JP2575316B2 - Ion sensor, sensor plate and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion sensor which does not require output calibration and has less variation in output characteristics, a sensor plate of the component, and a method of manufacturing these components.

[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 separated gate type ISFET in which the FET and the reference electrode terminal are connected to each other, and the FET and the reference electrode terminal are connected to an output circuit device for use.

The ion sensitive portion of such an isolation gate type ISFET ion sensor is formed by bonding a so-called printed wiring board having a 1.5 to 2 μm thick copper foil adhered on an insulating substrate, for example, a glass epoxy resin substrate, to a photolithographic method or the like. Is etched into a copper conductive pattern having a predetermined shape, and then electrolytic plating is performed using a commercially available silver plating bath for thickening, and a silver layer is formed on the surface to a thickness of about several μm to 20 μm. A silver chloride layer of several μm is formed on the surface of the silver layer by immersing it in a sodium chloride solution and performing electrolytic conversion treatment. Next, after forming an embankment with an insulating resin, for example, an epoxy resin so as to surround an electrode having a laminated structure of a silver layer and a silver chloride layer on a surface layer, ions containing a macrocyclic compound called an ionophore or an ion exchange resin are used. A sensitive film was formed, and this structure was proposed in an earlier application.

[Problems to be solved by the invention]

However, even if the conventional ion sensor is manufactured in the same manner under the same conditions, a difference occurs in the output corresponding to the same ion concentration, and a constant output cannot be obtained despite the constant ion concentration. There are many. 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.

This method has many steps, is troublesome, requires labor and labor, and has low productivity.

An object of the present invention is to provide an ion sensor that can be used without calibrating an output value corresponding to an ion concentration.

[Means for solving the problem]

The present invention provides, in order to solve the above-mentioned problems, an ion sensor in which a sensitivity value of a sample solution by an ion-sensitive film can be detected by a field-effect semiconductor, wherein a surface layer portion of a gate electrode on which the ion-sensitive film is formed is provided. It has a laminated structure of an upper layer mainly composed of silver chloride and a lower layer mainly composed of silver,
An object of the present invention is to provide an ion sensor characterized in that the surface roughness of the silver chloride layer is 200 nm or less. In addition, an isolation gate electrode to be used by being connected to the gate electrode of the field-effect semiconductor on an insulating substrate separate from the substrate of the field-effect semiconductor, and a comparison electrode provided separately from the field-effect semiconductor. A separate comparison electrode to be used in connection with the terminal is provided as an independent component, and the above-mentioned separation gate electrode has an ion-sensitive film and a lower layer mainly composed of silver and a silver chloride as a main component in the surface layer of the lower layer. A sensor plate having a laminated structure in which upper layers are sequentially laminated and the surface roughness of a silver chloride layer is set to 200 nm or less. Also,
An object of the present invention is to provide a method for manufacturing these ion sensors and sensor plates.

FunctionSince the roughness of the layer mainly composed of silver chloride is smoothed to 200 nm or less, the variation in the potential generated between the electrode and the ion-sensitive membrane is reduced, and the variation in the output of the ion sensor is reduced. .

Embodiment Next, an embodiment of the present invention will be described with reference to FIG. 1 and FIG.

Example 1 A copper foil adhered to a paper polyester substrate 1 was polished with a diamond slurry of 2 μm and finished to a mirror surface (surface roughness 200 nm measured by a stylus film thickness meter (Tencor thin film surface profiler Alpha step 200)). ,
Copper electrode 1a of predetermined shape by photolithographic method,
Formed 1b.

Next, using a commercially available cyan-based silver strike plating bath containing 1 g of silver and a constant current power source, the cathode current density was 0.5 A.
The substrate was immersed in a bath for 5 seconds in a state where the substrate was set at / dm ² , taken out, and washed with water. Then 20g of silver
Contains commercially available cyan electrolytic bright plating bath at a temperature of 50 ° C
, And subjected to electrolytic plating at a current density of 12 A / dm ² for 1 minute and 30 seconds to form silver layers 2 a and 2 b having a thickness of 15 μm.

