JPH08124540A - Xenon irradiation device and object surface modification device using the same - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a flat irradiation device having a large irradiation area with a large illuminance of vacuum ultraviolet light having a central wavelength of radiation near 172 nm, a good illuminance distribution, and a further irradiation device. An object surface treatment method using is provided. A xenon for forming an excimer by a dielectric barrier discharge is provided in a substantially cylindrical discharge container at least a part of which is formed of a window member 34 for extracting ultraviolet excimer light.
Alternatively, a dielectric barrier discharge lamp 31 filled with a discharge gas containing xenon as a main component is filled with helium, neon, krypton, in a casing covered with a window member 34 for extracting at least a flat ultraviolet excimer light. Argon,
It is arranged with at least one gas selected from xenon, hydrogen and nitrogen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved dielectric barrier discharge lamp used as an ultraviolet light source for photochemical reactions, and an object surface modification apparatus or modification method using the improved lamp.

[0002]

2. Description of the Related Art Techniques related to the present invention are, for example,
There is Japanese Patent Laid-Open Publication No. Hei 2-7353, in which a discharge vessel is filled with a discharge gas that forms excimer molecules, and a dielectric barrier discharge (also known as ozonizer discharge or silent discharge. Handbook)
This paper describes a radiator, that is, a dielectric barrier discharge lamp, which forms excimer molecules by taking out June 1993, Reprint 7th Edition, page 263, and extracts light emitted from the excimer molecules. On the other hand, in recent years, as a method of removing organic substances on the surface of the object to be treated, removal of unnecessary resist, precision dry cleaning, formation of an oxide layer on the metal surface, etc. O ₃ treatment was developed and put to practical use. UV /
Regarding the O ₃ treatment, for example, the principle is described in Chapter 9 (pages 301 to 313, (hereinafter referred to as document 1)) of the book “New Technology of Utilizing Ozone” (published by Sanyuu Shobo, November 20, 1986). , Equipment, cleaning effect, application, etc. are described in detail, but the light source used was a low pressure mercury lamp (radiation wavelength 254 nm, 185 nm). Igarashi et al., Proceedings of the 54th Annual Meeting of the Applied Physics Society of Japan 27
Wavelength 172 nm with xenon gas sealed with a-HE-2
It has been reported that by using a dielectric barrier discharge lamp having a central emission wavelength, the time required for surface modification of plastics is 1/10 or less that of a low pressure mercury lamp. In this way, the dielectric barrier discharge lamp has surface modification, UV / O
₃ It is known to be effective for cleaning.

By the way, when the lamp is used for UV / O ₃ treatment, it is necessary to use it in an oxygen atmosphere including the atmosphere. UV / O ₃ cleaning irradiates the surface of the sample with vacuum ultraviolet light, cuts off the binding of organic substances that are stains, is absorbed by oxygen, creates ozone and active oxygen, and oxidizes the organic substances with its strong oxidizing power. _An oxygen atmosphere is necessary because it is vaporized into NO ₂ and NO ₂ . Similarly, for surface modification of plastics and the like, it is necessary to irradiate the sample surface with ultraviolet light of short wavelength to break the bonds of organic substances, and to irradiate oxygen, ozone and active oxygen (for example, O ( ¹ D)) Made, oxidize organic matter, hydrophilic surface (OH group, COOH group, C
This is because it is necessary to introduce an O group). Wavelength 1
For application to the above purpose in a dielectric barrier discharge lamp having a central emission wavelength of 72 nm, the distance between the excimer light extraction window member and the sample surface must be within 7 mm in the atmosphere. Because the absorption coefficient of oxygen is as large as 15 cm ^-1 , the strength is 1/2 to 1/3 at 3 mm and ¹ at 7 mm.
Since it becomes / 8, the effect is remarkable if it is within 7 mm, and if possible between the window member and the sample surface within 3 mm.

When the shape of the dielectric barrier discharge lamp is cylindrical, the vacuum ultraviolet light reaching the sample even when the lamp is brought close to the sample is limited to only a part that is the closest to the sample. If the lamp is a flat type, it is advantageous to irradiate the sample with the sample while irradiating a large area at a time.

