KR100938323B1 - Method of surface treatment and surface-treated article - Google Patents

Abstract

In the present invention, the plasma generated in the water vapor bubbles 17 in the liquid 11 containing water is brought into contact with the article 15 in the liquid 11 whose contact angle with water is 90 degrees or less. The organics are also removed from the material by contacting the plasma with the organics attached to the article 15. By contacting the plasma article 15, the surface of the material is etched without destroying the article 15. The article 15 may include a material having both hydrophobic portions having a contact angle to water greater than 90 degrees and hydrophilic portions of 90 degrees or less, and contacting the plasma with the article 15 to etch only the hydrophobic portions.

Plasma, etching, surface treatment

Description

METHOD OF SURFACE TREATMENT AND SURFACE-TREATED ARTICLE}

The present invention relates to a surface treatment method of an article having a hydrophilic surface, and to an article surface treated by the method.

This application claims priority based on Japanese Patent Application No. 2005-089631 for which it applied on March 25, 2005, and uses the content here.

As a method of decomposing or removing an organic substance using plasma, the following method is known, for example.

(I) Oxygen gas or argon gas is put into a plasma state under atmospheric pressure, and the said plasma is sprayed on the surface of board | substrates, such as a silicon wafer and the glass substrate for liquid crystals, and the method of removing the organic substance adhering to the said board | substrate surface is known. (See Patent Documents 1 and 2). Moreover, the atmospheric pressure plasma surface treatment apparatus which put this method into practice is already commercialized.

(II) Ultrasonic waves are applied to a liquid such as an organic solvent containing an organic substance to generate bubbles in the liquid, and then the bubbles are irradiated with electromagnetic waves to generate plasma in the bubbles to form a plasma bubble. A method for decomposing dispersed organic matters has been proposed (see Patent Document 3).

(III) A technique of generating bubbles in water by supplying a gas such as oxygen or air to water, applying a high voltage pulse to the bubbles to instantaneously make the inside of the plasma a plasma state, and decomposing organic matter in water by plasma. It is described in patent documents 4-9.

(IV) A technique for generating a high temperature plasma bubble in a liquid, attaching a compound generated from the plasma bubble to the surface of the fiber, and performing surface modification such as irregularities on the surface of the fiber, and a functionalized fiber obtained from the technique. It is described in patent document 10.

In the method (I), (1) organic matter on the surface of heat-resistant articles such as inorganic materials can be decomposed or removed by plasma, but decomposed or unreacted organic matter floats in the atmosphere, and (2) high energy plasma gas Although it can generate | occur | produce, since the surface temperature of an article becomes very high, there exists a problem that application to an organic polymer material is difficult.

In the method of (II), (1) organic matter dispersed in the liquid can be decomposed, but it is unclear whether it can be applied to the removal of organic matter adhering to the surface of the article, and (2) if the plasma in the bubble contacts the article. Even if it attempts to decompose an organic substance, the surface temperature of an article becomes high similarly to the method of (I), and therefore, application to an organic polymer material is considered difficult.

In the method of (III), similarly to the above (II), the organic matter dispersed in the liquid (1) can be decomposed, but it is unclear whether it can be applied to the removal of the organic matter adhered to the surface of the article. In addition, since the plasma state lasts only for a short time, effective decomposition is difficult to occur when the frequency of contact between the bubbles in the plasma state (hereinafter referred to as plasma bubbles) and the organic material to be decomposed is low.

The specification of Patent Document 10 in (IV) describes that it is possible to perform surface modification of the fiber when the plasma bubbles are brought into contact with the fiber. The material of the fiber is not particularly limited. However, as described in Patent Document 3 of (II), the plasma bubble has a high temperature of about 5000K, whereas the organic polymer material generally does not have sufficient heat resistance to withstand such high temperatures. When the melting point or softening point of the material is lower than the temperature of the plasma bubbles, it is expected that the material melts and flows or reaches thermal decomposition or destruction when it comes into contact with the plasma bubbles. Therefore, it is difficult to apply plasma bubbles to fibers using such materials. Do. In addition, when using such a material with low heat resistance, it is anticipated that the fiber form itself will be destroyed rather than giving an uneven | corrugated function to a surface. In addition, although carbon fiber is shown in the Example, in a fiber fiber, not only a fiber is very thin but it also depends on the shape of the wrinkle of the fiber surface, the grade of the graphite structure of the surface, and the grade of flame resistance, but it is partially high temperature plasma. It is considered that the part of the fiber in contact with the bubbles excessively graphitizes due to heat, the fiber is locally weak, and the mechanical properties of the entire fiber are degraded. Moreover, when using a material with inferior heat resistance, there is no description about whether it can wash | clean without changing the form of a surface. Thus, the specification of patent document 10 has no description regarding selection of a material.

Patent Document 1: Japanese Patent Application Laid-Open No. 2002-143795

Patent Document 2: Japanese Patent Laid-Open No. 2004-311838

Patent Document 3: Japanese Patent Application Laid-Open No. 2004-306029

Patent Document 4: Japanese Patent Publication No. 2005-502456

Patent Document 5: Japanese Patent Application Laid-Open No. 2005-58887

Patent Document 6: Japanese Patent Application Laid-Open No. 2005-21869

Patent Document 7: Japanese Patent Application Laid-Open No. 2005-13858

Patent Document 8: Japanese Patent Application Laid-Open No. 2004-268003

Patent Document 9: Japanese Patent Application Laid-Open No. 2002-272825

Patent Document 10: Japanese Patent Application Laid-Open No. 2005-105465

SUMMARY OF THE INVENTION An object of the present invention is to decompose or remove organic substances such as contaminants attached to an article without scattering in the air, and a surface treatment method in which damage to the article is suppressed, and a surface treatment for etching the article surface while suppressing damage to the article. A method and a surface are highly cleaned, and it provides an article which is intact while etching the article or surface which is hardly damaged.

Composition and Action of the Invention

The surface treatment method of the present invention is characterized in that a plasma generated in steam bubbles in a liquid containing water is brought into contact with a material having a contact angle of 90 degrees or less in the liquid.

Moreover, the article of this invention is an article surface-treated by the said surface treatment method.

Effect of the Invention

According to the surface treatment method of the present invention, organic matter and the like adhering to the article can be decomposed or removed without being scattered in the air, and damage to the article can be suppressed. It is also possible to etch the surface of the article while suppressing damage to the article.

