JP2943281B2 - Small oxygen electrode and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding a small oxygen electrode, with a view to improving reliability, a hole formed by anisotropic etching on a semiconductor substrate and an insulating region on a sensitive portion region including the hole are provided. An oxygen electrode element having an anode electrode and a cathode electrode formed through the membrane, an electrolyte-containing body filled on the sensitive part region including the hole, and an oxygen-permeable membrane covering the electrolyte-containing body; The cylindrical housing is for accommodating the oxygen electrode element, and is fixed with a resin filled so that the area other than the sensitive area is not exposed to the external environment. A small oxygen electrode is formed as described above, a hole formed by anisotropic etching on a semiconductor substrate, and an anode electrode and a cathode electrode formed via an insulating film on a sensitive portion region including the hole. An electrode, an electrolyte-containing body filled on a sensitive area including the hole, In a method for manufacturing a small oxygen electrode having an oxygen electrode element comprising an oxygen permeable membrane covering the electrolyte-containing body, the oxygen electrode element is housed in a cylindrical housing, and the housing is filled with a resin. The manufacturing method of the small-sized oxygen electrode is configured to include a step of fixing the oxygen electrode element so that portions other than the sensitive portion are not exposed to the external environment.

[Industrial applications]

 The present invention relates to a small oxygen electrode with improved reliability.

The small oxygen electrode is used for measuring the dissolved oxygen concentration.

For example, the amount of biochemical oxygen supply (abbreviated as BOD) in water is measured from the viewpoint of water quality conservation, and an oxygen electrode is used to measure the dissolved oxygen concentration.

In the fermentation industry, it is necessary to adjust the dissolved oxygen concentration in the fermentation tank in order to promote efficient alcohol fermentation. An oxygen electrode is used for this measurement, and an oxygen electrode is used for the measurement of glucose and amino acids. An enzyme electrode having an enzyme immobilized on a gas permeable membrane is used.

In the field of clinical medicine, an oxygen electrode or an enzyme electrode is attached to a catheter (Katheter) and inserted into the body for use.

As described above, oxygen electrodes are used in various fields such as environmental measurement, fermentation industry, and clinical medicine.

[Conventional technology]

Conventional oxygen and enzyme electrodes are made of glass or a polymer compound, and have an anode and a cathode in a cylindrical cell with an open end. An oxygen electrode is formed by providing an oxygen permeable film in the portion.

In the case of an enzyme electrode, an enzyme is further fixed on the oxygen permeable membrane.

However, as long as such a structure is adopted, miniaturization is limited and mass production is difficult.

In order to solve this problem, the present inventors performed anisotropic etching using a silicon (Si) substrate to form a large number of holes with good pattern accuracy, and then used photolithography technology (photolithography). A new type of small oxygen electrode is proposed in which one electrode is formed, an electrolyte-containing body is accommodated in the hole, and finally the upper surface of the hole is covered with a gas permeable membrane.

(Japanese Patent Application Laid-Open No. 63-238548) This oxygen electrode is small in size, has little variation in characteristics, and is suitable for mass production.

And agarose gel (agar) was used as the electrolyte-containing body.

However, in the case of agarose gel, there is an inconvenience that it is necessary to repeatedly inject into the minute holes on the Si substrate one by one using a micropipette.

Therefore, the inventors used polyacrylamide gel,
We have found and applied for a method of injecting the gel at once only into the many micro holes provided on the Si substrate. (JP 63
-311158) In addition, an application has been filed for a device using a calcium alginate gel.

(Japanese Unexamined Patent Publication No. 2-27254) An application using a polymer electrolyte, polyvinyl-4-ethylpyridinium bromide (abbreviated as PVEP), as an electrolyte is also filed.

FIG. 2 is a sectional view of a small oxygen electrode element proposed by the inventors.

FIG. 1 is a perspective view of the small oxygen electrode housed in the housing according to the present invention, but there is no change in the oxygen electrode element.

Now, the structure and manufacturing process of a small oxygen electrode element using PVEP as an electrolyte will be described as follows.

Anisotropic etching is performed on the anode electrode forming portion of the Si substrate 1 having the (100) plane as a substrate surface by using a photolithography technique (photolithography), and a bathtub type hole 2 is formed.
The substrate 1 is thermally oxidized to form a Si oxide film 3 over the entire surface.

Next, when a polaro-type oxygen electrode element is to be formed on the Si substrate 1 having the bathtub-type hole 2, gold (Au) or platinum (Pt) is deposited, and the anode pattern 4 is formed by photolithography. And the cathode pattern 5 are formed, and the two anodes 6 at the tip of the anode pattern are formed including the bottom of the hole 2.

The cathode 7 is formed on the substrate between the two holes 2.

The rectangular area including the two anodes 6 and the cathode 7 is the sensitive area.

Next, the resist 10 is covered except for the sensitive area and the pads 8 and 9 for external connection between the anode 6 and the cathode 7.

