JPH03262952A - Production of small-sized oxygen electrode - Google Patents

Abstract

PURPOSE:To improve the efficiency of a stage for forming an anode and cathode by executing partial etching of gold or platinum and silver in this order, thereby forming the cathode of the gold or platinum and the anode of the silver on a semiconductor substrate. CONSTITUTION:A silicon oxide film 9 is deposited as an insulating film over the entire surface of the silicon substrate 1 having a hole formed by anisotropic etching and the rear surface is so formed as to be coated with a hydrophobic insulating film 13. A pair of the cathode and anode are deposited in the hole of the substrate 1. This cathode and anode are respectively partly extended to the outer side of the groove (hole). An electrolyte-contg. body 11 is filled in the hole of the substrate 1 and further the upper part of the hole is coated with a gas permeable film 12 in the form of covering the entire upper part of the substrate 1. The side surfaces and rear surface are also so formed that the film 12 is utilized as the insulating film.

Description

[Detailed Description of the Invention] [Summary] Regarding the manufacturing method of a small oxygen electrode, especially the manufacturing method of a small, low-cost, and mass-producible oxygen electrode, the efficiency of the anode and cathode formation process, which is the most important for this oxygen electrode, is important. The purpose of the present invention is to provide a method for manufacturing a compact oxygen electrode that improves the performance of the oxygen electrode.
A step of forming electrodes that will become a cathode and an anode from the lower part of the line groove to the surface of the substrate via an insulating film, and a gas that covers the surface of the substrate except for the exposed portion of the electrode and covers the electrolyte-containing body. In a method for manufacturing a small oxygen electrode that includes a step of forming a permeable film, a conductive material for adhesion, gold or platinum, and silver are laminated in this order on the semiconductor substrate, and each layer is partially etched. Alternatively, a platinum cathode and a silver anode may be formed.

[Industrial application field]

The present invention relates to a method for manufacturing a small-sized oxygen electrode, and particularly to a method for manufacturing an oxygen electrode that is small, inexpensive, and can be mass-produced.

Oxygen electrodes can be advantageously used to measure dissolved oxygen concentration in various fields. For example, biochemical oxygen requirements in water from the perspective of water quality conservation! This small oxygen electrode can be used as a measuring device for dissolved oxygen concentration in (BOD) measurement.

Furthermore, in the fermentation industry, in order to efficiently ferment alcohol and the like, 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, 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, vitamins, etc. For example, glucose is oxidized to gluconolactone by reacting with dissolved oxygen using vIs called glucose oxidase as a catalyst. Concentration can be measured.

As described above, the small oxygen electrode according to the present invention can be used in various fields such as environmental measurement, fermentation industry, and clinical medicine, but especially in the field of clinical medicine where it is attached to a catheter and inserted into the body. is small, 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 phosphor-free technology and anisotropic etching technology. (Unexamined Japanese Patent Publication No. 63-23854)
No. 8〉. This oxygen electrode is made by forming two electrodes through an insulating film over a hole formed on a silicon substrate by anisotropic etching, further accommodating an electrolyte-containing body inside the hole, and finally This is an oxygen electrode with a structure in which the upper surface of the hole is covered with a gas permeable membrane. This oxygen electrode is small and
Since there is little variation in characteristics and mass production is possible, the cost is low.

In order to further improve this point and make it more suitable for mass production, the present inventors changed the electrolyte-containing body from agarose gel to acrylamide gel (Japanese Patent Application Laid-Open No. 63-311158), calcium alginate gel (Japanese Patent Application Laid-Open No. 63-311158), Gansho 63-176
No. 978>, and polymer electrolytes (patent application No. 1-0615)
No. 31), which not only improved mass productivity but also improved the characteristics of the oxygen electrode. However, even with these improvements, there were still problems that needed to be solved in order to put it into practical use. By using a silver electrode as an anode,
(Patent Application No. 1-049002).

[Problem to be solved by the invention]

The method described in Japanese Patent Application No. 1-049002 is a very innovative mold-making method because it significantly improves the characteristics of the oxygen electrode. However, when this method is examined in detail, a gold electrode is first formed as a cathode, and then a silver electrode is formed as an anode. These two processes (
Gold electrode, silver electrode formation) are almost the same, so substrate cleaning - metal vapor deposition - photoresist film buttering -
The etching-photoresist film stripping process must be repeated twice.

An object of the present invention is to provide a method for manufacturing a compact oxygen electrode that improves the efficiency of the anode and cathode formation process, which is the most important step in an oxygen electrode.

[Means to solve the problem]

According to the present invention, the above-mentioned problem is solved by the step of forming a groove on a semiconductor substrate by anisotropic etching, and the formation of an electrode that will become a cathode and an anode from the bottom of the line groove to the surface of the substrate via an insulating film. and a step of forming a gas permeable membrane that covers the surface of the substrate except for the exposed portion of the electrode and covers the electrolyte-containing body, wherein a conductive material for adhesion on the semiconductor substrate; The problem is solved by a method for producing a small oxygen electrode characterized in that a gold or platinum cathode and a silver anode are formed by laminating gold or platinum and silver in this order and partially etching each layer.

