JPH03269254A - Small-sized oxygen electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To omit an electrolyte layer and to prevent the deterioration due to the formation of a gas transmitting film by sticking an electrolyte containing part and an electrode forming part comprising a plurality of electrodes whose parts are extending into a groove through an insulating film. CONSTITUTION:A plurality of substrates 1 are provided. One substrate 1 is an electrolyte containing part comprising an electrode containing groove 5 and a gas transmitting film 10 which is formed on the surface of the groove 5. The other substrate 1 is an electrode forming part comprising a plurality of electrodes 3a and 3b whose parts are extending into the groove 5. A plurality of the above described substrates 1 are stuck together through an insulating film 2. The groove 5 of one substrate 1 is formed by anisotropic etching, and the rear surface is covered with a hydrophobic insulator 7 which is hard to break. The groove 5 is filled with electrolyte when the electrodes 3a and 3b are used. Therefore, electrolyte is not formed, and the gas transmitting film 10 is not deteriorated.

Description

[Detailed Description of the Invention] [Summary] Regarding a small oxygen electrode and its manufacturing method, particularly regarding a gas permeable membrane and its manufacturing method, the present invention relates to a gas permeable membrane without an electrolyte layer (having a hole shape) to prevent deterioration of the gas permeable membrane. The purpose of the present invention is to provide a small oxygen electrode that does not generate oxygen, and a method for manufacturing the same, which includes a substrate, an electrolyte storage groove made on the substrate by anisotropic etching, and a gas permeable membrane formed on the surface of the electrolyte storage groove. and an electrode forming section formed on a flat substrate with an insulating film interposed therebetween, each of which partially extends into the groove. composition.

[Industrial application field]

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.

Small oxygen electrodes can be advantageously used for measuring dissolved oxygen concentrations in various fields.

(1) (2) For example, biochemical oxygen demand (BOD) in water is measured from the perspective of water quality conservation, and this small oxygen electrode can be used as a measuring device for dissolved oxygen concentration. can. 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 the small oxygen electrode of the present invention can be used as a measuring device for this purpose. 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.

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

[Conventional technology]

Since conventional glass oxygen electrodes cannot be miniaturized or mass produced, the inventors developed a new type of small oxygen electrode using lithography technology and anisotropic etching technology. Applied for a patent (Patent application 1986-
No. 71739, Japanese Unexamined Patent Publication No. 63-238548). In this oxygen electrode, two electrodes are formed on a hole (groove) formed by anisotropic etching on a silicon substrate, with an insulating film interposed therebetween, and an electrolyte-containing body is housed inside the hole. , and finally an oxygen electrode having a structure in which 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 cost.

[Problem to be solved by the invention]

The gas permeable membrane of the oxygen electrode is mainly limited to silicone rubber and other negative resist materials. In particular, (3) and (4) silicone rubber is formed only by a dip process, resulting in unstable film thickness and problems in adhesion to the silicon substrate.

Further, the electrolyte-containing body accommodated inside the hole (groove) contains water, which causes deterioration of the gas permeable membrane quality.

Furthermore, in the production of oxygen electrodes, it becomes necessary to form electrode patterns with hundreds of steps, which is by no means an easy process.

An object of the present invention is to provide a small-sized oxygen electrode having an electrolyte layer (in the form of a hole) that does not cause deterioration of a gas-permeable membrane, and a method for manufacturing the same.

[Means to solve the problem]

According to the present invention, the above-mentioned problem is solved by: a substrate; an electrolyte storage section comprising an electrolyte storage groove formed on the substrate by anisotropic etching; and a gas permeable membrane formed on the surface of the electrolyte storage groove; The problem is solved by a small-sized oxygen electrode, which is formed by pasting together an electrode forming part formed on a substrate with an insulating film interposed therebetween, and each of which partially extends into the groove. Ru.

Furthermore, according to the present invention, the above-mentioned problem is solved by forming an electrolyte storage groove on a substrate by anisotropic etching, forming an electrolyte storage part by forming a gas permeable film on the surface where the electrolyte storage groove is formed, and forming an electrolyte storage groove on a flat substrate. an electrode forming portion is formed by forming a plurality of electrodes through an insulating film, and the electrolyte accommodating portion and the electrode forming portion are stretched such that a portion of each electrode extends into the groove. The problem is solved by a method of manufacturing a small-sized oxygen electrode, which is characterized by combining the two.