Next, after filling the sensitive area with two holes 2 with a polymer electrolyte (PVEP), a small oxygen electrode is formed by coating a two-layer oxygen permeable membrane 13 composed of a resist and silicone rubber on this. It is configured.

Such a small oxygen electrode improves storage stability by using a polymer electrolyte such as PVEP instead of the conventional water-containing gel, and has a two-layered oxygen permeable membrane for strength. And improved water penetration.

 However, as a result of continued use, the following points became clear.

It is easily broken when stress is applied to the small oxygen electrode.

The value varies depending on the flow direction of the liquid for measuring the oxygen concentration.

There was a problem, such as the need for improvement.

[Problems to be solved by the invention]

The small oxygen electrode proposed by the inventors is significantly smaller in size than the conventional oxygen electrode, and has improved characteristics, but the mechanical strength is weak and the direction of the flow to be measured is small. Therefore, there was a problem that the measured value was different, and a solution was needed.

[Means for solving the problem]

The above object is to provide a hole formed on a semiconductor substrate (Si substrate) by anisotropic etching, an anode and a cathode formed on a sensitive portion region including the hole via an insulating film, An oxygen electrode element having an electrolyte-containing body (polymer electrolyte) filled on the sensitive part region containing the same, an oxygen permeable membrane covering the electrolyte-containing body, and a cylindrical housing. The housing is for accommodating the oxygen electrode element, and a small oxygen electrode configured to be fixed with a resin filled so that the area other than the sensitive area is not exposed to the external environment, and In the method for manufacturing the small oxygen electrode, the oxygen electrode element is housed in a cylindrical housing, and the housing is filled with a resin. Method for manufacturing small oxygen electrode configured to include step of fixing element It can be solved by.

[Action]

According to the present invention, the conventional small oxygen electrode element is housed in a cylindrical housing, and only the sensitive area is exposed.

That is, put in a cylindrical housing that can accommodate the Si substrate,
It is fixed by using a synthetic resin, whereby not only the mechanical strength is improved, but also the electrical characteristics are stabilized, and the influence of the flow direction can be eliminated.

〔Example〕

Example 1 (Example of Manufacturing Small Oxygen Electrode) FIG. 1 is a perspective view of a small oxygen electrode embodying the present invention, and FIGS. 3 (A) to 3 (C) show manufacturing steps of a small oxygen electrode element. It is sectional drawing.

First, a (100) plane was used as a substrate surface, and a Si substrate 1 having a thickness of 350 μm and a diameter of 2 inches was mixed with a mixed solution of hydrogen peroxide (H ₂ O ₂ ) and ammonia (NH ₃ ) and concentrated nitric acid (HNO ₃ ). After washing with
The Si substrate 1 is wet-oxidized at about 1000 ° C. in the presence of water vapor to form an oxide film of SiO ₂ having a thickness of about 0.8 μm on the entire surface of the Si substrate 1.

Next, a negative resist having a viscosity of about 60 cP (Oka Chemical Co., Ltd., O
After spin-coating MR-83) on the front and back of the Si substrate 1 to form a resist film, the resist film on the surface is projected and exposed.
Open the hole forming part.

Next, 50% hydrofluoric acid (HF): 40% ammonium fluoride (NH ₄ F) =
After immersing the Si substrate 1 in a 1: 6 aqueous solution to remove the oxide film on the exposed portion, the resist is subsequently removed using a sulfuric acid (H ₂ SO ₄ ): H ₂ O ₂ = 2: 1 solution. Next, when the liquid temperature is 80 ° C and the concentration is 35
% Potassium hydroxide (KOH) aqueous solution to perform anisotropic etching, etching to a depth of 300 μm, and holes 2
Is formed, the Si substrate 1 is thoroughly washed with pure water.

Then, the SiO ₂ film used at the time of etching is
After removal using an aqueous solution of% HF: 40% NH ₄ F = 1: 6, wet oxidation is again performed to form a 0.8 μm-thick SiO ₂ Si oxide film 3.

Next, chrome (C) was deposited on the Si substrate 1 by vacuum evaporation.
r) is formed to 400 Å and gold (Au) to 4,000 、, and then a resist pattern for forming an electrode is formed by using the same negative resist (OMR-83). ) 4g
And a solution prepared by dissolving 1 g of iodine (I ₂ ) in 40 ml of water. The Cr film was made of 0.5 g of caustic soda and 4 g of potassium ferricyanide [K ₃ Fe (CN) ₆ ].
Etching is performed using a solution dissolved in ml of water to form an anode pattern 4 and a cathode pattern 5.

Here, a rectangular portion including the anode 6 provided at the tip of the anode pattern 4 and the cathode 7 provided at the tip of the cathode pattern 5 is a sensitive portion. (FIG. 3A) Next, the resist film including the sensitive portion including the hole 2 on the Si substrate 1 and the Si substrate 1 excluding the pad from which the electrode is drawn out is covered with a negative resist (OMR-83). After the formation of 10, the photosensitive portion not covered with the resist is immersed in a 1 M NaOH solution to make it hydrophilic.