The article obtained by the surface treatment method of the present invention is highly cleaned or etched on the surface and there is little damage.

1 is a schematic configuration diagram showing an example of a plasma generator.

2 shows the contact angle of water with respect to the article surface.

FIG. 3 is a graph showing the contact angle dependence of the etching rate by water vapor bubbles in the plasma state (hereinafter referred to as water vapor bubble plasma).

It is a schematic diagram of a multilayer wiring damascene process.

Fig. 5 is a diagram showing the emission spectrum from water vapor bubble plasma (Example 1).

6 is an electron micrograph of the surface of the hollow fiber membrane sample that has been clogged.

7 is an electron micrograph of the surface of the hollow fiber membrane sample after the surface treatment.

<Brief description of symbols for the main parts of the drawings>

11: liquid

12: container

13: electrode

14: counter electrode

15: Goods

16: support

17: water vapor bubbles

18: water drop

19: Air phase

γ _SV : surface tension (room temperature, atmospheric pressure) of solid in adsorption equilibrium with vapor of liquid (water)

γ _SL : interfacial tension between solid and liquid

γ _LV : surface tension of liquid (water) in equilibrium with its vapor (water vapor)

Best Mode for Carrying Out the Invention

(Surface treatment method)

The surface treatment method of the present invention is a method of contacting a plasma generated in water vapor bubbles in a liquid containing water with an article having a hydrophilic surface in the liquid. The index of the hydrophilic material in the present invention is a material whose contact angle with water is 90 degrees or less.

As a plasma generating apparatus used for this invention, the plasma generating apparatus of Unexamined-Japanese-Patent No. 2003-297598 and Unexamined-Japanese-Patent No. 2004-152523 can be used.

Hereinafter, the specific plasma generating apparatus is enumerated and the surface treatment method of this invention is demonstrated.

1 is a schematic configuration diagram showing an example of a plasma generating apparatus used in the surface treatment method of the present invention. The plasma generator 10 includes a container 12 containing a liquid 11, an electrode 13 for radiating electromagnetic waves disposed in the container 12, and an electrode 13 disposed opposite to the electrode 13. Electromagnetic wave power source connected to the counter electrode 14, the support 16 which fixes the article 15 between the electrode 13, and the counter electrode 14, and the electrode 13 and the counter electrode 14. For example, a high frequency power supply (not shown) and a vacuum pump (not shown) for adjusting the pressure of the air phase 19 (gas phase) above the liquid 11 in the container 12 are schematically formed.

In the plasma generator 10, the electrode 13 is connected to an electromagnetic wave power source capable of supplying high frequency and high voltage. By supplying the electron energy of this power supply to the electrode 13, the electrode is heated, and the liquid 11 around the electrode vaporizes, and the water vapor bubble 17 which has water vapor as a main component adheres around the electrode.

When a high frequency and a high voltage are applied to the water vapor bubbles attached to the electrode, the molecular motion of the water molecules inside the bubble becomes severe, and electrons are released from the atoms constituting the water molecules to generate positive charge gas and electrons. A chain reaction occurs in which the emitted electrons sequentially attack separate water vapor, and positively charged gas and electrons are sequentially generated, and the inside of the water vapor bubble becomes a plasma state.

Water vapor bubbles in the plasma state (hereinafter referred to as vapor bubble plasma) emit light in a specific wavelength region. From this emission spectrum, the gas species which generate | occur | produce inside a plasma bubble can be known. Table 1 below describes the wavelength of the emission spectrum of the vapor bubble plasma and the attribution of the type of gas that is the cause of emission.

When the vapor bubble plasma around the electrode contacts contaminants containing organic matter on the surface of the article 15 immersed in the liquid 11, (1) thermal decomposition by heat of the vapor bubble plasma, and (2) OH radicals in the vapor bubble plasma. The contaminants are decomposed or removed by the two actions of oxidation.

Although details will be described later, in the present surface treatment, if the article is hydrophilic, water around the article is evaporated, the article surface is cooled for latent heat of evaporation, and thermal decomposition by heat of the water vapor plasma of (1) is reduced.

The liquid 11 may be a liquid containing water, for example, an aqueous solution containing water and an organic solvent mixed with water, an aqueous solution in which electrolyte ions are dissolved in water, and the like.

As an organic solvent mixed with water, Alcohol, such as methanol, ethanol, isopropyl alcohol, butanol; Acetone etc. can be mentioned. Electrolyte ions are ^{Mg 2 +, Ca 2 +,} Na +, Fe 2 +, Fe 3+, Cl - , and the like ^{-, NO 3 -, NO 2} -, OH.

The presence of electrolyte ions in the liquid 11 improves the electrical conductivity of water, and easily causes an arc discharge current to flow from the electrode 13 emitting the electromagnetic waves to the counter electrode 14 at the time of plasma generation. The organic solvent is carbonized by plasma, and the carbide may adhere to the article 15. In addition, when the volume fraction of water in a liquid composition becomes low, the cooling effect of the surface of the article 15 by water falls as mentioned later, and the surface of the article 15 becomes easy to be damaged. Therefore, it is preferable that the liquid 11 does not contain the organic solvent as much as possible, and it is especially preferable that it does not contain it at all. More preferably, pure water and ultrapure water used in a semiconductor manufacturing process or the like is preferably used.

The generation of the water vapor bubbles 17 is not limited to the method by heating the electrodes 13, a separate ultrasonic wave generator is provided, and cavitation bubbles are generated in the liquid 11 by ultrasonic waves from the ultrasonic wave generator, It may be a method of vaporizing the surrounding liquid 11 as vapor in the bubble and forming a vapor bubble 17.

The frequency of the electromagnetic wave irradiated to the steam bubble 17 is selected according to the use in the range of 1 MHz to 100 GHz.

When generating the steam bubble 17, the air phase 19 in the container 12 can also be decompressed by a vacuum pump. When the air phase 19 in the container 12 is decompressed, the boiling point of the liquid 11 is lowered, and water vapor tends to be generated, the vapor pressure inside the water vapor bubbles increases, and the number of water vapor molecules leading to plasma generation increases. Plasma discharge becomes easy. Once the inside of the water vapor bubble reaches the plasma state, plasma generation inside the bubble continues even after the vacuum pump is stopped to return the pressure in the air phase 19 to atmospheric pressure.