That is, the present inventors first form two electrodes such as a cathode and an anode, or multiple electrodes such as a working electrode, a reference electrode, and a counter electrode, as well as a gas permeable membrane, and introduce the electrolyte into the sensitive part after completion and before use. It was to be. In addition, the cathode, anode, working electrode, reference electrode, counter electrode, etc. are formed on a flat substrate, making it unnecessary to form a pattern on a step.

The feature of the present invention is that the above-mentioned problems are solved by applying basic technology of so-called micromachining. That is, a hole (groove) is made by anisotropic etching on a flat substrate with a cathode and an anode (5) (6) or a silicon substrate on which a working electrode, a reference electrode, and a counter electrode are formed, and then a hole (groove) is made on the surface with the hole. The present invention relates to a small oxygen electrode that is made by applying a water-repellent gas-permeable membrane, then bonding two substrates together using the gas-permeable membrane, and then introducing an electrolyte into the hole, and a method for manufacturing the same.

In carrying out the method of the present invention, a semiconductor substrate, particularly a silicon substrate, a glass substrate, or a ceramic substrate can be advantageously used as the substrate of the electrode body. 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.

[For production]

In the present invention, it is only necessary to introduce an electrolytic material such as an electrolytic solution into the electrolyte container immediately before use after completion, and mass production is possible using lithography technology and thin film forming technology.

〔Example〕

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

FIG. 1 is a perspective view showing a preferred example of a small-sized oxygen electrode according to the present invention. The illustrated oxygen electrode has a rectangular parallelepiped shape, and the sensitive part is covered with a gas permeable membrane 10, and the cathode 3as is connected to an attached device.
A part of the anode 3b is exposed. In this embodiment, the cathode 3as and the anode 3b serving as electrodes are made of gold electrodes as well as the picture electrode in order to have a polar mouth type.

The structure of the small oxygen electrode shown in FIG. 1 can be understood in detail from FIG. 2, which is a sectional view taken along line 1--2. One of the opposing silicon substrates 1 has a hole (groove) formed by anisotropic etching. In addition, a cathode 3a and an anode 3b are deposited as a pair on one silicon substrate 1, and the back surface of the substrate is covered with a sparse (7) (8) water-based insulating film 7 that is hard to tear. . Furthermore, a gas permeable membrane tank 10 is formed above the hole. When using this electrode, 0.1M is placed in the hole 5 of the silicon substrate 1 as an electrolyte.
KCI is satisfied. In the figure, L1 is 2 mm.

L2 is 15 mm.

The small oxygen electrode shown in FIGS. 1 and 2 is, for example,
It can be advantageously manufactured by the following steps (1) to (14) and the manufacturing process sequentially shown in FIG. In the following explanation, in order to facilitate understanding, 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 at the same time.

(1) Wafer Cleaning A silicon wafer (substrate) with a (100) surface of 2 inches and a thickness of 350 tnTl was prepared and was cleaned with a mixed solution of hydrogen peroxide and ammonia and concentrated nitric acid.

(2) Formation of SiO2 film A silicon wafer was subjected to wet thermal oxidation to form a 5102 film with a thickness of 0.8p on the entire surface.

(3) Formation of etching pattern After applying a negative photoresist (TOKYO OHKA OMR-83 (product name), viscosity 60 cP) to the rough substrate surface, exposure, development, and rinsing are performed to form the etching pattern on the wafer. A resist pattern was formed.

(4) Resist coating After coating the same negative photoresist as that used in the above step on the back surface of the substrate, it was baked at 150° C. for 30 minutes.

(5) Etching of SiO□ film 50% hydrofluoric acid: 40% ammonium fluoride 1:6
The wafer was immersed in an aqueous solution, and exposed portions 8102 not covered with photoresist were 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 continued until the hole was through. After etching was completed, the wafer was washed with pure water.

(9) (10) After completing this anisotropic etching, the 5102 film used during etching was removed. This was carried out in a 1:6 aqueous solution of 50% hydrofluoric acid: 40% ammonium fluoride as in 5.