Next, dissolve PVEP, which is a polymer electrolyte, in water, apply it to the sensitive part by attaching it to the tip of a fine rod, and bake at 120 ° C for 10 minutes to remove water in the electrolyte. did.

Next, the oxygen permeable membrane 13 is covered so as to cover the electrolyte.

This oxygen permeable film 13 is a negative type photoresist (OMR-8
3) and silicone rubber (product name KE-347T, Shin-Etsu Silicone Co., Ltd.) were spin-coated to form a two-layer film.

Next, after bonding Al lead wires having a diameter of 50 μm to the pads 8 and 9 of the completed small oxygen electrode element, a stainless steel elliptical cylinder having a diameter slightly larger than that of the Si substrate 1 is formed. , And silicone varnish (product name ES-1001, Shin-Etsu Silicone Co., Ltd.) was poured from the sides of the pads 8 and 9 except for the sensitive part, and baked at 150 ° C. for 1 hour. (The first
FIG. 1) Comparative Example 1: With respect to the small oxygen electrode according to the present invention formed as in Example 1, the current stability with respect to the bare small oxygen electrode having the conventional structure and the saturated dissolved O ₂ was compared.

Fig. 4 shows the current change that appeared on the self-recording recorder.
10 mM (mol / l) phosphate (H ₃ PO ₄ ) buffer solution shows the time course of both output currents in the state of saturated dissolved O ₂ , the absolute value of the current is the same. The oxygen electrode includes noise and fluctuates.

Next, sodium sulfite (Na ₂ SO ₄ ) is added to the measurement solution in this state.
When the dissolved O ₂ is eliminated by dropping the liquid, the current rapidly decreases to 0 in the small oxygen electrode according to the present invention, but the conventional structure gradually includes a lot of noise as shown in the figure. It decreases to zero.

As described above, the small oxygen electrode to which the present invention is applied is characteristically stable.

Comparative Example 2: 10 mM (mol / l) phosphate (H ₃ PO ₄ ) buffer solution was measured with flow direction at a flow rate of 10 cm / sec in the state of saturated dissolved O ₂ and the flow direction was measured. Was investigated.

Table 1 is a comparison between the case where the flow hits the small oxygen electrode from the front and the case where the flow hits from the back.

As described above, the small oxygen electrode to which the present invention is applied is not only mechanically stable, but also electrically stable, and can obtain a reproducible value.

〔The invention's effect〕

The small-sized oxygen electrode according to the present invention is obtained by enclosing an oxygen electrode element in a cylindrical housing, and can exhibit not only improved mechanical strength but also electrically stable values and reliability. Could be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the structure of a small oxygen electrode according to the present invention, FIG. 2 is a cross-sectional view of the oxygen electrode element taken along the line XX 'in FIG. 1, and FIG. FIG. 4 is a cross-sectional view showing a process, and FIG. In the figure, 1 is a Si substrate, 2 is a hole, 4 is an anode pattern, 5 is a cathode pattern, 6 is an anode, 7 is a cathode, 10 is a resist film, and 13 is an oxygen permeable film.

Continuation of the front page (72) Inventor Fumio Takei 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-61-170647 (JP, A) JP-A-61-30756 (JP, A) JP-A-59-160739 (JP, A) JP-A-60-173454 (JP, A) JP-A-60-111146 (JP, A) JP-A-62-39754 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) G01N 27/30

Claims (5)

(57) [Claims] 1. A hole formed on a semiconductor substrate by anisotropic etching, an anode and a cathode formed on a sensitive region including the hole via an insulating film, and a sensitive portion including the hole. An oxygen electrode element having an electrolyte-containing body filled on the region, an oxygen-permeable membrane covering the electrolyte-containing body, and a cylindrical housing, wherein the cylindrical housing includes the oxygen electrode element. A small oxygen electrode which is fixed with a resin filled so as not to be exposed to the external environment except for the sensitive portion area. 2. The small oxygen electrode according to claim 1, wherein said electrolyte-containing body is a polymer electrolyte. 3. The small oxygen electrode according to claim 1, wherein said oxygen permeable film is a multilayer structure film of different materials. 4. A method according to claim 1, wherein said sensitive portion region is formed on said substrate by two holes formed by anisotropic etching, an anode electrode formed from the bottom of said hole to the substrate surface, and formed on said substrate between said two holes. 2. The small oxygen electrode according to claim 1, further comprising a cathode electrode. 5. A hole formed on a semiconductor substrate by anisotropic etching, an anode electrode and a cathode electrode formed on a sensitive portion region including the hole via an insulating film, and the hole. A method for manufacturing a small oxygen electrode having an oxygen electrode element composed of an electrolyte-containing body filled on a sensitive region containing: and an oxygen-permeable membrane covering the electrolyte-containing body, comprising: A method for manufacturing a small-sized oxygen electrode, comprising the steps of: accommodating, filling a resin in the housing, and fixing the oxygen electrode element so that portions other than the sensitive portion are not exposed to an external environment.