As the article 15, an article having a hydrophilic surface is suitable, and specifically, a hydrophilic organic polymer material, glass, a ceramic, a silicon wafer, a metal (for example, aluminum, copper, tungsten, etc.), graphite, carbon fiber, etc. may be mentioned. Can be.

In the present invention, "hydrophilic surface" is defined as the value of the contact angle θ defined in FIG. A "hydrophilic surface" in the present invention is a surface at which the contact angle θ of water (drop 18) to the surface of article 15 at 25 ° C. is 90 degrees or less. The lower the contact angle of water to the hydrophilic surface, the more preferable. Specifically, 80 degrees or less is more preferable, and a range of 70 degrees to 0 degrees is more preferable.

The definition of the contact angle θ in the present invention is the same as the contact angle which is an indicator of the wetting of the material with respect to general water. As a reference on contact angles, refer to the information described in "Metal Functional Surfaces", Modern Editor, 1984, p.133. According to the above book, when a droplet which does not react with the surface is dropped on a smooth surface, and the droplet is in an equilibrium state by maintaining a specific contact angle with the surface, the following equation 1 is established in FIG.

γ _SV = γ _SL + γ _LV cosθ

γ _SV : surface tension of solid in parallel with adsorption of liquid and vapor

γ _SL : interfacial tension between solid and liquid

γ _LV : surface tension of liquid in equilibrium with steam

When Equation 1 is described as in Equation 2 below, the left side shows a decrease in surface energy when the solid surface is wetted with a liquid.

γ _SV γ _SL = γ _LV cosθ

Since this energy is surface free energy, the larger the decrease γ _LV cosθ is, the easier it is to wet, and when γ _LV is constant, the smaller the θ, the better the wettability. It is based on Equation 2 that the contact angle θ of the water droplet is used to quantify the wettability. In the present invention, the liquid is water and γ _LV is 72.8 dyn / cm (“Scientific time”, Maruzen Kabushiki Kaisha, 1993, p. 449) at 20 ° C.

In the present invention, a smooth material surface is prepared, the surface is kept horizontal, a drop of water is dropped on the surface, (? / 2) is measured by a contact angle meter, and the contact angle θ in Fig. 2 is obtained. When the surface of the material is porous or has irregularities, a smooth surface is prepared from the same material, and θ is obtained from the smooth surface. When the surface has irregularities in the organic polymer, the metal, the glass, or the ceramic, a smooth surface can be obtained by melting the same material. In the case of a material that cannot be melted, such as carbon fiber, a smooth sheet containing the precursor material (for example, polyacrylonitrile or polyimide) is prepared in advance, and then fired to smooth the carbon sheet containing the carbon material. Obtain a sheet with one side. Droplets are added to this sheet to measure the contact angle. The water used in the measurement of the contact angle is pure water such as ultrapure water and ion exchange water.

The contact angle (theta) (25 degreeC) of water with respect to typical organic polymer material and an inorganic material is shown in following Table 2 and Table 3 (Document a: "Chemical Handbook Revised 4th Edition Basic Edition II", Maruzen Kabukishiisha, 1993, II- 83 7.1.3 Contact Angle, Literature b: Yoshimi Ishii, Masumi Koishi, Mitsuo Tsunoda, "Wet Technology Handbook", Kabushiki Kaisha Techno System, 2001, b1: p.418, b2: p.92, b3: p.96, b4: p.102 to 103, b5: p.161, b6: p.198).

Also, "Metal Surface Handbook", Niggan High School Newspaper, 1988, p.183, stated that "the surface of the clean metal is wet with water and the contact angle is zero. If there is contaminant, the part will not get wet with water". have. According to Murakah, “Metal Functional Surfaces”, Modern Editor, 1984, p. 134-136, the solid surface tension of γ-Fe is determined to be 1670-2127 dyn / cm, the solid surface tension of copper is about 1500 dyn / cm by the measurement result of the molten state at high temperature, and it is described that it is much larger than the surface tension of a polymer. On the other hand, the surface tension of water is 72.8 dyn / cm. That is, the surface of the clean metal is a surface which is very easy to get wet with water. Clean metal materials with high surface energy can also be applied to the surface treatment of the present invention.

In the present invention, any material of organic polymer material, glass, ceramic, metal, graphite carbon material, carbon fiber, or the like can be applied as long as the material satisfies θ ≦ 90 degrees.

When the wavelength of atomic hydrogen (Hα: 656 nm) in the plasma in the water vapor bubble is converted into a temperature, the temperature is about 5000 K, and the instant of contacting the high temperature plasma gas with an article containing a general organic polymer material It is destroyed without a trace. Here, when the inventors use an article containing a hydrophilic material that satisfies θ≤90 degrees, the inventors can decompose or remove only the organic matter on the article surface and hardly damage the article surface. It has been found that the surface can be etched without breaking.

The idea of the present invention avoiding thermal decomposition is schematically shown in FIG. 3. As shown in Fig. 3, when the material is in contact with water vapor bubbles in water, the contribution of thermal decomposition etching by heat is small when the contact angle θ of the material with respect to water is 90 degrees or less, and when it exceeds 90 degrees, thermal decomposition It has been found that the contribution of the etching increases. The reason for this phenomenon is explained as follows.

A material having a θ of 90 degrees or less covers the surface with a layer of water in a liquid containing water, and even if a vapor bubble plasma approaches, water on the surface of the material evaporates to evaporate the latent heat of evaporation from the surroundings of the material. Since water is constantly supplied, a permanent cooling effect functions on the surface of the material so that the temperature rise of the article is suppressed. As a result, the surface temperature of the article does not exceed the heat resistance temperature of the material, and the contribution of etching due to thermal decomposition is small, and damage to the material is suppressed. This effect is also effective in preventing excessively graphitization locally by heat of plasma in the surface treatment of carbon fibers.

When organic substances, such as a contaminant, adhere to the surface of a hydrophilic article, it is known that wettability changes with hydrophobicity compared with the original hydrophilic surface. For example, according to Ishii Yoshimi, Koshi Masumi, Mitsuno Tsunoda, "Wet Technology Handbook", Kabushi Kiisha Techno Systems, 2001, p.83-84, pure metal surfaces are easy to get wet with water, but organic materials When left in the present atmosphere, it is described that hydrophobization of the metal surface proceeds at the same time as the organic material gradually adheres to the metal surface. Similarly, hydrophilic organic materials and ceramic surfaces tend to be hydrophobic due to contaminants caused by organic substances.

