JPH02240556A - Oxygen electrode - Google Patents

Abstract

PURPOSE:To allow easy and sure production of the oxygen electrode and to greatly improve the yield right after production and the reproducibility of electrode outputs by using a high-polymer electrolyte as an electrolyte. CONSTITUTION:A platinum cathode electrode 2, a silver anode electrode 3, an electrolyte film [poly-(4-vinyl-ethyl pyridinium bromide)] 4, and an oxygen permeable membrane 5 are formed on a glass substrate 1. The internal electrolyte 4 indispensable for the operation of the oxygen electrode is constituted by forming the layer thereof in a dry state in the production stage and the electrolyte 4 layer exists in the uniform dry state as well even at the time of the production of the film 5 in succession thereto; therefore, the solvent is evenly removed from the soln. prepd. by dissolving the membrane 5 material. The formed membrane 5, therefore, has no defects, such as pinholes, and the fraction defective of the oxygen electrode occurring therein is lowered. Since the thickness of the membrane 5 is controlled to a specified value, the specified oxygen electrode output is obtd. and the output reproducibility is improved. The oxygen electrode having excellent quality as the sensor is thus obtd.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a small oxygen electrode, and an object of the present invention is to provide an oxygen electrode in which the electrolyte and oxygen permeable membrane of the oxygen electrode are stably formed and the yield is improved. In an oxygen electrode having two electrodes serving as a cathode and an anode provided in the electrolyte and an oxygen permeable membrane covering the electrolyte, the oxygen electrode is configured using a polymer electrolyte as the electrolyte.

[Industrial application field]

The present invention relates to an oxygen electrode, and particularly to an oxygen electrode using a polymer electrolyte as an electrolyte material filled inside the oxygen electrode.

The oxygen electrode in the present invention is one of the electrode devices for measuring the dissolved oxygen concentration in an aqueous solution, and can be directly applied to environmental chemical measurement, brewing industry, food industry, clinical testing, etc. It can be applied as a component of a biosensor that takes advantage of its selectivity. In the latter case, by immobilizing enzymes or microorganisms on the tip of an oxygen electrode, a sensor can be obtained that can selectively detect substances that the immobilized enzymes or microorganisms react with or assimilate.

[Conventional technology]

The present inventors have disclosed a method of forming a small oxygen electrode using photolithography and anisotropic etching of a semiconductor substrate. (JP-A-63-238548, etc.) The oxygen electrode of JP-A-63-238548 is shown in FIGS. 3 and 4.

FIG. 4 is a sectional view taken along the line ■-■ of the small oxygen electrode shown in FIG. 3. The oxygen electrode shown in FIG. Parts of poles 33A and 33B are exposed on the substrate surface for connection to a device.

The structure of the small oxygen bridge in Fig. 3 is II-II fi
As shown in FIG. 4, which is a cross-sectional view along Furthermore, the back surface of the substrate is covered with a hydrophobic insulating film 37 that is hard to tear. silicon substrate 31
A cathode 33A and an anode 33B are fitted in pairs in the holes. As shown in FIG. 3, a portion of each of the cathode 33A and the anode 33B extends to the surface of the silicon substrate outside the groove (hole). Further, the holes in the silicon group vi31 are filled with an electrolyte-containing porous material, an electrolyte-containing gel, or a liquid electrolyte electrolyte 36.

The upper part of the hole is covered with a gas permeable film 38 so as to cover the entire upper part of the substrate 31 (excluding the exposed part in FIG. 3).

In recent years, with the miniaturization of various sensors, #element electrodes have been miniaturized. In miniaturizing the oxygen electrode, it is important to stably form the oxygen permeable membrane and the electrode interior 1 (TH, electrolyte).

The influence of the oxygen permeable membrane on the characteristics of the oxygen electrode is particularly large. Conventional oxygen permeable membranes mainly use fluorine-based resins, but fluorine-based resins have poor adhesion and processability, making it extremely difficult to fabricate small oxygen electrodes.

For this purpose, a resin solution of an oxygen permeable membrane forming material is applied onto an electrolyte-containing gel, an electrolyte-containing porous material, or a liquid electrolyte (a solution or an electrode internal solution held in a cohesive carrier), and the solvent is removed. As a result, an oxygen permeable film was formed. (Unexamined Japanese Patent Publication No. 63-238548, etc.) [Problems to be Solved by the Invention] However, - Most of the oxygen permeable membrane materials for boat fishing are soluble in solvents, and internal electrolyte solutions (mainly aqueous solutions) When the organic solvent is removed under conditions where (electrolyte-containing gel, electrolyte-containing porous substance, or liquid electrolyte) is present nearby,
Since evaporation of the organic solvent is hindered or non-uniform drying progresses, the formed oxygen permeable membrane tends to be incomplete. This has led to failure of the oxygen electrode due to membrane destruction or low F reproducibility of electrode output.

