JPH046456A - Oxygen electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a gas transmitting film for a long time and to make it possible to manufacture a compact electrode by providing a first substrate on the surface of which electrodes are formed, providing a second substrate wherein a hole is provided at a region corresponding to parts of the electrodes of the first substrate and a groove for communicating the hole and the end parts is provided so that the second substrate is bonded to the first substrate, and providing a gas transmitting film covering the hole. CONSTITUTION:Electrodes 3A and 3B are formed on a first substrate 1. A part of the substrate is exposed so that connection to another device is possible. A second substrate 2 wherein a hole 4 is provided at a region corresponding to the regions of respective parts of the electrodes 3A and 3B is provided. An electrolyte injecting grooves 5 for communicating the hole 4 and the end parts is formed on the surface which is bonded to the first substrate 1. An exposed gas transmitting film 6 is formed at a region which covers at least the hole 4 on the upper surface of the substrate 2. In the case of a galvanic type, one electrode of two electrodes is formed of gold or platinum and becomes a cathode. The other electrode is formed of silver or lead and becomes an anode. In the case of a polar type, both electrodes are formed of gold or platinum.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of an oxygen electrode that functions as an oxygen concentration detection means, an object of the present invention is to provide an oxygen electrode that does not cause damage to the gas permeable membrane over a long period of time and is small in size. is formed on the surface thereof; and the first substrate (1) is bonded onto the first substrate (1) and has one opening in a region corresponding to a partial region of each of the electrodes; A second substrate having a groove extending along the surface to be bonded to the first substrate and communicating the opening with the end, and an oxygen electrode having a gas permeable film covering the opening. .

[Industrial application field]

The present invention relates to an improvement in an oxygen electrode that functions as an oxygen concentration detection means, and an improvement in a method for manufacturing the same.

In particular, an improvement in the structure of an oxygen electrode that allows the electrolyte to be retained in a removed state to prevent damage to the gas permeable membrane, and a method for manufacturing an oxygen electrode that improves productivity. Regarding the improvement of.

[Conventional technology]

Oxygen electrodes are used to measure oxygen concentration in various fields. For example, it is used to measure biochemical oxygen demand (BOD) in water to maintain water quality, and in the fermentation industry, it is used to measure dissolved M in fermenters. Furthermore, in combination with enzymes, glucose is used to measure the concentration of sugars, alcohols, etc. For example, glucose reacts with dissolved oxygen using an enzyme called glucose oxidase as a catalyst and turns into gluconolactone. By utilizing the decrease in dissolved oxygen that diffuses into the cell, the glucose concentration can be measured from the amount of dissolved oxygen consumed.

In this way, oxygen electrodes can be widely used in various fields such as environmental measurement, fermentation industry, and clinical medicine.

By the way, there are two types of oxygen electrodes: a 28i type and a three-power type. There are two types of two-scraper type: galvanic type and polar mouth type.
The galvanic type is a self-power generation type in which the cathode is made of gold or platinum and the anode is made of silver or lead, and the oxygen concentration is measured by measuring the current flowing between the two electrodes without applying an external voltage. The mouth type is a voltage application type in which both the cathode and anode are made of gold or platinum, and the oxygen concentration is measured by applying a constant voltage from the outside and measuring the current flowing between the two electrodes. The three-electrode system is generally a polar type, in which the working and counter electrodes are made of gold or platinum, the reference electrode is made of silver coated with silver chloride, and there is a gap between the reference electrode and the working electrode. The oxygen concentration is measured by applying a constant voltage and measuring the current flowing between the counter electrode and the working electrode.

In order to miniaturize these oxygen electrodes, an oxygen electrode having the structure shown in FIG. 12 was developed by applying micromachining technology. This is because a recess 15 is formed in the silicon substrate 14 by anisotropic etching.
Two electrodes 3A and 3B are formed spaced apart from each other from the surface of the recess 15 with an insulation 1116 in between, the recess 15 is filled with an electrolyte-containing body 17, and a gas permeable membrane 18 is formed thereon. It has a built-in structure.