Based on FIG. 3, contaminants on the surface of the material are decomposed under the action of thermal decomposition by heat of the steam bubble plasma and oxidative decomposition by OH radicals. When the contaminant is removed, a more hydrophilic material surface appears, and thermal decomposition is suppressed by the above-mentioned water cooling effect, and a material surface with low damage is obtained.

In the case of a hydrophilic material having a contact angle of 90 or less, etching due to thermal decomposition can be suppressed, and the material can be gradually etched by oxidative decomposition with OH radicals. By this etching, various materials exhibiting hydrophilicity can be etched. For example, a hydrophilic polymer material, a metal material, a ceramic, glass which shows hydrophilicity, a carbon material which shows hydrophilicity, etc. can be etched.

In the surface treatment of the present invention, the time (hereinafter referred to as the contact time) for bringing the article 15 into contact with the vapor bubble plasma includes the heat resistance temperature of the article 15, the temperature inside the bubble plasma, the cooling effect of water generated on the article surface, And the degree of contaminants can be adjusted appropriately.

If the contact time is too long, the water on the surface of the article 15 is excessively evaporated by the vapor bubble plasma, and the water on the surface of the article 15 is insufficient, and the temperature of the material surface temporarily exceeds the heat resistance temperature, or the oxidation of OH radicals. The action is too strong and damages the article.

If the contact time is too short, the oxidative action of the OH radicals is weakened and the cleaning or etching of the article surface is likely to be insufficient.

In the present invention, the "contact time" is defined as the time for generating a plasma in the water vapor bubble 17 by applying a voltage to the electrode 13 and the counter electrode 14 when the article 15 is stopped. When the article 15 is moving in a fixed direction, it is defined as in Equation 3 below.

Contact time (s) = length (mm) of the moving direction of the article 15 of the area | region where the plasma generate | occur | produces / the moving speed of the article 15 (mm / s)

Although the heat resistance temperature of a material differs in the index by the kind of material, in this invention, the temperature which can maintain the form of a material is defined as heat resistance temperature.

In an organic polymer material, melting | fusing point which has crystallinity, and glass transition temperature which are amorphous have as an index of heat resistance temperature. The glass transition temperature (Tg) and melting point (Tm) of representative crystalline organic polymeric materials are shown in Table 4 below (Joel R. Fried, "Polymer Science and Technology", Prentice Hall, 1995, p. 140).

In ceramics, the melting point is an index of the heat resistance temperature. The melting point (Tm) of representative ceramics is shown in Table 5 below (Marcel Mulder, "Basic Principles of Membrane Technology", 2nd Edition, Kluwer Academic Publishers, 1996, p. 60).

In an optical glass material, glass transition temperature is an index of heat-resistant temperature. The glass transition temperatures of representative optical glass species are shown in Table 6 below (Optical Application Class Text, "Optical Materials III-9", Japan Opto Mechatronics Association, 1988, p. 30).

In the optical crystal material, the melting point of the material is used as an index of the heat resistance temperature. Melting points of representative optical crystal materials are shown in Table 7 below (Optical Application Class Text, "Optical Materials III-9", Japan Opto Mechatronics Association, 1988, p. 55).

In metals, silicon wafers (silicon), etc., melting | fusing point is made into the index of heat-resistant temperature. The melting points of representative metals are shown in Table 8 below (National Astronomical Companion, "Scientific Timeline", Maruzen Kabushiki Kaisha, 1993, p.469).

In carbon materials, carbonization-graphitization already proceeds at the same time as temperature, and since it is difficult to determine a definite heat resistance temperature, 3550 ° C., which is the melting point of the graphite single crystal of the related material, is used as an index of the structural transition of the carbon material. In the case of carbon fiber, the degree of crystallinity is low, and it is difficult to clearly distinguish between the amorphous part and the crystal part, or it is difficult to determine the transition point in the crystal structure. do.

(Applications)

The surface treatment method of the present invention comprises (1) cleaning an article to which organic substances such as contamination are adhered (deposited) to the material surface, (2) processing to etch the surface of the hydrophilic material, and (3) providing irregularities to the material surface. It can be applied to processing.

The washing of (1) will be described. Organics include viruses, bacteria, yeasts, fungi, seaweeds, protozoa, proteins, blood and blood components, animal or plant cells, hair, household waste, kitchen waste, drainage, organic matter, fertilizers, etc. All organic materials can be seen well.

Examples of washing of the article based on the surface treatment method of the present invention include the following examples. The object of washing | cleaning is not limited to the following examples, Any contact angle (theta) of water may be 90 degrees or less, and any hydrophilic material may be sufficient, and it can wash | clean if it selects the process suitable for the temperature and cooling effect conditions of a plasma bubble suitably.

(a) Plasma is brought into contact with a porous membrane having a hydrophilic surface used in the filtration treatment, and the porous membrane is decomposed and removed by thermal decomposition (or carbonization) or oxidation by OH radicals. Play it back.

(b) after being embedded in the human body, the plasma is contacted with a biocompatible material having a hydrophilic surface extracted from the human body, and the organic matter attached to the surface of the biocompatible material is subjected to thermal decomposition (or carbonization) or oxidation by OH radicals. Decomposes away and regenerates the biocompatible material. Examples of biocompatible materials include polymethyl methacrylate resins, polylactic acid resins, polyurethanes, hydrogels, celluloses, polyvinyl alcohols, and hydroxyapatite.

(c) Plasma is contacted with an organ having a hydrophilic surface extracted from the human body, and cancer cells present in the organ are decomposed and removed by thermal decomposition (or carbonization) or oxidation by OH radicals.

(d) Plasma is contacted with a contact lens having a hydrophilic surface, and organic matter such as a protein attached to the contact lens is decomposed and removed by thermal decomposition (or carbonization) or oxidation by OH radicals.

(e) contacting the plasma to a catheter or artificial blood vessel having a hydrophilic surface, sterilizing the catheter or artificial blood vessel, or contacting the plasma to a catheter or artificial blood vessel having a hydrophilic surface extracted from the human body, and thermally decomposing prior to embedding in the human body It decomposes | disassembles by (or carbonization) and the oxidative action by OH radical. After disassembly and removal, the catheter or artificial blood vessel is safely discarded.