Another possible method is to form an internal electrolyte in a dry state and form an oxygen permeable membrane thereon, but if a low molecular weight electrolyte such as an inorganic salt is used as the internal electrolyte, an inhomogeneous electrolyte layer will be formed due to crystallization. This also led to a decrease in the reproducibility of the electrode output.

The present invention seeks to provide a novel compact oxygen bridge that overcomes the above-mentioned problems.

[Means to solve the problem]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive studies on materials that can form an internal electrolyte layer without stable layer separation, and have found that they are polymeric substances, and that they can further dissociate into ions in water and form an electrolyte. Become. We have discovered that so-called polymer electrolyte materials can be used.

The present invention provides an oxygen electrode having an electrolyte, two electrodes provided in the electrolyte serving as a cathode and an anode, and an oxygen permeable membrane covering the electrolyte, which uses a polymer electrolyte as the electrolyte. achieved.

The above oxygen electrode is placed on the substrate as a cathode and an anode.
a step of forming a regular electrode pattern, a step of forming a polymer electrolyte film covering at least two electrode patterns, which will become the cathode and an anode, on the substrate, and a step of forming the polymer electrolyte film on the substrate. It can be manufactured by a method including a step of forming a covering oxygen permeable membrane.

The above polymer electrolyte membrane can be formed by applying and drying a solution of a polymer electrolyte forming material.

A solution containing a polyhydric alcohol can be used as the polymer electrolyte solution.

The oxygen permeable membrane can be formed by applying and drying a solution of an oxygen permeable membrane forming material onto a substrate on which the polymer electrolyte membrane is formed. In this case, the polymer electrolyte membrane needs to be insoluble in the solution or solvent of the oxygen permeable membrane forming material.

Polymer electrolyte materials are generally in an amorphous state in a dry state,
Many of them exist in a so-called glass state, making it possible to form a homogeneous film. Therefore, a complete oxygen permeable membrane can be obtained by forming a homogeneous polymer electrolyte solution layer, thoroughly drying it, applying a solution of the oxygen permeable membrane material thereon and drying it. Therefore, it becomes possible to operate stably as an oxygen electrode. In order for the internal electrolyte to function effectively, the presence of moisture is required. , it is possible to inject moisture into the interior as steam from the outside.

Polymer electrolytes include two synthetic polymer electrolytes (polyacrylic acid and its salts, polymethacrylic acid and its salts, polystyrene sulfonic acid and its salts, polystyrene, sulfonated polystyrene, polyvinyl sulfate, poly-4(2) vinyl Pyridine and its salts, ionene polymers N-) Realkylaminomethyl polystyrene, aminoacetalized polyvinyl alcohol, poly-4(5) vinyl imitasol, linear polyethyleneimine, polyethyleneimine, polydialkyldiallylammonium salt, dialkyldiallylammonium salt -3O! copolymer, polyvinylbenzylsulfonium salt, polyvinylbenzylphosphonium salt, etc.)'p, agarose, alginic acid, gelatin,
Natural polyelectrolytes derived from living organisms such as collagen can be applied.

Polyelectrolyte solvents include water, ethanol dimethyl sulfoxide (DMSO), dimethyl formamide (D
Polar solvents such as MF) can be applied.

When forming a polymer electrolyte film by applying and drying a solution of a polymer electrolyte forming material, mixing a polyhydric alcohol into the solution creates a more homogeneous layer with good adhesion to the substrate. Also suitable are those that do not interfere with the dissolution of the polymer electrolyte, such as glycerin or ethylene glycol.

As mentioned above, when an oxygen permeable membrane is formed by coating and drying a solution of an oxygen permeable membrane forming material on a substrate on which a polymer electrolyte membrane is formed, the polymer electrolyte membrane is formed by forming an oxygen permeable membrane. It is necessary that the material is not dissolved in the solution or solvent.

(Function) In the present invention, the electrolyte layer inside the oxygen electrode, which is essential for the operation of the oxygen electrode, is formed in a dry state in the first production step, and the electrolyte layer is kept in a homogeneous dry state during the subsequent production of the oxygen permeable membrane. To exist in.

