JP2838901B2 - Small oxygen electrode and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a small oxygen electrode and a method for producing the same, and particularly to a gas permeable membrane and a method for producing the same. A substrate, an electrolyte accommodating groove formed on the substrate by anisotropic etching, and a gas-permeable membrane formed on the surface of the electrolyte accommodating groove. And an electrode forming portion formed on a flat substrate via an insulating film and having a plurality of electrodes each partially extending into the groove. Configuration.

[Industrial applications]

The present invention relates to a small oxygen electrode and a method for manufacturing the same, and more particularly, to a gas permeable membrane and a method for manufacturing the same.

The small oxygen electrode can be advantageously used in various fields for measuring the concentration of dissolved oxygen. For example, the measurement of biochemical oxygen demand (BDD) in water is performed from the viewpoint of water quality conservation, and this small oxygen electrode can be used as a measuring device of the dissolved oxygen concentration. Further, in the fermentation industry, it is necessary to adjust the dissolved oxygen concentration in the fermenter in order to efficiently promote alcohol fermentation, and the small oxygen electrode of the present invention can be used as a measuring device. Furthermore, the small oxygen electrode can be used in combination with an enzyme to form an enzyme electrode and to measure the concentration of sugar, alcohol, and the like. For example, glucose reacts with dissolved oxygen and oxidizes to gluconolactone using an enzyme called glucose oxidase as a catalyst.By utilizing the fact that this reduces the amount of dissolved oxygen that diffuses into the oxygen electrode cell, The glucose concentration can be measured from the consumption.

As described above, the small oxygen electrode of the present invention can be used in various fields such as environmental measurement, the fermentation industry, and clinical medicine. It is very valuable because it is disposable and inexpensive.

[Conventional technology]

The present inventors have developed a new type of small-sized oxygen electrode using lithography technology and anisotropic etching technology because conventional glass oxygen electrodes cannot be miniaturized and mass production is impossible. Patent application (Japanese Patent Application No. Sho 62-
71739, JP-A-63-238548). This oxygen electrode has two electrodes formed on a hole (groove) formed on a silicon substrate by anisotropic etching via an insulating film.
Further, an oxygen electrode having a manufacturing method in which an electrolyte-containing body is accommodated inside the hole, and finally the upper surface of the hole is covered with a gas-permeable membrane. This oxygen electrode is small, has little variation in characteristics, and is low in cost.

[Problems to be solved by the invention]

The material of the gas permeable film of the oxygen electrode is mainly limited to silicon rubber and other negative resists. In particular, since silicon rubber is formed only by the dipping process, the film thickness becomes unstable, and adhesion to the silicon substrate becomes a problem.

Further, the electrolyte-containing body accommodated in the hole (groove) contains water and causes deterioration of the gas-permeable film quality.

In the manufacture of an oxygen electrode, it is necessary to form an electrode pattern on a step of several hundred μm, but this is not an easy process.

An object of the present invention is to provide a small-sized oxygen electrode having no electrolyte layer (having a hole shape) and not causing deterioration of a gas-permeable membrane, and a method for manufacturing the same.

[Means for solving the problem]

According to the present invention, there is provided an electrolyte housing comprising a substrate, an electrolyte housing groove formed on the substrate by anisotropic etching, and a gas permeable membrane formed on a surface on which the electrolyte housing groove is formed. And an electrode forming portion formed on a flat plate substrate via an insulating film and having a plurality of electrodes each partially extending into the groove, and the electrolyte accommodating groove is formed of an electrolyte. The small oxygen electrode is characterized by being a cavity into which an electrolyte is introduced, and having a hole for introducing an electrolyte into the electrolyte accommodating groove.

Further, according to the present invention, according to the present invention, an electrolyte accommodating groove and an electrolyte introduction hole communicating with the electrolyte accommodating groove are formed on a substrate by anisotropic etching. Forming an electrolyte containing portion by forming a conductive film; forming an electrode forming portion by forming a plurality of electrodes on a flat substrate via an insulating film; and forming the electrolyte containing portion and the electrode. And bonding the forming portion so that a part of each of the electrodes extends into the groove and the groove forms a cavity into which an electrolyte is introduced. Is solved.

