CN101599413B - Excimer lamp - Google Patents

Abstract

The invention provides an excimer lamp having an ultraviolet reflection layer, which can inhibit the degree of illumination decrease even after long-term lighting to efficiently emit vacuum ultraviolet light. An excimer lamp (10) with an ultraviolet reflection layer (30) formed on a part of the inner surface of a discharge container (20) is characterized in that the ultraviolet reflection layer (30) comprises: an accumulation body (A31) formed on at least a part of an electrode (11) at one side; and an accumulation body (B32) formed on at least a part outside the area corresponding to the electrode (11, 12), wherein the accumulation body (A31) comprises silicon dioxide particles containing OH groups and micro-particles having melting points higher than that of silicon dioxide, the accumulation body (B32) comprises micro-particles containing silicon dioxide particles having OH groups, and the concentration of OH groups in the silicon dioxide particles forming the ultraviolet reflection layer (30) is more than 10 wt ppm.

Description

excimer lamp

technical field

The present invention relates to an excimer lamp for performing surface treatment such as cleaning treatment, ashing treatment, and film-forming treatment on an object to be treated by irradiating ultraviolet rays.

Background technique

In recent years, the following technology has been developed and put into practical use: irradiating ultraviolet light with a wavelength below 200nm, that is, vacuum ultraviolet light, on glass substrates of liquid crystal display devices, semiconductor wafers, etc. For example, this technology includes cleaning treatment technology for removing organic pollutants adhering to the surface of the object to be processed or oxide film formation treatment technology for forming an oxide film on the surface of the object to be processed.

As a device for irradiating vacuum ultraviolet light, for example, a device equipped with an excimer lamp is used: a discharge gas is sealed in a discharge vessel made of a dielectric, an AC high voltage is applied through the discharge vessel to generate an excimer discharge, and vacuum ultraviolet light, that is, an excimer lamp, is emitted. Light. In such excimer lamps, many attempts have been made to efficiently emit higher-intensity ultraviolet rays.

Specifically, a technique has been developed in which an ultraviolet reflective layer is formed on the inner surface of the discharge vessel of an excimer lamp. The ultraviolet reflective layer is formed by laminating fine particles that transmit ultraviolet rays, such as laminating only silicon dioxide, or laminating silicon dioxide and silicon dioxide. Other fine particles include alumina, magnesium fluoride, calcium fluoride, lithium fluoride, magnesium oxide, and the like (see Patent Document 1).

In the excimer lamp with such a configuration, among the ultraviolet rays generated in the discharge vessel, the ultraviolet rays that are not directly radiated toward the light emitting portion enter the ultraviolet reflection layer, and are repeatedly refracted on the surface of a plurality of fine particles constituting the ultraviolet reflection layer. , Reflected and diffusely reflected, and radiated from the light emitting part. Thereby, ultraviolet rays can be emitted efficiently.

In lamps that emit ultraviolet rays, silica glass, for example, is widely used as a material constituting the discharge vessel. Therefore, as the microparticles constituting the ultraviolet reflective layer, in order to reduce or minimize the difference in thermal expansion coefficient with the silica glass constituting the discharge vessel and improve the adhesion of the ultraviolet reflective layer on the silica glass, it is preferable to contain Silica particles of the same material as the discharge vessel.

Surface-treated objects are often flat, such as glass substrates of liquid crystal panels. Therefore, in an excimer lamp in which the light emitting part is composed of a discharge vessel having the same flat shape as the object to be processed, by reducing the gap between the light emitting part and the object to be processed, the absorption of ultraviolet rays by oxygen can be suppressed, and thus the surface treatment can be effectively performed. . As an excimer lamp including a discharge vessel having such a shape, for example, Patent Document 2 discloses an excimer lamp including a square discharge vessel.

As an excimer lamp whose light emitting and emitting part is composed of a flat discharge vessel, there is a structure as shown in FIG. 10 . The excimer lamp 10 is constituted by a flat square discharge vessel 20 made of silica glass. The discharge vessel 20 is formed by connecting an upper wall plate 21, a lower wall plate 22, a side wall plate 23 and an end wall plate 24. Discharge gas is enclosed. In addition, a high-voltage supply electrode 11 is provided on the outer surface of the upper wall plate 21, and a ground electrode 12 is provided on the outer surface of the lower wall plate 22. These electrodes 11, 12 are arranged opposite to each other, and the excimer light generated in the discharge space S passes through and also serves as a light source. The lower wall plate 22 of the injection part emits to the outside.

Patent Document 1: Japanese Patent Laid-Open No. 2007-335350

Patent Document 2: Japanese Patent Laid-Open No. 2004-113984

However, when an excimer lamp provided with an ultraviolet reflection layer made of fine particles including silica particles is turned on for a long period of time, the illuminance maintenance rate gradually decreases with time. Therefore, for example, when performing surface treatment such as cleaning treatment, when it is desired to perform treatment with a constant illuminance, there arises a problem that the treatment capability of the excimer lamp varies with the lighting time.

Contents of the invention

The present invention is made in view of the above-mentioned circumstances, and its object is to provide an excimer lamp, equipped with an ultraviolet reflection layer composed of fine particles containing silica particles, which can suppress the decline in illuminance even if the lamp is turned on for a long time, and can effectively emits vacuum ultraviolet light.

The excimer lamp of the first invention of the present application includes a discharge vessel made of silica glass having a discharge space, a pair of electrodes are provided sandwiching the silica glass forming the discharge vessel, and the discharge space Discharge gas is enclosed, and an ultraviolet reflective layer is formed on a part of the inner surface of the discharge vessel. The excimer lamp is characterized in that the ultraviolet reflective layer includes: a deposition formed on at least a part of a region corresponding to one electrode. body A; and a deposition body B formed on at least a part of the region other than the region corresponding to the electrode, the deposition body A being composed of silicon dioxide particles containing OH groups and fine particles having a higher melting point than silicon dioxide, the deposition body B Composed of fine particles containing silica particles containing OH groups, the concentration of OH groups in the silica particles constituting the ultraviolet reflection layer is 10 wt ppm or more.