The hole for the sensitive part is formed in this way, and the hole for injecting the electrolyte is also formed in this way. Preferably, this is done before forming the sensitive pores.

(7) Formation of chromium and gold thin film On one side of the substrate on which the 5in2 film was formed in step 2, a chromium thin film (400 people, for adhesion between the gold and the substrate) was followed by a gold thin film (4000A) by vacuum evaporation. did.

(8) Formation of resist pattern for electrode formation Positive photoresist (TOKYO OHKA 0FPR-800 (product name),
A resist pattern for electrode formation was formed on the gold thin film of the wafer using a resist film having a viscosity of 20 cP.

(9) Gold and chromium etching The substrate on which the resist pattern was formed was immersed in the following gold and chromium etching solutions in this order, and the exposed gold and chromium portions were removed by etching. Furthermore, after washing with pure water, the resist was removed with acetone.

■ Gold etching solution: 4 g KI and 1 g I2 dissolved in 40 g of water. ■ Chrome etching solution: 0.5 g NaOH and 1 g K3Fe (CN) e dissolved in 4 g of water. It is shown in FIG. 3(b).

(10) Formation of a gas permeable film Apply a silicone face (manufactured by Shin-Etsu Silicone, KR-28
Apply 2). Shake at 150℃ for 30 minutes.

In this state, the fest has not completely dried and is still sticky (FIG. 3(a)).

(11) Laminating wafers The substrate 1 on which the electrodes 3a and 3b are formed and the substrate 1 on which the holes are formed are bonded together. After pasting, bake 2 times.
The test was carried out at 50°C for 2 hours.

(12) Form a hydrophobic insulating film 7 (manufactured by Shin-Etsu Silicone, B5-1001) on the back surface of the substrate.

(13) Cutting out the substrate 11) (12) A large number of oxygen electrodes formed on the substrate 1 were cut into chips.

(14) With the small oxygen electrode main body immersed in 0° IMKCI, the entire electrolyte is depressurized and the electrolyte 6 is introduced into the small oxygen electrode sensitive part. After this step, a miniature oxygen electrode that actually functions is obtained (FIG. 3(C)).

The small oxygen electrode thus completed is immersed in a buffer solution, for example, and a constant voltage is applied between the cathode and the anode to measure the reduction current of oxygen generated from the cathode.

〔Effect of the invention〕

According to the method of the present invention, since the step of forming an electrolyte layer is eliminated from the process, there is an advantage that a wafer can be manufactured all at once from beginning to end. Furthermore, since it can be stored in a dry state without an electrolyte layer, the gas permeable membrane is less prone to deterioration and can be stored for a long time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a preferred example of a small-sized oxygen electrode according to the present invention, FIG. 2 is a cross-sectional view of the electrode in FIG.
FIGS. 3(a) to 3(C) are sectional views sequentially showing the latter half of the manufacturing process of the small-sized oxygen electrode shown in FIGS. 1 and 2. 1... Silicon substrate, 2... Insulating film, 3a.3
b...electrode, 5...hole (groove), 6...electrolyte, 7...hydrophobic insulating film, 5...hole to put electrolyte in, 10...gas permeable membrane . (13) (14) Fig. 2 1... Silicon substrate 2... Insulating film 3a, 3b... Electrode (cathode, 7 notes) 5...
・Hole (groove) 6... Electrolyte 7... Hydrophobic insulating film 8... Hole for inserting electrolyte 10... Gas permeable membrane

Claims (1)

[Claims] 1. An electrolyte storage section consisting of a substrate, an electrolyte storage groove formed on the substrate by anisotropic etching, and a gas permeable membrane formed on the surface of the electrolyte storage groove; a flat plate; 1. A small oxygen electrode, comprising: an electrode forming section formed on a substrate with an insulating film interposed therebetween, and consisting of a plurality of electrodes, each of which partially extends into the groove. 2. Form an electrolyte storage groove on the substrate by anisotropic etching, form an electrolyte storage part by forming a gas permeable film on the surface where the electrolyte storage groove is formed, and form an electrolyte storage part on the flat substrate through an insulating film. The electrode forming part is formed by forming a plurality of electrodes, and the electrolyte accommodating part and the electrode forming part are pasted together so that a part of each electrode extends into the groove. A method for manufacturing a small oxygen electrode.