ion-sensitive part is created as a sensor plate of a component independent of the FET as described above, and used by connecting to the FET etc. In any of these cases, there is a storage time between the production and use of the ion sensor or sensor plate before use.If this storage is performed in the open air, the ion-sensitive membrane absorbs moisture, The characteristics change, and when used as an ion sensor, the output varies.

As described above, due to the manufacturing conditions, storage conditions, and other causes of the ion sensor and its components, when used as an ion sensor, a difference occurs in the output for the same ion concentration. Often no output is available. For this reason, individual ion sensors are used after being calibrated.

In the calibration method, after the ion sensor is connected to the output circuit device, two different predetermined solutions are prepared, the ion sensor is immersed in one ion concentration solution, and the output is read. If the value differs from the predetermined standard value, the circuit constant of the output circuit device is adjusted to match the standard output value. Next, the ion sensor is immersed in a solution having another ion concentration, and the circuit constant is adjusted in the same manner as described above so that the output value matches the standard value corresponding to the ion concentration. Thereafter, the ion sensor is immersed again in the one ion concentration solution, and if the output value is different from the corresponding standard value, the circuit constant is adjusted again in the same manner as above, and the same is performed for the other ion concentration. The calibration is repeated until the output value corresponding to the ion concentration becomes the standard value.

Such a calibration work involves many steps, is cumbersome, requires labor and labor, and is difficult to use as an ion sensor.

An object of the present invention is to provide an ion-sensitive membrane that is controlled to have certain characteristics without being affected by the humidity of the surrounding atmosphere when the ion-sensitive membrane is manufactured, when a product having the ion-sensitive membrane is stored, and when the product is stored. It is an object of the present invention to provide a method for manufacturing an ion sensor, a method for manufacturing a sensor plate, and a method for storing these, which do not require calibration in terms of the hygroscopicity of the membrane.

[Means for solving the problem]

The present invention provides a method for manufacturing an ion sensor in which a field-effect semiconductor can be used to detect a sensitivity value of a sample solution using an electrode coated with an ion-sensitive film, in order to solve the above-described problem. A method of manufacturing an ion sensor, wherein the step of coating the electrode is performed in an atmosphere controlled to a relative humidity of 10% or less, and the method of sealingly storing the ion sensor in an atmosphere having a relative humidity of 10% or less. An object of the present invention is to provide a method for storing an ion sensor.

In addition, a separation gate electrode used for connection with a gate electrode of the field effect semiconductor and an isolation comparison electrode are provided on an insulating substrate separate from the substrate of the field effect semiconductor, and the separation gate electrode is ion-sensitive. A method of manufacturing a sensor plate, comprising providing a membrane as an independent component, wherein the step of coating the electrode with the ion-sensitive membrane is performed in an atmosphere controlled to a relative humidity of 10% or less, and a method of manufacturing the sensor plate. Another object of the present invention is to provide a method for storing a sensor plate, wherein the sensor plate is hermetically stored in an atmosphere having a relative humidity of 10% or less.

[Action]

Since the process of coating the ion-sensitive membrane on the electrode and the storage of the product having the ion-sensitive membrane were performed in a low humidity atmosphere, the influence of moisture on the ion-sensitive membrane during manufacturing, the moisture on the ion-sensitive membrane and the electrode during storage, Can be eliminated and its characteristics can be made constant.

〔Example〕

Next, an embodiment of the present invention will be described based on FIG. 1 and FIG.

The copper foil adhered to the paper polyester substrate 1 is patterned by a photographic method, polished with a 2 μm diamond slurry, and mirrored (surface roughness measured by a stylus film thickness meter (Tencor thin film surface profiler alpha step 200)). 200 nm] to form copper electrodes 1a and 1b having a predetermined shape.

Then using the constant-current power supply and commercial cyanide silver strike plating bath 1 g / content, the copper electrodes 1a, and 1b cathode, a platinum-plated titanium mesh anode, cathode current density is to 0.5A / dm ² The substrate was immersed in a bath for 5 seconds in a state where it was set so as to be taken out, taken out, and washed with water.

Next, the copper electrode 1 was immersed in a commercially available cyan-based electrolytic silver bright plating solution containing 20 g of silver while maintaining the temperature at 50 ° C.
a, 1b as cathode, platinum-plated titanium mesh as anode,
Electrolytic plating at a cathode current density of 12 A / dm ² for 1 minute and 30 seconds
Silver layers 2a and 2b having a thickness of 15 μm were formed on the copper electrodes 1a and 1b, respectively.

Then, in 0.1 N (H) hydrochloric acid (HCl), the above substrate was used as an anode, a platinum-plated titanium mesh electrode was used as a cathode, and electrolysis was performed at an anode current density of 0.23 A / dm ² for 2 minutes and 40 seconds.
Silver chloride layers 3a and 3b were formed on the surfaces of silver layers 2a and 2b.