In addition, the second invention of the present application is characterized in that, in the first invention of the present application, when the installation area of the above-mentioned accumulation body A is a (cm ² ), the installation area of the above-mentioned accumulation body B is b (cm ^{2 )} . ), when the specific surface area of the stack B is c (cm ² /g), and the inner surface area of the discharge vessel is d (cm ² ), the relationship between them satisfies

b≥-5.0×10 ^-7 ac+0.35a, and b>0.02d.

By mixing fine particles having a melting point higher than that of silicon dioxide in the ultraviolet reflective layer, it is possible to prevent the grain boundaries from disappearing due to the bonding of adjacent fine particles, thereby suppressing a decrease in the reflectance of the ultraviolet reflective layer. In particular, the deposit A formed on the region corresponding to the electrode is susceptible to the heat of the plasma, so it is necessary to mix fine particles having a melting point higher than that of silicon dioxide to suppress a decrease in the reflectance of the ultraviolet reflective layer.

In addition, by containing OH groups in the silica particles constituting the ultraviolet reflective layer, it is possible to suppress the generation of internal defects in the silica particles contained in the ultraviolet reflective layer, prevent the ultraviolet reflective layer from absorbing light of wavelengths in the ultraviolet region, and maintain ultraviolet reflection. The reflectivity of the layer suppresses the reduction of the illuminance of the excimer lamp, and effectively emits vacuum ultraviolet light. In particular, by setting the concentration of OH groups in the silica particles constituting the ultraviolet reflection layer to 10 wtppm or more, both the reflection maintenance rate and the illuminance maintenance rate can be maintained at high values, which has an excellent effect of maintaining illuminance during long-term lighting.

When the ultraviolet reflection layer formed on the inner surface of the discharge vessel corresponding to the position where the electrode is provided contains OH groups, it is exposed to the discharge plasma and emits impurity gas mainly composed of water. When the impurity gas whose main component is water is combined with the discharge gas, the illuminance of plasma emission decreases. However, by forming an ultraviolet reflective layer on a part of the inner surface of the discharge vessel corresponding to the position where no electrode is provided, absorbing the water released by the ultraviolet reflective layer and absorbing oxygen generated by decomposing water in the plasma, it is possible Suppresses decrease in illuminance of excimer light. Therefore, even when the excimer lamp is turned on for a long time, it is possible to efficiently emit vacuum ultraviolet light while suppressing a decrease in illuminance.

Considering the specific surface area of the stack B, when the installation area of the stack A is a (cm ² ), the installation area of the stack B is b (cm ² ), and the specific surface area of the stack B is c ( cm ² /g), when the internal surface area of the discharge vessel is d(cm ² ), the relationship between them satisfies

b≥-5.0×10 ^-7 ac+0.35a, and b＞0.02d

Therefore, the amount of impurity gas released from stack A does not exceed the amount of impurity gas that can be adsorbed by stack B, and no impurity gas remains in the discharge space. Therefore, the decrease in illuminance of the excimer light caused by the combination of oxygen atoms contained in the impurity gas and the discharge gas can be suppressed, and even if the excimer lamp is turned on for a long time, the decrease in illuminance can be suppressed, and vacuum ultraviolet light can be efficiently emitted.

Description of drawings

Fig. 1 is an explanatory cross-sectional view showing the general structure of an example of an excimer lamp of the present invention, Fig. 1(a) is a cross-sectional view showing a section along the longitudinal direction of the discharge vessel, Fig. 1(b) is Fig. 1(a) A-A' line sectional view in.

Fig. 2 shows the experimental results of the excimer lamp.

Fig. 3 shows the experimental results of the excimer lamp.

Fig. 4 is a cross-sectional view illustrating a method of measuring illuminance of an excimer lamp according to an embodiment.

Fig. 5 shows the experimental results of the excimer lamp.

Fig. 6 shows the experimental results of the excimer lamp.

Fig. 7 shows the experimental results of the excimer lamp.

Fig. 8 shows the experimental results of the excimer lamp.

Fig. 9 shows the experimental results of the excimer lamp.

Fig. 10 is an explanatory perspective view showing a schematic configuration of a conventional excimer lamp.

Detailed ways

FIG. 1 is an explanatory sectional view showing a schematic configuration of an example of an excimer lamp 10 according to the present invention. Fig. 1(a) is a sectional view showing a section along the longitudinal direction of the discharge vessel 20, and Fig. 1(b) is a sectional view showing a line A-A' of Fig. 1(a).

The excimer lamp 10 includes a hollow long discharge vessel 20 having a rectangular cross-section whose both ends are hermetically sealed and a discharge space S is formed inside. This discharge vessel 20 comprises: an upper wall plate 21 and a lower wall plate 22 relative to the upper wall plate 21; a pair of side wall plates 23 connected to the upper wall plate 21 and the lower wall plate 22; and will be composed of these upper wall plates 21, A pair of end wall plates 24 that are sealed at both ends of the square cylindrical body formed by the lower wall plate 22 and the pair of side wall plates 23 . The discharge vessel 20 is formed of silica glass, such as synthetic quartz glass, which transmits vacuum ultraviolet light well.

In the discharge vessel 20, gas for discharge is sealed at a pressure of, for example, 10 to 80 kPa. Even if any gas is selected as the discharge gas, it will not affect the temporal change of the radiation intensity, but the center wavelength of the emitted excimer light varies depending on the type of discharge gas. For example, an excimer lamp sealed with xenon (Xe) generates excimer light with a center wavelength of 172nm, while an excimer lamp filled with a mixed gas of argon (Ar) and chlorine (Cl) generates an excimer light with a center wavelength of 175nm. Molecular light, an excimer lamp enclosed with a mixed gas of krypton (Kr) and iodine (I) produces excimer light with a center wavelength of 191nm, and an excimer lamp enclosed with a mixed gas of argon (Ar) and fluorine (F) The lamp generates excimer light with a wavelength of 193nm as the center wavelength, and the excimer lamp containing a mixed gas of krypton (Kr) and bromine (Br) generates excimer light with a center wavelength of 207nm, and contains krypton (Kr) and chlorine An excimer lamp of a mixed gas of (Cl) generates excimer light with a central wavelength of 222 nm, and an excimer lamp filled with a mixed gas of xenon (Xe) and chlorine (Cl) generates excimer light with a central wavelength of 308 nm.

