JPH04372626A - Process for bonding fluororesin film - Google Patents

Abstract

PURPOSE:To bond a fluororesin film firmly to a substrate by treating the surface of the film with a plurality of specified reagents and fusing this film to the substrate. CONSTITUTION:A process for bonding a fluororesin film (e.g. fluorinated ethylene/propylene copolymer film) to a substrate (e.g. silicon wafer) comprising treating the surface of the film with a reagent containing metallic sodium (e.g. Chemgrip, a product of Norton Co.) and then with a silane coupling agent (e.g. gamma-aminopropyltriethoxysilane) and fusing the treated film to the substrate.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for adhering a fluororesin film onto a substrate, and more specifically, the present invention relates to a method for firmly adhering a fluororesin film to a silicon wafer, glass substrate, etc. in the fields of semiconductor processing and micromachining. Regarding how to.

0002

[Prior art and problems to be solved by the invention] In the fields of semiconductor processing and micromachining,
For example, gas permeable membranes and fluororesin membranes as insulating materials,
There is a need for strong adhesion to silicon wafers, glass substrates, etc. For example, this is the case with small Clark-type (diaphragm-type) electrodes that utilize micromachine technology.

Incidentally, in recent years, oxygen electrodes have been advantageously used in various fields for measuring dissolved oxygen concentrations. For example, biochemical oxygen demand (BOD) in water is measured from the viewpoint of water quality conservation, and this small oxygen electrode can be used as a measuring device for dissolved oxygen concentration. 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.

[0004] As described above, small oxygen electrodes can be used in various fields such as environmental measurement, fermentation industry, and clinical medicine.
When used for insertion into the body, it is small, disposable, and inexpensive, making it very useful. Since conventional oxygen electrodes cannot be miniaturized and cannot be mass-produced, the present inventors developed a compact oxygen electrode using anisotropic etching (Japanese Patent Application Laid-Open No. 63-238548) or an anisotropic etching method. We have developed a small oxygen electrode (patent application No. 2-243849) using anodic bonding. These oxygen electrodes are small, have little variation in characteristics, and can be mass-produced at once, so they are low cost. Here, the gas permeable membrane was formed by forming a water-repellent polymer membrane by dip coating or spin coating in the former case, and by adhering a fluorine-based FEP membrane by thermal fusion in the latter case.

Although the method disclosed in JP-A-63-238548 is simple, it has problems with the selective formation of a film pattern and the strength of the film, and it is generally difficult to achieve both. In addition, the method disclosed in Japanese Patent Application No. 2-243849 uses an FEP membrane as a gas-permeable membrane, but this membrane is chemically very stable and requires a wafer-like structure throughout the entire process. This is an excellent method as it allows for the production of

By the way, when bonding fluororesin as a gas permeable film or insulating material to silicone wafers, glass substrates, etc. in conventional semiconductor processes, etc., there is a method of fusion bonding at the temperature at which the fluororesin melts (around 280°C). has been known for a long time. However, with this method, it is very easy to peel off due to air bubbles mixed in during fusion, changes in humidity, friction, etc., and it is particularly vulnerable to water wetting, which has been a problem.

[0007] Furthermore, when biosensors such as small sensors are used in the medical field, it is necessary to sterilize them with high-pressure steam in advance, but there is a problem that the gas permeable membrane often peels off during such high-pressure steam sterilization. Ta. This is a very serious problem in practice.

[0008]

[Means for Solving the Problems] As a result of intensive studies in order to solve the above problems, the present inventors have found that the above problems can be solved by the following two means, and have invented the present invention. solved. The first method is to chemically modify the fluororesin surface or the silicone wafer surface to form a chemical bond between the two to strengthen the adhesive force.

Fluororesin is characterized by its lack of reactivity, but by removing only the fluorine from the surface layer and treating it with a silane coupling agent, it can form a chemical bond with the silicone wafer and create a strong bond. It becomes possible. That is, the invention as the first means involves treating the surface of the fluororesin film with a reagent containing sodium metal, then treating it with a silane coupling agent, and then heat-sealing the thus treated fluororesin film and the substrate. Alternatively, the substrate surface is treated with a silane coupling agent, and the thus treated substrate and the fluororesin film are further heat-fused. In addition, in the latter method, a fluororesin membrane treated with a reagent containing metallic sodium can be used as the fluororesin, or a fluororesin membrane treated with a reagent containing metallic sodium and then treated with a silane coupling agent can be used. You can also do that.

[0010] The second means is specifically designed to deal with the latter problem mentioned above. In other words, the phenomenon of peeling during high-pressure steam sterilization is caused by air bubbles remaining between the film and the substrate during thermal fusion of the fluororesin film, which not only reduces the adhesion area between the film and the substrate, but also causes the bubbles to expand during high-pressure steam sterilization. It turned out that this was to cause the film to peel off. The inventors of the present invention have found that this problem can be solved by evaporating the air bubbles in a vacuum, or by performing the entire thermal fusion process in a vacuum.

Therefore, the second means of the invention is to treat the surface of a fluororesin film with a reagent containing sodium metal, then with a silane coupling agent, and then heat-fuse the fluororesin film thus treated onto a substrate. The heat-sealed substrate is then left in a vacuum, and then the heat-sealed substrate is returned to atmospheric pressure and then heat-sealed again.Alternatively, the surface of the fluororesin film is coated with metallic sodium. The fluororesin film treated in this way is then heat-sealed onto the substrate under vacuum, then left in vacuum, and then heat-sealed under vacuum again. It is characterized by being fused.