The present invention is an improvement in the structure of a small-sized oxygen electrode manufactured by applying such micromachining technology, and an improvement in a manufacturing method thereof.

[Problem to be solved by the invention]

The oxygen electrode according to the above-mentioned conventional technology can be manufactured using a wafer process up to the formation of the two electrodes 3A and 3B, but the subsequent steps are performed after each oxygen electrode is cut into chips. Since it is a chip process, it has the disadvantage of low productivity. Furthermore, since the electrolyte-containing body 17 and the gas-permeable membrane are in constant contact even during storage when not used for measurements, the gas-permeable membrane reacts with the electrolyte, deteriorates, and is easily damaged. .

The purpose of the present invention is to eliminate these drawbacks,
It has two independent purposes. The first objective is to provide an oxygen electrode in which the gas permeable membrane is not damaged over a long period of time and is compact.The second objective is to provide an oxygen electrode in which the gas permeable membrane is not damaged over a long period of time and is compact. The object of the present invention is to provide a method for manufacturing a small-sized oxygen electrode with high productivity.

[Means to solve the problem]

Of the two purposes above, the first purpose is to
B) is formed on the surface of the first substrate (1), and the electrodes (3A, 3
One opening (
4), a groove (4) extending along the surface to be bonded to the first substrate (1) and communicating the opening (4) with the end;
5) and an oxygen electrode comprising a gas permeable membrane (6) covering said opening (4).

Note that it is effective that the electrodes (3A, 3B) are embedded in the first substrate (1). Further, the first substrate (1) is a glass plate, the second substrate (2) is a silicon plate, and the gas permeable membrane (6) is a glass plate.
is preferably a film of exposed negative photoresist.

Of the above two objectives, the second objective can be achieved by any of the following means.

The first means includes electrodes (3A, 3B) on the first substrate (1).
), and the above-mentioned electrodes (3A,
One opening (4) is formed in a region corresponding to each one category area of the second substrate (3B), and a shallow groove (5) is formed that communicates this opening (4) with the end. 2) the surface with the groove (5) is fixed to the surface of the first substrate (1) on which the electrodes (3A, 3B) extend; This method of manufacturing an oxygen electrode includes the step of forming a gas permeable DI (6) to cover the opening (4).

The second means includes electrodes (3A, 3
B) is embedded, and one opening (4) is formed in the second substrate (2) in a region corresponding to one category region of each of the electrodes (3A, 3B), and this opening (4) A shallow groove (5) communicating with the end of the second substrate (2) is formed.
The surface with the groove (5) is fixed to the surface of the first substrate (1) on which the electrodes (3A, 3B) extend, and a gas is placed on the second substrate (2). This method of manufacturing an oxygen electrode includes the step of forming a permeable film (6) to cover the opening (4).

Note that the step of covering the opening (4) involves burying the opening (4) with a positive resist (12) and forming a negative photoresist film (13) on the positive resist (12). After that, a small area (covering the opening (4)) is exposed, and the negative photoresist film (13) in the unexposed area and the positive photoresist (12) are exposed.
) is preferably a step of dissolving and removing.

(Function) Since the oxygen electrode according to the present invention is not an electrolyte-sealed type, the electrolyte can be removed during storage, so the gas permeable membrane is not constantly in contact with the electrolyte.
Damage due to deterioration is prevented.

Furthermore, in micromachining technology, it is well known that the wafer process is highly efficient and the chip process is inefficient. Because it can be done, productivity is extremely high.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An oxygen electrode and a method for manufacturing the same according to an embodiment of the present invention will be described below with reference to the drawings.

