JP3828886B2 - Selective surface modification / cleaning method - Google Patents

Description

  The present invention relates to a method for modifying and cleaning a material surface. More particularly, the present invention relates to a method for selectively modifying and / or cleaning a part of a material surface such as a microchip for chemical analysis using excimer UV light.

  Conventionally, (1) improved wettability, printability, adhesion, (2) improved adsorption of cells and proteins, (3) introduction of functional groups, and (4) removal of organic matter and oil film, etc. For this purpose, material surface modification and / or cleaning has been performed.

The modification and / or cleaning of the material surface is generally performed using, for example, plasma, corona discharge, electron beam, ultraviolet light (UV light), vacuum ultraviolet light (VUV light), or the like. In particular, recently, as described in Patent Document 1, the use of vacuum ultraviolet light (excimer UV light) by excimers has become active. Excimer UV light includes the following wavelengths (center wavelengths) depending on the type of discharge gas. 126 nm (Ar ₂ ), 146 nm (Kr ₂ ), 172 nm (Xe ₂ ), 222 nm (KrCl), and 308 nm (XeCl). An irradiation lamp that emits excimer UV light is, for example, a dielectric barrier discharge lamp in which xenon gas is sealed. This dielectric barrier discharge lamp becomes an excimer state in which xenon atoms are excited (Xe ₂ ^* ), and generates light having a wavelength of about 172 nm when dissociated again from this excimer state into xenon atoms. When this light having a wavelength of 172 nm is irradiated to oxygen, ozone having a higher concentration than that obtained by irradiating oxygen with a light having a wavelength of 185 nm emitted from a conventional low-pressure mercury lamp can be obtained. An oxidative degradation product is also obtained. Due to the synergistic action of these high-concentration ozone and the active oxidative degradation product, the surface modification and / or cleaning effect of the object to be treated is dramatically enhanced. Dielectric barrier discharge lamps are described in detail in US Pat.

  Recently, as is known by the names such as Microscale Total Analysis Systems (μTAS) or Lab-on-Chip, a microchannel that forms a flow path of a predetermined shape in a substrate and Providing a fine structure such as a port and performing various operations such as chemical reaction, synthesis, purification, extraction, generation and / or analysis of substances within the fine structure has been proposed and partially put into practical use. A structure manufactured for such a purpose and having a fine structure such as a microchannel and a port in a substrate is generically called a “microchip”. (A microchip is sometimes called a microfluidic device.)

  Microchips can be used for a wide range of applications such as genetic analysis, clinical diagnosis, drug screening and environmental monitoring. Compared with the same type of equipment of the common size, the microchip is (1) significantly less sample and reagent usage, (2) shorter analysis time, (3) higher sensitivity, (4) carried on-site, It can be analyzed in the field and (5) can be disposable.

  Also in the field of such microchips, hydrophilicization (that is, improvement of wettability) and hydrophobization in the microchannel can be made separately (see, for example, Patent Document 4), coating properties of coating agents are improved, and functional materials are used. There are cases where improvement of modification property, improvement of adsorptivity of cells, proteins, etc. is required. In a special example, as a pretreatment for permanently bonding (permanent bonding) a polydimethylsiloxane (PDMS) substrate and a glass substrate constituting a microchip, surface modification is performed by irradiating the PDMS substrate with oxygen plasma. May do quality. This is because hydroxyl groups are formed on the surface of the PDMS substrate by oxygen plasma irradiation, and permanent adhesion to the glass substrate is achieved by the action of the hydroxyl groups.

  In fields such as microchips, when modifying and / or cleaning a substrate surface, only a portion of the substrate surface needs to be selectively treated. In a processing method using convergent light or an electron beam, the convergent light or electron beam can be scanned and irradiated only to the processing unit. However, since the processing time is long and the scanning function is provided, the processing apparatus is also used. Expensive. On the other hand, a processing method using plasma or excimer UV light can process the processing surface at a time and is inexpensive and productive. However, in order to perform selective processing, it is necessary to use a mask. However, in both processing methods of plasma and excimer UV light, ozone and excited oxygen atoms generated by oxygen plasma and excimer UV light must directly reach the processing surface and act. A mask cannot be used.