B.Elia is a flat type dielectric barrier discharge lamp.
The disk type of sson et al. is Applied PhysicsB, Vol. 46,299-303.
Page (1988). It consists of a stainless steel container that also serves as a ground electrode and an excimer light extraction window member made of disk-shaped synthetic quartz. However, there are two problems with this lamp. The first point is that electric field concentration is likely to occur at the edges, making stable discharge difficult. Second
The point is that the voltage of the lamp requires a high voltage of several kv to several tens of kv. In order to keep the voltage low, we want to make the thickness of the dielectric as thin as possible, but in the case of a planar structure, making it thinner increases the stress due to the pressure difference inside and outside the lamp,
This is because the strength of the dielectric is insufficient and destruction occurs, making it difficult to manufacture a large-sized lamp.

[0006] Japanese Unexamined Patent Publication No. 4-264349 discloses a plurality of structures in which electrodes are provided on the inner surface of a cylindrical dielectric in a rectangular parallelepiped container filled with a discharge gas and having a sealed UV transmission window. An irradiation device is described, which is arranged to generate a dielectric barrier discharge between electrodes and irradiates it to the outside.
Although the thickness of the irradiation window can be made thick, it is necessary to seal the inside of the container, and it is also necessary to introduce a high voltage part, which complicates the apparatus. On the other hand, a cylindrical lamp such as a double cylindrical lamp is relatively easy to manufacture and its length can be easily changed.
When it is irradiated in the atmosphere, it becomes a linear light source even if it comes close to the sample, and it cannot be used for the above purposes.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flat irradiation apparatus which has a large illuminance of vacuum ultraviolet light having a central wavelength of radiation near 172 nm, a good illuminance distribution, and a large irradiation area. An object of the present invention is to provide an object surface treatment method using an irradiation device.

[0008]

An object of the present invention is to provide a substantially cylindrical discharge vessel, at least a part of which is a window member for extracting ultraviolet excimer light, with a xenon for forming an excimer by dielectric barrier discharge. Alternatively, a dielectric barrier discharge lamp filled with a discharge gas containing xenon as a main component, at least a part of which is covered with a window member for extracting flat ultraviolet excimer light, in a casing covered with helium, neon, krypton, argon, It can be achieved by arranging with at least one gas selected from xenon, hydrogen and nitrogen.

Further, whether the inner surface of the housing also serves as a reflecting mirror, or the reflecting mirror is arranged inside the housing, or whether a part of the discharge vessel has a reflecting characteristic, the front of the housing The object of the present invention can be further achieved by setting the protrusion size of the above to within 5 mm from the window member.

A xenon irradiation device according to claim 1,
By constructing an object surface reforming apparatus including a processing table arranged in front of this apparatus and a driving means for bringing this processing table close to the window member of the housing of the apparatus within a distance of 7 mm, Cleaning can be performed by utilizing the synergistic action of ultraviolet excimer light and ozone.

[0011]

For UV / O ₃ cleaning and surface modification, it is effective to irradiate the sample surface with short wavelength ultraviolet light in an oxygen atmosphere.
However, with light of wavelength 172 nm, it is absorbed by oxygen,
Attenuation from 1/2 to 1/3 at a distance of about 3 mm is 1
It is 7 mm that attenuates to / 8. Even if the sample surface is irradiated with a cylindrical lamp, only a small part of the linear light emitted from the lamp can reach the sample, which is equivalent to a linear light source. In order to perform surface modification and cleaning of silicon wafers and liquid crystal display glass in the atmosphere with ultraviolet light having a wavelength of 172 nm, it is necessary to have a flat irradiation device that can efficiently allow the light emitted from the lamp to reach the sample. Is. The flat irradiation device can irradiate a certain area at a time, and the cleaning speed can be improved. However, when trying to manufacture a flat lamp, the voltage is designed to be set low, so it is desirable to make the thickness of the dielectric as thin as possible. However, in the case of a flat structure, the thinner the dielectric, the larger the container at the time of evacuation. However, the strength of the lamp is insufficient, and it is difficult to manufacture a large lamp.