See Figures 1a and 1b. Figure 1a shows a perspective view of a bipolar oxygen electrode as an example. Figure 1b is an X-Y cross-sectional view of Figure 1a.
In the figure, 1 is a first substrate made of a glass substrate, a ceramic substrate, a silicon substrate on which an insulating film is formed, etc. Two electrodes 3A and 3B are formed on the first substrate 1, and one of them is portions are exposed to allow connection with other devices. Reference numeral 2 denotes a second substrate made of silicon or the like and having an opening 4 in a region corresponding to a partial region of each of the two electrodes 3A and 3B (a region in which a reaction occurs and functions as an electrode body). A groove 5 for injecting an electrolytic solution is formed on the surface to be bonded to the first substrate 1, which communicates the opening 4 with the end.

A gas permeable WI 46 made of exposed negative photoresist, a silicon substrate, or the like is formed in a region covering at least the opening 4 on the upper surface of the second substrate 2 .

In the case of the galvanic type, one of the two electrodes is made of platinum and serves as a cathode, and the other electrode is made of silver or lead and serves as an anode. In the case of the polar mouth type, both electrodes are made of gold or platinum.

In addition, in the case of a three-electrode type, three electrodes are formed, two of the three are made of gold or platinum and serve as a working electrode and a counter electrode, respectively, and the remaining one is made of silver coated with silver chloride. Note that if the electrodes 3A and 3B are embedded in the first substrate 1, the first substrate 1
As an example, there is a method for manufacturing a bipolar polar mouth type (voltage application type) oxygen electrode, which is preferable because the adhesion between the second substrate 2 and the second substrate 2 is good, and there is no leakage of the electrolytic solution. I will explain about it.

Refer to Figure 2. A (100) silicon substrate with a thickness of 3,500 mm is used as the second substrate 2. After cleaning this using a mixed solution of hydrogen peroxide and ammonia and concentrated nitric acid, wet thermal oxidation is performed. A silicon dioxide film 7 with a thickness of about 0.8 nm is formed on the entire surface, a negative photoresist 8 such as OMR-83 manufactured by Tokyo Ohka Co., Ltd. is coated on the surface, and patterned using a photolithography method. The opening 9 is formed by removing from the area corresponding to the area where the sensitive part of the oxygen electrode is formed. The same negative photoresist 8 is applied to the back surface of the silicon substrate 2, and baked by heating to a temperature of 150° C. for 30 minutes.

See Figure 3. 50% hydrofluoric acid and 40% ammonium fluoride
The silicon substrate 1 is immersed in a solution mixed at a ratio of 6, and the area of the silicon dioxide film 7 exposed in the opening 9 formed in the negative photoresist film 8 (the figure shows the state after removal) is removed. The negative photoresist 8 is removed by etching and then using a solution containing sulfuric acid and hydrogen peroxide in a ratio of 2:1 to complete the shape shown.

Refer to Fig. 4. The silicon substrate 2 is immersed in a 35% potassium hydroxide aqueous solution at 80°C for anisotropic etching to form a penetrating opening 4 in the silicon substrate 2, and then washed with pure water. Then, the silicon dioxide film 7 used as an etching mask is removed by immersion in a solution containing 50% hydrofluoric acid and 40% ammonium fluoride in a ratio of 1:6.

Refer to Figure 5 Groove 5 for electrolyte injection using the same method as described above.
form. Note that the groove 5 can also be formed before the above-mentioned opening 4 is formed, and this is rather preferable.

Refer to FIG. 6. The first substrate 1 is a glass substrate, for example, manufactured by Corning.
No. 7740, negative photoresist 10
is coated, patterned using a photolithography method, and removed from the electrode formation area.

See Figure 7. 50% hydrofluoric acid and 40% 0% fluormonium
The glass substrate 1 is etched to a depth of about 2n by immersing it in a solution mixed at a ratio of 6 to 6, and a recess 1 is formed in the electrode formation area.
1 is formed, and the negative photoresist film 10 is removed and cleaned.

