JPH04125462A - Oxygen electrode - Google Patents

Abstract

PURPOSE:To enable difficulty in forming a selective pattern formation of an electrolyte layer and a gas-transmission type film to be excluded by providing a plane-shaped electrode substrate where a working electrode and a counter electrode are formed and a container substrate for forming a recessed part for storing an electrolyte opposing each electrode. CONSTITUTION:At least a working electrode 21 and a counter electrode 22 are formed on a plane-shaped electrode substrate B and a reference electrode 23 is further provided in a three-electrode configuration. And, a container substrate C has a recessed part 25 for storing an electrolyte 26 at parts correspond to electrodes 21 - 23 of a substrate B and a corresponding part of the electrode 21 penetrates to an opposite side of a substrate C. These substrates B and C laminated and the penetration hole is covered with a gas-transmission film 20, thus enabling electrolyte-forming process to be eliminated from a process, achieving collective production from the beginning to the end in wafer shape, and enabling cost to be reduced. Also, an electrode pattern can be formed easily by allowing the electrode to be formed on the plane-shaped substrate.

Description

[Detailed Description of the Invention] [Summary] Regarding a small oxygen electrode, the difficulty of selective patterning of an electrolyte layer and a gas permeable membrane, the accompanying unavoidability of the chip-by-chip fabrication process, and the linearity of a calibration curve. , for the purpose of ensuring stability during continuous use and stability during repeated use, a planar electrode substrate having at least two electrodes formed thereon, and a recessed portion facing the two electrodes for accommodating an electrolyte,
a container substrate bonded to the planar electrode substrate; a recessed portion of the recessed portion facing the electrode constituting the working electrode extends to a surface opposite to the planar electrode substrate to form a through hole; It is configured to have a gas permeable membrane covering the through hole.

[Industrial application field]

The present invention relates to an oxygen electrode and a method for manufacturing the same, and more particularly to a small-sized oxygen electrode using micromachining technology and a method for manufacturing the same.

Oxygen electrodes are advantageously used in various fields to measure dissolved oxygen concentration. For example, the biochemical oxygen demand (BOD) in water is measured from the viewpoint of water quality conservation. This oxygen electrode can be used as a measuring device for the dissolved oxygen concentration. Further, in the fermentation industry, in order to efficiently proceed with alcohol fermentation, it is necessary to adjust the dissolved oxygen concentration in the fermenter, and a small oxygen electrode can be used as a measuring device for this purpose. Furthermore, in the medical field, there is a demand for oxygen sensors that are small and disposable. Furthermore, the small oxygen electrode can be combined with an enzyme to form an enzyme electrode, which can be used to measure the concentration of sugars, alcohols, and the like. For example, glucose is oxidized to gluconolactone by reacting with dissolved oxygen using the enzyme glucose oxidase as a catalyst. Glucose concentration can be determined from consumption.

In this way, small oxygen electrodes can be used in various fields such as environmental measurement, fermentation industry, and clinical medicine. Particularly in the field of clinical medicine, where it is attached to a catheter and inserted into the body, it is of great utility because it is small, disposable, and inexpensive.

[Prior art]

The inventors found that in commercially available types of oxygen electrodes,
Since miniaturization and mass production were not possible, we developed a new type of compact oxygen electrode using lithography technology and anisotropic etching technology, and applied for a patent (Japanese Patent Application No. 71739/1983, No. 63-238548) (see Figures 7 to 9). This type of oxygen electrode has two electrodes, ie, an anode 4, placed over a hole 2 formed on a silicon substrate 1 by anisotropic etching, with an insulating film 3 interposed therebetween.
This oxygen electrode has a structure in which a cathode 5 is formed, an electrolyte containing body 6 is housed inside the hole, and finally the upper surface of the hole is covered with a gas permeable membrane 7. In the figure, 8 is a sensitive part and 9 is a pad. Such an oxygen electrode is small, has little variation in characteristics, and can be mass-produced in bulk, so it is low cost.

