JPH07288109A - Xenon radiation device and object surface quality improving device using it - Google Patents

Abstract

PURPOSE:To obtain an uniform surface light source, closely irradiate a sample, and enable effective sample washing and surface improvement to be carried out easily due to large-sized surface irradiation, by specifying the shape and structure of members of a radiation device and emitting ultraviolet-rays with its main components being Xenon gas. CONSTITUTION:Plural barrier electric discharge lamps 31 in each of which is used a cylindrical container which can easily be fabricated are provided in a cabinet 32 having a flat excimer light outlet window member 34 and are arranged so that the lamps 31 are enveloped by means of an ultraviolet-ray reflection mirror 33, and the cabinet inside is replaced with nitrogen gas via an inlet 37 and an outlet 38. By making such constitution, the surface irradiation in an area of approximately 40X80mm is obtained at an average radiation intensity of 8mw/cm<2> on the surface of a radiation window 32. By making the planar sample close to the radiation window of this device within 3mm, surface improvement and UV/O3 washing can be effectively performed.

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 Laid-Open Patent Publication No. 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. Revised new edition issued by the Institute of Electrical Engineers (discharge) Handbook)
This paper describes a radiator, that is, a dielectric barrier discharge lamp, which forms excimer molecules by taking out the resale 7th printing issue, June 1993, page 263) and takes out 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, refer to Chapter 9 (pages 301 to 313, (hereinafter referred to as document 1)) of the book “New Technology of Ozone Utilization” (published by Sanyuu Shobo, November 20, 1986). , Device, 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 3 mm in the atmosphere. Because the absorption coefficient of oxygen is as large as 15 cm ^-1 and the strength becomes 1 / 2-1 / 3 at 3 mm,
3 mm, and if possible, if the distance between the window member and the sample surface is within 1 mm, the effect is remarkable.

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 Physics B, Vol 46, pp.299-303
(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]

DISCLOSURE OF THE INVENTION The present invention provides a flat irradiation apparatus having a large irradiance of vacuum ultraviolet light having a central wavelength of radiation near 172 nm, a good illuminance distribution, and a large irradiation area. The object of the present invention is to provide a method for surface treatment of an object used.

[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 casing also serves as a reflecting mirror, or whether the reflecting mirror is arranged inside the casing, or whether a part of the discharge container has a reflection characteristic, The object of the present invention can be further achieved by setting the protrusion size in the front of the window within 2 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 3 mm, Cleaning can be performed by utilizing the synergistic action of ultraviolet excimer light and ozone.

[0011]

[Function] For UV / O ₃ cleaning and surface modification, it is effective to irradiate the sample surface with ultraviolet light in the short wavelength range in an oxygen atmosphere.
However, with light of wavelength 172 nm, it is absorbed by oxygen,
Most of the light does not reach even when the sample surface is irradiated with a cylindrical lamp, which attenuates to 1/2 to 1/3 at a distance of about 3 mm. With a cylindrical lamp, even if the lamp is held within 3 mm of the sample, 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 we want to make the thickness of the dielectric as thin as possible, but in the case of a flat structure,
If the container is made thin, the larger the container is, the smaller the strength of the dielectric is when it is evacuated, 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 a combination of a plurality of straight tube type lamps or a U-shaped tube and a mirror. Wavelength 1 for oxygen in the air
85 nm is absorbed, but the distance that decreases to 1 / 2-1 / 3 is 60 mm or more, and it takes 15 to attenuate to 1/10.
It is 0 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 emitting a wavelength shorter than 172 nm causes the same problem as a dielectric barrier discharge lamp containing xenon gas as a main component.
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 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 set to an atmosphere containing oxygen, and the sample is placed close to the irradiation device window member surface (within 3 mm, preferably 1 mm or less) to obtain a uniform illuminance distribution on the sample surface. Surface irradiation 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 a large area on a sample with a lamp having a very high absorption coefficient of oxygen, and such problems do not exist in conventional arc discharge lamps. It is only a problem of the dielectric barrier discharge lamp. Japanese Unexamined Patent Publication No. 5-174793 proposes a method of putting a dielectric barrier discharge lamp in a container, flowing a cooling body such as water in an atmosphere, cooling the lamp, and taking out light from an irradiation window. This time, the atmosphere gas is not intended for cooling, it is limited to a lamp (vacuum ultraviolet short wavelength center emission wavelength of about 172 nm) that uses xenon and its mixed gas as a discharge gas, and a surface irradiation device can be manufactured. It is a completely different invention in terms of purpose. When irradiating the sample, within 3 mm,
It is most desirable to irradiate within 1 mm, so that in order to carry the sample horizontally and by the transport mechanism, the projection of the window frame of the enclosure should be within 2 mm, preferably at all, protruding from the excimer light extraction window member of the irradiation device. It is better not to. In this case, the object to be treated can be cleaned and modified while heating. 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 3 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 having a total length of about 150 mm, and an inner tube 2 having an outer diameter of about 14 mm and a wall thickness of 1 mm and an outer tube 3 having 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 the formed structure. The outer tube 3 also serves as a dielectric barrier for dielectric barrier discharge and a light extraction window member,
A mesh electrode 4 that allows light to pass therethrough is provided.
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. A cooling fluid, for example, cooling nitrogen gas, can flow into the inner space 9 of the lamp 1 as required. 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 inside of the enclosure with nitrogen and combining a lamp and a mirror, the area of the illuminance distribution + -10% with an irradiation intensity of 8 mW / cm ^{2 on} average at the surface of the irradiation window 32 has an area of about 40 × 80 mm. A surface irradiation device 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 a dielectric barrier discharge lamp 31 and a 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 1 is water-cooled. The inside of the housing is replaced with nitrogen. By combining the lamp and the mirror, the area of the illuminance distribution + -10% with an average intensity of 30 mW / cm ² is about 250 mm × 250 m on the surface of the irradiation window 34.
A surface irradiation device having an area of m 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 1 mm from the irradiation window 34, and the surface thereof is irradiated. 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. Although the window frame 35 is projected from the outer surface of the window by 2 mm or more, the flat sample 4
0 moves horizontally to the lower surface of the irradiation device together with the processing table 43, and is then transferred to the outer surface of the window within 3 mm by the vertical transfer jig 42 at that position. 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 when the irradiation time was 12 seconds, the contact angle was 3 degrees or less over the entire area of the quartz glass plate. 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.
So that the distance from the outside surface of the window is close to 1 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 250 × 25
It is 0 mm × 0.3 mm. The processing system is the same as in the third embodiment. Before irradiation, the sample having a contact angle with water of 80 degrees changed to a contact angle of 40 over the entire area in an irradiation time of 2 seconds. When the surface is observed by ESCA, O is O / C and 0.
It changed from 35 to 0.65. It can be understood that the surface was modified by introducing hydrophilic groups such as COOH and OH groups into 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 view of an embodiment of the present invention, in which (a) shows the device in the longitudinal direction of the lamp from the side, 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 has a size of 2 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 3 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. .