The above problem is, of course, a problem peculiar to xenon gas or a dielectric barrier discharge lamp containing it as a main component, which is not found in conventional arc discharge lamps. For example, using UV light of wavelength 185 nm and wavelength 254 nm, UV /
Even in the case of surface irradiation in a low-pressure ultraviolet lamp for cleaning with O _3, it can be achieved by combining a plurality of straight tube type lamps or U-shaped tubes and mirrors. Wavelength 1 for oxygen in the air
85nm is absorbed, but the distance that decreases to 1 / 2-1 / 3 is more than 60mm, and it is 100 to attenuate to 1/8.
mm or more. During processing, the lamp can be easily brought closer to the sample surface than the above distance, so that the lamp and the sample can be processed in the same space containing oxygen, and there is no need to form a flat lamp. Of course, a lamp that emits a wavelength shorter than 172 nm causes the same problem as a dielectric barrier discharge lamp whose main component is xenon gas.
There is no high-power lamp that emits ultraviolet light having a wavelength shorter than 172 nm that can be used for O ₃ cleaning, and this is exactly a problem peculiar to xenon gas or a dielectric barrier discharge lamp containing it as a main component.

We have investigated a flat irradiation device which is easy to manufacture, has a large irradiation area, and has high illuminance. As a result of earnest study, the following device was invented. The lamp does not use a flat lamp which is difficult to manufacture, but uses a cylindrical lamp which is relatively easy to manufacture. The ultraviolet light having a wavelength of 172 nm is not absorbed by nitrogen, helium, argon, neon, krypton, and xenon gas, and the ultraviolet light is emitted with a certain solid angle, and therefore decreases according to the distance from the lamp. If this property, the reflectivity and shape of the reflection mirror, the number of lamps, the interval, and the distance to the excimer light extraction window member are taken into consideration, a uniform surface light source can be created on the surface of the excimer light extraction window member of the irradiation device. I understood. Further, the outside of the excimer light extraction window member of the irradiation device is made an atmosphere containing oxygen, and the sample is brought close to the irradiation device window member surface (within 7 mm,
By arranging 3 mm or less), surface irradiation with a uniform illuminance distribution on the sample surface can be achieved. UV / O ₃
Uniformity of the illuminance distribution needs to be about + -10% for cleaning and surface modification of plastics. With the above method, an area having the above uniformity can be obtained. In that case, it is desirable that at least the area of the above region is equal to or more than the outer diameter of the lamp × the light emission length. High-speed surface modification and cleaning can be performed in the above area.

Even in the case of a low-pressure mercury lamp, glass may be arranged between the sample and the lamp, but this is fundamentally different from the present invention in order to prevent dust from the lamp. The purpose of this time is to irradiate the sample in a large area with a lamp that emits light with a wavelength that has a very high absorption coefficient of oxygen, and there is no such problem in the conventional arc discharge lamp. Or, it is a problem only for dielectric barrier discharge lamps containing it as a main component. Japanese Patent Laid-Open Publication No. 5-174793 proposes a method of putting a dielectric barrier discharge lamp in a container, flowing a cooling body such as water as an atmosphere, cooling the lamp, and taking out light from an irradiation window. This time, the atmosphere gas is not intended for cooling, and a lamp using xenon and its mixed gas as the discharge gas (vacuum ultraviolet short wavelength center emission wavelength about 172 nm)
It is a completely different invention in that it is limited and that the purpose is to manufacture a surface irradiation device. When irradiating the sample, the irradiation is performed within 7 mm, most preferably within 3 mm. Therefore, in order for the sample to be transported horizontally by the transport mechanism, the window frame of the enclosure is projected from the excimer light extraction window member of the irradiation device. Within 5 mm, preferably no protrusion at all. In this case, wash the object to be processed while heating it,
It can also be modified. Alternatively, the area of the object to be processed is smaller than the area of the excimer light extraction window member of the irradiation device, the sample is conveyed horizontally to the window, is raised vertically, and irradiation is performed within 7 mm from the window. It has a remarkable effect on the quality.