(f) Plasma is brought into contact with a DNA sample detection device having a hydrophilic surface before or after use, and the organic matter on the surface of the device is decomposed and removed by thermal decomposition (or carbonization) or oxidation by OH radicals.

(g) Plasma is brought into contact with a nonwoven fabric having a hydrophilic surface, and the organic matter adhering to the nonwoven fabric surface is decomposed and removed by thermal decomposition (or carbonization) or oxidation by OH radicals.

(h) A vapor bubble plasma is brought into contact with a silicon wafer surface coated with a lithography material such as a photoresist thin film to remove the thin film. Alternatively, the vapor bubble plasma is contacted with a silicon wafer having contaminants attached to the surface to clean the contaminants on the silicon wafer.

(i) When cleaning the surface of the glass plate used by the master plate process of the glass plate, especially the glass plate used for a liquid crystal cell, and an optical disk, high cleanliness is calculated | required. Conventionally, although RCA cleaning technique using a chemical liquid is performed, since the cost of wastewater treatment of chemical liquids is high, the washing | cleaning which does not use a chemical liquid is calculated | required. When cleaning a glass plate by this technique, contaminants can be decomposed without damaging the surface of a glass plate by making OH radicals generate | occur | produce from a plasma bubble contacting a glass plate, and setting a contact time suitably. Decomposition products are carbides, carbon dioxide, and water, and no harmful waste fluid is generated.

(j) Contaminants on the surface of ceramic products such as Al ₂ O ₃ ceramic tiles having a hydrophilic surface are cleaned by the present technique.

(k) The surface of the photocatalyst tile product coated with titanium oxide particles having a hydrophilic surface is cleaned by the present technique. If contaminants are deposited to such an extent that ultraviolet rays do not reach the surface of the photocatalyst, it can be cleaned and regenerate the photocatalyst function.

(l) The surface of the carbon electrode modified on the hydrophilic surface is cleaned by the present technique. In particular, in the electrode of the secondary battery using electrolyte ions, a hydrophilic electrode is used in some cases. Contaminants may be generated in the electrolyte due to repeated charge and discharge, and contaminants may be generated on the electrode surface. According to the present invention, it is possible to clean the carbon electrode with contaminants.

(m) The fluorine-based electrolyte membrane (for example, Nafion membrane manufactured by DuPont) used as the solid electrolyte membrane has strong hydrophobicity. In this case, when the electrolyte membrane is immersed in water and swollen with water, the moisture content of the membrane increases and at the same time, the contact angle with respect to water decreases. The membrane surface whose contact angle is 90 degrees or less can be cleaned by the technique of the present invention.

The following example is mentioned as an example of the process of etching the above-mentioned (2) hydrophilic material surface.

(n) It can also be used for the damascene process of providing a gap on the insulating film in a semiconductor multi-layer wiring step, embedding a metal film such as copper, aluminum, tungsten, titanium and the like and removing an unnecessary metal film on the insulating film. The schematic diagram of a damascene process is shown in FIG. In FIG. 4, the process proceeds from a → b → c, where c is a patterning of wiring metal.

As described above, since the clean metal film is hydrophilic, it can be precisely processed while removing the metal atoms at the atomic level by electrochemical reaction of atomic hydrogen, OH radical and metal atoms generated from the steam bubble plasma. In that case, it is necessary to appropriately perform the etching rate control by OH radical.

Graduate School of Engineering, Osaka University Graduate School, Eiwa Goto, Hirose Kikuji, Kei Inada, Mori Yuzo, etc. 69, No. 9, 2003, at p. 1332-1336, a new ultrafine water is used to dissociate water in ultrapure water into H and OH by a catalyst, to form OH minus ions, and to chemically react the OH minus ions with workpiece surface atoms. It reports the development of precision and ultra clean processing methods. In the case of using Al (001) as the cathode, in the same literature report on the surface reaction subprocess, (1) when OH bonds to Al (001) surface atoms, the bond strength between surface first layer and second layer atoms is lowered. (2) OH and H act on the H-terminated Al (001) surface, and all the bonds between Al surface atoms are cleaved, and Al surface atoms are reported to be removed as AlH ₂ (OH) molecules. . In this document, although H and OH are produced by a catalyst and the electrochemical reaction using this OH is used, the research result by the OH radical which generate | occur | produces from a vapor bubble plasma was not reported. On the other hand, the inventors of the present invention, while the clean metal is hydrophilic with respect to water, by acting on the metal by the OH radical generated by the vapor bubble plasma of the present invention, while cutting the chemical bonds of atoms on the surface of the metal, as in the literature We also claim that the technique is applicable to precision etching processes that remove metals from materials.

(o) Hattori Daiwa describes a cleaning technique for a silicon wafer in "Electronic Materials", an annex, December 2005, p.93-101. This document introduces wet cleaning of silicon wafers whose surfaces are cleaned by RCA cleaning, and wet cleaning of acids, alkalis, dihydrogen fluoride water and ozone water while spinning the wafer. On the other hand, using the technique of the present invention, the wafer can be cleaned with OH radicals having a stronger oxidation power than ozone water cleaning. According to Yamabe Chobei, "Improvement of Water Quality by Discharge in Submerged Microbubbles", 2000-2002 Scientific Research Grant Subsidy-Based Research, (A) (2) Research Outcome Report, March 2003, OH Radicals It can be seen that the standard oxidation potential of is 2.84 eV, while the standard oxidation potential of ozone is 2.07 eV, and the OH radical has a stronger oxidation capacity than ozone.

Specifically, the silicon wafer can be cleaned by immersing the contaminated silicon wafer in the water of the reaction apparatus shown in FIG. 1 and rotating the silicon wafer in water while bringing the silicon wafer into contact with the vapor bubble plasma.

Hereinafter, washing | cleaning of the porous membrane which was clogged after using for the filtration process as described in (a) mentioned above as an example of article washing | cleaning is demonstrated. Examples of the porous membrane include hydrophilized polyethylene hollow fiber membranes, flat membranes, tubular membranes, and the like.