[Problem to be solved by the invention]

As described above, by improving the materials of conventional small-sized oxygen electrodes, it has become possible to obtain ones close to the practical level. However, there are still some problems that must be solved in order to manufacture this on a factory production line and sell it on the market. These are as follows.

(1) Formation of an electrolyte layer and a gas permeable membrane layer cannot be performed selectively in many cases. Therefore, the work for each chip increases, and productivity deteriorates. As a result, the price of small oxygen electrodes becomes extremely high.

(2) The work of forming an electrode pattern from the top to the bottom of a hole drilled by anisotropic etching becomes more difficult as the step becomes deeper, which not only reduces the accuracy of pattern formation, but also requires special techniques such as overprinting. It is very time consuming as it requires some ingenuity.

(3) Previous small oxygen electrodes have used electrolytes soaked in gel or solid polymer electrolytes in order to form gas-permeable membranes directly on the sensitive area, but it is difficult to precisely specify the amount of electrolyte. is difficult, and this affects problems such as variation in characteristics.

(4) The gas permeable membrane was formed by applying a liquid in the form of dip coating or spin coating, but the material used for the gas permeable membrane formed in this way (silicone resin etc.), many of them are
Storage stability on a year-by-year basis is not guaranteed, and it deteriorates over time.

(5) The gas-permeable membrane can be applied only to the vicinity of the working electrode, but in the aforementioned small oxygen electrode that uses only one silicon substrate as a substrate, it must also be formed in unrelated areas such as the anode area. However, the gas-permeable membrane is easily damaged.

8) [Means for Solving the Problems] The present invention has been made to solve the above problems, and the oxygen electrode of the present invention is a planar electrode formed with at least two electrodes (a working electrode and a counter electrode). An electrode substrate, a container substrate forming a recess facing the two electrodes and accommodating an electrolytic solution, and bonded to the planar electrode substrate, the container substrate facing the electrode constituting the working electrode in the recess. The recess extends to the surface opposite to the planar electrode substrate to form a through hole,
Furthermore, it is characterized by having a gas permeable membrane covering the through hole.

Furthermore, the method for manufacturing an oxygen electrode of the present invention includes a planar electrode substrate on which at least two electrodes (a working electrode and a counter electrode) are formed, a recess for injecting an electrolyte opposite to the counter electrode, and a recess at a position opposite to the working electrode. A container substrate provided with a through hole is laminated together, the through hole provided in the container substrate is covered with a gas permeable membrane to form a hole, and then an electrolytic solution is injected into the recess and the liquid hole. .

The present invention will be further explained below.

As mentioned above, the oxygen electrode of the present invention is extremely small,
The basic technology of so-called micromachining is used in the production of such small oxygen electrodes.

The key points of the method of the present invention using such basic technology are:
The following points apply.

(1) Instead of using only one substrate, two individually processed substrates are pasted together to complete the oxygen electrode.

(2) The electrolyte formation step is omitted. That is, the electrolyte is not injected by the manufacturer of the small oxygen electrode, but by the user immediately before use.

(3) Electrode patterns such as the working electrode, reference electrode, and counter electrode are not formed in deep steps, but are formed on a nearly flat substrate.

(4) A penetrating hole is made only in the working electrode portion, and a gas permeable membrane is applied only to this portion.

(5) Adhere the gas permeable membrane by thermal welding or the like.

Such an oxygen electrode of the present invention has two substrates, namely:
It can be created by pasting together an electrode substrate and a container substrate.

At least two electrodes are formed on the planar electrode substrate: a working electrode and a counter electrode.

When the electrode has a two-pole configuration, it consists of a cathode and an anode, with the cathode serving as a working electrode and the anode serving as a counter electrode.