Then, in 0.1 N (H) hydrochloric acid (HCl), the substrate was used as an anode, a platinum-plated titanium mesh was used as a cathode, and electrolysis was performed at an anode current density (0.2 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. The surface roughness was 200 nm as measured by the stylus thickness meter.

The silver chloride layer 3a is coated with an ion-sensitive film 4 containing a vinyl chloride copolymer as a main component, and an insulator of an epoxy resin is formed so as to surround the electrode formed with the ion-sensitive film and the silver chloride electrode 3b. Formed the embankment body 5.

In this way, the silver layers 2a, 2b and the silver chloride layers 3a, 3b are respectively laminated on the copper electrodes 1a, 1b, and the ion-sensitive film 4 is provided on the silver chloride layer 3a, while the silver chloride layer 3b is used as a separation reference electrode. The sensor plate is completed.

In this way, 80 sensor plates were prepared.
In these sensor plates, an electrode provided with an ion-sensitive film is used as a separation gate, and this is connected to a gate electrode of an FET not shown, while a separate comparison electrode is connected to a comparison electrode terminal not shown, and these FETs By connecting the reference electrode terminal to the output circuit device and immersing the sample liquid in the separation reference electrode and the ion-sensitive membrane, the concentration of ions contained therein can be measured as the output value of the ion sensor.

Potassium ion concentration of 1 mM, 3 mM, 10
mM, 30 mM solution was dropped, and the output of each was measured.After confirming that the output value had a linear relationship with the change in ion concentration, the potassium ion concentration of 10 mM was used as the sample solution. The output value of the ion sensor was measured, and then the sensor plate was separated from the FET.Then, in the same manner, 79 sensor plates were connected in the same manner as above, and the same measurement was performed for the ion sensor using these sensor plates. Was. These output values were statistically processed and their standard deviations were determined and are shown in the table.

Example 2 In Example 1, without polishing the copper electrode surface,
A silver electrode is formed and its surface is polished using a 0.5 μm diamond slurry.
After setting the thickness to 7 nm, 80 sensor plates were prepared in the same manner except that the surface roughness measured in the same manner was changed to 80 nm by forming a silver chloride layer. The deviation was determined and the results are shown in the table.

Example 3 In Example 1, without polishing the copper electrode surface,
A silver layer and a silver chloride layer were formed, and the silver chloride layer surface was polished to a surface roughness of 10 nm by polishing in the same manner as in Example 1 except that the copper foil was polished with a 2 μm diamond slurry. In this manner, 80 sensor plates were prepared, and the standard deviation of the output value was obtained for the ion sensor using each of them in the same manner as in Example 1. The results are shown in the table.

Example 4 A 5 μm-thick silver electrode was directly formed on a glass substrate by a sputtering method without using a copper electrode, using a normal glass substrate having a surface roughness of several nm instead of the paper polyester substrate. 80 sensor plates were prepared in the same manner as in Example 1 except that the surface roughness of the electrode was measured to be 7 nm in the same manner as described above, and the surface roughness of the silver chloride layer was measured to be 70 nm in the same manner. The standard deviation of the output value was determined for the ion sensor using each of them in the same manner as in Example 1, and the results are shown in the table.

Comparative Example In Example 1, 80 sensor plates having a silver chloride layer with a surface roughness of 1500 nm were prepared in the same manner as in Example 1 except that the surface of the copper electrode was not polished. The standard deviation of the output value of the ion sensor using is calculated in the same manner as in Example 1, and the results are shown in the table.

In the present invention, the layer mainly composed of silver chloride has a surface roughness of 200 nm or less, more preferably 100 nm or less.

[Effect of the Invention] According to the present invention, it has a laminated structure of a silver layer and a silver chloride layer,
The surface roughness of the silver chloride layer is reduced to an average of 200 nm or less by a surface roughness meter, an ion-sensitive film is provided thereon, and an ion sensor including an FET used as a gate electrode or a separation gate electrode is an ion sensor.
Since the standard deviation of the output value is small and the dispersion is small, there is no need to calibrate with a predetermined ion concentration, and the labor is greatly reduced, so that the productivity can be remarkably improved.