A high voltage supply electrode 11 is provided on the outer surface of the upper wall plate 21 of the discharge vessel 20, and a ground electrode 12 is provided on the outer surface of the lower wall plate 22, and these electrodes 11, 12 are arranged to face each other. Such electrodes 11 and 12 have a mesh structure, and light can pass through between the meshes. As a material, aluminum, nickel, gold, etc. are used, for example, and it forms by the method of screen printing or vacuum evaporation, for example. In addition, each electrode 11, 12 is connected to an appropriate high-frequency power source (not shown).

In the excimer lamp 10 described above, in order to efficiently utilize the vacuum ultraviolet light generated by the excimer discharge, the ultraviolet reflection layer 30 made of fine particles is provided on the inner surface of the discharge space S relative to the discharge vessel 20 . This ultraviolet reflection layer 30 is comprised from the accumulation body A31 and accumulation body B32. The accumulation body A31 is formed on a part of the inner surface of the discharge vessel 20 facing the discharge space S provided with the high voltage supply electrode 11, that is, formed on a part of the area corresponding to the high voltage supply electrode 11 on the inner surface of the upper wall plate 21. . In addition, the accumulation body B32 is formed on a part of the inner surface facing the discharge space S of the discharge vessel 20 not provided with the high-voltage supply electrode 11 or the ground electrode 12, that is, on the upper wall deviated from the area corresponding to the electrodes 11, 12. Any area on the inner surface of the panel 21 and the lower wall panel 22 and the inner surface of the side wall panel 23 and the end wall panel 24 . That is, the ultraviolet reflection layer 30 formed on the area corresponding to the high voltage supply electrode 11 on the inner surface of the upper wall plate 21 is referred to as accumulation body A31, and the ultraviolet reflection layer formed on other areas of the inner surface of the discharge vessel 20 is referred to as accumulation body A31. 30 is referred to as a stack B32.

On the other hand, the ultraviolet reflection layer 30 is not formed on the inner surface of the lower wall plate 22 of the discharge vessel 20 corresponding to the ground electrode 12, thereby constituting a light emitting portion.

The thickness of the deposit A31 is, for example, 5 to 1000 μm, and is composed of silica particles and fine particles having a melting point higher than that of silica and transmitting ultraviolet rays. Fine particles having a higher melting point than silica and which transmit ultraviolet rays include, for example, alumina, lithium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, and the like.

When the vacuum ultraviolet light enters the accumulation body A31, part of it is reflected on the surface of the microparticles, the other part is refracted and transmitted inside the particle, and is reflected or refracted on other surfaces again. Such reflection and refraction are repeated in many fine particles, and the vacuum ultraviolet light is diffusely reflected.

However, the silica particles are melted by the heat of the plasma generated by the excimer lamp 10 , the grain boundaries disappear, the vacuum ultraviolet light cannot be diffused and reflected, and the reflectance is lowered. In particular, the deposit A31 formed on the region corresponding to the high-voltage supply electrode 11 is easily heated by the plasma, and the silica particles constituting the deposit A31 are easily melted. On the other hand, tiny particles with a higher melting point than silicon dioxide do not melt even when exposed to the heat of plasma. Therefore, fine particles having a melting point higher than that of silicon dioxide are mixed into the deposit A31, and the adjacent fine particles are bonded to each other, thereby preventing disappearance of grain boundaries and suppressing a decrease in reflectance of the deposit A31.

The thickness of the accumulation body B32 is, for example, 10 to 1000 μm, and is composed of fine particles including silica particles. The microparticles constituting the stack B32 may consist of only silica particles, or may contain other substances that combine with oxygen, and may be mixed with insulating microparticles composed of substances that transmit ultraviolet rays, such as alumina, lithium fluoride, fluorine Magnesium chloride, calcium fluoride, barium fluoride.

Even if the vacuum ultraviolet ray enters the accumulation body B32, reflection and refraction repeatedly occur on a plurality of fine particles, and the vacuum ultraviolet ray is diffusely reflected. In addition, since the deposit B32 is formed on the inner surface of the discharge vessel 20 other than the regions corresponding to the electrodes 11 and 12, it is less likely to be affected by the heat of the plasma. Therefore, even if the accumulation body B32 is constituted only by silica particles, the disappearance of the grain boundary due to the bonding between adjacent fine particles does not easily occur.

Fine particles are particles defined as follows with a particle diameter in the range of, for example, 0.01 to 20 μm. The central particle diameter (the maximum value of the particle size distribution based on the number of particles) is, for example, preferably 0.1 to 10 μm, more preferably 0.1 to 3 μm in the aggregate A31, Similarly, for the deposit B32, for example, the thickness is preferably 0.1 to 20 μm.

The term "particle diameter" here refers to an enlarged projected image obtained with a scanning electron microscope (SEM) with the approximate middle position in the thickness direction on the cut section when the surface of the ultraviolet reflection layer 30 is cut perpendicular to the direction as the observation range. , and when two parallel lines in a certain direction sandwich any particle in the enlarged projection image, the interval between the parallel lines is the Feret diameter.

In addition, the "central particle diameter" refers to dividing the range of the maximum and minimum particle diameters of the particle diameters of each particle obtained above into a plurality of regions, for example, about 15 regions in the range of 0.1 μm. , the number of particles (degrees) belonging to each region is the central value of the largest region.

In this excimer lamp 10 , when lighting power is supplied to the high-voltage supply electrode 12 , excimer discharge occurs in the discharge space S between both electrodes 11 and 12 via the discharge vessel 20 . Thus, an excimer is formed, and vacuum ultraviolet light is emitted from the excimer. Part of the vacuum ultraviolet light generated in the discharge space S is directly emitted to the outside through the lower wall plate 22 having a light emitting portion. In addition, another part of the vacuum ultraviolet light is radiated toward the upper wall plate 21, diffused and radiated in the ultraviolet reflection layer 30, and radiated to the outside through the light emitting portion.

The microparticles constituting the ultraviolet reflection layer 30 have a particle diameter approximately equal to the wavelength of the vacuum ultraviolet light, so that the vacuum ultraviolet light can be effectively diffused and reflected.