The contaminated porous membrane is immersed in water and fixed near the electrode that emits electromagnetic waves. When electromagnetic waves are emitted from the electrodes, steam bubbles are generated around the electrodes and plasma is generated in the steam bubbles. When the plasma generated in the water vapor bubbles is brought into contact with the membrane surface of the porous membrane with a predetermined contact time, the organic matter adhered to the membrane surface is thermally decomposed by the plasma and fractionated. Since the hydrophilic surface exposed after the organic matter is collected is easily wetted with water, the hydrophilic surface is covered with a layer of water, is less likely to be damaged by plasma, and the pore structure formed in the porous membrane is almost maintained. The contact time is preferably 1 to 5 minutes. If the contact time is less than 1 minute, there is a fear that organic matters such as contaminants adhered to the porous membrane surface may not be sufficiently removed, and if the contact time exceeds 5 minutes, part of the surface of the porous membrane starts to melt. Although the specific example of above (a) was described, the contaminant can be wash | cleaned similarly about each case of (a)-(m). Moreover, this invention is applicable also to the etching of (n)-(o).

The surface treatment method of the present invention is also applicable to partial etching of articles. That is, when the plasma is brought into contact with an article having both a hydrophobic surface (θ> 90 degrees) and a hydrophilic surface (θ ≦ 90 degrees) in water, the etching rate of the hydrophobic surface is increased, and irregularities are formed on the article surface.

In order to form the uneven surface, it is necessary to appropriately select the contact time between the material and the vapor bubble plasma.

This uneven | corrugated formation technique is useful for the etching of a material in a semiconductor lithography process, and the fine uneven | corrugated processing of a plastic material (for example, the process for giving a non-glare function which prevents an image from being imaged on the surface of a transparent resin plate).

According to the surface treatment method of the present invention described above, since the surface of the article is brought into contact with the vapor bubble plasma in the liquid, contaminant decomposition products from the article do not scatter in the air. In particular, it is possible to safely decompose and remove water, without scattering viruses, harmful organic substances, etc. in the air. The decomposed product transferred into the water can be safely taken out in the water by being recovered by an adsorption filter or the like. In particular, articles (for example, catheters, artificial blood vessels, DNA sample detection devices, nonwoven fabrics having a function of virus capture, dialysis filtration membranes, microfiltration membranes, gas separation membranes, etc.) handled at medical sites such as hospitals and food production sites are used. When discarding, it is necessary to safely harmless organic substances such as various germs, viruses and the like adhering to the article surface, and the present invention is effective for this purpose.

In addition, since during the etching of the material by the surface treatment of the present invention, OH radicals generated from water are used for decomposition without using an electrolyte, sulfuric acid, hydrochloric acid, or hydrogen fluoride, etc. This does not happen. In addition, in the case of etching of metal, metal hydroxide precipitates, but since it is insoluble in water, solid-liquid separation is possible, and no waste liquid harmful to the environment is generated.

When the surface treatment is performed using a carbon fiber suitable for the present invention, the excessive graphitization caused by the high temperature of the water vapor bubble plasma is suppressed, and stable carbonization is maintained, and the surface treatment such as etching or cleaning with OH radicals is carried out as a whole. Since it can carry out evenly over, continuous carbon fiber with high added value industrially can be manufactured.

<Example 1>

Mitsubishi Rayon Co., Ltd. product, the domestic water purifier (brand name: cleanse 02) was prepared. A hydrophilized polyethylene hollow fiber membrane (contact angle of water of hydrophilized material (25 ° C.) = 55 degrees) is used as the filter cartridge of the water purifier. The hollow fiber membrane is a hollow fiber membrane having an inner diameter of 270 µm and a membrane thickness of 55 µm manufactured by Mitsubishi Rayon Co., Ltd., and fibrils containing polyethylene are oriented in the fiber direction of the hollow fiber membrane, and a plurality of these fibrils are in the thickness direction of the membrane. It has an overlapping slit-like pore structure.

This water purifier was attached to the tap of domestic tap water, and the tap water (Iwagunishi Mikasamachi) was intermittently passed through the filter cartridge for one year. Changed to. The clogging produced filter cartridge was removed from the water purifier body, and activated carbon was further removed from the filter cartridge to obtain a clogged hollow fiber membrane sample. The clogged hollow fiber membrane surface was observed with the electron microscope. An electron micrograph is shown in FIG. 6. In the clogged hollow fiber membrane, the slit-like pores on the membrane surface were blocked by the organic substance.

The clogging hollow fiber membrane was wash | cleaned as follows.

Since the length of the clogged hollow fiber membrane sample was as short as 50 mm, the hollow fiber membrane clogged to a hydrophilized hollow fiber membrane (Mitsubishi Rayon, EX-540V polyethylene hollow fiber membrane manufactured by Mitsubishi Rayon) with a length of 150 mm was bundled with a sample for the test sample. Ready.

The apparatus shown in FIG. 1 was used as a plasma generating apparatus. As the RF power supply, model T161-5766LQ manufactured by THAMWAY Corporation was used, and model T0202-5766LQ manufactured by THAMWAY Corporation was used as a matching box.

First, a test sample was immersed in a container filled with water, and fixed with a support in the vicinity of the electrode. Water was heated using the exothermic heat of the electrode, and this heat generated water vapor bubbles in the water. In Fig. 1, water vapor bubbles were irradiated with an electromagnetic wave (27.1 MHz) at an output of 300 W in a reduced pressure environment having a gas phase pressure of 30 hPa, and the water vapor in the bubbles was plasmaled, followed by the generation of a water vapor bubble plasma under atmospheric pressure. The emission spectrum from the water vapor bubble plasma when the gas phase is at atmospheric pressure is shown in FIG. 5. This spectral spectrum uses a PMA-11C-7473-36 type terunitana type small polychromator and a back-illuminated CCD liner image sensor made by Hamamatsu Photonics to emit light from bubbles emitted by the reaction apparatus of FIG. The spectral intensity was measured and determined for each wavelength. The number of light detection elements was 1024, the wavelength region was 200 to 950 nm, and the exposure time was 19 ms. The measurement was performed using a polychromometer and a linia image sensor in which wavelength sensitivity unevenness correction and wavelength axis correction were completed.

The vapor bubble plasma was brought into contact with the test sample for 3 minutes while the gas phase was at atmospheric pressure. After surface treatment, the hollow fiber membrane sample surface was observed with an electron microscope. An electron micrograph is shown in FIG. 7. The clogging organics were almost completely removed. In addition, damage was hardly recognized on the surface of the hollow fiber membrane sample, and the pore structure maintained its original shape.

<Example 2>

Using the same plasma generator as in Example 1, the test sample was immersed in a container filled with water, and fixed with a support in the vicinity of the electrode. A water vapor bubble plasma was generated under the same conditions as in Example 1 except that the ethylene vinyl alcohol copolymer film (hereinafter also referred to as EVAL film) shown in Table 9 was used as the sample, and the plasma was brought into contact with the sample for 3 minutes. . All films exhibited hydrophilicity, with a contact angle for water prior to plasma contact in the range of 64 to 71 degrees. All of these films survived the heat of the steam bubble plasma and remained in shape.

1) Ethylene: Ethylene Content

2) θ / 2: readings at the contact angle meter.

         In contact angle meter, we use CA-DT made by Kyowa Kaimen Kagaku Corporation.

         The droplet volume of pure water was 1 μl.

3) θ: contact angle

4) T: Temperature of the measuring room

5) RH: humidity of measuring room

6) "Plasma durability" means durability against water vapor bubble plasma in water.

7) "Weather is atmospheric pressure" means that the gaseous phase above the water surface is air of atmospheric pressure in FIG. 1, and steam vapor plasma was generated in this state.

8) "With durability" means that the original shape is maintained without breaking.

9) "No durability" means thermal decomposition after breaking by plasma heat.

In Table 10 and Table 11 shown below, the same symbol or term as in 1) to 9) shall have the same meaning.

In addition, the surface of the film of sample DC3203F was marked with oil-based ink. When the marked portion was in contact with the plasma, the oily ink was decomposed by the plasma and did not remain on the film. The film surface after washing | cleaning was smooth by visual observation.

<Example 3>

The Nafion 112 and Nafion 1035 films manufactured by DuPont were immersed in 25 ° C. ion-exchanged water for 5 minutes, swelled after swelling the membrane with water, and the contact angles were measured. Nafion 112 and Nafion 1035 shown in Table 10 were used as samples of the plasma treatment.

Using the same plasma generator as in Example 1, the sample was immersed in a container filled with water, and the sample was fixed with a support in the vicinity of the electrode. Subsequently, a water vapor bubble plasma was generated under the same conditions as in Example 1, and the plasma was brought into contact with the sample for 3 minutes. As shown in Table 10, both Nafion 112 and Nafion 1035 swollen with water remained morphologically resistant to the heat of the steam bubble plasma.

In addition, the surface of the Nafion 112 film was marked with oil-based ink. The marking was firmly stuck to the film. After the marked portion was brought into contact with the water vapor plasma in water for 3 minutes, when visually observed, the oily ink was decomposed by the plasma and did not remain on the sample. The film surface after washing | cleaning was smooth by visual observation.

<Example 4>

Using the same plasma generator as in Example 1, the sample was immersed in a container filled with water and fixed with a support in the vicinity of the electrode. A water vapor bubble plasma was generated under the same conditions as in Example 1 except that an optically polished glass plate (thickness 5 mm, 100 mm x 100 mm) was used as the sample, and the plasma was brought into contact with the glass plate for 3 minutes. The glass plate maintained its shape withstanding the heat of the steam bubble plasma. The contact angle with respect to the water of the glass plate before contacting the plasma was about 35 degrees.

In addition, the surface of the glass plate was marked with oil ink, and the marked portion was visually observed after contacting the vapor bubble plasma in water for 3 minutes. The oil ink was decomposed by the plasma and did not remain on the glass plate. The glass plate after washing was smooth by visual observation.

Example 5

Using the same plasma generator as in Example 1, the test sample was immersed in a container filled with water, and fixed with a support in the vicinity of the electrode. A water vapor bubble plasma was generated under the same conditions as in Example 1 except that an alumina ceramic sheet (γ-Al ₂ O ₃ sheet thickness 3 mm, 100 mm x 100 mm) was used as a sample, and the plasma was applied to the alumina ceramic sheet for 3 minutes. Contact. The alumina ceramic sheet after contact withstands the heat of the water vapor bubble plasma to maintain its original form. The contact angle with respect to water of the alumina ceramic sheet before contacting the plasma was about 55 degrees.

In addition, the surface of the alumina ceramic sheet was marked with an oil ink, and the marked portion was visually observed after contacting the vapor bubble plasma in water for 3 minutes. The oil ink was decomposed by the plasma and did not remain on the alumina ceramic sheet. The surface of the alumina ceramic sheet after washing was smooth by visual observation.

<Example 6>

Using the same plasma generator as in Example 1, the test sample was immersed in a container filled with water, and fixed with a support in the vicinity of the electrode.

An ethylene-vinyl alcohol copolymer film (32 mol% of ethylene content) is used as a substrate (thickness 3 mm, 100 mm x 100 mm), and a 5 mm wide polyethylene film (thickness 0.5 mm, 100 mm x 100 mm) is spaced from this substrate. Samples were prepared that were separated by 5 mm, adhered by thermal fusion, and included a hydrophilic surface / hydrophobic surface of a hydrophilic portion 5 mm wide and a hydrophobic portion 5 mm wide. The contact angle with respect to the water of the ethylene-vinyl alcohol copolymer film (the ethylene content rate of 32 mol%) was 67 degree, and the contact angle with respect to the water of the polyethylene film was 95 degree.

A water vapor bubble plasma was generated in the same manner as in Example 1 except that the prepared sample was used, and the plasma was brought into contact with the entire sample for 3 minutes. After the contact, when the sample was taken out from the reaction vessel, the polyethylene film as the hydrogen portion was etched by plasma and had an average thickness of 0.1 mm. However, the ethylene-vinyl alcohol copolymer film substrate maintained a smooth initial surface. Only the hydrogen portion was the result of being etched by the plasma.

Comparative Example 1

100 μm thick polytetrafluoroethylene film (contact angle to water (25 ° C.) = 110 degrees), polyethylene film (contact angle to water (25 ° C.) = 95 degrees) that is not hydrophilized as an article, polypropylene film (Contact angle with water (25 degreeC) = 96 degree | time) was prepared. Organic substances such as contaminants did not adhere to the surfaces of these films. These films were surface-treated in the same manner as in Example 1. All the films were thermally decomposed and broken by the high temperature of the plasma when the plasma contacted them.