  In the case of the surface treatment method using this mask, if the non-processed portion is extremely small with respect to the processing surface, or if a large number of small non-processed portions are dispersed and arranged, the mask cannot be created. Such a case will be described with reference to FIGS. As shown in FIG. 4, a specific portion 44 (non-processing portion) of the processing surface 42 of the processing object 40 such as a PDMS substrate of a microchip is not subjected to surface modification and / or cleaning, and other surfaces. Are all processed.

  As in this case, if the non-processing part is a part of the processing surface and is distributed and distributed in a plurality of locations, it is difficult to create a single mask. Therefore, as shown in FIG. 5, a pattern 46 for blocking oxygen plasma or the like is individually arranged on the processing surface 42 of the processing object 40 in accordance with the shape of the non-processing portion. Therefore, each pattern 46 must be individually aligned at an appropriate position, and operations such as positioning and arrangement become complicated. If the non-processing part 44 has a complicated shape or an extremely fine shape, it is difficult to create and handle the pattern 46.

Japanese Patent No. 2,705,023 Japanese Patent Laid-Open No. 2-7353 US Pat. No. 4,837,484 JP 2000-27813 A

  Accordingly, it is an object of the present invention to provide an inexpensive and efficient method for selectively modifying and / or cleaning a portion of a material surface.

In order to solve the above problems, the present invention adopts the following configuration.
(1) (1) preparing a mask having a light-shielding pattern of a predetermined shape on one surface of a substrate having transparency to excimer UV light having a center wavelength of 172 nm;
(2) a step of preparing a processing object;
(3) a step of aligning and placing the surface having the light shielding pattern of the mask on the surface to be processed of the processing object;
(4) A selective surface modification / cleaning method comprising a step of irradiating excimer UV light from the upper surface of the mask.
(2) The mask substrate is formed of a material selected from the group consisting of quartz glass, sapphire, calcium fluoride, magnesium fluoride, barium fluoride, and lithium fluoride.
(3) The said light shielding pattern is formed from the photoresist or the metal film, The thickness exists in the range of 10 micrometers-200 micrometers.
(4) The processing object is formed of polydimethylsiloxane (PDMS).
(5) (1) preparing a mask made of a base material having transparency to excimer UV light having a center wavelength of 172 nm;
(2) preparing a processing object in which a channel-shaped recess having a predetermined shape and a depth and width is formed on one surface;
(3) placing the mask on the recess forming surface of the processing object;
(4) A selective surface modification / cleaning method comprising the step of hydrophilizing the inner surface of the concave portion of the processing object by irradiating excimer UV light from the upper surface of the mask.
(6) The mask substrate is formed of a material selected from the group consisting of quartz glass, sapphire, calcium fluoride, magnesium fluoride, barium fluoride, and lithium fluoride.
(7) The object to be processed is a microchip formed from polydimethylsiloxane (PDMS).

  According to the present invention, in applications where surface modification / cleaning is selectively performed, a mask is formed on a processing object in which a non-processing portion is relatively small with respect to a processing surface or a plurality of non-processing portions are distributed. A surface modification / cleaning method that is easy to manufacture and easy to align during processing is obtained. In addition, according to the present invention, when a recess such as a channel is formed on one surface of an object to be processed such as a microchip formed from polydimethylsiloxane or the like, only the recess is selectively hydrophilized. You can also

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic sectional view of an example of a mask used for carrying out the surface modification / cleaning method of the present invention. The mask 1 is basically a base material 3 that is transparent to excimer UV light, and a substance that is disposed on one surface of the base material 3 and does not transmit excimer UV light. And a pattern 5 having a predetermined thickness formed into a corresponding shape.