However, when the excimer lamp 10 provided with the ultraviolet reflection layer 30 is turned on for a long time, the initial illuminance cannot be maintained, and the illuminance gradually decreases as the lighting time progresses. The inventor analyzed the reasons for the decrease in illuminance from all aspects, considering whether the decrease in the reflectivity of the ultraviolet reflective layer 30 is one of the main factors.

Therefore, the reflection intensity spectrum of the ultraviolet reflection layer 30 of the excimer lamp 10 at the beginning of lighting and the reflection intensity spectrum of the ultraviolet reflection layer 30 of the excimer lamp 10 after long-time lighting were measured, and the two were compared and analyzed. From this result, it can be seen that the ultraviolet reflective layer 30 of the excimer lamp 10 has an absorption band in the ultraviolet region after being turned on for a long time, and a part of ultraviolet rays is absorbed by the ultraviolet reflective layer 30, resulting in a decrease in illuminance.

The ultraviolet region absorption band of the ultraviolet reflective layer 30 is caused by the fact that the silicon dioxide particles constituting the ultraviolet reflective layer 30 are exposed to ultraviolet rays or plasma during discharge, undergo radiation damage, and generate light that absorbs ultraviolet region wavelengths. The internal defects, the ultraviolet rays are absorbed by the internal defects, so that the diffuse reflection is suppressed. Internal defects refer to Si-Si defects with an absorption end around a wavelength of 163nm or E' centers with an absorption band around a wavelength of 215nm, which are produced by exposing the Si-O-Si bonds of silica particles to ultraviolet light or plasma. (E'center)(Si·).

For the reasons described above, it is the silica particles that generate internal defects that absorb light at wavelengths in the ultraviolet region, and the absorption of light at wavelengths in the ultraviolet region that causes a decrease in illuminance depends on the internal defects of the silica particles. In addition, fine particles that transmit ultraviolet rays other than silicon dioxide particles, which are composed of alumina, lithium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, etc., do not emit radiation even when exposed to ultraviolet rays or plasma. damage. Therefore, by preventing the occurrence of internal defects in the silica particles constituting the ultraviolet reflection layer 30 , the reduction in illuminance can be suppressed, and a high illuminance maintenance rate can be maintained even when the lamp is turned on for a long time.

In order to prevent the generation of internal defects in the silica particles, it is effective to make the silica particles contain OH groups. By containing OH groups, generation of internal defects in the silica particles contained in the ultraviolet reflecting layer 30 can be suppressed, and a decrease in the reflectance of the ultraviolet reflecting layer 30 can be prevented.

Hereinafter, a method for forming the ultraviolet reflection layer 30 composed of fine particles containing silica particles containing OH groups will be described. The ultraviolet reflection layer 30 is, for example, formed a particle accumulation layer containing silica particles in a predetermined region of the inner surface of the discharge vessel forming material by a method called "flow down". For example, fine particles are mixed in a viscous solvent containing water and PEO resin (polyethylene oxide: polyethylene oxide) to adjust the dispersion, and the dispersion is flowed into the discharge vessel forming material. In addition, the particle accumulation layer can be formed by attaching the dispersion liquid to a predetermined region on the inner surface of the discharge vessel forming material, drying and firing to evaporate water and PEO resin. Here, the calcination temperature is, for example, 500°C to 1100°C.

As an example of a method of adding OH groups to silica particles, silica particles containing no OH groups are heated in an electric furnace (for example, 1000° C.) by supplying water vapor to produce silica particles containing a large amount of OH groups. By using such treated silica particles, it is possible to form the ultraviolet reflection layer 30 composed of fine particles of silica particles containing OH groups.

Alternatively, as another method, after attaching silica particles not containing OH groups to a predetermined region on the inner surface of the discharge vessel forming material, the silica particles may contain OH groups by supplying steam and firing. In addition, after forming the ultraviolet reflection layer 30 by calcining silica particles not containing OH groups, the silica particles may contain OH groups by supplying water vapor and heating in an electric furnace.

In addition, silica particles available by purchase also contain OH groups depending on the production method, but some products have a low concentration of OH groups, so it is preferable to contain a high concentration of OH groups by the above-mentioned method.

The concentration of OH groups contained in the silica particles can be adjusted to an arbitrary value by selecting various heating and exhaust conditions. For example, even if the temperature is kept constant, more OH groups can be removed as the holding time increases. Considering the amount of OH groups contained in the silica particles in advance, by heating the exhaust gas to adjust the amount of OH groups removed, the ultraviolet reflection layer 30 composed of fine particles of silica particles containing any OH group concentration can be formed. .

Indicates the first experiment related to the excimer lamp.

According to the structure shown in FIG.1(a), (b), the excimer lamp provided with the ultraviolet reflection layer was produced.

[Basic configuration of an excimer lamp]

The material of the discharge vessel is silica glass, the size is 15mm×43mm×350mm, and the thickness is 2.5mm.

The size of the high voltage supply electrode and the ground electrode is 30mm×300mm.

The ultraviolet reflective layer is composed of a mixture of silica particles with a central particle diameter of 1.5 μm in a composition ratio of 90% by weight and alumina particles with a central particle diameter of 1.5 μm in a composition ratio of 10% by weight, which are formed separately by a flow-down method and calcined. The temperature is 1000°C.

As a discharge gas, xenon was sealed in the discharge vessel at 40 kPa.

The concentration of OH groups in the silica particles, the reflection maintenance ratio, and the illuminance maintenance ratio were measured for the excimer lamp having the above configuration. All ultraviolet reflective layers were scraped off from the discharge vessel, and measured by thermal desorption spectroscopy. From this, the OH group concentration in the silica particles contained in the ultraviolet reflection layer was calculated. In addition, the component ratio of the silica particles contained in the shaved ultraviolet reflection layer was obtained, and the weight of OH groups with respect to the silica particles was calculated from the component ratio. In addition, using a vacuum ultraviolet spectrometer (VUV) and an ultraviolet illuminance measuring device, the reflection maintenance rate and illuminance maintenance rate of the ultraviolet reflection layer from the initial state after 500 hours of continuous lighting were measured.

Table 1 shows the measurement results of lamps 1 to 5.

