JP5223741B2 - Excimer lamp - Google Patents

Description

  The present invention relates to an excimer lamp that irradiates vacuum ultraviolet light.

An excimer lamp having the structure shown in FIG. 4 is known.
This excimer lamp has a so-called double tube structure in which a discharge vessel includes an outer tube and an inner tube, which are arranged substantially coaxially and joined at an end, and a cylindrical discharge space is formed. Have.

One electrode is disposed on the outer peripheral surface side (outside of the discharge space) of the outer tube, and the other electrode is disposed on the inner peripheral surface side (outside of the discharge space) of the inner tube, and an excimer discharge gas is disposed inside the discharge vessel. For example, xenon gas is sealed with 10 to 80 kPa.
By applying a high-frequency high voltage to the one and the other electrodes, a discharge is formed through the quartz glass wall constituting the discharge vessel (tube).
The reason why the discharge space is formed in a cylindrical shape as described above is to secure a stable illuminance distribution by making the discharge gap as constant as possible.

  Such excimer lamps are used for surface treatments such as substrate cleaning and modification. Recently, while increasing the throughput of workpieces, reducing the frequency of lamp replacement and increasing the operating rate, the cost of the entire line is increased. It is hoped that

However, in the excimer lamp, the quartz glass constituting the discharge vessel is deteriorated by ultraviolet light, and the transmittance of light having a main wavelength of 172 nm is lowered.
If the deterioration due to ultraviolet light further progresses, a crack occurs in the discharge vessel, the lamp is turned off, the crack spreads throughout the discharge vessel, and a piece of the vessel falls.

  Such a problem caused by ultraviolet distortion has been studied in the past. For example, in Patent Document 1, since ultraviolet distortion is particularly likely to enter the cooling portion of the discharge vessel, it is cooled by the cooling means in the discharge vessel. An excimer lamp is disclosed in which an ultraviolet reflecting film and / or an ultraviolet absorbing film is formed on the discharge space side surface corresponding to the region.

  As described in Patent Document 1, ultraviolet light in the range of 140 to 190 nm is emitted in the discharge space of the excimer lamp in addition to the wavelength of 172 nm, and the surface on the discharge space side of the quartz glass constituting the discharge vessel is Such ultraviolet light is constantly radiated. The damage that ultraviolet light gives to quartz glass is greater as the wavelength is shorter, considering the shape of the discharge vessel, the state of use, thermal strain remaining on the glass, etc., and protecting particularly fragile parts from such ultraviolet light, The discharge vessel can be prevented from being damaged, and the life of the lamp can be extended.

JP 2002-093377 A

However, in the technique described in Patent Document 1, even if the cooling part is protected and the life can be extended by delaying the damage in this part, it is not protected in other parts. The transmittance of ultraviolet light at 172 nm deteriorates, causing a decrease in illuminance.
Accordingly, an object of the present invention is to provide an excimer lamp that can realize a long life by suppressing deterioration of a discharge vessel, and that has high efficiency of extracting light and low decrease in illuminance.

In order to realize the excimer lamp, the present invention provides:
A discharge vessel made of quartz glass , comprising an outer tube and an inner tube arranged on the same axis, filled with a discharge gas forming excimer molecules, and forming a cylindrical discharge space;
In an excimer lamp comprising one electrode disposed on the outer peripheral surface of the outer tube and the other electrode disposed on the inner peripheral surface of the inner tube,
The one electrode covers a half or more on the outer peripheral surface of the outer tube in a cross section perpendicular to the tube axis of the excimer lamp, and includes a non-constant region forming part,
A protective film having absorption or reflection characteristics with respect to ultraviolet light having a wavelength of 150 nm or less is formed on the inner peripheral surface of the outer tube so as to cover the formation region of the one electrode. To do.
In addition, a film having absorption or reflection characteristics with respect to ultraviolet light having a wavelength of 150 nm or less is formed on the outer peripheral surface of the inner tube so as to cover beyond the arrangement region of the other electrode.
The film may be at least one selected from the group consisting of silica, alumina, titanium oxide, and yttrium oxide.

According to the excimer lamp according to the present invention, the portion exposed to the discharge in the outer tube of the discharge vessel is formed with a protective film having absorption or reflection characteristics with respect to ultraviolet light having a wavelength of 150 nm or less. It is not necessary to irradiate ultraviolet light having a wavelength of 147 nm, it is possible to suppress the deterioration of the discharge vessel due to the generation of distortion in the ultraviolet ray, and to suppress the breakage of the discharge vessel over a long period of time. It becomes possible to make a long-life excimer lamp.
Furthermore, by providing the protective film also on the outer peripheral surface of the tube, which is the discharge space side surface of the inner tube, it is possible to suppress the occurrence of ultraviolet distortion in the inner tube and to achieve a longer life. .
Further, it is possible to reliably prevent ultraviolet light having a wavelength of 150 nm or less from entering the discharge vessel by using at least one selected from the group consisting of silica, alumina, titanium oxide and yttrium oxide as the protective film. it can.