[0012] In the method of the present invention, the term "substrate" refers to silicon wafers, glass substrates, and the like. In addition, the silane coupling agent refers to a silicone compound such as γ-APTES (γ-aminopropyltriethoxysilane or hexamethyldisilazane). Of course, it is not limited to the example.

[0013]

Examples Example 1 FEP (fluorinated ethylene propylene, manufactured by Toray Industries, Inc., 12 μm thick) was used as the fluororesin membrane. The FEP membrane was then washed with ethanol and dried (first step). The washed sample was treated with a reagent containing Na (CHEMG).
RIP (manufactured by Norton) for 30 seconds to react.
Washed three times with acetone (second stage). Furthermore, γ-AP
TES (γ-aminopropyltriethoxysilane, silane coupling agent, manufactured by Aldrich) in a 10% aqueous solution.
It was immersed at 0° C. for 30 minutes to react (third stage).

[0014] In this way, samples were prepared that had been processed at each of the steps 1 to 3 above. On the other hand, a silicon wafer is used as a substrate, and this silicon wafer is used as an untreated silicon wafer (a
) and (b) treated with a silane coupling agent (γ-APTES) were prepared. Then (a) and (
The samples treated at each stage were placed on the two types of wafers of b), and fusion bonding was performed on a hot plate at 280°C. After that, autoclave and underwater high pressure sterilization (1
(20° C., 2 atm, 15 minutes), and the state of fusion bonding thereafter was examined.

Table 1 shows the FEP adhesion ratio after sterilization. The number of samples was 10 pieces each. Incidentally, the conventional adhesion method is (1)-(a), which is very easy to peel off in water. Comparing this with this, it can be seen that all the surface treated samples other than ■-(a) were firmly adhered without peeling even in water. In particular, ■-(b) had strong adhesive strength and was resistant to a peel test using cellophane tape.

[0016]

[Table 1]

Example 2 First, a substrate on which a sensor body such as a small oxygen electrode is formed is ultrasonically cleaned in pure water. Next, FEP membrane (manufactured by Toray,
The film (thickness: 12 μm) is immersed in a treatment agent containing metallic sodium (for example, CHEMGRIP) to remove fluorine atoms on the film surface. Furthermore, the FEP is isolated by silane coupling (γ-APTES).
Treat the membrane.

The thus surface-treated film is placed on a substrate heated to 270° C. and thermally bonded. To remove air bubbles remaining between the film and the substrate, the substrate with the film fused thereon was placed in a vacuum for 5 minutes, immediately returned to normal pressure, and then heated again to 270°C.
Heat to. Repeat the heating process if necessary. This step improves the adhesion of the film.

When a film is fused onto a flat substrate, sufficient strength can be obtained by treatment with metallic sodium and a silane coupling agent as described in Example 1, but as with an actual small-sized oxygen electrode, When fusion bonding is performed on a substrate with an uneven surface, air bubbles often form between the film and the substrate. This may expand during the high-pressure steam sterilization process and cause the membrane to peel off.
This reduces the contact area between the film and the substrate, resulting in poor adhesion. In such cases, vacuum treatment during film fusion is effective.

[0020] Table 2 shows the effect of removing air bubbles by treatment according to the method of Example 2. Here, a film treated with metallic sodium and γ-APTES as described in Example 2 is fused onto an untreated silicon substrate and subjected to vacuum treatment to complete a small oxygen electrode. On the other hand, a film treated with metallic sodium and γ-APTES was fused onto an untreated silicon substrate, and a small oxygen electrode without vacuum treatment was used as a control electrode. Each electrode was sterilized using high-pressure steam, and the state of membrane peeling after that was compared. The results are shown in Table 2.

[0021]

[Table 2]

From Table 2, it was confirmed that the vacuum treatment had a significant effect.

[0023]

As described above, since the present invention is configured, it is possible to firmly bond the substrate and the fluororesin film, and it is possible to prevent the fluororesin film from peeling off from the substrate. In particular, even when creating an actual small oxygen electrode and subjecting it to harsh conditions such as high-pressure steam sterilization, the vacuum treatment method of the present invention significantly improves the adhesion of the gas permeable membrane. The effect is that no peeling is observed at all.

Claims (6)

[Claims] 1. A method for bonding a fluororesin film onto a substrate, the surface of the fluororesin film being treated with a reagent containing sodium metal, and then treated with a silane coupling agent,
A method for adhering a fluororesin film, further comprising heat-sealing the fluororesin film treated in this way and a substrate. 2. A method for bonding a fluororesin film onto a substrate, the method comprising treating the surface of the substrate with a silane coupling agent and further heat-sealing the thus treated substrate and the fluororesin film. The method comprising: 3. The method according to claim 2, wherein the fluororesin membrane is a fluororesin membrane treated with a reagent containing sodium metal. 4. The method according to claim 2, wherein the fluororesin film is a fluororesin film treated with a reagent containing sodium metal and then treated with a silane coupling agent. 5. A method for adhering a fluororesin film onto a substrate, comprising: treating the surface of the fluororesin film with a reagent containing metallic sodium, and then treating it with a silane coupling agent;
Next, the fluororesin film treated in this way is heat-sealed onto the substrate, the heat-sealed substrate is left in a vacuum, and then the heat-sealed substrate is returned to atmospheric pressure and then heat-sealed again. The method comprising: 6. A method for adhering a fluororesin film onto a substrate, the surface of the fluororesin film being treated with a reagent containing sodium metal, and then treated with a silane coupling agent,
The method described above comprises the steps of: heat-sealing the fluororesin film treated in this way onto a substrate under vacuum, then leaving it as it is in vacuum, and then heat-sealing it again under vacuum.