That is, the present inventors first form a plurality of electrodes such as a cathode and an anode or a plurality of electrodes such as a working electrode, a reference electrode, and a counter electrode, and a gas permeable membrane, and introduce an electrolyte into a sensitive part after completion and before use. It was to be. Also, the cathode / anode or the working electrode / reference electrode / counter electrode etc. are formed on a flat substrate,
The formation of the pattern on the step is unnecessary.

The feature of the present invention resides in that the above-mentioned problems are solved by applying the so-called micromachining basic technology. That is, holes (grooves) are formed by anisotropic etching on a flat substrate on which a cathode, an anode or a working electrode, a reference electrode, and a counter electrode are formed, and a water-repellent gas-permeable film is formed on the surface of the holes Then, two substrates are adhered to each other with this gas-permeable membrane, and an electrolyte is introduced into the holes.

In carrying out the method of the present invention, a semiconductor substrate, in particular, a silicon substrate, a glass substrate, or a ceramic substrate can be advantageously used as the substrate of the electrode body. When a silicon substrate is used, the insulating film can be formed from a silicon oxide film or the like. The silicon oxide film can be easily formed by, for example, thermally oxidizing the substrate when the substrate is silicon.

(Operation)

In the present invention, an electrolytic material such as an electrolytic solution may be introduced into the electrolyte accommodating portion immediately after use after completion, and mass production can be performed using lithography technology and thin film formation technology.

〔Example〕

Next, a preferred example of the small oxygen electrode according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing a preferred example of a small oxygen electrode according to the present invention. The illustrated oxygen electrode has a rectangular parallelepiped shape. The sensitive portion is covered with the gas permeable membrane 10, and a part of the cathode 3a and the anode 3b are exposed for connection to an attached device. Cathode as electrode
In the case of the present example, both electrodes 3a and 3b were formed of gold electrodes in order to obtain a polaro type.

The structure of the small oxygen electrode of FIG. 1 can be understood in detail from FIG. 2, which is a sectional view taken along the line II-II.
One of the opposing silicon substrates 1 has a hole (groove) formed by anisotropic etching. A cathode 3a and an anode 3b are attached to one silicon substrate 1 in a pair, and the back surface of the substrate is covered with a hydrophobic insulating film 7 that is difficult to break. Further, a gas permeable membrane tank 10 is formed above the hole. When this electrode is used in the hole 5 of the silicon substrate 1, 0.1MK is used as an electrolyte.
Cl is filled. Figure L ₁ is 2 mm, L ₂ is 15 mm.

The small oxygen electrode shown in FIGS. 1 and 2 can be advantageously manufactured by, for example, the following steps (1) to (14) and the manufacturing process shown in FIG. In addition,
In the following description, in order to facilitate understanding, a case where only one oxygen electrode is formed on one wafer will be described. However, in practice, a plurality of small oxygen electrodes are simultaneously formed.

(1) Wafer cleaning A silicon wafer (substrate) having a thickness of 350 μm and a 2-inch (100) plane was prepared, and washed with a mixed solution of hydrogen peroxide and ammonia and concentrated nitric acid.

(2) Formation of SiO ₂ Film A silicon wafer was subjected to wet thermal oxidation to form a 0.8 μm thick SiO ₂ film on the entire surface.

(3) Formation of etching pattern A negative photoresist (OMR-83 (trade name, manufactured by Tokyo Ohka), having a viscosity of 60 cP) is applied to a rough substrate surface and then exposed and exposed.
After development and rinsing, an etching resist pattern was formed on the wafer.

(4) Application of Resist The same negative photoresist as that used in the above process was applied to the back surface of the substrate, and baked at 150 ° C. for 30 minutes.

(5) Etching of SiO ₂ Film The wafer was immersed in an aqueous solution of 50% hydrofluoric acid: 40% ammonium fluoride = 1: 6, and the exposed portions of the SiO ₂ that were not coated with the photoresist were removed by etching. Subsequently, the resist was removed with a sulfuric acid / aqueous hydrogen peroxide (2: 1) solution.

(6) Anisotropic etching of Si Anisotropic etching of silicon was performed in a 35% aqueous solution of potassium hydroxide at 80 ° C. The etching was continued until the hole was penetrated. After the completion of the etching, the wafer was washed with pure water.

After the completion of the anisotropic etching, the SiO ₂ film used at the time of etching was removed. This was carried out in a 50% hydrofluoric acid: 40% ammonium fluoride = 1: 6 aqueous solution as in the case of 5.