The solvent can be evenly removed from the solution containing the oxygen permeable membrane material. Therefore, the formed oxygen permeable film is free from defects such as pinholes, and the defective rate of the oxygen electrode due to this is reduced. Furthermore, since the thickness of the oxygen permeable membrane is also controlled to a constant value, the oxygen electrode output is also constant, the output reproducibility is improved, and the quality of the sensor is excellent.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

(Example 1) FIG. 1(A) An electrode pattern was formed on the Nigaras group Fi,l by platinum sputtering and silver vacuum evaporation.

The platinum cathode electrode 2 and the silver anode electrode 3 are each formed through the following steps.

A glass substrate 1 is placed on one electrode of a parallel plate type sputtering device, a platinum plate is placed on the other electrode side, a high frequency of 13 MHz is applied between both electrodes, argon gas is introduced, and 5XlO A platinum layer (1 layer) is formed by platinum sputtering on the glass substrate 1 through the hole of the stainless steel mask placed on the glass substrate 1.
000 people).

Through the above steps, platinum cathode electrode 2 is formed.

Next, the glass substrate l on which the platinum cathode electrode has been formed is placed in a vacuum evaporation apparatus, and silver is vacuum evaporated onto the glass substrate through the holes of a stainless steel mask placed on the glass substrate to form a grommet in a predetermined pattern. (3000 people).

Through the above steps, the silver anode electrode 3 is formed.

Figure 1 (B), Figure 1 (C); Next, ? As fi internal electrolyte 4, poly-(4-vinyl-ethylpyridinium bromide) (weight average molecule I
Mw = 5.3 x 10', quaternization rate 82%)
% aqueous solution to which an equal amount of glycerin was added was applied by dip coating and dried at 80°C for 20 minutes.

The thickness of the electrolytic film w4 formed after drying is about 50 μm.

Figure 1 (D), Figure 1 (E): OMI'?, which is a 2-ga type resist, is used as an oxygen permeable film material on the surface of this substrate. -83 (Tokyo Ohka@) was applied by dip coating method and heated at 80°C for 20 minutes.
Photocure by irradiating ultraviolet rays and further cure at 120°C for 20
The film was cured by heating for a minute to form an oxygen permeable film 5. .

The thickness of the oxygen II film 5 formed is approximately 20 IIm.

The poly-(4-vinyl-ethylpyridinium bromide) polymer electrolyte membrane 4 is not suitable for non-polar solvents such as toluene and xylene, which are the solvents for the negative resist OMR-83 used to form the oxygen permeable membrane 5. It will not dissolve.

A platinum cathode electrode 2, a silver anode electrode 3, an electrolyte membrane [poly-(4-vinyl-ethylpyridinium bromide)] 4, and an oxygen permeable membrane 5 were formed on the glass substrate 1.
The semi-finished oxygen electrode is immersed in water, exposed to a saturated steam atmosphere (25°C, 180 minutes), or autoclaved (120'CI, 5 minutes) to the electrolyte membrane 4 through the oxygen permeable membrane 5. By diffusing water vapor and converting the solid electrolyte into a liquid electrolyte, the yield of the completed oxygen electrode was over 98%. Furthermore, when the response characteristics were investigated in water saturated with oxygen, the fluctuation in output was within ±3%.

(Example 2) A method for manufacturing a small oxygen electrode according to another example of the present invention will be described with reference to the drawings.

This embodiment differs from the small oxygen electrode disclosed in JP-A-63-238548 mentioned above in that a polymer electrolyte is used as the internal electrolyte, and its manufacturing method is different.

In this example, the two electrodes are of polar type, the cathode is a gold electrode, and the anode is a silver/brominated gold electrode.

The silicon substrate 31 has holes formed by anisotropic etching and a silicon oxide film 32 on the entire surface.
is deposited as an insulating film. Furthermore, the back surface of the substrate is covered with a hydrophobic insulating film 37 that is hard to tear. In the hole of the silicon substrate 31.

A cathode 33A and an anode 33B are deposited as a pair. Cathode 33A and anode 33
B, as shown in Fig. 3, each part has a groove (
The hole extends to the surface of the silicon substrate outside the hole. Further, in the hole of the silicon substrate 31, the polymer electrolyte 3 of the present invention is
6 is fulfilled. Furthermore, the board 31 is placed on the top of the five large
A gas permeable membrane 3B is coated to cover the entire upper surface (excluding the exposed portion in FIG. 3).