The cathode and anode can vary depending on whether the electrodes being made are polar or galvanic. For example, when manufacturing a polar mouth type oxygen electrode, both side electrodes are made of gold or platinum electrodes, or the anode is used as a reference electrode, and a voltage is applied between both electrodes during measurement. In addition, when using a polar mouth type, a material that does not easily attack the silicone container part, such as 0
．． It is preferable to use a neutral aqueous solution such as a 1M aqueous potassium chloride solution. In addition, an electrode made of a metal such as lead or silver that is more likely to cause a chemical reaction than gold or platinum is used as the anode electrode, an electrode made of gold or platinum is used as the cathode electrode, and the electrolyte is a 1M potassium hydroxide aqueous solution, for example. A galvanic type oxygen electrode can be manufactured by using an alkaline aqueous solution such as

Further, in the case of a three-electrode configuration, a reference electrode is further provided, and the working electrode and the counter electrode are composed of a gold electrode or a platinum electrode, and a silver/silver chloride reference electrode or the like is preferably used as the reference electrode. Formation of such an electrode can be advantageously performed by, for example, a film forming method such as vacuum evaporation or sputtering.

Various electrolyte solutions can be used, such as a potassium chloride aqueous solution, potassium hydroxide, and a sodium sulfate aqueous solution.

Although it is essential that the gas permeable membrane is hydrophobic so that an aqueous solution cannot pass therethrough, it is also important that it can be adhered to a silicon substrate or a silicon oxide film with good adhesion by thermal welding or the like. Suitable gas permeable membrane materials include FEP as well as silicone container parts and the like.

Preferred embodiments of the oxygen electrode of the present invention are as follows.

A reference electrode is further formed on the planar electrode substrate, and a recess into which an electrolytic solution is poured is further formed in the container substrate facing the reference electrode.

Further, it is preferable that the electrodes formed on the planar electrode substrate are separated from each other to an extent that they are not affected by products on the surfaces of each electrode.

Preferred base materials for the planar electrode substrate include a Pyrex glass substrate, a lead glass substrate, a silicon substrate on which a borosilicate glass thin film containing Pyrex glass is formed,
Silicon substrates with a lead glass thin film formed on the surface, glass substrates with a borosilicate glass thin film containing Pyrex glass formed on the surface, glass substrates with a lead glass thin film formed on the surface, silicon substrates with a thermal oxide film formed on the surface, etc. can be mentioned.

A pad portion is preferably formed at one end of each electrode formed on the electrode substrate, and the size of this pad portion is such that it can be used by directly sandwiching a socket terminal of an IC.

On the other hand, a semiconductor substrate, particularly a silicon substrate, is advantageously used as the base material of the container substrate. Silicon substrates are especially (10
0) plane silicon substrate is preferred. When using a silicon substrate, the insulating film can be formed from a silicon oxide film or others. A silicon oxide film can be easily formed by thermally oxidizing a silicon substrate, for example. Although silicon nitride film has very good properties as an insulating film, it cannot be used as a bonding surface because it cannot be anodic bonded.

Furthermore, the electrolyte storage recesses formed in the container substrate can be connected to each other via elongated grooves.

Furthermore, in the present oxygen electrode, it is preferable that the electrode be formed in a shallow groove etched on a plane according to the pattern.

Further, it is preferable that a recess is provided on the surface of the container substrate, that is, the opposite side of the surface to be bonded to the electrode substrate, at the periphery of the through hole provided in the container substrate, and a gas permeable film is applied to this recess. . This is because with this configuration, the distance between the gas permeable membrane and the working electrode becomes shorter, and the sensitivity of the oxygen electrode itself can be improved.

On the other hand, as the gas permeable membrane, an FEP (tetrafluoroethylene-hexafluoroethylene copolymer) membrane is preferably used, and its thickness is preferably 20 squares or less.

As the working electrode (cathode), a gold electrode, a platinum electrode, a carbon electrode, etc. are preferably used, and as the counter electrode (anode), a gold electrode, a platinum electrode, a carbon electrode, etc. are similarly preferably used.

Furthermore, a silver/silver chloride electrode is preferred as the reference electrode.

On the other hand, as the electrolytic solution, a potassium chloride aqueous solution, a potassium hydroxide aqueous solution, or the like is preferably used.