Comparative Example 2

As the article, an organic polymer porous flat membrane having a thickness of 50 µm which is not hydrophilized (Millipore Co., Ltd., hydrophobic polytetrafluoroethylene membrane, contact angle to water (25 ° C) = 110 degrees, average pore diameter of 1 µm), thickness An organic polymer porous flat membrane (manufactured by Millipore, hydrophobic polyethylene membrane, contact angle to water (25 ° C) = 94 degrees, average pore diameter of 1 µm) of 100 µm was prepared. Organic substances such as contaminants did not adhere to the surfaces of these polymer porous flat membranes. These polymeric porous flat membranes were surface-treated in the same manner as in Example 1. All the flat membranes were thermally decomposed and broken by the high temperature of the plasma at the moment of contact with the plasma.

Comparative Example 3

As the sample, the same conditions as in Example 3 were used except that two kinds of Nafion membranes (Nafion 112, Nafion 1035) manufactured by Dupont, which were allowed to stand for 1 week in an atmosphere of 25 ° C and 55% RH, were used. The vapor bubble plasma was brought into contact with the sample.

The contact angles of Nafion 112 and Nafion 1035 to water before plasma contact were the values shown in Table 11 below. At the instant of contact with the plasma, both types of Nafion films were thermally decomposed and broken by the high temperature of the plasma.

<Comparative Example 4>

200 ml of pure water was prepared in a 300 ml beaker, the clogged hollow fiber membrane used in Example 1 was immersed in pure water at 25 ° C, and the hollow fiber membrane was washed for 1 hour with an ultrasonic cleaner having a power of 100 W and 20 KHz. It was. When the film | membrane after washing | cleaning was observed with the electron microscope, the organic substance clogged to the membrane surface was not removed.

Comparative Example 5

In Example 1, the electrode of the reaction apparatus was overheated to generate steam bubbles other than the plasma state, and the vapor bubbles were contacted with the hollow fiber membrane sample that had been clogged for 3 minutes. The organic substance clogged to the membrane surface was not removed.

The present invention is a surface treatment technique that decomposes or removes an organic substance adhered to an article without damaging the article by contacting the plasma generated in the water vapor bubble with an article having a hydrophilic surface in water. This surface treatment technique is useful, for example, for the regeneration of organic polymer porous membranes, ceramic porous membranes used for domestic water purifiers, industrial drainage filtration, air filtration, and safe disposal of porous membranes. In particular, it is effective as a method of safely regenerating or discarding a contaminant or a clogged membrane with a substance containing bacteria, such as a filtration membrane for toilet water in a hospital, an air filtration membrane for preventing infection in a hospital, and an air filtration membrane for a biohazard chamber.

In addition, the surface treatment method of the present invention includes a process for embedding a biocompatible material in a sieve and using it, and treating the material safely by thermally decomposing or carbonizing organic matter such as bacteria on the surface of the material after its use; Treatment to thermally decompose or carbonize cancer cells that coexist with an organ to be useful for life safety; It can be applied to a process for thermally decomposing or carbonizing and safely disposing organic substances such as bacteria, blood, and proteins attached to the contact lens after use. Moreover, the surface treatment method of this invention is sterilization, such as sterilization before catheter, artificial blood vessel, etc. are embedded in a body, and fungus adhered after taking out from a living body; A process of removing bacteria out of the test object from the DNA sample detection device; A process for safely discarding the DNA sample detection device at the end of use; It can also be applied to a process for thermally decomposing or carbonizing and safely disposing fungi attached to nonwoven fabrics used in air filters and masks.

In addition, the etching technique of the present invention can be used for processing to a privacy filter that gives fine irregularities to the surface of a hydrophilic transparent organic material, exhibits antireflection function in optical applications, or visibility may be expressed only at a specific viewing angle. . In addition, the surface of the metal film can be etched only with chemical species derived from moisture molecules, and the cost of waste liquid treatment can be reduced in the damascene process of high-density multilayer wiring in a semiconductor device, which is effective for reducing the manufacturing cost.

In recent years, in semiconductor multi-layer wiring devices, wiring density is increased and finer processing is required. In this case, a low dielectric constant material which is included as a porous silicon film in an insulating film has been proposed. Since the insulating film has a large pore volume and the material has a hydrophobic contact angle with water, it is difficult to polish the entire liquid after polishing the metal film by polishing the polishing liquid with the insulating film in a conventional chemical mechanical polishing process. On the other hand, by using the method of the present invention, a material having a contact angle with respect to water of 90 degrees or less is selected as the low dielectric constant film, so that the OH radicals in the vapor bubble plasma etch the low dielectric constant film, thereby obtaining a flat insulating / multilayer wiring metal structure. Can be.

In addition, in the etching technique of the present invention, only the hydrophobic portion can be selectively etched by controlling the contact time with the vapor bubble plasma in a short time. This technique can be applied when selectively etching hydrophobic portions on various materials such as organic materials, inorganic materials, and carbon materials having both hydrophilic surfaces and hydrophobic both surface portions. In particular, materials such as carbon materials, silicon wafers, and the like have a high heat resistance temperature, and thus surface processing is difficult, but etching can be easily performed by using the present technology.

Claims (14)

The surface treatment method of making the plasma which generate | occur | produced in the water vapor bubble in the liquid containing water contact the material whose contact angle with respect to water in this liquid is 90 degrees or less. delete The surface treatment method of removing the said organic substance from a material by making the plasma generate | occur | produced in the water vapor bubble in the liquid containing water contacting the organic substance adhering to the material whose contact angle with respect to water is 90 degrees or less in the said liquid. The surface treatment method according to claim 3, wherein the material is a polymeric porous membrane. The surface treatment method according to claim 3, wherein the material is a polymer electrolyte membrane. The surface treatment method according to claim 3, wherein the material is glass. 4. The surface treatment method according to claim 3, wherein the material is ceramic. delete And etching the surface of the material without destroying the material by bringing the plasma generated in the water vapor bubbles in the liquid containing water into a material having a contact angle of 90 degrees or less in the liquid. 10. The method of claim 9, wherein the material is a metal. The etching method of Claim 10 whose metal is 1 or more types chosen from copper, aluminum, tungsten. delete Etching the hydrophobic portion by bringing the plasma generated in the water vapor bubbles in the liquid containing water into a material having both a hydrophobic portion having a contact angle of more than 90 degrees and a hydrophilic portion of 90 degrees or less in the liquid. Etching method. By the etching method of claim 13, the hydrophobic portion is a recessed portion, a hydrophilic portion, in which only the hydrophobic portion of the material having both a hydrophobic portion having a contact angle to water greater than 90 degrees and a hydrophilic portion having 90 degrees or less is selectively etched. An article having an uneven surface to be this convex portion.

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