Refer to Figure 8. Using vacuum evaporation method etc., 400 layers of 0 chrome film and 4
After forming a laminated film (only the state after completion of the electrode is shown) with a gold film with a thickness of 0.000, a positive photoresist such as 0FPR-800 manufactured by Tokyo Ohka Co., Ltd. is coated to form a photoresist film (
(not shown) is formed, patterned using a photolithography method and removed from areas other than those corresponding to the recesses 11, and using this (not shown) as a mask, a bench etching solution (4 g of potassium iodide and 1g of iodine and 40mj
l! solution in water) and chrome etching solution for chromium (hydrocarbon soda 0.58 and Ks Fe (CN)
-1 g dissolved in 4 ml of water) to etch the laminated film, form electrodes 3A and 3B in the recess 11, and then wash with pure water, and further remove the positive photoresist. .

Refer to FIG. 9 After cleaning the glass substrate 1 and silicon substrate 2 with a mixed solution of hydrogen peroxide and ammonia water and pure water, the surface of the glass substrate 1 where the electrodes 3A and 3B are formed, and the silicon substrate 2 and the surface where the groove 5 for electrolyte injection is formed are overlapped, and using an anodic bonding method, it is heated to a temperature of 400°C, and a voltage of 350 V is applied between both substrates with the glass substrate 11 side being negative.
Apply voltage to fix it. Note that instead of the anodic bonding method, adhesive may be used for bonding.

Pour a positive photoresist 12 into the opening 4, as shown in Fig. 10.
Heat to temperature C and bake. The resist attached to the surface of the silicon substrate 2 is removed by repeating exposure and development, leaving the resist 12 only in the opening 4.

Next, a negative photoresist (
Rubber-based) 13 is applied and exposed to form a gas permeable film 6. At this time, only the region covering the opening 4 may be exposed, and the gas permeable film may be selectively formed only in the region covering the opening 4.

Gas permeable! Of course, the material of IF6 is hydrophobic and does not allow aqueous solutions to pass through it, but it is liquid in its raw material state and can be dip coated or spin coated, and has good adhesion to silicon substrates. ,
It is essential that the electrolyte does not leak outside.
In addition to negative photoresists (rubber-based), silicone rubber and the like are suitable, but Teflon (trade name) is not suitable.

Note that if the strength of the negative photoresist film alone is insufficient as a gas permeable film, silicone rubber such as KE347T manufactured by Shin-Etsu Silicon Co., Ltd. may be coated thereon.

Refer to FIG. 11. After immersing in an acetone solution and dissolving and removing the positive photoresist 12 in the opening 4 through the electrolyte injection groove 5,
A large number of oxygen electrodes formed on a substrate are cut into chips.

When measuring the oxygen concentration, the oxygen electrode is immersed in a neutral electrolytic solution such as a 0.1 M (Mora, MO1/I!) potassium chloride aqueous solution, and the electrolytic solution is depressurized. Gas permeable membrane 6
Since the gas permeates through the electrolyte injection groove 5, the above process allows the electrolyte injection groove 5 to be formed without applying excessive force to the gas permeable membrane 6.
An electrolyte can be injected into the opening 4 via.

After injecting the electrolyte into the opening 4, the electrolyte injection groove 5 may be sealed using an epoxy resin or the like, but sealing is not essential for short-term use.

T-2 In that case, it is desirable to use the device with the groove 5 facing upward.

When removing the electrolyte, immerse the entire oxygen electrode in distilled water, etc. to dilute the electrolyte, and then dry it naturally. The distilled water will vaporize and pass through the gas permeable membrane to be removed. .

After that, it can be stored for a long time if it is stored away from areas where active gas exists or high humidity.

In addition, when manufacturing a galvanic type oxygen electrode, one of the two electrodes is formed of gold or platinum,
The other electrode is made of silver or lead, and the electrolyte is an alkaline aqueous solution such as IM potassium hydroxide aqueous solution. In addition, when manufacturing a three-electrode oxygen electrode, three electrodes are formed, two of which are made of gold or platinum and serve as a working electrode and a counter electrode, respectively, and the remaining one is coated with silver chloride. A reference electrode is formed using silver, and a potassium chloride aqueous solution, a sodium sulfate aqueous solution, or the like is used as an electrolyte.