[For production]

The small oxygen electrode of the present invention has a working electrode (cathode) and a counter electrode (
It is used by applying a constant negative voltage to the anode) or reference electrode. With the sensitive part of the small oxygen electrode in this state immersed in the buffer solution, dissolved oxygen passes through the gas permeable membrane and reaches the working electrode (cathode), where it is reduced.

By measuring the current value generated at this time, the dissolved oxygen concentration can be determined using this as an index.

〔Example〕

Next, a preferred example of a method for manufacturing a small oxygen electrode according to the present invention will be explained with reference to the accompanying drawings (FIGS. 1 to 4).

FIG. 1 is a plan view of a small oxygen electrode A of the present invention.

The illustrated oxygen electrode has a rectangular parallelepiped shape, and has a sensitive part (
The working electrode portion) is covered with a gas permeable membrane 20, and
Working electrode 21, counter electrode 22 for connection to the attached device
A portion of the reference electrode 23 is exposed to form a pad 24. In this example, the working electrode 21 and the counter electrode 22 were made of gold electrodes. This electrode uses only a working electrode 21 and a counter electrode 22.
Although it can be used in a polar configuration, if a three-pole configuration is used, a reference electrode 23 consisting of a silver/silver chloride electrode is also used.

The structure of the miniature oxygen electrode of FIG. 1 may be better understood from FIGS. 3 and 4. That is, an electrode substrate B made of glass has a working electrode 21, a counter electrode 22, and a reference electrode 2.
3 is formed. On the other hand, the container substrate C made of silicon has an electrolytic solution 26 formed by anisotropic etching on the corresponding portions of the working electrode 21, the counter electrode 22, and the reference electrode 23.
In particular, the recess 25 in the working electrode 21 portion stores
5 a penetrates to the opposite side of the silicon substrate 2 in order to form a gas permeable film 27 . A gas permeable film 27 is formed on the upper surface of the recess 25a. Each hole is connected by a thin groove. The concave portion of the container substrate C is filled with, for example, 0.1M KCl as an electrolyte after completion.
Injection groove 26 for injecting this electrolyte into a minute hole
a and 26b are formed near the pad 24.

Oxygen electrode A of the present invention comprises the above electrode substrate B and container substrate C.
It is created by arranging the electrodes and recesses formed in the respective electrodes so that they correspond to each other, and pasting them together.

FIG. 2 shows a sectional view taken along the line 1--2 of the oxygen electrode A produced in this manner.

The miniature oxygen electrode shown in FIG. 1 can be advantageously manufactured, for example, by the manufacturing process shown in sequence in FIG. In addition, in the following explanation, in order to make it easier to understand,
Although the case where only one oxygen electrode is formed on a single wafer is described, it should be understood that in reality, many small oxygen electrodes are formed simultaneously. Also,
Although FIG. 5 schematically shows only the vicinity of the working pole, other parts are formed in the same manner.

(1) Preparation of electrode substrate ■ 2-inch Ishiro 7740 glass (commonly known as Pyrex)
A working electrode (cathode) to be formed later on one side of the substrate 30
, a counter electrode (anode), and a negative photoresist film having the same pattern as the reference electrode.

At this time, make sure that the glass in the electrode formation area is exposed.

■ After coating the entire surface with the same negative photoresist on the back side, bake at 150°C for 30 minutes.

(2) The exposed portion of the glass is etched by immersing the wafer in a 1:1:8 mixed solution of 50% hydrofluoric acid, concentrated nitric acid, and 40% ammonium fluoride for 1 hour. This is the etching depth 3 side.

■ Peel off the negative photoresist film formed in step ■■ above in a mixed solution of sulfuric acid: hydrogen peroxide = 2:1 (see Figure 5).
a)).

■ After thoroughly cleaning the substrate with a mixed solution of hydrogen peroxide and ammonia and pure water, dry it.

■ Form a thin gold film on the substrate by vacuum evaporation.

Note that since gold and glass have very poor adhesion, a thin chromium layer was interposed to improve their adhesion.