[Brief description of the drawings]

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

Claims (12)

(57) [Claims] 1. An ion sensor in which a sensitivity value of a sample solution by an ion-sensitive film can be detected by a field-effect semiconductor, wherein a surface layer of a gate electrode on which the ion-sensitive film is formed mainly contains silver chloride. It has a laminated structure of an upper layer and a lower layer mainly composed of silver, and the surface roughness of the upper layer is 200 n.
m or less. 2. The ion sensor according to claim 1, wherein the lower layer of the gate electrode on which the ion-sensitive film is formed is a bright plating layer, and the upper layer is an electrolytic conversion treatment layer. 3. An isolation gate electrode used in connection with a gate electrode of the field effect semiconductor on an insulating substrate separate from the substrate of the field effect semiconductor, and provided separately from the field effect semiconductor. A separate reference electrode to be used in connection with the reference electrode terminal is provided as an independent component, and the above-mentioned separation gate electrode has an ionic functional film and a lower layer containing silver as a main component and silver chloride in a surface layer of the lower layer. A sensor plate having a layered structure in which upper layers as main components are sequentially stacked, and having a surface roughness of 200 nm or less. 4. The sensor plate according to claim 3, wherein the upper layer has a surface roughness of 100 nm or less. 5. The sensor plate according to claim 3, wherein the lower layer is a bright plating layer, and the upper layer is an electrolytic conversion treatment layer. 6. A method of manufacturing an ion sensor, wherein a sensitivity value of a sample solution by an ion-sensitive film can be detected by a field-effect semiconductor. Forming a gate electrode, the step of forming the gate electrode, a lower layer mainly composed of silver and a surface layer portion of a laminated structure in which an upper layer mainly composed of silver chloride is laminated on the copper electrode; In addition, at this time, at least one of the copper electrode, the lower layer, and the upper layer is polished to reduce the surface roughness of the upper layer to 200 nm or less. 7. The method according to claim 6, wherein the lower layer of the gate electrode on which the ion-sensitive film is formed is a bright plating layer, and the upper layer is an electrolytic conversion treatment layer. 8. An isolation gate electrode having an ionic functional film to be used by being connected to a gate electrode of the field-effect semiconductor on an insulating substrate separate from the substrate of the field-effect semiconductor; A method for manufacturing a sensor plate which is provided as an independent component by providing a separation reference electrode to be used by being connected to a terminal for a comparison electrode provided separately from the above. A step of forming a gate electrode, wherein the step of forming the separation gate electrode includes a surface layer portion having a laminated structure in which a lower layer mainly composed of silver and an upper layer mainly composed of silver chloride are laminated on a copper electrode; And polishing at least one of the copper electrode, the lower layer and the upper layer at this time, so that the upper layer has a surface roughness of 200 nm or less. 9. The method according to claim 8, wherein the surface roughness of the upper layer is 100 nm or less. 10. The method according to claim 8, wherein the lower layer is a bright plating layer, and the upper layer is an electrolytic conversion treatment layer. 11. A method of manufacturing an ion sensor, wherein a sensitivity value of a sample solution by an ion-sensitive film can be detected by a field-effect semiconductor. Having a forming step,
In the step of forming the gate electrode, a lower layer mainly composed of silver is formed directly on a substrate having a surface roughness of 200 nm or less by a sputtering method, and then the lower layer is subjected to electrolytic conversion treatment to mainly form silver chloride. An upper layer as a component is formed on the lower layer, and the surface roughness of the upper layer is 200 nm or less. 12. An isolation gate electrode having an ion functional film to be used by being connected to a gate electrode of the field effect semiconductor on an insulating substrate separate from the substrate of the field effect semiconductor; A method for manufacturing a sensor plate which is provided as an independent component by providing a separation reference electrode to be used by being connected to a terminal for a comparison electrode provided separately from the above. The method includes the step of forming a gate electrode, and the step of forming the separation gate electrode includes forming a lower layer mainly composed of silver by a direct sputtering method on a substrate having a surface roughness of 200 nm or less, and then forming the lower layer. A method for manufacturing a sensor plate, wherein an upper layer mainly composed of silver chloride is formed on the lower layer by electrolytic conversion treatment, and the surface roughness of the upper layer is set to 200 nm or less.