It is sectional drawing which cut | disconnected the excimer lamp explaining embodiment of this invention in the orthogonal | vertical direction with respect to the tube axis. It is sectional drawing which cut | disconnected the excimer lamp explaining embodiment of this invention to the pipe-axis direction. It is principal part explanatory drawing which expands and shows the part enclosed with the circle | round | yen in FIG. It is sectional drawing which cut | disconnected the excimer lamp explaining other embodiment of this invention in the orthogonal | vertical direction with respect to the tube axis. It is sectional drawing which cut | disconnected the excimer lamp explaining a prior art in the orthogonal | vertical direction with respect to a tube axis.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory sectional view showing an outline of a configuration in an embodiment of an excimer lamp of the present invention.
The excimer lamp 10 is made of, for example, quartz glass, and has a cylindrical outer tube 12 and an outer diameter smaller than the inner diameter of the outer tube 12 disposed along the tube axis in the outer tube 12, for example, quartz. A discharge vessel 11 having a double tube structure having a cylindrical inner tube 13 made of glass and having an outer tube 12 and an inner tube 13 melt-bonded at both ends.

  The inner tube 13 constituting the discharge vessel 11 has, for example, a bent portion that is bent so that both end portions expand outward in the radial direction, and the bent portion of the inner tube 13 is connected to the outer tube 12. By joining, an end wall is formed by the bent portion 13 </ b> A, thereby forming an airtightly closed annular discharge space S between the inner peripheral surface of the outer tube 12 and the outer peripheral surface of the inner tube 13. Has been.

  The outer tube 12 constituting the discharge vessel 11 is fitted with a metal plate having a substantially C-shaped cross section formed by pressing an aluminum plate or the like in close contact with the outer peripheral surface thereof, whereby one electrode (hereinafter referred to as “outer side”). Electrode)) 14 is provided. The inner tube 13 is in close contact with the inner peripheral surface thereof, and is the other electrode made of, for example, aluminum, made of a pipe-like or substantially C-shaped (saddle-like) metal plate having a notch in part in the cross section. (Hereinafter referred to as “inner electrode”) 15 is provided. The outer electrode 14 and the inner electrode 15 are connected to a power supply device 19 made of, for example, a high frequency power source.

The discharge space S is filled with a discharge gas such as xenon gas that forms excimer molecules by excimer discharge generated between the outer electrode 14 and the inner electrode 15.
In FIG. 2, reference numeral 18 denotes the remainder of the exhaust pipe used when gas is sealed in the discharge vessel.

A protective film 20 having the following structure having absorption characteristics and / or reflection characteristics for light having a wavelength of 150 nm or less is formed in a predetermined region inside the discharge vessel.
The protective film is made of a dielectric and is preferably made of powder such as silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), yttrium oxide (Y ₂ O ₃ ), Such a dielectric powder is deposited on the inner peripheral surface of the outer tube. Such dielectric powders may be used singly or may be mixed and used in an appropriate combination. Of the above substances, silica particles protect the discharge vessel by the action of absorption characteristics with respect to light with a wavelength of 150 nm or less, and alumina particles mainly have absorption characteristics with respect to light with a wavelength of 150 nm or less, but slightly reflective characteristics. The discharge vessel is protected by both absorption and reflection characteristics.

In the case of using a mixture of silica particles and alumina particles, for example, the silica particles have a particle size of 0.4 μm to 1.5 μm, the center diameter: 0.7 μm, and the alumina particles have a particle size of 0.2 μm to 0.5 μm. The center diameter is 0.3 μm, and the alumina particle content is adjusted to 10% by mass.
The final film thickness is 1 μm or more, and can be appropriately selected within a range of 1 to 50 μm, for example. In addition, since the protective film can protect quartz glass if it is 1 μm or more, if it is formed in a portion that does not require transparency to ultraviolet light having a wavelength of 172 nm, the protective film is formed to be thick within the range that can be maintained. can do.

The region where the protective film 20 is formed is a portion corresponding to a portion where the electrodes 14 and 15 are disposed in the discharge vessel 11, and particularly a portion where ultraviolet distortion is likely to occur. In an excimer lamp having an outer tube 12 and an inner tube 13 and having a light transmission window formed in a part of the outer tube 12 as in the excimer lamp according to the present invention, an outer electrode 14 is disposed on the outer tube 12. And the entire circumference of the inner tube 13. However, the inner surface of the inner tube 13 is not essential because the temperature during operation is high and ultraviolet distortion is less likely to occur than the outer tube 12. Therefore, it is essential at the portion corresponding to the electrode on the inner surface (discharge space side surface) of the outer tube.
Since the portion where the outer electrode 14 is not disposed, ultraviolet light having a wavelength of 147nm xenon resonance line, which can not be reached by being absorbed by the unexcited Xe atom, plasma also can not be reached, ultraviolet Strain formation is slow. Therefore, the transmittance at a wavelength of 172 nm can be maintained at a high level without forming the protective film 20.