This small oxygen electrode can be manufactured, for example, by the manufacturing process shown in sequence in FIG.

Note that the main body after forming the cathode electrode shown in FIG. 2(A) can be manufactured through the following steps. In the following explanation, a case will be described in which only one oxygen electrode is formed on one wafer, but in reality, a large number of small oxygen electrodes are formed on one wafer at the same time. Here, a case will be described in which the same [poly-(4-vinyl-ethylpyridinium bromide)] as in Example 1 is used as the polymer electrolyte.

1. Wafer Cleaning A 2-inch (100)-sided silicon wafer with a thickness of 350 μm was prepared and cleaned with a mixed solution of hydrogen peroxide and ammonia and concentrated nitric acid.

2. Formation of SiJ film A silicon wafer was subjected to wet thermal oxidation to form a SiOg film with a thickness of 0.8 μm on the entire surface.

3. Formation of etching pattern using negative photoresist (TOKYO OHKA 01fl?-83)
An etching resist pattern was formed on the wafer using a resist film having a viscosity of 60 cP.

4. Application of resist for protection of backside of wafer The same negative photoresist as used in the above step was applied to the backside of the wafer and beta-coated at 9130°C for 30 minutes.

5. Etching of SiJ film 50% hydrofluoric acid: 40% ammonium fluoride = l:
The wafer was immersed in 6 aqueous solution, and the exposed portion 5iot not covered with photoresist was removed by etching. Subsequently, the resist was removed using a sulfuric acid:hydrogen peroxide solution (2:1).

6. Anisotropic etching of Si Anisotropic etching of silicon was performed in a 35% potassium hydroxide aqueous solution at 80°C. Etching depth 300
After completion of etching, the wafer was washed with water.

After completing this anisotropic etching, s+o*wA used during etching was removed. This is 50% like 5
Hydrofluoric acid: carried out in a 40% ammonium fluoride-1:6 aqueous solution.

7.3 Formation of iOtWA To grow a 5ins film on the silicon wafer surface,
1. Following the cleaning step, the wafer was wet thermally oxidized. A film with a thickness of 0.8 μm was formed.

8. Formation of Chromium and Gold Thin Films Following ROM Thin III (400 people, adhesion of gold and substrate), a gold thin film (4000 people) was formed by vacuum evaporation.

9. Formation of resist pattern for cathode electrode formation Negative photoresist (Tokyo Ohka type OMR-83° viscosity 60
cP) to form a resist pattern for forming a cathode electrode on the SiJ wafer.

10. Gold and chromium etching The substrate on which the resist pattern has been formed is immersed in the following gold and chromium etching solutions in this order, and the exposed gold and chromium parts are removed by etching. Furthermore, after washing with pure water, sulfuric acid: hydrogen peroxide solution (2:1)
The resist was removed using a solution (FIG. 2(A)).

■Gold etching solution: 4g KI and TGRZ dissolved in 40ml of water ■Chrome etching solution: 0.5g Na011
And 1 g KsFe (CN) a dissolved in 4 1 volume of water 11, chromium and! ! Formation of thin film Following the ROM thin film (400 people!! and adhesion of the substrate), a silver thin film (4000 people) was formed by vacuum evaporation (
Figure 2 (B)).

12.7 Formation of resist pattern for forming node electrodes A positive photoresist (Tokyo Ohka 0FPR-800°, viscosity 20 cP) is dropped and spread evenly over the wafer. Preferably, the amount of resist is just enough to cover the wafer. Do not spin coat. Bost bake at 80"C for 30 minutes.

After aligning the patterns with an aligner and performing exposure, development is performed, rinsed with water, and dried. As in this example,
If the positive photoresist is applied thickly,
- It is not exposed to light, and once the exposed area is removed to a certain depth, development will no longer proceed. Therefore, the aligner
After aligning the photomask pattern with the resist pattern in the middle of development and applying 1n light, development, rinsing, and drying are performed again.

Once the substrate surface has been completely developed, proceed to the next step.
If the exposure is still incomplete, the process of n-light → development → rinsing → drying is repeated, and a positive resist pattern remains only where the final silver pattern will be formed (FIG. 2(C)).

13.8 Etching of silver and chromium The substrate on which the resist pattern has been formed is immersed in the following etching solution for silver and chromium in this order, and the exposed resist and chromium parts are removed by etching (
After cleaning with pure water, the resist is removed by immersion in acetone (FIG. 2(E)).