The film thickness is chromium 4QnA and gold 400nA.

■ A positive photoresist film (
0FPR-5000 manufactured by Tokyo Ohka.

(2) Using the same pattern as in (2) above, form working electrode (cathode) and counter electrode (anode) patterns.

(2) The substrate on which the resist pattern was formed was immersed in the following etching solution all around, and the exposed gold portion was removed by etching. Furthermore, after washing with pure water, the resist was removed with acetone.

Dissolved in 1 ml of water ■ Immerse the substrate in the following etching solution to remove the exposed portion of chromium.

Chrome etching solution: 0.5 g NaOH and 1
gK3Pe(CN)6 dissolved in 4rd water■
After thoroughly cleaning the substrate with pure water, dry it.

When used in a bipolar system with only gold electrodes, the process ends here, but when used in a tripolar system, a reference electrode is further formed. This is done in the following steps.

■ Deposit silver at 400 nA on a substrate of 0.0 nm. Note that in the state (2), it is preferable from the viewpoint of adhesion that a gold electrode pattern is also formed on the reference electrode portion. When the gold pattern is underneath, the Cr layer is not necessary, unlike the case (2).

0 After applying a positive photoresist to the substrate surface, baking, exposing, and developing, a photoresist pattern is formed only in the portion where the reference electrode will be formed.

■ 29% ammonia: 31% hydrogen peroxide:
The silver is etched by immersing it in a mixed solution of 1:1:20 pure water.

■ After thoroughly cleaning the entire board with pure water, wash the entire board with 0 and 1
Immerse in M FeCl3 solution for 10 minutes to form a thin silver chloride layer on the silver surface.

■ Thoroughly wash the entire board with pure water.

Through the steps ① to [Yes], the electrode base is completed (FIG. 5(b)). In FIG. 5(b), numeral 31 indicates a working electrode (cathode).

(2) Preparation of container substrate ■ A 2-inch (100)-sided silicon wafer 32 with a thickness of 350 #l was prepared and washed with a mixed solution of hydrogen peroxide and ammonia and concentrated nitric acid.

■ Wet thermal oxidation of silicon wafer 32 (1050
℃, 200 minutes) and coated the entire surface with a film thickness of 1.0,1/III.
A 5102 film 33 was formed.

■ Negative photoresist (DMR-83 (trade name) manufactured by Tokyo Ohka Co., Ltd., viscosity 60cP) on the smooth surface of the silicon substrate.
) After coating, exposure, development, and rinsing are performed to form an etching resist pattern on the wafer.

(2) The wafer is immersed in a 1:6 mixed solution of 50% hydrofluoric acid and 40% ammonium fluoride to etch the exposed portion of 5IO2 (FIG. 5(C)).

(2) The negative photoresist film formed in (2) is peeled off in a mixed solution of sulfuric acid and hydrogen peroxide (2:1).

(2) Immerse the substrate in a 35% dipping solution of 80°C to perform anisotropic etching of silicon to form recesses corresponding to the electrode patterns created in (1). Note that if the pattern of the recesses is complex, steps ① to ① are performed multiple times. Finally, a container is obtained which has a cavity for storing the electrolyte in the counter electrode and reference electrode portions and a through hole 34 in the working electrode portion.

(2) If the 5in2 used as the surface of the silicon 2932 remains, it is completely removed in the etching solution (2) because a higher temperature is required than in the anodic bonding in (3).

Through the steps (1) to (2), a container substrate for storing the electrolyte is completed (FIG. 5(d)).

3) Adhesion of electrode substrate and container substrate■ The electrode substrate completed in steps (1) and (2) was ultrasonically cleaned in pure water, while the electrolyte storage container substrate was cleaned with hydrogen peroxide/ammonia aqueous solution and pure water. Wash thoroughly with water.

(2) Align the pattern of the electrode forming surface in (1) with the pattern of the surface on which the recesses are formed by etching (2) in a clean atmosphere.