Such a film is formed at the stage of manufacturing the lamp.
Here, the manufacturing method will be described.
1. First, the powder for film | membrane structure is prepared. A mixed powder prepared from silica powder and alumina powder having a predetermined average particle diameter and center particle diameter is combined with a binder liquid mixed with nitrocellulose and butyl acetate liquid at a weight ratio of 1: 4, and sufficiently stirred to obtain alumina. A slurry in which powder-silica powder is dispersed is prepared.
2. This slurry is applied to the inner surface of a glass tube for arc tube construction.
Although the application method is not particularly limited, a flow-down method, a suction method, a dipping method, or the like can be employed. In the case of using a method other than the flow-down method, it is preferable to mask a portion where a film is unnecessary.
3. After drying the slurry, the slurry is fired using an electric furnace so that the protective film is stably fixed.
The firing temperature is 1100 ° C. and is maintained for about 1 hour. In this firing step, the particles are bonded together and fused to the glass tube, and the glass layer is strongly bonded to the substrate.

Such a protective layer needs to be formed at least on the portion where the discharge plasma is formed (outer tube inner peripheral surface), beyond the portion where the outer electrode (one electrode) is disposed and the side end portion of the electrode. It is a desirable mode that it is formed up to the non-electrode forming side.
With reference to the cross-sectional views of FIGS. 1 and 3, a preferred embodiment thereof will be specifically described. A point where an imaginary line d connecting the discharge space S side surface of the inner tube 13 and the end of the outer electrode 14 intersects the discharge space S side surface of the outer tube 12 is A, the end B of the protective film 20, and the inside of the discharge vessel 11. When the Xe enclosure pressure (room temperature) enclosed in P is kPa (kPa), it is desirable that the distance AB of AB on the cross-sectional view is not less than L obtained by the following (Equation 1).
(Formula 1) L = 542 / P ² [mm]
The sealed pressure of xenon gas in the excimer lamp is 10 to 80 kPa, and may be appropriately set in a range of 0.5 to 5.5 mm for practical use.

Light having a wavelength of 147 nm that causes ultraviolet distortion is absorbed by non-excited Xe atoms because of the Xe resonance line. Therefore, the intensity of 147 nm light depends on the number of Xe atoms in the lamp. When the temperature is constant, the number of Xe atoms can also be expressed by pressure. Therefore, when the pressure is high, the intensity of 147 nm is low, and when the pressure is low, the intensity of 147 nm is high. Therefore, the distance L over which the light having a wavelength of 147 nm can be reached can be determined by the Xe sealing pressure P.
The reason why 542 is multiplied by the square of the pressure in the above equation 1 is described in J. Org. C. MOLINO GARCIA, J. MoI. Quant. Spectrosc. Radiant. Transfer, Vol. 57, no. 4, the absorption coefficient K (m ⁻¹ ) of Xe atoms at 147 nm is
(Formula 2) K = 0.085 (10P) ²
Can be expressed as Assuming that the initial light intensity is I ₀ and the light intensity after being absorbed and attenuated is I, the attenuation of light is (Equation 3) I / I ₀ = exp (−KL)
Therefore, when formula 2 is substituted into formula 3 and rearranged, the distance L at which light attenuates to 1/100 can be represented by formula 1 above.

According to the excimer lamp according to the present invention having the protective film, since the electrode is not formed in the light transmission window portion (electrode non-forming portion), the structure is not exposed to plasma during the lamp operation. Since the light having a wavelength of 147 nm, which causes ultraviolet distortion, is an Xe resonance line, it cannot be absorbed and reached by non-excited Xe atoms. In the quartz glass of the electrode forming part of the outer tube, a film having absorption or reflection characteristics for ultraviolet light with a wavelength of 150 nm or less is formed. , It is not required to be directly exposed to ultraviolet light and plasma having a wavelength of 147 nm, the progress of the deterioration of the glass can be suppressed, and the time until breakage can be greatly increased. They kill as to become.