[0015]

EXAMPLE FIG. 1 shows a xenon irradiation apparatus having a built-in dielectric barrier discharge lamp according to the first example of the present invention.
FIG. 2 shows a schematic view of the lamp. In FIG.
The discharge vessel 1 is made of synthetic quartz with a total length of about 150 mm, and an inner tube 2 with an outer diameter of about 14 mm and a wall thickness of 1 mm and an outer tube 3 with an inner diameter of about 24 mm and a wall thickness of 1 mm are coaxially arranged to form a hollow cylindrical discharge space 7. It is a structure that has formed. The outer tube 3 also serves as a dielectric barrier for dielectric barrier discharge and a light extraction window member, and is provided with a mesh electrode 4 that allows light to pass therethrough. On the outer surface of the inner tube 2 is provided an aluminum thin film electrode 5 which also serves as a light reflector and an electrode for dielectric barrier discharge. The discharge space 7 of the discharge container was filled with 250 torr of xenon gas as a discharge gas. A getter 6 is provided in the getter chamber 8. Inner space 9 of the discharge vessel 1
A cooling fluid, such as cooling nitrogen gas, can be flowed into the chamber as needed. Here, the dielectric barrier discharge lamp was turned on by the power supply 10 at an input of 20 watts. As a result, the ultraviolet light having the maximum emission value at the wavelength of 172 nm was efficiently emitted.

In FIG. 1, the above-mentioned dielectric barrier discharge lamp 31 is mounted in an enclosure 32 having a synthetic quartz flat irradiation window, that is, an excimer light extraction window member 34. Reference numeral 35 is a pressing flange or window frame of the synthetic quartz flat irradiation window 34. The thickness t of the flange or the window frame is the protrusion dimension in which the casing protrudes from the outer surface of the window. Reference numeral 33 is an ultraviolet light reflection mirror arranged so as to surround the lamp 31. Reference numeral 36 is a step-up transformer. 37 is an inlet of nitrogen gas for replacing the air in the casing, and 38 is its outlet. By replacing the nitrogen in the enclosure and combining a lamp and a mirror, the area of the illuminance distribution + -10% is about 40 mm x 80 mm at the irradiation intensity of 8 mW / cm ^{2 on} average on the surface of the irradiation window 32.
A surface irradiating device having a width of about 100 mm was obtained.

FIG. 3 shows a xenon irradiation apparatus having a built-in dielectric barrier discharge lamp according to the second embodiment of the present invention. Four sets of the dielectric barrier discharge lamp 31 and the reflection mirror 33 having a total length of 330 mm are mounted in an enclosure 32 having a synthetic quartz flat irradiation window 34 having an area of 300 mm × 300 mm. The inner space 9 of the lamp 31 is water-cooled. The inside of the housing is replaced with nitrogen.
By combining a lamp and a mirror, the irradiation window 34
A surface irradiation device having an area of about 250 mm × 250 mm in the area of illuminance distribution + -10% with an average intensity of 15 mW / cm ² was obtained.

FIG. 4 shows a xenon irradiation apparatus having a built-in dielectric barrier discharge lamp according to the third embodiment of the present invention. The lamp 31, the mirror 33, etc. are the same as in the second embodiment, but the excimer light extraction window member 34 and the window frame 35 are slightly different. That is, on the outside of the irradiation device,
The window member 34 and the window frame are tapered and assembled so as to form the same plane. In this case, the protrusion size is zero. The flange or the window frame may be designed as one body with the housing or as a separate body. The flat sample 40 is transported by the transport roller 41 with a gap of 5 mm from the irradiation window 34, and the surface thereof is illuminated. Since the irradiation device and the sample can be brought close to each other, it is possible to provide an irradiation system that is very effective in surface modification and UV / O ₃ cleaning.

A xenon irradiation apparatus incorporating a dielectric barrier discharge lamp according to a fourth embodiment of the present invention is shown in FIG. The irradiation device is the same as in the second embodiment. The window frame 35 protrudes from the outer surface of the window by 10 mm or more, but the flat sample 40 moves horizontally to the lower surface of the irradiation device together with the processing table 43, and then within 3 mm to the outer surface of the window by the vertical conveyance jig 42. Be transported to. This makes it possible to provide an irradiation system that is extremely effective in surface modification and UV / O ₃ cleaning, because the height accuracy during horizontal conveyance is not so much required and the irradiation device can be brought closer to it during irradiation.

The fifth embodiment of the present invention is U of quartz glass plate.
V / O ₃ cleaning. The size of the glass plate is 250 mm x 2
It is 50 mm × 1 mm. The irradiation device used was the device of the third embodiment. The glass plate was transferred to the lower surface of the irradiation device by a transfer jig and irradiated at a distance of 1 mm from the outer surface of the window. The surface of the glass plate was ultrasonically cleaned in isopropyl alcohol (hereinafter, IPA) for 5 minutes in advance, and a sample having a contact angle with water of 25 degrees was used. It was confirmed that the contact angle was 3 degrees or less in the entire area of the quartz glass plate after the irradiation time of 30 seconds. The same sample was used for a 450 W low-pressure mercury lamp (wavelength 25
Strength of 4nm 70mW / cm ^2, when the intensity of the wavelength 185nm is irradiated at a distance 5cm at 14mW / cm ^2), about 1
It can be seen that the invention is very good, varying up to 3 degrees in 80 seconds.

The sixth embodiment of the present invention is UV / O ₃ cleaning of a silicon wafer. The irradiation device, the processing table and the driving system are the same as those in the fourth embodiment. The silicon wafer is fixed to the processing table 43 with a vacuum chuck, and the vertical transfer jig 42 is used.
To bring the outer surface of the window closer to 3 mm. A wafer having a contact angle of water of 20 degrees before irradiation had an area of 5 degrees or less in 15 seconds after irradiation.

The seventh embodiment of the present invention is the surface modification of polyethyl terephthalate. Sample size is 250mm x
It is 250 mm × 0.3 mm. The processing system is the same as in the third embodiment. Before irradiation, the contact angle with water is 80
The contact angle of the sample of 10 degrees changed to 40 degrees in the entire area in the irradiation time of 10 seconds. When the surface is observed by ESCA, O is O /
C changed from 0.35 to 0.65. COOH on the surface
It can be seen that hydrophilic groups such as groups and OH groups were introduced to modify the surface.

[0023]

As can be understood from the above description of the embodiments, the present invention is difficult to realize in an irradiation apparatus using a dielectric barrier discharge lamp having a discharge gas containing xenon or a main component thereof. It is possible to provide a large surface irradiation device, which was previously described, relatively easily, and to provide effective cleaning and surface modification treatment technology.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, in which (a) shows the device in a direction orthogonal to the longitudinal direction of the lamp, and (b) shows it in the longitudinal direction of the lamp.

FIG. 2 is an explanatory view of an example of a double cylinder type dielectric barrier discharge lamp used in the present invention.

FIG. 3 is an explanatory diagram of another embodiment of the present invention.

FIG. 4 is an explanatory diagram of another embodiment of the present invention.

FIG. 5 is an explanatory diagram of another embodiment of the present invention.

[Explanation of symbols]

 1 Discharge container 2 Inner tube 3 Outer tube 4 Mesh electrode 6 Getter 7 Discharge space 8 Getter chamber 31 Dielectric barrier discharge lamp 32 Enclosure 33 Mirror 34 Window member 35 Window frame or flange 37 Nitrogen gas inlet 38 Nitrogen gas outlet 40 Sample 41 Transport roller 42 Vertical transport jig

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nozomi Hishinuma 1194 Sado, Bessho Town, Himeji City, Hyogo Prefecture Ushio Electric Co., Ltd.

Claims (5)

[Claims] 1. A xenon forming excimer by dielectric barrier discharge in a substantially cylindrical discharge vessel at least a part of which comprises a window member for extracting ultraviolet excimer light,
Alternatively, a dielectric barrier discharge lamp filled with a discharge gas containing xenon as a main component is filled with helium, neon, krypton, argon, in a casing covered with a window member for extracting at least a flat ultraviolet excimer light. A xenon irradiation apparatus, which is arranged with at least one gas selected from xenon, hydrogen, and nitrogen. 2. The inner surface of the housing also serves as a reflecting mirror, or the reflecting mirror is arranged inside the housing, or
The xenon irradiation device according to claim 1, wherein a part of the discharge vessel has a reflection characteristic. 3. The front projection of the housing is 5 mm from the window member.
It is within mm, The xenon irradiation apparatus of Claim 1 characterized by the above-mentioned. 4. The xenon irradiation apparatus according to claim 1, a processing table arranged in front of the apparatus, and driving means for bringing the processing table close to a window member of an enclosure of the apparatus within a distance of 7 mm. An object surface modification device comprising: 5. A method for cleaning an object surface, which comprises using the apparatus for modifying an object surface according to claim 4 to clean an object surface by utilizing a cooperative action of ultraviolet excimer light and ozone. .