The conductive material for adhesion according to the present invention is preferably chromium, titanium, tungsten, etc., and its thickness is several hundred, especially 300.
~500 people is preferred.

In addition, the thickness of each layer of gold or platinum, which becomes the cathode electrode, and silver, which becomes the anode electrode, is 2,000 to 10,000.
Gold and platinum are preferred, but gold and platinum cost 2,000 to 50
00 people is more preferable.

[For production]

According to the present invention, by taking advantage of the property of positive photoresist that multiple exposures are possible, by partially selectively etching a multilayered metal film, the evaporation or sputtering process is completed in one step. It becomes possible to get away with it. The silver anode of a conventional oxygen electrode wears out and disappears as it is used, so near the end of the oxygen electrode's lifespan, the anode becomes extremely thin, increasing its resistance and deteriorating its characteristics. Since there is a gold layer underneath, no increase in resistance occurs, making it possible to obtain stable characteristics until the silver is completely consumed.

〔Example〕

A preferred example of the method for manufacturing a small oxygen electrode according to the present invention will be described below 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 12, and a part of the electrode 6.7 is exposed on the substrate surface for connection to an attached device. . In this example, the electrodes 6 and 7 were of a polar type, the cathode 6 was a gold electrode, and the anode 7 was a silver/silver chloride reference electrode.

The structure of the small oxygen electrode of FIG. 1 can be understood in detail from FIG. 2, which is a cross-sectional view taken along the line I--I. The silicon substrate 1 has holes formed by anisotropic etching, and a silicon oxide film 9 is deposited as an insulating film on the entire surface thereof. Furthermore, the back surface of the substrate is covered with a hydrophobic insulating film 13 that is hard to tear. A pair of cathodes 6 and anodes 7 are fitted into the holes of the silicon substrate 1. As shown in FIG. 1, a portion of each of the cathode 6 and the anode 7 extends to the outside of the groove (hole). Further, the hole in the silicon substrate 1 is filled with an electrolyte-containing body 11 . Further, the upper part of the hole is covered with a gas permeable film 12 covering the entire upper part of the substrate 1 (excluding the exposed part in FIG. 2), and this is also applied as an insulating film to the side and back surfaces. covered.

The small oxygen electrode shown in FIGS. 1 and 2 is, for example,
It can be advantageously manufactured by the manufacturing process sequentially shown in steps (1) to (19) below and FIGS. 3(a) to (h). In the following explanation, in order to make it easier to understand, we will describe the case where only one oxygen electrode is formed on one wafer, but it is important to note that in reality, many small oxygen electrodes are formed at the same time. I want to be understood. Note that here, a case will be described in which a polymer electrolyte is used as an electrolyte-containing body.

(1) Wafer Cleaning A 2-inch (100)-sided silicon wafer 8 with a thickness of 250 to 500 mm was prepared and thoroughly cleaned with a mixed solution of hydrogen peroxide and ammonia and concentrated nitric acid.

(2) Formation of Sin□ film The wafer 8 is subjected to wet thermal oxidation, and the entire surface is coated with 0.8Ja
A thick SiO film was formed.

(3) Formation of etching pattern An etching pattern was formed on the wafer using a negative photoresist (OMR-83 manufactured by Tokyo Ohka Co., Ltd., viscosity 60 cP). Photoresist was also coated on the back side of the wafer and betaed at 130° C. for 30 minutes.

(4) Etching the Sin2 film Immerse the wafer in a 50% hydrofluoric acid + 40% ammonium fluoride aqueous solution (1:6 mixture),
2 was removed by etching. Furthermore, the resist was removed with concentrated sulfuric acid + 30% hydrogen peroxide aqueous solution (2:1 mixture).

(5) Anisotropic etching of silicon Anisotropic etching of silicon was performed in a 35% potassium hydroxide aqueous solution at 80°C. - I dug hole 10. After the anisotropic etching was completed, the 5i02 film used during etching was removed with the solution used in step <4>.

(6) Formation of SiO□ film (Fig. 3 (a)) In order to grow a 5i02 film on the wafer surface, the wafer was subjected to wet thermal oxidation following the same cleaning process as in step (1).
An 8-thick insulating film 9 was formed.

(7> Formation of chromium, gold and silver thin films Following chromium thin film 2 (400A) for adhesion to the gold substrate, gold thin film 3 (4000A) and silver thin film 4 (400A)
00 persons) was formed by vacuum deposition.

(8) Application of photoresist for electrode formation (Figure 3(b))
) Positive photoresist 5 (TOKYO OHKA 0FPR=80
0, viscosity 20cP or 0FPR-5000, viscosity 5
0 cP) was dropped and spread evenly over the silicon wafer. Preferably, the amount of photoresist is just enough to cover the wafer. Post-baking was performed at 80°C for 30 minutes.

(9) Formation of photoresist pattern for electrode formation The pattern was aligned with the glass mask using an aligner, and exposure and development were performed. As in this example, when the positive photoresist 5 was applied thickly, it was not exposed to light at -degrees, so the exposure and development steps were repeated. Finally, the positive photoresist 5 remains on the electrode pattern of the cathode and anode.

(10) Etching of silver and gold (Figure 3 (C)) The wafer is immersed in the following silver etching solution and the entire circumference etching solution in this order, and the exposed silver and gold parts are etched using each of the following etching solutions. It was removed by etching.

Etching solution for silver: 29% ammonia water + 31% hydrogen peroxide + water (1:120 mix) Edible F1 Chinda solution = 4g potassium iodide + 1g iodine + 40m! Water (11> Continued during formation of resist pattern for electrode formation,
The same process as (9) was performed on the remaining positive photoresist 5, leaving the positive photoresist 5 in the anode pattern.

(12) Etching of silver and gold (Fig. 3 (d)) The wafer was immersed in the silver etching solution of (10), and the exposed silver portion was removed by etching.

(13) Chromium etching (Figure 3 (e)) The wafer was immersed in the following chromium etching solution, and the exposed chromium portion was removed by etching.Furthermore, the remaining positive photoresist 5 was peeled off with acetone. did.

Etching solution for chromium: 0.5 g sodium hydroxide + 1 g potassium ferricyanide + 4-water (14) Formation of photoresist pattern for injection of electrolyte-containing body On the surface of the main body, except for the hole 10 and the pad part for electrical contact. Negative photoresist 14 (Tokyo Ohka O
MR-83, viscosity 60 cP).

This was done by applying a photoresist to the wafer surface and performing exposure and development after pre-baterization.

(15) Hydrophobic insulating type Ty on the back side of the substrate <Figure 3 (f)
> A hydrophobic insulating film 5 (Shin-Etsu Chemical Co., Ltd. B5100I) made of silicone resin or the like was coated on the back surface of the substrate in a --like manner and baked at a temperature of 150° C. for 30 minutes.

(16> Cutting out the substrate A large number of oxygen electrodes formed on the substrate were cut into chips.

(17) Making the inside of the hole hydrophilic The tip end of the chip was immersed for a short time in a 1M aqueous sodium hydroxide solution. As a result, the portions not covered with photoresist 14 become hydrophilic.

(r8) Filling of polymer electrolyte (FIG. 3(g)) Polymer electrolyte poly(vinyl-4-ethylpyridinium bromide) was used as the electrolyte-containing body 11. Polyelectrolyte 1
A 0% solution was dropped into the hole IO and allowed to dry.

(19) Covering the gas-permeable membrane (FIG. 3(h)) The gas-permeable membrane 12 was coated so as to cover the electrolyte-containing body 11. As a gas permeable membrane, a hydrophobic negative photoresist (Tokyo Ohka OMR-83, viscosity 60 cP) was applied by dip coating. This gas permeable film is also formed on the side and back surfaces, which has an advantageous effect in further improving the insulation properties.

〔Effect of the invention〕

As explained above, according to the present invention, the cathode and anode are formed by partially etching the laminated metal thin film, so that the vacuum evaporation or sputtering equipment can be used only once. In addition, the positive photoresist for the etching pattern only needs to be applied once, which greatly reduces the number of manufacturing steps. Furthermore, even when the characteristics deteriorate as the silver anode wears out, the presence of a thick gold layer under the silver suppresses the decrease in resistance, making it possible to obtain stable characteristics until close to the life of the oxygen electrode. Become.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an oxygen electrode according to the present invention, FIG. 2 is a cross-sectional view of an oxygen electrode according to the present invention, and FIGS. It is an explanatory diagram of the manufacturing method for oxygen concentration. 1...Silicon, 2...Chromium for adhesion improvement, 3...Gold or platinum, 4...Silver, 5...Positive photoresist, 6...Cathode, 7...Anode , 9...
・Insulating film, 10... Hole, 11... Electrolyte containing body, 12... Gas permeable membrane, 13... Hydrophobic insulating film, 14... Water repellent insulating film for injection of electrolyte containing body .

Claims (1)

[Claims] 1. A step of forming a groove on a semiconductor substrate by anisotropic etching, and forming an electrode that will become a cathode and an anode from the bottom of the groove to the surface of the substrate via an insulating film. and a step of forming a gas permeable membrane that covers the surface of the substrate except for the exposed portion of the electrode and covers the electrolyte-containing body, the method comprising: a conductive material for adhesion on the semiconductor substrate; gold or platinum,
and silver in this order and partially etching each layer to form a gold or platinum cathode and a silver anode.