The hole of the sensitive part is formed in this way, and the hole for injecting the electrolyte is also formed in this way. This is preferably performed before the formation of the sensitive hole.

(7) Formation of chromium and gold thin films On one surface of the substrate on which the SiO ₂ film was formed in ₂ , a chromium thin film (400 mm, for adhesion between the gold and the substrate), followed by a gold thin film (4
000Å) was formed by vacuum evaporation.

(8) Formation of resist pattern for electrode formation A resist pattern for electrode formation was formed on a gold thin film of a wafer using a positive photoresist (OFPR-800 (trade name, manufactured by Tokyo Ohka), viscosity: 20 cP).

(9) Etching of Gold and Chromium The substrate on which the resist pattern was formed was immersed in the following etching solution for gold and chromium in that order, and the exposed portions of gold and chromium were removed by etching.
Further, after washing with pure water, the resist was removed with acetone.

Gold etchant: 4GKI and 1 gI ₂ those were dissolved in 40ml water chromium etchant: 0.5GNaOH and 1gK ₃ Fe (CN)
FIG. 3 (b) shows a state where a gold electrode is formed by dissolving ₆ in 4 ml of water.

(10) Formation of gas permeable membrane A silicone varnish (Shin-Etsu Silicone, KR-28) was placed on the perforated surface of the substrate after the etching of (6).
2) Apply. Baking at 150 ° C for 30 minutes. In this state, the varnish is not completely dried and is still in a sticky state (FIG. 3 (a)).

(11) Wafer bonding The substrate 1 on which the electrodes 3a and 3b are formed and the substrate 1 on which holes are formed are bonded. After laminating, baking 250
C. for 2 hours.

(12) A hydrophobic insulating film 7 (made by Shin-Etsu Silicone,
ES-1001).

(13) Cutting out the substrate A large number of oxygen electrodes formed on the substrate 1 were cut out into chips.

(14) While the small oxygen electrode main body is immersed in 0.1 M KCl, the pressure of the electrolyte is reduced, and the electrolyte 6 is introduced into the small oxygen electrode sensitive part. After this step, a small oxygen electrode that actually functions is obtained (FIG. 3 (c)).

The small-sized oxygen electrode thus completed is immersed in a sensitive part, for example, in a buffer solution, and a reduction voltage of oxygen generated from the cathode is measured while a constant voltage is applied between the cathode and the anode.

〔The invention's effect〕

According to the method of the present invention, since the process of forming the electrolyte layer is eliminated from the process, there is an advantage that the wafer can be formed in a batch from the beginning to the end. Further, since the gas permeable membrane can be stored in a dry state without the electrolyte layer, deterioration of the gas permeable membrane does not easily occur, and long-term storage is possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a preferred example of a small oxygen electrode according to the present invention. FIG. 2 is a cross-sectional view of the electrode shown in FIG.
3 (a) to 3 (c) are cross-sectional views sequentially showing the latter half of the manufacturing process of the small oxygen electrode shown in FIGS. 1 and 2. DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Insulating film, 3a, 3b ... Electrode, 5 ... Hole (groove), 6 ... Electrolyte solution, 7 ... Hydrophobic insulating film, 8 ... Hole for electrolyte solution, 10 ... a gas permeable membrane.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-27254 (JP, A) JP-A-64-88245 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 27/30

Claims (2)

(57) [Claims] An electrolyte accommodating portion comprising a substrate, an electrolyte accommodating groove formed on the substrate by anisotropic etching, and a gas-permeable film formed on a surface on which the electrolyte accommodating groove is formed;
An electrode forming portion formed on a flat substrate via an insulating film, and a part of each of which extends into the groove; and an electrode forming portion into which the electrolyte is introduced. A small-sized oxygen electrode having a hollow cavity and a hole for introducing an electrolyte into the electrolyte accommodating groove. 2. An electrolyte-accommodating groove and an electrolyte-introducing hole connected to the electrolyte-accommodating groove are formed on a substrate by anisotropic etching, and a gas-permeable film is formed on a surface on which the electrolyte-accommodating groove is formed. Forming an electrolyte containing portion by forming an electrode forming portion by forming a plurality of electrodes on a flat substrate via an insulating film; and forming the electrolyte containing portion and the electrode forming portion, Bonding the electrode so that a part of each electrode extends into the groove and the groove forms a cavity into which an electrolyte is introduced.