(2) The electrode substrate and the container substrate are anodically bonded by applying 1200 V between the substrates at a temperature of 250°C.

At this time, the electrode substrate side was made negative (FIG. 5(e)).

(4) Formation of a gas permeable membrane■ On the surface opposite to the adhesive surface of the container substrate in (2), a gas permeable membrane 35 (for example, a 12 mm thick FE
Cut the P membrane (manufactured by Toshi) into an appropriate size and set it aside.

■ Heat the substrate in ■ to a temperature that melts the FEP. As a result, the FEP film adheres to the substrate (Fig. 5 (
f)).

(5) Cutting out the substrate■ Cutting out the oxygen electrodes formed on the substrate
Cut into chips using a .

(6) Injecting the electrolyte When injecting the electrolyte, if the hole inside the small oxygen electrode is large, insert the small oxygen electrode body into 0. This can be easily done by reducing the pressure of the entire electrolyte while immersed in lM KCl, but if it is difficult to do so, the electrolyte can be easily added by performing the following operation.

■ Place an electrolyte in a beaker, place the electrolyte injection groove of the small oxygen electrode in the electrolyte, place the gas permeable membrane in the gas phase, and place the entire body including the beaker in a sealed container substrate. and degas it with a vacuum pump.

■ After leaving it for a while, air is rapidly introduced into the container substrate. By this operation, the electrolytic solution 36 enters at once up to the gas permeable membrane.

■ If air bubbles remain in the gas permeable membrane, ■
Repeat step ■.

In addition, when injecting the electrolyte, sodium alginate containing the electrolyte is poured into the recesses and through-holes of the oxygen electrode, and then the entire oxygen electrode is immersed in an aqueous calcium chloride solution to soak into the recesses and through-holes. It is also possible to gel sodium to form calcium alginate, and then immerse it in the electrolyte aqueous solution to allow the electrolyte to soak in sufficiently. Alternatively, the gel can be introduced into the recesses and through holes inside the oxygen electrode by immersing it in molten agarose gel containing an electrolyte and using the method described above.

After completing these steps, a small oxygen electrode that actually functions can be obtained (FIG. 5(g)).

(7) Connection with external measuring equipment To use the small oxygen electrode created in this way, it is necessary to connect the electrode to an external amplifier or detector. If you make it thick (for example, you can remove the metal part of the IC socket here, attach a lead wire here, and connect it by sandwiching it with this), the pad part may also be immersed in the solution. If there is, you can also bond a lead wire (for example, an aluminum wire of about 50μφ) to this part and insulate the pad part and lead wire part with resin.If bonding strength is an issue, Cover everything up to the pad part with a container substrate (silicon), make a hole through the pad part as well as the sensitive part, insert the lead wire tip into the pad part, fix it with indium or silver paste, etc., and then insulate it. You can also use a method of hardening it with a synthetic resin.

(8) Example of use of small oxygen electrode The characteristics of the small oxygen electrode mentioned above are as follows:
The test was conducted in mM phosphate buffer. Applied voltage is -0.8V
(vs, Ag/AgC1). In use, stable output with less noise was obtained when the 0.1 M KCI electrolyte was soaked into calcium alginate gel rather than directly injected into the electrode. The 90% response time was about 2 minutes, and the residual current value at a dissolved oxygen concentration of O was about 7%.

Moreover, a calibration curve is shown in FIG. Dissolved oxygen concentration 8.2pI
Very good linearity was observed below 1 m (saturated dissolved oxygen concentration at 25°C).