[Table 1]

OH group concentration in silica particles (wtppm) Reflex maintenance rate (%) Illumination maintenance rate (%) Lamp 1 5 78 72 lamp 2 7 82 79 lamp 3 10 98 96 lamp 4 42 96 92 lamp 5 132 96 94

2 is a graph plotting the values of lamps 1 to 5 with the OH group concentration (wtppm) in the silica particles shown in Table 1 as the abscissa and the reflection retention (%) as the ordinate.

In addition, FIG. 3 is a graph plotting the numerical values of lamps 1 to 5 with the OH group concentration (wtppm) in the silica particles shown in Table 1 as the abscissa and the illuminance maintenance rate (%) as the ordinate.

In addition, the graphs shown in FIG. 2 and FIG. 3 are logarithmic graphs in which the abscissa is a logarithmic scale.

From the above results, it can be read that when the OH group concentration in the silica particles is less than 10 wtppm, both the reflection maintenance rate and the illuminance maintenance rate are low, and when the excimer lamp is turned on for a long time, the processing capacity decreases. On the other hand, when the OH group concentration in the silica particles is 10 wtppm or more, both the reflection maintenance rate and the illuminance maintenance rate are 90% or more, and the treatment capability can be maintained even if the excimer lamp is turned on for a long time. As shown in Figure 2 and Figure 3, it can be seen that when the OH group concentration is changed from less than 10wtppm to more than 10wtppm, the reflection maintenance rate and illuminance maintenance rate will increase sharply, so when the OH group concentration in the silica particles reaches 10wtppm or more, it will There is a significant difference, and it exhibits an excellent effect in maintaining illuminance during long-term lighting.

However, even if the concentration of OH groups in the silica particles constituting the ultraviolet reflection layer 30 is 10 wtppm or more, the illuminance of excimer light with a center wavelength of 172 nm in the excimer lamp may be low. In addition, when the excimer lamp 10 in which xenon is sealed as a discharge gas is turned on, the color of the discharge generated in the discharge space S may turn green, and it is confirmed that molecules (XeO) in which xenon atoms and oxygen atoms are bonded are generated. , and green light with a center wavelength around 550 nm is emitted from the molecule.

In addition, when the OH groups contained in the silicon dioxide particles constituting the ultraviolet reflection layer 30 are exposed to the discharge plasma generated in the discharge space, they are heated to release impurity gas mainly composed of water ( _H2O ). to the discharge space S. Oxygen atoms generated by decomposing the impurity gas mainly composed of water in the plasma are released into the discharge space S from the OH groups contained in the silicon dioxide particles constituting the ultraviolet reflection layer 30 .

When the ultraviolet reflective layer 30 made of fine particles is formed on the inner surface of the discharge vessel 20 , the surface area is larger than that of a flat surface of the discharge vessel 20 without the ultraviolet reflective layer 30 due to the unevenness of the fine particles. The impurity gas is generated from the ultraviolet reflective layer 30 exposed to the discharge plasma, so more impurity gas is generated when the ultraviolet reflective layer 30 is formed. In addition, since the volume of one particle is small, the fine particles constituting the ultraviolet reflection layer 30 have a smaller heat capacity than the discharge vessel 20 . Therefore, even if heating is performed within a short period of several tens of ns when the discharge plasma is generated, the temperature becomes high and impurity gases are easily released.

The accumulation body A31 is formed on the inner surface of the upper wall plate 21 corresponding to the high-voltage supply electrode 11, so it is directly exposed to the discharge plasma generated between the electrodes 11 and 12, so it is heated to release impurity gas to the discharge plasma. Inside the space S.

On the other hand, the accumulation body B32 is formed on the inner surface of the upper wall plate 21 deviated from the high voltage supply electrode 11 or the lower wall plate 22 deviated from the ground electrode 12, or formed in the side wall plate 23 or the end wall plate 24. Any area of the surface, thus facing the discharge space S, is not directly exposed to the discharge plasma generated between the electrodes 11,12. Therefore, it is considered that almost no impurity gas is generated from the stack B32. On the contrary, it is considered that the accumulation body B32 adsorbs the impurity gas, and this is confirmed by the following experiment.

As a second test subject, an excimer lamp in which only the deposit B was formed on the inner surface of the discharge vessel 20 and the deposit A was not formed was produced. Xenon was used as the gas for discharge, oxygen was also mixed when sealing the gas for discharge, and an excimer lamp in which oxygen was previously sealed as an impurity gas was used as an experimental object. The oxygen concentration enclosed in the discharge space S was 160 wtppm, and the pressure of the discharge gas was 40 kPa. When oxygen is mixed as an impurity gas, it reacts with a rare gas and has a great influence on the decrease in illuminance, and discharge light with a wavelength of 550 nm is generated, thereby making it easy to determine that oxygen has been mixed into the discharge space S.

Three types of excimer lamps were prepared which had accumulations B in which the particle composition ratios constituting the fine particles were different on the inner surface of the discharge vessel. Lamp 1 has a deposit B made of silica particles only, lamp 2 has a deposit B made of silica particles and alumina particles, and lamp 3 has a deposit B made of silica particles and calcium fluoride particles b. Moreover, as a comparative example, the lamp 4 in which the deposit B was not formed was prepared. The luminous intensity at 550 nm after continuous lighting for 15 minutes until the excimer discharge stabilized was measured for each lamp, and this was taken as "the luminous intensity at 550 nm at the initial stage of lighting". Thereafter, the excimer lamp was continuously turned on, and the luminous intensity at 550 nm after continuous lighting for 5 hours was measured, and this was defined as "luminous intensity at 550 nm after 5 hours of lighting".

[Table 2]

Table 2 shows the results of the second experiment. The numerical value of "luminous intensity at 550 nm after lighting for 5 hours" is a relative value when the numerical value of "luminous intensity at 550 nm at the initial stage of lighting" is taken as 100. In lamps 1 to 3 including stack B, the value of the luminous intensity at 550 nm decreased to 100 or less after 5 hours of lighting, and the number of molecules (XeO) combined with xenon atoms and oxygen atoms decreased compared to the initial stage of lighting. That is, oxygen previously mixed into the discharge space decreases. On the other hand, in the lamp 4 in which no deposits B were formed, the value of the luminous intensity at 550 nm remained at 100 after 5 hours of lighting, indicating that the amount of oxygen previously mixed into the discharge space did not change. From this, it can be seen that the 550 nm light can be reduced by providing the accumulation body B on the inner surface of the discharge vessel of the excimer lamp, and it is known that oxygen is adsorbed by the accumulation body B. In addition, since the accumulation body B is not exposed to the discharge plasma, the adsorbed impurity gas is not released into the discharge space.