After forming the embankment body 5 with an insulator of an epoxy resin so as to surround the silver chloride layer 3a and the silver chloride electrode 3b, the embankment body 5 is washed with tetrahydrofuran and pure water, and is vacuumed (−100 ° C.) using a vacuum drier. 760 mmHg) for 20 hours. Thereafter, it was allowed to cool in a desiccator in which dry nitrogen gas had been replaced.

After cooling, a resin solution containing a vinyl chloride-vinyl acetate copolymer is applied on the silver chloride layer 3a in a closed box in which the humidity is kept at 10% or less, and dried to form the ion-sensitive membrane 4. Formed.

The sensor plate was prepared in this manner, and silica gel was enclosed and sealed in an aluminum pack filled with dry nitrogen gas to shut off the sensor plate from the outside air. For this sealing method, an adhesive may be used,
Alternatively, an aluminum pack may be prepared from a composite material in which polyethylene is laminated on aluminum foil, and heat-sealed.

In this way, 80 sensor plates were prepared.
In these sensor plates, the electrode provided with the ion-sensitive film is used as a separation gate, which is connected to the gate electrode of the FET not shown, and the FET is connected to the output circuit device using the potential indicated by the separation comparison electrode as a reference value. Then, by dropping the test liquid on the inner side of the embankment, the concentration of ions contained therein can be measured as the output value of the ion sensor.

Immediately before using the sealed and stored sensor plate, open a solution with potassium ion concentration of 1 mM, 3 mM, 10 mM, and 30 mM on the ion sensor with the circuit formed as described above, measure the output of each, and measure the output value. Is linearly related to the logarithm of the ion concentration. Then the sensor rate
Separated from the FET, the 79 sensor plates were connected in the same manner as described above, and the same measurement was performed for ion sensors using these sensor plates. Of these output values, the output value when a solution having a potassium ion concentration of 10 mM was used as the sample liquid was taken out, statistically processed, and its standard deviation was determined.

Comparative Example In Example 1 described above, after the bank body 5 was formed, it was washed with tetrahydrofuran and pure water, and then dried at 100 ° C. using a dryer.
After drying at normal pressure for 30 minutes, let it cool down overnight in a vacuum desiccator under reduced pressure, and in the air with a relative humidity of 60%, create a sensor plate in the same manner except that an ion-sensitive film was formed. It was left in the air without storing. Eighty of these were prepared and left in the air, and each was measured in the same manner as in the above example to determine the standard deviation of the output values. The results are shown in the table.

[Effects of the Invention] According to the present invention, the step of coating an electrode with an ion-sensitive membrane and the storage of a product having this ion-sensitive membrane are performed at a relative humidity of 10%.
Since it was performed in the following low humidity atmosphere, the influence on the moisture of the ion sensitive membrane can be eliminated, and the influence of the moisture on the electrodes during product storage can be eliminated, and a stable ion sensor that is not affected by the surrounding atmosphere Is obtained. This can reduce the need for calibration.

[Brief description of the drawings]

FIG. 1 is a plan view of a sensor plate according to an embodiment of the present invention,
FIG. 2 is a sectional view taken along the line II-II. In the figure, 1 is a substrate, 2a and 2b are silver layers, 3a and 3b are silver chloride layers,
Denotes an ion-sensitive membrane, and 5 denotes a bank.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-112453 (JP, A) JP-A-54-128791 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 27/414

Claims (4)

(57) [Claims] 1. A method for manufacturing an ion sensor, wherein a sensitivity value of a sample solution can be detected by a field effect type semiconductor using an electrode coated with an ion-sensitive film, wherein the step of coating the electrode with the ion-sensitive film is relatively performed. A method for producing an ion sensor, wherein the method is performed in an atmosphere controlled to a humidity of 10% or less. 2. The ion sensor according to claim 1, wherein the relative humidity is 10%.
%. A method of storing an ion sensor, wherein the ion sensor is hermetically stored in an atmosphere of not more than 0.1%. 3. An isolation substrate provided on an insulating substrate separate from a substrate of a field-effect semiconductor, the isolation gate electrode being used in connection with a gate electrode of the field-effect semiconductor, and an isolation comparison electrode. A method for manufacturing a sensor plate, comprising providing an ion-sensitive film on an electrode and forming an independent component, wherein the step of coating the electrode with the ion-sensitive film is performed in an atmosphere controlled to a relative humidity of 10% or less. Method. 4. The sensor plate according to claim 3, wherein
A method for storing a sensor plate, wherein the sensor plate is sealed and stored in an atmosphere of 10% or less.