  FIG. 2 is an explanatory view showing a state in which the surface modification / cleaning method of the present invention is carried out using the mask 1 shown in FIG. As shown in FIG. 2, the surface of the mask 1 on which the pattern 5 is formed is aligned with the processing surface 9 of the processing object 7, and the pattern 5 and the treatment surface 9 are arranged so as to be in close contact with each other. At this time, an appropriate gap is generated between the processing surface other than the pattern 5 and the substrate 3 according to the thickness of the pattern 5, thereby forming the air layer 11. In this way, an appropriate amount of excimer UV light is irradiated from the upper surface side of the mask 1 in a gas atmosphere containing oxygen (generally an air atmosphere). The excimer UV light transmitted through the excimer UV light-transmitting substrate 3 directly affects the action of ozone and excited oxygen molecules generated from the oxygen molecules in the air layer 11 in the gap between the mask 1 and the object 7 to be processed. The processing surface 9 of the processing object 7 is subjected to desired surface modification and cleaning by the action of the photon energy of the irradiated excimer UV light. On the other hand, the non-processed surface 13 of the object to be processed shielded by the pattern 5 does not generate ozone or excited oxygen molecules, and is not affected by the photon energy of the excimer UV light. Absent.

The irradiation intensity of the excimer UV light ^generally preferably in the range of ^{5mW / cm 2 ~30mW / cm 2} . When the irradiation intensity is less than 5 mW / cm ² , the processing time becomes too long and the working efficiency is lowered. On the other hand, when the irradiation intensity is more than 30 mW / cm ² , there are few devices having such a high irradiation intensity, and even if they are expensive, the irradiation effective area is small and the size of the object to be processed is limited. . In addition, since a plurality of lamps are arranged densely, the uniformity of irradiation intensity may be low, and as a result, the degree of processing may be uneven. In general, the excimer UV light irradiation time is preferably in the range of 10 seconds to 5 minutes. The irradiation time of the excimer UV light has a reciprocal relationship with the irradiation intensity. When the irradiation intensity is high, the irradiation time is shortened. The optimum irradiation time for the irradiation intensity of the selected irradiation lamp can be easily determined by those skilled in the art by repeating the experiment.

The base material 3 of the mask 1 is, for example, quartz glass, sapphire (Al ₂ O ₃ ), calcium fluoride (CaF ₂ ), magnesium fluoride (MgF ₂ ), barium fluoride (BaF ₂ ), or lithium fluoride (LiF). A plate-like material formed from a synthetic optical crystal such as can be used. These materials preferably have the ability to transmit at least 50% of excimer UV light. When the excimer UV light transmittance is less than 50%, a desired surface modification / cleaning effect cannot be obtained. Needless to say, the substrate 3 most preferably has an excimer UV light transmittance of 100%.

  As a material for forming the pattern 5 of the mask 1, not only a substance having an excimer UV light transmittance of 0% but also a substance having a transmittance of 10% or less can be used in the present invention. In general, since there are few substances that transmit vacuum ultraviolet light (VUV light) such as excimer UV light, it is preferable to use a substance that can easily form a pattern as the pattern forming material. For pattern 5, for example, a resist is applied to the surface of substrate 3, exposed through a mask pattern, and a predetermined resist pattern is formed by photoetching, or a metal film such as aluminum or chromium is once deposited. And a metal pattern is formed thereon by an etching technique using a resist. If the non-treated surface that is not subjected to surface modification / cleaning is not fine, a pattern 5 can also be formed by cutting a thin plate such as stainless steel into the shape of the non-treated surface and affixing it to a predetermined position of the substrate 3 Can do.

  The pattern 5 preferably has a thickness of about 10 μm to 200 μm. When the thickness of the pattern 5 is less than 10 μm, it becomes difficult to maintain a uniform gap between the base material 3 of the mask 1 and the processing surface 9 of the processing object 7 to be surface-modified / cleaned. In addition, the surface modification / cleaning process becomes uneven. When the thickness of the pattern 5 exceeds 200 μm, it is too thick to make it difficult to form with a photoresist, and the effect of providing a gap is saturated, which is uneconomical. If the thickness of the pattern 5 is at least 50 μm, a sufficient surface modification / cleaning treatment effect can be expected. This is almost the same surface modification / cleaning treatment effect as that obtained when the excimer UV light is directly irradiated.

  FIG. 3 is an explanatory view showing a state in which another surface modification / cleaning method according to the present invention is carried out. As shown in FIG. 3, when a recess 15 such as a channel exists on the surface of the processing object 7A and only the recess 15 is to be subjected to surface modification / cleaning treatment, a flat plate shape on which no pattern or the like is formed is formed. The base material 3A is directly adhered to the processing object 7A and adhered thereto. Thereafter, excimer UV light is irradiated from the upper surface of the substrate 3A. In the recess 15 of the processing object 7A, ozone and excited oxygen atoms are generated from the air contained therein, whereby the inner surface of the recess 15 is modified and / or cleaned. On the other hand, since no air is present in the other portions, ozone and excited oxygen atoms are not generated. Therefore, the surface modification / cleaning treatment is hardly performed or only a very small amount is processed.

  In FIG. 3, when the processing object 7A is a PDMS substrate and the base material 3A is a microchip made of a facing substrate, the PDMS has high hydrophobicity in an air atmosphere. Even if it is once hydrophilized, if it is left in the air for a long period of time, it will become hydrophobic again. Therefore, immediately before the hydrophilicity is required, the PDMS substrate (processing object 7A) is irradiated with excimer UV light from the facing substrate (base material 3A) side, so that the channel inside the PDMS substrate remains in the form of a microchip. By subjecting the (concave portion 15) to surface modification / cleaning treatment as appropriate, the channel (concave portion 15) can be made hydrophilic again and used. If only a specific part of the channel is to be selectively made hydrophilic, the other part of the channel may be shielded with a mask and irradiated with excimer UV light. This is because even if oxygen (air) is present in the channel, oxygen and active oxidative decomposition products necessary for surface modification and cleaning are not generated unless the excimer UV light is irradiated. In this case, the facing substrate is preferably made of quartz glass.

  Further, when the processing object 7 is a PDMS substrate, a portion that selectively adheres permanently between the PDMS substrate and the silica glass plate can be created by irradiating excimer UV light through a patterned mask. For example, when excimer UV light is irradiated to a PDMS substrate through a mask with a pattern, the treated surface of the PDMS substrate irradiated with the excimer UV light is permanently bonded to the glass plate, but is not shielded by the pattern and irradiated with the excimer UV light. The treated surface can be configured not to be permanently bonded to the glass plate.

  A light source that emits far ultraviolet light can be used in combination with a dielectric barrier discharge lamp that emits excimer UV light. When excimer UV light having a wavelength of 172 nm emitted from a dielectric barrier discharge lamp is used to generate ozone and an active oxidative decomposition product, and the ozone and the active oxidative decomposition product are irradiated with light having a wavelength of 254 nm, which is far ultraviolet light, These activities are further enhanced, and the surface modification / cleaning effect is dramatically improved. The far ultraviolet light source is a high pressure mercury lamp, a low pressure mercury lamp, a krypton fluorine excimer lamp, a krypton fluorine excimer laser, or the like.

A mask having a cross-sectional structure as shown in FIG. 1 was produced. The substrate 3 was formed of synthetic quartz (grade ED-H, manufactured by Tosoh Quartz Co., Ltd.) having a plate thickness of 1 mm and a transmittance of 90% or more for excimer UV light having a wavelength of 172 nm. A thin plate made of stainless steel (thickness: 50 μm) was cut into a circle having a diameter of 5 mm, and this was adhered to one surface of the substrate 3 to form the light shielding pattern 5. A PDMS substrate having a plate thickness of 2 mm was used as the processing object. As the excimer UV light source, a dielectric barrier discharge lamp commercially available from USHIO INC. Located in Chiyoda-ku, Tokyo was used. A mask made of a synthetic quartz substrate with a pattern was bonded to one surface of the PDMS substrate, and excimer UV light was irradiated from the upper surface of the synthetic quartz substrate with a dielectric barrier discharge lamp under atmospheric pressure and air atmosphere. The wettability of the treated surface and the non-treated surface was measured by changing the irradiation intensity immediately below the dielectric barrier discharge lamp to 10 mW / cm ² and changing the irradiation time to 1, 2, and 3 minutes. Evaluation of wettability was performed by measuring the contact angle of a commonly used water droplet. Before treatment of the treatment surface irradiated with excimer UV light, it showed a high hydrophobicity of about 100 degrees, but it was about 50 degrees for an irradiation time of 1 minute, about 25 degrees for an irradiation time of 2 minutes, and almost at an irradiation time of 3 minutes. Although it was completely hydrophilic at 0 degrees, the contact angle of the non-treated surface of the portion shielded from light by the pattern 5 of the stainless steel thin plate remained the same 100 degrees as before the treatment.

As a base material, the base material of the same material as what was used in Example 1 was used except not having a light-shielding pattern. As a processing target, a PDMS substrate having a plate thickness of 2 mm, a channel having a depth of 50 μm, a width of 200 μm, and a length of 3 mm on one surface was used. The base material was bonded to the channel forming surface of the PDMS substrate. Excimer UV light was irradiated from the upper surface of the base material with a dielectric barrier discharge lamp under atmospheric pressure and air atmosphere. The irradiation intensity immediately below the dielectric barrier discharge lamp was 10 mW / cm ² and the irradiation time was 3 minutes. The wettability between the channel part and other parts was measured. The contact angle of the channel portion was almost 0 degrees, but the contact angle of the other portions was 50 degrees. Thereby, according to the present invention, it was confirmed that only the channel portion of the PDMS substrate can be selectively hydrophilized.

  The mask was peeled off from the PDMS substrate surface-modified and cleaned in Example 1, and a quartz glass plate was bonded. As a result, it was confirmed that the treated surface of the PDMS substrate irradiated with the excimer UV light was permanently bonded to the glass plate, but the non-treated surface not shielded with the pattern and irradiated with the excimer UV light was not permanently bonded to the glass plate. It was.

  The selective surface modification / cleaning method of the present invention can be used for a wide range of applications using PDMS microchips such as gene analysis, clinical diagnosis, drug screening and environmental monitoring. In addition, it can be used in all fields that require precise selective surface modification and cleaning, such as the semiconductor manufacturing field.

It is a schematic sectional drawing of an example of the mask used with the surface modification and washing | cleaning method of this invention. It is explanatory drawing which shows an example of the state which implements the surface modification and cleaning method of this invention using the mask shown by FIG. It is explanatory drawing which shows another embodiment of the surface modification and washing | cleaning method of this invention. It is a general | schematic perspective view of an example of the target object processed by the surface modification and washing | cleaning method of a prior art. It is explanatory drawing which shows the state which processes the process target object shown by FIG. 4 by the surface modification and washing | cleaning method of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mask 3, 3A Base material 5 Resist pattern 7, 7A Process target 9 Process surface 11 Air layer 13 Non-process surface 15 Channel (recessed part)

Claims (3)

A selective surface modification and cleaning method,
(1) preparing a mask made of a substrate having transparency to excimer UV light having a center wavelength of 172 nm;
(2) preparing a processing object in which a channel-shaped recess having a predetermined shape and a depth and width is formed on one surface;
(3) placing the mask on the recess forming surface of the processing object;
(4) A selective surface modification / cleaning method comprising the step of hydrophilizing the inner surface of the recess of the object to be processed by irradiating excimer UV light from the upper surface of the mask The mask substrate is quartz glass, sapphire, calcium fluoride, magnesium fluoride, barium fluoride, according to claim 1, characterized in that it is formed from a material selected from the group consisting of lithium fluoride Method. The method of claim 1 , wherein the object to be treated is a microchip formed from polydimethylsiloxane (PDMS).

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