Hereinafter, a third experiment was performed to confirm whether the phenomenon that oxygen was adsorbed on the stack B confirmed in the second experiment occurred by turning on the excimer lamp. The lamps 5 to 7 having the same configuration as the lamps 1 to 3 of the second test object were used as the third experiment. Moreover, as a comparative example, the lamp 8 in which the deposit B was not formed was prepared. The luminous intensity at 550 nm after continuous lighting for 15 minutes was measured for each lamp, and this was defined as "luminous intensity at 550 nm at the initial stage of lighting". Then, it was left unlit for 48 hours, then turned on, and the luminous intensity at 550 nm after continuous lighting for 15 minutes was measured, and this was defined as "the luminous intensity at 550 nm after lapse of 48 hours". Thereafter, the excimer lamp was continuously turned on, and the luminous intensity at 550 nm after continuous lighting for 5 hours was measured, and this was taken as "the luminous intensity at 550 nm after 5 hours of lighting after 48 hours".

[table 3]

Table 3 shows the results of the third experiment. The values of "luminous intensity at 550 nm after 48 hours" and "luminous intensity at 550 nm after 5 hours of lighting after 48 hours" are relative values when the value of "luminous intensity at 550 nm at the initial stage of lighting" is taken as 100. In the lamps 5 to 7 provided with deposits B, the value of the luminous intensity at 550 nm after 48 hours has elapsed is 100, and the value of the luminous intensity at 550 nm after 48 hours has elapsed and been turned on for 5 hours has decreased to 10 to 11. Excimer lamps will only reduce oxygen. As the principle of oxygen adsorption to the deposit B, on the surface of the fine particles of the deposit B, chemisorption occurs in which oxygen is chemically reacted and adsorbed by ultraviolet rays generated by lighting.

On the other hand, in the lamp 8 in which no accumulation body B was formed, the value of the luminous intensity at 550 nm after 48 hours and the value of the luminous intensity at 550 nm after 5 hours of lighting after 48 hours remained at 100, so it can be seen that it was mixed in the discharge space beforehand. The amount of oxygen does not change.

The tiny particles constituting the stack B adsorb impurity gas on the surface exposed to the discharge space, so the larger the surface area facing the discharge space, the more impurity gas can be adsorbed. Therefore, the larger the "specific surface area", that is, the sum of the surface areas of all particles contained in a unit weight of powder, the more impurity gas can be adsorbed. The specific surface area is measured, for example, by a measurement method called the BET method in which a molecular gas (such as nitrogen) having a known occupied area is previously adsorbed on the surface of fine particles, and the specific surface area is obtained from the amount. When measuring the specific surface area of the fine particles constituting the accumulation body B, the surface of the accumulation body B exposed to the discharge space is exposed to molecular gas for adsorption, and the specific surface area is obtained from the amount.

Hereinafter, a fourth experiment conducted to confirm the effect of the present invention is shown.

<subject>

According to the structure shown in FIG.1(a), (b), the excimer lamp provided with the stack A and the stack B was produced.

[Basic configuration of an excimer lamp]

The material of the discharge vessel is silica glass, the size is 15mm×43mm×540mm, and the thickness is 2.5mm.

The dimensions of the high voltage supply electrode and the ground electrode are 32 mm x 500 mm.

The size of the light emitting portion corresponding to the region where the accumulation body B is not formed on the lower wall plate is 36 mm×504 mm larger than the ground electrode by 2 mm.

The accumulation body A and the accumulation body B are respectively formed by the flow-down method, and the calcination temperature is 1000°C.

After heating and exhausting at 800° C. for 1 hour (time after temperature rise), xenon was sealed in the discharge vessel. Its sealing volume is 40kPa.

The OH group content of the stack A of the produced lamp was 500 wtppm.

As shown in Table 4, four types of constitutions of the accumulation body A were prepared: constitution (1-1), constitution (1-2), constitution (1-3), and constitution (1-4). The materials, particle diameters, central particle diameters, and composition ratios of the four structures are the same, but the installation area of the deposit A formed on the inner surface of the upper wall plate corresponding to the high voltage supply electrode is changed to 160cm ² and 128cm ² , 107cm ² , 40cm ² . The amount of impurity gas released into the discharge space depends on the installation area of the accumulation body A. Therefore, as shown in the composition (1-1), the larger the installation area of the accumulation body A is, the greater the amount of impurity gas is. As shown in 1-4), the smaller the installation area of the accumulation body A is, the smaller the amount of impurity gas is. In addition, in the configuration (1-2), the configuration (1-3), and the configuration (1-4), the installation area where the deposit A is formed is smaller than 160 cm ² which is the area where the high-voltage supply electrode is formed, so it is not The deposit A is formed over the entire area of the inner surface of the discharge vessel provided with the high-voltage supply electrode, but the deposit A is formed on a part thereof.

[Table 4]

In addition, as shown in Table 5, for the composition of the accumulation body B, four types of constitution (2-1), constitution (2-2), constitution (2-3), and constitution (2-4) were prepared. Composition (2-1), composition (2-2), and composition (2-3) consist only of silica particles, and composition (2-4) consists of silica particles and alumina particles. Composition (2-1), Composition (2-2), and Composition (2-3) The specific surface area was adjusted to 16×10 ⁴ cm ² /g, 4×10 ⁴ cm ^{2 /} g by changing the particle diameter of the silica particles. g, 1×10 ⁴ cm ² /g, etc. In addition, the specific surface area of the composition (2-4) was 4×10 ⁴ cm ² /g. The larger the specific surface area of the accumulation body B, the more impurity gas is adsorbed. Therefore, as shown in the composition (2-1), the larger the specific surface area of the accumulation body B is, the larger the surface area facing the discharge space is, so the impurities mixed into the discharge space The amount of gas decreases with lighting, and as shown in the configuration (2-3), the smaller the specific surface area of the deposit B, the smaller the amount of impurity gas mixed into the discharge space decreases with lighting.

[table 5]

With respect to the pile A having the structure (1-1), lamps having the pile B having the structures (2-1) to (2-4) were prepared as test objects. In addition, five types of lamps in which the installation area of the accumulation body B was changed were prepared for each combination. Similarly, with respect to the stacked body A of the configuration (1-2), the configuration (1-3), and the configuration (1-4), the stacked body B is the lamp of the configuration (2-1) to the configuration (2-3).

For each excimer lamp thus constituted, the tube wall load of the discharge vessel was turned on under the condition that the load on the wall of the discharge vessel became 0.6 W/cm ² , and the illuminance of xenon excimer light in the wavelength range of 150 nm to 200 nm after continuous lighting for 15 minutes was measured and the The illuminance of xenon excimer light in the wavelength range of 150nm to 200nm after continuous lighting for 500 hours under a constant tube wall load. The illuminance after 15 minutes of continuous lighting is taken as the initial illuminance, and the value of the illuminance after 500 hours of continuous lighting relative to the initial illuminance is taken as the illuminance maintenance rate, and [(illuminance after 500 hours of lighting)/(illuminance immediately after lighting) is calculated ] (%) as "500-hour illuminance maintenance rate". The reason for setting 500 hours is as follows. The decrease in illuminance due to impurity gas lasted until 500 hours, and the illuminance did not decrease thereafter. Therefore, the impurity gas contained in the ultraviolet reflective layer was completely released until 500 hours, and was not released thereafter.

As a product specification, an illuminance maintenance of 80% or more is required, so when the 500-hour illuminance maintenance rate is 80% or more, it is judged as "○", and when the 500-hour illuminance maintenance rate is 80% or less, it is judged as "×".

As shown in Fig. 4, the illuminance measurement is carried out as follows: the excimer lamp 10 is fixed on the ceramic support table 41 arranged inside the aluminum container 40, and at a position 1 mm away from the surface of the excimer lamp 10, with the excimer Fix the ultraviolet illuminance measuring device 42 so that the lamp 10 faces each other, and apply an AC high voltage of 5.0 kV between the electrodes 11 and 12 of the excimer lamp 10 under the condition that the inner atmosphere of the aluminum container 40 is replaced with nitrogen, thereby the Discharge was generated inside the capacitor 20, and the illuminance of the vacuum ultraviolet light radiated through the mesh of the ground electrode 12 was measured.

The experimental results are shown in FIGS. 5 and 6 . From the results, among the combinations of the configuration of the stack A and the stack B, the combination with the smallest installation area of the stack B among the excimer lamps with a 500-hour illuminance maintenance rate of 80% or more was extracted. For example, the lamp 3 is selected in a combination in which the configuration of the accumulation body A is "configuration (1-1)" and the configuration of the accumulation body B is "configuration (2-1)". Likewise, select Light 8, Light 13, Light 18, etc.

For the combinations thus extracted, the composition of the stack A, the composition of the stack B, the specific surface area of the stack B, and the installation area of the stack B are listed in Table 6.

[Table 6]

FIG. 7 is a graph showing the results of Table 6. FIG. The horizontal axis is the specific surface area of the stack B (×10 ⁴ cm ² /g), the vertical axis is the installation area of the stack B (cm ² ), and the numerical values are indicated according to the composition of the stack A.

Table 6 and FIG. 7 show that the larger the specific surface area, the smaller the installation area required to suppress the decrease in illuminance. For each constitution of the stack A, that is, constitution (1-1), constitution (1-2), and constitution (1-3), each installation area is proportional to the specific surface area. However, in the excimer lamp having the stacked body A having the configuration (1-4), even if the specific surface area is increased, the installation area does not become a value lower than 10 cm ² .

In the excimer lamp having the stack A configured as (1-4), the installation area of the stack B is too small compared to the internal volume of the discharge vessel, so the impurity gas diffused into the discharge space reaches the stack B The probability becomes lower, unable to show the adsorption effect. That is, there is a minimum area required for the accumulation body B with respect to the size of the discharge space. The size of the discharge space is represented by the inner surface area of the discharge vessel. In this case, the inner surface area is about 500 cm ² , while the installation area of the stack B is 10 cm ² . Therefore, the minimum required installation area of the accumulation body B is 0.02 times the inner surface area of the discharge vessel.

Hereinafter, the slopes and intercepts of the respective approximate straight lines of the configurations of the accumulation body A in FIG. 7 , that is, the configuration (1-1), the configuration (1-2), and the configuration (1-3), are derived. The results, that is, the composition of the accumulation body A, the installation area of the accumulation body A, the slope of the relationship between the specific surface area of the accumulation body B and the installation area, and the intercept of the relationship between the specific surface area of the accumulation body B and the installation area are listed in Table 7.

[Table 7]

Composition of accumulation body A Installation area of accumulation body A (cm ² ) The slope of the relationship between the specific surface area of the accumulation body B and the installation area (×10 ^-4 g) The intercept of the relationship between the specific surface area of the accumulation body B and the installation area (cm ² ) Composition (1-1) 160 -0.81 56 Composition (1-2) 128 -0.67 45 Composition (1-3) 107 -0.52 37

In FIG. 8 , the horizontal axis is the installation area (cm ² ) of the stack A, and the vertical axis is the slope (×10 ^-4 g) of the relationship between the specific surface area of the stack B and the installation area, and the values in Table 7 are indicated. The value of the result.

It can be seen from the graph that the slope of the relationship between the specific surface area of the stack B and the set area has a proportional relationship with a negative slope relative to the set area (cm ² ) of the stack A. When the installation area of the accumulation body A is a (cm ² ), the slope of the relationship between the specific surface area of the accumulation body B and the installation area can be expressed as -5.0×10 ⁻⁷ ×a.

In FIG. 9, the horizontal axis is the installation area (cm ² ) of the accumulation body A, and the vertical axis is the intercept (cm ² ) of the relationship between the specific surface area of the accumulation body B and the installation area, and the results of Table 7 are indicated. value.

It can be seen from the graph that the intercept of the relationship between the specific surface area of the stack B and the set area has a proportional relationship with a positive slope relative to the set area (cm ² ) of the stack A. When the installation area of the accumulation body A is a (cm ² ), the intercept of the relationship between the specific surface area of the accumulation body B and the installation area can be expressed as 0.35×a.

In addition, it can be seen from Fig. 7 that the installation area of the accumulation body B and the specific surface area of the accumulation body B have "the slope of the relationship between the specific surface area of the accumulation body B and the installation area" and "the relationship between the specific surface area of the accumulation body B and the installation area". The proportional relationship represented by the intercept". Therefore, when the installation area of the accumulation body B is b (cm ² ) and the specific surface area of the accumulation body B is c (cm ² /g), the installation area of the accumulation body B and the volume of the accumulation body B in Fig. 5 The relationship between the specific surface area can be expressed as

b = (the slope of the relationship between the specific surface area of the accumulation body B and the installation area) × c + (the intercept of the relationship between the specific surface area of the accumulation body B and the installation area)

In addition, from the results of Fig. 8 and Fig. 9, when the installation area of stack A is a (cm ² ), the slope of the relationship between the specific surface area of stack B and the installation area can be expressed as -5.0×10 ^-7 × a, the intercept of the relationship between the specific surface area of the accumulation body B and the installation area can be expressed as 0.35×a, so the relationship between the installation area of the accumulation body B and the specific surface area of the accumulation body B in Figure 7 can be expressed as follows.

b=-5.0×10 ^-7 ac+0.35a

In addition, it can be seen from the experimental results in Fig. 5 and Fig. 6 that if the installation area b of the accumulation body B is larger than the amount indicated by the relationship between the installation area of the accumulation body B and the specific surface area of the accumulation body B in Fig. 5, the illuminance at 500 hours The maintenance rate was 80% or more, and it was judged as ◯.

From the above results, in the excimer lamp including the stack A containing OH groups, in order to suppress a decrease in illuminance, the installation area of the stack B may satisfy the following relationship.

When the installation area of the accumulation body A is a (cm ² ), the installation area of the accumulation body B is b (cm ² ), and the specific surface area of the accumulation body B is c (cm ² /g), it is

b≥-5.0×10 ^-7 ac+0.35a

In addition, in FIG. 7 , in the excimer lamp having the accumulation body A having the configuration (1-4), even if the specific surface area of the accumulation body B is increased, the installation area of the accumulation body B will not become lower than 10 cm ² value, the relationship between the specific surface area of the accumulation body B and the design area is not the same as that of the accumulation body A having the constitution (1-1), the constitution (1-2), and the constitution (1-3). Therefore, in Table 7 and FIGS. 8 and 9 , the case where there is the stacked body A having the configuration (1-4) is not considered. That is, the condition to be satisfied by the installation area of the accumulation body B is to exclude the case where there is the accumulation body A having the configuration (1-4). Therefore, in the conditions to be satisfied by the installation area of the stack B, the case of having the stack A having the configuration (1-4) must be excluded.

The case where there is the accumulation body A having the configuration (1-4) means that the installation area of the accumulation body B is too small compared with the internal volume of the discharge vessel, so that the effect of adsorption cannot be exhibited. That is, the installation area of the stack B is about 0.02 times the inner surface area of the discharge vessel. Therefore, in order to suppress a decrease in illuminance, when the inner surface area of the discharge vessel is d (cm ² ), the relation of the installation area b (cm ² ) of the accumulation body B needs to satisfy the following conditions.

b>0.02d

From the above results, in the excimer lamp including the stack A containing an OH group, in order to suppress a decrease in illuminance, the configuration of the stack B must satisfy the following relationship. Let the installation area of the stack A be a (cm ² ), the installation area of the stack B be b (cm ² ), and the specific surface area of the stack B be c (cm ² /g). When the inner surface area of is set to d(cm ² ), it must satisfy

b≥-5.0×10 ⁻⁷ ac+0.35a, and b>0.2d.

By satisfying the above relationship, the amount of impurity gas released from stack A does not exceed the amount of impurity gas that can be adsorbed by stack B, and impurity gas does not remain in the discharge space. Therefore, the decrease in illuminance of the excimer light caused by the combination of oxygen atoms contained in the impurity gas and the discharge gas can be suppressed, and even when the excimer lamp is turned on for a long time, the decrease in illuminance can be suppressed to efficiently emit vacuum ultraviolet light.

In addition, the installation area a (cm ² ) of the accumulation body A and the installation area b (cm ² ) of the accumulation body B are measured assuming that the surface of the accumulation body A or the accumulation body B is smooth without considering the irregularities of the fine particles. value. In addition, the inner surface area d (cm ² ) of the discharge vessel is also a value measured assuming that the surface is smooth.

Claims (1)

1. Excimer lamp, comprise and have discharge vessel discharge space, that constituted by silica glass, be provided with pair of electrodes with the state that clips the silica glass that forms this discharge vessel, and in discharge space, enclose discharge gas is arranged, part at the inner surface of above-mentioned discharge vessel is formed with ultraviolet reflecting layer, and described Excimer lamp is characterised in that:

Above-mentioned ultraviolet reflecting layer comprises: the accumulation body A that at least a portion in the zone of answering with side's electrode pair forms; And the accumulation body B that forms of at least a portion beyond the zone of answering with electrode pair,

Above-mentioned accumulation body A is made of the silicon dioxide granule that contains the OH base and the melting point fine particle higher than silicon dioxide,

Above-mentioned accumulation body B is made of the fine particle that comprises the silicon dioxide granule that contains the OH base,

The OH base concentration that constitutes in the silicon dioxide granule of above-mentioned ultraviolet reflecting layer is more than the 10wtppm,

Be made as a (cm at the area that arranges with above-mentioned accumulation body A ²), the area that arranges of above-mentioned accumulation body B is made as b (cm ²), the specific area of accumulation body B is made as c (cm ²/ g), the internal surface area of discharge vessel is made as d (cm ²) time, relation each other satisfies

B 〉=-5.0 * 10 ^-7Ac+0.35a and b＞0.02d.

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