〔Effect of the invention〕

Since the present invention is constructed as described above, it is possible to eliminate the step of forming an electrolyte layer from the process. For this reason, oxygen electrodes can be manufactured in a wafer form from start to finish in one go, which has the effect of reducing costs without requiring much effort. Furthermore, since the electrodes are formed on a flat substrate without deep holes, it is easy to form an electrode pattern. In addition, the bag can be stored in a dry state without an electrolyte layer, and the gas-permeable membrane is less prone to deterioration, making it possible to store it for a long time. This provides various effects such as making the gas permeable membrane less likely to be damaged.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a small oxygen electrode according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. 4 is a plan view of an electrode substrate forming an electrode; FIG. 4 is a plan view of a container substrate forming an oxygen electrode shown in FIG. 1; FIGS. FIG. 6 is a graph showing a calibration curve of the small oxygen electrode of the present invention, and FIG. 7 is a graph showing the calibration curve of the small oxygen electrode of the present invention. FIG. 8 is a plan view of
FIG. 9 is a sectional view taken along line IX-IX of the oxygen electrode shown in FIG. 7. FIG. 9 is a sectional view taken along line IX-IX of the oxygen electrode shown in FIG. 20, 27, 35... gas permeable membrane, 21...
Working electrode, 22... Counter electrode, 23... Reference electrode, 25... Concave portion, 26, 36...
Electrolyte, 34... Through hole, A... Oxygen electrode, B... Electrode substrate, C... Container substrate. (b) (d) 3mu (f) -Eng.350J-1n -10

Claims (1)

[Claims] 1. A planar electrode substrate on which at least two electrodes (a working electrode and a counter electrode) are formed, and a recess for accommodating an electrolyte facing the two electrodes, and and a container substrate to be bonded together, the recess facing the electrode constituting the working electrode extends to the surface opposite to the planar electrode substrate to form a through hole, and further covers the through hole. An oxygen electrode characterized by having a gas permeable membrane. 2. The oxygen electrode according to claim 1, wherein a reference electrode is further formed on the planar electrode substrate, and a recessed portion for injecting an electrolytic solution is further formed on the container substrate facing the reference electrode. 3. The oxygen electrode according to claim 1 or 2, wherein the electrodes formed on the planar electrode substrate are separated by a distance sufficient to avoid being affected by products on the surfaces of each electrode. 4. The oxygen electrode according to claim 1 or 2, wherein each recess is connected by an elongated groove. 5. At the periphery of the through hole on the side opposite to the bonding surface of the container substrate,
5. The oxygen electrode according to claim 1, wherein a recess is provided and a gas permeable membrane is adhered to the recess. 6. The planar electrode substrate is a Pyrex glass substrate, a lead glass substrate, a silicon substrate on which a borosilicate glass thin film containing Pyrex glass is formed, a silicon substrate on which a lead glass thin film is formed, or a borosilicate glass containing Pyrex glass. Any one of claims 1 to 5, which is one selected from the group of a glass substrate with a thin film formed on its surface, a glass substrate with a lead glass thin film formed on its surface, and a silicon substrate with a thermal oxide film formed on its surface. Oxygen electrode described in Section. 7. The oxygen electrode according to claim 1 or 2, wherein the electrode is formed in a shallow groove etched in a pattern on a planar electrode substrate. 8. The oxygen electrode according to claim 1 or 2, wherein the silicon substrate is a (100) plane silicon substrate. 9. The oxygen electrode according to claim 1, wherein the gas permeable membrane is an FEP membrane. 10. A pad portion is formed at one end of each of the electrodes,
10. The oxygen electrode according to claim 1, wherein the pad portion is large enough to be used by directly sandwiching an IC socket terminal or the like. 11. A planar electrode substrate on which at least two electrodes (a working electrode and a counter electrode) are formed, a container substrate having a recess opposite to the counter electrode into which an electrolyte is injected, and a through hole at a position opposite to the working electrode. 1. A method for producing an oxygen electrode, which comprises bonding the container substrate together, covering a through hole provided in the container substrate with a gas permeable film to form a hole, and then injecting an electrolyte into the recess and the hole. 12. A reference electrode is further formed on the planar electrode substrate,
12. The method according to claim 11, wherein the container substrate further has a recess formed therein opposite to the reference electrode for injecting the electrolyte. 13. The method according to claim 11 or 12, wherein the oxygen electrode is immersed in an electrolytic solution, and the electrolytic solution is introduced into a cavity inside the oxygen electrode by a degassing operation.