Further, instead of forming the electrodes 3A and 3B by embedding them in the glass substrate 1, they may be formed on the glass substrate 1 and bonded to the silicon substrate 2 using an adhesive. Although it is simplified, it is inferior in terms of adhesiveness.

〔Effect of the invention〕

As explained above, in the oxygen electrode and its manufacturing method according to the present invention, there is no need to use an electrolyte-sealed type, so the electrolyte can be removed during storage, so the gas permeable membrane is always There is no need for it to be in contact with the electrolyte, so deterioration of the gas permeable membrane is avoided and damage is prevented. Further, since all steps can be performed in a wafer process using micromachining technology, small-sized oxygen electrodes can be manufactured with high productivity.

[Brief explanation of the drawing]

FIG. 1a is a perspective view of an oxygen electrode according to an embodiment of the present invention. FIG. 1b is an X-Y sectional view of FIG. 1a. 2 to 11 are process diagrams for manufacturing an oxygen electrode according to an embodiment of the present invention. FIG. 12 is a cross-sectional view of an oxygen electrode according to the prior art. 1 ・ ・ ・ 2 ・ ・ 3A, 3 4 ・ ・ ・ 5 ・ ・ 6 ・ −・ 7 ・ ・ 8 ・ ・ 9 ・ ・ ・ 10・ 14 ・ ・ 15 ・ ・ 16 ・ ・ ・ First substrate, second substrate, B...electrode, opening, groove, gas permeable film, silicon dioxide film, negative photoresist, opening, negative type Photoresist, recess, positive photoresist, negative photoresist, silicon substrate, recess, insulating film, 17...electrolyte-containing body, 8...gas permeable film.

Claims (1)

[Claims] [1] A first device having electrodes (3A, 3B) formed on its surface.
substrate (1), and the electrodes (3A, 3
One opening (
4), a groove (5) extending along the surface to be bonded to the first substrate (1) and communicating the opening (4) with the end portion;
An oxygen electrode characterized in that it has a second substrate (2) having: a gas permeable membrane (6) covering the opening (4). [2] The electrodes (3A, 3B) are connected to the first substrate (1
2. The oxygen electrode according to claim 1, wherein the oxygen electrode is embedded in a. [3] The oxygen electrode according to claim 1 or 2, wherein the first substrate (1) is a glass plate and the second substrate (2) is a silicon plate. [4] Claim [1], wherein the gas permeable film (6) is a film of an exposed negative photoresist;
[2] or the oxygen electrode described in [3]. [5] Form electrodes (3A, 3B) on the first substrate (1), and form electrodes (3A, 3B) on the second substrate (2) in areas corresponding to partial areas of each of the electrodes (3A, 3B). forming an opening (4) in the second substrate (2), forming a shallow groove (5) communicating the opening (4) with an end, and connecting the surface of the second substrate (2) with the groove (5) to the second substrate (2); 1
A gas permeable film (6) is fixed to the surface of the substrate (1) on which the electrodes (3A, 3B) extend, and a gas permeable film (6) is formed on the second substrate (2) to cover the opening (4). A method for manufacturing an oxygen electrode, comprising the steps of: [6] The electrodes (3A, 3B) are embedded on the first substrate (1), and the electrodes (3A, 3B) are embedded on the second substrate (2).
One opening (4) is formed in a region corresponding to each partial region of the second substrate (3B), a shallow groove (5) is formed that communicates the opening (4) with the end, and 2) Said groove (5)
A certain surface of the electrode (3A, 3) of the first substrate (1)
B) is fixed to the extending surface of the oxygen electrode, and includes the step of forming a gas permeable film (6) on the second substrate (2) to cover the opening (4). Production method. [7] The step of covering the opening (4) includes covering the opening (4).
4) with a positive resist (12), and a negative photoresist film (13) is placed on the positive resist (12).
), the step is to expose at least a region covering the opening (4), and dissolve and remove the negative photoresist film (13) and the positive resist (12) in the unexposed region. The method for manufacturing an oxygen electrode according to claim 5 or 6, characterized in that: