JPH02236154A - Preparation of small-sized oxygen electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The purpose of the present invention is to provide a method for manufacturing a small oxygen electrode, in which an electrolyte-containing gel is easily injected into a hole on a substrate, and an anisotropic etching process is performed on a semiconductor substrate. to form a groove (hole), form an insulating film covering the surface of the substrate, form two electrodes from the bottom of the substrate to the surface of the substrate via the insulating film, and In a method for producing a small oxygen electrode, the inside of which is filled with an electrolyte-containing porous material, and a gas permeable membrane is formed on the substrate to cover the electrolyte-containing porous material, A method for manufacturing small oxygen electrodes is constructed by filling the oxygen electrode with a screen printing method. [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. Small oxygen electrodes can be advantageously used to measure dissolved oxygen concentration in various fields. For example, biochemical oxygen demand (BOD) in water is measured from the standpoint of water quality conservation, and this small oxygen electrode can be used as a measuring device for dissolved oxygen concentration. Furthermore, 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, vitamins, etc. For example, glucose is oxidized to gluconolactone by reacting with dissolved oxygen using the enzyme glucose oxidase as a catalyst. Glucose concentration can be measured from the amount consumed. 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. It is also disposable and inexpensive, making it very useful. [Prior Art] Since conventional glass oxygen electrodes cannot be miniaturized and cannot be mass-produced, the present inventors developed a new type of small oxygen electrode using lithography technology and anisotropic etching technology. Developed an electrode and filed a patent application (Japanese Unexamined Patent Publication No. 1983-
(No. 238548) This oxygen electrode has two electrodes formed on a hole formed by anisotropic etching on a silicon substrate with an insulating film interposed therebetween, and an electrolyte-containing body is housed inside the hole. This is an oxygen electrode with a structure in which the top surface of the hole is covered with a gas-permeable membrane. This oxygen electrode is small and
There is little variation in characteristics, and it is low cost because it can be mass-produced at once. In the above-mentioned types of oxygen electrodes, the electrolyte-containing body is usually a gel impregnated with an electrolyte, such as an agarose gel. However, in the case of agarose gel, one micropipette is used to fill many tiny holes on a silicon substrate.
I had to inject it repeatedly. The present inventors have further improved this point, using polyacrylamide gel or calcium alginate gel as the gel, and covering the parts other than the holes on the silicon substrate with a water-repellent negative resist. We developed a method of forming a gel only in the holes by immersing it in a mold gel solution and utilizing the difference between hydrophilicity and hydrophobicity (Patent Application No. 1982-1).
No. 48221. (Patent Application No. 176978/1983). [Problems to be solved by the present invention] The above-mentioned Japanese Patent Application No. 148221/1982 and Japanese Patent Application No. 1983/1983
The method described in No. 76978 is an innovative manufacturing method in that it allows for mass production of extremely small oxygen electrodes. However, when this method was examined in detail, it was found that there were problems that needed to be resolved in order to put it into practical use. Injecting the gel solution takes advantage of the difference in hydrophobicity and hydrophilicity between the negative resist coated area and the uncoated area. There is no problem with hydrophobicity, but wood-philicity depends only on the cleanliness of the uncoated surface. For this reason, very slight dirt,
In particular, when contaminated with minute oil particles, etc., the difference between the hydrophobic part and the hydrophobic part decreased, making it difficult for the gel solution to enter the holes formed by anisotropic etching. This is a factor that reduces the yield of small oxygen electrodes. Furthermore, as the difference between hydrophilicity and hydrophobicity decreased, the gel solution also adhered to the hydrophobic areas. This is caused by the gel being caught between the gas permeable membrane and the oxygen electrode body, which deteriorates the adhesion of the gas permeable membrane, resulting in variations in the characteristics of the oxygen electrode, peeling of the gas permeable membrane, or a decrease in insulation. An increase in noise was occurring. These points are very disadvantageous in terms of reproducibility and reliability of the oxygen electrode. The purpose of the present invention is to improve the yield during manufacturing and solve the problem of decreased reproducibility and reliability during measurement when manufacturing oxygen electrodes that are small and can be mass-produced. [Means for Solving the Problems] The present invention provides grooves (
A hole) is formed, an insulating film is formed to cover the surface of the substrate, and two electrodes are connected from the bottom of the substrate to the surface of the substrate.
In a method for manufacturing a small oxygen electrode, the electrode is formed through a large electrode, the inside of the electrode is filled with an electrolyte-containing porous material, and a gas permeable membrane is formed on the substrate to cover the electrolyte-containing porous material. This is achieved by manufacturing a small oxygen electrode by filling the inside of the electrode with a porous material containing the electrolyte using a screen printing method. As the electrolyte-containing porous material, alginate gel, polyacrylamide gel, or agarose gel can be used. The present inventors have discovered that the reason why the gel solution does not enter only the holes is due to the incomplete hydrophilicity of the holes. In order to solve this problem, it is advantageous to apply the gel solution only to the necessary areas.However, using a micropipette as in the case of agarose gel is a problem in terms of productivity and quality. This is also undesirable from the viewpoint of uniformity.Therefore, the present invention attempts to solve the above problem by utilizing screen printing for injection of gel solution.According to the present invention, the hydrophilic and hydrophobic Even if there is no difference, the gel solution can be injected only to the necessary areas. This shows that a hydrophobic resist film is not necessarily necessary for gel injection, and it is possible to omit part of the manufacturing process. ．．
Moreover, in the conventional method, the gel solution must have a viscosity almost equivalent to that of water, and the inclusion of surfactants and substances that perform the same function was not allowed. However, the present invention greatly relaxes these limitations and allows the use of highly concentrated gel solutions or gels of types and compositions that cannot be used with conventional methods. [Example] An example of a method for manufacturing a small oxygen electrode according to the present invention will be explained. FIG. 1 is a perspective view showing an example of a small oxygen electrode according to the present invention. The illustrated oxygen electrode has the shape of a rectangular parallelepiped, and the sensitive part is covered with a gas permeable membrane 7, and part of the electrodes 3A and 3B are exposed for connection to an attached device. In this example, the electrodes 3A and 3B were both made of gold electrodes in order to have a polaro type. The structure of the small oxygen electrode shown in FIG. 1 is shown in FIG. 2, which is a cross-sectional view taken along I-1411. The silicon substrate 1 has a groove (hole) formed by anisotropic etching, and silicon oxide I1l! is formed on the entire surface thereof. 2 is deposited as an insulating film. Furthermore, the back surface of the substrate is covered with a tear-resistant hydrophobic insulating film 5. Two gold electrodes 3A and 3B are deposited in pairs in the holes of the silicon-based Fil. As shown in FIG. 1, a portion of each of the gold electrodes 3A and 3B extends to the outside of the groove. Further, the hole in the silicon substrate l is filled with an electrolyte-containing gel 6. Furthermore, the upper part of the hole has a gas permeability l! which covers the entire upper part of the substrate 1 (excluding the exposed part in FIG. 1). '7 is coated, and this is also covered on the side and back surfaces as an insulating film. The small oxygen electrode shown in FIGS. 1 and 2 is, for example,
It can be manufactured conveniently using the manufacturing process shown step by step in Figure 3. 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 in reality, many small oxygen electrodes are formed on one wafer at the same time. Please understand that this will be done. (1) Wafer cleaning A silicon wafer 1 with a thickness of 250 to 500 μm (100) was prepared and thoroughly cleaned with a mixed solution of hydrogen peroxide and ammonia and nitric acid. (2) Formation of SiOtII The wafer is wet thermally oxidized, and a 0.5 to 1μ thick Sins layer is deposited on the entire surface.
A film was formed. (3) Formation of etching pattern An etching pattern was formed on the wafer using photoresist.
Photoresist was also applied to the back side of the wafer and post-bake was performed. (4) S i O t @ etching Hydrofluoric acid/ammonium fluoride aqueous solution with u? The exposed portion of Sing was removed by etching, and the resist was further removed. (5) Anisotropic etching of silicon Anisotropic etching of silicon was performed in an aqueous solution of potassium hydroxide to form grooves of 200 to 400 μm. After the anisotropic etching was completed, the SSOx film used during etching was removed using the solution (4). (6
) Formation of SiO film In order to grow a SiO* film on the wafer surface, the wafer was subjected to wet thermal oxidation following the same cleaning process as in (1) to form a Sing film 2 with a thickness of 0.5 to 1 μs+. (
7) Formation of chromium and gold thin film Chromium thin film (100-5
00 people), followed by gold thin film (3000 ~ 5000 people)
(person) was formed by vacuum evaporation. (8) Formation of pattern for electrode formation A resist pattern for electrode formation was formed on the wafer using photoresist. (9) Etching of gold and chromium Figure 3 (A)
The wafer was immersed in an etching solution for gold and an etching solution for chromium in this order, and the exposed gold and chromium portions were removed by etching to obtain gold electrodes 3A and 3B. Furthermore, the resist was removed. A photoresist was applied to the surface of the OI hydrophobized wafer, exposed and developed after blebbing, and the resist was used to cover areas other than the holes 4 on the wafer surface to form a hydrophobic resist film 8. Although this step is not necessarily necessary, it was performed to make the wafer surface hydrophobic and to prevent the gel solution from flowing out due to the step created by the resist film. 01) Formation of a hydrophobic insulating film on the back side of the substrate A hydrophobic insulating film 5 made of silicone resin or the like was uniformly applied to the back side of the substrate and cured at a specified temperature (150"C). Filling (Figure 3 (B)
) The following two types of solutions were prepared for forming electrolyte-containing gels. Solution A: Sodium alginate dissolved in an aqueous solution of 0.1-IM potassium chloride, sodium chloride, sodium sulfate, etc. Sodium alginate concentration 0.05~
0.5%. Solution B: Add calcium chloride to the above salt solution (0.1 to IM
dissolved in an aqueous solution of potassium chloride, sodium chloride, sodium sulfate, etc.). Calcium chloride concentration 1-5
%. The wafer was placed on the stage of a screen printer, and using a mask that printed only the holes, liquid A was printed on the wafer. When the wafer was taken out of the printing press and immersed in or sprayed with liquid B, liquid A instantly gelled. Cutting out the O-water substrate The oxygen electrode formed on the substrate was cut into chips. (B) Covering the gas-permeable membrane (Fig. 3 (C)) The gas-permeable membrane 7 is coated on the electrolyte-containing gel 6 so as to cover the gel.
covered. Hydrophobic negative photoresist, silicone resin, fluororesin, etc. were applied as a gas permeable membrane by dip coating. The resist was exposed to light and cured. Completed gas permeable membrane and sidewall insulation membrane.

This gas-permeable film is also formed on the back surface, which has an advantageous effect in further improving insulation.

As another example of the present invention, each part of the above steps is modified as follows. Filling of polyallylamide gel (Figure 3) (B) For the formation of electrolyte-containing gel, 0.5-5% acrylamide was added in an aqueous solution of 0.1-IM potassium chloride, sodium chloride, sodium sulfate, etc. , 0 to 5% methylene bisacrylamide, a reaction initiator, etc. are dissolved in A' solution. Place the wafer on the stage of a screen printing machine and use a mask that prints only the holes to print this A' solution. The wafer was printed on the wafer. The wafer was irradiated with ultraviolet light to form a gel. Filling of 021" agarose gel (Fig. 3 (B)) To form an electrolyte-containing gel, 0.1 -LM of potassium chloride, chloride 0 in aqueous solutions of sodium, sodium sulfate, etc.
．． Prepare solution A'' in which 5-2% agarose is dissolved. Heat this solution A to 100°C to completely dissolve the agarose, then keep it warm at 50-60°C. Place the wafer on the stage of a screen printer, and use a mask to print only the holes. Print this A″ solution onto a wafer. When it cools down, it turns into a gel. Although the above example uses a silicon substrate as a semiconductor substrate that can be anisotropically etched, gallium arsenide,
A substrate made of germanium or the like may also be used.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a small oxygen electrode according to the present invention, FIG. 2 is a sectional view taken along line 1-1 of the electrode in FIG. 1, and FIGS. ) are sectional views sequentially showing the latter half of the manufacturing process of the small oxygen electrode shown in FIGS. 1 and 2. [Effects of the Invention] According to the present invention, the electrolyte-containing gel can be injected regardless of the difference between hydrophilicity and hydrophobicity on the substrate, which improves production yield and improves the adhesion of the gas permeable membrane. Through this improvement, long-term stability and noise reduction can be achieved. 3A 3B Figure 1 Figure 2 Figure 1: Silicon base 5: Hydrophobic barrier 2: Green film
6: tif! Containing Kel 3A, 38: Electrode
7: Gas permeable membrane 4: Six 8: Hydrophobic resist film tJ 哚 Oxygen electrode manufacturing process Figure 3

Claims (1)

[Claims] 1. Form a groove (hole) on a semiconductor substrate by anisotropic etching, form an insulating film covering the surface of the substrate, and connect two electrodes from the bottom of the hole to the surface of the substrate through the insulating film. In a method for producing a small oxygen electrode, the hole is formed through a hole, the inside of the hole is filled with an electrolyte-containing porous material, and a gas permeable membrane is formed on the substrate to cover the electrolyte-containing porous material. 1. A method for manufacturing a small-sized oxygen electrode, characterized in that the electrolyte-containing porous material is filled into the inside of the electrode by a screen printing method.