■Silver etching solution: 29x ammonia water: 31x hydrogen peroxide water; water/l F l: 20 solution.

■Chrome etching liquid: 0.5 g Na01l
Figure 2 (E) shows the completed state of the cathode and anode.
).

14. Forming a hydrophobic insulating film on the back side of the substrate A hydrophobic insulating film (KR-28 made by Shin-Etsu Silicone) was formed on the back side of the substrate.
2) Apply 37 evenly and bake at 250°C.

15. Formation of resist pattern for filling polymer electrolyte (second
Figure (F, )) The surface of the main body except for the hole 35 and the band portion for making electrical contact was covered with a negative photoresist (OMR-83 manufactured by Tokyo Ohka Co., Ltd., viscosity 60 cP) 34.

This was done by applying a photoresist to the surface of the wafer, exposing and developing after pre-beta.

16. Make the inside of the hole hydrophilic. Immerse the substrate in a 1M aqueous sodium hydroxide solution. As a result, the areas not covered with resist became hydrophilic.

17. Filling of polymer electrolyte (Fig. 2 (G)) Next, as an electrolyte inside the electrode, poly-(4-vinyl-ethylpyridinium bromide) (weight average molecular weight Mw-5,3X1
A solution prepared by adding an equal amount of glycerin to a 10% aqueous solution of 0', quaternization rate of 82%) was applied by dip coating and dried at 80'C for 20 minutes.

The holes 35 were filled with a polymer electrolyte 36 .

18. Coating with gas permeable film (Figure 2 (H)) OM, which is a negative resist, is applied to the surface of this substrate as an oxygen permeable film material.
R-83 (Tokyo Ohka II) was coated with dip coat method.
After coating and heating at 80° C. for 20 minutes, the chip is cut out. The scribe line is masked. Using the mask, exposure and development is performed by irradiating ultraviolet rays, and the gas permeable film on the scribe line is removed. 2 more at 120'C
The oxygen permeable film 38 was formed by heating and curing for 0 minutes.

Note that the thickness of the oxygen permeable film 38 formed is approximately 20 μm.

19. Cutting out the substrate A large number of oxygen electrodes formed on the substrate were cut out along scribe lines and divided into chips.

20. A metal sword electrode 33A and a silver anode electrode 33B are formed on the hole of the substrate, and a polymer electrolyte (poly(
4-vinyl-ethylpyridinium bromide)] 36 was filled in the hole, and oxygen permeation l! The semi-finished oxygen electrode with 38 formed thereon is immersed in water, exposed to a saturated steam atmosphere (25°C, 180 minutes), or autoclaved (120°C, 15 minutes). Water vapor is diffused into the polymer electrolyte 36 through the oxygen permeable M3B to change the solid electrolyte to a liquid electrolyte to form a completed oxygen electrode.

The yield of the completed oxygen electrode was 98% or more. Furthermore, when the response characteristics were investigated in water saturated with oxygen, the fluctuation in output was within ±3%.

【Effect of the invention〕

As shown above, the present invention makes it possible to manufacture an oxygen electrode more easily and reliably than in the past. In particular, the yield immediately after manufacturing was only about 30% in the conventional method, but it was significantly improved to more than 98%. In addition, the reproducibility of electrode output is ±3
It was about 0%, but now it is about ±3%, which is a big improvement.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the process of manufacturing an oxygen electrode according to an embodiment of the present invention, FIG. FIG. 4 is a perspective view for explaining an electrode and an oxygen electrode according to another embodiment of the present invention, and FIG. 4 is a cross-sectional view of the electrode in FIG. 3 taken along line 2-H. l is a glass substrate, 2 is a platinum cathode, 3 is a silver anode,
4 is an internal electrolyte, 5 is an oxygen permeable membrane, 31 is a substrate, 32 is an insulating film, 33A is a cathode electrode, 33B is an anode electrode, 34 is a photoresist film, 35 is a hole, 36 is a polymer electrolyte, and 37 is a hydrophobic The insulating film 38 is an oxygen permeable film. Small Vinegar Electrode / Type 1 7° U Se Human bud 2 Diagrams of the family F rod 1s Indication L Family Diagram Haya 1 Diagram Small size! ttVJ! /l1it 7'Use

Claims (1)

[Claims] An oxygen electrode comprising an electrolyte, two electrodes serving as a cathode and an anode provided in the electrolyte, and an oxygen permeable membrane covering the electrolyte, characterized in that a polymer electrolyte is used as the electrolyte. .