Still another embodiment will be described with reference to FIG. FIG. 4 is a view in which an excimer lamp is cut along a cross section perpendicular to the tube axis. In addition, in the same figure, the structure demonstrated previously in FIGS. 1-3 is shown with a same sign, and detailed description is abbreviate | omitted.
As shown in FIG. 4, the excimer lamp according to the present embodiment basically includes a configuration in which a protective film 20 is formed in a predetermined region on the inner peripheral surface of the outer tube 12, and the discharge space S of the inner tube 13. A protective film 21 having reflection characteristics or absorption characteristics with respect to light having a wavelength of 150 nm is formed on the outer peripheral surface of the tube (13) on the side surface. As described above, the protective film 21 is preferably made of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), yttrium oxide (Y ₂ O ₃ ), etc. Those in the state are mixed in a single or appropriate combination and deposited on the discharge space side surface of the tube to form a layer. The formation region of the protective film 21 is formed over substantially the entire circumference corresponding to the portion where the inner electrode 15 is disposed.
By forming the protective films 20 and 21 corresponding to all of the discharge forming regions in the discharge vessel 11 as in this embodiment, ultraviolet distortion is less likely to enter the discharge vessel 11 and the life of the excimer lamp is further extended. Will be able to.

  Although the present invention has been described above, it goes without saying that the replaceable configuration can be appropriately changed with respect to the configuration of the present invention. For example, the type of film is not limited to the above as long as it has absorption and / or reflection characteristics with respect to light of 150 nm.

Examples of the present invention will be described below.
Excimer lamps were manufactured according to the configuration shown in FIGS.
<Lamp 1>
Discharge vessel: material: quartz glass, total length: 1268 mm
Outer tube: outer diameter 40 mm, thickness 2 mm,
Inner tube; outer diameter 18mm, thickness 1mm
Outer electrode (cross-sectional semicircular shape): Aluminum, thickness 1 mm, length; 1205 mm
Inner electrode (C-shaped cross section): Aluminum, thickness 1 mm, length; 1205 mm
Protective film: The composition is as follows.
Silica particles: particle size 0.4 μm to 1.5 μm, center diameter: 0.7 μm
Alumina particles: 0.2 μm to 0.5 μm, center diameter: 0.3 μm
The content of alumina particles is 10% by mass, and the firing temperature is 1100 ° C.
Film thickness: 30 μm (average)
The film is deposited by mixing particles in a solvent to form a solution using a coating method called a flow-down method, and pouring the solution onto the inner surface of the discharge vessel. Then, it dried and baked. If the film thickness is 1 mm or more, it absorbs and reflects 150 nm light and can protect against 147 nm light. In this example, a 30 μm film was used. According to the film of this example, silica particles are the main component, so that the resonance line with a wavelength of 147 nm is absorbed and the discharge vessel can be protected.

  According to the following Table 1, lamp 1 to lamp 3 were manufactured by changing the film formation region and the Xe sealing pressure.

  Further, the basic structure of the lamp is the same as that of the above embodiment, and the lamps 4 to 6 according to the reference example, in which the protective film formation region is relatively small or has no protective film, were manufactured. Table 1 below collectively shows the Xe sealing pressures of these lamps 4 to 6 and the structure of the protective film.

The lamps 1 to 6 were turned on at the rated voltage and rated frequency of each lamp, and the time until breakage was compared. The results are shown in Table 1 below.
As is clear from this result, it has a protective film having absorption or reflection characteristics with respect to ultraviolet light having a wavelength of 150 nm or less so as to cover the outer electrode arrangement region covering more than half of the outer peripheral surface of the outer tube. Thus, a longer life can be achieved as compared with those having no film and those having no film beyond the electrode arrangement region. Further, the region where the film is formed (the length of AB) is formed in a wider range than the size calculated by L = 542 / P ^{2 in} relation to the xenon sealing pressure P in the lamp. The service life can be extended longer than the time.

11 Discharge vessel 12 Outer tube 13 Inner tube 13A Bent part 14 One electrode (outer electrode)
15 The other electrode (inner electrode)
18 Exhaust pipe remainder 19 Power supply device 20 Protective film S Discharge space

Claims (3)

A discharge vessel made of quartz glass , comprising an outer tube and an inner tube arranged on the same axis, and filled with xenon gas to form a cylindrical discharge space;
One electrode disposed on the outer peripheral surface of the outer tube;
In an excimer lamp comprising the other electrode disposed on the inner peripheral surface of the inner tube,
The one electrode covers a half or more on the outer peripheral surface of the outer tube in a cross section perpendicular to the tube axis of the excimer lamp, and includes a non-constant region forming part,
An excimer characterized in that a film having absorption or reflection characteristics with respect to ultraviolet light having a wavelength of 150 nm or less is formed on the inner peripheral surface of the outer tube so as to cover the arrangement region of the one electrode. lamp. The film having absorption or reflection characteristics with respect to ultraviolet light having a wavelength of 150 nm or less is formed on the outer peripheral surface of the inner tube so as to cover beyond the arrangement region of the other electrode. 1. An excimer lamp according to 1.   The excimer lamp according to claim 1, wherein the film is at least one selected from the group consisting of silica, alumina, titanium oxide, and yttrium oxide.

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